Tc Complexes Research Articles

EPR studies of technetium complexes in frozen solution

Analysis of the EPR spectra of Tc complexes in frozen solution has given information about the behaviour of these complexes not readily obtainable by other means. In particular, spectral simulations have enabled the determination of the quadrupole interaction parameter,Q, and thus to the evaluation of subtle electronic effects.

Synthesis and crystal structure of mixed-ligand Tc(I) complexes, with dimethylphenylphosphine and t-butylisonitrile

The reaction of mer-Tc(PMe2Ph)3Cl3 with t-butylisonitrile (TBI) in ethanol solution produced, depending on the experimental conditions, two compounds which were identified as trans-[Tc(PMe2Ph)2(TBI)4]+ and [Tc(PMe2Ph)(TBI)5]+. The proton NMR spectra of the two compounds showed that the complexes are quite pure. The two compounds were studied by X-ray diffraction methods. Trans-[Tc(PMe2Ph)2(TBI)4]PF6 (I) is monoclinic, space group C2/c with a = 17.933(9), b = 9.878(6), c = 25.675(18) Å and β = 105.29(5)°. The Tc atom is located on a center of inversion, while P (of PF6−) is located on a two-fold axis. [Tc(PMe2Ph)(TBI)5]PF6 (II) belongs to the tetragonal P4/n space group with a = 29.561(11), c = 10.614(5) Å. The geometry around the Tc atom is octahedral with TcC bonds from 2.036(15) to 2.045(13) Å for I and from 1.996(19) to 2.064(18) Å for II. The TcP bond distances are quite short for I (2.389(3) Å) and slightly longer in crystal II (2.403(6) Å). The short TcP bonds are caused by the presence of multiple bonding which increases as the oxidation state of Tc decreases, while the slightly longer TcP bond distance observed for crystal II is ascribed to a large trans influence of the isonitrile ligands, greater than the one of phosphines.

Cationic [99mTcIII(DIARS)2(SR)2]+ Complexes as Potential Myocardial Perfusion Imaging Agents (DIARS = o-phenylenebis(dimethylarsine); SR- = thiolate)

Reduction-substitution reactions on [99mTcO4]- with both o-phenylenebis(dimethylarsine) (DIARS) and various thiols produce a series of monocationic [99Tc(DIARS)2(SR)2]+ complexes. Addition of [99gTcO4]- to the above reaction mixtures allows the characterization of the "carrier-added" complexes by means of reverse-phase high-performance liquid chromatography with radiometric and optical detection systems. The identity of the [99mTc(DIARS)2(SR)2]+ complexes is confirmed by fast atom bombardment mass spectroscopy; equivalence of the [99gTc(DIARS)2-(SR)2]+ and [99mTc(DIARS)2(SR)2]+ species is demonstrated by identical HPLC retention times. All the [99mTc(DIARS)2(SR)2]+ complexes tested accumulate in the myocardium of Sprague-Dawley rats with an average uptake of 1.5-2.0% of injected dose/g at 30 min. Thus, as designed, these nonreducible Tc(III) complexes do not exhibit the rapid myocardial washout observed for reducible Tc(III) complexes. These [99mTc(DIARS)2(SR)2]+ complexes also exhibit an initially high liver uptake, but the presence of ether groups within the thiolate ligands causes this liver uptake to decrease over time without affecting the heart uptake, thereby improving the heart/liver ratio.

