1,3,5-Triphosphabenzenes: Synthesis, reactivity and theory

In this review, the synthesis, reactivity and theoretical studies on 1,3,5-triphosphorus analogues of benzene are discussed including all the literature up to September 2014. Whereas the structure, spectroscopic studies and theory all point towards a significant degree of aromaticity for 1,3,5-triphosphabenzenes, the chemistry that has thus far been demonstrated is largely distinct from its carbocyclic counterparts. This can be ascribed to the substituents that have thus far been employed in 1,3,5-triphosphabenzene synthesis. Hence the discussion of triphosphabenzene reactivity is broken down into four sections describing η¹-coordination, η⁶-coordination, 1,4-addition and ring-contraction reactions. Furthermore, the section on 1,4-addition reactions contains a subsection which highlights the reactions of 1,3,5-triphosphabenzenes with small molecules (principally dihydrogen, alkynes and alkenes), a facet of reactivity that has greater links to the chemistry of transition metals than traditional aromatic chemistry.