OXIDATIVE ADDITION OF METHYL-IODIDE TO MONOSUBSTITUTED AND DISUBSTITUTED-DERIVATIVES OF OSMIUM PENTACARBONYL

Oxidative addition at room temperature of CH3I to Os(CO)4L or Os(CO)3L2 (L = PMe3) gives complexes [Os(CO)4LCH3]I (3) or [OS(CO)3L2CH3]1 (5), rcspectively. Complexes 3 and 5 react at higher temperature (50-70-degrees-C) to give complexes OS(CO)3LCH31 (7) and Os(CO)2L2CH31 (9), respectively. If this reaction is carried out in chloride-containing solvents, the formation of OS(CO)3L(CH3)Cl (8) and Os(CO)2L2(CH3)Cl (10) is also observed. Chloride abstraction from solvent during the reaction suggests a radical mechanism for the oxidative addition reaction. During the purification of complexes 9 and 10 by HPLC with acetonitrile (CH3CN) as eluent, complex [Os(CO)3L(CH3CN)CH3]I was obtained; it was transformed by reaction with NaBPh4 to the complex [Os(CO)3L(CH3CN)CH3]BPh4 (14). The structures of complexes 14 and 9 have been solved by single-crystal X-ray diffraction methods. Complex 14 crystallizes in the monoclinic space group P2(1)/a with lattice parameters a = 20.877 (3) angstrom, b = 19.935 (3) angstrom, c = 8.887 (3) angstrom, and beta = 98.92 (2)-degrees; it contains 4 molecules/cell. The structure has been solved by using 2729 observed reflections and refined to R(w) = 0.059. Complex 9 crystallizes in the monoclinic space group P2(1)/a with lattice parameters a = 13.979 (3) angstrom, b = 9.124 (2) angstrom, c = 13.950 (3) angstrom, and beta = 107.70 (2)-degrees; it contains 4 molecules/cell. The structure has been solved by using 1617 observed reflections and refined to R(w) = 0.043.