Hafnium complexes, synthesis

Bis(arene)hafnium complexes, characteristics, 4, 697 Bis(arene)iron dications, characteristics, 6, 173 Bis(arene)niobium complexes, characteristics, 5, 95 Bis(arene)titanium(0) complexes, characteristics, 4, 243-244 Bis(arene)tricarbonylchromium complex, synthesis, 5, 258... 

Some commercially available hafnium derivatives are listed in Table 1. HfC is the major starting material for the different hafnium derivatives. Cp2HfCl2 is the hafnium complex that has found most widespread utility in carbohydrate synthesis [3] and, to some extent, in polymerization chemistry [4], The corresponding Cp (CsMes) complex is also available. Hf(OTf)4 was recently prepared from HfCU and CF3SO3H [5]. 

There are no previous reports concerning the synthesis of chalcogenocar-boxylic acid hafnium complexes. 

Good -selectivity (a as high as 1 16) was found on reaction of 4-Q-acetyl-6-deoxy-2,3-di-Q-methyl-/9-D-allopyranosyl fluoride (D-mycinosyl fluoride) with alcohols in the presence of silver perchlorate and bis(cyclopentadienyl)zirconium dichloride in benzene,and in related fashion a desosamine fluoride has been used to produce -glycosides under mild conditions involving a hafnium complex and the methods have been combined in a total synthesis of the macrocyclic glycoside mycinamycin IV. 

Cho J, Hollis TK, Valente EJ, Trate JM. CCC-N-heterocyclic carbene pincer complexes synthesis, characterization and hydroamination activity of a hafnium complex. J Organomet Chem. 2011 696 373-377. 

A simplified series of reactions between a hafnium salt and sulfuric acid is given in Fig. 4.3. The reactions showcase important facets of thin-film synthesis (but do not address the precise identities of intermediates or complexities of aqueous hafnium chemistry.) In the first step, a hafnium oxide chloride crystal hydrate is dissolved in water to disperse small hafnium-hydroxo molecular clusters. Sulfato ligands are subsequently added in the form of sulfuric acid. Since sulfato binds more strongly than chloro, hafnium-hydroxo-sulfato aqueous species are created. Under mild heating, these species readily poly-... 

Inter- and intramolecular (cyclometallation) reactions of this type have been ob-.served, for instance, with titanium [408,505,683-685], hafnium [411], tantalum [426,686,687], tungsten [418,542], and ruthenium complexes [688], Not only carbene complexes but also imido complexes L M=NR of, e.g., zirconium [689,690], vanadium [691], tantalum [692], or tungsten [693] undergo C-H insertion with unactivated alkanes and arenes. Some illustrative examples are sketched in Figure 3.37. No applications in organic synthesis have yet been found for these mechanistically interesting processes. 

In this chapter we will review the synthesis, structural aspects, and basic chemical properties of formally divalent and trivalent titanium and zirconium metallocene complexes. We have restricted our coverage to the low-valent bis(rj-cyclopentadienyl) and related metallocenes metal halide complexes and organometallic mixed metal systems will not be discussed here. We have not attempted to present an exhaustive coverage of the field. Rather, our aim has been to describe critically and to evaluate the often confusing chemistry that has been reported for the reactive low-valent titanium and zirconium metallocenes. More general reviews (7) and a book (2) on the organometallic chemistry of titanium, zirconium, and hafnium have been published. 

Analytical Chemistry of the Transition Elements Coordination Numbers Geometries Coordination Organometallic Chemistry Principles Hydride Complexes of the Transition Metals Oxide Catalysts in Sohd-state Chemistry Periodic Table Trends in the Properties of the Elements Sol Gel Synthesis of Solids Structure Property Maps for Inorganic Solids Titanium Inorganic Coordination Chemistry Zirconium Hafnium Organometallic Chemistry. 

F. Hoffmann und G. Roewer reported on reactions of cyclohexasilylpotassium with transition metal compounds, and C. Marschner described a Cp-fiee hafnium silyl-substituted complex. A series of four papers from the group of W. Malisch deal with the description of silanol functionalities in organometallic iron and tungsten complexes and the synthesis of perchlorinated metallo siloxanes. 

Eq.3. Synthesis of hafnium and zirconium trichlorotris(tiimethylsilyl)silyl complexes (3,4). 

Negishi, E. I., Takahashi, T. Product class 11 organometallic complexes of zirconium and hafnium. Science of Synthesis 2003, 2, 681-848. 

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