Chemistry of Thiocarboxylates: Synthesis and Structures of Neutral Copper(I) Thiocarboxylates with Triphenylphosphine

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 P1̄, a = 11.5844(3) Å, b =
13.2459(3) Å, c = 14.3433(3) Å, α = 64.019(1)°, β = 79.297(1)°, γ = 69.426(1)°, V = 1850.98(7) Å3, Z = 1,
Dcalcd = 1.439 g·cm-3. Crystal data for 2·0.5CH2Cl2·H2O:  triclinic space group P1̄, a = 12.4413(1) Å, b =
15.5443(1) Å, c = 20.4637(3) Å, α = 94.974(1)°, β = 95.976(1)°, γ = 100.450(1)°, V = 3848.09(7) Å3, Z = 2,
Dcalcd = 1.416 g·cm-3. Single-crystal data for 3:  monoclinic space group P21/n, a = 15.2746(2) Å, b = 23.2947(2)
Å, c = 19.0518(3) Å, β = 96.713(1)°, V = 6732.5(2) Å3, Z = 4, Dcalcd = 1.309 g·cm-3. Crystal data for 4: 
triclinic space group P1̄, a = 10.2524(3) Å, b = 12.9826(4) Å, c = 14.5340(4) Å, α = 87.723(1)°, β = 75.322(1)°,
γ = 75.978(1)°, V = 1815.14(9) Å3, Z = 2, Dcalcd = 1.327 g·cm-3. Compound 1, [(μ3-SC{O}Me-S)2(μ-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, μ3-S and μ2-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 [(μ3-SC{O}Ph-S3)(μ3-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,
μ3-S, have been observed for the R{O}CS- anions, in 1 and 2 and μ3-S2,O in 2. Compound 3, [(μ-SC{O}Me-S)(μ-SC{O}Me-S,O){Cu(PPh3)2}2] is a dimer with μ2-S and μ2-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.