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Structurally variable organochalcogen clusters containing palladium(II) and nickel(II) ions were assembled starting from the salicylidene-substituted dichalcogenides (Y-C

In situ prepared lithium arylselenolates {LiSePh, LiSe(2,6-Me2Ph), LiSe(2,4,6-Me3Ph)} or -tellurolates {LiTePh, LiTe(2,6-Me2Ph), LiTe(2,4,6-Me3Ph)} react with [ReOCl3(PPh3)2] and (NBu4)Br in good yields under formation of rhenium(V) complexes of the composition (NBu4)[ReO(L)4)]. The first oxidorhenium(V) complex with four monodentate phenolato ligands, [ReO(2,6-Me2Ph)4]−, was prepared and isolated in crystalline form. This allows a comparison of experimental and computational data of a full series of such compounds with basal O, S, Se and Te donor atoms. Similar reactions with [ReCl3(PPh3)2(CH3CN)] or [ReCl3(PMe2Ph)3] give trigonal bipyramidal rhenium(III) complexes of the compositions [Re(PPh3)(L)3(CH3CN)] or [Re(PPh3)2(L)3] depending on the chalcogenolate applied. The reported oxidorhenium(V) and rhenium(III) complexes were fully characterized by spectroscopic methods and X-ray diffraction. The bonding situation in the rhenium(V) and rhenium(III) chalcogenolates was assessed through density functional theory calculations based on the quantum theory of atoms in molecules (QTAIM), natural bonding orbital (NBO) analysis, charge analysis, the electron localization function (ELF) maps and topological descriptors at the {3,−1} critical points such as metallicities. Expectedly, the ionicity of the rhenium-chalcogen bonds decreases according to all three applied charge models from O to Te. Generally, the Re−Se and Re−Te bonds are more directional in the Re(III) complexes than in the oxidorhenium(V) compounds.

The first crystalline technetium complex in a negative oxidation state, [Tc−I(CO)(CNp-F-ArDArF2)4]−, was isolated and structurally characterized as its [Na(Crypt-2.2.2)]+ salt. It mirrors the properties of the textbook organometallic compound Na[Tc(CO)5], which has eluded isolation and structural characterization until today. [Na(Crypt-2.2.2)][Tc−I(CO)(CNp-F-ArDArF2)4] reacts expectedly as a nucleophile, which is demonstrated by reactions with HCl and ClSnMe3. They give the unprecedented monohydrido and trimethylstannyl complexes of technetium.

Reactions of [Re(NPhF)Cl3(PPh3)2] ({NPhF}2− = p-fluorophenylimide) with a variety of alkyl and aryl isocyanides have been studied. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1 : 1 and 1 : 2 exchange products of Re(V) with the general formulae mer-[Re(NPhF)Cl3(PPh3)(isocyanide)] and cis- or trans-[Re(NPhF)Cl3(isocyanide)2]. The stability of the obtained products is correlated with the substitution pattern of the isocyanide ligands. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy as well as mass spectrometry. The use of partially fluorinated starting materials and ligands allows the modulation of the solubilities of the starting materials and the products as well as the monitoring of the reactions by means of 19F NMR. The attachment of the CF3 or F substituent on the isocyanides gives control over the steric bulk and the electronic properties of the ligands and, thus, their reactivity.

