The ENDOR spectra of γ-irradiated single crystals of the urea-malonic acid 1: 1 adduct were recor... more The ENDOR spectra of γ-irradiated single crystals of the urea-malonic acid 1: 1 adduct were recorded at room temperature. The hyperfine coupling tensor of the α proton of the HOOC-CH-COOH free radical formed by irradiation were measured as well as the hyperfine ...
European Journal of Inorganic Chemistry, Oct 2, 2013
ABSTRACT The 3:1 molar reactions of MF5 (M = Nb, 1a; M = Ta, 1b) with 1,3-dimethoxybenzene in CHC... more ABSTRACT The 3:1 molar reactions of MF5 (M = Nb, 1a; M = Ta, 1b) with 1,3-dimethoxybenzene in CHCl3 led to the formation of the arenium salts [2,4-(OMe)(2)C6H5][M2F11] (M = Nb, 3a; M = Ta, 3b) in good yields. The reactions took place with the intermediate formation of (MF5)(2)[(2)-1,3-(OMe)(2)C6H4] (M = Nb, 2a; M = Ta, 2b), followed by single-electron oxidation of the arene and production of MF4 (identified by means of EPR spectroscopy as the acetonitrile adduct). Compounds 3a and b were fully characterised both in solution (NMR) and in the solid-state (X-ray, IR and elemental analysis), while 2a and b were identified by NMR spectroscopy in CD2Cl2 solution. The reactions of 1,3-dimethoxybenzene with Ag[NbF6] or Ag[Sb2F11] in CD2Cl2/CHCl3 afforded [2,4-(OMe)(2)C6H5](+). It was found that 1,3-dimethoxybenzene was inert towards the addition of aqueous H[SbF6] under comparable experimental conditions.
Reaction of [Ir (Me) 2Cp*(L)] complexes (Cp*= η5-C5Me5; L= PPh3, PMePh2, PMe2Ph, PMe3) with equim... more Reaction of [Ir (Me) 2Cp*(L)] complexes (Cp*= η5-C5Me5; L= PPh3, PMePh2, PMe2Ph, PMe3) with equimolar amounts of [Fe Cp2]+ in pyridine gives methane and the corresponding cationic derivatives [Ir (Me) Cp*(L)(pyridine)]+. Reaction with an excess of ...
ABSTRACT The spin system longitudinal magnetization at resonance, irradiated by two nearly resona... more ABSTRACT The spin system longitudinal magnetization at resonance, irradiated by two nearly resonant transversal waves, oscillates. The oscillation for low signal intensities depends linearly on the product T1·T2. This effect allows to resolve overlapping spectra which are usually not detectable.
M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H... more M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)), have been prepared by a modified Fischer-Hafner synthesis or by metal vapour techniques. The reaction of Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2) with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2)][E], where E = pcmcp, dbcp, or dbncp. Mo(eta(6)-arene)(2) derivatives (arene = toluene, 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)) are oxidized to [Mo(eta(6)-arene)(2)](+) by pcmcpH. The crystal and molecular structures of [M(eta(6)-1,3,5-R(3)C(6)H(3))(2)][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, (i)Pr) have been solved by X-ray single crystal diffraction.
ABSTRACT The computed structures of the long-lived radical cation salts [Arene][Nb2F11] [Arene = ... more ABSTRACT The computed structures of the long-lived radical cation salts [Arene][Nb2F11] [Arene = 1,4-F2-2,5-(OMe)2C6H2, 2; 1,4-(OMe)2C6H4, 3; 2,5-(OEt)2(Me)C6H3, 4; C6H6, 5] and that of the transient [1,3-(OMe)2C6H4][Nb2F11], 6, obtained for the gas-phase by DFT at the B3LYP/6-31G∗∗ level, are presented. The degree of inertness observed in chloroform solution seems to increase on decreasing the steric demand of the ring substituents, and may be correlated to the calculated distance between the cation-centroid and the niobium atoms. The room-temperature EPR spectra of 2–4, in CHCl3, are described in detail; the spectrum of 3 is compared to those of analogous 1,4-dimethoxybenzene radical species reported previously. The EPR spectra display a hyperfine structure due to coupling of the unpaired electron with nuclei belonging to both the cation (H and F in the case of 2) and the anion (F and eventually Nb). The UV–Vis spectra of 2–4 exhibit one strong absorption attributed to the cation and one anion-to-cation charge-transfer band (e.g. for 3 at 398 and 589 nm, respectively). Thermodynamic calculations indicate that the low yield formation of the benzene radical salt 5 occurs with Gibbs free energy variation significantly higher than those involved in the synthesis of 2–4 and 6.
The ENDOR spectra of γ-irradiated single crystals of the urea-malonic acid 1: 1 adduct were recor... more The ENDOR spectra of γ-irradiated single crystals of the urea-malonic acid 1: 1 adduct were recorded at room temperature. The hyperfine coupling tensor of the α proton of the HOOC-CH-COOH free radical formed by irradiation were measured as well as the hyperfine ...
