Synthesis and Characterization of Two Intensely Colored Tris(benzoylcyanoxime)iron(II) Anionic Complexes (original) (raw)
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Inorganica Chimica Acta, 2006
In this work, we present the synthesis and characterization of three mononuclear iron(III) complexes: dichloro [N-propanamide-N,N-bis-(2-pyridylmethyl)amine]iron(III) perchlorate (1), trichloro[N-methylpropanoate-N,N-bis-(2-pyridylmethyl)amine]iron(III) (2) and trichloro[bis-(2-pyridylmethyl)amine]iron(III) (3). The complexes were characterized by cyclic voltammetry, conductivimetry, elemental analyses, and by electronic, infrared and Mö ssbauer spectroscopies. Complex 1 was also characterized by X-ray structural analysis, which showed an iron center coordinated to one amide, one tertiary amine, two pyridine groups and two chloride ions. While for 1 the X-ray molecular structure and the infrared spectrum confirm the coordination of the amide group by the oxygen atom, the infrared spectrum of 2 indicates that the ester group present in the ligand is not coordinated, resulting in a N 3 Cl 3 donor set, similar to the one present in 3. However, in 3 there is a secondary amine while in 2 a tertiary amine exists. These structural differences result in distinguishable variations in the Lewis acidity of the iron center, which could be evaluated by the analysis of the redox potential of the complexes, as well as by Mö ssbauer parameters. Thus, the Lewis acidity decreases in the following order: 1 > 2 > 3. It is important to notice that 1 has the amide group coordinated to the iron center, a feature present in metalloenzymes as lipoxygenase and isopenicillin N synthase, and in a small number of mononuclear iron(III) complexes.
Journal of the American Chemical Society, 1993
Fe(I1) and Fe(1) u-alkynyl complexes of the general formula [(PP3)Fe(C=CR)]"+ (n = 1, 0) have been synthesized as BPh4-salts or neutral molecules and characterized by chemical, spectroscopic, X-ray, and electrochemical techniques [R = Ph, SiMe3, n-CjH7, n-C5HII, CMe3; PP3 = P(CH2CH*PPh2)3]. All of the compounds undergo electron-transfer reactions that encompass Fe(O), Fe(I), Fe(II), and Fe(II1) oxidation states of the metal. X-ray crystal structures of the 16-and 17-electron complexes [(PP3)Fe(C=-CPh)]BPhgC4H8O and [(PP3)Fe(C=CPh)] have been determined. The Fe(I1) compound crystallizes in the space group P2,/c, and the cation assumes an almost regular trigonal-bipyramidal structure with the alkynyl ligand trans to the bridgehead phosphorus atom of PP3 (P4-Fe-C7 bond angle = 177.2(6)'). The Fe(1) compound crystallizes in the space group P2,/n and assumes a strongly distorted trigonal-bipyramidal structure with the Pd-Fe-C, bond angle of 170.3(3)' and equatorial bond angles of 143.9(1)O, 102.4(1)O, and 1 1 1. 1 (1)O. A decrease in the Fe-P bond distances on going from Fe(I1) to Fe(1) is interpreted in terms of significant metalphosphorus r-back-bonding. In contrast, from a perusal of IR, structural, and electrochemical data, no significant d r (metal)r* (alkynyl) interaction occurs. All compounds are paramagnetic and have been characterized by X-band ESR spectroscopy (powder, frozen solution, fluid solution). The powder and frozen solution spectra of the Fe(1) alkynyls are interpreted in terms of S = ' / 2 and a rhombic g tensor. The fluid solution spectra show that the compounds exist in tetrahydrofuran solution as two isomeric formsexhibiting distorted trigonal-bipyramidal structures in a ratio that depends on the temperature. The ESR spectra of the Fe(1I) derivatives (powder and frozen solution) display unresolved line shape consistent with a S = 1 Hamiltonian with noticeable zero-field splitting effects at room temperature. q6-C6R6,5 q3-C8H136). To the best of our knowledge, no stable iron-(I) compound with a u-hydrocarbyl has ever been reported. In this paper, we describe the synthesis, the X-band ESR characterization, and the electrochemical behavior of a family of d7 low-spin u-alkynyl Fe(1) complexes of the general formula [(PP3)Fe(CWR)] (PP3 = P(CH2CH2PPh2)j; R = Ph, SiMe3, n-C3H7, n-CsHI I , CMe3).
