Concerning the Status of Bis(cyclopentadienyl)titanium

A Non-Metallocene Hydride of Titanium(III)

“…The characterization and reactivity of titanium(III) hydride complexes has been a recurring theme of research over the past 30 years, in part due to the high reactivity of such species in a variety of catalytic processes such as alkene hydrogenation and isomerization, imine hydrosilylation, , and silane polymerization, , and also because of the uncertainty in describing “titanocene”; − only in 1992 was the original formulation of titanocene as the bridging fulvalene hydride confirmed by X-ray crystallography . To date, however, all of the known titanium(III) hydridic species that have been reported have been based around cyclopentadienyl-derived ligands; employing C 5 H 5 and other nonbulky cyclopentadienyl ligands causes dimeric species to be formed, ,,, whereas the more sterically crowded environments dictated by C 5 Me 5 or alternatively C 5 Me 4 Ph result in the formation of monomeric Ti(III) hydrides. − Considering the recent upsurge in the chemistry of Group 4 complexes that incorporate noncyclopentadienyl ligands − and the high reactivity of Ti(IV) and Zr(IV) cations incorporating multidentate diamides toward processes such as alkene polymerization, − it seemed appropriate to develop the Ti(III) chemistry of the polydentate diamidoamine ligand, [(Me 3 SiNCH 2 CH 2 ) 2 NSiMe 3 ] 2- [NN 2 ].…”

Bis(η5-cyclopentadienyl)titanium(II) in the gas phase:

“…However, the formation of 6 in solution is known to take place at mild conditions. For example, the reduction of the titanocene dichloride, Cp 2 TiCl 2 , with sodium naphthalene in tetrahydrofurane yields 6 at 25°C [39]. Also the titanocene-BTMSA complex dissolved in xylene decomposes at 100°C to give 6 in a high yield [20].…”

The Extraordinary Cocatalytic Action of Polymethylaluminoxane (MAO) in the Polymerization of Terminal Olefins by Metallocenes: Chemical Change in the Group 4 Metallocene Dimethyl Derivatives Induced by MAO

“…The organic product was in each case exclusively (E,E)-1,4-dideuterio-1,2,3,4-tetraphenyl-1,3-butadiene (21a). The latter dideuteriated derivative presupposes the presence of the titanocycle 34, in the case of Cp 2 TiE 2 , which could have arisen from the generation of titanocene (32), the rapid addition of 32 to alkyne 19 to yield 33 and the further insertion of 19 into 33 (Scheme 2). [31] However, from what else is known about the stability of titanocene (32), such a divalent carbene-like inScheme 2.…”

“…For example, the reduction of Cp 2 TiCl 2 by sodium [32] or by sodium naphthalenide [33] or the reduction of Cp 2 Ti(CH 3 ) 2 by dihydrogen [34] at 20°C, each of which reactions was intended to generate 32, led instead to the isomeric titanocene(iii) hydride dimer 35 [Equation (13)]. [35] As corroborating experiments for the model reaction pathway proposed in Scheme 2 for titanocene dimethyl (24), the following reactions were carried out: 1) The reaction between 24 and 1 equiv.…”

“…Continuing support during the 1990s stemmed from the Solvay Corporation, Brussels, Belgium. Currently we have enjoyed the generous support of the Boulder Scientific Company and a stimulating scientific exchange with its president, Dr. John M. Birmingham, concerning the generation of titanocene (32).…”