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A scalable synthesis of the novel and highly reactive [Tc(OH2)(CO)3(PPh3)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(OH2)(CO)3(PPh3)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(PPh3)2]+ and [Tc(L)2(CO)2(PPh3)2]+ represent an interesting opportunity for the development of 99mTc complexes with potential use in radiopharmacy. The ready displacement of the aqua ligand highlights the synthetic value of [Tc(OH2)(CO)3(PPh3)2]+ as a reactive entry point for further studies in the little explored field of the organometallic chemistry of technetium.

Reactions between 3-amine-2-((pyridin-2-ylmethyl)selanyl)pyridine (L) and MX2 (M = Co, Cu, Zn; X = Cl, Br) result in the formation of the metal(II) molecular complexes 1–5 with the general formula [MX2(L)]. The organic ligand is coordinated to the metal center through nitrogen atoms of the pyridine rings, without interaction with the selenium atom. The rhenium(V) complex [ReO(apySe)2]Cl (6) is formed in two different ways, using [ReOCl3(PPh3)2] as precursor. Firstly, the formation of 6 was observed in the mother liquor, through Csp3–Se bond cleavage of the ligand L and formation of new Re–Se bonds. Secondly, the direct reaction between bis(3-amino-2-pyridyl)diselane (apySe)2 and [ReOCl3(PPh3)2] gave complex 6 in higher yields. The coordination compounds were characterized by spectroscopic and crystallographic methods. Furthermore, the antibacterial activity of the complexes 1–5 was evaluated against Gram-positive bacteria, Staphylococcus aureus (ATCC® 25923), and Gram-negative bacteria, Escherichia coli (ATCC® 25922). The results suggest that the complexes [CoCl2(L)] (1), [CuCl2(L)] (3), [CuBr2(L)] (4) and, [ZnCl2(L)] (5) possess significant bactericidal activity when compared with those of the free ligand and metal salts used in the synthesis.

A series of technetium complexes with (η5-cyclopentadienyl)tris(dimethyl phosphito-P)cobaltate(III), also known as the "Klaui ligand" {LOMe}-, has been prepared. The products span seven different oxidation states (+1 to +7) of the radioactive transition metal and comprise nitrosyl, halide, oxido and nitrido complexes. All members of this series ([TcI(NO)Cl(PPh3)(LOMe)], [TcII(NO)Cl2(LOMe)], [TcIIICl2(PPh3)(LOMe)], [TcIVCl3(LOMe)], [TcVOCl2(LOMe)], [TcVNCl(PPh3)(LOMe)], [TcVINCl2(LOMe)], and [TcVIIO3(LOMe)] are air- and water-stable compounds, which recommends this class of technetium complexes as potential candidates for nuclear medical imaging procedures.

Reactions of [Tc(NO)Cl(Cp)(PPh3)] with a series of monodentate ligands X– (X– = I–, I3–, F3CSO3–, CF3COO–, or SCN–) result in a ready replacement of the chlorido ligand and the formation of complex...

Reactions of (NBu4)[MOCl4] complexes (M = Tc or Re) with an excess of hexafluoroacetylacetone (Hhfac) give products with a composition of (NBu4)[MOCl3(hfac)] as bright yellow (Tc) or red (Re) solids. The products are stable as solids but rapidly decompose in solution. A number of related phenylimidorhenium(V) complexes were synthesized starting from [Re(NPhF)Cl3(PPh3)2], where (NPhF)2– is a para-fluorinated phenylimido ligand. Products with compositions of [Re(NPhF)Cl2(PPh3)(acac)], [Re(NPhF)Cl2(PPh3)(hfac)], [Re(NPhF)Cl2(PPh3)(tfac)], [Re(NPhF)Cl2(PPh3)(naphtfac)], and [Re(NPhF)Cl2(PPh3)(tbutfac)] (Hacac = acetylacetone, Htfac = trifluoroacetylacetone, Hnaphtfac = naphthoyltrifluoroacetylmethane, and Htbutfac = tert-butyroyltrifluoroacetylmethane) were isolated from reactions of the quite soluble [Re(NPhF)Cl3(PPh3)2] with the corresponding β-diketones and studied spectroscopically and by X-ray diffraction. The β-diketonates are coordinated in a meridional arrangement with the phenylimide. The formation o...

Three new neutral oxorhenium(V) complexes were prepared with a 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) ligand (H2bdtc): ReOCl(bdtc)(triphenylphosphine) [1] , ReOBr(bdtc)(triphenylphosphine) [2] and ReO(bdtc)(cysteamine) [3] . These rhenium complexes were characterized based on elemental, ESI(+)-MS, IR, NMR (1H and 31P), and X-ray diffraction analysis. The bdtc ligand took on different coordination arrangements for the three rhenium complexes, a planar conformation for 1 and a facial conformation for complex 3. Complexes 1 and 3 crystallize with monoclinic space groups P21/n and P21/c, respectively. The conformational stability caused by the unimolecular arrangement of the ligands was evaluated by the Density Functional Theory (DFT) calculation with the purpose of determining the balance involving the equilibrium among the possible stereoisomers in isolated phase and solvent. Moreover, frontier molecular orbitals, Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM), bond order indices and molecular electrostatic potential analysis were performed to understand the electronic properties.

