Facile Construction of Lanthanide Metallomacrocycles with the Bridging Imidazolate and Triazolate Ligands and Their Ring Expansions

Four novel tri- or tetranuclear organolanthanide metallomacrocycles [Cp2Ln(μ-Im)(THF)3 (Cp = C5H5, Ln =
Yb (1), Er (2)], [Cp2Dy(μ-Im)]4(THF)]3·2THF (3), and [Cp‘2Yb(μ-η1:η2-Tz)]4·2THF (Cp‘ = CH3C5H4) (4) have been
synthesized through protolysis of Cp3Ln or Cp‘3Yb with imidazole or triazole, indicating that both the bridge-ligand
size and the lanthanide-ion radii can be applied in the modulation of the metallomacrocycles. Further investigations
on the reactivity of complexes 1, 3, and 4 toward phenyl isocyanate reveal that PhNCO inserts readily into the
simple bridge Ln−N bonds of 1 and 3 to yield the corresponding insertion products [Cp2Ln(μ-η1:η2-OC(Im)NPh)]3
(Ln = Yb (5), Dy (6)) but cannot insert into the Ln−N bond with a μ-η1:η2-bonding mode in 4. The novel bridge
ligand [OC(Im)NPh] can expand the numbers of the ring members from 12 to 18 in 5 or 16 to 18 in 6. The number
of metal atoms in the metallacycles with the ligand [OC(Im)NPh] is independent of the lanthanide-ion size; both
trinuclear lanthanide macrocycles are observed in 5 and 6. All of these new complexes have been characterized
by elemental analysis and spectroscopic properties, and their structures have also been determined through X-ray
single-crystal diffraction analysis.