Substitution matters: isolating phosphorus diiminopyridine complexes.

The direct reactions of PI(3) with -H or -C(6)H(5) substituted diiminopyridine ligands yield the N,N',N''-chelated P(I) cations. The analogous chemistry with the ubiquitous -CH(3) substituted derivative produces a complex mixture of products underscoring the importance of the substitution on the α-carbon atom. The I(3)(-) counteranion of the compounds could be easily exchanged with the more robust B(12)Cl(12)(2-) dianion. Reactions of PCl(3) and PBr(3) with -CH(3) and -C(6)H(5) substituted ligands led to indiscernible mixtures or no reaction. However, heating PBr(3) 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.