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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33 views

Systematic IUPAC rules on certain complex coordination complexes

What is the systematic (possibly using the retained name pentalene) IUPAC name for this hypothetical species, because a molecule I'm kind of designing is zwitterionic and one of its constituent groups ...
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2answers
56 views

Coordination number of chromium(III) oxalate complex

The coordination number refers to the number of binders that interact with the central metal ion. So, in the complex $\ce{[Cr(C2O4)3]^3-}$ chromium is bound to three oxalate ions. Why its ...
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48 views

Why are group 7 to 9 elements good hydrogenation catalyst?

In my exam question came: statement 1- activity of hydrogenation catalyst increase from group 5 to 11 with maximum activity shown by group 7 to 9 group elements. Statement 2- reactants are very ...
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1answer
496 views

How is the bonding in the [Au6C(PPh3)6]2+ cluster explained?

How can carbon form six bonds in such a compound as $\ce{[Au6C(PPh3)6]^2+}?$ I understand how carbon with five bonds can be formed $(\ce{CH5+},$ for instance), but it shouldn't have enough electrons ...
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22 views

Why does no charge transfer occur in CoCl4^2-? [closed]

In my textbook it says that there are only d-d transitions in CoCl4^2-. Why is this the case? Why are there no LMCT or MLCT bands?
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1answer
50 views

What is the difference between cyanato, cyanido and cyano? When should i use which? [closed]

I understand that cyanido is the newly adopted naming in place of cyano but what is cyanato? Can anyone please give examples to illustrate the difference?
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Which one is the correct structure of CuSO4.5H20? [duplicate]

In this one we see that the SO4 2- ion is bonded/connected to the Cu2+ center by hydrogen bonds. And in this one we see that the oxygen atoms of SO42- form dative bonds with the Cu2+ atom. So which ...
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1answer
95 views

Why is chromate coloured but tungstate colourless?

I have to try and work this out using the tetrahedral molecular orbital diagram for $\ce{[WO4]^2-}$ but I am confused as both are $\mathrm d^0$ right?
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Specific examples of all-main-group complexes with significant d-orbital contribution

It is usually said that d-orbitals are not usually used in bonding, even for so-called "hypervalent" ones, in compounds that are made purely of main group compounds. However, after reading an article ...
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1answer
63 views

Why is iron pentacarbonyl known, but iron(III) hexacarbonyl is not?

Why is the neutral complex $\ce{[Fe(CO)5]}$ known, but the cationic carbonyl complex $\ce{[Fe(CO)6]^3+}$ is not known?
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Predicting colors of aqueous solutions

While going through my AP chem prep book again, I came across questions asking about the color of certain aqueous solutions. For example: Which of the following substances will produce a colorless ...
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30 views

Heating of hydrated salt

When $CuSO_4.5H_2O$ is heated, why is hydrogen-bonded water of crystallisation not lost first?
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Some special cases of inner orbital complexes

Following statements are for $\ce{[Co(CN)6]^{4-}}:$ $\ce{[Co(CN)6]^{4-}}$ has the configuration $\mathrm{t_{2g}^6 e_g^0}$ but is paramagnetic because the last electron resides in $\mathrm{5s}$ ...
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Definition of t2g orbitals in CFT

My textbook defines $\mathrm{t_{2g}}$ orbitals as $\mathrm{t_{2g}}$ stands for a set of three orbitals which are asymmetric with respect to $C_2$ axes, perpendicular to the highest $C_n$ axes, but ...
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3answers
123 views

Determining the oxidation state of a bridging platinum complex

I want to ask a question about determining the oxidation state of a Platinum complex. I was presented today with the following complex and asked to comment on the oxidation state and hence the d-...
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3answers
91 views

How to simplify these system of equilibrium equations

What is the pH when $0.025$ mol $\ce{NiCl2}$ is added to $\pu{1.00 L}$ of a $\pu{0.100 M}$ solution of $\ce{HCN}$, if the formation constant for $\ce{Ni(CN)4^2-}$ is $K_f=\pu{1.0e22}$, and the $K_a$ ...
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1answer
24 views

Optical activity of cis-trans isomers of a co-ordination compound [closed]

Why do geometrical (cis and trans) isomers of [Pt(NH3)(Br)(Cl)(py)] not show optical activity ? Thanks In Advance...
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25 views

Ion exchange resins

My problem is explained quite easily: I have no experience with ion exchange resins but I would like to test something out in order to exchange my sulfate ions in solution for nitrate (can also be ...
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1answer
28 views

Is specific rotation defined for mixtures of enantiomers or meso compounds?

