SYNTHESIS AND CHARACTERIZATION OF RING-COUPLED CYCLOPENTADIENYL AND INDENYL BIMETALLIC DERIVATIVES OF CR, MO AND W

A series of new ring-coupled bimetallic complexes M(2)(CO)(6)[eta(5),e ta(5)-C5H4-C(CH3)(2)-C5H4], where M = Cr, Mo, W, was synthesized by re action of the dianion of the ligand 2,2-bis(cyclopentadienyl)propane a nd M(CO)(3)(CH3CN)(3), M = Cr, Mo, W. Oxidation with acetic acid-Fe(II I) produced the bimetallic complexes in moderate yields. Using the sam e strategy, reactions of Mo(CO)(3)(CH3CN)(3) with the dianion of 2-cyc lopentadienyl-2-indenylpropane produced only the dimer [Mo(CO)(3)[eta( 5)-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 p rotonation, Evidence for the mechanism of this demetallation process i s presented. The dimetalloanion could be intercepted by methyl iodide to form O)(3)CH3](2)[eta(5),eta(5)-C5H4-C(CH3)(2)-(C9H6)]. Synthesis o f O)(6)[eta(5),eta(5)-C5H4-C(CH3)(2)-(3-RC(9)H(5))], where R = H, CH3, was achieved by aprotic oxidation of the intermediate dimetalloanion by ferricinium tetraphenylborate. The molecular structures of two comp ounds are reported: (CO)(6)[eta(5),eta(5)-C5H4-C(CH3)(2)-(3-CH3C9H5)]: triclinic, <P(1)over bar>, a = 8.777(3) Angstrom, b = 9.428(4) Angstr om, c = 14.915(4) Angstrom, alpha = 91.42(3)degrees, beta = 102.04(3)d egrees, gamma = 114.69(3)degrees, V = 1087.9(8) Angstrom(3), Z = 2, R( F)= O)(3)CH3](2)[eta(5),eta(5)-C5H4-C(CH3)(2)-(C9H6)]: triclinic, <P(1 )over bar>, a = 8.298(6) Angstrom, b = 11.662(6) Angstrom, c = 13.241( 8) Angstrom, alpha = 100.28(1)degrees, beta = 93.02(1)degrees, gamma = 99.72(1)degrees, V = 1238(1) Angstrom(3), Z = 2, R(F) = 3.99.%.