Chromium complexes coordinated with chelating disiloxane-1,3-diamido ligands as catalyst precursors for ethylene polymerization

Reaction of CrCl2 with 0.5 equivalents of Li4[(NtBuSiMe2)2O]2 (1) gave a new chromium(II) complex, Cr2[(NtBuSiMe2)2O]2 (2). Similar reaction of CrCl3 with 1 yielded the corresponding chromium(III) complex, Cr2[(NtBuSiMe2)2O]3 (3). The dinuclear structure of 3 was revealed by X-ray crystallography, in which the disiloxanediamido ligand can be regarded as an N,N-bidentate ligand. The complexes 2 and 3 showed relatively high catalytic activities for ethylene polymerization upon activation with diethylaluminum chloride.