Molecular and electronic structure of five-coordinate complexes of iron(II/III) containing o-diiminobenzosemiquinonate(1-) pi radical ligands

The reaction of the ligand N-phenyl-1,2-benzenediamine (N-phenyl-o-phenylenediamine), H2[L(PDI)], in dry acetonitrile with [FeIII(dmf)6](ClO4)3 (dmf = N,N-dimethylformamide) affords the dimer (mu-NH,NH)[FeIII(L(ISQ))(L(PDI))]2 (1), where (L(ISQ))*- represents the pi radical monoanion N-phenyl-o-diiminobenzosemiquinonate and (L(PDI))2- is its one-electron-reduced, closed-shell form. Complex 1 possesses a diamagnetic ground-state St = 0. Addition reactions of tri-n-butylphosphane, tert-butyl isocyanide, cyclohexyl isocyanide, 4,5-diphenylimidazole, and 4-(1-phenylpentyl)pyridine with 1 in acetonitrile or toluene yields [FeII(L(ISQ))2(PBu3)] (2), [Fe(II)(L(ISQ))2(CN-tBu)] (4), [FeII(L(ISQ))2(CNCy)] (5), [FeIII(L(ISQ))2(Ph2Im)] (6), and [FeIII(L(ISQ))(L(PDI))(BuPhCH-py)].BuPhCH-py (7). Oxidation of 1 with iodine affords [FeIII(L(ISQ))2I] (3), and oxidation of 2 with ferrocenium hexafluorophosphate yields [FeIII(L(ISQ))2(PBu3)](PF6) (2ox). The structures of complexes 2, 2ox, 3, 5, 6, and 7 have been determined by X-ray crystallography at 100(2) K. Magnetic susceptibility measurements and EPR, UV-vis, and M?ssbauer spectroscopy have established that mononuclear complexes containing the [FeII(L(ISQ))2X] chromophore (2, 4, 5) are diamagnetic (St = 0) whereas those with an [FeIII(L(ISQ))2X]n chromophore (3, 2(ox), 6) are paramagnetic (St = 1/2) and those with an [FeIII(L(ISQ))(L(PDI))X] chromophore (7) possess an St = 1 ground state. It is established that all ferric species have an intrinsic intermediate spin (SFe = 3/2) which is intramolecularly antiferromagnetically coupled to one or two (L(ISQ))*- ligand radicals yielding an St = 1 (7) or St = 1/2 (2ox, 3, 6) ground state, respectively. In the ferrous complexes 2, 4, and 5 the intrinsic spin at the iron ion is either low spin (SFe = 0) or intermediate spin (SFe = 1). Antiferromagnetic coupling between two radicals (L(ISQ))*- or, alternatively, between the intermediate spin ferrous ion and two radicals yields then the observed diamagnetic ground state. In 1 two [FeIII(L(ISQ))(L(PDI))] halves with S = 1 couple antiferromagnetically affording an St = 0 ground state.     

Molecular and electronic structures of oxo-bis(benzene-1,2-dithiolato)chromate(V) monoanions. A combined experimental and density functional study

Two oxo-bis(benzene-1,2-dithiolato)chromate(V) complexes, namely, [CrO(L(Bu))2]1- and [CrO(L(Me))2]1-, have been synthesized and studied by UV-vis, EPR, magnetic circular dichroism (MCD), and X-ray absorption spectroscopy and by X-ray crystallography; their electro- and magnetochemistries are reported. H2L(Bu) represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol, and H2L(Me) is the corresponding 4-methyl-benzene-1,2-dithiol. A structural feature of interest for both the complexes is the folding of the dithiolate ligands about the S-S vector providing Cs symmetry to the complexes. Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic and S K-edge X-ray absorption spectra. From DFT calculations, the Cs instead of C2v symmetry for the complexes is attributed to the strong S(3p) --> Cr(3d(x2-y2)) pi-donation in Cs geometry providing additional stability to the complexes.     

