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

The reactions of a phosphavinyl Grignard reagent, [CyP=C(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{C-2(Bu-t)(2)P2Cy2}, 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-t C{mu-P(Cy)}(2) {mu-ECl} CBut, 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, (BuC)-C-t{mu-P(Cl) P(Cy)} {mu-P(Cy)} {mu-P(Cl)}CBut, 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, P-2 (Cy)(2)C-2 (Bu-t)(2). All prepared compounds have been crystallographically characterised.