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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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1 answer
116 views

How to find the ligand field splitting of d orbitals in a square planar complex?

I am working with a Iron square planar complex with $\ce{NH2-}$ and $\ce{OH-}$ ligands having cis and trans conformation. My question is how to theoretically/computationally calculate the ligand filed ...
6 votes
1 answer
1k views

What should be the IUPAC name of [(NH3)5Co-NH2-Co(NH3)4(H2O)]?

What should be the IUPAC name of $\ce{(NH3)5Co-NH2-Co(NH3)4(H2O)]}$? This is similar to $\ce{[(NH3)5Co-NH2-Co(NH3)5](NO3)5}$, i.e. μ-amido-bis[pentaamminecobalt(III)] nitrate. But the two parts are ...
5 votes
1 answer
129 views

Is concept of weak and strong field ligands applicable in valence bond theory?

I study coordination chemistry at high school. I have read about valence bond theory (VBT) and crystal field theory (CFT) as well. My teacher taught me that VBT is based on the experimental values of ...
10 votes
0 answers
631 views

Identifying alkyl ligands as π-donors or π-acceptors in transition metal complexes

Is there a systematic way to identify an alkyl ligand as a π-acceptor or π-donor in a transition metal complex? Although various sources indicate that the weak field ligands are typically π-donors and ...
-3 votes
1 answer
51 views

Does cobalt form square planar complexes? [closed]

So I came across a question where we were required to identify the possible central metal atom using the following clues. An aqueous solution of metal ion M1 reacts separately with reagents Q and R ...
-2 votes
0 answers
25 views

Coordination compound isomerism

In bridging complexes, an exchange of non-bridging ligands between two metal cations gives rise to coordination position isomerism. But what if there is an exchange of bridging and non-bridging ...
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 ...
-1 votes
0 answers
36 views

Is ammonium a coordination compound?

According to IUPAC Gold Book, the definition of "complex" is preferably called "coordination entity" which is stated that: An assembly consisting of a central atom (usually ...
3 votes
2 answers
359 views

Why can't group 2B metals (Zn, Cd, Hg) form complexes with ligands such as CO, nitrosyl (NO), and olefins but do from complexes with NH3, CN- etc?

Why Group 2B metals (Zn, Cd, Hg) can form complexes with Ammonia ($\ce{NH3}$), Cyanide ($\ce{CN-}$) etc. and not with ligands such as carbonyl ($\ce{CO}$), nitrosyl ($\ce{NO}$), and olefins? What I ...
0 votes
1 answer
81 views

D-d splitting in transition metal ions

Cu+2 ion has total of 9 electrons in its 3d orbital. When it undergoes d-d splitting an electronic transition can take place between t2 and e as in {Cu(CN)4}-2 complex because of the presence of one ...
-2 votes
1 answer
70 views

Why is Chromium hexacarbonyl diamagnetic?

So there was a question in coordination chemistry regarding the nature of $\ce{[Cr(CO)_6]}$ The book had the question under VBT and solved it using "strong ligands cause all electrons to pair up&...
6 votes
0 answers
435 views

How to explain oxidizing power from Molecular Orbital Theory

I am trying to explain the oxidizing property of $\ce{Fe^3+}$ in $\ce{H2O}$ and $\ce{CN^-}$ which is $\ce{[Fe(H2O)6]^3+}$ and $\ce{[Fe(CN)6]^3-}$. The electrochemical reactions along with their ...
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 ...
2 votes
1 answer
123 views

Transition of electrons between t2g and eg to give colour of coordination compounds

In the case of a hexaaquairon (III) complex, the iron (III) ion has 5 electrons, each singly occupying one d orbital. As the d orbitals are occupied, the vacant 4s, 4p and 4d orbitals are hybridised ...
13 votes
3 answers
514 views

Comparison of C=O bond strength in metal carbonyls

Find the weakest $\ce{C=O}$ bond among $\ce{[Mn(CO)6]+},$ $\ce{Fe[(CO)5]},$ $\ce{[Cr(CO)6]}$ and $\ce{[V(CO)6]-}.$ I thought the $\ce{C=O}$ bond strength would be lowest in $\ce{[V(CO)6]-}$ since the ...
-3 votes
1 answer
46 views

Pairing of electrons in Nickel in presence of strong ligand(tetrahedral)

For tetrahedral CFSE, Nickel's last 6 electrons will go in the t2g set of orbitals. Since it is already the higher energy orbital, pairing should NOT happen right? However, all internet sources I ...
22 votes
8 answers
14k views

Do ligands with a positive charge exist?

Are there positively charged ligands which can bind to a central metal atom to form coordination compounds? My thoughts: I know that ligands are Lewis bases which donate a pair of electrons, and the ...
4 votes
2 answers
2k views

Pt[BrCl(PR₃)₂] cis, trans isomer nmr - Which is cis and which is trans?

