Understanding the Oxidative Addition of σ‐Bonds to Group 13 Compounds

Abstract

The oxidative addition reaction of X-H σ-bonds to Group 13 (E=Al, Ga, In) containing compounds has been computationally explored within the density functional theory framework. These reactions, which proceed concertedly involving the E(I) →E(III) oxidation, are exothermic and associated with relatively low activation barriers. In addition, the following trends in reactivity are found: (i) the activation barriers are lower for the X-H bonds involving the heavier element in the same group (ΔE(≠) : C>Si; N>P; O>S), (ii) the process becomes kinetically more favorable in going from left to right in the same period (ΔE(≠) : C>N>O; Si≈P>S), and (iii) the activation barrier systematically increases when heavier Group 13 elements are involved in the transformation (ΔE(≠) : Al<Ga<In). These reactivity trends are analyzed and quantitatively rationalized in detail by means of the activation-strain model of reactivity in combination with the energy decomposition analysis method.

The Unusual Role of Aromatic Solvent in Single‐Site AluminumI Chemistry: Insights from Theory

“…[15] There have been previous computational studies that have investigated the energetics of s-a nd p-bond activation by the NacNacAl I complex through direct oxidative addition. [17,[20][21][22][23] However, this work is the first to shed light on the explicit role of the aromatic solvent molecule, and show how it is able to considerably enhancethe potency of the NacNacAl I system.…”

“…More recently, the group of Nikonov also showed that the NacNacAl I complex could activate even stronger σ bonds, such as C−F, C−O, P−P, and C−S, and π bonds, such as C=S and P=S . It is believed that activation proceeds at a single group 13 metal center …”

“…Single‐site activation of H−H, H−P, H−N, and other such robust σ bonds by main‐group compounds (and by “single‐site” frustrated Lewis pairs) has generally proved to be difficult, with only a few reported instances . Hence, recent investigations into the NacNacAl I complex represent an important advance in the chemistry of main‐group elements.…”

“…[15,[19][20][21][22][23] Single-site activation of HÀH, HÀP, HÀN, and other such robust s bonds by main-group compounds (andb y" single-site" frustratedL ewis pairs [24] )h as generally proved to be difficult, with only af ew reported instances. [15,[19][20][21][22][23][24][25][26] Hence, recent investigations into the NacNacAl I complex represent an important advance in the chemistryofmain-group elements. However,w hat is notable is that the reactions of aluminum chemistry have alwaysb een carriedo ut in aromatic solvents:b enzene [11,15] toluene, [27][28][29][30] or anisole.…”

Reversible Alkene Binding and Allylic C–H Activation with an Aluminum(I) Complex

“…A structurally related TS has been calculated for the addition of H 2 to 1. 49,50 The geometry can be explained by considering the oxidative addition transition state in terms of a donation of electron density in the C]C p-bond to the vacant p-orbital on Al with concomitant back-donation from the Al sp 2 lone pair to the p* orbital of the alkene (vide infra).…”