Metal-arene complexes titanium

Some examples of polynuclear polymeric metal arene complexes, obtained by cryosynthetic reactions from tin, titanium, vanadium, chromium, and molybdenum, are represented [202,542,543]. However, the preparative possibilities of such syntheses are not yet clear [201,202]. 

The only route to dibenzenetitanium so far described is the reaction of titanium atoms with benzene the reductive routes that give access to arene complexes of Group V and VI metals fail for titanium. Although yields of about 30% are reported for the preparation of dibenzene-, ditoluene-, and dimesitylenetitanium, the reactions are more sensitive than most to the effect of excess metal. Unless the ligand-to-titanium ratio is high and the rate of deposition of titanium vapor kept low, the products seem to be catalytically decomposed by finely divided Ti metal 4a, 7). 

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... 

Sixteen-electron bis(arene) complexes of formally zero-valent zirconium, hafnium, and titanium have been made by cocondensation of the metal atoms with bulky ligands such as 1,3,5-tri-t-butylbenzene71 ... 

Heteroarene complexes, (C6R3H2E)2Ti (E = N, R=Buc E = P, R = Buc E = As, R = H, 20), can be prepared by metal-ligand vapor co-condensation of titanium with the corresponding arene (Scheme 4).15,16 Distinct 111 NMR resonances are observed for the aromatic protons at ambient temperature, suggesting restricted arene rotation. Variable-temperature NMR experiments provided barriers of 16 and 17kcalruol respectively, for the ring rotation. Reduction of either compound with potassium metal furnished the titanium(l) salts, KhC BuffTE )2Ti] (E = N, P 21). 

Titanium(II) arene complexes, (r -arene)Ti(AICl4)2, are readily obtained from the reaction between TiC, aluminium powder and aluminium chloride in refluxing aromatic solvent [182]. Metal halides have been used as Lewis acid catalysts for various... 

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]. 

Vinyl halides add to allylic amines in the presence of Ni(cod)2 where cod=l, 5-cyclooctodine, followed by reduction with sodium borohydride. Aryl iodides add to alkynes using a platinum complex in conjunction with a palladium catalyst. A palladium catalyst has been used alone for the same purpose, and the intramolecular addition of a arene to an aUcene was accomplished with a palladium or a GaCl3 catalyst, " AUcyl iodides add intramolecularly to aUcenes with a titanium catalyst, or to alkynes using indium metal and additives. The latter cyclization of aryl iodides to alkenes was accomplished with indium and iodine or with Sml2. " ... 

The unsubstituted para-t-butyl calixarenes themselves complex metals via their aryloxide groups. Since aryloxide complexes are frequently oligomeric, the simple calixarenes do not give monomeric complexes. Aryloxides are hard ligands, therefore they readily form complexes with oxo-philic hard metal ions such as alkali metals, early transition metals, lanthanides, and actinides. Complexation is often inferred because the calixarene acts as a carrier for the metal ion from an aqueous to an organic phase. With the /wa-/-butylcalix[ ]arenes in alkaline solution, a value of n = 6 gives the best carrier for lithium(I), sodium(I), and potassium(I), with a value of n 8 giving the best carrier for rubidium(I) and caesium(I).15,16 Titanium(IV) complexes have been characterized,17-19 as well as those of niobium(V) and tantalum(V).20-22 These complexes are classified as... 

An example of a macrocycle with oxygen donors to support a Ti catalyst for lactide polymerization has been reported by Frediani et a/. " The authors described several titanium chloride complexes bearing calix[4]arene ligands, which act as catalysts for solvent-free lactide polymerization (Figure 18). These complexes acted as dual-site catalysts with two polymer chains growing from one metal center. 

The electron-beam furnace is widely used industrially, and offers good temperature control and the ability to vaporize metals, non-metals, and ceramics at temperatures of up to 4000 °C. Such a furnace was originally used by Green and Young in a rotary apparatus vide infra) for the synthesis of bis(77-arene)titanium complexes. The essential features of the furnace are shown in Figure 6. 

The parent oxacalix[3] arenas show little ability to bind alkali metals,however, a range of quaternary ammonium cations are attracted to the symmetric cavity. Deprotonation of the phenol moieties allows them to bind to transition metals (scandium, titanium, vanadium, rhodium, molybdenum, gold, etc.), lanthanides (lutetium. yttrium, and lanthanum), and actinides (uranium as uranyl). Oxacalix[3]arenes derivatized on the lower rim can complex gallium, mercury, and alkali metals, including sodium, in a manner reminiscent of natural transmembrane cation filters. One major use was to purify crude samples of fullerenes. The pseudo-Cs symmetry of the macrocyclic cavity is complementary to threefold symmetry elements of Cgo. which binds preferentially in... 

The kinetic and thermodynamic selectivity for reactions of a titanium-imido complex with different types of C-H bonds has been determined. Reactions with substrates that possess primary and secondary C-H bonds occur selectively at the primary C-H bond. In addition, reactions with mixtures of alkanes and arenes occur selectively at the arene C-H bond. Like the stabilities of most low-valent, late metal complexes, the primary alkyl complex is thermodynamically more stable than the secondary alkyl complex, and the aryl complexes are more stable than the alkyl complexes. Activation of olefins at the ally-lie position occurs more slowly than reaction at the vinyl position, but when it does occur, the reaction generates a stable Ti -allyl complex. 

Related C-H activations by 1,2-additions across metal-ligand bonds have also been reported with unusual group 4 alkylidyne complexes. - As shown in Equation 6.58, a titanium(IV) trimethylsilylmethyl benzylidene complex eliminates tetramethylsilane to generate a Ti(IV) alkylidyne complex. This complex then reacts with benzene to add the arene C-H bond across the metal-alkylidyne unit to form an aryl benzylidene complex. 

The condensation of metallic titanium with benzene gave the first sandwich arene compound of titanium(O), [Ti(PhH)2]. This is a diamagnetic red-orange complex. 

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