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The homogeneously catalyzed Guerbet upgrading of ethanol to butanol can be modulated by the application of partial H2 pressure before the reaction. Ruthenium(II) PNP pincer complexes with methylene‐extended acridine‐based ligands and singly‐chelated ruthenium(II) complexes with PN ligands perform best at very low catalyst loadings and upon the application of catalyst‐specific pre‐reaction partial H2 pressure. The combination of ruthenium(II) PNP pincer complexes and manganese(I) pincer complexes with MACHO‐type PNP ligands allows for even lower ruthenium loadings while retaining low base load and consumption, thus enabling high space‐time yields, catalyst productivity and recyclability. Mechanistically, Mn is proposed to stabilize coordinatively unsaturated Ru species and allow coordination of ethoxide to Ru instead of attacking the electrophilic ligand backbone based on NMR spectroscopy and X‐ray crystallography. [ABSTRACT FROM AUTHOR]

Reactions of the technetium(I) nitrosyl complex [Tc(NO)(Cp)(PPh3)Cl] with triphenylphosphine chalcogenides EPPh3 (E = O, S, Se), and Ag(PF6) in a CH2Cl2/MeOH mixture (v/v, 2/1) result in an exchange of the chlorido ligand and the formation of [Tc(NO)(Cp)(PPh3)(EPPh3)](PF6) compounds. The cationic acetonitrile complex [Tc(NO)(Cp)(PPh3)(NCCH3)]+ is formed when the reaction is conducted in NCCH3 without additional ligands. During the isolation of the corresponding PF6− salt a gradual decomposition of the anion was detected in the solvent mixture applied. The yields and the purity of the product increase when the BF4− salt is used instead. The acetonitrile ligand is bound remarkably strongly to technetium and exchange reactions readily proceed only with strong donors, such as pyridine or ligands with 'soft' donor atoms, such as the thioether thioxane. Substitutions on the cyclopentadienyl ring do not significantly influence the ligand exchange behavior of the starting material. 99Tc NMR spectroscopy is a valuable tool for the evaluation of reactions of the complexes of the present study. The extremely large chemical shift range of this method allows the ready detection of corresponding ligand exchange reactions. The observed 99Tc chemical shifts depend on the donor properties of the ligands. DFT calculations support the discussions about the experimental results and provide explanations for some of the unusual findings. [ABSTRACT FROM AUTHOR]

A first example of an aryltellurium(II) compound with three different bonding modes to iodine featuring covalent and non‐covalent bonds such as two orthogonal, ambiphilic σ‐hole interactions is introduced: [MesTe(I)(I2)(I3)]−. It is a member of a series of mesityltellurenyl anions, which are formed during reactions of (MesTe)2 with ZnI2, phenanthroline (phen) and iodine. [Zn(phen)3][MesTe(I)2] (1), [Zn(phen)3][{MesTe(I)‐(I)...Te(I)Mes}{MesTeI2}] (2) and [Zn(phen)3][MesTe(I)(I2)(I3)][MesTeI2] (3) are isolated depending on the amount of iodine used. The products contain tellurium atoms bonded to a variety of iodine species (I−, μ2‐I−, I2 and I3−) and are, thus, perfectly suitable to explore the amphiphilic behavior of tellurium(II) and its relevance for the formation of non‐covalent bonds, where tellurium acts as both donor and acceptor simultaneously. The character of chalcogen and halogen bonds are evaluated by the combination of crystallographic data and computational methods. