Carboncarbon bond formation at diiron centres VII. New routes to anionic alkenyl-bridged diiron complexes, and reactions of the latter with propargyl chloride

New routes to [Fe2(CO)6(μ-CO)(μ-CRCR′H)]- anions have been devised, and compared with those previously described. Reaction of [HFe2(CO)8]- with the alkynes RCCR′ (R = R′ = H (1), Ph (2) and Me3Si (3)) gives the dinuclear alkenyl-bridged complexes in 80% yield, but with PhCCH a mixture of [Fe2(CO)6(μ-CO)(μ-CPhCH2)]- (4a) and [Fe2(CO)6(μ-CO)(μ-CHCPhH)]- (4b) is formed. Reaction of Na[BH4] with PhCCPh and Fe2(CO)9 or Fe3(CO)12 gives 2 in 40-45% yield. Treatment of PhCCPh with a [Fe(CHO)(CO)4]-/Fe2(CO)9 mixture in THF gives an 80% yield of 2. Cinnamoyl chloride and [Fe2(CO)8]2- react to give 2 in 50% yield. Reaction of propargyl chloride with the [Fe2(CO)6(μ-CO)(μ-CRCRH)]- (R = H and Ph) complexes in CH2CI2 yields the complexes Fe2(CO)6(μ-CRCRH)(μ-CHCCH2) (R = H (5) and Ph (6)), the structures of which are suggested on the basis of IR and NMR data. © 1991.