Ligand‐Modification Effects on the Reactivity,Solubility, and Stability of Organometallic Tantalum Complexes in Water

Tantalum complexes [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NMe₂)?CH)py}] ( 4 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NH₂)?CH)py}] ( 5 ), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ³‐N,O,O‐(OCH₂)(OCH)py}] (Cp*=η⁵‐C₅Me₅) with HC?CCH₂NMe₂ and HC?CCH₂NH₂, respectively. The reactions of [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(Ph)?CH)py}] ( 2 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH)py}] ( 3 ) with triflic acid (1:2 molar ratio) rendered the corresponding bis‐triflate derivatives [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(Ph)?CH₂)py}] ( 6 ) and [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH₂)py}] ( 7 ), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water‐soluble cationic complex [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH)py}]OTf ( 8 ). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H₂O){κ³‐N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH₂)py}](OTf)₂ ( 9 ). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH)py}](OTf)₂ ( 10 ), which afforded the corresponding protonolysis derivative [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH₂)py}](OTf) ( 11 ) in solution. Complex 8 reacted with CNtBu and potassium 2‐isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13 , respectively. The molecular structures of complexes 5 , 7 , and 10 were established by single‐crystal X‐ray diffraction studies.     

Darstellung und Struktur der Komplexverbindungen trans‐[CoIII(py)4F2][H2F3] und [Pd(py)4]F2 · 1,5 HF · 2 H2O

Synthesis and Crystal Structures of the Complexes trans ‐[Co^III(py)₄F₂][H₂F₃] and [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O The cobalt complex trans‐[Co(III)(py)₄F₂][H₂F₃] ( 1 ) has been prepared by electrochemical oxidation of CoF₂ in a pyridine/HF mixture and the palladium complex [Pd(py)₄]F₂ · 1.5 HF · 2 H₂O ( 2 ) has been obtained via halogen exchange between Pd(py)₂Cl₂ and AgF₂ in pyridine. 1 and 2 crystallize in the space group C2/c with a = 27.928(14), b = 9.019(3), c = 18.335(8) Å, β = 113.41(3)° for 1 and a = 28.183(9), b = 9.399(3), c = 17.397(6) Å, β = 104.66(3)° for 2 , respectively. Concerning the shape and location of the M(py)₄ fragments 1 and 2 are isostructural. The metal atoms occupy special positions in their unit cells with the result that four complex atoms have C₂ symmetry and four complex cations have C_i symmetry giving a total of Z = 8. In 1 two F^– ions complete an octahedral coordination around the Co atoms (Co–F 1.820(2) to 1.834(3) Å). In 2 the shortest Pd–F distance is 3.031(2) Å. This precludes the existence of Pd–F bonds. In 1 one can identify H₂F₃^– groups. In 2 there are larger aggregates, consisting of F^–, HF, and H₂O subunits, connected by H‐bridges. In spite of these differences, both complexes belong to the same type of structure, which may be of a common type M^x+(py)₄F_x · y HF · z H₂O.     

Cyano‐Bridged Aqua(N,N‐Dimethylacetamide)(cyanoiron)lanthanides from Samarium,Gadolinium, or Holmium Nitrate and Potassium Hexacyanoferrate: Crystal Structures and Magnetochemistry