The synthesis, characterization and substitution reactions of the mixed ligand technetium(I) nitrosyl complex trans—trans-[(NO)(NCCH3)Cl2(PPh3)2Tc

The techneium—nitrosyl complex n-Bu4N[Tc(NO)Cl4] reacts with excess triphenylphospine in refluxing acenotonitrile to give the Tc(I) mixed ligand complex [Tc(NO)Cl2(PPh3)2NCCH3 in good yield. The IR spectrum of this complex displays an absorption at 1690 cm−1 which is associated with v(NO). The FAB(+) mass spectrum shows the fragment of 723 mz which corresponds to [Tc(NO)Cl2(PPh3)2]+ which is generated from the loss of the acetonitrile ligand. The 1HNMRR spectrum of this species displays equivalent trans-triphenylphosphine ligands; however because of the liability of the acetnitrile ligand, two signals are observed from the coordinated and dissociated acetonitrile protons. The analogous reaction in the methanol gives the methanol adduct [Tc(NO)Cl2(PPh3)2HOCH3]. When pyridine is employed as solvent, the tris-pyridine complex [Tc(NO)Cl2(py)3] is isolated as the major product, with no phosphine coordination. The IR spectrum of this complex shows an absorption at 1688 cm−1 which is associated with v(NO). The FAB(+) mass spectrum shows the fragment of 436 m/z which corresponds to the parent ion [Tc(NO)Cl2(py)3]+. This diamagnetic Tc(I) complex displays a well resolved, narrow-lined 1H NMR spectrum. Crystal data for [Tc(NO)Cl2(py)3]∗d2CH3CN: monoclinic space group C2/c, (No. 15), a = 19.182(1), b = 10.8725(8), c = 11.9371(8) A, β = 116.580(7)°,V = 2226.5(6) A3, with Dcalc = 1.543 g cm−3 to give Z = 4. structure solution based on 2689 reflections converged at R = 0.025, Rw = 0.030, GOF = 1.41. The reaction chemistry of the acetonitrile adduct [Tc(NO)Cl2(PPh3)2NCCH3] with pyridine, 3,5-lutidine, bipyridine, phenanthroline and terpyridine is also presented.

Technetium(III), Technetium(II), and Technetium(I) Complexes with Pyridine Ligands. Can Pyridine Coordination Stabilize the Low Oxidation States of Technetium?

The substitution chemistry of TcCl(3)(PPh(3))(2)(CH(3)CN) is rather facile relative to the analogous rhenium complex, since both the chloride and phosphine ligands are easily substituted for various pyridine ligands. Consequently a series of Tc(III) complexes with amine, pyridine, and polypyridyl ligands were prepared and characterized by (1)H NMR and cyclic voltammetry. In addition, the zinc reduction of TcCl(4)(py)(2) in the presence of pyridine results in TcCl(2)(py)(4). Structural and spectroscopic data indicate that this Tc(II) complex exhibits strong metal-pyridine interactions characteristic of low-valent amine complexes of Re(II) and Os(II). For example, a decrease of 0.04 and 0.06 Å is observed for the trans-Tc-N bond length in TcCl(2)(py)(4 )relative to mer-TcCl(3)(pic)(3) and [TcCl(2)(py)(3)(PPh(3))](+), respectively. This ability of pyridine to function both as a strong sigma-donor and moderate pi-acid ligand has resulted in the isolation of technetium complexes in various oxidation states with similar ligand environments. As a result, a structural comparison of [TcCl(2)(py)(3)(PPh(3))](+), TcCl(2)(py)(4), TcCl(tpy)(py)(2), and other known Tc(III) and Tc(II) pyridine complexes is presented. Crystals of [TcCl(2)(py)(3)(PPh(3))]PF(6) are triclinic, with space group P&onemacr;, Z = 2, and lattice parameters a = 12.677(4) Å, b = 13.064(4) Å, c = 13.103(5) Å, alpha = 110.14(3) degrees, beta = 101.12(3) degrees, gamma = 96.61 degrees, V = 1959 Å(3), and R = 0.0615 (R(w) = 0.1148). Crystals of TcCl(2)(py)(4) are tetragonal, with space group I4(1)/acd, Z = 8, and lattice parameters a = 15.641(4) Å, c = 16.845(6) Å, V = 4121 Å(3), and R = 0.0373 (R(w) = 0.0290). Crystals of TcCl(tpy)(py)(2) are orthorhombic, with space group C222(1), Z = 4, and lattice parameters a = 9.359(3) Å, b = 16.088(6) Å, c = 18.367(4) Å, V = 2765 Å(3), and R = 0.0499 (R(w) = 0.0599).

