Coordination Chemistry of Perhalogenated Cyclopentadienes and Alkynes. 17. Reaction of Dichloroethyne With Platinum(0) Phosphine Complexes: Formation of a .pi.-Complex, Isomerization to .beta.-Chloroethynyl Complexes, and Syntheses of Diplatinioethyne Derivatives. Molecular Structures of (Ph3P)2Pt(.eta.2-ClC.tplbond.CCl) and Cl(Ph3P)2PtC.tplbond.CPt(PPh3)2Cl

Abstract

Dichloroethyne ClCECCl reacts with Pt(PPh3)2(C2H4) or Pt(PPh& to give the a-complex Pt(PPh3)2(+21C=CC1) (l),w hich can be isomerized by prolonged refluxing in toluene to trans- (Ph3P)zC1Pt-C==CC1 (2). 2 easily undergoes exchange reactions with alkylphosphines and with halide anions to yield trans-(R3P)2ClPt-C=CCl (R = Et (3)) Bu (4)) and trans-(Ph3P)z- (X)Pt-C=CCl (X = F (5a), Br (5b), I (5c)), respectively. The alkylphosphine complexes 3 and 4 can also be obtained by reaction of Pt(PR3)4 (R = Et, “Bu) with ClCECCl or from 1 and the corresponding phosphine. When Pt(PPh&(CzH4) is added to a solution of 3, a dinuclear complex 6 is formed, in which the C=C-Cl group acts as a a,a-bridging ligand. Upon standing, oxidative addition of the remaining C-C1 bond occurs and the p-ethynediyl complex trans- C1(R3P)2Pt-C=C-Pt(PPh3)2C1-Cis (R = Et (7a)) can be obtained. The corresponding p-ethynediyl complex 7b (R = Ph) is formed directly from 2 and Pt(PPh&(CzH4). 7b isomerizes upon heating in toluene to the symmetrical all-trans isomer 8. The molecular structures of 1 and 8 were determined by X-ray diffraction (1: C ~ ~ H ~ ~ C ~ Z P ~ Pa ~=C 10H.3Z11C(3~) AZ,, b = 10.392(4) A, c = 33.675(16) A, P = 90.17(3)’, monoclinic, P21/n, 2 = 4. 8: C74H&1zP4Ptz9 a = 12.938(2) A, b = 19.964(3) A, c = 24.844(3) A, P = 96.14(1)’, monoclinic, C2/c, 2 = 4)