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A series of diiron complexes based on the [Fe2Cp2(CO)x] skeleton (Cp = η5-C5H5, x = 2, 3; η4-C5H5Ph in place of one Cp in one case) and containing different bridging hydrocarbyl ligands (aminocarbyne, thiocarbyne, allenyl) were preliminarily investigated for their anticancer potential. The water solubility, stability in water and in the presence of a cell culture medium, and octanol/water partition coefficient were evaluated by spectroscopic techniques. The cytotoxicity was assessed in vitro toward the human ovarian carcinoma cell line A2780, the human triple negative breast cancer cell line MDA-MB-231, and the human vascular smooth muscle cell line SMC. Some aminocarbyne complexes exhibited a potent cytotoxicity, with IC50 values in the low micromolar/nanomolar range, and a strong selectivity for the A2780 cells in comparison to the SMC cell line. Several experiments were carried out in order to give insight into the mode of action of selected compounds, including an assessment of catalytic NADH oxidation and ROS production and studies of binding with DNA and with a model protein.

The design of new flame retardants (FR) that avoid the use of halogen and phosphorus additives is challenging and urgent. Herein we report on the synthesis of bis-amino functionalized N-heterocyclic carbene cyclopentadienone iron complexes aimed at promoting the production of iron containing epoxy resins. Iron complexes are successfully employed to obtain high Tg thermosets with as low as 5% hardener content. Moreover the obtained resins display an impressive charring ability that paves the way to the application of such systems for material with improved flame behavior.

The diiron μ-aminocarbyne complexes [Fe2{μ-CN(Me)(R)}(μ- CO)(CO)(CNR′)(Cp)2][SO3CF3] (R = R′ = Xyl, 2a; R = Xyl, R′ = Me, 2b; R = Xyl, R′ = But, 2c; R = Xyl, R′ = p-C6H4CF3, 2d; R = Me, R′ = Xyl, 2e; Xyl = 2,6-Me2C6H3), containing an isocyanide ligand, have been obtained via CO replacement with the appropriate CNR′ ligand from [Fe2{μ-CN(Me)(R)}(μ- CO)(CO)2(Cp)2][SO3CF3] (R = Xyl, 1a; R = Me, 1b). Compound 2a, upon treatment with NaBH4 and heating at reflux temperature in THF solution, is transformed into the aminocarbene−aldimine [Fe2{μ-η1(C):η1(N)-CN(Me)(Xyl)CHN(Xyl)}(μ-CO)2(Cp)2] (3) in moderate yield. The reactions occurs via formation of the formimidoyl complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO)(CO){C- (H)NXyl}(Cp)2] (4a), which has been isolated by reacting 2a with NaBH4 at 0 °C. Likewise, the formimidoyl complex [Fe2{μ-CN(Me)(R)}(μ-CO)(CO){C(H)NR′}(Cp)2] (R = Xyl, R′ = Me, 4b; R = Me, R′ = Xyl, 4c) have been obtained from 2b,e, respectively, upon reaction with NaBH4, but these complexes do not convert into the aminocarbene−aldimine complexes analogous to 3. Reactions of 2a with other nucleophiles have been investigated, without obtaining any product similar to 3. Complex 2a reacts with NaCN or with LiPPh2, resulting in isocyanide displacement and formation of [Fe2{μ-CN(Me)(Xyl)}(μ- CO)(CO)(CN)(Cp)2] (5) and [Fe2 {μ-CN(Me)(Xyl)}(μ-CO)(CO)(PPh2)(Cp)2] (6), respectively. Addition of the organocopper reagent Li2CuCNMe2 to 2a affords the acyl complex [Fe2{μ-CN(Me)(Xyl)}(μ-CO){C(O)Me}(CNXyl)(Cp)2] (7). The thiocarbyne complex [Fe2{μ-CSMe}(μ-CO)(CO)(CNXyl)(Cp)2][SO3CF3] (8), which shows analogies with 2a, reacts with NaBH4, affording the carbene derivative [Fe2 μ-{C(SMe)(H)}(μ-CO)(CO)(CNXyl)(Cp)2] (9). The molecular structures of 2a and 3 have been determined by X-ray diffraction studies.