Macrocyclic gold(I) complexes and [2]catenanes containing carbonyl functionalized diacetylide ligands

The carbonyl derivatized bis(alkyne) O=C(4-C₆H₄OCH₂CCH)₂ was converted into the imine derivatives RN=C(4-C₆H₄OCH₂CCH)₂ [R=OH, NHC(O)NH₂, NHC₆H₃-2,4-(NO₂)₂] and into the 4-bromomethyl-1,3-dioxolane derivative BrCH₂C₂H₃O₂C(4-C₆H₄OCH₂CCH)₂. The alkyne units in these compounds react with [AuCl(SMe₂)] in the presence of base to form the corresponding digold(I) diacetylide complexes, that exist as insoluble oligomers or polymers. They reacted with the diphosphines Ph₂PZPPh₂ [Z=CC, trans-HC=CH and (CH₂)_n, n=3–5] to give macrocyclic gold(I) complexes of the type [Au₂(μ-LL)(μ-PP)], where LL is the diacetylide and PP the diphosphine ligand. The ability of these macrocyclic complexes to self-assemble to [2]catenanes has been studied. The ketone and imine derivatives do not form [2]catenanes because the orientation of the aryl groups is unfavorable, but the 1,3-dioxolane derivatives may catenate if the ring size is optimum.     

Molecular and electronic structures of iron(II)/(III) complexes containing N,S-coordinated,closed-shell o-aminothiophenolato(1-) and o-iminothiophenolato(2-) ligands

The coordination chemistry of the ligands o-aminothiophenol, H(abt), 4,6-di-tert-butyl-2-aminothiophenol, H[L(AP)], and 1,2-ethanediamine-N,N'-bis(2-benzenethiol), H(4)('N(2)S(2')), with FeCl(2) under strictly anaerobic and increasingly aerobic conditions has been systematically investigated. Using strictly anaerobic conditions, the neutral, air-sensitive, yellow complexes (mu-S,S)[Fe(II)(abt)(2)](2) (1), (mu-S,S)[Fe(II)(L(AP))(2)](2).8CH(3)OH (2), and (mu-S,S)[Fe(II)('H(2)N(2)S(2'))](2).CH(3)CN (3) containing high spin ferrous ions have been isolated where (abt)(1-), (L(AP))(1-), and ('H(2)N(2)S(2'))(2-) represent the respective N,S-coordinated, aromatic o-aminothiophenolate derivative of these ligands. When the described reaction was carried out in the presence of trace amounts of O(2) and [PPh(4)]Br, light-green crystals of [PPh(4)][Fe(II)(abt)(2)(itbs)].[PPh(4)]Br (4) were isolated. The anion [Fe(II)(abt)(2)(itbs)](-) contains a high spin ferrous ion, two N,S-coordinated o-aminophenolate(1-) ligands, and an S-bound, monoanionic o-iminothionebenzosemiquinonate(1-) pi radical, (itbs)(-). Complex 4 possesses an S(t) = 3/2 ground state. In the absence of [PPh(4)]Br and presence of a base NEt(3) and a little O(2), the ferric dimer (mu-NH,NH)[Fe(III)(L(AP))(L(IP))](2) (5a) and its isomer (mu-S,S)[Fe(III)(L(AP))(L(IP))](2) (5b) formed. (L(IP))(2-) represents the aromatic o-iminothiophenolate(2-) dianion of H[L(AP)]. The structures of compounds 2, 4, and 5a have been determined by X-ray crystallography at 100(2) K. Zero-field M?ssbauer spectroscopy of 1, 2, 3, and 4 unambiguously shows the presence of high spin ferrous ions: The isomer shift at 80 K is in the narrow range 0.85-0.92 mm s(-1), and a large quadrupole splitting, |DeltaE(Q)|, in the range 3.24-4.10 mm s(-1), is observed. In contrast, 5a and 5b comprise both intermediate spin ferric ions (S(Fe) = 3/2) which couple antiferromagnetically in the dinuclear molecules yielding an S(t) = 0 ground state.     

The electronic structure of the isoelectronic, square-planar complexes [FeII(L)2]2- and [CoIII(L Bu)2]- (L2- and (L Bu)2-=benzene-1,2-dithiolates): an experimental and density functional theoretical study

