Chemistry question...complex ions?

Question

So we are given the complex ion: [Mn(h2o)2(en)(ox)]^+3

a) What is the formula of the chloride salt?

b) Suppose the (en) molecule is replaced by (OH-), write it without affecting the current coordination number...

c) Write the formula of a possible coordination compound containing the resulting complex ion?

d) Is the initial compound diamagnetic or para-?

Thanks for your help!

Answer 1

a) The chloride salt will be a neutral compound.  The complex has a charge of +3, so 3 Cl- ions must be added to balance the charge:

[Mn(H2O)2(en)(ox)]Cl3

b) en (ethylenediamine) is a bidentate ligand - each of the 2 N atoms in the molecule binds to the metal.  Thus, it contributes 2 to the total coordination number.  OH- is monodentate: it only binds once (at the oxygen), and thus only contributes 1 to the coordination number.  So we must replace the en with 2 OH- to meet the condition that the coordination number remains the same.

c)  The formula of this resulting ion would be [Mn(H2O)2(OH)2(ox)]+ (the charge changes because we add 2 negatively charged OH- groups).  Thus, a possible salt would be [Mn(H2O)2(OH)2(ox)]Cl.

d)  Water and ox are intermediate field ligands, but en is a  strong field ligand, so the compound will be low spin.  In this case, this turns out not to matter - the Mn is in a +5 oxidation state (make the charges balance - en is neutral, but ox (oxalate) has a 2- charge).  Mn5+ has 2 d electrons, and these go into the t2g level without pairing.  Thus, we have 2 unpaired spins, and the compound is paramagnetic.