Question

Which of the following statement is false for trisilylamine ?

• A. Three sp2 orbitals are used for $\sigma$ bonding, giving a plane triangular structure.
• B. The lone pair of electrons occupy a p-orbital at right angles to the plane triangle and this overlaps with empty p–orbitals on each of the three silicon atoms resulting in $\pi$ bonding.
• C. The N–Si bond length is shorter than the expected N–Si bond length.
• D. It is a weaker Lewis base than trimethyl amine.

Answer 1

Answer: (B)

The lone pair of electrons occupy a p-orbital at right angles to the plane triangle and this overlaps with empty p–orbitals on each of the three silicon atoms resulting in $\pi$ bonding.

Answer 2

There is p$\pi$–d$\pi$ delocalization of lone pair of electron on nitrogen atom and empty d-orbital of silicon but not p$\pi$ – p$\pi$, one of the 2s-orbital electrons jumps to the last Pz orbital and does not participate in sp2 hybridisation.