Synthesis, X-ray crystal structure, and reactivity of ternary complexes of crown ethers, organic π-acceptors, and salts
Abstract
Benzo- and dibenzo-18-crown-6 (1) and (2) form charge-transfer complexes with tetracyanoethylene (TCNE) in chloroform with association constants of 2.6 ± 0.2 and 4.5 ± 0.4 l mol–1. In the presence of 1 equiv. of t-butylammonium perchlorate (ButNH3ClO4) a solid ternary complex of (2), TCNE, and ButNH3ClO4 is formed. Single-crystal X-ray analysis of a similar ternary complex of (2), ButNH3ClO4 and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) revealed the close proximity of the perchlorate anion and DDQ. Ternary complexes of TCNE, crown ethers (1)–(3), and salts with nucleophilic anions (Br–, Cl–, and F–) react to give the TCNE–· radical anion as proven by e.s.r. spectroscopy. In the presence of water and/or oxygen 18-crown-6 (3), TCNE, and ButNH3Br react to yield the 18-crown-6·ButNH3(NC)2CC(CN)O complex.