TY - JOUR
T1 - Formation of trinuclear rhodium-hydride complexes [{Rh(PP*)H} 3- (μ2-H)3(μ3-H)][anion] 2 - During asymmetric hydrogenation?
AU - Kohrt, C.
AU - Baumann, W.
AU - Spannenberg, A.
AU - Drexler, H. J.
AU - Gridnev, I. D.
AU - Heller, D.
PY - 2013/6/3
Y1 - 2013/6/3
N2 - Recently described and fully characterized trinuclear rhodium-hydride complexes [{Rh(PP)H}3(μ2-H) 3(μ3-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(tBu-BisP)(mac)]BF4, [Rh(Tangphos)(mac)] BF4, [Rh(Me-BPE)(mac)]BF4, [Rh(DCPE)(mac)]BF4, [Rh(DCPB)(mac)]BF4), as well as rhodium-hydride species, both mono-([Rh(Tangphos)- H2(MeOH)2]BF4, [Rh(Me-BPE)H2(MeOH)2]BF4), and dinuclear ([{Rh(DCPE)H}2(μ2-H)3]BF4, [{Rh(DCPB)H}2(μ2-H)3]BF4), 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. Catalyst-substrate complexes containing the ligands tBu-BisP, Tangphos, Me-BPE, DCPE, DCPB, and mono- ([Rh(PP)(MeOH)2H2]BF4) or dinuclear ([{Rh(PP)H}2(μ2-H)3]BF 4) Rh-hydride species, are described (see figure). A sequence for the formation of the trinuclear Rh-hydride complexes is suggested. The presence of these complexes should be taken into account when discussing the mechanism of asymmetric hydrogenation.
AB - Recently described and fully characterized trinuclear rhodium-hydride complexes [{Rh(PP)H}3(μ2-H) 3(μ3-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(tBu-BisP)(mac)]BF4, [Rh(Tangphos)(mac)] BF4, [Rh(Me-BPE)(mac)]BF4, [Rh(DCPE)(mac)]BF4, [Rh(DCPB)(mac)]BF4), as well as rhodium-hydride species, both mono-([Rh(Tangphos)- H2(MeOH)2]BF4, [Rh(Me-BPE)H2(MeOH)2]BF4), and dinuclear ([{Rh(DCPE)H}2(μ2-H)3]BF4, [{Rh(DCPB)H}2(μ2-H)3]BF4), 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. Catalyst-substrate complexes containing the ligands tBu-BisP, Tangphos, Me-BPE, DCPE, DCPB, and mono- ([Rh(PP)(MeOH)2H2]BF4) or dinuclear ([{Rh(PP)H}2(μ2-H)3]BF 4) Rh-hydride species, are described (see figure). A sequence for the formation of the trinuclear Rh-hydride complexes is suggested. The presence of these complexes should be taken into account when discussing the mechanism of asymmetric hydrogenation.
KW - asymmetric hydrogenation
KW - catalyst-substrate complex
KW - hydrides
KW - reaction mechanisms
KW - rhodium
KW - solvate complex
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U2 - 10.1002/chem.201204336
DO - 10.1002/chem.201204336
M3 - Article
C2 - 23576440
AN - SCOPUS:84878249165
VL - 19
SP - 7443
EP - 7451
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 23
ER -