Acetylenes attached to poly(pentafluorophenyl)platinum(II) moieties. Syntheses and molecular structures of cis-[Pt(C6F5)2(PhCCPh)2] and [NBun4][Pt(C6F5)3(PhCCPh)]

Abstract

The complexes cis-[Pt(C₆F₅)₂(RCCR)₂](R = Et 1a or Ph 1b) have been prepared by treating cis-[Pt(C₆F₅)₂(thf)₂](thf = tetrahydrofuran) with the appropriate alkyne. They undergo facile ligand exchange with either cis-[Pt(C₆F₅)₂(thf)₂] or [NBuⁿ₄]₂[Pt(C₆F₅)₄] giving rise respectively to neutral cis-[Pt(C₆F₅)₂(thf)(RCCR)]2 or anionic [NBuⁿ₄][Pt(C₆F₅)₃(PhCCPh)]7b mono(η²-alkyne) derivatives. A series of mono(η²-alkyne) complexes of formulae cis-[Pt(C₆F₅)₂L(RCCR)](L = pyridine 3a, 3b; PPh₃4a; SbPh₃5b; or CO 6a, 6b) and [N(PPh₃)₂][Pt(C₆F₅)₃(EtCCEt)]7a has also been prepared. None of these complexes except 7b shows ν(CC) absorptions in their IR spectra. The molecular structures of complexes 1b and 7b have been established by X-ray diffraction studies: 1b, monoclinic, space group C2/c, a= 19.177(4), b= 8.4971(4), c= 19.790(3)Å, β= 103.297(14)° and Z= 4 (C₂ symmetry imposed); 7b, monoclinic, space group P2₁/c, a= 10.5179(9), b= 17.5834(20), c= 25.369(5)Å, β= 99.376(11)° and Z= 4. Parameters within the acetylene moiety of 1b suggest that the platinum→alkyne π-back bonding is minimal.