Questions tagged [organometallic-compounds]
For questions relating to organic compounds which contain a bond between a carbon atom and a metal.
210
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Relativistic effect: d-electrons in metallorganic complexes
With higher period the d-electrons of the metal are less strong bonded and therefore oxidative addition is easier for $\ce{Ir(I)}$ than for $\ce{Rh(I)}$ and much easier than for $\ce{Co(I)}$.
For ...
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4
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Why do Organolithium or Grignard reagents act as nucleophiles and not as bases with aldehydes and ketones
I've read entire Chapter 14: Organometallic Compounds of Francis Carey's "Organic Chemistry" but I still didn't get an answer to my question.
Quote from the book:
Because of their basicity ...
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19
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1
answer
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Why does benzene bend in this reaction?
From here
I can see why hapticity changes here, but not why it is necessary for the benzene ring to bend. The resonance energy of benzene is pretty large, and there's no balancing increase in ...
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1
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Propose a chemical formula for the white solid that forms during the initial stages of the reaction of Sn with benzyl chloride
In my inorganic class, we carried out the synthesis of chlorotribenzyltin, $\ce{SnCl(CH2C6H5)3}$.
The synthesis begins with a reflux I'll describe below:
In a hood, place 2.0 g (17 mmol) of 325 mesh ...
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18
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3
answers
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Why do Magnesium and Lithium form *covalent* organometallic compounds?
Lithium and magnesium are Group 1 and Group 2 elements respectively. Elements of these groups are highly ionic, and I've never heard of them forming significantly covalent inorganic compounds.
Yet ...
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17
votes
1
answer
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Are there any significant uses of the compound formed by magnesium and anthracene?
In an unusual reaction, magnesium reacts with anthracene in THF to form a grignard-like compound called, prosaically, magnesium anthracene:
I remember using it briefly in the 1980s. At the time there ...
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17
votes
1
answer
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How to name this quintuply-bonded chromium dimer?
Depicted below is a chromium compound with a metal–metal quintuple bond. It boasts two identical bridging ligands, derivatives of 1,3-diphenylbenzene. The aim of this question is to figure out
the ...
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16
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1
answer
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Why do halogen-metal exchanges happen?
I'm trying to understand organometallic raegents but am stuck at halogen-metal exchanges.
For example if you have $\ce{PhBr + BuLi}$ you get $\ce{PhLi + BuBr}$, I don't understand why $\ce{PhBu + ...
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16
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1
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Mechanism of a gold catalyzed addition to triple bond
I needed to draw the reaction mechanism for this reaction:
So, after consulting some literature I drew this mechanism:
But, I am not sure about the last step. Does the $\ce{H+}$ just substitute the $...
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15
votes
1
answer
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Can pi backdonation occur on non-metal centers?
The common example of back-donation is the interaction of a CO molecule with a metal center (d-orbitals) on a surface.
Can a similar mechanism occur between CO and a non-metal center, like oxygen on ...
- 315
15
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1
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Alkane deprotonation by organolithiums
Butyllithium isomers are all stored in alkane solvents. Theoretically, equilibrium should (given enough time) lead to formation of mostly n-hexyllithium in the case of n-BuLi stored in (mostly) n-...
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14
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2
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Why does magnesium prefer to insert into C–Br bonds over C–Cl bonds?
In the formation of a Grignard reagent from a compound possessing both bromine and chlorine, magnesium preferentially inserts into the C–Br bond over the C–Cl bond. For example, the formation of a ...
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13
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2
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Negative oxidation states of Si
According to List of oxidation states of the elements, silicon has a possible oxidation state of $-4$.
Now, I've been looking everywhere for a compound that contains Si(-IV), but I cannot find any ...
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2
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Do eta-4 benzene ligands participate in Diels Alder or other cycloadditions?
While refreshing myself on denticity to answer another question, I started to read about hapticity, which is the coordination of a ligand through multiple continuous atoms. A famous case is ferrocene (...
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12
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2
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Why can't the reaction of grignard reagent with carboxylic acid give a ketone?
I understand that a Grignard reagent can act both as a base and a nucleophile.
It acts as a base in the presence of a proton source (eg: alcohols, amine, water, etc). But when reacting with a ketone ...
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12
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1
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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.
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12
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1
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Mechanism of lithium-halogen exchange of primary alkyl iodide
On Clayden's page 190 this reaction is given for preparation of organometallics:
What is the mechanism of this reaction? I expected the "almost carboanion" part of the $\ce{t-BuLi}$ to attack as a ...
