Synthesis and characterization of [RhIIICl2 (η1-C6H5)(PYR)2(SbPh 3)], [RhIIICl2 (η1-C6H5)(PY)2(THZ)], [RhIIICl2 (η1-C6H5)(PY)2(PYR)]

Article abstract of DOI:10.1016/S0277-5387(97)00154-X

The mononuclear compounds trans-dichloro (η¹-phenyl)cis-bis(pyrazine) (triphenylstibine) rhodium(III) (1), and trans-dichloro(η ¹-phenyl){N-(2-cyanoethylpyrrole)}trans-bis(triphenylstibine)rhodium (III) (3) were prepared from trans-dichloro(η¹-phenyl)tris(triphenylstibine)rhodium(III) in ethanol. The mononuclear compounds trans-dichloro(η ¹-phenyl)trans-bis(pyridine)(thiazole)rhodium(III) (2) and trans-dichloro(η ¹-phenyl)trans-bis(pyridine)(pyrazine)rhodium(III) (4) were obtained from trans-dichloro(η¹-phenyl) tris(pyridine)rhodium(III) in methanol. Compounds 1 and 2 were analysed via X-ray diffraction techniques from single crystals. The four compounds were characterized by spectroscopy and elemental analysis. The coordination sphere geometry for all the complexes is octahedral; the trans influence exerted by the phenyl ligand is responsible for a long Rh - N bond distance (2.263(3) A) and of large downfield shifts for ¹H NMR signals. The pyrazine ligands are monodentate in both 1 and 4. In the solid state the pyrazine ligands do not bridge the metal centres. Compounds 1 and 2 are barely stable in solution at room temperature. The thiazole molecule of 2 binds the metal through the nitrogen atom whereas sulfur does not show any donating ability. An extended-Hueckel analysis shows that the pyrazine ligands contribute significantly to the frontier unoccupied molecular orbitals. The atomic charges on the non-metal bound nitrogen atoms of pyrazine ligands is -0.175 e in agreement with a bridging ability between two metal centres for this ligand.