Vasco Gama - Academia.edu (original) (raw)
Papers by Vasco Gama
Crystals
Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene... more Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO4− and SbF6− are reported, their electron transport and optical properties investigated, and then compared to the ClO4− salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β″-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (Ωcm)−1, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO4− and SbF6− salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that we...
Crystals
The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-... more The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF 4 − anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF 4 and β"-(CNB-EDT-TTF) 4 BF 4 , can be obtained. The 1:1 salt is an electrical insulator isostructural to the ClO 4 analogue previously described. The 4:1 salt is a new member of the family of 2D metals of this donor with different small anions X, (CNB-EDT-TTF) 4 X, characterized by a bilayer arrangement of the donors and it was obtained in a monoclinic polymorph with a β"-type donor packing pattern. The small anions in this compound are severely disordered between the donor bilayers, which present slightly larger lattice parameters than the isostructural ClO 4 analogue. Both electrical conductivity and thermoelectric power measurements in single crystals denote metallic properties as predicted by electronic band structure calculations. As a consequence of the anion disorder the metallic regime of the electrical conductivity denotes electronic localization effects with a progressive increase of resistivity below~25 K. Because of the larger lattice parameters the intermolecular interactions and electronic bandwidth are decreased compared to other (CNB-EDT-TTF) 4 X salts. The large and positive thermoelectric power S of this compound (~110 µV/K in the range 100-330 K) and its electrical conductivity σ = 20 S/cm at room temperature lead to a power factor S 2 σ = 24 µW/K 2 m, quite large among molecular conductors, placing these compounds as potential candidates for thermoelectric materials.
Chemical Engineering Communications
European Journal of Inorganic Chemistry, 2001
Inorganic chemistry, Jan 28, 2016
Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedi... more Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of triiodide I3(-) affords two different polymorphs (β″ and κ) with the composition (CNB-EDT-TTF)4I3, both with a bilayer structure of the donors. These polymorphs differ in the packing patterns (β″- and κ-type) of the donor molecules in each layer, in both cases with bifurcated C-N···H interactions effectively coupling head-to-head donor molecules between layer pairs. Two β″ polymorphs can be obtained with different degrees of anionic ordering. In one disordered phase, β″d, with a smaller unit cell, the triiodide anions are disordered over two possible positions in a channel between the donor bilayers, while in the ordered phase, β″o, the triiodide anions occupy only one of those positions in this channel, leading to the doubling of the unit cell in the layer plane. These results for β″ phases contrast with the κ polymorph previously...
… Section C: Crystal …, 2006
The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] ... more The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] x THF, where [Fe(Cp*)(2)](+) is the decamethylferrocenium cation, dmio is the 2-oxo-1,3-dithiole-4,5-dithiolate dianion and THF is tetrahydrofuran, crystallizes with two independent half-anion units [one Ni atom is at the centre of symmetry ({1/2}, {1/2}, 0) and the other is at the centre of symmetry ({1/2},0, {1/2})], one cation unit (located in a general position) and one THF solvent molecule in the asymmetric unit. The crystal structure consists of two-dimensional layers composed of parallel mixed chains, where pairs of cations alternate with single anions. These layers are separated by sheets of anions and THF molecules.
CrystEngComm, 2009
A new compound, [Fe(5-Cl-qsal) 2 ][Ni(a-tpdt) 2 ].CH 3 CN, where a-tpdt ¼ 2,3-thiophenedithiolate... more A new compound, [Fe(5-Cl-qsal) 2 ][Ni(a-tpdt) 2 ].CH 3 CN, where a-tpdt ¼ 2,3-thiophenedithiolate and H5-Cl-qsal ¼ N-(8-quinolyl)-5-chlorosalicylaldimine, was prepared and structurally and magnetically characterized. The crystal structure is based on an arrangement of alternate layers of [Fe(5-Cl-qsal) 2 ] + cations and [Ni(a-tpdt) 2 ] À anions. The magnetic measurements and M€ ossbauer spectroscopy revealed hybrid behavior in this compound, where a ferromagnetic cluster-glass behavior, ascribed to the anions network, and a spin crossover (SCO) of the [Fe(5-Cl-qsal) 2 ] + cations were observed. The glassy behavior, with a blocking temperature of ca. 7.5 K, results from the disorder in the anionic layer and the competition between ferro-and antiferromagnetic interactions in the anionic layers. The SCO process with T 1/2 ¼ 298 K (high spin fraction ¼ g HS ¼ 0.5) is rather sluggish in the limits of the conversion (g HS $ 0 and g HS $ 1), which is attributed to the effect of the anions that seem to restrict somehow the structural distortions of the cations associated with the SCO process.
