Question

${BCl}_3$ does not exist as dimer but ${BH}_3$ exist as dimer ${(B}_2{H}_6)$ because:

• A. Chlorine is more electronegative than hydrogen
• B. There is $p\pi -p\pi$ back bonding in ${BCl}_3$ but ${BH}_3$ does not contain multiple bonding
• C. Large sized chlorine atoms do not fit in between the small boron atoms, whereas small sized hydrogen atoms get fitted in between boron atoms
• D. None of the above

Answer 1

Answer: (B), (C)

The correct options are
B There is $p\pi -p\pi$ back bonding in ${BCl}_3$ but ${BH}_3$ does not contain multiple bonding
C Large sized chlorine atoms do not fit in between the small boron atoms, whereas small sized hydrogen atoms get fitted in between boron atoms

$BC{l}_3$ does not exist as dimer but $B{H}_3$ exists as dimer ($B_2{H}_6$) because of two reasons.
A) There is $p\pi -p\pi$ back bonding in ${BCl}_3$ but ${BH}_3$ does not contain multiple bonding.
B) Large sized chlorine atoms do not fit in between the small boron atoms, whereas small sized hydrogen atoms get fitted in between boron atoms.