European Journal of Inorganic Chemistry, Oct 2, 2013
ABSTRACT The 3:1 molar reactions of MF5 (M = Nb, 1a; M = Ta, 1b) with 1,3-dimethoxybenzene in CHC... more ABSTRACT The 3:1 molar reactions of MF5 (M = Nb, 1a; M = Ta, 1b) with 1,3-dimethoxybenzene in CHCl3 led to the formation of the arenium salts [2,4-(OMe)(2)C6H5][M2F11] (M = Nb, 3a; M = Ta, 3b) in good yields. The reactions took place with the intermediate formation of (MF5)(2)[(2)-1,3-(OMe)(2)C6H4] (M = Nb, 2a; M = Ta, 2b), followed by single-electron oxidation of the arene and production of MF4 (identified by means of EPR spectroscopy as the acetonitrile adduct). Compounds 3a and b were fully characterised both in solution (NMR) and in the solid-state (X-ray, IR and elemental analysis), while 2a and b were identified by NMR spectroscopy in CD2Cl2 solution. The reactions of 1,3-dimethoxybenzene with Ag[NbF6] or Ag[Sb2F11] in CD2Cl2/CHCl3 afforded [2,4-(OMe)(2)C6H5](+). It was found that 1,3-dimethoxybenzene was inert towards the addition of aqueous H[SbF6] under comparable experimental conditions.
Reaction of [Ir (Me) 2Cp*(L)] complexes (Cp*= η5-C5Me5; L= PPh3, PMePh2, PMe2Ph, PMe3) with equim... more Reaction of [Ir (Me) 2Cp*(L)] complexes (Cp*= η5-C5Me5; L= PPh3, PMePh2, PMe2Ph, PMe3) with equimolar amounts of [Fe Cp2]+ in pyridine gives methane and the corresponding cationic derivatives [Ir (Me) Cp*(L)(pyridine)]+. Reaction with an excess of ...
ABSTRACT The spin system longitudinal magnetization at resonance, irradiated by two nearly resona... more ABSTRACT The spin system longitudinal magnetization at resonance, irradiated by two nearly resonant transversal waves, oscillates. The oscillation for low signal intensities depends linearly on the product T1·T2. This effect allows to resolve overlapping spectra which are usually not detectable.
M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H... more M(eta(6)-arene)(2) species (M = Cr, arene = 1,3,5-Me(3)C(6)H(3); M = Mo, arene = 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)), have been prepared by a modified Fischer-Hafner synthesis or by metal vapour techniques. The reaction of Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2) with the fulvene derivatives pentacarbomethoxycyclopentadiene (pcmcpH), 1-benzoyl-6-hydroxy-6-phenylfulvene (dbcpH), or 1-benzoyl-3-nitro-6-hydroxy-6-phenylfulvene (dbncpH) proceeds with evolution of dihydrogen and formation of the ionic derivatives [Cr(eta(6)-1,3,5-Me(3)C(6)H(3))(2)][E], where E = pcmcp, dbcp, or dbncp. Mo(eta(6)-arene)(2) derivatives (arene = toluene, 1,3,5-Me(3)C(6)H(3), 1,3,5-(i)Pr(3)C(6)H(3)) are oxidized to [Mo(eta(6)-arene)(2)](+) by pcmcpH. The crystal and molecular structures of [M(eta(6)-1,3,5-R(3)C(6)H(3))(2)][pcmcp] (M = Cr, R = Me; M = Mo, R = Me, (i)Pr) have been solved by X-ray single crystal diffraction.
ABSTRACT The computed structures of the long-lived radical cation salts [Arene][Nb2F11] [Arene = ... more ABSTRACT The computed structures of the long-lived radical cation salts [Arene][Nb2F11] [Arene = 1,4-F2-2,5-(OMe)2C6H2, 2; 1,4-(OMe)2C6H4, 3; 2,5-(OEt)2(Me)C6H3, 4; C6H6, 5] and that of the transient [1,3-(OMe)2C6H4][Nb2F11], 6, obtained for the gas-phase by DFT at the B3LYP/6-31G∗∗ level, are presented. The degree of inertness observed in chloroform solution seems to increase on decreasing the steric demand of the ring substituents, and may be correlated to the calculated distance between the cation-centroid and the niobium atoms. The room-temperature EPR spectra of 2–4, in CHCl3, are described in detail; the spectrum of 3 is compared to those of analogous 1,4-dimethoxybenzene radical species reported previously. The EPR spectra display a hyperfine structure due to coupling of the unpaired electron with nuclei belonging to both the cation (H and F in the case of 2) and the anion (F and eventually Nb). The UV–Vis spectra of 2–4 exhibit one strong absorption attributed to the cation and one anion-to-cation charge-transfer band (e.g. for 3 at 398 and 589 nm, respectively). Thermodynamic calculations indicate that the low yield formation of the benzene radical salt 5 occurs with Gibbs free energy variation significantly higher than those involved in the synthesis of 2–4 and 6.
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