Unusual nature of lanthanide chloride–alkali metal chloride M3LnCl6 compounds in the solid state

Flexible coordination environments of lanthanide complexes grown from chloride-based ionic liquids

“…We also chose to study the more readily available hydrated LnCl 3 salts, and conduct the studies in the open atmosphere, rather than utilize the stricter and more expensive anhydrous conditions previously studied. [13][14][15]18,20 It was anticipated that the Cl À anion would help solubilize the hydrated lanthanide salts and also provide a Cl À -rich environment leading to higher coordination numbers. Evidence for this has come from spectroscopic investigations revealing the presence of non-octahedral f-element centers in solution, 23 as well as our own work with the isolation of unique coordination environments of f-element centers from ILs.…”

“…Crystal structures such as [C 3 mpyr] 2 [Yb(NTf 2 ) 4 ] (C 3 mpyr = 1-propyl-1-methylpyrrolidinium) are also known, where the coordination of the 'non-coordinating' [NTf 2 ] À anion 16 and other weakly coordinating IL anions show that even the most non-interacting ILs can help stabilize unique environments in both the solid and solution states. A recent paper has even suggested lanthanide-containing 'IL-like' materials are possible where the lanthanide complex anion serves as the IL counterion, as for example in 17 The [LnCl 6 ] 3À anion can be prepared in high-temperature ionic melts composed of metal-metal chloride (M 3 LnCl 6 ) environments with the use of organic halide directing agents, 18 but in molecular solvents, the chloride ions are quickly replaced by water. Even in 14.0 M LiCl, only partial chloride complexation and further dehydration of the metal center is observed.…”