Redistributions Catalyzed by Transition Metal Complexes

Bamford et al. (5) found that I PtsCL, (L = alkene or phosphine) complexes were especially efficient catalysts for Eq. (12), giving gums with 

The mechanism of this polymerization has been discussed by Cundy et al. (9). The first step is apparently the insertion of a low-valent metal into the strained C—Si bond to give a silametallacyclopentane. Metallacycles 4 and 5 have in fact been isolated from the reactions of Fe2(CO)9 and CpMn(CO)3 with 1, respectively (10, 11). Complex 4 when treated with phosphines gives polymer and LFe(CO 4. If the metallacycle resulting from insertion (6) is unstable, repeated insertions (oxidative additions) and reductive eliminations lead to polymer. Chain termination results from reductive elimination of =SiH [Eq. (13)]. 

Silacyclobutanes with metal substituents may also be polymerized to give novel polymers with pendant metal groups [Eq. (14)] (12). The inter- 

In a similar way, the exceedingly strained silacyclopropenes undergo dimerization (13a) [Eq. (16)] upon catalysis by L2PdCl2 salts. 1,1-Di-methyl-2,3-bis(trimethylsilyl)-l-silacyclopropene undergoes a thermal 

No reactions of the type shown in Eq. (18) have been reported to be catalyzed by transition metal derivatives. Sufficiently vigorous conditions (or the proper catalyst) have not been investigated or the ring strain inher- 

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