Studies of Equilibria, Reactions, and Solvent Effects

Studies of Equilibria, Reactions, and Solvent Effects.—Lanthanide shift reagents have been found to be effective for phosphines and phosphoryl compounds, but not for thiophosphoryl compounds. - In a comparison of various shift reagents, europium nitrate hexadeuterium oxide (26) was found to give large shifts of 8 for phosphates and phosphonates. A contact contribution to the Sp shifts was established. When there are two possible sites for co-ordination, as in the aminophosphine (27), steric effects play an important role. Co-ordination occurs at nitrogen in (27 R = H) but at phosphorus in (27 R = Me). The n.m.r. parameters 

A linear correlation is reported between 8p(phosphine) and the change in chemical shift that occurs upon co-ordination of tertiary phosphines with a number of transition metals. The half-neutralization potential, the Taft a, and Sp of the complexes of tertiary phosphines and titanium tetrachloride have been found to be related. The equilibria involving the co-ordination of phosphoryl compounds and water with metal ions such as Al + are sufficiently slow to be studied by n.m.r. and P n.m.r. spectroscopy. Discrete signals from co-ordinated and unco-ordinated ligands are observed. Where this does not occur the equilibrium constant can be estimated from a plot involving chemical shift and concentration of reactant.  

and tri-alkyl phosphates have very similar Sp values. Separation of the signals may be achieved by the addition of di-(2-ethyl-hexyl)amine. The methoxide phosphonium salts (32) and (33) have 

Oshima, K. Asano, T. Nishishita, H. Tsuji, and H. Yokogawa, J. Japan Petrol Inst., 1971, 14, 499. 

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