The electronic structures of two formally isoelectronic transition-metal dithiolato complexes [Fe(L)2]2- (1) and [Co(L Bu)2]1- (2) both possessing a spin triplet ground state (St=1) have been investigated by various spectroscopic and density functional methods; H2L Bu represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol and H2L is the corresponding unsubstituted benzene-1,2-dithiol. An axial zero-field splitting (D) of +32 cm(-1) for 2 has been measured independently by SQUID magnetometry, far-infrared absorption, and variable-temperature and variable-field (VTVH) magnetic circular dichroism spectroscopies. A similar D value of +28 cm(-1) is obtained for 1 on the basis of VTVH SQUID measurements. The absorption spectra of 1 and 2 are found, however, to be very different. Complex 1 is light yellow in color with no intense transition in the visible region, whereas 2 is deep blue. DFT calculations establish that the electronic structures of the [Fe(L)2](2-) and [Co(L)2]1- anions are very different and explain the observed differences in their absorption spectra. On the basis of these spectroscopic and theoretical analyses, 1 is best described as containing an intermediate spin FeII ion, whereas for the corresponding cobalt complex, oxidation states describing a d6 (CoIII) or d7 (CoII) electron configuration cannot be unambiguously assigned. The physical origin of the large zero-field splitting in both 1 and 2 is found to be due to the presence of low-energy spin-conserved d-d excitations which lead to a large Dzz through efficient spin-orbit coupling. Differential covalency effects appear to be of limited importance for this property.     

Synthesis and characterization of binuclear half-sandwich metal (Co, Ir and Ru) complexes containing ancillary ortho-carborane-1,2-dithiolato ligands

The assembly of soluble, air-stable, binuclear structures, namely {(p-cymene)Ru[S(2)C(2)(B(10)H(10))]}(2)(micro-pyz), {Cp*Co[S(2)C(2)(B(10)H(10))]}(2)(micro-pyz), {Cp*Co[S(2)C(2)(B(10)H(10))]}(2)(micro-bpy), {Cp*Co[S(2)C(2)(B(10)H(10))]}(2)(micro-bpe) and {Cp*Ir[E(2)C(2)(B(10)H(10))]}(2)(micro-bpo) (E = S (), Se), in which organometallic units are bridged by pyridyl-based organic linkers, are synthesized. The complexes have been fully characterized by IR and NMR spectroscopy, as well as elemental analysis. The molecular structures are established through X-ray crystallography.     

Dinuclear Bis(1,2-diaryl-1,2-ethylenedithiolato)iron complexes: [FeIII2(L)4]n (n = 2-, 1-, 0, 1+)

The electronic structures of four members of the electron-transfer series [Fe2(1L)4]n (n = 2-, 1-, 0, 1+) have been elucidated in some detail by electronic absorption, IR, X-band electron paramagnetic resonance (EPR), and M?ssbauer spectroscopies where (1L)(2-) represents the ligand 1,2-bis(4-tert-butylphenyl)-1,2-ethylenedithiolate(2-) and (1L*)- is its pi-radical monoanion. It is conclusively shown that all redox processes are ligand-centered and that high-valent iron(IV) is not accessible. The following complexes have been synthesized: [FeIII2(1L*)2(1L)2]0 (1), [FeIII2(2L*)2(2L)2].2CH2Cl2 (1') where (2L)(2-) is 1,2-bis(p-tolyl)-1,2-ethylenedithiolate(2-) and (2L*)- represents its pi-radical monoanion, [Cp2Co][FeIII2(1L*))(1L)3].4(toluene).0.5Et2O (2), and [Cp2Co]2[FeIII2(1L)4].2(toluene) (3). The crystal structures of 1' and 2 have been determined by single-crystal X-ray crystallography at 100 K. The ground states of complexes have been determined by temperature-dependent magnetic susceptibility measurements and EPR spectroscopy: 1' and 1 are diamagnetic (S(t) = 0); 2 (S(t) = 1/2); 3 (S(t) = 0); the monocation [Fe(III)2(1L*)3(1L)]+ possesses an S(t) = 1/2 ground state (S(t) = total spin ground state of dinuclear species). All species contain pairs of intermediate-spin ferric ions (S(Fe) = 3/2), which are strongly antiferromagnetically coupled (H = -2JS(1).S(2), where S1 = S2 = 3/2 and J = approximately -250 cm(-1)).     

