Isothiocyanato complexes of rhenium VI. Synthesis, characterization and structures of cis-and trans-[ReCl2(NCS)(Me2PhP)3]

Article abstract of DOI:10.1016/0020-1693(95)04760-3

The reaction of [ReCl₃(Me₂PhP)₃] with excess KSCN or trimethylsilylisothiocyanate leads to the replacement of only one chloro ligand. Initially, mer,trans-[ReCl₂(NCS) (Me₂PhP)₃] is formed. The compound crystallizes in the monoclinic space group P2₁/n with a unit cell of dimensions a = 14.992(2), b = 10.846(1), c = 19.117(6) A, β = 112.89(2)°, Z=4. The chloro ligands are coordinated in trans position to each other. An Re-N bond length of 2.071(4) A was found for the nitrogen bound NCS^- ligand. Mer,trans-[ReCl₂(NCS)(Me₂PhP)₃] isomerizes to mer,cis-[ReCl₂(NCS) (Me₂PhP)₃] at longer reaction periods. The cis complex crystallizes in the monoclinic space group P2₁/n, Z=4. A unit cell of dimensions a = 14.824(7), b = 13.158(2), c = 16.212(7) A, β=112.92(2)° was determined for this compound. The rhenium atom is six-coordinate with cis-positioned chloro ligands. The Re-N bond distance is shortened by 0.038 A with respect to mer,trans-[ReCl₂(NCS) (Me₂PhP)₃]. The coordination geometry of the two isomers of mer-[ReCl₂(NCS) (Me₂PhP)₃] can be derived from FAB-MS studies. Fragmentation occurs by the loss of complete ligands. It takes place in a strong dependence on the structural trans influences of the coordinated ligands. The relative intensities of the main fragments clearly indicate the geometry of the coordination sphere.