Robert Szilagyi | The University of British Columbia (original) (raw)
Papers by Robert Szilagyi
The Journal of Physical Chemistry A, 2012
In this work, we demonstrate the potential of multi-edge X-ray absorption near-edge structure (XA... more In this work, we demonstrate the potential of multi-edge X-ray absorption near-edge structure (XANES) analysis in completely defining the ground state electronic structure of a prototypical biomimetic complex of the [2Fe]-subcluster of the catalytic H-cluster of FeFe-hydrogenase. The spectral features at the ionization thresholds for Fe, S, C, and O 1s (K-edge) and Fe 2p (L-edge) core electrons were considered simultaneously to obtain the atomic compositions of the unoccupied frontier molecular orbitals. A systematic error analysis was carried out at the most informative S K-edge for spectra collected by multiple detection methods, at various data collection temperatures, and different sample preparation protocols. As expected for the difference in bonding between bridging and terminal Fe-S(thiolate) coordination, the Fe-S bond is more covalent in the [2Fe]-biomimetic complex with formally iron(I) centers (36 ± 2% S character per Fe-S bond) than in the previously described [2Fe-2S] clusters (25 ± 3% S character per Fe-S bond) with formally iron(III) centers. An electron hole-based analysis of the pre-edge features at Fe K-, Fe L-, and S K-edges experimentally defines the composition of the first three frontier unoccupied molecular orbitals to contain 4% Fe 4p, 44% Fe 3d, and 24% S 3p contributions per electron hole, respectively. The complementary CO ligand contribution thus can be defined as 28% per electron hole. These experimental orbital covalency values are important in rationalizing redox properties, electrophilicity of the metals, or nucleophilicity of the ligands, and critically evaluating the absolute accuracy of electronic structure calculations.
Acta crystallographica. Section C, Structural chemistry, 2016
Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination... more Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination chemistry due to the ease of introduction of steric and electronic substitutions at the pyrazole rings. The development and use of the tris(pyrazolyl)hydroborate ligand, called a `scorpionate', were pioneered by the late Professor Swiatoslaw Trofimenko. He developed a second generation for his ligand system by the introduction of 3-tert-butyl and 3-phenyl substituents and this new ligand system accounted for many remarkable developments in inorganic and coordination chemistry in stabilizing monomeric species while maintaining an open coordination site. Bismuth is remarkably harmless among the toxic heavy metal p-block elements and is now becoming popular as a replacement for highly toxic metal elements, such as lead. Two bismuth(III) complexes of the anionic sulfur-containing tripod tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate ligand were prepared. By recrystalliza...
Acta crystallographica. Section C, Structural chemistry, 2016
Tris(pyrazolyl)borate (scorpionate) ligands can be considered as the most prolific ligands in con... more Tris(pyrazolyl)borate (scorpionate) ligands can be considered as the most prolific ligands in contemporary coordination chemistry due to the availability of various steric and electronic substituents at the pyrazolyl rings that allow fine-tuning of the open-coordination site for metal centres. The thallium(I) complexes of anionic tridentate-chelating scorpionate ligands, namely [tris(3-mesityl-5-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]thallium(I) monohydrate, [Tl(C39H46BN6)]·H2O, (I), and [bis(3-mesityl-5-methyl-1H-pyrazol-1-yl-κN(2))(5-mesityl-3-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]thallium(I), [Tl(C39H46BN6)], (II), show a {Tl(I)N3} coordination, with average Tl(I)-N bond lengths of 2.53 and 2.55 Å in (I) and (II), respectively. The overall Tl(I) coordination geometry is distorted trigonal pyramidal, with the average N-Tl(I)-N angle being approximately 73° for both. The dihedral angle between the planes of the pyrazolyl and benzene rings of the mesityl group is 82° in (I), wh...
Inorganic chemistry, Jan 6, 2017
Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M... more Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M(II)(itao)(SO4)(H2O)0,1] (M = Co, Ni, Cu) and [Cu(Me6tren)(SO4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO4)] but not of [Cu(Me6tren)(SO4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M(II)(SO4)(H2O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-d...