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The chemistry of the rhenium trihydrido complex [ReH3(PPh3)4] (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 [TcH3(PPh3)4] having a capped‐octahedral coordination sphere. The PPh3 ligands surround the Re atom in a trigonal‐pyramidal mode with a short apical Re−P bond (2.300(2) Å) and three longer basal bonds (2.429(2)–2.449(2) Å). Reactions of 1 with monodentate phosphines such as PMe3 or PBu3 give the mono‐substituted complexes [ReH3(PPh3)3(PMe3)] (2) and [ReH3(PPh3)3(PBu3)] (3) under retention of the apical PPh3 ligand and substitution of one of the basal PPh3 ligands. The stability of the phosphine trihydride complexes decreases in the order PPh3>PMe3>PBu3. Treatment of [ReH3(PPh3)4] with trityl hexafluorophosphate in CH3CN does not result in a hydride abstraction, but gives the tetrahydrido cation [ReH4(NCCH3)(PPh3)3]+ (4), while reactions with nitriles give unstable azavinylidene complexes of the composition [ReH2(PPh3)3(NC(H)R)] (5). They are formed by an insertion of the nitrile into a Re−H bond. The solid‐state structure of the methyl derivative [ReH2(PPh3)3(NC(H)CH3)] (5 a) was determined showing a linear Re−N−C unit with rhenium−nitrogen and nitrogen−carbon double bonds, while the N=CH−C bond is clearly bent with an angle of 124°. Two previously unknown polymorphs of [ReH5(PPh3)3] were isolated from reactions of 1 with HOC6H3(CH3)2 and thiourea after prolonged heating in toluene and characterized by IR spectroscopy and X‐ray diffraction. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)2[TcO(OTf)5]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO3(OTf)], and intermediate TcVI species. 99Tc nuclear magnetic resonance (NMR) has been used to study the TcVII compound and electron paramagnetic resonance (EPR), 99Tc NMR and X‐ray absorption near‐edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)4[{TcO(TcO4)4}4] ⋅10 H2O. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The number of crystal structures of pertechnetates derived from aqueous solutions has been expanded from seven to over 30. We report the conversion of NH 4 TcO 4 to aqueous HtcO 4 via acidic cation exchange. This is followed by the synthesis and structural elucidation of pertechnetate salts of alkaline earth (AE), transition metal I and lanthanoids (Ln) elements. Various degrees of hydration and coordination are discussed. Where possible, a comparison with the perrhenate homologues is made. The described syntheses and materials may be used as novel starting materials for extended technetium research., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reactions of the technetium(I) nitrosyl complex [Tc(NO)(Cp)(PPh 3 )Cl] with triphenylphosphine chalcogenides EPPh 3 (E = O, S, Se), and Ag(PF 6 ) in a CH 2 Cl 2 /MeOH mixture ( v / v , 2/1) result in an exchange of the chlorido ligand and the formation of [Tc(NO)(Cp)(PPh 3 )(EPPh 3 )](PF 6 ) compounds. The cationic acetonitrile complex [Tc(NO)(Cp)(PPh 3 )(NCCH 3 )] + is formed when the reaction is conducted in NCCH 3 without additional ligands. During the isolation of the corresponding PF 6 - salt a gradual decomposition of the anion was detected in the solvent mixture applied. The yields and the purity of the product increase when the BF 4 - salt is used instead. The acetonitrile ligand is bound remarkably strongly to technetium and exchange reactions readily proceed only with strong donors, such as pyridine or ligands with 'soft' donor atoms, such as the thioether thioxane. Substitutions on the cyclopentadienyl ring do not significantly influence the ligand exchange behavior of the starting materia l . 99 Tc NMR spectroscopy is a valuable tool for the evaluation of reactions of the complexes of the present study. The extremely large chemical shift range of this method allows the ready detection of corresponding ligand exchange reactions. The observed 99 Tc chemical shifts depend on the donor properties of the ligands. DFT calculations support the discussions about the experimental results and provide explanations for some of the unusual findings.

