The reaction of isophthaloylbis(N,N-diethylthiourea), H2L1, with FeCl3·6H2O gives the dinuclear tris-complex [Fe2(L1)3] (5), possessing a cryptand-like structure. A similar reaction with the ligand 2,6-dipicolinoylbis(N,N-diethylthiourea), H2L2, however, results in the formation of the anionic, mononuclear Fe(III) complex [Fe(L2)2]− (6), which could be isolated as its “Tl+ salt” by the subsequent addition of Tl(NO3). A tighter view to the solid state structure of the obtained product, however, characterizes compound 6 as a one-dimensional coordination polymer, in which four-coordinate Tl+ ions connect the {[Fe(L2)2]−} units to infinite chains. When Fe3+ ions and Tl+ ions are added to H2L2 simultaneously in a one-pot reaction, a different product is obtained: a cationic trinuclear complex of the composition {M⊂[Fe2(L2)3]}+. It has been isolated as a PF6– salt and represents a {2}-metallacryptate with a nine-coordinate Tl+ ion in the central void. Structurally related products of the compositions {M⊂[Fe2(L2)3]}(PF6) (M = Na+, K+, Rb+) (8(PF6)) could be isolated from analogous reactions with alkaline salts instead of Tl(NO3). {2}-Metallacryptates with larger central voids were synthesized with the ether-spaced aroylbis(N,N-diethylthiourea) H2L3. The compounds {M⊂[Fe2(L3)3]}(PF6) (M = K+, Rb+, Tl+ or Cs+) (9(PF6)) were prepared by a similar protocol like those with H2L2 with the simultaneous addition of the metal ions to a solution of H2L3. Due to the larger spacer between the aroylthiourea units, the coordination number of the central M+ ions is 12 by six carbonyl and six ether oxygen atoms. All products were characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis. Cyclic voltammetric studies were carried out with the three representative complexes [Fe2(L1)3], {K⊂[Fe2(L2)3]}(PF6), and {K⊂[Fe2(L3)3]}(PF6). The obtained voltammograms indicate the dependence of the redox properties of the oligonuclear systems on the conjugation in the organic backbones of the ligands.

Fluoridotetrakis(trifluoroacetato)nitrosyltechnetate(II) was prepared by the dissolution of Cs2[Tc(NO)F5] in trifluoroacetic acid and addition of (NBu4)F·3H2O. The compound crystallizes as a mixed Cs+/NBu4+ salt in the form of green crystals. Unlike the [Tc(NO)F5]2− salts, the product is soluble in organic solvents and can be used as a precursor for ongoing ligand exchange procedures with organic ligands. The corresponding reactions with triphenylphosphine (PPh3), 1,2-bis(diphenylphosphino)ethane (DPPE) or pyridyldiphenylphosphine (pyPPh2) give technetium(I) complexes of the compositions Cs[Tc(NO)(PPh3)2(CF3COO)2F], [Tc(NO)(DPPE)2(OOCCF3)](PF6) and [Tc(NO)(κN,P-pyPPh2)(κP-pyPPh2)(CF3COO)2]. The products were studied spectroscopically and by X-ray diffraction. The 99Tc NMR resonances of the novel Tc(I) nitrosyls appear between −627 and +952 ppm, which is at a remarkably high field and in the range where normally the signals of Tc(III) compounds are observed.

Fluoridotetrakis(trifluoroacetato)nitrosyltechnetate(II) was prepared by the dissolution of Cs2[Tc(NO)F5] in trifluoroacetic acid and addition of (NBu4)F·3H2O. The compound crystallizes as a mixed Cs+/NBu4+ salt in the form of green crystals. Unlike the [Tc(NO)F5]2− salts, the product is soluble in organic solvents and can be used as a precursor for ongoing ligand exchange procedures with organic ligands. The corresponding reactions with triphenylphosphine (PPh3), 1,2-bis(diphenylphosphino)ethane (DPPE) or pyridyldiphenylphosphine (pyPPh2) give technetium(I) complexes of the compositions Cs[Tc(NO)(PPh3)2(CF3COO)2F], [Tc(NO)(DPPE)2(OOCCF3)](PF6) and [Tc(NO)(κN,P-pyPPh2)(κP-pyPPh2)(CF3COO)2]. The products were studied spectroscopically and by X-ray diffraction. The 99Tc NMR resonances of the novel Tc(I) nitrosyls appear between −627 and +952 ppm, which is at a remarkably high field and in the range where normally the signals of Tc(III) compounds are observed.