Zwitterionic compounds such as pyridine-containing tellurenyl compounds are interesting building blocks for heterometallic assemblies. They can act as ambiphilic donor/acceptors as is shown by the products of reactions of the zwitterions HpyTeCl2 or HCF3pyTeCl2 with the rhenium(V) complex [ReOCl3(PPh3)2]. The products have a composition of [ReO2Cl(pyTeCl)(PPh3)2] and [ReO2Cl(CF3pyTeCl)(PPh3)2] with central {O=Re=O…Te(Cl)p⏠y}+ units. The Re-O bonds in the products are elongated by approximately 0.1 Å compared with those to the terminal oxido ligands and establish Te…O contacts. Thus, the normally easily assigned concept of oxidation states established at the two metal ions becomes questionable (ReV/TeII vs. ReIII/TeIV). A simple bond length consideration rather leads to a description with the coordination of a mesityltellurenyl(II) chloride unit to an oxido ligand of the Re(V) center, but the oxidation of the tellurium ion and the formation of a tellurinic acid chloride cannot be ruled out completely from an analysis of the solid-state structures. DFT calculations (QTAIM, NBO analysis) give clear support for the formation of a Re(V) dioxide complex donating into an organotellurium(II) chloride and the alternative description can at most be regarded as a less favored resonance structure.

The first consistent series of mononuclear 17-electron complexes of three Group 7 elements has been isolated in crystalline form and studied by X-ray diffraction and spectroscopic methods. The paramagnetic compounds have a composition of [M0(CO)(CNp-F-ArDarF2)4] (M = Mn (1), Tc (3), Re (6); ArDArF2 = 2,6-(3,5-(CF3)2C6H3)2­C6H3)) and are stabilized by four sterically encumbering isocyanides, which prevent the metalloradicals from dimerization. They have a square pyramidal structure with the carbonyl ligands as apexes. The frozen-solution EPR spectra of the rhenium and technetium compounds are clearly anisotropic with large 99Tc and 185,187Re hyperfine interactions for one component. High-field EPR (Q band and W band) has been applied for the elucidation of the EPR parameters of the manganese(0) complex.

Organometallic approaches are of ongoing interest for the development of novel functional 99mTc radiopharmaceuticals, while the basic organotechnetium chemistry seems frequently to be little explored. Thus, structural and reactivity studies with the long-lived isotope 99Tc are of permanent interest as the foundation for further progress in the related radiopharmaceutical research with this artificial element. Particularly the knowledge about the organometallic chemistry of high-valent technetium compounds is scarcely developed. Here, phenylimido complexes of technetium(V) with different isocyanides are introduced. They have been synthesized by ligand-exchange procedures starting from [Tc(NPh)Cl3(PPh3)2]. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1:1 and 1:2 exchange products of Tc(V) with the general formulae [Tc(NPh)Cl3(PPh3)(isocyanide)], cis- or trans-[Tc(NPh)Cl3(isocyanide)2], but also the reduction in the metal and the formation of cationic technetium(I) complex of the formula [Tc(isocyanide)6]+ when p-fluorophenyl isocyanide is used. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy. DFT calculations on the different isocyanides allow the prediction of their reactivity towards electron-rich and electron-deficient metal centers by means of the empirical SADAP parameter, which has been derived from the potential energy surface of the electron density on their potentially coordinating carbon atoms.

A scalable synthesis of the novel and highly reactive [Tc(OH2)(CO)3(PPh3)2]+ cation is described. The ligand-exchange chemistry of this compound with neutral ligands coordinating through C, N, O, S, Se, and Te has been explored systematically. The complexes either retain the original mer-trans tricarbonyl core under exclusive exchange of the aqua ligand or form dicarbonyl complexes by thermal decarbonylation. Ligand exchange reactions starting from [Tc(OH2)(CO)3(PPh3)2]+ proceed under mild conditions and are generally almost quantitative. Some of the formed complexes are remarkably stable and inert, while others provide products with one labile ligand for further reactions. The derived complexes of the type [Tc(L)(CO)3(PPh3)2]+ and [Tc(L)2(CO)2(PPh3)2]+ represent an interesting opportunity for the development of 99mTc complexes with potential use in radiopharmacy. The ready displacement of the aqua ligand highlights the synthetic value of [Tc(OH2)(CO)3(PPh3)2]+ as a reactive entry point for further studies in the little explored field of the organometallic chemistry of technetium.

p-Fluorophenylisocyanide (CNPhpF) reacts with [Re(CO)5Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation of fac-[Re(CO)3Br(CNPhpF)2] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPhpF)6]+ cation. The progress of the reactions has been studied by 19F NMR spectroscopy and the structures of [Re(CO)Br(CNPhpF)4] and [Re(CNPhpF)6](BPh4) have been elucidated by X-ray diffraction.

