Synthesis of Pt(II)-Pt(II) and Pt/Pd(II)-Pt(0) monoalkynylphosphine bridging complexes

Article abstract of DOI:10.1021/om020374w

The monoalkynylphosphine complexes cis-[Pt(C₆F₅)₂(PPh₂C≡CR)(tht)] (R = Ph 1a, Tol 1b, tBu 1e, tht = tetrahydrothiophene) have been prepared by bridge splitting [{Pt(C₆F₅)₂(μ-tht)}₂] or by displacement of only one tht ligand from cis- [Pt(C₆F₅)₂(tht)₂] with PPh₂C≡CR. Complexes 1 react with cis- [Pt(C₆F₅)₂(thf)₂] to give binuclear derivatives [(C₆F₅)₂Pt(μ-tht)-(μ-1κP:2η ²-PPh₂C≡CR)Pt(C₆F₅)₂ ] (R = Ph 2a, Tol 2b, tBu 2c), containing a mixed tht/PPh₂C= CR bridging system. In contrast, treatment of 1 with [Pt(η²-C₂H₄)(PPh₃)₂] affords mixed-valence Pt(II)-Pt(0) complexes [{(C₆F₅)₂(tht)Pt(μ-1κP:2η² -PPh₂C≡CR)}Pt(PPh₃)₂] (R = Ph 3a, Tol 3b) stabilized by only one κP:η² bridging alkynyl phosphine. The molecular structures of 2a and 3a have been confirmed by single-crystal X-ray diffraction. Similarly, reactions of cis-bis(diphenylphosphino)alkyne complexes cis- [M(C₆F₅)₂(PPh₂C≡CR)₂ ] and cis-[Pt(C≡CR′)₂-(PPh₂C≡CR)₂] (M = Pt, Pd; R = Ph, Tol; R′ = Ph, tBu) with 1 or 2 equiv of [Pt(η²-C₂H₄)-(PPh₃)₂] yield the corresponding mixed-valence binuclear complexes cis-[{(C₆F₅)₂M(PPh₂C≡ CR)(μ-1-κP:2η²-PPh₂C≡CR)}Pt(PPh₃ )₂J (M = Pt, R = Ph 4a, Tol 4b; M = Pd, R = Ph 5a, Tol 5b) and cis-[{(C≡CR′)₂Pt(PPh₂C≡CR)(μ-1κ P:2η²-PPh₂C≡CR)}Pt(PPh₃)₂] (R′ = Ph, R = Ph 6a, Tol 6b; R′ = tBu, R = Ph 7a, Tol 7b), bearing only one PPh₂C≡CR η²-coordinated to a Pt(0)(PPh₃)₂ fragment.