Titanium, Zirconium, and Hafnium

indenyl, and fluorenyl analogues have been described. 

Three studies of titanium(m) compounds have been described. Full details have now been given of the five-co-ordinate bis(trimethylamino)titanium tribromide structure which has trigonal-bipyramidal geometry. The titanium co-ordination polyhedron has, within the limits of experimental error, i s symmetry, in contrast to that of the analogous chromium compound, which has a distorted geometry. The lack of distortion in the titanium(in) structure is ascribed to the location of the single unpaired electron in a non-deforming e orbital. 

In all of the non-organometallic compounds of Tii for which structures have been reported, the metal is octahedrally co-ordinated. In the TiO octahedra found in the mixed oxides TiTejOg, BaTigOig, and BaiTiigOjo, the Ti-0 distances range between 1.79 and 2.15 A, but in all cases the average is very close to 1.95 A. 

Two centrosymmetrically related, edge-sharing TiO, octahedra are found in the tetraphenoxytitanium(iv) monophenolate dimer. The Ti-O distances also vary, but these can be correlated with the function of the oxygen atoms 

Chlorine bridges are also found in diethylaminotitanium trichloride. In the TiNClj co-ordination sphere, four of the chlorine atoms are bridging, with Ti-Cl distances in the range 2.46—2.71 A, and the terminal Ti-Cl bond length is 2.25 A. The Ti-N distance of 1.85 A is shorter than expected for a single bond and may indicate N- Ti 7r-bonding. 

Despite disorder between Cl and CN at two sites, the configuration of c -tetrachlorodiformonitrilotitanium(iv) is uniquely determined. The 

Savignac, P. Cadiot, and F. Mathey, Inorg. Chim. Acta, 1980, 45, L43. 

Titanium, Zirconium, and Hafnium.—Several reports on the photochemistry of titanocene derivatives have appeared this year. Harrigan et e/.180 observed that the photolysis ( 480 nm) of Cp2TiCI2 in chlorinated hydrocarbons gave CpTiCl3, and they proposed that light-induced cleavage of the Ti-Cp bond occurs, as in reactions (57) and (58). In support of this mechanism, photo- 

These findings are consistent with a recent report of the photoelectron spectra of Cp2MCl2 (M = Ti, Zr, or Hf), which shows that transitions involving electron 

Titanium, Zirconium, and Hafnium.—more accurate crystal structure determination of (C6H5)4Zr has established that one - and three rings are 

A variety of new zirconocene derivatives has been isolated from additions of CO to LjZrRa (L = Cp, R = alkyl L = Cp, R aryl ) and to LaZr(R)H (L = Cp or Cp R = alkyl). Reactions of CpaTi(CO)2 with acyl chlorides and with XCN (X = Br or I) have afforded CpaTi( j -COR)Cl and Cp8Ti(CN)X, respectively, and the structures of the unusual products (9) and (10) obtained from reactions with diphenylketene have been established by crystallographic studies. 

Reactions of CpaTiAra with CO2 and alkynes under thermal conditions, and in benzene under photochemical conditions have been studied. Several new titanocene derivatives of the type CpaTi(XY) containing a bidentate chelating 

Isagawa, K. Tatsumi, and H. Kosugi, Chem. Letters (Tokyo), 1977, 1017. 

Antropiusova, V. Hanus, and K. Mach, Transition Metal Chem. (Weinheim), 1978, 3, 

Titanium, Zirconium, and Hafnium - The displacement of MeB(C6F5)3] from [(T 5-C5H5)2ZrMe(n-CH3)B(C6F5)3] has been investigated. NMR 

Vanadium - The oxovanadium(V)-induced oxidative coupling of organo-lithium and -magnesium compounds has been investigated by V NMR spectroscopy. NMR spectroscopy has been used to follow the reaction of [V02(acac)] with 

The structural characterisation of a range of heterodimetallic Zr/Pd and Zr/Rh catalyst precursors, which contain the C5H4PPh2 ligand, such as complex shown below as 8 has also been the priority of the same research group.  

In a paper on the synthesis of tetranuclear bis(p -alkynyl) transition metal complexes the crystal structure of [(p -C5H4SiMc3)2Ti(CCFc)2]CuBr has been described. The synthetic work was based on the metathesis reactions of trinuc-lear [Ti](CCFc)2 with one equivalent of [MX] (M = Cu, Ag X = Cl, Br, OTf, BF4).  

