New complexes of lanthanide chlorides.: Reversible isomerization in octahedral [LaCl 3(HMPA) 3] and the crystal structure of fac-[SmCl 3(HMPA) 3

Abstract

Complexes of [LnCl 3L] (Ln=La, Nd, Sm, Eu, and L=diethylene glycol dimethyl ether, diglyme; Ln=La, Pr, and L=dimethoxyethane, DME) were prepared from the lanthanide oxides and hydrogen chloride, which was formed in situ from chlorotrimethylsilane and water. When hexamethylphosphoramide (HMPA) was added to the suspension of the prepared DME and diglyme complexes in toluene, fac-[LnCl 3(HMPA) 3] (Ln=La, Pr, Nd, Sm, Eu, Gd) complexes, isomorphous according to the unit cell determination, were formed. The crystal structure of [SmCl 3(HMPA) 3] was determined. Each samarium atom is octahedrally coordinated by three chlorine atoms and three HMPA molecules, which are distributed in a facial mode. The exchange of coordinated and free HMPA, as well as the reversible fac– mer isomerization of [LaCl 3(HMPA) 3], was observed by variable temperature 1H NMR spectroscopy. The associative mechanism of the exchange and isomerization was proposed.