Potential tetradentate thiocarbamoylbenzamidine derivatives H4L have been synthesized from the corresponding benzimidoyl chlorides and triglycine. They are suitable chelating agents for the oxidotechnetium(V) and oxidorhenium(V) cores and form stable, neutral [MO(HL)] complexes with an equatorial SN3 coordination sphere and an additional, uncoordinated carboxylic group, which can be used for bioconjugation. Representatives of the rhenium and 99Tc products have been isolated and analyzed with spectroscopic methods and X-ray diffraction. Bioconjugates of these complexes with angiotensin-II have been synthesized and structurally characterized. Analogous 99mTc complexes have been produced and tested in vitro and in vivo. The experiments confirm a considerable stability for the [99mTc(HL)] product as well as for its bioconjugate and recommend this class of compounds for further bioconjugation studies towards clinical applications.

Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl, mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII complexes) coordinated technetium atoms. Density functional theory calculations indicate that the Tc–chalcogen bonds in the TcIII compounds have a greater bond order than those in the TcV compounds.

Stable organogold(III) compounds of the composition [AuIII(Hdamp)(L1)]Cl are formed from reactions of [AuCl2(damp)] with H2L1 (damp− = dimethylaminomethylphenyl; H2L1 = N′-(diethylcarbamothioyl)benzimidothiosemicarbazides). The cationic complexes can be neutralized by reactions with weak bases under the formation of [AuIII(damp)(L1)] compounds. The structures of the products show interesting features like relatively short Au⋯H contacts between the methylene protons of the Hdamp ligand and the gold(III) ions. Preliminary biological studies on the uncoordinated compounds H2L1 and their gold complexes indicate considerable cytotoxicity for the [AuIII(Hdamp)(L1)]Cl complexes against MCF-7 cells. The in vitro trypanocidal activity was evaluated against the intracellular form of Trypanosoma cruzi. The organometallic complexes display a remarkable activity, which is dependent on the alkyl substituents of the thiosemicarbazone building blocks of the ligands. One representative of the cationic [AuIII(Hdamp)(L1)]Cl complexes, where H2L1 contains a dimethylthiosemicarbazide building block, shows a trypanocidal activity against the intracellular amastigote form in the same order of magnitude as that of the standard drug benznidazole. Furthermore, no appreciable toxicity to mice spleen cells is observed for this compound resulting in a therapeutic index of about 30, which strongly recommends it as a promising candidate for the development of a future antiparasitic drug.

Reactions between [TcI(NO)X2(PPh3)2(CH3CN)] complexes (X = Cl, Br) and KCp form the pseudotetrahedral organotechnetium compounds [TcI(NO)(Cp)(PPh3)X]. The halide ligands can readily be replaced by other halides or organometallic ligands giving access to a novel family of technetium(I) compounds with the robust {Tc(NO)(Cp)(PPh3)}+ core.

Similar reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea) (H2La) with: (i) Ni(NO3)2·6H2O, (ii) a mixture of Ni(NO3)2·6H2O and AgNO3, (iii) a mixture of Ni(OAc)2·4H2O and PrCl3·7H2O and (iv) a mixture of Ni(OAc)2·4H2O and BaCl2·2H2O give the binuclear complex [Ni2(La)2(MeOH)(H2O)], the polymeric compound [NiAg2(La)2]∞, and the heterobimetallic complexes [Ni2Pr(La)2(OAc)3] and [Ni2Ba(La)3], respectively. The obtained assemblies can be used for the build up of supramolecular polymers by means of weak and medium intermolecular interactions. Two prototype examples of such compounds, which are derived from the trinuclear complexes of the types [MII2LnIII(L)2(OAc)3] and [MII2Ba(L)3], are described with the compounds {[CuII2DyIII(La)2(p-O2C-C6H4-CO2)(MeOH)4]Cl}∞ and [MnII2Ba(MeOH)(Lb)3]∞, H2Lb = 2,6-dipicolinoylbis(N,N-morpholinoylthiourea).