The preparation and first X-ray structure of a zirconocene p-keto ester enolate, shown as 13, have been reported.  

A series of co-catalysts which are A1-, Nb- and Ta-based perfluoroaryloxide anions such as the example shown as 14 have been developed for use in metallocene-mediated Ziegler-Natta olefin polymerisation.  

The half-sandwich metallocene n -(C5Me4)SiMe2N(Bu )TiCl2 when treated with a stoichiometric quantity of dibutylmagnesium in tetrahydrofuran forms a robust monobutyl monochloride ri -(C5Me4)SiMe2N(Bu )Ti(Bu)Cl, shown as 15, which contains an undistorted ri -butyl ligand. The former of these complexes is a catalyst for the carboalumination of olefins in the presence of excess of triethylaluminum.  

The reactive intermediate complex [Cp2Ti(THF)has been proposed from e.s.r. and ENDOR spectral studies of [Cp,TiXj-ZnX  

Mixed ring complexes Cp CpMCl (M = Hf, Ti) have been 134  

As is usual in this report, this group is only sparsely represented. However, a number of carbonyl and phosphine adducts of open titanocenes (and vanadocenes - see below) have been synthesized and have had their solid state structures reported (along with a considerable amount of spectroscopic data) 

The discovery of hafnium was one of chemistry s more controversial episodes In 1911 G. Urbain, the French chemist and authority on rare earths , claimed to have isolated the element of atomic number 72 from a sample of rare-earth residues, and named it celtium. With hindsight, and more especially with an understanding of the consequences of H. G. J. Moseley s and N. Bohr s work on atomic structure, it now seems very unlikely that element 72 could have been found in the necessary concentrations along with rare earths. But this knowledge was lacking in the early part of the century and, indeed, in 1922 Urbain and 

Dauvillier claimed to have X-ray evidence to support the discovery. However, by that time Niels Bohr had developed his atomic theory and so was confident that element 72 would be a 

Ab initio MO calculations gave values for vibrational wavenumbers for TiH, where x = 2,3 or 4 Laser-ablated M atoms (= Ti, Zr or Hf) and H2O react to form HMOH and H2M(OH)2. Matrix-IR gave detailed assignments for these, e.g. for H2Ti(OH)2, VeTiH2 1688.3 cm , VasTiH2 1666.2 cm- for HTiOH, vTiH is at 1549.1 cm-. 2  

DFT calculations of vibrational wavenumbers for M(acac)3, where M = Ti, V, Cr, Mn, Fe, Co, Ni or Se, allowed assignments to be made to many low-wavenumber features - involving extensive coupling of skeletal deformations and low-wavenumber ligand modes.  

The UV resonance Raman spectrum of titanium-sihcahte-1 (TS-1) includes bands due to the titanium framework at 490, 530 and 1125 cm. The Raman spectrum of the mineral baotite contained bands due to TiOe units 192, 322 cm (big), 460,488 cm (Cg) and 622 cm (aig).  

The thermal and radiation-indueed eubie/monoelinie phase transitions in Zr02 were probed by using Raman speetroseopy. IR and Raman spectra gave assignments to modes of cubic and tetragonal Zr02 samples.  

4 CHEMISTRY OF METAL CARBONYLS 4.1 Titanium, Zirconium and Hafnium 

This reporter has not found any work on simple Ti, Zr or Hf carbonyls. 

A dimeric adduct is formed on treatment of CpZrCls with a biaryUacton and the reaction between pentafluorophenylboron and pentamethylcyclopentadienyl-(benzamidinato)zirconium derivatives has been used to prepare conqxiunds such as the dinuclear zirconocene dimer 4. Finally, extended Huckel calculations have been carried out on the model complex [Cp2Zr0i-CH3)0i-dimethoxyphenyl)].  

There are no dinitrogen complexes of any of these metals that contain a phosphine ligand. The considerable amount of nitrogen-fixing chemistry reported for titanium, and to a lesser extent zirconium, involves alkoxide, cyclopentadienyl, and halide complexes.The catalytic nitriding reactions of titanium will be reviewed in Section 3. 

Titanium(IV) chloride forms a number of different adducts with trans-[ReCl(N2)(PMe2Ph)4] (see Table 1) that are believed to involve dinitrogen bridging between rhenium and titanium. Hydrolysis or treatment of these adducts with ethanol results in the virtual quantitative recovery of the original rhenium-dinitrogen complex. 