Three cyano‐bridged aqua(N,N‐dimethylacetamide)(cyanoiron)lanthanide complexes were synthesized by the reaction of K₃Fe(CN)₆, Ln(NO₃)₃⋅6 H₂O (Ln=Sm, Gd, Ho), and N,N‐dimethylacetamide (DMA). The obtained complexes 1 – 3 exhibit different coordination geometries and crystal structures. The polymeric {[Sm(DMA)₂(H₂O)₄Fe(CN)₆⋅5 H₂O}_n ([SmFe]_n; 1 ) has a one‐dimensional chain structure with approximately parallel trans‐positioned bridging CN ligands between the Sm‐ and Fe‐atoms. [(Gd(DMA)₃(H₂O)₄)₂Fe(CN)₆]⋅[Fe(CN)₆]⋅3 H₂O (Gd₂Fe; 2 ) is an isolated trinuclear Gd(1)−Fe−Gd(2) complex with two approximately perpendicular cis‐positioned bridging CN ligands between the two Gd‐atoms and the Fe‐atom. [Ho(DMA)₃(H₂O)₃Fe(CN)₆]⋅3 H₂O (HoFe; 3 ) adopts a single dinuclear crystal structure with only one bridging CN between the Ho‐ and Fe‐atom. Magnetochemistry experiments establish weak antiferromagnetic interactions between Gd^III (and Ho^III) and Fe^III atoms. Especially the [SmFe]_n complex 1 exhibits long‐range magnetic ordering, T_c=3.5 K, and a stronger coercive force, H_c=1400 Oe.     

Synthesis,Spectral and Magnetic Properties,and Crystal Structures of Copper(II) Pyridinecarboxylate Adducts with N‐Heterocyclic Ligands

Synthesis and characterization of seven new complexes [Cu(2‐MeSnic)₂(CH₃OH)]₂ (where 2‐MeSnic is 2‐methylthionicotinate), [Cu(2‐MeSnic)₂L₂]₂ (where L is pyridine — py, ethylnicotinate — Etnic and butylnicotinate — Bunic), [Cu(2‐MeSnic)₂L₂(H₂O)₂] (where L is py and nicotinamide — nia) and [Cu(2‐MeSnic)₂(N‐Menia)₂(H₂O)₂]·2H₂O (where N‐Menia is N‐methylnicotinamide) are reported. The characterization were based on elemental analysis, infrared, electronic and EPR spectra, and magnetic susceptibility measurements over a temperature range of 1.8 — 300 K or 70 — 300 K. Three complexes of different type were studied by X‐ray analysis. The molecule of [Cu(2‐MeSnic)₂(CH₃OH)]₂ has dimeric paddle‐wheel cage structure with a tetragonal pyramidal arrangement around Cu^II. The dimer results from the fact that carboxyl groups of four 2‐MeSnic anions function as bridging in a syn‐syn arrangement. On the other hand [Cu(2‐MeSnic)₂(py)₂]₂ forms dimers with hexacoordinated Cu^II atoms in highly distorted coordination octahedra, each with two oxygen atoms of bridging carboxyl groups in an anti‐anti arrangement of two 2‐MeSnic anions, with two oxygen atoms of one asymmetrically chelating 2‐MeSnic anion and with two nitrogen atoms of two pyridine ligands. The temperature independent EPR spectrum for this complex exhibits an axial signal which corresponds to almost isolated S = ¹/₂ magnetic ions. Magnetic data for the dimer show a weak antiferromagnetic interaction between the two metal ions with J = —0.65 cm^—1. The Cu^II atom in complex [Cu(2‐MeSnic)₂(py)₂(H₂O)₂] is hexacoordinated in an elongated centrosymmetrical tetragonal‐bipyramidal arrangement (4 + 2). Based on the molecular structure the electronic, infrared, electron paramagnetic resonance spectra and magnetic properties are discussed and stereochemistry as well as the mode of ligand coordination in new solid complexes under study have been determined.     

Hydrogen‐bonded supramolecular networks of N,N′‐bis(4‐pyridylmethyl)oxalamide and 4,4′‐{[oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrate

The molecule of N,N′‐bis(4‐pyridylmethyl)oxalamide, C₁₄H₁₄N₄O₂, (I) or 4py‐ox, has an inversion center in the middle of the oxalamide group. Adjacent molecules are then linked through intermolecular N—H...N and C—H...O hydrogen bonds, forming an extended supramolecular network. 4,4′‐{[Oxalylbis(azanediyl)]dimethylene}dipyridinium dinitrate, C₁₄H₁₆N₄O₂²⁺·2NO₃⁻, (II), contains a diprotonated 4py‐ox cation and two nitrate counter‐anions. Each nitrate ion is hydrogen bonded to four 4py‐ox cations via intermolecular N—H...O and C—H...O interactions. Adjacent 4py‐ox cations are linked through weak C—H...O hydrogen bonding between an α‐pyridinium C atom and an oxalamide O atom, forming a two‐dimensional extended supramolecular network.     

