Decamethyltitanocene hydride intermediates in the hydrogenation of the corresponding titanocene-(eta(2)-ethene) or (eta(2)-alkyne) complexes and the effects of bulkier auxiliary ligands

0482774 - ÚFCH JH 2018 RIV GB eng J - Článek v odborném periodiku
Pinkas, Jiří - Gyepes, R. - Císařová, I. - Kubišta, Jiří - Horáček, Michal - Mach, Karel
Decamethyltitanocene hydride intermediates in the hydrogenation of the corresponding titanocene-(eta(2)-ethene) or (eta(2)-alkyne) complexes and the effects of bulkier auxiliary ligands.
Dalton Transactions. Roč. 46, č. 25 (2017), s. 8229-8244. ISSN 1477-9226. E-ISSN 1477-9234
Grant CEP: GA ČR(CZ) GAP207/12/2368; GA ČR GP203/09/P276
Institucionální podpora: RVO:61388955
Klíčová slova: spin-resonance spectra * cyclopentadienyl ligands * dinitrogen complexes * sandwich complexes * carbon-monoxide
Obor OECD: Physical chemistry
Impakt faktor: 4.099, rok: 2017

H-1 NMR studies of reactions of titanocene [Cp*Ti-2] (Cp*=eta(5)-C5Me5) and its derivatives [Cp*(eta(5):eta(1)-C5Me4CH2)TiMe] and [Cp*Ti-2(eta(2)-CH2=CH2)] with excess dihydrogen at room temperature and pressures lower than 1 bar revealed the formation of dihydride [Cp*2TiH2] (1) and the concurrent liberation of either methane or ethane, depending on the organometallic reactant. The subsequent slow decay of 1 yielding [Cp*2TiH] (2) was mediated by titanocene formed in situ and controlled by hydrogen pressure. The crystalline products obtained by evaporating a hexane solution of fresh [Cp*Ti-2] in the presence of hydrogen contained crystals having either two independent molecules of 1 in the asymmetric part of the unit cell or cocrystals consisting of 1 and [Cp*Ti-2] in a 2 : 1 ratio. Hydrogenation of alkyne complexes [Cp*Ti-2(eta(2)-(RC)-C-1 CR2)] (R-1 = R-2 = Me or Et) performed at room temperature afforded alkanes (RCH2CH2R2)-C-1, and after removing hydrogen, 2 was formed in quantitative yields. For alkyne complexes containing bulkier substituent(s) R-1 = Me or Ph, R-2 = SiMe3, and R-1 = R-2 = Ph or SiMe3, successful hydrogenation required the application of increased temperatures (70-80 degrees C) and prolonged reaction times, in particular for bis(trimethylsilyl)acetylene. Under these conditions, no transient 1 was detected during the formation of 2. The bulkier auxiliary ligands eta(5)-(CMe4Bu)-Me-5-Bu-t and eta(5)-C5Me4SiMe3 did not hinder the addition of dihydrogen to the corresponding titanocenes [(eta(5)-(C5Me4Bu)-Bu-t)(2)Ti] and [(eta(5)-C5Me4SiMe3) Ti-2] yielding [(eta(5)-(C5Me4Bu)-Bu-t)(2)TiH2] (3) and [(eta(5)-C5Me4SiMe3)(2)TiH2] (4), respectively. In contrast to 1, the dihydride 4 did not decay with the formation of titanocene monohydride, but dissociated to titanocene upon dihydrogen removal...
Trvalý link: http://hdl.handle.net/11104/0278150