A special class of compounds in which a electron deficient central atom (usually a metal ion) is bonded to many electron donors called ligands. These compounds are highly stable and are widely found in nature. They also have a wide variety of industrial applications.

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why is cobalt hexacyano complex uncommon?

In huheey they have written hexacyano cobalt(II) is uncommon but pentacyanoaqua cobalt (II) is common. They mentioned something about Jahn Teller distortion but I could not get the meaning
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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 ...
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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^+}\\ ...
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Oxo ligand molecular orbital diagram with metal center

With highly oxidizing metal center, we expect that the hydroxide ligand's proton becomes acidic and will be lost to the surrounding media, creating an oxo ligand. The oxo ligand is a $\pi$ basic ...
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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 ...
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Calculation of CFSE

I need to find CFSE for these: $\ce{[Ti(H2O)6]^3+}$, OK $\rm Ti$ is $\rm 4s^23d^2$, $\rm Ti^{3+}$ is $\rm 4s^03d^1$. Afterwards it becomes $\rm d^4sp^2$ or $\rm t_{2g}^5e_g^4$ so CFSE is ...
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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 ...
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How would you compare stability of complexes of a same metal with different ligands?

Let's take $\ce{[Fe(H2O)6]^3+,[Fe(en)3]^3+,[Fe(ox)3]^3+}$ and $\ce{[FeCl6]^3+}$. Which is more stable? I can say that these are $\ce{sp^3d^2,d^2sp^3,d^2sp^3,sp^3d^2}$. I hope you understand that I ...
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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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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?
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Can any atom donate more than 1 lone pair as a coordinate bond to the same metal?

This would mean the formation of a sigma and one or two pi bonds, all coordinate. I haven't heard of this happening, like fluorine anion or water with 2 lone pairs on O will donate only one lone pair, ...
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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 ...
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What is the highest possible expanded octet?

Often called "hypervalent", chemicals like Phosphorous Pentachloride and Sulfur Hexaflouride are possible due to the fact that their central atoms form covalent bonds with more than four other atoms, ...
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Decomposition 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 ...
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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 ...
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Why Bari centre is considered as Zero energy level?

Why the degenerate energy level of d orbitals before forming complex is considered zero? what advantages are there for taking the mean of t2g and eg orbitals as zero?
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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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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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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, ...
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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?
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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 ...
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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 ...
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Ratio of copper(II) ions to EDTA?

One question in a test I am preparing for is: 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 ...
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Why does Fe(CO)₄ adopt a tetrahedral, as opposed to square planar, geometry?

Why does $\ce{Fe(CO)4}$ adopt a tetrahedral, as opposed to square planar, geometry? Here's my analysis: Factors for square planar: coordination: 4 $\ce{Fe(0)}$: d8 $\ce{CO}$: strong field ligand ...
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Bipyridyl complex isomers

What type of stereoisomers do these two complex compounds represent?
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Why is inner orbital complex more stable than outer orbital complex?

I learnt that $\ce{Cr(II)}$ ion is a stronger reducing agent than $\ce{Fe(II)}$ In an aqueous solution as inner orbital complexes more stable than outer orbital complexes? I cannot understand why is ...
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Are there ways to fully dissociate a complex salt?

A complex salt is a salt where the metal and ligands do not dissociate in water. For eg : $\space\ce{K_4[Fe(CN)_6]}$ when put into $\space\ce{H_2O}$ dissociates as : $\space\ce{4K^+} + ...
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Why do electrons not get paired up in [Fe(H2O)5NO]2+?

The magnetic moment of [Fe(H2O)5NO]2+ is 3.87 Bohr magneton, which implies there are 3 unpaired electrons. Since iron is in +1 oxidation state (due to charge transfer with nitrosyl group), it's ...
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MO scheme for coordination complexes (tetrahedral) - Heteroligand vs. homoligand

How is the MO diagram drawn for a tetrahedral complex with heteroligands (e.g. $\ce{[NiCl2(PPh3)2]}$) different from a tetrahedral complex with the same type of ligand? Do we consider the same "a1 and ...
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Why is copper (II) coordination number so big?

Consider tetraaminecopper (II) ion. $\ce{[Cu(NH3)4]++}$ or $\ce{[Cu(NH3)4(H2O)2]++}$ Copper (II) ion has electron configuration $\ce{[Ar] 3d^9}$. How do the 4 electron pairs from ammonia atoms form ...
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Effect of radioactivity on bonding [duplicate]

What effect does $\alpha$ or $\beta$ decay have on the bonding in molecules? In particular the example I was thinking of was if you have a radioactive metal at the centre of a complex ion. I had a ...
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Is tetraammine dichloro cobalt (III) an optically active compound?