Metal−Metal Multiply-Bonded Complexes of Technetium. 4.1 Photodissociation of the Tc≡Tc Triple Bond in [Tc2(CH3CN)10][BF4]4

Efficient (i.e., essentially quantitative) photolysis of multiple bonds, including metal-metal multiple bonds, neither is to be generally expected nor has been observed, with the sole exception of photocleavage of the quadruple bond in [Re{sub 2}Cl{sub 8}]{sup 2-}, which occurs in acetonitrile and affords ReCl{sub 3}(CH{sub 3}CN){sub 3} as the final product. We report here a striking example of such a process, wherein the [(CH{sub 3}CN){sub 5}Tc=Tc(CH{sub 3}CN){sub 5}]{sup 4+} ion is photolyzed in CH{sub 3}CN to give two [Tc(CH{sub 3}CN){sub 6}]{sup 2+} ions in nearly quantitative isolated yield. A plausible idea (admittedly not yet supported experimentally) is that photoexcitation produces a mixed-valent, charge-separated Tc(I)-Tc(III) complex that undergoes metal-metal bond cleavage to produce mononuclear Tc(I) and Tc(III) nitrile complexes. These mononuclear species could then undergo a comproportionation reaction to yield 2 consistent with the observed electrochemical potentials of the Tc(I)/Tc(II) and Tc(II)/Tc(III) redox couples. 17 refs., 2 figs.

Thrombus Imaging Using Technetium-99m-Labeled High-Potency GPIIb/IIIa Receptor Antagonists. Chemistry and Initial Biological Studies

Platelet-specific compounds which are radiolabeled with gamma-emitting radionuclides may be particularly useful for the noninvasive in vivo detection of thrombi. The synthesis of peptides which are potent inhibitors of platelet aggregation and which contain a chelator for the radionuclide technetium-99m are described. The target compounds were designed such that stable, oxotechnetium(V) species could be prepared where the site of metal coordination was well defined. A strategy was employed where the pharmacophore-Arg-Gly-Asp-(RGD), or RGD mimetic, was constrained in a ring which was formed by the S-alkylation of a cysteine residue with an N-terminal chloroacetyl group. Binding affinities were enhanced by the replacement of arginine with the arginine mimetics S-(3-aminopropyl)cysteine and 4-amidinophenylalanine. Further enhancements could be obtained by the synthesis of oligomers which contained two or more rings containing receptor binding regions. The increase in binding affinity seen was more than that expected from a simple stoichiometric increase of pharmacophore. The most potent compounds described had IC50s of approximately 0.03 microM for the inhibition of human platelet aggregation. Two of the more potent peptides (P280 and P748) were labeled with technetium-99m and assessed in a canine thrombosis model. The 99m Tc complexes of the peptides prepared in this work hold promise as thrombus imaging agents due to their high receptor binding affinity, ease of preparation, and expected rapid pharmacokinetics.

Novel hexakis(areneisonitrile)technetium(I) complexes as radioligands targeted to the multidrug resistance P-glycoprotein.

