Writing the formula of coordinate compounds

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Josh Ku 3H
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Joined: Wed Sep 21, 2016 2:59 pm

Writing the formula of coordinate compounds

Postby Josh Ku 3H » Sun Nov 13, 2016 9:01 pm

Hi sorry I was just a little confused on which ligands are supposed to come first when writing out the formula.
In the textbook it says the chemical symbols of ligands are written in alphabetical order.
To my understanding, I believe it is talking about the actual symbol and not the name.

But in the course reader on page 118 it writes the chloro ligand after the ammine ligands in the formula. Shouldn't Cl come before NH3?
In the toolbox 17.1 (page 741 in textbook) it had molecules where the Cl came before the NH3 in coordination compounds.

Also, just wondering, is it mandatory to write aqua as OH2? In the quiz preps show it as just regular H2O but won't this possibly change the order that the ligands are written in (according to the method used by the textbook)?

MelanieAu1G
Posts: 32
Joined: Wed Sep 21, 2016 2:58 pm
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Re: Writing the formula of coordinate compounds

Postby MelanieAu1G » Mon Nov 14, 2016 1:41 pm

When writing out the name of a compound, not the formula, ligand names are always written alphabetically in regard to the actual ligand, not the prefix indicating the number of ligands. In the course reader, writing chloro after ammine is correct because C comes after A. In the textbook, the compound names including Cl and NH3 are written with Cl after ammine, alphabetically. I think you may be referring to the actual compound formulas, in which case Cl can be written before ammine, because the formulas are not necessarily written in alphabetical order.
As for aqua, most sources I have seen use H2O, however our book does refer to aqua as OH2. This is most likely because the O atom is the atom in a water molecule which would attach to the central TM atom in a coordination compound; therefore, they are emphasizing this point by writing it that way.

I hope that this helps. Best of luck with studying!


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