New complexes of lanthanide chlorides. Reversible isomerization in octahedral [LaCl3(HMPA)(3)] and the crystal structure of fac-[SmCl3(HMPA)(3)]

Complexes of [ LnCl(3)L] (Ln = La, Nd, Sm, Eu, and L = diethylene glycol di methyl ether, diglyme; Ln = La, Pr, and L = dimethoxyethane, DME) were prep ared from the lanthanide oxides and hydrogen chloride, which was formed in situ from chlorotrimethylsilane and water. When hexamethylphosphoramide (HM PA) was added to the suspension of the prepared DME and diglyme complexes i n toluene, fac-[LnCl(3) (HMPA)(3)] (Ln = La, Pr, Nd, Sm, Eu, Gd) complexes, isomorphous according to the unit cell determination, were formed. The cry stal structure of [SmCl3(HMPA)(3)] was determined. Each samarium atom is oc tahedrally coordinated by three chlorine atoms and three HMPA molecules, wh ich are distributed in a facial mode. The exchange of coordinated and free HMPA, as well as the reversiblefac-merisomerization of [LaCl3(HMPA)(3)], wa s observed by variable temperature H-1 NMR spectroscopy. The associative me chanism of the exchange and isomerization was proposed. (C) 2000 Elsevier S cience Ltd All rights reserved.