Screening Carbon‐Boron Frustrated Lewis Pairs for Small‐Molecule Activation including N₂, O₂, CO, CO₂, CS₂, H₂O and CH₄: A Computational Study

Abstract

Dinitrogen (N 2 ) activation is particularly challenging under ambient conditions because of its large highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap (10.8 eV) and high bond dissociation energy (945 kJ mol À 1 ) of the N�N triple bond, attracting considerable attention from both experimental and theoretical chemists. However, most effort has focused on metallic systems. In contrast, nitrogen activation by frustrated Lewis pairs (FLPs) has been initiated recently via theoretical calculations. Here we perform density functional theory (DFT) calculations to screen a series of experimentally viable FLPs for small-molecule activation including N 2 , O 2 , CO, CO 2 , CS 2 , H 2 O and CH 4 . In addition, aromaticity is found to play an important role in most of these small-molecule activation. The particularly thermodynamic stabilities of the activation products and low reaction barriers could be a step forward for the development of FLP towards small-molecule activation including N 2 , inviting experimental chemists' verification.

Cooperative Activation of Small Molecules by Base-Stabilized Borylenes

“…All of the structures were fully optimized without any symmetry constraints using the ωB97XD functional in conjunction with the 6-311+G* basis set. , Our choice of the ωB97XD functional was motivated by previous reports on attainment of similar or comparable energetics for boron-based systems by this functional with those employing the high-level CCSD­(T) calculations. , Frequency calculations were performed at the same theoretical level to characterize the nature of the stationary points. All of the ground state structures were verified as minima on the potential energy surface with real vibrational frequencies, whereas transition states were characterized by the presence of only one imaginary frequency, which was further confirmed by performing intrinsic reaction coordinate (IRC) analysis .…”

“…In a series of ground-breaking studies that highlight the promise of borylenes in the fixation and functionalization of the highly stable and inert dinitrogen molecule, one of our groups reported the synthesis and isolation of a borylene–N 2 complex ( IX ) and showed the ability of base-stabilized borylenes in the reductive coupling of dinitrogen as well as the conversion of dinitrogen to ammonium chloride. , In a recent computational study, we have investigated the efficiency of several base-stabilized borylenes in binding N 2 as mono- and diborylene–N 2 adducts and found the binding to be effective as marked by their low activation barriers . Zhu and co-workers also contributed in this field by investigating the reaction mechanisms of metal-free activation and coupling of N 2 by carbene-stabilized borylenes. , Furthermore, several studies exist on the activation of small molecules by carbon–boron-frustrated Lewis pairs (FLPs). − Thus, there is a need as well as scope for the design and development of other base-stabilized borylenes as such studies may help toward replacement of toxic and expensive metal systems by environmentally benign main group systems. It is with this motivation that we undertook a comprehensive study to probe the potential of several base-stabilized borylenes (L → B–R, Scheme ) in the binding of ligands such as CO and CNMe as well as the activation of E–H bonds (E = H, NH 2 , SiH 2 Ph, and CH 3 ) by employing a variety of carbenes (that possess different degrees of electron donation and acceptance abilities) and substituents (that possess different degrees of π-donation ability).…”

Ru(II)-Anionic-Naked-NHC Complexes as Cooperative Lewis Pairs: Parallels in Structure and FLP-type Chemical Reactivity

“…[12][13][14][15] Starting from the possibility of metal-free hydrogenation reactions, [16][17][18][19][20][21] the use of FLPs for a variety of small molecule activation reactions has been reported. [22][23][24][25][26][27][28][29][30][31] Recent developments with the so called transition metal frustrated Lewis pairs (TMFLPs) incorporating transition metals into FLP chemistry have opened up new possibilities for the exploration of rich chemistry and their applications in the field of small molecule activation and catalysis. [32][33][34][35][36][37] TMFLPs developed by groups of Stephen, Wass, Erker, Carmona, and others have shown potential in various catalytic reactions, including hydrogenation, C-H activation, and CO2 reduction, among others (Figure 1).…”

Systematic Assessment of the Catalytic Reactivity of Frustrated Lewis Pairs in C-H Bond Activation

“…On the other hand, the applications of FLPs as versatile catalysts have extended to multiple aspects of chemistry. In the beginning, research on the applications of FLPs paid attention mainly to the activation of the E-H (E = O [ 17 , 18 , 19 ], S [ 20 ], N [ 21 , 22 ], Si [ 23 , 24 ], B [ 25 , 26 ], etc.) bond and their interaction with a variety of small molecules [ 27 , 28 ], which are often thought to be the typical domain of transition metal-containing chemistry.…”