Annulated 1,4-Disilabenzene-1,4-diide and Dihydrogen Splitting
Falk Ebeler, Yury V. Vishnevskiy, Beate Neumann, Hans‐Georg Stammler, Dariusz W. Szczepanik, Rajendra S. Ghadwal
Abstract
The isolation of silicon analogues of phenyl anions such as (C 6 H 5 ) − and (C 6 H 4 ) 2– is challenging owing to their extremely high reactivity associated with their silylene character and weak C–Si π-interaction. Herein, we report the first annulated 1,4-disilabenzene-1,4-diide compound [(ADC)Si] 2 ( 5 ) based on anionic dicarbene (ADC) scaffolds (ADC = PhC{N(Dipp)C} 2; Dipp = 2,6- i Pr 2 C 6 H 3 ) as a green-yellow crystalline solid. Compound 5 is prepared by KC 8 reduction of the Si(IV) chloride [(ADC)SiCl 3 ] 2 ( 3 ) or the cyclic bis-chlorosilylene [(ADC)SiCl] 2 ( 4 ), which are also prepared for the first time. 5 is a neutral molecule, and each of the two-coordinated Si(I) atoms has a lone pair and an unpaired electron. Experimental and theoretical data indicate delocalization of the silicon unpaired electrons, resulting in a 6π-electron C 4 Si 2 ring in 5 . The diradical character ( y ) for 5 amounts to 15%. At room temperature, 5 readily reacts with dihydrogen (H 2 ) to form the elusive bis-hydridosilylenes [(ADC)SiH] 2 ( Z )- 6 and ( E )- 6 . The [4 + 2]-cycloaddition of 5 and PhC≡CPh in yielding the barrelene-type bis-silylene [(ADC)SiCPh] 2 ( 7 ) emphasizes the diradical reactivity of 5 . With elemental sulfur, 5 results in the S 2 - and S 3 -bridged silathione derivatives [(ADC)Si(S)] 2 (μ-S 2 ) ( 8a ) and [(ADC)Si(S)] 2 (μ-S 3 ) ( 8b ). Moreover, the treatment of 5 with Fe 2 (CO) 9 affords the Fe(0) complex [(ADC)Si(Fe(CO) 4 )] 2 (μ-CO) ( 9 ), in which each silicon atom serves as a two-electron σ-donor ligand and shares one electron with the bridging CO unit to form two Si–C bonds. The molecular structures of all compounds have been established by X-ray diffraction, and representative compounds have been analyzed by quantum chemical calculations.