Molecular and electronic structures of tetrahedral complexes of nickel and cobalt containing N,N'-disubstituted, bulky o-diiminobenzosemiquinonate(1-) pi-radical ligands

The reaction of 2 equiv of the bulky ligand N,N'-bis(3,5-di-tert-butylphenyl)-1,2-phenylenediamine, H2[3L(PDI)], excess triethylamine, and 1 equiv of M(CH3CO2)2.4H2O (M = Ni, Co) in the presence of air in CH3CN/CH2Cl2 solution yields violet-black crystals of [Ni(II)(3L(ISQ))2] CH3CN (1) or violet crystals of [Co(3L)2] (3). By using Pd(CH3CO2)2 as starting material, green-blue crystals of [Pd(II)(3L(ISQ))2].CH3CN (2) were obtained. Single-crystal X-ray crystallography revealed that 1 and 3 contain (pseudo)tetrahedral neutral molecules [M(3L)2] (M = Ni, Co) whereas in 2 nearly square planar, neutral molecules [Pd(II)(3L(ISQ))2] are present. Temperature-dependent susceptibility measurements established that 1 and 2 are diamagnetic (S = 0) whereas 3 is paramagnetic with an S = 3/2 ground state. It is shown that 1 contains two pi radical benzosemiquinonate(1-)-type monoanions, ((3L(ISQ))(1-*), S(rad) = 1/2), and a central Ni(II) ion (d8; S = 1) which are antiferromagnetically coupled yielding the observed S(t) = 0 ground state. This result has been confirmed by broken symmetry DFT calculations of 1. In contrast, the S(t) = 3/2 ground state of 3 is more difficult to understand: the two resonance structures [Co(III)(3L(ISQ))(3L(PDI))] <--> [Co(II)(3L(PDI))(3L(IBQ))] might be invoked (for tetrahedral [Co(II)(3L(ISQ))2] containing an S(Co) = 3/2 with two antiferromagnetically coupled pi-radical ligands an S(t) = 1/2 is anticipated). Complex 2 is diamagnetic (S = 0) containing a Pd(II) ion (d8, S(Pd) = 0 in an almost square planar ligand field) and two antiferromagnetically coupled ligand radicals (S(rad) = 1/2). The electrochemistry and spectroelectrochemistry of 1, 2, and 3 have been studied, and electron-transfer series comprising the species [M(L)2]z (z = 2+, 1+, 0, 1-, 2-) have been established. All oxidations and reductions are ligand centered.     

Electronic structure of square planar bis(benzene-1,2-dithiolato)metal complexes [M(L)(2)](z) (z = 2-, 1-, 0; M = Ni, Pd, Pt, Cu, Au): an experimental, density functional, and correlated ab initio study

The three diamagnetic square planar complexes of nickel(II), palladium(II), and platinum(II) containing two S,S-coordinated 3,5-di-tert-butylbenzene-1,2-dithiolate ligands, (L(Bu))(2-), namely [M(II)(L(Bu))(2)](2-), have been synthesized. The corresponding paramagnetic monoanions [M(II)(L(Bu))(L(Bu)(*))](-) (S = (1)/(2)) and the neutral diamagnetic species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt) have also been generated in solution or in the solid state as [N(n-Bu)(4)][M(II)(L(Bu))(L(Bu)(*))] salts. The corresponding complex [Cu(III)(L(Bu))(2)](-) has also been investigated. The complexes have been studied by UV-vis, IR, and EPR spectroscopy and by X-ray crystallography; their electro- and magnetochemistry is reported. The electron-transfer series [M(L(Bu))(2)](2-,-,0) is shown to be ligand based involving formally one (L(Bu)(*))(-) pi radical in the monoanion or two in the neutral species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt). Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic spectra. For the three neutral species a detailed analysis of the orbital structures reveals that the species may best be described as containing two strongly antiferromagnetically interacting ligand radicals. Furthermore, multiconfigurational ab initio calculations using the spectroscopy oriented configuration interaction (SORCI) approach including the ZORA correction were carried out. The calculations predict the position of the intervalence charge-transfer band well. Chemical trends in the diradical characters deduced from the multiconfigurational singlet ground-state wave function along a series of metals and ligands were discussed.     

Electronic structure of mononuclear bis(1,2-diaryl-1,2-ethylenedithiolato)iron complexes containing a fifth cyanide or phosphite ligand: a combined experimental and computational study