Journal de Physique I, 1993
In this work we present and discuss the temperature variation of X-ray, EPR and nuclear spin-latt... more In this work we present and discuss the temperature variation of X-ray, EPR and nuclear spin-lattice relaxation rate measurements for the two quasi-one-dimensional compounds alpha-(Per)2Fe(mnt)2 and alpha-(Per)2Co(mnt)2. From X-ray and EPR intensity data, a Peierls instability of the Perylene stacks is found to take place at 58 K and 75 K for the Fe and Co derivatives respectively. In contrast to other members of this series of two-chain compounds, the M(mnt)2, stacks are found to play no role in the Peierls instability. As for diffusive excitations of localized spins in dimerized Fe(mnt)2, stacks, their influence is shown to dominate the temperature variation of both the spin-lattice nuclear relaxation rate and the previously measured Faraday spin susceptibility.
Acta Crystallographica Section A Foundations of Crystallography
Synthetic Metals, 1991
ABSTRACT E.S.R., electrical transport and structural data are reported for new members of the fam... more ABSTRACT E.S.R., electrical transport and structural data are reported for new members of the family Per2[M(mnt)2], with M=Cu, Ni, Co, and Fe. The experimental results revealed the existence of two types of behaviour for M=Cu, Ni one metallic (α-phase) and another with semiconducting properties (β-phase). Results are compared with the early reported for M=Au, Pt and Pd.
[
ABSTRACT The phase transitions of the low dimensional conductors (Per)2[M(mnt)2] (M = Cu, Ni, Co ... more ABSTRACT The phase transitions of the low dimensional conductors (Per)2[M(mnt)2] (M = Cu, Ni, Co and Fe) were studied by X-ray diffuse scattering techniques. The metal-insulator transitions observed at 33, 25, 73 and 58 K for the Cu, Ni, Co and Fe compounds respectively, were found to correspond to a tetramerization on the perylene chains in the case of the Ni and Cu derivatives and to a dimerization for the Fe and Co derivatives. In all cases, the periodic lattice distortion can be associated to a 2kF Peierls instability of the perylene chains. The Ni compound shows in addition to the 2kF distortion also a lattice instability at twice this wave vector, which corresponds to a dimerization of the Ni(mnt)2 chain of localized 1/2 spin towards a non magnetic Spin-Peierls like ground state. The results are compared with previous studies of the Au, Pt and Pd analogs and the subtle nature of the lattice instabilities occurring in these compounds is discussed.
ABSTRACT The synthesis, electrocrystallisation and characterisation of (Perylene)2Au(cdc)2 single... more ABSTRACT The synthesis, electrocrystallisation and characterisation of (Perylene)2Au(cdc)2 single crystals, where cdc=cyanodithiocarbimate, are reported. The electrical conductivity and thermoelectric power exhibit metallic character at room temperature, with typical values σRT=150 S. cm−1 and S =35μV.K−1, respectively. Both resistivity and thermopower exhibit shallow minima in the range 100–150 K. Static magnetic susceptibility measurements show a Pauli-like behaviour ascribed to the perylene chains, with indication of a transition at ≈45 K. These properties are compared with those of other perylene conductors containing dithiolate complexes and the role of disorder is discussed.
