Ga(I) arene complex
[Ga(arene)x][Al(ORF)4] - a promising catalyst for the polymerisation of isobutylene
Catalysts used for the polymerisation have one significant advantage compared to their initiating congeners. As they favour a coordinative, less exothermic polymerisation mechanism, cooling of the reaction becomes increasingly obsolete.
In 2010 Slattery et al. were able to establish a simple route to univalent gallium salts of WCAs .[98, 99] The latter, not only being a promising starting material for further gallium(I)-chemistry, are excellent catalysts for the polymerisation of isobutylene. Thus using [Ga(C6H5F)2.5][Al(OC(CF3)3)4] (Figure 1) the synthesis of PIB can be carried out at relatively high reaction temperatures up to 0 °C, in a non carcinogenic and non water-hazardous solvent, i.e. toluene, as well as using relatively low concentrations of the initiating or catalyzing species, down to 0.007 mol%.
Figure 1 : Molecular structure of the [Ga(C6H5F)2]+ cation in [Ga(C6H5F)2.5][Al(OC(CF3)3)4].
The asymmetric unit of the crystal structure also contains a [Ga(C6H5F)3]+ cation.
The experimental results were backed by quantum-chemical calculations giving a first hint on a coordinative polymerisation mechanism (Link onto computer chemistry).