Di- and tri-nuclear platinum complexes with double acetylide bridges. Molecular structure of [NBu4]2[Pt3(C6F5)4(µ-CCPh)4]·4thf (thf = tetrahydrofuran)

Abstract

The homoleptic σ-bonded tetrakis (acetylide) complexes [NBu₄]₂[Pt(CCR)₄]·2H₂O (R = Bu^t or SiMe₃) reacted with cis-[Pt(C₆F₅)₂(thf)₂](thf = tetrahydrofuran) in a 1 : 1 molar ratio to give the dinuclear derivatives [NBu₄]₂[(C₆F₅)₂Pt(µ-CCR)₂Pt(CCR)₂]·H₂O (R = Bu^t1 or SiMe₃2). Similar treatment of [NBu₄]₂[Pt(CCR)₄]·nH₂O (R = Ph, n= 0; R = Bu^t or SiMe₃, n= 2) with cis-[Pt(C₆F₅)₂(thf)₂] in a 1 : 2 molar ratio afforded the trinuclear bridging tetraacetylide complexes [NBu₄]₂[(C₆F₅)₂Pt(µ-CCR)₂Pt(µ-CCR)₂Pt(C₆F₅)₂](R = Ph 3, Bu^t4 or SiMe₃5). Complexes 4 and 5 are also obtained from the reaction of 1 and 2 with cis-[Pt(C₆F₅)₂(thf)₂](1 : 1 molar ratio). An unambiguous structural assignment for the trinuclear bridging tetrakis (acetylide) complexes 3–5 has been established by an X-ray diffraction study on [NBu₄]₂[(C₆F₅)₂Pt(µ-CCPh)₂Pt(µ-CCPh)₂Pt(C₆F₅)₂]3. The structure of the anion has shown that one of the σ-alkynyl groups of [Pt(CCPh)₄]^2– has migrated to one of the two ‘Pt(C₆F₅)₂’ fragments yielding a formally dianionic dinuclear fragment [(C₆F₅)₂Pt(µ-CCPh)₂Pt(CCPh)₂] which in its turn acts as chelate metallo ligand to the other ‘Pt(C₆F₅)₂’ unit.