MCl₂(ampy)(dppf) (M = Ru, Os): Multitasking Catalysts for Carbonyl Compound/Alcohol Interconversion Reactions

Abstract

The easily accessible complexes [MCl2(dppf)(ampy)] (M = Ru (cis-1), Os (trans-2); dppf = 1,1′-bis(diphenylphosphino)ferrocene; ampy = 2-aminomethylpyridine) in the presence of base (NaOiPr, KOtBu) are efficient catalysts for several reactions involving carbonyl compounds and alcohols. The derivatives 1 and 2 catalyze the selective transfer hydrogenation of aldehydes and ketones to alcohols with 2-propanol using 0.1–0.005 mol % of catalyst at 82 °C with TOF values up to 3.0 × 105 h–1. These compounds (0.1–0.02 mol %) promote the hydrogenation of aldehydes and ketones in EtOH or a MeOH/EtOH mixture at 30–90 °C (5 atm of H2) and the acceptorless dehydrogenation of alcohols to ketones in tBuOH at 130–145 °C (0.4 mol %). Complexes 1 and 2 (0.5 mol %) catalyze the racemization of chiral alcohols at 70 °C in 2-propanol and the isomerization of allylic alcohols to ketones in tBuOH at 70–120 °C (1 mol %). In addition, 1 and 2 (0.5 mol %) promote the α alkylation of α-tetralone with primary alcohols (EtOH, nPrOH, and nBuOH) at 120 °C in a tBuOH/toluene mixture (1/2 v/v). Complex 2 is easily obtained in 93% yield from [OsCl2(PPh3)3], dppf, and ampy in toluene.

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.…”

Ruthenium and osmium complexes containing 2-(aminomethyl)pyridine (Ampy)-based ligands in catalysis

“…We recently prepared the derivative cis-RuCl 2 (dppf)(ampy) 18 (Scheme 10) which was found to catalyze a variety of organic transformations involving ketones and alcohols [18]. Treatment of RuCl 2 (PPh 3 ) 3 with 1,1-bis(diphenylphosphino)ferrocene (dppf) and Ampy in toluene at 50 • C gave in 92% yield the derivative 17 with trans-configuration, which by heating in toluene at reflux temperature for 24 h afforded the thermodynamically more stable cis-isomer 18 (Scheme 10) [19].…”

“…Treatment of RuCl 2 (PPh 3 ) 3 with 1,1-bis(diphenylphosphino)ferrocene (dppf) and Ampy in toluene at 50 • C gave in 92% yield the derivative 17 with trans-configuration, which by heating in toluene at reflux temperature for 24 h afforded the thermodynamically more stable cis-isomer 18 (Scheme 10) [19]. The Ru-complex 18 catalyzed efficiently the selective TH of aldehydes and ketones to alcohols [18]. By using a catalyst loading of 0.1-0.0005 mol% and in the presence of NaOi-Pr (2 mol%) in 2-propanol, quantitative conversion of several carbonyl compounds was achieved at 82 • C in a short time, affording TOF up to 1.0 × 10 5 h −1 (Scheme 11).…”

“…Scheme 11. TH of aldehydes or ketones catalyzed by the Ru-complex 18 [18]. (23) and cis-RuCl 2 [(S,R)-Josiphos*][(R)-19c] 24 were also prepared using the bulkier (S,R)-Josiphos* in place of (R,S)-Josiphos.…”

“…We recently carried out a study to compare the ability of the Oscomplex trans-OsCl 2 (dppf)(Ampy) 79 (Scheme 44) and the related Ru-complex cis-RuCl 2 (dppf)(Ampy) (18) (Scheme 10) to catalyze a variety of organic transformations involving ketones and alcohols [18]. Treatment of OsCl 2 (PPh 3 ) 3 with 1 equiv.…”