Redox Isomerization of Allylic Alcohols Catalyzed by Osmium and Ruthenium Complexes Containing a Cyclopentadienyl Ligand with a Pendant Amine or Phosphoramidite Group: X-ray Structure of an η³-1-Hydroxyallyl-Metal-Hydride Intermediate

Abstract

Complexes [MCl 2 (η 6 -p-cymene)] 2 (M = Os (1a), Ru (1b)) react with Li(C 5 H 4 CH 2 CH 2 NHMe) (LiCp N ) and KPF 6 to give the sandwich derivatives [M(η 5 -Cp N )(η 6 -p-cymene)]PF 6 (M = Os (2a), Ru (2b)). Treatment of 2a and 2b with (2,2 0 -biphenol)PCl leads to [M(η 5 -Cp P )(η 6 -p-cymene)]PF 6 (M = Os (3a), Ru (3b); Cp P = C 5 H 4 CH 2 CH 2 N(Me)P(2,2 0 -biphenol)). The photolysis of 2a, 2b, 3a, and 3b in acetonitrile produces the release of the p-cymene group and the coordination of the cyclopentadienyl pendant substituent to the metal center to afford [M(η 5 -C 5 ,κ-N-Cp N )(CH 3 CN) 2 ]PF 6 (M = Os (4a), Ru (4b)) and [M(η 5 -C 5 ,κ-P-Cp P )(CH 3 CN) 2 ]PF 6 (M = Os (5a), Ru (5b)). Complex 4a, which has been characterized by X-ray diffraction analysis, is a more efficient catalyst precursor than 4b for the redox isomerization of primary allylic alcohols, while the latter is more efficient than the former for the redox isomerization of secondary allylic alcohols. From the catalytic solutions containing 4a and 2-methyl-2-propen-1-ol, the η 3 -1-hydroxyallyl complex [OsH(η 5 -C 5 ,κ-N-Cp N ){η 3 -CH 2 C(CH 3 )CH-OH}]PF 6 (6) has been crystallized and characterized by spectroscopic methods and X-ray diffraction analysis. The structure shows a N-H 3 3 3 O hydrogen bond (2.22 A ˚) between the NH-hydrogen atom of the coordinated pendant amine group and the oxygen atom of the hydroxy substituent of the allyl ligand.

Half‐Sandwich Guanidinate–Osmium(II) Complexes: Synthesis and Application in the Selective Dehydration of Aldoximes

“…In particular, given the good results obtained with the ruthenium-guanidinate derivatives A and B (Figure 1) in the redox isomerization of allylic alcohols, we ini- tially focused on this catalytic transformation. It should be mentioned at this point that, although the osmium complexes have been much less studied than the ruthenium complexes, [10] the recent work of Esteruelas [11] and Baratta [12] and their co-workers has demonstrated that efficient catalysts can also be obtained from this metal (TOF up to 460 h -1 ). However, the catalytic activities observed for 3a-m in the isomerization of the model substrate 1-octen-3-ol were very disappointing.…”

General, Simple, and Chemoselective Catalysts for the Isomerization of Allylic Alcohols: The Importance of the Halide Ligand

“…[21] Moreover, incorporationo fd euterium at Ca cannoto ccur through mechanism C ([D 1 ]2p in Scheme 4). In addition, the excellent yields for both primary and sec-alcohols contrast with those reported in isomerizations through mechanism C. [19] The crossover experiments also rule out mechanism A,s ince it necessarily involvesn on-bound[ IrÀH] species, which would result in deu-Scheme1.Isomerization of opiates.…”

“…An alternative mechanism C,v ia p-allyl intermediates, was also considered. [19] Isotopic labeling investigations were performed with sec-alcohols 1l and 1p and with primary alcohols 1x and 1z.I somerization of [D 1 ]1l afforded [D 1 ]2l,w ith deuterium exclusively at Cb (Scheme 4). In contrast, deuterium was found at both Ca and Cb in [D 1 ]2p.F or primary [D 2 ]1z,d euterium was not detected at Ca and one deuterium was exclusively transferred to Cb (see the Supporting Information).…”

Redoxkontrolle eines dendritischen Ferrocenyl‐basierten Homogenkatalysators

“…Da Übergangsmetalle die Verschiebung von C- C-Doppelbindungen katalysieren, kann der Allylalkohol in ein Enol überführt werden, das dann über Keto-Enol-Tautomerie in die entsprechende Carbonylverbindung übergeht. [11] Neben Rhodiumkomplexen finden besonders Rutheniumkomplexe Anwendung in der atomçkonomischen Redoxisomerisierung. [12] Die Reaktion wurde bereits sowohl in vielen großtechnischen Mehrstufensynthesen [13] als auch in der Dendrimerkatalyse [14] erfolgreich angewendet.…”