Phosphane ligands .6. The remarkable tridentate coordination of 4,6-bis(diphenylphosphanyl)dibenzofuran in ruthenium(II) complexes

4,6-Bis (diphenylphosphanyl) dibenzofuran (1), despite its large P ... P distance of 5.74 Angstrom and its bite angle of ca. 131 degrees, was found to be capable of tridentate coordination to ruthenium(II) chloride. Single crystal X-ray structure analyses of the new ruthenium(II) complexes 3, 4, and 5 revealed that the ligand 1 coordinates to a single ruthenium atom with both phosphorus centers and the dibenzofuran oxygen atom. The remarkable ligand deformation resulting from the coordination is evident from the decrease of the P ... P distance by 1 Angstrom to 4.75 Angstrom and the increase of the bite angle (P-Ru-P) by 25 degrees to 155 degrees-157 degrees. The unprecedented in-plane coordination of the dibenzofuran oxygen atom to ruthenium is interesting in view of the hybridisation of the oxygen.