Chemistry and catalytic properties of ruthenium and osmium complexes. 2. Synthesis and characterization of new mononuclear and dinuclear complexes with hydride, carboxylate, and phosphine ligands. X-ray crystal and molecular structures of OsBr(OCOMe)(CO)(PPh3)2, RuCl(OCOMe)(CO)(PPh3)2, and [PPh3Me]+[Ru2Cl2(.mu.-Cl)3(CO)2(PPh3)2]-