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The diiron bridging vinyliminium complexes [Fe2{µ-η1-η3-C=;N(Me)2C(R')=C(R'')}(µ-CO)(CO)(Cp)2][SO3CF3] (R' = H, R''; = SiMe3, 3a; R' = H, R'' = Tol =4-MeC6H4, 3b; R' = Me, R'' = Me, 3c; R' = SPh, R'' = Me, 3d; R' = H, R'' = Fc = [Fe(C5H4)(Cp)], 6e) react with propargyl alcohol (HC≡CCH2OH), in refluxing toluene, affording the polysubstituted ferrocenes as mixtures of two isomeric forms: [1-NMe2-2-R'-3-R''-5-CH2OCH2C≡CH-Fc] (R' = H, R'' = SiMe3, 6a; R' = H, R'' = Tol, 6b; R' = Me, R'' = Me, 6c; R' = SPh, R'' = Me, 6d, R' = H, R'' = Fc, 6e) and [1-NMe2-2-R'-3-R''-4-CH2OCH2C≡CH-Fc] (R' = H, R'' = SiMe3, 7a; R' = H, R'' = Tol, 7b; R' = Me, R'' = Me, 7c; R' = SPh, R'' = Me, 7d) in overall yields of about 55–65%. Formation of the functionalized cyclopentadienyl in the ferrocene products takes place through the assembly of two propargyl units with the bridging vinyliminium ligand: one alkynol is incorporated by a [3 + 2] cycloaddition with the bridging C3 ligand; a second alkynol unit gives rise to a pendant chain through -OH substitution. Investigations show that the substitution step is catalyzed by the parent diiron complex itself or by a mononuclear iron fragment (likely the Fp+ complex). The pendant propargyl chain has been exploited to connect the ferrocene to other molecular fragments: in particular, the reaction of 6a with 4-biphenyl azide, by copper-catalyzed azide–alkyne cycloaddition (CuAAC), leads to the formation of the triazole-functionalized ferrocene [1-NMe2-2-CH2OCH2-N3(C6H4Ph)C2H-4-SiMe3-Fc] (12). Moreover, 6a reacts with Co2(CO)8, affording the complex [Co2{µ-η2-HC≡CR}(CO)6] (13), (HC≡CR = 6a), where the alkyne adopts a η2 coordination to a dicobalt hexacarbonyl fragment. The molecular structure of 7a has been determined by X-ray diffraction studies.

The diiron bridging enaminoalkylidene complex [Fe2{μ-η1:η3-C(Fc)CHCH(NMe2)}(μ-CO)(CO)- (Cp)2] (2), containing a ferrocenyl group on the bridging ligand, reacts with HC≡CR, affording the corresponding 3-R-substituted 1,100-biferrocene (R =CPh2OH, 4a; R = Tol, 4b; R = CO2Me, 4c; R = CH2OH, 4d). In a related reaction, the μ-vinylaminoalkylidene complex [Fe2{μ-η1:η3-C- (NMe2)CHCH(CO2Me)}(μ-CO)(CO)(Cp)2] (1a), upon treatment with ethynylferrocene, leads to the formation of 2-NMe2-4-CO2Me-1,100-biferrocene (4f). Conversely, the μ-enaminoalkylidene complex [Fe2{μ-η1:η3-C(Tol)CHCH(NMe2)}(μ-CO)(CO)(Cp)2] (1b) reacts with ethynylferrocene, affording a mixture of monosubstituted biferrocene 4b and disubstituted 2-NMe2-4-Tol-1,100- biferrocene (4e), in comparable yields. Reaction of 2 with ethynylferrocene (HC≡CFc) leads to the formation of a mixture of 1,3-terferrocene (5a) and the 5-NMe2-substituted 1,3-terferrocene (5b). Investigation of the reactivity of the vinyliminium complex [Fe2{μ-η1:η3-C(Fc)CHCNMe2}(μ-CO)- (CO)(Cp)2][SO3CF3] (3) with HC≡CCPh2OH is also reported: the reaction affords selectively the 3-NMe2-4-R-disubstituted 1,100-biferrocene (6). The molecular structure of 5a has been determined by X-ray diffraction studies.

The reactions of vinyliminium complexes [Fe2{μ-η1:η3- C(R)=C(H)C=N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Xyl, R = Me, 1a; R = Xyl, R = Tol, 1b; R = Xyl, R = COOMe, 1c; R = Me, R = Me, 1d; R = Me, R = nBu, 1e; R = p-MeOC6H4, R = Me, 1f; Tol = 4-C6H4Me, Xyl = 2,6-Me2C6H3) with CS2 and NaH resulted in the replacement of CH hydrogen (in the bridging frame) with CS2 to give the corresponding dithiocarboxylate- vinyliminium complexes [Fe2{μ-η1:η3-C(R)=C- (CS2)C=N(Me)(R)}(μ-CO)(CO)(Cp)2] (2a–2f). Analogously, 1a and 1d reacted with NaH and SCNPh to afford the complexes [Fe2{μ-η1:η3-C(R)=C{C(NPh)S}C=N(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Xyl, R = Me, 3a; R = Me, R = Me, 3b), respectively. Complex 2b was methylated at the dithiocarboxylate group Introduction Organic molecules acting as bridging ligands are expected to exhibit reaction patterns different to those observed when the same species are uncoordinated or are bound to a single metal centre.[1] An example is offered by the chemistry of the bridging vinyliminium diiron complexes I (Scheme 1).[2] Indeed, bridging vinyliminium ligands undergo nucleophilic addition at the iminium carbon or the adjacent α-carbon position[3] instead of the 1,4-conjugated addition normally observed in α,β-unsaturated iminium species.[4] Another unique feature of μ-vinyliminium ligands is the activation of α-C–H (C2–H in Scheme 1), which does not occur in uncoordinated conjugated iminium species.[5] The deprotonation of μ-vinyliminium ligands has been exploited to introduce a variety of substituents and functionalities into the bridging frame, as shown in Scheme 1. The carbon atoms in the bridging chain have been numbered as shown in Scheme 1 to make clearer the discussions presented hereafter. [a] Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy [b] Dipartimento di Chimica Fisica e Inorganica, Università di Bologna, Viale Risorgimento 4, 40136 Bologna, Italy E-mail: valerio.zanotti@unibo.it © 2011 Wiley-VCH Verlag 1260 GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2011, 1260–1268 upon treatment with CH3SO3CF3 to yield [Fe2{μ-η1:η3- C(R)=C(CS2Me)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (4a). Likewise, the zwitterionic complexes 2d–f underwent addition of the metal fragment [Fe(CO)2Cp]+ at the dithiocarboxylate group to yield the corresponding triiron complexes [Fe2{μ-η1:η3-C(R)=C(CS2Fp)C=N(Me)(R)}(μ-CO)(CO)(Cp)2]- [SO3CF3] [R = R = Me, 4b; R = Me, R = nBu, 4c; R = p- MeOC6H4, R = Me, 4d; Fp = Fe(CO)2Cp]. In a related reaction with [Pd(CH3CN)2Cl2], 2a binded to Pd through the dithiocarboxylate group as chelating ligand to afford the complex [PdCl2{κ2-(S,S)-2a}] (5). The X-ray structures of 2b, 3a and 4d have been determined.

Molybdenum sulfide catalysts of varying surface areas were prepared by thermal decomposition of MoS3 at 300, 350, 400, 450 and 500°. The surface areas has been found to be strongly dependent on the rate of heating suggesting a competition between the rate of nucleation and that of sintering of MoS2. The specific activities toward thiophene hydrodesulfuration and cyclohexene hydrogenation have been studied and their complementary trends have been attributed to the presence of at least two active centers. The catalytic properties and the variable surface area values found for the MoS3-MoS2 system have been correlated to X-Ray and analytical data.

The synthesis of a novel class of alcohol- and ether-functionalized indenyl ligands, focusing on the haptotropic rearrangements of the hybrid O-indenyl rhenium species, is herein described. η1- Indx OMeRe(CO)5 (12x) and η3-IndxOMeRe(CO)4 (13x, x=a, d) [IndaOMe=C9H6CH2CH(Me)OMe, 1a; Indd OMe=C9H6CH(CH2)3CHOMe, 1da] are examples of σ and allylic intermediates in the Cp substitution. The tuning of stereoelectronic effects of the functionalized alkyl chain or the coordinating solvent (MeCN, THF) allows the study of the relative stabilities of the intercepted solvento species η5-Indb OMeRe(CO)2(NCMe), 14b, η5-Indc OMeRe(CO)2(THF), 15c, or the chelate [η5:k1-OIndb, c ORe(CO)2], 16b,c {Indb OMe=[C9H6CH2CH(Ph)OMe]-, 4b; Indc OMe=[C9H6CH(Ph)CH2OMe]-, 4c}. DFT calculations reported on some of the IndO systems have been compared with those of smaller (CpO) 5a or larger (Flua O) 10a congeners, confirming the experimental findings. As peculiar examples of the underrepresented low-valent rhenium alkoxy species, the isolation of k1-O-HIndxORe(CO)5 [x=a, b] is also reported

