New alpha-Imido-beta-diarylphosphorylpropanoates and their Complexes with Gadolinium(III)

A practical route is described for the preparation of alpha-imido-beta-diarylphosphorylpropanoates based on the phosphine-catalyzed alpha-umpolung/beta-Michael addition reaction. One of the products has been tested for coordination the Gd3+ cation using NMR relaxation method in solution and by IR spectroscopy to solids. The exact structures of two isomers of the obtained complex have been determined by single crystal analysis. The structures of all isomers were investigated by quantum-chemical calculations in solution. Quantum-chemical calculations results show the presence of stereoselective effect in solution: the trans-isomer with two ligands having different chirality is energetically more favorable. The cis-isomer with ligands of different chirality is the least advantageous in terms of energy and therefore presents in solution in small amounts. The cis- and trans-isomers with two ligands of the same chirality are very close in energy but are somewhat inferior to the most stable isomer.