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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8
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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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516 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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72 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 ...
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Why does beryllium have an exceptionally high hydration energy?

You would expect solubility of Group $2$ fluorides to increase down the group, as lattice energy plummets much more sharply than hydration energy does. For the most part, this is true: $\ce{BaF2}$ is ...
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155 views

Interference of Ca-EDTA with fluoride delivery in mouthwash

The goal of fluoride mouthwash is to deliver $\ce{F-}$ to the surface of the teeth to turn hydroxyapatite in the dental enamel into fluorapatite. Typically sodium fluoride or stannous fluoride are ...
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1k views

Why is hexacyanoferrate(II) colored and at the same time diamagnetic?

I am wondering why $\ce{[Fe(CN)6]^4-}$ is colored and at the same time diamagnetic. For a transition metal to be diamagnetic all the electrons should be paired up in the d orbitals and at the same ...
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1k views

Does the wavelength of light absorbed by a complex depend upon extent of splitting or stability?

Background: we were doing Crystal Field Theory in school when this question popped up. Specifically we were talking about stability obtained due to the chelate effect and if the extra stability in a ...
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343 views

Why do nitrogen molecules not act as ligands in haemoglobin?

Nitrogen molecules $(\ce{N2})$ have lone pairs, which, as far as I know, is the property of oxygen molecules $(\ce{O2})$ that allows them to act as ligands bonding to iron in haemoglobin in the blood. ...
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42 views

Cytotoxicity of Ru-complexes

I have a basic question: why are Ru(II)-complexes cytotoxic? What I know is that depending on the used ligand some of them interact with the DNA either via DNA-pi-stacking (intercalation) or binding ...
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139 views

Effects on Stretching Frequencies in Organometallic Complexes

If you added a negative charge to $\ce{Mo(CO)_6}$ how would this effect the $\ce{CO}$ stretching frequency in an IR spectrum? My thoughts are that it would lower the $\ce{CO}$ stretching frequency ...
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297 views

Possible causes for flawed results of an EDTA titration for the Ca content of milk

Earlier today I was trying to find the calcium content of different milks as a part of a school assignment. I used this setup as the basis for my experiment: I was using $\pu{0.1 M}$ EDTA solution ...
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How to use Sodium Thiosulfate for fixing dicopper (I) tetraiodomercurate (II)?

DISCLAIMER DO NOT TRY TO DEMERCURATE USING DESCRIBED PROCEDURE. CONSULT YOUR EMERGENCY SERVICE. I found a discrepancy between a government-approved procedure of living quarters demercuration and the ...
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60 views

Metal coordination in enzymes: What type and number of bonds form between amino acid residues and Fe(II)?

My understanding: Transition (d-block) metals, as found in intracellular proteins, are limited to about 10 elements including amongst others Fe, Ni, and Cu. Due to the reductive environments inside ...
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171 views

Protonated forms of EDTA and their constants of formation with metal ions

It is widely known that the fully deprotonated form of EDTA (usually written as Y4-) is the only form that is significantly involved in complexation reactions. From what I have read, this accounts for ...
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938 views

Does fluoride anion ever act as a strong field ligand?

In the case of $\ce{[Fe(H2O)6]^3+}$ there are $5$ unpaired electrons as water acts as a weak field ligand. But instead of fluoride acting as a weak field ligand in the $\ce{[MnF6]^4-}$ , why does it ...
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7k views

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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45 views

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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1k views

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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56 views

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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319 views

Differences between hexaaqua cobalt (III) complex and hexammine cobalt (III) complex in aqueous solution

Why is $\ce{[Co(H2O)6]^3+}$ a strong oxidizing agent and $\ce{[Co(NH3)6]^3+}$ stable in Aqueous solution? I think this has got to do with Pairing Energy and Ligand strengths of $\ce{H_2O}$ and $\ce{...
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120 views

π-ligands in trigonal prismatic complexes

We recently had a discussion here about the symmetry problems for the often postulated s- and p-mixing with the d-orbitals in complexes to somehow allow a d-d-transition. It was pointed out back then ...
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216 views

Why does the electrolyte used in Lechlanché cell turn blue?

In my school there are jars which are turned into Lechlanché cells. Basically the cell has aqueous ammonium chloride solution as the electrolyte which is obviously transparent in the beginning. The ...
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156 views

What will happen if ligand orientation is changed?

How we came to know ligand should approach from t2g orbitals in d5 configuration for tetrahedral complexes? What will be the difference in energy if ligand approach from eg? As far as I can think, ...
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303 views

Precise explanation of macrocyclic effect

In most of the books, the reason of macrocyclic effect is given that It occurs due to preorganised structure of macro-cyclic ligand.  But a proper explanation of these two particular examples isn't ...
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Why is the geometry of [Ni(CN)4)]2- square planar? Why is it colorless?

Why is the geometry of $\ce{[Ni(CN)4)]^{2-}}$ square planar given that it has a coordination number of 4? Shouldn't its geometry be tetrahedral as it would minimise the bond angle and hence repulsion?...
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2k views

Shape of nickel tetracarbonyl

Is nickel tetracarbonyl a square planar complex or a tetrahedral complex? According to the crystal field theory, $\ce{CO}$ is a strong field ligand and should hence cause the $t_{2g}$ electrons of ...
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3k views

dsp2 and sp3 hybrid orbital shapes in coordination chemistry

Why is $\mathrm{dsp}^2$ square planar but $\mathrm{sp}^3$ tetrahedral in shape? I am unable to find a reason anywhere. I know how to figure which hybridisation a compound is, but not why.
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Why is tetrachlorocuprate (II) yellow if it is high-spin?

