Synthesis and characterization of cationic dinuclear hydridoplatinum complexes: Crystal and molecular structure of [Pt2(μ-H,μ-CO)(dpe)2][BF4] (dpe = 1,2-bis(diphenylphosphino)ethane)

Reaction of [Pt2H3(L-L)2][A], L-L = Ph2P(CH2)2PPh2 (dpe), Ph2P(CH2)3PPh2 (dpp), or Ph2P(CH2)4PPh2 (dpb), A = BF4 (a) or I (b), with CO or CNR leads to displacement of dihydrogen and formation of the corresponding salts of [Pt2H(L\u2032)(L-L)2]+: 1a or 1b, L-L = dpe, L\u2032 = CO; 2a, L-L = dpp, L\u2032 = CO; 3a, L-L = dpb, L\u2032 = CO; 4a or 4b, L-L = dpe, L\u2032 = CNCH3; 5a or 5b, L-L = dpe, L\u2032 = CNC6H4-p-CH3; 6a, L-L = dpe, L\u2032 = CNCMe3. The infrared absorptions of the cations 1+-5+ are consistent with the presence of a bridging carbonyl or isocyanide ligand. For 6+, however, infrared evidence suggests that the hydrogen atom and the CNCMe3 group are terminally bonded. At 213 K limiting 1H and 31P NMR spectra of the cation 3+ indicate the hydrogen to be coupled to two phosphorus nuclei in trans and two in cis positions. At room temperature the spectra indicate fluxional behavior with rapid exchange of the phosphorus atom positions with respect to the bridging hydrogen atom. Crystal and molecular structure determination of 1a was undertaken at 115 K, confirming a bridging position each for the hydrogen atom and for the carbonyl group. The salt crystallizes in the monoclinic space group P2/n with the following cell dimensions: a = 13.477 (5), b = 11.090 (4), c = 15.976 (8) \uc5; \u3b2 = 97.40 (3)\ub0. There are two [Pt2(\u3bc-H,\u3bc-CO)(dpe)2]+ cations and two BF4- anions per unit cell. The cation possesses crystallographically imposed C2 symmetry. The bidentate phosphine groups are chelated each to a separate metal atom. The coordination around each metal atom is close to a square plane consisting of two cis-coordinated phosphorus atoms, the bridging hydrogen atom, and the carbon of the bridging CO group. The Pt-Pt distance (bridged by hydrogen and CO) is 2.716 (1) \uc5 with Pt-C\u3bc and Pt-H\u3bc, at 2.018 (1) and 1.55 (4) \uc5, respectively. \ua9 1983 American Chemical Society