Mixed-Valence Heptanuclear Iron Complexes with Ferromagnetic Interaction
Inorganic Chemistry, 2012
Three new Prussian blue analogues, heptanuclear mixed-valence iron complexes of the type [Fe II (CN) 6 {Fe III (1 −2H )} 6 ]Cl 2 ·nH 2 O, were synthesized and structurally and spectrally characterized, and their magnetic properties were investigated (1 −2H corresponds to doubly deprotoned Schiff-base pentadentate ligands 1a, N,N′bis(2-hydroxybenzylidene)-1,5-diamino-3-azapentane, 1b, N,N′-bis(3-ethoxy-2-hydroxybenzylidene)-1,7-diamino-4-azaheptane, or 1c, N,N′-bis(3-methoxy-2-hydroxybenzylidene)-1,6-diamino-3-azahexane). These compounds were formed by assembling the [Fe(CN) 6 ] 4− building block with mononuclear complexes of the [Fe(1 −2H )Cl] type. Xray structure analysis revealed that the complexes adopt a star-like architecture: the Fe(II) ion lies at the very center, and on its octahedral nodes the Fe(III) sites are coordinated in the Fe II −CN−Fe III manner. The Schiff-base pentadentate ligand moiety 1 −2H coordinates a single Fe(III) center in two complexes 3b and 3c. Ligands 1a −2H in the complex cation of 3a adopt an unusual coordination mode: three donor atoms of the same ligand (one O and two N) coordinate one Fe(III), whereas the remaining N′ and O′ donor atoms coordinate the neighboring Fe(III) center creating the {Fe(ON 2 )(N′O′)N″} chromophore involving two 1a −2H ligand moieties. Moreover, three Fe(III) centers are interconnected with three 1a −2H ligands in such a manner that two {Fe III 3 (1a −2H ) 3 } units form two intramolecular rings. Magnetic investigation of the heptanuclear complexes revealed the high-spin state of all six Fe(III) coordination sites (s = 5/2), while the very central Fe(II) site is in the low-spin state (s = 0). At low temperature, the ferromagnetic exchange interactions stay evident for all three complexes. Mossbauer spectra of compounds 3a and 3b revealed a presence of two different doublets for both compounds: the major doublet is related to six Fe(III) high-spin coordination sites and the minor doublet refers to the low-spin very central Fe(II).
Iron(II) complexes based on electron-rich, bulky PNN- and PNP-type ligands
Inorganica Chimica Acta, 2006
Reaction of the PNN ligand ((2-(di-tert-butylphosphinomethyl)-6-diethylaminomethyl)pyridine) with 1 equiv. of anhydrous FeCl 2 in THF results in the formation of (PNN)FeCl 2 (1). The cationic complex [(PNN)Fe(THF)Cl](PF 6 ) (2) was obtained by chloride abstraction from 1 with 1 equiv. of TlPF 6 . Similarly, the PNP-type complexes 3 and 4 were obtained from FeCl 2 with 1 equiv. of t-Bu-PNP (2,6bis(di-tert-butylphosphinomethyl)pyridine) and i-Pr-PNP (2,6-bis(di-iso-propylphosphinomethyl)pyridine), respectively. Complexes 1 and 3 were characterized by X-ray diffraction and elemental analyses. In both structures the Fe(II) centers exhibit a distorted square pyramidal geometry comprising two chloride ligands and one tridentate PNN or PNP ligand. The magnetic properties of the paramagnetic complexes 1-4 are discussed.
Intermediate-Spin Iron(III) Complexes Having a Redox-Noninnocent Macrocyclic Tetraamido Ligand
Inorganic chemistry, 2018
An iron(III) complex having a dibenzotetraethyltetraamido macrocyclic ligand (DTTM), (NEt)[Fe(DTTM)Cl] (1), was synthesized and characterized by crystallographic, spectroscopic, and electrochemical methods. Complex 1 has a square-pyramidal structure in the S =/spin state. The complex exhibited two reversible redox waves at +0.36 and +0.68 V (vs SCE) in the cyclic voltammogram measured in CHClat room temperature. The stepwise oxidation of 1 using chemical oxidants allowed us to observe clear and distinct spectral changes with distinct isosbestic points for each step, in which oxidation occurred at the phenylenediamido moiety rather than the iron center. One-electron oxidation of 1 by 1 equiv of [Ru(bpy)](ClO)(bpy = 2,2'-bipyridine) in CHClafforded square-pyramidal (NEt)[Fe(DTTM)Cl] (2), which was in the S = 1 spin state involving a ligand radical and showed a slightly distorted square-pyramidal structure. Complex 2 showed an intervalence charge-transfer band at 900 nm, which was ...
