Successive Ligand and Metal Oxidation: Redox Reactions Involving Binuclear Cu^I Complexes of Chelating Guanidine Ligands

Abstract

New binuclear complexes of three-coordinate Cu I have been synthesized with the ligand 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb). Subsequent oxidation of the ligand unit was achieved by reaction with Br 2 or I 2 . Reaction with Br 2 leads to oxidation of both the ligand and the copper ions and formation of a bicationic dinuclear Cu II complex. On the other hand, oxidation with I 2 leads only to oxidation of the ligand during the first step. A metastable coordination polymer of ladder-type structure results, in which the coordi-

Synthesis and Application of New Guanidine Copper Complexes in Atom Transfer Radical Polymerisation

“…[1][2][3][4][5][6] Among the numerous N donor ligands studied so far, guanidines represent a rather young ligand class, which has been investigated with the main focus on copper coordination chemistry. [7][8][9][10] Generally, guanidines have proven to be powerful N donor ligands in coordination per(I). Tetramethylguanidine units act as stronger donors than dimethylethyleneguanidine units.…”

“…[11][12][13][14][15] They should also be suitable for application in ATRP because of three reasons: (i) strong complexation of the transition metal (copper), (ii) stabilisation of the higher oxidation state of the transition metal and (iii) tunable redox potentials of the guanidine complexes. [7][8][9][10][11][12][13][14][15] Atom transfer radical polymerisation (ATRP) was developed in 1995 and has considerably widened the field of accessible polymeric materials. [16] The basis of ATRP as a controlled radical polymerisation is an equilibrium between a dormant species, commonly an alkyl or aryl halide, and the propagating radical (Scheme 1).…”

Trapped in a Complex: the 1,2,4,5‐Tetrakis(tetramethylguanidino)benzene Radical Cation (ttmgb+·) with a Bisallylic Structure

“…We recently reported on the synthesis and properties of the strong electron donor ttmgb [1,2,4,5-tetrakis(tetramethylguanidino)benzene]. [7][8][9] Oxidation, e.g. with I 2 , [7] leads to the dication [ttmgb] 2+ (see Scheme 2) under removal of two of the aromatic π-electrons.…”

Donor‐Acceptor Couples and Late Transition Metal Complexes of Oxidation‐Labile 1,4,5,8‐Tetrakis(guanidino)naphthalene Superbases

“…2+ with intact Cu-N bonds as shown in Equation (2). [23] While four electrons can be removed from 3, compound 1 offers only two electrons. Due to the strong basicity of guanidines, 1 and 2 are still able to act as ligands upon two-electron oxidation.…”

“…[19] In additional work, the GFA-4 compound 1 was used for the synthesis of a variety of dinuclear metal complexes and also coordination polymers. [22][23][24] 2 , with a relatively low band gap (1.05 eV). [23] Results and Discussion…”