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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 [tag:carbonyl-complexes] 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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My problem with Tollen's reagent [duplicate]

The formula of Tollen's reagent is $\ce{[Ag(NH3)2]+}$. What is the bond existing between the silver(I) atom and the ammonia groups? Because ammonia is stable, it doesn't need to gain or donate any ...
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Ligand Field Theory: Why do we use the t2g p-orbitals instead of the t2g d-orbitals in the combination with LGOs [on hold]

With the premise that it's the first time that I try to understand the Ligand Field Theory, I'm having issues in fully understanding the MO diagram of a $\sigma$-complex, as shown below: I understand ...
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Structure of (CH3COO)3Fe

I'm a grade 12 student trying to comprehend MOT & LFT in Co-ordination compounds. For one of our salt analysis(practicals), the test for acetate ion includes the addition of Neutral Ferric ...
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1answer
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Why is carbon monoxide a monodentate ligand

Carbon monoxide has lone pairs on both the carbon and the oxygen atoms. However, I have never seen any complex where the oxygen atom or both the oxygen and the carbon atoms are the donors. I know ...
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Why is [Cu(NH3)6]2+ unstable? [duplicate]

why does it convert to $$ [Cu(NH3)_{4}(H2O)_2]^{2+}? $$
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Why does hydration enthalpy decreases instead of increasing down the group?

I have seen in my text book that for group 1 and 2 metals the hydration enthalpy decreases down the group.The reason I have found on the postWhich d-block cation has the maximum hydration enthalpy? is ...
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1answer
52 views

Why does ligand substitution occur when OH- is a better ligand than NH3?

$$\ce{[Cr(H2O)3(OH)3](s) + 6NH3 -> [Cr(NH3)6]^3+ + 3H2O + 3OH-}$$ When excess $\ce{NH3}$ is added to triaquatrihydroxychromium(III), why does ligand substitution occur when $\ce{OH-}$ is a better ...
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Vibronic coupling: How do I determine the new point group after vibration?

So I was recently discussing the transitions in Egyptian Blue ($\ce{CaCu[Si4O10]}$) with some of my students, who had to prepare this compound. What I like in particular in this case is how, at least ...
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2answers
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What is the bond in H2O (water) molecule ? And why? [duplicate]

Is it covalent or coordinate covalent bond ? Because it can be a bond between O and 2 H atoms and so it will be covalent bond . And it can be a bond between H (+ve) ion and Oh(-ve)ion and it will be ...
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How to understand MO diagrams for cationic octahedral transition metal complexes

I am having problems understanding the construction of MO diagrams in octahedral transition metal complexes within ligand field theory (LFT) when the metal center is asumed as an cation: I am ...
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1answer
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How can I get create complex metal ion solution such that the majority of the central metal ions only have one specific ligand?

I'm looking for a way to have the ligand, Chloride ion, datively bond with Copper Sulphate. I understand it is as simple as creating a solution of Hydrochloric Acid and dissolving Copper Sulphate ...
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1answer
53 views

Second order Jahn-Teller effect for d0 complexes

I was wondering why the second order Jahn-Teller effect is also said to happen for many d0-systems? It makes sense to me that due to relativistic effects and the stabilization of the s-Orbital and ...
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1answer
73 views

Optical Isomerism in Coordination Compounds of type MA₂B₂(CC)

I was asked the following question: How many optical isomers are there for $\ce{[Cr(NH3)2Cl2(en)]^+}$ ? First of all I figured out the following four geometrical isomers of the above complex: Out ...
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1answer
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UV Absorption of iodine with some solvent

$I_2$ in solution is typically absorbing around $525 \; nm$ this is why it appear to be magenta, I recently learn that with some solvent : Benzene Toluene $o$-Xylene $p$-Xylene The coordination ...
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Fluoride anion as a strong field ligand

In the case of $\ce{[Fe(H_2O)_6]^{3+}}$ there are $5$ unpaired electrons as water acts as a weak field ligand. But instead of flouride acting as a weak field ion in the $\ce{[MnF_6]^4-}$ , why does it ...
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1answer
89 views

Explain the structure of HNC (Hydrogen Isocyanide)

What are the different types of bonds present in the structure? Does Nitrogen donates one electron from its lone pair to carbon and acquires a positive charge? How do I determine the Oxidation state ...
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1answer
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Oxidation No. of Fe and NO in Nitroprusside ion [duplicate]

