Oxime-based salen-type tetradentate ligands with high stability against imine metathesis reaction.

摘要: Although salen and its analogues are versatile chelate ligands in inorganic organometallic chemistry, synthesis of unsymmetrical derivatives consisting two different salicylideneimine moieties is difficult because the CN bond recombination. To develop stable salen-type ligands, we synthesized a series new salamo (=1,2-bis(salicylideneaminooxy)ethane) on basis O-alkyl oxime instead imine moiety. Eight 1a−h were prepared 64−88% yields as colorless crystals from corresponding salicylaldehydes 2a−h. The crystal structure 1a−c suggests that oxime-OH form more predominant than keto-NH form. reaction 2a−e with excess 1,2-bis(aminooxy)ethane gave monooximes 3a−e 59−86%, which further reacted salicylaldehyde to afford 4−8 51−70%. No took place when mixture 1a 1b was treated at 40 °C H2O/MeCN (5:95). However, t...