STEREOSELECTIVE FORMATION OF ORGANOOSMIUM COMPLEXES WITH AMINOCARBOXYLATE LIGANDS

The chelate osmium complexes {C6H6Os[OC(O)CH(R)NH2](PiPr3)}X (3,4) and (C6H6Os[OC(O)CH(R)NH2](PMetBu2)}X (5-7) have been prepared almost quantitatively from [C6H6Os(PR3)I2] precursors and alpha-aminocarboxylates. Owing to the NMR spectroscopic data, for L-alaninate as substrate one diastereoisomer and for D/L-phenylalaninate one pair of enantiomers is preferentially formed. The X-ray structural analysis of 6 (R = CH3; X = I) confirms the presence of the R(M)S(C) diastereoisomer in the crystal lattice. The reaction of the five-coordinate chloro(hydrido)metal compounds [MHCl(CO)(PMetBu2)2] (M = Ru, Os) with glycinate and D/L-phenylalaninate gives the octahedral complexes {MH[OC(O)CH(R)NH2](CO)(PMetBu2)2] (10-12) in 75-85% yield.