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Bereau VM, Khan SI, Abu-Omar MM: Synthesis of enantiopure oxorhenium (V) and arylimidorhenium (V) "3 + 2" Schiff base complexes. Inorg Chem. 2001 Dec 17;40(26):6767-73.
X-ray diffraction, cyclic voltammetry, UV-vis, and circular dichroism characterizations.. Two new oxorhenium (V) and two new arylimidorhenium (V) complexes of the Schiff base ligands 2-hydroxybenzaldehyde-((1R,2S)-1-amino-2-indanol) imine (1) (H (2) L (1)) and 3-(1-adamantyl)-2-hydroxy-5-methylbenzaldehyde-((1R,2S)-1-amino- 2-indanol) imine (2) (H (2) L (2)) have been prepared from the reaction of the precursor Re (O)(PPh (3))(2) Cl (3), Re (NC (6) H (5))(PPh (3))(2) Cl (3), or Re (NC (6) H (4) OCH (3))(PPh (3))(2) Cl (3) and the free ligands H (2) L (1,2). The complexes Re (O)(HL (1))(L (1)) (3), Re (O)(HL (2))(L (2)) (4), Re (NC (6) H (5))(HL (1))(L (1)) (5), and Re (NC (6) H (4) OCH (3))(HL (1))(L (1)) (6) have been isolated and fully characterized by IR, (1) H NMR, circular dichroism, LRMS-FAB, and elemental analysis. All the complexes have a chiral center at rhenium. A single enantiomer is obtained in all cases. Suitable crystals of 3 and 5 were used in X-ray structural determinations. Crystal data: (3) C (32) H (27) N (2) O (5) Re.CH (2) Cl (2), orthorhombic, P2 (1) 2 (1) 2 (1), a = 9.5599 (16) A, b = 9.9579 (16) A, c = 31.712 (5) A, V = 3018.9 (9) A (3), T = 100 (2) K, Z = 4. (5) C (40) H (38) N (3) O (5) Re, monoclinic, P2 (1), a = 9.286 (3) A, b = 18.759 (6) A, c = 9.957 (3) A, beta = 102.817 (6) degrees, V = 1691.3 (10) A (3), T = 100 (2) K, Z = 2. The major characteristic of these complexes is the presence of two coordination modes for the Schiff base ligands on rhenium, a tridentate ligand (noted L (1,2)) and another bidentate ligand (noted HL (1,2)). In the latter, the -OH group of the indanol is free and tilts away from the coordination sphere. X-ray structural analyses in conjunction with circular dichroism were used to assign the absolute configuration at rhenium (C). Cyclic voltammetry, UV-vis, and circular dichroism data are presented and discussed. The complexes were found to be highly stable and to resist reduction even when treated with organic phosphanes. |
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