%0 Journal Article %1 Vergara.2009 %A Vergara, Monica M. %A Garcia Posse, Monica E. %A Fagalde, Florencia %A Katz, Nestor E. %A Fiedler, Jan %A Sarkar, Biprajit %A Sieger, Monika %A Kaim, Wolfgang. %D 2009 %J Inorganica Chimica Acta %K bis complex cyanides diruthenium ligand mixed pyridyl terminal valency %N 1 %P 163--167 %R 10.1016/j.ica.2009.09.018 %T Mixed-valency with cyanides as terminal ligands: Diruthenium(III,II) complexes with the 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine bridge and variable co-ligands (CN- vs. bpy or NH3) %V 363 %X New diruthenium complexes (PPN)4(NC)4Ru(m-bptz)Ru(CN)4, (PPN)4 1, and (bpy)2Ru(m-bptz)Ru(CN)4, 2, (PPN+ = bis(triphenylphospine)iminium; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; bpy = 2,2'-bipyridine), were synthesized and characterized by spectroscopic and electrochem. techniques. The comproportionation const. Kc = 107.0 of the mixed-valent species (NC)4Ru(m-bptz)Ru(CN)43- as obtained by oxidn. of 14- in CH3CN is much lower than the Kc = 1015.0 previously detected for (H3N)4Ru(bptz)Ru(NH3)45+, reflecting the competition between CN- and bptz for the p-electron d. of the metals. Comparison with several other bptz-bridged diruthenium(II,III) complexes reveals an approx. correlation between Kc and the diminishing effective p acceptor capacity of the ancillary terminal ligands. In addn. to the intense MLCT absorption at lmax = 624 nm, the main IVCT (intervalence charge transfer) band of 13- was detected by spectroelectrochem. at lmax = 1695 nm (in CH3CN; e = 3200 M-1 cm-1). The exptl. bandwidth at half-height, Dn1/2 = 2700 cm-1, is slightly smaller than the theor. value Dn1/2 = 3660 cm-1, calcd. from the Hush approxn. for Class II mixed-valent species. In agreement with comparatively moderate metal-metal coupling, the mixed-valent intermediate 1 3- was found to be EPR silent even at 4 K. The unsym. mixed-valent complex (bpy)2RuII(m-bptz)RuIII(CN)4+, obtained in situ by bromine oxidn. of 2 in CH3CN/H2O, displays a broad NIR absorption originating from an IVCT transition at lmax = 1075 nm (e $\approx$ 1000 M-1 cm-1, Dn1/2 $\approx$ 4000 cm-1). In addn., the lifetime of the excited-state of the mononuclear precursor complex Ru(bptz)(CN)42- was measured in H2O by laser flash photolysis; the obtained value of t = 19.6 ns reveals that bptz induces a metal-to-ligand electronic delocalization effect intermediate between that induced by bpy and bpz (bpz = 2,2'-bipyrazine) in analogous tetracyanoruthenium complexes. on SciFinder(R)

@article{Vergara.2009, abstract = {New diruthenium complexes (PPN)4[(NC)4Ru(\textgreek{m}-bptz)Ru(CN)4], (PPN)4 1, and [(bpy)2Ru(\textgreek{m}-bptz)Ru(CN)4], 2, (PPN+ = bis(triphenylphospine)iminium; bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; bpy = 2,2'-bipyridine), were synthesized and characterized by spectroscopic and electrochem. techniques. The comproportionation const. Kc = 107.0 of the mixed-valent species [(NC)4Ru(\textgreek{m}-bptz)Ru(CN)4]3- as obtained by oxidn. of 14- in CH3CN is much lower than the Kc = 1015.0 previously detected for [(H3N)4Ru(bptz)Ru(NH3)4]5+, reflecting the competition between CN- and bptz for the \textgreek{p}-electron d. of the metals. Comparison with several other bptz-bridged diruthenium(II,III) complexes reveals an approx. correlation between Kc and the diminishing effective \textgreek{p} acceptor capacity of the ancillary terminal ligands. In addn. to the intense MLCT absorption at \textgreek{l}max = 624 nm, the main IVCT (intervalence charge transfer) band of 13- was detected by spectroelectrochem. at \textgreek{l}max = 1695 nm (in CH3CN; \textgreek{e} = 3200 M-1 cm-1). The exptl. bandwidth at half-height, \textgreek{Dn}1/2 = 2700 cm-1, is slightly smaller than the theor. value \textgreek{Dn}1/2 = 3660 cm-1, calcd. from the Hush approxn. for Class II mixed-valent species. In agreement with comparatively moderate metal-metal coupling, the mixed-valent intermediate 1 3- was found to be EPR silent even at 4 K. The unsym. mixed-valent complex [(bpy)2RuII(\textgreek{m}-bptz)RuIII(CN)4]+, obtained in situ by bromine oxidn. of 2 in CH3CN/H2O, displays a broad NIR absorption originating from an IVCT transition at \textgreek{l}max = 1075 nm (\textgreek{e} $\approx$ 1000 M-1 cm-1, \textgreek{Dn}1/2 $\approx$ 4000 cm-1). In addn., the lifetime of the excited-state of the mononuclear precursor complex [Ru(bptz)(CN)4]2- was measured in H2O by laser flash photolysis; the obtained value of \textgreek{t} = 19.6 ns reveals that bptz induces a metal-to-ligand electronic delocalization effect intermediate between that induced by bpy and bpz (bpz = 2,2'-bipyrazine) in analogous tetracyanoruthenium complexes. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Vergara, Monica M. and {Garcia Posse}, Monica E. and Fagalde, Florencia and Katz, Nestor E. and Fiedler, Jan and Sarkar, Biprajit and Sieger, Monika and Kaim, Wolfgang.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/26dc4ee03d5434cc6f2236dd357b2bddc/huebleriac}, doi = {10.1016/j.ica.2009.09.018}, interhash = {ecc67fe4dc325a13104dd4c0779e689e}, intrahash = {6dc4ee03d5434cc6f2236dd357b2bddc}, issn = {0020-1693}, journal = {Inorganica Chimica Acta}, keywords = {bis complex cyanides diruthenium ligand mixed pyridyl terminal valency}, number = 1, pages = {163--167}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Mixed-valency with cyanides as terminal ligands: Diruthenium(III,II) complexes with the 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine bridge and variable co-ligands (CN- vs. bpy or NH3)}, volume = 363, year = 2009 }