Macrocycle complexation chemistry 34. Polyethylene glycol and glycolate complexes of Th 4+. Preparation and structural characterization of [ThCl 3(pentaethylene glycol)]Cl·CH 3CN and the (Th 4+) 4 cluster, [Th 4Cl 8(O)(tetraethylene glycolate) 3]·3CH 3CN

Abstract

The reaction of pentaethylene glycol with ThCl 4 in 3/1 CH 3CN/CH 3OH produced [ThCl 3(EO5)]Cl·CH 3CN upon slow evaporation. The same reaction with tetraethylene glycol exhibits reduced ThCl 4 solubility. The only isolable product, a (Th 4+) 4 cluster, is the result of ionization of the glycol and incorporation of oxide impurities, [Th 4Cl 8(O)(EO4 2−) 3]·3CH 3CN. Both products were crystallographically characterized. [ThCl 3(EO5)]Cl·CH 3CN is monoclinic, Pc with (at 22 °C) a=8.857(2), b=12.364(4), c=9.685(2) Å, β=92.75(2)°, U=1059 Å 3, D calc=2.05 g cm −3 for Z=2 formula units, and R=0.031 for 1624 independent observed ( F o⩾5σ( F o)) reflections. [Th 4Cl 8(O)(EO4 2−) 3]·3CH 3CN is triclinic, P 1 with (at 22 °C) a=12.277(3), b=12.404(3), c=18.738(4) Å, α=73.01(2), β=77.71(2), γ=75.49(2)°, U=2611.7 Å 3, D calc=2.45 g cm −3 for Z=2 formula units, and R=0.040 for 5849 observed reflections. In the EO5 complex, the glycol wraps the metal ion with all six donor atoms coordinated to thorium. There are only three tight ion pairs with the fourth chloride anion accepting hydrogen bonds from the two alcoholic oxygen atoms. There are four Th 4+ ions in the glycolate cluster bridged by a μ 4-oxide. Each of the three tetraethylene glycolate ligands wraps one Th atom and bridges it (via the terminal alkoxide) to two other Th atoms in the cluster. There are two bridging and six terminal chloride anions. The four thorium atoms are crystallographically unique, however, there are only three different Th environments.