Synthesis and reactions of tert-butylimidotellurium dihalides: X-ray structures of [Cl2Te(mu- (NBU)-B-t)(2)TeCl2](3) and ((BuO)-Bu-t)(2)Te(mu-(NBu)-Bu-t)(2)Te((OBu)-Bu-t)(2)

An improved synthesis of the tellurium diimide dimer (BuNTe)-Bu-t(mu-(NBu)- Bu-t)(2)(TeNBu)-Bu-t (1) using THF as solvent is reported. The reactions of 1 with tellurium tetrahalides (1:2 molar ratio) in THF give high yields of tert-butylimidotellurium dihalides ((BuNTeX2)-Bu-t)(n) (2a, X = Cl, n 6; 2 b, X = Br). The intermediate (BuNTe)-Bu-t(mu-(NBu)-Bu-t)(2)TeCl2 (3) is obt ained when a 3:2 molar ratio is used. The dibromide 2b may also be prepared by halide exchange between 2a and 2 equiv of Me3SiBr. The crystal structur e of 2a.2THF reveals a hexamer formed by linking three ((BuNTeCl2)-Bu-t)(2) dimers via chloride bridges. The Cl ligands in the central dimer occupy th e axial positions of a distorted trigonal bipyramid on both Te atoms. In th e two terminal dimers one of the Te atoms has both Cl ligands in axial posi tions, whereas the other Te is attached to one axial Cl substituent and one equatorial Cl substituent. There are weak Te CI interactions between hexam er units in the range 3.107(1)-3.704(1) A. Crystals of 2a.2THF are monoclin ic, space group C2/c, a = 35.2264(9) Angstrom, b = 11.4548(3) Angstrom, c = 14.3656(4) Angstrom, beta = 101.645(1)degrees, V = 5677.4(3) Angstrom(3), and Z = 8. The reaction of 2a with 2 equiv of (KOBu)-Bu-t in THF produces ( (BuO)-Bu-t)(2)Te(mu-(NBu)-Bu-t)Te((OBu)-Bu-t)2 (4). The crystal structure o f 4 comprises a centrosymmetric dimer with a planar Te2N2 ring and signific antly different Te-N bond lengths [1.933(4) and 2.217(4) Angstrom]. Crystal s of 4 are triclinic, space group P (1) over bar, a 9.646(5) Angstrom, b = 10.899(5) Angstrom, c = 9.439(4) Angstrom, alpha = 94.12(4)degrees, beta = 118.89(3)degrees, gamma = 65.26(4)degrees, V = 778.5(7) Angstrom(3), and Z = 2.