Cyclization reactions dominated attempts to synthesize N-alkyl- or N-dialkyl-N′-benzoylthiourea ligands having an alkyne group at the amine residue. While exclusively thiazolidine or thiazole derivatives could be isolated during reactions of benzoyl chloride, (NH4)SCN and N-methypropargylamine, an open-chain benzoylthiourea was obtained with unsubstituted propargylamin. But also the latter product isomerized under the influence of a strong base and heat to the corresponding cyclic derivatives.The resulting heterocycles, a 5-methylenthiazolidine (HL4) and a 5-methylthiazole (HL5), react with (NBu4)[ReOCl4]/PPh3 mixtures or [ReOCl3(PPh3)2] under formation of the neutral Re(III) complex [ReCl2(PPh3)2(L4)] and the cationic Re(V) compound [ReO2(PPh3)2(HL5)], respectively. The products have been isolated in crystalline form and studied spectroscopically and by X-ray diffraction.N-Propargyl-N′-benzoylthiourea undergoes a subsequent cyclization and isomerization upon treatment with KOH and heating. The formed thiazolidines and thiazoles form stable Re(III) or Re(V) complexes.

Thiocarbamoylbenzimidoyl chlorides, PhC(Cl)═N–(C═S)–NR1R2, react with 2-(iminodiacetic acid)benzylamine under formation of the potentially pentadentate ligands H3L (R1, R2 = Et) and H3L–COOEt (R1 = Me, R2 = C6H4-4-COOEt) in high yields. Hydrolysis of H3L–COOEt in NaOH/MeOH gives quantitatively another benzamidine ligand H3L–COOH. The novel ligands readily react with (NBu4)[MOCl4] (M = Re, Tc) under formation of stable complexes with the general composition [MO(L)], in which they are triply deprotonated and fully occupy the remaining five coordination positions of the {MO}3+ cores. In a “proof-of-principle” reaction for possible bioconjugations, the complex [ReO(L–COOH)] has been labeled with triglycine ethyl ester in high yields.

A novel aroylbisthiourea, H3pyr(Et2tu)2 (V), has been prepared from 2,5-pyrroledicarboxylic chloride, NH4SCN and diethylamine. The compound reacts with (NBu4)[ReOCl4] in MeOH under formation of the dimeric oxidorhenium(V) complex [{ReO(OMe)}2{Hpyr(Et2tu)2}2] (VI), which undergoes a condensation in wet acetonitrile and forms the μ-oxido-bridged tetramer [(Re2O3)2{Hpyr(Et2tu)2}4] (VII). The pyrrole rings remain protonated and do not contribute to the coordination of the transition metal. The tetrameric complex is able to accommodate a molecule of water in its molecular cavity.A novel aroylbisthiourea reacts with (NBu4)[ReOCl4] under formation of a dimeric oxidorhenium(V) complex or the cage-like tetramer [(Re2O3)2{Hpyr(Et2tu)2}4] depending on the conditions applied. The tetrameric complex hosts a molecule of water in the central cavity.

The potentially tetradentate benzamidine/thiosemicarbazone ligand, Et2N–(CS)–NH-C(Ph) = N–(o-C4H6)–C(Me) = N–NH–(CS)–NH–Me (H2L) readily reacts with Ni(CH3COO)2, [PdCl2(CH3CN)2], [PtCl2(PPh3)2] and (NBu4)[ReOCl4] under formation of complexes of the compositions [M(L)] (M = Ni (1), Pd (2), Pt (3)) and [ReO(L)(OMe)] (4). In all complexes, H2L is doubly deprotonated and bonded to the central metal ion via its N2S2 donor set. Complexes 1, 2 and 3 have distorted square-planar coordination spheres, while the rhenium compound 4 is an octahedral trans oxido/methoxido complex. The H2L proligand shows a medium cytotoxicity with an IC50 value of 21.1 μM. While the rhenium complex 4 exhibits a stronger antiproliferative effect (IC50 = 5.52 μM), the nickel, palladium and platinum complexes are almost inactive.The potentially tetradentate benzamidine/thiosemicarbazone ligand H2L forms stable transition metal complexes of the compositions [M(L)] (M = Ni, Pd, Pt) and [Re(OMe)(L)]·H2L. The oxidorhenium(V) complex show a considerably cytotoxicity, while the nickel, palladium and platinum complexes are almost inactive.

