Syntheses and Structures of Strontium, Barium, and Europium Bis(diphosphanylamido) Complexes

Bis(diphosphanylamido) complexes of strontium and europium, [{(Ph2P)2N}2M(THF)3] (M = Sr (1), Eu (2)), have been prepared by reaction of [K(THF)n][N(PPh2)2] (n = 1.25, 1.5) and MI2. The single-crystal X-ray structures of compounds 1 and 2 always show a η2 coordination of the ligand via the nitrogen and one phosphorus atom. In solution, a dynamic behavior of the ligand is observed, which is caused by the rapid exchange of the two different phosphorus atoms. As a result of the radius of the larger ion, treatment of [K(THF)n][N(PPh2)2] with BaI2 gives the coordination polymer [{(Ph2P)2N}2Ba(THF){(Ph2P)2N}K]n (3). Two of the three {(Ph2P)2N}- ligands of compound 3 bind to the metal in η2 (N, P) while the third shows a heteroallylic (P, P) coordination mode. In the solid state, the infinite chain is formally held together by π coordination of the phenyl rings to the potassium atoms.