Nature and Strength of M–H···S and M–H···Se (M = Mn, Fe, & Co) Hydrogen Bond

Abstract

The significance of dispersion contribution in the formation of strong hydrogen bonds (H-bonds) can no more be ignored. It was illustrated that less electronegative and electropositive H-bond acceptors such as S, Se, and Te are also capable of forming strong N–H···Y H-bonds, mostly due to the high polarizabilities of H-bond acceptor atoms. Herein, for the first time, we report the evidence of formation of nonconventional M-H···Y H-bonds between metal hydrides (M-H, M = Mn, Fe, Co) and chalcogen H-bond acceptors (Y = O, S, or Se). The nature and the strength of unusual M-H···Y H-bonds were revealed by several quantum chemical calculations and H-bond descriptors. The structural parameters, electron density topology, donor–acceptor natural bond orbital (NBO) interaction energies, and spectroscopic observables such as M-H stretching frequencies and 1H chemical shifts are well-correlated to manifest the existence and strength of M-H···Y H-bonding. The M-H···Y H-bonds are dispersive in nature, and the computed H-bond energies are found to be in the range from ∼5 to 30 kJ/mol, which can be compared to those of the conventional H-bonds such as O–H···O, N–H···O, and N–H···OC H-bonds, etc.

Transition Metal‐Controlled Direct Regioselective Intermolecular Amidation of C−H Bonds with Azodicarboxylates: Scope, Mechanistic Studies, and Applications

“…Interestingly, in 2016, Zhang and coworkers reported that the same substrate ( 1 o ) in the Co(OAc) 2 /Ag 2 CO 3 system gave carbonylation product 5 . In the same year, Baidya and coworkers independently reported that 1 o with DEAD in the Cu(OTf) 2 /Ag 2 CO 3 system gave amidation product 3 o (Scheme ). Our studies demonstrated that our Ag‐catalyzed approach is highly regioselective for the C5‐position of the quinoline and produces C−H amidation product 3 o without Pd, Cu, or Co catalysts.…”

Hexafluoro‐2‐propanol Promotes para‐Selective C–H Amination of Free Anilines with Azodicarboxylates

“…For example, hydrazide product 3aa could be straightforwardly transformed into p-phenylenediamine (8) in 70 % yield by removal of the Cbz group and cleavage of the N-N bond in a single step. [7] One of the advantages to have a free amine in reactions is the possibility to remove or use it in other transformations. [15] By means of the well-known Sandmeyer reaction, diazotization of 3aa with NaNO 2 followed by treatment with NaI produced 4-iodophenylhydrazine (9) in 73 % yield.…”

“…[6] Moreover, a similar process was reported with readily available azodicarboxylates (Scheme 1c). [7] However, the introduction and subsequent removal of protecting groups not only requires addi-found to be highly regioselective and provided a series of paminophenylhydrazine derivatives in excellent yields. Moreover, compatibility with a free amino group makes this protocol an attractive strategy in synthetic chemistry.…”

Copper‐Catalyzed Oxidative C(sp3)−H/N−H Cross‐Coupling of Hydrocarbons with P(O)−NH Compounds: the Accelerating Effect Induced by Carboxylic Acid Coproduct

“…Recently, the development of chelation‐assisted transition‐metal catalysis has provided a new complementary route for facile construction of various C−N bonds . Reactions of copper‐chelation system can be performed even at room temperature ,,. The intramolecular dehydrogenative amidation protocol have been well established by researchers such as Shi, Kanai, Ge,, Shi, and Bedford (Scheme c).…”