%0 Journal Article %1 Berger.2004 %A Berger, Sascha %A Fiedler, Jan %A Reinhardt, Ralf %A Kaim, Wolfgang. %D 2004 %J Inorganic Chemistry %K bond chloride chloro cleavage complex dipyridophenazine electrochem iridium iridium;metal ligand pentamethycyclopentadienyl redn rhodium %N 4 %P 1530--1538 %R 10.1021/ic0351388 %T Metal vs. Ligand Reduction in Complexes of Dipyrido3,2-a: 2',3'-cphenazine and Related Ligands with (C5Me5)ClM+ (M = Rh or Ir): Evidence for Potential Rather Than Orbital Control in the Reductive Cleavage of the Metal-Chloride Bond %V 43 %X Complexes between the chlorometal(III) cations (C5Me5)ClM+, M = Rh or Ir, and the 1,10-phenanthroline-derived a-diimine (N N) ligands dipyrido3,2-a:2',3'-cphenazine (dppz), 1,4,7,10-tetraazaphenanthrene (tap), or 1,10-phenanthroline-5,6-dione (pdo) were studied by cyclic voltammetry, EPR, and UV-visible-NIR spectroelectrochem. with respect to either ligand-based or metal-centered (and then chloride-dissociative) redn. Two low-lying unoccupied MOs are present in each of these 3 N$\cap$N ligands; however, their different energies and interface properties are responsible for different results. Metal-centered chloride-releasing redn. was obsd. for complexes of the DNA-intercalation ligands dppz and tap to yield (N N)(C5Me5)M in a 2-electron step. The sepn. of a-diimine centered optical orbitals and phenazine-based redox orbitals is apparent from the EPR and UV-visible-near IR spectroelectrochem. of (dppz)(C5Me5)M0/.bul.-/2-. But the pdo complexes undergo a reversible 1-electron redn. to yield o-semiquinone radical complexes (pdo)(C5Me5)ClM.bul. before releasing the chloride after the 2nd electron uptake. The fact that the dppz complexes undergo a Cl--dissociative 2-electron redn. despite the presence of a lowest lying p* MO (b1(phz)) with very little overlap to the metal suggests that an unoccupied metal/chloride-based orbital is lower in energy. This assertion is confirmed both by the half-wave redn. potentials of the ligands (tap, -1.95 V; dppz, -1.60 V; pdo, -0.85 V) and by the typical redn. peak potentials of (L)(C5Me5)ClM(PF6) (tap, -1.1 V; dppz, -1.3 V; pdo, -0.6 V; all values against Fc+/0). on SciFinder(R)

@article{Berger.2004, abstract = {Complexes between the chlorometal(III) cations [(C5Me5)ClM]+, M = Rh or Ir, and the 1,10-phenanthroline-derived \textgreek{a}-diimine (N N) ligands dipyrido[3,2-a:2',3'-c]phenazine (dppz), 1,4,7,10-tetraazaphenanthrene (tap), or 1,10-phenanthroline-5,6-dione (pdo) were studied by cyclic voltammetry, EPR, and UV-visible-NIR spectroelectrochem. with respect to either ligand-based or metal-centered (and then chloride-dissociative) redn. Two low-lying unoccupied MOs are present in each of these 3 N$\cap$N ligands; however, their different energies and interface properties are responsible for different results. Metal-centered chloride-releasing redn. was obsd. for complexes of the DNA-intercalation ligands dppz and tap to yield [(N N)(C5Me5)M] in a 2-electron step. The sepn. of \textgreek{a}-diimine centered optical orbitals and phenazine-based redox orbitals is apparent from the EPR and UV-visible-near IR spectroelectrochem. of [(dppz)(C5Me5)M]0/.bul.-/2-. But the pdo complexes undergo a reversible 1-electron redn. to yield o-semiquinone radical complexes [(pdo)(C5Me5)ClM].bul. before releasing the chloride after the 2nd electron uptake. The fact that the dppz complexes undergo a Cl--dissociative 2-electron redn. despite the presence of a lowest lying \textgreek{p}* MO (b1(phz)) with very little overlap to the metal suggests that an unoccupied metal/chloride-based orbital is lower in energy. This assertion is confirmed both by the half-wave redn. potentials of the ligands (tap, -1.95 V; dppz, -1.60 V; pdo, -0.85 V) and by the typical redn. peak potentials of [(L)(C5Me5)ClM](PF6) (tap, -1.1 V; dppz, -1.3 V; pdo, -0.6 V; all values against Fc+/0). [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Berger, Sascha and Fiedler, Jan and Reinhardt, Ralf and Kaim, Wolfgang.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/21e2632df8b720a6e07dc051b07c8c4ec/huebleriac}, doi = {10.1021/ic0351388}, interhash = {06e5e8637666af5a85740695c92952bc}, intrahash = {1e2632df8b720a6e07dc051b07c8c4ec}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {bond chloride chloro cleavage complex dipyridophenazine electrochem iridium iridium;metal ligand pentamethycyclopentadienyl redn rhodium}, number = 4, pages = {1530--1538}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Metal vs. Ligand Reduction in Complexes of Dipyrido[3,2-a: 2',3'-c]phenazine and Related Ligands with [(C5Me5)ClM]+ (M = Rh or Ir): Evidence for Potential Rather Than Orbital Control in the Reductive Cleavage of the Metal-Chloride Bond}, volume = 43, year = 2004 }