Stabilization of 2-Pyridyltellurium(II) Derivatives by Oxidorhenium(V) Complexes

Zwitterionic compounds such as pyridine-containing tellurenyl compounds are interesting building blocks for heterometallic assemblies. They can act as ambiphilic donor/acceptors as is shown by the products of reactions of the zwitterions HpyTeCl(2) or HCF(3)pyTeCl(2) with the rhenium(V) complex [ReOCl3(PPh3)(2)]. The products have a composition of [ReO2Cl(pyTeCl)(PPh3)(2)] and [ReO2Cl(CF(3)pyTeCl)(PPh3)(2)] with central {O=Re=O horizontal ellipsis Te(Cl)p?y}+ units. The Re-O bonds in the products are elongated by approximately 0.1 & ANGS; compared with those to the terminal oxido ligands and establish Te horizontal ellipsis O contacts. Thus, the normally easily assigned concept of oxidation states established at the two metal ions becomes questionable (Re-V/Te-II vs. Re-III/Te-IV). A simple bond length consideration rather leads to a description with the coordination of a mesityltellurenyl(II) chloride unit to an oxido ligand of the Re(V) center, but the oxidation of the tellurium ion and the formation of a tellurinic acid chloride cannot be ruled out completely from an analysis of the solid-state structures. DFT calculations (QTAIM, NBO analysis) give clear support for the formation of a Re(V) dioxide complex donating into an organotellurium(II) chloride and the alternative description can at most be regarded as a less favored resonance structure.

Automated summary

The zwitterionic compounds, such as pyridine-containing tellurenyl compounds, are versatile building blocks for heterometallic assemblies. Reactions of these compounds with the rhenium(V) complex result in the formation of [ReO2Cl(pyTeCl)(PPh3)(2)] and [ReO2Cl(CF(3)pyTeCl)(PPh3)(2)], which exhibit elongated Re-O bonds and Te-O contacts. The oxidation states of the metal ions are ambiguous, and DFT calculations suggest the formation of a Re(V) dioxide complex donating into an organotellurium(II) chloride.