Reactions of cis-[tBuNTe(μ-NtBu)]2 with CF3SO3Me and M[O3SCF3] (M = Ag, Cu): Chelation, Cis → Trans Isomerization, and the Spirocyclic Ligand [tBuNTe(μ-NtBu)2Te(μ-O)]2

Abstract
The first investigations of coordination complexes of the tellurium diimide dimer [tBuNTe(μ-NtBu)]2 (1a) are presented. The coinage metals Ag+ and Cu+ were chosen to evaluate the ability of 1a to function as a chelating or bridging ligand. Reaction of 1a with Ag[O3SCF3] in toluene produces [Ag2L2][O3SCF3]2 (5, L = 1a) or, in the presence of LiCl, [Ag2L2(μ-Cl)][O3SCF3] (3). In 4 the two Ag+ ions bridge two molecules of cis-1a and engage in a weak Ag···Ag bonding interaction. In 3 the Cl- ion bridges two Ag+ ions, which are each chelated to the terminal NtBu groups of 1a. Treatment of 1a with Cu[O3SCF3] in toluene yields {[CuL][CF3SO3]}n (5) which, in turn, reacts with 1a to form [Cu2L3][CF3SO3]2 (6). In 6 the two Cu+ ions bridge cis and trans forms of 1a. The hydrolysis products {[tBuNTe(μ-NtBu)2Te(μ-O)]2[M(H2NtBu)]2}[O3SCF3]2 (7a, M = Ag; 7b, M = Cu) and [Cu2L(tBuNH2)2][O3SCF3]2 (8) were also structurally characterized. The complexes 7a,b contain the dimer [tBuNTe(μ-NtBu)2(μ-O)]2 in which one of the terminal NtBu ligands in 1a is replaced by an O atom. The central Te2O2 ring in this spirocyclic ligand is planar with unsymmetrical oxygen bridging [d(Te−O) = 1.885(7) and 2.170(7) Å in 7b]. The ligand 1a in 8 is in the trans conformation. Mono- or dimethylation of 1a with CF3SO3Me was shown to occur at the terminal nitrogens by 1H and 125Te NMR spectroscopy.