Proton magnetic resonance study of the exchange of trimethyl phosphate on the tetrakis(trimethyl phosphato)beryllium(II) complex

Abstract

The exchange of trimethyl phosphate in the complex [Be{(MeO)₃PO}₄]²⁺ is characterised by the rate law (i), Rate = 4k_ex[Be{(MeO)₃PO}₄²⁺](i), where k_ex(298 K)= 3·6 ± 0·6 s^–1, ΔH^‡= 56·9 ± 4·2 kJ mol^–1, and ΔS^‡=–43·9 ± 12 ± 6 J K^–1 mol^–1 are typical values observed in the presence of methylene chloride diluent. The observed zero-order exchange-rate dependence on the concentration of free trimethyl phosphate is considered symptomatic of a dissociative trimethyl phosphate exchange mechanism.