SYNTHESES AND REACTIONS OF SA-[2,2-BIS(ETA-CYCLOPENTADIENYL)PROPANE]-TUNGSTEN AND -[2,2-BIS(ETA-CYCLOPENTADIENYL)PROPANE]-MOLYBDENUM COMPOUNDS

Reaction between [MCl(4)(dme)] (M = W or Mo; dme = 1,2-dimethoxyethane ) with Li-2[C(5)H(4)CMe(2)C(5)H(4)] gave the ansa-bridged metallocene dichlorides [M{(eta-C5H4)CMe(2)(eta-C5H4)}Cl-2] (M = W or Mo). Treatme nt of these with LiAIH(4) or ZnMe(2) gave respectively the dihydrides [M{(eta-C5H4)CMe(2)(eta-C5H4)}H-2] (M = W or Mo) and the dimethyl deri vatives [M{(eta-C5H4)CMe(2)(eta-C5H4)}Me(2)] (M = W or Mo). Treatment of [W{(eta-C5H4)CMe(2)(eta-C5H4)}Me(2)] with HX (X = PhCO(2) or NH3I) gave [W{eta-C5H4)CMe(2)-(eta- C5H4)}Me(Y)] with Y = PhCO(2) or I, resp ectively. Both of these react with Na[AIH(2)(OCH(2)CH(2)OMe)(2)] givin g the methylhydride [W{(eta-C5H4)CMe(2)(eta-C5H4)}Me(H)]. The latter i s thermally stable in refluxing benzene. Ultraviolet photolysis of [Mo {(eta-C5H4)CMe(2)(eta-C5H4)}H-2] in benzene gave the phenylhydride der ivative [Mo{(eta-C5H4)CMe(2)(eta-C5H4)}Ph(H)]; the corresponding tungs ten derivative [W{(eta-C5H4) -CMe(2)(eta-C5H4)}H-2] is not photosensit ive. The crystal structures of [W{(eta-C5H4)CMe(2)(eta-C5H4)}Cl-2], [W {(eta-C5H4)CMe(2)(eta-C5H4)}H-2], (two modifications) and [Mo{(eta-C5H 4)CMe(2)(eta-C5H4)}H-2] have been determined by X-ray diffraction. The ansa-bridged bis(eta-cyclopentadienyl) compounds show marked differen ces in reactivity compared to non-ansa analogues and this is discussed in terms of the modifications of the electronic structure as a conseq uence of the ansa bridge.