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Interaction of Organoplatinum(II) Complexes with Monovalent Coinage Metal Triflates

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posted on 22.04.2009, 00:00 authored by Marc-Etienne Moret, Peter Chen
The organoplatinum(II) complexes [(NN)PtMe2] and [(NN)PtPh2] (NN = ArNC(Me)C(Me)NAr, Ar = 2,6-dichlorophenyl) can act as donor ligands for copper(I) and silver(I) triflates, affording a series of homo- and heteroleptic complexes which were characterized by X-ray diffraction. [(NN)PtMe2] binds to the coinage metals through short, ligand-unsupported d−d10 contacts that are best described as Pt→M dative bonds (M = Cu, Ag), in which the dz2 orbital of the square-planar Pt(II) center donates electron density to the Lewis-acidic metal. Spectroscopic studies in solution and DFT calculations corroborate this description. [(NN)PtPh2] binds preferentially by η1 or η2 complexation of the ipso carbon atoms of the phenyl groups to the coinage metal, affording homoleptic complexes {[(NN)PtPh2]2M}+{TfO} in the solid state. The 1:1 adducts of formula {[(NN)PtPh2]M(OTf)}n (M = Cu, n = 1; M = Ag, n = 2) are observed in solution, and a 1:2 adduct of formula {[(NN)PtPh2]Ag2(OTf)2(C6H6)}n was characterized in the solid state, showing that unsupported Pt→M bonds are also accessible for [(NN)PtPh2]. The thermolyses of the complexes [(NN)PtMe2]MOTf in benzene affords moderate yields of [(NN)PtPh2] through an oxidatively induced double C−H activation process.