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(N^tBu)­(μ-N^tBu)]₂^2– (<b>L</b>^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 <b>L</b>^2– (E = S, Se). In the case of group 13 trihalides MCl₃ (M = Ga, In), neutral spirocyclic complexes (<b>L</b>)­M­[N^tBu­(Te)­P^V(μ-N^tBu)₂P^IIIN­(H)^tBu)] (M = Ga, In) comprised of a Te,Te′-chelated ligand <b>L</b>^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 (<b>L</b>)­(Se) and (<b>L</b>)­(SeSe) obtained from the reaction of Se₂Cl₂ with <b>L</b>^2– (E = Te). Single-crystal X-ray structures were obtained for the spirocyclic In complex (<b>9</b>), (<b>L)</b>GePh₂ (E = Te, <b>10</b>), (<b>L)</b>Sn^tBu₂ (E = Te, <b>12a</b>); E = Se, <b>12aSe</b>, E = S, <b>12aS</b>) and (<b>L</b>)­(μ-SeSe) (E = Te, <b>16</b>)