Development of efficient bond formation reactions remains important in organic and main-group-element chemistry. Herein, we report the metal-free one-pot condensation reaction of 1iodo-3-trimethylsilyl-substituted bicyclo[1.1.1]pentasilane (BPS) in the presence of 4-(dimethylamino)pyridine (DMAP) providing oligomers of BPS, persila[n]staffanes (n = 2, 3), which involves the successive Si−Si bond formation reaction accompanied by the concomitant formation of iodotrimethylsilane (TMSI) in the form of a DMAP complex. The computational study suggests that the formation of a pentasila[1.1.1]propellane−DMAP complex resulting from the elimination of TMSI from the BPS is a key intermediate.

A fascinating but still rare bicyclic siloxane, bicyclo[3.3.3]pentasiloxane, was synthesized by the oxidation of a bicyclic silicon cluster and characterized using a combination of NMR spectroscopy and X-ray diffraction analysis. The bridgehead OSiMe groups of the siloxane were selectively and efficiently converted to OK (siloxide) by treating with BuOK in the presence of 18-crown-6-ether. The resulting siloxides provided various bridgehead-functionalized bicyclo[3.3.3]pentasiloxanes after treatment with electrophiles.

Treatment of 1,3-di­(t-butyldimethylsilyl)-1,3-disilabicyclo­[1.1.0]­butane 1a with excess lithium in THF provided 1,3-dilithio-1,3-disilabicyclo[1.1.0]­butane 2 via reductive cleavage of the exocyclic Si–Si bonds at the bridgehead silicon atoms. In the single crystals obtained by recrystallization in the presence of 1,2-dimethoxyethane (DME), 2 exists as a solvent-separated ion pair, and its anionic part forms an aggregate that contains three lithium atoms sandwiched by two 1,3-disilabicyclo[1.1.0]­butan-1,3-diide units. Treatment of 2 with chlorotri­isopropylsilane provided triisopropylsilyl-substituted 1,3-disilabicyclo[1.1.0]­butane 1b. The structural characteristics of 1b are close to that of the short-bond isomer, which is consistent with previous theoretical predictions concerning the steric effects of the bridgehead substituents on the structure of silabicyclo[1.1.0]­butane.