Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands
The series of complexes [OsII(CN)5L]n-, with L = pyridine or pyrazine derivatives, were prepared in aqueous solution and, in some cases, as sodium or potassium salts. The main feature in the UV-visible spectra is the appearance of an intense, asymmetric MLCT band, split under spin-orbit coupling. Th...
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todo:paper_00201669_v35_n21_p6327_Slep2023-10-03T14:16:44Z Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands Slep, L.D. Baraldo, L.M. Olabe, J.A. The series of complexes [OsII(CN)5L]n-, with L = pyridine or pyrazine derivatives, were prepared in aqueous solution and, in some cases, as sodium or potassium salts. The main feature in the UV-visible spectra is the appearance of an intense, asymmetric MLCT band, split under spin-orbit coupling. The energies and intensities of the MLCT bands decrease and increase, respectively, with the electron-acceptor ability of L, and strong solvatochromic energy shifts are observed in different organic media. The Os(II) complexes can be oxidized chemically or electrochemically to the Os(III) species; the latter show typical LMCT bands in the visible region, independent of L. The redox potentials for the OsIII.II couples (range 0.6-1.0 V (NHE)), shift positively when L becomes more electron-withdrawing or less basic. Reduction potentials for the bound and free Mepz+ ligand showed similar values, ca. -0.53 V (NHE), for the three [M(CN)5L]n- complexes, suggesting similar back-bonding abilities of Fe, Ru, and Os toward a given L ligand; this is confirmed by the linear plots with unit slope obtained for the energy of the MLCT bands of the [M(CN)5L]n- complexes (M = Fe, Ru) against the values for the [Os(CN)5L]n- complexes. The IR spectra show intense and weak bands at ca. 2050 and 2100 cm-1, associated with equatorial and axial cyanide stretchings, respectively. The dissociation rate constant for pyrazine release from the [Os(CN)5pz]3- ion shows a saturation kinetic behavior, typical of dissociative mechanisms found for the iron and ruthenium analog complexes; the specific dissociation rate constant, k-pz = 2.0 × 10-8 s-1 (25 °C, I = 0.5 M), is about 3 and 4 orders of magnitude slower than the values found for [Ru(CN)5pz]3- and [Fe(CN)5pz]3-, respectively; this is ascribed mainly to the strong σ interaction in the Os-L bond. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00201669_v35_n21_p6327_Slep |
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Universidad de Buenos Aires |
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I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| description |
The series of complexes [OsII(CN)5L]n-, with L = pyridine or pyrazine derivatives, were prepared in aqueous solution and, in some cases, as sodium or potassium salts. The main feature in the UV-visible spectra is the appearance of an intense, asymmetric MLCT band, split under spin-orbit coupling. The energies and intensities of the MLCT bands decrease and increase, respectively, with the electron-acceptor ability of L, and strong solvatochromic energy shifts are observed in different organic media. The Os(II) complexes can be oxidized chemically or electrochemically to the Os(III) species; the latter show typical LMCT bands in the visible region, independent of L. The redox potentials for the OsIII.II couples (range 0.6-1.0 V (NHE)), shift positively when L becomes more electron-withdrawing or less basic. Reduction potentials for the bound and free Mepz+ ligand showed similar values, ca. -0.53 V (NHE), for the three [M(CN)5L]n- complexes, suggesting similar back-bonding abilities of Fe, Ru, and Os toward a given L ligand; this is confirmed by the linear plots with unit slope obtained for the energy of the MLCT bands of the [M(CN)5L]n- complexes (M = Fe, Ru) against the values for the [Os(CN)5L]n- complexes. The IR spectra show intense and weak bands at ca. 2050 and 2100 cm-1, associated with equatorial and axial cyanide stretchings, respectively. The dissociation rate constant for pyrazine release from the [Os(CN)5pz]3- ion shows a saturation kinetic behavior, typical of dissociative mechanisms found for the iron and ruthenium analog complexes; the specific dissociation rate constant, k-pz = 2.0 × 10-8 s-1 (25 °C, I = 0.5 M), is about 3 and 4 orders of magnitude slower than the values found for [Ru(CN)5pz]3- and [Fe(CN)5pz]3-, respectively; this is ascribed mainly to the strong σ interaction in the Os-L bond. |
| format |
JOUR |
| author |
Slep, L.D. Baraldo, L.M. Olabe, J.A. |
| spellingShingle |
Slep, L.D. Baraldo, L.M. Olabe, J.A. Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| author_facet |
Slep, L.D. Baraldo, L.M. Olabe, J.A. |
| author_sort |
Slep, L.D. |
| title |
Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| title_short |
Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| title_full |
Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| title_fullStr |
Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| title_full_unstemmed |
Synthesis and Electronic Structure of Pentacyanoosmate(II) Complexes with N-Heterocyclic Ligands |
| title_sort |
synthesis and electronic structure of pentacyanoosmate(ii) complexes with n-heterocyclic ligands |
| url |
http://hdl.handle.net/20.500.12110/paper_00201669_v35_n21_p6327_Slep |
| work_keys_str_mv |
AT slepld synthesisandelectronicstructureofpentacyanoosmateiicomplexeswithnheterocyclicligands AT baraldolm synthesisandelectronicstructureofpentacyanoosmateiicomplexeswithnheterocyclicligands AT olabeja synthesisandelectronicstructureofpentacyanoosmateiicomplexeswithnheterocyclicligands |
| _version_ |
1807316607765053440 |