A series of mononuclear square-based pyramidal complexes of iron containing two 1,2-diaryl-ethylene-1,2-dithiolate ligands in various oxidation levels has been synthesized. The reaction of the dinuclear species [Fe(III)2(1L*)2(1L)2]0, where (1L)2- is the closed shell di-(4-tert-butylphenyl)-1,2-ethylenedithiolate dianion and (1L*)1- is its one-electron-oxidized pi-radical monoanion, with [N(n-Bu)4]CN in toluene yields dark green crystals of mononuclear [N(n-Bu)4][Fe(II)(1L*)2(CN)] (1). The oxidation of 1 with ferrocenium hexafluorophosphate yields blue [Fe(III)(1L*)2(CN)] (1ox), and analogously, a reduction with [Cp2Co] yields [Cp2Co][N(n-Bu)4][Fe(II)(1L*)(1L)(CN)] (1red); oxidation of the neutral dimer with iodine gives [Fe(III)(1L*)2I] (2). The dimer reacts with the phosphite P(OCH3)3 to yield [Fe(II)(1L*)2{P(OCH3)3}] (3), and [Fe(III)2(3L*)2(3L)2] reacts with P(OC6H5)3 to give [Fe(II)(3L*)2{P(OC6H5)3}] (4), where (3L)2- represents 1,2-diphenyl-1,2-ethylenedithiolate(2-). Both 3 and 4 were electrochemically one-electron oxidized to the monocations 3ox and 4ox and reduced to the monoanions 3red and 4red. The structures of 1 and 4 have been determined by X-ray crystallography. All compounds have been studied by magnetic susceptibility measurements, X-band EPR, UV-vis, IR, and M?ssbauer spectroscopies. The following five-coordinate chromophores have been identified: (a) [Fe(III)(L*)2X]n, X = CN-, I- (n = 0) (1ox, 2); X = P(OR)3 (n = 1+) )3ox, 4ox) with St = 1/2, SFe = 3/2; (b) [Fe(II)(L*)2X]n, X = CN-, (n = 1-) (1); X = P(OR)3 (n = 0) (3, 4) with St = SFe = 0; (c) [Fe(II)(L*)(L)X]n <--> [Fe(II)(L)(L*)X]n, X = CN- (n = 2-) (1red); X = P(OR)3 (n = 1-) (3red, 4red) with St = 1/2, SFe = 0 (or 1). Complex 1ox displays spin crossover behavior: St = 1/2 <--> St = 3/2 with intrinsic spin-state change SFe = 3/2 <--> SFe = 5/2. The electronic structures of 1 and 1(ox) have been established by density functional theoretical calculations: [Fe(II)(1L*)2(CN)]1- (SFe = 0, St = 0) and [Fe(III)(1L*)2(CN)]0 (SFe = 3/2, St = 1/2).     

1-[2-(N-甲基-N-取代苄基)氨基-2-(4-叔丁基苯基)乙基]-1H-1,2,4-三唑类化合物的合成及抗真菌活性

根据氮唑类和苄胺类抗真菌药物的构效关系和作用机理,设计合成了23种1-[2-(N-甲基-N-取代苄基)氨基-2-(4-叔丁基苯基)乙基]-1H-1,2,4-三唑类化合物,其结构经元素分析、红外光谱及核磁共振谱分析证实.体外抑菌实验结果表明:目标化合物对常见的9种致病真菌均有一定活性,对浅表真菌活性优于深部真菌,其中化合物3,4,6,10,12,14和15对羊毛样小孢子菌具有较强的活性.     

Photoluminescence properties of four-coordinate gold(I)-phosphine complexes of the types [Au(diphos)2]PF6 and [Au2(tetraphos)2](PF6)2

Numerous reports describe the photoluminescence of two- and three-coordinate gold(I)-phosphine complexes, but emission in their analogous four-coordinate complexes is almost unknown. This work examines the luminescence of tetrahedral gold(I) complexes of the types [Au(diphos)(2)]PF(6) (diphos = 1,2-bis(diphenylphosphino)ethane, 1) and [Au(2)(tetraphos)(2)](PF(6))(2) (tetraphos = (R,R)-(+/-)/(R,S)-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane, (R,R)-(+/-)/(R,S)-2). Although nonemitting in solution, these complexes luminesce with an intense yellow color (lambda(max) 580-620 nm) at 293 K in the solid state or when immobilized as molecular dispersions within solid matrixes. The excited-state lifetimes of the emissions (tau 4.1-9.4 micros) are markedly dependent on the inter- and intramolecular phenyl-phenyl pairing interactions present. At 77 K in an ethanol glass, two transitions are observed: a minor emission at lambda(max) 415-450 nm and a major emission at lambda(max) 520-595 nm. For [Au(1)(2)]PF(6), lifetimes of tau 251.0 +/- 20.5 micros were determined for the former transition and tau 14.9 +/- 4.6 micros for the latter. Density functional theory (DFT) calculations and comparative studies indicate that the former of these emissions involves triplet LMCT pi(Ph) --> Au(d)-P(p) transitions associated with individual P-phenyl groups. The latter emissions, which are the only ones observed at 293 K, are assigned to LMCT pi(Ph-Ph) --> Au(d)-P(p) transitions associated with excited P-phenyl dimers. Other tetrahedral gold(I)-phosphine complexes containing paired P-Ph substituents display similar emissions. The corresponding phosphine ligands, whether free, protonated, or bound to Ag(I), do not exhibit comparable emissions. Far from being rare, luminescence in four-coordinate Au(I)-phosphine complexes appears to be general when stacked P-phenyl groups are present.     