Metal chalcogenide cluster compounds are interesting substances by virtue of their intrinsic electronic and optical properties and their potential usage as single-source precursors for semiconductor materials. Herein, the synthesis and structural characterization of six new [HgTe]-based cluster compounds derived from bis(2-pyridyl)ditellane (oPy2Te2), and different mercury salts are described: four neutral clusters of the composition [Hg4(PPh3)2(μ-oPyTe)6Cl2] (1), [Hg4(PPh3)2(μ-oPyTe)6Br2] (2), [Hg4(PPh3)2(μ-oPyTe)6I2]⋅DMF (3) and ([Hg8(μ-oPyTe)12SCl2]⋅5.25DMF (4), and the two zwitterionic clusters [Hg8(μ-HoPyTe)0.93(μ-oPyTe)11.07SBr2.93])⋅7.62DMF (5) and [Hg8(μ-HoPyTe)0.83(μ-oPyTe)11.17SI2.83])⋅7.25DMF (6) (oPy = 2-pyridyl). The compounds were studied by single-crystal X-ray diffraction, FT-IR spectroscopy, and confocal Raman microspectroscopy. Furthermore, the optical energy gaps of the compounds were estimated by solid-state UV–Vis diffuse reflectance spectroscopy. The compounds with the smaller core structure (1–3) presented the larger Eg values, confirming small-particle optical properties’ strong dependence on the core structure’s size and composition.

The β-emitting

[Re(CO)Br(CNArDArF2)4] and [Tc(CO)Cl(CNArDArF2)4] (ArDArF = 2,6-(3,5-(CF3)2C6H3)2-4-F-C6H2) were prepared by reactions of [Re(CO)5Br] or (NBu4)[Tc2(CO)6(μ-Cl)3] with the sterically encumbered isocy...

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate (MeOTf) gives [W(CNMe)8][O...

Two potentially tripodal ligands, tris(1-phenyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP((1,2,3)Tz(1-Ph))(3)) and tris(1-benzyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP((1,2,3)Tz(1-benz))(3)), were used in reactions with [Re(CO)(5)Br] and (NEt4)(2)[Tc(CO)(3)Cl-3]. While the formation of rhenium complexes with bidentate and tridentate coordinated phosphine oxides was observed, for technetium only cationic complexes with tripodal coordinated OP((1,2,3)Tz(1-R)) ligands were isolated. The products have been characterized spectroscopically and by single crystal X-ray diffraction.

Reactions between 3-amine-2-((pyridin-2-ylmethyl)selanyl)pyridine (L) and MX2 (M = Co, Cu, Zn; X = Cl, Br) result in the formation of the metal(II) molecular complexes 1–5 with the general formula [MX2(L)]. The organic ligand is coordinated to the metal center through nitrogen atoms of the pyridine rings, without interaction with the selenium atom. The rhenium(V) complex [ReO(apySe)2]Cl (6) is formed in two different ways, using [ReOCl3(PPh3)2] as precursor. Firstly, the formation of 6 was observed in the mother liquor, through Csp3–Se bond cleavage of the ligand L and formation of new Re–Se bonds. Secondly, the direct reaction between bis(3-amino-2-pyridyl)diselane (apySe)2 and [ReOCl3(PPh3)2] gave complex 6 in higher yields. The coordination compounds were characterized by spectroscopic and crystallographic methods. Furthermore, the antibacterial activity of the complexes 1–5 was evaluated against Gram-positive bacteria, Staphylococcus aureus (ATCC® 25923), and Gram-negative bacteria, Escherichia coli (ATCC® 25922). The results suggest that the complexes [CoCl2(L)] (1), [CuCl2(L)] (3), [CuBr2(L)] (4) and, [ZnCl2(L)] (5) possess significant bactericidal activity when compared with those of the free ligand and metal salts used in the synthesis.

