Fluorine perfluorinated ligand

The limitations of the system with regard to substrates and oxidants was attributed to the strong electron-withdrawing character of the perfluorinated chains and the lower steric hindrance in the position adjacent to phenols, in marked contrast to the ferf-butyl groups present in Jacobsen s catalyst, hi view of this, a second generation of fluorinated salen ligands le and If was... 

Figure 7 Representative literature-reported perfluorinated MOFs used for gas adsorption or separation, (a) Fully fluorinated FMOF-1 synthesized from perfluorinated ligand 3,5-bis(trifluoromethyl)-l,2,4-triazolate. (b) Partially fluorinated Zn5(l,2,4-triazolate) (tetra fluoroterephthalate)2(H20)2 4H2O MOF synthesized from tfbda and 1,2,4-triazolate. (c) Partially fluorinated FMOF-2 synthesized from 4,4 -(hexafluoroisopropylidene)-bis(benzoic acid). (d) Representative structure of a series of Cu-based [l,l 3, l"-ter- phenyl]-3,3",5,5"-tetracarboxylic acid functionalized MOFs. (e) Partially fluorinated Zn(bpe)(tftpa) cyclohexanone MOF synthesized from 2,3,5,6-tetrafluoro-l,4-benzenedicarboxylic acid and 1,2-bis(4-pyridyl)ethane (Hydrogen atoms and solvent molecules are omitted for clarity.)...

Only a few years after the development of the homogeneous chiral Mn(salen) complexes by Jacobsen and Katsuki, several research groups began to study different immobiUzation methods in both liquid and soUd phases. Fluorinated organic solvents were the first type of Uquid supports studied for this purpose. The main problem in the appUcation of this methodology is the low solubility of the catalytic complex in the fluorous phase. Several papers were pubUshed by Pozzi and coworkers, who prepared a variety of salen ligands with perfluorinated chains in positions 3 and 5 of the saUcyUdene moiety (Fig. 2). 

On the basis of their previous experiences with lithium borates coordinated by substituted ligands. Barthel and co-workers modified the chelatophos-phate anion by placing various numbers of fluorines on the aromatic ligands. Table 13 lists these modified salts and their major physical properties. As expected, the introduction of the electron-with-drawing fluorines did promote the salt dissociation and reduce the basicity of phosphate anion, resulting in increased ion conductivity and anodic stability. The phosphate with the perfluorinated aromatic ligands showed an anodic decomposition limit of 4.3 V on Pt in EC/DEC solution. So far. these modified lithium phosphates have attracted only academic interest, and their future in lithium ion cell applications remains to be determined by more detailed studies. 

Another biphasic technique uses a fluorinated substance (fluorous phase), which is immiscible with water and most non-fluorinated solvents at room temperature, but which can form a single phase at higher temperatures. Products can thus be separated at room temperature and the soluble catalyst recycled. One such catalyst is made by adding two perfluorinated chains to dba, a classic palladium(0) ligand. 

The required perfluorinated phospane ligand can easily be prepared in three steps starting from 4-iodoaniline. The fluorinated chain was introduced via an Ullmann-type reaction with F13C6I in presence of copper-bronze in DMSO at 120°C for 1 h leading to the perfluoroalkyl substituted aniline 35 in 86% yield... 

Fluorous biphasic systems typically require that the catalyst contain a fluo-rinated ligand to enforce fluorous-phase solubility on the catalyst. While such Teflon ponytails are most commonly perfluorinated alkyl groups, several groups have shown that fluorinated polymers are equally suitable fluorous-... 

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