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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 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 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).

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.

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.

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 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.

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.).

Zwitterionic vinyliminium complexes [Fe2{u-eta1:eta3-C(R’)=C(E)C=N(Me)(R)}(-CO)(CO)(Cp)2][SO3CF3] (R = R’ = Me, E = Se, 1a; R = Xyl R’ = Tol, E = Se, 1b; R = Xyl, R’ = Tol, E = S, 2a; R = Xyl, R’ = Tol, E = S, 2b; Tol = 4-MeC6H4, Xyl = 2,6-Me2C6H3), undergo alkyne addition by different reaction modes. Complexes 1a and 2a undergo 1,3 dipolar cycloaddition with alkynes [HCCCO2Me, and C2(CO2Me)2], affording new 1-(2-amino)-seleno(thio)phene-alkylidene diiron complexes [Fe2{μ-1(N):1(C):1(C):-C(R’)CEC(CO2Me)=C(R’’)CN(Me)(R)}(μ-CO)(CO)(Cp)2] (R = R’ = Me, E = Se, R’’ = CO2Me, 3a; R = R’ = Me, E = Se, R’’ = H, 3b; R = Me, R’ = Tol, E = S, R’’ = CO2Me, 4). The hemilabile character of the bridging ligand in 3a is investigated by reaction with CNBut, which replace NMe2 coordination affording [Fe2{μ-C(Me)CSeC(CO2Me)=C(CO2Me)CN(Me)2}(μ-CO)(CO)(CNBut)(Cp)2] (5). Complexes 2a, 2b react with two equivalents of HCCCO2Me, leading to the formation in formation of [Fe2{-1(O):1(C):3(C)-C(CCCO2Me)C(R’)C(SCH=CHCO2Me)CON(Me)(Xyl)}(-CO)(Cp)2] (R’ = Tol, 6a; R’ = Me, 6b). Finally, complexes 1b, 2a and 2b react with different alkynes, in the presence of NH4PF6, affording the vinyl sufide and vinyl selenide vinyliminium complexes [Fe2{μ-1:3-C(R’)=C(ECR’’=CHCO2Me)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][PF6] (R’ = Tol, E = S, R’’= H, 7a; R’ = Me, E = S, R’’ = H, 7b; R’ = Tol, E = S, R’’= CO2Me, 7c; R’ = Me, E = S, R’’= CO2Me, 7d; R’ = Tol, E = Se, R’’= H, 8a; R’ = Tol, E = Se, R’’= CO2Me, 8b). The molecular structures of 3a, 5, and 6b have been elucidated by X-ray diffraction.

The μ-aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R = Me, 1a; Xyl, 1b; Xyl = 2,6-Me2C6H3) react with ethynylferrocene to give the corresponding bridging vinyliminium complexes [Fe2{μ-η1:η3-C N(Me)(R)CHC(Fc)}(μ-CO)(CO)(Cp)2][SO3CF3] (R = Me, 2a; R = Xyl, 2b). Insertion of the ethynylferrocene in the metal–carbyne bond is regiospecific, and leads to the formation of only one isomer. Complexes 2a and 2b undergo hydride addition (by NaBH4) affording the enaminoalkylidene complex [Fe2{μ-η1:η3-C(H)(N(Me)2)CHC(Fc)}(μ-CO)(CO)(Cp)2] (3a) and the bis-alkylidene [Fe2{μ-η1:η2-C(N(Me)(Xyl))CH2C(Fc)}(μ-CO)(CO)(Cp)2] (3b), respectively. Upon treatment with NaH, compounds 2a and 2b undergo fragmentation, affording the 1-metalla-2-aminocyclopenta-1,3-dien-5-one complexes [Fe(CO)(Cp){C(N(Me)(R))}CHC(Fc)C(O)}] (R = Me, 4a; R = Xyl, 4b). The molecular structures of 2b, 3b and 4b have been determined by X-ray diffraction studies.

Vinylalkylidene transition metal complexes have been extensively used as ‘multitalent tools’ in organic synthesis, covering a broad field of applications. The vinylalkylidene ligands can be monodentate; alternatively they can adopt a bridging coordination mode in complexes with two adjacent metal atoms. As for other unsaturated organic ligands which can bond in both mono- and di-nuclear modes, the bridging coordination can give rise to new and different chemical properties from those found when the ligand is bound to a single metal centre. Likewise, the synthetic routes to bridging vinylalkylidene complexes offer a broader range of possibilities compared to those used to make mononuclear vinylalkylidenes. In spite of the fact that bridging vinylalkylidene complexes have been known for about 40 years, their synthetic potential as C 3 activated fragments has so far been under-exploited. Comparison with other C 3 bridged ligands (allenyls and allyls) indicates that vinylalkylidene ligands are reactive and versatile species. This review article gives an overview of the chemistry of bridging vinylalkylidene complexes to focus attention on their potential as synthetic tools.

