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The reactions of the bis(η5-cyclopentadienyl)methylzirconium cation (1) with ketones and aldehydes in the gas phase have been studied by Fourier transform ion cyclotron resonance mass spectrometry. Reactions of 1 with a majority of the ketones studied resulted in consecutive addition of one and two substrate molecules and/or elimination of alkanes. Deuterium-labeled substrates and methylzirconocene were used to investigate the mechanistic details. On the basis of DFT calculations, the key products of the elimination reaction(s) were identified as η3-enolate complexes formed via an insertion/elimination mechanism. Similar product ion structures are postulated for the reaction of 1 with aldehydes in cases where these complexes are either the only or the major reaction product. A multiple-step mechanism is proposed, which involves migratory insertion of an aldehyde molecule into the methylzirconocene cation, followed by β-H elimination, and, via a six-membered cyclic transition state, formation of the result...

Free energies of ionization (ΔGi°) in the gas phase have been determined for the seven fluorine-substituted ruthenocenes with formulas (η5-C5Me5)(η5-C5H5-nFn)Ru (n = 1−5) and (η5-C5H5)(η5-C5F5)Ru. In (η5-C5Me5)(η5-C5H5-n Fn)Ru (n = 1−5), each additional fluorine was found to increase the ionization free energy by 3.7 ± 0.5 kcal mol-1, and the ΔGi° difference between the two possible isomers for n = 2 and n = 3 was found to be ≤ 1 kcal mol-1. Therefore, the intrinsic effect of each fluorine substituent on ionization energy is approximately additive.