Untitled

Abstract

Treatment of hexakis(2,4,6-triisopropylphenyl)tetrasilabuta-1,3-diene (1), R 2 Si=SiR±SiR=SiR 2 , with ammonia and chlorine furnishes the correspondingly substituted 1,4diaminotetrasilane (3) and 1,2,3,4-tetrachlorotetrasilane (6). While product 6 crystallizes as a racemate, 3 forms a con-glomerate of enantiomerically pure crystals. The change of colors during the formation of 6 indicates a stepwise reaction sequence. Ammoniak-und Chloradditionen an ein Tetrasilabuta-1,3-dien: Konglomerat versus Racemat-Kristallisation [1]Inhaltsu È bersicht. Die Reaktion von Hexakis(2,4,6-triisopropylphenyl)tetrasilabuta-1,3-dien R 2 Si=SiR±SiR=SiR 2 mit Ammoniak oder Chlor ergibt das entsprechend substituierte 1,4-Diaminotetrasilan (3) und das 1,2,3,4-Tetrachlortetrasilan (6). Wa È hrend 6 als Racemat kristallisiert, bildet 3 ein Konglomerat enantiomerenreiner Kristalle. Der Farbwechsel wa È hrend der Bildung von 6 deutet auf eine schrittweise verlaufende Reaktionssequenz hin.

Precise Activation of Ammonia and Carbon Dioxide by an Iminodisilene

“…[7] This reactivity is quite peculiar as the analogous structure,u niformly substituted disilene IIa,turned out to be absolutely inert to this reagent. [7] This reactivity is quite peculiar as the analogous structure,u niformly substituted disilene IIa,turned out to be absolutely inert to this reagent.…”

“…Interestingly,c loser investigations revealed that, if the reaction time at À78 8 8Cisreduced to 10 min or the treatment with NH 3 is conducted directly at room temperature,a lmost exclusively the colorless aminosilane 2b as formal oxidative addition product of the respective silylene with NH 3 was obtained instead (yield 94 %). [7,8] To explain the controllable product formation depending on the reaction conditions,weperformed DFT calculations at the B3LYP-D3(BJ)/def2-SVP level of theory.I na greement with our reported trans-hydrogenation, [13a] an analogous antitransition state (TS1) was found with al ow energy barrier involving two ammonia molecules (7.7 kcal mol À1 )(Scheme 2; see the Supporting Information). The 1 J(Si-H) of 174 Hz of 2a,however, is in fact comparable with the coupling constant of IIb' ' (187 Hz) and as expected smaller than the one of silane 2b (202 Hz).…”

“…reported the regioselective addition of NH 3 to both conjugated Si=Si bonds of tetrasilabutadiene I to give the respective 1,4-diaminotetrasilane I' '. [7] This reactivity is quite peculiar as the analogous structure,u niformly substituted disilene IIa,turned out to be absolutely inert to this reagent. In this context, Scheschkewitz and co-workers recently isolated the asymmetric disilene IIb in which the induced polarization of the Si = Si bond, resulting from the replacement of one Tipp ligand of IIa with a2 ,4,6-trimethoxyphenyl (TMOP) group,r e-enabled the quantitative and regioselective formation of Tipp 2 HSiÀSiNH 2 (Tipp)TMOP IIb' ' with ammonia.…”

Functional Disilenes in Synthesis

“…Reaction of either lithium bromide in the presence of trifluoroacetic acid or very pure HSiCl 3 gives disilenes 34 a or 34 b in 70 % and 47 % yield, respectively (Scheme ) . With small polar molecules such as hydrogen halides, chlorine, ammonia and hydrazine, however, tetrasilabuta‐1,3‐diene 3 reacts exclusively in the sense of double 1,2‐addition addition reactions to yield the corresponding tetrasilanes 35 a , b under mild conditions (Scheme ) . Apparently, the 1,4‐addition reactions (Scheme ) occur only with very small concentrations of the hydrogen halides, generated from the applied HX sources ( 34 a : HSiCl 3 ; 34 b : LiBr, F 3 CCOOH).…”

Synthesis and Structure of a 1,4-Dihydrazinotetrasilane

“…The higher reactivity of the double bonds in 1 a as compared to isolated silicon-silicon double bonds is reflected in the ready two-fold 1,2-addition of ammonia to 1 a to afford a 1,4-diaminotetrasilane [8]. In the solid state this product exists as a conglomerate of enantiomerically pure crystals, thus exhibiting a rather unusual crystallization behavior [9].…”