Chiral functionalized bisphosphine ligands: Transition metal complexes of 1,2-bis(tert-Butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12)

When rac- or meso-1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12) (1a or 1b) is reacted with [M(CO)₄(NBD)] (M = Cr, Mo, NBD = norbornadiene), [Mo(CO)₄(EtCN)₂] or [W(CO)₆], rac-[Cr(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (2), rac- or meso-[Mo(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (3a or 3b) and rac-[W(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (4) could be isolated as pure diastereomers. UV irradiation of 1 with [Cr(CO)₆] in moist THF proceeds with hydrolysis and formation of [Cr(CO)₄{1,2-(P(OH)^tBu)₂C₂B₁₀H₁₀}] (5) which contains the metal complex-stabilized phosphinous acid. Compounds 2–5 were characterized spectroscopically (¹H, ³¹P, ¹¹B, ¹³C NMR), by mass spectrometry and by X-ray structure determination.     

Molecular and electronic structures of iron complexes containing N,S-coordinated,open-shell o-iminothionebenzosemiquinonate(1-) pi radicals

The reaction of the dinuclear species (mu-NH,NH)[Fe(III)(L(IP))(L(AP))](2) dissolved in CH(2)Cl(2) with dioxygen affords black microcrystals of diamagnetic (mu-S,S)[Fe(III)(L(IP))(L(ISQ))](2).n-hexane (6) upon the addition of n-hexane, where (L(IP))(2)(-) represents the dianion of 4,6-di-tert-butyl-2-aminothiophenol, (L(AP))(-) is the corresponding monoanion, and (L(ISQ))(-) is the corresponding o-iminothionebenzosemiquinonate(1-) pi radical monoanion; similarly, the dianion ('H(2)N(2)S(2)')(2)(-) is derived from 1,2-ethanediamine-N,N'-bis(2-benzenethiol), and ('N(2)S(2)(*)')(3)(-) is its monoradical trianion. The above reaction in a CH(2)Cl(2)/CH(3)OH (1:1) mixture yields the diamagnetic isomer (mu-NH,NH)[Fe(III)(L(IP))(L(ISQ))](2).5CH(3)OH (7), whereas air oxidation of (mu-S,S)[Fe(II)('H(2)N(2)S(2)')](2) in CH(3)CN yields diamagnetic (mu-S,S)[Fe(III)('N(2)S(2)(*)')](2) (8). Complexes 6 and 8 were shown to undergo addition reactions with phosphines, phosphites, or cyanide affording the following complexes: trans-[Fe(II)(L(ISQ))(2)(P(OPh)(3))] (9; S(t) = 0) and [N(n-Bu)(4)][Fe(II)(L(ISQ))(2)(CN)] (S(t) = 0). Oxidation of 6 in CH(2)Cl(2) with iodine, bromine, and chlorine respectively yields black microcrystals of [Fe(III)(L(ISQ))(2)X] (X = I, Br, or Cl) with S(t) = (1)/(2). The structures of complexes 6-9 have been determined by X-ray crystallography at 100 K. The oxidation level of the ligands and iron ions in all complexes has been unequivocally established, as indicated by crystallography; electron paramagnetic resonance, UV-vis, and M?ssbauer spectroscopies; and magnetic-susceptibility measurements. The N,S-coordinated o-iminothionebenzosemiquinonate(1-) pi radicals have been identified in all new complexes. The electronic structures of the new complexes have been determined, and it is shown that no evidence for iron oxidation states >III is found in this chemistry.     