The reaction of isophthaloylbis(N,N-diethylthiourea), H2L1, with UO2(CH3COO)2·2H2O and NEt3 as a supporting base gives a tetranuclear, anionic complex of the composition [{UO2(L1)}4(OAc)2]2–, in which the uranyl ions are S,O-chelate bonded. Each two of them are additionally linked by an acetato ligand. Similar reactions of various uranyl starting materials (uranyl acetate, uranyl nitrate, (NBu4)2[UO2Cl4]) with corresponding pyridine-centered ligands (pyridine-2,6-dicarbonylbis(N,N-dialkylthioureas), H2L2) yield mononuclear, neutral compounds, in which the thiourea derivatives are coordinated as S,N,N,N,S-five-dentate chelators. The equatorial coordination spheres of the formed hexagonal bipyramidal complexes [UO2(L2)(solv)] are completed by solvent ligands (H2O, MeOH, or DMF). Attempted reactions without a supporting base result in decomposition of the organic ligands and the formation of hexanuclear uranyl complexes with pyridine-2,6-dicarboxylato ligands, while the use of an excess of base results in co...

Nine thiosemicarbazone ligands (H2Ln, n = 1–9) containing benzothiazole or benzoxazole groups at the C(2) atom of the thiosemicarbazone have been prepared and characterized. A crystal structure study was performed on six of these free ligands and the role of the π–π interactions in the molecular association was analyzed. The coordination behavior of the thiosemicarbazones towards the {Re(CO)3}+ fragment was investigated and three types of complexes were obtained: mononuclear fac-[ReX(H2Ln)(CO)3], X = Cl or Br, with bidentate ligands, dinuclear [Re2(HLn)2(CO)6] with monodeprotonated bridging thiosemicarbazonates yielding Re2S2 cores and tetranuclear [Re4(L2)2(CO)12(EtOH)2] with an unusual bideprotonated thiosemicarbazonate ligand. The intermolecular interactions before and after metal coordination were analyzed. In the dinuclear complexes, two different approximate symmetries were observed depending on the relative orientation of the thiosemicarbazonate ligands with respect to the Re2S2 diamond. The intramolecular interactions in the dimers and their relationship with the two possible symmetric dispositions were analyzed. The findings, in conjunction with theoretical calculations, allowed the main stabilizing factors for each type of symmetry to be elucidated.

The deep blue, paramagnetic Cs2[TcII(NO)F5] is formed during reactions of pertechnetate, acetohydroxamic acid, and CsF in aqueous HF. A reaction of Cs2[Tc(NO)F5] with BF3·MeOH in acetonitrile gives yellow blocks of the fluorido-bridged dimer [{TcI(NO)(CH3CN)4}2F](BF4)3. The compound is stable as solid and in acetonitrile solutions. The complex cation contains a bent μ-F– ligand and two linear nitrosyl groups.

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.

Reactions of thiosemicarbazone ligands (H2L1) with [ReX3(NPh)(PPh3)2] (X = Cl or Br) led to the formation of stable rhenium(V) complexes of composition [ReX(NPh)(HL1)(PPh3)]X. The Re(V) complexes have been characterized by diverse techniques including FTIR, 1H and 31P NMR, elemental analysis, HRMS and single-crystal X-ray diffraction analysis. The crystal structures of the complexes rhenium complexes showed the formation a distorted octahedron environment around the Re(V) metal center, with the axial positions being occupied by the halogen atom and by the nitrogen atom from the phenylimido moiety, while the equatorial positions are occupied by the S,N,S-thiosemicarbazonate and the triphenylphosphane ligands. Furthermore, the “3 + 2” mixed ligand complex [Re(NPh)(L1b)(Et2btu)], where HEt2btu is N,N-diethyl-N’-benzoylthiourea, could be obtained from an equimolar reaction of [ReCl(NPh)(HL1)(PPh3)]Cl with the bidentate thiourea in the presence of NEt3. Finally, DFT calculations were applied in order to propose a complex suitable for biocouplings upon substitution of a NH2 group at the 4-position of the phenylimido ligand in [Re(NPh)(L1b)(Et2btu)]. The compounds studied here represent the first examples of phenilimidorhenium(V) complexes with thiosemicarbazones.

2,6-Diacetylpyridine-bis(benzoylhydrazone), H2LPh, reacts with Pb(OAc)2·3H2O and NEt3 as a supporting base forming a polymeric solid of the composition [Pb(LPh)]n. A reaction with pyridine results in cleavage of the polymer and formation of the dimeric, crystalline compound [Pb(py)(LPh)]2. Similar reactions with PbX2 salts (X = Cl, Br, I) also give almost insoluble solids of the tentative composition [Pb(H2LPh)X2]n. After ongoing reactions with DMSO, single deprotonation of the organic ligand and the formation of pseudo-dimeric [Pb(HLPh)X]2 complexes was observed. Depending on the presence of solvent molecules they form different supramolecular aggregates by π–π interactions. The use of Pb(NO3)2 results in a dimeric structure with relatively short Pb–O bonds of 2.442(2) A between the monomeric sub-units. The formed dimers aggregate to a polymeric assembly by hydrogen bonds. The products were studied by spectroscopic methods and X-ray diffraction.

The potentially tetradentate benzamidine/thiosemicarbazone ligand, Et2N–(C S)–NH-C(Ph) = N–(o-C4H6)–C(Me) = N–NH–(C S)–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.