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12
votes
1
answer
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Noyori hydrogenation and the Curtin–Hammett principle
My question is relating to how the Curtin–Hammett principle applies to homogeneous hydrogenation using chiral ligands.
Figure 0: An example of a quadrant diagram used as a mnemonic to predict the ...
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11
votes
3
answers
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Where to find common inorganic/organometallic molecules?
I'm working on a project to create a large open repository of quantum calculations, largely for teaching purposes.
I can get thousands of common organic compounds easily from sources like PubChem or ...
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11
votes
1
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527
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Terminal Alkyne in Suzuki Coupling
I've done a very similar reaction to the one below but by TLC I observe only starting materials. It's super clear that nothing else is going on. Conditions: K3PO4, Pd(dppf)Cl2, dioxane/water, heat to ...
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10
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1
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How does cyclopentadienyl anion act as reducing agent?
I am a second year university student, so I'm afraid my chemistry isn't great. I am looking for an explanation of how the $\ce{Cp-}$ anion acts as a reducing agent.
To contextualise - in a simple ...
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10
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1
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How can the solid state structure of cyclopentadienyllithium be explained?
In the solid state, LiCp adopts a polymeric multidecker structure where Li atoms are sandwiched between two Cp rings (shown in this diagram from Organometallics 1997, 16 (17), 3855–3858):
If we ...
9
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1
answer
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Can ferrocene type sandwich compounds be made with fluorene?
Ferrocene will be well known to made members of this site. It consists of two cyclopentadienyl anions sandwiching an iron-II ion.
During my first year organic chemistry course (about 40 years ago) I ...
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9
votes
1
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What's wrong with using tin in medicinal chemistry?
I just read this In the Pipeline post and I was slightly confused by a statement on the use of tin. Lowe reports on this paper, which describes a synthetic route to spiro heterocycles using tin ...
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9
votes
1
answer
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Ketone/aldehyde synthesis from N-acylazetidines or aziridines
A common principle in organic chemistry is to make sure the product is less reactive than the starting material, to prevent overreaction. So, for example, the treatment of an ester with a Grignard ...
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8
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2
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Is the term "heteroatom" reserved for exclusive elements?
From my experience, typically in organic chemistry, the implication of "hetero-atom" in some molecule is understood as B, N, O, S, P or a halogen -- or any nonmetallic element, perhaps.
If one ...
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8
votes
1
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Organic reaction of dry ice and Grignard reagent
Which of the following product is formed in the reaction $\ce{CH3MgBr}$ in DryIce/acid?
A) $\ce{CH3COOH}$
B) $\ce{CH4}$
C) $\ce{CH3OH}$
D) $\ce{CH3CH2CHO}$
My answer is A, since dry ice is $...
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8
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1
answer
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Reduction of alkyl halides to alkanes
For all the three parts, only methane has been given as the product in my textbook.
In 1) and 2), according to the mechanism I wrote, I get both ethane and methane as products. I think both these ...
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8
votes
1
answer
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How to interpret the relation between CO stretch frequencies and backbonding strength for polycarbonyl compounds?
I am working on a series of octahedral complexes of the type $\ce{[M(CO)2(CH3)X3]-}$ where $\ce{M} = \ce{Co}, \ce{Rh}, \ce{Ir},$ and $\ce{X}$ is a range of ligands (halide, cyanide, nitrosyl, etc.). ...
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7
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2
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Reaction of Grignard reagents with esters
Suppose I have a phenyl Grignard and methyl benzoate.
If I react the two, can I expect benzophenone and a triphenylmethoxide ion as my products?
I ask because I know that Grignards react with ...
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7
votes
2
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Why do the protons in pentacarbonylmethylmanganese show up at –0.21 ppm?
The $\ce{^1H}$ NMR of $\ce{Mn(CO)5CH3}$ shows a resonance at –0.21 ppm, which has to be due to the methyl group. Why are the protons so shielded?
I would have thought that all the pi backdonation ...
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7
votes
1
answer
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Role of Cu in Corey-House synthesis
What does $\ce{Cu}$ do? And why do we need it? Can we not do $\mathrm{S_N}2$ without it? And is there any other metal that can help in this? Maybe something like $\ce{Ag}$? I'm guessing this because ...
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1
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Why is the cyclic voltammetry of my ferrocene compound not showing a standard shape?
