Selective Syntheses of 1,3‐Diphosphacyclobutadiene, Dewar‐1,3,5‐triphosphabenzene, 1,3,5‐Triphosphabenzene, and 1,3,5,7‐Tetraphosphabarrelene by Cyclooligomerization of Phosphaalkynes

Abstract

By varying the temperature, tBuCP reacts in the presence of η4-butadiene(η8-cyclooctatetraene)hafnium complexes to give different cyclooligomers. Thus, the triphosphabenzene 1 is formed at -78 °C and the dewar-triphosphabenzene 2 at 0 °C. Both compounds are initially bound to the complex and can be liberated with hexachloroethane in a redox reaction. Compounds 1 and 2 are the first compounds of these classes of substances. Cyclodimers or cyclotetramers are obtained at higher temperature.