Fabrication of novel Fe (III), Co (II), Hg (II), and Pd (II) complexes based on water-soluble ligand (NaH2PH): structural characterization,cyclic voltammetric,powder X-ray diffraction,zeta potential,and biological studies

Sodium4-hydroxy-3-([2-picolinoylhydrazineylidene]methyl)benzenesulfonate (NaH₂PH) was synthesized as a novel water-soluble ligand, by the condensation of picolinohydrazide with sodium 3-formyl-4-hydroxybenzenesulfonate. The (NaH₂PH) ligand and its isolated Co (II), Fe (III), Hg (II), and Pd (II) complexes were analyzed by elemental analysis and characterized by spectroscopic (Fourier transform infrared spectroscopy, UV–visible, powder XRD, ¹H NMR,¹³C NMR, MS) and magnetic measurements. By comparing IR spectra of both ligand and the metal complexes, one can assume that the (NaH₂PH) ligand behaves as a bi-negative tetradentate (ONNO) in [Co (NaPH)(H₂O)₂].3H₂O, and a mono-negative tridentate (ONO) in [Fe (NaPH)Cl₂(H₂O)] complex, whereas in [Hg₂(NaPH)Cl₂(H₂O)] complex, (NaH₂PH) coordinates as a bi-negative pentadentate (ONNNO) ligand via deprotonated OH group of phenolic ring (C=N)_Py and (C=N*) coordinated to one of Hg (II) ion and the oxygen atom of enolic group and (C=N)_az group with the another Hg (II) ion. Moreover, (NaH₂PH) acts as bi-negative tridentate (ONO) ligand in [Pd (NaPH)(H₂O)].2H₂O complex. The geometries of complexes were suggested based on the UV–visible spectra, magnetic measurements and confirmed by applying discrete Fourier transform (DFT) optimization studies. The thermal fragmentation of both [Pd (NaPH)(H₂O)].2H₂O and [Co (NaPH)(H₂O)₂].3H₂O complexes was performed, and the kinetic and thermodynamic parameters were computed using the Coats–Redfern and Horowitz–Metzger methods. The redox behavior of divalent ions of cobalt and mercury were discussed by the cyclic voltammetry technique in the presence and absence of (NaH₂PH) ligand. Biological potencies of the ligand and its metal complexes were evaluated as antioxidants (ABTS and DPPH), anticancer, DNA, and antimicrobial (Staphylococcus aureus and Bacillus subtilis as Gram (+) bacteria, Escherichia coli and Pseudomonas aeruginosa as Gram (−) bacteria, and Candida albicans as fungi).     

Iron pyrrole‐based PNP pincer ligand complexes as catalyst precursors

The structure of a pincer ligand consists of a backbone and two `arms' which typically contain a P or N atom. They are tridentate ligands that coordinate to a metal center in a meridional configuration. A series of three iron complexes containing the pyrrole‐based PNP pincer ligand 2,5‐bis[(diisopropylphosphanyl)methyl]pyrrolide (PN^pyrP) has been synthesized. These complexes are possible precursors to new iron catalysts. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}carbonylchlorido(trimethylphosphane‐κP )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₃H₉P)(CO)] or [Fe(PN^pyrP)Cl(PMe₃)(CO)], (I), has a slightly distorted octahedral geometry, with the Cl and CO ligands occupying the apical positions. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}chlorido(pyridine‐κN )iron(II), [Fe(C₁₈H₃₄NP₂)Cl(C₅H₅N)] or [Fe(PN^pyrP)Cl(py)] (py is pyridine), (II), is a five‐coordinate square‐pyramidal complex, with the pyridine ligand in the apical position. {2,5‐Bis[(diisopropylphosphanyl)methyl]pyrrolido‐κ³P ,N ,P ′}dicarbonylchloridoiron(II), [Fe(C₁₈H₃₄NP₂)Cl(CO)₂] or [Fe(PN^pyrP)Cl(CO)₂], (III), is structurally similar to (I), but with the PMe₃ ligand replaced by a second carbonyl ligand from the reaction of (II) with CO. The two carbonyl ligands are in a cis configuration, and there is positional disorder of the chloride and trans carbonyl ligands.     

