Roger Alberto - Curiosity, Passion, Excellence.

Prof. Dr. Roger Alberto - A Special Collection of articles honouring an outstanding scientist, collaborator, and friend.

Bimetallic Uranium Complexes with 2,6-Dipicolinoylbis(,-Dialkylthioureas).

2,6-Dipicolinoylbis(-dialkylthioureas), HL, readily react with uranyl salts under formation of monomeric or dimeric complexes of the compositions [UO(L)(solv)] (solv = donor solvents such as HO, MeOH or DMF) or [{UO(L)(µ-OMe)}] (). In such complexes, the uranyl ions are exclusively coordinated by the "hard" ,, or donor atom sets of the central ligand unit and the lateral sulfur donor atoms do not participate in the coordination. Different conformations have been found for the dimeric anions.

Nitrosyl and Thionitrosyl Complexes of Technetium and Rhenium and Their Reactions with Hydrotris(pyrazolyl)borates.

The very limited number of structurally known thionitrosyl complexes of technetium was increased by the synthesis of [Tc(NS)Cl(PPh)] () and [Tc(NS)Cl(PPh)(OPPh)] () and their reaction products with hydrotris(pyrazolyl)borates, {HB(pz)}. Similar reactions were conducted with [Tc(NO)Cl(PPh)(CHCN)] and related rhenium thionitrosyls. Remarkably, most such reactions result in a rapid cleavage of the boron-nitrogen bonds of the ligands and the formation of pyrazole complexes of the two group 7 metals.

Phenylseleninate-Connected Telluroxane Clusters.

Hydrolysis of PhTeI in the presence of sodium phenylseleninate and M ions (M = Y, Nd, Ce) gives well-defined, bowl-shaped telluroxane clusters. Each of the two half-spheres of the compositions [(PhTe){ML}O] ({ML} = {Y(NO)(HO)} (), {Nd(NO)(HO)} (), or {Ce(NO)} ()) are connected by two (compound ) or four (compounds and ) PhSeO bridges. The resulting chalcogenoxane spheres have internal volumes of approximately 1500 Å.

Gold(I) and Silver(I) Complexes Containing Hybrid Sulfonamide/Thiourea Ligands as Potential Leishmanicidal Agents.

Leishmaniasis is a group of parasitic diseases with the potential to infect more than 1 billion people; however, its treatment is still old and inadequate. In order to contribute to changing this view, this work consisted of the development of complexes derived from M metal ions with thioureas, aiming to obtain potential leishmanicidal agents. The thiourea ligands (HL) were obtained by reactions of -toluenesulfohydrazide with R-isothiocyanates and were used in complexation reactions with Ag and Au, leading to the formation of complexes of composition [M(HL)]X (M = Ag or Au; X = NO or Cl).

[Tc(NO)(Cp)(PPh)Cl] and [Tc(NO)(Cp)(PPh)(NCCH)](PF), and Their Reactions with Pyridine and Chalcogen Donors.

Reactions of the technetium(I) nitrosyl complex [Tc(NO)(Cp)(PPh)Cl] with triphenylphosphine chalcogenides EPPh (E = O, S, Se), and Ag(PF) in a CHCl/MeOH mixture (/, 2/1) result in an exchange of the chlorido ligand and the formation of [Tc(NO)(Cp)(PPh)(EPPh)](PF) compounds. The cationic acetonitrile complex [Tc(NO)(Cp)(PPh)(NCCH)] is formed when the reaction is conducted in NCCH without additional ligands. During the isolation of the corresponding PF salt a gradual decomposition of the anion was detected in the solvent mixture applied.

Metallacages with 2,6-dipicolinoylbis(N,N-dialkylthioureas) as novel platforms in nuclear medicine for Ga, Lu and Au.

Background: Heterometallic gold metallacages are of great interest for the incorporation of several cations. Especially in nuclear medicine, those metallacages can serve as a platform for radionuclides relevant for imaging or therapy (e.g.

Gold-Based Coronands as Hosts for M Metal Ions: Ring Size Matters.

The controlled, self-assembled synthesis of multinuclear coordination compounds can be performed via different approaches. Frequently, steric, geometric and/or electronic factors located at the ligand systems predefine the way in which metal ions can assemble them to large aggregates. For the compounds in the present paper, also the Pearson's acidities and preferred coordination geometries of the metal ions were used as organization principles.

Technetium Complexes with an Isocyano-alkyne Ligand and Its Reaction Products.

The attachment of an ethyne substituent in the para position of phenylisocyanide, CNPh, enables the isocyanide to replace carbonyl ligands in the coordination sphere of common technetium(I) starting materials such as (NBu)[Tc(μ-Cl)(CO)]. The ligand exchange proceeds under thermal conditions and finally forms the corresponding hexakis(isocyanide)technetium(I) complex. The product undergoes a copper-catalyzed cycloaddition ("Click" reaction), e.

