238423-82-0Relevant articles and documents
The (PH)2nacnac ligand in organochromium chemistry
MacAdams, Leonard A.,Kim, Woo-Kyu,Liable-Sands, Louise M.,Guzei, Ilia A.,Rheingold, Arnold L.,Theopold, Klaus H.
, p. 952 - 960 (2008/10/08)
A novel class of β-diketiminato chromium complexes was prepared to serve as a homogeneous model system for the heterogeneous Phillips ethylene polymerization catalyst. (Ph)2nacnacCrCl2(THF)2 (1, (Ph)2nacnac = N,N′-diphenyl-2,4-pentanediimme anion) was found to polymerize ethylene in the presence of excess methylaluminoxane (MAO). Reaction of 1 with 1.0 equiv of an alkylzinc compound yielded dimeric, chloride-bridged monoalkyl complexes of the type [(Ph)2nacnacCrR(μ-Cl)THF]2 (R = Me (3a), Et (3b)). Reaction of 1 with 2.0 equiv of alkyllithium reagents resulted in a disproportionation to [(Ph)2nacnac]2Cr (2) and CrR4. 2 could be oxidized by treatment with tetrachloroethane to give trigonalbipyramidal [(Ph)2nacnac]2CrCl (5). Attempted alkylation of 5 with aluminum alkyls yielded the ortho-metalated product (Ph)2nacnac(η1-C6H4-Ph)nacnacCr (6). However, the chromium-(III) aryl complex [(Ph)2nacnac]2CrPh (4) could be synthesized by reaction of CrPh3(THF)3 with 2 equiv of (Ph)2nacnacH. Square-pyramidal 4 featured both a normal planar η2-nacnac and a nonplanar η3-nanac ligand. Thermolysis of 4 resulted in the loss of benzene along with the formation of 6. The crystal structures of 2, 3a, and 4-6 were determined by X-ray diffraction, Complexes 1 and 3-5 catalyzed the polymerization of ethylene when activated with MAO, but they did not catalyze the polymerization by themselves.
