Large metal ion-centered template reactions. A uranyl complex of cyclopentakis(2-iminoisoindoline)

The reaction of o-dicyanobenzene with anhydrous uranyl chloride does not yield a cyclic, four-subunit phthalocyanine complex. Rather, it yields an expanded, cyclic five-subunit pentakis(2-iminoisoindoline) complex-a "superphthalocyanine". Dioxocyclopentakis(2-iminoisoindoline)uranium(VI), UO₂(N₂C₈H₄)₅, crystallizes in the monoclinic space group, P2_1/c, with a = 8.210 (3) Å, b = 21.667 (7) Å, c = 18.462 (5) Å, β = 103.16 (2)°, and Z = 4 (ρ_cald = 1.891, ρ_obsd = 1.882 g/cm³). Intensity measurements were made for 9564 independent reflections having 2θ_{Mo Kᾱ} <60.4° at 20 ± 1° with Nb-filtered Mo Kᾱ radiation on a Syntex P_-i autodiffractometer. The structure was solved using the heavy atom technique. Cycles of anisotropic full-matrix least-squares refinement have given a final value of 0.054 for the conventional unweighted residual, R, for 4709 independent reflections having I > 3σ(I). The coordination geometry of the uranium atom approximates an idealized compressed pentagonal bipyramid. The two axial ligands are oxygen atoms with an average U-O bond length of 1.744 (8) Å. The equatorial coordination is by five nitrogen atoms (the average U-N bond length is 2.524 (9) Å) of the 20-atom "inner" ring of the 50-atom (excluding hydrogens) macrocycle. The cyclopentakis(2-iminoisoindoline) ligand is severely and irregularly distorted from planarity, presumably as a consequence of appreciable steric strain within the macrocycle.