Organometallic Complexes of Iridium, Palladium, Chromium and Iron from 2-Phenyl-5(4H)-oxazolones − Organometallic Labelled Dipeptides

Abstract

Reactions of 2-phenyl-4-R-5(4H)-oxazolones (R = Me, CH2Ph, CHMeEt) with [(η5-C5Me5)IrCl2]2 afforded the cyclometallated complexes (η5-C5Me5)(Cl)Ir(L) (1−3) [L = 2-phenyl-4-R-5(4H)-oxazolone(C-o,N)]. 2-Phenyl-5(4H)-oxazolone reacts with [(η5-C5Me5)IrCl2]2 and palladium(II) acetate to give complexes with a C-o,N-bridging oxazolone [(η5-C5Me5)(Cl)Ir]2(μ-Cl)(μ-L-H+) (4) and Pd3(μ-ac)5(μ-L-H+) (5). 2-Phenyloxazolone anions were added to the π ligands of [(η5-C6H7)Fe(CO)3]+ and [(η7-C7H7)Cr(CO)3]+ to give the adducts 6−11. Dipeptide derivatives 12−18 were obtained by reaction of 1, 2 and by reaction of the adduct 6 from [(η5-C6H7)Fe(CO)3]+; and the anion of 2-phenyloxazolone with α-amino acid esters. These reactions may be used for the labelling of peptides. Saponification of 15−18 yields the organometallic substituted peptide acids 19−22. Their dianions (deprotonation of COOH and peptide amide) were used as ligands towards (Ph3P)2PtCl2 to yield the bimetallic complexes 23−25. The structures of 4, 5, 9 and 10 were determined by X-ray diffraction.