The synthesis and characterization of a cationic technetium(V) phenylimido complex. The X-ray crystal structure of [TcCl₂(NPh)(PMe₂Ph)₃](BPh₄)

The reaction of the neutral Tc(V) phenylimido complex [TcCl₃(NPh)(PPh₃)₂] with excess PMe₂Ph in refluxing MeOH gives the cationic, tris-dimethylphenylphosphine complex [TcCl₂(NPh)(PMe₂Ph)₃]⁺, which is isolated as the tetraphenylborate salt. The IR spectrum of the crystalline product shows a medium intensity band at 1102 cm^-1 which is assigned to ν(TcN) from the phenylimido core. The ¹H NMR spectrum of the diamagnetic complex shows a series of multiplets in the aryl region and three distinct signals near 2 ppm from the phosphine methyl groups. The X-ray crystal structure, which is the first for a cationic technetium organoimido complex, shows a meridional arrangement of phosphine ligands with a chloride ligand coordinated trans to the phenylimido unit. The TcN bond length of 1.711(2) Å is consistent with the dianionic nature of the organonitrogen core. The TcNC bond angle of 178.8(2)° reflects the sp hybridization of the phenylimido nitrogen atom. The coordination geometry is best described as a distorted octahedron. Crystal data for C₅₄H₅₈BCl₂NP₃Tc: triclinic space group P1, a = 11.337(2), b = 13.054(3), c = 17.854(4) A ̊, α = 72.36(3), β = 88.51(3), γ = 89.76(3)°, V = 2517.2(13) A ̊³, with D_calc = 1.311 g cm^-3. Structure solution based on 9986 observed reflections converged at R = 3.65%, R_w = 5.43%, GOF = 1.82.