Crystal Structures and Hydrogen Bonding of Two Complexes containing the [Ammine‐chlorido‐ethylenediamine‐bis(pyridine)cobalt(III)]2+ Cation

The crystal structures of two classical cobalt(III) complexes comprising the [CoCl(NH₃)(en)(py)₂]²⁺ cation were determined by single‐crystal X‐ray diffraction. Both complexes, dark red [CoCl(NH₃)(en)(py)₂]Cl₂ · H₂O ( 1 ) and purple [CoCl(NH₃)‐(en)(py)₂][HgCl₄] · 1.125H₂O ( 2 ), crystallize in the triclinic space group P1 . In both compounds, the Co atom exhibits a typical octahedral coordination and the configuration index of the complex is OC‐6‐43. In the case of the chloride ( 1 ), the asymmetric unit comprises one formula unit, whereas there are two formula units in the case of the tetrachloridomercurate ( 2 ). Complex cations, anions, and crystal water molecules are interconnected by various N–H ··· N, N–H ··· Cl, N–H ··· O, O–H ··· Cl, and O–H ··· O bridge bonds. As a result, compound 1 features a two‐dimensional layer structure and compound 2 exists as a three‐dimensional network.     

Self-assembly of copper(II) complexes with substituted aroylhydrazones and monodentate N-heterocycles: synthesis,structure and properties

Two ternary copper(II) complexes [Cu(L¹)(py)] (1) and [Cu(L²)(Himdz]?·?CH₃OH (2) with substituted aroylhydrazones, 5-bromo-salicylaldehyde-3,5-dimethoxy-benzoylhydrazone (H₂L¹) and 5-bromo-salicylaldehyde-p-methyl-benzoylhydrazone (H₂L²), pyridine (py) and imidazole (Himdz), have been synthesized. Their crystal structures and spectroscopic properties have been studied. In each complex, the metal is in a square-planar N₂O₂ coordination formed by the phenolate-O, the imine-N and the deprotonated amide-O atoms of L^2?, and the sp²?N atom of the neutral heterocycle. In the solid state, 1 exists as a centrosymmetric dimer due to very weak apical coordination of the metal bound phenolate-O. Complex 2 has no such apical coordination and exists as a monomer. Self-assembly via C–H?···?O, N–H?···?O and O–H?···?N interaction leads to a one-dimensional chain arrangement; other non-covalent interactions such as C–H?···?π and π?···?π are not involved.     

Synthesis,Structures and DFT Studies of Imido‐bridged and (Bis)ligand‐coordinated Titanium Complexes

Syntheses and structures of five imido‐bridged dinuclear titanium complexes and two (bis)ligand‐coordinated mononuclear titanium complexes are reported. Addition of 1 or 2 equiv. of Schiff base ligand (((1H‐pyrrol‐2‐yl)methylene)amino)‐2,3‐dihydro‐1H‐inden‐2‐ol (H₂L) to Ti(NMe₂)₄ resulted in transamination with 4 equiv. of dimethylamides generating a (bis)ligand‐coordinated complex Ti(L)₂ ( 1 ). Treatment of Ti(NMe₂)₄ with 1 equiv. of ^tBuNH₂ followed by addition of 1 equiv. of H₂L afforded an imido‐bridged complex [Ti(L)(N^tBu)]₂ ( 2 ). 1:1:1:1 reaction of Ti(NMe₂)₄/RNH₂/H₂L/py(or phen) produced imido‐bridgedcomplexes [Ti(L)(NPh)(py)]₂ ( 3 ), [Ti(L)(4‐F‐PhN)(py)]₂·Tol ( 4 ·Tol), [Ti(L)(4‐Cl‐PhN)(py)]₂·Tol·THF ( 5 ·Tol·THF), [Ti(L)(4‐Br‐PhN)(py)]₂·Tol ( 6 ·Tol) and a (bis)ligand‐coordinated complex Ti(L)₂·phen ( 7 ) (py = pyridine, phen = 1,10‐phenanthroline). Attempts to prepare the monomeric titianium imido complexes were unsuccessful. DFT studies show that the assumed compound which contains Ti = N species is less stable than imido‐bridged Ti‐N(R)‐Ti complexes, providing the better understanding of the experimental results.     

