TY - JOUR
T1 - Phenoxaphosphine-Based diphosphine ligands. synthesis and application in the hydroformylation reaction
AU - Zuidema, E.
AU - Goudriaan, P. Elsbeth
AU - Swennenhuis, B.H.G.
AU - Kamer, P.C.J.
AU - van Leeuwen, P.W.N.M.
AU - Lutz, M.
AU - Spek, A.L.
PY - 2010
Y1 - 2010
N2 - The synthesis of a new series of diphosphine ligands based on 2,7-di-tert-butyl-9,9-dimethylxanthene (1),
p-tolyl ether (2), ferrocene (3), and benzene (4) backbones, containing one or two 2,8-dimethylphenoxaphosphine
moieties, is reported. The ligands were employed in the rhodium-catalyzed hydroformylation of
1-octene. For all four ligand backbones, introduction of phenoxaphosphine moieties led to an increase in
catalytic activity and a decrease in regioselectivity toward the linear aldehyde product. Xanthene-based
ligands 1a-1c yielded highly active and regioselective hydroformylation catalysts; ligands containing p-tolyl
ether and ferrocene backbones 2a-2c and 3a-3c provided less active and less regioselective catalysts.
Catalysts containing benzene-derived ligands 4a and 4b showed a remarkable preference for the formation
of the branched aldehyde product. The coordination behavior of ligands 1-4 under hydroformylation
conditions was investigated using high-pressureNMRand IRspectroscopy, revealing the distinct steric and
electronic properties of the diphenylphosphine and 2,8-dimethylphenoxaphosphine moieties in ligands
1-4. The phosphacyclic moieties proved to be less basic and less sterically demanding toward other ligands
in metal complexes than the acyclic diphenylphosphine moieties. For ligands that contain rigid backbones,
the lack of conformational freedom in these phosphacyclic moieties does lead to repulsive interactions
between the substituents of the two phosphorus donor atoms, resulting in an increase in the bite angle of the
ligand. The low catalytic activity of rhodium catalysts modified by benzene-based ligands 4a-4c was
attributed to the quantitative formation of HRh(L)2 under hydroformylation conditions.
AB - The synthesis of a new series of diphosphine ligands based on 2,7-di-tert-butyl-9,9-dimethylxanthene (1),
p-tolyl ether (2), ferrocene (3), and benzene (4) backbones, containing one or two 2,8-dimethylphenoxaphosphine
moieties, is reported. The ligands were employed in the rhodium-catalyzed hydroformylation of
1-octene. For all four ligand backbones, introduction of phenoxaphosphine moieties led to an increase in
catalytic activity and a decrease in regioselectivity toward the linear aldehyde product. Xanthene-based
ligands 1a-1c yielded highly active and regioselective hydroformylation catalysts; ligands containing p-tolyl
ether and ferrocene backbones 2a-2c and 3a-3c provided less active and less regioselective catalysts.
Catalysts containing benzene-derived ligands 4a and 4b showed a remarkable preference for the formation
of the branched aldehyde product. The coordination behavior of ligands 1-4 under hydroformylation
conditions was investigated using high-pressureNMRand IRspectroscopy, revealing the distinct steric and
electronic properties of the diphenylphosphine and 2,8-dimethylphenoxaphosphine moieties in ligands
1-4. The phosphacyclic moieties proved to be less basic and less sterically demanding toward other ligands
in metal complexes than the acyclic diphenylphosphine moieties. For ligands that contain rigid backbones,
the lack of conformational freedom in these phosphacyclic moieties does lead to repulsive interactions
between the substituents of the two phosphorus donor atoms, resulting in an increase in the bite angle of the
ligand. The low catalytic activity of rhodium catalysts modified by benzene-based ligands 4a-4c was
attributed to the quantitative formation of HRh(L)2 under hydroformylation conditions.
U2 - 10.1021/om901041r
DO - 10.1021/om901041r
M3 - Article
SN - 0276-7333
VL - 29
SP - 1210
EP - 1221
JO - Organometallics
JF - Organometallics
IS - 5
ER -