Coupling of Allenes with μ‐Alkylidyne Ligands in Diiron Complexes: Synthesis of Novel Bridging Thio‐ and Aminobutadienylidene Complexes

The diiron aminocarbyne complexes [Fe 2 {μ‐CN(Me)(R)}(μ‐CO)(CO) 2 (Cp) 2 ][SO 3 CF 3 ] (R = Xyl, 1a ; R = 4‐C 6 H 4 OMe, 1b ; R = Me, 1c ; Xyl = 2,6‐Me 2 C 6 H 3 ) react with allenes of the type CH 2 =C=CR′R″, in the presence of Me 3 NO/Et 3 N, to give the novel butadienylidene complexes [Fe 2 {μ‐η 1 :η 3 ‐C α N(R)(Me)C β (H)C γ C δ (R′)(R″)}(μ‐CO)(CO)(Cp) 2 ] (R = Xyl, R′ = R″ = Me, 3a ; R = Xyl, R′ = Me, R″ = H, 3b ; R = Xyl, R′ = CO 2 Et, R″ = H, 3c ; R = 4‐C 6 H 4 OMe, R′ = CO 2 Et, R″ = H, 3d ; R = R′ = R″ = Me, 3e ; R = Me, R′ = CO 2 Et, R″ = H, 3f ) in high yields. Analogously, the diiron thiocarbyne complex [Fe 2 (μ‐CSMe)(μ‐CO)(CO) 2 (Cp) 2 ][SO 3 CF 3 ] ( 2 ) reacts with CH 2 =C=CR′R″, in the presence of Me 3 NO/Et 3 N, to afford the compounds[Fe 2 {μ‐η 1 :η 3 ‐C α S(Me)C β (H)C γ C δ (R′)(R″)}(μ‐CO)(CO)(Cp) 2 ](R′ = R″ = Me, 4a ; R′ = CO 2 Et, R″ = H, 4b ; R′ = SiMe 3 , R″ = Me, 4c ). Complexes 3 – 4 exist in solution as mixtures of cis and trans isomers. Compounds 3a and 3e , upon treatment with HSO 3 CF 3 , are transformed into the corresponding vinyliminium complexes [Fe 2 {μ‐η 1 :η 3 ‐C γ (C δ HMe 2 )C β HC α N(R)(Me)}(μ‐CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R = Xyl, 5a ; R = Me, 5b ), in nearly quantitative yields. Conversely, compounds 4a , b undergo methylation (by CH 3 SO 3 CF 3 ) at the sulfur to give the cationic complexes [Fe 2 {μ‐η 1 :η 3 ‐C α (SMe 2 )C β (H)C γ C δ (R′)(R″)}(μ‐CO)(CO)(Cp) 2 ][SO 3 CF 3 ] (R′ = R″ = Me, 7a ; R′ = CO 2 Et, R″ = H, 7b ). Protonation of 3a is not reversible: treating 5a with sodium hydride results in the formation of the 1‐metalla‐2‐amino‐cyclopenta‐1,3‐dien‐5‐one species [Fe(Cp)(CO){CN(Me)(Xyl)CHC(CHMe 2 )C(O)}] ( 6 ). The molecular structures of cis ‐ 3a , cis ‐ 4b , 5a [CF 3 SO 3 ]·CH 2 Cl 2 and 7a [CF 3 SO 3 ]·0.5CH 2 Cl 2 have been determined by X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)