The present report is concerned with the development of some new highly active catalysts for the dimerization of ethylene or propylene. With this type of catalyst ethylene can be dimerized to butene and propylene can be dimerized either to 2-methylpentenes or to 2,3-dimethylbutenes: Fig. 1 (The positions of the double bonds of the products The following points will be discussed: are not shown.) The nature and the preparation of the catalyst Performance of the dimerization reaction and the reaction products Propylene dimerization in a pilot plant Possible technical uses of the dimeric Propylenes.
THE NATURE AND THE PREPARATION OF THE CATALYST The basic component of the dimerization catalyst is a x-allylnickel halide. x-Allynickel halides (chlorides, bromides, and iodides) are dimeric compounds with structures, determined by X-ray analysis, as shown in Fig. 2.
Fig. 2 by B. BOGDANOVIC and G. WILKE, Max-Planck-Instiîut fur Kohlenforschung, Germany. x-Allylnickel halides were first described by E. O.
Fischer and G. Bürger', who prepared them in low yields (6 to 10 percent) through the reaction of nickel tetracarbonyl with allylhalides. Catalytic properties have not been investigated.
Our investigations on x-allylic compounds of transition metals have their origin in the study of the reaction mechanism of the cyclododecatriene synthesis.
As it is known2 using nickel (O) as catalyst three molecules of butadiene can be combined to give high yields (about 90 percent) of trans, trans, trans-cyclododecatriene: Fig. 3 During these studies a definite compound3, which is in intermediate of the butadiene cyclotrimerization on nickel was isolated. For this compound we proposed the following structure (Fig. 4) consisting of a linear twelve-membered hydrocarbon chain combined with nickel by means of two Tc-ally1 groups and a transdouble bond.
Fig. 4 Since at that time no transition metal compounds of this type were known we tried to synthesize a model compound, bis(x-allyI)ni~kel[4]~, that is two x-ally1 groups combined with nickel without the rest of the hydrocarbon chain. The chemical properties of bis (x-ally1)-nickel should be analogous to those of the intermediate. Bis(x-ally1)-nickel could in fact be prepared as a yellow orange, crystalline, and volatile 351 352 Polymerization in Conjunction with Petroleum Raw Materials compound through the reaction of allylmagnesium bromide with anhydrous nickel bromide in ether. 4- 3 CHZ=CH-CHzMgBr + NiBr2 - Ni Fig. 5 Both the synthesis and the chemical properties of bis(%-ally1)nickel supplied a strong evidence in favour of the proposed structure for the intermediate.
In connection with the chemical properties of bis(%-ally1)nickel compounds the cleavage reaction with hydrogen halides s