The chemistry of the rhenium trihydrido complex [ReH 3 (PPh 3 ) 4 ] (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 3 (PPh 3 ) 4 ] having a capped-octahedral coordination sphere. The PPh 3 ligands surround the Re atom in a trigonal-pyramidal mode with a short apical Re-P bond (2.300(2) Å) and three longer basal bonds (2.429(2)-2.449(2) Å). Reactions of 1 with monodentate phosphines such as PMe 3 or PBu 3 give the mono-substituted complexes [ReH 3 (PPh 3 ) 3 (PMe 3 )] (2) and [ReH 3 (PPh 3 ) 3 (PBu 3 )] (3) under retention of the apical PPh 3 ligand and substitution of one of the basal PPh 3 ligands. The stability of the phosphine trihydride complexes decreases in the order PPh 3 >PMe 3 >PBu 3 . Treatment of [ReH 3 (PPh 3 ) 4 ] with trityl hexafluorophosphate in CH 3 CN does not result in a hydride abstraction, but gives the tetrahydrido cation [ReH 4 (NCCH 3 )(PPh 3 ) 3 ] + (4), while reactions with nitriles give unstable azavinylidene complexes of the composition [ReH 2 (PPh 3 ) 3 (NC(H)R)] (5). They are formed by an insertion of the nitrile into a Re-H bond. The solid-state structure of the methyl derivative [ReH 2 (PPh 3 ) 3 (NC(H)CH 3 )] (5 a) was determined showing a linear Re-N-C unit with rhenium-nitrogen and nitrogen-carbon double bonds, while the N=CH-C bond is clearly bent with an angle of 124°. Two previously unknown polymorphs of [ReH 5 (PPh 3 ) 3 ] were isolated from reactions of 1 with HOC 6 H 3 (CH 3 ) 2 and thiourea after prolonged heating in toluene and characterized by IR spectroscopy and X-ray diffraction., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A scalable synthesis of the novel and highly reactive [Tc(OH 2 )(CO) 3 (PPh 3 ) 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(OH 2 )(CO) 3 (PPh 3 ) 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 (PPh 3 ) 2 ] + and [Tc(L) 2 (CO) 2 (PPh 3 ) 2 ] + represent an interesting opportunity for the development of 99m Tc complexes with potential use in radiopharmacy. The ready displacement of the aqua ligand highlights the synthetic value of [Tc(OH 2 )(CO) 3 (PPh 3 ) 2 ] + as a reactive entry point for further studies in the little explored field of the organometallic chemistry of technetium.

A series of 16 "3 + 2" mixed-ligand complexes of the general composition [ReO(L1)(L2)] (H 2 L1a-H 2 L1d = tridentate thiosemicarbazones having a phenyl group with 4-H, 4-F, 3,5-di-F, and 4-CF 3 substituents; HL2a-HL2d = bidentate N , N -diethyl- N '-benzoylthioureas with 4-H, 4-F, 3,5-di-F, and 4-CF 3 substituents at the benzoyl groups) have been synthesized and characterized by spectroscopic methods and X-ray diffraction. Irrespective of the individual fluorine substitution, the complexes are stable and possess the same general structure. Some systematic electronic effects of the fluorine-substitution patterns of the ligands have been found on the 13 C NMR chemical shifts of the N-C═N carbon atoms of the {L1} 2- and the C═O carbon atoms of the {L2} - ligands. Antiparasitic properties of the rhenium complexes have been tested against epimastigotes and trypomastigotes forms of two Trypanosoma cruzi strains and the amastigotes form of one of them. The results of this study indicate that the activity of the rhenium complexes can clearly be modulated by fluorine substitution of their ligands. Some of the fluorinated compounds show a high activity against epimastigotes and trypomastigotes forms of the parasites. Reactions between (NBu 4 )[TcOCl 4 ] and two representatives of the fluorinated ligands (H 2 L1b, 4-F-substituted, and H 2 L1c, 4-CF 3 -substituted) form stable complexes of the composition [TcOCl(L1b)] and [TcOCl(L1c)]. Subsequent reactions of these products with HL2b (4-F-substituted) give the corresponding [TcO(L1)(L2)] mixed-ligand complexes. Also, the technetium compounds are stable as solids and in solutions and have structures corresponding to those of their rhenium analogues.