Electrophilic Cationic Ethylidene Complexes of Ir(III). Comparative α-Migratory Insertion Processes into Hydride and Ethyl Groups

A Series of Vinylidene‐, Vinyl‐, Carbene‐ and Carbyneruthenium(II) Complexes with [Ru(PCy3)2] and [Ru(PiPr3)2] as Molecular Building Blocks

“…Since both the 1 H and 13 C NMR spectra of 32 show a single set of signals for the protons and carbon atoms of the CH 3 CN ligands and since the molecule is diamagnetic, instead of a trigonal-bipyramidal structure a fluxional square-pyramidal geometry is more likely. With regard to the mechanism of the conversion of 31 to 32, we assume, in agreement with results recently reported by Carmona [19] and Gimeno [20] and their co-workers, that the carbene ligand CHCH 2 Ph rearranges by an intramolecular 1,2-H shift to styrene. As the bonding of an olefin to a twofold positively charged metal center is, in general, considered to be weak, styrene is eliminated from the intermediate and the five-coordinate complex 32 is formed.…”

Generation and reactivity of sterically hindered iridium carbenes. Competitive α- vs. β-hydrogen elimination in iridium(iii) alkyls

“…Acetonitrile, a better donor toward cationic Ir() centres, yields the expected alkyl product. 30 We have also investigated the migratory insertion chemistry of iridium alkylidenes resulting from protonation of the vinyl complexes Tp Me2 Ir(CH᎐ ᎐ CH 2 )(X)(PMe 3 ), 33 for X = H, C 2 H 5 . As summarized in Scheme 12, the room-temperature protonation of Tp Me2 Ir(CH᎐ ᎐ CH 2 )(H)(PMe 3 ) with [H(OEt 2 ) 2 ][BArЈ 4 ] gives a cationic hydride olefin compound, alternatively accessible from the direct reaction of Tp Me2 Ir(C 2 H 4 )(PMe 3 ) with the acid.…”

Synthetic, Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers

“…These calculations suggest that a suitable choice of the metal complex may allow accomplishment of this goal, a hypothesis that also finds some experimental support. Thus, although the conversion of a metal alkylidene into the corresponding metal alkene is a general reaction of electrophilic alkylidenes,1b, 5b–e and the opposite transformation, namely, the alkene‐to‐alkylidene rearrangement is a rarely observed process,6 in recent years new examples of equilibria between metal–alkene and –alkylidene isomers have been found, which add to the very few already known 7. Gusev and co‐workers have shown that olefin and carbene isomers form in the reactions of [{RuCl 2 ( p ‐cymene)} 2 ] with bulky pincer ligands, as a result of CH bond activation and α‐ and β‐H eliminations from the pincer‐ligand framework 8a.…”