I recently had to do an experiment where we had to make a racemic mixture of D and L complexes and then resolve the enantiomers, and measure the optical rotation of the racemic mixture, and the ...
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1answer
50 views

Triphenylphosphine (PPh3) vs. 1,2-bis(diphenylphosphino)ethane (dppe) ligand?

What about $\ce{NiCl2(dppe)}$ makes it a more efficient catalyst for Suzuki cross-coupling as opposed to $\ce{NiCl2(PPh3)2}$ or $\ce{NiCl2(PCy3)2}$? How does the dppe ligand increase the reactivity of ...
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What prevents inner-sphere electron transfer from oxalato-iron(II) to chloro-platinum(II)?

In this book (p. 237), when talking about the reduction of $\ce{[PtCl4]^{2-}}$ by $[\ce{(C2O4)2Fe]^{2-}}$, the author states that There is no easy route for imparting electrons onto the $\ce{PtCl4}^...
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Why does thiocyanate bind to Fe³⁺ with the S side instead of the N side?

According to hard and soft acids and bases (HSAB) theory, "soft" Lewis bases bind to "soft" Lewis acids, and "hard" Lewis bases bind to "hard" Lewis acids. $\ce{Fe^3+}$ is a hard Lewis acid. In $\ce{...
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Energy diagram of copper iodide complex

We did an experiment where copper iodide 4-methylpyridine and copper iodide imidazole was formed and now we are asked what orbital the electron is excited from and to. After much research we still ...
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1answer
25 views

Ligand substitution reaction in coordination compounds

I know that the following substitution reaction can take place: $$\ce{[Cu(H2O)4]^2+ (aq) + 4NH3 (aq) -> [Cu(NH3)4]^2+ (aq) + 4H2O (l)}$$ This is because ammonia is a stronger ligand than water. ...
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Benzannulation of 18-crown-6

I know crown ethers can be used to complex metal ions. Question: What important properties do 18-crown-6 change during the benzannulation from 18-crown-6 to DB18C6 (dibenzo-18-crown-6)? How do these ...
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1answer
36 views

Naming a coordination compound

I was asked to determine the coordination compound which has the name: $$\text{triamminetrinitritocobalt(I)}$$ I thought it must be: $$\ce{[Co(NH3)3(ONO)3]^2-}$$ The $-2$ charge can be deduced by ...
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1answer
50 views

Why is the solution of (NH4)2[Ce(NO3)6] used as an oxidizing agent? [closed]

In an MCQ, the correct statement regarding the abovementioned compound is that its solution is used as an oxidizing agent. I do not understand why that is so.
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Counterion exchange

I have a quick question about counterion exchange. I have this very practical problem at my hands that I have a ethyl sulfate $(\ce{EtSO4-})$ counterion for a $\ce{R4N+}$ moiety ($\ce{R}$ = 3 ...
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2answers
301 views

Chromium cyanide complexes

I have rarely seen any chromium $(\ce{Cr})$ square planar complexes and I have been told that $\ce{[Cr(CN)4]-}$ is tetrahedral. So, if the statement is actually correct, are there any other known ...
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44 views

Why is [NiCl2(PPh3)2] tetrahedral and [NiCl2(PMe3)2] square planar? [duplicate]

I'm confused here since PPh3 is a strong field ligand and would try to make the molecule square planar but is bulky and would tend to adopt tetrahedral geometry to minimise sterric hindrance. And why ...
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1answer
92 views

Confused on how to draw cis-[Ni(H2O)4(NH3)2]Cl2 [closed]

I got a question on my practice exam telling me to draw cis-diamminetetraaquanickel(II) chloride, but I'm not sure on how to place the two $\ce{Cl}$ atoms.
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1answer
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Isomerism and namegiving

Is this the right chemical formula of the $\ce{Rb[Pt(NH3)Br2Cl]}$ complex: rubidium amminedibromidochloridoplatinate(II)? And is it correct that it has geometric isomerism, being square planar with a ...
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1answer
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Should we expect Jahn–Teller distortion in bis(ethylenediamine)nickel(II)?

(ii) The stepwise stability constants of the following complexes in aqueous solution at $\pu{25 °C}$ are given below: $$ \begin{array}{cll} \hline \ce{M} & \ce{[M(en)2(H2O)2]^2+} & \ce{[M(...
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32 views

Why do statistical effects impact stepwise stability constants?