A simple and expeditious microwave-assisted procedure for the synthesis of a variety of Shvo-type ruthenium complexes has been developed by reacting Ru3(CO)12 with variously functionalized tetraarylcyclopentadienones under microwave irradiation in MeOH. Ligand precursors have also been prepared under microwave heating by a bis-aldol condensation of 1,3-diphenylacetone with variously functionalized aromatic diketones. All the reactions were very fast and clean, leading to good yields and purities.

The diiron µ-aminocarbyne imidoyl complexes [Fe2µ-CN(Me)(R)(µ-CO)(CO)C(C≡CR′)=NXylCp2] [R = Xyl, R′ = Ph (1a);[1] R = Xyl, R′ = Tol (1b);[1] R = Me, R′ = Ph (1c); R = Me, R′ = SiMe3(1d); Xyl = 2,6-C6H3Me2, Tol = 4-C6H4Me] have been prepared by the addition of lithium acetylides to precursors containing a terminal isocyanide ligand. The treatment of 1a–c with CF3SO3CH3afforded the alkynyl(amino)carbene derivatives [Fe2µ-CN(Me)(R)(µ-CO)(CO)C(C≡CR′)N(Me)(Xyl)Cp2][SO3CF3] [R = Me, R′ = Ph (2a); R = Xyl, R′ = Ph (2b); R = Xyl, R′ = Tol (2c)] in high yields. The reactions of 2b,c with CH3OH/NaBF4, NH2R and NaBH4led to [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=C(Ph)OMe)N(Me)(Xyl)Cp2][BF4] (3), [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=C(Tol)NHR)N(Me)(Xyl)Cp2][SO3CF3] [R = Et (4a); R = Ph (4b)], and [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)C(CH=CHTol)N(Me)(Xyl)Cp2][SO3CF3] (5) in yields of 65–80 %. Complexes 3–5 were formed by the selective functionalization of the alkynyl group in 2b,c. Complex 2c reacted with NaCH(CN)2/CH2(CN)2and NaCH(CO2Me)2to yield [Fe2µ-CN(Me)(Xyl)(µ-CO)(CO)CN(Me)(Xyl)CH=C(Tol)C(CN)C(NH2)C(CN)2Cp2] (6) and [Fe2µ-C(NXyl)C(C(Tol)=C(CO2Me)2)CN(Me)(Xyl)(µ-CO)2Cp2] (7) in yields of 65 and 60 %, respectively. All the products were purified by alumina chromatography, alumina being presumably involved in the formation of 3, and characterized by elemental analysis and IR and NMR spectroscopy. The structures of 2b, 3, 5, and 6 were ascertained by single-crystal X-ray diffraction analysis.

Homologation of bioethanol to butanol and higher alcohols by means of Guerbet reaction was performed with a novel ruthenium based bifunctional catalyst under homogeneous conditions in the presence of a basic cocatalyst. Reaction screening demonstrated that the new catalyst shows conversions and selectivity comparable with some of ruthenium based bifunctional catalysts recently reported in the literature. The reaction occurs in pure ethanol as well as in ethanol from wine waste furnished by CAVIRO distillery with up to 46% conversion of ethanol and an overall selectivity to higher alcohols of 91% and a minor carbon loss. Based on the laboratory results, an industrialization study was carried out in order to propose a viable technological solution. The experimental data consistency was verified, and the results were up-scaled to design a reactor working in a batch or, potentially, semibatch operation mode. Further analysis of the overall process, together with the introduction of dedicated figures of merit have allowed the estimation of the process performance both in mass and energetic terms, and the outcome was integrated into a life cycle analysis. Although preliminary, the multidisciplinary approach has converged toward complementary results; more specifically, the adoption of the base cocatalyst NaOEt has showed similar performance in terms of specific alcohols production and energy demand compared to the NaOH case. Moreover, this last case proves to be better from an environmental perspective (LCA).