An iron(III) 18-metallacrown-6 complex: synthesis,crystal structure,and bioactivity

A macrocyclic hexanuclear iron(III) 18-metallacrown-6 complex, [Fe₆(C₉H₆BrN₂O₃)₆(CH₃OH)₄(H₂O)₂]?·?7CH₃OH?·?4H₂O, has been prepared using a trianionic pentadentate ligand N-acetyl-5-bromosalicylhydrazidate, abshz^3–, and characterized by X-ray diffraction. The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Fe(III) and six abshz^3– ligands. The 18-membered metallacrown ring is formed by combination of six structural moieties, [Fe(III)–N–N]. Due to meridional coordination of ligand to Fe³⁺, the ligand enforces the stereochemistry of the Fe³⁺ ions as a propeller configuration with alternating Δ/Λ forms. Methanol and water are linked with Fe1, Fe1A, Fe,3 and Fe3A. The ratios of methanol to water are 0.76?:?0.24 for Fe1 and Fe1A, and 0.30?:?0.70 for Fe3 and Fe3A, which results in four component crystals of metallacrown rings with ratio of 0.168?:?0.072?:?0.532?:?0.228. Antibacterial screening data showed that the iron metallacrown has moderate antimicrobial activity against Bacillus subtilis.     

A long Nb=O double bond in bis(pyridinium) tetra­chlorooxo(pyridine‐κN)niobate(V) chloride

The asymmetric unit of the title compound, (C₅H₆N)₂[NbCl₄O(C₅H₅N)]Cl or (pyH)₂[O=NbCl₄(py)]Cl (py is pyridine), contains a discrete anionic niobium(V) complex, [O=NbCl₄(py)]⁻, and two protonated pyridine mol­ecules, which form medium–strong hydrogen bonds with the Cl⁻ counter‐ion. The Nb=O distance of 1.7643 (17) Å is the longest among those in congener niobium complexes reported to date. Extensive density functional theory studies of conformations of [O=NbCl₄(py)]⁻ and structural data mining raise doubts regarding the reliability of the length of this Nb=O double bond.     

1H, 13C, 15N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl, and a new synthesis of mer-[Co(py)3Cl3]

trans-[Co(py)₄Cl₂]Cl·6H₂O, mer-[Co(py)₃Cl₃] and mer-[Co(py)₃(CO₃)Cl] were studied by UV-Vis, far-IR and ¹H, ¹³C, ¹⁵N NMR. The formation of Co-N bonds lead to variable in sign and magnitude changes of ¹H NMR chemical shifts, heavily dependent on proton position, coordination sphere geometry and character of auxiliary ligands. ¹³C nuclei were deshielded upon Co(III) coordination, while ¹⁵N NMR studies exhibited ca. 85–110 ppm shielding effects (ca. 15–25 ppm more expressed for nitrogens trans to N than trans to Cl or O). ¹³C and ¹⁵N CPMAS spectra revealed a slight inequivalency of formally identical Co-py bonds in trans-[Co(py)₄Cl₂]Cl·6H₂O and mer-[Co(py)₃Cl₃], suggesting for the latter complex an existence of distortion isomers. In chloroform, a spontaneous trans-[Co(py)₄Cl₂]Cl → mer-[Co(py)₃Cl₃] + py reaction was monitored by ¹H NMR and UV-Vis. This process of py → Cl substitution allowed the design of a more convenient and efficient method of mer-[Co(py)₃Cl₃] preparation.      

