Rearrangement of tetramethylthiourea to dimethyldithiocarbamate and crystal structures of [Tc(O)(C5H12N2S)2((CH3)2NCSS)](PF6)2 and [Tc(DPPE)2((CH3)2NCSS)](PF6)

Abstract

The reaction of [Tcv(O)(tetramethylthiourea)4](PF6)3 with bis(diphenylphosphino)ethane (DPPE) in DMF solution produced at least two compounds, which were identified by X-ray diffraction methods as [Tcv(O)(tetramethylthiourea)2((CH3)2NCSS)](PF6)2 and [TcII(DPPE)2((CH3)2NCSS)](PF6). The bidentate dithiocarbamate ligand was produced from the reaction of bonded tetramethylthiourea in the reaction medium. The crystals of the Tc(V) compound, [Tc(O)(tetramethylthiourea)2((CH3)2NCSS)](PF6)2 are monoclinic with P21/c space group, a=9.388(4), b=26.745(20), c=11.990(3) Å, β=101.62(3)° and Z=4. The structure was refined to R=0.059 and Rw=0.069. The geometry around the Tc atom is square pyramidal. The TcO bond distance is 1.661(6) Å while the TcS bond lengths are 2.328(2) and 2.343(2) Å for tetramethylthiourea and 2.349(2) and 2.353(2) Å for dimethyldithiocarbamate. The crystals of [Tc(DPPE)2((CH3)2NCSS)](PF6) are monoclinic, P21 space group with a=11.693(8), b=19.282(7), c=12.148(6) Å, β=104.78(5)° and Z=2. The structure was refined to R=0.074 and Rw=0.063. The Tc(II) complex has a distorted octahedral geometry. The TcP bond distances vary from 2.413(6) to 2.473(6) Å while the TcS distances are 2.439(6) and 2.448(7) Å. The bidentate dimethyldithiocarbamate ligand is planar. A mechanism for the formation of the ligand is suggested.