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Beispielpublikationen aus der Rheniumchemie


Thomaz Arruda Wioppiold, Janine Ackermann, Ernesto Schulz Lang, Ulrich Abram

Bi- and Tetranuclear Oxidorhenium(V) Complexes with a Bipodal Pyrroloylthioureato Ligand

Polyhedron 87 (2015) 202.

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 m-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.


Hung Huy Nguyen, Pham Chien Thang, Ulrich Abram

ReVO and ReVNPh Complexes with Pentadentate Benzamidines – Synthesis, Structural Characterization and DFT Evaluation of Isomeric Complexes

Polyhedron 99 (2015) 216.

Novel, potentially pentadentate ligands (H3L) for an optimal coordination of {MVO}3+ and {MV(NPh)}3+ cores (M = Re, Tc) have been tailored by a computer-aided procedure. They can be prepared by reactions of2-aminobenzyliminodiacetic acid diethylester with N,N-[(dialkylamino)(thiocarbonyl)]benzimidoyl chlorides and subsequent hydrolysis. The ligands react with [ReOCl3(PPh3)2] or [Re(NPh)Cl3(PPh3)2] under triple deprotonation and form compounds of the general compositions [ReO(L)] and [Re(NPh)(L)], respectively. The organic ligands occupy the remaining five coordination positions of the {ReO}3+ and {Re(NPh)}3+ cores in all compounds studied. The phenylimido complexes hydrolyze in basic media under formation of their oxidorhenium(V) analogs.


Vania D. Schwade, Ernesto Schulz Lang, Karsten Klauke, Fabian Mohr, Ulrich Abram

Oxidorhenium(V) Complexes with Benzoylselenoureas

Eur. J. Inorg. Chem. (2014) 1949.

Oxidorhenium(V) complexes with N,N-dialkyl-N’-benzoyl­seleno­ureas (HL) were prepared from reactions with (NBu4)[ReOCl4]. The formation of compounds such as [ReO(L-kO,Se)2(OMe)] or [{ReO(L-kO,Se)2}2O] suggests parallels to the established chemistry of corresponding benzoylthioureas, while the isolation of unusual species such as [ReO(L-kO,Se)2(L-kSe)], [{ReO(L-kO,Se)2}2Se3] and the formation of the respective diselenide prove a more complicated reaction pathway with the instable selenium compounds, where also degradation products of the ligands play a role.


Roberta Cargnelutti, Ernesto S. Lang, Paulo Piquini, Ulrich Abram

Synthesis and Structure of [ReOSe(2-Se-py)3]: a rhenium(V) complex with Selenium(0) as a ligand

Inorg. Chem. Commun. 45 (2014) 48.

Bis(2-pyridyl) diselenide (2-py2Se2, 1) reacts with [ReOCl3(PPh3)2] under 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) Å and a Se-Re 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).


Juan Daniel Castillo Gomez, Hung Huy Nguyen, Adelheid Hagenbach and Ulrich Abram

Oxidorhenium(V) Complexes with Tetradentate Thiourea Derivatives

Polyhedron 43 (2012) 123.

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.



Pedro I. da S. Maia, Hung Huy Nguyen, Adelheid Hagenbach, Silke Bergemann, Ronald Gust, Victor M. Deflon, and Ulrich Abram

Rhenium mixed-ligand complexes with S,N,S-tridentate thiosemicarbazone/thiosemicarbazide ligands

Dalton Trans. 42 (2013) 5111.

Mixed-ligand complexes of rhenium(V) 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)] is readily replaced and reactions with ammonium thiocyanate or potassium cyanide to give [ReO(NCS)(L1)] and [ReO(CN)(L1)], 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)], in which the pro-ligand H2L1 is only singly deprotonated. An oxo-bridged, dimeric nitridorhenium(V) compound of the composition [{ReN(HL1)}2O] is obtained from a reaction of (NBu4)[ReOCl4], H2L1 and sodium azide. The six-coordinate complexes [ReO(L1)(Ph2btu)], 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.




