Frontier Elements: Connections with f-Elements

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Bis(tetramethylcyclopentadienyl)titanium Chemistry. Molecular Structures of [(C5HMe4)(μ-η1:η5-C5Me4)Ti]2and [(C5HMe4)2Ti]2N2

“…The dihydride 9 can lose dihydrogen in a subsequent equilibrium reaction to form the titanocene 10 (eq 4). Such equilibria have been proposed by Bercaw to explain the decomposition of (C 5 Me 5 ) 2 TiH 2 29b …”

“…The brown product showed no reaction with 1,3-butadiene; therefore, it cannot be hydride 5 32a. In analogy with the formation of (C 5 Me 5 ) 2 Ti upon degassing [(C 5 Me 5 ) 2 Ti] 2 N 2 ,29b this compound was tentatively identified as titanocene (C 5 HMe 4 ) 2 Ti ( 10 ). Admission of H 2 to solutions of 10 resulted in formation of hydride 5 .…”

“…(C 5 HMe 4 ) 2 TiH (5) and Reaction with N 2 . Hydrogenolysis of (C 5 Me 5 ) 2 TiR produces a monomeric titanium(III) hydride, (C 5 Me 5 ) 2 TiH. 27a, Recently the molecular structure of the first monomeric titanocene(III) hydride (C 5 PhMe 4 ) 2 TiH has been determined . These titanocene(III) hydrides are intriguing compounds, because of their key role in the “titanocene enigma” and their activity as catalysts for many organic reactions …”

(Alkyl)(monocyclopentadienyl)niobium and ‐tantalum Complexes in Insertion Processes

“…The CϭO stretching vibration in η 2 -acyl compounds ranges from 1453 to 1625 cm Ϫ1 and the lowest stretching frequencies occur for η 2 -acyl complexes containing high-valent metal atoms (as we also found). This has been attributed to the participation of a ''carbene-like'' resonance form [37] or to the contribution of a ''carbenium-ion-like'' acceptor orbital on the undistorted η 2 -acyl structure. [38] The η 2 -acyl [39] and η 2 -carbamoyl [40] (61) carbon resonances appear at δ ഠ 317 and 228 ppm, respectively, in the typical ranges for both types of complexes.…”

Carbon−Hydrogen Bond Activation of Aromatic Imines by (Cp*2SmH)2

“…In particular, we have examined the hydrogenation of imines and have recently reported the first early transition metal catalyst for the asymmetric reduction of imines . As an extension of this research, we have initiated an investigation of the reactivity of imine substrates with lanthanide complexes, given the similarity of the chemistry exhibited by Ti(III) and group 3 (Sc, Y, Ln) transition metal complexes . Herein, we report that (Cp* 2 SmH) 2 reacts with aromatic imines via ortho-metalation, rather than the anticipated 1,2-insertion of the imine into the SmH bond to form an amide complex (eq 1).…”