Metal-free reduction of CO2 with hydroboranes: two efficient pathways at play for the reduction of CO2 to methanol

Guanidines and amidines prove to be highly efficient metal-free catalysts for the reduction of CO2 to methanol with hydroboranes such as 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane (catBH). Nitrogen bases, such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (Me-TBD), and 1,8-diazabicycloundec-7-ene (DBU), are active catalysts for this transformation and Me-TBD can catalyze the reduction of CO2 to methoxyborane at room temperature with TONs and TOFs of up to 648 and 33 h(-1) (25 °C), respectively. Formate HCOOBR2 and acetal H2C(OBR2)2 derivatives have been identified as reaction intermediates in the reduction of CO2 with R2BH, and the first C-H-bond formation is rate determining. Experimental and computational investigations show that TBD and Me-TBD follow distinct mechanisms. The N-H bond of TBD is reactive toward dehydrocoupling with 9-BBN and affords a novel frustrated Lewis pair (FLP) that can activate a CO2 molecule and form the stable adduct 2, which is the catalytically active species and can facilitate the hydride transfer from the boron to the carbon atoms. In contrast, Me-TBD promotes the reduction of CO2 through the activation of the hydroborane reagent. Detailed DFT calculations have shown that the computed energy barriers for the two mechanisms are consistent with the experimental findings and account for the reactivity of the different boron reductants.

Ferro- and antiferromagnetic coupling in a chlorido-bridged, tetranuclear Cu(ii) complex

A binuclear complex of copper(ii) chloride with a heptadentate bispidine-like ligand undergoes dimerisation in the solid state involving chloride bridging and leading to both ferro- and antiferromagnetic coupling of the Cu(ii) centres.

Catalytic hydrosilylation of oxalic acid: chemoselective formation of functionalized C2-products

Oxalic acid is an attractive entry to functionalized C₂-products because it can be formed by C–C coupling of two CO₂ molecules under electrocatalytic reduction. Herein, we describe the first attempts to reduce oxalic acid by catalytic hydrosilylation, using B(C₆F₅)₃ as a Lewis acidic catalyst.

Mota AJ, Ephritikhine M. Structural, magnetic and theoretical calculations of a ferromagnetically coupled tetranuclear copper(ii) square complex

Ferromagnetic interactions in a tetranuclear copper(ii) square complex containing a Schiff base ligand.

Bent thorocene complexes with the cyanide, azide and hydride ligands

Reaction of the linear thorocene with NC(-), N3(-) and H(-) led to the bent derivatives [(Cot)2Th(X)](-) (X = CN, N3) and the bimetallic [{(Cot)2Th}2(μ-H)](-), whereas only [(Cot)2U(CN)](-) could be formed from (Cot)2U.

A N-aryloxy-β-diketiminate ligand in 4d, 4f and 5f-metals complexes

A new class of functionalized β-diketiminate ligands has been prepared from commercially available reagents. The novel N-aryloxy-β-diketiminate ligand proves to be an excellent ligand to support 4d, 4f and 5f metal ions.