A series of lanthanide complexes with general formula [Ln(NTA)3X] were prapared [Ln = Y (a), Er (b), Eu (c), NTA = naphthoyltrifluoroacetone, X = H2O (1), phen = phenanthroline (2), bpyO1 = 2, 2′-bipyridine N-oxide (3), and bpyO2 = 2, 2′-bipyridine-N,N′-dioxide (4)]. The crystal structures of [Eu(NTA)3bpyO2] (4b), [Er(NTA)3bpyO1] (3c), and [Er(NTA)3phen] (2c) were determined. X-ray crystallographic analysis reveals that the complexes are of mononuclear structure with three NTA and one ancillary ligand. The photoluminescence spectra of 3c and 4b exhibit strong characteristic emissions arising from Eu3+ central ion due to the efficient sensitization of bpyO1 and bpyO2, respectively.

N-[3-(Phenyltellanyl)propyl]picolinamide (HL1) or N-[N″,N″-methyl(phenyl)aminothiocarbonyl]-N′-[3-(phenyltellanyl)propyl]benzamidine (HL2) react with equivalent amounts of PtCl2 or PdCl2 with formation of neutral [MCl(L1-κN,N′,Te)] or [MCl(L2-κS,N,Te)] chelates. A corresponding reaction of HL2 with HgCl2 results in the formation of [HgCl2(HL2-κS,Te)]. Treatment of [PtCl(L1-N,N′,Te)] with elemental iodine results in the exclusive oxidation of the metal ion and the platinum(IV) complex [PtI3(L1-κN,N′,Te)] could be isolated in reasonable amounts. A decomposition of the tellurium-containing ligand and the formation of [PdI2(PhTeI)2] was observed during a similar procedure with the corresponding palladium complex. The bonding situation inside the latter compound was analyzed through density functional theory calculations.

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.

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...

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 (NBu 4 )[Tc(NO)Cl 4 (MeOH)] ( 1 ) with (2-aminomethylphenyl)diphenylphosphine, H 2 L1, give different products depending on the conditions applied. An equimolare reaction in MeOH gives the technetium(II) monochelate [Tc(NO)Cl 3 (H 2 L1-κ N , 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)Cl 2 (H 2 L1-κ N , P )(H 2 L1-κ N )] ( 3 ) and [Tc(NO)Cl(H 2 L1-κ N , P ) 2 ]Cl ( 4 ), besides some (NBu 4 )[Tc(NO)Cl 4 (H 2 L1-κ N )] ( 5 ), is observed when an excess of the H 2 L1 is used in the same solvent. Reactions in acetonitrile are less defined and only the Tc(II) compound (NBu 4 )[Tc(NO)Cl 4 (H 2 L1O-κ N )] ( 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.

New neutral tricarbonylrhenium(I) complexes with bidentate thiosemicarbazone ligands derived from resorcinol have been prepared. Ligands were obtained by condensation reactions of 2,4-dihydroxybenzaldehyde (dhb) and 2,4-dihydroxyacetophenone (dha) with thiosemicarbazide derivatives. The metal complexes have been characterized by elemental analysis, mass spectrometry, spectroscopic methods (IR, 1 H NMR) and the crystal structures for eight of these compounds have been elucidated. The Re(I) metal centers are coordinated through the azomethine nitrogen and the sulfur atoms establishing five-membered chelate rings (κ- S , N (3)). The deprotonation of the ligand HL 6 and the labilization of the halogen produces the formation of the dimeric complex [Re 2 (L 6 ) 2 (CO) 6 ] by Re–S–Re bridges, where S is the thiolate sulfur atom from a κ- S , N (3)-bidentate thiosemicarbazonate ligand.

Reactions of 3,3,3′,3′-tetraethyl-1,1-isophthaloylbis(thiourea), H 2 L1a, with InCl 3 , Pb(acetate) 2 , [AuCl(PPh 3 )] and [CuCl(PPh 3 )] 4 gave complexes of the compositions [In 2 (L1a-κ O , S ) 3 ], [{Pb(L1a-κ O , S )} 2 ] ∞ , [{Au(PPh 3 )} 2 (L1a-κ S )] and [{Cu(L1a-κ O , S )} 2 ], respectively. The products have been studied spectroscopically and by single-crystal X-ray diffraction. Depending on the specific requirements of the metal ions used, complexes of completely different basic structures have been obtained: a binuclear complex with two octahedrally coordinated indium atoms, a polymeric lead compound with two differently coordinated Pb 2+ ions, a binuclear gold compound in which two {Au(PPh 3 )} + building blocks are connected by a L1a 2− ligand and a binuclear copper(II) complex with two cis-coordinated metal centers.

Potassium hexafluoridotechnetate(IV), K2[TcF6], slowly reacts in aqueous solution with acetohydroxamic acid with formation of the ammine nitrosyltechnetium(I) complex [Tc(NO)(NH3)4F]+. The product crystallizes as mixed TcF62–/HF2– salt of the composition [Tc(NO)(NH3)4F]4[TcF6][HF2]2. [Tc(NO)(NH3)4F]+ represents the first nitrosyltechnetium complex with a fluorido ligand in its coordination sphere. The Tc–F bonds in two crystallographically independent species are 1.987(2) and 2.034(2) A, respectively. This is slightly longer than in the [TcF6]2– counterion.

