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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 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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Why is it wrong to use the concept of hybridization for transition metal complexes?

I have asked a lot of questions on coordination chemistry here before and I have gone through a lot others here as well. Students, including me, attempt to answer those questions using the concept of ...
Arishta's user avatar
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25 votes
1 answer
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How can the intense color of potassium permanganate be explained with molecular orbital theory?

In the permanganate ion, manganese is in the $+7$ oxidation state, therefore it is a $\ce{d^0}$ ion. $\ce{d^0}$ and $\ce{d^1^0}$ ions don't absorb visible spectrum radiation because there are no ...
Nilay Ghosh's user avatar
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21 votes
2 answers
6k views

What is the perfect definition for chirality?

Why is chirality defined differently for organic and inorganic compounds? Why are inorganic compounds deemed to be optically active if they have more than one of the same ligands attached to the ...
JM97's user avatar
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9 votes
2 answers
9k 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 ...
Subhadip Pal's user avatar
69 votes
8 answers
75k views

Is iron in the brown ring compound in a +1 oxidation state?

In the standard brown ring test for the nitrate ion, the brown ring complex is: $$\ce{[Fe(H2O)5(NO)]^{2+}}$$ In this compound, the nitrosyl ligand is positively charged, and iron is in a $+1$ ...
ManishEarth's user avatar
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9 votes
2 answers
4k views

Why do copper (II) complexes contain so many valence electrons?

Consider tetraaminecopper (II) ion. $\ce{[Cu(NH3)4]^2+}$ or $\ce{[Cu(NH3)4(H2O)2]^2+}$. The copper(II) ion has the electron configuration $\mathrm{[Ar]\ 3d^9}$. How do the 4 electron pairs from the ...
Armadillomon's user avatar
38 votes
1 answer
79k views

Why is [PdCl4]2- square planar whereas [NiCl4]2- is tetrahedral?

The molecule $\ce{[PdCl4]^2-}$ is diamagnetic, which indicates a square planar geometry as all eight d electrons are paired in the lower-energy orbitals. However, $\ce{[NiCl4]^2-}$ is also $\mathrm{d^...
user avatar
15 votes
1 answer
5k views

The bond in coordination complexes

This is a very basic question and I'm surprised it only just struck me. The nature of the bond in coordination complexes is a coordinate covalent bond. Only the ligand donates electrons for bond ...
Keerthana A.K.'s user avatar
21 votes
4 answers
10k 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)...
Ivan's user avatar
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15 votes
2 answers
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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 ...
docscience's user avatar
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6 votes
2 answers
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What is the hybridisation of titanium in the hexaaqua- and hexaamminetitanium(III) complex?

I want to check if their hybridizations are as follows: $\mathrm{sp^3d^2}$ in $\ce{[Ti(NH3)6]^3+}$ and $\mathrm{d^2sp^3}$ in $\ce{[Ti(H2O)6]^3+}$.
BEWARB's user avatar
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41 votes
4 answers
134k views

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 ...
bonCodigo's user avatar
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16 votes
3 answers
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Why is anhydrous copper(II) sulfate white while the pentahydrate is blue, even though both have one unpaired electron?

We all know that $\ce{CuSO4.5H2O}$ is blue and it turns to $\ce{CuSO4}$ on heating which is white. I also learnt about coordination complexes and d–d transitions and how transition metal compounds are ...
Kartik's user avatar
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16 votes
1 answer
54k views

What is the product of the chemical reaction between phenol and ferric chloride?

The chemical reaction between phenol and ferric chloride is a test for the presence of phenol. They react with each other to produce a violet complex. However, the reaction is given differently in ...
Nilay Ghosh's user avatar
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11 votes
1 answer
7k 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 ...
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10 votes
1 answer
40k views

How do I find the ground state term symbol for transition metal complexes?

I have a problem where I'm trying to match metal complexes with the proper ground state term symbol. I've tried doing a Google search and looking for a process, but haven't had any luck. I decided ...
MattyT's user avatar
  • 355
42 votes
6 answers
9k 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 ...
Anoneemus's user avatar
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26 votes
3 answers
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Solutions of Group 1 and Group 2 metals in Ammonia

When we add Group-1 and Group-2 metals to liquid ammonia, they dissolve to form metal cations and solvated electrons. $$\ce{M + NH3(liq) -> M+ + e-}$$ Now, when the G-1 solutions evaporate, we get ...
Ayushmaan's user avatar
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18 votes
3 answers
5k views

Where does the label ‘Dq’ to denote the field split in coordination compounds come from?

