NITROSYL N-O BOND-CLEAVAGE INDUCED BY REDUCING AGENTS - SYNTHESIS AND CHARACTERIZATION OF NOVEL NITRIDO-BRIDGED BIMETALLIC COMPLEXES OF MOLYBDENUM AND TUNGSTEN

Reduction of Cp*W(NO)(R)Cl (Cp* = eta(5)-C(5)Me(5); R = CH(2)CMe(3), CH(2)SiMe(3), Ph) with an excess of zinc powder in THF results in the formation of [Cp*W(NO)(R)](mu-N)[Cp*W(O)(R)] [R = CH(2)CMe(3) (1), CH(2)SiMe(3) (2), Ph (8)3], which are isolable in good yields. Similar treatment of a 2:1 mixture of Cp*W(NO)(CH(2)CMe(3))Cl and Cp*W(NO)Cl-2 affords the related bimetallic complex, [Cp*W(NO)(CH(2)CMe(3))](mu-N)[Cp*W(O)Cl] (4), in 24% isolated yield. In an analogous manner, exposure of C6H6 solutions of Cp'Mo(NO)(CH(2)SiMe(3))(2) [Cp' = CP* or Cp(phi)(eta(5)-C-5-Ph(4)H)] to dihydrogen results in the formation of the dimolybdenum complexes, [Cp'Mo-(NO)(CH(2)SiMe(3))](mu-N)[Cp'Mo(O)(CH(2)SiMe(3))] [Cp' = Cp* (5) or Cp(phi) (6)], which are isolable in 40% and 53% yields, respectively. Complexes 4 and 5 have been subjected to single-crystal X-ray crystallographic analyses at 190 K; Crystals of 4 are triclinic, space group P1; Z = 2; a = 10.923(2) Angstrom; b = 11.328(4) Angstrom; c = 12.151(6) Angstrom; alpha = 109.16(4)degrees; beta = 90.88(3)degrees; gamma 101.92(2)degrees; V = 1384.0 Angstrom(3); R(F) = 0.026 for 4268 data [I-o greater than or equal to 2.5 sigma(I-o)] and 278 variables. Crystals of 5 are triclinic, space group P1; Z = 2, a = 10.284(4) Angstrom; b = 11.043(2) Angstrom; c = 16.979(3) Angstrom; alpha = 85.97(2)degrees; beta = 75.29(2)degrees; gamma = 65.70(2)degrees; V= 1698.5 Angstrom(3); R(F) = 0.037 for 4422 data [I-o greater than or equal to 2.5o(I-o)] and 331 variables. Both structures were solved by standard heavy-atom methods and were refined by full-matrix least-squares procedures. The most chemically interesting feature about the solid-state molecular structures of 4 and 5 is the orthogonal orientation of the metal-containing units about the essentially linear M-N-M (M = Mo, W) bridging linkages, an aspect consistent with the existence of multiple bonding in these linkages. It is proposed that all the bimetallic products result via transient formation of a coordinatively unsaturated Cp'M(eta(2)-NO)(X) (X = R or Cl) species that then combines with another molecule of the original nitrosyl reactant.