SYNTHESIS OF A TRIS(PYRAZOLYL)BORATE-STABILIZED MOLYBDENUM ALKYLIDENEAND ITS HYDROLYSIS PRODUCTS - CRYSTAL-STRUCTURES OF TPMO(CH2C(ME)(2)PH)(NAR)(O) AND [TPMO(NAR)(O)](2)O

The synthesis of a tris(pyrazolyl)borate-stabilized molybdenum (VI) im ido alkylidene complex, TpMo(CHC(Me)(2)Ph)(NAr) (OTf) (1) [Ar = 2,6-i- Pr-2-C6H3, Ph = C6H5, OTf = OSO2CF3], has been achieved by addition of potassium hydridotris(1-pyrazolyl)borate (KTp) to Mo(CHC(CH3)(2)Ph)(N Ar)(OTf)(2)(DME). Stirring compound 1 over alumina in the presence of H2O gave TpMo(CH2C(Me)(2)Ph)(NAr)(O) (2). Alternatively, compound 1 wa s converted to 2 by the addition of CsOH . H2O in THF. A single crysta l of [TpMo(NAr)(O)]O-2 (4) was isolated from a solution of 2. Compound s 2 and 4 have been characterized by X-ray crystallography and the bon ding considerations about the molybdenum atoms are discussed.