Ethylene and 1-hexene polymerization using zirconium iminophosphonamide complexes (1)

Ethylene polymerization was studied using a variety of iminophosphonamide (P[N.sub.2]) complexes of zirconium. Bis(P[N.sub.2]) dichloride complexes [[P[h.sub.2]P[(NR').sub.2]].sub.2]Zr[X.sub.2[ (X = Cl; 1a: R' = p-tolyl; 1b: R' = Bn; 1c: R' = [C.sub.6][F.sub.5]) or dimethyl complexes (X = Me; 2a: R' = p-tolyl; 2b: R' = Bn) and cyclopentadienyl(P[N.sub.2])zirconium dichloride complexes [[η.sup.5] - [C.sub.5][R''.sub.5]][[R.sub.2] P[(NR').sub.2]]Zr[Cl.sub.2] (3a: R' = p-toyl, R = Ph, R'' = H; 3b: R' = Si[Me.sub.3], R = Et, R'' = H; 3c: R' = [C.sub.6][F.sub.5], R = Ph, R'' = H; 3e: R' = 3,5-[(C[F.sub.3]).sub.2]Ph, R = Ph, R'' = H; 3f: R' = 3,5-[(C[F.sub.3]).sub.2]Ph, R = Ph, R'' = Me) or dimethyl analogs [[η.sup.5] - [C.sub.5][R.sub.5]] [[R.sub.2]P[(NR').sub.2]]Zr[Me.sub.2] (4a: R' = p-toyl, R = Ph, 4b: R' = Si[Me.sub.3] R = Et) were evaluated under a range of conditions using methylaluminoxane (PMAO) activator. Complexes 1 and 2 behave as precursors to single-site polymerization catalysts under the conditions studied, while complexes 3 or dialkyls 4 show more complex behavior and formation of poly(ethylene) with a bimodal molecular weight distribution. In contrast, activation of dialkyl complexes 4 with [[Ph.sub.3]C][B[([C.sub.6][F.sub.5]).sub.4]] and polymerization in the presence of small amounts of PMAO or TIBAL as scavenger, led to single-site behavior. PMAO reacts with the neutral dialkyls via ligand abstraction to produce a number of P-containing species that may explain the multi-site behavior observed when using this activator. Dialkyls 4 react cleanly with [[Ph.sub.3]C][B[([C.sub.6] [F.sub.5]).sub.4]] in haloarene or even dichloromethane solution to furnish the corresponding cationic alkyls 5, which were characterized by multinuclear NMR spectroscopy. Fluxional dinuclear species are formed in the presence of excess dialkyl and these are susceptible to C--H activation to form μ-Me,μ-C[H.sub.2] complexes one of which could be isolated in pure form. The cationic alkyls initiate the polymerization of 1-hexene at room temperature in chlorobenzene solution, but extensive chain transfer occurs and the systems are not living. Key words: single site, early metal olefin polymerization catalysis. On a etudie la polymerisation de l'ethylene a l'aide d'une variete de complexes a base d'iminophosphonamide (P[N.sub.2]) du zirconium. Utilisant le methylaluminoxane (PMAO) comme activateur dans une grande variete de conditions, on a evalue les complexes avec le dichlorure de bis(P[N.sub.2]) [[P[h.sub.2]P[(NR').sub.2]].sub.2]Zr[X.sub.2] (X = Cl; 1a: R' = p-tolyl; 1b: R' = Bn; 1c: R' = [C.sub.6][F.sub.5]) ou les complexes dimethyles (X = Me; 2a: R' = p-tolyl; 2b: R' = Bn), et le dichlorure de cyclopentadienyl (P[N.sub.2])[[η.sup.5] - [C.sub.5][R''.sub.5]][[R.sub.2] P[(NR').sub.2]]Zr[Cl.sub.2] (3a: R' = p-toyl, R = Ph, R'' = H; 3b: R' = Si[Me.sub.3], R = Et, R'' = H; 3c: R' = [C.sub.6][F.sub.5], R = Ph, R'' = H; 3e: R' = 3,5-[(C[F.sub.3]).sub.2]Ph, R = Ph, R'' = H; 3f: R' = 3,5-[(C[F.sub.3]).sub.2]Ph, R = Ph, R'' = Me) ou de leurs analogues dimethyles [[η.sup.5] - [C.sub.5] [R.sub.5]][[R.sub.2]P[(NR').sub.2]]Zr[Me.sub.2] (4a: R' = p-toyl, R = Ph, 4b: R' = Si[Me.sub.3] R = Et). Dans les conditions etudiees, les complexes 1 et 2 se comportent comme des precurseurs de catalyseurs a site unique alors que les complexes 3 ou les dialkyles 4 presentent un comportement plus complexe avec une formation de poly(ethylene) presentant une distribution bimodale des poids moleculaires. Par ailleurs, l'activation des complexes de dialkyles avec du [[Ph.sub.3]C][B[([C.sub.6] [F.sub.5]).sub.4]] avec des polymerisations en presence de faibles quantites de PMAO ou de TIBAL comme piege conduit a un comportement a site unique. Le PMAO reagit avec les dialkyles neutres par le biais d'un enlevement de ligand conduisant a la formation de diverses especes contenant du phosphore qui peuvent expliquer le comportement multisite observe quand on utilise ce compose pour faire l'activation. Les complexes dialkyles 4 reagissent proprement avec le [[Ph.sub.3]C][B[([C.sub.6][F.sub.5]).sub.4]] en solution darts des halogenoarenes et meme dans le dichloromethane et ces reactions conduisent a la formation des complexes cationiques alkyles correspondants 5 qui ont ete caracterises par spectroscopie RMN multinucldaire. Il se forme des especes binucleaires fluxionnelles en presence d'exe's de derives dialkyles et ces especes sont susceptibles a une activation C--H conduisant a la formation de complexes μ-Me et μ-C[H.sub.2] desquels un a pu etre isole dans une forme pure. Les complexes alkyles cationiques initient la polymerisation du hex-1-ene a la temperature ambiante, en solution dans le chlorobenzene, mais il se produit beaucoup de transfert de chaine et les systemes ne sont pas vivants. Mots cles : precurseurs de catalyseurs a site unique de la polymerisation d'alcenes par des metaux de transition. [Traduit par la Redaction]
Introduction The synthesis of novel group 4 complexes is of considerable interest in the context of olefin polymerization using 'non-metallocene' catalysts (1). A wide variety of complexes based on the [...]