Binucleating Macrocyclic [14]N₄Ligands and Their Complexes. Synthesis of the Free Ligand 2,3-Dioxo-5,6:13,14-dibenzo-9,10- (4′,5′-dimethylbenzo)-1,4,8,11 -tetraazacyclotetradeca-7,11-diene (L) and of the 7,12-Me₂-L Metal Complexes and Derivatives. Crystal Structures and Properties of the [M′][M(7,12-Me₂-L)] Complexes (M = Ni(II); M = Co(II); M′ = ZnCl₂, M = Ni(II); M′ = [Na(5-crown-15)]⁺, M = Ni(II); M′ = [(C₂H₅)₄N]⁺, M = Ni(II))

The free macrocyclic ligand 2,3-dioxo-5,6:13,14-dibenzo-9,10-(4′,5′-dimethylbenzo)-1,4,8,11 -tetraazacyclotetradeca-7,11 -diene, abbreviated α-diketo-TAD-Me₂, and its complexes with Ni(II) and Co(II) have been synthesized. The Ni(II) complex readily undergoes reduction and by virtue of the α-diketone function, appended to the macrocyclic ring, can bind to other metal ions. Complexes of the 2,3-dioxo-5,6:13,14-dibenzo-7,12-dimethyl-9,10-(4′,5′-dimethylbenzo)-l,4,8,l l-tetraazacyclotetradeca-7,11-diene, abbreviated α-diketo-TAD-Me₄, also have been synthesized. The structures of Ni(α-diketo-TAD-Me₄) (IVa), of the reduction derivatives (Et₄N)[Ni(a-diketo-TAD-Me₄+H)] (V) and [Na(5-crown-15)][Ni(α-diketo-TAD-Me₄+H)] (VI), and of the binuclear complex [Ni(α-diketo-TAD-Me₄)]ZnCl₂(VII) are reported. Crystals of IVa are orthorhombic, space group Pnam; a = 7.934 (4) Å,b = 12.663 (6) Å, and c = 20.922 (9) Å. Crystals of V are monoclinic, space group P2₁/a; a = 14.789 (6) Å, b = 17.582 (5) Å, c= 15.372 (6) Å, and β = 108.36 (3)°. Crystals of VI are monoclinic, space group P2¹/n; a = 17.201 (11) Å, b= 12.113 (11) Å, c = 17.426 (12) Å, and β = 75.32 (5)°. Crystals of VII are monoclinic, space group P2₁c; a = 11.139 (9) Å,b= 16.19 (2) Å, c = 16.15 (1) Å, and β = 98.03 (7)°. Refinements by full-matrix least squares of 151 parameters on 1085 data for IVa, of 371 parameters on 2455 data for V, of 349 parameters on 2440 data for VI, and of 215 parameters on 1514 data for VII converged to the R values of 0.044, 0.073, 0.078, and 0.073, respectively. In all structures the hydrogen atoms were included in the structure factor calculations but were not refined. In IVa the macrocycle adopts a saddle-shaped conformation and the molecules stack along the crystallographic a axis. The planar NiN₄chromophores are equally spaced with a Ni-Ni distance of 4.059 (1) Å. In V and VI the reduction has resulted in the saturation of one of the imino bonds, and in the structure of VI the Na⁺ion is coordinated by the α-diketo function and is found at 5.070 (9) Å from the Ni atom. In VII the Zn atom also is coordinated by the a-diketo function and is located 5.140 (3) A from the Ni atom. The electrochemistry and electronic spectra of the complexes are reported. Co(α-diketo-TAD-Me₂), which is a high-spin, square-planar Co(II) complex, shows a quasireversible reduction at −0.86 V vs SCE and binds O₂reversibly.