Amine, imine, and aminocarbene complexes of platinum(II)

Abstract

Solutions of the chloride-bridged binuclear platinum complexes [Pt₂(µ-Cl)₂Cl₂L₂](L = PMe₂Ph or PBu₃) readily react with the amines NH₂Ph, 4-NO₂C₆H₄NH₂, 3-MeOC₆H₄NH₂, NHPh₂, or NH₂Me to produce trans-[PtCl₂(am)L] in the presence or absence of phenylethyne. The imines PhCHNPh, PhCHNMe, 2-MeC₆H₄CHNPh, or Ph₂CNH also react with [Pt₂(µ-Cl)₂Cl₂L₂] to produce the analogous N-bonded imine complexes, but reactions of the amines NHEt₂ or NH₂Bu^t with the binuclear compounds lead to additional platinum-containing compounds resulting from ligand redistribution reactions. The complexes of NH₂Ph, 4-NO₂C₆H₄NH₂, 3-MeOC₆H₄NH₂, and NHPh₂ react with phenylethyne over several days at ambient temperature to yield aminocarbene complexes cis-[PtCl₂{C(NR¹R²)CH₂Ph}L](R¹R²= H, Ph; H, C₆H₄NO₂-4; H, C₆H₄OMe-3; or Ph₂). Treatment of the imine complexes or any of the other amine complexes with PhCCH, however, led only to decomposition. 2-Aminophenylethyne reacts rapidly with [Pt₂(µ-Cl)₂Cl₂L₂] to produce the cyclic carbene complex cis-[PtCl₂{[graphic omitted]H}L] in only 1 h, and although the amine-N complexes were observed in solution as transients they were not isolated. Treatment of the carbene complexes with tertiary phosphine, L, leads to cationic complexes trans-[PtCl{C(NR¹R²)CH₂Ph}L₂]Cl. Both the uncharged and cationic aminocarbene compounds are less reactive than their alkoxycarbene analogues, and show no reaction with Cl^– and little tendency towards H/D exchange with CD₃OD. Hydrogen-1, ¹³C, and ³¹P n.m.r. spectroscopic parameters for the complexes are reported and related to the likely solution conformations.