Aluminum complexes ligand exchange reactions

Both CO2 activation and enolate formation are combined in the preparation of malonic acid derivatives. The reaction of CO2 with methacrylic esters or methacry-lonitrile and under visible light irradiation produced the corresponding aluminum porphyrin malonate complex. When diethylzinc was added to this system, Al(TPP)Et could be regenerated by axial ligand exchange reactions, and the malonic acid derivatives were formed catalytically with respect to the aluminum porphyrins in a one-pot photosynthetic route (Scheme 1). The first step in this... 

The yellow CpFe1 (//6-arene) salts (most commonly BF4 or PF6 ) are usually stable up to at least 200 °C, are stable in concentrated sulfuric acid, and are very resistant towards oxidation (until recently, it was believed that they could not be oxidized [23] vide infra). They are not easy to reduce either [23] (vide infra). The chloride salts [CpFe+( f -arene) Cl- are water-soluble they are formed upon hydrolysis following ligand-exchange reactions between ferrocene and the arene in the presence of aluminum chloride [21]. Such aqueous solutions may sometimes be directly used for nucleophilic reactions [22] (vide infra). The BF4- salts are also sometimes quite soluble in water, but the PF6- salts are much less so. Electrophilic reactions that are readily undergone by the free arenes, such as Friedel-Crafts reactions, are no longer possible on the CpFe+( /6-arene) complexes [19, 23]. On the other hand, a range of nucleophilic reactions that are impossible or very difficult to carry out with free arenes become possible under ambient or mild conditions with the CpFe+()/6-arene) complexes (Scheme 2) [16-20]. 

Some of the hydrolysis products of the ligand exchange reaction are mononuclear, which means that only one central atom of aluminum is in the complex and some are polynuclear, which means that more than one central atom of aluminum exists in the complex. Because the water molecule is not charged, Al(H20)g may simply be written as Af This is the symbol to be used in the complex reactions that follow. Without going into details, we will simply write at once all the complex ligand exchange equilibrium reactions. 

The fluoride ion chemisorbs on clays and oxides by ligand exchange of surface OH", a reaction favored at low pH and on oxide and silicate minerals of low crystallinity. Fluoride, a hard base, has a particular affinity for a hard acid. Soluble AP -fluoride cationic and anionic complexes are quite stable, and can dominate the speciation of dissolved aluminum in low-humus soils. The mobility of A1 can be increased by the presence of F soluble complex formation with A1 may explain the rather high solubility and mobility of F in acid soils. 

The complexation of 1 with CpFe+ was performed by ligand exchange with a Cp group of ferrocene [47]. The reaction proceeded in the presence of aluminum powder and aluminum chloride without a solvent under argon at 120 °C for 19 h. The counteranion of the crude complex was replaced by hexafluorophosphate, giving [CpFe(sumanene)]PFg (15) as an orange solid. The use of excess ferrocene and aluminum chloride selectively afforded the desired monometallated complex in 91% yield (Scheme 35.2). However, the reaction in decahydronaphthalene as a solvent did not yield 15 [47]. The complex 15 was fully characterized by fast atom bombardment (FAB) mass spectrometry, and C NMR spectroscopy, and X-ray crystallography. 

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