Reactions of the vinylalkylidene complexes [Fe2{μ- η1:η3-CRCHCH(NMe2)}(μ-CO)(CO)(Cp) 2](R) SiMe3, 1a; Tol, 1b; CO2Me, 1c, Tol) 4-MeC6H4) with HC t CR′ (R′) CPh 2OH, CO2Me, Ph) lead to the formation of a mixture of 1,3-disubstituted ferrocenes [1-R-3-R′-Fc] (5, 7, 9, 11) and 1,2,4-trisubstituted ferrocenes [1-NMe2-2-R′-4-R-Fc] (4, 6, 8, 10)(R) SiMe3, R′) CPh2OH, 4 and 5; R) SiMe 3, R′) CO2Me, 6 and 7; R) SiMe3, R′) Ph, 8 and 9; R) Tol, R′) CPh2OH, 10 and 11). The polysubstituted Cp ring of the ferrocenyl products results from the cycloaddition of the alkyne with the bridging vinylalkylidene ligand and involves the cleavage of one of the two substituents (H or NMe2) on the vinyl moiety, as well as of the Fe - Fe bond. The cycloaddition reaction has been extended to a variety of bridging vinylalkylidene diiron complexes with different substituents and functionalities on the C3 bridging ligand, and to different alkynes. Thus, the vinylalkylidene complex 1b reacts with HC t CPh, yielding a mixture of four different ferrocenes, due to the absence of regioselectivity in the alkyne cycloaddition: [1-NMe2-2-Ph-4-Tol-Fc] (12), [1-Tol-3-Ph-Fc] (13), [1-NMe2-3-Ph-4-Tol-Fc] (14), and [1-Tol-2-Ph-Fc] (15). Conversely, the reactions with symmetric alkynes do not produce regioisomers: treatment of 1b and 1c with R′ C t CR′ (R′) Et, Ph) affords a mixture of 1,2,3-trisubstituted ferrocenes [1-R-2-R′-3-R′-Fc] (17, 19, 21, 23) and tetrasubstituted ferrocenes [1-NMe2-2-R′-3-R′-4-R-Fc] (16, 18, 20, 22)(R) SiMe 3, R′) Et, 16 and 17; R) Tol, R′) Et, 18 and 19; R) Tol, R′) Ph, 20 and 21; R) CO2Me, R′) Ph, 22 and 23). Likewise, the vinylalkylidene complexes [Fe2{μ-η1: η3-C(X)CHCH(R)}(μ-CO)(CO)(Cp)2](R) CO 2Me, X) NMe2, 2a; R) CN, X) NMe2, 2b; R) CO2Me, X) SMe, 3a; R) CN, X) SMe, 3b) react with alkynes HC t CR′ (R′) Tol, Ph), yielding a mixture of trisubstituted ferrocenes [1-X-2-R′-4-R-Fc] (24, 26, 28) and [1-X-3-R′-4-R-Fc] (25, 27, 29)(X) NMe2, R) CO2Me, R′) Tol, 24 and 25; X) NMe 2, R) CN, R′) Tol, 26 and 27; X) SMe, R) CO2Me, R′) Ph, 28 and 29). Finally, the reactions of 2a and 3b with PhC t CPh afford the tetrasubstituted ferrocenes 22 and [1-SMe-2-Ph-3-Ph-4-CN-Fc] (30), respectively. The crystal structures of 4 and 11 have been determined by X-ray diffraction studies.

Thiocarbonyl (CS), homologous to the ubiquitous carbonyl ligand, has interesting and unique properties as ligand. Nevertheless it did not reach the widespread use of CO in the formation of transition metal complexes. This short account, dedicated to professor R.J. Angelici, is focused on the multisite coordination of thiocarbonyl ligand in di- and poly-nuclear transition metal complexes, and to its transformation into thiocarbyne and thiocarbene ligands. These latter, in turn, can be transformed, providing access to a variety of new ligands and functionalities, which are here briefly reviewed.

The zwitterionic vinyliminium complex [Fe2{μ-η1:η3-C(R′) C(S)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (2a) (R′ = p-Me-C6H4 (Tol), Xyl = 2,6-Me2C6H3) undergoes electrophilic addition at the S atom by HSO3CF3, MeSO3CF3, SiMe3Cl, BrCH2Ph, ICH2CH CH2 affording the complexes [Fe2{μ-η1:η3-C(Tol) C(SX)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][Y] (X = H, Y = SO3CF3, 4a; X = Me, Y = SO3CF3, 4b; X = SiMe3, Y = Cl, 4c; X = CH2Ph, Y = Br, 4d; X = CH2CH CH2, Y = I, 4e). Compound 2a and the corresponding vinyliminium complexes 2b and 2c (R′ = CH2OH, 2b; R′ = Me, 2c) react also with etherated BF3 leading to the formation of the corresponding S-adducts [Fe2{μ-η1:η3-C(R′) C(SBF3)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (R′ = Tol, 5a; R′ = CH2OH, 5b; R′ = Me, 5c). In analogous reactions, the zwitterionic vinyliminium complexes undergo S-metalation upon treatment with in situ generated [Fp]+[SO3CF3]− [Fp = Fe(CO)2(Cp)], leading to the formation of [Fe2{μ-η1:η3-C(R′) C(S–Fp)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3](R′ = CH2OH, 6a; R′ = Me, 6b; R′ = Bun, 6c). Similarly, zwitterionic vinyliminium containing Se in the place of S also undergo Se-electrophilic addition. Thus, the complexes [Fe2{μ-η1:η3-C(R′) C(SeX)C N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = X = Me, R′ = Tol, 7a; R = Xyl, R′ = Me, X = Fp+, 7b) are obtained upon treatment of the neutral zwitterionic precursors with MeSO3CF3 and [Fp][SO3CF3], respectively. Alkylation at the S or Se atom of the bridging ligand is also accomplished by CH2Cl2, used as solvent, although the reaction is slower compared to more efficient alkylating reagents. The complexes formed by this route are [Fe2{μ-η1:η3-C(R′) C(E-CH2Cl)C N(Me)(R)}(μ-CO)(CO)(Cp)2][X] [E = S, R = Xyl, R′ = Tol, X = Cl, 8a; E = S, R = Xyl, R′ = Me, X = Cl, 8b; E = Se, R = R′ = Me, X = BPh4, 8c]. Finally, treatment of the zwitterionic vinyliminium complexes with I2 results in the oxidative coupling with formation of S–S (disulfide) or Se–Se (diselenide) bond. The reactions, performed in the presence of NaBPh4 afford the tetranuclear complexes [Fe2{μ-η1:η3-C(R′) C(E)C N(Me)(R)}(μ-CO)(CO)(Cp)2]2[BPh4]2 [R = Xyl, R′ = CH2OH, E = S, 9a; R = Xyl, R′ = Me, E = S, 9b; R = Xyl, R′ = Bun, E = S, 9c; R = Xyl, R′ = Me, E = Se, 9d; R = Me, R′ = Bun, E = Se, 9e]. The molecular structures of 4a, 8c and 9e have been determined by X-ray diffraction studies.

The diiron aminocarbyne complexes [Fe 2 {μ-CN(Me)(R)}(μ-CO)(CO)2(Cp) 2 ][S03CF3] (R = Xyl, la; R = 4-C 6 H 4 OMe, 1b; R = Me, 1c; Xyl = 2,6-Me 2 C 6 H 3 ) react with allenes of the type CH 2 =C=CR'R", in the presence of Me 3 NO/Et 3 N, to give the novel butadienylidene complexes [Fe 2 [μ-η 1 :η 3 -C α N(R)(Me)-Cp(H)C γ C δ (R')(R")}(μ-CO)(CO)(Cp)2] (R = Xyl, R' = R" = Me, 3a; R = Xyl, R' = Me, R" = H, 3b; R = Xyl, R' = CO 2 Et, R" = H, 3c; R = 4-C 6 H 4 OMe, R' = CO 2 Et, R" = H, 3d; R = R' = R" = Me, 3e; R = Me, R' = CO 2 Et, R" = H, 3f) in high yields. Analogously, the diiron thiocarbyne complex [Fe 2 (μ-CSMe)-(μ-CO)(CO)2(Cp) 2 ][SO 3 CF 3 ] (2) reacts with CH 2 =C=CR'R", in the presence of Me 3 NO/Et 3 N, to afford the compounds [Fe 2 {μ-η 1 :η 3 -C α S(Me)Cp(H)C γ C δ (R')(R")}(μ-CO)(CO)(Cp) 2 ] (R' = R" = Me, 4a; R' = CO 2 Et, R" = H, 4b; R' = SiMe 3 , R" = Me, 4c). Complexes 3-4 exist in solution as mixtures of cis and trans isomers. Compounds 3a and 3e, upon treatment with HSO 3 CF 3 , are transformed into the corresponding vinyl-iminium complexes [Fe 2 {μ-η 1 :η 3 -C γ (C δ HMe 2 )C β HC α N(R)-(Me)}(μ-CO)(CO)(Cp) 2 ][SΟ 3 CF 3 ] (R = Xyl, 5a; R = Me, 5b), in nearly quantitative yields. Conversely, compounds 4a,b undergo methylation (by CH 3 SO 3 CF 3 ) at the sulfur to give the cationic complexes [Fe 2 {μ-η 1 :η 3 -C α (SMe2)Cp(H)C γ C δ (R')-(R")}(μ-CO)(CO)(Cp)2][S03CF3] (R' = R" = Me, 7a; R' = CO 2 Et, R" = H, 7b). Protonation of 3a is not reversible: treating 5a with sodium hydride results in the formation of the 1-metalla-2-amino-cyclopenta-1,3-dien-5-one species [Fe(Cp)-(CO){CN(Me)(Xyl)CHC(CHMe2)C(O)}] (6). The molecular structures of cis-3a, cis-4b, 5a[CF 3 SO 3 ]·CH 2 Cl 2 and 7a[CF 3 SO 3 ]·0.5CH 2 Cl 2 have been determined by X-ray diffraction studies.

The vinyliminium complexes [Fe2{μ-η1:η3-C(R′){double bond, long}C(R)C{double bond, long}NMe2}(μ-CO)(CO)(Cp)2][SO3CF3] (R = H, R′ = Tol, 6a; R = H, R′ = Me, 6b; R = R′ = Me, 6c; R = H, R′ = CO2Me, 6d; R = R′ = Et, 6e; R = H, R′ = nBu 6f; Tol = p-MeC6H4) react with HC{triple bond, long}CCPh2OH affording the corresponding polysubstituted ferrocenes [1-NMe2-2-CPh2OH-4-R′-5-R-Fc] (7a-f). The polysubstituted Cp ring results from [3 + 2] cycloaddition of the bridging ligand with the alkyne, and formation of ferrocenyl products implies fragmentation of the diiron parent complexes. The reaction of 6a yields also the oxo-η5-cyclohexadienyl complex [Fe{η5-C6H2O(NMe2)(Tol)(CPh2OH)}(Cp)] (8), which results from a [3 + 2 + 1] cycloaddition involving the bridging vinyliminium, the alkynol and CO. The bis-alkylidene complex [Fe2{μ-η1:η2-C(R′)CH2C = N(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (9) (Xyl = 2,6-Me2C6H3) reacts similarly with alkynes (HC≡CR, R = Ph, CPh2OH, CO2Me) affording polysubstituted ferrocenes as a mixture of the two isomeric forms: [1-N(Me)(Xyl)-3-R-4-Tol-Fc] (R = Ph, 10a; R = CPh2OH, 11a, R = CO2Me 12a) and [1-N(Me)(Xyl)-2-R-4-Tol-Fc] (10b, 11b, 12b), respectively. Likewise, the μ-enimine complex [Fe2{μ-η1:η3-C(Et) = C(Et)C=NMe}(μ-CO)(CO)(Cp)2] (13) undergoes [3 + 2] cycloaddition with alkynes (HC{triple bond, long}CR, R = Tol, CH2OH) leading to the formation of the corresponding polysubstituted ferrocenes [1-NH(Me)-2-R-4-Et-5-Et-Fc] (R = Tol, 14; R = CH2OH, 15). The X-ray molecular structure of 7c has been determined.

