40 research outputs found
Trigonal-bipyramidal vs. octahedral coordination in indium(III) complexes with potentially S,N,Sâtridentate thiosemicarbazones
Three bisâchelates of indium(III) with (partially fluorinated) S,N,Sâtridentate thiosemicarbazones (H2L) were prepared and their structures were studied in solution and in the solid state by NMR, ESI MS and singleâcrystal Xâray diffraction. The three compounds are isostructural in solution with fiveâcoordinate InIII ions and two differently coordinated thiosemicarbazonato ligands, [In(L)(HL)]. A temperatureâdependent 1H NMR study reflects the presence of dynamic processes in the molecules such as the resolution of hindered rotation around CN bonds with partial doubleâbond character and the pHâtriggered isomerization between 5â and 6âcoordinate species. The latter is confirmed by the isolation of compounds with different solidâstate structures, [In(L)(HL)] and [In(L)2]â, depending on fluorineâsubstitutions in the periphery of the thiosemicarbazones
Tricarbonylrhenium(I) Complexes with Tridentate Schiff Bases
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
Tricarbonylrhenium(I) and âtechnetium(I) Complexes with Tris(1,2,3âtriazolyl)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, [TcâI(CO)(CNp-F-ArDArF2)4]â, 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)][TcâI(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 selenolatoâ and tellurolatoâsubstituted Schiff bases â Released PPh3 as a facile reductant
The salicylidene Schiff bases of bis(2âaminophenyl)diselenide and âditelluride 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 O2â or NPhR2â 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 â+5â. 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 âKlĂ€ui-typeâ Ligand
The reaction of [TcI(NO)(LOMe)(PPh3)Cl] ({LOMe}â=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.âg. 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 â a study on the reactivity of different âtrisâ 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
Oneâpot reactions of the catecholâscaffolding aroylbis(N,Nâdiethylthiourea) 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}âmetallacoronates with the composition of {M â [Au2(Lcat)2]} (1). Similar reactions with the pyridineâcentered aroylbis(N,Nâdiethylthiourea) H2Lpy, however, produce complexes with the same metalâtoâligand ratio but with higher nuclearity {2M â [Au4(Lpy)4]} (2). In both 1 and 2, Au(I) ions are exclusively Sâbonded with the organic ligands and adopt a virtually linear coordination fashion. Such metalâligand binding is responsible for the formation of metallacoronands, which accommodate alkaline earth metal ions in their molecular voids, thereby resulting in hostâguest coordination assemblies. The level of metalâligand aggregation in the resulting assemblies is dependent on the denticity, size and flexibility of the centered building block of the aroylbis(N,Nâdiethylthiourea) 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