Is $$ \text{Co}[{(\text{N}{\text{H}}_{3})}_{4}{\text{Cl}}_{2}]$$ optically active? If so, write its stereo-isomers. I know that for a compound to be optically active, it should ...
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Why would there be differences in UV/Vis spectrum?

$\ce{[NEt4]2[NiBr4]}$ dissolved in $\ce{MeCN}$ and $\ce{[NEt4]2[NiBr4]}$ dissolved in $\ce{H2O}$ have different UV/visible spectra in the visible region. How would they differ, for example would one ...
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What is this compound that was made? [closed]

1.25g $\ce{Ni(en)2Cl2}$ in 10ml water + 2 drops of pyridine + 1g 2,4-pentanedione in 10ml $\ce{MeOH}$ refluxed for 2 hours, large crystals formed It is a $\ce{Ni(II)}$ square planar compound Mass ...
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Thermogravimetric Analysis of hydrated compounds

I have been given this thermogravimetric analysis of my compound $\ce{NiBr2.$x$\,H2O}$ and I need to work out the number of moles of water in the complex. Also why are there two steps in the data?
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What does it mean in a Ni(II)complex if the HNMR spectrum appears unbroadened and unshifted & what does this tell you about the coordination geometry?

I am trying to work out the an unknown Ni(II) complex. I don't known the geometry and I have read that broad lines on the nmr spectrum indicate large compounds with symmetric environments. Does this ...
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Why does Cobalt have different coordination numbers in its complexes with water and thiocyanate?

I'd like to know why does cobalt(II), $\ce{Co^2+}$, form $\ce{[Co(H2O)6]^2+}$ complex with water while it forms $\ce{[Co(SCN)4]^2-}$ with the thiocyanate? Why is there $\ce{6H2O}$ but only $\ce{4 ...
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Are these reaction equations for the formation of the brown ring complex correct?

The above are the reactions given in my book for the qualitative analysis of nitrate ion (formation of the brown ring complex). I think that the reactions above are incorrect. The first one shows ...
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How do I find the oxidation number of a coordination complex

I actually know how to calculate the oxidation number for coordination complexes but some complexes like the below are giving some reistance $\ce{[Cu(NH3)_2][Fe(H2O)_3]}$ (diamminecopper(?) ...
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Reference request- List of common Coordination Complexes? [closed]

I'm studying for a big chemistry exam that always has a question about predicting reactions. One thing that almost always trips me up is coordination complexes. For example, one such question asked ...
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Why is nickel tetracyanonickelate square planar?

Why is nickel tetracyanonickelate, $\ce{[Ni(CN)4]^{2-}}$ square planar? CN, for being a strong field, would not follow Hückel's rule. the central atom $\ce{Ni}$ would have a +2 charge so its ...
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Magnetic moments of tetrahedral Cobalt (II) and (III) complexes

From the spin-only formula we can predict that for tetrahedral cobalt (II) complexes $$m_{eff} = 3.87 \mu_B $$ This ignores orbital angular momentum effects, which result in higher magnetic moments ...
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Cu2+ octahedral complexes

$\ce{Cu}^{2+}$ has nine d-electrons, regardless of the ligand field strength it will have one free electron (so it is paramagnetic. Are $\ce{Cu}^{2+}$ octahedral complexes high spin or low spin?
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Why are square planar coordination compounds with four different ligands optically inactive?

Why square planar co- ordination compounds of type Mabcd do not show optical activity, although they contain 4 different ligands ( i.e. chiral central metal atom)
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Which ligands would be exchanged in this reaction?

I have this reaction and need to state what the products would be: $\ce{(CF3)2PH + [W(CO)5(THF)] -> }$ THF stands for Tetrahydrofuran. Would this just be a simple ligand exchange, and if so ...
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Absorbtion of light by a Coordination Compound

A $\ce{[M(H2O)6]^{2+}}$ complex typically absorbs at around $600$ nm. It is allowed to form a new complex $\ce{[M(NH3)6]^{2+}}$ that should have absorbtion at? The absorbtion is beacuse of transition ...
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What are t2g and eg in CFT?

In the Crystal Field Theory, when the splitting of the d-orbital occurs, it gets divided into two parts... The upper part with higher Energy is the $t_{2g}$ and the lower part with lower Energy is ...
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Symmetry labels for orbitals

What are the symmetry labels for the p and d orbitals of $\ce {[PtCl4]^{2-}}$ ? I understand the concept of symmetry labels for molecules. some explanation of how it applies to orbitals would be ...