The crystal structure of a many-fold connected complex of lanthanum in Cs3La(N3)6

An unexpected lanthanum chloride carbonate hydrate: synthesis, crystal structure, vibrational spectra and thermal degradation of LaCl[CO3]·3H2O

Microcrystalline powders of LaCl[CO3]·3H2O were precipitated and isolated from stoichiometric aqueous solutions of LaCl3·7H2O and Na2[CO3]·10H2O. This confirmed the surprising emergence of corresponding single crystals during a reaction of equimolar aqueous solutions of LaCl3·7H2O and Na[N3] under ambient conditions by the uptake of atmospheric CO2. According to the X-ray structure analysis of colorless, transparent and rectangular single-crystals, LaCl[CO3]·3H2O adopts an orthorhombic structure, space group Pbca with the unit-cell parameters a=856.82(5), b=1598.57(9) and c=967.68(6) pm for Z=8. The tenfold coordination polyhedron around La3+ consists of two monodentate as well as two bidentate [CO3]2− anions together with three oxygen atoms from coordinating water molecules and one chloride anion. According to DSC/TG studies and X-ray powder diffraction, LaCl[CO3]·3H2O loses first its water and then carbon dioxide under thermal treatment up to 900°C to leave LaOCl behind. Vibrational infrared and Raman spectra confirmed the presence of H2O and [CO3]2− in LaCl[CO3]·3H2O and its stepwise degradation at elevated temperatures.