A new synthetic route for obtaining α-6-hydroxy-6-methyl-4-enyl-2H-pyran-3-one, a useful synthon for the preparation of biologically active compounds, has been developed from the bio-based platform derivative (2,5-bis-hydroxymethylfuran) BHMF. The reaction occurs with good selectivity in water, under mild conditions and employing an heterogeneous recyclable acid (Amberlyst 15®) as catalyst, avoiding the use of oxidizing agents. The reaction provides access to poly-oxygenated compounds characterized by a molecular motif commonly found in many natural products.

The iron complex [Fp][OTf] {Fp(+) = [Fe(CO)(2)(Cp)](+), OTf- = SO3CF3-} is an efficient catalyst for the direct substitution of the OH group in ferrocenylmethanol [Fc-CH2OH] by thiols, aromatic amines, diphenylphosphane, and carbon nucleophiles (furan, pyrrole, and indole). This approach offers a convenient route to ferrocenes containing side chains with different functional groups. The advantages of the method are associated with the use of a catalyst based on iron, which is a nontoxic and readily available transition metal, and in the direct OH substitution, which produces water as the only byproduct.

Diiron complexes with bridging hydrocarbyl ligands and containing CO and Cp ligands (Cp = η5-C5H5) have been investigated as possible electrocatalysts for H2 production. In particular, studies included the vinyliminium complexes [Fe2{μ-η1:η3-C(R′)=CRCNMe2}(μ-CO)(CO)- (Cp)2][SO3CF3] (R′ = Tol (4-MeC6H4), R = H, 1a; R′ = CH2OH, R = H, 1b; R′ = CH2OH, R = SPh, 1c), the vinylalkylidene [Fe2{μ-η1:η3- C(Tol)CHCHNMe2}(μ-CO)(CO)(Cp)2] (2), the aminoalkylidyne [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(L)(Cp)2][SO3CF3] (R = Me, L = CO, 3a; R = Me, L = NCMe, 3b; R = Xyl (2,6-Me2C6H3), L = CO, 3c), [Fe2{μ- CN(Me)2}(μ-L′)(CO)(L)(Cp)2] (L′ = CO, L = CN, 4; L′ = H, L = CO, 5), the thiocarbyne complexes [Fe2(μ-CSEt)(μ-CO)(CO)2(Cp)2][BF4], (6) and [Fe2(μ-CSMe)(μ-CO)(CO)(CN)(Cp)2] (7), and the alkylidene complexes [Fe2{μ-C(CN)(SMe)}(μ-CO)(CO)2(Cp)2][SO3CF3] (8) and [Fe2{μ-C(CN)(PMe2Ph)}(μ-CO)(CO)2(Cp)2][SO3CF3] (9). Cyclic voltammograms (CV) of the above complexes in CH3CN have been recorded in the presence of increasing amounts of acetic acid to evidence electrocatalytic proton reduction. In spite of the fact that the above diiron complexes do not resemble the typical diiron dithiolate model systems, the aminocarbyne 4 and the thiocarbyne complex 7 exhibit significant electrocatalytic properties for proton reduction (e.g., for 4, the turnover number (TON) is 15.5).

Readily synthesized aryl α-diimine derivatives have been used as efficient ligands for the palladium-catalyzed oxidative bis-alkoxycarbonylation reaction of 1,2-disubstituted olefins. The most active catalyst A was formed insitu from bis-(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabutadiene and Pd(TFA)2(TFA=trifluoroacetate). This catalytic system was able to selectively convert 1,2-disubstituted olefins into 2,3-disubstituted-succinic diesters with total diastereospecificity, in good yields (up to 97%) with 2mol% of catalyst loading, under mild reaction conditions (4bar of CO at 20°C in presence of p- toluenesulfonic acid as additive and p-benzoquinone as oxidant). The optimized reaction conditions could be successfully applied to 1,2-disubstituted aromatic, aliphatic, cyclic olefins and to unsaturated fatty acid methyl esters, employing methanol or benzyl alcohol as nucleophiles. The use of the bulky, less reactive isopropyl alcohol has allowed to better understand the mechanisms involved in the catalytic process. The geometry of the carbonylated products can be explained as a consequence of a concerted syn addition of the Pd-alkoxycarbonyl moiety to the olefin C=C bond. Catalyst A was isolated, characterized and analyzed by single crystal X-ray diffraction analysis.

