Substitution matters: isolating phosphorus diiminopyridine complexes

Abstract

The direct reactions of PI₃ with –H or –C₆H₅ substituted diiminopyridine ligands yield the N,N′,N′′-chelated P(I) cations. The analogous chemistry with the ubiquitous –CH₃ substituted derivative produces a complex mixture of products underscoring the importance of the substitution on the α-carbon atom. The I₃⁻ counteranion of the compounds could be easily exchanged with the more robust B₁₂Cl₁₂²⁻ dianion. Reactions of PCl₃ and PBr₃ with –CH₃ and –C₆H₅ substituted ligands led to indiscernible mixtures or no reaction. However, heating PBr₃ with the –H derivative in the presence of a halide trap produced the corresponding phosphorus(I) cation as the bromide salt. These species represent the first phosphorus diiminopyridine complexes reported.