141091-19-2Relevant academic research and scientific papers
Carbonylation of organoplatinum dimers bridged by (diphenylphosphino)cyclopentadienyl ligands. Structural characterization of complexes containing 1,1- or 1,2-substituted η1-cyclopentadienyl groups and reductive elimination of ketones
Fallis, Kathleen A.,Anderson, Gordon K.,Lin, Minren,Rath, Nigam P.
, p. 478 - 488 (2008/10/08)
The complexes [Pt2R2(μ-C5H4PPh 2)2] (1a-e: R = Me, Et, neo-Pe (CH2CMe3), Ph, Bz (CH2-Ph)) react with carbon monoxide to produce [Pt2R2(CO)2(μ-η1-C 5H4PPh2)2] (2a-e), in which the cyclopentadienyl groups are 1,2-substituted by Pt and P. The R and CO ligands occupy mutually trans positions, and the complexes exist in solution as both syn and anti forms. The molecular structures of the methyl and neopentyl derivatives have been determined by X-ray diffraction, and they adopt anti and syn conformations, respectively. Thermolyses of these complexes in the presence of CO leads to the platinum(I) dimer [Pt2(CO)2(μ-η1-C5H 4PPh2)2] (5), in which both cyclopentadienyl rings are 1,1-substituted, and the appropriate ketone. The molecular structure of 5 reveals a Pt-Pt distance of 2.583(1) A?. Careful monitoring by NMR spectroscopy of the carbonylation/reductive-elimination sequence allows the identification of the intermediates [Pt2R(COR)(μ-η1-C5H4PPh 2)2] (3b,c) and [Pt2R(CO)(COR)(μ-η1-C5H 4PPh2)2] (4b,c). The molecular structure of 4c indicates that the complex contains one 1,1- and one 1,2-substituted cyclopentadienyl moiety and a Pt→Pt dative bond. A mechanism for the carbonylation/reductive-elimination sequence is proposed.
Platinum dimers bridged by diphenylphosphinocyclopentadienyl ligands. Molecular structures and NMR studies of two isomeric forms of the complexes [Pt2R2(μ-C5H4PPh 2)2]
Lin, Minren,Fallis, Kathleen A.,Anderson, Gordon K.,Rath, Nigam P.,Chiang, Michael Y.
, p. 4687 - 4693 (2007/10/02)
Reactions of [PtClR(cod)] with TlC5H4PPh2 yield dimeric complexes of the type [Pt2R2(μ-C5H4PPh 2)2] (1a, R = Me; 1b, R = Et, 1c, R = Np; 1d, R = Ph). The crystal structure of la has been determined. The compound crystallizes in the monoclinic space group P21/n with a = 10.155 (2) A?, b = 14.696 (3) A?, c = 21.080 (5) A?, β= 90.02 (2)°, V = 3146.0 (11) A?3, and Z = 4. Least-squares refinement converged at R = 0.0490 and RW = 0.0550 based on 6340 reflections with F > 4.0σ(F). The molecular structure reveals a structure of the type [Pt2Me2(μ-η5-C5H 4PPh2)(μ-η1-1,1-C5H 4PPh2], in which the cyclopentadienyl group of one dppc ligand coordinates in the usual η5 mode, whereas the other is bound in η1 fashion, with both platinum and phosphorus attached to the same carbon atom giving a spirocyclic structure and a four-membered Pt2PC ring containing a Pt→Pt dative bond. The dimers are fluxional in solution at ambient temperature, but the solid-state structure of la is consistent with the NMR parameters obtained in solution at low temperature for all the complexes. A minor species is detected in solution for 1c and 1d, which is consistent with a symmetrical dimer of the type [Pt2R2(μ-η5-C5H 4PPh2)2]. Crystals of 1d were obtained by slow evaporation of an ether solution and the crystal structure was determined. This compound crystallizes in the triclinic space group P1? with a = 10.256 (4) A?, b = 13.693 (5) A?, c = 14.687 (7) A?, α = 95.52 (3)°, β = 109.68 (3)°, γ = 101.87 (3)°, V = 1869.7 (13) A?3, and Z = 2. Least-squares refinement converged at R = 0.0221 and RW = 0.0266 based on 6759 reflections with F > 6.0σ(F). The molecular structure reveals that both cyclopentadienyl groups are indeed bonded in η5 fashion, but the molecule is distorted and does not possess a center of symmetry. An equilibrium between the two forms in solution is proposed, and the symmetrical dimer, or a closely related analogue, is suggested to be an intermediate in the fluxional process observed for the unsymmetrical dimer at ambient temperature.
