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O-Alkyl dithiocarbonate (xanthate) derivatives of halodimethyltellurium(IV), Me 2 TeX[S 2 COR], 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 1 H, 13 C, and 125 Te NMR spectroscopy. The crystal structures of Me 2 -TeCl[S 2 COEt] (2) and Me 2 TeI[S 2 CO(i-Pr)] (9) were determined. Me 2 TeCl[S 2 COEt] (2), which crystallizes in the monoclinic space group P2 1 /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) Å 3 , and Z ) 8, and Me 2 TeI[S 2 CO(i-Pr)] (9), which crystallizes in the triclinic space group P1 h (No. 2), has the cell parameters a ) 11.332(5) Å, b ) 11.83(2) Å, c ) 10.19(2) Å, R ) 94.8(2)°, β ) 105.53( 7)°, γ ) 85.10(7)°, V ) 1309(3) Å 3 , 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.

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Isolation of Me2Te[(SPPh2)2N]2, Me2Te[(OPPh2)(SPPh2)N]2, and the halo derivatives Me2TeX[(SPPh2)2N] and Me2TeX[(OPPh2)(SPPh2)N], where X = Cl, Br, I, was attempted. Four of these were characterized by single crystal X-ray diffraction, while the formation of the others was confirmed by multinuclear NMR spectroscopy. Me2Te[(SPPh2)2N]2, 1; P21/n (No. 14) with cell parameters a = 14.908(3) Å, b = 11.122(5) Å, c = 30.384(6) Å, β = 92.67(2)°, V = 5032(2) Å3, Z = 4, R = 0.0661, Rw = 0.0696. Me2TeCl[(SPPh2)2N], 2; P[Formula: see text] (No. 2) with cell parameters a = 10.553(2) Å, b = 15.512(2) Å, c = 8.769(3) Å, α = 103.19(2)°, β = 94.27(2)°, γ = 85.76(2)°, V = 1391.3(7) Å3, Z = 2, R = 0.0377, Rw = 0.0328. Me2TeI[(SPPh2)2N], 4; P[Formula: see text] (No. 2) with cell parameters a = 10.954(3) Å, b = 15.580(3) Å, c = 8.751(3) Å, α = 103.49(2)°, β = 93.11(3)°, γ = 87.33(2)°, V = 1449.3(7) Å3, Z = 2, R = 0.0586, Rw = 0.0613. Me2TeCl[(OPPh2)(SPPh2)N], 6; P21/c (No. 14) with cell parameters a = 10.441(9) Å, b = 13.672(10) Å, c = 19.521(9) Å, β = 97.16(6)°, V = 2764(3) Å3, Z = 4, R = 0.0546, Rw = 0.0572. The immediate environment about Te is that of a sawhorse structure in which the lone pair is apparently stereochemically active and occupying an equatorial position in a distorted trigonal bipyramid. In 1, 2, and 4, one sulfur atom of (SPPh2)2N occupies an axial position. If the second sulfur atom is included in the coordination sphere, then the environment about Te becomes distorted octahedral, for 1, and square pyramidal, for 2 and 4. By contrast, in Me2TeCl[(OPPh2)(SPPh2)N], 6, the oxygen atom, rather than sulfur, is bound to tellurium in the axial position, with the S atom, at best, having a very weak interaction with Te.Key words: structure, tellurium, methyl, tetraphenyldichalogenoimidodiphosphinates.