Journal of the Chemical Society, Dalton Transactions, 2001
Two novel complexes: [Fe(L 2Ј )][BPh 4 ] 2 , 1, and [Fe(L 3Ј )][BPh 4 ] 2 , 2, with the hexadentate nitrogen ligands, L nЈ = 1,9-bis(2Ј-pyridyl)-5-[(R-2Љ-pyridyl)methyl]-2,5,8-triazanon-1-ene, where R = ethoxy for L 2Ј and methoxy for L 3Ј , were obtained from the iron() complex of the pentadentate ligand, L 1 = 1,9-bis(2Ј-pyridyl)-2,5,8-triazanonane. Complexes 1 and 2 were also obtained by making the hexadentate ligands: 1,9-bis(2Ј-pyridyl)-5-[(ethoxy-2Јpyridyl)methyl]-2,5,8-triazanonane (L 2 ) and 1,9-bis(2Ј-pyridyl)-5-[(methoxy-2Љ-pyridyl)methyl]-2,5,8-triazanonane (L 3 ) react with Fe(), respectively. The structures of complexes 1 and 2 were characterized by COSY, HMBC, HMQC and NOESY NMR studies, and both structures were also confirmed by X-ray analysis. In both cases, the geometry around iron is a distorted octahedron. Since 1 and 2 are diamagnetic at 298 K they are low-spin iron() species. Both preparative methods are examples of oxidative dehydrogenation of a Fe() polyamine complex, in which the thermodynamically and kinetically stable final product is a low spin Fe() imine complex. In the case of the first method an increase in the size and denticity of the starting ligand is observed. Fig. 1 Structures of the ligands. H p (B 4 ) 6.74 t(8) J m-p-o (7) 6.75 t(8) J m-p-o (7) H m (B 4 ) 6.89 t(16) J o-m-p (7) 6.90 dd(16) J m-o (8) J m-p (7) H3
Mono- and Binuclear Complexes of Iron(III) with 1,2-Bis(2-hydroxybenzamido)ethane
Monatshefte fuer Chemie/Chemical Monthly, 1998
Complexes of the type [(Fe(L)) 2 O] Á H 2 O (H 2 L 1,2-bis(2-hydroxybenzamido)ethane), [(Fe(L)) 2 ter] Á 5H 2 O H 2 ter terephthalic acid), [Fe(L)bpy]BPh 4 (bpy 2,2 H -bipyridyl), and [Fe(L)phen]ClO 4 Á H 2 O (phen o-phenanthroline) were prepared and studied by elemental analysis, magnetochemical measurements, and spectroscopic methods. [(Fe(L)) 2 O] Á H 2 O and [(Fe(L)) 2 ter] Á 5H 2 O are probably binuclear, and the weak antiferromagnetic exchange interaction, (" eff per one atom of iron(III) was found to be 3.59 BM/77 KÀ4.91 BM/290 K (J À7 cm À1 , H À2JS 1 S 2 , S 1 S 2 5/2) for the "-oxo complex and 4.21 BM/82 KÀ5.35 BM/297 K (J À5 cm À1 ) for the "terephthalato complex. The iron(III) complexes with bpy or phen are probably mononuclear; their anomalous " eff values (3.51 BM/80 KÀ3.68 BM/297 K for (Fe(L)bpy]BPh 4 and 4.93 BM/259 K for [Fe(L)phen]ClO 4 Á H 2 O, respectively) agree neither with high spin (5.7±6.1 BM) nor with low spin (2.1±2.5 BM) con®gurations.