Hung Huy Nguyen, Jesudas J. Jegathesh, Pedro I. da S. Maia, Victor M. Deflon, Ronald Gust, Silke Bergemann and Ulrich Abram

Synthesis, Structural Characterization and Biological Evaluation of Oxorhenium(V) Complexes with a Novel Type of Thiosemicarbazones Derived from N-[(Dialkylamino)­(thiocarbonyl)]benzimidoyl Chlorides

Inorg. Chem. 48 (2009) 9356

 

 

Reactions of N-(N’,N’-diethylaminothiocarbonyl)benzimidoyl chloride with 4,4-dialkyl­thio­semi­car­ba­zides give a novel class of thiosemicarbazides/thiosemicarbazones, H2L, 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 (NBu4)[ReOCl4]. 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 PPh3 ligand (by the replacement of the oxo unit by a nitrido ligand) completely terminated the cytotoxicity of the metal complexes.


 

Ali Barandov, Ulrich Abram

Rhenium(V) Complexes with Pentadentate P,N,O Ligands

Inorg. Chem. 48 (2009) 8072

 

 

 

Novel rhenium(V) complexes were isolated from reactions of [NBu4][ReOCl4] with the potentially pentadentate Schiff base PhP{C6H4-2-(HCN(C6H4-2-OH))}2, H2L1, and the corresponding amine PhP{C6H4-2-(CH2-NH(C6H4-2-OH))}2, H4L2. While the Schiff base undergoes partial hydrolytic decomposition and a redox reaction, the amine remains intact and acts as a pentadentate ligand, which encapsulates the metal atom of the {ReVO}3+ core or stabilizes a {ReVCl}4+ center by the formation of an imidotype ligand system.


 

Jennifer Schroer, Ulrich Abram

Novel thiourea derivatives of α-amino acids and their oxorhenium(V) complexes

Polyhedron 28 (2009) 2277

 

 

N-[(Dialkylamino)(thiocarbonyl)]benzimidoyl chlorides react with α-amino acid esters under formation of the corresponding N-[(dialkylamino)(thiocarbonyl)]benzamidines. Derivatives with glycine ethylester, HL(GlyOEt), cysteine methylester and S-benzyl protected cysteine ethylester, HL(S-Bzl-CysOEt), were prepared and isolated in crystalline form. The reaction with cysteine methylester yields the corresponding sulfur-bridged dimeric compound {HL(CysOMe)}2.

Starting from [ReOCl3(PPh3)2], complexes of these new ligands could be obtained in two different coordination modes: monodentate coordination by only the thiourea sulfur atom or S,N,O tridentate coordination after ester hydrolysis.

 


 

Ali Barandov, Ulrich Abram

Heterofunctionalized phosphines derived from (2-formylphenyl)diphenylphosphine and their reactions with oxorhenium(V) complexes

Polyhedron 28 (2009) 1155

 

 

Reactions of [ReOCl3(PPh3)2] with a potentially tridentate Schiff base derived from (2-formylphenyl)diphenylphosphine and 2-aminophenol, HL1P, (HL1P = Ph2PC6H4-2-HCdouble bond; length as m-dashN(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-HCdouble bond; length as m-dashN(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.

 


 

Nguyen Hung Huy, U. Abram

Synthesis and Reactivity of Structurally Analogous Phenylimido and Oxo Complexes of Rhenium(V) with N,N-Dialkyl-N’-benzoylthiourea

Z. Anorg. Allg. Chem. 634 (2008) 1560.

[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.

