Synthesis and Spectroscopic Characterization of Halodimethyl(O-alkyl dithiocarbonato)tellurium(IV) Compounds. Crystal Structures of Me₂TeCl[S₂COEt] and Me₂TeI[S₂CO(i-Pr)]

O-Alkyl dithiocarbonate (xanthate) derivatives of halodimethyltellurium(IV), Me₂TeX[S₂COR], where R = Me, Et, and i-Pr and X = Cl, Br, and I, have been prepared in 75−88% yields by the reaction of the potassium salt of the appropriate dithiocarbonic acid with dimethyltellurium dihalide in equimolar ratio. The compounds were characterized by infrared, Raman, and ¹H, ¹³C, and ¹²⁵Te NMR spectroscopy. The crystal structures of Me₂TeCl[S₂COEt] (2) and Me₂TeI[S₂CO(i-Pr)] (9) were determined. Me₂TeCl[S₂COEt] (2), which crystallizes in the monoclinic space group P2₁/a (No. 14), has the cell parameters a = 9.583(2) Å, b = 10.264(3) Å, c = 22.502(2) Å, β = 97.86(1)°, V = 2192.4(8) ų, and Z = 8, and Me₂TeI[S₂CO(i-Pr)] (9), which crystallizes in the triclinic space group P1̄ (No. 2), has the cell parameters a = 11.332(5) Å, b = 11.83(2) Å, c = 10.19(2) Å, α = 94.8(2)°, β = 105.53(7)°, γ = 85.10(7)°, V = 1309(3) ų, and Z = 2. The immediate environment about tellurium in both molecules can be described as that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. The two methyl groups occupy the other equatorial positions with a sulfur atom of the dithiocarbonate group and a halogen atom occupying the axial positions. However, intermolecular Te--I interactions between the two molecules of the asymmetric unit of 9 suggest that it is better described as dimeric, whereas the intermolecular Te--Cl associations in 2 lead to polymeric strands rather than dimers. Supramolecular associations are discussed in terms of Pauling bond orders.