Redox Isomerism in Main‐Group Chemistry: Tin Complex with o‐Iminoquinone Ligands

Abstract

The bis‐chelate tin complex 1, based on the 4,6‐di‐tert‐butyl‐N‐(tert‐butyl)‐ortho‐aminophenol ligand and representing the first example of a redox‐isomeric compound in main‐group chemistry, is synthesized and characterized by X‐ray diffraction analysis. Complex 1 exists in two electromeric forms in nonpolar solvents: a diamagnetic pseudotetrahedral (AP)2SnIV (1a) and a paramagnetic tetragonal‐pyramidal structure of low‐valence tin (imSQ)2SnII (1b) (where AP and imSQ are the dianionic and radical‐anionic forms of the ligand, respectively). The reversible redox‐isomeric rearrangement between 1a and 1b is investigated in solution by means of magnetochemistry, EPR spectroscopy, UV/Vis spectroscopy, and 119Sn Mössbauer spectroscopy. This interconversion can be quenched by an addition of a strong donor ligand, such as pyridine (Py), resulting in an octahedral complex (AP)2SnIV(Py)2 (2) that does not undergo redox isomerism.

Insight into the Electron Density Distribution in an O,N‐Heterocyclic Stannylene by High‐Resolution X‐ray Diffraction Analysis

“…The preparation of the 3,5,7‐tri‐ tert ‐butyl‐1,3,2‐benzoxazastannol‐2‐ylidene 1 was achieved by a Bronstedt acid‐base reaction between bis[bis(trimethylsilyl)amido]tin(II) and t BuAPH 2 (where t BuAPH 2 = 4,6‐di‐ tert ‐butyl‐N‐( tert ‐butyl)‐ o ‐aminophenol) in Et 2 O solution (Scheme ). Compound 1 was obtained as yellow crystalline material from a saturated Et 2 O solution in 76 % yield.…”

“…All manipulations on complexes were performed under vacuum conditions, in which oxygen and moisture were excluded. Sn[N(SiMe 3 ) 2 ] 2 , t BuAPH 2 and Fe 2 (CO) 9 were prepared according to known procedures. Solvents were purified by standard methods .…”

Polyfunctional Sterically Hindered Catechols with Additional Phenolic Group and Their Triphenylantimony(V) Catecholates: Synthesis, Structure, and Redox Properties

“…This feature can significantly expand or change the reactivity of metal complexes. Studies of non-transition metal complexes containing redox-active ligands of the o-quinonato type have allowed to reveal an expansion of the valence potentials of non-transition metals due to redox-active ligands [12,13], to observe of the phenomenon of redox isomerism in the main group metals' chemistry [14], and also to observe and investigate the ability of antimony(V) complexes to reversible fixation of molecular oxygen [15][16][17][18][19], to observe the fixation of nitrogen(II) oxide (by zinc(II) and lead(II) catecholates) [20]. There are several approaches that allow to change the properties of ligands and their metal complexes: (1) a modification of the ligands' structure by the variation of heteroatoms (O, N, S) or the presence of bulky organic substituents; (2) the introduction of different electron donor/acceptor groups or additional redox-active as well as chelating fragments at various positions of the quinoid ring; and (3) a combination of a redox-active ligand and an additional coordination center.…”

“…catechol and phenolic aromatic rings planes is equal to 54.7(1)°, the torsion angle is 47.9(1)°, and the torsion angle C(1)C(6)C 7 (14), O(2)-C(2) 1.3804 (14), O(3)-C(11) 1.3806 (14), S(1)-C(7) 1.8527 (12), S(1)-C(8) 1.7765 (11), C(1)-C(2) 1.3967 (16), C(1)-C(6) 1.3987 (16), C(2)-C(3) 1.3910 (16), C(3)-C(4) 1.4029 (15), C(4)-C(5) 1.4016 (15), C(5)-C(6) 1.4150 (15), C(6)-C(7) 1.5101 (15), C(8)-C(9) 1.3907 (16), C(8)-C(13) 1.3893 (16), C(9)-C(10) 1.3947 (16), C(10)-C(11) 1.4118 (15), C(11)-C(12) 1.4139 (15), C(12)-C(13) 1.3949 (16).…”

The coordination behavior of 2,3-bis(diphenylphosphino)maleic-N-phenylimide towards copper, silver, gold and palladium

“…Similar electron transfer processes have also been described for various complexes containing so-called non-innocent ligands. [9][10][11][12][13] Examples for these ligands are indigo, 14 2,2-azobispyridine, 15 iminoquinones, 16,17 phenanthroline, 18 o-iminosemiquinones 19,20 and o-iminobenzosemiquinonato. 21,22 Another characteristic of this class of ligands is their tendency of undergoing various substitution and addition reactions in the coordination sphere of transition metals.…”