Aktuelle Publikationen zur Technetiumchemie
H. H Nguyen, U. Abram
Rhenium and Technetium Complexes with Pentadentate Thiocarbamoylbenzamidines
Inorg. Chem. 54 (2015) 5949.
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) to form stable complexes with the general composition of [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.
S. M. Balasekaran, J. Spandl, A. Hagenbach, K. Köhler, M. Drees, U. Abram
Fluoridonitrosyl Complexes of Technetium(I) and Technetium(II). Synthesis, Characterization, Reactions, and DFT Calculations
Inorg. Chem. 52 (2013) 7094
A mixture of [Tc(NO)F5]2- and [Tc(NO)(NH3)4F]+ is formed during the reaction of pertechnetate with acetohydroxamic acid 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, acetohydroxamic acid, HF and pyridine 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 DFT calculations on [Tc(NO)F5]2-, [Tc(NO)(py)4F]+, [Tc(NO)(NH3)4F)]+ and [Tc(NO)(NH3)4F)]2+.
S. M. Balasekaran, M. Molski, J. Spandl, A. Hagenbach, R. Alberto, U. Abram
Hexafluoridotechnetate(IV) Revisited
Inorg. Chem. 52 (2013) 7094
Novel synthetic routes for several M2[TcF6] salts (M = Na, K, Rb, Cs, NH4, and NMe4) were developed, and their single-crystal X-ray structures were determined. [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−, was isolated and studied structurally.
E. Oehlke, S. Kong, P. Arciszewski, S. Wiebalck, U. Abram
Aryl and NHC Compounds of Technetium and Rhenium
J. Am. Chem. Soc. 134 (2012) 9118
Air- and water-stable phenyl complexes with nitridotechnetium(V) cores can be prepared by straightforward procedures. [TcNPh2(Ph3P)2] is formed during the reaction of [TcNCl2(Ph3P)2] with PhLi. The analogous NHC compound [TcNPh2(HLPh)2], were 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 NHC’s does not resemble that of corresponding Re complexes, where CH activation and orthometallation dominates.
E. Oehlke, R. Alberto, U. Abram
Synthesis, Characterization, and Structures of R3EOTcO3 Complexes (E = C, Si, Ge, Sn, Pb) and Related Compounds
AgTcO4 reacts with compounds such as R3EOTcO3 (E = C, Si, Ge, Sn, Pb; R = Me, iPr, tBu, Ph), tBu2SnCl2, or PhMgCl under formation of organometallic pertechnetates. The carbon and silicon derivatives undergo rapid decomposition, while germanium, tin, and magnesium compounds could be isolated in crystalline form and studied by X-ray diffraction. The reaction of AgTcO4 with iPr3SiCl was found as an unexpected route for the synthesis of a solvent adduct of the neutral technetium(V) oxychloride TcOCl3.
H. H. Nguyen, P. I. da S. Maia, V. M. Deflon, U. Abram
Oxotechnetium(V) Complexes with a Novel Class of Tridentate Thiosemicarbazide Ligands
A novel tridentate thiosemicarbazide-type ligand class with an SNS donor set, H2L1, was prepared by reactions of N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chlorides with thiosemicarbazides. H2L1 ligands readily react with (NBu4)[TcOCl4] in MeOH under the formation of red oxotechnetium(V) complexes of composition [TcOCl(L1)]. The monomeric, five-coordinate compounds are air-stable and bind (L1)2−tridentate in the equatorial coordination sphere. The compounds represent the first examples of oxotechnetium(V) complexes with NS chelate-bonded thiosemicarbazones.
S.A. Saucedo Anaya, A. Hagenbach, U. Abram
Tricarbonylrhenium(I) and –technetium(I) Complexes with Bis(2-pyridyl)phenylphosphine and Tris(2-pyridyl)phosphine
(NEt4)2[Re(CO)3Br3] or (NEt4)2[Tc(CO)3Cl3] react with bis(2-pyridyl)phenylphosphine or tris(2-pyridyl)phosphine under formation of neutral tricarbonyl complexes of the composition [M(CO)3(halide)(phosphine)]. The ligands coordinate solely via two of their nitrogen atoms.
A reaction of [Re(CO)3(THF)3](NO3) with Ppy3 yielded the complex [Re(CO)3(NO3)(Ppy3-N,N’)] with a monodentate coordinated nitrato ligand.
