Cobalt discovery

Cobalt exists in the +2 or +3 valence states for the majority of its compounds and complexes. A multitude of complexes of the cobalt(III) ion [22541-63-5] exist, but few stable simple salts are known (2). Werner s discovery and detailed studies of the cobalt(III) ammine complexes contributed gready to modem coordination chemistry and understanding of ligand exchange (3). Octahedral stereochemistries are the most common for the cobalt(II) ion [22541-53-3] as well as for cobalt(III). Cobalt(II) forms numerous simple compounds and complexes, most of which are octahedral or tetrahedral in nature cobalt(II) forms more tetrahedral complexes than other transition-metal ions. Because of the small stabiUty difference between octahedral and tetrahedral complexes of cobalt(II), both can be found in equiUbrium for a number of complexes. Typically, octahedral cobalt(II) salts and complexes are pink to brownish red most of the tetrahedral Co(II) species are blue (see Coordination compounds). 

Early efforts to prepare metal soaps involved attempts to dissolve the natural materials in oils. By the latter part of the nineteenth century, substantial progress had been made in the preparation of fused resinates and linoleates of lead and manganese. The utiUty of cobalt as a drying catalyst was discovered close to the turn of the century, but the factors that led to its ultimate discovery are not recorded. 

Co balticyanide discovery, 1,3 Cobaltitungstates, 3,1042 Cobalt(II) salts catalysts... 

In the late 1950 s two groups - one at ICI (ref. 1) and the other at the Mid-Century Corporation (ref. 2) - independently discovered that p-xylene is oxidized to terephthalic acid in almost quantitative yield when soluble bromides are used together with cobalt and manganese catalysts in acetic acid solvent at temperatures > 130 °C (ref. 3). This discovery formed the basis for what became known as the Mid-Century process and later, when the Mid-Century Corporation was acquired by Amoco, as the Amoco MC process for the commercial production of terephthalic acid. A large part of the ca. 6 million tons of the latter that are manufactured annually, on a worldwide basis, are produced via this method. This makes it the most important catalytic oxidation process (ref. 4). 

M Since the discovery of the magnetic properties of the cobalt alloy, samarium has been the "superstar" of the lanthanides. Music fans have their ears covered with samarium in the form of modem earphones... 

Lenhert and Hodgkin (15) revealed with X-ray diffraction techniques that 5 -deoxyadenosylcobalamin (Bi2-coenzyme) contained a cobalt-carbon o-bond (Fig. 3). The discovery of this stable Co—C-tr-bond interested coordination chemists, and the search for methods of synthesizing coen-zyme-Bi2 together with analogous alkyl-cobalt corrinoids from Vitamin B12 was started. In short order the partial chemical synthesis of 5 -de-oxyadenosylcobalamin was worked out in Smith s laboratory (22), and the chemical synthesis of methylcobalamin provided a second B 12-coenzyme which was found to be active in methyl-transfer enzymes (23). A general reaction for the synthesis of alkylcorrinoids is shown in Fig. 4. 

Just a few years after the discovery of the deposition and electroactivity of Prussian blue, other metal hexacyanoferrates were deposited on various electrode surfaces. However, except for ruthenium and osmium, the electroplating of the metal or its anodizing was required for the deposition of nickel [14], copper [15,16], and silver [9] hexacyanoferrates. Later studies have shown the possibilities of the synthesis of nickel, cobalt, indium hexacyanoferrates similar to the deposition of Prussian blue [17-19], as well as palladium [20-22], zinc [23, 24], lanthanum [25-27], vanadium [28], silver [29], and thallium [30] hexacyanoferrates. 

Electrocatalysis in oxidation has apparently first been shown for ascorbic acid oxidation by Prussian blue [60] and later by nickel hexacyanoferrate [61]. More valuable for analytical applications was the discovery in the early 1990s of the oxidation of sulfite [62] and thiosulfate [18, 63] at nickel [62, 63] and also ferric, indium, and cobalt [18] hexacyanoferrates. More recently electrocatalytic activity in thiosulfate oxidation was shown also for zinc [23] hexacyanoferrate. Prussian blue-modified electrodes allowed sulfite determination in wine products [64], which is important for the wine industry. 

Meanwhile, Wacker Chemie developed the palladium-copper-catalyzed oxidative hydration of ethylene to acetaldehyde. In 1965 BASF described a high-pressure process for the carbonylation of methanol to acetic acid using an iodide-promoted cobalt catalyst (/, 2), and then in 1968, Paulik and Roth of Monsanto Company announced the discovery of a low-pressure carbonylation of methanol using an iodide-promoted rhodium or iridium catalyst (J). In 1970 Monsanto started up a large plant based on the rhodium catalyst. 

The mechanistic and synthetic puzzle of alkyne hydrosilylation opened more fully with the discovery that rhodium will catalyze the /r.mr-hydrosilylation of terminal alkynes.22 There is much work extant in this area, and good summaries of the various catalytic systems exist.11 A trans-addition process to give (Z)-j3-silane products G is well precedented with trialkylsilanes (Table 3), for both rhodium and mixed rhodium-cobalt complexes (entry 4).22,26 However, the selectivity erodes significantly upon switching to Me2PhSiH (entry 5), and, due to the mechanistic requirements for equilibration of the /3-silyl vinylrhodium intermediate, electron-poor silanes react exclusively to give CE)-/3-silane products B (see entries 6 and 7). 