Inorganic and Organometallic Polymers with Special Properties, NATO ASI SeriesVolume 206, p163-177, 1992
Synthetic Metals, 2001
ABSTRACT Cited By (since 1996): 3, Export Date: 24 April 2012, Source: Scopus
Topics in Organometallic Chemistry, 2009
ABSTRACT The properties of the salts based on metallocenium cations and transition metal bisdicha... more ABSTRACT The properties of the salts based on metallocenium cations and transition metal bisdichalcogenide anions are reviewed and particular attention is paid to the correlation between the magnetic properties correlated and the crystal and molecular structures. The large majority of these salts have crystal structures based on linear chain arrangements of alternating cation (D+) and anion (A−) stacks which are classified in four major structural types, depending on the stacking motifs. The magnetic properties of these salts, which at low temperatures can present a wide range of magnetic order type and phase transitions, are correlated with the type of magnetic interaction between the magnetic building blocks, which in the large majority of the cases can be well described by the McConnell model using spin density calculations. KeywordsCrystal structures–Magnetic properties–Metallocenium salts–Metal-bisdithiolenes
![Research paper thumbnail of Magnetic properties of [Fe(Cp*)2]+ salts of M(dmit)2 and M(dmio)2 (M = Ni, Pd and Pt) anions](https://attachments.academia-assets.com/44472708/thumbnails/1.jpg)
](Synthetic Metals, 1999
The synthesis and the magnetic properties of decamethylferrocenium salts of the planar radical an... more The synthesis and the magnetic properties of decamethylferrocenium salts of the planar radical anions [M(dmix)d-, where M = Ni, Pd and Pt; and dmix = dmio and dmit, are presented.
Acta crystallographica. Section C, Crystal structure communications, 2006
The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] ... more The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] x THF, where [Fe(Cp*)(2)](+) is the decamethylferrocenium cation, dmio is the 2-oxo-1,3-dithiole-4,5-dithiolate dianion and THF is tetrahydrofuran, crystallizes with two independent half-anion units [one Ni atom is at the centre of symmetry ({1/2}, {1/2}, 0) and the other is at the centre of symmetry ({1/2},0, {1/2})], one cation unit (located in a general position) and one THF solvent molecule in the asymmetric unit. The crystal structure consists of two-dimensional layers composed of parallel mixed chains, where pairs of cations alternate with single anions. These layers are separated by sheets of anions and THF molecules.
Journal of the Chemical Society, Dalton Transactions, 2002
ABSTRACT The new compound [Co(η5-C5H5)(dppf-P,P′)I]I, 1, was synthesised by the stoichiometric re... more ABSTRACT The new compound [Co(η5-C5H5)(dppf-P,P′)I]I, 1, was synthesised by the stoichiometric reaction of the Co(III) complex [Co(η5-C5H5)(CO)I2], 2, with 1,1′-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2, and was characterised by multinuclear NMR spectroscopy. Exposure to air of THF or CH2Cl2 solutions of compound 1 gave, in an unexpected way, a polymeric chain comprising bridging 1,1′-bis(oxodiphenylphosphoranyl)ferrocene (dppfO2) joining tetrahedral Co(II) units [CoI2(μ-dppfO2)]n, 3. Attempts to obtain the polymeric chain 3 by the direct reaction of dppfO2 with CoI2, in CH2Cl2, gave instead the monomeric compound [CoI2(dppfO2)], 4, in which dppfO2 is coordinated in a chelating mode. The structural characterisation of compounds 2, 3, and 4 was carried out by single crystal X-ray diffraction studies. The magnetic behaviour of [CoI2(dppfO2)] and [CoI2(μ-dppfO2)]n was studied, and the results are consistent with tetrahedral S = 3/2 CoII, possessing a 4A2 ground state, and S = 0 FeII. In these compounds, CoII negative zero field splittings were determined from an analysis of the magnetic susceptibility temperature dependence, with D/k = −13 and −14 K for CoI2(dppfO2) and [CoI2(μ-dppfO2)]n, respectively. DFT calculations were performed in order to understand the electronic structure of [Co(η5-C5H5)(dppf-P,P′)I]I, 1, as well as that of the paramagnetic specie [CoI2(dppfO2)], 4. The [CoI2(μ-dppfO2)]n chain was also analysed and found to behave very similarly to the monomeric iodine derivative 4. The calculations showed the unpaired electrons to be localized on the Co(II) centre in all these species. The rather complicated electrochemical behaviour exhibited by the dppf complex [CoIII(η5-C5H5)(dppf-P,P′)I]I and by [Co(dppfO2)I2] is discussed.
Crystals
Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene... more Two new members of the family of bilayer compounds (CNB-EDT-TTF)4X, (CNB-EDT-TTF = 5-cyanobenzene-ethylenedithio-tetrathiafulvalene) with anions X = ReO4− and SbF6− are reported, their electron transport and optical properties investigated, and then compared to the ClO4− salt that was previously described. These compounds share the same structural type, i.e. bilayers of donors, which are packed in a β″-type pattern and then separated by layers of highly disordered anions. The absolute values of the electrical resistivity measured in single crystals within the layers were found in the range of 5 to 18 (Ωcm)−1, with a significantly sample dependence being ascribed to intrinsic disorder effects. The ClO4− and SbF6− salts exhibit metallic behavior with the resistivity decreasing upon cooling almost linearly with temperature until a broad minimum is reached between 15 and 80 K, depending on crystal quality; this is followed by an upturn of resistivity reaching values at T = 1.5 K that we...
