Niobium complexes arene

Using an electron-gun source, tungsten atoms were reacted with benzene, toluene, or mesitylene at 77 K, to form the expected (arene)2W complex (42) in a yield of 30%, compared with the —2% yield from the previously published, bis(benzene)W synthesis (32). These arene complexes are reversibly protonated, to give the appropriate [(T7-arene)2WH] species. By using the same technique, the analogous, niobium complexes were isolated (43). 

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,... 

The cocondensation of Nb atoms with toluene has yielded bis( -toluene)niobium, which serves as a useful intermediate for the preparation of a wide series of mono- and bis-arene derivatives. While Ti, V, Nb, Cr, Mo, and W form (Ar)2M sandwich complexes, Mn, Tc, and Re appear less promising, because Mn-arene complexes have already been shown to be unstable, Tc is radioactive, and Re remains to be investigated. As already mentioned, Ti forms fairly labile bis(arene)Ti complexes. The unstable 16-electron sandwich complexes from elements of group 4 can be stabilized with phosphine ancillary ligands, yielding bis-arene derivatives as in Table 6. 

Niobium carbide is used as a protective coating for niobium metal.[10] It can be prepared by the reaction of elemental niobium metal with methane or by reacting NbCIs with CCI4 and H2. It also has been obtained from the arene complex Nb(CH3-C(,H,[Pg.385]

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... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

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... 

The first tris(arene) niobium complex, [Nb(l-4-jj -anthracene)3], prepared by the Na or K anthracene reduction of NbCl4(THF)2, undergoes facile anthracene displacement in the presence of CO to afford [K(18-crown-6)(THF)2][Nb(CO)6]. Reduction of TaCls by sodium naphthalene provides [Na(THF)][Ta(jj -naphthalene)3], the first homoleptic naphthalene complex of a third row transition metal. This complex reacts with CO and anthracene to give [Ta(CO)e] and [Ta(l-4-jj -anthracene)3], respectively. The latter product reacts with cyclooctatetraene (COT) to give [Ta(COT)3]-.==i= ... 

In other systems, N—cleavage gives bis(/i-nitrido)dimetal diamond cores as the products of N2 cleavage. A reduced niobium complex of calix[4]arene reduces N2 in the presence of sodium metal, and a number of intermediates can be isolated. A related tridentate aryloxide ligand also splits N2 to give a diamond core with lithium ions bound to the nitrides. A vanadium diamidoamine complex reacts with N2 to give a product with a similar core structure, which may be further reduced by potassium graphite to a compound with one unpaired electron. This... 

In parallel with the catalytic reactivity of early-transition-metal-alkoxo complexes, the catalytic reactivity of lanthanide-alkoxo and -phenoxo complexes has been developed. The homogenous hydrogenation of a variety of arene substrates can be catalyzed by niobium... 

There is some material of relevance in a review on niobium and tantalum coordination chemistry. 1 The thermal reactions of the ions M" " (M = Ta, Nb, NbO, NbN) with arenes in the gas phase results in cleavage of the arenes to form metallacyclopentadiene ion complexes via retro-alkyne cyclotrimerization mechanisms. ... 

Vanadium, Niobium, Tantalum and Zirconium Mixed sandwich complexes of vanadium containing arene rings have been described in two reports. The bisindenylbisvanadium complex (41) has been structurally characterised and contains a metal-metal bond length of 2.35A. The complex is formed in the reductive... 

Fryzuk MD, Kozak CM, Bowdridge MR et al (2002) Cyclohexadienyl niobium complexes and arene hydrogenation catalysis. Organometallics 21 5047-5054... 

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