Five new PdII complexes are reported and have been obtained by the reaction of monomeric [Pd(bipy)(py)2]2+, which serves as a builing block, and substituted (ArSe)2 or Pd(SeAr)2. Complexes [Pd2(μ-SeAr)2(bipy)2](PF6)2, Ar = Ph (1), p-ClC6H4 (2), p-FC6H4 (3), [Pd3(μ3-Se)2(bipy)3](PF6)2·5THF (4) and [Pd3(μ-SeMes)4(bipy)2](PF6)2·2MeCN (5) showed that the nuclearity of these structures is affected by electron donating groups (EDGs) and electron withdrawing groups (EWGs) from the selenium-containing ligands, where changing the stoichiometry ratio of the reactants does not affect the number of palladium centers. The distinct behaviors of 1–5 in the solid state, solution phase and gas phase were investigated by single-crystal XRD, NMR and ESI-TOF-MS. In solution, the dinuclear 1–3 structures exist in equilibrium with trinuclear species. In the gas phase, trinuclear and tetranuclear aggregates of 1–3 are detected, as well as dinuclear and tetranuclear aggregates for 5, while compound 4 maintains the same nuclearity. The solid-state electrochemical behavior was studied, and all complexes were electrochemically active, exhibiting irreversible electrochemical processes, where selenium is indicated to be the active species which oxidizes under such conditions. The complexes are potential candidates to act as semiconductor sensitizers for photocatalytic hydrogen evolution, as they absorb in the visible region with optical band gap energies in the range of 2.6 eV.

The first technetium complexes containing anionic alkynido ligands in an end-on coordination mode have been prepared by using the nonprotic, cationic precursor

A series of technetium complexes with (η5-cyclopentadienyl)tris(dimethyl phosphito-P)cobaltate(III), also known as the "Klaui ligand" {LOMe}-, has been prepared. The products span seven different oxidation states (+1 to +7) of the radioactive transition metal and comprise nitrosyl, halide, oxido and nitrido complexes. All members of this series ([TcI(NO)Cl(PPh3)(LOMe)], [TcII(NO)Cl2(LOMe)], [TcIIICl2(PPh3)(LOMe)], [TcIVCl3(LOMe)], [TcVOCl2(LOMe)], [TcVNCl(PPh3)(LOMe)], [TcVINCl2(LOMe)], and [TcVIIO3(LOMe)] are air- and water-stable compounds, which recommends this class of technetium complexes as potential candidates for nuclear medical imaging procedures.

A series of technetium complexes with the sterically encumbered m-terphenyl isocyanides CNArDipp2 (Dipp = 2,6-diisopropylphenyl) and CNArMes2 (Mes = 2,4,6-trimethylphenyl) has been prepared. The pr...

Reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea), H2Lpy, InCl3, MCl salts (M = Rb+, K+, Na+ or NH4+) and NEt3 in methanol give cationic {2}-metallacryptates of the composition [M⊂{In2(Lpy)3}]+ (M+ = Rb+, K+, Na+ or NH4+). They can be isolated as PF6− salts. The structural characterization of the products by means of spectroscopic methods and X-ray crystallography reveals host–guest assemblies, in which a monovalent guest cation M+ is encapsulated in the cryptand-like host compound {In2(Lpy)3}. The host–guest directional interactions are coordination or hydrogen bonds depending on the nature of the guest cation. A 15N NMR spectroscopic study on the inclusion compound with 15NH4+ cations reveals a dynamic structure of the corresponding {2}-metallacryptate in solution and partial exchange of the ammonium ions by coordinating solvents.

[Tc(OH

One-pot reactions of the catechol-scaffolding aroylbis(N,N-diethylthiourea) H2Lcat with mixtures of CoCl2 and MCl (M+ = Cs+, Rb+, K+, Tl+, or NH4+) or with a Co(NO3)2/TlNO3 mixture lead to the self...

