Chemistry of thiocarboxylates: synthesis and structures of neutral copper(I) thiocarboxylates with triphenylphosphine.

Abstract

The reactions of Na+ R[O]CS- (R = Me, Ph) with mixtures of CuCl and PPh3 in stoichiometric ratios yielded the compounds [Cu4(SC[O]Me)4(PPh3)4] (1), [Cu4(SC[O]Ph)4(PPh3)3] (2), [Cu2(SC[O]Me)2(PPh3)4] (3), [Cu(SC[O]Ph)(PPh3)2] (4), and [Cu2(SC[O]Ph)2(PPh3)3] (5) quantitatively. Compound 2 was also obtained from mixtures of CuCl, PPh3, and NaSC[O]Ph in the ratio 1:1:1. The analogous thioacetate compound similar to 2 and the thiobenzoate analogue of 1 could not be obtained. Attempts to prepare the unsymmetrical dimer of a thioacetate compound similar to 5 gave a mixture of 1 and 3. The structures of 1-4 have been determined by single-crystal X-ray diffraction methods. Crystal data for 1: triclinic space group Pl, a = 11.5844(3) A, b = 13.2459(3) A, c = 14.3433(3) A, alpha = 64.019(1) degrees, beta = 79.297(1) degrees, gamma = 69.426(1) degrees, V = 1850.98(7) A3, Z = 1, Dcalcd = 1.439 g.cm-3. Crystal data for 2.0.5CH2Cl2.H2O: triclinic space group P1, a = 12.4413(1) A, b = 15.5443(1) A, c = 20.4637(3) A, alpha = 94.974(1) degrees, beta = 95.976(1) degrees, gamma = 100.450(1) degrees, V = 3848.09(7) A3, Z = 2, Dcalcd = 1.416 g.cm-3. Single-crystal data for 3: monoclinic space group P2(1)/n, a = 15.2746(2) A, b = 23.2947(2) A, c = 19.0518(3) A, beta = 96.713(1) degrees, V = 6732.5(2) A3, Z = 4, Dcalcd = 1.309 g.cm-3. Crystal data for 4: triclinic space group P1, a = 10.2524(3) A, b = 12.9826(4) A, c = 14.5340(4) A, alpha = 87.723(1) degrees, beta = 75.322(1) degrees, gamma = 75.978(1) degrees, V = 1815.14(9) A3, Z = 2, Dcalcd = 1.327 g.cm-3. Compound 1, [mu 3-SC[O]Me-S)2(mu-SC[O]Me-S)2(CuPPh3)4], is a tetramer with a distorted stepladder structure in which two copper atoms are trigonally coordinated and the other two are tetrahedrally coordinated. Two bonding modes, namely, mu 3-S and mu 2-S, were observed for the Me[O]CS- anion. The structure of 2 may be described as a highly distorted cubanoid structure and formulated as [(mu 3-SC[O]Ph-S3)(mu 3-SC[O]Ph-S2,O)3(Cu)(CuPPh3)3]. In 2, three copper atoms have tetrahedral coordination geometry and one copper atom is trigonally coordinated. Unprecedented bonding modes, namely, mu 3-S, have been observed for the R[O]CS- anions, in 1 and 2 and mu 3-S2,O in 2. Compound 3, [(mu-SC[O]MeS)(mu-SC[O]Me-S,O)[Cu(PPh3)2]2] is a dimer with mu 2-S and mu 2-S,O bonding modes of Me[O]CS- ligands. Monomeric structure was found in 4 in which the copper atom has trigonal planar geometry with a very weak intramolecular interaction with O. Variable temperature 31P NMR studies in solution show the presence of various species in equilibria.