Transport substrates and modulators of the human multidrug resistance (MDR1) P-glycoprotein (Pgp) are generally lipophilic cationic compounds, many with substituted aryl moieties. We sought to synthesize aromatic technetium-isonitrile complexes to enable functional detection in vivo of Pgp expression in tissues. A series of substituted aromatic isonitrile analogs were synthesized from their corresponding amines by reaction with dichlorocarbene under phase transfer-catalyzed conditions, and the non-carrier-added hexakis(areneisonitrile)Tc-99m(I) complexes were produced by reaction with pertechnetate in the presence of sodium dithionite. Cellular accumulation in vitro, whole body biodistribution, and the imaging properties of these lipophilic, monocationic organometallic complexes were determined in Chinese hamster lung fibroblasts expressing MDR Pgp, in normal rats, and in rabbits, respectively. For this initial series, verapamil (50 microM), the classical Pgp modulator, significantly enhanced cellular accumulation or displaced binding of Tc complexes of 1b, 1d, 1h, 2a, 2d, 3a, and 3b, indicative of targeted interactions with Pgp. Most complexes, despite their modestly high lipophilicity, were excluded by the blood/brain barrier, and several complexes displayed simultaneously high hepatobiliary and renal excretion in vivo, consistent with the physiological expression pattern of Pgp in these tissues. Selected Tc- and Re-areneisonitrile complexes of this class have potential applicability to the functional imaging and modulation, respectively, of MDR Pgp in human tissues.

Metal carbonyl syntheses XXII. Low pressure carbonylation of [MOCl 4] − and [MO 4] −: the technetium(I) and rhenium(I) complexes [NEt 4] 2[MCl 3(CO) 3

Low pressure carbonylation (1 atm) of [MOCl 4] − or [MO 4] − in the presence of BH 3-tetrahydrofuran and halides X − results in the clean formation of [NEt 4] 2[MX 3(CO) 3] containing monovalent rhenium or technetium (MRe or Tc; X Cl or Br). In the case of the radioactive element technetium this low pressure synthesis is an important progress since potential hazards of traditional high pressure carbonylations are thus avoided. The complex [NEt 4] 2[ReBr 3(CO) 3] crystallizes in the space group P 1 with a = 10.166(2), b = 16.393(4), c = 17.243(5) A ̊ , and α = 69.27(20, β = 86.42(2), γ = 88.61(2) °, Z = 4 and V = 2682(1) A ̊ 3 . [NEt 4] 2[MX 3 (CO) 3] is a versatile precursor compound of other Re(I) and Tc(I) complexes; substitution of the halide ligands by a variety of σ-donor ligands is facile even under mild conditions. Examples include reactions with CN tBu to yield quantitatively TcCl(CN tBu) 2(CO) 3 and with a tetradentate phosphine ligand to yield the dinuclear complex [Re 2Br 2(CO) 6(tetraphos)]. The x-ray structures of both compounds were determined. Dissolution of [NEt 4] 2[MX 3(CO) 3] in water under aerobic conditions results in the unusual organometallic aqua cation [(M(OH 2) 3(CO) 3] +; this species is stable in water for days (IR spectroscopy).

Metal carbonyl syntheses XXII. Low-pressure carbonylation of [MOCl 4] − and [MO 4] −. The technetium(I) and rhenium(I) complexes [NEt 4] 2[MCl 3(CO) 3

Low pressure carbonylation (1 atm) of [MOCl 4] − or [MO 4] − in the presence of BH 3/THF and halides X − results in the clean formation of [NEt 4] 2[MX 3(CO) 3] containing monovalent rhenium or technetium (M = Re, Tc, X = Cl, Br). In the case of the radioactive element technetium this low pressure synthesis is an important progress since the potential hazards of traditional high-pressure carbonylations are thus avoided. The complex [NEt 4] 2[ReBr 3(CO) 3] crystallizes in the space group P-1 with a = 10.166(2), b = 16.393(4), c = 17.243(5) A ̊ and α = 69.27(2), β = 86.42(2), γ = 88.61(2)°, Z = 4, and V = 2682(1) A ̊ 3 . [NEt 4] 2[MX 3(CO) 3] is a versatile precursor compound of other Re(I) and Tc(I) complexes: substitution of the halide ligands by a variety of σ-donor ligands is facile even under mild conditions. Examples include reactions with Cn tBu to yield quantitatively TcCl(CN tBu) 2(CO) 3 and with a tetradentate phosphine ligand to yield the dinuclear complex [Re 2Br 2(CO) 6(tetraphos)]. The X-ray structures of both compounds were determined. Dissolution of [NEt 4] 2[MX 3(CO) 3] in water under aerobic conditions results in the unusual organometallic aqua cation [M(OH 2) 3(CO) 3] +, which species is stable in water for days (IR spectroscopy).