Tetrachloroauric acid HAuCl4 reacts with the ionic liquid 1-(2-aminoethyl)-3-methylimidazolium nitrate [NH2(CH2)2ImMe]NO3, (2b) or its dicationic ammonium salt [NH3(CH2)2ImMe][NO3]2, (3) in methanolic solutions to give the novel gold(III)-aminoethyl imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe][AuCl4] (4). The reaction of 4 with [nBu4]Cl gives [NH2(CH2)2ImMe][AuCl4] (2c) whereas with acetone the dicationic, iminium-functionalized, imidazolium aurate salt [Me2C=N(H)(CH2)2ImMe][AuCl4]2 (5) has been isolated. The structures in the solid state of 2c, 3, 4, and 5 have been determined by X-ray diffraction. The electrochemical behaviour of 4 has been examined by Cyclic voltammetry in acetonitrile and compared with 2c and KAuCl4.

The reactions of [Fe 2 {μ-C(CN)SMe 2 }(μ-CO)(CO) 2)(Cp)[in2 ]SO 3 CF 3 (Cp = η-C 5 H 5 ) with alcohols and alkoxides have been investigated. Nucleophilic attack of the oxygen atom on the μ-C carbon with displacement of the Me 2 S molecule was observed in all cases. The resulting μ-cyanoalkoxycarbene derivatives [Fe 2 {μ-C(CN)OR}(μ-CO)(CO) 2 (Cp) 2 ] (R = Me, 2a ; Et, 2b ; i Pr, 2c ; CH 2 Ph, 2d ; CH 2 CHCH 2 , 2e ; CH 2 CH 2 NMe 2 , 2f ; CH 2 CH 2 OH, 2g ; C 6 H 5 , 3a ; C 6 H 4 - o -NO 2 , 3b ) have been characterized spectroscopically. The complex [Fe 2 {μ-C(CN)OCH 2 CHCH 2 }(μ-CO)(CO) 2 (Cp) 2 ] ( 2e ) undergoes a photolytically-promoted intramolecular CO substitution by the olefinic termination to give [Fe Fe{μ-C(CN)OCH 2 CH CH 2 }(μ-CO)(CO)(Cp) 2 ] ( 5 ), which was be subjected to an X-ray diffraction study. Some structural features were as expected, in particular the location of Cp in a cis disposition with respect to the CN group. The molecule is asymmetric as a consequence of the coordination of the allyl in the place of a terminal CO group; the configurations of the four chiral centres are discussed.

Reactions of the vinyliminium complexes [Fe2{m-h1:h3-Cg(R')Cb(H)CaN(Me)(R)}(m-CO)(CO)(Cp)2][SO3CF3] (R = Xyl, R' = Me, 1a; R = Xyl, R' = CO2Me, 1b; R = 4-C6H4OMe, R' = CO2Me, 1c; Xyl = 2,6-Me2C6H3) with isocyanides (CNR''), in the presence of NaH, lead to abstraction of the Cb-H proton and to isocyanide addn. with formation of a carbon-carbon double bond. The obsd. products are the ketenimine-bis(alkylidene) complexes [Fe2{m-h1:h2-Cg(R')Cb(CNR'')CaN(Me)(R)}(m-CO)(CO)(Cp)2] (R = Xyl, R' = Me, R'' = Xyl, 2a; R = Xyl, R' = CO2Me, R'' = Xyl, 2b; R = Xyl, R' = CO2Me, R'' = But, 2c; R = Xyl, R' = CO2Me, R'' = 4-C6H4CN, 2d; R = 4-C6H4OMe, R' = CO2Me, R'' = But, 2e), obtained in 60-70% yields. Conversely, the vinyliminium complex [Fe2{m-h1:h3-Cg(CO2Me)Cb(H)CaN(Me)2}(m-CO)(CO)(Cp)2][SO3CF3] (1d) undergoes double isocyanide addn. Reactions of 1d with a 2-fold excess of CNXyl or CNBut, in the presence of NaH, afford [Fe(CO)(Cp)Ca(NMe2)Cb(CNXyl)Cg(CO2Me)C(NXy)Fe(CO)(Cp)] (3) and [Fe(CO)(Cp)C(NBut)Ca(NMe2)CbCg(CO2Me)Fe(Cp)(CO)CNBut] (4), resp. Finally, the vinyliminium complex [Fe2{m-h1:h3-Cg(H)Cb(H)CaN(Me)2}(m-CO)(CO)(Cp)2][SO3CF3] (1e), treated with CNBut and NaH, yields a mixt. of the diiron aminocarbyne complexes [Fe2{m-CN(Me)2}(m-CO)(CO)(Cp)(C5H5CH2CN)(CNBut)], (6) and [Fe2{m-CN(Me)2}(m-CO)(CO)(Cp)2(CNBut)] (5). The mol. structures of 2a,b, 3×1.5CH2Cl2, 4, and 6×0.5Et2O have been ascertained by x-ray diffraction studies.

