Nitrosyltechnetium(I) Complexes with 2‐(Diphenylphosphanyl)aniline

[Tc^I(NO)Cl(H₂L1)₂]⁺ cations (H₂L1 = 2‐(diphenylphosphanyl)aniline) are formed during reactions of H₂L1 with (NBu₄)[Tc(NO)Cl₄(MeOH)] or (NH₄)TcO₄/HCl/NH₂OH mixtures. Different isomers were isolated depending on the counterions and solvents used. The technetium(I) complexes cis‐NO,Cl,trans‐P,P‐[Tc^I(NO)Cl(H₂L1)₂]Cl, trans‐NO,Cl,cis‐P,P‐[Tc^I(NO)Cl(H₂L1)₂]₂(TcCl₆), and trans‐NO,Cl,trans‐P,P‐[Tc^I(NO)Cl(H₂L1)₂](PF₆) were isolated in crystalline form and studied by spectroscopic methods and X‐ray crystallography. DFT calculations show that there are only minor energy differences between the three isomers and the formation of the individual compounds is most probably strongly influenced by interactions with solvents and counterions.     

Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles

Reductive immobilization of radioactive pertechnetate (⁹⁹TcO₄^?) in simulated groundwater was studied by prepared carboxymethyl cellulose (CMC) and starch stabilized zero valent iron nanoparticles (nZVI), and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions. The stabilized nZVI can effectively reduce soluble ⁹⁹Tc(VII) to insoluble ⁹⁹Tc(IV), and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation. In this study, CMC-stabilized nZVI showed higher reactivity than that using starch as the stabilizer. Batch experiments indicated that more than 99% of ⁹⁹Tc(VII) (C₀ = 12 mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2% (w/w) at a broad pH of 5–8. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses further confirmed that ⁹⁹Tc(VII)O₄^? transformed into ⁹⁹Tc(IV)O₂ (s). The presence of bicarbonate exhibited insignificant effect on Tc immobilization, while humic acid (HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes. More interesting, the immobilized Tc(IV) remained insoluble even after 120 d under anoxic condition, while only ～21% was remobilized when exposed to air. Therefore, bio-macromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.     

[Au(Et2dtc)2][TcNCl4] – Darstellung und Struktur

[Au(Et₂dtc)₂][TcNCl₄] – Synthesis and Structure [Au(Et₂dtc)₂][TcNCl₄] (Et₂dtc^– = N,N‐diethyldithiocarbamate) is formed by the reaction of [Au(CO)Cl] with [TcN(Et₂dtc)₂] in dichloromethane. The solid state structure of the compound is characterized by a large triclinic unit cell (space group, P1, a = 9.422(2), b = 22.594(5), c = 32.153(7) Å, α = 72.64(1), β = 85.19(1), γ = 86.15(1)°, Z = 12) and shows an unusual arrangement due to long‐range contacts between the technetium atoms and sulfur atoms of the [Au(Et₂dtc)₂]⁺ units (3.45–3.56 Å) which assemble two anions and one cation to {[TcNCl₄][Au(Et₂dtc)₂] · [TcNCl₄]}^– moieties.     

[Tc(NBCl2Ph)Cl2(Me2PhP)3] und [Tc(NBH3)Cl2(Me2PhP)3] – die ersten Technetium‐Komplexe mit Nitridobrücken zwischen Technetium und Bor

[Tc(NBCl₂Ph)Cl₂(Me₂PhP)₃] and [Tc(NBH₃)Cl₂(Me₂PhP)₃] – the First Technetium Complexes with Nitrido Bridges between Technetium and Boron [TcNCl₂(Me₂PhP)₃] reacts with BCl₂Ph or BH₃ · THF at low temperatures under formation of complexes containing a nitrido bridge between technetium and boron. The compounds are instable and decompose at room temperature under cleavage of the N–B bonds. The pale‐purple [Tc(NBCl₂Ph)Cl₂(Me₂PhP)₃] crystallizes in the orthorhombic space group Fdd2. The Tc≡N bond is only slightly lengthened by the formation of the N–B bond of 1.564(4) Å. However, a considerable lengthening of the Tc–Cl bond in trans position to the nitrido ligand is observed which can be attributed to an decreasing of the structural trans influence of the nitrido moiety. A similar structural feature can be found in [Tc(NBH₃)Cl₂(Me₂PhP)₃] which is the first structurally characterized transition metal complex containing a nitrido bridge to unsubstituted borane.     

