Diisopropyl(2,4,6‐tri‐tert‐butylphenylimino)silane—a very Stable, Free Silaimine

Abstract

Once again we have found bulky substituents that enable the synthesis of a stable compound with a moiety that has virtually been discarded and contradicts the double bond rule. The silaimine 1, synthesized by thermal cleavage of LiCl, is an orange‐colored crystalline compound that melts without decomposition at 97–99°C.

Efficient Synthesis of a NHC‐Coordinated Trisilacyclopropylidene and Its Coordination Behavior

“…[13] With the idea to take advantageo ft he ability of Lewis base coordination to stabilize transienti ntermediates we aimed to build-up clusterf ragments in co-reduction reactions of NHCadducts of SiCl 4 and mono-a nd diaryl-substituted silicon(IV) precursors. In comparison to the 29 Si NMR chemicals hifts of the trisilacyclopropylidene derivative II of Scheschkewitz( d = À65.7 ppm for Si(Trip) 2 and d = À110.5 ppm forS iNHC iPr2Me2 )t he signals forS i(Mes) 2 of 1 are similar.H owever,t he signal for the carbene-coordinated silicon atom in 1 is shiftedt oh igher field which is probablyr elatedt o the higher s-character of the lone pair of 1. Thus, in contrastt oI-III access to 1 proceeds in only one step.…”

“…Singlec rystals of 1 were grown in diethyle ther.A ttemptst og row crystals of the second compound were not successful. In comparison to the 29 Si NMR chemicals hifts of the trisilacyclopropylidene derivative II of Scheschkewitz( d = À65.7 ppm for Si(Trip) 2 and d = À110.5 ppm forS iNHC iPr2Me2 )t he signals forS i(Mes) 2 of 1 are similar.H owever,t he signal for the carbene-coordinated silicon atom in 1 is shiftedt oh igher field which is probablyr elatedt o the higher s-character of the lone pair of 1.…”

“…[12] Besides NHCsa ni ntramolecular imine coordination allowed the isolation of as ila-cycloprop-1-ylidene III which was obtained after a thermal rearrangemento fapenta-coordinates ilirene (Scheme 1). According to multinuclear NMR spectroscopy of the reactionm ixture as econd compound is formed throughout this reduction because in the 29 Si NMR spectrum two further signals (at À46.8 and À155.7 ppm) besides the signals at À68.6 and À132.3 ppm belongingt o1 were detected. Among an umbero fc ombinations only the co-reduction of NHC iPr2Me2 !SiCl 4 and two equivalents of Mes 2 SiCl 2 using lithium naphthalenide (Li(Naph)) as the reducing agent was successful and afforded unprecedentedly the NHC-coordinated trisilacyclopropylidene (SiMes 2 ) 2 SiNHC iPr2Me2 1 (see Scheme2 and Figure 1) in form of an orange powder from a red solution in around 23 %y ield.…”

“…Thus, in contrastt oI-III access to 1 proceeds in only one step. According to multinuclear NMR spectroscopy of the reactionm ixture as econd compound is formed throughout this reduction because in the 29 Si NMR spectrum two further signals (at À46.8 and À155.7 ppm) besides the signals at À68.6 and À132.3 ppm belongingt o1 were detected. Singlec rystals of 1 were grown in diethyle ther.A ttemptst og row crystals of the second compound were not successful.…”

Crystallographic analysis of thermochromic, unsolvated tetramesityldisilene at 173 K and 295 K

“…The solvated compound (1 .C7Hs) is a yellow solid both at room temperature and below, but when heated 1.C7H8 darkens to orange and then melts to a red liquid at 178°C. Other tetraaryldisilenes are also thermochromic [S], as is a silaimine (contains Si=N) [ 6 ] , a digermene (contains Ge=Ge) [7], and a germene (contains Ge=C) [81.…”