Synthesis, Characterization, and Stereochemistry of Oxorhenium(V) Complexes with 2-Aminoethanethiolate

A series of oxorhenium(V) complexes with 2-aminoethanethiolate (aet), [ReO(aet-N,S)(d-pen-N,O,S)] (2), [{ReO(aet-N,S)₂}₂O] (3), [ReO(Cl)(aet-N,S)₂] (4), and [ReO(aet-N,S)(Haet-S)₂]Cl₂ ([5]Cl₂) was newly prepared starting from ReO₄^-. The reaction of NH₄ReO₄ with a 1:1 mixture of Haet·HCl and d-H₂pen (d-penicillamine) in the presence of SnCl₂·2H₂O in water gave 2, 3, and the known complex [ReO(d-Hpen-N,S)(d-pen-N,O,S)] (1). These complexes were fractionally precipitated by controlling the pH of the reaction solution. The complex 2 was also prepared in a higher yield by a similar reaction using methanol as a solvent. The crystal structure of 2 was determined by X-ray crystallography; 2 crystallizes in the tetragonal space group P4₃ with a = 9.621(1), c = 12.911(1) Å, V = 1195.0(3) ų, and Z = 4. The oxorhenium(V) core in 2 is coordinated by a bidentate-N,S aet ligand and a tridentate-N,O,S d-pen ligand, having a distorted octahedral geometry with a cis-N cis-S configuration in the equatorial plane perpendicular to the O−Re−O axis. The 1:2 reaction of NH₄ReO₄ with Haet·HCl in the presence of SnCl₂·2H₂O in methanol produced 4, which is interconvertible with 3, while the corresponding 1:3 reaction resulted in the isolation of [5]Cl₂. The complexes 4 and 5 were also structurally characterized; 4 crystallizes in the monoclinic space group P2₁/c with a = 6.839(1), b = 10.0704(6), c = 14.1075(8) Å, β = 91.729(8)°, V = 971.2(2) ų, and Z = 4, while [5]Cl₂ crystallizes in the triclinic space group P1̄ with a = 11.938(3), b = 12.366(3), c = 5.819(1) Å, α = 102.71(2), β = 101.28(2), γ = 75.41(2)°, V = 802.0(3) ų, and Z = 2. In 4, the oxorhenium(V) core is octahedrally coordinated by two bidentate-N,S aet ligands, which form a cis-N cis-S configurational equatorial plane with a Cl^- ion trans to the oxo ligand. On the other hand, the oxorhenium(V) core in [5]²⁺ is coordinated by one bidenate-N,S aet and two monodentate-S Haet ligands, having a distorted trigonal-bipyramidal geometry with S and N donors at the apical positions.