Bis-acetonitrile(dibromo)dioxomolybdenum(VI) and derivatives: synthesis, reactivity, structures and catalytic applications

We report on the preparation and spectroscopic properties of complexes of t he general formula MoBr2O2Ln with L = NCCH3, (n = 2), NCC(CH3)(3) (n = 1), NCC6H5 (n = 2). The complex MoBr2O2(CH3CN)(2) is additionally examined by s ingle crystal X-ray structure determination. The MoBr2O2Ln complexes are ve ry electron deficient (O-17-, Mo-95-NMR evidence) and readily react with el ectron donor N-Iigands to give more stable complexes e.g. MoBr2O2(bipyrimid ine). The structure of the latter compound has been determined by single cr ystal X-ray crystallography. Reactions with organometallic complexes of the type [Cp'Mo(CN)(2)(CO)(2)]K (Cp' = Cp or Cp*) and Cp(CO)(2)Fe(CN) or [Cp(C O)Fe(CN)(2)]K result in the immediate reduction of the Mo(VI) center, as sh own by EPR spectroscopy. The MoBr2O2Ln complexes are catalysts for the epox idation of cyclooctene but decompose slowly during the course of the reacti on due to their pronounced moisture sensitivity. (C) 1999 Elsevier Science S.A. All rights reserved.