[Tc(NO)Cl(Cp)(PPh₃)] – A Technetium(I) Compound with an Unexpected Synthetic Potential

Abstract

Reactions of the chiral organometallic technetium(I) compound [Tc(NO)Cl(Cp)(PPh3)] (1 a) with phosphines and alkynes give unexpected products such as the dimeric cation [{Tc(NO)(Cp)(PPh3)}2Cl]+ (4) or the Fischer‐type carbene [Tc(NO)(Cp)(PPh3){C(OR)C2H4PPh3}]2+ (5). Both products could be isolated as PF6− salts and studied by spectroscopic methods and X‐ray diffraction. While [Tc(NO)(Cp)(PMe3)(PPh3)](PF6) (2PF6) can be obtained from 1 a, PMe3 and Ag(PF6) under ambient conditions, the synthesis of the corresponding bis‐triphenylphosphine complex [Tc(NO)(Cp)(PPh3)2](PF6) (3PF6) requires high temperatures and long reaction times. The products are stable in air.

[{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.…”

“…One of the isolated technetium(I) complexes, [Tc(NO)(L OMe )(PPh 3 )Cl] (2) in Figure 1, is structurally related to the cyclopentadienyl compound 1, for which we recently had to note some unexpected behavior. [23] An illustrative example is the reaction of 1 with Ag(PF 6 ). Not all chlorido ligands are abstracted from technetium in this reaction and the dimeric, chlorido-bridged complex [{Tc-(NO)(Cp)(PPh 3 )} 2 Cl](PF 6 ) is formed instead.…”

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

“…Thus, the unsaturated 16-electron complex [Tc­(dppe) 2 Cl] reacts with alkynes under exclusive formation of vinylidene carbene complexes and the protonation of such complexes also did not lead to side-on alkyne complexes but rather to the formation of technetium carbyne complexes containing a TcC bond . Also, the unexpected formation of phosphonio oxycarbene complexes with a composition of [Tc­(C­(OR)­CH 2 CH 2 PPh 3 )­(Cp)­(NO)­(PPh 3 )] 2+ from reactions of [TcCl­(Cp)­(NO)­(PPh 3 )] with AgPF 6 , Me 3 SiCC–CH 3 , and alcohols probably proceeds via an alkyne- or vinylidene-coordinated intermediate, as well as the insertion of electron-poor alkynes into the Tc–H bond of [TcH­(CO) 3 (PPh 3 ) 2 ] …”

“…Although there are some pathways for the preparation of carbene complexes of technetium by nucleophilic attack on coordinated carbonyl ligands, − detailed structural knowledge of technetium carbene complexes is still scarce. The few complexes, in which carbene type structures have been proven unambiguously, e.g., by X-ray diffraction, are [Tc­{CPh­(OEt)}­(Cp*)­(CO) 2 ], [Tc­[Tc­(CC­(H)­Ph)­(dppe) 2 Cl], [Tc­(C­(OMe)­CH 2 CH 2 PPh 3 )­(Cp)­(NO)­(PPh 3 )]­(PF 6 ) 2 , and the isocyanide complex [Tc­(CN t Bu) 4 (bpy)]­(PF 6 ), for which a bent, carbene-like structure has been discussed …”

Reactions of TcI(NO) and TcVN Complexes with Alkynes and Alkynides

“…Having in mind our previous experience with reactions of [Tc(NO)(Cp)Cl(PPh 3 )] with alkynes and lithium alkynides (Scheme 1), which did not give the intended products with η 1or η 2 -bonded alkynes, 41,42 (L = tertiary phosphines or phosphites) have been isolated and structurally characterized. 44,45 Heating of [Tc(NO)-Cl 2 (PPh 3 ) 2 (CH 3 CN)] with RC�CR (R = Ph, Et, n Bu) in toluene results in a gradual dissolution of the sparingly soluble starting material and the formation of orange-red solutions, from which approximately 50% of the Tc separates as a purple oil upon cooling.…”