The vinyliminium complexes [Fe2μ-η1:η3-C(CO2Me)C(H)CN(Me)(R)(μ-CO)(CO)(Cp)2][SO3CF3] [R = Me, 1a; R = 4-C6H4OMe, 1b; R = CH2Ph, 1c] react with primary amines (NH2R′ R′= Me, Et, Bun, (CH2)2NH2, CH2Ph) and ammonia to give the corresponding bridging amidine-alkylidene complexes [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(R)(NR′)(μ-CO)(CO)(Cp)2] (4a-j) in 70-90% yields. Likewise, the vinyliminium complex [Fe2μ- η1:η3-C(CO2Me)C(CO2Me)CN(Me)2(μ-CO)(CO)(Cp)2][SO3CF3] (1d) reacts with NH2R′ (R′= Me, Et) to form the corresponding amidine-alkylidene [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH(CO2Me)C(NMe2)(NR′)(μ-CO)(CO)(Cp)2] [R′= Me, 8a; R′ = Et, 8b], generating selectively one of the two diastereoisomers associated with the presence of the methylidene unit CH(COO2Me)- within the bridging ligand. Amination of the vinyliminium complexes 1a-c takes place also with hydrazine, resulting in the formation of [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(R)(NNH2)(μ-CO)(CO)(Cp)2] [R = Me, 5a; R = 4-C6H4OMe, 5b; R = CH2Ph, 5c]. Complexes 1b and 1d react with NHMe2, affording the en-(1,1)diamino-alkylidene complexes [Fe2μ- η1:η3-C(CO2Me)C(R′)C(NMe2)N(Me)(R)(μ-CO)(CO)(Cp)2] [R = 4-C6H4OMe, R′ = H, 9b; R = Me, R′ = CO2Me, 9d]. The reaction of 1c with piperidine results in formation of the amidine-alkylidene [Fe2μ-κ1(N): η1(C): η1(C)-C(CO2Me)CH2CN(Me)(CH2Ph)(CH2CH2CH2CH=CH2)(μ-CO)(CO)(Cp)2] (10), which implies piperidine ring-opening. All the products have been purified by alumina chromatography and characterized by analytical and spectroscopic methods; in addition, the molecular structures of 4f, 5b, and 8a have been ascertained by X-ray diffraction studies.

Insertion of propyne or 2-butyne into the Fe-carbyne bond belonging to the fragment [Fe2Cp2(CO)(μ-CO)μ-CNMe(R)]+ (R = Me or Xyl = 2,6-C6H3Me2) was investigated via density functional theory (DFT), and plausible intermediates were identified along the formation of the vinyliminium complexes [Fe2Cp2(CO)(μ-CO)μ-η1:η3-C(Me)C(R″)CN(Me)(R)]SO3CF3, [2a-d]+, thus allowing us to explain regio- and stereochemical features. The X-ray structure of [2a]SO3CF3 (R = Me, R″ = H) was determined by single crystal X-ray diffraction. Novel C-C and C-S bond forming pathways involving the vinyliminium ligand were then explored. Thus, [2b]SO3CF3 (R = Xyl, R″ = H) reacted with cyclopentadiene (or cyclopentene), triphenylphosphonium methylide, and benzyl bromide, in tetrahydrofuran in the presence of sodium hydride, respectively, to give [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)CC(CH)4CN(Me)(Xyl)], 3, [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)C(CH2)CN(Me)(Xyl)], 4, and [Fe2Cp2(CO)(μ-CO)μ-η1:η3-C(Me)C(CH2Ph)CN(Me)(Xyl)]Br, [5]Br, in good yields. Unstable complex 4 (detected by IR spectroscopy) readily converted into [2c]SO3CF3 (R = Xyl, R″ = Me) upon HSO3CF3 protonation of the methylide function. [5]Br was obtained as E/Z isomeric mixture, which was then quantitatively converted into the most stable Z form, by heating in methanol solution at 50 °C. The reactions of [2c,d]SO3CF3 (R = Me, Xyl, R″ = Me) with PhSSPh/NaH selectively yielded the aminoalkylidyne species [Fe2Cp2(SPh)(CO)(μ-CO)μ-CN(Me)(Xyl)], 6, and the bis-alkylidene [Fe2Cp2(CO)(μ-CO)μ-η1:η2-C(Me)C(Me)(SPh)CN(Me)2], 7, respectively, probably via the intermediacy of radical compounds 2c,d. The structures of 3-7 and 2c,d were elucidated by DFT calculations, and the isolated products were characterized by analytical and spectroscopic methods.