N-(diethylthiocarbamoyl)benzimidoyl chloride reacts with o-aminoacetophenone 4-methylthiosemicarbazone under formation of a novel N2S2 benzamidine/thiosemicarbazone ligand (H2L). The reaction of H2L with [ReNCl2(PPh3)2] yields a red complex of the composition [ReN(L)]. The molecular structure of [ReN(L)] reveals a square-pyramidal environment around the Re atom, in which the organic ligand occupies all four positions of the equatorial plane. The reaction of H2L with [TcNCl2(PPh3)2] results in a mixture of [TcN(L)] and a side-product of the composition [TcN(PPh3){Et2NC(S)NH}(L′)] (L′ = 1,10b-dimethyl-5-phenyl-1,10b-dihydro-[1,2,4]triazolo[1,5-c]quinazoline-2-thiolate). The formation of diethylthiourea and HL′ is the result of a metal-driven decomposition of H2L followed by cyclization.

Cationic bis[1,3-diethyl-4,5-diarylimidazol-2-ylidene]gold(I) complexes with 4-OCH(3) or 4-F substituents in the aromatic rings and Br(-) (3a,b) or BF(4)(-) (7a,b) counterions were synthesized, characterized, and investigated for tumor growth inhibitory properties in vitro. Analogous to auranofin, the N-heterocyclic carbenes (NHCs) were also combined with a phosphine ligand (triphenylphosphine, 4a,b) and 2',3',4',6'-tetra-O-acetyl-β-D-glucopyranosyl-1-thiolate (5a,b). The growth inhibitory effect against MCF-7, MDA-MB 231, and HT-29 cells, which is more than 10-fold higher than that of cisplatin or 5-FU, was independent of the oxidation state (Au(III), 6a,b) and the anionic counterion. Bis[1,3-diethyl-4,5-bis(4-fluorophenyl)imidazol-2-ylidene]gold(I) bromide 3b as the most cytotoxic compound reduced the growth of MCF-7 cells with IC(50) = 0.10 μM (cisplatin, 1.6 μM; 5-FU, 4.7 μM). The thioredoxin reductase (TrxR), the estrogen receptor (ER), and the cyclooxygenase (COX) enzymes, which have to be considered as possible targets based on the drug design, can be excluded from being involved in the mode of action.

Reactions of 2-(diphenylphosphinomethyl)aniline, H2L1, with [MNCl2(PPh3)2] complexes (M = Re, Tc) give the bis-chelates [MNCl(H2L1)2]Cl (M = Re, Tc) or the mono-chelate [ReNCl2(PPh3)(H2L1)] depending on the conditions applied. The aminophosphine reacts as a bidentate, neutral ligand in all three cases. The complexes were studied spectroscopically and by X-ray crystallography.

Tetrameric complexes of the composition [MO(L1)]4 (M = Tc, Re), where (L1)3– represents an asymmetric, trianionic cyclisation product with thiocarbamoylbenzamidinato and mercaptotriazolato donor sites, were formed during reactions of [TcOCl4]– or [ReOCl4]– with a potentially multidentate ligand derived from thiocarbohydrazide and N-[N',N'-diethylamino(thiocarbonyl)]benzimidoyl chloride.

[MNCl2(PPh3)2] complexes (M = Re, Tc) react with N-[(dialkylamino)(thiocarbonyl)]-N′-(2-hydroxyphenyl)benzamidines (H2L1) with formation of neutral, five-coordinate nitrido complexes of the composition [MN(L1)(PPh3)]. The products have distorted square-pyramidal coordination spheres with each a tridentate, double-deprotonated benzamidine and a PPh3 ligand in their basal planes.

Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-27T11:25:30Z No. of bitstreams: 0Bitstream added on 2014-05-27T14:36:11Z : No. of bitstreams: 1 2-s2.0-79952004829.pdf: 909499 bytes, checksum: fc1e013a3cbd9b8e53c179e18c451644 (MD5) Made available in DSpace on 2014-05-27T11:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-24 The reaction of 2,6-diformylpyridine-bis(benzoylhydrazone) [dfpbbh] and 2,6-diformylpyridine-bis(4-phenylsemicarbazone) [dfpbpsc] with lanthanides salts yielded the new chelates complexes [Eu(dfpbpsc-H +) 2]NO 3 (1), [Dy(fbhmp) 2][Dy(dfpbbh-2H +) 2]·2EtOH·2H 2O (fbhmp = 2-formylbenzoylhydrazone-6-methoxide-pyridine; Ph = phenyl; Py = pyridine; Et = ethyl) and [Er 2(dfpbbh-2H +) 2(μ-NO 3)(H 2O) 2(OH)]·H 2O. X-ray diffraction analysis was employed for the structural characterization of the three chelate complexes. In the case of complex 1, optical, synthetic and computational methods were also exploited for ground state structure determinations and triplet energy level of the ligand and HOMO-LUMO calculations, as well as for a detailed study of its luminescence properties. © 2010 Elsevier Ltd. All rights reserved. Universidade Federal de Santa Maria UFSM Departamento de Química, 97105-900 Santa Maria, RS Universidade Estadual Paulista UNESP Laboratório de Materiais Luminescentes, Rua Francisco Degni s/n, 14800-900 Araraquara, SP Freie Universität Berlin Institute of Chemistry and Biochemistry, Fabeckstr. 34-36, D-14195 Berlin Universidade Estadual Paulista UNESP Laboratório de Materiais Luminescentes, Rua Francisco Degni s/n, 14800-900 Araraquara, SP

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 Se N bonds of 2.13 (1) and 2.28 (1) A and a Se Re bond of 2.387 (1) A. The oxidation state of the Se(0) atom has been analyzed using calculated atomic charges and the electron localization function (ELF).

