Polymers with Tin in the Backbone

The (diaryl)stanna-[l]-ferrocenophanes are relatively more stable than the (di-/-butyl)tin analog. - The bis(triisopropylphenyl)tin-ferrocenophane is stable in the presence of both air and moisture, and does not undergo anionic or transition-metal catalyzed ROP. However, at elevated temperature it undergoes 

ROP at 180°C to an insoluble polymer . The (dimesityl)tin-[l]-ferrocenophane, on the other hand, produces a soluble polymer with Mw/Mn = 155 000/82 000. It also undergoes slow ROP in benzene, (50% conversion) and a high molecular weight fraction, Mw/M = 1 350 000/1 050 000 is formed along with cyclic dimers. 

Two new mechanisms in ROP of poly(ferrocenylstannanes) have been proposed in which both basic and acidic impurities seemed to play a role in ROP. A mechanism involving nucleophile-assisted ringopening in which traces of amines or other nucleophile impurities are involved, while another mechanism proceeds via traces of cationic species, such as H+ or Bu3Sn+.  

Only two reports have appeared on the formation and properties of linear unsaturated polycarbostannanes and this is a fruitful area for continued study. Such materials have been synthesized by acylic diene metathesis (ACDMET) of bis(4-pentenyl)dibutyltin either with Schrock s Mo-alkylidene, Mo(=CHMe2Ph)( A-2,6-C6H3 - i -Pr2)(OCMe(CF3 )2)2, or with the aryloxo-tungsten catalyst W(0)Cl2(0-2,6-C6H3-Br2)2, Equation 3.8.8).  

Given the wide commercial applications associated with polysiloxanes, it is surprising that related polystannasiloxanes, i.e. systematic substitution of R2Si by R2Sn groups, have not been extensively studied. Such polystannasiloxane chains have been obtained from the reaction of di-/-butyltin dichloride with [Ph2(0H)Si]20, as shown in Equation (3.8.9).  

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