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In this study, a novel half-sandwich phosphinesulfonate cobaltic complex (Co(dppbsa)) was prepared and characterized, which surprisingly enabled the chemoselective N,N-dimethylation of nitroaromatics with CO2 using NaBArF4 as the promotor and a combination of PhSiH3 and Et3SiH as the reductant. Further studies demonstrated that the catalytic activity for reduction of nitroaromatics and CO2 could be modulated, respectively, by using a specific structure and composition of hydrosilanes. The semi-reduction products nitrosoarene and silyl formate are the key intermediates affording the most efficient C–N coupling for the N,N-dimethylation of nitroaromatics with CO2. [ABSTRACT FROM AUTHOR]

The vapor‐phase nitrilation of dimethyl adipate (DMA) with ammonia (NH3) is an environmentally benign route leading to adiponitrile (ADN) with great application value. In this study, the performance of HZSM‐5 zeolites, widely used in industry as the solid acid catalysts, was investigated. It exhibits a strong correlation between the SiO2/Al2O3 ratio (SAR) in HZSM‐5 zeolites and the reactivity (both activity and selectivity). The influence of Al density closely related to the value of SAR on the reactivity of HZSM‐5 was thus elucidated by mechanistic experiments. As a result, the introduction of Al element to the framework is beneficial to the activation of ester functionality, thus improving the activity, especially at a high liquid hourly space velocity (LHSV). However, a high Al density will lead to poor selectivity and deactivation due to too strong adsorption of esters and intermediates (e. g., amides). Herein, the balanced adsorption/desorption capability was reached on HZSM‐5 with SAR as 631 (i. e., HZSM‐5‐631), which provides the best selectivity to nitriles (SADN+MCP, 92.5 %) at a high single‐pass conversion of DMA (CDMA, 98.0 %). [ABSTRACT FROM AUTHOR]

In this study, palladium‐based heterogeneous catalysts were successfully prepared by encapsulating the palladium diphosphine complexes into an imine‐linked 2D‐COF (TPB‐DMTP‐COF) through a one pot self‐assembly approach. It not only prevents the oxidation of phosphine‐based ligand during the stepwise impregnation but also suppresses the coordination of imine linkers at the COF host to the palladium guest, thus enabling highly efficient encapsulation of the active bidentate phosphine chelated palladium complex by the widely explored imine‐linked COF. Besides, the dosage of diphosphine ligand (Xantphos‐SO3H, L) and the ratio of palladium to L in the preparation of [Pd]@COF hybrids can be readily adjusted under such one pot procedure to satisfy the requirement of crystallinity, porosity, active sites, and CO adsorption capacity for the catalytic performance in the methoxycarbonylation of olefins. The resultant [Pd]@COF‐A‐0.25‐0.5 provides satisfied catalytic performance for both aliphatic and aromatic olefins with total esters up to 92.1 % under optimized conditions. These findings provide the basis for a novel design concept to design heterogeneous catalysts with high efficiency for reaction processes comprising the alkoxycarbonylation of olefins. [ABSTRACT FROM AUTHOR]