Pentamethylcyclopentadienyl Titanium(IV) Amido Pyridylene Phenylene and Pentamethylcyclopentadienyl Titanacyclopropane Amido Complexes and their Behavior in the Polymerization of Ethylene and Cyclic Olefins

Abstract

AbstractThe reaction of pentamethylcyclopentadienyl titanium trichloride (Cp*TiCl3) with lithium N,N‐bis{6‐[2‐(diethylboryl)phenyl]pyridyl‐2‐yl}amide resulted in the formation of chlorido[η3‐N‐{6‐[2‐(diethylboryl)phenyl]pyridyl‐2‐yl}‐N‐(6‐C6H4)pyrid‐2‐yl)amido]pentamethylcyclopentadienyltitanium (Ti‐1). The structure of Ti‐1 was elucidated by using single‐crystal XRD. The same compound is formed upon the reaction of Cp*TiCl3 with lithium N‐{6‐[2‐(diethylboryl)phenyl]pyridyl‐2‐yl}‐N’‐[6‐(2‐bromophenyl)pyridyl‐2‐yl]amide. The reaction of N,N‐bis[6‐(2‐bromophen‐1‐yl)pyrid‐2‐yl]amine (4) with lithium hexamethyldisilazide followed by the addition of Cp*TiCl3 leads to the formation of [N,N‐bis{6‐(2‐bromophen‐1‐yl)pyrid‐2‐yl}amide]dichloridopentamethylcyclopentadienyltitanium (Ti‐2). The reaction of Ti‐1 with benzylmagnesium chloride yields the pentamethylcyclopentadienyl titanium vinyl complex pentamethylcyclopentadienyl{N‐(6‐phenylpyridyl‐2‐yl)‐N‐[6‐(2‐ethyl‐η2‐vinylboryl‐C6H4)pyrid‐2‐yl]amido}titanium (Ti‐3) by C−H activation; Ti‐3 is best described as a monosubstituted titanacyclopropane. Upon activation with methylaluminoxane (MAO), Ti‐1 produces linear, high‐density polyethylene with molecular weights >6×106 g mol−1, whereas Ti‐2 yielded ethyl‐branched polyethylene. Both Ti‐1 and Ti‐2 are able to copolymerize ethylene (E) with norborn‐2‐ene (NBE) and E with cyclopentene (CPE) and to terpolymerize E with NBE and CPE. Ti‐1 activated by MAO is also active in the ring‐opening metathesis polymerization of NBE to produce up to 97 % cis‐syndiotactic poly(NBE). The polymer structure of all resulting homo‐ and copolymers was elucidated by using 13C NMR spectroscopy.