Bifunctional yttrium(III) and titanium(IV) NHC catalysts for lactide polymerisation.

Lewis acidic yttrium(III) and titanium(IV) derivatives of anionic, metal-tethered carbenes apparently act as bifunctional catalysts for the polymerisation of D,L-lactide, using a combination of Lewis acid and base functionalities to initiate ring opening of the cyclic monomer; the alcohol- and amino-functionalised carbenes from which they derive provide models for the first insertion step, and also display metal-free polymerisation catalysis to generate polylactic acid.

Thermally stable potassium N-heterocyclic carbene complexes with alkoxide ligands, and a polymeric crystal structure with distorted, bridging carbenes.

Alkoxide-functionalized N-heterocyclic carbenes (NHCs) stabilise the potassium-imidazole-2-ylidene fragment against 1,2 alkyl rearrangement reactions; this allows the first structural characterisation of a potassium NHC complex, which reveals distorted and unusual bonding interactions between the imidazole ring and the potassium cation.

Asymmetric lithium(I) and copper(II) alkoxy-N-heterocyclic carbene complexes; crystallographic characterisation and Lewis acid catalysis.

A one-pot synthesis of a wide range of bidentate, alkoxide-N-heterocyclic carbene ligands provides new lithium alkoxy-carbenes and a range of covalently bound organometallic Cu(II) carbene complexes, which are catalytically active, in some cases enantioselectively, for conjugate addition reactions.