Cyclopentadienyl-containing low-valent early transition metal olefin polymerization catalysts

#This invention relates to a cylcopentadienyl-containing low-valent transition metal catalyst that is useful in polymerizing and co-polymerizing polar and non-polar olefin monomers, and more particularly relates to an in situ reduced Group 4 metal polymerization catalyst that is capable of forming polymers and copolymers of conjugated monomers such as methyl methacrylate (MMA) and styrene.

#Catalysts based on early transition metal d0 complexes, such as Ziegler-Natta catalysts, are used extensively for coordination polymerization of nonpolar olefins such as ethylene and propylene. However, due to their highly oxophilic nature, these catalysts typically are incompatible with functionalized vinyl monomers in achieving either insertive polymerization of polar olefins or copolymerization of nonpolar olefins with polar comonomers.

#Late transition metal catalysts are less oxophilic; however, most often they effect olefin dimerization or oligomerization rather than polymerization to high molecular weight polymers. Recently, Brookhart and co-workers (J. Am. Chem. Soc., 1996, 118, 267-268) reported examples of late transition metal-catalyzed insertive copolymerizations of nonpolar olefins (ethylene and propylene) with alkyl acrylates to give high molar mass (high molecular weight) polymers. However, activities become significantly lower as the polar comonomer concentration increases and polar groups are only detected at the end of polymer chain branches. Polymerization of olefins containing functional groups in a position remote from the vinyl group by early transition metal catalysts has been reported as have been very oxophilic catalysts such as lanthanocene and zirconocene to catalyze polymerization of polar monomers such as MMA or lactones through a Michael addition mechanism.

#Polymerization of Styrene Catalyzed by an In Situ Generated Ti(III) Catalyst

#A portion of dry styrene (2.0 milliliters (mL), 19 mmol) was vacuum transferred into a 50 mL flame-dried oxygen-free, moisture-free flask having a side outlet fitted with a rubber septum and equipped with a magnetic stirrer and was placed in a 21° C. water bath. A 2 mL Wilmad screw-capped vial and an air-tight syringe were brought into a glovebox and 7.0 mg (31 μmol) of Cp*TiMe3, 28.0 mg (31.0 μmol) of (C6F5)3C+ B(C6F5)4−, and about 1 mL of toluene was charged into the vial, followed by vigorous shaking for 2 minutes to allow the reagents to react. Then 15 mg (225 μmol) of Zn powder was added to the solution and the mixture allowed to stand for 75 min. The solution color changed from orange to dark brownish-green. The solution was removed from the glovebox and the supernatant injected into the stirring styrene solution by syringe. After vigorously stirring for 15 min, the reaction was quenched by addition of 20 mL of methanol (MeOH). The resulting polymer was collected by filtration and then redissolved in 20 mL of C2H2Cl4 at 90° C. After addition of 100 mL MeOH to precipitate the polymer, the suspension was filtered to remove any catalyst residue. The colorless polymeric material was then triturated with 100 mL of MeOH by vigorously stirring for 24 h. The solid polymer was then collected by filtration, washed three times with 10 mL portions of MeOH, and dried at 120° C. under vacuum for 24 hours. The yield was 1.2 grams. Results are shown in Table 1.

#Polymerization of MMA Catalyzed by an In Situ Generated Ti(III) Catalyst