Trigonal-bipyramidal vs. octahedral coordination in indium(III) complexes with potentially S,N,S‐tridentate thiosemicarbazones

Three bis‐chelates of indium(III) with (partially fluorinated) S,N,S‐tridentate thiosemicarbazones (H2L) were prepared and their structures were studied in solution and in the solid state by NMR, ESI MS and single‐crystal X‐ray diffraction. The three compounds are isostructural in solution with five‐coordinate InIII ions and two differently coordinated thiosemicarbazonato ligands, [In(L)(HL)]. A temperature‐dependent 1H NMR study reflects the presence of dynamic processes in the molecules such as the resolution of hindered rotation around CN bonds with partial double‐bond character and the pH‐triggered isomerization between 5‐ and 6‐coordinate species. The latter is confirmed by the isolation of compounds with different solid‐state structures, [In(L)(HL)] and [In(L)2]–, depending on fluorine‐substitutions in the periphery of the thiosemicarbazones

Tricarbonylrhenium(I) and ‐technetium(I) Complexes with Tris(1,2,3‐triazolyl)phosphine Oxides

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

Na[Tc(CO)(CNp-F-ArDArF2)4]: an isocyanide analogue of the elusive Na[Tc(CO)5]

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

Rhenium(V) complexes with selenolato‐ and tellurolato‐substituted Schiff bases – Released PPh3 as a facile reductant

The salicylidene Schiff bases of bis(2‐aminophenyl)diselenide and ‐ditelluride react with [ReOCl3(PPh3)2] or the arylimidorhenium(V) compounds [Re(NPhR)Cl3(PPh3)2] (R = H, F, CF3) with formation of rhenium(V) complexes with tridentate {O,N,Se/Te} chalcogenolato ligands. The ligands adopt a facial coordination mode with the oxygen donors trans to the multiply bonded O2– or NPhR2– ligands. The reduction of the dichalcogenides and the formation of the chalcogenolato ligands occurs in situ by released PPh3 ligands. The absence of additional reducing agents provides good yields of products with rhenium in the high formal oxidation state “+5”. A mechanism for the dichalcogenide reduction is proposed on the basis of the experimental results. In accordance with the proposed mechanism, best yields are obtained with a strict exclusion of oxygen, but in the presence of water

[{TcI(NO)(LOMe)(PPh3)Cl}2Ag](PF6) and [TcII(NO)(LOMe)(PPh3)Cl](PF6): Two Unusual Technetium Complexes with a “Kläui-type” Ligand

The reaction of [TcI(NO)(LOMe)(PPh3)Cl] ({LOMe}−=η5-cyclopentadienyltris(dimethyl phosphito-P)cobaltate(III)) with Ag(PF6) gives two unexpected products: the dimeric technetium(I) complex [{Tc(NO)(LOMe)(PPh3)Cl}2Ag](PF6) with a central Ag+ ion and the cationic Tc(II) compound [Tc(NO)(LOMe)(PPh3)Cl](PF6). The products have been studied spectroscopically and by X-ray diffraction

Rhenium Complexes with p-Fluorophenylisocyanide

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

Functional polyoxometalates from solvothermal reactions of VOSO4 with tripodal alkoxides – a study on the reactivity of different “tris” derivatives

We report a study on the structure directing effects of functional groups and counterions. The aim was to find a facile and high yielding synthetic procedure to obtain polyoxometalate (POM) building blocks for post- functionalisation. Therefore, solvothermal reactions of VOSO4 with various tris(hydroxymethyl)methane derivatives in alkaline methanolic solutions were investigated. In doing so, new POM fragments were isolated and characterised. The binding modes of the functionalised tripodal alkoxides turned out to be surprisingly different

Structural Diversity of Alkaline Earth Centered Gold(I) Metallacoronates

One‐pot reactions of the catechol‐scaffolding aroylbis(N,N‐diethylthiourea) H2Lcat with mixtures of alkaline earth nitrates M(NO3)2 (M2+ = Ca2+, Sr2+ or Ba2+) and (NEt4)[AuCl4] or [Au(tht)Cl] (tht = tetrahydrothiophene) in methanol in the presence of Et3N as supporting base give rise to neutral trinuclear gold(I) {2}‐metallacoronates with the composition of {M ⊂ [Au2(Lcat)2]} (1). Similar reactions with the pyridine‐centered aroylbis(N,N‐diethylthiourea) H2Lpy, however, produce complexes with the same metal‐to‐ligand ratio but with higher nuclearity {2M ⊂ [Au4(Lpy)4]} (2). In both 1 and 2, Au(I) ions are exclusively S‐bonded with the organic ligands and adopt a virtually linear coordination fashion. Such metal‐ligand binding is responsible for the formation of metallacoronands, which accommodate alkaline earth metal ions in their molecular voids, thereby resulting in host–guest coordination assemblies. The level of metal‐ligand aggregation in the resulting assemblies is dependent on the denticity, size and flexibility of the centered building block of the aroylbis(N,N‐diethylthiourea) ligands

The Chemistry of Phenylimidotechnetium(V) Complexes with Isocyanides: Steric and Electronic Factors

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

An Unexpected Rhenium(IV)–Rhenium(VII) Salt: [Co(NH3)6]3[ReVIIO4][ReIVF6]46H2O

The title hydrated salt, tris[hexaamminecobalt(III)] tetraoxidorhenate(VII) tetrakis[hexafluoridorhenate(IV)] hexahydrate, arose unexpectedly due to possible contamination of the K2ReF6 starting material with KReO4. It consists of octahedral [Co(NH3)6] 3+ cation (Co1 site symmetry 1), tetrahedral [ReVIIO4] anions (Re site symmetry 1) and octahedral [ReIVF6] 2 anions (Re site symmetries 1and 3). The [ReF6] 2 octahedral anions (mean Re—F = 1.834 A˚ ), [Co(NH3)6] 3+ octahedral cations (mean Co—N = 1.962 A˚ ), and the [ReO4] tetrahedral anion (mean Re—O = 1.719 A˚ ) are slightly distorted. A network of N—HF hydrogen bonds consolidates the structure. The crystal studied was refined as a two-component twin