Conformationally Switchable Silylone: Electron Redistribution Accompanied by Ligand Reorientation around a Monatomic Silicon

Abstract

Complexes that could be switched between two electronic states by external stimuli have attracted much attention for their potential application in molecular devices. However, a realization of such a phenomenon with low-valent main-group element-centered complexes remains challenging. Herein, we report the synthesis of cyclic (alkyl)(amino)silylene (CAASi)ligated monatomic silicon(0) complexes (silylones). The bis-(CAASi)-ligated silylone adopts a π-localized ylidene structure (greenish-black color) in the solid state and a π-delocalized ylidene structure (dark-purple color) in solution that could be reversibly switched upon phase transfer (ylidene [L: → :Si = L ↔ L = Si: ← :L]). The observed remarkable difference in the physical properties of the two isomers is attributed to the balanced steric demand and redox noninnocent character of the CAASi ligand which are altered by the orientation of the two terminal ligands with respect to the Si−Si−Si plane: twisted structure (π-localized ylidene) and planar structure (π-delocalized ylidene). Conversely, the CAASi/CDASi-ligated heteroleptic silylone (CDASi = cyclic dialkylsilylene) only exhibited the twisted π-localized ylidene structure regardless of the phase. The synthesized silylones also proved themselves as monatomic silicon surrogates. Thermolysis of the silylones in the presence of an ethane-1,2-diimine afforded the corresponding diaminosilylenes. Analyses of the products suggested a stepwise mechanism that proceeds via a disilavinylidene intermediate.

Synthesis and Reactivity of N‐Heterocyclic Silylene Stabilized Disilicon(0) Complexes

“…Theoretical studies suggested that this compound could be viewed as a cyclic alkyl silylene‐stabilized ylidone [12] . Iwamoto and co‐workers were able to isolate the monoatomic silicon(0) complex ( IV ) with an ylidene structure by employing a cyclic (alkyl)(amino)silylene ligand [3i] . Driess et al.…”

Precise Transfer of an Aluminium Atom: An Avenue to Aluminium Heterocycles

“…[9] In addition, compounds of [L2E][X] [10] and NaECO [11] (L = two-electron donor ligand; E = P, As; X= counter anion) are two representative examples of E-atom transfer reagents. For group 14 elements, the fascinating ability of a few zero-valent silicon species, namely silylones C [12] and a base-stabilized disilicon D [13] , have been demonstrated as surrogates of elemental silicon. [14] Scheschkewitz et al showed atomically precise expansion of unsaturated silicon clusters through SiCp*2 (E) [15] and (NHC)GeCl2 (NHC = 2,3,4,5-tetramethylimidazolylidene) [16] , while the group of Wesemann disclosed a base-stabilized germasilenylidene F that delivers a Si atom.…”

Transfer of an Aluminium Atom: An Avenue to Aluminium Heterocycles

“…17 In addition, compounds of [L2E][X] [18][19][20] and NaECO [21][22][23][24][25] (L = two-electron donor ligand; E = P, As; X= counter anion) are two representative examples of E-atom transfer reagents. For group 14 elements, the fascinating ability of a few zero-valent silicon species, namely silylones C 26 and a base-stabilized disilicon D 27 , have been demonstrated as surrogates of elemental silicon. 28 Scheschkewitz et al showed atomically precise expansion of unsaturated silicon clusters through SiCp*2 (E) 29 and (NHC)GeCl2 (NHC = 2,3,4,5tetramethylimidazolylidene) 30 , while the group of Wesemann disclosed a base-stabilized germasilenylidene F that delivers a Si atom.…”