Formation of peptides at half-sandwich complexes using beta- and gamma-amino acid esters and a facile dipeptide synthesis from an N,O-glycinato half sandwich complex [RuCl(NH2CH2CO2)(eta(6)-C6Me6)]

The tripeptide ester complexes 2 and 3 are obtained from the diglycine este r complex [RuCl(N,N ' -glyglyOMe-H+)(eta (6)-C6Me6)] and the amino acid est ers H2N(CH2)(n)CO2Me (n = 2, 3). The reaction of the N,O-glycinato complex [RuCl(NH2CH2CO2)(eta (6)-C6Me6] with the beta-, gamma- and delta -amino aci d methyl esters H2N(CH2)(n)CO2Me (n = 2,3,4) in CH3OH and in the presence o f NaOMe affords the eta (3)-N,N 'O-dipeptide complexes [Ru{H2N(CH2)(n)CONCH 2CO2}(eta (6)-C6Me6)] 5-7 in good yields, These complexes are also obtained in a one pot reaction from [RuCl(mu -Cl)(eta (6)-C6Me6)](2), glycine and t he amino acid ester. The formation of small peptides at the metal represent s a facile procedure which does not require either a protecting/activating group or a coupling agent.