Intramolecular N⋯E interactions in N-functionalised alkyl complexes R′ECl2 (E=P, As, Sb; R=6-Me-2-Pyr(SiMe3)2C−)

The metathetical exchange reactions of R′Li.Et2O [R′=6-Me-2-Pyr(SiMe3)2C−] with ECl3 (E=P, As, Sb) give the neutral E(III) complexes, R′ECl2. All complexes have been crystallographically characterised and exhibit extremely short intramolecular N⋯E dative bonds, with the phosphorus derivative exhibiting the shortest neutral N⋯P dative bond of 2.238(1) Å. Theoretical studies performed with approximate density functional theory successfully model the unusual structural features of compound R′PCl2, although the magnitude of the effect is somewhat underestimated. Under the same conditions, the lithium complex of the less bulky ligand r′ [r′=6-Me-2-Pyr(SiMe3)CH−] affords a weakly associated, dimeric complex [r′SbCl2]2, (via SbCl⋯Sb bridging) which is a consequence of less steric compression from the alkyl group around the metal centre; intramolecular N⋯Sb coordination is also present.