JBIC Journal of Biological Inorganic Chemistry, 2016
The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitroge... more The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitrogen-based ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), was prepared by the reaction of the potassium salt of the ligand with the nickel-nitrosyl precursor [Ni(NO)(Br)(PPh 3 ) 2 ]. The obtained nitrosyl complexes as well as the corresponding chlorido complexes [Ni(NO)(Cl)(PPh 3 ) 2 ] and [Ni(Cl)(L3)] were characterized by X-ray crystallography and different spectroscopic methods including IR/far-IR, UV-Vis, NMR, and multi-edge X-ray absorption spectroscopy at the Ni K-, Ni L-, Cl K-, and P K-edges. For comparative electronic structure analysis we also performed DFT calculations to further elucidate the electronic structure of [Ni(NO)(L3)]. These results provide the nickel oxidation state and the character of the Ni-NO bond. The complex [Ni(NO)(L3)] is best described as [Ni (II) (NO (-) )(L3)], and the spectroscopic results indicate that the phosphane complexes have a similar [Ni (II) (NO (-) )(X)(PPh 3 ) 2 ] ground state.
Journal of the American Chemical Society, Jun 23, 2010
Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation... more Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations have been used to determine the electronic structures of two Mo bis-dithiolene complexes, [Mo(OSi)(bdt) 2 ] 1and [MoO(OSi)(bdt) 2 ] 1-, where OSi ) [OSiPh 2 t Bu] 1and bdt ) benzene-1,2-dithiolate(2-), that model the Mo(IV) and Mo(VI)dO states of the DMSO reductase family of molybdenum enzymes. These results show that the Mo(IV) complex undergoes metal-based oxidation unlike Mo tris-dithiolene complexes, indicating that the dithiolene ligands are behaving innocently. Experimentally validated calculations have been extended to model the oxo transfer reaction coordinate using dimethylsulfoxide (DMSO) as a substrate. The reaction proceeds through a transition state (TS1) to an intermediate with DMSO weakly bound, followed by a subsequent transition state (TS2) which is the largest barrier of the reaction. The factors that control the energies of these transition states, the nature of the oxo transfer process, and the role of the dithiolene ligand are discussed.
Dalton transactions (Cambridge, England : 2003), Jan 11, 2016
Potential energy surface mapping was completed for the entire catalytic cycle of palladium-cataly... more Potential energy surface mapping was completed for the entire catalytic cycle of palladium-catalysed cyanoesterification onto norbornene (NBE) using density functional theory calculations. We found that after the oxidative addition step of the reagent methyl cyanoformate, the reaction proceeds through an insertion of olefin into a Pd(II)-COOMe bond first. Subsequently, reductive elimination occurs by transferring the cyanide group from the Pd center to NBE. This rearrangement is triggered by the rotation of the ester group into a π-interaction with the Pd(II) centre. The regioselectivity of olefin insertion is controlled by ionic and covalent interactions in the precursor π-complex formation step. Importantly, all of the intermediates and transition states along the exo pathway were found to be more stable than the corresponding structures of the endo pathway without any sign of crossing over between the two surfaces via isomerization. The rate-determining step is the reductive elim...
