Synthesis, structure and reactivity of guanidinate rare earth metal bis(o-aminobenzyl) complexes

Abstract

A series of guanidinate rare-earth metal complexes [(PhCH₂)₂NC(NC₆H₄ⁱPr₂-2,6)₂]RE(CH₂C₆H₄NMe₂-o)₂ (RE = Y (2a), La (2b), Dy (2c), Lu (2d)) were synthesized by the acid–base reaction of RE(CH₂C₆H₄NMe₂-o)₃ with (PhCH₂)₂N[C(NHR)(NR)] (R = 2,6-ⁱPr₂-C₆H₃) (1) in THF. Treatment of complexes 2 with two equivalents of carbon dioxide, sulfur and phenyl isothiocyanate gave the corresponding insertion products {[(PhCH₂)₂NC(NC₆H₄ⁱPr₂-2,6)₂]RE(μ-η²:η¹-O₂CCH₂C₆H₄NMe₂-o)(μ-η¹:η¹-O₂CCH₂C₆H₄NMe₂-o)}₂ (RE = Y (3a), La (3b), Dy (3c), Lu (3d)), {[(PhCH₂)₂NC(NC₆H₄ⁱPr₂-2,6)₂]RE[μ-S(CH₂C₆H₄NMe₂-o)]₂}₂ (RE = Y (4a), La (4b), Dy (4c), Lu (4d)) and {[(PhCH₂)₂NC(NC₆H₄ⁱPr₂-2,6)₂]RE{SC(CH₂C₆H₄NMe₂-o)NPh}₂ (RE = Y (5a), La (5b), Dy (5c), Lu (5d)) in good yields, respectively. All new complexes were fully characterized by NMR spectroscopy and elemental analysis. The structures of 1, 2d, 3, 4a, 4c–d, 5a, and 5c–d were established by X-ray diffraction studies. Complexes 2 were found to have a high activity and excellent 3,4-selectivity for isoprene polymerization in the presence of [Ph₃C][B(C₆F₅)₄].