1-(2-Quinoxalyl)-, 1-[3,5-Di(trifluoromethyl)phenyl]-, 1-(2-Carboxyphenyl)-, and 1-Ethoxycarbonyl-4-oxo-4,5,6,7-tetrahydroindazoles

The corresponding 1-(2-quinoxalyl)-, 1-[3,5-di(trifluoromethyl)phenyl]-, and 1-ethoxycarbonyl-3-methyl-4-oxo-4,5,6,7-tetrahydroindazoles have been obtained from reactions of 2-acetyl-1,3-cyclohexanedione, its 5,5-dimethyl and 5-(2-furyl) derivatives, with 2-hydrazinoquinoxaline, 3,5-di(trifluoromethyl)phenylhydrazine, and ethoxycarbonylhydrazine. On interaction with ethoxycarbonylhydrazine the intermediate 2-[1-(-ethoxycarbonyl)hydrazino]ethylidene-1,3-cyclohexanediones were also isolated. From the potassium salt of 2-formyldimedone and 2-carboxyphenylhydrazine hydrochloride, 2-(2-carboxyphenyl)hydrazinomethylene-5,5-dimethyl-1,3-cyclohexanedione was obtained, the cyclization of which in ethanol in the presence of HCl led to 1-(2-carboxyphenyl)- and 1-(2-ethoxycarbonylphenyl)-6,6-dimethyl-4-oxo-4,5,6,7-tetrahydroindazole.     

1,2-Bis-[(5-methyl/chloro/nitro)-2-1H-benzimidazolyl]-1,2-ethanediols and their PdCl2 complexes

1,2-Bis-[(5-methyl)-2-1H-benzimidazolyl]- (L ¹), 1,2-bis-[(5-chloro)-2-1H-benzimidazolyl]- (L ²), 1,2-bis-[(5-nitro)-2-1H-benzimidazolyl]-1,2-ethanediol (L ³) and their PdCl₂ complexes were synthesized and characterized by elemental analysis, molar conductivity, i.r. and ¹H-n.m.r. spectra. The benzene ring substituents lead to a decrease in melting point. The methyl group reduces the solubility and the acidity of L ¹ and Pd(L ¹)Cl₂, whereas the Cl and NO₂ groups increase the solubility and the acidity of L ², L ³, Pd(L ²)Cl₂ and Pd(L ³)Cl₂. In Pd(L ¹)Cl₂ and Pd(L ²)Cl₂ complexes, the ligands act as a bidentate through two nitrogen atoms. In Pd(L ³)Cl₂, ligand coordination occurs through one OH group oxygen atom and one of the benzimidazole nitrogen atoms.     

One- and two-electron reduced 1,2-diketone ligands in [CrIII(L*)3] (S = 0) and Na2(Et2O)2[VIV(LRed)3] (S = 1/2)

The electronic structures of chromium and vanadium centers coordinated by three reduced 1,2-diketones have been elucidated by using density functional theory (DFT) calculations and a host of physical methods: X-ray crystallography; cyclic voltammetry; ultraviolet-visible (UV-vis), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopy; and magnetic susceptibility measurements. The metal center in octahedral [CrIII(L*)3]0 (1), a CrIII (d3) ion is coupled antiferromagnetically to three monoanionic ligand pi-radicals affording an S ) 0 ground state. In contrast, Na2(Et2O)2[VIV(LRed)3] (2) (S ) 1/2), possesses a central VIV (d1) ion O,OE-coordinated to three closed-shell, doubly reduced ligands which in turn are coordinated by two Na cations enforcing a trigonal prismatic geometry at the vanadium center. 2 can be oxidized electrochemically by one and two electrons generating a monoanion, [V(L)3]1-, and a neutral species, [V(L)3]0, respectively. DFT calculations atthe B3LYP level show that the one-electron oxidized product contains an octahedral VIV ion coupled antiferromagnetically to one monoanionic ligand pi-radical [VIV(L*)(LRed)2]1- (S ) 0). In contrast, the two-electron oxidized product contains a VIII ion coupled antiferromagnetically to three ligand pi-radicals in an octahedral field[VIII(L*)3]0 (S ) 1/2).     

A strategy for the build-up of transition-metal complexes containing tripodal [ArPOS2]2- and [ArPS3]2- ligands (Ar = 4-anisyl)

The investigation presents new synthetic methods for the generation of tripodal P/S ligands by reactions of metal alkoxides and carboxylates with the organoperthiophosphinic acid anhydride Lawesson's reagent. Four new transition-metal complexes containing various tripodal ligand sets were synthesised and characterised.