New neutral Pd(II) and Pt(II) complexes of the type [M(L)(PPh(3))] (M = Pd or Pt) were prepared in crystalline form in high-yield synthesis with the S-benzyldithiocarbazates and S-4-nitrobenzyldithiocarbazates derivatives from 2-hydroxyacetophenone, H(2)L(1a) and H(2)L(1b), and benzoylacetone, H(2)L(2a) and H(2)L(2b). The new complexes [Pt(L(1a))(PPh(3))] (1), [Pd(L(1a))(PPh(3))] (2), [Pt(L(1b))(PPh(3))] (3), [Pd(L(1b))(PPh(3))] (4), [Pt(L(2a))(PPh(3))] (5), [Pd(L(2a))(PPh(3))] (6), [Pt(L(2b))(PPh(3))] (7) and [Pd(L(2b))(PPh(3))] (8) were characterized on the basis of elemental analysis, conductivity measurements, UV-visible, IR, electrospray ionization mass spectrometry (ESI-MS), NMR ((1)H and (31)P) and by X-ray diffraction studies. The studies showed that differently from what was observed for the H(2)L(1a) and H(2)L(1b) ligands, H(2)L(2a) and H(2)L(2b) assume cyclic forms as 5-hydroxypyrazolinic. Upon coordination, H(2)L(2a) and H(2)L(2b) suffer ring-opening reaction, coordinating in the same manner as H(2)L(1a) and H(2)L(1b), deprotonated and in O,N,S-tridentate mode to the (MPPh(3))(2+) moiety. All complexes show a quite similar planar fourfold environment around the M(II) center. Furthermore, these complexes exhibited biological activity on extra and intracellular forms of Trypanosoma cruzi in a time- and concentration-dependent manner with IC(50) values ranging from 7.8 to 18.7 μM, while the ligand H(2)L(2a) presented a trypanocidal activity on trypomastigote form better than the standard drug benznidazole.

2,3-Dihydroxynaphthalene (H2dhn) reacts with [ReOCl3(PPh3)2] or [ReOBr3(PPh3)2] in a 1:1 molar ratio with formation of the isostructural complexes [ReOCl2(PPh3)2(Hdhn)] (4) and [ReOBr2(PPh3)2(Hdhn)] (5). They have distorted octahedral coordination spheres with the halide and the triphenylphosphine ligands arranged in equatorial trans positions to each other. The Hdhn– ligand coordinates monodentately in trans position to the oxo ligand. Intramolecular hydrogen bonds between the Hdhn– and the halogeno ligands stabilize this coordination mode. The products represent the first examples of oxorhenium(V) complexes with monodentate catecholate-type ligands.

Oxorhenium(V) complexes [ReOX3(PPh3)2] (X = Cl, Br) react with phenylacetylene under formation of complexes with ylide-type ligands. Compounds of the compositions [ReOCl3(PPh3){C(Ph)C(H)(PPh3)}] (1), [ReOBr3(OPPh3){C(Ph)C(H)(PPh3)}] (2), and [ReOBr3(OPPh3){C(H)C(Ph)(PPh3)}] (3) were isolated and characterized by X-ray diffraction. They contain a ligand, which was formed by a nucleophilic attack of released PPh3 at coordinated phenylacetylene. The structures of the products show that there is no preferable position for this attack. Cleavage of the Re–C bond in 3 and dimerization of the organic ligand resulted in the formation of the [{(PPh3)(H)CC(Ph)}2]2+ cation, which crystallized as its [(ReOBr4)(OReO3)]2– salt.

[ReNCl2(PPhMe2)3] reacts with the glycine ethylester derivative Et2NC(S)NC(Ph)NHCH2COOEt, HL(GlyEt), in methanol under hydrolysis of the ester and formation of the tetrameric, nitrido-bridged rhenium(V) compound [{ReN{fac-L(Gly)}(PMe2Ph)}{ReN{mer-L(Gly)}(H2O)}]2. Both facial and meridional coordination has been found for the tridentate {L(Gly)}2− ligand in the building blocks of the tetramer. Syn and anti isomers with respect to the PPhMe2 ligands have been isolated and characterized by X-ray diffraction.

A potentially tridentate ligand with an S,N,O donor set, H2L, is formed by the reaction of N-[(diethylaminothiocarbonyl)benzimidoyl chloride with benzoylhydrazine. Reactions of H2L with (NBu4)[MOCl4] complexes (M = Re, Tc) give five-coordinate, neutral oxo complexes of the composition [MOCl(L)]. Mixed-ligand complexes of rhenium(V) containing the tridentate L2− ligand and bidentate N,N-dialkyl-N′-benzoylthioureato ligands (R2btu−) are formed in high yields when (NBu4)[ReOCl4] is treated with mixtures of H2L and HR2btu. Another approach to the mixed-ligand products is the reaction of [ReOCl(L)] with an equivalent amount of HR2btu.

