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

Abstract The reaction of pentamethylcyclopentadienyl titanium trichloride (Cp*TiCl 3 ) with lithium N , N ‐bis{6‐[2‐(diethylboryl)phenyl]pyridyl‐2‐yl}amide resulted in the formation of chlorido[η 3 ‐ N‐ {6‐[2‐(diethylboryl)phenyl]pyridyl‐2‐yl}‐ N‐ (6‐C 6 H 4 )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*TiCl 3 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*TiCl 3 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‐ η 2 ‐vinylboryl‐C 6 H 4 )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 >6×10 6 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 13 C NMR spectroscopy.