I have a question regarding the stepwise stability constants of metal complex formation/substitution. My lecture notes say that if we have a metal complex, say $\ce{[MX_{6}]}$, and a substitution ...
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53 views

Stability order of chelate complexes of nickel and iron

Which stability order is correct? $\ce{[Ni(en)2]^2+} > \ce{[Ni(dmg)2]}$ $\ce{[Fe(edta)]^2-} > \ce{[Fe(en)3]^3+}$ In the first case I think the stability depends upon the strength ...
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What is the order of crystal field stabilisation energy for tris(ethylenediamine)chromium(III) chloride and hexaaquachromium(III) chloride?

In my book it is given that the crystal field stabilisation energy for $\ce{[Cr(en)3]Cl3}$ is more than that of the complex $\ce{[Cr(H2O)6]Cl3}.$ By what I have studied, the crystal field ...
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0answers
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Why CO is a weak pi-acid ligand?

This question was given by my chemistry professor, but I doubt that this question is not correct. Following the lewis definition of the acid, any molecule or atom acts as a acid if it accepts an ...
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1answer
56 views

Why is dimethylglyoximate a bidentate ligand and not a tetradentate ligand?

Why can't the 2 oxygen atoms donate a lone pair and hence become binding sites? Is it because of the angle made by the oxygen and Nitrogen atoms?
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1answer
101 views

Optical activity of cis coordination compounds

I came across a statement saying, "Consider a Octahedral coordination compound of type [MA2X2]. Then, if the compound is in a cis form, it shows optical activity as there is no plane of ...
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3answers
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Which would have a more intense transition: a low spin d6 complex or a high spin d5 complex?

I have an assignment question for second year inorganic which asks to rank the intensity of d-d transitions for a number of complexes. Two are $\ce{[Fe(OH2)6]^3+}$ and $\ce{[Fe(CN)6]^4-}.$ Both will ...
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1answer
157 views

Ionization isomerism in coordination compounds

Ionization isomerism is defined as complexes which have same empirical formula but ionize to different ions in solution. Consider the complex $\ce{[Pt(NH3)4Cl2]I2}$. The other possible ionization ...
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2answers
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Relation between the oxidation state of central atom and its coordination number in a complex compound? [closed]

We know for a complex say $\ce{[Co(NH3)3Cl3]}$ we have $\ce{Co^{3+}}$ and its coordination number here is 6. And for this if we know either oxidation state or coordination number then other is fixed. ...
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What's an appropriate ligand for Pd-Ag redox?

I want to reduce palladium with silver (in cellulose): $\ce{Pd^{2+} + 2Ag->2Ag+ +Pd}$. What is a good ligand and spectator ion for both metals? (The pH is not critical.) Ones I have considered: $\...
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0answers
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Will disodium EDTA effectively destroy Tollens' reagent?

As I understand it, if I mix $\ce{[Ag(NH3)2]NO3}$ and $\ce{Na2EDTA}$ the silver will complex much more strongly with the EDTA than the ammonia, and the hydrogen ions will protonate the ammonia, ...
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1answer
55 views

Sulfate and carbonate ions as ligands

The pentahydrate salt of copper (II) sulfate exists as a blue solid while the anhydrous and monohydrate salts appear as white solids. The structures of these salts are discussed here. The blue colour ...
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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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1answer
47 views

About Fe(III) and Fe(II) coordination complexes

Why does Fe(III) form octahedral coordination complexes if it has 5 electrons in its d-orbitals? I understand that Fe(II) has 6 electrons in its d-orbitals and 6 lone pairs from 6 ligands as the 12 ...
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4answers
2k 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 ...
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1answer
65 views

Formation of green precipitation whilst adding potassium fluoride to aqueous solution of copper(II) sulfate [closed]

Aqueous copper sulfate solution (blue) gives a green precipitation with aqueous potassium fluoride. Explain these experimental results. I've read answers like, $\ce{H2O}$ is a weak ligand and ...
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1answer
211 views

Magnetic nature of tetraamminedichlorocobalt(III) chloride

I know how to predict magnetic nature when the compound contains only strong field or only weak field ligands. But in $\ce{[Co(NH3)4Cl2]Cl},$ $\ce{NH3}$ is a strong ligand whereas $\ce{Cl-}$ is a weak ...