Transition-Metal Complexes of Superstructured Cyclidene Macrobicycles: Structural Features and Their Chemical Consequences. 1. Complexes of the Unbridged Cyclidene Ligands and of Precursor Ligands

The cyclidene macrocycle is particularly favorable for the attachment of superstructures and the promotion of dioxygen adduct formation by iron(II) and cobalt(II). Consequently, a number of families of cyclidene derivatives have been developed, including synthetic lacunar dioxygen carriers and vaulted hosts for inclusion complexation. As the initial phase of full structural characterization of these families of complexes, the syntheses and X-ray structures of seven unbridged complexes are reported and analyzed here. The structures of five of these unbridged complexes show the saddle conformation that is critical to the bridging reaction which produces the cavities in the lacunar and vaulted complexes. Four of these complexes contain the 16-membered parent cyclidene ring while the fifth has a 15-membered ring. The driving force for adoption of the saddle shape is identified with the favored boat and chair conformations of the saturated 6-membered chelate rings. In turn, this causes the unsaturated rings to be thrust upward on the same side of the N₄coordination plane. Additional boat-shaped distortion of the unsaturated rings is correlated with the π-electron distribution, as revealed by bond lengths. This distribution is strongly influenced by substituents, but it does not closely reflect the formal bond' pattern or the net charge. The remaining two structures contain 14-membered and 15-membered cyclidene rings. The 14-membered ring derivative is essentially planar, the only substantial deviations being due to substituents and the skew conformations of the saturated 5-membered chelate rings. In the final structure, the saddle is converted into a Z-conformation by folding one of the unsaturated rings from above to below the N₄plane. This converts the saturated 6-membered ring into a skew conformation. Both this Z-form and the planar structure are ill-suited to bridge formation. Crystal data: compound 1, C₁₇H₂₄N₄O₂Ni•0.5C₅H₅N, triclinic, P1, a = 7.824 (2) A, b = 10.538 (3) A, c = 14.283 (4) A, a = 115.84 (1)°, β = 112.81 (2)°, y = 85.79 (2)°, Z = 2; compound 2, C₂₀H₃₀N₄O₂Ni, orthorhombic, Pnma, a = 12.055 (2) A, b = 15.701 (3) A, c = 10.650 (2) A, Z = 4; compound 3, C₁₈H₂₀N₄O₂Cl₆Ni, triclinic, Pi, a = 10.013 (1) A, b = 1 1.935 (2) A, c = 11.613 (2) A, a = 108.52 (1)°,β = 101.18 (1)°, y = 103.12 (1)°, Z = 2; compound 4, C₁₆H₂₂N₄0₂Ni, monoclinic, P2_:/n, a - 5.253 (1) A, b = 18.047 (5) A, c = 8.682 (2) A, β — 107.56 (2)°, Z = 2; compound 5, C₁₉H3₀N₄O₁₀Cl₂Ni, orthorhombic, Pbcm, a = 8.257 (7) A, b = 13.940 (11) A, c = 22.108 (14) A, Z = 4; compound 6, C₂₀H₃₄N₆P₂F₁₂Cu, monoclinic, F2j/w, a = 10.480 (2) A, b = 12.148 (2) A, c = 11.958 (3) A, j9 = 91.37 (2)°, Z = 2; compound 7, C₃₄H₅₄N₁₀P₂F₁₂Cu, triclinic, Pi, a = 13.922 (2) A, b = 14.654 (3) A, c = 11.674 (2) A, a = 98.98 (2)°, β = 104.68 (1)°, γ = 95.92 (2)°, Z = 2.