Zirconium complex compounds

Otherwise, TBP derivatives with high boiling points and containing C = O groups are zirconium complexing compounds (31). 

Zirconium bromide, anhydrous, 1 49 Zirconium complex compounds, nonelectrolytes, with acetylacetone, ZrCCsHjOili-lOHaO, 2 121 Zirconium oxybromide, formation of, from zirconium bromide, 1 51... 

The crystal structure of a mono(cyclopentadienyl)zirconium complex containing a novel Me2Si-linked bis(amidinate) ligand was reported (Scheme 203). In this compound the central Zr atom is octahedrally coordinated with the bis(amidi-nate) acting as a tridentate ligand. ... 

As Scheme 16 shows, vinyl(methyl)zinc compounds 17 were obtained from the hydrozirconation of terminal alkynes with Cp2ZrHGl, followed by treatment with dimethylzinc. The initially formed vinyl zirconium complex undergoes rapid transmetallation with ZnMe2 to yield the product.44... 

Although in the recent years the stereochemical control of aldol condensations has reached a level of efficiency which allows enantioselective syntheses of very complex compounds containing many asymmetric centres, the situation is still far from what one would consider "ideal". In the first place, the requirement of a substituent at the a-position of the enolate in order to achieve good stereoselection is a limitation which, however, can be overcome by using temporary bulky groups (such as alkylthio ethers, for instance). On the other hand, the ( )-enolates, which are necessary for the preparation of 2,3-anti aldols, are not so easily prepared as the (Z)-enolates and furthermore, they do not show selectivities as good as in the case of the (Z)-enolates. Finally, although elements other than boron -such as zirconium [30] and titanium [31]- have been also used succesfully much work remains to be done in the area of catalysis. In this context, the work of Mukaiyama and Kobayashi [32a,b,c] on asymmetric aldol reactions of silyl enol ethers with aldehydes promoted by tributyltin fluoride and a chiral diamine coordinated to tin(II) triflate... 

The scarcity of compounds involving the heavier main-group elements and the early transition metals, apparent in previous discussions, is also apparent in the chemistry of tellurium. Thiele (147) has described the preparation of the zirconium complex [ Zr(C5Me5)2(/i-Te) 2], 152, from a divinyl complex... 

Many stable metal complexes of arynes are known but in most of their reactions of synthetic interest, the yields are poor. For example, thermolysis of titanocene (Cp2TiPh2) at 80-100 C gives rise to a tita-nium-benzyne complex which reacts with molecular nitrogen to afford aniline with low efficiency.29 However, procedures are available for in situ generation of zirconium complexes (14) and for their coupling reactions to synthesize functionalized aromatic compounds in preparatively useful yields (Scheme I).30 Whether such complexes should be regarded as ir-bonded benzynes or o-bonded o-phenylenes, remains a debatable point.31... 

Mono(cyclooctatetraenyl) lanthanide(III) compounds, synthesis and characteristics, 4, 124 Mono(cyclooctatetraenyl) zirconium(III) compounds, preparation and reactions, 4, 743 Mono(cyclopentadienyl) amido complexes alkane elimination, 4, 446 amine elimination, 4, 442 HCL elimination, 4, 446 metathesis reactions, 4, 438 miscellaneous reactions, 4, 448 properties, 4, 437... 

A zirconium complex of tropyne has been prepared by hydride abstraction from a mixture of 231a-c (Scheme 28).87 This compound is extremely thermally unstable, decomposing to a complex mixture of products above —50°C. Identification of both 230 and 232 rests exclusively on low-tempera-ture, multinuclear NMR spectra. Attempts to couple 232 with reagents such as alkenes, alkynes, nitriles, or ketones gave only complex mixtures of products. 

The stepped frequency approach has been adopted in a range of more complex zirconium-containing compounds including NaZr03,223 Na2Zr-SiC>5,224 where the two crystallographically inequivalent zirconium sites could... 

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