New Insights into Hydrosilylation of Unsaturated Carbon–Heteroatom (CO, CN) Bonds by Rhenium(V)–Dioxo Complexes

The hydrosilylation of unsaturated carbon–heteroatom (CO, CN) bonds catalyzed by high-valent rhenium­(V)–dioxo complex ReO₂I­(PPh₃)₂ (<b>1</b>) were studied computationally to determine the underlying mechanism. Our calculations revealed that the ionic outer-sphere pathway in which the organic substrate attacks the Si center in an η¹-silane rhenium adduct to prompt the heterolytic cleavage of the Si–H bond is the most energetically favorable process for rhenium­(V)–dioxo complex <b>1</b> catalyzed hydrosilylation of imines. The activation energy of the turnover-limiting step was calculated to be 22.8 kcal/mol with phenylmethanimine. This value is energetically more favorable than the [2 + 2] addition pathway by as much as 10.0 kcal/mol. Moreover, the ionic outer-sphere pathway competes with the [2 + 2] addition mechanism for rhenium­(V)–dioxo complex <b>1</b> catalyzing the hydrosilylation of carbonyl compounds. Furthermore, the electron-donating group on the organic substrates would induce a better activity favoring the ionic outer-sphere mechanistic pathway. These findings highlight the unique features of high-valent transition-metal complexes as Lewis acids in activating the Si–H bond and catalyzing the reduction reactions

Mechanistic Investigation Into Catalytic Hydrosilylation with a High-Valent Ruthenium(VI)–Nitrido Complex: A DFT Study

Density functional theory calculations with the B3LYP-D function have been performed to investigate the mechanism of carbonyl hydrosilylation reactions catalyzed by the high-valent nitridoruthenium­(VI) complex [RuN­(saldach)­(CH₃OH)]⁺[ClO₄]⁻ (<b>1</b>; saldach is the dianion of racemic <i>N</i>,<i>N</i>′-cyclohexanediylbis­(salicylideneimine)). Our computational results indicate a favored ionic outer-sphere mechanistic pathway. This pathway initiates with a silane addition to the Ru^VI center, which proceeds through a S_N2-Si transition state corresponding to the nucleophilic attack of the carbonyl on the silicon center. This attack then prompts the heterolytic cleavage of Si–H bond. The rate-determining energy of the S_N2-Si transition state is calculated to be 22.9 kcal/mol with benzaldehyde. In contrast, our calculations indicate that the initial silane addition to the nitrido ligand does not represent an intermediate of the catalytic process leading to the silyl ether products, since it involves high-energy transition states (29.2 and 37.8 kcal/mol) in the reduction of carbonyls. Moreover, the computational results show that the Ru^III–saldach species afforded by N–N coupling (with an activation barrier of 24.2 kcal/mol) of the nitridoruthenium­(VI) complex provides a competitive hydrosilylation reaction by favoring the ionic outer-sphere mechanistic pathway, associated with a significantly small activation barrier (3.7 kcal/mol). This study provides theoretical insight into the novel properties of the high-valent transition-metal Ru^VI–nitrido catalyst in catalytic reduction reactions

An Unprecedented Homochiral Metal–Organic Framework Based on Achiral Nanosized Pyridine and V‑Shaped Polycarboxylate Acid Ligand

A unique homochiral metal–organic framework has been successfully synthesized by solvothermal reaction of an achiral flexible V-shaped ligand and a nanosized π-electron-deficient pyridine ligand based on cobalt­(II) salt, [Co­(L)­(DPNDI)_0.5]_<i>n</i> (<b>1</b>) (H₂L = 4,4′-dicarboxydiphenylamine, DPNDI = <i>N</i>,<i>N</i>′-di-(4-pyridyl)-1,4,5,8-naphthalenediimide); the helixes assembled by H₂L and cobalt­(II) paddle-wheel centers are left-handed and transform the framework to chiral. Also, the inserting of the DPNDI transforms the original <b>dia</b> net constructed by H₂L and cobalt­(II) paddle-wheel centers to a 3-fold <b>jsm</b> net. This is the first example of interpenetrated <b>jsm</b> net. In addition, the chiral property of bulk products is confirmed by circular dichroism spectra (CD), and the thermal stability and the magnetic properties are also investigated

An Unprecedented Homochiral Metal–Organic Framework Based on Achiral Nanosized Pyridine and V‑Shaped Polycarboxylate Acid Ligand

A unique homochiral metal–organic framework has been successfully synthesized by solvothermal reaction of an achiral flexible V-shaped ligand and a nanosized π-electron-deficient pyridine ligand based on cobalt­(II) salt, [Co­(L)­(DPNDI)_0.5]_<i>n</i> (<b>1</b>) (H₂L = 4,4′-dicarboxydiphenylamine, DPNDI = <i>N</i>,<i>N</i>′-di-(4-pyridyl)-1,4,5,8-naphthalenediimide); the helixes assembled by H₂L and cobalt­(II) paddle-wheel centers are left-handed and transform the framework to chiral. Also, the inserting of the DPNDI transforms the original <b>dia</b> net constructed by H₂L and cobalt­(II) paddle-wheel centers to a 3-fold <b>jsm</b> net. This is the first example of interpenetrated <b>jsm</b> net. In addition, the chiral property of bulk products is confirmed by circular dichroism spectra (CD), and the thermal stability and the magnetic properties are also investigated