Mechanistic Study and Ligand Design for the Formation of Zinc Formate Complexes from Zinc Hydride Complexes and Carbon Dioxide

Abstract

Density functional theory (DFT) study of the reactions of mononuclear phenolate diamine zinc hydride complexes and CO 2 reveals a direct insertion mechanism with a rate-determining C−H bond formation step. A total of 16 zinc hydride complexes with various functional groups, including 3 experimental structures and 13 newly proposed complexes, have been optimized. The influences of various substituents at different positions, the ring size of nitrogen bidentate ligands, and the ortho groups of nitrogen on the reaction rate are investigated. Computational results indicate that the ortho effect of nitrogen is the most effective factor in reducing the reaction energy barrier, and the complex with isopropyls as the ortho groups of the nitrogen atom has the lowest barrier of 10.9 kcal/mol.

Hydrosilylation of Aldehydes and Ketones Catalyzed by a Terminal Zinc Hydride Complex, [κ3-Tptm]ZnH

“…A similar mechanism would also apply for the insertion of the carbonyl group into the Si–H bonds of Ph 2 SiH 2 . Precedent for these steps is provided by the observations that (i) CO 2 inserts into the Zn–H bond of [κ 3 -Tptm]­ZnH, , and (ii) silanes are capable of reacting with the Zn–O bonds of [Tptm]­ZnOR and [Tptm]­ZnO 2 CH to form [κ 3 -Tptm]­ZnH. , …”

Activation of Carbon Dioxide by CoCDn– (n = 0–4) Anions

“…In contrast, with the addition of a single C atom in CoCH 1–4 – , the hydrogenation behavior of CoCH 1–3 – is completely suppressed because more H atoms are captured to form the stable C–H bond (3.47 eV) . Direct approach of CO 2 toward the terminal H site of a metal hydride, a generally accepted mechanism of C–H bond formation, − has also been considered for the CoCH – + CO 2 couple, while it cannot find an intermediate with CO 2 attached on the H site of CoCH – . It indicates that CO 2 prefers to be trapped by the Co site of CoCH – rather than the terminal H site (Figure S6), then the terminal H atom can further transfer from the Co site to the C atom of CO 2 to form (HCO 2 )­CoC – .…”

Reaction Mechanisms of CO2 Reduction to Formaldehyde Catalyzed by Hourglass Ru, Fe, and Os Complexes: A Density Functional Theory Study

“…As an abundant and non-toxic C 1 -building block, carbon dioxide can be reduced to various chemicals, such as carbon monoxide [1], methanol [2], formaldehyde [3], acetals [4,5], formic acid [5], formate [6,7], formamides [8], methylamines [8], formamidines [8], imines [3] and methane [9]. Recently, Beller and co-workers [10] reported the methylation of aromatic C-H bonds using CO 2 and H 2 with the assistance of a ruthenium triphos catalyst.…”