Germyliumylidene: A Versatile Low Valent Group 14 Catalyst.

Debotra Sarkar,Emeric Schubert,Shigeyoshi Inoue,Sayan Dutta,Catherine Weetman,Debasis Koley

doi:10.1002/chem.202102233

Abstract

Bis‐NHC stabilized germyliumylidenes [RGe(NHC)2]+ are typically Lewis basic (LB) in nature, owing to their lone pair and coordination of two NHCs to the vacant p‐orbitals of the germanium center. However, they can also show Lewis acidity (LA) via Ge−CNHC σ* orbital. Utilizing this unique electronic feature, we report the first example of bis‐NHC‐stabilized germyliumylidene [MesTerGe(NHC)2]Cl (1), (MesTer=2,6‐(2,4,6‐Me3C6H2)2C6H3; NHC= IMe4=1,3,4,5‐tetramethylimidazol‐2‐ylidene) catalyzed reduction of CO2 with amines and arylsilane, which proceeds via its Lewis basic nature. In contrast, the Lewis acid nature of 1 is utilized in the catalyzed hydroboration and cyanosilylation of carbonyls, thus highlighting the versatile ambiphilic nature of bis‐NHC stabilized germyliumylidenes.

Highlights

The ability of main group complexes to mimic transition metals has gained tremendous attention in recent years, driven by the desire for new sustainable processes.[1]
Activation of small molecules by low-valent main group centers has been achieved and is the preliminary step towards transition metal-free catalysis.[1a,e] their catalytic application is still limited due to challenges in reductive elimination from the resultant high-oxidation state complex.[1d,e,2] Recently, low valent germanium compounds have found themselves to be a diverse tool in enabling chemical transformations, attributed to the relative ease in which the + II and + IV oxidation states can be accessed.[2b–g,3] This includes the first example of low-valent main group dihydrogen activation and the use of multiple bonds in catalysis.[2f,3a] Among the low valent germanium compounds, germyliumylidenes [RÀGe:]+ possess a unique electronic feature,[4] due to the presence of a lone pair and two vacant p-orbitals at the germanium center
Due to the ability of the GeÀCNHC σ* orbitals to accept electrons, which provides an additional cooperative site for potential catalytic application. Despite these unique electronic features, the catalytic application of germyliumylidenes is in its infancy

Summary

Introduction

The ability of main group complexes to mimic transition metals has gained tremendous attention in recent years, driven by the desire for new sustainable processes.[1]. Due to the ability of the GeÀCNHC σ* orbitals to accept electrons, which provides an additional cooperative site for potential catalytic application. Despite these unique electronic features, the catalytic application of germyliumylidenes is in its infancy. It has been shown that the Lewis acidity and Lewis basicity are both important for the catalytic transformation of CO [2d,e,h,8] 2 This encouraged us to examine the recently reported bis NHC stabilized germyliumylidene [MesTerGe(NHC)2]Cl (1) towards a range of catalytic reductive functionalization reactions, with a particular emphasis on C=O reduction i. This encouraged us to examine the recently reported bis NHC stabilized germyliumylidene [MesTerGe(NHC)2]Cl (1) towards a range of catalytic reductive functionalization reactions, with a particular emphasis on C=O reduction i. e., CO2 and carbonyls

Results and Discussion

Conclusion

Conflict of Interest