The vinyliminium complexes [M2{μ-η1:η3-Cγ(R‘)CβHCαN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (1a−f) react with ethyl diazoacetate in the presence of NaH, affording the azine−bis(alkylidene) [M2{μ-η1:η2-Cγ(R‘)Cβ{NNCδ(COOMe)H}CαN(Me)(R)}(μ-CO)(CO)(Cp)2] (M = Fe, R = 2,6-Me2C6H3 (Xyl), R‘ = Me (2a), p-C6H4Me (Tol) (2b), CO2Me (2c), Bun (2d); M = Fe, R = R‘ = Me (2e); M = Ru, R = Xyl, R‘ = Me (2f)) in 70÷77% yields. Analogous reactions with N2CPh2 lead to the formation of [Fe2{μ-η1:η2-Cγ(R‘)Cβ(NNCδPh2)CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (R‘ = Me (3a), COOMe (3b)). The azine−bis(alkylidene) ligand easily undergoes electrophilic addition, affording the cationic hydrazone−vinyliminium complexes [Fe2{μ-η1:η3-Cγ(R‘)Cβ{N(E)NCδ(R‘ ‘)(R‘ ‘‘)}CαN(Me)(Xyl)}(μ-CO)(CO)(Cp)2]+ (R‘ = Me, R‘ ‘ = CO2Et, R‘ ‘‘ = E = H, 4a; R‘ = Me, R‘ ‘ = COOEt, R‘ ‘‘ = H, E = Me, 4b; R‘ = Bun, R‘ ‘ = COOEt, R‘ ‘‘ = H, E = Me, 4c; R‘ = Me, R‘ ‘ = R‘ ‘‘ = Ph, E = Me, 4d). Reactions of 4b,d with NaBH4 result in the addition of hydride at the Cα of the vinylim...

Alkynes (RC⋮CR‘) insert into the metal−isocyanide bond of [Fe2(CNMe)(CO)3(Cp)2] (1), under UV irradiation, affording the complexes [Fe2{μ-η1:η3-C(R)C(R‘)CN(Me)}(μ-CO)(CO)(Cp)2] (R = R‘= Ph, 2a; R = R‘ = Me, 2b; R = R‘ = Et, 2c; R = Ph, R‘ = H, 2d; R = Tol, R‘ = H, 2e; R = SiMe3, R‘ = H, 2f; R = Me, R‘ = H, 2g; R = CH2OH, R‘ = H, 2h; Tol = 4-MeC6H4), with displacement of one CO ligand. Compounds 2b,c exist as a mixture of cis and trans isomers (with reference to the mutual Cp position), whereas 2a,d−h exclusively have the cis geometry. The insertion of terminal alkynes is regioselective, since C−C bond formation occurs selectively between the isocyanide and the nonsubstituted carbon of HC⋮CR. Compound 1 reacts with 2 equiv of HC⋮CCO2Me under UV irradiation, affording [Fe2{μ-η2:η4-C(OH)C(CO2Me)C(H)CN(Me)(CHCHCO2Me}(CO)(Cp)2] (4). Complexes 2a,c undergo electrophilic addition at the N atom by treatment with HSO3CF3, allyl iodide (ICH2CHCH2), and methyl chloroformate (ClCOOMe), affording the corresponding vin...

The bridging diiron thiocarbyne complex [Fe2{μ-CS(Me)}(μ-CO)(CO)2(Cp)2]ISO 3 CF 3 ] (1) reacts with activated olefins (methyl acrylate, acrylonitrile, styrene, diethyl maleate), in the presence of Me 3 NO and NaH, to give the corresponding μ-allylidene complexes [Fe 2 {μ-η 1 :η 3 -C α (SMe)C β (R')C γ (H)(R")} (μ-CO)(CO)(Cp) 2 ] (R" = CO 2 Me, R'= H, 3a; R" = CN, R'= H, 3b; R" = C 6 H 5 , R'= H, 3c; R" = R' = CO 2 Et, 3d). The coupling reaction of olefin with thiocarbyne is regio- and stereospecific, leading to the formation of only one isomer. C-C bond formation occurs between the less substituted alkene carbon and the thiocarbyne. Moreover, olefinic hydrogens of the bridging ligands are mutually trans. The reactions of 3a-b with MeSO 3 CF 3 result, selectively, in the formation of the cationic μ-sulphonium allylidene complexes [Fe 2 [μ-η 1 :η 3 -C α (SMe 2 )C β (H)C γ (H)(R)}(μ-CO)(CO)(Cp)2][SΟ 3 CF 3 ] (R = CΟ 2 Me, 4a; R = CN, 4b). Compound 4a undergoes displacement of the SMe 2 group by nucleophiles such as NaBH 4 , NBu 4 CN and NaOMe, affording the complexes [Fe 2 ( μ-η 1 :η 3 -C α (R)C β (H)C γ H)(CΟ 2 -Me)}(μ-(CO)(Cp) 2 ] (R = H, 5a; R = CN, 5b; R = OMe, 5c), respectively. The molecular structures of 3a and 5a have been determined by X-ray diffraction studies.

The diiron vinyliminium complexes [Fe2{μ-η1:η3-C(R‘)CHCN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R‘ = Me, 1a; R = Xyl, R‘ = Tol, 1b; R = Xyl, R‘ = CO2Me, 1c; R = Xyl, R‘ = CH2OH, 1d; R = Xyl, R‘ ...

Different protic nucleophiles (i.e.Ph2C NH, PhSH, MeCO2H, PhOH) can be added to the C C bond of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(OMe)C CTol}(Cp)2][SO3CF3] (1), affording new diiron alkenyl methoxy carbene complexes.The additions of Ph2C NH and MeCO2H are regio and stereoselective, resulting in the formation of the 5-aza-1-metalla-1,3,5-hexatriene [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβH Cγ(Tol)(N CPh2)}(Cp)2][SO3CF3] (2), and the 2-(acyloxy)alkenyl methoxy carbene complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβH Cγ(Tol)OC(O)Me)}(Cp)2][CF3SO3] (5); the E isomer of the former and the Z of the latter are formed exclusively.Conversely, the addition of PhSH is regio but not stereoselective; thus, both the E and Z isomers of [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(OMe)CβH Cγ(Tol)(SPh)}(Cp)2][SO3CF3] (3) are formed in comparable amounts.Compounds 3 and 5 are demethylated upon chromatography through Al2O3, resulting in the formation of the acyl complexes [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(O)CβH Cγ(Tol)(SPh)}(Cp)2] (4) and [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){Cα(O)CβH Cγ(Tol)OC(O)Me}(Cp)2] (6), respectively, both with a Z configured Cβ Cγ bond.Finally, the reaction of 1 with PhOH proceeds only in the presence of an excess of Et3N affording the 2-(alkoxy)alkenyl acyl complex [Fe2{μ-CN(Me)(Xyl)}(μ- CO)(CO){Cα(O)CβH Cγ(Tol)(OPh)}(Cp)2] (7). The crystal structures of 4 · CH2Cl2 and 7 · 0.5CH2Cl2 have been determined by X-ray diffraction experiments.

Primary alkynes R′C CH [R′ = Me3Si, Tol, CH2OH, CO2Me, (CH2)4C CH, Me] insert into the metal–carbon bond of diruthenium μ-aminocarbynes [Ru2{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)2][SO3CF3] [R = 2,6-Me2C6H3 (Xyl), 1a; CH2Ph (Bz), 1b; Me, 1c] to give the vinyliminium complexes [Ru2{μ-η1:η3-C(R′) CHC N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] [R = Xyl, R′ = Me3Si, 2a; R = Bz, R′ = Me3Si, 2b; R = Me, R′ = Me3Si, 2c; R = Xyl, R′ = Tol, 3a; R = Bz, R′ = Tol, 3b; R = Bz, R′ = CH2OH, 4; R = Bz, R′ = CO2Me, 5a; R = Me, R′ = CO2Me, 5b; R = Xyl, R′ = (CH2)4C CH, 6; R = Xyl, R′ = Me, 7a; R = Bz, R′ = Me, 7b; R = Me, R′ = Me, 7c]. The related compound [Ru2{μ-η1:η3-C[C(Me) CH2] CHC N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3], (9) is better prepared by reacting [Ru2{μ-CN(Me)(Xyl)}(μ-CO)(CO)(Cl)(Cp)2] (8) with AgSO3CF3 in the presence of HC CC(Me) CH2 in CH2Cl2 at low temperature.In a similar way, also secondary alkynes can be inserted to give the new complexes [Ru2{μ-η1:η3-C(R′) C(R′)C N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Bz, R′ = CO2Me, 11; R = Xyl, R′ = Et, 12a; R = Bz, R′ = Et, 12b; R = Xyl, R′ = Me, 13). The reactions of 2–7, 9, 11–13 with hydrides (i.e., NaBH4, NaH) have been also studied, affording μ-vinylalkylidene complexes [Ru2{μ-η1:η3-C(R′)C(R″) C(H)N(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Bz, R′ = Me3Si, R″ = H, 14a; R = Me, R′ = Me3Si, R″ = H, 14b; R = Bz, R′ = Tol, R″ = H, 15; R = Bz, R′ = R″ = Et, 16), bis-alkylidene complexes [Ru2{μ-η1:η2-C(R′)C(H)(R″)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)2] (R′ = Me3Si, R″ = H, 17; R′ = R″ = Et, 18), acetylide compounds [Ru2{μ-CN(Me)(R)}(μ-CO)(CO)(C CR′)(Cp)2] (R = Xyl, R′ = Tol, 19; R = Bz, R′ = Me3Si, 20; R = Xyl, R′ = Me, 21) or the tetranuclear species [Ru2{μ-η1:η2-C(Me)CCN(Me)(Bz)}(μ-CO)(CO)(Cp)2]2 (23) depending on the properties of the hydride and the substituents on the complex. Chromatography of 21 on alumina results in its conversion into [Ru2{μ-η3:η1-C[N(Me)(Xyl)]C(H)C CH2}(μ-CO)(CO)(Cp)2] (22). The crystal structures of 2a[CF3SO3] · 0.5CH2Cl2, 12a[CF3SO3] and 22 have been determined by X-ray diffraction studies.

