[Tc(OH₂)(CO)₃(PPh₃)₂]⁺: A Synthon for Tc(I) Complexes and Its Reactions with Neutral Ligands

Abstract

A scalable synthesis of the novel and highly reactive [Tc(OH 2 )(CO) 3 (PPh 3 ) 2 ] + cation is described. The ligandexchange chemistry of this compound with neutral ligands coordinating through C, N, O, S, Se, and Te has been explored systematically. The complexes either retain the original mer-trans tricarbonyl core under exclusive exchange of the aqua ligand or form dicarbonyl complexes by thermal decarbonylation. Ligand exchange reactions starting from [Tc(OH 2 )(CO) 3 (PPh 3 ) 2 ] + proceed under mild conditions and are generally almost quantitative. Some of the formed complexes are remarkably stable and inert, while others provide products with one labile ligand for further reactions. The derived complexes of the type [Tc(L)-(CO) 3 (PPh 3 ) 2 ] + and [Tc(L) 2 (CO) 2 (PPh 3 ) 2 ] + represent an interesting opportunity for the development of 99m Tc complexes with potential use in radiopharmacy. The ready displacement of the aqua ligand highlights the synthetic value of [Tc(OH 2 )(CO) 3 (PPh 3 ) 2 ] + as a reactive entry point for further studies in the little explored field of the organometallic chemistry of technetium.

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

“…mer , trans -[Tc­(OH 2 )­(CO) 3 (PPh 3 ) 2 ]­(BF 4 ) and the nonprotic synthon mer , trans -[Tc­(SMe 2 )­(CO) 3 (PPh 3 ) 2 ]­(BF 4 ) show a strong tendency to react with halides and form the corresponding technetium­(I) halido complexes [Tc­(X)­(CO) 3 (PPh 3 ) 2 ] (X = Cl, Br, or I). Such a reaction pathway was also observed during reactions with corresponding Grignard reagents, where no alkyl or aryl products could be obtained . Such undesired side reactions could be avoided by using methyllithium and phenyllithium.…”

“…In recent communications, we described the syntheses of a number of complexes with the mer , trans -{Tc­(CO) 3 (PPh 3 ) 2 } + or cis , trans -{Tc­(CO) 2 (PPh 3 ) 2 } + motifs, which were derived from reactions between the hydrido complex [TcH­(CO) 3 (PPh 3 ) 2 ] and Brønsted acids or the cationic technetium­(I) complex mer , trans -[Tc­(OH 2 )­(CO) 3 (PPh 3 ) 2 ]­(BF 4 ) ( 1 ) and a variety of neutral and anionic ligands. , The water ligand of the mer , trans -[Tc­(OH 2 )­(CO) 3 (PPh 3 ) 2 ] + cation is labile, and thus, the complex acts as a functional analogue of the highly reactive 16-electron metallo-Lewis acid {Tc­(CO) 3 (PPh 3 ) 2 } + enabling the isolation of complexes with C, N, O, S, Se, Te, Cl, Br, and I donor atoms. , A “nonprotic” alternative to aqua complex 1 can be prepared by a reaction of compound 1 with dimethyl sulfide. The resulting cationic complex [Tc­(SMe 2 )­(CO) 3 (PPh 3 ) 2 ]­(BF 4 ) ( 2 ) can be obtained via a scalable reaction in high yields (Scheme ).…”

Stand der Technik in der Radiopharmazie

“…Die direkte Reduktion von Pertechnetat mit Natriumborhydrid hat den Zugang zu einem neuen metallorganischen Kern ermöglicht, [Tc I (CO) 3 (OH 2 ) 3 ] + , der sich als äußerst wirksame Einheit für neue potenzielle SPECT-Radiopharmazeutika erwiesen hat. Die d 6 -Niedrigspin Elektronenkonfiguration von Technetium(I) macht die [Tc(CO) 3 ] + -Einheit kinetisch inert, ist einfach herzustellen und chemisch robust 25 26 .…”

Synthesis of [99Tc(CO)6]+ Cation under Ambient Conditions

“…However, the majority of papers concerning Tc carbonyls deal with tricarbonyl complexes, as these complexes can be readily prepared from the precursors synthetically accessible at atmospheric pressure: [ 99m Tc(CO) 3 (H 2 O) 3 ] + on the tracer level [1] and [ 99 TcCl 3 (CO) 3 ] 2À on the macroscopic level. [2] Until recently, there were no reports on synthesis of higher technetium carbonyls (CO : Tc > 3) at atmospheric pressure (the compound [ 99 Tc 3 H 3 (CO) 12 ] reported by Alberto et al [3] seems to be the only exception). All the syntheses were performed at high CO pressures, [4][5][6][7][8] which does not comply with the modern safety requirements adopted in the majority of developed countries.…”

“…Carbonyls are typical coordination compounds of many d‐elements, and Tc is not an exception. However, the majority of papers concerning Tc carbonyls deal with tricarbonyl complexes, as these complexes can be readily prepared from the precursors synthetically accessible at atmospheric pressure: [ 99m Tc(CO) 3 (H 2 O) 3 ] + on the tracer level [1] and [ 99 TcCl 3 (CO) 3 ] 2− on the macroscopic level [2] . Until recently, there were no reports on synthesis of higher technetium carbonyls (CO : Tc>3) at atmospheric pressure (the compound [ 99 Tc 3 H 3 (CO) 12 ] reported by Alberto et al [3] .…”