An x-ray crystallographic and single-crystal EPR investigation of the cationic, iron-centered radical tricarbonylbis(triphenylphosphine)iron(I), {Fe(CO)3(PPh3)2+}. A theoretical examination of the structural preferences of five-coordinated seventeen-electron complexes

MacNeil, Joseph H.; Chiverton, Antony C.; Fortier, Suzanne; Baird, Michael C.; Hynes, Rosemary C.; Williams, Antony J.; Preston, K. F.; Ziegler, Tom

doi:10.1021/ja00026a019

Cited by 33 publications

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“…20 The solid state data are consistent with [ 3 ]BF 4 featuring a Ni( ii ) center. The Fe center is situated in an approximately square-pyramidal S 2 P(CO) 2 environment, a geometry often adopted by mononuclear Fe( i ) 23 and dinuclear Fe( i )Fe( ii ) compounds. 24,25 The Fe-C basal distances (1.799, 1.790 Å) are somewhat shorter than the Fe-C apical distance (1.833 Å), as might be expected for a complex with CO ligands trans to strong σ-donors.…”

Section: Resultsmentioning

confidence: 99%

Mixed-Valence Nickel–Iron Dithiolate Models of the [NiFe]-Hydrogenase Active Site

et al. 2012

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A series of mixed-valence iron-nickel dithiolates is described. Oxidation of (diphosphine)Ni(dithiolate)Fe(CO)3 complexes 1, 2, and 3 with ferrocenium salts affords the corresponding tricarbonyl cations [(dppe)Ni(pdt)Fe(CO)3]+ ([1]+), [(dppe)Ni(edt)Fe(CO)3]+ ([2]+) and [(dcpe)Ni(pdt)Fe(CO)3]+ ([3]+), respectively, where dppe = Ph2PCH2CH2PPh2, dcpe = Cy2PCH2CH2PCy2, pdtH2 = HSCH2CH2CH2SH and edtH2 = HSCH2CH2SH. The cation [2]+ proved unstable, but the propanedithiolates are robust. IR and EPR spectroscopic measurements indicate that these species exist as Cs-symmetric species. Crystallographic characterization of [3]BF4 shows that Ni is square planar. Interaction of [1]BF4 with P-donor ligands (L) afforded a series of substituted derivatives of type [(dppe)Ni(pdt)Fe(CO)2L]BF4 for L = P(OPh)3 ([4a]BF4), P(p-C6H4Cl)3 ([4b]BF4), PPh2(2-py) ([4c]BF4), PPh2(OEt) ([4d]BF4), PPh3 ([4e]BF4), PPh2(o-C6H4OMe) ([4f]BF4), PPh2(o-C6H4OCH2OMe) ([4g]BF4), P(p-tol)3 ([4h]BF4), P(p-C6H4OMe)3 ([4i]BF4), PMePh2 ([4j]BF4). EPR analysis indicates that ethanedithiolate [2]+ exists as a single species at 110 K, whereas the propanedithiolate cations exist as a mixture of two conformers, which are proposed to be related through a flip of the chelate ring. Mössbauer spectra of 1 and oxidized S = ½ [4e]BF4 are both consistent with a low-spin Fe(i) state. The hyperfine coupling tensor of [4e]BF4 has a small isotropic component and significant anisotropy. DFT calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the SOMOs in complexes of the present type are localized in a Fe(i)-centered d(z2) orbital. The DFT calculations allow an assignment of oxidation states of the metals and rationalization of the conformers detected by EPR spectroscopy. Treatment of [1]+ with CN- and compact basic phosphines results in complex reactions. With dppe, [1]+ undergoes quasi-disproportionation to give 1 and the diamagnetic complex [(dppe)Ni(pdt)Fe(CO)2(dppe)]2+ ([5]2+), which features square-planar Ni linked to an octahedral Fe center.

