The synthesis of a technetium(V) phenylimido complex from pertechnetate. The single crystal X-ray structure of [TcCl 3(NPh)(PPh 3) 2]·CH 2Cl 2

Abstract

The reaction of (NH 4)[TcO 4] with triphenylphosphine and the organohydrazine N-acetyl, N′-phenylhydrazine (PhNHNHCOCH 3) in methanol with a minimal amount of HCl (aq) gives the neutral Tc(V) complex [Tc(NPh)Cl 3(PPh 3) 2] in very good yields. The IR spectrum of this complex displays a strong band in the 1090 cm −1 region which has tentatively been assigned to v(TcN). The (+)FAB mass spectrum does not show the peak associated with the neutral parent species [TcCl 3(NPh)(PPh 3) 2]. However, a prominent feature of 784 m/ z is associated with the fragment generated from the loss of a chloride ligand, giving the cationic species [TcCl 2(NPh)(PPh 3) 2] +. Other peaks present in the mass spectrum correspond to the fragments [TcCl 2(NPh)(PPh 3)] + of 522 m/ z and [TcCl(NPh)(PPh 3)]·H + of 488 m/ z. The diamagnetic Tc(V) complex displays a 1H NMR spectrum with the proton signals from the imido-phenyl group resolved from those of the phosphine-phenyl groups. The complex displays distorted octahedral molecular coordination geometry, with mutually trans triphenylphosphine ligands and equatorial phenylimido and chloride ligands. The technetium-nitrogen bond length is 1.704(4) Å with a technetium-nitrogen-carbon bond angle of 171.8(4)°, which reflects the sp hybridization of the phenylimido nitrogen atom. Bond lengths and angles involving the chloride and phosphine ligands are unexceptional for technetium in the +5 oxidation state. Crystal data for C 43H 37NP 2Cl 5Tc: triclinic space group P 1 , a=10.8651(9), b=12.2236(9), c=16.867(2) Å, a=71.998(7)°, β=74.078(7)°, γ=80.336(7)°, V=2040.2 Å 3, with D calc=1.455 g cm −3 to give Z=2. Structure solution based on 9334 reflections converged at R=0.054, R w=0.053, GOF=1.35. In an analogous reaction, [TcO 4] − reacts with benzoylhydrazine (PhCONHNH 2) and triphenylphosphine in methanol with HCl to give the Tc(V) nitrido complex [TcNCl 2(PPh 3) 2] in excellent yields.