A new chromogenic agent for iron(III): Synthesis, structure and spectroscopic studies
Journal of Chemical Sciences, 2010
A heterocyclic hydrazone ligand, diacetyl monoxime-2-pyridyl hydrazone, HL, 1, was investigated as a new chromogenic agent for selective detection of Fe3+. The ligand 1, undergoes 1: 2 complexation with Fe3+ and Ni2+ to form complexes [FeIII(HL)2]Cl3, 1a and [NiII(HL)2]Cl2, 1b respectively. The iron(III) complex 1a gives a characteristic absorption peak at 487 nm with distinct reddish-pink colouration. The change in colour can easily be distinguished from other metal complexes by the naked eye. No obvious interference was observed in presence of other metal ions (Na+, K+, Ca2+, Mg2+, Al3+, Mn2+, Ni2+, Cu2+, Zn2+, Co2+, Pb2+, Hg2+, Cd2+). The bands appearing in the UV region (200–340 nm) are characteristics of the ligand, HL, 1. In the complexes [FeIII(HL)2]Cl3, 1a, and [NiII(HL)2]Cl2, 1b, these ligand centered bands are accompanied by multiple bands extending into the visible region (350–500 nm). The association constants (K ass, UV-Vis) were found to be (6·4865 ± 0·004) × 105 for the complex 1a and (1·1960 ± 0·002) × 105 for the complex 1b at 298 K determined by the UV-Vis spectroscopy. On excitation at 285 nm, the ligand HL, 1 strongly emits at 364 nm due to an intraligand1(π − π*) transition. The complexes are luminescent (λ ex 285 nm, λem 365 nm) with F/F 0 0·75 for 1a and 0·81 for 1b. In both the cases, the 1: 2 binding is confirmed by Job’s method. Molecular structure of the complex 1b has been determined by single crystal X-ray diffraction studies. Here, two crystallographically distinct but metrically very similar molecules making an enantiomeric pair constitute the asymmetric unit in which both metal atoms are tris chelated in meridional geometry.
Syntheses and structures of iron(III) complexes of simple N-donor ligands
Polyhedron, 2002
Syntheses and structures of mer -[FeCl 3 (pyrazole) 3 ] (1), mer -[FeCl 3 (N -methylimidazole) 3 ] (2), mer -[FeCl 3 (terpy)] (3) (terpy 0/2,2?: 6?,2ƒ-terpyridine), mer -[FeCl 3 (tptz)] (4) (tptz0/2,4,6-tris(2-pyridyl)-1,3,5-triazine) and trans -[FeCl 2 (3-methylpyrazole) 4 ]Cl (5) are reported. The structures demonstrate intramolecular N Ã/HÁ Á ÁCl; intramolecular C Ã/HÁ Á ÁCl; and intermolecular N Ã/HÁ Á ÁCl interactions. Syntheses and analytical data are also reported for [FeCl 3 (imidazole) 4 ] (6), but crystals suitable for X-ray study were not obtained. #
Inorganic Chemistry, 2005
Acyclic pyridine-2-carboxamide-and thioether-containing hexadentate ligand 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H 2 bpctb), in its deprotonated form, has afforded purple low-spin (S) 0) iron(II) complex [Fe-(bpctb)] (1). A new ligand, the pyrazine derivative of H 2 bpctb, 1,4-bis[o-(pyrazine-2-carboxamidophenyl)]-1,4dithiobutane (H 2 bpzctb), has been synthesized which has furnished the isolation of purple iron(II) complex [Fe(bpzctb)]‚ CH 2 Cl 2 (4) (S) 0). Chemical oxidation of 1 by [(η 5-C 5 H 5) 2 Fe][PF 6 ] or [Ce(NO 3) 6 ][NH 4 ] 2 led to the isolation of low-spin (S) 1/2) green Fe(III) complexes [Fe(bpctb)][PF 6 ] (2) or [Fe(bpctb)][NO 3 ]‚H 2 O (3), and oxidation of 4 by [Ce(NO 3) 6 ][NH 4 ] 2 afforded [Fe(bpzctb)][NO 3 ]‚H 2 O (5) (S) 1/2). X-ray crystal structures of 1 and 4 revealed that (i) in each case the ligand coordinates in a hexadentate mode and (ii) bpzctb 2binds more strongly than bpctb(2-), affording distorted octahedral M II N 2 (pyridine/pyrazine)N′ 2 (amide)S 2 (thioether) coordination. To the best of our knowledge, 1 and 4 are the first examples of six-coordinate low-spin Fe(II) complexes of deprotonated pyridine/ pyrazine amide ligands having appended thioether functionality. The Fe(III) complexes display rhombic EPR spectra. Each complex exhibits in CH 2 Cl 2 /MeCN a reversible to quasireversible cyclic voltammetric response, corresponding to the Fe III −Fe II redox process. The E 1/2 value of 4 is more anodic by ∼0.2 V than that of 1, attesting that compared to pyridine, pyrazine is a better stabilizer of iron(II). Moreover, the E 1/2 value of 1 is significantly higher (∼1.5 V) than that reported for six-coordinate Fe(II)/Fe(III) complexes of the tridentate pyridine-2-carboxamide ligand incorporating thiolate donor site.