Oligomerization of styrenes mediated by cationic allyl nickel complexes containing triphenylstibine or triphenylarsine (original) (raw)

The cationic complexes [Ni(h 3 -CH 2 C(R)CH 2 )(SbPh 3 ) 3 ][BAr¢ 4 ] (R = CH 3 1a, H 1b; [BAr¢ 4 ] (L = SbPh 3 3, AsPh 3 4), and the neutral derivatives [Ni(h 3 -CH 2 C(R)CH 2 )Br(L)] (L = SbPh 3 , R = CH 3 5a, H 5b; L = AsPh 3 , R = CH 3 6a, H 6b) have been prepared and characterized. The X-ray crystal structures of 1a-b, 2b, 3, 5a and 6b have been determined. These complexes are very active catalyst precursors for the low-molecular weight oligomerization of RC 6 H 4 CH=CH 2 to mainly dimers and trimers of styrene (R = H) or 4-methylstyrene (R = CH 3 ). They also catalyse the oligomerization of a-methylstyrene to dimers and trimers, or to higher oligomers depending upon the reaction conditions (solvent and temperature). The oligomerization reactions were carried out at 25 • C in most cases, in dichloromethane, 1,2-dichloroethane or fluorobenzene, using a olefin/catalyst ratio equal to 2000. The oligomerization products were characterised by means of GPC/SEC.