Figure S1: Mulliken Population Analysis (MPA) for the β-Frontier Molecular Orbitals (FMOs) of a p... more Figure S1: Mulliken Population Analysis (MPA) for the β-Frontier Molecular Orbitals (FMOs) of a prototypical [Fe 2 (µ-S) 2 (MeS) 4 ] 2cluster. The α-manifold is an energetically degenerate mirror image Figure S2: Mechanism proposed by Pilet et al. The precursor molecule is dehydroglycine. Thiolate ligands have been omitted for the sake of clarity Figure S3: Mechanism proposed by Pilet et al. Free energy and enthalpy (in parenthesis) values in kJ·mol -1 . Spin densities for the Fe atoms, bridging sulfide (Sb) and terminal thiolate (St) ligands are also shown. Thiolate ligands have been truncated for the sake of clarity Figure S4: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for a Cys 3 His coordination environment for the intermediates of path B2 Imz (dotted line). Spin densities for the Fe atoms, bridging sulfide (S b ) and terminal thiolate (S t ) ligands are also shown. Thiolate ligands have been truncated for the sake of clarity. The respective diagram for the Cys 4 coordination environment is also presented for comparison (grey solid line) Figure S5: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for the intermediates of path A1 red (dotted line). Thiolate ligands have been omitted for the sake of clarity. The respective diagram for path A1 is also shown for comparison (grey solid line) Figure S6: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for the intermediates of path B1 red (dotted line). Thiolate ligands have been omitted for the sake of clarity. The respective diagram for path B1 is also shown for comparison (grey solid line) Figure S7: Transition state structure with displacement vectors corresponding to the -196 cm -1 normal mode frequency for coupling of a ring-opened, C-based biradical epoxide to the reactant [Fe 2 S 2 (SEt) 3 (Imidazole)]cluster. The formation of the former from epoxide requires about 146 kJ/mol in the absence of a unique enzymatic process
The biosynthesis of the active site of the [FeFe]-hydrogenases (H-cluster) remains a tantalizing ... more The biosynthesis of the active site of the [FeFe]-hydrogenases (H-cluster) remains a tantalizing puzzle due to its unprecedented and complex ligand environment. It contains a [2Fe] cluster ([2Fe] H ) bearing cyanide and carbon monoxide ligands attached to low-valence Fe ions and an abiological dithiolate ligand (SCH 2 XCH 2 S) 2À that bridges the two iron centers. Various experimentally testable hypotheses have already been put forward regarding the precursor molecule and the biosynthetic mechanism that leads to the formation of the dithiolate ligand. In this work, we report a density functional theory-based theoretical evaluation of these hypotheses. We find preference for a mechanistically simple and energetically favorable pathway that includes known radical-SAM (S-adenosylmethionine) catalyzed reactions. We modeled this pathway using a long alkyl chain precursor molecule that leads to the formation of pronanadithiolate (X ¼ CH 2 ). However, the same pathway can be readily adopted for the biosynthesis of the dithiomethylamine (X ¼ NH) or the dithiomethylether (X ¼ O) analog, provided that the proper precursor molecule is available. V C 2011 Wiley Periodicals, Inc. J Comput Chem 32: [3194][3195][3196][3197][3198][3199][3200][3201][3202][3203][3204][3205][3206] 2011
![Research paper thumbnail of Electronic structure of [Ni(II)S4] complexes from S K-edge X-ray absorption spectroscopy](https://attachments.academia-assets.com/54082053/thumbnails/1.jpg)
](Coordination Chemistry Reviews, 2013
The journal of physical chemistry. A, Jan 20, 2015
X-ray absorption spectroscopy is a unique experimental technique that can provide ground state el... more X-ray absorption spectroscopy is a unique experimental technique that can provide ground state electronic structure information about transition metal complexes with unoccupied d-manifold. The quantitative treatments of pre-edge and rising-edge features have already been developed for the sulfur- and chlorine-ligand K-edge excitations. The complementarity of using multiple core excitation edges from hard, tender, and soft X-ray energy regions has been defined for the first paper of this series. The given study provides compelling evidence for the transferability of the empirical transition dipole integral from ligand K-edge to metal L-edge and back to ligand K-edge in the tender X-ray energy range. The case study was performed for a series of homoleptic chloropalladium compounds at the chlorine K- and palladium L-edges. We propose the method described here to be generally applicable for other core level excitations, where complementarity of ground state electronic structural informa...
Inorganic chemistry, Jan 18, 2014
The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converte... more The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converted into the binuclear oxalatocopper(II) complex [{Cu(L1)}2(μ-C2O4)] upon exposure to O2/CO2 gas. (13)C-labeling experiments revealed that oxalate ions partially incorporated (13)CO2 molecules. Furthermore, the bicarbonatocopper(I) complex (NEt4)[Cu(L1){O2C(OH)}] in an Ar atmosphere and the α-ketocarboxylatocopper(I) complex Na[Cu(L1){O2CC(O)CH(CH3)2}] in an O2 atmosphere were also transformed spontaneously into the oxalato complex [{Cu(L1)}2(μ-C2O4)].
