GOLD(I) PHOSPHINE COMPLEXES - MERCAPTOOXOPURINE BASE INTERACTIONS - MOLECULAR AND CRYSTAL-STRUCTURE OF (8-MERCAPTOTHEOPHYLLINATO-S)(TRIPHENYLPHOSPHINE)GOLD(I)

The interaction of chloro(triphenylphosphine)gold(I) and [mu-1,2-bis(diphenylphosphino)ethane]bis[bromogold(I)] with mercaptooxopurine derivatives (8-mercaptotheophylline, 8-mercapto-2-thiotheophylline, and 8-(methylthio)theophylline) under basic conditions yields complexes of the type [Au(PPh3)L], [{Au(PPh3)}2(mu-L)], [Au(mu-dppe)(mu-L)Au], and [LAu(mu-dppe)AuL] [L = mercaptooxopurine anion, dppe = 1,2-bis(diphenylphosphino)ethane], which contain either one S8-bonded or two N7,S8-bonded gold(I) phosphine groups. These complexes were characterized by means of H-1, C-13, and P-31 NMR and IR spectroscopy. Besides this, the crystal structure of the complex (8-mercaptotheophyllinato)(triphenylphosphine)gold(I) was determined from X-ray diffraction data. The compound crystallizes in triclinic space group P1BAR with a = 8.035 (1) angstrom, b = 12.749 (5) angstrom, c = 13.172 (4) angstrom, alpha = 102.89 (5)-degrees, beta = 103.03 (2)-degrees, gamma = 103.77 (5)-degrees, V = 1221.0 (8) angstrom 3, Z = 2, R = 0.037, and R(w) = 0.039. The structure consists of neutral [Au(PPh3)(HL1)] (HL1 = 8-mercaptotheophyllinato anion) held together in pairs by two N7-H---O6 hydrogen bonds and related by a crystallographic center of inversion. The coordination of the gold atom is almost linear, P-Au-S8 = 178.6 (2)-degrees, with Au-S and Au-P bond distances of 2.308 (2) and 2.256 (2) angstrom, respectively. The substitution reaction between [Au(PPh3)(HL1)] and [(AuBr)2(mu-dppe)] to give the complex [Au(mu-dppe)(mu-L1)Au] was studied. It seems that the reaction takes place through the intermediate complexes K[(L1)Au(mu-dppe)AuBr].4H2O and [{Au(PPh3)}2(mu-L1)].