Silicon transition-metal complex anions

The relief of ring-strain present in silicon-bridged ferrocenophanes can be utilized as the driving foree for its ring-opening polymerization (ROP). Manners and coworkers have shown that it is possible to induce the ROP of silicon-bridged ferrocenophanes by at least three different synthetic approaches [3,7,44-46], These are (a) thermal ROP (b) anionic ROP and (c) transition-metal-complex eatalyzed ROP. 

Although the loss of some anionic or other good leaving group is the usual consequence of such reactions at carbon centres, this is not the case when the electrophilic centre is an element such as silicon, sulfur, phosphorus or a transition metal with available d orbitals in the valence shell. In these cases, a simple addition reaction may occur to give a product of increased co-ordination number. This may involve simple reactions such as the addition of an anion to a neutral molecule or more complex processes (Fig. 4-3). 

Sfiica impregnated with saturated and unsaturated hydrocarbons (squalene, paraffin oil), silicone and plant oils, complexing agents (silver ions, boric add and borates, unsaturated and aromatic compounds), tigands (EDTA, digitonin), and transition metal salts silanized silica gel impregnated with anionic and cationic surfactants Cross-linked, polymeric dextran gels (Sephadex)... 

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