1,2,4,5‐Tetrakis(tetramethylguanidino)benzene: Synthesis and Properties of a New Molecular Electron Donor

Abstract

The molecular electron donor 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb) was synthesised by reaction between 1,2,4,5-tetraaminobenzene and 2-chloro-1,1Ј,3,3Ј-tetramethylformamidinium chloride. Protonation and oxidation of the molecule were analysed. In the course of titration of initially yellow-coloured solutions of ttmgb with HCl intense and fully reversible colour changes were observed; the diand tetraprotonated forms are green-and blue-coloured, respectively. The tetraprotonated molecule crystallised with Cl -, and the diprotonated molecule crystallised with PF 6 -as counterions. Oxidation, which already occurs slowly in air, was followed by CV measurements. Oxidation with I 2 leads to deeply green-coloured solutions, from which purple-black

Guanidino‐Functionalised Aromatic Electron Donors at Work: Competing Hydrogen‐ and Electron‐Transfer Reactions in the Course of the Synthesis of Gold Acetylide Complexes

“…of 1 in CH 3 CN. Although CH 3 CN was shown to be reactive in our previous work, [6] the experiments indicate that CH 3 CN deprotonation does not occur in the presence of acetylenes in the solution. Two types of products were isolated.…”

“…More intriguing, the reaction does not work if 1 is replaced by the stronger base 2 [1,2,4,5-tetrakis(tetramethylguanidino)benzene, see Scheme 2, pK a = 25.3 for 2 in CH 3 CN]. [6] Scheme 2.…”

“…[6] Bright-yellow crystals formed containing the [Au(CH 2 CN)PPh 3 ] units together with 0.5 equiv. of neutral 1.…”

A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex

“…[17] With the synthesis of guanidino-functionalized aromatics (GFAs), [18] our group developed a new class of redox-active ligands with strong electron-donating abilities. Initial studies focused on 1,2,4,5-tetrakis(tetramethylguanidino)benzene (3) [19] (see Scheme 1), 1,4,5,8-tetrakis(tetramethylguanidino)naphthalene (4), [20] and 2,3,5,6-tetrakis(tetramethylguanidino)pyridine (5) [21] (see Scheme 2).The Lewis structures explaining the redox activity of these GFA ligands are comparable with those for the oxidation of o-dioxolene ligands (e.g. twofold deprotonated catechol 1) and the tetraoxolene tetraanion 2.…”

On the Electronic Structure of NiII Complexes That Feature Chelating Bisguanidine Ligands

“…Hence, some of us recently showed that tetrakis(tetramethylguanidino)benzene (ttmgb; see Scheme 1) can be oxidized readily, for example, by O 2 in the air or by I 2 . [10] A two-electron oxidation wave was measured at E 1/2 A C H T U N G T R E N N U N G (CH 3 CN) = À0.32 V versus SCE (see Figure S1 in the Supporting Information). In its oxidized form, the positive charges are delocalized, with two of the resonance structures being sketched in Scheme 1.…”