Zirconium amides, mixe

Note also the stereochemistry. In some cases, two new stereogenic centers are formed. The hydroxyl group and any C(2) substituent on the enolate can be in a syn or anti relationship. For many aldol addition reactions, the stereochemical outcome of the reaction can be predicted and analyzed on the basis of the detailed mechanism of the reaction. Entry 1 is a mixed ketone-aldehyde aldol addition carried out by kinetic formation of the less-substituted ketone enolate. Entries 2 to 4 are similar reactions but with more highly substituted reactants. Entries 5 and 6 involve boron enolates, which are discussed in Section 2.1.2.2. Entry 7 shows the formation of a boron enolate of an amide reactions of this type are considered in Section 2.1.3. Entries 8 to 10 show titanium, tin, and zirconium enolates and are discussed in Section 2.1.2.3. 

Treatment of 3-borolenes or 2-boraindans with bulky lithium amides yields the dihthiated aromatic borolide dianions, which are applicable as hgand precursors for transition-metal complexes. Many borole complexes including a number of unusual multidecker sandwich complexes and mixed-metal clusters have been described. 4 3,2i2 An unexpected new entry into the synthesis of borole complexes has been recently discovered. Bochmann found that attack of B(C6Fs)3 at a zirconium bound diene leads to a pentafluorophenylborole complex throngh snccessive C-H activation steps. ... 

Titanium and zirconium tetrabenzyl and the mixed metal—benzyl halides are soluble in hydrocarbon solvents and will polymerize ethylene and a-olefins, the latter to stereo-specific polymers [64], The structures of the true initiators are not known but they are unlikely to be the simple organo-metal compounds. Catalysts of higher activity are obtained when they are used in combination with aluminium alkyls. It is of interest to note that titanium tetra(dimethyl amide) reacts with acrylonitrile to form an active species, which then forms high molecular weight polymer by coordination polymerization [65]. 

Ceramic powders of exceptional purity with very fine particle sizes (ca. 10 nm) have been prepared by precipitation of hydrolyzed oxides from high purity alkoxides . Yttria-stabilized zirconia is prepared by mixing high purity zirconium and yttrium isopropoxides in n-hexane, with water added dropwise to precipitate the oxides quantitatively. The homogeneity of the oxides results in stabilized cubic Zr02 at very low temperatures. Cyclic organoaluminum amides are used to prepare nonoxides such as sulfides and AIN- . 

Dicarbonyl complexes of mixed cyclopentadienyl bis(phosphine)amide zirconium compounds have also been prepared by ligand-induced disproportionation of (775-C5H5)ZrBH4[N(SiMe2CH2PPr12)2] 47, yielding the bis(tetra-hydroborate) complex (775-C5H5)Zr(BH4)2[N(SiMe2CH2PPr12)2] 48 and the dicarbonyl derivative... 

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