Search results for "Paramagnetic"
showing 10 items of 600 documents
Spin Trapping of Carbon-Centered Ferrocenyl Radicals with Nitrosobenzene
2015
In contrast to metal centered 17 valence electron radicals, such as [Mn(CO)5]•, ferrocenium ions [Fe(C5H5)2]+ (1+), [Fe(C5Me5)2]+ (2+), [Fe(C5H5)(C5H4Et)]+ (3+), [Fe(C5H5)(C5H4NHC(O)Me)]+ (4+), and [Fe(C5H5)(C5H4NHC(S)Me)]+ (5+) do not add to nitrosobenzene PhNO to give metal-coordinated stable nitroxyl radicals. In the presence of the strong and oxidatively stable phosphazene base tert-butylimino-tris(dimethylamino)phosphorane, the quite acidic ferrocenium ions 1+–5+ are deprotonated to give a pool of transient and persistent radicals with different deprotonation sites [1–Hx]•–[5–Hx]•. One rather persistent iron-centered radical [4–HN]•, deprotonated at the nitrogen atom, has been detected…
From a fixed bed Ag–alumina catalyst to a modified reactor design: how to enhance the crucial heterogeneous–homogeneous reactions in HC-SCR
2004
Abstract A highly active Ag/alumina catalyst for continuous reduction of NO to nitrogen with n-octane under lean conditions was prepared. It was observed in the reactor set-up experiments for optimization of the converter, that surface generated gas phase species are crucial for obtaining high conversion. EPR and matrix isolated FTIR studies at low temperature (10–18 K) were performed for identification of the radicals. Experimental data, observed at steady state conditions in the temperature range 300–550 °C, was used to produce an artificial neural network model of the catalytic converter with four catalyst beds.
Radical cation salts of BEDT-TTF, enantiopure tetramethyl-BEDT-TTF, and TTF-Oxazoline (TTF-Ox) donors with the homoleptic TRISPHAT anion
2011
International audience; The synthesis and crystal structures of five radical cation salts based on the organic donors bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF), racemic ethylenedithio-methyl-oxazoline-tetrathiafulvalene (EDT-TTF-MeOx) and the enantiopure (S,S,S,S) and (R,R,R,R) tetramethyl-bis(ethylenedithio)tetrathiafulvalene (TMBEDT-TTF) and the D3-symmetric anion tris(tetrachlorobenzenediolato)phosphate(V) (TRISPHAT) are reported. The salts are formulated as [BEDT-TTF][(rac)-TRISPHAT]·CH2Cl2 (1), [BEDT-TTF][(rac)-TRISPHAT]·2CH3CN (2), [(rac)-EDT-TTF-Ox][(rac)-TRISPHAT]·CH3CN (3), [(S,S,S,S)-TMBEDT-TTF][(rac)-TRISPHAT]·2CH3CN (4), and [(R,R,R,R)-TMBEDT-TTF][(rac)-TRISPHAT]·2CH3CN (…
Synthesis and structural, spectroscopic and magnetic characterization of iron(II) and iron(III) complexes of N-2-pyridinylcarbonyl-2-pyridinecarboxim…
1993
Abstract One iron(II) complex of N -2-pyridinylcarbonyl-2-pyridinecarboximidate monoanion (bpca), [Fe(bpca) 2 ]·H 2 O ( 1 ), and three iron(III) complexes, [Fe(bpca)Cl 2 (H 2 O)]·(CH 3 ) 2 CO ( 2 ), [Fe(bpca) 2 ](NO 3 )·1.67H 2 O ( 3 ), [Fe(bpca) 2 ](ClO 4 ) ( 4 ), have been prepared and characterized by means of IR, UV-Vis and EPR spectroscopy and magnetic susceptibility measurements, where appropriate. The crystal structures of 1 – 3 have been determined from single crystal X-ray data, showing that the metallic ions are surrounded in all cases by distorted octahedral coordination spheres. From magnetic measurements it is evident that compounds 1 and 3 are practically in the low-spin state…
Synthesis, structural characterization and electrochemical activity of oxidovanadium(IV/V) complexes of a diprotic ONS chelating ligand
2010
Abstract The present work reports the chemistry of a few oxidovanadium(IV) and (V) complexes of the ONS chelating ligand S-benzyl-β-N-(2-hydroxyphenylethylidine) dithiocarbazate (H2L). Major objective of this work is to arrive at some general conclusions about the influence of binding environment generated by the replacement of an O-donor center by a S-donor point in a ligand (of a similar arrangement of the other O- and N-donor points) on the redox behavior and on the structural features of comparable [VO(OEt)(ONS)] and [VO(OEt)(ONO)] complexes. Synthesis, characterization by various physicochemical techniques (UV–Vis, IR, EPR and elemental analysis), exploration of electrochemical activit…
[Fe III (bztpen)(OCH 3 )](PF 6 ) 2 : Stable Methoxide–Iron(III) Complex Exhibiting Spin Crossover Behavior in the Solid State
2010
Complex [Fe III (bztpen)(OCH 3 )](PF 6 ) 2 (1) crystallizes as the major yellow-brown product from spontaneous oxidation of its corresponding iron(II) counterpart in methanol solution. Magnetic measurements and EPR spectra demonstrate that 1 undergoes a poorly cooperative 6 A 1 ↔ 2 T 2 spin conversion in the temperature range 300-50 K, with characteristic thermodynamic parameters ΔH = 6.15 kJ mol -1 , ΔS = 39.88 J K -1 mol -1 , and T 1/2 = 154 K. The crystal structure of 1 has been investigated at 100 and 293 K.
