Cerium isopropoxide

The sol-gel synthesis of some rare earths oxides has been carried out for the first time in 1971. For the preparation of ceria-based oxides, cerium isopropoxide, cerium acetylacetonate, cerium nitrate are used as the precursors. The water necessary for the hydrolysis reactions is brought in by adding directly or by the hydrated cerium nitrate. Using this method, Ce02, Ce02-PrOx, Ce02-Zr02, and CeOj-... 

Cerium isopropoxide catalyzes the highly diastereoselective pinacol coupling of aliphatic and aromatic aldehydes (eq. (15)) [139]. 

Dimeric solvated solute species [Ce2(OiPr)8(iPrOH)2] are formed when cerium isopropoxide is dissolved in its parent alcohol. These solutions are very sensitive to moisture and can be stabilized with acetylacetone. Molecular clusters are formed when a small amount of water is added. Red crystals have been... 

Use of less basic triphenylsiloxide ligands also allowed the isolation of mononuclear complexes (Table 1) [46,47]. In addition to the silylamide route, anhydrous nitrates and isopropoxides were employed as synthetic precursors (Eqs. 1,2). The siloxide bridges in the solvent-free dimeric systems Ln2(OSiPh3)6 are readily disrupted by donor solvents like THF, OP Bu3 or DME. The m s-THF adducts of lanthanum, cerium (Fig. 5) and yttrium adopt an approximately /ac-octahedral geometry. 

The aUcoxides Ce(OR)4 are another well-developed class of Ce compounds. The aUcoxide group plays an important role in stabilising the Ce(lV) state, witness the existence of [CeCp2(OBu )2] and [CeCp3(OBu )], when other Ce(lV) organometalhcs cannot be isolated. The isopropoxide is volatile in vacuo below 200 °C (its bis(isopropanol) adduct has six-coordinate cerium). General methods are available to... 

The synthesis and preliminary X-ray structure of the first organometallic Ce(IV) complex Ce(CsH8)2 was reported in 1976 [115] and reproduced in 1985 [116] by the reaction of cerium(IV) isopropoxide with triethylaluminum in the presence of cyclooctatetraene, as shown in Figure 8.35. The accurate sandwich molecule structure of cerocene has been eon-firmed by an X-ray structural study on the methyl substituted cerocene [Ce(MeCOT)2] [117], Subsequently, two more substituted cerocene analogs have been synthesized via a more efficient method, for example, controlled oxidation of cerium(III) precursors and one of these complexes has been structurally characterized [118],... 

The compound [Ce40(0-/-Pr)i3(HO-(-Pr)] (Fig. 75) (500) consists of a butterfly (rather than common tetrahedral) arrangement of four cerium atoms around the oxo ligand. The molecule possesses a crystallographic C2 axis that passes through the oxo ligand and the center of a symmetric hydrogen bond between the coordinated isopropanol and one terminal isopropoxide. 

The following chemicals have been used Almninium isopropoxide, 98+ (Aldrich), cerium (III) 2-ethyUiexanoate, 49% in 2-ethyUiexanoic acid (Alfa Aesar), copper (II) 2-ethyUiexanoate, 98% (Alfa Aesar), platinum (II) acetyl-acetonate, 97% (Alfa Aesar), zinc 2-ethyIhexanoate, 99% (Alfa Aesar) and zirconium (IV) n-propoxide, 70% w/w in n-propanol (Alfa Aesar)... 

The hydrolysis of J-diketonate-modified cerium(IV) isopropoxide leads to the formation of colloidal solutions or gels. The complexation ratio (x = acac/Ce) appears to be the key parameter to tailor the size of cerium oxide particles. Precipitation is observed when x < 0.1, whereas sols are obtained when 0.1 < X < 1. The mean hydrodynamic diameter of these particles decreases from 450 to 15 A when x goes from 0.1 to 1. Only solute molecular clusters are formed when the complexing ratio becomes larger than 1 (1 < x < 2). 

Greco, Cesca and Bertolini have reported that Ce(CgHQ)2 is an air-sensitive, brownish-red crystalline material that is synthesized in the reaction of cerium(IV) isopropoxide with triethylaluminum in cyclooc-tatetraene (COT). 3 ... 

A bimetallic mono-[8]annulene complex containing cerium(lll) and aluminuro(III) has been synthesized.67 [8]Annulenecerium(III)-di-u isopropoxydiethylaluminum was synthesized by the reaction of cerium(IV) isopropoxide with triethylaluminum in the presence of cyclooctatetraene and toluene as the solvent. 

This bimetallic complex was characterized by elemental analysis, infrared spectrum and mass spectrum. The infrared indicates that the eight-membered ring is present as [8]annulene. It was suggested from the mass spectrum and iH-NMR studies that this complex exists with the isopropoxide ligands bridging between the cerium and aluminum ions (Figure 11). The bimetallic [8]annulene complex has also been made as its acetonitrile adduct. 7... 

The differences in solubility of metal isopropoxides and their alcoholates have led to the crystallization of pure isopropoxide isopropanolates of some tetravalent elements. For example, zirconium tetraisopropoxide is a viscous supercooled liquid which dissolves in excess of isopropyl alcohol and crystallizes out in the form of pure white crystals which were characterized as Zr(OPr )4.Pr OH. Similarly tin tetraisopropoxide and cerium tetraisopropoxide have been obtained as crystalline alcoholates, Sn(OPr )4.Pr OH ° and Ce(OPP)4.Pr OH which were used as the starting materials for the synthesis of a number of new alkoxides. 

The isopropoxides of cerium and thorium also show higher association (3.1 and 3.8, respectively, in boiling benzene) than titanium, zirconium, and hafnium alkoxides. 

Ce(acac)3 may be used instead of isopropoxide, but in this case the obtained product is less pure. The cerium complex is crystallized from the reaction mixture as black needles. The compound is pyrophoric and slowly decomposed by deaerated water. Its structure has been confirmed by the data of elemental analysis, IR-, NMR and mass spectrometry (the molecular ion is present in the spectrum) and the preliminary X-ray data. 

The methoxides and ethoxides of lanthanoids are insoluble solids. The derivatives of phenols and higher alcohols are amorphous or crystalline substances soluble in common organic solvents. Some of them (isopropoxides, tert-butoxides and derivatives of 2,6-di-tert-butylphenols) are sublimed in vacuum at 190-250 C. The cerium tetra-alkoxides with tertiary-radicals appear to be distillable liquids. The mixed alkoxide of lanthanum La(0C3H7-i)2(0CH2C4H70) containing the residue of tetrahydrofurfuryl alcohol OCH2C4H7O and the isopropoxy groups remains liquid at room temperature [14]. 

The product is isolated as yellow solid which is high sensitive to moisture and oxygen. The complex contains some amount of toluene which cannot be removed in vacuum at room temperature. The solvate-free compound may be obtained when toluene in the complex is substituted with acetonitrile. Acetonitrile is easy removed in vacuum at temperature below 0°C. The alcoholysis of the complex with i-C3H70H gives cyclo-octatetraene, a mixture of isomers of cyclooctatriene and a mixture of cerium and aluminium isopropoxides. 

Ribot F., Toledano P., Sanchez C. Hydrolysis-condensation process of /S-dikctonates-modified cerium(IV) isopropoxide. Chem. Mater. 1991 3 759 Samuels J.A., Foiling K., Huffman J.C., Caulton K.G. Structure/volatility correlation of sodium and zirconium fluoroalkoxides. Chem. Mater. 1995 7 929 Schmidbaur H., Adlkofer J., Shiotani A. Heterosiloxanes of copper, silver, and gold, Bct. 1972 105 3389... 

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