[Tc^I(NO)X(Cp)(PPh₃)] Complexes (X^–= I^–, I₃^–, SCN^–, CF₃SO₃^–, or CF₃COO^–) and Their Reactions

Abstract

Reactions of [Tc(NO)Cl(Cp)(PPh 3 )] with a series of monodentate ligands X − (X − = I − , I 3 − , F 3 CSO 3 − , CF 3 COO − , or SCN − ) result in a ready replacement of the chlorido ligand and the formation of complexes of the general composition [Tc(NO)X(Cp)(PPh 3 )]. Technetium retains its oxidation state "+1" and its pseudotetrahedral coordination environment. [Tc(NO)(SCN)(Cp)(PPh 3 )] is the first technetium complex with an S-coordinated SCN − ligand. The complexes are stable as solids. In solution, however, a slow isomerization of the thiocyanato compound into the thermodynamically more stable isothiocyanato species is observed, while solutions of [Tc(NO)(I 3 )(Cp)(PPh 3 )] undergo an internal oxidation under formation of the technetium(II) complex [Tc(NO)(I) 2 (Cp)]. All products were characterized by elemental analysis, NMR and IR spectroscopy, and X-ray structure analysis. Particularly, 99 Tc NMR spectroscopy proved to be a valuable method for these types of technetium(I) compounds.

Structural and Redox Variations in Technetium Complexes Supported by m-Terphenyl Isocyanides

“…28,42−45 However, particularly in the case of [Tc(NO)Cl 2 (PPh 3 )(CNAr Dipp2 ) 2 ], it is striking that the position within the entire range of Tc I (NO) complexes, which spans from +2000 to −1800 ppm, is close to that of nitrosyl complexes with coligands having no or only weak π-acceptor properties such as halides, H 2 O, and PPh 3 . 45 This is consistent with the CNAr Dipp2 ligands functioning as predominantly σ donors when other strongly π acidic ligands are present and has been observed previously in a series of mixed isocyanide/ carbonyl cobalt complexes. 27 The isocyanide ν(CN) stretch for [Tc(NO)Cl 2 (PPh 3 )(CNAr Dipp2 ) 2 ] (2170 cm −1 ) further supports this view, as it is considerably higher in energy that that of free CNAr Dipp2 (2124 cm −1 ).…”

[{TcI(NO)(LOMe)(PPh3)Cl}2Ag](PF6) and [TcII(NO)(LOMe)(PPh3)Cl](PF6): Two Unusual Technetium Complexes with a “Kläui‐type” Ligand

“…As for all other technetium(I) complexes, [16,17,[22][23][24][25] the ν NO vibration of compound 3 appears as an intense band at a relatively low frequency. This is readily explained by the high degree of back-donation from orbitals of the d 6 Tc(I) ion into π* orbitals of the NO ligand.…”

“…[8,[10][11][12][13][14][15] Recently, we reported a number of technetium complexes having the {Tc(NO)(Cp)(PPh 3 )} + core. [16,17] The chlorido ligand of their parent compound [Tc(NO)(Cp)(PPh 3 )Cl] (1) can readily be replaced by other anionic or neutral ligands. Stimulated by the versatility of this core, we decided to undertake some efforts for the synthesis of similar compounds with ligands, which are isolobal to Cp À .…”

One Ligand, One Metal, Seven Oxidation States: Stable Technetium Complexes with the “Kläui Ligand”

“…A notable line broadening of 31 P signals is frequently observed for diamagnetic technetium complexes and explained by scalar couplings between 31 P and the large quadrupole moment of 99 Tc. 22,23,57,58 In many cases (as in [Tc I (NO)Cl(PPh 3 )(L OMe )] and [Tc V NCl(PPh 3 )(L OMe )] of the present study), such broadenings make the related 31 It should be mentioned that a number of Re(V) and Re(VI) complexes with the related Klaüi ligand {L OEt } − have been synthesized, among them the nitrido complexes [Re V NCl-(PPh 3 )(L OEt )] and [Re VI NCl 2 (L OEt )]. 39,40 Unlike the technetium complexes of the present study, they readily react with Lewis bases such as electron-poor metal complexes or carbenium salts with formation of heterobimetallic complexes or imido compounds.…”