One-pot reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea) (H2L) with Co(CH3COO)2·4H2O and LnCl3, where Ln = La, Ce, Nd, Sm, Gd, Dy, Er, and Yb, in warm methanol in the presence of Et3N, give st...

A scalable synthesis of the novel and highly reactive [Tc(OH

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH$_{4}$)$_{2}$ [TcO(OTf) $_{5}$]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO$_{3}$(OTf)], and intermediate Tc$^{VI}$ species. $^{99}$Tc nuclear magnetic resonance (NMR) has been used to study the Tc$^{VII}$ compound and electron paramagnetic resonance (EPR), $^{99}$Tc NMR and X-ray absorption near-edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH$_{4}$)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH$_{4}$)$_{4}$ [{TcO(TcO$_{4}$)$_{4}$}$_{4}$] ���10 H$_{2}$O. Single-crystal X-ray crystallography was used to determine the solid-state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species.

2-(2-Furyl)-3-hydroxychromone (HL) reacts with MII ions in the formation of quadratic [Cu(L)2] (3), octahedral [M(L)2(OH2)2] (M = Co (1), Ni (2), Zn (4), Mn (5)) and seesaw [M(L)2] (M = Sn (6), Pb (7)) complexes. Recrystallization of complexes 1-3 in presence of pyridine lead to [M(L)2(py)2] (1a-3a) adducts. All compounds were characterized by Fourier transform infrared spectroscopy (FTIR). Complexes 1-7 were analyzed by UV-Vis and diffuse reflectance spectroscopies. The estimated band gap energies range from 2.90-3.15 eV. The crystal structure of complexes 6 and 7 revealed the influence of the stereochemically active lone pair due to their electronic configuration ns2. An intense fluorescence emission band centered at approximately 600 nm (λexc centered at 340 nm) has been observed for complex 6 in the solid state. In N,N‑dimethylformamide (DMF) solution, complex 6 showed two emission bands (468 and 538 nm) when excited from 300 to 380 nm, and only one emission band (468 nm) when excited from 385 to 420 nm.

Reactions of [Tc(NO)Cl(Cp)(PPh3)] with a series of monodentate ligands X– (X– = I–, I3–, F3CSO3–, CF3COO–, or SCN–) result in a ready replacement of the chlorido ligand and the formation of complex...

Aim: Obtain radioimages of amyloid-β fibers using 99mTc-complexes. Methodology: Tridentate thiosemicarbazone and thiocarbonohydrazone ligands containing fragments (stilbene, azobenzene, benzothiazole or benzoxazole) with affinity for amyloid-ß fibers and its Re(I) complexes have been prepared. The molecular structures of several ligands and complexes were determined by x-ray diffraction. Binding affinity studies toward Aß1-42 fibers were performed for the ligands and Re(I) complexes. The ability of formation of some 99mTc(I) complexes, their biodistribution and in vivo stability have been established. Results & conclusion: Complexes of stilbene and benzothiazole thiosemicarbazonates show similar affinity for amyloid-β fibers to the free ligand. These 99mTc complexes present a reasonable in vivo stability and a low capability to cross the blood–brain barrier although not sufficient to brain amyloid imaging.

Chagas disease remains a serious public health concern with unsatisfactory treatment outcomes due to strain-specific drug resistance and various side effects. To identify new therapeutic drugs agai...