Gemischtligandkomplexe des Technetiums. XVI. Darstellung und Struktur von (1,2-Dicyanoethen-1,2-dithiolato)bis(dimethylphenylphosphan)nitridotechnetium (V), [TcN(Me2PhP)2(mnt)]

Mixed-Ligand Complexes of Technetiums. XVI Synthesis and Structure of (1,2-Dicyanoethene-1,2-dithiolato)bis(dimethylphenylphosphine)nitridotechnetium(V), [TcN(Me₂PhP)₂(mnt)] [TcN(Me₂PhP)₂(mnt)] is formed from [TcNCl₂(Me₂PhP)₃] and one equivalent of the sodium salt of 1,2-dicyanoethene-1,2-dithiolate (Na₂mnt). The same reaction yields [TcN(mnt)₂]^2?, when a large excess of the ligand and long reaction periods are applied. The complex anion can be isolated as tetraalkylammonium or tetraphenylarsonium salts. [TcN(Me₂PhP)₂(mnt)] crystallizes in the triclinic space group P1 (a = 10.000(5), b = 14.182(6), c = 17.77(1) Å, α = 98.77(3), β = 103.77(3), γ = 104.55(3)°; Z = 4). The coordination sphere is a square pyramid with the sulfur and phosphorus atoms as basal plane. Tc is situated out of this plane by 0.56 Å towards the nitrido ligand.     

Reactions of Rhenium and Technetium Nitrido Complexes with ER3 Fragments (E = B,Ga, Al,C, P; R = H,Alkyl, Aryl)

Terminal ‘N^3—’ ligands in rhenium and technetium nitrido complexes are sufficiently nucleophilic to react with Lewis acids under formation of nitrido‐bridged compounds. The reactivity of the nucleophilic centre and the nature of the formed compounds are strongly dependent on the Lewis acid and the composition of the metal complex used. Air‐stable compounds with Re≡N‐ER₃ bridges are formed when ER₃ is BR₃ (R = H, Cl, Br, Ethyl, Phenyl, C₆F₅), BCl₂Ph, GaCl₃, CPh₃⁺, or PPh₃. The six‐co‐ordinate rhenium(V) complexes [ReNX₂(PMe₂Ph)₃] (X = Cl, Br), [ReN(X)(Et₂dtc)(PMe₂Ph)₂] (Et₂dtc^— = diethyldithiocarbamate) and [ReN(Et₂dtc)₂(PMe₂Ph)] have been proved to be excellent starting materials for this type of reactions, whereas the five‐co‐ordinate precursors [ReNCl₂(PPh₃)₂], [ReN(Et₂dtc)₂], [ReN{Ph₂P(S)NP(S)Ph₂}₂] or [ReNCl₄]^— only react with the most reactive Lewis bases of the examples mentioned above such as BCl₂Ph or B(C₆F₅)₃. The rhenium‐nitrido bond lengths remain almost unchanged by the adduct formation, whereas a significant decrease of the trans‐influence of the nitrido complexes has been observed as can be seen by a shortening of the corresponding bond lengths or dimerization of five‐co‐ordinate precursors. Electrophilic attack of the Lewis acid to a donor atom of the equatorial co‐ordination sphere of the rhenium complex results in the formation of ‘underco‐ordinate’ metal centres which resemble to di‐, tri or tetrameric units with asymmetric nitrido bridges between each two rhenium atoms. EPR spectroscopy is an excellent tool to reflect the formation of nitrido bridges at the paramagnetic (d¹) [ReNX₄]^— core (X = F, Cl, Br, NCS). The spectral parameters derived for the products of reactions of [ReNCl₄]^— with various boron compounds indicate an increase of the covalency of the equatorial Re‐L bonds as a consequence of the formation of a nitrido bridge. The tendency for the formation of nitrido bridges with Lewis acids is significantly lower for technetium compounds compared to their rhenium analogues. Only a few examples with BH₃ and BPhCl₂ have been established.     

