Questions tagged [coordination-compounds]

This tag is for questions concerning coordination compounds including but not limited to ligand properties, metal properties, orbital splitting, micro- and macroscopic properties of entire complexes etc. For complexes where carbon monoxide is the only ligand, use the [carbonyl-complexes] tag instead. For organic catalysts or proteins, the tag is applicable if the question is about the metal’s direct coordination sphere.

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4
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2answers
724 views

Colorless nature of carbonyl complexes

Researching the coloration of transition metal complexes one day, I came across this reference on Wikipedia 1: I am not sure why this is so. Take $\ce{Mo(CO)_6}$, or any other carbonyl complex of the ...
6
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3answers
5k views

Colour intensity of transition metal complexes

Even though they are both $\mathrm{d^7}$ complexes, the colour of $\ce{[Co(H2O)6]^2+}$ is pale whereas that of $\ce{[CoCl4]^2-}$ is more intense. Does the octahedral or tetrahedral geometry matter in ...
3
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1answer
343 views

Crystal field splitting pattern with strong field and weak field ligands

What will be crystal field splitting pattern for octahedral complexes if some of the ligands are strong and some are weak field ligands?
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1answer
170 views

Tollen's Test and Werner's Theory

The production of silver ions in Tollen's test violates Werner's theory of non - ionizable secondary valency since we are using the diamminesilver(I) complex as the reagent. How does one reason this??...
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3answers
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Why don't electrons pair in [Fe(NH3)6]2+?

Why doesn't electron pairing take place in $\ce{[Fe(NH3)6]^2+}$ though $\ce{NH3}$ is a strong ligand field producer?
1
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1answer
2k views

Name the following coordination complex

What are the IUPAC rules when naming a coordination complex like: $$\ce{[Pt(NH3)4][Pt(NH3)Cl3]}$$ Now according to my textbook, it is named as tetraammineplatinum(II) amminetrichloridoplatinate(II)...
1
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1answer
79 views

Ligand Binding Paradox?

I have a ligand $\ce{L}$ and a receptor $\ce{R}$. As can easily be shown, with dissociation constant $K_\mathrm{D} = \frac{[\ce{L}][\ce{R}]}{[\ce{LR}]}$ the fraction of receptors occupied by ligand is ...
3
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2answers
5k views

Can a high-spin complex be diamagnetic?

There are two nickel complexes: one is octahedral and the other square planar. One complex is diamagnetic, the other is paramagnetic. Both are high-spin. Now, $\ce{Ni^2+}$ that is octahedral should ...
4
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2answers
913 views

Why do ligands have such a small effect on overall absorption of a complexed ion?

When a metal cation is complexed, there is strong UV-Vis absorption due to the splitting of its $d$ orbitals, thereby allowing electronic transitions. My understanding is that ligands contribute very ...
15
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3answers
40k views

Why is tetraamminecopper(II) a square planar and not a tetrahedral species?

In $\ce{[Cu(NH3)4]^2+}$, the $\ce{Cu^2+}$ ion has 9 electrons in the $\mathrm{3d}$ orbital with only one unpaired electron. How is it a square planar geometry? Where is that unpaired electron going?
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3answers
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Why does carbon monoxide have a greater affinity for hemoglobin than oxygen?

Hemoglobin is an iron-containing oxygen transport metalloprotein in the red blood cells of most mammals. Simply put, it's a carrier protein. Interestingly it doesn't carry carbon dioxide in the same ...
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1answer
2k views

What is that process called in which we add water molecules to an ion to form a complex?

An example would be $\ce{[Fe(H2O)6]^2+}$ in which it has 6 water molecules associated with it. What is the process of adding these water molecules called?
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0answers
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Trans effect on square planar complex [closed]

We've learnt about the trans effect but I have a question regarding how this plays a role with water in the equation. trans-effect: $$\ce{H2O < NH3 < Cl-}$$ Based on this, given cis-$\ce{[Pt(...
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0answers
524 views

Identifying Alkyl Ligands as Pi Donors or Pi Acceptors in Transition Metal Complexes

Just wondering if there was a systematic way to identify an alkyl ligand as a $\pi$ acceptor or $\pi$ donor in a transition metal complex? Although various sources indicate that weak field ligands ...
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3answers
3k views

Are all complexes with a polydentate ligand examples of chelation?

I'm getting a little confused about the definition of chelation and its implications (I should probably point out I'm only an A2 Chemistry student). The IUPAC defines chelation as the following: ...
8
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1answer
5k views

Why are compounds of V5+ and Cr6+ colored? [duplicate]

As far as my knowledge goes, transition metal complex ions show a color due to a transfer of electrons between the levels of split $\mathrm d$-orbitals. In the case of $\ce{V^5+}$ and $\ce{Cr^6+}$ ...
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3answers
8k views

Why doesn't EDTA complex with alkali metal ions?