---

The manufacture of refractory metals such as titanium, zirconium, and hafnium by sodium reduction of their haHdes is a growing appHcation, except for titanium, which is produced principally via magnesium reduction (109—114). Typical overall haHde reactions are... 

R. J. H. Clark, D. C. Bradley, and P. Thornton, Chemistry of Titanium, Zirconium, and Hafnium, Pergamon Press, New York, 1975. 

Boron forms B—N compounds that are isoelectronic with graphite (see Boron compounds, refractoryboron compounds). The small size also has a significant role in the interstitial alloy-type metal borides boron forms. Boron forms borides with metals that are less electronegative than itself including titanium, zirconium, and hafnium. 

Table 21.2 Oxidation states and stereochemistries of titanium, zirconium and hafnium...

The effect of the metals used was then examined (Table 5.4). When the group 4 metals, titanium, zirconium, and hafnium, were screened it was found that a chiral hafnium catalyst gave high yields and enantioselectivity in the model reaction of aldimine lb with 7a, while lower yields and enantiomeric excesses were obtained using a chiral titanium catalyst [17]. 

Systematic chemistry of the transition elements — recent chemistry of titanium, zirconium and hafnium. F. K. McTaggart, Rev. Pure Appl. Chem., 1951,1,152-170 (31). 

Hydrogen reduction has a major advantage in that the reaction generally takes place at lower temperature than the equivalent decomposition reaction. It is used extensively in the deposition of transition metals from their halides, particularly the metals of Groups Va, (vanadium, niobium, and tantalum) and Via (chromium, molybdenum, and tungsten). The halide reduction of Group IVa metals (titanium, zirconium, and hafnium) is more difficult because their halides are more stable. 

Tullock C.W. et al.. Polyethylene and elastomeric polypropylene using alumina-supported bis(arene) titanium, zirconium, and hafnium catalysts, J. Polym. Sci, Part A, Polym. Chem., 27, 3063, 1989. Mueller G. and Rieger R., Propene based thermoplastic elastomers by early and late transition metal catalysis. Prog. Polym. Sci., 27, 815, 2002. 

For an overview of organozirconium and -hafnium chemistry, see P. C. Wailes, R. S. P. Coutts, H. Weigold, Organometallic Chemistry of Titanium, Zirconium, and Hafnium, Academic Press, New York, 1974, p. 302. D. J. Cardin, M. F. Lappeet, C. L. Raston Chemistry of Organozirconium and Hafnium Compounds, John Wiley Sons, New York, 1986, p. 451. 

Minkler, W. W., The Production of Titanium, Zirconium and Hafnium, Metal. Treatises, 1981, 171 (Chem. Abstr., 96, 184821). 

Titanium, zirconium and hafnium in normal conditions crystallize in the hexagonal close-packed structure (a modification) with a c/a slightly smaller than the ideal one c/a = 1.587 (Ti), 1.593 (Zr) and 1.581 (Hf). At high temperature they have the bcc W-type structure ((3 modification). High-pressure transformations are known (Tables 5.21-5.23). 

We first studied group 4 metals (titanium, zirconium and hafnium) supported on a silica dehydroxylated especially at 700 °C (Table 3.8). Following the laboratory-developed strategy, surface-species have been well-characterized by classical techniques (IR, solid-state NMR gas evolvement, reactivity, etc.). Catalysis results show that titanium is the most active even if its activity is far less than that of homogeneous catalysts. In addition, an important amount of metal was lost by lixiviation even if this phenomenon seemed to stop after a certain time. 

Reaction of tris(neopentyl) complexes of titanium, zirconium and hafnium with molecular oxygen furnishes the corresponding tris(neopentoxy) complexes [42, 43, 51]. A peroxo complex is an intermediate in this reaction, being relatively stable in the case of titanium [42]. The alkoxide species can also be formed upon reaction with alcohols under mild conditions [42, 52]. The alcoholysis reaction is fast, with a low dependence on the steric hindrance of the alkyl chain [42]. Hydrolysis leads to ](=SiO)M(OH)3] or ](=SiO)2M(OH)2], depending on the precursor species. Deu-... 

Iodine is used in many dyes and as a colorant for foods and cosmetics. Its silver salt is used in photographic negative emulsions. Other industrial applications include dehydrogenation of butane and butylenes to 1,3-butadiene as a catalyst in many organic reactions in treatment of naphtha to yield high octane motor fuel and in preparation of many metals in high purity grade, such as titanium, zirconium and hafnium. 

---