metal and the presence of the CO ligands with the strong LF.
However, the energies of the empty p orbitals localized on
diimine ligands, typically 2,2^0 -bipyridine (bpy) and
1,10-phenanthroline, are low because of the relatively large con-
jugatedpsystem. Therefore, the ligandp orbital energy is lower
FIG. 1. Structures of rhenium(I) diimine complexes with
abbreviations.
140 HIROYUKI TAKEDAet al.