Experimental and Theoretical Investigations of Tellurium(IV) Methanediides and Their Insertion Products with Sulfur and Iodine

The reactions of Li2[C­(Ph2PS)2] with tellurium tetrahalides in a 1:1 molar ratio in toluene afford the complexes {TeX2[C­(Ph2PS)2]}2 (7a, X = Cl; 7b, X = Br; 7c, X = I). These complexes dimerize through halide bridges in the solid state, and the tridentate ligand is S,C,S-coordinated to the tellurium center with a Te–C bond length of 2.024(3), 2.030(6), and 2.045(8) Å, respectively. In the case of TeBr4, small amounts of the complex TeX2[SC­(Ph2PS)2] (8b, X = Br) were isolated and shown by X-ray analysis to be the result of formal sulfur insertion into the Te–C bond of 7b. Complex 8b and the corresponding dichloride and diiodide, 8a (X = Cl) and 8c (X = I), may be prepared in good yields by the metathetical reactions of Li2[SC­(Ph2PS)2] with TeX4 in toluene. The complex TeI2[(I2)­C­(Ph2PS)2] (9) was isolated as a minor product from the reaction of Li2[C­(Ph2PS)2] and TeI4 and identified by X-ray crystallography. Complex 9 is constructed from the insertion of an iodine atom of an I2 molecule into the Te–C bond of 7c, resulting in a T-shaped geometry at that iodine atom and an almost linear Te–I–I unit with an elongated I–I bond; the C–I bond length is typical for a C­(sp3)–I bond. DFT calculations supplemented with Hirshfeld charge analysis, Boys–Foster localization of molecular orbitals, and evaluation of the electron localization functions indicate that in these species the ligand engages predominantly in σ bonding through the lone pairs on the carbon and sulfur atoms. The latter atoms participate in three-center interactions with tellurium. The bonds between the heavy elements and carbon are strongly polarized, and the character of the latter atom ranges from sp2 to sp3.