Isolation of a 1‑Magnesium-2,3-disilacyclopropene and a Related Bis(disilenide)

Herein we report the first synthesis of a 1-magnesium-2,3-disilacyclopropene and a related bis­(disilenide). Reduction of (boryl)­tribromosilane (1, boryl = (HCArN)2B, Ar = 2,6-iPr2C6H3) with magnesium in THF afforded boryl-substituted magnesium complex [(boryl)­Si]2Mg­(THF)3 (2) in good yield, whereas reduction of (boryl)­trichlorosilane (3) with KC8 in THF led to the isolation of bridged alkoxy alkyl bis­(disilenide) (THF)­K­(boryl)­SiSi­(boryl)­O­(CH2)4(boryl)­SiSi­(boryl)­K­(THF) (4) via ring opening of a THF molecule. X-ray diffraction analysis of 2 confirmed the presence of the novel Si2Mg three-membered ring as well as the SiSi double bond, which existed in a noticeably twisted B–Si–Si–B array. Complex 2 also represents the first reported example of a stable disilyne dianion.