Crystals
The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-... more The preparation and characterization of new salts based on the dissymmetrical TTF derivative CNB-EDT-TTF (cyanobenzene-ethylenedithio-tetrathiafulvalene) and BF 4 − anions, are reported. Depending on the electrocrystallization conditions salts with different stoichiometries, (CNB-EDT-TTF)BF 4 and β"-(CNB-EDT-TTF) 4 BF 4 , can be obtained. The 1:1 salt is an electrical insulator isostructural to the ClO 4 analogue previously described. The 4:1 salt is a new member of the family of 2D metals of this donor with different small anions X, (CNB-EDT-TTF) 4 X, characterized by a bilayer arrangement of the donors and it was obtained in a monoclinic polymorph with a β"-type donor packing pattern. The small anions in this compound are severely disordered between the donor bilayers, which present slightly larger lattice parameters than the isostructural ClO 4 analogue. Both electrical conductivity and thermoelectric power measurements in single crystals denote metallic properties as predicted by electronic band structure calculations. As a consequence of the anion disorder the metallic regime of the electrical conductivity denotes electronic localization effects with a progressive increase of resistivity below~25 K. Because of the larger lattice parameters the intermolecular interactions and electronic bandwidth are decreased compared to other (CNB-EDT-TTF) 4 X salts. The large and positive thermoelectric power S of this compound (~110 µV/K in the range 100-330 K) and its electrical conductivity σ = 20 S/cm at room temperature lead to a power factor S 2 σ = 24 µW/K 2 m, quite large among molecular conductors, placing these compounds as potential candidates for thermoelectric materials.
Chemical Engineering Communications
European Journal of Inorganic Chemistry, 2001
Inorganic chemistry, Jan 28, 2016
Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedi... more Electrocrystallization from solutions of the dissymmetrical ET derivative cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF) in the presence of triiodide I3(-) affords two different polymorphs (β″ and κ) with the composition (CNB-EDT-TTF)4I3, both with a bilayer structure of the donors. These polymorphs differ in the packing patterns (β″- and κ-type) of the donor molecules in each layer, in both cases with bifurcated C-N···H interactions effectively coupling head-to-head donor molecules between layer pairs. Two β″ polymorphs can be obtained with different degrees of anionic ordering. In one disordered phase, β″d, with a smaller unit cell, the triiodide anions are disordered over two possible positions in a channel between the donor bilayers, while in the ordered phase, β″o, the triiodide anions occupy only one of those positions in this channel, leading to the doubling of the unit cell in the layer plane. These results for β″ phases contrast with the κ polymorph previously...
… Section C: Crystal …, 2006
The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] ... more The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] x THF, where [Fe(Cp*)(2)](+) is the decamethylferrocenium cation, dmio is the 2-oxo-1,3-dithiole-4,5-dithiolate dianion and THF is tetrahydrofuran, crystallizes with two independent half-anion units [one Ni atom is at the centre of symmetry ({1/2}, {1/2}, 0) and the other is at the centre of symmetry ({1/2},0, {1/2})], one cation unit (located in a general position) and one THF solvent molecule in the asymmetric unit. The crystal structure consists of two-dimensional layers composed of parallel mixed chains, where pairs of cations alternate with single anions. These layers are separated by sheets of anions and THF molecules.