 


E. Lopez, U. Abram

Rhenium Complexes with Triazine Derivatives Formed from Semicarbazones and Thiosemicarbazones

Inorg. Chem. 47 (2008) 2890

Benzil bis(semicarbazone), H2L1, reacts with common rhenium(V) nitrido complexes such as [ReNCl2(PPh3)2] or [ReNCl2(PR2Ph)3] (R = Me, Et) under the release of one semicarbazone unit, cyclization, and formation of stable triazine-3-onato complexes of rhenium(V). The resulting 5,6-diphenyltriazine-3-one, HL2, acts as monodentate or chelating, monoanionic ligand depending on the reaction conditions applied. Complexes of the compositions [ReNCl(L2N 2O)(PR2Ph)2] (R = Me, Et) or [ReN(L2N 2,O)(L2N 2)(PPh3)2] were isolated. The N2 nitrogen atom is the preferred binding site of the monodentate form of the ligand. This contrasts the behavior of the analogous thione HL3, which preferably coordinates to nitridorhenium(V) centers via the sulfur atom. HL3 is readily formed by the abstraction of methanol from 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]triazine-3-thione, H2L3OCH3. In the presence of [ReNCl2(PPh3)2] or [ReNCl2(PR2Ph)3] complexes (R = Me, Et), this reaction yields stable complexes of the composition [ReN(L3N 2S)(L3S)(PR2Ph)2] (R = Me, Et, Ph) in good yields. Reduction of the metal atom and formation of the seven-coordinate [Re(PPh3)(L3N 2S)3] was observed during reactions of H2L3OCH3 with [ReOCl3(PPh3)2] or [ReO2I(PPh3)2], while no rhenium complexes could be isolated during similar reactions with H2L1, although cyclization of the bis(semicarbazone) and the formation of H2L2OEt were observed.

 


A. Barandov, U. Abram

Chloro{2-(diphenylphosphino)benzaldehyde 4-phenylsemicarbazonato-P, N, N’)methoxooxorhenium(V) – a semicarbazone complex with an unusual coordination mode

Z. Anorg. Allg. Chem. 633 (2007) 1897

(NBu4)[ReOCl4] reacts with 2-(diphenylphosphino)benzaldehyde 4-phenyl­semi­carbazone (HL1) in methanol under formation of the red rhenium(V) complex [ReOCl(OMe)(L1)]. The semicarbazonato ligand is singly deprotonated and coordinates meridio­nally via the phosphorus atom and two nitrogen atoms. This unusual coordination mode of a semicarbazone is confirmed by IR and NMR spectroscopy and by the solid state structure of the product.

 


H. Braband, E. Oehlke, U. Abram

Nitridorhenium(V) Complexes with 1,3-Dialkyl-4,5-dimethylimidazole-2-ylidenes

Z. Anorg. Allg. Chem. 632 (2006) 779

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 2.195 Å are comparably 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].


H. Braband, S. Neubacher, S. Grosskopf, U. Abram

Nitridorhenium(V) Complexes with 1,3,4-Triphenyl-1,2,4-triazol-5-ylidene

Z. Anorg. Allg. Chem. 631 (2005) 1645

[ReNCl2(PPh3)2] and [ReNCl2(PMe2Ph)3] react with the N-heterocyclic carbene (NHC) 1,3,4-triphenyl-1,2,4-triazol-5-ylidene (HLPh) under formation of the stable rhenium(V) nitrido complex [ReNCl(HLPh)(LPh)], which contains one of the two NHC ligands with an additional orthometallation. The rhenium atom in the product is five-coordinate with a distorted square-pyramidal coordination sphere. The position trans to the nitrido ligand is blocked by one phenyl ring of the monodentate HLPh ligand. The Re–C(carbene) bond lengths of 2.072(6) and 2.074(6) Å are comparably long and indicate mainly σ-bonding between the NHC ligand and the electron deficient d2 metal atom.

