Synthesis of Pt(II)-Pt(II) and Pt/Pd(II)-Pt(0) Monoalkynylphosphine Bridging Complexes

Résumé

The monoalkynylphosphine complexes cis-[Pt(C 6F 5) 2(PPh 2C≡CR)(tht)] (R = Ph 1a, Tol 1b, tBu 1e, tht = tetrahydrothiophene) have been prepared by bridge splitting [{Pt(C 6F 5) 2(μ-tht)} 2] or by displacement of only one tht ligand from cis- [Pt(C 6F 5) 2(tht) 2] with PPh 2C≡CR. Complexes 1 react with cis- [Pt(C 6F 5) 2(thf) 2] to give binuclear derivatives [(C 6F 5) 2Pt(μ-tht)-(μ-1κP:2η 2-PPh 2C≡CR)Pt(C 6F 5) 2] (R = Ph 2a, Tol 2b, tBu 2c), containing a mixed tht/PPh 2C= CR bridging system. In contrast, treatment of 1 with [Pt(η 2-C 2H 4)(PPh 3) 2] affords mixed-valence Pt(II)-Pt(0) complexes [{(C 6F 5) 2(tht)Pt(μ-1κP:2η 2-PPh 2C≡CR)}Pt(PPh 3) 2] (R = Ph 3a, Tol 3b) stabilized by only one κP:η 2 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(C 6F 5) 2(PPh 2C≡CR) 2] and cis-[Pt(C≡CR′) 2-(PPh 2C≡CR) 2] (M = Pt, Pd; R = Ph, Tol; R′ = Ph, tBu) with 1 or 2 equiv of [Pt(η 2-C 2H 4)-(PPh 3) 2] yield the corresponding mixed-valence binuclear complexes cis-[{(C 6F 5) 2M(PPh 2C≡ CR)(μ-1-κP:2η 2-PPh 2C≡CR)}Pt(PPh 3) 2J (M = Pt, R = Ph 4a, Tol 4b; M = Pd, R = Ph 5a, Tol 5b) and cis-[{(C≡CR′) 2Pt(PPh 2C≡CR)(μ-1κ P:2η 2-PPh 2C≡CR)}Pt(PPh 3) 2] (R′ = Ph, R = Ph 6a, Tol 6b; R′ = tBu, R = Ph 7a, Tol 7b), bearing only one PPh 2C≡CR η 2-coordinated to a Pt(0)(PPh 3) 2 fragment.