Dehydrocoupling of dimethylamine–borane promoted by manganese(ii) m-terphenyl complexes

Abstract

Low-coordinate m-terphenyl complexes are precatalysts for dehydrocoupling of dimethylamine–borane, where small changes in coordination environment effect significant mechanistic differences.

A Highly Active Bidentate Magnesium Catalyst for Amine‐Borane Dehydrocoupling: Kinetic and Mechanistic Studies

“…In addition to starting material, product (3), and trace amountso fM e 2 N=BH 2 (4), the linear species Me 2 NH-BH 2 -NMe 2 -BH 3 (5)i sa lso observedd uring the reaction. [52] Compound 5 is ac ommonly observed intermediate in the dehydrocoupling of Me 2 NH·BH 3 , [14,16] and its concentration remains low throughout the reaction, gradually dropping to zero as the reaction nears completion (Figure 1b). Compound 4 appearst of orm in the early stages of the reaction, and its concentration remains relatively constant throughout (Figure 1b).…”

“…Given the dominance of transition metals in catalysis, it is unsurprising that the d-block has received the most attention in this field, with early dehydrocoupling catalysts based on rhodium and iridium. [12,13] Driven by considerations of resourcea vailability and sustainability, recenti nvestigations have focusedo n base metals such as titanium, [14,15] manganese, [16][17][18][19] iron, [20,21] cobalt, [22,23] and nickel. [5] Looking beyondthe transition metals,there has been significant work in recent years on catalysis with main group species.…”

“…Given the dominance of transition metals in catalysis, it is unsurprising that the d‐block has received the most attention in this field, with early dehydrocoupling catalysts based on rhodium and iridium . Driven by considerations of resource availability and sustainability, recent investigations have focused on base metals such as titanium, manganese, iron, cobalt, and nickel …”

Low-coordinate first-row transition metal complexes in catalysis and small molecule activation

“…The manganese complexes 17, 19 (Scheme 11a) and the xylyl-substituted analogue catalyse the dehydrocoupling of dimethylamine-borane (Scheme 12), 72 which is of interest in the chemical storage and release of hydrogen. [73][74][75][76] While the reaction was slow at room temperature, increasing the reaction temperature to 60°C provided relatively clean conversion to the cyclic dimer [Me 2 NBH 2 ] 2 in high yields and reasonable timeframes.…”

“…This was confirmed by isolation of the manganese nanoparticles from reactions between 19 and Me 2 NH•BH 3 , followed by characterisation by transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX). 72 This reaction serves as an example of how small changes in the steric properties of the flanking aryl groups of m-terphenyl ligands can result in significant differences in reactivity.…”