Phenylimido complexes of rhenium: fluorine substituents provide protection, reactivity, and solubility.

Reactions of [Re(NPhF)Cl(PPh)] ({NPhF} = -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 -[Re(NPhF)Cl(PPh)(isocyanide)] and - or -[Re(NPhF)Cl(isocyanide)].

Na[Tc(CO)(CN-F-Ar)]: an isocyanide analogue of the elusive Na[Tc(CO)].

The first crystalline technetium complex in a negative oxidation state, [Tc(CO)(CN-F-Ar)], was isolated and structurally characterized as its [Na(Crypt-2.2.2)] salt.

A Complete Triad of Zero-Valent 17-Electron Monoradicals of Group 7 Elements Stabilized by m-Terphenyl Isocyanides.

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 [M (CO)(CNp-F-Ar ) ] (M=Mn, Tc, Re; Ar =2,6-(3,5-(CF ) C H ) C H F) 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.

[ReH (PPh ) ] - A Key Compound in the Rhenium Hydride Chemistry.

The chemistry of the rhenium trihydrido complex [ReH (PPh ) ] (1) has been reinvestigated. An improved synthesis and the solid-state structure of the compound as well as several reactions are reported. The solid-state structure of 1 is similar to that of [TcH (PPh ) ] having a capped-octahedral coordination sphere.

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

Organometallic approaches are of ongoing interest for the development of novel functional Tc radiopharmaceuticals, while the basic organotechnetium chemistry seems frequently to be little explored. Thus, structural and reactivity studies with the long-lived isotope Tc 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.

Mixed-Isocyanide Complexes of Technetium under Steric and Electronic Control.

Reactions of the alkyl isocyanide -[Tc(CO)(CNR)Cl] complexes () (CNR = CNBu or CNBu) with the sterically encumbered isocyanide CN-FAr [DArF = 3,5-(CF)CH] allow a selective exchange of the carbonyl ligands of and the isolation of the mixed-isocyanide complexes ,-[Tc(CN-FAr)(CNR)Cl] (). Depending on the steric requirements of the residues , the remaining chlorido ligand can be replaced by another isocyanide ligand. Cationic complexes such as -[Tc(CN-FAr)(CNBu)] () or ,-[Tc(CN-FAr)(CNBu)(CNBu)] () have been prepared in this way and isolated as their PF salts.

Shedding Light on the Enigmatic TcO ⋅ xH O Structure with Density Functional Theory and EXAFS Spectroscopy.

The β-emitting Tc isotope is a high-yield fission product in U and Pu nuclear reactors, raising special concern in nuclear waste management due to its long half-life and the high mobility of pertechnetate (TcO ). Under the conditions of deep nuclear waste repositories, Tc is retained through biotic and abiotic reduction of TcO to compounds like amorphous TcO  ⋅ xH O precipitates. It is generally accepted that these precipitates have linear (Tc(μ-O) (H O) ) chains, with trans H O.

Unlocking Air- and Water-Stable Technetium Acetylides and Other Organometallic Complexes.

The first technetium complexes containing anionic alkynido ligands in an end-on coordination mode have been prepared by using the nonprotic, cationic precursor ,-[Tc(SMe)(CO)(PPh)]. This cation acts as a functional analogue of the highly reactive 16-electron metallo Lewis acid {Tc(CO)(PPh)} in reactions with alkynes, acetylides, and other organometallic reagents. Such reactions give a variety of organometallic technetium complexes in excellent yields and enable the preparation of [Tc(CH)(CO)(PPh)], [Tc(Ph)(CO)(PPh)], [Tc(Cp)(CO)(PPh)], [Tc(═CCHCHCHO)(CO)(PPh)], [Tc(═CCHCHCHCHO)(CO)(PPh)], [Tc(C≡C-H)(CO)(PPh)], [Tc(C≡C-Ph)(CO)(PPh)], [Tc(C≡C-Bu)(CO)(PPh)], [Tc(C≡C-Bu)(CO)(PPh)], [Tc(C≡C-SiMe)(CO)(PPh)], and [Tc{C≡C-CH(CF)}(CO)(PPh)].

Calix[4]arene-Analogous Technetium Supramolecules.

Calix[4]arene-analogous technetium supramolecules ( and ) were assembled using (NBu)[Tc(μ-Cl)(CO)] and neutral flexible bidentate nitrogen-donor ligands (L and L) consisting of four arene units covalently joined via methylene units. The neutral homoleptic technetium macrocycles adopt a partial cone/cone-shaped conformation in the solid state. These supramolecules are the first example of -[Tc(CO)] core-based metallocalix[4]arenes and second example of -[Tc(CO)] core-based metallomacrocycles.