The diiron frame Fe 2 Cp 2 CO 2 allows the coordination of a variety of carbene ligands, including heteroatom substituted (Fischer type) and alkylidenes, in both bridging and terminal coordination modes. Synthetic strategies have been devised for obtaining aminocarbenes and thiocarbenes, by nucleophilic addition on the corresponding bridging amino- and thio-carbyne cationic complexes [Fe 2 (μ-CX)(μ-CO)(CO) 2 (Cp) 2 ][SO 3 CF 3 ] (X = SMe, NMe 2 , N(Me)Xyl), respectively. A more general approach to the synthesis of diiron complexes bridged by carbenes, exploits the electrophilic character of the sulphonium complex [Fe 2 {μ-C(CN)(SMe 2 )}(μ-CO)(CO) 2 (Cp) 2 ][SO 3 CF 3 ] and the facile displacement of the SMe 2 moiety by nucleophiles. These methods afford a large variety of heteroatom (N, P, O, S) substituted carbene complexes and also μ-alkylidenes. Terminally bonded alkynyl methoxy carbene complexes have been obtained by the classical Fischer method, consisting in nucleophilic addition at a terminal CO, to generate an acyl intermediate, followed by oxygen atom methylation. The coordination to diiron cationic complexes makes the alkynylmethoxy carbene ligands very reactive towards the addition of nucleophiles, like amines and carbanions. These additions are regio- and stereoselective, occurring exclusively at the alkynyl moiety. Finally, new multidentate and functionalized bridging ligands are described. They are anchored to the diiron frame through an aminocarbene, or an alkylidene binding end, or both. These ligands result from intramolecular couplings and rearrangements which involve the μ-aminocarbyne, the terminally bonded nitrile ligands and acetylides.

The vinyliminium complexes [Fe2{μ-η1:η3-C(R′) C(R′)C N(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Me, R′ = Et, 1a; R = Me, R′ = Ph, 1b; R = R′ = Me, 1c; R = Xyl, R′ = Me, 1d; R = Xyl, R′ = Et, 1e; R = Xyl, R′ = Ph, 1f; Xyl = 2,6-Me2C6H3), react with MeLi affording the corresponding μ-vinylalkylidene complexes [Fe2{μ-η1:η3-C(R′)C(R′) CHN(Me)(R)}(μ-CO)(CO)(Cp){C5H4(Me)}] (2a–f). The formation of 2a–f is believed to proceed via nucleophilic attack at the Cp ligand, followed by hydrogen migration from the resulting cyclopentadiene to the iminium carbon. Similarly, the complex [Fe2{μ-η1:η3-C(Ph) C(Ph)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] reacts with PhLi to give [Fe2{μ-η1:η3-C(Ph)C(Ph) CHN(Me)(Xyl)}(μ-CO)(CO)(Cp){C5H4(Ph)}] (4). Treatment of 2a with CF3SO3CH3 results in methylation of the nitrogen, yielding the complex [Fe2{μ-η1:η3-C(Et)C(Et)CH(NMe3)}(μ-CO)(CO)(Cp){C5H4(Me)}][CF3SO3] (5). Analogously, the μ-vinylalkylidene complexes [Fe2{μ-η1:η3-C(R′)C(R″) CHN(Me)(R)}(μ-CO)(CO)(Cp)2], (R = Me, R′ = Tol, R″ = H, 3a; R = Me, R′ = SiMe3, R″ = H, 3b; R = Me, R′ = R″ = Et, 3c; R = Me, R′ = R″ = Ph, 3d; R = Bz, R′ = Tol, R″ = H, 3e; R = Bz, R′ = SiMe3, R″ = H, 3f; R = Bz, R′ = COOMe, R″ = H, 3g; R = Bz, R′ = R″ = COOMe, 3h; R = Bz, R′ = R″ = Me, 3i; Bz = CH2Ph), react with CF3SO3CH3 to give the corresponding ammonium-functionalized μ-allylidene complexes [Fe2{μ-η1:η3-C(R′)C(R″)CH(NMe2R)}(μ-CO)(CO)(Cp)2][CF3SO3] (6a–i). The molecular structures of 5 and 6c have been elucidated by X-ray diffraction studies. Finally, protonation of [Fe2{μ-η1:η3-C(Et)C(Et) CH(NMe2)}(μ-CO)(CO)(Cp)2] (3c), with HBF4, affords the complex [Fe2{μ-η1:η3-C(Et)C(Et)CH(NHMe2)}(μ-CO)(CO)(Cp)2]][BF4] (7).

Addition of cyanide ions to the alkynyl(methoxy)carbene complexes [Fe 2 (μ-CN(Me)(R)}(μ-CO)(CO)(Ca(OMe)C β ≡C γ R')-(Cp) 2 ] + (R = Xyl, R' = Tol, la; R = Xyl, R' = Ph, 1b; R = Xyl, R' = Me 3 Si, 1c; R = Me, R' = Tol, 1d; R = Me, R' = Ph, 1e) occurs selectively at Ca to afford the 1,1-disubstituted σ-propargyl complexes [Fe 2 {μ-CN(Me)(R)}(μ-CO)(CO)(C(OMe)-(CN)(C≡CR')}(Cp) 2 ] (R = Xyl, R' = Tol, 2a; R = Xyl, R' = Ph, 2b; R = Xyl, R' = Me 3 Si, 2c; R = Me, R' = Tol, 2d; R = Me, R' = Ph, 2e). Conversely, the stabilised carbanaions [CH(R) 2 ] - (R = CN, CO 2 Me) add at the C γ position with subsequent hydrogen migration to Cp to give the 1-σ-buta-1,3-dienyl complexes [Fe 2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(C α -(OMe)=C β HC γ (Tol)=C δ (R) 2 )(Cp) 2 ] (R = CN, 3a; CO 2 Me, 3b). No migration is possible in the absence of hydrogen atoms at C δ , therefore addition of [C(Me)(CO 2 Me) 2 ] - to la results in the formation of the σ-allenyl complex [Fe 2 {μ-CN(Me)-(Xyl)}(μ-CO)(CO){C α (OMe)=C β =C γ (Tol)C δ (Me)(CO 2 Me) 2 }-(Cp) 2 ] (4). Protonation of the neutral complexes 3b and 4 affords the vinyl(methoxy)carbene complexes [Fe 2 {μ-CN-(Me)(Xyl)}(μ-CO)(CO){C α (OMe)C β H=C γ (Tol)C δ (R)(CO 2 -Me) 2 }] + (R = H, 5; Me, 6), which exist in solution as mixtures of (E)- and (Z)-isomers in dynamic equilibrium, as shown by VT NMR studies. The cationic complex 6 shows electrophilic behaviour. Thus, addition of CN - results in the σ-allyl complex [Fe 2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(Ca(OMe)(CN)-[C β H=C γ (Tol)C δ (Me)(CO 2 Me) 2 ])(Cp) 2 ] (7), whereas the reaction with Me 2 NH affords the vinyl acyl complex [Fe 2 {μ-CN(Me)(Xyl)}(μ-CO)(CO){C α (O)C β H=C γ (Tol)C δ (Me)(CO 2 -Me) 2 }(Cp) 2 ] (8). The crystal structures of 2b and 3a.CH 2 Cl 2 have been determined.

The C β -H hydrogen in the diiron vinyliminium complexes [Fe 2 {μ-η 1 :η 3 -C γ (R')=C β HC α = N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Me, 1; R = Bz, 2 (Bz = CH 2 Ph); R = Xyl, 3 (Xyl =2,6-Me 2 C 6 H 3 )) is easily removed by sodium hydride; different products are consequently formed, depending on the nature of the substituents R and R'. Thus, deprotonation of [Fe 2 {μ-η 1 :η 3 -C(R')=CHC=N(Me)(R)}(μ-COXCOXCp) 2 ][SO 3 CF 3 ] (R = Me, R' = COOMe, la; R = Me, R' = Me, 1b; R = Bz, R' = COOMe, 2a) yields the tetranuclear complexes [Fe 2 {μ-η 1 :η 2 -C(R')-CCN(Me)(R)}(M-CO)(CO)(Cp) 2 ] 2 (R = Me, R' = COOMe, 4a; R = Me, R' = Me, 4b; R = Bz, R' = COOMe, 4c). Conversely, treatment with NaH of the vinyliminium complexes [Fe 2 {μ-η 1 :η 3 -C(R')=CHC=N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Me, R' = SiMe 3 , 1d; R = Me, R' = Tol, 1e; R = Bz, R' = SiMe 3 , 2b; R = Bz, R' = Tol, 2c (Tol = 4-MeC 6 H 4 ); R = Xyl, R' = SiMe 3 , 3a; R = Xyl, R' = Tol, 3b; R = Xyl, R' = Ph, 3c) leads to the selective formation of the corresponding μ-aminocarbyne alkynyl complexes [Fe 2 -{μ-CN(Me)(R)}(μ-CO)(CO)(C≡CR')-(Cp) 2 ] (R = Me, R' = SiMe 3 , 5a; R = Me, R' = Tol, 5b; R = Bz, R' = SiMe 3 , 5c; R = Bz, R' = Tol, 5d; R = Xyl, R' = SiMe 3 , 5e; R = Xyl, R' = Tol, 5f; R = Xyl, R' = Ph, 5g). Compounds 5c,d react with methyl iodide to give the vinyliminium cations [Fe 2 {μ-η 1 :η 3 -C(R')=C(Me)C= N(Me)(Bz)}(μ-CO)(CO)(Cp) 2 ] + (R' = SiMe 3 , 6a; R' = Tol, 6b). Finally, the reactions of [Fe 2 {μη 1 :η 3 -C(R')=CHC=N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Me, R' = Bu n , 1c; R = Xyl, R' = Me, 3d; R = Xyl, R' = COOMe, 3e; R = Xyl, R' = CMe 2 OH, 3f) with NaH afford the 1-metalla-2-aminocyclopenta-1,3-dien-5-one species [Fe(Cp)(CO){CN(Me)(R)CHC(R')C(O)}] (R = Me, R' = Bu n , 7a; R = Xyl, R' = Me, 7b; R = Xyl, R' = COOMe, 7c; R = Xyl, R' = CMe 2 OH, 7d). The molecular structures of 4a.CH 2 Cl 2 , 4b, 5e, and 7b have been determined by X-ray diffraction studies.