两种新型μ－氧桥联－双铁(III)席夫碱配合物：X-衍射分析，IR, UV-Vis, CD光谱，磁性质和电化学性质

热力学稳定的带有大环配体的μ－氧桥联－双铁配合物，由于其两个铁中心之间的有趣的电子结构和磁相互作用而受到广泛关注。μ－氧桥联－双铁席夫碱配合物，[{Fe(tbusalphn)}₂(μ-o)] (1)和[{Fe(R,R-salchxn)}₂(μ-o)] (2), 通过用咪唑或N－甲基咪唑的水溶液处理相应的单核铁氯化物，Fe(L)Cl，而获得。1和2的晶体结构通过x-射线结构分析而被确定。1属于三斜晶系，P－1空间群。2属于单斜晶系，P2₁/c空间群。由于1的配体带有庞大的叔丁基取代基，导致形成μ－氧桥联－双铁配合物时的空间拥挤，因此，其Fe-O-Fe夹角为176.5 ^o，几乎成平角。而2则由于配体上没有庞大的取代基，其Fe-O-Fe夹角为149.6^o，明显小于1的Fe-O-Fe夹角。 本文还对两种μ－氧桥联－双铁席夫碱配合物及相应的单核铁氯化物的红外光谱、紫外－可见吸收光谱及圆二色光谱性质进行了研究。与相应的单体铁配合物相比较，生成μ－氧桥联－双铁席夫碱配合物后，出现一新的红外吸收带，归属于ν_Fe-O-Fe振动。有趣的是，其数值与Fe-O-Fe夹角大小相对应。1和2除具有明显不同的Fe-O-Fe夹角外，它们的圆二色光谱却是相似的。 对1和2的磁性质研究表明，在这类化合物中两个铁(III)离子之间存在着强烈的分子内抗铁磁性偶合作用。另外，本文还采用循环伏安法对1和2的电化学性质进行了研究。     

Solvent water tapes in two hydrates of μ‐oxo‐bis­[bis­(2,2′‐bipyridine‐κ2N,N′)(sulfato‐κO)iron(III)]

The title compound, [Fe₂O(SO₄)₂(C₁₀H₈N₂)₄], crystallizes as two different hydrates, viz. 11H₂O, (I), and 15H₂O, (II). The complex is binuclear, in which the two Fe^III atoms are coordinated in an octa­hedral geometry to four N atoms from the two bipyridine ligands, to one O atom from the sulfate ion and to an oxide ion on a twofold axis, which acts as a bridge between the symmetry‐related units. The Fe⋯Fe separation is 3.556 (4) Å and the Fe—O—Fe angle is 161.6 (2)° in (I); the corresponding values are 3.544 (1) Å and 165.8 (2)° in (II). In (II), one of the O atoms of the sulfate ion is disordered over two positions. In both compounds, the solvent water mol­ecules form slightly different one‐dimensional hydrogen‐bonded networks which pass along the c axis of the unit cell. In (I), three solvent water mol­ecules and, in (II), one solvent water mol­ecule, are situated on the twofold axis. In both (I) and (II), the central O atom of the metal complex lies on a twofold axis.     

