The selective insertion of carbon dioxide into a lanthanide(III) 2,6-di-t-butyl-phenoxide bond

An investigation of the CO2(g) insertion products for a series of fully characterized monomeric lanthanide 2,6-di-t-butyl-phenoxide compounds ([Ln(DBP)(3)]; Ln = Ce (1), Sm (2), Dy (3), Y (4), Er (5), Yb (6), and Lu (7)) was undertaken at low pressure (<5 psi). From the products isolated, only one CO2(g) molecule per molecule [Ln(DBP)(3)] was found to insert, forming either the [Ce(mu(c)-O2C-DBP)(DBP)(2)](2) (8) or [Ln(mu-O2C-DBP)(DBP)(2)](2) (Ln = Sm (9), Dy (10), Y (11), Er (12), Yb (13), and Lu (14)) structure. The purity of the bulk powders of 8-14 were verified by FT-IR and elemental analyses; however solution structures could not be studied due to the low solubility of the complexes. Higher pressures to increase the degree of CO2(g) insertions did not alter the degree of substitution. The selectivity of CO2(g) insertion was attributed to an interaction of the methyl moieties of the DBP ligand blocking coordination sites on the Ln metal center, as observed in the solid and solution state of 1-7. (c) 2012 Elsevier Ltd. All rights reserved.