Main group tellurium heterocycles anchored by a P₂^VN₂ scaffold and their sulfur/selenium analogues

A comprehensive investigation of reactions of alkali-metal derivatives of the ditelluro dianion [TeP^V(NtBu)(μ-NtBu)]₂^2– (L^2–, E = Te) with p-block element halides produced a series of novel heterocycles incorporating P₂^VN₂ rings, tellurium, and group 13–16 elements. The dianion engages in Te,Te′-chelation to the metal center in Ph₂Ge and R₂Sn (R = ^tBu, ⁿBu, Ph) derivatives; similar behavior was noted for group 14 derivatives of L^2– (E = S, Se). In the case of group 13 trihalides MCl₃ (M = Ga, In), neutral spirocyclic complexes (L)M[N^tBu(Te)PV(μ-N^tBu)₂P^IIIN(H)^tBu)] (M = Ga, In) comprised of a Te,Te′-chelated ligand L^2– and a N,Te-bonded ligand resulting from loss of Te and monoprotonation were obtained. In reactions with RPCl₂ (R = ^tBu, Ad, ⁱPr₂N) a significant difference was observed between Se- and S-containing systems. In the former case, Se,Se′-chelated derivatives were formed in high yields, whereas the N,S-chelated isomers predominated for sulfur. All complexes were characterized by multinuclear (¹H, ³¹P, ⁷⁷Se, ¹¹⁹Sn, and ¹²⁵Te) NMR spectroscopy; this technique was especially useful in the analysis of the mixture of (L)(Se) and (L)(SeSe) obtained from the reaction of Se₂Cl₂ with L^2– (E = Te). Single-crystal X-ray structures were obtained for the spirocyclic In complex (9), (L)GePh₂ (E = Te, 10), (L)Sn^tBu₂ (E = Te, 12a); E = Se, 12aSe, E = S, 12aS) and (L)(μ-SeSe) (E = Te, 16).