A mixture of [Tc(NO)F5]2– and [Tc(NO)(NH3)4F]+ is formed during the reaction of pertechnetate with acetohydroxamic acid (Haha) in aqueous HF. The blue pentafluoridonitrosyltechnetate(II) has been isolated in crystalline form as potassium and rubidium salts, while the orange-red ammine complex crystallizes as bifluoride or PF6– salts. Reactions of [Tc(NO)F5]2– salts with HCl give the corresponding [Tc(NO)Cl4/5]−/2– complexes, while reflux in neat pyridine (py) results in the formation of the technetium(I) cation [Tc(NO)(py)4F]+, which can be crystallized as hexafluoridophosphate. The same compound can be synthesized directly from pertechnetate, Haha, HF, and py or by a ligand-exchange procedure starting from [Tc(NO)(NH3)4F](HF2). The technetium(I) cation [Tc(NO)(NH3)4F]+ can be oxidized electrochemically or by the reaction with Ce(SO4)2 to give the corresponding Tc(II) compound [Tc(NO)(NH3)4F]2+. The fluorido ligand in [Tc(NO)(NH3)4F]+ can be replaced by CF3COO–, leaving the “[Tc(NO)(NH3)4]2+ core” untouched. The experimental results are confirmed by density functional theory calculations on [Tc(NO)F5]2–, [Tc(NO)(py)4F]+, [Tc(NO)(NH3)4F]+, and [Tc(NO)(NH3)4F]2+.

•Novel Tc nitrosyl complexes were prepared.•A hitherto less regarded aminophosphine ligand was used.•(2-Aminomethylphenyl)diphenylphosphine coordinates mono- or bidentate.•Tc(II) or Tc(I) complexes are formed depending on the conditions.•EPR spectra were measured for the Tc(II) compounds.Reactions of (NBu4)[Tc(NO)Cl4(MeOH)] (1) with (2-aminomethylphenyl)diphenylphosphine, H2L1, give different products depending on the conditions applied. An equimolare reaction in MeOH gives the technetium(II) monochelate [Tc(NO)Cl3(H2L1-κN,P)] (2) as the sole product, which could be isolated. Reduction of the metal ion and the formation of the Tc(I) complexes [Tc(NO)Cl2(H2L1-κN,P)(H2L1-κN)] (3) and [Tc(NO)Cl(H2L1-κN,P)2]Cl (4), besides some (NBu4)[Tc(NO)Cl4(H2L1-κN)] (5), is observed when an excess of the H2L1 is used in the same solvent. Reactions in acetonitrile are less defined and only the Tc(II) compound (NBu4)[Tc(NO)Cl4(H2L1O-κN)] (6) could be isolated from such reactions in crystalline form.The products were studied spectroscopically and by X-ray diffraction. The aminophosphine acts as monodentate nitrogen donor ligand or as N,P chelator.Graphical abstractThe reaction of (NBu4)[Tc(NO)Cl4(MeOH)] with one equivalent of (2-aminomethylphenyl)diphenyl phosphine, H2L1, forms in MeOH a novel technetium(II) complex. Technetium(I) complexes were formed by using an excess of H2L1. All compounds were studied spectroscopically and by X-ray diffraction.

