25
votes
Accepted
What is the oxidation state of Mn in HMn(CO)5?
On negative oxidation states, in general
Although it's usually a topic that's covered relatively late in a chemistry education, negative oxidation states for transition metals[1] are actually quite ...
- 71.1k
19
votes
Accepted
Can Fe(CO)5 adopt both square pyramidal and trigonal bipyramidal geometries?
Your book was correct that a five coordinate metal complex is able to adopt both square pyramidal and trigonal bipyramidal geometries, and in both cases the sp3d hybridisation scheme applies (if you ...
- 17.1k
13
votes
Accepted
Is there an iron–iron bond in diiron nonacarbonyl?
tl;dr: There probably isn’t an Fe–Fe bond. We should probably stop drawing an Fe-Fe bond. Textbooks and lecturers should really stop teaching students that there is an Fe-Fe bond. But all that said, ...
- 17.1k
10
votes
Is there an iron–iron bond in diiron nonacarbonyl?
To supplement the accepted answer, here is something else I found.
Bonding in bridging carbonyls
An alternative explanation for the bonding in $\ce{[Fe2(CO)9]}$ is presented in a 2012 article by ...
- 71.1k
9
votes
Accepted
Why does iron carbonyl have five carbonyl groups instead of six or four?
In organometallic chemistry there is something known as the 18-electron rule, which essentially suggests that stable complexes have an 'electron count' of 18. A general discussion of electron counting ...
- 71.1k
9
votes
Accepted
Why does the 31P{1H} NMR spectrum of cis-[Mo(CO)2(dppe)2] show two signals?
In this complex there are two different 31P environments which are not related by symmetry:
The two green phosphorus nuclei can be interconverted by a $C_2$ rotation (the rotation axis bisects the OC–...
- 71.1k
8
votes
Can Fe(CO)5 adopt both square pyramidal and trigonal bipyramidal geometries?
The most recent single crystal structure investigation (high precision, $R_1 = 1.9\%$, $wR_2 = 5.7\%$) of molecular iron pentacarbonyl [1] suggests trigonal bipyramidal coordination environment (also ...
- 37.4k
7
votes
Why is the oxidation state of Co -1 in [Co(CO)4]-?
Ignore list of "allowed oxidation states" for metal complexes. "allowed oxidation states" might be the most common, but definitely not the only ones the atom is allowed to be in. For example, for $\ce{...
- 21.5k
7
votes
Does Fe(CO)6 really exist?
There is an iron hexacarbonyl, not as a neutral compound but as a dication which satisfies the 18-electron rule. This along with its heavier Group 8 congeners is reported by Finze et al. [1]. The ...
- 53.4k
7
votes
Effect of metal identity on CO bond length in carbonyl complexes
Let's look at the molecular orbital diagram calculated with JSmol.
As you know, the principal effect is back-donation from the metal to the π-antibonding orbitals of the carbon monoxide. But not all ...
- 53.4k
6
votes
Accepted
Why is there no neutral [Cr(OC)6] or anionic [Fe(NC)6] - isomers of cyanide and carbonyl complexes?
In the case of cyanide we actually do have iron coordinated to the nitrogen ends of the cyanide ligands in Prussian blue. In fact iron atoms are coordinated to both ends of the cyanide ion ligands; ...
- 53.4k
6
votes
Why do the protons in pentacarbonylmethylmanganese show up at –0.21 ppm?
Unfortunately, you don't give an indication of what you expect the chemical shift for the -Me to be, other than higher than is observed. However, you are correct in your assumption; the π back ...
- 11.9k
6
votes
Why is Diiron nonacarbonyl so exceptional?
Wikipedia (primary reference) suggests a possible reason for $\ce{Fe2(CO)9}$ dissolving preferentially in THF versus nonpolar solvents: it reacts according to the scheme
$\ce{Fe2(CO)9 + THF <=>...
- 53.4k
5
votes
Accepted
Why is carbon monoxide a monodentate ligand
It is possible for carbon monoxide to coordinate through oxygen, as reported here. However, there is indeed a strong tendency for carbon monoxide to coordinate through carbon, essentially due to the ...
- 53.4k
4
votes
Accepted
How to interpret the relation between CO stretch frequencies and backbonding strength for polycarbonyl compounds?
Disclaimer: This is not going to be an answer to the question. This is just a collection of thoughts on it, which hopefully helps to form a better understanding.
First and foremost, and this should go ...
- 43.8k
4
votes
Why is MP2 failing to calculate proper IR frequencies for [Co(CO)4]- and [Fe(CO)4]2-?
Some months later but here we go...
I agree with most of the comments that multiconfigurational effects should be present for this system, and maybe they are very strong. But I tend to think that ...
- 1,987
3
votes
Accepted
Why are palladium and platinum carbonyls unstable at room temperature?
Tl, dr: It's not just a matter of size. A combination of coordination geometry, node distribution in the $d$-orbital wavefunctions, and atomic size all conspire to weaken $\pi$ overlap in palladium ...
- 53.4k
3
votes
CO-vibration in metal carbonyl
I think the mistake you're making is this conclusion: "Higher atomic charge. . . -> higher electron density -> more pi-backbonding". With higher (ie more positive or less negative) atomic charge, ...
- 10.1k
2
votes
Can a carbon that has 5 bonds be explained by saying that one of its bonds is a coordination bond?
If you have only ever heard of Lewis diagrams,* then you might misinterpret the shown representation.
Instead of bonding the focus of this diagram is more on structure, even though it compromises on ...
- 43.8k
2
votes
Accepted
Why there are more examples of carbonylate anions than metal carbonyl cations?
Yes there are more carbonylate ions than metal carbonyl cations, but the latter do exist. A salt $\ce{[Mn(CO)6^+][BF4^-]•SO2}$ has been synthesized in a superacid medium.
Metal carbonyl cations are ...
- 53.4k
2
votes
Relativistic effect: d-electrons in metallorganic complexes
First off, be aware that oxidative addition occurs by several mechanisms which are governed by different factors.[1]
As you move down a period, the outer electrons become more easily accessed, as the ...
- 429
2
votes
Why do the protons in pentacarbonylmethylmanganese show up at –0.21 ppm?
Going to assume the solvent is CDCl3.
It is true that pi Back-donation withdraws electron density from the Metal Center to deshield it, but also note that carbonyl groups are still electron donating ...
- 2,110
1
vote
Reaction of anisole and succinic anhydride in presence of aluminium chloride
Aluminium chloride ($\ce{AlCl_3}$) is mainly used for this Friedel-Crafts alkylation or acylation, where this compound acts as catalyst, and also controls the production of the desired compound.
For ...
- 5,593
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