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

The metathetical exchange reactions of R'Li . Et2O [R' = 6-Me-2-Pyr(SiMe3)( 2)C-] with ECl3 (E = P, As, Sb) give the neutral E(III) complexes, R'ECl2. All complexes have been crystallographically characterised and exhibit extr emely short intramolecular NE dative bonds, with the phosphorus derivative exhibiting the shortest neutral N ... P dative bond of 2.238(1) Angstrom. T heoretical studies performed with approximate density functional theory suc cessfully model the unusual structural features of compound R'PCl2, althoug h the magnitude of the effect is somewhat underestimated. Under the same co nditions, the lithium complex of the less bulky ligand r' [r'=6-Me-2-Pyr(Si Me3)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 coordinat ion is also present. (C) 2000 Elsevier Science S.A. All rights reserved.