Preparation of zwitterion-type chromium(II) complexes for ethylene oligomerization

Zwitterion-type Cr(II) complexes ([Et2Al(PCy2)2]2Cr(II), [Et2Al(NC4H8)2]2Cr(II), {[Et2Al(NiPr2)2]Cr(I0049)-μ2-Cl}2, {[(C6F5)2B(PCy2)2]Cr(II)-μ2-Cl}2) were prepared and characterized by X-ray crystallography. None of them were active in ethylene oligomerization.