Sciencemadness Discussion Board

Easily preparable organometallics and their properties.

BromicAcid - 13-10-2004 at 15:25

As to it's categorization, that might be a matter of debate ;)

Running though a book I picked up a few weeks ago on the subject of organometallic compounds I found an entry that sounded easily produceable.
Quote:
Electrolytic reduction of acetone with a lead cathode gives a red liquid, easily oxidized, from which di-isopropyl-lead dibromide was obtained on bromination. The liquid may have contained di-isopropyl lead (ref), (iso-C3H7)2Pb.


ref: J. Tafel, Ber., 1911, 44, 323; G. Renger, ibid., p. 377.

quoted from: G. E. Coates, Organo-Metallic Compounds., 1960; Butler & Tanner Ltd., p. 212

Organometallics have always been an interest of mine, but seemingly unavailable or at least outside the realm of easy study. However this book has several entries which seem somewhat simple to produce.

What defines easy to produce for me?

  1. Does not require the use of organo-mercuric compounds during production.
  2. Does not require the use of a Grignard reagent to produce.
  3. Is not so reactive as to make its properties difficult to study.
  4. Does not require elevated pressures or extraneous reaction times.
  5. Precursors must be reasonably available or obtainable.

Yes, there are some out there that meet these criteria. The alkali metals perform a variety of reactions with compounds to give organometallics but their availability is limited. Examples: Sodium will react with naphthalene in a donor solvent, e.g., THF or ether to produce sodium naphtalide and hydrogen gas, the sodium compound is brightly colored. A sodium potassium alloy will readily cleave ethers and produce the corresponding alkoxide and alkyl derivative, if a large excess of solvent is used, the reaction between an alkali metal and an organohalide can be used to produce the corresponding organometallic compound, but it competes with the Wittig reaction.

The alkali earths for a variety of organometallic compounds, but nearly every metallic element forms some number of compounds with a bond direct to carbon. I am going to reread this book specifically looking for those easily prepared organometallics and will be sure to post back here.

Any additional entries are highly welcomed.

(Thread inspired by the question on methyl aluminum chloride compounds which are also somewhat easy to prepare.)

sounds fun...

halogen - 16-10-2004 at 06:34

say, would organo-lanthanide componds be easy to produce, seeing as lanthanides are found in lighter flints, and the reaction with HCl, than taking the lanthanide chlorides and react with NaR?
Sounds nice.

BromicAcid - 17-10-2004 at 11:41

But to make NaR halogen, that can be a pain.

Today I tried di-isopropyl lead. I took a beaker containing about 200 ml acetone and added about .05 g LiCl and .1 g PbCl2 to the solution to attempt to make it more conductive to electricity. Into the solution was inserted a large flat lead electrode, with my thinking being, maximize the surface area and maximize electron flow. The anode was a graphite rod to minimize any side reactions that may have occured.

I ended up wrapping the lead electrode into the circle and putting the graphite rod into the center suspended so it didn't touch the side. I set my power source (battery charger) to 12 V 10 A and left it alone for a while (the indicator on the charger showing the number of amps going through the solution stayed at zero, so maybe 100 mA tops). A short time later the anode had a white 'smoke' coming off it under the acetone, satisfied that something was happening I left the solution for three hours longer.

When I came back the anode was covered in a powdery off-white precipitate. No color had developed in the solution that would have lead me to believe that the organometiallic compound had developed.

Hoping for the best I removed that anode and tapped it on a watch glass, the precipitate fell off and I waited for it to dry. It dried in small needles and did nothing more, it was slightly more yellow. Thinking that if this was an orgnometallic lead compound it should be flammable I lead a flame to it, nothing, it just dried it more completely. Maybe an impurity in my electrode.

If I access the original claim it may help, maybe acetone was not the solvent, just something solvated in a larger reaction, maybe I needed a lead anode too, who knows.

[Edited on 10/17/2004 by BromicAcid]

BromicAcid - 28-10-2004 at 07:12

Went to the library today to look up some more details on the electrolysis I tried with the lead cathode. Turns out the electrolysis was origionally preformed with 20% H2SO4 with acetone added. No clue on the ratios. Additionally all organic lead +2 compounds are highly unstable, very few, if any ever isolated. Might try it again anyway just to get some nice colors.

Organic tin and germanium compounds are more stable. Electrolysis of an alkaline solution of acetonitrile with tin electrodes yeilds a complex organic compound. Might give that a shot too.

BromicAcid - 8-4-2006 at 19:32

I've been meaning to write this post for a long time but it has been delayed repeatedly and to be honest I still don't feel that I have anywhere near the information to write it. Nevertheless here goes.

Sometime back in November I was contacted in a U2U from Polverone regarding the aforementioned orgnometallic lead compound.
Quote:
.... So I added a dash of sulfuric acid to a mixture of approx. 2 parts acetone and 1 part water and applied current from a small battery charger through two electrodes made of thick lead wire (fishing weight stuff).

