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

Abstract The novel triethylantimony(v) o- amidophenolato (AP-R)SbEt 3 (R =  i -Pr, 1 ; R = Me, 2 ) and catecholato (3,6-DBCat)SbEt 3 ( 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 Et 3 Sb. The addition of 4,6-di- tert -butyl- N -(3,5-di- tert -butyl-2-hydroxyphenyl)- o- iminobenzoquinone to Et 3 Sb at low temperature gives hexacoordinate [(AP-AP)H]SbEt 3 ( 4 ) which decomposes slowly in vacuum with the liberation of ethane yielding pentacoordinate complex [(AP-AP)]SbEt 2 ( 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 Et 3 Sb[L-iPr]O 2 ( 6 ) or Et 3 Sb[L-Me]O 2 ( 7 ) containing trioxastibolane rings. This reaction proceeds slowly and reaches the equilibrium at 15–20% conversion five times more than for (AP-R)SbPh 3 analogues. Molecular structures of 1 and 5 were determined by X-ray analysis.