How do you know the order of ligands?

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In summary, the formula for triammineaquadihydroxochromium(III) chloride is [Cr(OH)2(H2O)(NH3)3]Cl, following the IUPAC naming rules where the transition metal is listed first, followed by the anionic ligand and then neutral ligands in alphabetical order.
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AMan24
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Homework Statement


So i have triammineaquadihydroxochromium(III) chloride and i have to write the formula.

Homework Equations

The Attempt at a Solution


So there's (NH3)3, H2O, (OH)2, Cr and a Cl anion

I know the transition metal goes first, and the charge of the complex is 1+ so it'll be = {Cr - - - ] Cl

But now how do i know what order to put the (NH3)3, H2O, (OH)2? I don't think it has to be alphabetical. If it is alphabetical then this is simple. And it can't just be put the metal, then the neutral ligands then charged ligand because there are two neutral ligands, (NH3)3 and H2O, so which one of those would go first...
 
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so i think i found out how to do it, neutrals should come before charged ligands, and neutrals should be organized alphabetically according to chemical symbol, not name.

So this will be [CrH2O(NH3)3(OH)2]Cl

But I am really not too sure, i see so many complexes that have the metal then a negatively charged ligand then the neutral. Like [CrCl2(H2O)4]
 
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  • #3
TBH I am not sure what the correct answer ism but the only authoritative source on that will be one of the IUPAC books defining naming rules. Quick googling suggests it is a so called "Red book".
 
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  • #4
As IUPAC Rule
First is always Cation and then anion
In your example cation is a complex and anion is Cl-
triammineaquadihydroxochromium(III) ...Now here first write the Transition metal (Cr) ,then anionic ligand (2OH-) and then neutral ligand alphabetically (first H2O and then NH3 )
a
So The answer is [Cr(OH)2(H2O)(NH3)3]Cl
 

1. How do you determine the order of ligands in a coordination complex?

The order of ligands in a coordination complex is determined by using spectroscopic techniques such as UV-Vis, IR, or NMR spectroscopy. These techniques allow for the identification of the different ligands present and their relative strengths. Additionally, X-ray crystallography can also be used to determine the order of ligands in a coordination complex by analyzing the distances between the central metal ion and the surrounding ligands.

2. What is the significance of knowing the order of ligands in a coordination complex?

The order of ligands in a coordination complex is important because it affects the properties and reactivity of the complex. The ligands in a coordination complex can have different bonding strengths and therefore influence the stability and electronic structure of the complex. Knowing the order of ligands can also provide insight into the geometry of the complex and its potential applications in various fields such as catalysis and materials science.

3. Can the order of ligands change in a coordination complex?

Yes, the order of ligands in a coordination complex can change. This can occur through ligand substitution reactions, where one ligand is replaced by another, or through isomerization reactions, where the ligands rearrange around the central metal ion. The order of ligands in a coordination complex can also be affected by changes in temperature, pressure, or pH.

4. How does the coordination number of a metal ion affect the order of ligands?

The coordination number of a metal ion, which refers to the number of ligands bonded to the metal, can influence the order of ligands in a coordination complex. For example, in a coordination complex with a high coordination number, the ligands may be arranged in a particular order to minimize steric hindrance. Additionally, the coordination number can also affect the stability of the complex, which can impact the order of ligands.

5. What are some other methods for determining the order of ligands in a coordination complex?

In addition to spectroscopic techniques and X-ray crystallography, other methods for determining the order of ligands in a coordination complex include electrochemical methods and computational modeling. Electrochemical methods involve measuring the oxidation or reduction potentials of the complex, which can provide information about the ligand order. Computational modeling, using quantum chemical calculations, can also be used to predict the order of ligands based on their electronic and geometric properties.

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