CrystEngComm, 2009
A new compound, [Fe(5-Cl-qsal) 2 ][Ni(a-tpdt) 2 ].CH 3 CN, where a-tpdt ¼ 2,3-thiophenedithiolate... more A new compound, [Fe(5-Cl-qsal) 2 ][Ni(a-tpdt) 2 ].CH 3 CN, where a-tpdt ¼ 2,3-thiophenedithiolate and H5-Cl-qsal ¼ N-(8-quinolyl)-5-chlorosalicylaldimine, was prepared and structurally and magnetically characterized. The crystal structure is based on an arrangement of alternate layers of [Fe(5-Cl-qsal) 2 ] + cations and [Ni(a-tpdt) 2 ] À anions. The magnetic measurements and M€ ossbauer spectroscopy revealed hybrid behavior in this compound, where a ferromagnetic cluster-glass behavior, ascribed to the anions network, and a spin crossover (SCO) of the [Fe(5-Cl-qsal) 2 ] + cations were observed. The glassy behavior, with a blocking temperature of ca. 7.5 K, results from the disorder in the anionic layer and the competition between ferro-and antiferromagnetic interactions in the anionic layers. The SCO process with T 1/2 ¼ 298 K (high spin fraction ¼ g HS ¼ 0.5) is rather sluggish in the limits of the conversion (g HS $ 0 and g HS $ 1), which is attributed to the effect of the anions that seem to restrict somehow the structural distortions of the cations associated with the SCO process.
Journal de Physique I, 1993
In this work we present and discuss the temperature variation of X-ray, EPR and nuclear spin-latt... more In this work we present and discuss the temperature variation of X-ray, EPR and nuclear spin-lattice relaxation rate measurements for the two quasi-one-dimensional compounds alpha-(Per)2Fe(mnt)2 and alpha-(Per)2Co(mnt)2. From X-ray and EPR intensity data, a Peierls instability of the Perylene stacks is found to take place at 58 K and 75 K for the Fe and Co derivatives respectively. In contrast to other members of this series of two-chain compounds, the M(mnt)2, stacks are found to play no role in the Peierls instability. As for diffusive excitations of localized spins in dimerized Fe(mnt)2, stacks, their influence is shown to dominate the temperature variation of both the spin-lattice nuclear relaxation rate and the previously measured Faraday spin susceptibility.
Acta Crystallographica Section A Foundations of Crystallography
Synthetic Metals, 1991
ABSTRACT E.S.R., electrical transport and structural data are reported for new members of the fam... more ABSTRACT E.S.R., electrical transport and structural data are reported for new members of the family Per2[M(mnt)2], with M=Cu, Ni, Co, and Fe. The experimental results revealed the existence of two types of behaviour for M=Cu, Ni one metallic (α-phase) and another with semiconducting properties (β-phase). Results are compared with the early reported for M=Au, Pt and Pd.
[
ABSTRACT The phase transitions of the low dimensional conductors (Per)2[M(mnt)2] (M = Cu, Ni, Co ... more ABSTRACT The phase transitions of the low dimensional conductors (Per)2[M(mnt)2] (M = Cu, Ni, Co and Fe) were studied by X-ray diffuse scattering techniques. The metal-insulator transitions observed at 33, 25, 73 and 58 K for the Cu, Ni, Co and Fe compounds respectively, were found to correspond to a tetramerization on the perylene chains in the case of the Ni and Cu derivatives and to a dimerization for the Fe and Co derivatives. In all cases, the periodic lattice distortion can be associated to a 2kF Peierls instability of the perylene chains. The Ni compound shows in addition to the 2kF distortion also a lattice instability at twice this wave vector, which corresponds to a dimerization of the Ni(mnt)2 chain of localized 1/2 spin towards a non magnetic Spin-Peierls like ground state. The results are compared with previous studies of the Au, Pt and Pd analogs and the subtle nature of the lattice instabilities occurring in these compounds is discussed.
ABSTRACT The synthesis, electrocrystallisation and characterisation of (Perylene)2Au(cdc)2 single... more ABSTRACT The synthesis, electrocrystallisation and characterisation of (Perylene)2Au(cdc)2 single crystals, where cdc=cyanodithiocarbimate, are reported. The electrical conductivity and thermoelectric power exhibit metallic character at room temperature, with typical values σRT=150 S. cm−1 and S =35μV.K−1, respectively. Both resistivity and thermopower exhibit shallow minima in the range 100–150 K. Static magnetic susceptibility measurements show a Pauli-like behaviour ascribed to the perylene chains, with indication of a transition at ≈45 K. These properties are compared with those of other perylene conductors containing dithiolate complexes and the role of disorder is discussed.
