Oxidn. of (Me3Si)3CBCl2 with Li2O in THF gave 95% (Me3Si)3CB(Cl)OB(Cl)C(SiMe3)3 which on dechlorination with Na-K alloy in hexane gave 57% title compd. I. I is unreactive towards CO, BH3, EtB.tplbond.NCMe3, or alkynes (EtC.tplbond.CEt, Me3SiC.tplbond.CSiMe3). However, oxidative addn. reaction of I with RCO2H (R = H, Me) gave 71-82% diboratrioxacyclohexanes II.