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

The first investigations of coordination complexes of the tellurium diimide dimer [(BuNTe)-Bu-t(mu-(NBu)-Bu-t)](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(mu-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 (NBu)-Bu-t 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 {[(BuNTe)-Bu-t(mu-(NBu)-Bu-t)(2)Te(mu-O)](2)[M((H2NBu)-Bu-t)](2)}[O3SCF3](2) (7a, M = Ag; 7b, M = Cu) and [Cu2L((BuNH2)-Bu-t)(2)][O3SCF3](2) (8) were also structurally characterized. The complexes 7a,b contain the dimer [(BuNTe)-Bu-t(mu-(NBu)-Bu-t)(2)(mu-O)](2) in which one of the terminal (NBu)-Bu-t 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) Angstrom in 7b]. The ligand la in 8 is in the trans conformation. Mono- or dimethylation of la with CF3SO3Me was shown to occur at the terminal nitrogens by H-1 and Te-125 NMR spectroscopy.