Titanium tetra-iodide

The polymerization of butadiene with an aluminum trialkyl-titanium tetra-iodide catalyst system apparently yields a polybutadiene containing more than 85% cis-1,4- structure (19). The limited amount of data available does not cover a sufficiently wide range of Al/Ti ratios to permit the drawing of conclusions analogous to those drawn in the case of the trans-l,4-polybutadienes. However, as shown in Table III, over the range of Al/Ti ratios from 1.5 to 5.0, the polybutadiene prepared in benzene at 30° C. contains 85 to 93% cis-1,4-, 3 to 11% tram-1,4-, and 3 to 5% 1,2- structures. 

High molecular weight polybutadiene homopolymers are prepared commercially with anionic catalysts and with coordination ones. Polybutadiene formed with sodium dispersions was prepared industrially in the former USSR, and perhaps might still be produced in that area today. This sodium-catalyzed polybutadiene contains 65% of 1,2-adducts [112]. Many of the preparations by others, however, utilize either alkyllithium or Ziegler-Natta type catalysts prepared with titanium tetra iodide or preferably containing cobalt. 

The crude titanium is held in position by a molybdenum grid around the wall of the reactor, and is maintained at a suitable temperature. 100 to 200°C is satisfactory in practice for the production of titanium tetra-iodide at the maximum rate. If higher wall temperatures are used, the rate of deposition on the filament decreases, approaching zero at 400°C, since the system then contains entirely titanium di-iodide instead of tetra-iodide, produced by the reaction... 

Polymerization with ir-Allyl Nickel Iodide/Titanium Tetra-... 

Thorium tetra-iodide is more stable than the iodides of titanium or zirconium and temperatures as high as possible are required for its dissociation into thorium metal and iodine. At intermediate temperatures of say 500-600°C, the tetra-iodide reacts with thorium metal to produce the tri-iodide. This, particularly on long heating. The feed material tends to become coated with this lower iodide if maintained at temperatures below 600°C and, because of its lower volatility than the tetra-iodide, the rate of decomposition on the filament is considerably reduced. 

Pentafluorocthyl iodide is of practical interest, particularly as a precursor of higher perfluoroal-kyl iodides. There are several patents for the preparation of the key compound from tetra-fluoroethene, iodine pentafluoride and iodine at 75-80 C in the presence of catalysts anti-mony(III) fluoride, titanium(lV) chloride, boron trifluoride, vanadium(V) fluoride, niobium(V) fluoride, and molybdenum(Vl) fluoride.11-13 The agents iodine monofluoride" and bromine monofluoride" can add to branched pcrfluoroalkcnes, e.g. perfluoro-2-methylbut-2-ene gives perfluoro-2-iodo-2-methylbutane.1415... 

---