See image — AITS & Test Series Chemistry Question

💡 Solution & Explanation

In NH(SiH3)2 electron density or lone pair at N-atom is involved in back bonding only with two empty 3d-orbitals of two silicon atoms while in N(SiH3)3 it is involved with three empty 3d-orbitals of three silicon atoms. Strength of back bonding in NH(SiH3)2 is higher than in N(SiH3)3 hence N – Si bond length in NH(SiH3)2 is less than that of in N(SiH3)3.