New Organometallic Technetium Complexes in High and Low Oxidation States

Alberto, Roger; Herrmann, Wolfgang A.; Bryan, Jeff C.; Schubiger, P. A.; Baumgärtner, F.; Mihalios, Dimitrios

doi:10.1524/ract.1993.63.special-issue.153

Cited by 13 publications

(8 citation statements)

References 22 publications

(23 reference statements)

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“…The importance of basic organometallic chemistry of elements as the fundament for a rational chemical design is indisputable in many disciplines such as surface chemistry, material science, catalysis, bioorganometallic chemistry, and medicinal chemistry. While the organometallic chemistry of most elements steeply develops to reveal an astonishing complexity of structure, binding, and reactivity, − that of technetium has mostly been developed around carbonyl, − isonitrile, − arene, − and cyclopentadienyl ligands. − Recently, some N-heterocyclic carbene (NHC) complexes of technetium have also been studied. − The related research is mainly attributed to the surprising stability of the resulting complexes containing Tc–C bonds and their potential for applications in radiopharmaceutical solutions.…”

Section: Introductionmentioning

confidence: 70%

Unlocking Air- and Water-Stable Technetium Acetylides and Other Organometallic Complexes

Jungfer

Abram

2022

Inorg. Chem.

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The first technetium complexes containing anionic alkynido ligands in an end-on coordination mode have been prepared by using the nonprotic, cationic precursor mer,trans-[Tc(SMe2)(CO)3(PPh3)2]+. This cation acts as a functional analogue of the highly reactive 16-electron metallo Lewis acid {Tc(CO)3(PPh3)2}+ in reactions with alkynes, acetylides, and other organometallic reagents. Such reactions give a variety of organometallic technetium complexes in excellent yields and enable the preparation of [Tc(CH3)(CO)3(PPh3)2], [Tc(Ph)(CO)3(PPh3)2], [Tc(Cp)(CO)2(PPh3)], [Tc(CCH2CH2CH2O)(CO)3(PPh3)2]+, [Tc(CCH2CH2CH2CH2O)(CO)3(PPh3)2]+, [Tc(CC–H)(CO)3(PPh3)2], [Tc(CC–Ph)(CO)3(PPh3)2], [Tc(CC– t Bu)(CO)3(PPh3)2], [Tc(CC– n Bu)(CO)3(PPh3)2], [Tc(CC–SiMe3)(CO)3(PPh3)2], and [Tc{CC–C6H3(CF3)2}(CO)3(PPh3)2]. The bonding situation in the alkynyl complexes is compared to that in corresponding alkyl- and arylnitrile and -isonitrile complexes. [Tc(NC–Ph)(CO)3(PPh3)2](BF4), [Tc(CN–Ph)(CO)3(PPh3)2](BF4), [Tc(NC– t Bu)(CO)3(PPh3)2](BF4), and [Tc(CN– t Bu)(CO)3(PPh3)2](BF4) were prepared in high yields by ligand exchange reactions starting from mer,trans-[Tc(OH2)(CO)3(PPh3)2](BF4). The novel complexes were characterized by single-crystal X-ray diffraction and spectroscopic methods. In particular, 99Tc nuclear magnetic resonance spectroscopy proved to be an invaluable and sensitive tool for the characterization of the complexes. Density functional theory calculations strongly suggest similar bonding situations for the related alkynyl, nitrile, and isonitrile complexes of technetium.

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Section: Introductionmentioning

confidence: 70%

Unlocking Air- and Water-Stable Technetium Acetylides and Other Organometallic Complexes

Jungfer

Abram

2022

Inorg. Chem.

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“…These frequencies indicate much weaker donation of nota in comparison to the cationic [Re(tacn)(CO) 3 ] + (2014 and 1881 cm –1 ) . The 99 Tc NMR of compound [ 4 ] 2‑ showed a broad signal (Δν 1/2 = 1320 Hz) at −912.3 ppm, shifted toward lower field as compared to [ 99 Tc(tacn)(CO) 3 ] + (−1012 ppm) . In contrast to the 13 C NMR spectrum of the Re compound [ 3 ], which shows a signal for the carbonyl carbon atoms at 196.23 ppm, the 13 C NMR signal of the Tc compound [ 4 ] cannot be observed in the 13 C NMR spectrum, due to the scalar coupling to the 99 Tc quadrupole nucleus (spin 9 / 2 ).…”

