The title cobalt(II) complexes were prepared from the reaction of CoL(Cl)H2O2+ with Cr2+(aq) in 1.0 M HClO4, and crystals of 1 and 2 were obtained from acetone. Structures were determined from single-crystal X-ray diffraction data collected with use of Cu Ka radiation. Crystallographic data: 1, N-rac-[CoL(H2O)](ClO4)2·0.6H 2O, Pbcn, a = 15.654 (4) Å, b = 14.623 (2) Å, c = 55.221 (11) Å, V = 12640 (7) Å3, Z = 20 (R = 0.113, Rw = 0.135); 2, N-rac-[CoL(OClO3)]ClO4, P21/c, a = 10.336 (3) Å, b = 17.094 (1) Å, c = 13.890 (2) Å, β = 105.59 (2)°, V = 2363 (1) Å3, Z = 4 (R = 0.061, Rw = 0.087). Both 1 and 2 contain a five-coordinate cobalt(II) center with the four nitrogen atoms of N-rac-L forming the base of a square pyramid and axial water (1, Co-OH2 = 2.25 (5) Å) or axial perchlorate ion (2, Co-OClO3 = 2.305 (5) Å) forming the apex of the square pyramid. Studies of N-rac- and N-meso-CoL2+ in solution (perchlorate salts) are described: the lowest energy d-d band (1400-1700 nm, depending upon solvent) provides a probe of the isomeric composition of the solutions, since this band is 2-3 times more intense for the N-rac than for the N-meso isomer. Equilibration of the two isomers is slow at room temperature (-7 s-1) in organic solvents and in acidic aqueous solutions; it is, however, rapid in alkaline media, and the N-rac isomer is favored at equilibrium.
|Number of pages||6|
|Publication status||Published - 1989|
ASJC Scopus subject areas
- Inorganic Chemistry