The reaction of cis-[RuCl2(P–P)(N–N)] type complexes (P–P = 1,4-bis(diphenylphosphino)butane or (1,1′-diphenylphosphino)ferrocene; N–N = 2,2′-bipyridine or 1,10-phenantroline) with monodentate ligands (L), such as 4-methylpyridine, 4-phenylpyridine and benzonitrile forms [RuCl(L)(P–P)(N–N)]+ species. Upon characterization of the isolated compounds by elemental analysis, 31P{1H} NMR and X-ray crystallography it was found out that the type of the L ligand determines its position in relation to the phosphorus atom. While pyridine derivatives like 4-methylpyridine and 4-phenylpyridine coordinate trans to the phosphorus atom, the benzonitrile ligand (bzCN), a good π acceptor, coordinates trans to the nitrogen atom. A 31P{1H} NMR experiment following the reaction of the precursor cis-[RuCl2(dppb)(phen)] with the benzonitrile ligand shows that the final position of the entering ligand in the complex is better defined as a consequence of the competitive effect between the phosphorus atom and the cyano-group from the benzonitrile moiety and not by the trans effect. In this case, the benzonitrile group is stabilized trans to one of the nitrogen atoms of the N–N ligand. A differential pulse voltammetry experiment confirms this statement. In both experiments the [RuCl(bzCN)(dppb)(phen)]PF6 species with the bzCN ligand positioned trans to a phosphorus atom of the dppb ligand was detected as an intermediate complex.

Reactions of N-[N',N'-diethylamino(thiocarbonyl)]benzimidoyl chloride with 4,4-dialkylthiosemicarbazides give a novel class of thiosemicarbazides/thiosemicarbazones, H(2)L, which causes a remarkable reduction of cell growth in in vitro experiments. These strong antiproliferative effects are also observed for oxorhenium(V) complexes of the general composition [ReOCl(L)], which are formed by reactions of the potentially tridentate ligands with (NBu(4))[ReOCl(4)]. A systematic substitution of the alkyl groups in the thiosemicarbazone building blocks of the ligands do not significantly influence the biological activity of the metal complexes, while the replacement of the chloro ligand by a PPh(3) ligand (by the replacement of the oxo unit by a nitrido ligand) completely terminated the cytotoxicity of the metal complexes.

Reactions of [ReOCl3(PPh3)2] with a potentially tridentate Schiff base derived from (2-formylphenyl)diphenylphosphine and 2-aminophenol, HL1P, (HL1P = Ph2PC6H4-2-HC N(C6H4-2-OH)) result in a rapid decomposition of the Schiff base and the formation of a large number of hitherto non-identified metal-containing species, while from similar reactions with the analogoue phosphine oxide HL1PO, (HL1PO = Ph2P(O)C6H4-2-HC N(C6H4-2-OH)) products of the compositions [ReOCl2(PPh3)(L1PO)] (1) and [Re(NC6H4-2-OH)Cl3(PPh3)2] (2) could be isolated. The structure of 2 is an experimental proof of the preceding, metal-induced cleavage of the C–N double bond. A subsequent reaction of the released 2-aminophenol forms the final phenylimido ligand. Reduction of HL1P with NaBH4 gives the phosphine amine H2L2P (H2L2 = Ph2P(C6H4-2-CH2NH(C6H4-2-OH))) in good yield. Reactions of H2L2P with common oxorhenium(V) complexes result in the formation of the stable rhenium(V) complex [ReOCl2(HL2P)] (3) with a facially coordinated HL2P− ligand.

Reactions of [Re(NPh)Cl3(PPh3)2] with N-[(N′,N′-dialkylamino)(thiocarbonyl)]benzamidines (H2R2tcb) (R2 = Et2, (CH2)2O(CH2)2) in methanol give mono-chelates of the composition [Re(NPh)Cl2(PPh3)(HR2tcb)] as the sole products independent of the amount of the added H2R2tcb. Addition of a supporting base such as NEt3 results in hydrolysis of the Re=NPh bonds and partial hydrolysis of the thiocarbamoylbenzamidines. Orange-brown, cationic oxorhenium(V) compounds of the formula [ReO(HR2tcb)2]Cl were isolated from such reaction mixtures in good yields, and the formation of small amount of the unusual sulfido/persulfido-bridged ReV dimer [{ReO(HEt2tcb)}2(μ-S)(μ-S2)] give evidence for a considerable degree of ligand decomposition under such conditions. The products have been characterized by spectroscopic methods and X-ray crystallography. Acidification of orange-brown solutions of the five-coordinate ReV oxo complex [ReO(HEt2tcb)2]Cl causes an immediate change of the color and deep blue crystals of the neutral, six-coordinate [ReOCl(HEt2tcb)2] can be isolated from the resulting mixture. Alternatively, the product can be prepared by a ligand-exchange protocol starting from (NBu4)[ReOCl4] and H2Et2tcb. The pH-dependent isomerization between [ReO(HEt2tcb)2]Cl and [ReOCl(HEt2tcb)2] is reversible.

