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

Abstract

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.