Sergio Bambirra

Neutral versus cationic Group 3 metal alkyl catalysts: performance in intramolecular hydroamination/cyclisation

The relative catalytic activity of neutral dialkyl versus cationic monoalkyl Group 3 metal catalysts in the intramolecular hydroamination/cyclisation of the 2,2-dimethyl-4-pentenylamine reference substrate was investigated. This was found to depend strongly on the nature of the monoanionic ancillary ligand. With a bidentate amidinate ligand, the neutral catalysts were quite effective, but their cationic derivatives showed a much lower activity. The reaction kinetics suggest that this reflects an intrinsically higher activation barrier for the insertion of the olefinic moiety into the metal-amide bond for the cationic catalysts. In contrast, the neutral catalysts with tetradentate triamine-amide ligands showed a much lower activity than their cationic derivatives. It appears that this higher activity of the cationic triamine-amide catalysts reflects the beneficial effect of the additional available coordination space relative to the neutral species. The cationic triamine-amide yttrium catalysts are more active than the cationic amidinate catalysts of the same metal, possibly reflecting a stronger Y-amide bond in the latter, which is the more electron-deficient system.

Yttrium alkyl complexes with a sterically demanding benzamidinate ligand: synthesis, structure and catalytic ethene polymerisation

The benzamidinate yttrium dialkyl complexes [PhC(NAr)2]Y(CH2SiMe3)2(THF)n (Ar = 2,6-diisopropylphenyl; n = 1, 2) were prepared; when activated with [PhNMe2H][B(C6F5)4], the species with n = 1 polymerises ethene to polyethene with a narrow polydispersity.

Tris(4-methylbenzyl)(1,4,7-trimethyl-1,4,7-triazacyclononane)lanthanum(III)

The title compound, [La(C8H9)(3)(C9H21N3)], incorporating a fac-kappa N-3 ligand and formed by reaction of La(CH2C6H4-4-Me)(3) (THF)(3) (THF is tetrahydrofuran) and 1,4,7-trimethyl-1,4,7-triazacyclononane (Me-3-TACN), was synthesized in THF solution. In the crystal structure, the La atom is seven-coordinated by three N atoms from a TACN ligand and four C atoms from three benzyl ligands, one of which is bound eta(2).

An octa­hedrally coordinated trialk­ylyttrium(III): tris­(trimethyl­silylmeth­yl)(1,4,7‐trimethyl‐1,4,7‐triaza­cyclo­nona­ne)yttrium(III)

The crystal structure of the title compound, [Y(C4H11Si) 3( C9H21N3)], consists of monomeric species. In each of the three independent molecules in the asymmetric unit, the Y atom is in a slightly distorted octahedral environment, formed by the C atoms of three trimethylsilylmethyl ligands ( average Y - C = 2.427 angstrom) and three facially bound N atoms of the 1,4,7-trimethyl-1,4,7-triazacyclonane ligand ( average Y - N = 2.601 angstrom).

An octahedrally coordinated trialkylyttrium(III)

The crystal structure of the title compound, [Y(C4H11Si) 3( C9H21N3)], consists of monomeric species. In each of the three independent molecules in the asymmetric unit, the Y atom is in a slightly distorted octahedral environment, formed by the C atoms of three trimethylsilylmethyl ligands ( average Y - C = 2.427 angstrom) and three facially bound N atoms of the 1,4,7-trimethyl-1,4,7-triazacyclonane ligand ( average Y - N = 2.601 angstrom).

An octahedrally coordinated trialkylyttrium(III) : tris(trimethylsilylmethyl)(1,4,7-trimethyl-1,4,7-triazacyclononane)yttrium(III)

The crystal structure of the title compound, [Y(C4H11Si) 3( C9H21N3)], consists of monomeric species. In each of the three independent molecules in the asymmetric unit, the Y atom is in a slightly distorted octahedral environment, formed by the C atoms of three trimethylsilylmethyl ligands ( average Y - C = 2.427 angstrom) and three facially bound N atoms of the 1,4,7-trimethyl-1,4,7-triazacyclonane ligand ( average Y - N = 2.601 angstrom).

Neutral and cationic yttrium alkyl complexes with linked 1,4,7-triazacyclononane-amide monoanionic ancillary ligands: synthesis and catalytic ethene polymerisationElectronic supplementary information (ESI) available: experimental, spectroscopic and polymerization details. See http://www.rsc.org/suppdata/cc/b1/b101012n/Netherlands Institute for Catalysis Research (NIOK) publication no. RUG 01-4-01.

Yttrium dialkyl complexes [N,N′-R2-tacn-N″-(CH 2)2NBut]Y(CH2SiMe3) 2 (R = Me, Pri; tacn = 1,4,7-triazacyclononane) were prepared; when activated with [PhNMe2H][B(C6F5)4] these complexes form cationic alkyl species that are active ethene polymerisation catalysts.