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), which 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~P~C H Z C~Z , a = 10.311(3) A, 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).

Von sp3-Kohlenstoff-Helices umgebene sp-Kohlenstoffketten: eine Klasse von Molekülen, die durch Selbstorganisation zugänglich und Modellverbindungen für „isolierte“ molekulare Bauelemente sind Wir danken der Deutschen Forschungsgemeinschaft (SFB 583), Johnson Matthey PMC (Platin-Spende), dem Ministerio de Educación y Ciencia und der Fulbright Commission (Stipendien, J.M.M.-A.) für finanzielle Unterstützung und Dr. A. M. Arif für die Mithilfe bei einer Kristallstrukturanalyse.

“…Bei den ersten Versuchen nutzten wir den [Pt(CC) 4 Pt]‐Komplex 1 (Schema ),15 der eine Tetrain‐Brücke mit acht Kohlenstoffatomen und planar‐quadratische Endgruppen aufweist. Bei einem verwandten [PtCCPt]‐Komplex war gezeigt worden, dass Phosphanaustausch leicht stattfindet 16. Reaktionen von 1 mit Diphosphanen, bei denen die Phosphoratome durch bewegliche Brücken von 12 sp 3 ‐Kohlenstoffatomen voneinander getrennt sind, finden schon unterhalb der Raumtemperatur schnell statt.…”

sp Carbon Chains Surrounded by sp3 Carbon Double Helices: A Class of Molecules that are Accessible by Self-Assembly and Models for “Insulated” Molecular-Scale Devices We thank the Deutsche Forschungsgemeinschaft (SFB 583), Johnson Matthey PMC (platinum loan), the Spanish Ministerio de Educación y Ciencia, and the Fulbright Commission (Fellowships, J.M.M.-A.) for support, and Dr. A. M. Arif for assistance with the analysis of one crystal structure.

“…A related [PtCCPt] complex had been shown to undergo facile phosphane substitution. [16] Reactions of 1 with diphosphanes, in which the phosphorus atoms were separated by flexible bridges of twelve sp 3 carbon atoms, proceeded rapidly below room temperature. One product formed, as assayed by 31 P NMR spectroscopy and thin layer chromatography.…”

A Quest for Atropisomerism in Cojoined Square‐Planar Metal Complexes: Synthesis and Structures of Sterically Congested Diplatinum Ethynediyl Adducts

“…In addition to 4 and 5 , two other diplatinum ethynediyl complexes, both with the formula trans , trans ‐[(X)(R 3 P) 2 PtC≡CPt(PR 3 ) 2 (X)], have been structurally characterized. One of these, trans , trans ‐[(Cl)(Ph 3 P) 2 PtC≡CPt(PPh 3 ) 2 (Cl)] ( 6 ), has been prepared by a different type of route involving 1,2‐dichloroethyne . The other, trans , trans ‐[(I)(Me 3 P) 2 PtC≡CPt(PMe 3 ) 2 (I)] ( 7 ), was synthesized by cross‐coupling platinum ethynyl and chloride complexes using protocols similar to that in Scheme (HNEt 2 , CuCl) .…”