07/12/2012 - Organolithium Ether Cleavage

There comes a point in a compound's life when there is a question of whether there is an easier way to make it, and in 1930 Karl Ziegler questioned this with organolithium compounds.  Not only did he find more simpler ways of preparing such organolithium compounds but he developed many applications for the use of the light metal.  The largest application of these compounds is in organic chemistry as organolithium reagents, used in creating those precious carbon-carbon bonds. But one of the first applications that Ziegler developed was the ability of Lithium to cleave an ether bond, demonstrated in the following reaction:

PhCH₂OMe + 2Li → PhCH₂Li + MeOLi

7/11/2012 - Generation of Alkyl Radicals

The next year in 1929 one of the pioneers of radio chemistry, Friedrich Adolf Paneth, an Austrian scientist who did the majority of his early work at Königsberg University, completed a journey set out by Sir Edward Frankland.  This discovery gained humanity the ability to create alkyl radicals, and the identification of such radicals through their ability to displace a metallic mirror (silver mirror etc.).  This was performed through the pyrolysis (thermal decomposition) of a lead organometallic with the general formula of PbR_4.

7/9/2012 - Synthesis of Tetraethyllead Pt. II

In the year of 1922 two chemists working with General Motors Corportation Thomas Midgley and T.A. Boyd discovered an additive to gasoline that would prevent engine knocking, meaning uncontrollable combustion.  This additive was Tetraethyllead, an organometallic discovered back in Germany in 1854 but not utilized until this point.  This great discovery 'lead' to the creation of new gasoline solutions which have since phased out due to the high toxicity of lead in the exhaust fumes.  The synthesis of Pb(C₂H₅)₄ is performed through the following reaction of a sodium lead alloy with chloroethane:

4NaPb + 4CH₃CH₂Cl → (CH₃CH₂)₄Pb + 4NaCl + 3Pb

Source: 

3/26/2012 - Synthesis of Arsphenamine

     At this point in time, in 1909, medicine was very limited on what cured versus what merely treating a disease, and there were many breakthroughs in this field all of the time.  A year prior to this date a man named Paul Ehrlich invented the chemotherapy method in fighting cancer through using toxic compounds.  With his knowledge of toxic material he was experimenting on what other diseases could be helped through this method and he synthesized a molecule called Arsphenamine, or also known as Salvarsan, used to treat syphilis.  It was found through synthesizing hundreds of organic arsenical compounds and testing each one.  This was also the first organic antisyphilic, meaning that before this compound was produced, syphilis was only treated with inorganic compounds such as Mercury.

3/20/2012 - Synthesis of Iodotrimethyl Platinum (IV)

     An english chemist of the name William J. Pope worked in researching stereochemistry, but one of his major achievements, in 1909, came with the synthesis of IodoTrimethyl Platinum, or (CH₃)₃PtI. This synthesis was carried out through the mixing of Potassium chloroplatinate, K₂PtCl₆, along with a Grignard methyl complex, CH₃MgI. This compound holding it's historical significance through the fact that it became the first σ-organotransition-metal compound meaning that the organic group is connected through a sigma bond to the transition metal.

3/18/2012 - Synthesis of Diphenylsilicone

     At the turn of the century in 1901, there is a chemist named L. Kipping working strongly with different silicone chemistry.  This year he synthesizes a molecule he calls to be diphenylsilicone despite stating of a much higher molecularity.

3/13/2012 - Synthesis of Nickel tetracarbonyl

    About a decade after Mendeleev made his predictions of Eka-Si(C₂H₅)₄, in 1890, a scientist by the name of Ludwig Mond became the first to synthesize Nickel tetracarbonyl, Ni(CO)₄.  This was performed by passing carbon monoxide over Nickel metal to make a light yellow liquid.  This technology was then harnessed to refine nickel when Mond founded the company Imperial Chemical Industries.