Reactions of (NBu4)[MOCl4] complexes (M = Tc or Re) with an excess of hexafluoroacetylacetone (Hhfac) give products with a composition of (NBu4)[MOCl3(hfac)] as bright yellow (Tc) or red (Re) solids. The products are stable as solids but rapidly decompose in solution. A number of related phenylimidorhenium(V) complexes were synthesized starting from [Re(NPhF)Cl3(PPh3)2], where (NPhF)2– is a para-fluorinated phenylimido ligand. Products with compositions of [Re(NPhF)Cl2(PPh3)(acac)], [Re(NPhF)Cl2(PPh3)(hfac)], [Re(NPhF)Cl2(PPh3)(tfac)], [Re(NPhF)Cl2(PPh3)(naphtfac)], and [Re(NPhF)Cl2(PPh3)(tbutfac)] (Hacac = acetylacetone, Htfac = trifluoroacetylacetone, Hnaphtfac = naphthoyltrifluoroacetylmethane, and Htbutfac = tert-butyroyltrifluoroacetylmethane) were isolated from reactions of the quite soluble [Re(NPhF)Cl3(PPh3)2] with the corresponding β-diketones and studied spectroscopically and by X-ray diffraction. The β-diketonates are coordinated in a meridional arrangement with the phenylimide. The formation o...

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu

Homoleptic eight-fold coordinated methylisocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate MeOTf gives [W(CNMe)8][OTf]4. The even stronger methylating mixture of methyl fluoride MeF and arsenic pentafluoride AsF5 in liquid sulfur dioxide SO2 is able to fully alkylate both [NBu4]4[W(CN)8] and [NBu4]3[W(CN)8]. The paramagnetic octakis(methylisocyanide)- tungsten(V) [W(CNMe)8][AsF6]5 is thermally highly unstable above −30 °C. All compounds have been characterized via single-crystal X-ray diffraction, IR and Raman, as well as NMR or EPR spectroscopy

Phenyltelluroxane clusters of the composition [{(PhTe)19O24}2I18(solv)] (1) are formed during the hydrolysis of [PhTeI3]2 or the oxidation of various phenyltellurium(II) compounds with iodine under hydrolytic conditions. The compounds consist of two half‐spheres with a {(PhTe)19O24}9+ network, which are connected by 18 iodine atoms. The spherical clusters can accommodate solvent molecules such as pyridine or methanol in the center of two rings formed by iodine atoms. The presence of other metal ions during the cluster formation results in a selective replacement of the central {PhTe}3+ units of each half‐sphere as has been demonstrated with the isolation of [{(PhTe)18({Ca(H2O)2}O24}2I16] (2) and [{(PhTe)18({Y(NO3)(H2O)}O24}2I16] (3). A crownether‐like coordination by six oxygen atoms of the telluroxane network is found for the {Ca(H2O}2}2+ and {Y(NO3)(H2O)}2+ building blocks. Mass spectrometric studies show that considerable amounts of the intact clusters are transferred to the gas phase without dissociation., Large telluroxane clusters are formed during the hydrolysis of [PhTeI3]2 or the oxidation of [PhTe]2 with iodine under hydrolytic conditions. They consist of two half‐spheres with {(PhTe)19O24}9+ networks, which are connected by 18 iodine atoms. The central {PhTe}3+ units of each half‐sphere can be replaced by other metal ions. Mass spectrometry shows that the intact clusters are transferred to the gas phase without dissociation.

Potentially tridentate, phosphine-containing Schiff bases with P,N,O and P,N,P donor sets have been prepared from 2-(diphenylphosphino)benzaldehyde, salicylaldehyde, 2-aminophenol and 2-((diphenylphosphino)phenyl)methylamine and reacted with (NEt4)(2)[Re(CO)(3)Br-3] in methanol. Deprotonation and the formation of neutral [Re(CO)(3)(L)] complexes with tridentate coordination of the Schiff bases has been obtained for the salicylidene derivatives, while the potential P,N,P ligand L-3 forms [Re(CO)(3)Br(L-3)] with the Schiff base in a bidentate bonding mode. The formation of a cationic [Re(CO)(3)(L-3)](+) complex with tripodal coordination of the organic ligand could be achieved by the addition of Ag(PF6) to the reaction mixture. The obtained rhenium(I) complexes were studied spectroscopically and by X-ray diffraction.