Synthesis, characterization, and crystal structure of [ReO(Me(4)tu)(4)](PF6)(3) (tu = thiourea)

A new Re-V oxo complex with tetramethylthiourea, [ReO(Me(4)tu)(4)](PF6)(3), has been synthesized by reduction of perrhenate with tin(II) chloride in s trongly acidic solution in the presence of excess tetramethylthiourea. The complex has been characterized by elemental analysis and electronic and FTI R spectroscopy. The molecular structure of the compound was determined by X -ray diffraction methods. The coordination polyhedron is a regular square p yramid with the substituted thiourea sulfur atoms in the equatorial positio ns [d(Re-S) = 2.339(3) Angstrom] and the oxo ligand located in the summit [ d(Re-O)=1.63(2)Angstrom]. Computational methods were employed to analyze th e geometric and electronic structures of tetramethylthiourea and thiourea. Quantum mechanical studies suggest steric hindrance as the reason for the s tabilization of the ReO3+ center instead of the Re-III one.