COUPLING OF ACETYLENES HELD PROXIMATE TO A METAL - ALKYNE-ALKYNE INTERACTIONS IN CIS-PHOSPHINOACETYLENE COMPLEXES, INCLUDING STRUCTURAL CHARACTERIZATION OF THE UNSYMMETRICAL DIPHOSPHINE 1-PHENYL-2,3-BIS(DIPHENYLPHOSPHINO)NAPHTHALENE AND 3 PLATINUM(II) COMPLEXES OF PH2PC-EQUIVALENT-TO-CPH

The diphenyl(phenylethynyl)phosphine complexes cis-PtX(Y)(Ph2PC=CPh)2 [X = Y = Cl, I, CF3, C6F5, Me; X (Y) = o-C6H4O2, Me(Cl)] have been synthesized, and for all of the complexes except the dimethyl complex, intramolecular coupling of the phosphinoacetylene ligands occurs on heating to form cis-PtX(Y){o-C16H10(PPh2)2}. A mixture of the two possible structural isomers is formed for cis-PtMe(Cl){o-C16H10(PPh2)2}. The complex cis-PtMe2{o-C16H10(PPh2)2} has been obtained by reaction of the dichloro analogue with methyllithium. The unsymmetrical diphosphine 1-phenyl-2,3-bis(diphenylphosphino)naphthalene [o-C16H10(PPh2)2], produced as a coordinated ligand via these intramolecular coupling reactions, has been isolated in moderate yield from the dichloro complex and its structure determined by X-ray diffraction. Crystals of o-C16H10(PPh2)2 are triclinic, space group P1, with a = 11.437(13) angstrom, b = 9.628(12) angstrom, c = 16.712(21) angstrom, a = 82.31(9)-degrees, beta = 119.08(3)-degrees, gamma = 110.03(5)-degrees, and Z = 2. The structure was solved and refined to R = 0.058, R(w) = 0.070. Structure determinations of cis-PtCl2(Ph2P=Ph)2.2MeCN, cis-PtMe(Cl)(Ph2P=Ph)2.0.5CH2Cl2, and cis-PtMe2(Ph2PC=CPh)2 have been carried out to evaluate interligand interactions in the complexes. Crystallographic data: cis-PtCl2(Ph2-PC=CPh)2.2MeCN, monoclinic, space group P2(1)/c, a = 11.604(2) angstrom, b = 18.416(5) angstrom, c = 19.344(3) angstrom, beta = 98.63-degrees, Z = 4, R = 0.031, R(w) = 0.035; cis-PtMe(Cl)(Ph2PC=CPh)2.0.5CH2Cl2, orthorhombic, space group Pbca, a = 16.910(2) angstrom, b = 17.207(1) angstrom, c = 25.300(2) angstrom, Z = 8, R = 0.039, R(w) = 0.044; cis-PtMe2(Ph2PC=CPh)2, orthorhombic, space group Pbca, a = 11.934(2) angstrom, b = 16.885(3) angstrom, c = 34.098(8) angstrom, Z = 8, R = 0.037, R(w) = 0.042. Factors affecting the occurrence of intramolecular coupling are assessed, together with a comparison of this reaction with related reactions of organic diacetylenes. The complex cis-PtMe(Cl)(Ph2PC=CPh)2 reacts with diphenylphosphine to form a mixture of the two structural isomers of cis-PtMe(Cl){Ph2PCH=C(Ph)PPh2}.