Metathesis Polymerization of Olefins and Polymerization of Alkynes, 1998
Inorganic Chemistry, 2014
One-electron-oxidized Ni(III)-phenoxide complexes with salen-type ligands, [Ni(salen)py2](2+) ([1... more One-electron-oxidized Ni(III)-phenoxide complexes with salen-type ligands, [Ni(salen)py2](2+) ([1(en)-py](2+)) and [Ni(1,2-salcn)py2](2+) ([1(cn)-py](2+)), with a five-membered chelate dinitrogen backbone and [Ni(salpn)py2](2+) ([2(pn)-py](2+)), with a six-membered chelate backbone, have been characterized with a combination of experimental and theoretical methods. The five-membered chelate complexes [1(en)-py](2+) and [1(cn)-py](2+) were assigned as Ni(III)-phenoxyl radical species, while the six-membered chelate complex [2(pn)-py](2+) was concluded to be a Ni(II)-bis(phenoxyl radical) species with metal-centered reduction in the course of the one-electron oxidation of the Ni(III)-phenoxide complex [2(pn)-py](+). Thus, the oxidation state of the one-electron-oxidized Ni(III) salen-type complexes depends on the chelate ring size of the dinitrogen backbone.
The Journal of Physical Chemistry A, 2012
In this work, we demonstrate the potential of multi-edge X-ray absorption near-edge structure (XA... more In this work, we demonstrate the potential of multi-edge X-ray absorption near-edge structure (XANES) analysis in completely defining the ground state electronic structure of a prototypical biomimetic complex of the [2Fe]-subcluster of the catalytic H-cluster of FeFe-hydrogenase. The spectral features at the ionization thresholds for Fe, S, C, and O 1s (K-edge) and Fe 2p (L-edge) core electrons were considered simultaneously to obtain the atomic compositions of the unoccupied frontier molecular orbitals. A systematic error analysis was carried out at the most informative S K-edge for spectra collected by multiple detection methods, at various data collection temperatures, and different sample preparation protocols. As expected for the difference in bonding between bridging and terminal Fe-S(thiolate) coordination, the Fe-S bond is more covalent in the [2Fe]-biomimetic complex with formally iron(I) centers (36 ± 2% S character per Fe-S bond) than in the previously described [2Fe-2S] clusters (25 ± 3% S character per Fe-S bond) with formally iron(III) centers. An electron hole-based analysis of the pre-edge features at Fe K-, Fe L-, and S K-edges experimentally defines the composition of the first three frontier unoccupied molecular orbitals to contain 4% Fe 4p, 44% Fe 3d, and 24% S 3p contributions per electron hole, respectively. The complementary CO ligand contribution thus can be defined as 28% per electron hole. These experimental orbital covalency values are important in rationalizing redox properties, electrophilicity of the metals, or nucleophilicity of the ligands, and critically evaluating the absolute accuracy of electronic structure calculations.
Acta crystallographica. Section C, Structural chemistry, 2016
Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination... more Tris(pyrazolyl)hydroborate ligands have been utilized in the fields of inorganic and coordination chemistry due to the ease of introduction of steric and electronic substitutions at the pyrazole rings. The development and use of the tris(pyrazolyl)hydroborate ligand, called a `scorpionate', were pioneered by the late Professor Swiatoslaw Trofimenko. He developed a second generation for his ligand system by the introduction of 3-tert-butyl and 3-phenyl substituents and this new ligand system accounted for many remarkable developments in inorganic and coordination chemistry in stabilizing monomeric species while maintaining an open coordination site. Bismuth is remarkably harmless among the toxic heavy metal p-block elements and is now becoming popular as a replacement for highly toxic metal elements, such as lead. Two bismuth(III) complexes of the anionic sulfur-containing tripod tris(3-tert-butyl-2-sulfanylidene-1H-imidazol-1-yl)hydroborate ligand were prepared. By recrystalliza...
