Triphenylantimony(V) 6-alkoxymethyl-3,5-di-tert-butylcatecholates. Structure and redox-properties.

Abstract A number of mononuclear triphenylantimony(V) 3,5-di- tert -butylcatecholates of the type (6-AlkOCH 2 -3,5-DBCat)SbPh 3 functionalized with alkoxymethyl group in the 6th position of aromatic ring in catecholato ligand, where Alk = Me ( 1 ), Et ( 2 ), iPr ( 3 ), tBu ( 4 ), n-Hexyl ( 5 ), and binuclear bis-catecholate Ph 3 Sb(3,5-DBCat-CH 2 OCH 2 -3,5-DBCat)SbPh 3 ( 6 ) have been synthesized and characterized in details. The molecular structures of 1 ·0.5 (n-hexane), 2 , 3 , 4 , 5 ·2MeOH, 6 ·2 (n-hexane) and 6 ·acetone have been determined by means of single-crystal X-ray analysis. The presence of alkoxymethyl-group in catecholate ligand does not lead to its coordination to the central antimony atom. Complexes 1 – 4 and 6 possess pentacoordinated environment of the central antimony atoms varying from the trigonal bipyramidal to the distorted tetragonal pyramidal. In crystal, molecules of complexes 1 – 5 form pairs where the “C Ph –H … π-system” interactions were found. The coordination environment of the central antimony atom in 5 ∙2MeOH is a distorted octahedral with coordinated methanol; the second methanol molecule is fixed between thehydroxyl group of coordinated methanol and the oxygen atom of hexyloxymethyl-group in the 6th position of catecholate ligand through the intramolecular hydrogen bonding. The electrochemical oxidations of complexes 1 – 4 proceed as two one-electron oxidations (the quasireversible oxidation “catecholate/o-semiquinolate” and the irreversible oxidation “o-semiquinolate/o-benzoquinone”). The first half-wave potential (E1 1/2 ) depends weakly on the alkyloxy substituent in AlkO-CH 2 group due to a weak inductive effect of AlkO group to the catecholate aromatic ring through the methylene linker. For binuclear bis-catecholate 6 , the first redox stage is two-electronic quasi-reversible peak without the separation of two stages into two one-electron processes, which indicates the absence of the electronic interaction between the two catecholate fragments. Graphical abstract A series of new 6-substituted 3,5-di-tert-butylcatecholato complexes of triphenylantimony(V) based on 6-alkoxymethyl-3,5-di-tert-butylcatechols and o-benzoquinones (where alkoxy group is methoxy, ethoxy, isopropoxy, tert-butoxy, n-hexoxy functions) have been synthesized. Novel redox active catechol, o-benzoquinone ligands and triphenylantimony(V) catecholates have been characterized in details. The molecular structures of mono- and binuclear triphenylantimony(V) catecholates in crystal were determined using single-crystal X-ray analysis. The electrochemical behaviour of complexes and influence of alkoxy methyl group were studied by cyclic voltammetry. Image 1 Highlights • Mononuclear triphenylantimony(V) catecholates with additional functional group. • Binuclear bis-catecholate Ph 3 Sb(3,5-DBCat-CH 2 OCH 2 -3,5-DBCat)SbPh 3. • New functionalized 3,5-di- tert -butylcatechol and o-benzoquinone with AlkylOCH 2 group. • The weak influence of AlkOCH2 group on the first oxidation potential of complexes. [ABSTRACT FROM AUTHOR]