Trans-effects in octahedral transition metal complexes

Catalytic ethylene oligomerization represents a topic of considerable current academic and industrial interest, in particular for the production of linear α-olefins in the C4−C10 range, whose demand is growing fast. Identifying and fine-tuning the parameters that influence the activity and selectivity of metal catalysts constitute major challenges at the interface between ligand design, coordination/organometallic chemistry, and homogeneous catalysis. In this Account, we show how comparative studies aiming at modulating the coordinating properties of functional ligands for a metal, such as nickel, which is used in industrial processes, lead to beneficial effects in catalytic ethylene oligomerization.

Catalytic Ethylene Dimerization and Oligomerization: Recent Developments with Nickel Complexes Containing P,N-Chelating Ligands

The early years of alkyne metathesis were marked by a somewhat ironic state of affairs: the proposed mechanism was swiftly validated and more than one effective catalyst became available shortly after the discovery of this transformation; surprisingly, however, the impact on synthesis remained very limited for a long period of time. Recent advances, however, suggest that this situation is about to change: the remarkable activity, functional-group tolerance, and reliability of the latest generation of catalysts open the door for highly advanced applications. The resulting (cyclo)alkynes are amenable to numerous postmetathetic transformations, which diversify the product portfolio and bring many different structural motifs into reach. Since the catalysts have also evolved from the glovebox to the benchtop, there should be little barrier left for a wider use of this reaction in organic synthesis.

Alkyne metathesis on the rise.

There has been rapid progress and growing interest in alkyne metathesis within the past decade. The availability of highly active catalysts as well as their applications in both organic synthesis and polymer chemistry has served to motivate the advancement of this field. In this article, the development of several different metathesis catalysts, including two heterogeneous ones, are reviewed with an emphasis on comparing strengths and weaknesses. In Section 4, the applications of alkyne metathesis to synthesis of natural products, conjugated polymers as well as shape-persistent macrocycles are discussed. In the last section, a comparison of alkyne metathesis to the well established alkene metathesis is given. Developing an alkyne metathesis catalyst with both high reactivity and robustness to air and moisture remains an unsolved problem of this important and useful reaction.

Alkyne Metathesis: Catalysts and Synthetic Applications

This invention relates to a polymer comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 15 mole % of ehtylene, where the polymer has: a) a Dot T-Peel of 1 Newton or more; and b) a branching index (g') of 0.95 or less measured at the Mz of the polymer; c) an Mw of 100,000 or less and to a continuous process to produce a branched olefin polymer comprising 1) selecting a first catalyst component capable of producing a polymer having an Mw of 100,000 or less and a crystallinity of 5% or less under selected polymerization conditions; 2) selecting a second catalyst component capable of producing polymer having an Mw of 100,000 or less and a crystallinity of 20% or more at the selected polymerization conditions; 3) contacting the catalyst components in the presence of one or more activators with one or more C3 to C40 olefins, and, optionally one or more diolefins; 4) at a temperature of greater than 100°C; 5) at a residence time of 120 minutes or less; 6) wherein the ratio of the first catalyst to the second catalyst is from 1:1 to 50:1; 7) wherein the activity of the catalyst components is at least 100 kilograms of polymer per gram of the catalyst components; and wherein at least 20% of the olefins are converted to polymer.

Multiple catalyst system for olefin polymerization and polymers produced therefrom

Novel chromlum-containing compounds, such as, for example, chromium pyrrolides, are prepared by forming a mixture of a chromium salt, a metal amide, and an electron pair donor solvent, such as, for example, an ether. These novel chromium-containing, or chromium pyrrolide, compounds can be used either unsupported or supported on an inorganic oxide support to trimerize and/or polymerize olefins.

Chromium compounds and uses thereof

Reactions involving alkynes and tungsten-tungsten triple bonds supported by alkoxide ligands

Evidence for Equilibria between μ‐Alkyne and Alkylidyne Complexes of Tungsten Alkoxides: [W2(OR)6(μ‐C2R′2)] ⇌ 2[(RO)3W ≡ CR′]

Olefin polymerization catalysts, processes for preparing the catalysts and processes for producing polyolefins utilizing the catalysts are provided. The catalysts are basically comprised of a trialkylsilylamide-chromium complex adsorbed on an activated inorganic compound.

Brian K. Conroy

Papers

Chromium compounds and uses thereof

Reactions involving alkynes and tungsten-tungsten triple bonds supported by alkoxide ligands

Evidence for Equilibria between μ‐Alkyne and Alkylidyne Complexes of Tungsten Alkoxides: [W2(OR)6(μ‐C2R′2)] ⇌ 2[(RO)3W ≡ CR′]

Olefin polymerization catalysts and processes

Competitive carbon-carbon bond formation and cleavage and cluster formation in the reaction between 3-hexyne and hexaisopropoxyditungsten