A straightforward and efficient synthetic route to novel Ru N-heterocyclic carbene (NHC) complexes by transmetallation of non-bulky silver NHC to ruthenium dicarbonyl tetraarylcyclopentadienone is described. The same procedure with sterically demanding NHC leads to unprecedented heterobimetallic Ru–Ag(NHC) complexes.

The bio-based substrate and target product 2,5-bishydroxymethylfuran (BHMF) demonstrated to influence the reaction kinetics in the homogeneous reduction of 5-hydroxymethylfurfural (HMF) catalyzed by the Ru-based Shvo's catalyst. A combined experimental and computational study supports an important role of the –CH2OH moiety which may be involved in the catalytic cycle toward the formation of different intermediates from HMF and BHMF. The reaction is selective and leads to quantitative formation of BHMF working under mild conditions. Furthermore, an optimized recycling procedure which avoids the use of water, allows recover and reuse of the catalyst without loss of activity. The mechanistic insights from this work may be extended to provide a general description of the chemistry of the Shvo's catalyst feeding further bio-based molecules.

The growing effort to design new sustainable synthetic methodologies, based on readily available and environmentally friendly transition metals, has boosted research on iron complexes. This review article focuses on C-C-C-bond-forming reactions occurring at bridging ligands in diiron complexes, aimed at evidencing distinctive aspects and advantages associated with the presence of two adjacent iron centres. A number of diironmediated C-C-bond-forming reactions reported in the literature, including nucleophilic and electrophilic additions and insertion and cycloaddition reactions, have been accumulated over the years, which, together with more recent developments, indicate that diiron complexes might provide promising alternatives to precious metals in the challenging field of metal-promoted C-C bond formation.

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 complex [Fe2{μ-к1(O):η1(C):η3(C)–C(N(Me)(Xyl))C(H) C(Me)C(O)OMe}(μ-CO)(Cp)2] (2) has been obtained from the diiron bridging vinyliminium [Fe2{μ-η1:η3–C(Me) C(H)C N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][SO3CF3] (1; Xyl = 2,5-C6H3Me2) upon treatment with NaH in the presence of CH2 C CMe2, followed by chromatography on alumina with MeOH as eluent. The reaction consists in the incorporation of a methylcarboxylate unit, assembled from CO and MeO−, into the bridging vinyliminium ligand. The resulting complex 2 exhibits a C4 fragment bridging the two iron centres through the carbonyl oxygen atom and the allylidene moiety. The X-ray molecular structure of 2 has been determined.

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.

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.

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.

Internal alkynes (RC≡CR) react with [Fe2(CS)(CO)3(Cp)2] (1), under UV radiation, to give the complexes [Fe2μ-η1:η3-C(R)=C(R)C=S(μ-CO)(CO)(Cp)2] [R = Et, 2a; R = Ph, 2b; R = CO2Me, 2c], as a result of CO displacement and alkyne insertion into the metal-CS bond of 1. In addition, the reaction of 1 with EtC≡CEt affords the metallacycle species [Fe2μ- η2:η2-C(S)C(Et)=C(Et)C(O)(CO)2(Cp)2] (3) as secondary product. The molecular structures of 2a and 3 have been elucidated by X-ray diffraction studies. Compound 1 reacts with HC≡CCO2Me, affording the complex [Fe2μ- η1:η3-C(H)=C(CO2Me)C=S(μ-CO)(CO)(Cp)2] (2d) in modest yield. Complexes 2a,b undergo selective methylation at the sulfur atom, generating the cationic complexes [Fe2μ- η1:η3-C(R)=C(R)=C(SMe)(CO)(μ-CO)(Cp)2][CF3SO3] [R = Et, 4a; R = Ph, 4b]. The X-ray structure of 4a has also been determined. Finally, 4b undergoes nucleophilic addition of hydride and cyanide (from NaBH4 and NBun4CN, respectively) to form the vinylalkylidene complexes [Fe2μ- η1:η3-C(Ph)C(Ph)=C(X)(SMe)(CO)(μ-CO)(Cp)2] [X = H, 5; X = CN, 6].

