~(19)F-NMR研究镍系催化丁二烯聚合中氟的存在状态

<正> Ziegler-Natta型Ni(naph)_2-Al(i-Bu)_3-BF_3OEt_2(简称Ni-Al-B)催化体系在丁二烯(Bd)聚合过程中,活性中心络合物上氟的状态和数量控制着单体配位、引发、增长和链转移等步骤。文献[1—6]曾指出该体系显高催化活性的Al/B(mol比)范围在0.5—1.0之间,即F/Al=6—3.Al/B>1或F/Al<3时,聚合活性显著降低。最近,我们采用了添加酸、醇、酚和酯类等方法来改进体系中B组分的分散及氟的反应性,Al/B显著拓宽为0.3—3,氟的利用率得到提高。在此基础上,本文将讨论用~(19)F-NMR法研究氟

19F-NMR STUDIES OF FLUORINE SITUATION IN NICKEL CATALYST SYSTEM FOR POLYMERIZATION OF BUTADIENE

19F-NMR studies of the nickel catalyst system, Ni(naph)2-Al (i-Bu)3-BF3OEt2 (abbr. Ni-Al-B), has been tested. In Ni-B system contained "F-B-Ni" complex,19F chemical shift moves to downfield from-153.55 ppm to -148.85ppm, because of the magnetic diploe-dipole interaction between unpaired eelectrons in the 3d8 orbital of N1(II) and fluorine nucleus as a ligand bonded with Ni(II). In B-A1 system the value of coupling constant 1JE-A1 was measured to be equal to 19.2 Hz, the over range of 19F is about from -145 ppm to-155 ppm. And in the real nickel catalyst system, one of "F resonances is from -135 ppm to -136 ppm at the downfield, which might be assigned to the resonance of fluorine-bridged nucleus on the bimeta-lic complexes, such as Ni(I) ,due to the presence of dipole-dipoleinteraction between Ni(I) and F nuclei, which has been identified by the equation