The diiron complexes [Fe(Cp)(CO){μ-η 2 :η 2 -C[N(Me)(R)]N C(C 6 H 3 R′)C CH(Tol)}Fe(Cp)(CO)] (R = Xyl, R′ = H, 3a ; R = Xyl, R′ = Br, 3b ; R = Xyl, R′ = OMe, 3c ; R = Xyl, R′ = CO 2 Me, 3d ; R = Xyl, R′ = CF 3 , 3e ; R = Me, R′ = H, 3f ; R = Me, R′ = CF 3 , 3g ) are obtained in good yields from the reaction of [Fe 2 {μ-CN(Me)(R)}(μ-CO)(CO)( p -NCC 6 H 4 R′)(Cp) 2 ] + (R = Xyl, R′ = H, 2a ; R = Xyl, R′ = Br, 2b ; R = Xyl, R′ = OMe, 2c ; R = Xyl, R′ = CO 2 Me, 2 d; R = Xyl, R′ = CF 3 , 2e ; R = Me, R′ = H, 2f; R = Me, R′ = CF 3 , 2g ) with TolC CLi. The formation of 3 involves addition of the acetylide at the coordinated nitrile and C–N coupling with the bridging aminocarbyne together with orthometallation of the p -substituted aromatic ring and breaking of the Fe–Fe bond. Complexes 3a – e which contain the N(Me)(Xyl) group exist in solution as mixtures of the E - trans and Z - trans isomers, whereas the compounds 3f,g , which posses an exocyclic NMe 2 group, exist only in the Z-cis form. The crystal structures of Z - trans - 3b , E - trans - 3c , Z - trans - 3e and Z - cis - 3g have been determined by X-ray diffraction experiments.

Acetonitrile is easily displaced from [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)2][SO3CF3] (R = 2,6-Me2C6H3 (Xyl) (1a); Me (1b)) upon stirring in THF at room temperature in the presence of [NBu4][SCN]. The resulting complexes trans-[Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)2] (R = Xyl (trans-2a); Me (trans-2b)) are completely isomerised to cis-[Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCS)(Cp)2] (R = Xyl (cis-2a); Me (cis-2b)) when heated at reflux temperature. Similarly, the complexes cis-[M2{μ-CN(Me)(R)}(μ-CO)(CO)(NCO)(Cp)2] (M = Fe, R = Me (4a); M = Ru, R = Xyl (4b); M = Ru, R = Me (4c)) and cis-[M2{μ-CN(Me)(R)}(μ-CO)(CO)(N3)(Cp)2] (M = Fe, R = Xyl (5a); M = Fe, R = Me (5b); M = Ru, R = Xyl (5c)) can be obtained by heating at reflux temperature a THF solution of [M2{μ-CN(Me)(R)}(μ-CO)(CO)(MeCN)(Cp)2][SO3CF3] (M = Fe, R = Xyl (1a); M = Fe, Me (1b); M = Ru, R = Xyl (1c); M = Ru, R = Me (1d)) in the presence of NaNCO and NaN3, respectively. The reactions of 5 with MeO2CC CCO2Me, HC CCO2Me and (NC)(H)C C(H)(CN) afford the triazolato complexes [M2{μ-CN(Me)(R)}(μ-CO)(CO){N3C2(CO2Me)2}(Cp)2] (M = Fe, R = Xyl (6a); M = Fe, R = Me (6b); M = Ru, R = Xyl (6c)), [M2{μ-CN(Me)(R)}(μ- CO)(CO){N3C2(H)(CO2Me)}(Cp)2] (M = Fe, R = Me (7a); M = Ru, R = Xyl (7b)) and [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){N3C2(H)(CN)}(Cp)2] (8), respectively. The asymmetrically substituted triazolato complexes 7–8 are obtained as mixtures of N(1) and N(2) bonded isomers, whereas 6 exists only in the N(2) form. Methylation of 6–8 results in the formation of the triazole complexes [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){N3(Me)C2(CO2Me)2}(Cp)2][CF3SO3] (9), [M2{μ-CN(Me)(R)}(μ-CO)(CO){N3(Me)C2(H)(CO2Me)}(Cp)2][CF3SO3] (M = Fe, R = Me (10a); M = Ru, R = Xyl (10b)) and [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){N3(Me)C2(H)(CN)}(Cp)2][CF3SO3], 11. The crystal structures of trans-2b, 4b · CH2Cl2, 5a, 6b · 0.5CH2Cl2 and 8 · CH2Cl2 have been determined.

A terminally coordinated CO ligand in the complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2][SO3CF3] (R = Me, 1a; R = Xyl, 1b; Xyl = 2,6-Me2C6H3), is readily displaced by primary and secondary amines (L), in the presence of Me3NO, affording the complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = NH2Et, 4a; R = Xyl, L = NH2Et, 4b; R = Me, L = NH2Pri, 5a; R = Xyl, L = NH2Pri, 5b; R = Xyl, L = NH2C6H11, 6; R = Xyl, L = NH2Ph, 7; R = Xyl, L = NH3, 8; R = Me, L = NHMe2, 9a; R = Xyl, L = NHMe2, 9b; R = Xyl, = NH(CH2)5, 10). In the absence of Me3NO, NH2Et gives addition at the CO ligand of 1b, yielding [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C(O)NHEt}(Cp)2] (11). Carbonyl replacement is also observed in the reaction of 1a–b with pyridine and benzophenone imine, affording [Fe2{μ-CN(Me)R}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = Py, 12a; R = Xyl, L = Py, 12b; R = Me, L = HN CPh2, 13a; R = Xyl, L = HN CPh2, 13b). The imino complex 13b reacts with p-tolylacetylide leading to the formation of the μ-vinylidene-diaminocarbene compound [Fe2{μ-η1:η2- C C(Tol)C(Ph)2N(H)CN(Me)(Xyl){(μ-CO)(CO)(Cp2)] (15) which has been studied by X-ray diffraction.

Addition of acetylides R′C≡CLi [R′ = Tol, Ph, Me3Si, nBu, C(Me)=CH2] to the diruthenium complexes [Ru2{μ-CN(Me)(R)}(μ-CO)(CO)(NCCMe3)(Cp)2]+ (R = Xy, 2a; Bz, 2b; Me, 2c) results in the formation of [Ru2{μ-CN(Me)(R)}(μ-CO)(CO){N(H)=C(CMe3)(C≡CR′)}(Cp)2]+ (R = Xy, R′ = Tol, 3a; R = Bz, R′ = Tol, 3b; R = Me, R′ = Tol, 3c; R = Xy, R′ = Ph, 4a; R = Bz, R′ = Ph, 4b; R = Me, R′ = Ph, 4c; R = Bz R′ = H, 5; R = Xy, R′ = nBu, 6; R = Xy, R′ = [C(Me)=CH2], 7), which contain an alkynylimino ligand, formed from addition of the acetylide to the Me3CCN ligand. Structural and spectroscopic studies show that all these complexes contain the two Cp ligands in a relative cis arrangement, whereas two isomers arise from the different orientation of the substituents on the bridging aminocarbyne μ-CN(Me)(R) when R ≠ Me. Addition of secondary amines to 3−7 results in a stereo- and regioselective cis amination of the C−C triple bond to give the new complexes [Ru2{μ-CN(Me)(R)}(μ-CO)(CO){N(H)=C(CMe3)C(H)=C(NMe2)(Tol)}(Cp)2]+ (R = Xy, 8a; Bz, 8b; Me, 8c), [Ru2{μ-CN(Me)(Xy)}(μ-CO)(CO){N(H)=C(CMe3)C(H)=C(NC5H10)(Tol)}(Cp)2]+(9) and [Ru2{μ-CN(Me)(Xy)}(μCO)(CO){N(H)=C(CMe3)C(H)=C(NMe2)C(Me)=CH2)}(Cp)2]+ (10) containing the hitherto unknown new imino-2-en-3-amine ligand. The solid-state structures of these products have been analyzed by X-ray analysis and, in solution, by NOE spectroscopic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The reaction of the μ-aminocarbyne complex [Fe 2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(NCCMe 3 )(Cp) 2 ][SO 3 CF 3 ] ( 2 ) (Xyl=2,6-Me 2 C 6 H 3 ) with tolylacetylide, followed by treatment with HSO 3 CF 3 affords the complex [Fe 2 {μ-η 1 :η 3 C(Tol)CC(CMe 3 )N(H)CN(Me)(Xyl)}(μ-CO)(CO)(Cp 2 )][SO 3 CF 3 ] ( 3 ) (Tol=4-MeC 6 H 4 ). The X-ray molecular structure of 3 reveals the peculiar character of the bridging ligand, which exhibits both η 1 :η 2 allene and aminocarbene nature. The formation of 3 proceeds through several intermediate species, which have been detected by IR spectroscopy. Addition of HSO 3 CF 3 at an early stage of the reaction between 2 and LiCCTol leads to the formation of the imine complex [Fe 2 {μ-CN(Me)Xyl}(μ-CO)(CO){NHC(CCTol)CMe 3 }(Cp) 2 ][SO 3 CF 3 ] ( 6 ) indicating that the first step of the reaction consists in the acetylide addition at the coordinated NCCMe 3 . The molecular structure of 6 has been elucidated by an X-ray diffraction study.

