Questions tagged [organometallic-compounds]

For questions relating to organic compounds which contain a bond between a carbon atom and a metal.

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38
votes
1answer
953 views

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 ...
21
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4answers
6k views

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 ...
19
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1answer
1k views

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 ...
18
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1answer
598 views

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 ...
17
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1answer
410 views

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 ...
16
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3answers
18k views

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 ...
15
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1answer
4k views

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 + ...
15
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1answer
1k views

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-...
14
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1answer
856 views

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 ...
14
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2answers
147 views

Mechanism of a Gold catalyzed organometallic reaction: Confusion regarding the last step

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 $...
13
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2answers
733 views

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 ...
13
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2answers
541 views

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 (...
12
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1answer
484 views

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 ...
12
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0answers
107 views

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 ...
11
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3answers
206 views

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 ...
11
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1answer
253 views

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 ...
10
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1answer
124 views

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 ...
10
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1answer
930 views

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 ...
8
votes
2answers
959 views

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 ...
8
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1answer
128 views

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 ...
8
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1answer
192 views

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 ...
8
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1answer
1k views

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.
7
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1answer
6k views

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 $...
7
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1answer
9k views

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 ...
7
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2answers
539 views

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 ...
7
votes
1answer
685 views

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 ...
7
votes
1answer
2k views

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: ...
7
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0answers
68 views

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 $\alpha,\beta$-...
7
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0answers
918 views

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 ...
6
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1answer
2k views

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?
6
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1answer
175 views

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. ...
6
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1answer
642 views

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
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1answer
681 views

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 ...
6
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1answer
2k views

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 ...
6
votes
1answer
388 views

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 ...
6
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0answers
428 views

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 ...
6
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0answers
302 views

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 ...
5
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2answers
5k views

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 ...
5
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1answer
545 views

Why are 3 equivalents of organolithium needed in synthesis of ketone from carboxylic acid?

For the reaction of a carboxylic acid and organolithium reagents to synthesise a ketone, Clayden's, on p 219, mentions: Notice that three equivalents of organolithium are needed in this reaction: ...
5
votes
1answer
263 views

Reaction of CpFe(CO)2Cl with phenyllithium

The reaction of $\ce{(C5H5)Fe(CO)2Cl}$ with an equimolar amount of $\ce{Li+[C6H5]-}$ gives a product. Draw its structure and apply the 18 electron rule. In a question I was given the molecular weight ...
5
votes
1answer
5k views

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 $...
5
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0answers
160 views

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-...
5
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0answers
147 views

Regioselectivity in Ziegler–Natta polymerisation of α-olefins

Why does the Ziegler–Natta polymerization display the regioselectivity shown in the image? Internal nucleophiles (coordinated to the metal) should attack the alkene on the less substituted end, like ...
4
votes
2answers
436 views

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 ...
4
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2answers
40 views

Best reagents state for air free chemistry. Choosing halide for grignard synthesis

I am planning to synthesize a grignard and I have a choice between the iodo or chloro aryl halide. The iodo is a solid and the chloro is borderline. For my previous reaction I melted the chloro and ...
4
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1answer
2k views

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 ...
4
votes
1answer
204 views

Triflate use in metathesis reactions

Why are triflates so widely used in coupling reactions, but not tosylates, mesylates nor nosylates?
4
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1answer
2k views

Grignard Reagent in THF vs in Diethyl ether

While learning about the Grignard reagent I was taught this by my teacher, but I couldn’t justify why it was so.. I cannot see how Grignard reagent would react differently in basically an ethereal ...
4
votes
1answer
54 views

Is it possible to have a ferrocenol?

I'm specifically talking about having a hydroxy- group on the ferrocene ring. Is it simply impossible because the ring is anionic? I haven't seen any hydroxyferrocene molecules available online. (...
4
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2answers
2k views

Removing unreacted Mg metal in a Grignard reaction

A Grignard reagant was prepared from an alkyl halide and magnesium chips, then reacted with a ketone. The resulting solution has been stirring for a few days at low temperature (0-5°C). It's now time ...