Circular dichroism of cobalt(II) complex between 1700 and 1200 cm-1. Spin-orbit and tetragonal field splitting of the 1T1g ground state manifold

Abstract

Measurements of the room temperature circular dichroism (CD) of the dimer of bis[3-(trifluoromethylhydroxymethylene)-i/-camphorato]cobalt reveal six bands between 1680 and 1200 cm-1. The observed CD is assigned to electronic transitions of Co2+ from the ground and first excited Kramers doublets to the higher Kramers levels of the 4Tib ground manifold, which is split by spin-orbit coupling and a ligand field of tetragonal symmetry. stretch), two strong peaks at 1745 and 1705 cm-1 (C=0 stretching modes), and a relatively strong band at 1650 cm-1 (C=C stretch of the enol form), in addition to the bands expected from the camphor skeleton and the CF3 group. These data agree with the ir study by Lintvedt and Fatta12 on methylhydroxymethylened-camphor and are those expected for a 3-diketone.Complexes. Complexes of tfhmc with the ions Co2+, Ni2+, Cu2+, and Fe2+ were prepared by dissolving the tfhmc in an ethanol: water mixture (7:3 v/v), adjusting the pH to 6-7, and adding to this mixture a solution of Co(N03)2, Ni(N03)2, CuCl2, or FeCl2 in the same ethanol:water solvent.13 Evaporation of the ethanol caused precipitation of the complex. The product was filtered, redissolved (11) K.

Activation of molecular oxygen and its use in stereoselective tetrahydrofuran-syntheses from δ,ε-unsaturated alcohols

“…EtOH and aq. NaOH (for 4, Table 1, entry 4) 25 furnished cobalt complexes as red-brown (5, 7 26 ), red (6), 27 or orange (8) crystalline solids. In view of its propensity to liberate diketone 1 upon drying at 20-25 • C under reduced pressure, compound 5 was applied as an in situ preparation.…”

“…The cobalt atom in, e.g., complex 6 poses a stereogenic center. 27 The configuration at this site, either in the reagent or in the active oxidant, is entirely unknown. Formation of diastereomerically pure all-trans-3,5diaryl-4-methyl-2-hydroxymethyl-tetrahydrofuran 10h, a derivative of the natural product magnosalicin, of multiple substituted tetrahydrofurans.…”

“…Yield: 25.9 mg (15%) from 160 mg of 9i, R f 0. (10), 147 (91), 129 (45), 117 (22), 104 (100), 91 (99), 77 (27) and 51 (15). (C5), 34.9 (C7), 39.2 and 39.3 (C3), 68.0 and 68.2 (C2), 79.9 (C6).…”

“…(C5), 34.9 (C7), 39.2 and 39.3 (C3), 68.0 and 68.2 (C2), 79.9 (C6). m/z (EI, 70 eV) 141 (M + − CHO, 1%), 117 (8), 99 (63), 87 (16), 81 (100), 71 (18), 57 (58), 43 (36), 29 (9) (14), 170 (5), 147 (4), 133 (27), 120 (55), 105 (100), 77 (56), 59 (29), 55 (21).…”

Experimental studies of gyrotropy of crystals

“…Гиротропия в области 1200-1700 см' 1 была наблюдена в комплексе Со с органическим лигандом 343 , однако она, видимо, связана с электронным переходом между компонентами *T 2g -4 7\ g уровня i F 1 , расщепленного (в тетрагональной координации) из-за спин-орбитальной связи (ср. гл.…”