Hydrogenolysis of Polysilanes Catalyzed by Low-Valent Nickel Complexes

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

This review surveys the synthesis and reactivity of low-oxidation state metalate anions of the d-block elements, with an emphasis on contributions reported between 2006 and 2022. Although the field has a long and rich history, the chemistry of transition metalate anions has been greatly enhanced in the last 15 years by the application of advanced concepts in complex synthesis and ligand design. In recent years, the potential of highly reactive metalate complexes in the fields of small molecule activation and homogeneous catalysis has become increasingly evident. Consequently, exciting applications in small molecule activation have been developed, including in catalytic transformations. This article intends to guide the reader through the fascinating world of low-valent transition metalates. The first part of the review describes the synthesis and reactivity of d-block metalates stabilized by an assortment of ligand frameworks, including carbonyls, isocyanides, alkenes and polyarenes, phosphines and phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. Thereby, the reader will be familiarized with the impact of different ligand types on the physical and chemical properties of metalates. In addition, ion-pairing interactions and metal-metal bonding may have a dramatic influence on metalate structures and reactivities. The complex ramifications of these effects are examined in a separate section. The second part of the review is devoted to the reactivity of the metalates toward small inorganic molecules such as H2, N2, CO, CO2, P4 and related species. It is shown that the use of highly electron-rich and reactive metalates in small molecule activation translates into impressive catalytic properties in the hydrogenation of organic molecules and the reduction of N2, CO, and CO2. The results discussed in this review illustrate that the potential of transition metalate anions is increasingly being tapped for challenging catalytic processes with relevance to organic synthesis and energy conversion. Therefore, it is hoped that this review will serve as a useful resource to inspire further developments in this dynamic research field.

Germanium hydrides as an efficient hydrogen-storage material operated by an iron catalyst

The use of metal hydrides such as NaBH₄ as hydrogen-storage materials has recently received substantial research attention on account of the worldwide demand for the development of efficient hydrogen-production, -storage, and -transportation systems. Here, we report the quantitative production of H₂ gas from a germanium hydride, Ph₂GeH₂, mediated by an iron catalyst at room temperature via dehydrogenative coupling, concomitant with the formation of (GePh₂)₅. Of particular importance is that Ph₂GeH₂ can be facilely recovered from (GePh₂)₅ by contact with 1 atm of H₂ or PhICl₂/LiAlH₄ at 0 °C or 40 °C, respectively. A detailed reaction mechanism for the iron-catalyzed dehydrogenative coupling of Ph₂GeH₂ is proposed based on the isolation of four intermediate iron species.

POSS-based starlike hybrid helical poly(phenyl isocyanide)s: their synthesis, self-assembly, and enantioselective crystallization ability

Well-defined starlike hybrid helical poly(phenyl isocyanide)s with POSS cores were designed and synthesized, and their self-assembly behaviour and enantioselective crystallization ability were investigated.