Synthesis, structure, and first-principles calculations of [TcBr2(PMe3)4] and [Tc2Br4(PMe3)4] complexes

Abstract

The new technetium(II) complexes, [TcBr₂(PMe₃)₄] 1 and [Tc₂Br₄(PMe₃)₄] 2, were synthesized from TcBr₃ and characterized by single-crystal X-ray diffraction (XRD), first-principles calculations and UV-vis spectroscopy. Complex 1 is the first of the trans-dihalo-tetrakis-trialkylphosphine metallate(II) class reported for group VII, while 2 is the first Tc(II) dimer with bromide ligands. Compounds 1 and 2 are isostructural with their molybdenum analogs. XRD analysis indicates that 1 crystallizes in the tetragonal space group I2m, with D_2d molecular point-group symmetry, and with Tc–Br = 2.5925(7) Å and Tc–P = 2.4213(11) Å. Compound 2 crystallizes in the monoclinic space group C2/c with Tc–Br = 2.520(1) Å, Tc–P = 2.441(1) Å and Tc–Tc = 2.1316(5) Å. Density functional theory (DFT) calculations for 1 and 2, as well as for the molybdenum homologues, are in good overall agreement with the XRD structural data.