•[ReOSe(2-pySe)3] has been prepared from [ReOCl3(PPh3)2].•The product is the pyridylselenolato complex of rhenium.•The product is the first rhenium complex with an equatorial Se4 coordination sphere.•An unusual Se(0) atom is bonded as ligand to rhenium.•The oxidation state of the Se atom in the Se(0) ligand is supported by DFT results.Bis(2-pyridyl) diselenide (2-py2Se2, 1) reacts with [ReOCl3(PPh3)2] under the formation of the unusual oxidorhenium(V) complex [ReOSe(2-pySe)3], which was isolated in crystalline form and studied by spectroscopic methods and X-ray diffraction. The oxidorhenium(V) core is bonded to three 2-pyridineselenolato ligands together with a selenium(0) atom. While the rhenium atom is coordinated in a common distorted octahedral coordination sphere, the selenium(0) atom shows a bent T-shaped coordination with SeN bonds of 2.13 (1) and 2.28 (1) Å and a SeRe bond of 2.387 (1) Å. The oxidation state of the Se(0) atom has been analyzed using calculated atomic charges and the electron localization function (ELF).Bis(2-pyridyl) diselenide reacts with [ReOCl3(PPh3)2] under the formation of the unusual oxidorhenium(V) complex [ReOSe(2-pySe)3] having a Se(0) atom as ligand. The product was studied by spectroscopic methods, X-ray diffraction and DFT methods.

Novel synthetic routes to hexafluoridotechnetate(IV) are reported, and for the first time the single-crystal X-ray structures of several M2[TcF6] salts (M = Na, K, Rb, Cs, NH4, and NMe4) were determined. The ammonium and the alkaline metal salts crystallize in the trigonal space group P3̅m, while the NMe4+ salt belongs to the space group R3̅. [TcF6]2– salts are widely stable in aqueous solution. In alkaline media, however, a slow hydrolysis is observed, and the first hydrolysis product, the dimeric, oxido-bridged complex [F5Tc–O–TcF5]4–, could be studied structurally.

Rhenium(V) complexes containing tridentate thiosemicarbazones/thiosemicarbazides (H2L1) derived from N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chlorides with 4,4-dialkylthiosemicarbazides have been synthesized by ligand-exchange reactions starting from [ReOCl(L1)]. The chlorido ligand of [ReOCl(L1)] (4) is readily replaced and reactions with ammonium thiocyanate or potassium cyanide give [ReO(NCS)(L1)] (6) and [ReO(CN)(L1)] (7), respectively. The reaction of (NBu4)[ReOCl4] with H2L1 and two equivalents of ammonium thiocyanate, however, gives in a one-pot reaction [ReO(NCS)2(HL1)] (8), in which the pro-ligand H2L1 is only singly deprotonated. An oxo-bridged, dimeric nitridorhenium(V) compound of the composition [{ReN(HL1)}2O] (11) is obtained from a reaction of (NBu4)[ReOCl4], H2L1 and sodium azide. The six-coordinate complexes [ReO(L1)(Ph2btu)] (12), where HPh2btu is N,N-diphenyl-N′-benzoylthiourea, can be obtained by treatment of [ReOCl(L1)] with HPh2btu in the presence of NEt3. Studies of the antiproliferative effects of the [ReOX(L1)] system (X = Cl−, NCS− or CN−) on breast cancer cells show that the lability of a monodentate ligand seems to play a key role in the cytotoxic activity of the metal complexes, while the substitution of this ligand by the chelating ligand Ph2btu− completely terminates the cytotoxicity.

Air- and water-stable phenyl complexes with nitridotechnetium(V) cores can be prepared by straightforward procedures. [TcNPh2(PPh3)2] is formed by the reaction of [TcNCl2(PPh3)2] with PhLi. The analogous N-heterocyclic carbene (NHC) compound [TcNPh2(HLPh)2], where HLPh is 1,3,4-triphenyl-1,2,4-triazol-5-ylidene, is available from (NBu4)[TcNCl4] and HLPh or its methoxo-protected form. The latter compound allows the comparison of different Tc–C bonds within one compound. Surprisingly, the Tc chemistry with such NHCs does not resemble that of corresponding Re complexes, where CH activation and orthometalation dominate.

