Synthesis, characterization, and reactivity of mono(phospholyl)lanthanoid(III) bis(dimethylaminobenzyl) complexes

Reaction of 2,5-di-tert-butyl-3,4-dimethylphospholide potassium [K(Dtp)] with YCl3 or SmI3(THF)(3.5) in THF followed by reaction with o-dimethylaminobenzylpotassium [K(CH2C6H4NMe2-o)] afforded the solvent-free mono(phospholyl)lanthanoid bis(benzyl) complexes [(Dtp)Ln(CH2C6H4NMe2-o)] (Ln = Y (3-Y), Sm (3-Sim)). The Sc analogue could not be obtained under these conditions, as the reaction between K(Dtp) and ScCl3 in THF led to the THF-ring-opened product [{Sc[mu-O(CH2)(4)(Dtp)]Cl-2(THF)(2)}(2)] (5). Replacing THF by a mixture of toluene/pyridine gave [(Dtp)ScCl2(pyridine)] (6), which on further reaction with [K(CH2C6H4NMe2-o)] in toluene afforded [(Dtp)Sc(CH2C6H4NMe2-o)(2)] (3-Sc). Protonation of [K(Dtp)] with p-toluenesulfonic acid gave the 1H phosphole Dtp-H (7), which could not be isolated pure but is stable in solution at room temperature. 3-Sc could also be obtained from the reaction between the in-situ-prepared 7 and [Sc(CH2C6H4NMe2-o)(3)] in toluene. Complexes 3-Ln were activated with [Ph3C][B(C6F5)(4)] and tested in the syndiospecific polymerization of styrene. Whereas 3-Sm did not show any activity, 3-Y and 3-Sc gave good to excellent results.