HYDRIDE TO CARBENE MIGRATION IN THE CPMH(=C(NHET)PH)(CO)2 (M = MO, W) SYSTEM - X-RAY CRYSTAL-STRUCTURE OF CPMO(ETA-2-CH(PH)NHET)(CO)2

Addition of acetic acid to solutions of the anions [CpM{=C(NHEt)Ph}(CO)2]- (M = Mo or W) affords the hydrido metal carbene complexes CpMH{=C(NHEt)Ph}(CO)2 as a mixture of cis and trans isomers. The molybdenum complex isomerizes rapidly to form fluxional CpMo{eta-2-CH(Ph)NHEt}(CO)2 which has been characterized by X-ray crystallography. The corresponding tungsten complex isomerizes more slowly. The simplest rationalization for these isomerizations involves a 1,2 hydride to carbene migration by the hydrides CpMH{=C(NHEt)Ph}(CO)2 in forming CpM{eta-2-CH(Ph)NHEt}(CO)2.