Heterobinuclear Complexes of Manganese and Molybdenum Containing Amino Acidato and Related O,N and S,N Bridges

The addition of NaOMe to [MnMo(CO)₆(μ-S₂CPCy₃)(μ-Br)] (1) produces [MnMo(CO)₆(μ-S₂CPCy₃)(μ-OMe)] (2), containing a methoxide bridge between Mn and Mo. Compound 2 reacts with α-amino acids to yield, upon elimination of MeOH, the complexes [MnMo(CO)₅(μ-S₂CPCy₃){μ-OC(O)CR¹R²NR³₂}] (3a−f), in which the oxygen atom of the carboxylato group acts as a bridge between Mn and Mo, while the amino function coordinates the molybdenum atom, displacing one carbonyl ligand. In a similar reaction, the addition of ethanolamine to 2 affords the μ₂(O)-η²(O,N)-aminoethanolato complex [MnMo(CO)₅(μ-S₂CPCy₃)(μ-OCH₂CH₂NH₂)] (4). Reaction of 2 with cysteine methyl ester hydrochloride and NaOMe affords [MnMo(CO)₅(μ-S₂CPCy₃){μ-SCH₂C(COOMe)NH₂}] (5), with the sulfur atom in the bridging position. The new complexes have been characterized by analytical and spectroscopic methods, and their structures have been determined by X-ray crystallography for 2, 3e (2,2-dimethylaminobutyrato), and 4.