Gemischtligandkomplexe des Technetiums. XV. Zur Reaktion von [TcNCl2(Me2PhP)3] mit Dialkyldithiocarbamaten und N,N-Dialkylthiocarbamoylbenzamidinen

Mixed-ligand Complexes of Technetium. XV. The Reaction of [TcNCl₂(Me₂PhP)₃] with Dialkyldithiocarbamates and N,N-Dialkylthio-carbamoylbenzamidines [TcN(Cl)(Me₂PhP)₂(Et₂dtc)], [TcN(Me₂PhP)(Et₂dtc)₂], and [TcN(Et₂dtc)₂] can be prepared by stepwise ligand exchange reactions starting from dichlorotris(dimethylphenylphosphine)nitridotechnetium(V), [TcNCl₂(Me₂PhP)₃], and diethyldithiocarbamate. In contrast to this, only one intermediate, [TcN(Cl)(Me₂PhP)₂(HEt₂tcb)], could be isolated during the reaction with N,N-Diethlthiocarbamoylbenzamidine, which yields the bis chelate [TcN(HEt₂tcb)₂]. [TcN(Me₂PhP)(Et₂dtc)₂] crystallizes in the monoclinic space group P2₁/c; a = 17.369(5) Å, b = 15.024(1) Å, c = 9.906(3) Å, β = 76.47(1)º, Z = 4. The phosphine is coordinated equatorially. The multiply bonded nitrogen ligand (Tc? N(1) 1.624(3) Å) strongly labilizes the trans positioned donor atom (distance Tc? S(4) 2.826(1) Å). [TcN(HEt₂tcb)₂] crystallizes in the triclinic space group P1 with a = 9.749(4) Å, b = 11.264(4) Å, c = 12.359(4) Å, α = 75.34(2)º, β = 79.69(2)º, γ = 87.55(2)º, Z = 2. The metal is five-coordinate with the nitrido donor atom occupying the apex of a square pyramid. It's basal plane is formed by the cis-coordinated chelate ligands. The technetium is situated over the basal plane by about 0.6 Å. The Tc?N distane was found to be 1.610(5) Å.     

Ein Beitrag zu Rhenium(II)‐, Osmium(II)‐ und Technetium(II)‐Thionitrosylkomplexen vom Typ [M(NS)Cl4py]—: Darstellung,Strukturen und EPR‐Spektren