As established in a previous question, coordination compounds typically have a field split between the $\mathrm{t_{2g}}$ and the $\mathrm{e_g}$ d-orbitals.[1] This energy difference can be explained ...
Jan's user avatar
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16 votes
1 answer
7k views

Splitting of $d$ orbitals when ligands approach central metal ion

In my high school chemistry book, it is written that when ligands approach the central metal ion (transition metal ion) to form dative bonds, the $3d$ orbitals split into two: two which are in higher ...
Eliza's user avatar
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13 votes
2 answers
12k views

Why do octahedral metal ligand complexes have greater splitting than tetrahedral complexes?

Octahedral complexes have greater splitting in the d orbitals. Is it because octahedral complexes have more atoms and thus more interactions?
CognisMantis's user avatar
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13 votes
1 answer
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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 ...
bon's user avatar
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12 votes
1 answer
2k views

Inorganic chemistry reaction mechanisms

Are there well developed reaction mechanisms in inorganic chemistry like those in organic chemistry? If yes, please suggest an easy to follow reference.
DSinghvi's user avatar
  • 1,796
11 votes
1 answer
909 views

How does potassium hexfluoronickelate(IV) exist in a stable state?

Nickel generally does not exist in a $+4$ oxidation state. Wikipedia has the following to say regarding nickel(IV): Ni(IV) is present in the mixed oxide $\ce{BaNiO3}$. ....... Ni(IV) remains a rare ...
Aniruddha Deb's user avatar
11 votes
1 answer
11k views

Bonding of the complex when both weak and strong field ligand are present

In the complex $\ce{[Ni(H2O)2(NH3)4]^2+}$ the magnetic moment ($\mu$) of $\ce{Ni}$ is – Zero $2.83~\mathrm{BM}$ $1.73~\mathrm{BM}$ $3.87~\mathrm{BM}$ It is easy to find the unpaired electrons and ...
Arishta's user avatar
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8 votes
1 answer
1k views

Difference between sodium ion and a transition metal ion dissolving in water?

In class, I learned that when $\ce{NaCl}$ is dissolved in water, the partially negative oxygen part of the water molecules surround the $\ce{Na+}$ ion and energy is given off (hydration enthalpy) ...
Eliza's user avatar
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7 votes
2 answers
5k views

How do copper sulphate and the like change crystal structure on adding water of hydration?

Copper sulphate, in its hydrated form, is crystalline, whereas the anhydrous form is amorphous. Gypsum has a similar story-- on heating the crystalline dihydrate we get an amorphous hemihydrate. (...
ManishEarth's user avatar
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7 votes
1 answer
1k views

What is the chemical composition of Ferrous Ferrocyanide?

To this day, iron-cyanide complexes confuses me. So, I want to settle this once and for all. After scavenging the internet, I gathered the following result: $$ \ce{Ferr} \color{blue}{\ce{ous}}~\ce{...
Nilay Ghosh's user avatar
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6 votes
1 answer
2k views

Is [Co(NH₃)₄Cl₂]Cl paramagnetic or diamagnetic?

$\ce{NH3}$ is known to be a strong field ligand, while $\ce{Cl}$ is known to be a weak field ligand. Is $\ce{[Co(NH3)4Cl2]Cl}$ a high spin complex or a low spin complex? I assumed this to be a high ...
McSuperbX1's user avatar
5 votes
1 answer
982 views

Formation of MnO2 vs [Mn(H2O)6]4+ in aqueous solution

I am looking for reasons why $\ce{Mn(IV)}$ wouldn't be stable as a hydrate. I know that from standard reduction potentials it exists as a ppt of $\ce{MnO2}$, but what is stopping it from being a ...
gamma1's user avatar
  • 1,120
3 votes
2 answers
7k views

Predicting bond-strength of metal carbonyls

The metal carbonyls (and similar organometallic compounds) involve a combination of sigma bond, a pi bond and backbonding. The bond strengths under consideration are the metal-carbon bond and the ...
stochastic13's user avatar
  • 6,775
3 votes
1 answer
856 views

Stereoisomers of octahedral co-ordination compounds of the form [Ma3b3]

Does $\ce{[Co(H2O)3Br3]}$ show geometrical and optical isomerism? According to me $\ce{Co}$ should be $\mathrm{sp^3d^2}$ hybridised giving an octahedral geometry. It is of the form $\ce{[Ma3b3]}$ type....
Utkarsh Barsaiyan's user avatar
3 votes
2 answers
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?
EJC's user avatar
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2 votes
2 answers
6k views

What is the optical nature of the tris(ethylenediamine)cobalt(III) cation?

The molecule I've drawn has neither a plane of symmetry nor a center of symmetry, even though some books refer to this as optically inactive. Can you please elaborate why is this so, or those books ...
Arvind Tiwari's user avatar
36 votes
4 answers
127k views

Tetrahedral or Square Planar

How can one predict whether a given complex ion will be square planar or tetrahedral when its coordination number is 4 using crystal field theory ? Is it possible to theoretically predict this?
Sameer's user avatar
  • 477
28 votes
1 answer
104k views

What are t2g and eg in CFT?

