New Ni(II)-Ni(II) Dinuclear Complex, a Resting State of the (-diimine)NiBr₂/AlMe₃ Catalyst System for Ethylene Polymerization

A novel room-temperature stable diamagnetic nickel complex 2 was detected upon activation of Brookhart-type ethylene polymerization pre-catalyst LNiBr2 (1, L = 1,4-bis-2,4,6-trimethylphenyl-2,3-dimethyl-1,4-diazabuta-1,3-diene) with AlMe3. Using in situ H-1, H-2, and C-13 NMR spectroscopy, as well as DFT calculations, this species has been identified as an antiferromagnetically coupled homodinuclear complex [LNiII(mu-Me)(mu-CH2)(NiL)-L-II]Br-+(-). Its behavior in the reaction solution is characteristic of the resting state of nickel catalyzed ethylene polymerization.