The hydroformylation of hex-1-ene and styrene with syngas (30 bar of 1:1 CO/H 2 ) in the presence of the alkoxycarbonylcyclopentadienyl rhodium(I) complexes [Rh{C 5 H 4 CO 2 X}(L,L)] [X=CH 2 CHCH 2 , (CHR) 2 OH (R=H, Me); L,L=2CO, NBD] has been studied and compared with the unsubstituted system [Rh(C 5 H 5 )NBD]. The influence of various reaction parameters on the catalytic activity and selectivity is presented and discussed.

The complexes [Fe 2 {μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp) 2 ] [SO 3 CF 3 ] (R = Xyl, la; R = Me, 1b; R = CH 2 Ph, 1c; Xyl = 2,6-Me 2 C 6 H 3 ), containing a labile NCMe ligand, react under mild conditions with a variety of terminal alkynes HC≡CR' (R'= SiMe 3 , Me, Bu n , Tol, Ph, H; Tol = 4-MeC 6 H 4 ) to give the bridging vinyliminium complexes [Fe 2 {μ-σ:η 3 -C(R')=CHC=N(Me)-(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Xyl, R' = SiMe 3 , 2a; R = Me, R' = SiMe 3 , 2b; R = CH 2 Ph, R' = SiMe 3 , 2c; R = Xyl, R' = Me, 3a; R = R' = Me, 3b; R = Xyl, R' = Bu n , 4; R = Xyl, R' = Tol, 5a; R = Me, R' = Tol, 5b; R = CH 2 Ph, R' = Tol, 5c; R = Xyl, R' = Ph, 6; R = Xyl, R' = H, 7). Insertion of the alkyne into the metal-carbyne carbon bond is regiospecific, resulting only in the product containing the R' group on the carbon bound to Fe. Similarly, insertion of the disubstituted alkynes R'C≡CR' (R' = Me, Et) affords the analogous compounds [Fe 2 {μ-σ:η 3 -C(R')=C(R')C=N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Xyl, R' = Me, 8a; R = R'= Me, 8b; R = CH 2 Ph, R' = Me, 8c; R = Xyl, R' = Et, 9a; R = Me, R' = Et, 9b). The molecular structure of complex 2a has been elucidated by an X-ray diffraction study.

The ring-opening reaction of meso-4,5-dimethyl-1,3-dioxolan-2-one or (4S,5S)-dimethyl-1,3-dioxolan-2-one with NaCp yields the sodium hydroxyalkoxycarbonylcyclopentadienides Na[rac-C5H4CO2(CHMe)2OH]...

Reaction of [Fe2(μ-CS)(μ-CSMe)Cp2(CO)2]+ (1) with sodium N,N-dimethyldithiocarbamate [Me2dtc]Na affords a mixture of the dithiocarbene [Fe Fe(μ-CS){μ-C(SMe)S C(S)NMe2}Cp(CO)] (2) and the thiocarbyne [Fe2(μ-CS)(μ-CSMe)(μ-S2CNMe2)Cp2] (3). Complex 2 is quantitatively converted into 3 by photochemical irradiation. The X-ray molecular structure of 3 demonstrates the presence of three bridging ligands and exhibits the shortest FeFe interaction found in similar systems [2.453(1) A]. Complex 3 can also be obtained by reacting [Me2dtc]− with the di-solvento thiocarbyne [Fe2(μ-CS)(μ-CSMe)(NCMe)2Cp2]+ (1a). By contrast no stable addition product has been isolated in analogous reactions involving the thiocarbyne [Fe2(μ-CO)(μ-CSMe)Cp2(CO)2]+ (1b). The [Me2dtc]− nucleophilic addition at the μ-C to form [Fe2(μ-CO){μ-C(CN)SC(S)NMe2}Cp2(CO)2] (4a) is obtained starting from [Fe2(μ-CO){μ-C(CN)(SMe2)}Cp2(CO)2]SO3CF3 (1d). Photochemical reaction of the cyanocarbene 4a causes intramolecular ring closure affording [Fe Fe(μ-CO){μ-C(CN)S C(S)NMe2}Cp2(CO)] (5a).

The one-step synthesis of Na[C5H4CO2CH2CHCH2] (1) from NaCp and diallyl carbonate is presented together with a simple pathway for the synthesis of sodium hydroxyalkoxycarbonylcyclopentadienide, Na[C5H4CO2(CH2)2OH] (2). The latter new reagent is obtained in high yield by reacting NaCp with 1,3-dioxolan-2-one (ethylene carbonate). When (±)-4-methyl-1,3-dioxolan-2-one [(±)-1,2-propylene carbonate] is used, the ring-opening reaction leads to a mixture of the two regioisomers Na[C5H4CO2CH2CH(Me)OH] (3a) and Na[C5H4CO2CH(Me)CH2OH] (3b) in a 7:3 ratio. Reactions of 1 and 2 with FeCl2 and [Rh(L,L)Cl]2 [L,L = CO or L,L = 2,5-norbornadiene (NBD)] lead to the respective metal complexes [Fe(C5H4CO2CH2CHCH2)2] (4), [Fe{C5H4CO2(CH2)2OH}2] (5), [Rh(C5H4CO2CH2CHCH2)(CO)2] (6), [Rh{C5H4CO2(CH2)2OH}(CO)2] (7), and [Rh{C5H4CO2(CH2)2OH}(NBD)] (8). Additionally in the reaction of 2 with [Rh(L,L)Cl]2 the diester-bridged dinuclear adducts [Rh2{μ-(C5H4CO2CH2)2}(L,L)2] [L,L = CO (9); L,L = NBD (10)] are isolated. The reaction of ...

The disubstituted alkyl- and aryloxycarbonylcyclopentadienides of sodium Na[C5H3(CO2R)2-1,2] [R = Me (3a), Et (3b), Ph (3c)] are obtained in a two-step synthesis. The known Na[C5H4(CO2R)] [R = Me (1a), Et (2b)] and the hitherto unknown Na[C5H4(CO2Ph)] (1c), prepared from NaCp and dialkyl- or diphenyl carbonate, are subsequently reacted with the corresponding chloroformates ROCOCl to give 3 contamined with variable amounts of 1,3 isomers. Treatment of 3b with [18]-crown-6 affords the buff-colored crystalline salt [Na([18]-crown-6)][C5H3(CO2Et)2-1,2] (4b). Reactions of 4b and 3c with MBr(CO)5 [M = Mn, Re] or [RuCl2(CO)3]2 lead to the respective metal complexes [M{η5-C5H3(CO2R)2-1,2}(CO)3] [R = Et and M = Mn (5b) or Re (6b), R = Ph and M = Mn (5c)] and [Ru{C5H3(CO2Et)2-1,2}(CO)]2(7b). The solid state structure of 4b reveals ion pairs in which the anion adopts an idealized C2v conformation and chelates the sodium (κ2O,O‘-coordination). The structure of [Mn{C5H3(CO2Ph)2-1,2}(CO)3] (5c) confirms the expected η5...

The complexes [Fe2{μ-CN(Me)R}(μ-CO)(NCMe)(CO)(Cp)2]SO3CF3 (R=Me, 2a; 2,6-Me2C6H3, 2b; CH2Ph, 2c), easily obtained from the corresponding [Fe2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2]SO3CF3 (1a–c) precursors, react with NBu4CN affording the cyano complexes [Fe2{μ-CN(Me)R}(μ-CO)(CN)(CO)(Cp)2] (3a–c) by displacement of the MeCN ligand. The analogous reaction with NBu4Cl leads to the formation of [Fe2{μ-CN(Me)R}(μ-CO)(Cl)(CO)(Cp)2] (4a–b). The μ-hydride complexes [Fe2{μ-CN(Me)R}(μ-H)(CO)2(Cp)2] (5a–b) have been prepared by reaction of 1a–b with NaBH4. The corresponding diruthenium compound [Ru2(μ-CNMe2)(μ-H)(CO)2(Cp)2] (6) has been similarly obtained from [Ru2(μ-CNMe2)(μ-CO)(NCMe)(CO)(Cp)2]SO3CF3. The X-ray molecular structure of 5a is that expected for cis isomers of this family of compounds. It shows a chiral conformation of the C5H5 ligands and the crystals are a conglomerate of enantiomeric individuals. NMR spectra of the various compounds, which are indicative of the presence of α–β or cis–trans isomeric mixtures, are reported and discussed.

The reaction of [M2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2]SO3CF3 (M=Fe, R=Me, 1a; M=Fe, R=CH2Ph 1b, M=Ru, R=CH2Ph, 1c) with a mixture of KH and acetonitrile affords [(Cp)(CO) MC{NMe(R)}N(H)C(Me)C (CN)] (2a–c). The X-ray structure of 2a (M=Fe, R=Me) shows the formation of a pyrrole-like metallaring FeC(2)NC(4)C (5). The double bond character of the C(4)C(5) interaction [1.309(7)] suggests the enammine nature of the N(H)C(Me)C(CN) fragment which originates from condensation of two acetonitrile molecules. A mechanism for the formation of 2a–c is proposed in light of the 13C-NMR and IR evidence. Complex 2a can be methylated at the N-end of the hexocyclic CN group, forming a cationic metallacyclo complex containing the CCN+Me nitrilium moiety.

