Macrocycle complexation chemistry 32. Modification of the lanthanide ion coordination sphere via electrocrystallization of hydrated lanthanide chloride complexes of 12-Crown-4

Abstract

Electrochemical techniques have been utilized to modify the crystallization of 12-crown-4 complexes of PrCl 3· nH 2O from CH 3CN:CH 3OH (3:1) solutions. [PrCl 3(OH 2)(12-crown-4)]·12-crown-4 crystallized from a 10:1 (12-crown-4:Pr) solution in the centric space group Pnma, with a = 23.338(7), b = 13.103(5), c = 7.713(4) Å and D calc = 1.74 g cm −3 for Z = 4. [PrCl 3(OHMe)(12-crown-4)] crystallized in the centric P 1 , with a = 7.486(3), b = 9.365(4), c = 11.268(4) Å, α = 91.92(3), β = 93.87- (3), γ = 102.00(3)° and D calc = 1.96 g cm −3 for Z = 2. Both complexes differ markedly from the series of 12-crown-4 early lanthanide chloride complexes that were obtained by slow evaporation ([M(OH 2) 5− (12-crown-4)]Cl 3·2H 2O).Utilization of an electrochemical cell produces complexes in which all three chloride anions are in the metal's primary coordination sphere, the coordination number is reduced, and most of the water or solvent molecules are eliminated.