Triethylantimony(V) complexes with bidentate O,N-, O,O- and tridentate O,N,O′-coordinating o-iminoquinonato/o-quinonato ligands: Synthesis, structure and some properties

The novel triethylantimony(v) o-amidophenolato (AP-R)SbEt3 (R = i-Pr, 1; R = Me, 2) and catecholato (3,6-DBCat)SbEt3 (3) complexes have been synthesized and characterized by IR, NMR spectroscopy (AP-R is 4,6-di-tert-butyl-N-(2,6-dialkylphenyl)-o-amidophenolate, alkyl = isopropyl (1) or methyl (2); 3,6-DBCat is 3,6-di-tert-butyl-catecholate). Complexes 1–3 have been obtained by the oxidative addition of corresponding o-iminobenzoquinones or o-benzoquinones to Et3Sb. The addition of 4,6-di-tert-butyl-N-(3,5-di-tert-butyl-2-hydroxyphenyl)-o-iminobenzoquinone to Et3Sb at low temperature gives hexacoordinate [(AP-AP)H]SbEt3 (4) which decomposes slowly in vacuum with the liberation of ethane yielding pentacoordinate complex [(AP-AP)]SbEt2 (5). [(AP-AP)H]2− is O,N,O′-tridentate amino-bis-(3,5-di-tert-butyl-phenolate-2-yl) dianion and [(AP-AP)]3− is amido-bis-(3,5-di-tert-butyl-phenolate-2-yl) trianion. The decomposition of 4–5 accelerates in the presence of air. o-Amidophenolates 1 and 2 bind molecular oxygen to give spiroendoperoxides Et3Sb[L-iPr]O2 (6) or Et3Sb[L-Me]O2 (7) containing trioxastibolane rings. This reaction proceeds slowly and reaches the equilibrium at 15–20% conversion five times more than for (AP-R)SbPh3 analogues. Molecular structures of 1 and 5 were determined by X-ray analysis.