Optically active transition metal compounds 112. Synthesis of chiral carbonylnitrosylcobalt complexes with bidentate PP∗, PN∗ and NN∗ ligands

The substitution of two carbonyl groups in Co(CO)3(NO) by optically active unsymmetrical bidentate ligands LL∗ yields pairs of diastereomers Co(CO)(NO)(LL∗), which differ only in the configuration at the Co atom. LL∗ can be a bisphosphane, trisphosphane, phosphaneimine or pyridineimine. For the complexes 2 ( LL ∗ = ( S,S)-norphos ), 3 ( LL ∗ = ( R )-1,2,4- triphos ) and 4 ( LL ∗ = ( R )-1,2,5- triphos ) the diastereomer ratios of 45:55 (2a:2b), 83:17 (3a:3b) and 63:37 (4a:4b) respectively indicate an optical induction from the ligand to the metal configuration during the synthesis. By crystallization it is possible to separate the diastereomers of 1 ( LL ∗ = ( R )- prophos ), 2 and 3, 1a and 3a are obtained as pure diastereomers, 2a as an enriched sample (2a:2b 73:27). The crystal structures and absolute configurations of (SCo, RC)-1a and (SCo, RC)-3a were determined by X-ray analysis. In 3a the cobalt center is configurationally stable at room temperature, whereas 1a epimerizes in benzene-d6 at 35°C with a half-life of τ 1 2 = 141 min and 2a in CDCl3 at 24°C with τ 1 2 = 160 min .