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.

A significant acceleration effect of a beta-silicon atom was observed on the electrocyclic ring-opening reaction of benzocyclobutene derivatives to form o-quinodimethanes. This acceleration effect could be attributed to an electronic sigma-donating nature of the C(alpha)-Si(beta) bond, associated with alpha-anion driven pericyclic reactions.

Methyl and n-butyl thorium complexes of a rigid 2,6-bis(anilidomethyl)pyridine ligand have been prepared; the n-butyl complex is thermally stable, even at 60 degrees C, while the methyl complexes exhibit a high tendency to eliminate methane via sigma-bond metathesis.

The bond energy (BE) of CC in CH3-CH3 with respect to geometry frozen fragments follows a sigmoidal increase as function the θ = HCC pyramidalization angle. Using dynamic orbital forces BE index, same behaviour unique 〈θ〉 parameter, mean angle substituents, is found for 24 single bonds various hydrocarbons. Thus parameter appears straightforward and robust index geometrical constraints which ca...

We provide a rigorous model-free definition and a detailed theoretical analysis of the electron-charge displacements making up the donation and back-donation components of the Dewar-Chatt-Duncanson model in some realistic catalytic intermediates of formula L-Au(I)-S in which L is an N-heterocyclic carbene or Cl(-) and S is an eta(2)-coordinated substrate containing a C-C multiple bond. We thus ...

The simplest transport problem, namely finding the maximum flow of current, or maxflow, is investigated on critical percolation clusters in two and three dimensions, using a combination of extremal statistics arguments and exact numerical computations, for power-law distributed bond strengths of the type P(sigma) approximately sigma(-alpha). Assuming that only cutting bonds determine the flow, ...

Let $A$ be a Noetherian ring, $I$ be an ideal of $A$ and $sigma$ be a semi-prime operation, different from the identity map on the set of all ideals of $A$. Results of Essan proved that the sets of associated prime ideals of $sigma(I^n)$, which denoted by $Ass(A/sigma(I^n))$, stabilize to $A_{sigma}(I)$. We give some properties of the sets $S^{sigma}_{n}(I)=Ass(A/sigma(I^n))setminus A_{sigma}(I...