The bridging aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)2(Cp)2][S03CF3] (R = Me, 1a; Xyl, 1b; 4-C 6 H 4 OMe, 1c; Xyl = 2,6-Me 2 C 6 H 3 ) react with acrylonitrile or methyl acrylate, in the presence of Me 3 NO and NaH, to give the corresponding μ-ally-lidene complexes [Fe 2 {μ-η 1 :η 3 - C,(N(Me)(R))C β (H)C,(H)(R')}(μ-CO)(CO)(Cp)2] (R = Me, R' = CN, 3a; R = Xyl, R' = CN, 3b; R = 4-C 6 H 4 OMe, R' = CN, 3c; R = Me, R' = CO 2 Me, 3d; R = 4-C 6 H 4 OMe, R' = CO 2 Me, 3e). Likewise, la reacts with styrene or diethyl maleate, under the same reaction conditions, affording the complexes [Fe2{μ-η 1 :η 3 -C α (NMe2)Cβ(R')Cy(H)(R")}(μ-CO)(CO)(Cp)2] (R' = H, R" = C 6 H 5 , 3f; R' = R" = CO 2 Et, 3g). The corresponding reactions of [Ru2{μ-CN(Me)(CH2Ph)}(μ-CO)(CO)2(Cp)2][S03CF3] (1d) with acrylonitrile or methyl acrylate afford the complexes [Ru2{μ-η 1 :η 3 -C,(N(Me)(CH2Ph))Cβ(H)C γ (H)(R')}(μ-CO)(CO)(Cp)2] (R' = CN, 3h; CO 2 Me, 3i), respectively. The coupling reaction of olefin with the carbyne carbon is regio- and stereospecific, leading to the formation of only one isomer. C-C bond formation occurs selectively between the less substituted alkene carbon and the aminocarbyne, and the C β -H, C γ -H hydrogen atoms are mutually trans. The reactions with acrylonitrile, leading to 3a-c and 3h involve, as intermediate species, the nitrile complexes [M2{μ-CN(Me)(R)} (μ-CO)(CO)(NC-CH=CH2)(Cp)2][S03CF3] (M = Fe, R = Me, 4a; M = Fe, R = Xyl, 4b; M = Fe, R = 4-C 6 H 4 OMe, 4c; M = Ru, R = CH 2 C 6 H 5 , 4d). Compounds 3a, 3d and 3f undergo methylation (by CH 3 SO 3 CF 3 ) and protonation (by HSO 3 CF 3 ) at the nitrogen atom, leading to the formation of the cationic complexes [Fe2{μ-η 1 :η 3 -C,(N(Me)3)C β (H)C,(H)(R)}(μ-CO)(CO)(Cp)2][S03CF3] (R = CN, 5a; R = CO 2 Me, 5b; R = C 6 H 5 , 5c) and [Fe2{μ-η 1 :η 3 -C α (N(H)(Me)2)Cβ(H)C γ (H)(R)}(μ-CΟ)(CO)(Cp)2][S03CF3] (R = CN, 6a; R=CΟ 2 Me, 6b; R = C 6 H 5 , 6c), respectively. Complex 3a, adds the fragment [Fe(CO) 2 (THF)(Cp)] + , through the nitrile functionality of the bridging ligand, leading to the formation of the complex [Fe2{μ-η 1 :η 3 -C,(NMe2)Cβ(H )C γ (H)(CNFe(CO)2Cp)}(μ-CO)(CO)(Cp)2][S03CF3] (9). In an analogous reaction, 3a and [Fe2{μ-CN(Me)(R)((μ-CO)(CO)2(Cp)2][S03CF3], in the presence of Me 3 NO, are assembled to give the tetrameric species [Fe2{μ-η 1 :η 3 -C,(NMe2)Cβ(H)C γ (H)(CN[Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(Cp)2])}(μ-CO)(CO)(Cp)2][S03CF3] (R = Me, 10a; R = Xyl, 10b; R = 4-C 6 H 4 OMe, lOc). The molecular structures of 3a and 3b have been determined by X-ray diffraction studies.