The anode turned a matte black, while the cathode took on a brightly polished appearance. Droplets of dark liquid clung to its surface and eventually dripped off to the bottom of the jar. I am confident these are (or at least contain) an organometallic lead compound.

He goes onto describe some of the properties of this compound in details greater then any that I have found for this compound of lead.
Quote:
Interesting things: the drops seem slightly soluble in isopropanol (they'll at least tinge it orange), but not in water or in my aqueous acid/acetone.

....they react with sodium sulfide solution to give a dark brown precipitate.

It's my working theory that some of the material at least undergoes hydrolysis fairly readily, which would explain the material's disappearance and the white cloudiness (probably just lead sulfate).

MEK also forms colored products when used in place of acetone. Because of lower solubility, I have a layer of MEK floating on top of acid/water/MEK. All the colored products formed dissolved into this layer. Just a few minutes after turning the cell off, though, the top layer is almost completely colorless again.

The oil is red-brown to yellow in thin layers or when diluted, it just looks black in larger droplets. I don't think the coloration is due to any colloid because it goes almost completely colorless when exposed to air for a while, and I'd expect a colloid to remain colored.


These communications took place from 11/20 - 12/17 of last year. They served to get me experimenting with these compounds and I noticed some other interesting things. The red/yellow liquid does in fact decompose from contact with air and thus also from the bubbles coming up from the other electrode. But, if the two are separated via a glass barrier (just so the bubbles do not come into contact with each other) the rate of production of the liquid decreases despite the current being consumed remaining constant.

I never attained large amounts of the oil, after running the cell for some time I could pull up the cathode and the red liquid was in a sheet across the surface but it quickly decomposed. The problem is that this compound is the one that is produced as a side reaction and the main product (the tetraisopropyl lead) is colorless. As such after the electrolysis is discontinued and the mixture allowed to sit in the air a precipitate forms and the mixture becomes cloudy from the subsequent hydrolysis/oxidation of the lead in the solution and its reaction with the sulfuric present to form lead sulfate (Polverone also noted this).



The picture above shows a beaker with the reaction mixture in it after it was allowed to site for some time after an electrolysis run. When the electrolysis was freshly completed the mixture was slightly yellow but there was no suspended matter, now look at it. Although the red compound attracts the most attention because of its coloration the colorless compound is present in higher amounts. I have experimented with extracting the acetone/water/H<sub>2</sub>SO<sub>4</sub> solution with xylene (and running it under xylene) and it does infact suck up organic materials that decompose fairly quickly within it.

These organolead compounds are very interesting for other reasons too and have several practical applications. One interesting use is that the tetraalkyl compounds when mixed with the halogens substitute two of their alkyl groups with halides and the alkyl groups pop off as alkyl halides, an interesting preparation.

There are many other simple organometallic electrolysis experiments though, many of them using radicals as the intermediate, many metals are subject to attack from organic radicals and therefore it might prove fruitful to perform a Kolbe type reaction with a electrode susceptible to reaction.

To point people onto their own path check out this little article from the 1950's regarding the preparation and use of organometallic compounds.

http://sciencemadness.destructve.com/cr60171a004.pdf

Sergei_Eisenstein - 9-4-2006 at 00:40

For those interested in organometallics, it should be pointed out there is a very good book available:

http://www.organische-chemie.ch/index3.htm?http://www.organi...

It contains many recipes and even more references. The newest edition is from 2004 and can probably be found in most university libraries.

IrC - 4-3-2015 at 21:58

Quote: Originally posted by BromicAcid  


To point people onto their own path check out this little article from the 1950's regarding the preparation and use of organometallic compounds.

http://sciencemadness.destructve.com/cr60171a004.pdf


I have seen this same link listed in another thread in 08. The link is invalid, does anyone have a working location for the article?

Chemosynthesis - 5-3-2015 at 07:44

Quote: Originally posted by BromicAcid  

  • Does not require the use of a Grignard reagent to produce.

    • Does this also rule out lithium dialkyl cuprates due to chemical similarity?

    Steam - 5-3-2015 at 09:15

    I have made Copper (II) aspirinate before by dissolving acetylsalicylate in water a solution of sodium bicarbonate to produce the salt of ASA. The bicarbonate is necessary because any excess OH ions will hydrolyze the product. Next I simply added the solution of the copper salt (I used Copper (II) Sulfate but any copper 2 salt will suffice) to the dissolved ASA. The Insoluble Cu (II) AS then precipitated. I think it is used to (Ineffectively) treat arthritis. If anything it is a pretty blue color.

    DJF90 - 5-3-2015 at 09:32

    Thats not an organometallic compound, but rather a complex between a ligand and a metal.