Hydrostibination

Abstract

Ar igid naphthalenediamine framework has been used to prepare antimony hydrides that feature LUMO shapes and energies similar to those found in secondary boranes.B y exploiting this feature,w ei ntroduce the first examples of uncatalyzed hydrostibination reactions of robust CC, C=C, C = O, and N = Nb onds as new elementary hydrometalation reactions analogous to hydroboration. These results endorse the notion of ad iagonal relationship between the lightest p-block element and the heaviest Group 15 elements and may lead to the conception of novel reaction chemistry.

Hydrostibination of Alkynes: A Radical Mechanism

“…22,23 As part of our exploration into new structure and reactivity at antimony and bismuth centres, 24,25 we recently reported the first definitive catalyst-and additive-free addition of stibines to alkenes, alkynes, ketones, and azobenzene. The reaction proceeds under ambient conditions with near-quantitative yields (Figure 1b), 26 and is directly analogous to uncatalyzed hydroboration, furthering our unusual proposal of a "diagonal relationship" 27,28 between the lightest p-block element and heavy Group 15 metals. Despite this superficial similarity, the complexity of this simple two-component reaction was indicated by the observation that hydrostibination showed the opposite stereochemical outcomes to hydroboration.…”

“…Breunig, Tokitoh, Scheer, Power, and we have shown that primary and secondary stibines can be deprotonated in the presence of alkyllithium bases, amino bases, and alkali metals. 26,[33][34][35][36][37][38][39] In contrast, Huang has implied hydride-like reactivity for Ph2SbH in AlCl3-catalyzed hydrostibination of C=O bonds. 22 We and others have previously shown that stibines react with the trityl cation Ph3C + to yield Ph3C-H and stibenium ions, further evidencing hydridic reactivity for the Sb-H bond.…”

“…22 We and others have previously shown that stibines react with the trityl cation Ph3C + to yield Ph3C-H and stibenium ions, further evidencing hydridic reactivity for the Sb-H bond. 26,40 Besides these heterolytic reaction modes, homolysis of Sb-H bonds has also been demonstrated. For example, primary arylstibines and diarylstibines were found to hydrogenate styrene to ethylbenzene in the presence of azobisisobutyronitrile (AIBN) as a radical initiator.…”

“…[44][45][46] Secondly, we and others have shown that the Sb-H bonds can break heterolytically in the presence of a Lewis acids. 26 Finally, even formally neutral Sb(III) centers can exhibit substantial electrophilicity, [47][48][49] allowing autoionization processes to proceed. 43 Radical mechanism D involves H-atom abstraction from 1H by the acetylene (TSD1) to…”

“…We attempted to detect the transient compound 1 • that is generated upon H atom removal from 1H by performing the reaction in the precooled cavity of an EPR spectrometer, but were unsuccessful in detecting a signal for this species. This is ascribed to the rapid dimerization of 1 • to give the known distibine (1)2, 26,51,52…”