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‘ ...

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.

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 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 bis-isocyanide aminocarbyne diiron complexes [Fe2{μ-CN- (Me)(R)}(μ-CO)(CNR′)2(Cp)2][SO3CF3] (R = R′ = Xyl, 1a; R = Me, R′ = Xyl, 1b; R = Xyl, R′ = tBu, 1c; Xyl = 2,6-C6H3Me2) and the analogous thiocarbyne complex [Fe2{μ-CS(Me)}(μ-CO)(CNXyl)2(Cp)2][SO3CF3], 2, were prepared in high yields from [Fe2{μ-C(E)}(μ-CO)(CO)2(Cp)2][SO3CF3] [E = N(Me)(R) or SMe, respectively], by reaction with Me3NO in the presence of the appropriate isocyanide. The addition of LiCCR′′ to 1a−b promoted intramolecular C−N coupling between the two isocyanide moieties, resulting in the formation of [Fe2(μ- CO){μ-CN(Me)(R)}{μ-C(NXyl)N(Xyl)C(CCR′′)}(Cp)2] (R = Xyl, R″ = Ph, 3a; R = Xyl, R″ = Tol, 3b; R = Me, R″ = Ph, 3c; Tol = 4-C6H5Me), in ca. 60% yields. The reaction of 1a with LiCCSiMe3 proceeded with coupling between two dinuclear units, to give the tetranuclear complex C2[Fe2(μ-CO)(Cp)2{μ- CN(Me)(Xyl)}{μ-C(NXyl)N(Xyl)C}]2, 4, in 65% yield. The reaction of 2 with LiCCTol resulted in the formation of a mixture of nonidentified products. The new complexes were purified by alumina chromatography and fully characterized by analytical techniques, IR and NMR spectroscopy. The molecular structures of 3b and 4 were ascertained by X-ray diffraction studies.

Novel iron complexes bearing both cyclopentadienone and N-heterocyclic carbene ancillary ligands were obtained by a straightforward synthesis from Fe2(CO)9. The preparation represents a rare example of silver transmetallation involving iron. The reaction is general and occurs in the presence of variously functionalized NHC and cyclopentadienones.

A series of novel cationic hydroxycyclopentadienyl and methoxycyclopentadienyl N-heterocyclic carbene ruthenium(II) complexes have been synthesized from the corresponding neutral ruthenium(0) complexes containing both the non-innocent cyclopentadienone ligand and variously functionalized N-heterocyclic carbenes (NHCs). In particular an NHC derivative containing a pyridine group in the side chain has been designed and developed in order to evaluate the influence of a basic, potentially cooperative substituent in the catalytic activity of these complexes. All the prepared complexes were employed as selective catalysts for transfer hydrogenation reactions employing refluxing iPrOH as a hydrogen source and several ketones and aldehydes as substrates. We found that while the presence of oxidizing additives such as CAN and benzoquinone is mandatory to activate the neutral ruthenium(0) complexes, no activation is needed for the cationic Ru(II) catalysts. The catalytic activity of the latter is also influenced by the coordinating ability of the counterion, and indeed the cationic complexes having a pyridine-functionalized NHC ligand and CF3SO3− as counterion, present the best conversion (>99%) thus demonstrating the fundamental role played by the basic pyridine in the catalytic activity. With regard to the hydrogenation reaction mechanism, the release of the CO ligand was demonstrated to be the key step and the presence of hydride species has been detected at the end of the reaction.

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 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 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 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.