Rhenium chelate complexes with maltolate or kojate

Abstract

Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal) 2] ( 1), [ReOCl 2(mal)(PPh 3)] ( 2), [ReOBr 2(mal)(PPh 3)] ( 3), [ReOCl 2(koj)(PPh 3)] ( 4) and [ReOBr 2(koj)(PPh 3)] ( 5). The products have been characterized by FTIR, 1H, 13C, and 31P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex 1 crystallizes monoclinic, space group C2/ c, Z = 8. It contains two O,O′-bidentate maltolate ligands and one chloro ligand at the (ReO) 3+ unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P2 1/ n and Z = 4. In complexes 2– 5, the (ReO) 3+ unit is coordinated by a monoanionic O, O-bidentate unit of the maltolate ( 2 and 3) or kojate ( 4 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other.