Section: Resultsmentioning

confidence: 94%

“…21 The 99 Tc NMR of compound [4] 2showed a broad signal (Δν 1/2 = 1320 Hz) at −912.3 ppm, shifted toward lower field as compared to [ 99 Tc(tacn)(CO) 3 ] + (−1012 ppm). 22 In contrast to the 13 C NMR spectrum of the Re compound [3], which shows a signal for the carbonyl carbon atoms at 196.23 ppm, the 13 C NMR signal of the Tc compound [4] cannot be observed in the 13 C NMR spectrum, due to the scalar coupling to the 99 Tc quadrupole nucleus (spin 9 / 2 ). The weaker coordination properties of nota•3H in comparison to the tacn ligand are evident from the X-ray crystal structures of Na 2 [Re(nota)(CO) 3 ] (Na 2 [3]) and [ 99 Tc(nota•3H)(CO [3]) can be found in the Supporting Information (Table SI1).…”

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confidence: 95%

Combining Bifunctional Chelator with (3 + 2)-Cycloaddition Approaches: Synthesis of Dual-Function Technetium Complexes

et al. 2012

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A new concept for the synthesis of dual-functionalized technetium (Tc) compounds is presented, on the basis of the reactivity of fac-{Tc(VII)O(3)}(+) complexes. The concept combines the "classical" bifunctional chelator (BFC) approach with the new ligand centered labeling strategy of fac-{TcO(3)}(+) complexes with alkenes ((3 + 2)-cycloaddition approach). To evidence this concept, fac-{(99)TcO(3)}(+) model complexes containing functionalized 1,4,7-triazacyclononane (tacn) derivatives N-benzyl-2-(1,4,7-triazonan-1-yl)acetamide (tacn-ba) and 2,2',2″-(1,4,7-triazonane-1,4,7-triyl)triacetic acid (nota·3H) were synthesized and characterized. Whereas [(99)TcO(3)(tacn-ba)](+) [2](+) can be synthesized following a established oxidation procedure starting from the Tc(V) complex [(99)TcO(glyc)(tacn-ba)](+) [1](+), a new synthetic pathway for the synthesis of [(99)TcO(3)(nota)](2-) [5](2-) had to be developed, starting from [(99)Tc(nota·3H)(CO)(3)](+) [4](+) and using sodium perborate tetrahydrate (NaBO(3)·4H(2)O) as oxidizing reagent. While [(99)TcO(3)(nota)](2-) [5](2-) is a very attractive candidate for the development of trisubstituted novel multifunctional radioprobes, (3 + 2)-cycloaddition reactions of [(99)TcO(3)(tacn-ba)](+) [2](+) with 4-vinylbenzenesulfonate (styrene-SO(3)(-)) demonstrated the suitability of monosubstituted tacn derivatives for the new mixed "BFC-(3 + 2)-cycloaddition" approach. Kinetic studies of this reaction lead to the conclusion that the alteration of the electronic structure of the nitrogen donors by, e.g., alkylation can be used to tune the rate of the (3 + 2)-cycloaddition.

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“…The catalytic cycle presumably runs through a glycolate complex similar to (34) (Scheme 12). 49 Tris(arylimido) alkyl complexes are much easier to prepare, and are more stable and less volatile than the isoelectronic trioxo compound (32). Tris(arylimido)trimethylsiloxytechnetium(VII) reacts with Grignard reagents to form [Tc(NAr) 3 R] (35) (Ar = 2,6-diisopropylphenyl, 2,6-dimethylphenyl; R = Me, Et, T I '-allyl, CH 2 TMS) (Equation (4) 4 (u-NAr) 2 ] (Ar = 2,6-dimethylphenyl) (Scheme 13).…”

Section: Scheme 12mentioning

confidence: 99%

“…Substitution at axial sites is preferred under thermolytic conditions, and substitution at both axial and equatorial sites was observed under photolysis. PPh 3 , CO; ii, PPh3 , CO; H i , [E^E 2 ]"; iv, lithium salt of t h e Schiff base N-o-hydroxybenzylidene-2-thiazolylimine; v, 1,4,7-triazacyclononane; vi, K[HBpz 3 ]Scheme 3Several synthetically useful precursors for technetium(I) carbonyl compounds containing nitrogen and/or phosphorus donor ligands have been reported 49. ' 62 " 4 The most practical precursors are those described by Alberto et al, which are prepared f r o m common starting materials such as [TcOJ" or [TcOCl 4 ]~ under mild conditions and do not involve the intermediate formation o f volatile compounds.…”

mentioning

confidence: 99%