Syntheses of the First Coordination Compounds of the New Strong Molecular Electron Donor and Double Proton Sponge 1,4,5,8‐Tetrakis(tetramethylguanidino)naphthalene

Abstract

Keywords: Electron donor ligands / Cobalt / Aluminum / N ligandsHerein we report on the synthesis and properties of a new electron donor featuring an aromatic system to which four guanidino groups are attached, namely, 1,4,5,8-tetrakis(tetramethylguanidino)naphthalene (ttmgn). The molecule is a double proton sponge with an asymmetric N-H···N bridge being formed in the protonated form. Oxidation is followed electrochemically, and two oxidation waves at E 1/2 (CH 3 CN) = -0.25 and +0.50 V vs. SCE are observed. Chemical oxidation with I 2 yields ttmgn(I 3 ) 2 , in which the I 3 units interact with the ttmgn 2+ cations through I···C contacts. Reaction with an excess amount of Br 2 leads to removal of four electrons from the aromatic system and formation of the salt (ttmgn)-Br 4 with a chair-type conformation of the C 10 core. The binuclear Al alkyl complex [(ttmgn)(AlMe 2 ) 2 ][BPh 4 ] 2 can be pre- [a] Anorganisch- Synthesis and CharacterisationThe synthesis of 3 turned out to be much more difficult than that of 2. Nevertheless, its preparation was achieved www.eurjic.org

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.…”

Successive Ligand and Metal Oxidation: Redox Reactions Involving Binuclear CuI Complexes of Chelating Guanidine Ligands

“…[26] As anticipated, the signals in the NMR spectrum were too broad for detection. We showed for the example complexes [{(MeCN) 2 Cu} 2 -(ttmgb)] [8] and [(Cl 2 Co) 2 (ttmgb)] [7] that magnetic superexchange in complexes that feature either the dicationic or the neutral ttmgb ligand and square-planar or tetrahedral coordination of electron-rich transition metals is weak (antiferromagnetic coupling). The variations in the C-C bond lengths within the C 6 ring clearly indicate removal of two electrons from the ligand 6π-electron aromatic system.…”

“…Two representatives of this family are 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb, see Scheme 1) [6] and 1,4,5,8-tetrakis(tetramethylguanidino)naphthalene (ttmgn). [7] Oxidation with I 2 gives the two salts [ttmgb](I 3 ) 2 (1) and [ttmgn](I 3 ) 2 , the structures of which were recently reported by us. [6,7] Both GFAs have already been used to synthesize binuclear complexes of various metals, including Cu II [8] and Co II .…”

“…[7] Oxidation with I 2 gives the two salts [ttmgb](I 3 ) 2 (1) and [ttmgn](I 3 ) 2 , the structures of which were recently reported by us. [6,7] Both GFAs have already been used to synthesize binuclear complexes of various metals, including Cu II [8] and Co II . [7] Herein we now report on binuclear Cu I complexes of ttmgb and their oxi-nation number of the Cu I ions increases to four.…”

“…[6,7] Both GFAs have already been used to synthesize binuclear complexes of various metals, including Cu II [8] and Co II . [7] Herein we now report on binuclear Cu I complexes of ttmgb and their oxi-nation number of the Cu I ions increases to four. Electrical measurements show that this polymer is semiconductive with a band gap of around 1 eV.…”