Living and block polymerization of α-olefins using a Ni(II)-α-diimine catalyst containing OSiPh2tBu groups

Abstract A new siloxy-substituted α-diimine compound and its corresponding Ni(II) complex, {bis[ N , N ′-(4- tert -butyl-diphenylsiloxy-2,6-dimethylphenyl)imino]acenaphthene}dibromonickel ( 6 ), were successfully synthesized and the molecular structure of 6 characterized by X-ray crystallography. The precatalyst 6 activated by methylaluminoxane (MAO) or diethylaluminum chloride (DEAC) was tested in the polymerization of ethylene, showed to be highly active (e.g. 2.2×10 7 and 1.8×10 7  g polymer (mol Ni.h.bar) −1 , respectively) and led to a branched polyethylene (ca. 35–55 branches/1000 C). The catalyst system 6 /methylaluminoxane (MAO) catalyzes, at −11 °C, living polymerization of propylene, to a polypropylene showing a syndiotactic-rich microstructure ( P r =0.74). 1-Hexene was also successfully polymerized via a living process, both at −11 and +16 °C. The 13 C NMR spectra of the poly(1-hexene)s obtained at room temperature show a microstructure almost exclusively composed by n -butyl and methyl branches, the latter being present in a much higher number. Diblock polypropylene- block -poly(1-hexene) and triblock poly(1-hexene)- block -poly(propylene- ran -1-hexene)- block -poly(1-hexene) copolymers have also been synthesized and characterized by GPC/SEC, DSC and NMR.