SYNTHESIS OF BIS((TRICARBONYLMETAL)-ETA-5-CYCLOPENTADIENYL)METHANE DERIVATIVES OF MOLYBDENUM AND TUNGSTEN - MOLECULAR-STRUCTURES OF BIS((TRICARBONYLTUNGSTENIO)-ETA-5-CYCLOPENTADIENYL)METHANE AND ITS 2-ACYL DERIVATIVE

Bis((tricarbonylmetal)-eta-5-cyclopentadienyl)methane derivatives of molybdenum and tungsten, 1 and 2, respectively, have been prepared by reaction of the disodium salt of bis(cyclopentadienyl)methane with tris(acetonitrile)metal tricarbonyl complexes of molybdenum and tungsten. Oxidation of the resulting dianions gives compounds 1 and 2 in good yields. Variable-temperature studies of 1 and 2, which have C2 symmetry in the solid, reveal a fluxional twisting motion for which the DELTA-G double-ended dagger of the tungsten complex is slightly larger than that of the molybdenum complex. An acyl derivative of 2 has been isolated from an incompletely neutralized batch of 2. The pathway leading to this new material, 3, is not yet clear. 2 has been characterized by X-ray crystallography: triclinic, P1BAR, a = 7.670 (4) angstrom, b = 7.757 (4) angstrom, c = 15.536 (9) angstrom, alpha = 86.22 (3)-degrees, beta = 81.87 (3)-degrees, gamma = 67.67 (3)-degrees, V = 846.2 angstrom 3, Z = 2, and R(F) = 4.96%. 3 was also characterized by crystallography: orthorhombic, p2(1)2(1)2(1), a = 8.254 (2) angstrom, b = 12.527 (3) angstrom, c = 18.103 (4) angstrom, V = 1871.7 angstrom 3, Z = 4, and R(F) = 3.58%.