Ru‐Catalyzed Cross Dehydrogenative Coupling Leading to Si−O and Si−S Bond Formations and Also Stimulating an Alternative Scope for Hydrogenation of C=O, C=N and N=N Bonds

Abstract

Reaction pathways involved in catalytic Cross Dehydrogenative Coupling (CDC) reactions leading to formation of Si−O and Si−S bonds have been formulated and explored theoretically using Density Functional Theory (DFT). The advantage of the weak Si−H bond has been exploited to carry out coupling with water, alcohol and thiol, along with H2 release. Ru complex, [K(dme)2][Ru(H)(trop2dad)] when reacts with water generates a neutral complex, [Ru(trop2dad)]. This neutral complex has been employed to act as a catalyst in CDC reactions. It has also been found that the complex, [Ru(H2)(trop2dad)] formed within the catalytic cycle may also be used for hydrogenation of C=O, C=N and N=N bonds. The optimized geometries of all the complexes and transition states have been obtained using wB97xd functional in conjunction with 6‐31++G(d,p) basis set. The whole assisting phenomena in solvent medium has been investigated through the implementation of conductor‐like screening solvation model (COSMO) considering tetrahydrofuran as the bulk solvent medium. The Turnover frequency (TOF) has been calculated by Energetic Span Model. The theoretical investigation extends the role of the ruthenium catalyst to the regime of ‘element to element’ bond formation, along with H2 release, which may be significant in the field of energy storage, and also triggers an alternative possibility of hydrogenation of carbonyls, imines and diazo compounds.

Predicting Small Molecule Activation including Catalytic Hydrogenation of Dinitrogen Promoted by a Dual Lewis Acid

“…Hidai and co‐workers reported in 1998 that hydrosulfo‐bridged dinuclear complexes [52] and a ruthenium hydride complex [53] respectively realized the hydrogenation of coordinated dinitrogen on tungsten, providing a new strategy to further activate and transform the coordinated dinitrogen by the hydrogenation with metal hydride. According to the recent report, [54] [Ru(H 2 )(trop 2 dad)] was used as a catalyst for N=N, C=O, and C=N hydrogenation, so we applied it to the hydrogenation of product 1‐P . As shown in Figure 5, the formation of a thermodynamically more stable hydrogenation product 1‐PP could be achieved by the catalyst [Ru(H 2 )(trop 2 dad)] step by step.…”

“…In addition, as shown in Figure 4, the reduced vibration frequency of the NÀ N bond (from 2489 cm À 1 to Hidai and co-workers reported in 1998 that hydrosulfobridged dinuclear complexes [52] and a ruthenium hydride complex [53] respectively realized the hydrogenation of coordinated dinitrogen on tungsten, providing a new strategy to further activate and transform the coordinated dinitrogen by the hydrogenation with metal hydride. According to the recent report, [54] [Ru(H 2 )(trop 2 dad)] was used as a catalyst for N=N, C=O, and C=N hydrogenation, so we applied it to the hydrogenation of product 1-P. As shown in Figure 5, the formation of a thermodynamically more stable hydrogenation product 1-PP could be achieved by the catalyst [Ru(H 2 )(trop 2 dad)] step by step. However, in the process of the second hydrogen transfer, the Gibbs free energy of the transition state TS Ru•2 , which was confirmed by intrinsic reaction coordinate (IRC) calculations (employed to find the association of transition states with the corresponding reagents and products), [55,56] is slightly lower than that of the intermediate INT Ru.1 (0.6 kcal mol À 1 ), but its electronic energy is higher by 1.1 kcal mol À 1 than of the intermediate INT Ru.1 .…”