Sciencemadness Discussion Board

Metal Complex Reaction Equations

tekkado - 5-5-2018 at 01:34

Hi guys,
Im struggling a little bit with my reaction equations.
For our lab practical we prepared different metal complexes and now have to provide the reaction equations for them in our report.

As an example we prepared [NiCl2(PPh3)2]
This was done by refluxing triphenylphosphine in isopropanol, to which was added a solution of NiCl2.6H2O in ethanol that was prepared prior. This was refluxed and the precipitate collected.

I understand writing them out as their species and balancing them but how do i write out the first part that consisted of two seperate solutions?

Boffis - 5-5-2018 at 02:27

I am not sure I quite understand your problem. The making of the two separate solutions do not involve reactions. The alcohols are just the medium and can be ignored in the equation. It is just possible that some of the nickel chlorides coordinated water may be lost to the ethanol and in part replaced by the latter but this sort of interaction with the solvent is generally ignored unless it has bearing on the outcome of the reaction.

Your example is unusual in that there is no real reaction, no ions or electrons exchanged, no hard bonds broken. You are merely exchanging co-ordinated water molecules for triphenylphosphine molecules. It forms a coordination complex with the nickel by sharing its free electron pair with the nickel. The water simply goes into the solution.

Hegi - 5-5-2018 at 08:04

Quote: Originally posted by tekkado  
Hi guys,
Im struggling a little bit with my reaction equations.
For our lab practical we prepared different metal complexes and now have to provide the reaction equations for them in our report.

As an example we prepared [NiCl2(PPh3)2]
This was done by refluxing triphenylphosphine in isopropanol, to which was added a solution of NiCl2.6H2O in ethanol that was prepared prior. This was refluxed and the precipitate collected.

I understand writing them out as their species and balancing them but how do i write out the first part that consisted of two separate solutions?


This question sounds very strange for the person who is already in the lab preparing coordination compounds. You should be already familiar with theoretical aspects of coordination chemistry. The first step is just dissolution of your ligand in a hot solvent - no need to write anything. The second step is the reaction where coordination bonds are formed and the old ones are broken down. So yes simply said it is substitution. You get a low-spin diamagnetic square planar complex according to literature.