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

The new technetium(II) complexes, [TcBr(2)(PMe(3))(4)] 1 and [Tc(2)Br(4)(PMe(3))(4)] 2, were synthesized from TcBr(3) 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 I42m, with D(2d) molecular point-group symmetry, and with Tc-Br = 2.5925(7) A and Tc-P = 2.4213(11) A. Compound 2 crystallizes in the monoclinic space group C2/c with Tc-Br = 2.520(1) A, Tc-P = 2.441(1) A and Tc-Tc = 2.1316(5) A. 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.