Air-sensitive materials

Cobaltocene, [Co ()7 -C5H5)2], is a dark-purple air-sensitive material, prepared by the reactions of sodium cyclopentadiene and anhydrous C0CI2... 

D F Shriver The Manipulation of Air-Sensitive Materials, McGraw-Hill Book Co., New York, 1969... 

That the air-sensitive materials are handled in an inert atmosphere throughout. 

The red-brown polynuclear complex Ni4[(CH3)3CNC]7 can be recrystallized from diethyl ether in a Dry Ice-acetone bath to give a microcrystalline material which displays terminal and bridging isocyanide stretching frequencies at 2020 and 1605 cm"1, respectively. This highly air-sensitive material may be used as an intermediate in the preparation of nickel isocyanide complexes of unsaturated molecules simply by the addition of the desired molecules to a hexane or ether suspension. 

Caution All operations must be carried out in the absence of oxygen and moisture. All reaction vessels must be heated with a heat-gun, evacuated repeatedly to 5 x 10-3 mbar, and purged with argon prior to use. For all manipulations of the air-sensitive materials, the Schlenk technique is employed. 

Oxygen is readily soluble in organic solvents, and merely pouring such liquids in air serves to saturate them with oxygen. This should be kept in mind when determining the reactivity of air-sensitive materials in solution in organic solvents. Note that many organic substances such as ethers readily form peroxides or hydroperoxides in air. 

Air sensitive materials mnst be handled nsing a special sample transfer chamber. 

To make the reactive fulleride compound KeCeo in the Fe-Ceo synthesis, fullerenes and a slight excess of potassium were sealed in a glass tube under vacuum and heated for approximately four days at 250 °C. Both solid-state NMR and Raman spectroscopy were employed to determine that the KeCeo compound was in fact synthesized. The KeCeo product was then reacted in an inert atmosphere with cyclopentadienyl-iron-dicarbonyl-iodide (CpFe(CO)2l) in tetrahydrofuran (THF) to form the complex. The recovered product was dried in an inert atmosphere. Manipulations of air-sensitive materials were carried out in a glove box or using standard Schlenk techniques. THF was distilled just prior to use from sodium benzophenone ketyl. Ceo was obtained from Aldrich, and CpFeCCOjol was obtained from Strew. 

The reactivity of 8b deserves specific attention. When treated with 2equiv of methyl triflate (in CDCI3), the / -(methylseleno)alkyl phosphonium triflate was obtained as a highly air-sensitive material in 76% yield (Scheme 10) <2002JA9706>. It is reasonable to assume that methyl triflate undergoes an electrophilic attack on the negatively charged selenium center of 8b, and this is followed by dissociation of the polarized Se-P bond (see Section 1.15.3). 

Handling, Storage, and Precautions no specific information is available for CAMPHOS. In general, alkyldiarylphosphines are air-sensitive materials all operations, including handling and storage, should be carried out under an inert atmosphere. In addition, compounds of this type are irritants skin contact should be avoided, and vapors should not be inhaled. 

Reagents which are neither sensitive to the atmosphere nor toxic are normally stored in ordinary bottles on the shelf and they are usually easy to handle. However, if you are going to use this type of reagent for reactions with air sensitive materials, they must also be dry and be stored with the atmosphere excluded It is no use carefully setting up an anhydrous reaction, then adding a reagent straight from an unsealed bottle on the shelf. 

Generally argon is preferred when using this technique because it is more dense than air, and will fill the reaction flask, pushing out any air more effectively than would nitrogen. This technique can also be employed when syringing air-sensitive materials from bottles or containers. 

When a product has been isolated from a reaction the next step is to purify it. The degree of purity required will depend on the use for which the sample is intended, a synthetic intermediate might only require rough purification, whereas a product for elemental analysis would require rigorous purification. This section describes the most important purification techniques, crystallization, distillation, sublimation, and chromatography. It is assumed that the reader is familiar with the basic principles of these methods, so the emphasis is on more demanding applications such as the purification of air-sensitive materials, and purifications on a micro-scale. 

DRILAB. A Vacuum Atmospheres Corp. DRILAB containing dry argon gas was used for containment and manipulation of air-sensitive materials and vacuum-dried capillaries. Continuous monitoring of the oxygen conent of the DRILAB was accomplished with a glowing incandescent lamp filament. 

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