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I have looked around and most of the sites suggest that bond angle of $\ce{OBr2}$ is greater than $\ce{OCl2}$ and it is explained by stating the electronegativity difference and looking at electron repulsion (VSEPR). However none of the websites actually give any experimental data so i am unsatisfied. I think that extent of back bonding would be more for $\ce{OCl2}$ and hence its bond angle should be greater.

Can someone please explain why i may be wrong and give experimental data on bond angle along with it?

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  • $\begingroup$ It is indeed larger, but the difference is only 1.1 degree. This is negligible and a lot of different effects could cause it. $\endgroup$ – permeakra Nov 22 '16 at 21:38
  • $\begingroup$ Related: chemistry.stackexchange.com/q/18697/7475 $\endgroup$ – Jan Nov 22 '16 at 23:37
  • $\begingroup$ I found some old data (J. Chem. Soc. A, p658,1968) on $\ce{Cl2O}$ which gives an experimental bond angle of $111^{\circ}$ and bond length of $171$ pm. There are several sites that quote an angle of $105^{\circ}$ for $\ce{Br2O}$ but don't say whether this is measured. $\endgroup$ – porphyrin Nov 23 '16 at 9:20
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I think steric effects may play a role in that chlorine atoms are smaller than bromine atoms. The bromine atomic radius is about 0.15 Angstroms larger than the chlorine atomic radius. The larger bond angle can be in part explained by the need to accommodate the larger atoms.

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