REACTIONS OF ACETYLENES WITH NOBLE-METAL CARBONYL HALIDES .12. SYNTHESIS, REACTIVITY, AND SOLUTION STRUCTURES BY MULTINUCLEAR NMR-STUDIES OF SIGMA-ALKENYLPLATINUM(II) COMPLEXES - X-RAY STRUCTURE-ANALYSIS OF [PT(C(C6H5)=C(H)C(=O)ME)(CO)CL] AND [PT(C(C6H5)=C(H)C(=NC6H5)ME)(PPH3)2CL]

The cluster compound [Pt(CO)2]3n2-, in chloroform solution at room temperature, reacts with H[Pt(CO)Cl3] and C6H5C≡CC(O)Me to give [Pt{C(C6H5)=C(H)C(=O)Me}(CO)Cl], 1. With PPh3, compound 1 yields [Pt{C(C6H5)=C(H)C(=O)Me}(PPh3)2Cl], 3, and with aromatic amines [Pt{C(C6H5)=C(H)C(=NR)-Me}(CO)Cl] (4, R = p-MeC6H4; 5, R = C6H5). Derivative 5 reacts with 1 and 2 mol equiv of triphenylphosphine to give complexes [Pt{C(C6H5)=C(H)C(=NC6H 5)Me}(PPh3)Cl], 6, or [Pt{C(C6H5)=C(H)C(= NC6H5)Me}(PPh3)2Cl], 7, respectively. The solution structures of compounds 1-7 was determined by a multinuclear NMR study (1H, 13C, 15N, 31P, and 195Pt), and the crystal structures of 1 and 7 were determined by X-ray diffraction. Crystals of 1 are monoclinic, space group C2/c, a = 18.516 (4) Å, b = 8.501 (1) Å, c = 14.108 (3) Å, β = 91.16 (2)°, Z = 8. The final disagreement factor was R = 0.0282 for 1199 observed reflections. The Pt atom adopts a square-planar coordination with distortions imposed by the coplanar five-membered metallacycle. An extensive π delocalization, not involving the Pt atom, spans the organic fragment. Relevant distances are Pt-C(1) = 2.017 (11) Å, Pt-O [trans to (CO)] = 2.048 (7) Å, and Pt-Cl [trans to C(sp2)] = 2.360 (3) Å. The molecules are arranged in the crystal in infinite stacks running parallel to the c axis with alternating Pt⋯Pt separations of 3.4467 (9) and 3.6675 (10) Å. Crystals of 7 are triclinic, space group P1, a = 9.0807 (14) Å, b = 13.0394 (8) Å, c = 19.4935 (24) Å, α = 80.239 (7)°, β = 78.065 (12)°, γ = 72.667 (8)°, Z = 2. The final disagreement factor is R = 0.0229 for 6240 observed reflections. The Pt atom has a distorted square-planar coordination with the phosphine ligands in the trans position; relevant distances are Pt-C(1) = 2.014 (4) Å, Pt-P(1) = 2.3045 (9) Å, Pt-P(2) = 2.3097 (10) Å, Pt-Cl = 2.4067 (11) Å. The organic moiety is perpendicular to the metal coordination plane due to the presence of the bulky triphenylphosphine ligands and is oriented so that the nitrogen approaches the platinum atom at the short Pt⋯N separation of 3.109 (3) Å.