A nitrogen-base catalyzed generation of organotin(ii) hydride from an organotin trihydride under reductive dihydrogen elimination

Abstract

Amine bases are shown to induce reductive elimination of dihydrogen from terphenyltin trihydride.

Access to Base Adducts of Low‐Valent Organotin‐Hydride Compounds by Controlled, Stepwise Hydrogen Abstraction from a Tetravalent Organotin Trihydride

“…[6] However,t he subtle changes from Me NHC adducts, for which no hints for comparable equilibria have been observed by NMR spectroscopy, to the bulkier iPr NHC adducts are noteworthy.Am ore labile SnÀcarbene bond serves to explain the results of av ariety of differing reactionc onditions that will be discussed later (see below). Carbene exchange at lowvalent Group 14 centres forming af avourable adduct with more stable EÀcarbeneb onds in the case of less bulky carbenes hasbeen described previously.…”

“…[15] However,w ef ound that the direct treatment of (Ar'Li) 2 with SnCl 4 does not offer as atisfyingly reliable access to Ar'SnCl 3 .F ollowing our recently reported procedure, the oxidation of the readily crystallising tin(II) derivative (Ar'SnCl) 2 with mercury dichloride provided almostq uantitative accesst oA r 'SnCl 3 . [6,16] Moreover,w ef ound that upon treatment of (Ar'Li) 2 with an excess of 3-4 equivalents of SnCl 2 in toluene, Ar'SnCl 3 was formed along with elemental tin and smaller amounts( 10-15 %) of side-products that can be removed by subsequent recrystallisation. Similarr eactivity of stannylenes with SnCl 2 ,s erving as an oxidantt oy ield dichloro stannanes, has been previously reported by Lappert and co-workers.…”

“…In this context we werea blet os how that nitrogen bases such as DMAP (4-(N,N-dimethylamino)pyridine) can induce dehydrogenationa nd finally the base adducts of terphenyltin(II) hy-drides were observed. [6] We also reported the successful stoichiometric abstraction of H 2 from bulky substituted Ar*SnH 3 (Ar* = 2,6-(trip) 2 phenyl, trip = 2,4,6-triisopropylphenyl) with two equivalents of simple N-heterocyclic carbenes (NHCs) to yield the NHC adducts of Ar*SnHi na lmost quantitative yields. [13] We now wish to report on the variety of products observed in the stoichiometric dehydrogenation of Ar'SnH 3 with simple N-heterocyclic carbenes of slightly increasing stericb ulk.…”

“…Although organotint rihydrides are long known,adiorganodistannane has only recently been reported. [6] Seminal contributionst ot he field of tin(II) hydrides have been presented by Power and coworkers, who described the observation of isomers of (ArSnH) 2 (Ar = various bulky terphenyl moieties). The dimers revealed either symmetrical m-H bridging or valence isomerism to give dihydrostannylstannylenes.…”

Hydride Abstraction and Deprotonation – an Efficient Route to Low Coordinate Phosphorus and Arsenic Species

“…Interestingly, in a recent mechanistic study [40] of room temperature hydrogen elimination from an organotin trihydride, assisted by a nitrogen base, a similar transition state to TS13a was located on the reaction coordinate computationally. However, similar to TS13a, its associated G ‡ was too high for a reaction occurring at room temperature, and an alternative polar mechanism was suggested to account for the difference.…”