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Section: Resultsmentioning

confidence: 99%

Mixed-Valence Nickel–Iron Dithiolate Models of the [NiFe]-Hydrogenase Active Site

et al. 2012

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“…CH 2 Cl 2 ) is a one-electron reversible process leading to the paramagnetic 17-electron species. 15,16 Due to the large atomic hyperfine constants 17 of 31 P, EPR is a very efficient method of determining the localization of the unpaired electron in the reduction or oxidation compounds of transition metal complexes of organophosphorus ligands. 18,19 We, therefore, decided to investigate by EPR the oxidation behavior of the iron and of the ruthenium complexes of the redox active chelating diphosphine 3,4-dimethyl-3 0 ,4 0 -bis-(diphenylphosphino)-tetrathiafulvalene (P2).…”

Section: Introductionmentioning

confidence: 99%

Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies

Gouverd

Biaso

Cataldo

et al. 2005

Phys. Chem. Chem. Phys.

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The radical cation of the redox active ligand 3,4-dimethyl-3 0 ,4 0 -bis-(diphenylphosphino)-tetrathiafulvalene (P2) has been chemically and electrochemically generated and studied by EPR spectroscopy. Consistent with DFT calculations, the observed hyperfine structure (septet due to the two methyl groups) indicates a strong delocalization of the unpaired electron on the central S 2 CQCS 2 part of the tetrathiafulvalene (TTF) moiety and zero spin densities on the phosphine groups. In contrast with the ruthenium(0) carbonyl complexes of P2 whose one-electron oxidation directly leads to decomplexation and produces P2 1 , one-electron oxidation of [Fe(P2)(CO) 3 ] gives rise to the metal-centered oxidation species [Fe (I) (P2)(CO) 3 ], characterized by a coupling with two 31 P nuclei and a rather large g-anisotropy. The stability of this complex is however modest and, after some minutes, the species resulting from the scission of a P-Fe bond is detected. Moreover, in presence of free ligand, [Fe (I) (P2)(CO) 3 ] reacts to give the complex [Fe (I) (P2) 2 (CO)] containing two TTF fragments. The two-electron oxidation of [Fe(P2)(CO) 3 ] leads to decomplexation and to the P2 1 spectrum. Besides EPR spectroscopy, cyclic voltammetry as well as FTIR spectroelectrochemistry are used in order to explain the behaviour of [Fe(P2)(CO) 3 ] upon oxidation. This behaviour notably differs from that of the Ru(0) counterpart. This difference is tentatively rationalized on the basis of structural arguments.

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“…15 The X-band EPR spectrum of electrochemically generated [1] + recorded at 77 K in MeCN/0.2 M [N n Bu 4 ][BF 4 ] (Fig. 3a) shows striking similarities to those of Ni I N 2 S 2 complexes (S = thiolato, thioether or sulfonato, N = amine donors; g J = 2.18-2.25; g > = 2.057-2.071), generated by chemical reduction of their Ni II counterparts, 16 and, crucially, is substantially different to those of Fe I centres including [Fe(CO) 3 (PPh 3 ) 2 ] + (g xx = 2.053, g yy = 2.090, g zz = 2.001) 17 and [(dppe)Ni(mpdt)Fe(CO) 3 ] + (g xx = 2.052, g yy = 2.050, g zz = 2.005 for one isomer). 7 Thus, the EPR spectroscopic data are consistent with a formal Ni I Fe II unit in [1] + where the Ni I centre adopts a d 9 , S = 1/2 configuration in which the unpaired electron resides in d-orbital orientated in the equatorial plane of the Ni I N 2 S 2 unit with associated spin Hamiltonian parameters g zz 4 g xx E g yy 4 g e .…”

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A Ni(i)Fe(ii) analogue of the Ni-L state of the active site of the [NiFe] hydrogenases

et al. 2015

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An x-ray crystallographic and single-crystal EPR investigation of the cationic, iron-centered radical tricarbonylbis(triphenylphosphine)iron(I), {Fe(CO)3(PPh3)2+}. A theoretical examination of the structural preferences of five-coordinated seventeen-electron complexes

Cited by 33 publications

References 0 publications

Mixed-Valence Nickel–Iron Dithiolate Models of the [NiFe]-Hydrogenase Active Site

Mixed-Valence Nickel–Iron Dithiolate Models of the [NiFe]-Hydrogenase Active Site

Tetrathiafulvalene–phosphine-based iron and ruthenium carbonyl complexes: Electrochemical and EPR studies

A Ni(i)Fe(ii) analogue of the Ni-L state of the active site of the [NiFe] hydrogenases

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