Hydrogenation of titanocene and zirconocene bis(trimethylsilyl)acetylene complexes

0492081 - ÚFCH JH 2019 RIV GB eng J - Journal Article
Pinkas, Jiří - Gyepes, Robert - Císařová, I. - Kubišta, Jiří - Horáček, Michal - Žilková, Naděžda - Mach, Karel
Hydrogenation of titanocene and zirconocene bis(trimethylsilyl)acetylene complexes.
Dalton Transactions. Roč. 47, č. 27 (2018), s. 8921-8932. ISSN 1477-9226. E-ISSN 1477-9234
R&D Projects: GA ČR(CZ) GA17-13778S
Institutional support: RVO:61388955
Keywords : X-Ray structure * carbon-monoxide * acetylene complexes
OECD category: Physical chemistry
Impact factor: 4.052, year: 2018

Reactions following the addition of dihydrogen under maximum atmospheric pressure to bis(trimethylsilyl) acetylene (BTMSA) complexes of titanocenes, [(η5-C5H5−nMen)2Ti(η2-BTMSA)] (n = 0, 1, 3, and 4) (1A–1D), and zirconocenes, [(η5-C5H5−nMen)2Zr(η2-BTMSA)] (n = 2–5) (4A–4D), proceeded in diverse ways
and, depending on the metal, afforded different products. The former complexes lost, in all cases, their BTMSA ligand via its hydrogenation to bis-1,2-(trimethylsilyl)ethane when reacted at 80 °C for a prolonged reaction time. For n = 0, 1, and 3, the titanocene species formed in situ dimerised via the formation of fulvalene ligands and two bridging hydride ligands, giving known green dimeric titanocenes (2A–2C). For n = 4, a titanocene hydride [(η5-C5HMe4)2TiH] (2D) was formed, similarly to the known [(η5-C5Me5)2TiH] (2E) for n = 5. However, in contrast to this example, 2D in the absence of dihydrogen spontaneously dehydrogenated to the known Ti(III)–Ti(III) dehydro-dimer [{Ti(η5-C5HMe4)(μ-η1:η5-C5Me4)}2] (3B). This complex has now been fully characterised via spectroscopic methods, and was shown through EPR spectroscopy to attain an intramolecular electronic triplet state. The zirconocene-BTMSA complexes 4A–4D reacted uniformly with one hydrogen molecule to give Zr(IV) zirconocene hydride alkenyls, [(η5-C5H5−nMen)2ZrH{C(SiMe3)vCH(SiMe3)}] (n = 2–5) (5A–5D). These were identified through their 1H and 13C NMR spectra, which show features typical of an agostically bonded proton, vCH(SiMe3). Compounds 5A–5D formed equilibria with the BTMSA complexes 4A–4D depending on hydrogen pressure and
temperature.
Permanent Link: http://hdl.handle.net/11104/0285645