Tc(IV)Cl 4(PPh 3) 2 and Tc(III)Cl 3(CH 3CN)(PPh 3) 2 as precursors of trans dioxo technetium(V) complexes with chelating amines and tetraazamacrocycles

The trans dioxo complexes [TcO 2(L)] + (L = 1,4,8,11-tetraazacyclotetradecane (cyclam), 1,4,8,11-tetraazacyclotetradecane-5-one, 1,4,8,11-tetraazacyclotetradecane-5,7-dione) have been prepared through a new alternative route involving the reaction of excess of the appropriate ligand with the complexes [TcCl 4(PPh 3) 2] and [TcCl 3(CH 3CN)(PPh 3) 2] in CH 3CN solution, at room temperature. The yields of formation of the final products obtained through this new synthetic method (30–55%) are significantly higher than that found in the synthesis of the complex [TcO 2(cyclam)] + (7%) obtained through a previously reported procedure involving pertechnetate reduction by Na 2S 2O 3 in alkaline solution and in the presence of the ligand or by substitution reaction onto the mono-oxo complex [TcOCl 4] −. The new synthetic method was also efficiently applied to the synthesis of the trans dioxo complexes [TcO 2(L′) 2] + (L = enthylenediamine, 1,3-propanediamine) and [Tc 2(tad)] + (tad = 1,5,8,12-tetraazadodecane), containing bidentate and tetradentate chelating amines, giving final yields similar to those obtained using [TcOCl 4] − as starting substrate. These results indicate that the complex [TcCl 4(PPh 3) 2] and [TcCl 3(CH 3CN)(PPh 3) 2] are superior precursors for the synthesis, at macroscopic level, of trans dioxo Tc(V) complexes with tetraazamacrocylic ligands as compared to [TcO 4] − and [TcOCl 4] −. All the complexes have been characterized by elemental analysis, FTIR and mass spectra, and magnetic susceptibility measurements in solution.

Kinetics and Mechanism of Oxygen Exchange and Inversion along the M:O Axis in the Diprotonated and Monoprotonated Dioxotetracyanometalate Complexes of Re(V), Tc(V), W(IV), and Mo(IV)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics and Mechanism of Oxygen Exchange and Inversion along the M:O Axis in the Diprotonated and Monoprotonated Dioxotetracyanometalate Complexes of Re(V), Tc(V), W(IV), and Mo(IV)Andreas Roodt, Johann G. Leipoldt, Lothar Helm, Amira Abou-Hamdan, and Andre E. MerbachCite this: Inorg. Chem. 1995, 34, 3, 560–568Publication Date (Print):February 1, 1995Publication History Published online1 May 2002Published inissue 1 February 1995https://doi.org/10.1021/ic00107a007RIGHTS & PERMISSIONSArticle Views87Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

Structural survey of technetium complexes

The review, with 294 references and 41 figures, reports on the main structural features of 240 Tc complexes whose X-ray crystal structure has been determined during the period 1986–1992. It comprises seven major sections: oxo-; nitrido-; diazenido-, hydrazido- and imido-; Schiff base-; chalcogenide-; pnictide-; nitrosyl- and thionitrosyl-technetium complexes. The survey concludes with two comprehensive tables summarizing some properties of Tc complexes vs. oxidation state.