Nickel Tetracarbonyl

3/1/2012 - Synthesis of the First Metal Carbonyl Complex

     In 1868 a French man by Marcel-Paul Schützenberger (a mathematician who also studied medicine) began a new form of organic complexes by creating the first metal carbonyl complex.  These complexes gain importance through the catalytic reactions of Carbon monoxide, which is a piece in the creation of many molecules of biological importance.  The bonding of the CO with the metal is also of some relevance due to the unique character (not shown in the picture below) where the orbitals of the metal bond with the pi-orbitals of the C≡O.  The complex, Dicarbonyldichloroplatinum [Pt(CO)₂Cl₂] was formed through him passing carbon monoxide and chlorine over powdered Platinum (also known as Platinum black).

2/29/2012 - Synthesis of Diethylmagnesium

     Up to the point in 1866 there had been no way of synthesizing a magnesium organometallic compound without having attached a halide to the complex.  James Alfred Wanklyn (famous for methods of determining water quality) came up with a method of synthesis to exclude any presence of a halide anywhere in the synthesis.  This involved the use of Frankland's development of diethylmercury  and mixing it in dissolved magnesium yielding a mixture of diethylmagnesium and dissolved mercury.

(C₂H₅)₂Hg + Mg → (C₂H₅)₂Mg + Hg

2/28/2012 - Synthesis of Organochlorosilanes

   Again following the history of organometallics, a very important duo comes into the scene Charles Friedel, and James Mason Crafts (the brains behind the technology of Friedel-Crafts reactions) and harnessed their chemistry to the production of organochlorosilanes.  These molecules create the very important bond between a Carbon and a Silicon atom in many different mole ratios (up to 4 different Carbon-Silicon bonds around the silicon center).  The way this reaction is performed is through the addition between a silicon tetrachloride and a alkylzinc compound to produce the organochlorosilane and a zinc chloride salt.

SiCl₄ + (k/2)ZnR₂ →   R_kSiCl_4-k + (k/2)ZnCl₂

2/18/2012 - Synthesis of Dimethylmercury

    In the following years Edward Frankland continued researching organometallic compounds as he realized how much new chemistry can be harnessed from these studies.  In 1852 he branched into Mercury chemistry and then following into Tin and Boron reactions.  With these reactions he focused on simple methyl additions onto the metal creating a linear dimethylmercury through the reaction 2CH₃X + 2Na + Hg → (CH₃)₂Hg + 2NaX.  This dimethylmercury compound is extremely toxic, to the degree that one drop on a latex glove will absorb through and  absorbs into the skin and months later the fatality takes over.  And as stated before he transcended these alkylhalide reactions into adding different R groups onto Hg, Sn, and B.

2/17/2012 - Preparation of Ethyl Radical

    Bunsen took on students at Marburg, and one of those students was Edward Frankland  and he set out to synthesis an ethyl radical from the combination of 3C₂H₅I and 3Zn, thinking that would create ZnI₂ and 2C₂H₅, but instead revealed that the products were a pyrophoric liquid of (C₂H₅)₂Zn (diethylzinc), ZnI₂, and a solid of C₂H₅ZnI.  He also harnessed this technology to make the methyl analogue to synthesize dimethylzinc as well.  I do realize that I have already done a post regarding the synthesis of diethylzinc, but this here was the historical method of the first sythensis, different from todays methods.  Sorry again for my absences, I have been under a significant amount of pain.

2/11/2012 - Studies of Alkarsine Derivatives

   Then in 1840 Robert Bunsen continued the studies of the arsenic compounds synthesised in Paris a century earlier (cacodyl compounds).  He used these compounds to synthesize a numbed of derivatives of R₂As-AsR₂ into molecules (CH₃)₂AsCN.  After the synthesis Bunsen supposedly tasted this dangerous concoction, and luckily he lived to tell the tale.

 


Photo source

2/10/2012 - Synthesis of Zeise's Salt

     The next advancement in organometallic chemistry didn't happen until 1827 by a Danish chemist by the name William Christopher Zeise in Copenhagen.  When this compound was first synthesized, chemists were baffled on what the molecular structure of this grand molecule was. It wasn't until recently that it was determined to be a square planar complex where the ethylene molecule coordinated to the Platinum in a η² fashion (meaning that it was the bond of the ethylene that was bonding).  The synthesis happened when Zeise was PtCl₄ being boiled in ethanol to create the final salt of K[PtCl₃(η²-C₂H₂)]-H₂O.

