Chiral “P–N–P” ligands, (C20H12O2)PN(R)PY2 [R=CHMe2, Y=C6H5, OC6H5, OC6H4-4-Me, OC6H4-4-OMe or OC6H4-4-tBu] and their allyl palladium complexes

Abstract

Chiral “P–N–P” ligands, (C20H12O2)PN(R)PY2 [R = CHMe2, Y = C6H5 (1), OC6H5 (2), OC6H4-4-Me (3), OC6H4-4-OMe (4) or OC6H4-4-tBu (5)] bearing the axially chiral 1,1′-binaphthyl-2,2′-dioxy moiety have been synthesised. Palladium allyl chemistry of two of these chiral ligands (1 and 2) has been investigated. The structures of isomeric η3-allyl palladium complexes, [Pd(η3-1,3-R2′-C3H3){κ2-(racemic)-(C20H12O2)PN(CHMe2)PY2}](PF6)(R′ = Me or Ph; Y = C6H5 or OC6H5) have been elucidated by high field two-dimensional NMR spectroscopy. The solid state structure of [Pd(η3-1,3-Ph2-C3H3){κ2-(racemic)-(C20H12O2)PN(CHMe2)PPh2}](PF6) has been determined by X-ray crystallography. Preliminary investigations show that the diphosphazanes, 1 and 2 function as efficient auxiliary ligands for catalytic allylic alkylation but give rise to only moderate levels of enantiomeric excess.