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A selective and efficient route for the deoxygenative reduction of primary to tertiary amides to corresponding amines has been achieved with pinacolborane (HBpin) using simple and readily accessible 2,6-ditertbutyl phenolate...

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The isolation of unusual compounds with low‐valent main‐group elements would not have been possible without the development of a series of sterically demanding ligands with bulky substituents. While early literature recognizes the advent of the sterically demanding tris(trimethylsilyl)silyl (SiMe3)3Si‐group, also known as hypersilyl group, to stabilize species with new coordination modes for the main group elements, it has largely been more recent studies that have utilized this group for isolating stable compounds with low‐valent main‐group elements. Such compounds are not only interesting from the structure‐bonding point of view but showcase potential for small molecule activation under ambient conditions. This review will cover the recent developments in stabilizing unusual compounds with group 14 elements using the exceptionally strong σ‐donor properties and pronounced steric effects of the hypersilyl moiety, emphasizing their synthesis, structure, and reactivity.

This paper describes the rare use of a 6‐membered saturated N‐heterocyclic carbene (NHC) known as 1,3‐di(2,6‐diisopropylphenyl) tetrahydropyrimidine‐2‐ylidene (abbreviated as 6‐SIDipp) as a ligand in zinc chemistry. We report on the investigation of the reactions between 6‐SIDipp and ZnX2, which resulted in a range of new monomeric 6‐SIDipp⋅ZnX2 complexes (X=Et (1), Cl (2), Br (3), and I (4)). We also prepared a new NHC zinc complex where the two substituents of the zinc atom are different, 6‐SIDipp⋅Zn(Et)Br (7) through the reaction of the proligand [6‐SIDippH]Br with ZnEt2. We have observed that the reactions of complex 1 with sulfur and HBpin led to the removal of the ZnEt2 moiety, resulting in the formation of a C=S double bond and a B−H activation product, respectively. Lastly, the reaction of 1 with five‐membered NHCs led to the exchange of carbene and the formation of either 5‐IDipp⋅ZnEt2 (8) or 5‐SIDipp⋅ZnEt2 (9).

In this paper, we have used two N,O‐ketiminato ligands (L1 and L2) with biphenyl and terphenyl substituent on the nitrogen atom. Deprotonation of L1 with KN(SiMe3)2 and subsequent reaction with MgI2 led to a homoleptic dinuclear magnesium complex (1) with a Mg2O2 four‐membered ring. Deprotonation with nBuLi and subsequent reaction with MgI2 afforded a unusual dinuclear magnesium complex (2) with a Mg2O2 ring. Extension of the ligand for calcium resulted in a trinuclear calcium complex (3) with six four‐membered Ca2O2 rings. We could not isolate any chelating complex when L2 was used as a ligand, and only oxygen bound magnesium (4) and calcium (5) adducts were isolated. DFT studies were performed to understand this dissimilar behavior. More diverse results were obtained when lithiated L1 and L2 were treated with germanium dichloride. We were able to stabilize a monomeric germylene monochloride (7) with L1. However, with L2, an unusual ligand scrambling, and a C−C coupling take place, leading to the formation of a secondary carbocation with GeCl3‐ as a counter‐anion (8). Besides, a germanium dichloride adduct (9) bound to the oxygen center of the ligand was obtained as the minor product.

In this manuscript, several backbone germylene-functionalized zwitterionic compounds were prepared conveniently from the corresponding N-heterocyclic carbenes or N-heterocyclic olefins in a single step through backbone C−H activation. Our initial motivation was to generate a silylene from C 10 H 6 (Me 3 SiN) 2 SiHCl (2) using ItBu [ItBu = (1,3-ditert-butyl)imidazol-2-ylidene], but instead, the reaction led to deprotonation from the imidazolium backbone of ItBu, forming the imidazolium salt with a silyl backbone at the C4 position (3). We presumed that the reaction proceeded through the generation of an ephemeral silylene. We subsequently prepared the analogous germylene (4) and reacted it with IDipp [IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], ItBu, and IDipp=CH 2 . Spectroscopic and crystallographic analysis of these complexes revealed that, in all cases, there was deprotonation from the backbone and formation of zwitterionic products (5−7). When the hydrogen in the NHC backbone was replaced with methyl groups such as IDipp Me (1,3-bis(2,6-diisopropylphenyl)-4,5-dimethylimidazol-2-ylidene), simple adduct formation occurred, exemplified by the isolation of IDipp Me •Ge(NSiMe 3 ) 2 C 10 H 6 (8).

With the development of the synthesis of compounds with heavier group 14 elements, their applications in catalysis was the next logical target. The past few years have witnessed tremendous headway in the field of catalysis by compounds with heavier group 14 elements, which can be seen from the exponential number of recent publications in high‐impact journals. In this article, recent developments in the utilization of well‐defined germylenes in catalysis will be presented, which has been the starting point for rich and exciting chemistry, with the prospect of numerous remarkable contributions from synthetic, theoretical, and materials chemistry. Emphasis has been given in elucidating the mechanism of the germylene‐catalyzed reactions.