2/9/2012 - Cacidyl oxide synthesis

     As an apology for my absence my next couple of reactions will follow along the chronological order for the history of organometallic chemistry.  The first ever synthesis of an organometallic occured in Paris, in 1760, at a military pharmacy, where there was a cadet who was working in creating synthetic inks containing cobalt salts, and in extracting the cobalt from the raw form arsenic was removed.  In this removal the As₂O₂ is combined with CH3COOK to produce a fuming liquid containing the organometallic product of [(CH₃)₂As]₂O (also known as Cacidyl oxide)

2/2/2012 - Stille Reaction

   This organometallic catalyzed reaction causes the creation of a carbon carbon bond between an organotin compound (R¹SnBu₃) and an sp² hybridized organohalide (R²-X). The reaction can be thought of as in a reaction cycle to better visualize the reactions going on here. The catalyzing material here is the Paladium complex with a number of variable ligands surrounding it. This reaction was discovered by the chemist John Kenneth Stille in 1977 and is continued to be used in many organic synthesis processes used for molecules of biomedical significance.

1/26/2012 - Synthesis of Imines from Alcohols Catalyzed by a Ruthenium Complex

     This reaction involves turning a primary alcohol into an imine product with the alleviation of hydrogen gas, catalyzed in the presence of a Ruthenium N-Heterocyclic Carbene complex in the presence of DABCO (which acts as a ligand).  The mechanism is quite complicated but it incolves the exchange of Cl's for H's onto the Ruthenium, and then the addition of the alcohol, followed by the loss of H2, and then the addition of the amine, and then the alleviation of the final imine product.  This reaction was researched by Agnese Maggi and Robert Madsen out of the Department of Chemistry at the Technical University of Denmark.

Picture: from source.

Source: Organometallics 2012, 31, 451−455

1/25/2012 - Activation and Functionalization of a Linear Alkane through Tungsten Complex

    Here is another reaction involving the activation of a carbon hydrogen bond where after the activation the alkane can be functionalized through the addition of iodine into the system under liquid nitrogen.  The study was performed out of my home department of chemistry at the University of British Columbia done by Peter Legzdins, Jenkins Y.K. Tsang, and Miriam S.A. Buschhaus in 2007.  The tungsten complex was particularly a tungsten allyl nitrosyl complex, which allows the linear ƞ3 alkane to be attacked by the I2 in creating the selective alkyl halide at the terminal position (1-iodopentane here specifically).

Image: From source
Source: J. AM. CHEM. SOC. 2007, 129, 5372-5373

1/24/2012 - Oxidative Addition of the Carbon-Hydrogen Bonds of Neopentane to a Iridium(I) Complex

   In this organometallic reaction we are presented with a carbon hydrogen bond activation where the bond is cleaved.  These reactions are very important in modern chemistry as it is able to turn very cheap organic molecules into functionally expensive organic molecules.  In this reaction in particular, developed in 1982 by J.K Hoyano and W.A.G Graham out of the University of Alberta, it harnesses photochemical energy to cause an Iridium (I) organometallic complex to take up the neopentane molecule and to strip a hydrogen from the alkane.  The resulting complex contains the same number of metal carbon bonds, as there is a CO group leaving during the reaction, but there is a new Metal hydrogen bond created as the activation.

Image: Taken from source below
Source: J.K Hoyano, W.A.G Graham. J. Am. Chem. SOC. 1982, 104, 3123-3125

1/23/2012 - Biological Organometllics: Zinc protoporphyrin

   When asking someone of an example of an organometallic molecule within a human, one would usually answer with Hemoglobin, but there also exsists another within the red blood cells.  Zinc protoporphyrin is produced by the red blood cells under the conditions of lead inhibition of hemoglobin, or merely the lack of iron to produce the hemoglobin.  Because of this the presence of this molecule can act as a diagnostic tool to identify lead poisoning and a numerous number of ailments involving the red blood cells.  And when looking at the chemical structure below, it can be observed that with a simple replacement of an Iron, it can act as an oxygen carrier as there is a heme group in it.