SYNTHESIS AND SPECTROSCOPIC CHARACTERIZATION OF O-ALKYL DITHIOCARBONATE (XANTHATE) DERIVATIVES OF DIMETHYLTELLURIUM(IV) AND DIPHENYLTELLURIUM(IV) - CRYSTAL-STRUCTURES OF ME(2)TE[S(2)COET](2) AND PH(2)TE[S(2)COET](2)

Two series of O-alkyl dithiocarbonate (xanthate) derivatives of dimethyl- and diphenyltellurium(IV), Me(2)Te[S-2-COR](2) and Ph(2)Te[S(2)COR](2), where R = Me, Et, i-Pr, n-Pr, and n-Bu, have been prepared in 60-71% yields by the reaction of the potassium salt of!the appropriate dithiocarbonic (xanthic) acid with dichlorodimethyltellurium-(IV). The products were characterized principally by infrared, Raman, and H-1, C-13, and Te-125 NMR spectroscopy. The crystal structures of Me(2)Te[S(2)COE](2) and Ph(2)Te[S(2)COEt](2) were determined. Me(2)Te[S(2)COEt](2) (2) crystallizes in space group (P $($) over bar$$ 1, No. 2) with the cell parameters a = 10.588(2) Angstrom, b = 11.974(2) Angstrom, c = 6.458(3) Angstrom, alpha = 104.06(3)degrees, beta = 90.67(2)degrees, gamma = 7125(1)degrees, V = 770.2(8)Angstrom(3), and Z = 2; R = 0.0310, R(w) 0.0286. Ph(2)Te[S-2-COEt](2) (7) also crystallizes in space group (P $($) over bar$$ 1, No. 2) with the cell parameters a 11.320(3) Angstrom, b = 13.062(4) Angstrom, c = 8.225(4)Angstrom, alpha = 107.88(3)degrees, beta = 110.72(3)degrees, gamma = 79.91(3)degrees, V = 1078.3(8) Angstrom(3), and Z = 2; R = 0.0366, R(w) = 0.0329. The immediate environment about tellurium in both molecules is essentially that of a sawhorse structure in which the lone pair is !apparently stereochemically active and occupies an equatorial position in a distorted trigonal bipyramid. The two methyl or phenyl groups occupy the other equatorial positions with Te-C bond lengths of 2.104(6) and 2.125(6) Angstrom and a C-Te-C angle of 96.2(2)degrees in 2. The corresponding values for 7 are 2.127(5) and 2.139(5) Angstrom and 99.3(2)degrees. The axial positions are occupied by a sulfur atom from each of the dithiocarbonate groups to give anisobidentate linkages resulting in Te-S bonding distances of 2.590(2) and 2.677-(2) Angstrom, an S-Ge-S angle of 16638(5)degrees, and S-Te-C angles ranging from 82.3(2) to 90.9(2)degrees in 2. The corresponding distances and angles for 7 are 2.607(2) and 2.629(1) Angstrom, 168.31(4)degrees, and a range from 83.0(1) to 90.4(1)degrees. There are also secondary intramolecular interactions involving both terminal sulfur atoms resulting in Te-S distances of 3.274(2) and 3.332(2) Angstrom in 2 and 3.265(2) and 3.336(2) Angstrom in 7. These distances are discussed in terms of Pauling's partial bond orders, and if they are included as part of the coordination sphere, then the structure of 2 is better described as a pseudo pentagonal bipyramid with the supposed lone pair occupying an axial position, whereas the structure of 7 appears to be a distorted octahedron with an apparently inactive lone pair. The NMR spectra of the Ph(2)Te[S(2)COR](2) series indicate that, for these five derivatives, reductive elimination is evident even in spectra recorded immediately following dissolution of the products.