Synthesis and Reactions of tert-Butylimidotellurium Dihalides:  X-ray Structures of [Cl₂Te(μ-N^tBu)₂TeCl₂]₃ and (^tBuO)₂Te(μ-N^tBu)₂Te(O^tBu)₂

An improved synthesis of the tellurium diimide dimer ^tBuNTe(μ-N^tBu)₂TeN^tBu (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 (^tBuNTeX₂)_n (2a, X = Cl, n = 6; 2b, X = Br). The intermediate ^tBuNTe(μ-N^tBu)₂TeCl₂ (3) is obtained 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 structure of 2a·2THF reveals a hexamer formed by linking three (^tBuNTeCl₂)₂ dimers via chloride bridges. The Cl ligands in the central dimer occupy the axial positions of a distorted trigonal bipyramid on both Te atoms. In the two terminal dimers one of the Te atoms has both Cl ligands in axial positions, whereas the other Te is attached to one axial Cl substituent and one equatorial Cl substituent. There are weak Te···Cl interactions between hexamer units in the range 3.107(1)−3.704(1) Å. Crystals of 2a·2THF are monoclinic, space group C2/c, a = 35.2264(9) Å, b = 11.4548(3) Å, c = 14.3656(4) Å, β = 101.645(1)°, V = 5677.4(3) ų, and Z = 8. The reaction of 2a with 2 equiv of KO^tBu in THF produces (^tBuO)₂Te(μ-N^tBu)Te(O^tBu)₂ (4). The crystal structure of 4 comprises a centrosymmetric dimer with a planar Te₂N₂ ring and significantly different Te−N bond lengths [1.943(4) and 2.217(4) Å]. Crystals of 4 are triclinic, space group P1̄, a = 9.646(5) Å, b = 10.899(5) Å, c = 9.439(4) Å, α = 94.12(4)°, β = 118.89(3)°, γ = 65.26(4)°, V = 778.5(7) ų, and Z = 2.