Zirconium organometallic compounds

Zirconium tetrachloride is instantly hydrolyzed in water to zirconium oxide dichloride octahydrate [13520-92-8]. Zirconium tetrachloride exchanges chlorine for 0x0 bonds in the reaction with hydroxylic ligands, forming alkoxides from alcohols (see Alkoxides, METAl). Zirconium tetrachloride combines with many Lewis bases such as dimethyl sulfoxide, phosphoms oxychloride and amines including ammonia, ethers, and ketones. The zirconium organometalLic compounds ate all derived from zirconium tetrachloride. 

Zirconium monochloride, 26 646, 647 Zirconium organometallic compounds as catalysts, 26 656-657 Zirconium oxide... 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

Organometallic Compounds. Certain zirconium organometaUic compounds are highly reactive toward low molecular weight unsaturated... 

Section 14.15 Coordination polymerization of ethylene and propene has the biggest economic impact of any organic chemical process. Ziegler-Natta polymerization is canied out using catalysts derived from transition metals such as titanium and zirconium. ir-Bonded and a-bonded organometallic compounds aie intennediates in coordination polymerization. 

The ethylene polymerization was observed (9a) also in the presence of c-organometallic compounds of titanium and zirconium, containing such ligands as -CH i(CH3) , -CH(C H6)Si(CH3)3, -CH2C(CH3)3,... 

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

Only a small number of zirconium(III) and hafnium(III) complexes are known. Nearly all of these are metal trihalide adducts with simple Lewis bases, and few are well characterized. Just one zirconium(III) complex has been characterized structurally by X-ray diffraction, the chlorine-bridged dimer [ ZrCl PBu,) ]- Although a number of reduced halides and organometallic compounds are known in which zirconium or hafnium exhibits an oxidation state less than III, coordination compounds of these metals in the II, I or 0 oxidation states are unknown, except for a few rather poorly characterized Zr° and Hf° compounds, viz. [M(bipy)3], [M(phen)3] and M Zr(CN)5 (M = Zr or Hf M = K or Rb). 

Silanes and H2 parallel each other in reactivity with organometallic compounds (105), and silanes react with coordinated N2 and sulfide ligands much like H2. As in the H2 heterolysis shown in Eq. (23) above, the macrocyclic zirconium system of Fryzuk et al. (90) heterolyzes Si-H bonds [Eq. (30)]. 

Ziegler-Natta Catalysts (Heterogeneous). These systems consist of a combination of a transition metal compound from groups IV to VIII and an organometallic compound of a group I—III metal.23 The transition metal compound is called the catalyst and the organometallic compound the cocatalyst. Typically the catalyst is a halide or oxyhalide of titanium, chromium, vanadium, zirconium, or molybdenum. The cocatalyst is often an alkyl, aryl, or halide of aluminum, lithium, zinc, tin, cadmium, magnesium, or beryllium.24 One of the most important catalyst systems is the titanium trihalides or tetra-halides combined with a trialkylaluminum compound. 

Apart from organometallic compounds there are a few other compounds of zerova-lent zirconium. The reduction of ZrCLt with lithium in the presence of bipyridine in THF gives violet Zr(bipy)4 where, doubtless, there is considerable delocalization of electrons over the ligands. The reaction of KCN or RbCN with ZrCl3 in liquid ammonia is reported to give M Zr(CN)5. 

Metathesis reactions and the use of dilithio compounds are the most frequently used methods for synthesis of these organometallic compounds. These reactions use almost exclusively zirconapentalenes, especially disubstituted with two cyclopentadiene rings on a zirconium atom. Ring expansions or contractions have not been reported. 

Alkynes are carbometallated with several organometallic compounds under mild conditions [3] but carbocupration has probably the greatest synthetic possibilities [4], associated with the zirconium-catalyzed methylalumination [5] reaction both proceed with very high stereoselectivity and afford the syn addition product as described in Scheme 7-2. 

D. J. Cardin, M. F. Lappert and C. L. Raston, Chemistry of Organo-zirconium and -hafnium Compounds , Wiley, New York, 1986 R. S. P. Courts, P. C. Wailes and H. Weigold, Organometallic Chemistry of Titanium, Zirconium, Hafnium , Academic Press, New York, 1974 G. E. Coates, M. L. H. Green and K. Wade, in Organometallic Compounds , Chapman and Hall, London, 1968, vol. 2. 

Vapor decomposition is a powder preparation technique useful in a few cases when a vapor phase precursor exists (often an organometallic compound) which can be decomposed to the desired composition . The vapor decomposition usually takes place at elevated temperatures. Single component oxide powders of high purity can be prepared by vapor decomposition of metal alkoxides for example, Zr02 is prepared by pyrolyzing zirconium tetra-t-butoxide. ... 

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