Nitrogen (N) atom in trimethyl amine [N(CH3)3] is sp3 hybridised and tetrahedral ( bond angle ~107) due to non bonding electron pair of N is localised (more basic). On the other hand N atom of trisilyl amine [N(SiH3)3] is sp2 hybridised and trigonal planner (bond angle~120).This is due to the participation of non-bondlng pair of N into pπ-dπ back banding. Due to this delocalization of non-bonding electron pair of N in trisilyl amine it is also less basic
Generally neutral atom donates only one lone pair to back bonding because after that, electron density on that atom itself highly reduced but the compound [(CF3)2-Al-O-Al-(CF3)2] is a rare example of two lone pair donation.
Q (1):
which is greater x or y?
Q (2):
which is greater x or z?
Q (3):
which have greater extent of back Bonding?
SOLUTION:
Ans: (1): ‘y’ is greater than ‘x’ because of steric repulsion
of -CH3 group.
Ans: (2): “z’ will be greater because one lone pair going two
places.
Ans; (3): the extant of back bonding is 3rd >1st > 2nd
SOLUTION:
Extent Back Bonding is 3>1>2
and bond length order is y>x>z
(1) Angle O-B-O =120
(2) Angle H-O-B >109
(3) Hybridization of atom O close to sp2 and
(4) Molecule is non planer and non polar
Answer: Statement (4) is wrong because molecule is planer and polar
