C-C bond formation by cyanide addition to dinuclear vinyliminium complexes

The diiron vinyliminium complexes [Fe₂{μ-η¹:η³-C(R′)C(H)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Me, R′ = SiMe₃ (1a); R = Me, R′ = CH₂OH (1b); R = CH₂Ph, R′ = Tol (1c), Tol = 4-MeC₆H₄; R = CH₂Ph, R′ = COOMe (1d); R = CH₂Ph, R′ = SiMe₃ (1e)) undergo regio- and stereo-selective addition by cyanide ion (from ), affording the corresponding bridging cyano-functionalized allylidene compounds [Fe₂{μ-η¹:η³-C(R′)C(H)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp)₂] (3a-e), in good yields. Similarly, the diiron vinyliminium complexes [Fe₂{μ-η¹:η³-C(R′)C(R′)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = R′ = Me (2a); R = Me, R′ = Ph (2b); R = CH₂Ph, R′ = Me (2c); R = CH₂Ph, R′ = COOMe (2d)) react with cyanide and yield [Fe₂{μ-η¹:η³-C(R′)C(R′)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp)₂] (9a-d). The reactions of the vinyliminium complex [Fe₂{μ-η¹:η³-C(Tol)CHCN(Me)(4-C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (4) with NaBH₄ and afford the allylidene [Fe₂{μ-C(Tol)C(H)C(H)N(Me)(C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂] (5) and the cyanoallylidene [Fe₂{μ-C(Tol)C(H)C(CN)N(Me)(C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂] (6), respectively. Analogously, the diruthenium vinyliminium complex [Ru₂{μ-η¹:η³-C(SiMe₃)CHCN(Me)(CH₂Ph)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (7) reacts with to give [Ru₂{μ-η¹:η³-C(SiMe₃)CHC(CN)N(Me)(CH₂Ph)}(μ-CO)(CO)(Cp)₂] (8).Finally, cyanide addition to [Fe₂{μ-η¹:η³-C(COOMe)C(COOMe)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (2e) (Xyl = 2,6-Me₂C₆H₃), yields the cyano-functionalized bis-alkylidene complex [Fe₂{μ-η¹:η²-C(COOMe)C(COOMe)(CN)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (10). The molecular structures of 3a and 9a have been elucidated by X-ray diffraction.     

C-C bond formation through olefin-thiocarbyne coupling in diiron complexes

The bridging diiron thiocarbyne complex [Fe₂{μ-CS(Me)}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃] (1) reacts with activated olefins (methyl acrylate, acrylonitrile, styrene, diethyl maleate), in the presence of Me₃NO and NaH, to give the corresponding μ-allylidene complexes [Fe₂{μ-η¹:η³-C_α(SMe)C_β(R′)C_γ(H)(R″)} (μ-CO)(CO)(Cp)₂] (R″ = CO₂Me, R′ = H, 3a; R″ = CN, R′ = H, 3b; R″ = C₆H₅, R′ = H, 3c; R″ = R′ = CO₂Et, 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 MeSO₃CF₃ result, selectively, in the formation of the cationic μ-sulphonium allylidene complexes [Fe₂{μ-η¹:η³-C_α(SMe₂)C_β (H)C_γ(H)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = CO₂Me, 4a; R = CN, 4b). Compound 4a undergoes displacement of the SMe₂ group by nucleophiles such as NaBH₄, NBu₄CN and NaOMe, affording the complexes [Fe₂{μ-η¹:η³-C_α(R)C_β (H)C_γ(H)(CO₂Me)}(μ-CO)(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.     

Olefin-aminocarbyne coupling in diiron complexes: Synthesis of new bridging aminoallylidene complexes

The bridging aminocarbyne complexes [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃] (R = Me, 1a; Xyl, 1b; 4-C₆H₄OMe, 1c; Xyl = 2,6-Me₂C₆ H₃) react with acrylonitrile or methyl acrylate, in the presence of Me₃NO and NaH, to give the corresponding μ-allylidene complexes [Fe₂{μ-η¹:η³- C_α(N(Me)(R))C_β(H)C_γ(H)(R′)}(μ-CO)(CO)(Cp)₂] (R = Me, R′ = CN, 3a; R = Xyl, R′ = CN, 3b; R = 4-C₆H₄OMe, R′ = CN, 3c; R = Me, R′ = CO₂Me, 3d; R = 4-C₆H₄OMe, R′ = CO₂Me, 3e). Likewise, 1a reacts with styrene or diethyl maleate, under the same reaction conditions, affording the complexes [Fe₂{μ-η¹:η³-C_α(NMe₂)C_β(R′)C_γ(H)(R″)}(μ-CO)(CO)(Cp)₂] (R′ = H, R″ = C₆H₅, 3f; R′ = R″ = CO₂Et, 3g). The corresponding reactions of [Ru₂{μ-CN(Me)(CH₂Ph)}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃] (1d) with acrylonitrile or methyl acrylate afford the complexes [Ru₂{μ-η¹:η³-C_α(N(Me)(CH₂Ph))C_β(H)C_γ(H)(R′)}(μ-CO)(CO)(Cp)₂] (R′ = CN, 3h; CO₂Me, 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-CHCH₂)(Cp)₂][SO₃CF₃] (M = Fe, R = Me, 4a; M = Fe, R = Xyl, 4b; M = Fe, R = 4-C₆H₄OMe, 4c; M = Ru, R = CH₂C₆H₅, 4d).Compounds 3a, 3d and 3f undergo methylation (by CH₃SO₃CF₃) and protonation (by HSO₃CF₃) at the nitrogen atom, leading to the formation of the cationic complexes [Fe₂{μ-η¹:η³-C_α(N(Me)₃)C_β(H)C_γ(H)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = CN, 5a; R = CO₂Me, 5b; R = C₆H₅, 5c) and [Fe₂{μ-η¹:η³-C_α(N(H)(Me)₂)C_β(H)C_γ(H)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = CN, 6a; R = CO₂Me, 6b; R = C₆H₅, 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-η¹:η³-C_α(NMe₂)C_β(H)C_γ(H)(CNFe(CO)₂Cp)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (9).In an analogous reaction, 3a and [Fe₂{μ-CN(Me)(R)}(μ-CO)(CO)₂(Cp)₂][SO₃CF₃], in the presence of Me₃NO, are assembled to give the tetrameric species [Fe₂{μ-η¹:η³-C_α(NMe₂)C_β(H)C_γ(H)(CN[Fe₂{μ- CN(Me)(R)}(μ-CO)(CO)(Cp)₂])}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = Me, 10a; R = Xyl, 10b; R = 4-C₆H₄OMe, 10c).The molecular structures of 3a and 3b have been determined by X-ray diffraction studies.