REACTION OF CATIONIC DIIRON MU-ETA-1-ETA-2-ACETYLIDE COMPLEXES [(FP)2(C=CR)]BF4 (R = H, PH) WITH CARBON NUCLEOPHILES AND HYDRIDE - FORMATION OF MU-VINYLIDENE COMPLEXES

The reaction of a cationic diiron mu-eta-1:eta-2-acetylide complex [(FP)2(C = CH)]BF4 (1) with RLi (R = n-Bu, t-Bu) affords an acyl-substituted vinylidene complex Cp*2Fe2(CO)2(mu-CO)[mu-C = CH(COR)] (3a, R = n-Bu; 3b, R = t-Bu). The structure of 3b has been determined by single-crystal X-ray diffraction study. [Crystal data for 3b: space group P2(1)/c, a = 17.460 (2) angstrom, b = 9.495 (2) angstrom, c = 17.446 (2) angstrom, beta = 100.480 (9)-degrees, V = 2843.8 (7) angstrom 3, Z = 4, R = 0.0822.] 3 may be formed by an initial nucleophilic attack of R- to a CO ligand in the cationic Fp* part, followed by insertion of the C = C part into the Fe-C(O)R bond and metal-metal bond formation. The reaction of 1 with LiHBEt3 affords a parent mu-vinylidene complex Cp*2Fe2(CO)2(mu-CO)(mu-C = CH2) (4). A plausible reaction pathway involves nucleophilic addition of H- to a CO ligand and successive intramolecular hydride transfer from the formyl ligand to the beta position of the C = CH ligand.