Vanadocene complexes of amino acids containing secondary amino group: the first evidence of O,O-bonded carboxylic group to vanadocene(IV) moiety.

Reaction of vanadocene dichlorides (Cp(2)VCl(2) and (eta(5)-C(5)H(4)Me)(2)VCl(2)) with amino acids containing secondary amino groups gives three types of complexes: a) compounds with N,O-bonded amino acid, b) O-bonded amino acids and c) O,O-bonded amino acid. The complexes with N,O-bonded amino acid and O-bonded amino acids were observed in the case of l-proline and N-methylglycine (NMG). Reactions with N-phenylglycine (NPG) give O,O-chelates as the sole products. All three types of the complexes were characterized by spectroscopic methods. Structures of [(eta(5)-C(5)H(4)Me)(2)V(O-Pro)][BPh(4)], [Cp(2)V(O-Pro)(2)][PF(6)](2), [Cp(2)V(N,O-NMG)][BPh(4)].MeOH, [(eta(5)-C(5)H(4)Me)(2)V(N,O-NMG)][BPh(4)].MeOH, [Cp(2)V(O-NMG)(2)][Cl](2).2H(2)O, [(eta(5)-C(5)H(4)Me)(2)V(O-NMG)(2)][Cl](2).H(2)O and [(eta(5)-C(5)H(4)Me)(2)V(O,O-NPG)][BPh(4)] were determined by X-ray crystallography.