Molecular and crystal structure of a mixed-phosphine ligand Tc(II) complex, Tc(PMe2Ph)2(DMPE)Cl2

The reaction of Tc(PMe2Ph)3Cl3 with an excess of bis(dimethylphosphino)ethane (DMPE) in ethanol solution produced a yellow compound, which was identified by X-ray diffraction methods as a mixed-ligand Tc(II) complex, Tc(PMe2Ph)2(DMPE)Cl2. The compound crystallizes in the P21/c space group with a = 12.899(6), b = 13.142(8), c = 19.088(9) Å, β = 121.13(3)°, V = 2770(2) Å3, Z = 4, R = 0.061, and Rw = 0.051. The geometry around the Tc atom is octahedral with the chloro ligands trans to each other, while the two PMe2Ph ligands are in cis positions. The Tc—Cl bond distances are 2.431 (5) and 2.431 (5) Å while the Tc—P bond lengths are 2.434(4) and 2.435(4) Å for PMe2Ph and 2.400(4) and 2.398(4) Å for the bidentate DMPE ligand. An increase of multiple bonding of the Tc—P bond, as the oxidation state of Tc decreases, is suggested.

Technetium-99m N,N'-bis(2-mercapto-2-methylpropyl)-2-aminobenzylamine: technetium-99m complexes of a novel bis(aminoethanethiol) ligand.

A new N2S2 ligand system, N,N'-bis(2-mercapto-2-methylpropyl)-2- aminobenzylamine, U-BAT, 1, containing uneven amine groups (two amine groups with different pKa values) for complexing [TcVO]3+, was prepared. The reaction of this novel ligand with [99mTc]pertechnetate, in the presence of stannous tartrate as the reducing agent, produces the neutral and lipid-soluble [99mTc]TcVO(U-BAT), TcS2C15H23N2O, 2. However, when the same reaction was carried out at a higher pH, 9-10, and with 30 min of heating (100 degrees C), a second neutral but more lipid-soluble complex, [99mTc]TcVO(OU-BAT), TcS2C15H21N2O, 3, was isolated. The X-ray crystallography data of the 99Tc complexes show square pyramidal coordination with N2S2 as the base and the Tc = O in the apical position. Compound 3 can be derived from 2 by an oxidation of the ligand to form an imine. After iv injection into rats, the neutral and lipid-soluble technetium-99m complexes showed significant brain uptake, 1.54 and 1.07% dose/organ at 2 min for [99mTc]TcVO(U-BAT) and TcVO(OU-BAT), respectively. The novel Tc chemistry of this new ligand system may provide a useful foundation for designing Tc complexes with a built-in redox mechanism.

Coupled radiometric and electrochemical study of the reduction of TcO 4− ions at a gold electrode in acidic medium (mechanistic aspects of Tc deposition)

The reduction of TcO 4 − ions at a smooth gold electrode was studied in 1 mol dm −3 H 2SO 4 supporting electrolyte using coupled voltammetric and volt-radiometric measurements and steady state measurements. The problems of the existence of parallel pathways leading to the formation of a Tc layer and dissolved Tc(IV) complexes are discussed. A general scheme is suggested for the interpretation of the phenomena.

Reactions of the technetium(V) phenylimido complex [TcX 3(NPh)(PPh 3) 2] with aromatic thiolate ligands (where X=Cl, Br)

