Naked (C5Me5)2M cations (M = Sc, Ti, and V) and their fluoroarene complexes.

The ionic metallocene complexes [Cp*(2)M][BPh(4)] (Cp* = C(5)Me(5)) of the trivalent 3d metals Sc, Ti, and V were synthesized and structurally characterized. For M = Sc, the anion interacts weakly with the metal center through one of the phenyl groups, but for M = Ti and V, the cations are naked. They each contain one strongly distorted Cp* ligand, with one (V) or two (Ti) agostic C-H.

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.

Structure of the decamethyl titanocene cation, a metallocene with two agostic C-h bonds, and its interaction with fluorocarbons.

The tetraphenylborate salt of the decamethyl titanocene cation, [Cp*2Ti][BPh4] (1, Cp* = C5Me5), was prepared by reaction of Cp*2TiH with [Cp2Fe][BPh4] and by reaction of Cp*2TiMe with [PhNMe2H][BPh4]. The crystal structure of 1 shows that the Cp*2Ti cation has a bent metallocene structure with agostic interactions with the metal center of two adjacent methyl groups on one of the Cp* ligands. Compound 1 reacts readily with THF to give the adduct [Cp*2Ti(THF)][BPh4] (2).

Benzyl anion abstraction from a (beta-diiminato)Fe(II) benzyl complex.

The 3-coordinate 12 VE iron(II) benzyl complex [(nacnac)-Fe(CH2Ph)] reacts with B(C6F5)3 to yield a paramagnetic contact ion pair with an eta 2-(o,m)-[PhCH2B(C6F5)3] anion, which was characterised by X-ray diffraction.

A highly efficient titanium-based olefin polymerisation catalyst with a monoanionic iminoimidazolidide pi-donor ancillary ligand.

The titanium complex Cp[1,3-(2',6'-Me2C6H3)2(CH2N)2C=N]Ti(CH2Ph)2, with a monoanionic eta 1-iminoimidazolidide ancillary ligand, is shown to be a highly efficient catalyst for olefin polymerisation when activated with the Lewis acid B(C6F5)3.

Switching a Catalyst System from Ethene Polymerization to Ethene Trimerization with a Hemilabile Ancillary Ligand.

A drastic ligand effect was observed in the catalytic ethene conversion by the substituted mono(cyclopentadienyl)titaniumtrichloride/methylalumoxane (MAO) catalysts shown. The catalyst with R=Me produces polyethene, whereas the catalyst with R=Ph selectively trimerizes ethene to 1-hexene. This switch in catalyst performance appears to be the result of a hemilabile behavior of the cyclopentadienyl ligand with the pendant arene group, involving reversible coordination of the arene moiety.