{Bis[N,N'-dicyclo-hexyl-N'',N''-bis-(tri-meth-yl-sil-yl)guanidinato-κ(2)N,N']neo-dymium(III)}di-µ-chlorido-[bis-(tetra-hydro-furan-κO)lithium].

In the title monomeric rare earth complex, [LiNd(C(19)H(40)N(3)Si(2))(2)Cl(2)(C(4)H(8)O)(2)], the [(Me(3)Si)(2)NC(NCy)(2)](2)Nd(+) (Me is methyl, Cy is cyclo-hex-yl) and Li(THF)(2) (+) units (THF is tetra-hydro-furan) are connected by two bridging Cl atoms. The Nd(3+) ion is coordinated by two guanidinate ligands and two Cl atoms, forming a distorted chelating octa-hedral geometry. The Li(+) ion is four-coordinated by two Cl atoms and two O atoms from THF mol-ecules in a distorted tetra-hedral geometry.

Rare earth metal bis(silylamide) complexes bearing pyridyl-functionalized indenyl ligand: synthesis, structure and performance in the living polymerization of L-lactide and rac-lactide.

Amine elimination of rare earth tris(silylamide) complexes Ln[N(SiHMe(2))(2)](3)(THF)(2) (Ln = La, Sm, Er, Lu) with 1 equiv. of the pyridyl-functionalized indenyl ligand C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α afforded a series of neutral mono-indenyl-ligated rare earth metal bis(silylamide) complexes (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)Ln[N(SiHMe(2))(2)](2) (Ln = La (1), Sm (2), Er (3), Lu (4)) in 83-87% isolated yields. Reaction of La[N(SiHMe(2))(2)](3)(THF)(2) with 2 equivalents of C(9)H(7)CMe(2)CH(2)C(5)H(4)N-α provided the neutral bis(indenyl) lanthanum mono(silylamide) complex (C(9)H(6)CMe(2)CH(2)C(5)H(4)N-α)(2)LaN(SiHMe(2))(2) (5). These complexes were characterized by elemental analysis, FT-IR and NMR (except for 3 for the strong paramagnetic property of the central metal). X-ray single crystal structural diffraction showed that 1-4 are isostructural and the central metals are four-coordinated by one indenyl ring, one nitrogen atom from the pendant pyridyl group, and two amide groups to form a distorted tetrahedral geometry; while the central metal in 5 is five-coordinated by two indenyl rings, two nitrogen atoms from the pendant pyridyl groups, and one amide group to adopt a distorted pyramidal geometry, if the indenyl ring is regarded as occupying an independent vertex. The monoanionic pyridyl-functionalized indenyl ligand is bonded to the central metal in η(5)/κ(1) constrained geometry configuration (CGC) mode. 1-4 are highly active for the ring-opening polymerization of L-lactide and rac-lactide. In the presence of 2 equivalents of benzyl alcohol, 1 shows high activity toward L-lactide and rac-lactide in a living fashion.