The chloro ligand in [ReNCl(HLPh)(LPh)] is labile and can be replaced by ligands such as pseudohalides or monoanionic thiolates such as diphenyldithiophosphinate (Ph2PS2-) or pyridine-2-thiolate (pyS-). X-ray structure analyses of [ReN(CN)(HLPh)(LPh)] and [ReN(pyS)(HLPh)(LPh)] show that the bonding situation of the NHC ligands (Re–C(carbene) distances between 2.086(3) and 2.130(3) Å) in the product is not significantly influenced by the ligand exchange. The potentially bidentate pyS- ligand is solely coordinated via its thiolato functionality.

Hydrogen atoms of each one of the phenyl rings come close to the unoccupied sixth coordination positions of the rhenium atoms in the solid state structures of all complexes. Re–H distances between 2.620 and 2.712 Å do not allow to discuss bonding, but with respect to the strong trans labilising influence of “N3-“, weak interactions are indicated.

 


T. I. Kückmann, U. Abram

Rhenium(V) Oxo Complexes with N-Heterocyclic Carbenes

Inorg. Chem. 43 (2004) 7068

Air-stable rhenium(V) oxo complexes are formed when [ReOCl3(PPh3)2] is treated with N-heterocyclic carbenes of the 1,3-dialkyl-4,5-dimethylimidazol-2-ylidene type, LR (R = Me, Et, i-Pr). Complexes of the compositions [ReO2(LR)4]+, [ReOCl(LR)4]2+, or [ReO(OMe)(LR)4]2+ can be isolated depending on the alkyl substituents at the nitrogen atoms of the ligands and the reaction conditions applied. Despite the steric overcrowding of the equatorial coordination spheres of the metal atoms by each of the four carbene ligands, stable complexes with six-coordinate rhenium atoms are obtained. Steric demands of the alkyl groups allow control of the stability of the mono-oxo intermediates. Air-stable cationic complexes of the compositions [ReOCl(LMe)4]2+, [ReOCl(LEt)4]2+, and [ReO(OMe)(LMe)4]2+ have been isolated, whereas reactions of [ReOCl3(PPh3)2] or other rhenium(V) precursors with the more bulky 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (Li-Pr) directly yield the dioxo complex [ReO2(Li-Pr)4]+. X-ray structures of [ReO2(Li-Pr)4][ReO4], [ReO2(Li-Pr)4][PF6], [ReO2(LMe)4][ReO4]0.45[PF6]0.55, [ReO(MeOH)(LMe)4][PF6]2, and [ReOCl(LEt)4][PF6]2 show that the equatorial coordination spheres of the rhenium atoms are essentially planar irrespective of the steric demands of the individual carbene ligands

 


I. Garcia Santos, U. Abram, R. Alberto, E. Vazquez Lopez, A. Sanchez

Tricarbonylrhenium(I) Complexes with Thiosemicarbazone Derivatives of 2-Acetylpyridine and 2-Pyridine Formamide Showing Two Unusual Coordination Modes of Tridentate Thiosemicarbazone Ligands

Inorg. Chem. 43 (2004) 1834

[NEt4]2[Re(CO)3Br3] reacts with 2-acetylpyridine phenylthiosemicarbazone (HL1) and 2-pyridine formamide thiosemicarbazone (HL2) under formation of air-stable, neutral rhenium(I) complexes of the compositions [Re(CO)3(L1-N,N,S)] and [Re(CO)3Br(HL2-N,N)]. Spectroscopic studies and X-ray crystallography show that the potentially tridentate thiosemicarbazones adopt unusual coordination modes. Whereas HL1 deprotonates and binds to the metal in a nonplanar fashion, HL2 acts as neutral N,N donor ligand. The bond lengths inside the chelate rings are almost uninfluenced by the overall bonding situation.


H. Braband, U. Abram

Stable nitridorhenium(V) complexes with an N-heterocyclic carbene

Chem. Commun. 2003, 2436

Nitridorhenium(V) complexes with the nucleophilic cyclocarbene 1,3,4-triphenyl-1,2,4-triazol-5-ylidene have been synthesised being the first representatives of a new class of high-valent metallocarbenes


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