Inorganic and Organometallic Polymers with Special Properties, NATO ASI SeriesVolume 206, p163-177, 1992
Synthetic Metals, 2001
ABSTRACT Cited By (since 1996): 3, Export Date: 24 April 2012, Source: Scopus
Topics in Organometallic Chemistry, 2009
ABSTRACT The properties of the salts based on metallocenium cations and transition metal bisdicha... more ABSTRACT The properties of the salts based on metallocenium cations and transition metal bisdichalcogenide anions are reviewed and particular attention is paid to the correlation between the magnetic properties correlated and the crystal and molecular structures. The large majority of these salts have crystal structures based on linear chain arrangements of alternating cation (D+) and anion (A−) stacks which are classified in four major structural types, depending on the stacking motifs. The magnetic properties of these salts, which at low temperatures can present a wide range of magnetic order type and phase transitions, are correlated with the type of magnetic interaction between the magnetic building blocks, which in the large majority of the cases can be well described by the McConnell model using spin density calculations. KeywordsCrystal structures–Magnetic properties–Metallocenium salts–Metal-bisdithiolenes
Synthetic Metals, 1999
The synthesis and the magnetic properties of decamethylferrocenium salts of the planar radical an... more The synthesis and the magnetic properties of decamethylferrocenium salts of the planar radical anions [M(dmix)d-, where M = Ni, Pd and Pt; and dmix = dmio and dmit, are presented.
Acta crystallographica. Section C, Crystal structure communications, 2006
The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] ... more The title compound, [Fe(C(10)H(15))(2)][Ni(C(3)OS(4))(2)].C(4)H(8)O or [Fe(Cp*)(2)][Ni(dmio)(2)] x THF, where [Fe(Cp*)(2)](+) is the decamethylferrocenium cation, dmio is the 2-oxo-1,3-dithiole-4,5-dithiolate dianion and THF is tetrahydrofuran, crystallizes with two independent half-anion units [one Ni atom is at the centre of symmetry ({1/2}, {1/2}, 0) and the other is at the centre of symmetry ({1/2},0, {1/2})], one cation unit (located in a general position) and one THF solvent molecule in the asymmetric unit. The crystal structure consists of two-dimensional layers composed of parallel mixed chains, where pairs of cations alternate with single anions. These layers are separated by sheets of anions and THF molecules.
Journal of the Chemical Society, Dalton Transactions, 2002
ABSTRACT The new compound [Co(η5-C5H5)(dppf-P,P′)I]I, 1, was synthesised by the stoichiometric re... more ABSTRACT The new compound [Co(η5-C5H5)(dppf-P,P′)I]I, 1, was synthesised by the stoichiometric reaction of the Co(III) complex [Co(η5-C5H5)(CO)I2], 2, with 1,1′-bis(diphenylphosphino)ferrocene (dppf) in CH2Cl2, and was characterised by multinuclear NMR spectroscopy. Exposure to air of THF or CH2Cl2 solutions of compound 1 gave, in an unexpected way, a polymeric chain comprising bridging 1,1′-bis(oxodiphenylphosphoranyl)ferrocene (dppfO2) joining tetrahedral Co(II) units [CoI2(μ-dppfO2)]n, 3. Attempts to obtain the polymeric chain 3 by the direct reaction of dppfO2 with CoI2, in CH2Cl2, gave instead the monomeric compound [CoI2(dppfO2)], 4, in which dppfO2 is coordinated in a chelating mode. The structural characterisation of compounds 2, 3, and 4 was carried out by single crystal X-ray diffraction studies. The magnetic behaviour of [CoI2(dppfO2)] and [CoI2(μ-dppfO2)]n was studied, and the results are consistent with tetrahedral S = 3/2 CoII, possessing a 4A2 ground state, and S = 0 FeII. In these compounds, CoII negative zero field splittings were determined from an analysis of the magnetic susceptibility temperature dependence, with D/k = −13 and −14 K for CoI2(dppfO2) and [CoI2(μ-dppfO2)]n, respectively. DFT calculations were performed in order to understand the electronic structure of [Co(η5-C5H5)(dppf-P,P′)I]I, 1, as well as that of the paramagnetic specie [CoI2(dppfO2)], 4. The [CoI2(μ-dppfO2)]n chain was also analysed and found to behave very similarly to the monomeric iodine derivative 4. The calculations showed the unpaired electrons to be localized on the Co(II) centre in all these species. The rather complicated electrochemical behaviour exhibited by the dppf complex [CoIII(η5-C5H5)(dppf-P,P′)I]I and by [Co(dppfO2)I2] is discussed.