Paramagnetic (benzyl)chromium complexes as homogeneous ethylene polymerization catalysts

Article abstract of DOI:10.1021/om00002a023

The (benzyl)chromium(III) complexes [Cp*Cr(Bz)(μ-Cl)]₂ (D, Cp*Cr(py)(Bz)₂ (2), Cp*Cr-(THF)(Bz)₂ (3), [Cp*Cr(THF)₂Bz]BPh₄ (4), [Cp*Cr(bpy)Bz]BPh₄ (5), Li[Cp*Cr(Bz)₃] (6), and [Li(TMEDA)₂][Cp*Cr(Bz)₃] (7) have been prepared. Reaction of 5 with strong bases (^tBuLi or LiN(TMS)₂) yielded Cp*Cr(bpy)Bz (8), the product of a reduction. The same complex was also produced by treatment of 2 or 3 with 2,2′-bipyridyl (bpy). The crystal structures of 1 (monoclinic, C2/c, a = 14.960(4) A?, b = 16.803(5) A?, c = 13.662(6) A?, β = 110.4(3)°, Z = 4), 2 (monoclinic, P2₁/n, a = 9.345(3) A?, b = 16.923(5) A?, c = 16.161(5) A?, β = 104.36(2)°, Z = 4), 6 (monoclinic, P2₁/n, a = 11.125(2) A?, b = 15.287(3) A?, c = 15.410(4) A?, a = 94.11(2)°, Z = 4), and 8 (triclinic, P1, a = 9.056(3)A?, b = 11.568(6) A?, c = 11.602(4) A?, α = 73.56(3)°, β = 88.47(5)°, γ = 79.35(3)°, Z = 4) have been determined by X-ray diffraction. ²H NMR spectroscopy was used to characterize complexes with perdeuteriated benzyl ligands; signal narrowing factors (W(¹H)/W(²H)) ranged from 12 to 36. Neutral 3, cationic 4, and anionic 6 catalyzed the polymerization of ethylene.