New practical tungsten(VI) based catalyst systems for ring opening metathesis polymerisation Ari Lehtonen a, * , Reijo Sillanp€a€a b a Department of Chemistry, University of Turku, FIN-20014 Turku, Finland b Department of Chemistry, University of Jyv€askyl€a, P.O. Box 35, FIN-40351 Jyv€askyl€a, Finland Received 18 January 2002; accepted 8 February 2002 Abstract Tungsten(VI) complexes of the type trans-[WCl 2 (diol)(OAr) 2 ] were studied as catalyst precursors for ROMP of norbornene and dicyclopentadiene. These compounds form active catalysts when treated by simple Grignard reagents, such as methyl magnesium iodide or neophyl magnesium chloride. Moreover, polymerisations can be run under ambient atmosphere without complicated inert atmosphere techniques. Ó 2002 Elsevier Science B.V. All rights reserved. Keywords: Alkoxide complexes; Chloro complexes; Phenolate ligands; Tungsten; Catalysis 1. Introduction Early transition metal alkoxides are widely studied due to their applications in organometallic and catalytic chemistry [1]. Many of these studies have been stimu- lated by the proven ability of various tungsten compounds containing alkoxide and aryloxide ligands to catalyse ring opening metathesis polymerisation (ROMP) and acyclic diene metathesis (ADMET) reac- tions [2,3]. For example, tungsten phenoxides of the type [WCl 6x ðOArÞ x ] and [WOCl 4y ðOArÞ y ] are used on a regular basis as precursors for two-component catalyst systems, typically in the presence of a organometallic activator [4–7]. Some well-defined Mo catalysts are also available, either commercially or through trustworthy syntheses [8]. However, the design of versatile, highly active and well-characterised catalysts is still one of the main objectives of the research in this field. We have previously studied alkoxide chemistry of tungsten(VI) and prepared a new class of compounds, i.e., trans-[WCl 2 (diol)(OAr) 2 ] (compounds 1–3, Scheme 1) [9]. These complexes are stable in air and they can be easily purified by column chromatography and crystal- lisation. As they appear promising catalyst precursors, we are currently making use of them in metathesis re- actions. In the present study we used these compounds as precursors in two-component catalyst system for polymerisation of norbornene and dicyclopentadiene. 2. Results and discussion Substituted tungsten(VI) chlorides, e.g., compounds of the type [WCl 3 (OAr) 3 ] and [WOCl 2 (OAr) 2 ] can be activated by main-group organometallics to obtain active metathesis catalysts [3–7]. The role of these acti- vators is most probably to replace two chloride ligands on tungsten with alkyl groups; the resultant organo- tungsten intermediate would then undergo an a-elimi- nation reaction to afford the corresponding alkylidene derivative [2]. Although several different cocatalyst like EtAlCl 2 , Et 3 Al 2 Cl 3 or R 4 M (R ¼ Me, Et or Bu, M ¼ Sn or Pb) have been used, it seems that simple Grignard reagents do not activate frequently used oxotung- sten(VI) based precursors. Activities of new metathesis catalyst precursors (see Scheme 1) were investigated using ROMP of norborn- ene and dicyclopentadiene as test reactions. Experi- mentation was carried out employing a 1:5:50 tungsten precatalyst:activator:monomer ratio. Six-coordinated Inorganic Chemistry Communications 5 (2002) 267–268 www.elsevier.com/locate/inoche * Corresponding author. Tel.: +358-2-3336733; fax: +358-2-3336700. E-mail address: Ari.Lehtonen@utu.fi (A. Lehtonen). 1387-7003/02/$ - see front matter Ó 2002 Elsevier Science B.V. All rights reserved. PII:S1387-7003(02)00380-5