Cobalt(I), -(II), and -(III) complexes of a tetraaza 14-membered macrocycle, 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene (L). Crystal and molecular structures of [CoL(CO)]ClO4, trans-CoLCl2, and cis-[CoL(CO3)]ClO4

The carbon monoxide adduct of the cobalt(I) title macrocycle has been prepared via reaction of CoL⁺ with CO₂ and with CO and isolated as a perchlorate salt: IR (Nujol) v_CO 1916 cm^-1; UV-vis (CH₃CN, λ_max (ε)) 310 nm (3900 M^-1 cm^-1), 430 sh (770), 510 sh (360), 1040 (240). In CH₃CN solvent its stability constant is ∼3 × 10⁸ M^-1 at 25°C. Structures of the square-pyramidal carbonyl complex and two other complexes of the title macrocycle have been determined from single-crystal X-ray diffraction data collected with use of Mo Ka radiation. Crystallographic data: [CoL(CO)](ClO₄) (1), C2, a = 15.362 (3) Å, b = 7.580 (5) Å, c = 9.611 (3) Å, β = 108.91 (2)°, V = 1059 (1) ų, Z = 2 (R = 0.057, R_w = 0.069); N-meso,trans-CoLCl₂ (2), Pbca, a = 11.570 (3) Å, b = 12.695 (3) Å, c = 13.309 (2) Å, V = 1954 (1) ų, Z = 4 (R = 0.075, R_w = 0.070); cis-[CoL(CO₃)]ClO₄ (3), C2, a = 15.072 (5) Å, b = 7.603 (4) Å, c = 9.703 (3) Å, β = 109.74 (3)°, V = 1047 (1) ų, Z = 2 (R = 0.033, R_w = 0.048). The three structures contain square-pyramidal, five-coordinate cobalt(I) (1), strongly axially distorted "six"-coordinate cobalt(II) (2), and six-coordinate cobalt(III) with L occupying cis-coordination positions (3). They thus provide a striking illustration of the adaptability of L to a variety of coordination numbers and oxidation states.