The complex CpRh(PMe3)PhH (Cp* = C5Me5) reacts thermally with selenop
hene to give a C-Se insertion product. X-ray structural characterizati
on shows a planar 6-membered ring containing a localized butadiene str
ucture. Se-77 NMR studies display an. upfield resonance consistent wit
h a non-aromatic metallaselenabenzene ring.