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].