PARAMAGNETIC (BENZYL)CHROMIUM COMPLEXES AS HOMOGENEOUS ETHYLENE POLYMERIZATION CATALYSTS

The (benzyl)chromium(III) complexes [Cp*Cr(Bz)(mu-Cl)](2) (1), Cp*Cr(py)(Bz)(2) (2), Cp*Cr-(THF)(Bz)(2) (3), [Cp*Cr(THF)(2)Bz]BPh(4) (4), [Cp*Cr(bpy)Bz]BPh(4) (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 ((t)BuLi 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) Angstrom, b = 16.803(5) Angstrom, c = 13.662(6) Angstrom, beta = 110.4(3)degrees, Z = 4), 2 (monoclinic, P2(1)/n, a = 9.345(3) Angstrom, b = 16.923(5) Angstrom, c = 16.161(5) Angstrom, beta = 104.36(2)degrees, Z = 4) 6 (monoclinic, P2(1)/n, a = 11.125(2) Angstrom, b = 15.287(3) Angstrom, c = 15.410(4) Angstrom, beta = 94.11(2)degrees, Z = 4), and 8 (triclinic , P1, alpha = 9.056(3) Angstrom, b = 15.287(6) Angstrom, c = 11.602(4)Angstrom, alpha - 73.56(3)degrees, beta = 88.47(5)degrees, gamma = 79.35(3)degrees, Z = 4) have been determined by X-ray diffraction. H-2 NMR spectroscopy was used to characterize complexes with perdeuteriated benzyl ligands; signal narrowing factors (W(H-1)/W(H-2)) ranged from 12 to 36. Neutral 3, cationic 4, and anionic 6 catalyzed the polymerization of ethylene.