Associative reactions of dihydridobis(trimethylphosphine)platinum(II). Molecular structures of (diphenylacetylene)bis(trimethylphosphine)platinum and hydridotris(trimethylphosphine)platinum(II) tetraphenylborate

Article abstract of DOI:10.1021/om00091a025

Olefinic and acetylenic ligands such as diphenylacetylene, ethylene, tert-butylethylene, and trans-stilbene displace H₂ from PtH₂(PMe₃)₂ to form zerovalent π complexes. The complex Pt(PhC=CPh) (PMe₃)₂ crystallizes in the orthorhombic space group P2₁2₁2₁ with Z = 4, a = 9.508 (2) A?, b = 13.524 (4) A?, c = 16.124 (4) A?, and V = 2073.5 A?³. Refinment of 2040 unique observations >3σ(I) led to R = 0.043 and R_w = 0.056. The complex adopts a nearly square-planar geometry, with Pt-P distances of 2.262 (4) and 2.284 (4) A?, Pt-C distances of 2.06 (1) and 2.04 (1) A?, and a C-C distance of 1.29 (2) A? for the bound acetylenic moiety. The reaction between tert-butylethylene and PtH₂(PMe₃)₂ follows a second-order rate law first order in olefin and platinum complex, with k = (1.95 ± 0.24) × 10^-3 M^-1 s^-1 at 21°C. Hydrogenation of the unsaturated substrate does not occur, which agrees with theoretical predictions for a five-coordinate platinum hydride intermediate. Allyl chloride oxidatively adds to PtH₂(PMe₃)₂ to produce Pt(C₃H₅) (PMe₃)₂⁺, isolated as the BPh₄^- salt. The family of substrates HMPh₃ (M = Si, Ge, and Sn) undergo oxidative addition reactions to yield cis-PtH(SiPh₃) (PMe₃)₂, and cis,trans,cis-PtH₂(MPh₃)₂(PMe₃) ₂ for M = Ge and Sn. The reaction between methanol and PtH₂(PMe₃)₂ produces [Pt(PM₃)₂(μ-H)₂Pt(PMe₃) ₂H][OCH₃], and on addition of NaBPh₄, [PtH(PMe₃)₃][BPh₄] precipitates. The compound [PtH(P(CH₃)₃)₃][B(C₆H ₅)₄] crystallizes in the monoclinic space group P2₁/n with a = 10.011 (2) A?, b = 12.948 (3) A?, c = 26.699 (4) A?, β = 92.15 (2)°, V = 3458.2 A?³, and Z = 4 at T = 296 (1) K. Refinement of the structure led to R_w = 0.048 for 4325 unique reflections with I > 3μ(I). The PtH[P(CH₃)₃]₃⁺ species adopts a square-planar geometry. The Pt-P bond trans to hydrogen of 2.324 (1) A is longer than the other two Pt-P bonds by 0.030 A?, demonstrating that hydride ligand has a greater trans influence than trimethylphosphine. The P-Pt-Pt angles of 100.69 (6) and 100.56 (6)° open up from 90° to accommodate the bulk of the phosphine ligands.