Acta crystallographica. Section C, Structural chemistry, 2016
Tris(pyrazolyl)borate (scorpionate) ligands can be considered as the most prolific ligands in con... more Tris(pyrazolyl)borate (scorpionate) ligands can be considered as the most prolific ligands in contemporary coordination chemistry due to the availability of various steric and electronic substituents at the pyrazolyl rings that allow fine-tuning of the open-coordination site for metal centres. The thallium(I) complexes of anionic tridentate-chelating scorpionate ligands, namely [tris(3-mesityl-5-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]thallium(I) monohydrate, [Tl(C39H46BN6)]·H2O, (I), and [bis(3-mesityl-5-methyl-1H-pyrazol-1-yl-κN(2))(5-mesityl-3-methyl-1H-pyrazol-1-yl-κN(2))hydroborato]thallium(I), [Tl(C39H46BN6)], (II), show a {Tl(I)N3} coordination, with average Tl(I)-N bond lengths of 2.53 and 2.55 Å in (I) and (II), respectively. The overall Tl(I) coordination geometry is distorted trigonal pyramidal, with the average N-Tl(I)-N angle being approximately 73° for both. The dihedral angle between the planes of the pyrazolyl and benzene rings of the mesityl group is 82° in (I), wh...
Inorganic chemistry, Jan 6, 2017
Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M... more Sulfur K-edge X-ray absorption spectroscopy (XAS) spectra of the monodentate sulfate complexes [M(II)(itao)(SO4)(H2O)0,1] (M = Co, Ni, Cu) and [Cu(Me6tren)(SO4)] exhibit well-defined preedge transitions at 2479.4, 2479.9, 2478.4, and 2477.7 eV, respectively, despite having no direct metal-sulfur bond, while the XAS preedge of [Zn(itao)(SO4)] is featureless. The sulfur K-edge XAS of [Cu(itao)(SO4)] but not of [Cu(Me6tren)(SO4)] uniquely exhibits a weak transition at 2472.1 eV, an extraordinary 8.7 eV below the first inflection of the rising K-edge. Preedge transitions also appear in the sulfur K-edge XAS of crystalline [M(II)(SO4)(H2O)] (M = Fe, Co, Ni, and Cu, but not Zn) and in sulfates of higher-valent early transition metals. Ground-state density functional theory (DFT) and time-dependent DFT (TDDFT) calculations show that charge transfer from coordinated sulfate to paramagnetic late transition metals produces spin polarization that differentially mixes the spin-up (α) and spin-d...
JBIC Journal of Biological Inorganic Chemistry, 2016
The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitroge... more The linear nickel-nitrosyl complex [Ni(NO)(L3)] supported by a highly hindered tridentate nitrogen-based ligand, hydrotris(3-tertiary butyl-5-isopropyl-1-pyrazolyl)borate (denoted as L3), was prepared by the reaction of the potassium salt of the ligand with the nickel-nitrosyl precursor [Ni(NO)(Br)(PPh 3 ) 2 ]. The obtained nitrosyl complexes as well as the corresponding chlorido complexes [Ni(NO)(Cl)(PPh 3 ) 2 ] and [Ni(Cl)(L3)] were characterized by X-ray crystallography and different spectroscopic methods including IR/far-IR, UV-Vis, NMR, and multi-edge X-ray absorption spectroscopy at the Ni K-, Ni L-, Cl K-, and P K-edges. For comparative electronic structure analysis we also performed DFT calculations to further elucidate the electronic structure of [Ni(NO)(L3)]. These results provide the nickel oxidation state and the character of the Ni-NO bond. The complex [Ni(NO)(L3)] is best described as [Ni (II) (NO (-) )(L3)], and the spectroscopic results indicate that the phosphane complexes have a similar [Ni (II) (NO (-) )(X)(PPh 3 ) 2 ] ground state.
