η5-Pentamethylcyclopentadienylruthenium(II) complexes containing η6-co-ordinated dipeptides with aromatic side chains

Abstract

The η⁶-co-ordinated amino acid complexes [Ru(η⁵-C₅Me₅)(η⁶-HaaOH)][CF₃SO₃][HaaOH =L-HPheOH (phenylalanine) or L-HTrpOH (tryptophan)] were prepared by reaction of [Ru(η⁵-C₅Me₅)(MeCN)₃][CF₃SO₃] with the relevant amino acid in tetrahydrofuran. Dipeptide complexes of the type [{Ru(η⁵-C₅Me₅)}₂(µ-η⁶ : η⁶-pep)][CF₃SO₃]₂[pep = HPhe-PheOH, cyclo(-Phe-Phe-), HTrp-TrpOH, or cyclo (-Trp-Trp-)] may be obtained under analogous conditions. Ultraviolet irradiation of [{Ru(η⁵-C₅Me₅)}₂{cyclo(-Phe-Phe-)}][CF₃SO₃]₂ leads to photochemical release of cyclo(-Phe-Phe-) in quantitative yield. The feasibility of peptide synthesis from individual amino acid complexes was demonstrated by the preparation of [Ru(η⁵-C₅Me₅){η⁶-cyclo(-Phe-Phe-)}]Cl from [Ru(η⁵-C₅Me₅)(η⁶-L-HPhe-OMe)]Cl by the carbodiimide method. A crystal structure analysis was carried out for [{Ru(η⁵-C₅Me₅)}₂{cyclo(-Phe-Phe-)}][CF₃SO₃]₂.