The reactions of [Fe 2 {μ-C(X)SMe 2 }(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=CN 2a , H 2b ; Cp=η-C 5 H 5 ) with Li 2 Cu(CN)R 2 (R=Me, Bu n , Ph, CCC 6 H 4 Me-4, C 4 H 3 S) give the neutral μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 3 ) arising from nucleophilic attack at the bridging carbon and SMe 2 displacement. Likewise, 2a , b react with the sodium salt of dimethylmalonate, diethylmalonate, ethylacetoacetate, 2,4-pentanedione, dibenzoylmethane and benzylcyanide, resulting in the formation of the corresponding functionalized μ-alkylidene complexes [Fe 2 {μ-C(X)R}(μ-CO)(CO) 2 (Cp) 2 ] ( 5 – 7 ) (X=CN, H; R=CH(COOMe) 2 , CH(COOEt) 2 , CH(COOMe)(COMe), CH(COMe) 2 , CH(COPh) 2 , CH(Ph)CN). The dichetone adducts [Fe 2 {μ-C(X)CH(COR) 2 }(μ-CO)(CO) 2 (Cp) 2 ] (X=CN, H; R=Me, Ph) undergo deacylation upon treatment with alumina, leading to the formation of the complexes [Fe 2 {μ-C(X)CH 2 C(O)R}(μ-CO)(CO) 2 (Cp) 2 ]. Reactions of 2a , b with LiBu or PhLi result in the formation the metallacycles [Fe 2 {μ-C(X)S(Me) CH 2 }(μ-CO)(C O)(CO)(Cp) 2 ] (X=CN, 4a ; H 4b ) which arise from the deprotonation of an SMe group and the intramolecular addition at a terminally coordinated carbonyl. Finally, a comparison of the reactivity of 2a , b with that of the μ-carbyne diiron complexes [Fe 2 (μ-CX)(μ-CO)(CO) 2 (Cp) 2 ]SO 3 CF 3 (X=H, SMe, NMe 2 ) is presented.

The reaction of [Fe(CO) 2 (SR)(Cp)] (R=Et, Ph; Cp=η-C 5 H 5 ) with [Mn(CO) 2 (thf)(C 5 H 4 Me)] (thf=tetrahydrofuran), under photolytic conditions, leads to the formation of the novel heterodinuclear bridged thiolate complexes [FeMn(μ-CO)(μ-SR)(CO) 2 (Cp)(C 5 H 4 Me)] in low yields. [FeMn(μ-CO)(μ-SEt)(CO) 2 (Cp)(C 5 H 4 Me)] consists of a mixture of cis and trans isomers which have been separated and characterized by IR and NMR spectroscopy. The μ-phosphido complex [FeMn(μ-CO)(μ-PPh 2 )(CO) 2 (Cp)(C 5 H 4 Me)] has been prepared analogously from [Fe(CO) 2 (PPh 2 )(Cp)] and [Mn(CO) 2 (thf)(C 5 H 4 Me)]. Variable temperature NMR spectra of the latter heterodinuclear complex, in CDCl 3 , show the presence of an equilibrium mixture of the two interconverting cis and - trans isomers. The X-ray molecular structure of cis -[FeMn(μ-CO)(μ-SEt)(CO) 2 (Cp)(C 5 H 4 Me)] shows a bonded Fe–Mn interaction [2.617(2) A] reinforced by a μ-CO and a μ-SEt ligands. The molecule contains chiral centers at the iron, manganese and sulfur atoms and the diastereoisomer under study exhibits optimized non bonded contacts between the alkyl groups.

The reactions of [Ru2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2]SO3CF3 (R=Me 1a, CH2Ph 1b; Cp=η-C5H5) with Li2Cu(CN)R′2 (R′=Me, Bun, Ph) result in CC bond formation at the CO ligand affording the acyl complexes [Ru2{μ-CN(Me)R}(μ-CO)(COR′)(CO)(Cp)2] 2. The crystal structure of [Ru2{μ-CNMe2)(μ-CO)(COPh)(CO)(Cp)2] 2a reveals the double bond character of the μ-CN group and the interligand interaction involving the acyl oxygen and the μ-CNMe2 moiety. Type 2 complexes are also formed by reacting 1a–b with LiR′ (R′=Me, Bun, Ph), whereas reactions with ClMgCH2Ph yield both [Ru2{μ-CN(Me)R}(μ-CO)(COCH2Ph)(CO)(Cp)2] and [Ru2{μ-CN(Me)R}(μ-CO)(CO)2(η4-C5H5CH2Ph)(Cp)]. A comparison of the reactivity of 1a–b with that of the corresponding diiron complexes [Fe2{μ-CN(Me)R}(μ-CO)(CO)2(Cp)2]SO3CF3 is also presented.

The heteropolynuclear cyano-bridged complexes [(C5H5)Fe(CO)(CNMLn)(CNM′L′n)], {MLn = M′L′n = (C5H5)Fe(CO)2 or W(CO)5, MLn = (C5H5)Fe(CO)2, M′L′n = W(CO)5} and mixed isocyanide complexes [(C5H5)Fe(CO)(CNMLn)(CNR)], {MLn = W(CO)5, R = CPh3; MLn = (C5H5)Fe(CO)2, R = CH3} have been obtained by metallation or alkylation of the two terminal CN ligands of K[(C5H5)Fe(CO)(CN)2]. Comparison of the bonding properties of the CNMLn and CNR ligands, based upon their relevant spectroscopic data, are discussed. Furthermore, two new isomeric heterobinuclear cyano-bridged complexes of the form [(C5H5)(CO)2FeCNW(CO)5] and [(C5H5)(CO)2FeNCW(CO)5] have been synthesized and fully characterized by spectroscopic techniques. Finally the reactions with nucleophiles of the last two compounds have been also examined.

The reactions of [Fe2{µ-CN(Me)R}(µ-CO)(CO)2(Cp)2]SO3CF3 (Cp = η-C5H5, R = Me 2a or CH2Ph 2b) with a variety of carbon nucleophiles result in C–C bond formation at different sites of the molecules depending on the nature of the carbanions: (i) R′Li (R′ = Me, Bun or Ph) and R′MgCl (R′ = Me, CH2Ph or Pri) added at the Cp ligand giving η4-cyclopentadiene complexes [Fe2{µ-CN(Me)R}(µ-CO)(CO)2(η4-C5H5R′)(Cp)] 3; (ii) Li2Cu(CN)R′2 (R′ = Me or Bun) and LiCCR′ (R′ = Ph or p-tolyl) afforded the stable acyl complexes [Fe2{µ-CN(Me)R}(µ-CO)(CO){C(O)R′}(Cp)2] 4 and [Fe2{µ-CN(Me)R}(µ-CO)(CO){C(O)CCR′}(Cp)2] 5, respectively. With R ≠ Me the NMR spectra of type 3–5 derivatives show the presence of two isomers arising from the double-bond character of the µ-CN group ascertained from the crystal structure of [Fe2(µ-CNMe2)(µ-CO)(CO){C(O)Bun}(Cp)2] 4b. The structural study reveals the presence of interligand interactions involving the acyl oxygen and the µ-CNMe2 moiety which is also in accord with an extended-Huckel calculation of the charge distribution.

The bis(µ-thiocarbene)[(cp)(OC)Fe{µC(CN)SMe}{µ-C([graphic omitted]e(cp)](X = H or CN; cp =µ-C5H5) and all the intermediate species obtained from the thiocarbyne derivative cis-[Fe2(µ-CS){µ-C(SMe)}(CO)2(cp)2]-[SO3CF3]viaµ-C stereoselective addition of X–, photochemical formation of [(cp)[graphic omitted]Me)X}(µ-CS)Fe-(CO)(cp)] followed by stepwise addition of MeSO3CF3 and (NBu4n)CN at the bridging CS group have been prepared and characterized. Attempts to obtain the bis(µ-thiocarbene)[{Fe[µ-C(CN)SMe](CO)(cp)}2] failed. The crystal structure of [{[graphic omitted]Me](cp)}2] which demonstrates the presence of two doubly bridging thiocarbene groups has been determined. The results show that bis(µ-thiocarbene) derivatives are stable when at least one of the ligands acta as a double bridge via a S–Fe bond.

Electrochemistry of the μ-cyanoalkylidene complexes [Fe 2 (CO) 2 (cp) 2 ( μ -CO){ μ -C(CN)(X)}] n + ( n = 0, X = CN, H, Me, SMe, OMe, OEt, OPh, OCH 2 CH=CH 2 , PEt 2 , piperidinyl; n = 1, X = PMe 2 Ph) in nonaqueous solutions shows a one-electron reduction to the corresponding paramagnetic monoanions, which have been characterized by EPR spectroscopy. The presence of the positive charge in [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(CN)(PMe 2 Ph)}] + makes the one-electron addition significantly easier than to the neutral complexes. None of the 19-electron anions are fully stable and all undergo slow decomposition reactions, the rates of which are a function of the X substituent. Access to the radical anion intermediates [Fe 2 (CO) 2 (cp) 2 (μ-CO){μ-C(CN)(X)}] − does not trigger Electron Tra Chain catalytic substitution reactions of CO by phosphines, but allows these reactions to be successfully carried out by different methods, such as chemical reduction, CO photolysis and use of Me 3 NO. The CO-substituted derivatives [Fe 2 (cp) 2 (CO)(PMe 2 Ph)(μ-CO){μC(CN)(X) (X = CN, H, SMe) and [Fe 2 (cp) 2 ( μ -CO)( μ -dppm){ μ -C(CN)(X)}], (X = H, CN; dppm = Ph 2 PCH 2 PPh 2 ) were obtained. The one-electron reduction of the monophosphine-substituted complexes is fully irreversible and occurs at potentials 0.3–0.4 V more negative than those of the corresponding precursors. The different methods for promoting CO displacement in the μ-alkylidene complexes have been compared; the photolytic method affords the highest yields.