Journal of the American Chemical Society, Jun 23, 2010
Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculation... more Sulfur K-edge X-ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations have been used to determine the electronic structures of two Mo bis-dithiolene complexes, [Mo(OSi)(bdt) 2 ] 1and [MoO(OSi)(bdt) 2 ] 1-, where OSi ) [OSiPh 2 t Bu] 1and bdt ) benzene-1,2-dithiolate(2-), that model the Mo(IV) and Mo(VI)dO states of the DMSO reductase family of molybdenum enzymes. These results show that the Mo(IV) complex undergoes metal-based oxidation unlike Mo tris-dithiolene complexes, indicating that the dithiolene ligands are behaving innocently. Experimentally validated calculations have been extended to model the oxo transfer reaction coordinate using dimethylsulfoxide (DMSO) as a substrate. The reaction proceeds through a transition state (TS1) to an intermediate with DMSO weakly bound, followed by a subsequent transition state (TS2) which is the largest barrier of the reaction. The factors that control the energies of these transition states, the nature of the oxo transfer process, and the role of the dithiolene ligand are discussed.
Dalton transactions (Cambridge, England : 2003), Jan 11, 2016
Potential energy surface mapping was completed for the entire catalytic cycle of palladium-cataly... more Potential energy surface mapping was completed for the entire catalytic cycle of palladium-catalysed cyanoesterification onto norbornene (NBE) using density functional theory calculations. We found that after the oxidative addition step of the reagent methyl cyanoformate, the reaction proceeds through an insertion of olefin into a Pd(II)-COOMe bond first. Subsequently, reductive elimination occurs by transferring the cyanide group from the Pd center to NBE. This rearrangement is triggered by the rotation of the ester group into a π-interaction with the Pd(II) centre. The regioselectivity of olefin insertion is controlled by ionic and covalent interactions in the precursor π-complex formation step. Importantly, all of the intermediates and transition states along the exo pathway were found to be more stable than the corresponding structures of the endo pathway without any sign of crossing over between the two surfaces via isomerization. The rate-determining step is the reductive elim...
Figure S1: Mulliken Population Analysis (MPA) for the β-Frontier Molecular Orbitals (FMOs) of a p... more Figure S1: Mulliken Population Analysis (MPA) for the β-Frontier Molecular Orbitals (FMOs) of a prototypical [Fe 2 (µ-S) 2 (MeS) 4 ] 2cluster. The α-manifold is an energetically degenerate mirror image Figure S2: Mechanism proposed by Pilet et al. The precursor molecule is dehydroglycine. Thiolate ligands have been omitted for the sake of clarity Figure S3: Mechanism proposed by Pilet et al. Free energy and enthalpy (in parenthesis) values in kJ·mol -1 . Spin densities for the Fe atoms, bridging sulfide (Sb) and terminal thiolate (St) ligands are also shown. Thiolate ligands have been truncated for the sake of clarity Figure S4: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for a Cys 3 His coordination environment for the intermediates of path B2 Imz (dotted line). Spin densities for the Fe atoms, bridging sulfide (S b ) and terminal thiolate (S t ) ligands are also shown. Thiolate ligands have been truncated for the sake of clarity. The respective diagram for the Cys 4 coordination environment is also presented for comparison (grey solid line) Figure S5: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for the intermediates of path A1 red (dotted line). Thiolate ligands have been omitted for the sake of clarity. The respective diagram for path A1 is also shown for comparison (grey solid line) Figure S6: Free energy and enthalpy (in parenthesis) values in kJ mol -1 for the intermediates of path B1 red (dotted line). Thiolate ligands have been omitted for the sake of clarity. The respective diagram for path B1 is also shown for comparison (grey solid line) Figure S7: Transition state structure with displacement vectors corresponding to the -196 cm -1 normal mode frequency for coupling of a ring-opened, C-based biradical epoxide to the reactant [Fe 2 S 2 (SEt) 3 (Imidazole)]cluster. The formation of the former from epoxide requires about 146 kJ/mol in the absence of a unique enzymatic process
