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Formation of Trinuclear Rhodium‐Hydride Complexes [{Rh(PP*)H} 3 ‐ (μ 2 ‐H) 3 (μ 3 ‐H)][anion] 2 —During Asymmetric Hydrogenation?
Author(s) -
Kohrt C.,
Baumann W.,
Spannenberg A.,
Drexler H.J.,
Gridnev I. D.,
Heller D.
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201204336
Subject(s) - rhodium , hydride , chemistry , medicinal chemistry , catalysis , asymmetric hydrogenation , ion , stereochemistry , hydrogen , organic chemistry , enantioselective synthesis
Recently described and fully characterized trinuclear rhodium‐hydride complexes [{Rh(PP*)H} 3 (μ 2 ‐H) 3 (μ 3 ‐H)][anion] 2 have been investigated with respect to their formation and role under the conditions of asymmetric hydrogenation. Catalyst–substrate complexes with mac (methyl ( Z )‐ N ‐acetylaminocinnamate) ([Rh( t Bu‐BisP*)(mac)]BF 4 , [Rh(Tangphos)(mac)]BF 4 , [Rh(Me‐BPE)(mac)]BF 4 , [Rh(DCPE)(mac)]BF 4 , [Rh(DCPB)(mac)]BF 4 ), as well as rhodium‐hydride species, both mono‐([Rh(Tangphos)‐ H 2 (MeOH) 2 ]BF 4 , [Rh(Me‐BPE)H 2 (MeOH) 2 ]BF 4 ), and dinuclear ([{Rh(DCPE)H} 2 (μ 2 ‐H) 3 ]BF 4 , [{Rh(DCPB)H} 2 (μ 2 ‐H) 3 ]BF 4 ), are described. A plausible reaction sequence for the formation of the trinuclear rhodium‐hydride complexes is discussed. Evidence is provided that the presence of multinuclear rhodium‐hydride complexes should be taken into account when discussing the mechanism of rhodium‐promoted asymmetric hydrogenation.