EDTA complexes with all the other metal ions in the periodic table except those from the group 1. Why is this so ? What is the coordination chemistry behind this ?
42
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6answers
7k views

Can an atom bond with more than 8 other atoms?

Is it possible for an atom to bond with 8 other elements (same or other type)? If yes, then please give some examples. If no, then what could be the possible reason for it? My question is not about ...
7
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2answers
4k views

Calculating the number of ligands of complex ions in d- block

How do you know the number of ligands surrounding a metal ion? Example: the obtained complex of $\ce{Ni^2+}$ ion in $\ce{NH3}$ solution is written as $\ce{[Ni(NH3)6]^2+}$ but $\ce{Cu^2+}$ in $\ce{NH3}...
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0answers
216 views

Why does the value of Δo increase with increased charge on the metal?

A greater positive charge means the ligand is strongly attracted and pulled closer, and thus it creates a stronger crystal field. The potential energy value of the barycentre should thus be higher, ...
12
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2answers
429 views

Water exchange at Al (III)

Why is the rate of water exchange at Al(III) centres so slow ? According to this medical book (p.5) it is $10^{5}$ times faster at Mg(II).
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0answers
171 views

Methyl orange coordination compound chemistry

Methyl orange changes colors depending on the acidity or basicity of the solution. But I have read that it forms complexes with certain ions. Can anybody suggest any resource regarding the ...
4
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1answer
8k views

Nomenclature of complexes: Cyano vs Cyanido ; Chloro vs Chlorido

What is the correct nomenclature for $\ce{CN^-}$ and $\ce{Cl^-}$ ligands in coordination compounds? Wikipedia says the coding name(?) as cyanido and chlorido while this suggests cyano and chloro.
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2answers
37k views

In Crystal Field Theory what does Δo=10Dq mean?

While studying the Crystal Field Theory I was told $\mathrm{Dq}$ is a unit, related to the unit $\Delta_{\mathrm{O}}$ by the relation $\Delta_{\mathrm{O}} = 10\ \mathrm{Dq}$. But aren't $\Delta_{\...
14
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2answers
902 views

What's so special about chelation? [duplicate]

There is another closely related post here , and I've also read the referenced wiki article including applications of chelation, but I still don't see what's so special about chelation. I understand ...
4
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1answer
229 views

Determining spin of metal complex

Is there any way to determine the spin of $\ce{[Fe(OH)6]^{4-}}$ without looking at the spectrochemical series?
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1answer
2k views

Purpose of ammine in Tollens' reagent

In this previous question the mechanism for the reaction of Tollens' reagent was outlined. As I understand it the oxidising agent in Tollens' is the diamminesilver(I) complex $\ce{[Ag(NH3)2]+}$ but ...
6
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1answer
116 views

Why would hexacyanidocobaltate(II) be uncommon while pentacyanidoaquacobaltate(II) is common?

In Huheey's Inorganic Chemistry it is written that hexacyanidocobaltate(II) is uncommon but pentacyanidoaquacobaltate(II) is common. Something is mentioned about Jahn-Teller distortion, but I don't ...
2
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1answer
6k views

High or low spin complex of Zn2+ and Ti3+

The zinc ion in its +2 state can show no more pairing, since all the electrons are already paired - so in any complex it forms it will have the same magnetic moment as it does right now. $\ce{Ti}$ in ...
20
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4answers
7k views

Why is ligand substitution only partial with copper(II) ions and ammonia?

When studying ligand substitution (at UK year 13 level), the following example has been given: \begin{align} \ce{[Cu(H2O)_6]^2+ + 2NH3 &<=> [Cu(OH)_2(H2O)_6] + 2NH4^+}\\ \ce{[Cu(OH)_2(H2O)...
14
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1answer
3k views

Molecular orbital diagram of a complex including an oxido ligand

With highly oxidized metal centers, we expect that the hydroxido ligand's proton becomes acidic and will be lost to the surrounding media, creating an oxido ligand. The oxo ligand is a $\pi$ basic ...
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0answers
43 views

Is hydrolytic polymerisation the mechanism by which the precipitate forms from the neutral complex?

From basic coordination chemistry and acid-base equilibria we understand that a metal hexa-aqua ion can be deprotonated until it's positive charge is balanced by the negative charge of the hydroxides ...
2
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1answer
4k views

Calculation of CFSE

I need to find CFSE for these: $\ce{[Ti(H2O)6]^3+}.$ $\ce{Ti}$ is $\mathrm{(4s)^2(3d)^2}$, $\ce{Ti^3+}$ is $\mathrm{(4s)^0(3d)^1}.$ Afterwards it becomes $\mathrm{d^4sp^2}$ or $\mathrm{t_{2g}^5e_g^4}$...
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1answer
671 views

Reaction with silver oxalate?

