The interaction of phosphavinyl Grignard reagents with group 15 halides: synthesis and structural characterisation of novel heterocyclic and heterocage compounds

Abstract

The reactions of a phosphavinyl Grignard reagent, [CyPC(Bu^t)MgCl(OEt₂)], Cy = cyclohexyl, with a variety of group 15 halide compounds in a number of stoichiometries have been investigated. When the Grignard reagent is reacted with Ph₂PCl or CyPCl₂, Cy = cyclohexyl, in a 1∶1 and 2∶1 stoichiometry respectively, the 1,3-diphosphapropene, Ph₂PC(Bu^t)PCy, and triphosphabicyclo[2.1.0]pentane compound, CyP{C₂(Bu^t)₂P₂Cy₂}, are formed. The 2∶1 and 3∶1 reactions of the Grignard reagent with either PCl₃ or AsCl₃ lead to the strained triphospha- and arsadiphosphabicyclo[1.1.1]pentanes, Bu^tC{μ-P(Cy)}₂{μ-ECl}CBu^t, E = P or As in moderate yield. The related 1∶1 reaction of the Grignard reagent with PCl₃ affords two products, a phosphino-substituted phosphorus ylide, Cl₂PC(Bu^t)P(Cy)(Cl)₂, and a tetraphosphabicyclo[2.1.1]hexane, Bu^tC{μ-P(Cl)P(Cy)}{μ-P(Cy)}{μ-P(Cl)}CBu^t, the mechanism of formation of which is discussed. An analogous 1∶1 reaction of the Grignard reagent with SbCl₃ led to an unusual heterocyclic compound, (Cl₂Sb)(Bu^t)CSb(Cl)C(Bu^t)P(Cl)(Cy)P(Cy), which quantitatively decomposes in solution to yield the known 1,2-dihydro-1,2-diphosphete, P₂(Cy)₂C₂(Bu^t)₂. All prepared compounds have been crystallographically characterised.