TY - JOUR
T1 - Chiral organometallic triangles with Rh-Rh bonds. 2. Compounds prepared from enantiopure cis-Rh2(C6H4PPh 2)2(OAc)2(HOAc)2 and their catalytic potentials
AU - Cotton, F. Albert
AU - Murillo, Carlos A.
AU - Stiriba, Salah E.
AU - Wang, Xiaoping
AU - Yu, Rongmin
PY - 2005/11/14
Y1 - 2005/11/14
N2 - Enantiomers of the orthometalated dirhodium compound cis-Rh 2(C6H4PPh2)2(OAc) 2(HOAc)2 (R-1 and S-1) were prepared from carboxylate exchange reactions of the resolved diasteroisomers of cis-Rh2(C 6H4PPh2)2(protos) 2-(H2O)2 (protos = N-4-methylphenylsulfonyl-L- proline anion) and acetic acid. These compounds react with excess Me 3OBF4 in CH3CN, producing the enantiomers of [cis-Rh2(C6H4PPh2) 2(CH3CN)6](BF4)2 (R-2 and S-2) which have six labile and replaceable CH3CN ligands in equatorial and axial positions. Reactions of R-2 and S-2 with tetraethylammonium salts of the linear dicarboxylic acids, terephthalic acid (HO 2CC6H4CO2H), oxalic acid (HO 2-CCO2H), and 4,4′-diphenyl-dicarboxylic acid (HO2CC6H4C6H4CO 2H) afford the enantiopure triangular supramolecules [cis-Rh 2(C6H4PPh2)2(O 2CC6H4CO2)(py)2] 3, RRR-3 and SSS-3, Rh6(cis-C6H 4PPh2)6(O2CCO2) 3(py)5(CH2Cl2), RRR-4 and SSS-4, and Rh6(cis-C6H4PPh2) 6(O2CC6H4C6H 4CO2)3(py)4(CH2Cl 2)2, RRR-5 and SSS-5, respectively. The absolute structures of each of the enantiomers of 1, 3, 4, and 5 were determined by X-ray diffraction analyses. The enantiomers of 3, 4, and 5 were found to be enantiomorphically isostructural, whereas R-1 and S-1 crystallized in different space groups. In 4 and 5, CH2Cl2 molecules coordinate to rhodium atoms in the axial positions. The 1H and 31P{ 1H} NMR spectra of all compounds are reported. The triangular compounds are redox-active, and their electrochemistry is also discussed. An assay of the catalytic activity/selectivity performance of the triangles for typical metal carbene transformation, using the model intermolecular cyclopropanation of styrene with ethyl diazoacetate in both homogeneous and heterogeneous phases, show that these chiral triangles are very active and have remarkable selectivity when compared with simple Rh2 paddlewheel catalysts with chiral amidate ligands.
AB - Enantiomers of the orthometalated dirhodium compound cis-Rh 2(C6H4PPh2)2(OAc) 2(HOAc)2 (R-1 and S-1) were prepared from carboxylate exchange reactions of the resolved diasteroisomers of cis-Rh2(C 6H4PPh2)2(protos) 2-(H2O)2 (protos = N-4-methylphenylsulfonyl-L- proline anion) and acetic acid. These compounds react with excess Me 3OBF4 in CH3CN, producing the enantiomers of [cis-Rh2(C6H4PPh2) 2(CH3CN)6](BF4)2 (R-2 and S-2) which have six labile and replaceable CH3CN ligands in equatorial and axial positions. Reactions of R-2 and S-2 with tetraethylammonium salts of the linear dicarboxylic acids, terephthalic acid (HO 2CC6H4CO2H), oxalic acid (HO 2-CCO2H), and 4,4′-diphenyl-dicarboxylic acid (HO2CC6H4C6H4CO 2H) afford the enantiopure triangular supramolecules [cis-Rh 2(C6H4PPh2)2(O 2CC6H4CO2)(py)2] 3, RRR-3 and SSS-3, Rh6(cis-C6H 4PPh2)6(O2CCO2) 3(py)5(CH2Cl2), RRR-4 and SSS-4, and Rh6(cis-C6H4PPh2) 6(O2CC6H4C6H 4CO2)3(py)4(CH2Cl 2)2, RRR-5 and SSS-5, respectively. The absolute structures of each of the enantiomers of 1, 3, 4, and 5 were determined by X-ray diffraction analyses. The enantiomers of 3, 4, and 5 were found to be enantiomorphically isostructural, whereas R-1 and S-1 crystallized in different space groups. In 4 and 5, CH2Cl2 molecules coordinate to rhodium atoms in the axial positions. The 1H and 31P{ 1H} NMR spectra of all compounds are reported. The triangular compounds are redox-active, and their electrochemistry is also discussed. An assay of the catalytic activity/selectivity performance of the triangles for typical metal carbene transformation, using the model intermolecular cyclopropanation of styrene with ethyl diazoacetate in both homogeneous and heterogeneous phases, show that these chiral triangles are very active and have remarkable selectivity when compared with simple Rh2 paddlewheel catalysts with chiral amidate ligands.
UR - http://www.scopus.com/inward/record.url?scp=28244437178&partnerID=8YFLogxK
U2 - 10.1021/ic051282c
DO - 10.1021/ic051282c
M3 - Article
AN - SCOPUS:28244437178
SN - 0020-1669
VL - 44
SP - 8223
EP - 8233
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 23
ER -