I was asked which geometrical isomer of $\ce{[M(NH3)2Cl2]}$, viz. cis or trans would react with silver oxalate. The possible reaction could be formation of silver chloride but since the coordination ...
5
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1answer
2k views

Rate constants for water exchange

Are rate constants for water exchange of transition metal aqua-complexes tabulated anywhere ? I haven't been able to find a resource which is anywhere near comprehensive.
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0answers
2k views

Why [MnCl6]^2- has got 4 unpaired electrons instead of 3?

In $\ce{[MnCl_6]}^{2-}$, $\ce{Mn}$ has +4 oxidation state which gives it a $\ce{3d^3}$ $\ce{4s^0}$ configuration. But how is it having 4 unpaired electrons?
5
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1answer
2k views

Why do charges result on atoms when coordinate bonds are formed?

I have not been able to get my head around it yet. For instance in the reaction between ammonia and borontrifloride why is it that a positive and a negative charge results? Is it that ammonia ...
6
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3answers
4k views

Can any atom donate more than 1 lone pair as a coordinate bond to the same metal?

This would mean the formation of a σ and one or two π bonds, all coordinate. I haven't heard of this happening, like a fluorine anion or water with two lone pairs on oxygen will donate ...
11
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1answer
6k views

How hydrate isomerism results difference in colours?

The standard example is $\ce{CrCl3.6H2O}$, which can have three distinctly different crystalline compounds now known as $\ce{[Cr(H2O)6]Cl3}$ (violet), $\ce{[CrCl(H2O)5]Cl .H2O}$ (blue-green), and ...
5
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1answer
244 views

Why macromolecule ligands such as Crown ethers form more stable complexes than open chain ligands?

This was in J. Huheey's book and no explanation was given
4
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1answer
64 views

Decomposition products of hexaurea-chromic-chloride-trihydrate

I am sitting over a TG diagram of the decomposition steps of hexaurea-chromic-chloride-trihydrate ($\ce{[Cr(CO(NH2)2)6]Cl3 \cdot 3 H2O}$) and cannot really make sense of the products it might ...
2
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1answer
2k views

Changing solubility of metal complex by adding ethanol

After creating a solution of copper(II)-sulfate-pentahydrate, water and concentrated ammonia, the newly formed complex (tetraamminecopper(II)-sulfate-monohydrate) is completely dissolved in water. By ...
3
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2answers
5k views

Does sodium form complexes like transition metal ions?

I realise that there is a similar question here Difference between sodium ion and a transition metal ion dissolving in water? and it seems to answer my question, however I was reading about how ...
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2answers
2k views

Iodine color change in different complexes

Why does the color of iodine differ when it forms a charge transfer complex with benzene (pi donor) - pink and ethanol (electron pair donor) - brown? Does the HOMO-LUMO energy differ, if so how?
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1answer
357 views

Why member ring is favoured in chelates?

why chelates which form 3 or 4 member rings or 6 or 7 member rings are as stable as 5 member ring chelates? for example if we measure stability of chelates with oxygen donors, say oxalate, malonate, ...
2
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1answer
402 views

what are possible isomers of (meso-stilbenediamine)(isobutylenediamine) palladium (II)?

It can form a square planar and a tetrahedral complex but within square planar or within tetrahedral can there be isomers possible?
2
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3answers
637 views

Does tetramine copper dissolve cellulose?

I saw a Youtube video which showed that cotton (cellulose) dissolves in deep blue solution of tetramine copper made by adding 20% ammonia in copper carbonate salt. I tried to replicate the process ...
2
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1answer
608 views

Why should a complexometric titration be kept neutral?

In my next lab, I'll be doing a complexometric titration of a copper solution with EDTA and a murexide indicator. The lab guide advises to keep the pH level nearly neutral by adding a diluted $\ce{NH3}...
4
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2answers
4k views

Green and red crystals of [Ni(Ph2EtP)2Br2]

From the reaction of $\ce{NiBr2}$ and $\ce{Ph2EtP}$, it is possible to isolate green and red crystals of $\ce{[Ni(Ph2EtP)2Br2]}$? A) coordination number and geometries of the complexes? B) possible ...
3
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1answer
3k views

Ratio of copper(II) ions to EDTA?

What is the ratio of copper(II) ions to EDTA in a $\ce{[Cu(EDTA)]^{2-}}$ complex? I know that EDTA forms up to 6 coordinate bonds with the central atom, but is that what they are asking for with "...