From my knowledge of transition metal complexes, tetrahedral complexes generally have less splitting (compared to octahedral complexes) because they only involve four ligands are they aren't placed ...
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51 views

Which acetate salt is blue and turns yellow when dissolved in water?

***Update Some questions I am considering to try to answer this question; When dissolving the powder in acetic acid, which ions are present? From what I've read, I haven't found any acetate salts ...
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38 views

Distinguishing between different geometries of bromochlorobis(triphenylphosphine)platinum(II) using ¹⁹⁵Pt NMR

Question The question off which I am basing my question assumes that $\ce{[PtClBr(PPh3)2]}$ can exist in either the square-planar or tetrahedral geometry. If one would use $\ce{^{195}Pt}$ NMR ...
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141 views

Why does the binding of DMSO to metal via the S atom (k-S) strengthens the S=O bond?

So, DMSO (dimethyl sulfoxide) can form metal complexes in both $\mathrm{\kappa O}$ and $\mathrm{\kappa S}$ mode i.e. binding with the oxygen or the sulfur respectively. The general explanation given ...
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386 views

Reaction between Sodium Thiosulfate and Iron Chloride

I'm doing a paper on catalytic effectiveness in this reaction, and am trying to identify how the catalysts are speeding up the reaction. Based on what I can find, $\ce{Fe}$ starts as $\ce{Fe^3+}$, ...
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924 views

Effect of Synergic Bonding on Bond Lengths in Metal Carbonyls

Consider the metal carbonyl, pentacarbonyl iron(0). There exists synergic bonding between the central metal atom, iron and the neutral carbonyl ligands. This strengthens the metal-ligand bond but ...
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523 views

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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302 views

Crystal Field Theory - Operator Equivalent Methods

I am a bit confused by some of the points of operator equivalent methods in crystal field theory. I would appreciate any help I could get with any of my questions. First, I am confused as to the ...
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64 views

Why does some compound as given in the image below change from low spin to high spin above a particular transition temperature?

Magnetic moment sudden increase at a particular temperature is explained by CFT. But why does it happen at all?
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446 views

How do counter-ions influence the color of coordination compounds?

I've been asking myself for a while now how counter-ions sometimes change the colors of coordination compounds. Like when I use d-metals as counter-ions to precipitate Cyanoferrates. I looked at ...
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41 views

Are there any stable complexes where an (N-unsubstituted) imine is bound eta^2 to a (late) transition metal?

I've been looking for an example of a stable complex where a $\ce{C=N}$ is coordinated $\eta^2$ to a (late) transition metal, but could not find any. Do they exist at all? For $\ce{C=C}$ there are ...
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140 views

Why is the spin magnetic moment for nickel(II) given as 1.7 Bohr magnetons in some references?

I read some theoretical articles concerning $\ce{Ni-O}$ system, where $\ce{Ni}$ sits at the center of the octahedron formed by $\ce{O}$. The calculated magnetic moment on the $\ce{Ni}$ sites is about $...
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Classes of Organometallic Compounds - Where do I put Grignard Reagents?

[Note- I've already seen this question Why do Magnesium and Lithium form *covalent* organometallic compounds? as user Mithoron was kind enough to point out, but the problem that I face is different ...
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Ligand Field Theory with non-identical ligands?

Lots of undergraduate inorganic textbooks deal with complexes with $O_h$ or $T_d$ symmetry. So, if ligands are not same(like $\ce{[Ni(NH_3)_4(H_2O)_2]^{2+}}$), what methods are used to interpret their ...
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985 views

How do we decide which ligand is monodentate, bidentate, etc.?

I went through a question about the EAN rule. At first, it was all clear to me, but now I'm just confused on how to decide which ligand will donate how many electrons. How do we decide which ligand is ...
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57 views

How do partially protonated sulfate ligands affect a metal's charge?

I'm currently reviewing the Periana-Catalytica system and I have a question about one of the intermediates, namely $\ce{[(bpym)Pt(OSO3H)2]^+}$, which is found in the following tutorial review. How do ...
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214 views

Why do isomeric bis-ethylenediamine cobalt complexes react differently?

A compound $\ce{Co(en)2(NO2)2Cl}$ has been prepared in a number of isomeric forms.One form undergoes no reaction with $\ce{AgNO3}$ or $\ce{(en)}$ and is optically inactive. A second form reacts with $...
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187 views

Formation of Coordination Compounds

While reading applications of coordination compounds, I read that Hardness of water can be checked using Na2EDTA in hard water containing Ca+2 and Mg+2 which form complexes with EDTA. Also, Lead (Pb),...
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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 ...
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1answer
1k views

Why can't oxalate ion donate two pairs of electrons from the two double-bonded oxygen atoms

So, I read that an oxalate ion is a bidentate ligand but since I saw that it has 4 oxygen atoms I was confused as to why it isn't a tetradentate ligand instead. I searched it on Google and found this:...
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1answer
339 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
585 views

Do ligands in ionisation isomerism interchange?

The text says: This form of isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace ligand which can then become the counter ion. For other ...
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Toxicity of Mercury (II) Iodide and dicopper (I) tetraiodomercurate (II)

This is a continuation from my previous post. Could you please give me some info on the toxicity of compounds $\ce{HgI2}$ and $\ce{Cu2[HgI4]}$? I found on sigmaaldrich.com that these are very ...