Page 1 of 1

Bidentate or Polydentate

Posted: Sun Nov 22, 2015 11:18 pm
by Chu 3J
I am confused as to why oxalato is considered bidentate, even though it has at least two lone pairs on each of the four oxygen atoms. If each oxygen atom were only able to form one of these types of bonds, wouldn't oxalato be able to donate 4 electron pairs making it a polydentate?

Re: Bidentate or Polydentate

Posted: Sun Nov 22, 2015 11:34 pm
by Kanwaldeep Rai 2H
Oxygen, in oxalato, tends to only make two bonds from the single bonded oxygens. According to electronegativity, only the oxygens with three lone pairs attracts another atom. This is the reason that it is a bidentate and not a polydentate. I know it's confusing but that is what I was told. Also, you can think of it in terms of formal charge with two oxygens having +1 charge and two have 0. So the two with +1 will form bonds.

Re: Bidentate or Polydentate

Posted: Sun Nov 22, 2015 11:44 pm
by Rachel Risoleo 3G
Also, due to the shape of the oxalato complex, only two of the oxygen atoms will be able to bond, because they are opposite each other. It has less to do with the double or single nature of the bond because, as we know due to resonance structures, in nature all bonds will tend to be the same, with a mix of double and single bond characteristics.