The cyclopentadienide nucleophilic ring opening on the cyclopentene oxide affords diastereoselectively an efficient entry to a new polyalcoholic (1,2,4)-C5H2[CH(CH2)3CHOH]3 propeller-like, hybrid ligand CpOOO. The diastereoselective rhodium complexation gives rise almost quantitatively to a new class of racemic CpOOORh(L,L) (L,L ) nbd, cod, C2H4, CO) complexes. Thermal treatment gives predominantly the air-stable CpOOORh(nbd) rac-4a (73.5%), having SP planar chirality, as determined by X-ray diffraction studies. It has also been possible to isolate its stable atropisomer rac-4c (20.5%), while the minor kinetic isomer rac-4b, showing opposite planar chirality (∼10%), has been identified by NOESY NMR experiments. The high solubility in water and benzene, evidencing the amphiphilic character, has been measured by the n-octanol/water partition coefficient. The intermolecular H-binding, due to the hydroxy groups, plays a crucial role in selecting the rhodium coordination in the reaction mixture, whereas in the solid, it determines the supramolecular organization. DFT calculations in vacuo are in agreement with the spectroscopically identified structures.

The SPh functionalized vinyliminium complexes [Fe 2 {μ-η 1 :η 3 -C γ (R')=C β (SPh)C α =N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SΟ 3 CF 3 ] [R=Xyl, R' = Me, 2a; R=Me, R' = Me, 2b; R = 4-C 6 H 4 ΟMe, R'=Me, 2c; R=Xyl, R' CH 2 OH, 2d; R = Me, R' CH 2 OH, 2e; Xyl = 2,6-Me 2 C 6 H 3 ) are generated in high yields by treatment of the corresponding vinyliminium complexes [Fe 2 {μ-η 1 : η 3 -C γ (R')=C β (H)C α =N(Me)(R)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (la-e) with NaH in the presence of PhSSPh. Likewise, the diruthenium complex [Ru 2 {μ-η 1 :η 3 -C γ (Me)=C β (SPh)C α =N(Me)(Xyl)}(μ-CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (2f) was obtained from the corresponding vinyliminium complex [Ru2{μ-η 1 :η 3 -C γ (Me)=C β (H)C α =N(Me)(Xyl)}(μ-CO)(CO)(Cp )2] (1f). The synthesis of 2c is accompanied by the formation, in comparable amounts, of the aminocarbyne complex [Fe 2 {μ-CN (Me)(4-C6H40Me))(SPh)(μ-CO )(CO)(Cp)2] (3). The molecular structures of 2d, 2e and 3 have been determined by X-ray diffraction studies.

The synthesis of the Boc-protected 1-(2-aminoethyl)-3-methylimidazolium salts [BocNHCH2CH2ImMe]X ([2]X, X = I, PF6) and their straightforward transformation into [NH2CH2CH2ImMe]X ([3]X) was achieved by reaction of 1-[2-(N-Boc)aminoethyl]imidazole with MeI, followed by thermal deprotection. The reaction between [2]X and Ag2O leads to the formation in the solid state of three different bonding motifs: a biscarbene salt [(NHC-NHBoc)2Ag]PF6 ([4]PF6, NHC-NHBoc = 1-(2-BocNH-ethyl)-3-methyl-2-imidazolinylidene), a tetranuclear complex [Ag(NHC-NHBoc)2]2[Ag2I4], (5), and a polymeric silver "staircase" [(NHC-NHBoc)Ag(.mu.-I)AgI]n, (6) composed of Ag4I4 clusters, bearing two carbene ligands at the opposite Ag centers. The same reaction carried out with [3]I showed that a primary silver mono-NHC-NH2 carbene complex of the type [(NHC-NH2)AgI] (7) is likely to form but it is unstable in soln. The solid state mol. structures of [4]PF6, 5 and 6 were detd. by x-ray diffraction anal., whereas PGSE NMR expts. were employed to investigate the hydrodynamic dimension of the imidazolium salts and silver complexes and, consequently, to gain information on the level of aggregation in soln. PGSE NMR studies were complemented by NOE NMR investigations in order to obtain information on anion-cation relative orientation within aggregates.