For the complex $\ce{[Fe(CN)5NO]^{2-}}$ wikipedia cites that the oxidation no. of Fe is +2 and that of NO is +1. CN being -1 the net charge thus becomes -2. However at certain places I read that NO is ...
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Hydrate isomerism

My book specifically mentions in the solution to a question: $\ce{[CrBrCl2 (H2O) (NH3)2].H2O}$ is not the hydrate isomer of $\ce{[CrCl2 (H2O)2 (NH3)2]Br}$ But the author hasn't provided any ...
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1answer
189 views

Bonding in Zeise's salt

I am not sure I completely understand the bonding in coordination compounds formed by donation of pi electron cloud by the ligands to the central atom. For example, consider Ziese's salt: I came ...
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1answer
60 views

Lewis acids as ligands

Usually Lewis bases as my textbook says: 2.3 Ligands The ligands are the ions or molecules bound to the central atom/ion in the coordination entity. This is better visualized as the combination ...
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Conformations in complex compounds with polydentate chelating ligands?

Does conformational Isomerism also occur in complex compounds where chelation occurs like in organic chemistry and if it happens is the stability order also similar like in Anti Staggered , skew , ...
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Inorganic IUPAC for Compounds with bridged ligands?

Can we use bis(tetraammine) instead of octaammine is the 2nd example ? As in the 1st example they used bis(pentaammine) and also in the 3 one the used bis(carbonylcyclopentadienyliron)
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Color change of aqueous ferric salt when reacted with phosphate

I have a question about an equilibrium system: $$\ce{Fe^3+ (aq) + SCN-(aq) <=> [Fe(SCN)]^2+ (aq)}\\ \text{(yellow)} \quad \text{(colorless)}\quad \qquad\text{(red)}\qquad\quad$$ The question ...
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Rhombohedral second-order Jahn–Teller effect in Au(II) complex?

I was recently listening to a talk about the following work[1] when the author mentioned that they explained the following. In this $\ce{Au(II)}$-porphyrin complex you observe two sets of $\ce{Au-N}$ ...
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Why are 5-ringed saturated chelates more stable than unsaturated ones while 6-ringed unsaturated chelates are more stable than saturated ones?

5-ringed saturated chelates seem to be more stable than unsaturated ones. On the other hand, 6-ringed unsaturated chelates are more stable than saturated ones. Why do these hold true?
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Why is the probability of a didentate ligand to form a chelate with a central atom, high?

When one ligating group of didentate ligands (like ethylenediamine) is coordinated with a central atom, then the probability of the other ligating group being coordinated, and hence forming a chelate, ...
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π-backbonding in tungsten complexes

I need to find in which of the following complexes the M-CO bond is stonger: [WO3(CO)3] and [W(CH3)3(CO)3]. According to my knowledge this is chiefly determined by the π-backbonding and how good ...
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Help understanding the pi-properties of the NCS- ligand

Course knowledge When considering the NCS- ion, I take all atoms to be sp hybridized. This means that there are 8 electrons that are accommodated in the $\pi$-system. There are two orthogonal 3-...
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1answer
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Is (Zn(OH)4)2- acidic or alkaline?

My chemistry teacher told me that $\ce{Al(OH)4^-}$, $\ce{Pb(OH)4^2-}$, $\ce{Zn(OH)4^2-}$ are called complex ions. So will they break down in some conditions and give out $\ce{OH-}$ to show alkaline ...
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Are crown ethers “recycled”, typically?

I know that crown ethers have the interesting property of strongly complexing alkali metals, which allows them to be used in organic solvents (eg. as "dissolving-activity enhancing agents" for ...
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1answer
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In Diazonium Ion why does N contain 4 bonds?

Nitrogen's valenc number is 3. Sometimes it can form a co-ordinate bond by donating it's lone pair electrons. In diazonium ion N has 4 bonds, then one of those 4 bonds must be a co-ordinate bond. ...
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Identification for qualitative analysis

The flow chart is indicative of a compound with a silver cation, because $\ce{Ag+}$ reacts with $\ce{I-}$ to form yellow $\ce{AgI}$. Since $\ce{Ag+}$ does not form a hydroxide complex, it forms the ...
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1answer
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Why is there only one ionization isomer of [Cr(NH3)5(NO2)]Cl2?