(NEt4)2[Re(CO)3Br3] or (NEt4)2[Tc(CO)3Cl3] react with bis(2-pyridyl)phenylphosphine (PPhpy2) or tris(2-pyridyl)phosphine (Ppy3) under formation of neutral tricarbonyl complexes of the composition [M(CO)3X(L)] (M = Re, X = Br; M = Tc, X = Cl; L = PPhpy2 or Ppy3). In all isolated products, the ligands coordinate solely via two of their nitrogen atoms. All attempts to force a tripodal coordination of the phosphinopyridines failed. Removal of the bromo ligands from (NEt4)2[Re(CO)3Br3] by the addition of AgNO3 in THF/water, and subsequent reaction of the resulting [Re(CO)3(THF)3](NO3)with Ppy3 yielded the complex [Re(CO)3(NO3)(Ppy3-N,N′)] with a monodentate coordinated nitrato ligand. The products have been characterized spectroscopically and by X-ray structure analyses.

Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal)2] (1), [ReOCl2(mal)(PPh3)] (2), [ReOBr2(mal)(PPh3)] (3), [ReOCl2(koj)(PPh3)] (4) and [ReOBr2(koj)(PPh3)] (5). The products have been characterized by FTIR, 1H, 13C, and 31P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex 1 crystallizes monoclinic, space group C2/c, Z = 8. It contains two O,O′-bidentate maltolate ligands and one chloro ligand at the (ReO)3+ unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P21/n and Z = 4. In complexes 2–5, the (ReO)3+ unit is coordinated by a monoanionic O,O-bidentate unit of the maltolate (2 and 3) or kojate (4 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other.

[ReOCl3(PPh3)2] and [Re(NPh)Br3(PPh3)2] react at room temperature with equivalent amounts of N,N-dialkyl-N′-benzoylthioureas (HR1R2btu) in CH2Cl2 under formation of the rhenium(V) complexes [ReOCl2(R1R1btu)(PPh3)] and [Re(NPh)Br2(R1R2btu)(PPh3)], respectively. The products are structurally analogous with the oxygen atoms of the benzoylthioureas binding in trans positions to the oxo or phenylimido ligands. Prolonged reaction times result in the reduction of the oxo compound by the released PPh3 and the formation of rhenium(III) complexes of the composition [ReCl2(PPh3)2(R1R2btu)], while such a second reaction path is excluded for the phenylimido compound. Phenylimido species with more than one N,N-dialkyl-N′-benzoylthioureato ligand could not be isolated, even when a large excess of HR1R2btu was used during the reaction.

N-[(Dialkylamino)(thiocarbonyl)]benzimidoyl chlorides react with functionalized amines such as 2-aminophenol, 2-methylaminopyridine, and 2-aminobenzoic acid in clean and high-yield procedures with the formation of the novel tridentate N-[(N",N"-dialkylamino)(thiocarbonyl)]-N'-substituted benzamidine ligands H 2 L 1 , HL 2 , and H 2 L 3 . By starting from (NBu 4 )[MOCl 4 ] (M = Re, Tc) or [ReOCl 3 (PPh 3 ) 2 ] and H 2 L 1 , a series of oxorhenium(V) and oxotechnetium(V) complexes of the composition [MOCI(L1)] were synthesized and characterized by spectroscopic methods and X-ray crystallography. The monomeric, five-coordinate compounds are air-stable and bind (L 1 ) 2- tridentate in the equatorial coordination sphere. Dimeric products of the compositions [(ReOCl(L 2 )} 2 O] and [ReOCl(L 3 )] 2 were isolated during reactions with HL 2 and H 2 L 3 . While dimerization in [(ReOCl(L 2 )} 2 O] is established via an oxo bridge, the metal atoms in [ReOCl(L 3 )] 2 are connected by the carboxylic group of the ligand, and the product represents the first example of a high-oxidation state rhenium complex displaying such a bonding feature.

Thiocarbamoylbenzimidoyl chlorides, PhC(Cl)═N-(C═S)-NR(1)R(2), react with 2-(iminodiacetic acid)benzylamine under formation of the potentially pentadentate ligands H3L (R(1), R(2) = Et) and H3L-COOEt (R(1) = Me, R(2) = 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.

The novel ferrocenylcarbaldehyde benzoylhydrazone ligand H(Fe)L 1 has been prepared and its reaction with fac -[ReBr(CO) 3 (CH 3 CN) 2 ] in chloroform gave [ReBr(CO) 3 {H(Fe)L 1 }] in good yield. Both compounds have been characterized by elemental analysis, MS, IR, UV–Vis and 1 H NMR spectroscopic methods and their structures elucidated by X-ray diffraction. Four crystallographically independent molecules of H(Fe)L 1 are associated by N1–H and N2 or O atoms of a neighbouring ligand or methanol molecules to give chains running along the b axis. The hydrazide group is O,N-bidentate and affords a five-membered chelate ring in the rhenium complex. The geometry around the metal is fac -octahedral. The intermolecular associations based on C(Fc)–H⋯O hydrogen bonds are also discussed.

