Synthesis and reactivity of N-acetylamino acidate(2–) and related complexes of platinum(II)

Abstract

Treatment of the complexes [PtCl₂L₂](L = P-donor ligand) with the N-acetyl derivatives of the amino acids glycine, DL-alanine, DL-methionine or L-phenylalanine in the presence of an excess of silver(I) oxide in refluxing dichloromethane affords [[graphic omitted]L₂](R = H, Me, CH₂CH₂SMe or CH₂Ph) respectively, and with L-proline the complexes [[graphic omitted]L₂] are produced. Similar treatment with the N-formyl or N-trifluoroacetyl derivatives of glycine gave the complexes [[graphic omitted]L₂](R = CHO or COCF₃) respectively. An X-ray crystal structure study on the N-acetylglycinato(2–)-N,O complex [[graphic omitted](dppe)](dppe = Ph₂PCH₂CH₂PPh₂) indicated the presence of an almost planar five-membered ring with substantial electron delocalisation within the carboxylate and amide functionalities. Treatment of the complexes [PtCl₂L₂] with DL-mandelic (α-hydroxybenzeneacetic) acid, 2-acetamidophenol, pyrrole-2-carboxylic acid, mercaptoacetic acid or oxamic acid in the presence of an excess of Ag₂O in refluxing dichloromethane afforded the complexes [[graphic omitted]L₂], [[graphic omitted]L₂], [[graphic omitted]L₂], [[graphic omitted]L₂], [[graphic omitted]L₂] respectively. The cycloocta-1,5-diene (cod) ligand of [[graphic omitted](cod)] and [[graphic omitted](cod)] is readily displaced by tertiary phosphines. One mole equivalent of Bu^tNC stereospecifically displaces the PPh₃ ligand opposite oxygen in the complex [[graphic omitted](PPh₃)₂]. Treatment of [[graphic omitted](PPh₃)₂] in refluxing ethanol with an excess of either diphenylacetylene or PPh₃ leads to the formation of [Pt(PhCCPh)(PPh₃)₂] or [Pt(PPh₃)₄] respectively, in good yield. Treatment of the same metal complex in ethanol at room temperature with either SO₂ or CO led to the formation of the bis(ethanesulfonate) or bis(ethoxycarbonyl) complexes respectively. The complex [[graphic omitted](PPh₃)₂] induces the polymerisation of hexaflurobut-2-yne.