184 research outputs found
Triazolium-containing metal-organic frameworks: Control of catenation in 2-D Copper(II) paddlewheel structures
Paper accepted for publication 6th November 2012One approach to exploit MOFs as heterogeneous catalyst platforms requires the development of materials containing groups that can be utilised to anchor a catalytic moiety into the links within the structure. Here we report the synthesis of the first integrated triazolium-containing MOF linker and the first MOFs containing linkers of this type. 1,4-Bis(4-benzoic acid)-1-methyl-1H-1,2,3-triazolium chloride, HâL1áŽčá”, was synthesised in three steps by a 'Click' reaction of methyl 4-ethynylbenzoate with methyl 4-azidobenzoate, methylation using methyl triflate, followed by ester hydrolysis in overall 74% yield. The equivalent neutral triazole precursor, 1,4-bis(4-benzoic acid)-1H-1,2,3-triazole hydrochloride, HâL1(HCl), was also prepared and a comparison of the chemistry with Zn(NOâ)2·6HâO and Cu(NOâ)â·3HâO is presented. [Zn(L1)â(HâO)â] is a 2-D MOF with infinite chains of zinc carboxylates bridged by L1, while an equivalent structure is not observed for L1áŽčá”. In turn, two catenation isomers of [Cuâ(DMF)2(L1áŽčá”)2](NO3)â were isolated from a single reaction of L1áŽčá” and Cu(NOâ)â·3HâO. The α-form, a close-packed 3-fold interpenetrated structure, was obtained from reactions undertaken in the presence of nitric acid or at lower temperatures, while undertaking the reaction at higher temperatures leads to a predominance of the 2-fold interpenetrated and potentially porous ÎČ-form of the structure. The work presented provides further support for the use of reaction conditions to control interpenetration and additional evidence that charge on structurally similar ligands can drastically alter the types of structures that are accessible due to the requirements for charge balance in the final product.Alexandre M. Burgun, Christian J. Doonan, and Christopher J. Sumb
Chirality transfer in metal-Ââcatalysed intermolecular addition reactions involving allenes
Allene chemistry in the presence of transition metal complexes is nowadays a very important topic that underpins many challenges and advances in organic synthesis. The amount of research articles covering new transformations of allenes is vast and the development of enantioselective reactions involving allenes has flourished in the last 10-15 years. In this review we cover three important topics in allene chemistry that we feel are timely appropriate for this special issue celebrating the work of Prof Trost: the metal-catalysed reactions involving chirality transfer from chiral allenes to products; the analysis of the possible racemization processes that have been observed in the interaction of some metals with allenes; and the chirality transfer using racemic allenes in reactions catalysed by metal complexes bearing chiral ligands to produce enantioriched products. We have focussed the review on intermolecular addition reactions as they are still much less explored than the intramolecular version
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