Reactivity of a Phosphinito-Bridged Pt(I)-Pt(I) Complex with Nucleophiles: Substitution versus Addition

As a result of the strong electrophilic character of the Pt bound to O, the phosphinito-bridged Pt1 complex [(PHCy2)R(μ-PCy 2){κ2P, O-μ-P(O)Cy2}Pt(PHCy 2)](Pt-Pt) (1) undergoes attack at the O-bound Pt atom by molecules such as diand tricyclohexylphosphane, dicyclohexylphosphane oxide, and dicyclohexylphosphane sulfide. Thus, reaction of 1 with PHCy2 gives the symmetric PtI dimer [(PHCy2)Pt(μ-PCy 2)]2(Pt-Pt) (2), while the hydrido-bridged complex syn-[(PHCy2){κP-P(O)Cy2}Pt(μ-PCy 2)(μ-H)Pt(PHCy2){κP-P(O)Cy2}](Pt-Pt) (4) is obtained from reaction of 1 with P(O)HCy2; the thiophosphinito complex [(PHCy2)Pt(μ-PCy2){κ2P,S- μ-P(S)Cy2}Pt(PHCy2)](Pt-Pt) (8) forms selectively in reaction of 1 with P(S)HCy2. For comparison, the reaction with PCy3 results only in ligand substitution, affording [(PCy 3)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy 2}Pt(PHCy2)](Pt-Pt) (5). DFT studies confirmed the remarkable electrophilicity of the oxygen-bound Pt and shed light on the nature of the metal-metal bond in Pt dimers.