FeIII in a high-spin state in bis(5-bromosalicylaldehyde 4-ethylthiosemicarbazonato-κ3O,N1,S)ferrate(III) nitrate monohydrate,the first example of such a cationic FeIII complex unit

The synthesis and crystal structure (100 K) of the title compound, [Fe(C₁₀H₁₁BrN₃OS)₂]NO₃·H₂O, is reported. The asymmetric unit consists of an octahedral [Fe^III(HL)₂]⁺ cation, where HL^? is H-5-Br-thsa-Et or 5-bromosalicylaldehyde 4-ethylthiosemicarbazonate(1?) {systematic name: 4-bromo-2-[(4-ethylthiosemicarbazidoidene)methyl]phenolate}, a nitrate anion and a noncoordinated water molecule. Each HL^? ligand binds via the thione S, the imine N and the phenolate O atom, resulting in an Fe^IIIS₂N₂O₂ chromophore. The ligands are orientated in two perpendicular planes, with the O and S atoms in cis and the N atoms in trans positions. This [Fe(HL)₂](anion)·H₂O compound contains the first known cationic Fe^III entity containing two salicylaldehyde thiosemicarbazone derivatives. The Fe^III ion is in the high-spin state at 100 K. In addition, a comparative IR spectroscopic study of the free ligand and the ferric complex is presented, demonstrating that such an analysis provides a quick identification of the degree of deprotonation and the coordination mode of the ligand in this class of metal compounds. The variable-temperature magnetic susceptibility measurements (5–320 K) are consistent with the presence of a high-spin Fe^III ion with a zero-field splitting D = 0.439 (1) cm^?1.     

Slow Magnetic Relaxation,Antiferromagnetic Ordering,and Metamagnetism in MnII(H2dapsc)-FeIII(CN)6 Chain Complex with Highly Anisotropic Fe-CN-Mn Spin Coupling

Reactions of [Mn(H₂dapsc)Cl₂] ⋅ H₂O (dapsc=2,6- diacetylpyridine bis(semicarbazone)) with K₃[Fe(CN)₆] and (PPh₄)₃[Fe(CN)₆] lead to the formation of the chain polymeric complex {[Mn(H₂dapsc)][Fe(CN)₆][K(H₂O)_3.5]}_n ⋅ 1.5n H₂O ( 1 ) and the discrete pentanuclear complex {[Mn(H₂dapsc)]₃[Fe(CN)₆]₂(H₂O)₂} ⋅ 4 CH₃OH ⋅ 3.4 H₂O ( 2 ), respectively. In the crystal structure of 1 the high-spin [Mn^II(H₂dapsc)]²⁺ cations and low-spin hexacyanoferrate(III) anions are assembled into alternating heterometallic cyano-bridged chains. The K⁺ ions are located between the chains and are coordinated by oxygen atoms of the H₂dapsc ligand and water molecules. The magnetic structure of 1 is built from ferrimagnetic chains, which are antiferromagnetically coupled. The complex exhibits metamagnetism and frequency-dependent ac magnetic susceptibility, indicating single-chain magnetic behavior with a Mydosh-parameter φ=0.12 and an effective energy barrier (U_eff/k_B) of 36.0 K with τ₀=2.34×10⁻¹¹ s for the spin relaxation. Detailed theoretical analysis showed highly anisotropic intra-chain spin coupling between [Fe^III(CN)₆]³⁻ and [Mn^II(H₂dapsc)]²⁺ units resulting from orbital degeneracy and unquenched orbital momentum of [Fe^III(CN)₆]³⁻ complexes. The origin of the metamagnetic transition is discussed in terms of strong magnetic anisotropy and weak AF interchain spin coupling.     

A rare octacoordinated mononuclear iron(III) spin‐crossover compound: synthesis,crystal structure and magnetic properties

