B. Temme et G. Erker, OXIDATIVE ETA(2)-IMINOACYL FORMATION BY REACTION OF AMIDOZIRCONOCENE COMPLEXES WITH TRIS(PENTAFLUOROPHENYL)BORANE, Journal of organometallic chemistry, 488(1-2), 1995, pp. 177-182
Methyl(N-pyrrolyl)zirconocene (8a) reacts with tris(pentafluorophenyl)
borane selectively by transfer of the heterocyclic ligand to give the
methylzirconocene cation, which is an active ethylene polymerization c
atalyst when generated in situ in toluene. In contrast, (diethylamido)
methylzirconocene (8b) undergoes only transfer of the methyl group whe
n treated with the B(C6F5)(3) Lewis acid, to give the (diethylamido)zi
rconocene cation (10b). The [(Et(2)N)ZrCp(2)(+) MeB(C6F5)(3)(-)] salt
is not stable and rapidly reacts at room temperature with methane elim
ination and formation of a cationic (eta(2)-iminoacyl)metallocene syst
em. The resulting [Cp(2)Zr(eta(2)-MeC=NEt)(+) HB(C6F5)(3)(-)] species
(11b) is isolated with an 84% yield. Methyl(N-piperidyl)zirconocene (8
c) reacts similarly when treated with B(C6F5)(3) to give the (eta(2)-i
minoacylium)zirconocene (11c) via the intermediate 10a.