Formation in solution, synthesis and crystal structure of μ-oxalatobis[bis(2-pyridylcarbonyl)amido] dicopper(II)
1989
Abstract The compound μ-oxalatobis[bis(2-pyridylcarbonyl)amido] dicopper(II), [Cu 2 {(NCsH 5 CO) 2 N} 2 - (C 2 O 4 )] was synthesized and characterized by spectroscopy, EPR and diffraction methods. It crystallizes in the triclinic space group P 1 with cell constants: a =7.6793(6), b =9.238(2), c =10.007(2) A, α=83.80(1), β=68.37(1) and γ=69.44(1)°; V =617.7(3) A 3 , D (calc., Z =2)=1.80 g cm −3 , M r =667.6, F (000)=336, λ, (Mo Kα)=0.71069 A, μ (Mo Kα)=17.895 cm −1 and T =295 K. A total of 3587 data were collected over the range of 1 ⩽ θ ⩽ 30°; of these, 2391 (independent and with I⩾2σ( I )) were used in the structural analysis. The final R and R w residuals were 0.049 and 0.053, respective…
Heterotetranuclear Complexes of Reduced and Non-reduced Bridging 1,2,4,5-Tetrazine Ligands with 1,1′-Bis(diphenylphosphanyl)-ferrocene-copper(I)
2015
The complexes {(μ-bptz)[Cu(dppf)]2}(BF4)2 [(1)(BF4)2] [bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, dppf = 1,1′-bis(diphenylphosphanyl)ferrocene] and {(μ-bpztz)[Cu(dppf)]2}(PF6)2 [(2)(PF6)2] [bpztz = 3,6-bis(2-pyrazinyl)-1,2,4,5-tetrazine] contain two redox-active heterodinuclear FeIICuI moieties, bridged by a redox-active ligand. A crystal structure determination of (1)(BF4)2·2CH2Cl2 confirms the non-reduced aromatic nature of the bridge, in contrast to previous results on dicopper(I) complexes of bptz. Facile one-electron reduction produces the radical complexes {(μ-bptz)[Cu(dppf)]2}+ (1+) and {(μ-bpztz)[Cu(dppf)]2}+ (2+), which could be isolated [as (1)(BF4)] and studied by variable freq…
Extended structures of copper(II) complexes with 2-di1H-2-imidazolylmethylmalonate (DIMMAL), a versatile bis(imidazole)–bis(carboxylate) ligand: Solu…
2008
Abstract Copper(II) complexes of 2-di1H-2-imidazolylmethylmalonate (DIMMAL) have been studied by potentiometric methods. The data revealed that the CuHL 2 - and CuL 2 2 - species are prevalent in the studied pH range. Moreover, this paper reports the synthesis, structure solution and spectroscopic characterization of two new DIMMAL containing complexes, (NH4)2[Cu(DIMMAL)2] · 4H2O (1) and [Cu(DIMMAL)(en)(H2O)] · 5H2O (2). The structure of compound 1 consists of centrosymmetric mononuclear anionic [Cu(DIMMAL)2]2− units, NH 4 + cations and lattice water molecules, in which DIMMAL2− acts as a tridentate ligand through two imidazole nitrogen atoms and one oxygen atom from a carboxylate group. Th…
Formation of New η5-Rhodium(III) Complexes from η5-Rh(I) Rhodacarborane-Containing Charge-Compensated Ligands
2004
A series of new Rh(I) half-sandwich complexes of formula [3,3-(PPh 3 ) 2 -8-L-closo-3,1,2-RhC 2 B 9 H 1 0 )] (L = SMe 2 (2a), SEt 2 (2b), S(CH 2 ) 4 (2c), SEtPh (2d)) and [1-Me-3,3-(PPh 3 ) 2 -8-L-closo-3,1,2-RhC 2 B 9 H 9 )] (L = SMe 2 (2e), SEt 2 (2f)) have been prepared by reaction of the respective monoanionic charge-compensated ligands [10-L-nido-7,8-C 2 B 9 H 1 0 ] - and [7-Me-10-L-7,8-C 2 B 9 H 9 ] - with [RhCl(PPh 3 ) 3 ]. Complex [3,3-(cod)-8-SMe2-closo-3,1,2-RhC 2 B 9 H 1 0 ] (3) has also been prepared by reaction of K[10-SMe 2 -nido-7,8-C 2 B 9 H 1 0 ] with [RhCl(cod)] 2 . Rh(I) complexes 2a-d may be easily oxidized to the corresponding Rh(III) complexes 4a-d under N 2 atmosphere…