N–H Group Transfer and Oxidative Addition Chemistry Promoted by Isolable Bis(cyclopentadienyl)titanium Sandwich Complexes

Abstract

Addition of propylenimine (2‐methylaziridine) to the bis(cyclopentadienyl)titanium sandwich complexes, (η5‐C5Me4R)2Ti (R = iPr, SiMe3), resulted in rapid [NH] group transfer followed by C–H activation of a cyclopentadienyl methyl group to yield the corresponding cyclometalated titanocene amido compounds. Exposure of these molecules to 4 atm of H2 at 55 °C resulted in hydrogenolysis of the metal–carbon bond to form the titanium amido hydride compounds, (η5‐C5Me4R)2Ti(NH2)H. Deuteriolysis with DCl gas confirmed exclusive cyclometalation from the positions adjacent to the isopropyl and trimethylsilyl substituent. Oxidative addition of the N–H bonds of amines has also been observed. Addition of NH3 to either (η5‐C5Me4SiMe3)2Ti or (η5‐C5Me4iPr)2Ti yielded the corresponding titanocene amido hydrides along with the titanocene(III) amides, (η5‐C5Me4R)2TiNH2, arising from formal deprotonation by unreacted sandwich from the putativetitanocene ammonia complex.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Preparation and Reactions of Base-Free Bis(1,3-di-tert-butylcyclopentadienyl)titanium, Cp′2Ti, and Related Compounds

“…Cooling to −55 °C results in the disappearance of the broad resonance, the four sharp features due to Cp′ 2 TiH 2 appear at δ 1.13 (CMe 3 ), and the A 2 B ring resonances appear as a doublet at δ 5.10 ( J = 3 Hz), a triplet at δ 8.01 ( J = 3 Hz), and a singlet at δ 2.62 due to Ti−H increase in intensity. The chemical shift for the Ti−H resonance is intermediate between δ 0.28 in (C 5 Me 5 )TiH 2 and δ 3.25 in (C 5 Me 4 iPr) 2 TiH 2 . Returning the sample to 30 °C yields the original spectrum.…”

Einfacher Zugang zu modifizierbarem Schwartz‐Reagens – Oxidative Addition von amidischen N‐H‐Bindungen an reduzierte Zirconocenkomplexe

“…B. N‐H‐Bindungen, sind lediglich einige wenige Beispiele mit Metallen der 4. Gruppe beschrieben worden 9. Aus der oxidativen Addition einer N‐H‐Bindung eines Aminoborans resultierte dabei der einzige strukturell charakterisierte Komplex auf diesem Themengebiet: ein Zirconocen‐Amidoborankomplex 10.…”

Group transfer reactions of d0 transition metal complexes: redox-active ligands provide a mechanism for expanded reactivity

“…5). 65 Titanocene-dinitrogen adducts can serve as masked sources of titanium(II) for stoichiometric group transfer reactions (Fig. 6).…”

“…5 and contrasting to the reactivity of 17, the reaction of the mono-substituted trimethylsilyl derivative 12-SiMe 3 with N 3 SiMe 3 does not generate a stable imido species; C-H activation of one of the methyl groups of the Cp ligand occurs, giving rise to a cyclometalated titanium amido complex. 65 Atom-transfer reactivity of sulfur ligands has also been investigated for titanium systems. In 1999, the research groups of Bergman and Andersen reported the preparation of titanium-sulfido and -disulfido complexes and their reactivity with phosphines and dihydrogen.…”