Perfluoro ligands

The replacement of an alkyl ligand by an aryl ligand on Fe(Por)(R) for a given porphyrin macrocycle increases the fraction of the complex present in a high spin form. This is shown in Table 4 and explains why the only high spin states are seen for Fe(Por)(R) with perfluoro ligands. 

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

Betzemeier et al. (1998) have used f-BuOOH, in the presence of a Pd(II) catalyst bearing perfluorinated ligands using a biphasic system of benzene and bromo perfluoro octane to convert a variety of olefins, such as styrene, p-substituted styrenes, vinyl naphthalene, 1-decene etc. to the corresponding ketone via a Wacker type process. Xia and Fell (1997) have used the Li salt of triphenylphosphine monosulphonic acid, which can be solubilized with methanol. A hydroformylation reaction is conducted and catalyst recovery is facilitated by removal of methanol when filtration or extraction with water can be practised. The aqueous solution can be evaporated and the solid salt can be dissolved in methanol and recycled. 

Except for the perfluoro cases, aryl sulfonates are generally less reactive than the halides. However certain catalyst systems can achieve reactions with benzenesulfonates and tosylates. The hindered biphenyphosphines are the most effective ligands. 

In another study the kinetics and mechanism of an unprecedented T/2-vinyl isomerization of a highly fluorinated tungsten(II) metalla-cyclopropene complex was studied (92). Photolysis of a tungsten(II) tetrafluoroaryl metallacycle 1 and perfluoro-2-butyne results in the formation of the kinetic rf -vinyl complex 2 in which the fluoride is trans to the inserted acetylene and cis to both carbonyl ligands. Upon heating 2 is converted to the thermodynamic rf -vinyl complex 3 in which the fluoride ligand is now cis to the inserted alkyne and trans to one CO and cis to the second CO ligand as shown in Scheme 1. 

In a novel procedure, chemical modification of uncrosslinked atactic polystyrene by acetylation followed by a Claisen condensation with ethyl perfluoro-propanoate has been used to prepare a macromolecular ligand bearing phenyl,... 

In view of results obtained in the rhodium chemistry of OFCOT (see Section VIII,F,1), the molecular formula and spectroscopic data for 65 do not allow a distinction to be made between the l,2-f/2-C8F8 and l,4-f/2-C8F8 ligation modes for the OFCOT ligand. The latter structure would also be consistent with that observed for the complex 37 formed between perfluoro- 1,3-butadiene and the [Fe(CO)4] fragment (see Section III,E). 

This supramolecular dendritic assembly serves as a valuable soluble model for the interaction of perfluoro-tagged catalysts with insoluble supports such as fluorous silica gel and clearly reveals the ligand diffusion from the complex at elevated temperatures. This behavior can also explain the high catalytic activity of the heterogeneous FPS system. 

Dialkyl metallocenes and other dialkyl Group 4 transition metal complexes are useful as precatalysts in combination with co-catalysts such as tris(perfluoro-aryl)boranes or tetrakis(periluoroaryl)borate salts [18]. Recently, an expedient procedure for the production of dimethyl metallocenes and Cp-amido dimethyl metal complexes in high yields and purity has been reported. The direct synthesis of Group 4 dimethylmetallocenes [19] consists of the one-pot reaction between the r-ligand, a 2-fold excess of MeLi, and MtCU. This simple method produces the dimethylated complexes in higher overall yield, and saves on reaction time and solvents, compared to the classic two-step route, which consists in the synthesis of the metallocene dichloride followed by its methylation with 2 equiv. MeLi. 

---