Structure and Reactivity of (η-C5R5)Mo(NO)2−Halide, −Halomethyl, and −Alkyl Complexes: Consecutive Aerobic Methylene and Nitrosyl Ligand Oxidation

Abstract

Cp‘Mo(NO)2(CH2X) complexes are isolated in 80−90% yield after the treatment of the Cp‘Mo(NO)2X complexes in CH2Cl2 with ethereal diazomethane in the presence of Cu powder (Cp‘ = η-C5H5 (Cp), η-C5(CH3)5 (Cp*); X = Cl, Br). The Cp‘Mo(NO)2(CH2I) derivatives are obtained in over 90% yield by treating the Cp‘Mo(NO)2(CH2Cl) derivatives with NaI in THF. Four new halomethyl complexes have been characterized by X-ray crystallography and are compared to the related CpMo(NO)2Br, Cp*Mo(NO)2Cl, and Cp*Mo(NO)2(CH3) derivatives. The structural data and IR data indicate the donor properties of the halomethyl ligands to be intermediate between halide and alkyl ligands. The Cp‘Mo(NO)2(CH2X) complexes react initially with O2 to give CH2O and the regeneration of the parent Cp‘Mo(NO)2X complexes. The Cp‘Mo(NO)2Cl complexes react with O2 after an induction period to give the well-known Cp‘MoO2Cl complexes, NO2, NOCl, and N2O. Exposure of CpCr(NO)2(CH(CH3)Br) to 18O2 gives 18OCH(CH3) and 16O-labeled CpCr(NO)2Br. The Cp‘Mo(NO)2−alkyl complexes react with O2 to give the corresponding Cp‘MoO2−alkyl derivatives in 40−70% yield (alkyl = CH3, CH2CH3). Electrochemical data show the Mo complexes to oxidize at 0.2−0.3 V lower than the Cr congeners.