Efficient Synthesis of Ruthenium(II) η⁵-Dienyl Compounds Starting from Di-μ-chlorodichloro- bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(IV). Versatile Precursors for Enantioselective Hydrogenation Catalysts

Abstract

The dimeric complex di-μ-chlorodichloro-bis[(1−3η:6−8η)-2,7-dimethyloctadienediyl]diruthenium(IV) in the presence of base reacts with cyclic and acyclic dienes to the corresponding bis(η5-dienyl)ruthenium(II) compounds. Crystalline yellow compounds have been isolated in high yields for dienyl = cyclopentadienyl, pentamethylpentadienyl, cycloheptadienyl, indenyl, dimethylpentadienyl, and trimethylpentadienyl. The analogous reaction of cyclohexa-1,3-diene gives the ruthenium(0) compound (η6-benzene)(η4-cyclohexa-1,3-diene)ruthenium. The “open” bis(dienyl)ruthenium complexes can be converted into half-sandwich complexes through protonation and subsequent ligand exchange. These compounds can be used as precursors for efficient enantioselective hydrogenation catalysts.

One‐Step Preparation of [RuCp*(η6‐arene)]+ Sandwich Complexes

“…[21] The isolated yields obtained by our one-step procedure are similar to the more complicated protocols and vary from 35% (5, 10) to 80% (8), relative to ruthenium (Table 1) addition of arene or Cp*H is indicated by the rapid colour change of the ethanolic solution from cherry red to dark blue. The excessive Zn may also act as a quencher of HCl after the subsequent reduction of the η 6 -arene, Cp*H, and NaPF 6 , as suggested by Salzer et al [22] The [RuCp*] ϩ sandwich complexes of the electron-rich arenes 3Ϫ8 (entries 1Ϫ6) were prepared in order to establish the synthetic route. Compounds 3, 6, 8, 10, and 12 have been prepared before by other protocols.…”

Key Enantioselective Hydrogenation Steps in the Syntheses of Two Renin Inhibitors: Missing Origin and Incorrect Description

“…7 See Salzer et al for a related approach. 8 Previous work leading up to ours and previous reports on presumed dications and one authentic dication [Ru(P−P)(sol) n ] 2+ are fully discussed in our papers. Two groups (Bruneau et al, 9 and Zhang et al 10 ) later used the recipe involving [Ru(COD)(methallyl) 2 ] and 2 equiv HBF 4 •Et 2 O and quoted us but did not identify the precatalysts and catalysts they had in hand.…”

Discovery and Comparison of Homogeneous Catalysts in a Standardized HOT‐CAT Screen with Microwave‐Heating and qNMR Analysis: Exploring Catalytic Hydration of Alkynes

“…Notable activity in the order of 5–10 mol% was found for RuO 2 −ISIPHOS−CSA (8 % K , 4 % A ; cf. Scheme ), RuCl 2 (COD) (9 % K ), (arene)RuCl 2 (8–15 % K ), [(η 3 ,η 3 )‐(2,7‐dimethyloctadienediyl)RuCl 2 ] (13 % K , 5 % A ) and Cp*RuCl 2 −ISIPHOS−2 AgOTf (7 % A ); the latter example is notable since Cp*Ru‐fragments had shown a lack of activity, e. g. in the complex [Cp*RuCl( t BuPyPHOS) 2 ] . These ruthenium catalysts are not very chemoselective, with ≤20 mol% alkyne hydration products at ≥90 % conversion.…”