Isolable Tin(II) Hydrides Featuring Sterically Undemanding Pincer-Type Ligands and Their Dehydrogenative Sn–Sn Bond Forming Reactions to Distannynes Promoted by Lewis Acidic Tri-sec-butylborane

Unlike isolable tin(II) hydrides supported by bulky ligands reported in the literature, this research describes the synthesis and characterization of thermally stable tin(II) hydrides L Ph SnH ( 1-H ) and Me LSnH ( 2-H ) stabilized by sterically undemanding N,N,N-coordinating pincer-type ligands ( L Ph = 2,5-dipyridyl-3,4-diphenylpyrrolato; Me L = 2,5-bis(6-methylpyridyl)pyrrolato). The results from previous reports reveal that attempts to access tin(II) hydrides containing less-bulky ligands have had limited success, and decomposition to tin(I) distannynes often occurs. The key to the successful isolation of 1-H and 2-H is the identification of the role of Lewis acidic B s Bu 3, generated upon delivering hydride from commonly used hydride reagents M[B s Bu 3 H] (“selectrides”, M = Li or K). This study details compelling experimental evidence and theoretical results of the role played by B s Bu 3, which catalyzes the dehydrocoupling reactions of 1-H and 2-H to yield tin(I) distannynes L Ph Sn–SnL Ph ( 1 2 ) and Me LSn–Sn Me L ( 2 2 ) with the liberation of H 2 . To avoid the interference of B s Bu 3, 1-H and 2-H can be isolated in pure forms using pinacolborane as the hydride donor with L Ph SnOMe ( 1-OMe ) and Me LSnOMe ( 2-OMe ) as reactants, respectively. DFT calculations and experimental observations indicate that the coordination of the Sn–H bond of 1-H to B s Bu 3 leaves an electrophilic tin center, rendering the nucleophilic attack by the second equivalent of 1-H forming a Sn–Sn bond.