Both `N(SiH_(3))_(3) and NH(SiH_(3))_(2)` compounds have trigonal planar skeleton. Incorrect statement about both compounds is :

Options

A. `SiNSi` bond angle in `NH(SiH_(3))_(2)gtSiNSi` bond angle in `N(SiH_(3))_(3))`
B. `N-Si` bond length in `NH(SiH_(3))_(2)gtN-Si` bond length in `N(SiH_(3))_(3))`
C. `N-Si` bond length in `NH(SiH_(3))_(2)ltN-Si` bond length in `N(SiH_(3))_(3))`
D. Back bonding strength in `NH(SiH_(3))_(2)gt` Back bonding strength in `N(SiH_(3))_(3))`

Answer

B

Explanation

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