Low-valent chemistry: an alternative approach to phosphorus-containing oligomers.

A convenient preparative approach to low-valent phosphorus-rich oligomers is presented. Ligand substitution reactions involving anionic diphosphine ligands of the form [(PR2)2N](-) and [(PPh2)2C5H3](-) and a triphosphenium bromide P(I) precursor result in the formation of phosphorus(I)-containing heterocycles, several of which are of types that have never been prepared before. The methodology described also allows for the preparation of the known heterocycle cyclo-[P(PPh2)N(PPh2)]2 in better yields and purity than the synthetic approach reported previously. Preliminary reactivity studies demonstrate the viability of such zwitterionic oligomers as multidentate ligands for transition metals.

Lewis base sequestered chalcogen dihalides: synthetic sources of ChX2 (Ch = Se, Te; X = Cl, Br).

The synthesis and comprehensive characterization of a series of base-stabilized ChX(2) (Ch = Se, Te; X = Cl, Br) is reported using aryl-substituted diazabutadiene and 2,2'-bipyridine (bipy) as the ligands. In stark contrast to free ChX(2) the complexes display excellent thermal stability. Their use as viable ChX(2) reagents that may be stored for later use is demonstrated in principle. The syntheses are simple and high-yielding from commercially available or easily synthesized reagents. The bipy complexes are exceedingly rare examples of this ubiquitous ligand being utilized within Group 16 chemistry; the Se examples are the first to be characterized by X-ray crystallography, and the Te species are only the second.