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(CH₂C ₆H₄NMe₂-o)] afforded the solvent-free mono(phospholyl)lanthanoid bis(benzyl) complexes [(DtP)Ln(CH₂CoH ₄NMe₂-o)] (Ln = Y (3-Y), Sm (3-Sm)). 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[μ-O(CH ₂)₄(Dtp)]Cl₂(THF)₂}₂] (5). Replacing THF by a mixture of toluene/pyridine gave [(Dtp)ScCl ₂(pyridine)] (6), which on further reaction with [K(CH ₂C₆H₄NMe₂-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(CH₂C₆H₄NMe ₂-o)₃] in toluene. Complexes 3-Ln were activated with [Ph₃C]-[B(C₆Fs)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.