Synthesis and characterization of oxorhenium(V)-catecholate complexes. Crystal and molecular structures of (CH 3) 4N[ReO (O 2C 6H 4) 2] and (CH 3) 4N[ReO(PPh 3) (O 2C 6H 4) 2]·CH 3OH

Abstract

The reactions of ReOCl 3(PPh 3) 2 with catechol and substituted catechols in methanol in the presence of triethylamine and tetramethylammonium chloride under N 2 yield the green complexes [(CH 3) 4N] +[ReO(cat) 2(PPh 3)] − (cat=O 2C 6H 4 ( 2), 4CH 3O 2C 6H 3 ( 3), O 2C 6Cl 4 ( 4)). The reactions of 2 and 3 with pyridine in methylene chloride yield [(CH 3) 4N] +[ReO(cat) 2(py)] − ( 5) and [(CH 3) 4N] +[ReO(4Mecat) 2(py)] − ( 6). Variable temperature 1H and 31P NMR spectroscopy studies on these complexes indicate that the ancillary ligands (PPh 3: 2, 3; py: 5, 6) undergo a dissociation-association process in solution along with concomitant cis-trans isomerization of the catecholate ligands. The reaction of [(CH 3CH 2) 4N] +[ReO 2(cat) 2] − ( 8) with triphenylphosphine in refluxing ethanol yields the reduced rhenium(V) square pyramidal complex [(CH 3CH 2) 4N] +[ReO(cat) 2] − ( 7) as an air and moisture-sensitive tan solid where triphenylphosphine acts as a reducing agent. These complexes were characterized by elemental analysis, variable temperature 1H and 31P NMR spectroscopy and IR and UV-Vis spectroscopies. Complexes 2 and 7 were also characterized by X-ray crystallography. Crystal data: C 20H 28NO 5Re ( 2): tetragonal space group I4/ m, a=19.890(3), c=10.438(2) Å, V=4129(2) Å 3, Z=8, D calc=1.766 g cm −3; structure solution and refinement based on 976 reflections (Mo Kα, λ=0.71073 Å) converged at R=0.043. C 36H 43NO 7PPe ( 7): monoclinic space group C2/ c, a=25.485(5) Å, b=9.127(2), c=30.590(6) Å, β=101.84(3)°, V=6964(3) Å 3, Z=8, D calc=1.563 g cm −3; 3298 reflections, R=0.047.