New morpholine- and piperazine-functionalized triphenylantimony(V) catecholates: The spectroscopic and electrochemical studies

Abstract

Novel functionalized triphenylantimony(V) catecholates – Ph 3Sb[4-O(CH 2CH 2) 2N-3,6-DBCat] ( 1), Ph 3Sb[4-PhN(CH 2CH 2) 2N-3,6-DBCat] ( 2), Ph 3Sb[4-Ph 2CHN(CH 2CH 2) 2N-3,6-DBCat] ( 3), Ph 3Sb[4,5-Piperaz-3,6-DBCat] ( 4) and binuclear bis-catecholate Ph 3Sb[3,6-DBCat-4-N(CH 2CH 2) 2N-4-3,6-DBCat]SbPh 3 ( 5) were synthesized by the oxidative addition reaction of corresponding o-quinones with triphenylantimony. The [4-O(CH 2CH 2) 2N-3,6-DBCat] 2−, [4-PhN(CH 2CH 2) 2N-3,6-DBCat] 2−, [4-Ph 2CHN(CH 2CH 2) 2N-3,6-DBCat] 2− and [4,5-Piperaz-3,6-DBCat] 2− are 4-(morpholin-1-yl)-, 4-(4-phenyl-piperazin-1-yl)-, 4-(4-dephenylmethyl-piperazin-1-yl)-, and 4,5-(piperazin-1,4-diyl)-3,6-di- tert-butyl-catecholate dianionic ligands, correspondingly. Complexes 1–5 were characterized in details by IR-, 1H and 13C NMR spectroscopy and cyclic voltammometry. Molecular structure of 4·CH 3OH was determined by X-ray crystallography to be a distorted tetragonal–pyramidal. The NMR spectroscopic and electrochemical investigations of complexes in the presence of air reveal the reactions of complexes with dioxygen leading to the formation of spiroendoperoxides of 1,2,4,3-trioxastibolane type in a NMR yield of 25–37%.