Solvents and Ligands Matter: Structurally Variable Palladium and Nickel Clusters Assembled by Tridentate Selenium- and Tellurium-Containing Schiff Bases.

Structurally variable organochalcogen clusters containing palladium(II) and nickel(II) ions were assembled starting from the salicylidene-substituted dichalcogenides (Y-CH-N═CH-CH-OH) ({HL}, where Y = Se or Te), and palladium or nickel acetate. The tetrameric palladium clusters contain reduced chalcogenolato ligands {Y-CH-N═CH-CH-O)} ({L'}, where Y = Se or Te), while the initially formed trimeric nickel clusters contain the intact, coordinated dichalcogenides. The palladium clusters have a general formula of [Pd(L')] and represent the first examples of palladium complexes where both a gyrobifastigial and a pseudocubane arrangement of the central PdY unit could be established with the same ligand, only depending on the solvents used for crystallization.

Technetium(I) Carbonyl Chemistry with Small Inorganic Ligands.

[Tc(OH)(CO)(PPh)](BF) has been used as a synthon for reactions with small inorganic ligands with relevance for the treatment of nuclear waste solutions such as nitrate, nitrite, pseudohalides, permetalates (M = Mn, Tc, Re), and BH. The formation of bond isomers and/or a distinct reactivity has been observed for most of the products. [Tc(NCO)(CO)(PPh)], [Tc(NCS)(CO)(PPh)], [Tc(CN)(CO)(PPh)], [Tc(N)(CO)(PPh)], [Tc(NCO)(OH)(CO)(PPh)], [Tc(η-OON)(CO)(PPh)], [Tc(η-NO)(CO)(PPh)], [Tc(η-OONO)(CO)(PPh)], [Tc(η-ONO)(CO)(PPh)], [Tc(η-OO(CCH))(CO)(PPh)], [Tc(η-SSC(SCH))(CO)(PPh)], [Tc(η-SSC(OCH))(CO)(PPh)], [Tc(η-SSC(CH))(CO)(PPh)], [Tc(η-SS(CH))(CO)(PPh)], [Tc(OTcO)(acetone)(CO)(PPh)], [Tc(OTcO)(CO)(PPh)], and [Tc(η-HHBH)(CO)(PPh)] have been isolated in crystalline form and studied by X-ray crystallography.

Ammonium Pertechnetate in Mixtures of Trifluoromethanesulfonic Acid and Trifluoromethanesulfonic Anhydride.

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH ) [TcO(OTf) ]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO (OTf)], and intermediate Tc species. Tc nuclear magnetic resonance (NMR) has been used to study the Tc compound and electron paramagnetic resonance (EPR), Tc NMR and X-ray absorption near-edge structure (XANES) experiments indicate the presence of the reduced technetium species.

[Tc(OH)(CO)(PPh)]: A Synthon for Tc(I) Complexes and Its Reactions with Neutral Ligands.

A scalable synthesis of the novel and highly reactive [Tc(OH)(CO)(PPh)] 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 tricarbonyl core under exclusive exchange of the aqua ligand or form dicarbonyl complexes by thermal decarbonylation.

Large Telluroxane Bowls Connected by a Layer of Iodine Ions.

Phenyltelluroxane clusters of the composition [{(PhTe) O } I (solv)] (1) are formed during the hydrolysis of [PhTeI ] or the oxidation of various phenyltellurium(II) compounds with iodine under hydrolytic conditions. The compounds consist of two half-spheres with a {(PhTe) O } 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.

Eightfold Electrophilic Methylation of Octacyanotungstate [W(CN)]: Preparation of Homoleptic, Eight-Coordinate Methyl Isocyanide Complexes [W(CNMe)].

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu][W(CN)] with methyl triflate (MeOTf) gives [W(CNMe)][OTf]. The even stronger methylating mixture of methyl fluoride (MeF) and arsenic pentafluoride (AsF) in liquid sulfur dioxide (SO) is able to fully alkylate both [NBu][W(CN)] and [NBu][W(CN)].

Signatures of technetium oxidation states: a new approach.

A general strategy for the determination of Tc oxidation state by new approach involving X-ray absorption near edge spectroscopy (XANES) at the Tc L3 edge is shown. A comprehensive series of 99Tc compounds, ranging from oxidation states I to VII, was measured and subsequently simulated within the framework of crystal-field multiplet theory. The observable trends in the absorption edge energy shift in combination with the spectral shape allow for a deeper understanding of complicated Tc coordination chemistry.