Polymeric technetium tetrachloride reacts with monodentate donor ligands such as THF, acetonitrile, DMSO, thioxane (1-oxa-4-thiacyclohexane), PMe2Ph, PPh3, OPPh3, or OH2 via cleavage of the polymeric network and the formation of [TcCl4(L)2] complexes. The configuration of the products is dependent on the donor atoms such that trans coordination is established with "soft" donor atoms such as sulfur or phosphorus, while cis-[TcCl4(L)2] complexes are formed with the "harder" donors oxygen or nitrogen. The ambivalent thioxane binds to technetium via the sulfur atom. The trans products are air stable and resistant to hydrolysis. The cis complexes, however, undergo stepwise hydrolysis, during which complexes of the composition [Cl3(L)2TcOTc(L)2Cl3] (L = CH3CN, DMSO, or OH2) are formed. They are the first representatives of a new class of technetium(IV) complexes with a bridging oxo ligand. The Tc-O bond lengths in these bridges are between 1.803(1) and 1.823(2) A.

The nitridorhenium(V) complexes [ReNCl2(PR2Ph)3] (R = Me, Et) react with the N-heterocyclic carbenes (NHC) 1,3-diethyl-4,5-dimethylimidazole-5-ylidene (LEt) or 1,3,4,5-tetramethylimidazole-2-ylidene (LMe) in absolutely dry THF under complete replacement of the equatorial coordination sphere. The resulting [ReNCl(LR)4]+ complexes (LR = LMe, LEt) are moderately stable as solids and in solution, but decompose in hot methanol under formation of [ReO2(LR)4]+ complexes. With 1,3-diisopropyl-4,5-dimethylimidazole-5-ylidene (Li-Pr), the loss of the nitrido ligand and the formation of a dioxo species is more rapid and no nitridorhenium intermediate could be isolated. The Re-C bond lengths in [ReNCl(LEt)4]Cl of approximately 2.195A are relatively long and indicate mainly σ-bonding in the electron-deficient d2 system under study. The hydrolysis of the nitrido complexes proceeds via the formation of [ReO3N]2− anions as could be verified by the isolation and structural characterization of the intermediates [{ReN(PMe2Ph)3}{ReO3N}]2 and [{ReN(OH2)(LEt)2}2O][ReO3N].

The phenylimidorhenium(V) complexes [Re(NPh)X3(PPh3)2] (X = Cl, Br) react with the N-heterocyclic carbene (NHC) 1,3-diethyl-4,5-dimethylimidazole-2-ylidene (LEt) under formation of the stable rhenium(V) complex cations [Re(NPh)X(LEt)4]2+ (X = Cl, Br), which can be isolated as their chloride or [PF6]− salts. The compounds are remarkably stable against air, moisture and ligand exchange. The hydroxo species [Re(NPh)(OH)(LEt)4]2+ is formed when moist solvents are used during the synthesis. The rhenium atoms in all three complexes are coordinated in a distorted octahedral fashion with the four NHC ligands in equatorial planes of the molecules. The Re–C(carbene) bond lengths between 2.171(8) and 2.221(3) A indicate mainly σ-bonding between the NHC ligand and the electron deficient d2 metal atoms. Attempts to prepare analogous phenylimido complexes from [Re(NPh)Cl3(PPh3)2] and 1,3-diisopropyl-4,5-dimethylimidazole-2-ylidene (Li−Pr) led to a cleavage of the rhenium-nitrogen multiple bond and the formation of the dioxo complex [ReO2(Li−Pr)4]+.

[ReOX 3 (PPh 3 ) 2 ] complexes (X = Cl and Br) react with equivalent amounts of 2-hydroxypyridine (Hhp) under formation of the mono-substituted, zwitterionic complexes mer -[ReOCl 3 (Hhp)(PPh 3 )] ( 1 ) and mer -[ReOBr 3 (Hhp)(PPh 3 )] ( 2 ). Crystal structure determinations of 1 · CH 2 Cl 2 and 2 revealed the Cl and Br ligands adopt a mer arrangement. The Hhp ligands coordinate neutral and monodentate via their exocyclic oxygen atoms in axial positions, trans to the oxo groups. The distorted octahedral coordination sphere of the rhenium(V) complexes is completed by the phosphorus atom of the remaining PPh 3 ligand.

Asymmetric, potentially pentadentate ligands (H 2 L 3 ) are formed by subsequent condensation of a semicarbazide and benzoylhydrazine on 2,6-diacetylpyridine. Two equivalents of H 2 L 3 reacts with CeCl 3 .7H 2 O, Ce(SO 4 ) 2 .4H 2 O, or EuCl 3 .6H 2 O under formation of [Ln I I I (HL 3 ) 2 ] + cations (Ln = Ce, Eu) with exclusive deprotonation of the benzoylhydrazone ligand arms. The Ce 4 + ion of the sulfate salt is reduced during the reaction and forms 10-coordinate singly charged complex cations, the structure of which is identical to the product of the reaction of cerium(lll) chloride. The exact position of deprotonation in the ligands is resolved by infrared spectroscopy, bond lengths considerations, and the hydrogen bonding in the solid-state structures of the products. A similar approach allows the synthesis of mixed semicarbazone/thiosemicarbazone ligands (H 2 L 4 ). The reaction of H 2 L 4 with Sm-(NO 3 ) 3 .6H 2 O leads to the first structurally characterized lanthanide complex with thiosemicarbazone coordination. The solid-state structure of the 10-coordinate complex [Sm(HL 4 ) 2 ]NO 3 .H 2 O shows exclusive deprotonation of the thiosemicarbazone arms of the ligands. All isolated complexes are air stable and do not undergo ligand exchange reactions or hydrolysis in the presence of water.