Nguyen Hung Huy, J. Grewe, J. Schroer, B. Kuhn, U. Abram
Rhenium and Technetium Complexes with Tridentate N-[(N”,N”-Dialkylamino)(thiocarbonyl)]-N’-(substituted) Benzamidine Ligands
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 H2L1, HL2 and H2L3.
Starting from (NBu4)[MOCl4] (M = Re, Tc) or [ReOCl3(PPh3)2] and H2L1, a series of oxorhenium(V) and oxotechnetium(V) complexes of the composition [MOCl(L1)] was synthesized and characterized by spectroscopic methods and X-ray crystallography. The monomeric, five-coordinate compounds are air-stable and bind (L1)2- tridentate in the equatorial coordination sphere. Dimeric products of the compositions [{ReOCl(L2)}2O] and [ReOCl(L3)]2 were isolated during reactions with HL2 and H2L3. While dimerization in [{ReOCl(L2)}2O] is established via an oxo bridge, the metal atoms in [ReOCl(L3)]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
Nguyen Hung Huy, U. Abram
Rhenium and Technetium complexes with N,N-Dialkyl-N’-benzoylthioureas
N,N-Dialkyl-N’-benzoylthioureas, HR1R2btu, react under single deprotonation and formation of air-stable chelate complexes with common rhenium or technetium complexes such as (NBu4)[MOCl4] (M = Re, Tc) or [ReOCl3(PPh3)2]. Compositions and molecular structures of the products are strongly dependent on the precursors used and the reaction conditions applied. Reactions with [ReOCl3(PPh3)2] in CH2Cl2 give complexes of the general formula [ReOCl2(R1R2btu)(PPh3)] (3), with the benzoyl oxygen atom of the chelating benzoylthiourea being trans to the oxo ligand, and/or Re(III) complexes of the composition [ReCl2(R1R2btu)(PPh3)2] (4) with the PPh3 ligands in trans position to each other. In polar solvents such as MeOH, EtOH or acetone, corresponding reactions without addition of a supporting base only result in intractable brown solutions, from which no crystalline complexes could be isolated. The addition of NEt3, however, allows the isolation of the bis-chelates [ReOCl(R1R2btu)2] (1) in good yields. In this type of complexes, one the chelating R1R2btu- ligands coordinates equatorially, while the second occupies the position trans to the oxo ligand with its oxygen atom. The latter compounds can also be prepared from (NBu4)[ReOCl4] in MeOH when no base is added, while the addition of NEt3 results in the formation of [ReO(OMe)(R1R2btu)2] (5) complexes with the methoxo ligand trans to O2-. Compounds of the type 5 can alternatively be prepared by heating 1 in MeOH with addition of NEt3. A reversible conversion of 5 into oxo-bridged dimers of the composition [{ReO(R1R1btu)2}2O] (6) is observed in water-containing solvents.
Starting from (NBu4)[TcOCl4], a series of technetium complexes of the type [TcOCl(R1R2btu)2] (2) could be prepared. The structures of such compounds are similar to those of the rhenium analogues 1. Reduction of 2 with PPh3 in CH2Cl2 gives Tc(III) complexes of the composition [TcCl(R1R2btu)2(PPh3)] (7) having the chloro and PPh3 ligands in cis position. When this reaction is performed in presence of excess of the chelating ligand, the Tc(III) tris-chelates [Tc(R1R2btu)3] (8) are formed.
H. Braband, U. Abram
Technetium Complexes with Triazacyclononane
[NBu4][TcOCl4] reacts with ethylene glycol and 1,4,7-triazacyclononane (tacn) in MeOH under the formation of the deep-blue oxotechnetium(V) cation [TcO(OC2H4O)(tacn)]+, which can readily be oxidized by air to give the stable technetium(VII) compound [TcO3(tacn)]+. The reaction with aqueous HCl results in reduction and the formation of the cationic technetium(III) complex [TcCl2(OH2)(tacn)]Cl. The products were isolated in crystalline form and studied spectroscopically and by X-ray diffraction.
A. Hagenbach, E. Yegen, U. Abram
Technetium Tetrachloride as a Precursor for Small Technetium(IV) Complexes
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) Å.