The two square planar isomers of $\ce{Pt[BrCl(PR_{3})2]}$ have different $\ce{^{31}P}$-NMR spectra. One shows single group of lines, the other shows two distinct resonances, each one being similar to ...
-1 votes
1 answer
68 views

Charge of a complex ion [closed]

Consider $\ce{[Cr(H2O)6]^3+}$, the charge on the Chromium before the water molecules react is $3+$, clearly each water ligand contributes one lone pair, meaning the formal charge should be $3-6=-3$ (...
1 vote
2 answers
5k views

Naming and structure of PtCl4.2HCl (complex/coordination compound)

Given that $\ce{PtCl4.2HCl}$ when reacted with excess of $\ce{AgNO3}$ produced zero moles of $\ce{AgCl}$, I understand that all the chlorine atoms are inside the coordination sphere. But what will the ...
-2 votes
1 answer
138 views

Colour of coordination compounds due to d-d transition

Hexaaquanickel(II) is green but tetracyanidonickelate(II) is colourless. On internet I found two explanations. One used valence bond theory that claimed there is no excitation of electron in ...
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 ...
4 votes
1 answer
1k views

Is the dimethylglyoximate anion ambidentate or not?

In class, my professor said that dimethylglyoximate is a special ambidemtate ligand that can donate lone pairs via both nitrogen (which it normally does), and oxygen (very rarely). On googling ...
0 votes
0 answers
59 views

Why do the carbonyl oxygens in EDTA not participate in coordination?

I recently had two, very brief lectures on coordination compounds. In those lectures, my teacher mentioned EDTA because of its importance in analytical chemistry and its very stable complexes and ...
0 votes
0 answers
31 views

Question on electron density

I was working with ammonia ($\ce{NH3}$) and phosphine($\ce{PH3}$). Both have lone pair electron. But $\ce{NH3}$ is stronger base (Lewis base) than $\ce{PH3}$. I was told by my instructor that it is ...
0 votes
1 answer
71 views

Determining High Spin or Low Spin Configuration: Influence of Weak and Strong Field Ligands

Can a coordination complex be classified as high spin if it possesses the same number of unpaired electrons in both weak and strong field ligand environments? I am curious about the factors that ...
3 votes
1 answer
485 views

Colour of diamagnetic compounds using Crystal Field Theory

I know that the colour in coordination compounds can be explained by CFT in terms of d-d transitions. Are d-d transitions possible in diamagnetic complexes? Why does $\ce{[Co(NH3)6]^3+}$ show colour? ...
0 votes
1 answer
58 views

Electron configuration in benzene chromium tricarbonyl

I am not sure what is the electron configuration in benzene chromium tricarbonyl? From what I can work out, Cr is in 0 oxidation state (since all ligands are neutral). The complex is tetrahedral so ...
3 votes
1 answer
168 views

Infra red stretching frequency of carbon monoxide ligand in borane carbonyl compared to that of free carbon monoxide

Why is the infrared stretching frequency of $\ce{CO}$ in the borane carbonyl $\ce{BH3CO}$ more than that of free $\ce{CO}$? Is there any real explanation for this? There will be a small amount of ...
0 votes
0 answers
85 views

Jahn-Teller Distortion: How to compare magnitudes (in Cu2+ complexes)?

Octahedral complex of copper(II) undergo structural distortion (Jahn-Teller). Which one of the given copper(II) complexes will who the maximum structural distortion? (en - ethylenediamine) (A) $[Cu(...
0 votes
0 answers
54 views

On the geometry of quadra-coordinated coordination complexes [duplicate]

How do we tell whether a complex with a four coordinated central metal ion takes on a square planar geometry or a tetrahedral geometry?
13 votes
5 answers
9k views

Explanation for why nickel turns green in hydrochloric acid

My daughter has a chemistry test that I am helping her prepare for. One question is Nickel sulfate, $\ce{NiSO4(aq)}$ is a green solution. Nickel chloride, $\ce{NiCl2(aq)},$ is a yellow solution. If ...
2 votes
1 answer
2k views

How does crystal field stabilisation energy relate to the stability of a complex?

I know how the crystal field stabilization energy is calculated, but how does it reflect stability? CFSE measures the energy relative to the barycentre, not the initial energy of the $d$ orbitals. For ...
0 votes
0 answers
148 views

Products formed on reaction of aqueous solution of iron(III) nitrate nonahydrate

Crystalline iron(III) nitrate nonahydrate, Fe(NO3)3.9H2O, has a very pale violet color. When added to water, the crystals dissolve to form a brown solution. Treatment of this brown solution with ...
1 vote
2 answers
86 views

Why wont Al(OH)3 form in this reaction?

