The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-y ne 1 with diethylamine or diphenylamine produced the corresponding amino-substituted disilenes R(R'N-2)Si=SiHR 2a, b (R = (SiPr)-Pr-i[CH(SiMe3)(2)](2), R' = Et (2a), Ph (2b)). The reaction of 1 with 9-borabicyclo[3.3.1]nonane afforded the boryl-substituted disilene R(R '' B-2)Si=SiHR 3 (R '' B-2 = 9-borabicyclo[3.3.1]nonan-9-yl). Spectroscopic and X-ray crystallographic analyses of 2a, b, and 3 showed that 2a and 3 have a coplanar arrangement of the Si=Si double bond and amino or boryl groups, giving pi-conjugation between the Si=Si double bond and the lone pair on the nitrogen atom or vacant orbital on the boron atom, whereas 2b exhibits no such conjugation.