A phosphorus-31 magnetic resonance study of ligand exchange on tetrakis(hexamethylphosphoramide)zinc(II) ion

Abstract

The rate of the associative ligand exchange process on tetrakis (hexamethylphosphoramide)zinc(II) ion in CD₂Cl₂ solution, determined by ³¹P n.m.r. spectroscopy, is given by:

                    rate = 4k₂[O=P(Nme₂)₃][Zn(O=P(NMe₂)₃)₄²⁺]

The characteristic kinetic parameters are: k₂(240 K) 304±17 dm³ mol^-1 s^-1, ΔH₂^‡ 22.7±0.9 kJ mol^-1, and ΔS₂^‡ -101±4 J K^-1 mol^-1.    

The preparations of [Zn(O=P(NMe₂)₃)₄](ClO₄)₂, [Zn(O=P(OMe)₃)₅] (ClO₄)₂ and [Zn {O=P(Me)-(OMe)₂}₅](ClO₄)₂ are reported. The rate of ligand exchange upon the last two species was found to be in the fast-exchange limit of the n.m.r. time scale.