In the crystal field theory (CFT), when the splitting of the d-orbital occurs, it gets divided into two parts. The upper part with higher energy is the $\mathrm{e_g}$ and the lower part with lower ...
NeilRoy's user avatar
  • 1,673
25 votes
4 answers
4k views

How may copper acetate ligands be manipulated to change colors?

I have a solution of copper acetate and I would like to play around with the ligands to get different colors. Background: The copper acetate was made through mixing vinegar (5% acetic acid), $\ce{...
Dale's user avatar
  • 2,674
23 votes
2 answers
4k views

Why is the cyanide ion toxic?

As the title implies, what is the molecular basis of cyanide toxicity? I did some searching around at the CDC and it only states that it prevents cells from using oxygen. I also read how it could take ...
Aubrey Champagne's user avatar
21 votes
5 answers
12k views

Why is the magnesium(II) ion preferred over other ions in chlorophyll?

Chlorophyll has a $\ce{Mg^2+}$ ion. Why is it preferred over other ions? For example, what happens if there is $\ce{Zn^2+}$ or $\ce{Ca^2+}$ or any other (divalent) cation instead of $\ce{Mg^2+}$?
adianadiadi's user avatar
21 votes
3 answers
12k views

Why is manganese(II) coloured although the transition should be spin-forbidden?

In every basic coordination chemistry class, at some early point the crystal field theory and LFSE will be taught, explaining that there will be an energy difference between d-orbitals (typically ...
Jan's user avatar
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17 votes
2 answers
4k views

What happens to electrons in metal complexes after excitation by visible light?

My book writes: When white light shines through a solution of a complex ion of a transition metal, photons of a particular frequency are absorbed and their energy promotes an electron from lower ...
Eliza's user avatar
  • 2,413
16 votes
1 answer
800 views

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), ...
mykhal's user avatar
  • 6,212
16 votes
2 answers
341 views

What are the mechanisms for capture of As(III) and As(V) by magnetite from water?

Magnetite, $\ce{Fe3O4}$ is able to capture $\ce{As(III)}$ and $\ce{As(V)}$ from drinking water through the following mechanisms. Bidentate-binuclear complex Monodentate-binuclear complex (both from ...
jonsca's user avatar
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15 votes
3 answers
17k views

What is the reason of the color difference for the cis/trans isomers of tetraamminedichloridocobalt(III) chloride?

The cis and trans isomers of $\ce{[CoCl2(NH3)4]Cl}$ are quite famous as one is purple and the other one is green which is a huge difference in color. Now I can't find any information to why this is ...
Justanotherchemist's user avatar
13 votes
1 answer
4k views

The IUPAC name of sodium nitroprusside, and back-bonding in it

In the standard test for the sulfide ion, sodium nitroprusside $(\ce{Na^_2[Fe(CN)5(NO)]})$ is used. The IUPAC name for this compound as stated by Wikipedia is sodium pentacyanidonitrosylferrate(II) I ...
miyagi_do's user avatar
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12 votes
1 answer
1k views

What is the Structure of FeSO₄ • NO?

What is the structure of $\ce{FeSO4 \cdot NO}$ that is formed when $\ce{NO}$ is passed through ferrous sulfate solution? If it is a brown ring complex then why does the complex sphere break upon ...
ACat's user avatar
  • 1
12 votes
1 answer
16k views

Why do tetrahedral complexes have approximately 4/9 the field split of octahedral complexes?

I am trying to calculate the relationship between the octahedral field splitting parameter ($\Delta_\mathrm{o}$) and the square planar field splitting parameter ($\Delta_\mathrm{sp}$) and thought a ...
Vlad's user avatar
  • 1,021
12 votes
4 answers
6k views

Are complex ions thermochromic?

Does raising the temperature of a complex ion (formed from a transition metal ion and ligand(s)) affect its color? For example, if the temperature of $\ce{[Cr(H2O)6]^3+}$ is raised, will its color ...
sepehr78's user avatar
  • 179
12 votes
1 answer
6k views

Will the bond order of CO be greater in its existence as carbon monoxide or in metal carbonyl?

$$\text{Bond order} = \frac{N(b) - N(a)}{2}$$ Where $N(b)$ is the number of electrons in bonding orbitals and $N(a)$ is the number of electrons in antibonding orbitals. As in metal carbonyls, there is ...
Resorcinol's user avatar
  • 1,439
11 votes
2 answers
12k views

Why is Ni[(PPh₃)₂Cl₂] tetrahedral?

Since PPh₃ is strong field ligand and, the famous Wilkinson's catalyst, which also possess this ligand is square planar, then what makes the above complex tetrahedral?
user226375's user avatar