Synthesis and characterization of ring-coupled cyclopentadienyl and indenyl bimetallic derivatives of Cr, Mo and W

Article abstract of DOI:10.1016/S0022-328X(96)06277-8

A series of new ring-coupled bimetallic complexes M₂(CO)₆[η⁵,η⁵-C₅H₄-C(CH₃)₂-C₅H₄], where M = Cr, Mo, W, was synthesized by reaction of the dianion of the ligand 2,2-bis(cyclopentadienyl)propane and M(CO)₃(CH₃CN)₃, M = Cr, Mo, W. Oxidation with acetic acid-Fe(III) produced the bimetallic complexes in moderate yields. Using the same strategy, reactions of Mo(CO)₃(CH₃CN)₃ with the dianion of 2-cyclopentadienyl-2-indenylpropane produced only the dimer [Mo(CO)₃[η⁵-C₅H₄-C(CH₃)₂-C₉H₇]₂ in which the indenyl ring was unmetallated. Subsequent detailed studies revealed that the desired dimetalloanion was initially formed, but that the indenyl bound metal was lost upon protonation. Evidence for the mechanism of this demetallation process is presented. The dimetalloanion could be intercepted by methyl iodide to form [Mo(CO)₃CH₃]₂[η⁵,η⁵-C₅H₄-C(CH₃)₂-(C₉H₆)]. Synthesis of Mo₂(CO)₆[η⁵,η⁵-C₅H₄-C(CH₃)₂-(3-RC₉H₅)], where R = H, CH₃, was achieved by aprotic oxidation of the intermediate dimetalloanion by ferricinium tetraphenylborate. The molecular structures of two compounds are reported: Mo₂(CO)₆[η⁵,η⁵-C₅H₄-C(CH₃)₂-(3-CH₃C₉H₅)]: triclinic, P1, a = 8.777(3) A, b = 9.428(4) A, c = 14.915(4) A, α = 91.42(3)°, β = 102.04(3)°, γ=114.69(3)°, V-1087.9(8) A³, Z = 2, R(F) = 3.03%.[Mo(CO)₃CH₃]₂[η⁵,η⁵-C₅H₄-C(CH₃)₂-(C₉H₆)]: triclinic, P1, a = 8.298(6) A, b= 11.662(6) A, c= 13.241(8) A, a = 100.28(1)°, β = 93.02(l)°, γ - 99.72(1)°, V-1238(1) A3, Z=2, R(F) = 3.99.%.