文摘
The synthesis of the iron allenylidene complexes [(η5-C5Me5)(η2-dppe)Fe(=C=C=C(Ph)Ph)][X] (5a, X = PF6, 95 % ; 5b, X = BPh4, 91 % ; dppe = 1,2-bis(diphenylphosphino)ethane) was achieved by reacting the complex (η5-C5Me5)(η2-dppe)FeCl (10) with 1 equiv of 1,1-diphenyl-prop-2-yn-1-ol in methanol in the presence of KPF6 or NaBPh4. Surprisingly, when the reaction was carried out in the presence of the tetraphenylborate anion, the final product contained both 5b and the hydroxyvinylidene [(η5-C5Me5)(η2-dppe)Fe(=C=C(H)C(OH)(Ph)2)][BPh4] (14b) in the 1:1 ratio. Further treatment of the mixture with Amberlyst 15 in methanol provided the allenylidene 5b as a pure sample. The allenylidene complexes [(η5-C5Me5)(η2-dppe)Fe(=C=C=C(Me)Ph)][PF6] (6) and [(η5-C5Me5)(η2-dppe)Fe(=C=C=C(Me)Et)][PF6] (7) were prepared according to the same procedure and they were isolated as purple powders in 90 % yield. The X-ray crystal structures were determined for the vinylidene complexes [(η5-C5Me5)(η2-dppe)Fe(=C=CH2)][PF6] (3) and [(η5-C5Me5)(η2-dppe)Fe(=C=C(Ph)H)][PF6] (4), and the allenylidene derivative 5a. In the homogeneous series of complexes [(η5-C5Me5)(η2-dppe)Fe(=(C)n(R)R)][PF6], (n = 1, R = H, R′ = Me, X = PF6, 1; n =1, R = H, R = OMe, X = PF6, 2a; n = 1, R = H, R = OMe, X = CF3OSO2, 2b; n = 2, R = R′ = H, X = PF6, 3; n = 2, R = H, R′ = Ph, X = PF6, 4; n = 3, R = R′ = Ph, X = PF6, 5a; n = 3, R = R′ = Ph, X = BPh4, 5b; n = 3, R = Me, R′ = Ph, X = PF6, 6; n = 3, R = Me, R′ = Et, X = PF6, 7; n = 3, R = Me, R′ = OMe, X = BPh4, 8), an empiric relationship between the Mössbauer parameters, δ and QS, was found. This observation would indicate that the positive charge on the iron nucleus decreases with the Fe=C bond order. Moreover, in this series of iron cumulenylidene derivatives, comparison of the variation of the metal–carbon bond distances determined by X-ray analyses with the Mössbauer QS values allows the observation of a linear correlation (R = 0.99). To cite this article: G. Argouarch et al., C. R. Chimie 6 (2003).