Organozinnverbindungen, VII. Über Diphenylzinn

Abstract

Kristallines, farbloses Dodccaphenyl-cyclohexastannan (1) entsteht in hohen Ausbcuten sowohl durch katalytische Kondensation von Diphenylzinn-dihydrid als auch durch Chlorabspaltung aus Diphenylzinn-dichlorid mittels Naphthalinnatriums. Unter anderen Bedingungen bildet sich das kristalline Decaphenylcyclopentastannan (111). Die tatsachliche Natur verschiedener, in der Literatur als Diphenylzinn beschriebener Praparate wird mittels spezifischer Abbauverfahren aufgekllrt. -Die UV-Spektren einiger offcnkettiger und ringfBrmiger Phenylzinn-Verbindungen werden diskutiert.Bei Untersuchungen uber die Hydrostannierung von Olefinen und anderen ungeslttigten organischen Verbindungen1.3) stieBen wir auf die Moglichkeit, Dialkylzinn-dihydride katalytisch unter Austritt von Wasserstoff zu kondensieren, wobei z. B. das kristalline, an der Luft entflammende, nonamere und ringformige Diathylzinn entstehtja). Die ubertragung der Reaktion auf Diphenylzinn-dihydrid lieferte uns nun unter strengem AusschluB von Luft fast quantitativ das ringformige hexamere Diphenylzinn I [GI. (l)], das Dodecaphenyl-cyclohexastannan4) (uber die Art der Katalysdtoren siehe S. 3):

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

“…To the best of our knowledge, apart from suggestions and general observations, literature does not provide conclusive evidence of the chemical processes for the dihydrogen release from R 2 SnH 2 (R = alkyl or aryl). 5 , 6 , 10 , 14 Moreover, existing studies on amine-catalysed dehydrogenation of organotin dihydrides R 2 SnH 2 (R = various alkyl or aryl) go along with the formation of Sn–Sn bonds to yield catenated oligomers or polymers. On account of extensive studies Neumann et al suggested that the essential dehydrogenation processes are intermolecular and take place at the ends of growing chains H–(R 2 Sn) n –H without the involvement of intermediately generated free diorgano stannylenes R 2 Sn that condense to polymeric chains.…”

“… 10 , 12 Moreover they observed the dehydrogenation to be unaffected by addition of quinones and therefore excluded a radical chain mechanism in favour of a polar one. 5 …”

“… 10 Especially amine-base catalysed dehydrogenation of some organotin dihydrides purified by distillation was observed to be much slower or incomplete compared to crops of organotin dihydride that have not been purified by distillation. 5 It was suggested that some tin halide impurities may stay in a pre-equilibrium with hydride–halide exchange that result in formation of R 2 Sn(H)Cl from which hydrogen is known to be readily eliminated in the presence of bases forming dichloro distannanes. 10 , 67 However, the respective reaction rate was reported to be unaffected by the addition of pyridinium chloride, what somehow contradicts the assumption of the halide supported catalysis.…”

Reduction of dichlorodiphenylstannane

“…Reaction of (Ph 2 Sn) 6 (5) 27 with excess lithium gave triphenylstannyllithium (6) as a major product together with 1,2-dilithiodistannane (7; Scheme 3). The 6-to-7 ratio was estimated to be 3 : 1 by signal intensities in 119 Sn NMR.…”

“…Reduction of (Ph 2 Sn) 6 (5) with lithium monitored by 119 Sn NMR A mixture of 5 27 (226 mg, 0.14 mmol) and lithium (18 mg, 2.65 mmol) in THF (2.6 ml) was stirred at room temperature for 0.5 h. An aliquot (0.7 ml) of the resulting deep-red solution was placed in an NMR tube with C 6 D 6 (0.3 ml), degassed by freeze-pump-thaw cycles and sealed. 119 Sn NMR: δ −108.9, −142.3 ( 1 J(Sn-Sn) = 1732 Hz).…”