Repeated stepwise addition of CH 3 SO 3 CF 3 and Bu 4 NCN to the diisocyanide complex [Ru 2 (CO) 2 (Cp) 2 (CNBz) 2 ] (Cp = η -C 5 H 5 ; BzCH 2 Ph) has led to the formation of the new bis- μ -aminoalkylidene complex [Ru 2 (CO) 2 (Cp) 2 { μ -C(CN)N(Me Bz} 2 ], which has been characterized by X-ray diffraction. The crystal contains a racemic mixture of the isomer with the same chirality at the amine nitrogens. The molecule conforms to a C 2 idealized symmetry. Selected bond distances are RuRu 2.662(1), Ru( μ -C) 2.088 (av), μ -CN(amine) 1.479 (av) A. All the intermediate species: [Ru 2 (CO) 2 (Cp) 2 ( μ -CNBz){ μ -CN(Me)Bz}SO 3 CF 3 , [Ru 2 (CO) 2 (Cp) 2 { μ -CNBz)} μ -C(CN)N(Me)Bz}] and [Ru 2 (CO) 2 (Cp) 2 { μ -CN(Me)Bz}{ μ -C(CN)-N(Me)Bz}]SO 3 CF 3 have been isolated and characterized spectroscopically. Attempts to extend the synthetic method to the iron diisocyanide [Fe 2 (CO) 2 (Cp) 2 (CNBz) 2 ] led to [Fe 2 (CO)(CNBz)(Cp) 2 ( μ -CO){ μ -CN(Me)Bz} SO 3 CF 3 and [Fe 2 (CO)(CNBz)-(Cp) 2 ( μ -CO)} μ -C(CN)N(Me)Bz}] but not to the bis(aminoalkylidene) derivative.

The aminocarbyne [W{CN(Et)Me}(CO)2(cp)]1(cp =η-C5H5) reacts with [Au(C6F5)(tht)](tht = tetrahydrothiophene) and CuCl to give the adducts [AuW{µ-CN(Et)Me}(C6F5)(CO)2(cp)]2 and [{CuW{µ-CN(Et)Me}Cl(CO)2(cp)}2]3 respectively which have been structurally characterized by X-ray diffraction. Complex 2 crystallizes in space group P, a= 9.840(5), b= 11.577(6), c= 8.296(6)A, α= 99.03(5), β= 91.01(6), γ= 81.92(4)°, Z= 2. Complex 3 crystallizes in space group P21/a, a= 7.788(2), b= 14.880(5), c= 11.712(5)A, β= 95.35(3)°, Z= 2. Both adducts exhibit a molecule of 1 bonded to Au(C6F5) or Cu2Cl2 fragments, respectively, through one of the W–C(carbyne)π bonds. A WCM ring is formed in which 1 preserves most of its identity and the coinage metals attain their preferred electron counts. The cationic Group 11 fragments [M(PPh3)+](M = Cu, Ag or Au) also react with complex 1 to form [M{W[µ-CN(Et)Me](CO)2(cp)}2]+5; when M = Au NMR spectroscopy indicates that in addition to the trinuclear species 5, the dimetallacyclopropene [AuW{µ-CN(Et)Me}(CO)2(cp)(PPh3]+4 is also present. All these adducts have been spectroscopically characterised.

The iron complex [Fe(CO)2(Cp)]OTf is found to be an excellent catalyst in the dehydrative etherification of ferrocenylmethol (I) with alcohols, in particular with propargyl alcohol.

The zwitterionic bridging vinyliminium complex [Fe2{μ-η1:η3-C(Tol) C(CS2)C N(Me)2}(μ-CO)(CO)(Cp)2] (5a) undergoes the addition of two equivalents of MeO2C–C C–CO2Me affording the bridging bis-alkylidene complex [Fe2{μ-η1:η3-C(Me)C{C(CO2Me)C(CO2Me)CSC(CO2Me)C(CO2Me)S}CNMe2}(μ-CO)(CO)(Cp)2] (6). One alkyne unit inserts into a C–CS2 bond of the bridging ligand, with consequent rearrangement that leads to the formation of a diene. The reaction shows analogies with the enyne metathesis. The second alkyne is incorporated into the bridging frame via cycloaddition at the thiocarboxylate function, affording a 1,3-dithiolene. The complexes [Fe2{μ-η1:η3-C(R′) C(CS2)C N(Me)(R)}(μ-CO)(CO)(Cp)2] (R = Xyl, R′ = Tol, 5b; R = p-C6H4OMe, R′ = Me, 5c; Xyl = 2,6-Me2C6H3), treated with MeO2C–C C–CO2Me and then with HBF4, undergo the cycloaddition of the alkyne with the dithiocarboxylate group and protonation of the dithiocarboxylate carbon, affording the complexes [Fe2{μ-η1:η3-C(R′) C{C(H)SC(CO2Me)C(CO2Me)S}C N(Me)(R)}(μ-CO)(CO)(Cp)2][BF4] (R = Xyl, R′ = Tol, 7a; R = p-C6H4OMe, R′ = Me, 7b), respectively. The X-ray molecular structure of 6 has been determined.

Upgrading of bio-oils obtained from the fast pyrolysis of biomasses requires the development of efficient catalysts able to work under mild conditions and to cope with the complex chemical nature of the reactant. The present work focuses on the use of the ruthenium based Shvo homogeneous catalyst for the hydrogenation of model mixtures (vanillin, cinnamaldehyde, methylacetophenone, glycolaldehyde, acetol, acetic acid) and of a real bio-oil. The hydrogenation of model compounds has been investigated both in mono- and biphasic mixtures under a P(H2) = 10 atm in the temperature range of 90–145 °C varying the substrate to catalyst molar ratio from 2000:1 to 200:1. Employing the most active reaction conditions (substrate/catalyst 200:1, T = 145 °C, P(H2) = 10 atm) the Shvo catalyst maintains its performances under acidic “bio-oil conditions” leading to the almost quantitative conversion of the polar double bonds within 1 h. The activity of the Shvo catalyst was also investigated for the hydrogenation of a bio-oil from poplar in solvent free conditions. Hydrogenation deeply changed the chemical nature of the pyrolysis oil. Aldehydes, ketones and non-aromatic double bonds were almost totally hydrogenated. The catalytic system also promoted the hydrolysis of sugar oligomers into monomers.

The amide-functionalized imidazolium salts [BocNHCH2CH2ImR]X (R = Me, X = I, 1a; R = benzyl, X = Br, 1b; R = trityl, X = Cl, 1c) bearing increasingly bulky N-alkyl substituents were prepared in high yields by direct alkylation of the (2-imidazol-1-yl-ethyl)carbamic acid tert-butyl ester; 1c is a crystalline solid also characterized by X-ray diffraction. These salts are precursors for the synthesis of rhodium(I) complexes [Rh(NBD)X(NHC)] (NHC = 1-(2-NHBoc-ethyl)-3-R-imidazolin-2-ylidene; X = Cl, R = Me (3a), R = benzyl (3b), R = trityl (3c); X = I, R = Me (4a)). All the complexes display restricted rotation about the metalcarbene bond; however, while the rotation barriers calculated for 3a,b and 4a matched the experimental values, unexpectedly this was not true in the case of 3c, where the experimental value was equal to that obtained for compound 3b (58.6 kJ mol1) and much smaller with respect to the calculated one (100.0 kJ mol1). The catalytic activity of the neutral rhodium(I) complexes 3ac in the hydrosilylation of terminal alkynes with HSiMe2Ph has been investigated with PhCtCH, TolCtCH, nBuCtCH, Et3SiCtCH, and (CPh2OH)CtCH as substrates. The steric hindrance on the N-heterocyclic ligand and on the alkyne substrates affects conversion and selectivity: for the former the best results were achieved employing the less encumbered 3a catalyst with TolCtCH, whereas by employing hindered alkynes such as Et3SiCtCH or (CPh2OH)CtCH the hydrosilylation leads only to the formation of the β-(E)-vinylsilane and α-bis(silyl)alkene isomers. The complexes 3a,b have also been employed in the addition of arylaldehydes with phenylboronic acid, and like in the hydrosylylation case, the best results were obtained using 3a in the presence of aldehydes bearing electron-withdrawing groups, such as 4-cyanobenzaldehyde and 4-acetylbenzaldehyde as substrates.

The complex [Fe 2 (CO) 2 (Cp) 2 (μ-CS)(μ-CSMe)]SO 3 CF 3 ( 1 ) reacts with N n Bu 4 NCO to give [Fe 2 (CO) 2 (Cp) 2 (μ-CS){μ-CNC(O)SMe}] ( 2 ). This reaction has been carried out separately for both the cis and trans isomers of 1 . Complex cis - 2 undergoes S -methylation with MeOSO 2 CF 3 affording the novel thiocarbyne derivative [Fe 2 (CO) 2 (Cp) 2 (μ-CSMe) {μ-CNC(O)SMe}]SO 3 CF 3 ( 3 ), into which in turn an additional NCO − anion inserts to yield the bis(μ-acylisocyanide) complex [Fe 2 (CO) 2 (Cp) 2 {μ-CNC(O)SMe} 2 ] ( 4 ). All the reactions described are stereospecific and the derivatives 2–4 do not exhibit cis-trans isomerization.

The isocyanide complex [RU 2 CP 2 (CO) 3 (CNCH 2 Ph)], obtained by the reaction of [RU 2 CP 2 (CO) 4 ] with CNCH 2 Ph in the presence of Me 3 NO, has been N-alkylated, yielding the cationic μ-alkylidyne complex [Ru 2 CP 2 (CO) 3 {μ-CN(Me)CH 2 Ph}]SO 3 CF 3 . The compound yielded undergoes nueleophilic addition using NaBH 4 or NaBu 4 CN at the μ-C alkylidyne carbon to give the novel μ-aminoalkylidene complexes [Ru 2 Cp 2 (CO){μ-C(X)N(Me)CH 2 Ph}] (X = H, CN). The derivative with X = CN adopts the expected geometry and an idealized C s symmetry if the phenyl substituent is ignored. The relevant bond distances are as follows: RuRu, 2.711(1) A; Ru-μ-C(carbene), 2.090(4) A (ave.); C(carbene)-N, 1.477(5) A; N-C(alkyl), 1.474(5) A (ave.).

A large number of iron and ruthenium dinuclear complexes containing heteroatom substituted carbene ligands have been obtained by two different synthetic routes. The first method consists in reacting heteroatom substituted μ-carbyne cationic complexes with CN− ion. The second involves the displacement of the SMe2 molecule in the sulfonium [Fe2{μ-C(CN)(SMe2)}(μ-CO)(CO)2CP2]SO3CF3 by appropriate nucleophilesX− (X=OR, SR, NR2, PR2). Spectroscopic (IR, NMR) and structural investigations together with reactivity studies on these complexes have greatly contributed to better understanding the factors which favor bridging vs. terminal coordination of heteroatom substituted carbene ligands.