Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone |
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| Authors: | Serenella Medici Marcella Gagliardo Scott&#x;B Williams Preston&#x;A Chase Serafino Gladiali Martin Lutz Anthony&#x;L Spek Gerard&#x;P&#x;M van&#x;Klink Gerard van&#x;Koten |
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| Institution: | 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 |
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| Abstract: | Achiral P‐donor pincer‐aryl ruthenium complexes (RuCl(PCP)(PPh3)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of 1,3‐phenylenebis(methylene)]bisdiisopropylphosphine] ( 2c ) or 1,3‐phenylenebis(methylene)]bisdiphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex RuCl{2,6‐(Me2NCH2)2C6H3}(PPh3)], ( 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*)(PPh3)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐1,3‐phenylenebis(methylene)]bis(alkyl)(phenyl)phosphines] 2a , b (alkyl=iPr or tBu, P*CHP*) and the complex RuCl{2,6‐(Me2NCH2)2C6H3}(PPh3)], ( 3 ; Scheme 3). The crystal structures of achiral RuCl(equation/tex2gif-sup-3.gifPCP)(PPh3)] 4c and of chiral (S,S)‐RuCl(equation/tex2gif-sup-6.gifPCP)(PPh3)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral RuCl(PCP)(PPh3)] complexes and chiral RuCl(P*CP*)(PPh3)] 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. |
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