Synthesis and characterization of homoleptic lanthanide guanidinate complexes and their catalytic activity for the ring-opening polymerization of trimethylene carbonate

Two methods to synthesize homoleptic guanidinate lanthanide complex are described. The samarium guanidinate complex [Sm{Ph2NC(NCy)(2)}(3)](.)2C(7)H(8) (1) can be synthesized by the metathesis reaction of lithium guanidinate with anhydrous samarium trichloride in a 3:1 molar ratio. The analogous complexes [Ln{Ph2NC(NCy)(2)}(3)](.)2C(7)H(8) [Ln = Yb (2), Nd (3)] can also be synthesized by the insertion reaction of N,N'-dicyclohexylcarbodiimide into the Ln-N bond of [(THF)(4)Li][Ln(NPh2)(4)] in a 3:1 molar ratio in good yield. Complexes 1-3 were characterized by elemental analysis, IR and H-1 NMR spectroscopy. The molecular structures of complexes 1 and 3 were further determined by X-ray diffraction techniques. These complexes showed high activity for the ring-opening polymerization of trimethylene carbonate (TMC), giving polymers with M-w/M-n ranging from 1.41-1.73. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.