Synthesis, Reactivity, and Computational Analysis of Halophosphines Supported by Dianionic Guanidinate Ligands

The reported chemistry and reactivity of guanidinate
supported
group 15 elements in the +3 oxidation state, particularly phosphorus,
is limited when compared to their ubiquity in supporting metallic
elements across the periodic table. We have synthesized a series of
chlorophosphines utilizing homo- and heteroleptic (dianionic)­guanidinates
and have completed a comprehensive study of their reactivity. Most
notable is the reluctancy of these four-membered rings to form the
corresponding N-heterocyclic phosphenium cations,
the tendency to chemically and thermally eliminate carbodiimide, and
the scarcely observed ring expansion by insertion of a chloro­(imino)­phosphine
into a P–N bond of the P–N–C–N framework.
Computational analysis has provided corroborating evidence for the
unwillingness of the halide abstraction reaction by demonstrating
the exceptional electron acceptor properties of the target phosphenium
cations and the underscoring strength of the P–X bond.