Room Temperature Dehydrogenation of Ethane, Propane, Linear Alkanes C4–C8, and Some Cyclic Alkanes by Titanium–Carbon Multiple Bonds

摘要: The transient titanium neopentylidyne, [(PNP)Ti≡CtBu] (A; PNP–≡N[2-PiPr2-4-methylphenyl]2–), dehydrogenates ethane to ethylene at room temperature over 24 h, by sequential 1,2-CH bond addition and β-hydrogen abstraction afford [(PNP)Ti(η2-H2C═CH2)(CH2tBu)] (1). Intermediate A can also dehydrogenate propane propene, albeit not cleanly, as well linear volatile alkanes C4–C6 form isolable α-olefin complexes of the type, [(PNP)Ti(η2-H2C═CHR)(CH2tBu)] (R = CH3 (2), CH2CH3 (3), nPr (4), nBu (5)). Complexes 1–5 be independently prepared from [(PNP)Ti═CHtBu(OTf)] corresponding alkylating reagents, LiCH2CHR H, CH3(unstable), CH2CH3, nPr, nBu). Olefin 1 3–5 have all been characterized a diverse array multinuclear NMR spectroscopic experiments including 1H–31P HOESY, in case adducts 2–5, formation mixtures two diastereomers (each with their pair enantiomers) has unequivocally established. latter b...