Synthesis of Carboxylate Cp*Zr(IV) Species: Toward the Formation of Novel Metallocavitands

With
the intent of generating metallocavitands isostructural to species
[(CpZr)3(μ3-O)­(μ2-OH)3­(κO,O,μ2-O2C­(R))3]+, the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids
was carried out. Depending on the reaction conditions, five new complexes
were obtained, which consisted of Cp*2ZrCl­(κ2-OOCPh) (1), (Cp*ZrCl­(κ2-OOCPh))2­(μ-κ2-OOCPh)2 (2), [(Cp*Zr­(κ2-OOCPh))2­(μ-κ2-OOCPh)2­(μ2-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2]­(μ-Cl)­(μ-OH)­(μ-O2CC6H5)­[Cp*Zr]]2­(μ-O2CC6H5)2 (4),
and [Cp*ZrCl4]­[(Cp*Zr)3­(κ2-OOC­(C6H4Br)3­(μ3-O)­(μ2-Cl)2­(μ2-OH)] [5]+[Cp*ZrCl4]−. The
structural characterization of the five complexes was carried out.
Species 3·Et2O exhibits host–guest properties where the diethyl
ether molecule is included in a cavity formed by two carboxylate moieties.
The secondary interactions between the cavity and the diethyl ether
molecule affect the structural parameters of the complex, as demonstrated
be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural
to the [(CpZr)3­(μ3-O)­(μ2-OH)3­(κO,O,μ2-O2C­(R))3]+ metallocavitands.