Meanwhile attempts to find an air oxidation route directly from p-xylene to terephthalic acid (TA) continued to founder on the relatively high resistance to oxidation of the /Moluic acid which was first formed. This hurdle was overcome by the discovery of bromide-controlled air oxidation in 1955 by the Mid-Century Corporation [42, 43] and ICI, with the same patent application date. The Mid-Century process was bought and developed by Standard Oil of Indiana (Amoco), with some input from ICI. The process adopted used acetic acid as solvent, oxygen as oxidant, a temperature of about 200 °C, and a combination of cobalt, manganese and bromide ions as catalyst. Amoco also incorporated a purification of the TA by recrystallisation, with simultaneous catalytic hydrogenation of impurities, from water at about 250 °C [44], This process allowed development of a route to polyester from purified terephthalic acid (PTA) by direct esterification, which has since become more widely used than the process using DMT. 

In 1975 Kuntz has described that the complexes formed from various rhodium-containing precursors and the sulfonated phosphines, TPPDS (2) or TPPTS (3) were active catalysts of hydroformylafion of propene and 1-hexene [15,33] in aqueous/organic biphasic systems with virtually complete retention of rhodium in the aqueous phase. The development of this fundamental discovery into a large scale industrial operation, known these days as the Ruhrchemie-Rhone Poulenc (RCH-RP) process for hydroformylation of propene, demanded intensive research efforts [21,28]. Tire final result of these is characterized by the data in Table 4.2 in comparison with cobalt- or rhodium-catalyzed processes taking place in homogeneous organic phases. 

It should be noted that the catalytic version of the PK reaction was envisioned from the time of discovery, yet it was not until 1990 that the first example was reported using cobalt [10]. Since that report other variations of catalytic PK reactions employing cobalt, as well as titanium [11] and ruthenium [12], complexes have been reported. In addition to these examples, rhodium has been shown to catalyze the PK reaction, in which it was clear from the outset that this metal had a number of unique features [13]. A proposed mechanism for the generahzed PK-type reaction is illustrated in Scheme 11.3. 

On the other hand, Paracelsus did make some legitimate chemical discoveries, including a method for obtaining metallic arsenic from arsenic sulfide, and he might have been the first to describe the properties of two other metals, bismuth and cobalt. Although he was unable to break these substances down further, he failed to recognize that they were elements. He couldn t have, not without repudiating the alchemical theories that were common in his day. 

There is some uncertainty about this. The discovery of cobalt is normally dated much later, in 1735. 

After the discovery of phosphorus, 66 years passed before another new element, cobalt, was discovered. Cobalt compounds were known since ancient times and had been used to color glass since the sixteenth century. They were collectively known under the name kobold. Miners believed that the presence of these substances in mines was the work of malicious gnomes called kobolds, who wanted to poison the miners. 

Sympathetic Ink. Although die discovery of the cobalt sympathetic ink, which remains invisible until wanned, has often been attributed to Jean Hellot, who first made it known publicly, he was not the first person to prepare it. Hellot himself stated that a German artist of Stol-berg had shown him a reddish salt which, when exposed to heat, became blue. It had been prepared by dissolving Schneeberg cobalt in aqua regia (119). H. F. Teichmeyer of Jena was also familiar with this cobalt ink, perhaps even before Hellot made its composition public in 1737... 

Cobalt in Meteorites. The Quarterly Journal of Science and the Arts for 1819 has a note on the discovery of cobalt in meteorites M. Stro-... 

Many chemists in Sweden and in other parts of the world immediately accepted Cronstedt s claim to the discovery of a new element, but B.-G. Sage (22) and A.-G. Monnet in France believed that his nickel was merely a mixture of cobalt, arsenic, iron, and copper (7). As a matter of fact, it was somewhat contaminated with iron, cobalt, and arsenic, and there-... 

Combinatorial chemistry and solid-phase synthesis have evolved in the last decade to become one of the most important techniques to save time for drug discovery. To reach its full potential, the solid-phase synthesis has to incorporate many versatile organometallic reactions developed over recent several decades. The first example of the Nicholas reaction on solid phase was reported by Kann and his co-workers in 2002, which involves the reaction of polymer-bound cobalt complexes 51 with various carbon-centered nucleophiles in the presence of a Lewis acid to... 

The importance of the theory was further demonstrated by the discovery of the existence of optically active inorganic compounds, and the isolation of the exact number of optical isomers theoretically possible for the spatial arrangement of the atoms.1 Friend 2 and others criticised the theory on the grounds that in simple compounds, such as sodium chloride or cobaltous chloride, the chlorine is ionised and yet is attached to sodium or cobalt atom directly, whereas in the ammino-coinpounds the acid capable of ionisation is that which is not directly attached to metal. For instance, in chloro-pentammino-cobaltic chloride, [CoCI(NH3)5]C12, it is the chlorine outside the first zone which is ionised in solution. Also, the dissociable acidic groups are not attached to any point within the complex, but simply hover round the central complex in an indefinite manner. Thus a definite valency for ionisable... 

Regarding the cobalt-catalyzed reactions, the electrochemical analyses of the involved processes allowed the discovery of a chemical way for the synthesis of these organozinc compounds. This chemical way will be evoked in this chapter. 

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