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

2009-04-22T00:00:00Z (GMT) by Marc-Etienne Moret Peter Chen
The organoplatinum(II) complexes [(NN)PtMe<sub>2</sub>] and [(NN)PtPh<sub>2</sub>] (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)PtMe<sub>2</sub>] binds to the coinage metals through short, ligand-unsupported d−d<sup>10</sup> contacts that are best described as Pt→M dative bonds (M = Cu, Ag), in which the d<sub><i>z</i><sup>2</sup></sub> 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)PtPh<sub>2</sub>] binds preferentially by η<sup>1</sup> or η<sup>2</sup> complexation of the <i>ipso</i> carbon atoms of the phenyl groups to the coinage metal, affording homoleptic complexes {[(NN)PtPh<sub>2</sub>]<sub>2</sub>M}<sup>+</sup>{TfO}<sup>−</sup> in the solid state. The 1:1 adducts of formula {[(NN)PtPh<sub>2</sub>]M(OTf)}<sub><i>n</i></sub> (M = Cu, <i>n</i> = 1; M = Ag, <i>n</i> = 2) are observed in solution, and a 1:2 adduct of formula {[(NN)PtPh<sub>2</sub>]Ag<sub>2</sub>(OTf)<sub>2</sub>(C<sub>6</sub>H<sub>6</sub>)}<sub><i>n</i></sub> was characterized in the solid state, showing that unsupported Pt→M bonds are also accessible for [(NN)PtPh<sub>2</sub>]. The thermolyses of the complexes [(NN)PtMe<sub>2</sub>]MOTf in benzene affords moderate yields of [(NN)PtPh<sub>2</sub>] through an oxidatively induced double C−H activation process.