A Valence Tautomeric Dinuclear Copper Tetrakisguanidine Complex.
We report on the first valence tautomeric dinuclear copper complex, featuring 2,3,5,6-tetrakis(tetramethylguanidino)pyridine as a bridging redox-active GFA (guanidino-functionalized aromatic) ligand. The preferred electronic structure of the complex is massively influenced by the environment. In the solid state and in nonpolar solvents a paramagnetic, dinuclear Cu(II) complex with a neutral GFA ligand is present. In polar solvents, the electronic structure changes to a diamagnetic, dinuclear Cu(I) complex with a twofold-oxidized GFA ligand. Using acetone as a solvent, both electronic structures are accessible due to a temperature-dependent equilibrium between the two valence tautomeric complexes. Our results pave the way for a broader use of valence tautomeric transition-metal complexes in catalytic reactions since anionic coligands can now be tolerated owing to the neutral/positively charged GFA ligand.
Anorganisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Sven
http://orcid.org/0000-0002-0641-9131
S
Wiesner
Anorganisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Arne
A
Wagner
Anorganisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Elisabeth
E
Kaifer
Anorganisch-Chemisches Institut, Ruprecht-Karls Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany. hans-jorg.himmel@aci.uni-heidelberg.de.
Hans-Jörg
HJ
Himmel
coordination compounds; copper; electronic structures; guanidine; valence tautomers