In this paper a novel ligand of the type [PNPNH] is presented for the application in a new homogeneous highly selective ethene trimerization system for the formation of 1‐hexene, which consists of the chromium source CrCl3(thf)3, the ligand Ph2PN(iPr)P(Ph)N(iPr)H (1), and Et3Al as an activator in toluene. The excellent characteristics of this new system, e.g. very high selectivity to C6 with highest purity of the C6 fraction (>99 % 1‐hexene), activity on a constant level on a long timescale, use of small amounts of Et3Al as a cheap activator, and only very low production of PE, make it to a hot candidate for industrial application. Its organometallic background gives an indication of the nature of the active catalyst species.

The first ruthenium olefin metathesis catalyst with rigid cis stereochemistry of two phosphane ligandsin a square-pyramidal structure, [

Cationic Ru carbene complexes with tBu PCH PtBu (dtbpm) as a chelating ligand, which are accessible by chloride abstraction from neutral precursors [(κ -dtbpm)Cl Ru=CHR] with trimethylsilyl triflate, are established as highly efficient ring opening metathesis polymerization catalysts (see scheme). Solv=solvent.

The bonding nature of metallocene acetylene complexes Cp 2 M(η 2 -H 3 SiC 2 SiH 3 ) 1M and Cp 2 M(η 2 -HC 2 H) 1M 0 (M = Ti, Zr, Hf) was studied by density functional theory method. It is found that this acetylene complex has indeed a metallacyclopropene moiety with two in-plane M-C σ-bonds and one out-of-plane π-bond interacting with the metal center, resulting in the formation of a delocalized three-center and two-electron (3c-2e) system. Along with its delocalized out-of-plane bonding, this complex has been characterized as aromatic on the basis of the computed stabilizing energy and negative nucleus-independent chemical shifts (NICS). The aromatic stabilization increases from Ti to Zr and Hf, and this is because of the increased charge separation between the Cp 2 M fragment and the H 3 SiC 2 SiH 3 (also HC 2 H) unit. The decrease of the M-C bond length from Zr to Hf is attributed to the increased s character of both M and C hybridization of the M-C σ-bonds.

Cp*2Ti(OTf) (2) was prepared by oxidation of the known(alkyne)titanocene complex Cp*2Ti(η2‐Me3SiC2SiMe3) with Fe(OTf)3. This reaction is highly selective; formation of Cp*2Ti(OTf)2 by using an excess of the oxidizing agent was not observed. Complex 2 was treated with water to give Cp*2Ti(OH)(OTf) (5) and hydrogen gas. This reaction was monitored by GC and volumetric analysis. Complexes 2 and 5 were characterized by X‐ray crystallography and investigated by DFT analysis.