Thermal C–P and C–H cleavage in co-ordinated phosphines leading to dinuclear platinum complexes and contrasting reactions with M(PPh3)+ (M = Cu, Ag or Au) and HgCl2†

Abstract

The dinuclear complex [Pt₂(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂] was prepared by controlled thermolysis of [Pt(C₂H₄)(PPh₃)₂] and it contains both a diphenylphosphido and an ortho-metallated triphenylphosphine ligand that bridge the Pt^I–Pt^I bond [2.657(1) Å in 3 and 2.677(5) Å in the CH₂Cl₂ adduct]. Addition of the electrophilic metal reagents [M(PPh₃)]⁺ (M = Cu, Ag or Au) occurs at the Pt–Pt bond, affording [Pt₂{µ-M(PPh₃)}(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂]⁺ (M = Cu, Ag or Au) whereas selective oxidation by HgCl₂ gives the dinuclear platinum(II) complex [Pt₂Cl₂(µ-PPh₂){µ-(o-C₆H₄PPh₂)}(PPh₃)₂] which is shown to have a “mixed-geometry” structure at the metal centres (square planar and flattened tetrahedral). The new complexes have been analysed by ³¹P-{¹H} and ¹⁹⁵Pt NMR spectroscopy and the structures of three complexes have been determined by X-ray diffraction.