I am trying to set-up a new cyclic voltammetry measurement station in my lab but the results are very poor. I am using the following parameters:
...
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7
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0
answers
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How can organocuprates generated with catalytic Cu(I) be competitive in 1,4-addition to an enone?
Organocopper compounds (e.g. $\ce{LiCuR_2}$) are often prepared from an organolithium or Grignard reagent when a soften nucleophile is needed, such as for a conjugate addition to an $\alpha,\beta$-...
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2
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Nature of a1g Molecular Orbital Interactions in Ferrocene
While learning about ferrocene I've come across this molecular orbital diagram.
What particularly confused me is the nature of the a'1g orbital. My professor taught that a'1g and e2g are considered ...
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1
answer
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What makes R-MgX a more reactive Grignard reagent than R-Cu?
What makes $\ce{R-MgX}$ a more reactive Grignard reagent than $\ce{R-Cu}$? Has it to do with solvation, bond enthalpy, electronegativity?
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1
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Effect of metal identity on CO bond length in carbonyl complexes
In organometallic carbonyl complexes, a back-donation effect occurs: the σ molecular orbital of CO yields electron density to an orbital of the appropriate metal atom, and in turn, a d orbital of ...
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1
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Molecular Oxygen in Suzuki Homocoupling
I'm curious as to the role of molecular oxygen in Suzuki homocoupling reactions, as discussed here.
In a standard Suzuki cross-coupling reaction, molecular oxygen is not required. However, this paper ...
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6
votes
1
answer
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Volatile alkali metal compounds
Most elements are or have compounds that are gases or have a significant vapor pressure at room temperature. Fluoride is a powerful tool for producing highly oxidized covalent and volatile compounds. ...
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1
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How are Grignard reagents stable in an ethereal solution? [duplicate]
I have heard of the leveling effect, which mentions that highly basic ions cannot exist in a solvent if it's acidity is high enough to be deprotonated by the base.
Considering that, check out the ...
6
votes
1
answer
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Dissociation rates: trans-effect rule in square planar complexes
In lecture, the trans-effect was described.
A ligand $L^t$ with a higher trans-effect as $L$ (cis to $L^t$) leads to a faster dissociation of ligand $L^d$ (trans to $L^t$). I would expect that the ...
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1
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Why do aromatic compounds have an upfield shift upon coordination to metals?
Why do aromatic compounds have an upfield shift upon coordination to metals e.g. ferrocene? The 1H NMR shows a single environment at ~4.1 ppm. This is in contrast to the usual aromatic shift of ...
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1
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What is the mechanism of formation of Grignard's Reagent?
What is the mechanism of formation of Grignard reagents? I couldn't find much in my book or on the Internet. This page says something which I am unable to understand. Why are the $2$ electrons in the $...
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votes
0
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Treatment of ketones with excess Tebbe reagent
The reaction in black below was presented in a set of lecture notes as an example of the use of the Tebbe reagent, however it's not immediately obvious (to me, at least) that the product should be the ...
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0
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I found transition states (TS), but calculations aren't supported by experiment. Do I look for more TSs or somewhere else?
I'm using Gaussian to investigate a catalyst system.
Experimental evidence showed that one of three analogues (R = phenyl, Ph), yielded a benzosultam
when treated with 2,4,6-...
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0
answers
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Why do catalysts have limited turnover numbers in practice?
I quote the Wikipedia page definition for Turnover number:
In other chemical fields, such as organometallic catalysis, turnover number (abbreviated TON) has a different meaning: the number of moles ...
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5
votes
2
answers
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How does the Wurtz reaction produce alkynes?
Wikipedia mentions that alkynes can be produced from geminal dihalides through the Wurtz reaction. However, I am unsure of the reaction mechanism for this reaction. I have not been able to find any ...
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5
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1
answer
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Triflate use in metathesis reactions
Why are triflates so widely used in coupling reactions, but not tosylates, mesylates nor nosylates?
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1
answer
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Why do Grignard reagents react with epoxides but not THF?
THF is used as a solvent for Grignard reagents, but epoxides react with Grignard reagents. There is only a small difference between epoxides and THF, what causes the difference in reactivity towards ...
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2
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Will ferrocene undergo electrophilic aromatic substitution?
Ferrocene has two structures (1 and 2). It is bonded to the aromatic cyclopentadienyl anion. Aromatic species such as benzene, cyclopentadienyl anion undergo electrophilic aromatic substitutions.
Then,...
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