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AQA A Level Chemistry Transition metals

https://mmerevise.co.uk/wp-content/uploads/2017/11/AQA-CHEM5-W-QP-JAN11.pdf
For Q4)e iii How do you predict the coordination number please?
You need to count the total number of lone pairs donated by the ligands. 1 +1 +porphyrn. I think porphyrn is 4.
(edited 11 months ago)
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Original post by anon25x
https://mmerevise.co.uk/wp-content/uploads/2017/11/AQA-CHEM5-W-QP-JAN11.pdf
For Q4)e iii How do you predict the coordination number please?


This question is old spec, so don't worry about trying to answer it (or most of the paper to be honest). On the old spec the behaviour of chromium was required knowledge and possibly porphyrin aswell. However, to try and answer the question you look at the reaction of porphyrin with the hexaaquferro complex (Fe(H2O)6), and see that when the porphyrin joins the complex it displaces 4 water molecules. This tells you that porphyrin is capable of forming 4 bonds to the central metal ion. Then, in predicting cobalt's co- number, its 4 for porphyrin, plus 1 for the cyanide (also old spec knowledge) and one for the other unnamed ligand, but you are told it is unidentate, so forming one bond to the ion. Therefore the coordination number is 6.

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