Novel P-Stereogenic PCP Pincer-Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone
✍ Scribed by Serenella Medici; Marcella Gagliardo; Scott B. Williams; Preston A. Chase; Serafino Gladiali; Martin Lutz; Anthony L. Spek; Gerard P. M. van Klink; Gerard van Koten
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- German
- Weight
- 137 KB
- Volume
- 88
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh~3~)]) 4c,d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] (2c) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] (2d) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me~2~NCH~2~)~2~C~6~H~3~}(PPh~3~)], (3; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh~3~)] 4a,b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a,b (alkyl=^i^Pr or ^t^Bu, P*CHP*) and the complex [RuCl{2,6‐(Me~2~NCH~2~)~2~C~6~H~3~}(PPh~3~)], (3; Scheme 3). The crystal structures of achiral [RuCl(PCP)(PPh~3~)] 4c and of chiral (S,S)‐[RuCl(PCP)(PPh~3~)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh~3~)] complexes and chiral [RuCl(P*CP*)(PPh~3~)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.