A Contribution to Rhenium(II)‐, Osmium(II)‐, and Technetium(II)‐Thionitrosyl‐Complexes: Preparation, Structures, and EPR‐Spectra The reaction of [Re^VINCl₄]^— and [Os^VINCl₄]^— with S₂Cl₂ leads to the formation of the thionitrosyl complexes [M^II(NS)Cl₄]^— (M = Re, Os) which could not be isolated as pure compounds. Addition of pyridine to the reaction mixture results in the formation of the stable compounds trans‐(Ph₄P)[Os^II(NS)Cl₄py], trans‐(Hpy)[Os^II(NS)Cl₄py], trans‐(Ph₄P)[Re^II(NS)Cl₄py], and cis‐(Ph₄P)[Re^II(NS)Cl₄py]. The crystal structure analyses show for trans‐(Ph₄P)[Os^II(NS)Cl₄py] (monoclinic, P2₁/n, a = 12.430(3)Å, b = 18.320(4)Å, c = 15.000(3)Å, β = 114.20(3)°, Z = 4), trans‐(Hpy)[Os^II(NS)Cl₄py] (monoclinic, P2₁/n, a = 7.689(1)Å, b = 10.202(2)Å, c = 20.485(5)Å, β = 92.878(4)°, Z = 4), trans‐(Ph₄P)[Re^II(NS)Cl₄py] (triclinic, P1¯, a = 9.331(5)Å, b = 12.068(5)Å, c = 15.411(5)Å, α = 105.25(1)°, β = 90.23(1)°, γ = 91.62(1)°, Z = 2), and cis‐(Ph₄P)[Re^II(NS)Cl₄py] (monoclinic, P2₁/c, a = 10.361(1)Å, b = 16.091(2)Å, c = 17.835(2)Å, β = 90.524(2)°, Z = 4) M‐N‐S angles in the range 168‐175°. This indicates a nearly linear coordination of the NS ligand. The metal atom is octahedrally coordinated in all cases. The rhenium(II) thionitrosyl complexes (5d⁵ “low‐spin” configuration, S = 1/2) are studied by EPR in the temperature range 295 > T > 130 K. In addition to the detection of the complexes formed during the reaction of [Re^VINCl₄]^— with S₂Cl₂ EPR investigations on diamagnetically diluted powders and single crystals of the system (Ph₄P)[Re^II/Os^II(NS)Cl₄py] are reported. The ^{185, 187}Re hyperfine parameters are used to get information about the spin‐density distribution of the unpaired electron in the complexes under study. [Tc^VINCl₄]^— reacts with S₂Cl₂ under formation of [Tc^II(NS)Cl₄]^— which is not stable and decomposes under S₈ elimination and rebuilding of [Tc^VINCl₄]^— as found by EPR monitoring of the reaction.     

Exploring the nitrosyl-approach: “Re(CO)2(NO)”- and “Tc(CO)2(NO)”-complexes provide new pathways for bioorganometallic chemistry

Nitrosylation reactions are rare in the context of low valent Re(I)- and Tc(I)-tricarbonyl complexes so far. We herein describe a method for the conversion of a “M(CO)₃-moiety” (M = Re, Tc) into a dicarbonyl-nitrosyl moiety “M(CO)₂NO”, the synthesis of important precursor complexes and intermediates and possible applications for this new kind of Re- and Tc-chemistry.The behavior of the complex [ReCl₃(CO)₂(NO)]⁻ in water was studied in detail and compared to that of [ReCl₃(CO)₃]²⁻. Contrary to the conversion of [ReCl₃(CO)₃]²⁻ to the mixed aquo-carbonyl complex [Re(OH₂)₃(CO)₃]⁺ in water, one chloride remains initially bound to the metal center in the dicarbonyl-nitrosyl complex, making [ReCl(OH₂)₂(CO)₂(NO)]⁺ the main species for further reactions. In this context, we isolated and characterized the complex [Re(μ₃-O)(CO)₂(NO)]₄. Examples of complexes with different bi- and tridentate ligands based on ReCl₃(CO)₂(NO)]⁻ are discussed.For the development of potential new radiopharmaceuticals we also adapted the nitrosylation technique to the n.c.a. level with ^99mTc. [^99mTc(OH₂)₃(CO)₃]⁺ served as starting material to form a ^99mTc(CO)₂(NO)-core. Labelling reactions with ligands such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and diethylenetriamine pentaacetic acid (DTPA) were performed, resulting in the complexes [^99mTc(IDA)(CO)₂(NO)], [^99mTc(NTA)(CO)₂(NO)] and [^99mTc(DTPA)(CO)₂(NO)]. In this way, the “nitrosyl-approach” adds a new and challenging synthetic tool to the already established organometallic chemistry of Re- and Tc-tricarbonyl complexes.     

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 (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.