The reaction of KTcO 4 with triphenylphosphine and 1-acetyl-2-phenylhydrazine in methanol with HBr gives the Tc(V) phenylimido complex [TcBr 3(NPh)(PPh 3) 2], analogous to the published reaction with HCl. The phenylimido complex reacts with unsubstituted thiophenol and a proton scavenger (R 3N) in methanol to give the Tc(V) oxo complex (R 3NH)[TcO(SPh) 4] in excellent yield. The IR spectrum of this complex shows an absorption at 936 cm −1 associated with v(Tc=O). The Tc(V) complex [TcCl 3(NPh)(PPh 3) 2] reacts with a four-fold excess of the sterically-hindered thiol 2,3,5,6-tetramethylbenzenethiol (TMBTH) and a proton sponge to give the Tc(V) complex [Tc(NPh)(TMBT) 3(PPh 3)]. The IR spectrum of this complex displays an absorption at 1100 cm −1 which is associated with v(TcN). The positive mode fast atom bombardment mass spectrum of this species displays an extensive fragmentation profile, including fragment of 947 m/z, which corresponds to the parent ion [Tc(NPh)(TMBT) 3(PPh 3)] +. The analogous reaction with a five-fold excess of 2,6-dimethylbenzenethiol (DMBTH) and a proton sponge gives the anionic Tc(V) complex (R 3NH)[Tc(NPh)(SAr) 4]. The IR spectrum of this complex displays an absorption at 1100 cm −1 which is associated with v(TcN). The positive mode fast atom bombardment mass spectrum of this anionic species displays an extensive fragmentation profile, including fragments of 998 m/z, which corresponds to {(R 3NH) 2[Tc(NPh)(DMBT) 4]} + and 868 m/z which corresponds to {(R 3NH)[Tc(NPh)(DMBT) 4]} +. The reaction of the Tc(V) complex [TcCl 3(NPh)(PPh 3) 2] with the tetradentate phosphinetrithiol ligand [P(C 6H 4- o-SH) 3], and a proton scavenger in methanol gives the neutral Tc(III) complex [Tc(PPh 3)(PS 3)]. The FAB(+) mass spectrum of this complex shows the parent ion of 716 m/z and the peak associated with the fragment generated by the loss of the triphenylphosphine of 454 m/z. The IR spectrum shows no absorptions in either the region associated with v(TcO) or v(TcN). The 1H NMR spectrum of the diamagnetic Tc(III) complex shows only narrow-line signals associated with the aryl protons.

Technetium-Carbon Multiple Bonds: Synthesis and Structure of Tc(:C:CHPh)Cl(dppe)2 and [Tc(.tplbond.CCH2-t-Bu)Cl(dppe)2

The 16-electron complex TcCl(dppe)[sub 2] reacts with terminal alkynes to form neutral vinylidene complexes of the type Tc(=C=CHR)Cl(dppe)[sub 2] (R = Ph, Me, t-Bu). Treatment of these vinylidene complexes with acid (HBF[sub 4] for R = Ph, HNMe[sub 3]BPh[sub 4] for R = t-Bu) yields the respective terminal carbyne complexes Tc([triple bond]CCH[sub 2]R)-Cl(dppe)[sub 2][sup +] (R = Ph, t-Bu). These vinylidene and carbyne compounds represent the first examples of technetium carbenes or carbynes. X-ray structures of Tc(=C=CHPh)Cl(ddpe)[sub 2] and Tc([triple bond]CCH[sub 2]-t-Bu)Cl(dppe)[sub 2[minus]+] were determined, and the Tc-C bond lengths obtained were 1.861(9) and 1.724(7) A, respectively. 13 refs., 2 figs.

Electrolytic formation of technetium complexes with π-acceptor ligands

Electrolytic reduction of pertechnetate was performed in aqueous solution containing π-acceptor ligands. Cyanide and 1,10-phenanthroline were the selected ligands. In both cases, electrolyses produced a cathodic TcO2 deposit and soluble Tc complexes. When cyanide was the ligand, the complexes formed were [Tc (CN)6]5− and [TcO2 (CN)4]3−. When working with the amine, [Tc (phen)3]2+ and another positively charged species were found after reaction. Results are compared with previous studies with amines, and the usefulness of the electrolytic route to obtain Tc complexes is evaluated.

A new convenient method for the synthesis of mixed-ligand β-diketonato Tc(III) complexes

A new convenient method has been proposed to synthesize mixed-ligand β-diketonato Tc(III) complexes, using the ligand exchange reaction [Tc(acac)2(CH3CN)2]++L−→[Tc(acac)2L]+ +2CH3CN where L is bza, dpm or dbm. The yield was about 30–40%. UV-visible and IR spectra of these complexes were measured. Characteristic features of the compounds were compared with those of the corresponding complexes of ruthenium.