Adam J. Clarke

Spacer Control of Directionality in Supramolecular Helicates Using an Inexpensive Approach

Careful selection of the spacer group used to separate the metal-binding domains allows control of the directionality in a helix; self-assembly leads uniquely to a double-helical cation with a head-to-tail (HT) configuration (shown schematically) in both the solid state and solution.

Catalytic alkene cyclohydroamination via an imido mechanism

Chiral-at-metal half-sandwich diamide complexes catalyse enantioselective cyclohydroamination of aminoalkenes at unexpectedly high rates given their high coordination number and steric bulk; substantial evidence is presented which argues against the established sigma-bond insertion process and is strongly indicative of an imido [2+2] cycloaddition mechanism.

Solvents for ring-closing metathesis reactions

A study of the influence of eight diverse solvents on a Grubbs II-catalysed ring-closing metathesis (RCM) reaction reveals a complex dependence of the different reaction steps on the solvent and suggests acetic acid as a useful solvent for RCM reactions.

Efficient predetermination of chirality-at-zirconium

Only one of eight possible diastereomers of the organometallic chiral-at-metal complex [ZrL2(CH2Ph)2] (L = a bidentate, chiral non-racemic pyrdine alcoholate) is observed by NMR spectroscopy in the slow exchange regime.

Problems and solutions for alkene polymerisation catalysts incorporating Schiff-bases; migratory insertion and radical mechanisms of catalyst deactivation

Steric blocking of an intramolecular 1,2-migratory insertion reaction of a zirconium salicylaldiminato complex leads to a long-lived catalyst for ethene polymerisation, but promotes a new radical catalyst decomposition mechanism in certain instances; kinetic and thermodynamic parameters for both pathways have been established.

Umbrella motion in aziridines: use of simple chemical inputs to reversibly control the rate of pyramidal inversion

The molecular motion associated with atomic inversion at an aziridine nitrogen can be essentially halted by metal complexation; addition of a second chemical input that decomplexes the metal from the aziridine restores fast inversion (k=40 s(-1) at 303 K).