DIMETALLIC IMIDO COMPLEXES OF MOLYBDENUM AND TUNGSTEN WITH BRIDGED BIS(ETA(5)-CYCLOPENTADIENYL) LIGANDS - MOLECULAR-STRUCTURE F[(MOO)(2)(MU-N(T)BU)(2)((ETA(5)-C5H4)(2)SIME(2))]

New imido and oxo dimetallic complexes of Mo and W with the monobridge d or dibridged bis(cyclopentadienyl) ligands Cp(1)Cp or Cp(2)Cp [Cp(1) Cp = (eta(5)-C5H4)(2)SiMe(2), Cp(2)Cp = (eta(5)-C5H3)(2)(SiMe(2))(2)] have been synthesized. The Cp(2)Cp complexes have been obtained as bot h cis and trans isomers which differ in the stereodisposition of the t wo metal fragments with respect to the Cp(2)Cp system, the stereochemi stry being unchanged in all the reactions described. Addition of H(2)N (t)Bu to [(MCl(4))(2)(mu-Cp(n)Cp)] (M = Mo, n = 1, ia; n = 2, 2b; M = W, n = 2, 2c) affords the imido M(V) complexes [{M(N(t)Bu)Cl-2}(2)(mu- Cp(n)Cp)] (4a-c). Complexes 4a,c are oxidized by PCI5 to give [{M(N(t) Bu)Cl-3}(2)(mu-Cp(n)Cp)] (5a,c). Both 4a and 5a afford [{MoCl(mu-N(t)B u)}(2)(mu-Cp(1)Cp)] (6) by reduction with sodium amalgam. The differen ces found between this reaction and the related reductions of the mono nuclear Cp analogues are discussed. Reaction of 6 with HgO affords the oxo complex [{MoO(mu-N(t)Bu)}(2)(mu-Cp(1)Cp)] (7). [(MoOCl)(2)(mu-O)( mu-Cp(2)Cp)] (3) is obtained by reaction of [{Mo(CO)(3)Cl}(2)(mu-Cp(2) Cp)] with CH3-NO2 or bubbling air through a THF solution of cis-[(MoCl 4)(2)(mu-Cp(2)Cp)]. The molecular structure of 7 has been determined b y a single-crystal X-ray analysis.