Acetonitrile complex preparation

The Re oxafluoro acetonitrile complex prepared by Schrobilgen and coworkers1020 [Eq. (4.251)] and characterized by spectroscopic methods ( H, 13C, 19F NMR and Raman) has a pseudooctahedral cis-dioxo arrangement. The acetonitrile ligands are tram to the oxygens and the fluorines are trans to each other. 

In most cases oxidation of uncharged borabenzene complexes produces cations which can only be observed electrochemically. The iron compounds 62 and 63 may serve as an example. Oxidation is fully reversible in rigorously dried CH2C12 but irreversible in more basic solvents such as THF and acetonitrile (62). Preparative oxidation with Ce(IV) salts cleanly produces monosubstituted ferricenium cations 64 (Scheme 10) (66). In contrast to the above mentioned boranediyl extrusions, the substituent at boron is retained here in the newly formed cyclopentadienyl ring. 

To determine if CP was indeed lost in the chemical step the potential was held at — 1.7 V for 30s, then a positive-going scan initiated up to 1.5 V. A number of anodic peaks were observed with the largest and most significant at 1.2 V. This was unequivocally attributed to the oxidation of CP to Cl2 on the basis of a second experiment in which tetrabutylammonium chloride was added to the base electrolyte and the potential regime repeated. Hence, the chemical step after the addition of the first electron involves the ejection of the chloride anion. The identity of the species formed subsequent to this process was determined thus O Toole et al. prepared and characterised the hydrido and acetonitrile complexes (as the bipyridine derivatives) and determined their E° values as —1.46 V and —1.25 V, respectively, far removed from the observed value — 1.62 V hence neither of these species were taken as being the product. 

The only known example of this type of compound is a i74-trichlorosi-lylcyclohexadienetricarbonyliron complex, prepared (89% yield) by the reaction of cyclohexadienyltricarbonyliron tetrafluoroborate with tri-chlorosilane-triethylamine adduct in acetonitrile at 40° (117) ... 

Stereoselective syntheses of all E, 9Z-retinoic-acids and llZ-retinal were developed from P-ionone-tricarbonyliron complex [12]. Treatment of the complex (prepared from p-ionone and dodecacarbonyliron, (Fe3(CO)i2)), with the lithium salt of acetonitrile, Wada et al. obtained the nitrile, in 88% yield, Fig. (22). 

A pure acetonitrile complex of uranium(IV) iodide cannot be isolated,8 but the salt [(CeHj As UI (red) can be readily prepared by the procedure described above in subsection 1, the pure halide being used instead of the acetonitrile complex. f( C H )4NJPaBr6 is extremely soluble in acetonitrile but it can be isolated in 100% yield by room-temperature evaporation of the solvent containing equimolar amounts of the component bromides. 

Compound CuClPhNC is also known. By contrast, similar acetonitrile complexes are easily air oxidized, but they can be prepared by reducing CuXg (X = Cl, Br) with copper in MeCN (230) several alkyl or aryl nitriles complex with CuCl (290). 

An easily prepared acetonitrile complex of hypofluorous acid (HOF-CH3CN) serves an excellent reagent for the oxidation of alkenes with pendant alcohol or carboxylic acid functionalities <1996TL531>. 

Enantioselective Aziridination of Alkenes. Copper complexes with neutral methylenebis(oxazoline) ligands (1) and (2) have also been employed as enantioselective catalysts for the reaction of alkenes with (Al-tosylimino)phenyliodinane, leading to A-tosylaziridines. The best results have been reported for cinna-mate esters as substrates, using 5 mol % of catalyst prepared from CuOTf and the phenyl-substituted ligand (2) (eq 6). The highest enantiomeric excesses are obtained in benzene, whereas in more polar and Lewis basic solvents, such as acetonitrile, the selectiv-ities are markedly lower. The chemical yield can be substantially improved by addition of 4X molecular sieves. Both Cu - and Cu"-bisoxazoline complexes, prepared from Cu or Cu triflate, respectively, are active catalysts, giving similar results. In contrast to the Cu-catalyzed cyclopropanation reactions discussed above, in which only Cu complexes are catalytically active, here Cu complexes are postulated as the actual catalysts. ... 

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