An Isolable 2,4-Diaminotetrasilabicyclo[1.1.0]but-1(3)-ene: Effects of Amino Groups at the Bridge Positions

Tetrasilabicyclo[1.1.0]but-1(3)-enes, compounds containing an Si=Si double bond with an inverted geometry, have recently emerged as a new class of stable π-electron systems of silicon. Herein, we report the synthesis of 2,4-diaminotetrasilabicyclo[1.1.0]but-1(3)-enes 1t and 1c that have amino groups at the bridge positions. XRD analysis and theoretical calculations revealed that inverted Si=Si double bonds in 1t and 1c lengthen up to 2.55 Å likely due to the interaction between the π(Si=Si) and σ*(Si–N) orbitals.