Metallocenes oxygen sensitivity

PMS required UV curing for 1.5 h prior to pyrolysis in order to retain the fiber shape. Additionally, the use of metallocene catalysts renders PMS highly oxygen-sensitive and pyrophoric. 

The chemical reactivity of metallocenes varies widely with the metal and the substituents on the rings a general discussion of such properties is outside the scope of this review. The particular case of air (oxygen) sensitivity, however, can be analyzed with reference to the metal electron... 

The main starting materials used in this area of chemistry are Cp2TiCl2 and Cp2ZrCl2, both of which are commercially available and may be handled in air. All the other metallocene complexes described are moisture and, in most cases, oxygen sensitive, and therefore all reactions must be carried out under anhydrous and oxygen-free conditions. Hydroxyl groups are not tolerated in... 

A major limitation of such Group IVB metallocene catalysts is that they are air- and moisture-sensitive and not tolerant to heteroatom-containing monomers. In the case of heteroatom-containing monomers the unbonded electron pairs on the heteroatom, such as oxygen, preferentially coordinate to the Lewis acid metal center in place of the carbon-carbon double bond. Some so-called middle and late transition metal organometallics are more tolerant to the presence of such heteroatoms and can be used as effective cocatalysts. These include some palladium, iron, cobalt, and nickel initiators. 

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