Mixed-ligand guanidinate derivatives of rare-earth metals. Molecular structures of { (Me3Si)2NC(N-cyclo-Hex)2}Y[N(SiMe3)2]2, [{ (Me3Si)2NC(N-cyclo-Hex)2}YbI(THF)2]2, and [{(Me3Si)2N} Y(THF)(µ-Cl)]2 complexes

The insertion of N,N′-dicyclohexylcarbodiimide at one of the Y-N bonds of the [(Me3Si)2N]3Y complex in toluene at 70 °C afforded the monoguanidinate diamide derivative { (Me3Si)2NC(N-cyclo-Hex)2}Y[N(SiMe)3]2 (1) (cyclo-Hex is cyclohexyl) in 72% yield. The reaction of equimolar amounts of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate, which was prepared in situ from {(Me3Si)2N}Na and N,N′-dicyclohexylcarbodiimide, and YbI2(THF)2 in THF gave the [{(Me3Si)2NC(N-cyclo-Hex)2}YbI(THF)2]2 complex (2). An attempt to use this procedure for the synthesis of the yttrium compound { (Me3Si)2NC(NSiMe3)2}2YCl containing the sterically more hindered guanidinate ligand unexpectedly led to the formation of the diamide chloride complex [{(Me3Si)2N}2Y(THF)(µ-Cl)]2 (3). The structures of complexes 1–3 were established by X-ray diffraction. Compound 1 is mononuclear. Complexes 2 and 3 are dinuclear and contain two µ2-bridging halide ligands.