Novel chiral 1,5-diaza-3,7-diphosphacyclooctane ligands and their transition metal complexes

Abstract

Reaction of bis(hydroxymethyl)phenylphosphine with (R)- or (S)-α-methylbenzylamine leads to the novel cyclic chiral bisphosphine ligands 1,5-(R,R)- and 1,5-(S,S)-bis(α-methylbenzyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane (1r or 1s). Novel chiral chelate complexes of Pt^II (2r, 3r and 3s), Pd^II (4s, 5s) and Re^I (6r) have been obtained by reaction of 1r or 1s with [MCl₂(cod)] (M = Pt, Pd; cod = 1,5-cyclooctadiene) and [{ReBr(CO)₃(thf)}₂]. Compounds 1–6 were characterised by multinuclear NMR (¹H, ¹³C, ³¹P) and IR spectroscopy. The former technique revealed the presence of two inequivalent phosphorus atoms in 6r. The molecular structure of 1r confirmed the absolute configuration of the chiral centers and a chair-chair conformation of the heterocycle with equatorial orientation of the substituents on phosphorus and axial on nitrogen atoms. Compound 1s was used to form a palladium catalyst for the co-polymerisation of carbon monoxide and norbornadiene. The structures of the co-polymers obtained were characterised by GPC, ¹H and ¹³C NMR spectroscopy and elemental analysis.