Highly active aluminium catalysts for room temperature ring-opening polymerisation of rac-lactide.

A new series of aluminium complexes bearing 'catam' ligands has been synthesised and fully characterised. They were found to exhibit high activity at room temperature for rac-lactide ring-opening polymerisation, a rather rare feature for aluminium-based catalysts.

The impact of ionic liquids on the coordination of anions with solvatochromic copper complexes.

Solvatochromic transition metal (TM)-complexes with weakly associating counter-anions are often used to evaluate traditional neutral solvent and anion coordination ability. However, when employed in ionic liquids (IL) many of the common assumptions made are no longer reliable. This study investigates the coordinating ability of weakly coordinating IL anions in traditional solvents and within IL solvents employing a range of solvatochromic copper complexes. Complexes of the form [Cu(acac)(tmen)][X] (acac = acetylacetonate, tmen = tetramethylethylenediamine) where [X]- = [ClO4]-, Cl-, [NO3]-, [SCN]-, [OTf]-, [NTf2]- and [PF6]- have been synthesised and characterised both experimentally and computationally. ILs based on these anions and imidazolium and pyrrolidinium cations, some of which are functionalised with hydroxyl and nitrile groups, have been examined. IL-anion coordination has been investigated and compared to typical weakly coordinating anions. We have found there is potential for competition at the Cu-centre and cases of anions traditionally assigned as weakly associating that demonstrate a stronger than expected level of coordinating ability within ILs. [Cu(acac)(tmen)][PF6] is shown to contain the least coordinating anion and is established as the most sensitive probe studied here. Using this probe, the donor numbers (DNs) of ILs have been determined. Relative donor ability is further confirmed based on the UV-Vis of a neutral complex, [Cu(sacsac)2] (sacsac = dithioacetylacetone), and DNs evaluated via23Na NMR spectroscopy. We demonstrate that ILs can span a wide donor range, similar in breadth to conventional solvents.

Single operation palladium catalysed C(sp3)-H functionalisation of tertiary aldehydes: investigations into transient imine directing groups.

Simple amine and diamine derivatives can promote the palladium catalysed direct ß-C-H arylation of aliphatic aldehydes via transient imine formation. Trifluoroacetate was shown to be crucial in promoting the reaction. Sub-stoichiometric quantities of simple N-tosylethylenediamine was shown to form a bidentate directing group with an imine linkage. Isolation of an unsymmetrical palladacycle has shown different potential binding modes of the secondary NTs coordinating group by single crystal X-ray diffraction analysis, suggestive of a hemilabile ligand.

Tetravalent silicon connectors MenSi(p-C6H4CO2H)(4-n) (n = 0, 1, 2) for the construction of metal-organic frameworks.

A series of silicon-centered connecting units, Me(n)Si(p-C6H4CO2H)(4-n) (n = 0, 1, 2), have been prepared and their coordination polymers with Zn(II) metal atoms studied. The tetra-acid L1 (n = 0) acts as a tetrahedral node and reacts with Zn(II) centers to give 1, a novel interpenetrating 3D network containing distorted tetrahedral bimetallic secondary building units (SBUs). The triacid L2 (n = 1) acts as a trigonal pyramidal node and forms an intercalated 2D layered network, 2, with Zn(II) ions, containing distorted octahedral tetranuclear SBUs. Last, the bent diacid L3 (n = 2) reacts with Zn(II) centers to give 3, a corrugated 2D layered structure containing 1D zinc hydroxo chains. Together these three new coordination polymers demonstrate the potential versatility of tetravalent silicon containing connecting ligands for metal-organic framework construction.