FURTHER-STUDIES OF THE KINETIC COORDINATION TEMPLATE EFFECT IN THE METAL-ION CATALYZED FORMATION OF ARYLPHOSPHONIUM SALTS

The reactions of a series of bis-imines (derived from o-bromobenzaldehyde and α,ω-diamines) with tertiary phosphines in the presence of nickel(II) bromide in ethanol proceed with replacement of the o-halogen to form the related bis(arylphosphonium) salts, each o-haloarylimino moiety providing a kinetic coordination template for the substitution process. Only for bis-imines able to form five-, six- or seven-membered chelate systems with the metal ion is the substitution reaction inhibited or the yield reduced. Kinetic template effects in arylphosphonium salt formation have also been observed in the related reactions of 2,3-bis(o-chlorophenyl)quinoxaline, 1-(N-benzylidene)amino-8-bromonaphthalene and o-iodobenzoic acid. The structural requirements of the coordination template are discussed in the light of these and earlier results. © 1990.