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

Novel functionalized triphenylantimony(V) catecholates – Ph3Sb[4-O(CH2CH2)2N-3,6-DBCat] (1), Ph3Sb[4-PhN(CH2CH2)2N-3,6-DBCat] (2), Ph3Sb[4-Ph2CHN(CH2CH2)2N-3,6-DBCat] (3), Ph3Sb[4,5-Piperaz-3,6-DBCat] (4) and binuclear bis-catecholate Ph3Sb[3,6-DBCat-4-N(CH2CH2)2N-4-3,6-DBCat]SbPh3 (5) were synthesized by the oxidative addition reaction of corresponding o-quinones with triphenylantimony. The [4-O(CH2CH2)2N-3,6-DBCat]2−, [4-PhN(CH2CH2)2N-3,6-DBCat]2−, [4-Ph2CHN(CH2CH2)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·CH3OH 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%.