Na[AuCl4]·2H2O reacts with tridentate thiosemicarbazide ligands, H2L1, derived from N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chloride and thiosemicarbazides under formation of air-stable, green [AuCl(L1)] complexes. The organic ligands coordinate in a planar SNS coordination mode. Small amounts of gold(I) complexes of the composition [AuCl(L3)] are formed as side-products, where L3 is an S-bonded 5-diethylamino-3-phenyl-1-thiocarbamoyl-1,2,4-triazole. The formation of the triazole L3 can be explained by the oxidation of H2L1 to an intermediate thiatriazine L2 by Au3+, followed by a desulfurization reaction with ring contraction. The chloro ligands in the [AuCl(L1)] complexes can readily be replaced by other monoanionic ligands such as SCN– or CN– giving [Au(SCN)(L1)] or [Au(CN)(L1)] complexes. The complexes described in this paper represent the first examples of fully characterized neutral Gold(III) thiosemicarbazone complexes. All the [AuCl(L1)] compounds present a remarkable cell growth inhibition against human MCF-7 breast cancer cells. However, systematic variation of the alkyl groups in the N(4)-position of the thiosemicarbazone building blocks as well as the replacement of the chloride by thiocyanate ligands do not considerably influence the biological activity. On the other hand, the reduction of AuIII to AuI leads to a considerable decrease of the cytotoxicity.

Potentially tetradentate, binegative thiocarbamoylbenzamidines derived from o-phenylenediamines (H2L or H3L) are shown to be suitable ligand systems for oxidorhenium(V) cores. They readily react with (NBu4)[ReOCl4] or [ReOCl3(PPh3)2] under formation of monoxido complexes of the composition [ReO{(H)L}(Y)] with various co-ligands (Y = ReO4−, F3CCO2−, Cl− or methanol) or μ-oxido dimers depending on the reaction conditions applied. Representative products were isolated and studied spectroscopically and by X-ray diffraction.Substitutions in the periphery of the ligands allow the introduction of a carboxylic substituent, which may serve as anchor group for future bioconjugation of appropriate rhenium (or technetium) complexes.Graphical abstractPotentially tetradentate, binegative thiocarbamoylbenzamidines derived from o-phenylenediamines readily react with (NBu4)[ReOCl4] under formation of monoxido complexes. Substitutions in the periphery of the ligands may allow bioconjugation of metal complexes with suitable stability.Highlights► Tetradentate ligands with S,N,N,S donor sets form stable oxidorhenium(V) complexes. ► The ligands can be modified in their periphery with a carboxylic group. ► Complexes with the modified ligands are candidates for bioconjugation. ► The solid state structures of the complexes show networks of hydrogen bonds.

2-(Diphenylphosphinomethyl)aniline, H2L1, reacts with [RuCl2(PPh3)3] to yield the monomeric complexes [RuCl2(H2L1)(PPh3)(CH3CN)], [RuCl2(H2L1)2] and the chloro-bridged dimer [(H2L1)(PPh3)Ru(μ-Cl)2Ru(PPh3)(H2L1)] depending on the conditions applied. Exclusively the monochelate [RuCl2(H2L1)(dmso)2] is formed during reactions of H2L1 with [RuCl2(dmso)4]. H2L1 acts as a neutral, bidentate ligand in all complexes. The products are studied spectroscopically and by X-ray diffraction.Graphical abstract2-(Diphenylphosphinomethyl)aniline, H2L1, reacts with [RuCl2(PPh3)3] to yield the monomeric complexes or chloro-bridged dimers depending on the conditions applied, while exclusively the monochelate [RuCl2(H2L1)(dmso)2] is formed from reactions starting from [RuCl2(dmso)4].Highlights► 2-(Diphenylphosphinomethyl)aniline, H2L1, forms stable ruthenium(II) complexes. ► Monomers or dimers are formed from [RuCl2(PPh3)3] on the conditions applied. ► The monochelate [RuCl2(H2L1)(dmso)2] is formed from [RuCl2(dmso)4]. ► The products are characterized spectroscopically and by X-ray diffraction. ► H2L1 acts as a neutral, bidentate ligand in all complexes.

