Chiral palladium(II) complexes bearing tetradentate nitrogen ligands: synthesis, crystal structure and reactivity towards the polymerization of norbornene
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- 作者：Abu-Surrah ; Adnan S. ; Thewalt ; Ulf ; Rieger ; Bernhard
- 关键词：Palladium(II) polymerization catalysts ; Tetradentate nitrogen ligands ; Schiff bases ; Chirality ; Crystal structure ; Norbornene polymerization
- 刊名：Journal of Organometallic Chemistry
- 出版年：1999
- 出版时间：September 15, 1999
- 年：1999
- 卷：587
- 期：1
- 页码：58-66
- 全文大小：201 K
文摘
A synthesis for a series of tetrapodal nitrogen ligands (N,N′-dibenzyl-N,N′-di(quinoline-2-methyl)-1,2-ethylene diamine (DBQED, 1), N,N′-dimethyl-N,N′-di(quinoline-2-methyl)-1,2-ethylene diamine (DMQED, 2), (1R,2R)-(−)-N,N′-di(quinoline-2-methylene) diiminocyclohexane (DQEDC, 3), N,N′-di(quinoline-2-methylene)-1,2-phenylene diimine (DQPD, 4) and for their corresponding neutral and cationic palladium(II) complexes of the types [(1,2,4)PdCl2] (5a, 6a, 7) and [(1,2,3,4)Pd(NCCH3)x](Y)2 (5b, 5c, 6b, 6c, 8, 9), x=0, 2; Y=BF4 −, NO3 − is reported. The dicationic palladium(II) complex [Pd(DBQED)(NO3)2·H2O] (5c) crystallizes in the monoclinic space groups P21/c (no. 14) with a=11.458(1), b=15.302(1) Å, c=20.644(2) Å, β=99.23(1)° and V=3572.7 Å3, Z=4. All four nitrogen donors are attached to the Pd(II)-center in the chiral and C2-symmetric complex 5c. The two quinoline nitrogen atoms of the more rigid Schiff bases (DQEDC, 3; DQPD, 4) do not coordinate coincidentally to Pd(II). A fluxional coordination behavior is suggested for these quinoline donors, which enables this new complex family to act as catalysts for norbornene polymerization, even when chloride is present as a counter ion. Introduction of an enantiomerically pure trans-1,2-cyclohexyl bridge into the Schiff base ligand systems afforded the formation of partially stereoregular polynorbornene.