Main group multiple bonds for bond activations and catalysis

Since the discovery that the so called ‘double-bond’ rule could be broken, the field of molecular main group multiple bonds has expanded rapidly. With the majority of homodiatomic double and triple bonds realised within the p-block, along with many heterodiatomic combinations, this minireview examines the reactivity of these compounds with a particular emphasis on small molecule activation. Furthermore, whilst their ability to act as transition metal mimics has been explored, their catalytic behavior is somewhat limited. This minireview aims to highlight the potential of these complexes towards catalytic application and their role as synthons in further functionalisations making them a versatile tool for the modern synthetic chemist

Experimental realisation of elusive multiple-bonded aluminium compounds : a new horizon in the aluminium chemistry

The synthesis and isolation of stable main group compounds featuring multiple bonds has been of great interest for several decades. A plethora of such multiply bonded complexes have been obtained by using sterically demanding substituents that provide both kinetic and thermodynamic stability. Most of these compounds have unusual structural and electronic properties that challenge the classical concept of covalent multiple bonding. In contrast, analogous aluminium compounds are scarce in spite of its high natural abundance. The parent dialumene (Al2H2) has been calculated to be extremely unstable, thus making compounds containing Al multiple bonds a challenging synthetic target. This Review provides an overview of the recent advances in the cutting edge synthetic approaches and the careful ligand design used to obtain aluminium homo‐ and heterodiatomic multiply bonded complexes. In addition, the reactivity of these novel compounds towards various small molecules and reagents will be discussed herein

Destruction of chemical warfare agent simulants by air and moisture stable metal NHC complexes

The cooperative effect of both NHC and metal centre has been found to destroy chemical warfare agent (CWA) simulants. Choice of both the metal and NHC is key to these transformations as simple, monodentate N-heterocyclic carbenes in combination with silver or vanadium can promote stoichiometric destruction, whilst bidentate, aryloxide-tethered NHC complexes of silver and alkali metals promote breakdown under mild heating. Iron–NHC complexes generated in situ are competent catalysts for the destruction of each of the three targetted CWA simulants

CO2 fixation and catalytic reduction by a neutral aluminum double bond

CO2 fixation and reduction to value‐added products is of utmost importance in the battle against rising CO2 levels in the Earth's atmosphere. An organoaluminum complex containing a formal aluminum double bond (dialumene), and thus an alkene equivalent, was used for the fixation and reduction of CO2. The CO2 fixation complex undergoes further reactivity in either the absence or presence of additional CO2, resulting in the first dialuminum carbonyl and carbonate complexes, respectively. Dialumene (1 ) can also be used in the catalytic reduction of CO2, providing selective formation of a formic acid equivalent via the dialuminum carbonate complex rather than a conventional aluminum–hydride‐based cycle. Not only are the CO2 reduction products of interest for C1 added value products, but the organoaluminum complexes isolated represent a significant step forward in the isolation of reactive intermediates proposed in many industrially relevant catalytic processes

NHI- and NHC-supported Al(III) hydrides for amine–borane dehydrocoupling catalysis

The catalytic dehydrocoupling of amine–boranes has recently received a great deal of attention due to its potential in hydrogen storage applications. The use of aluminum catalysts for this transformation would provide an additional cost-effective and sustainable approach towards the hydrogen economy. Herein, we report the use of both N-heterocyclic imine (NHI)- and carbene (NHC)-supported Al(III) hydrides and their role in the catalytic dehydrocoupling of Me2NHBH3. Differences in the σ-donating ability of the ligand class resulted in a more stable catalyst for NHI-Al(III) hydrides, whereas a deactivation pathway was found in the case of NHC-Al(III) hydrides

Facile kinetic induction of a dihydropyridide to pyrrolide ring contraction

A sterically demanding N-aryl carbodiimide reacts with magnesium 1,4-dihydropyridides to initiate heterocyclic ring contraction and pyrrolide formation under unprecedentedly mild conditions.</p

Isolation of cyclic aluminium polysulfides by stepwise sulfurization

Despite the notable progress in aluminium chalcogenides, their sulfur congeners have rarely been isolated under mild conditions owing to limited synthetic precursors and methods. Herein, facile isolation of diverse molecular aluminium sulfides is achievable, by the reaction of N -heterocyclic carbene-stabilized terphenyl dihydridoaluminium ( 1 ) with various thiation reagents. Different to the known dihydridoaluminium 1 Tipp , 1 features balanced stability and reactivity at the Al center. It is this balance that enables the first monomeric aluminium hydride hydrogensulfide 2 , the six-membered cyclic aluminium polysulfide 4 and the five-membered cyclic aluminium polysulfide 6 t o be isolated, by reaction with various equivalents of elemental sulfur. Moreover, a rare aluminium heterocyclic sulfide with Al-S-P five-membered ring ( 7 ) was obtained in a controlled manner. All new compounds were fully characterized by multinuclear NMR spectroscopy and elemental analysis. Their structures were confirmed by single-crystal X-ray diffraction studies

Magnesium-catalysed hydroboration of isonitriles

A β-diketiminato magnesium alkyl complex is shown to be an effective pre-catalyst for the first reported catalytic hydroboration of organic isonitriles, RNC, with HBpin.</p