Redox potentials and HPLC behavior of cobalt and iron complexes with pyridylazo compounds.

The redox potentials of cobalt and iron complexes with ten pyridylazo compounds, E(0)(ML2) (ML(2)(+/0); M: Co(III/II), Fe(III/II); L(-): pyridylazo compounds), have been determined in order to explore the difference in their reversed-phase HPLC behavior. The redox potentials of Co complexes were in the range of -0.62 - 0.03 V, while those of Fe complexes were -0.06 - 0.59 V relative to 0.20 V for ferricinium/ferrocene. The redox potentials of both the Co and Fe complexes were linearly correlated to the basicities of the ligands. The correlation was quantitatively explained by a difference in dependence of the stabilities of M(III) and M(II) complexes on the ligand basicities. The complex of [Co(III)L(2)](+) or [Fe(II)L(2)] with any compound injected in the reversed-phase HPLC system was detected without any change in the composition. When [Co(II)L(2)] was injected, only those complexes having the highest potentials of E(0)(CoL2) congruent with 0.0 V were detected as [Co(II)L(2)], while other complexes having lower potentials gave a peak of [Co(III)L(2)](+). When [Fe(III)L(2)](+) was injected, only complexes having the lowest potentials of E(0)(FeL2) congruent with 0.0 V were detected as [Fe(III)L(2)](+), while others having higher potentials gave a peak of [Fe(II)L(2)].

Lithium chloride: an active and simple catalyst for cyanosilylation of aldehydes and ketones.

LiCl acts as a highly effective catalyst for cyanosilylation of various aldehydes and ketones to the corresponding silylated cyanohydrins. The reaction proceeds smoothly with a substrate/catalyst molar ratio of 100-100,000 at 20-25 degrees C under solvent-free conditions. alpha,beta-Unsaturated aldehydes are completely converted to the 1,2-adducts. The cyanation products can be isolated by direct distillation of the reaction mixture.