[giosoton]

Hi there inorganic,

I'm a biochem undergrad and I've come across a problem concerning calcium signalling.

Why, when Ca2+ is coordinated do the ligands have variable bond lengths, compared to Mg2+ where the ligands have constricted coordination bond lengths?

So in essence, why is calcium coordination more flexible than magnesium?

Note, this is generally regarding oxygen ligands.

[giosoton]

I just want to make this clear, this is not homework. I just find it interesting and would like to know more.

[Dark Vaati]

Well, basically calcium is a softer metal than magnesium, so it does not coordinate to oxygen so strongly because it prefers to interact with N-donors. That could be a possible explanation...