Metal Complexes of Biologically Important Ligands, LXX.- Synthesis, Stereochemistry and Reactions of Ruthenium(II) and Osmium(II) Complexes with -Amino Carboxylates. The reactions of MHCl(CO)(PPh3)3 with salts of -amino acids give the hydrido-N,O-chelate complexes MH(CO)(NH2CHR-COO)(PPh3)2 (1a-g;) M = Ru, Os). Complexes 1a-c can alternatively be prepared by oxidative addition of the appropriate -amino acid to Ru(CO)3(PPh3)2. The crystal structure of 1b has been determined by an X-ray structural analysis. The leucinato compound 1c is an effective catalyst for the decomposition of formic acid. In contrast, reactions of RuHCl-(CO)(PPh3)3 with -amino acids afford the chloro-N,O-che-late complexes RuCl(CO)(NH2CHRCOO)(PPh3)2 2a-h. The decomposition reactions of 2c, 2g and2h have been investigated.