A Disilene Base Adduct with a Dative Si–Si Single Bond

Abstract

An experimental and theoretical study of the base-stabilized disilene 1 is reported, which forms at low temperatures in the disproportionation reaction of Si2 Cl6 or neo-Si5 Cl12 with equimolar amounts of NMe2 Et. Single-crystal X-ray diffraction and quantum-chemical bonding analysis disclose an unprecedented structure in silicon chemistry featuring a dative Si→Si single bond between two silylene moieties, Me2 EtN→SiCl2 →Si(SiCl3 )2 . The central ambiphilic SiCl2 group is linked by dative bonds to the amine donor and the bis(trichlorosilyl)silylene acceptor, which leads to push-pull stabilization. Based on experimental and theoretical examinations a formation mechanism is presented that involves an autocatalytic reaction of the intermediately formed anion Si(SiCl3 )3 (-) with neo-Si5 Cl12 to yield 1.

Intercepting the Disilene‐Silylsilylene Equilibrium

“…This is consistent with the highfield resonance observed for Si2 in the 29 Si NMR spectrum (d À202.2), which is typical for silyl anions. [19] Scheme 3 shows the three major Lewis resonance representations of compound 3D zwitterionic 3a,d isilene adduct 3b,o rw ith dative CÀSi and SiÀSi bonds (3c)a ss uggested for IX. [11b,18] TheN HC-coordinated disilene 3 is reminiscent of the amine-coordinated disilene Me 2 EtN!SiCl 2 !Si(SiCl 3 ) 2 IX recently reported by some of us (Scheme 3).…”

“…[14,17] TheN HC C1À Si1 bond distance,1 .945 (2) ,i stypical of NHC-silicon bonds. [19] To evaluate the bonding in 3,w ep erformed density functional theory (DFT) calculations. [19] Scheme 3 shows the three major Lewis resonance representations of compound 3D zwitterionic 3a,d isilene adduct 3b,o rw ith dative CÀSi and SiÀSi bonds (3c)a ss uggested for IX.…”

“…[19] Scheme 3 shows the three major Lewis resonance representations of compound 3D zwitterionic 3a,d isilene adduct 3b,o rw ith dative CÀSi and SiÀSi bonds (3c)a ss uggested for IX. TheN LMO corresponding to the C1ÀSi1 bond is notably less polarized than that for the amine N1 À Si1 bond in IX [19] [20] An atural bond orbital (NBO) analysis reveals an atural localized molecular orbital (NLMO) with s-character representing the lone pair at Si2, whilst two further NLMOs correspond to 2e-2c Si1ÀSi2 and C1ÀSi1 single bonds,p olarized towards Si1 and C1, respectively ( Figure 2a).…”

“…[21] QTAIM analysis of 3 discloses am olecular graph with bond paths between the central Si(H)Cp* group and the carbene C1 atom as well as the Scheme 2. [19] 3:R= pentamethylcyclopentadienyl, L = Me I i Pr. Lewis structure representations of disilenes 3, 4,and 6 and IX.…”

Das schwach koordinierende Tris(trichlorsilyl)silyl‐Anion

“…Reaktion von Cl 3 SiSiCl 3 mit Me 2 EtN) [9] und dem kationischen Tr isilankomplex [(NHC iPr ) 3 Si 3 Cl 5 ] + (erhalten aus der Reaktion des metastabilen SiCl 2 mit NHC iPr ). [26] FürS i-(SiCl 3 ) 3 À und Me 2 EtNSi(Cl 2 )Si(SiCl 3 ) 2 [9] sind die durchschnittlichen Si-Si-Bindungslängen (ca.…”