M. Hecht, S. Saucedo Anaya, A. Hagenbach, U. Abram
Rhenium(V) and Technetium(V) Complexes with Phosphoraneimine and Phosphoraneiminato Ligands
Air-stable rhenium(V) nitrido complexes are formed when [ReOCl3(PPh3)2], [NBu4][ReOCl4], or [NBu4][ReNCl4] are treated with an excess of silylated phosphoraneiminates of the composition Me3SiNPPh3 or Ph2P(NSiMe3)CH2PPh2 in CH2Cl2. Complexes of the compositions [ReNCl(Ph2PCH2PPh2NH)2]Cl (1), [ReN(OSiMe3)(Ph2PCH2PPh2NH)2]Cl (2) or [ReNCl2(PPh3)2] (3) were isolated and structurally characterized. The latter compound was also produced during a reaction of the rhenium(III) precursor [ReCl3(PPh3)2(CH3CN)] and Me3SiNPPh3. Nitrogen transfer from the phosphorus to the rhenium atoms and the formation of nitrido ligands were observed in all examples. All products of reactions with an excess of the potentially chelating phosphoraneiminate Me3SiNP(Ph2)CH2PPh2 contain neutral Ph2PCH2PPh2NH ligands. The required protons are supplied by a metal-induced decomposition of the solvent dichloromethane. The Re-N(imine) bond lengths (2.055-2.110 Å) indicate single bonds, whereas the N-P bond with lengths between 1.596 Å and 1.611 Å reflect considerable double bond character. An oxorhenium(V) phosphoraneiminato complex, the dimeric compound [ReOCl2(µ-N-Ph2PCH2PPh2N)]2 (4), is formed during the reaction of [NBu4][ReOCl4] with an equivalent amount of Ph2P(NSiMe3)CH2PPh2 in dry acetonitrile. The blue neutral complex with two bridging phosphoraneiminato units is stable as a solid and in dry solvents. It decomposes in solution, when traces of water are present. The rhenium-nitrogen distances of 2.028(3) and 2.082(3) Å are in the typical range of bridging phosphoraneiminates and an almost symmetric bonding mode. Technetium complexes with phosphoraneimine ligands were isolated from reactions of [NBu4][TcOCl4] with Me3SiNPPh3, and [NBu4][TcNCl4] with Me3SiNP(Ph2)CH2PPh2. Nitrogen transfer and the formation of a five-coordinate nitrido species, [TcNCl2(HNPPh3)2] (5), was observed in the case of the oxo precursor, whereas reduction of the technetium(VI) starting material and the formation of the neutral technetium(V) complex [TcNCl2(Ph2PCH2PPh2NH)] (6) or [TcNCl(Ph2PCH2PPh2NH)2]Cl (7) was observed in the latter case. Both technetium complexes are air stable and X-ray structure determinations show bonding modes of the phosphoraneimines similar to those in the rhenium complexes.
E. Yegen, A. Hagenbach, U. Abram
TcCl4(H2O)2] and [Cl3(H2O)2TcOTc(H2O)2Cl3]– two molecular intermediates of the hydrolysis of technetium(IV)
Chem. Commun. (2005) 5575.
Two molecular intermediates of the hydrolysis of technetium tetrachloride, cis-[TcCl4(H2O)2] and [Cl3(H2O)2TcOTc(H2O)2Cl3], were isolated and structurally characterised, suggesting that the hydrolytic degradation of technetium(IV) compounds occurs stepwise with the polymeric {TcO2 x n H2O} as a less defined final product.
S. Pereiras-Gabian, E. Vazques-Lopez, H. Braband, U. Abram
Mono- and Dinuclear Tricarbonyltechnetium(I) Complexes with Thiosemicarbazones
[NEt4]2[Tc(CO)3Cl3] reacts with thiosemicarbazones derived from 2,2'-dipyridyl ketone (HL3) and 4-acetylpyridine (HL4) to form stable technetium(I) complexes of the compositions [Tc(CO)3Cl(HL3-Npy,Npy)] and [Tc2(CO)6Cl2(µ-HL4-Npy,S)]. Whereas exclusively the pyridine nitrogen atoms are involved in coordination in the monomeric complex, the binuclear compound represents the first technetium complex with a coordinated thiosemicarbazone functionality.
H. Braband, U. Abram
Nitridotechnetium(V) Complexes with Heterocyclic Carbenes and Unexpected {OSiMe2OSiMe2O}2- Coligands
Organometallics 24 (2005) 3362
Reactions of [TcNCl2(PPhR2)3] complexes (R = Me, Et) with 1,3-diethyl-4,5-dimethylimidazol-2-ylidene yield air-stable nitridotechnetium(V) complexes with N-heterocyclic carbenes with up to four of these bulky ligands and, depending on the reaction conditions applied, 1,1,3,3-tetramethyldisiloxane-1,3-diolato coligands which were abstracted from silicon-based grease.