Stable organogold(III) compounds of the composition [AuIII(Hdamp)(L1)]Cl are formed from reactions of [AuCl2(damp)] with H2L1 (damp− = dimethylaminomethylphenyl; H2L1 = N′-(diethylcarbamothioyl)benzimidothiosemicarbazides). The cationic complexes can be neutralized by reactions with weak bases under the formation of [AuIII(damp)(L1)] compounds. The structures of the products show interesting features like relatively short Au⋯H contacts between the methylene protons of the Hdamp ligand and the gold(III) ions. Preliminary biological studies on the uncoordinated compounds H2L1 and their gold complexes indicate considerable cytotoxicity for the [AuIII(Hdamp)(L1)]Cl complexes against MCF-7 cells. The in vitro trypanocidal activity was evaluated against the intracellular form of Trypanosoma cruzi. The organometallic complexes display a remarkable activity, which is dependent on the alkyl substituents of the thiosemicarbazone building blocks of the ligands. One representative of the cationic [AuIII(Hdamp)(L1)]Cl complexes, where H2L1 contains a dimethylthiosemicarbazide building block, shows a trypanocidal activity against the intracellular amastigote form in the same order of magnitude as that of the standard drug benznidazole. Furthermore, no appreciable toxicity to mice spleen cells is observed for this compound resulting in a therapeutic index of about 30, which strongly recommends it as a promising candidate for the development of a future antiparasitic drug.

Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl, mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII complexes) coordinated technetium atoms. Density functional theory calculations indicate that the Tc–chalcogen bonds in the TcIII compounds have a greater bond order than those in the TcV compounds.

Reactions between [TcI(NO)X2(PPh3)2(CH3CN)] complexes (X = Cl, Br) and KCp form the pseudotetrahedral organotechnetium compounds [TcI(NO)(Cp)(PPh3)X]. The halide ligands can readily be replaced by other halides or organometallic ligands giving access to a novel family of technetium(I) compounds with the robust {Tc(NO)(Cp)(PPh3)}+ core.

Similar reactions of 2,6-dipicolinoylbis(N,N-diethylthiourea) (H2La) with: (i) Ni(NO3)2·6H2O, (ii) a mixture of Ni(NO3)2·6H2O and AgNO3, (iii) a mixture of Ni(OAc)2·4H2O and PrCl3·7H2O and (iv) a mixture of Ni(OAc)2·4H2O and BaCl2·2H2O give the binuclear complex [Ni2(La)2(MeOH)(H2O)], the polymeric compound [NiAg2(La)2]∞, and the heterobimetallic complexes [Ni2Pr(La)2(OAc)3] and [Ni2Ba(La)3], respectively. The obtained assemblies can be used for the build up of supramolecular polymers by means of weak and medium intermolecular interactions. Two prototype examples of such compounds, which are derived from the trinuclear complexes of the types [MII2LnIII(L)2(OAc)3] and [MII2Ba(L)3], are described with the compounds {[CuII2DyIII(La)2(p-O2C-C6H4-CO2)(MeOH)4]Cl}∞ and [MnII2Ba(MeOH)(Lb)3]∞, H2Lb = 2,6-dipicolinoylbis(N,N-morpholinoylthiourea).

Rhenium(V) complexes containing tridentate thiosemicarbazones/thiosemicarbazides (H2L1) derived from N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chlorides with 4,4-dialkylthiosemicarbazides have been synthesized by ligand-exchange reactions starting from [ReOCl(L1)]. The chlorido ligand of [ReOCl(L1)] (4) is readily replaced and reactions with ammonium thiocyanate or potassium cyanide give [ReO(NCS)(L1)] (6) and [ReO(CN)(L1)] (7), respectively. The reaction of (NBu4)[ReOCl4] with H2L1 and two equivalents of ammonium thiocyanate, however, gives in a one-pot reaction [ReO(NCS)2(HL1)] (8), in which the pro-ligand H2L1 is only singly deprotonated. An oxo-bridged, dimeric nitridorhenium(V) compound of the composition [{ReN(HL1)}2O] (11) is obtained from a reaction of (NBu4)[ReOCl4], H2L1 and sodium azide. The six-coordinate complexes [ReO(L1)(Ph2btu)] (12), where HPh2btu is N,N-diphenyl-N′-benzoylthiourea, can be obtained by treatment of [ReOCl(L1)] with HPh2btu in the presence of NEt3. Studies of the antiproliferative effects of the [ReOX(L1)] system (X = Cl−, NCS− or CN−) on breast cancer cells show that the lability of a monodentate ligand seems to play a key role in the cytotoxic activity of the metal complexes, while the substitution of this ligand by the chelating ligand Ph2btu− completely terminates the cytotoxicity.