The phosphorus-nitrogen heterocycle cis-[(tBuNH)P(μNtBu)2P(NHtBu)], A, is readily oxidized at phosphorus with chalcogens to yield the corresponding dichalcogenide cis-[(tBuNH)Ch=P(μNtBu)2P=Ch(NHtBu)], B. Both A and B can be deprotonated to yield dianionic ligands, but while A encapsulates metals and nonmetals as a desirable chelating N, N’ diamide, B forms the less desirable N, Ch chelates, which are less reactive. Here we report on the post-chelation oxidation of Group 15 chelates of B in which the ligand functions as the desired N, N’ diamide. Chelates of P, As, and Sb, each bearing the monodentate ligands Cl, Ph, and N3 were oxidized to mono- and dichalcogenides with elemental sulfur and selenium. The nature of the monodentate ligands had only minor effects on the rate of oxidation, but selenium was always the much faster oxidant. At elevated temperatures the chelated phosphorus atom was oxidized to yield tri-chalcogenides, but chelated As and Sb were never oxidized. At sufficiently high temperature even the loss of tert-butyl groups and of Cl from the chelates was observed to furnish a phosphorus nitride. The solid-state structures of most products were studied and are discussed.
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