How many isomers are possible for $\ce{[Cr(NH3)5(NO2)]Cl2}$? Consider all possible types of isomerism and draw each isomer. My texbooks presents only three possible isomers: $\ce{[Cr(NH3)5(NO2)]Cl2}$ ...
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Molecular orbital diagram for terminal metal-oxo complex with dative bonds

I am interested in terminal metal-oxo complexes and their electronic structure, specifically those with coordination numbers of 6, including the oxo ligand. I know that Fe(IV)-oxo complexes tend to ...
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1answer
281 views

Why is CO ligand higher than CN- in the spectrochemical series?

I've drawn MO diagrams for both molecules and they are isoelectronic. The main difference is that $\ce{C}$ is closer in electronegativity to $\ce{N}$ than it is to $\ce{O}$ so there will be less ...
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1answer
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why do the complex [Cu(NH3)5NO2]SO4 show ionisation isomerism?

In ionisation isomerism, secondary valencies can be replaced by primary valencies on the condition that net charge going outside the coordination sphere must be equal to net charge coming inside it . ...
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IUPAC name of C₆(CH₃)₆²⁺

What is the correct IUPAC name (or least incorrect one, if the current rules can't precisely describe that) of the interesting species $\ce{[C6(CH3)6]^{2+}}$ (which is extensively discussed here), ...
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IUPAC nomenclature of chelates

I could finally get a copy of the Red Book 2005 from a library. In the chapter dedicated to nomenclature of coordinate complexes, while explaining the κ-system of specifying donor atoms, the following ...
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Cobalt Chloride in various solvent/water mixtures - tested

In a recent post the solvatochromic behaviour of cobalt chloride in acetone was discussed. There were some ideas how the acetone might influence the ratio between the blue $\ce{[CoCl4]^2-}$ and the ...
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1answer
284 views

Considering the d-d transition how, does tetracyanidonickelate(II) ion exist as a colored complex?

As I refer on google, the resources indicated that, the d block elements which have unpaired electrons as in their ions, when they are making complexes with ligands, they can absorb different ...
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What reactions will occur at the anodes and electodes of two iron electrolytic cells?

What reactions will occur at the anodes and electrodes of two iron electrolytic cells: both with iron metal electrodes, one with an iron(II) sulphate electrolyte, the other with an iron(III) sulphate ...
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Will potassium oxalate form stable complexes with Al 3+ AND Fe 3+ in an acidic solution?

I am trying to perform a complexometric titration of both Al 3+ and Fe 3+ in a sulfuric acid solution. I would be measuring the titration using a thermistor. The goal in this would be to complex all ...
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1answer
208 views

Why is the oxidation state of Co -1 in [Co(CO)4]-?

In $\ce{[Co2(CO)8]}$, most people say the charge of $\ce{Co}$ is 0. How does it become $\ce{[Co(CO)4]-}$? Most answers would say that $\ce{Co}$'s charge becomes -1. How does this work? -1 is not ...
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79 views

What is an uninegative ligand

I can't find a simple definition via google. All I get are research papers, that I don't understand.
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Failure to Locate Stationary Point in GAMESS

I'm currently trying to optimize the geometry of a complex using GAMESS at the B3LYP level. However, I keep failing to converge the SCF. I've already tried the following: increasing the number of ...
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1answer
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Ammonia complex [closed]

I am desperately trying to find an aqueous chemical that will selectively form a complex with ammonia gas. Any suggestions please? I am building a gas sensor for ammonia
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Is there anyway to derive the number of water molecules in a hydrated salt, given just the formula for the anhydrous salt?

Is there anyway to derive the number of water molecules in a hydrated salt, given just the formula for the anhydrous salt? That's pretty much it. If not, why? For coordinated water, my guess is ...
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1answer
115 views

Why or why not can hydroquinone and 2H-pyrrole act as ligands?

I want to understand why hydroquinone and 3H-pyrrole can or cannot act as ligands in transition metal complexes. If they are ligands, then what is their denticity? I'm trying to understand the ...
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1answer
170 views

Is there a theoretical way to predict the coordination number a metal can have in a complex? [closed]

We know that metals can form complexes with different coordination numbers, but I was told that certain metals have a greater probability to have a certain coordination number. But I was not able to ...
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What is the hybridization of iron pentacarbonyl?

What is the hybridization of $\ce{[Fe(CO)5]}$? Is this correct?