The chemistry of transition‐metal complexes with unusually high coordination numbers has been of interest because of their application in catalytic and biological systems. Deprotonation of the ionogenic tetradentate ligand 6,6′‐bis(1H‐tetrazol‐5‐yl)‐2,2′‐bipyridine [H₂bipy(ttr)₂] in the presence of iron(III) and tetra‐n‐butylammonium bromide, [n‐Bu₄N]Br, in solution resulted in the synthesis of a rare octacoordinated anionic mononuclear complex, tetra‐n‐butylammonium bis[6,6′‐bis(tetrazol‐1‐id‐5‐yl)‐2,2′‐bipyridine]iron(III) methanol hemisolvate dihydrate, (C₁₆H₃₆N)[Fe(C₁₂H₆N₁₀)₂]·0.5CH₃OH·2H₂O or [n‐Bu₄N][Fe{bipy(ttr)₂}₂]·0.5CH₃OH·2H₂O ( 1 ), which has been structurally characterized by elemental analysis, powder X‐ray diffraction (PXRD) and single‐crystal X‐ray diffraction. In 1 , the coordination sphere of the iron(III) ion is a distorted bis‐disphenoid dodecahedron, in which the eight coordination positions are occupied by eight N atoms from two independent tetradentate [bipy(ttr)₂]^2? anionic ligands, therefore forming the anionic [Fe{bipy(ttr)₂}₂]^? unit, with the negative charge balanced by a free [n‐Bu₄N]⁺ cation. An investigation of the magnetic properties of 1 revealed a gradual incomplete spin‐crossover behaviour below 150 K.     

Kinetics of the reaction of nitric oxide with polypyridylamine iron(II) complexes

The reactions of three polypyridylamine ferrous complexes, [Fe(TPEN)]²⁺, [Fe(TPPN)]²⁺, and [Fe(TPTN)]²⁺, with nitric oxide (NO) (where TPEN = N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine, TPPN = N,N,N′,N′-tetrakis(2-pyridylmethyl)-1,2-propylenediamine, and TPTN = N,N,N′,N′-tetrakis(2-pyridylmethyl)trimethylenediamine) were investigated. The first two complexes, which are spin-crossover systems, presented second-order rate constants for complex formation reactions (k_f) of 8.4 × 10³ and 9.3 × 10³ M^?1 s^?1, respectively (pH 5.0, 25 °C, I = 0.1 M). In contrast, the [Fe(TPTN)]²⁺ complex, which is in low-spin ground state, did not show any detectable reaction with NO. k_f values are lower than those of high-spin Fe(II) complexes, such as [Fe(EDTA)]^2? (EDTA = ethylenediaminetetraacetate) and [Fe(H₂O)]²⁺, but higher than low-spin Fe(II) complexes, such as [Fe(CN)₅(H₂O)]^3? and [Fe(bipyridine)₃]²⁺. The release of NO from the [Fe(TPEN)NO]²⁺ and [Fe(TPPN)NO]²⁺ complexes were also studied, showing the values 15.6 and 17.7 s^?1, respectively, comparable to the high-spin aminocarboxylate analogs. A mechanism is proposed based on the spin-crossover behavior and the geometry of these complexes and is discussed in the context of previous publications.     

Oxo–Group‐14‐Element Bond Formation in Binuclear Uranium(V) Pacman Complexes

Simple and versatile routes to the functionalization of uranyl‐derived U^V–oxo groups are presented. The oxo‐lithiated, binuclear uranium(V)–oxo complexes [{(py)₃LiOUO}₂(L)] and [{(py)₃LiOUO}(OUOSiMe₃)(L)] were prepared by the direct combination of the uranyl(VI) silylamide “ate” complex [Li(py)₂][(OUO)(N”)₃] (N”=N(SiMe₃)₂) with the polypyrrolic macrocycle H₄L or the mononuclear uranyl (VI) Pacman complex [UO₂(py)(H₂L)], respectively. These oxo‐metalated complexes display distinct U? O single and multiple bonding patterns and an axial/equatorial arrangement of oxo ligands. Their ready availability allows the direct functionalization of the uranyl oxo group leading to the binuclear uranium(V) oxo–stannylated complexes [{(R₃Sn)OUO}₂(L)] (R=nBu, Ph), which represent rare examples of mixed uranium/tin complexes. Also, uranium–oxo‐group exchange occurred in reactions with [TiCl(OiPr)₃] to form U‐O? C bonds [{(py)₃LiOUO}(OUOiPr)(L)] and [(iPrOUO)₂(L)]. Overall, these represent the first family of uranium(V) complexes that are oxo‐functionalised by Group 14 elements.