The biosynthesis of the active site of the [FeFe]-hydrogenases (H-cluster) remains a tantalizing ... more The biosynthesis of the active site of the [FeFe]-hydrogenases (H-cluster) remains a tantalizing puzzle due to its unprecedented and complex ligand environment. It contains a [2Fe] cluster ([2Fe] H ) bearing cyanide and carbon monoxide ligands attached to low-valence Fe ions and an abiological dithiolate ligand (SCH 2 XCH 2 S) 2À that bridges the two iron centers. Various experimentally testable hypotheses have already been put forward regarding the precursor molecule and the biosynthetic mechanism that leads to the formation of the dithiolate ligand. In this work, we report a density functional theory-based theoretical evaluation of these hypotheses. We find preference for a mechanistically simple and energetically favorable pathway that includes known radical-SAM (S-adenosylmethionine) catalyzed reactions. We modeled this pathway using a long alkyl chain precursor molecule that leads to the formation of pronanadithiolate (X ¼ CH 2 ). However, the same pathway can be readily adopted for the biosynthesis of the dithiomethylamine (X ¼ NH) or the dithiomethylether (X ¼ O) analog, provided that the proper precursor molecule is available. V C 2011 Wiley Periodicals, Inc. J Comput Chem 32: [3194][3195][3196][3197][3198][3199][3200][3201][3202][3203][3204][3205][3206] 2011
Coordination Chemistry Reviews, 2013
The journal of physical chemistry. A, Jan 20, 2015
X-ray absorption spectroscopy is a unique experimental technique that can provide ground state el... more X-ray absorption spectroscopy is a unique experimental technique that can provide ground state electronic structure information about transition metal complexes with unoccupied d-manifold. The quantitative treatments of pre-edge and rising-edge features have already been developed for the sulfur- and chlorine-ligand K-edge excitations. The complementarity of using multiple core excitation edges from hard, tender, and soft X-ray energy regions has been defined for the first paper of this series. The given study provides compelling evidence for the transferability of the empirical transition dipole integral from ligand K-edge to metal L-edge and back to ligand K-edge in the tender X-ray energy range. The case study was performed for a series of homoleptic chloropalladium compounds at the chlorine K- and palladium L-edges. We propose the method described here to be generally applicable for other core level excitations, where complementarity of ground state electronic structural informa...
Inorganic chemistry, Jan 18, 2014
The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converte... more The α-ketocarboxylatocopper(II) complex [{Cu(L1)}{O2CC(O)CH(CH3)2}] can be spontaneously converted into the binuclear oxalatocopper(II) complex [{Cu(L1)}2(μ-C2O4)] upon exposure to O2/CO2 gas. (13)C-labeling experiments revealed that oxalate ions partially incorporated (13)CO2 molecules. Furthermore, the bicarbonatocopper(I) complex (NEt4)[Cu(L1){O2C(OH)}] in an Ar atmosphere and the α-ketocarboxylatocopper(I) complex Na[Cu(L1){O2CC(O)CH(CH3)2}] in an O2 atmosphere were also transformed spontaneously into the oxalato complex [{Cu(L1)}2(μ-C2O4)].
Metathesis Polymerization of Olefins and Polymerization of Alkynes, 1998
Inorganic Chemistry, 2014
One-electron-oxidized Ni(III)-phenoxide complexes with salen-type ligands, [Ni(salen)py2](2+) ([1... more One-electron-oxidized Ni(III)-phenoxide complexes with salen-type ligands, [Ni(salen)py2](2+) ([1(en)-py](2+)) and [Ni(1,2-salcn)py2](2+) ([1(cn)-py](2+)), with a five-membered chelate dinitrogen backbone and [Ni(salpn)py2](2+) ([2(pn)-py](2+)), with a six-membered chelate backbone, have been characterized with a combination of experimental and theoretical methods. The five-membered chelate complexes [1(en)-py](2+) and [1(cn)-py](2+) were assigned as Ni(III)-phenoxyl radical species, while the six-membered chelate complex [2(pn)-py](2+) was concluded to be a Ni(II)-bis(phenoxyl radical) species with metal-centered reduction in the course of the one-electron oxidation of the Ni(III)-phenoxide complex [2(pn)-py](+). Thus, the oxidation state of the one-electron-oxidized Ni(III) salen-type complexes depends on the chelate ring size of the dinitrogen backbone.