I am in grade 11. We were learning qualitative salt analysis and my teacher wrote a reaction on board - $$\ce{Al^3+ +H2O\rightarrow[Al(H2O)6]^3+}.$$ Now as far as structure of the complex is concerned ...
7 votes
0 answers
570 views

Does solvate isomers exist for coordination compounds with ammonia solvent as ligand?

I could find many sources confirming the hydrate isomerism(with water as solvent) but I couldn't find any information about any other solvent. In all the sources "hydrate/solvate isomerism" ...
1 vote
1 answer
183 views

Why do most sulphate salts have water of crystallization in them?

I mean looking at most of the sulphate salts (there are so many but just to name some Epsom salt, blue vitirol, gypsum...) they have some amount of water crystallized within them (Epsom salt is MgSO4....
1 vote
0 answers
41 views

Why does the answer given consider octahedral splitting even though there is no specification of the complex

My textbook (NCERT Chemistry Part 1) gives this question as an example: Why is $\ce{Cr^2+}$ reducing and $\ce{Mn^3+}$ oxidising when both have $d^4$ configuration? And the solution given along with ...
17 votes
3 answers
5k views

Disproportionation of Au(II)

$\ce{Cu(II)}$ and $\ce{Ag(II)}$ complexes are known to exist while $\ce{Au(II)}$ is unstable and disproportionates to $\ce{Au(I)}$ and $\ce{Au(III)}$. My guess as to possible reasons to this effect ...
3 votes
1 answer
61 views

Deriving population of $t_{2g}$ orbitals in transition metal oxides

I have recently studied ligand field theory but there is one thing I do not understand. Consider an octaedral geometry of ligands around a transition metal with a $t_{2g}$ - $e_g$ splitting of atomic $...
1 vote
0 answers
771 views

UV–Vis spectra of hexaaquacobalt(II) ion

I observe the UV–Vis spectrum of $\ce{[Co(H2O)6]^{2+}}$ and there is a little peak at $\sim\pu{640 nm}$. By observing the Tanabe–Sugano diagram I see that the spin allowed transitions are: $$ \begin{...
1 vote
1 answer
677 views

Is the Co-ordination number of Cobalt always 6 in every co-ordination compound?

For example in the following compounds CoCl3.6H2O CoCl3.6NH3 CoCl3.5NH3 CoCl3.4NH3 in all of these complexes, we took the a)oxidation state of Cobalt as +3 ( since there are 3 Cl- ions and NH3 and ...
5 votes
2 answers
207 views

Is tetraoxidocobaltate(V) low-spin

After hearing that hexaamminecobalt(III) and hexafluoridonickelate(IV) are both low-spin due to the central metals' high oxidation states (even though both bear pi-donor ligands), I began to wonder if ...
-2 votes
1 answer
75 views

Bond length in square planar coordination complex of Platinum

(Q): Select the correct statements for $[Pt(NH_3)_2Cl_2]$ : (a): Geometrical Isomerism (b): Optical Isomerism (c): All bond length are equal. (d): Chelation effect is effect. (e): Hydrogen bonding is ...
2 votes
3 answers
227 views

How to calculate the pH of a solution with addition of a complex

The scenario is this. I have $50$ mL of $0.1$ M $\ce{NH4^+}$ at a certain temperature which gives it a $K_a=5.2\times 10^{-8}$. To this solution, I add $0.02$ moles of $\ce{Cd(NO_3)_2}$. It is known ...
2 votes
0 answers
83 views

Isomers of Pentaaminechlorocobalt(III) chloride

What kind of isomers does $\ce{[Co(NH3)5Cl]Cl2}$ exhibit? I can rule out geometrical and optical due to there being $\ce{5 NH3}$ ligands which central metal atom cannot have different positions of $\...
16 votes
3 answers
8k views

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 ...
4 votes
2 answers
3k views

How is an aqueous Ag+ the same as [Ag(H2O)2]+?

$\ce{Ag^{+}_{(aq)}}$ can be written as $\ce{[Ag(H2O)2]+}$ but how would you know that it bonds with 2 water molecules? I don't get when ligands randomly form 6, 4, 2 bonds.
1 vote
0 answers
149 views

Color of coordination compounds

My book(Page $259$ section $9.5.5$) says that the color mainly comes from absorption of light in the coordination compound: The color is complementary of the wavelength it absorbs , the wavelength ...
-1 votes
1 answer
332 views

Reason behind paramagnetic substances having color

I've read in many books that paramagnetic substances are coloured while diamagnetic substances are colourless (yes there are some exceptions too). But nowhere i could find a reason for this phenomenon....

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