Synthesis and characterization of some new 22-membered chalcogenoaza macrocycles and their Co<SUP>II</SUP> and Ni<SUP>II</SUP> complexes

The [2+2] cyclocondensation of bis(o-formylphenyl)chalcogenides (9, 10) with trans-1,2-diaminocyclohexane affords novel macrocyclic ligands 11 and 12 in very good yields. Crystals of 11 are triclinic, space group Pequation image with a=11.4037(11), b=11.8184(12), c=14.6835(14) &#197;, Z=4 and those of 12 are triclinic, space group P1&#x0305; with a=11.2692(9), b=12.8612(11), c=15.2439(12) &#197; and Z=2. Reduction of 11 with sodium borohydride affords macrocycle 13. The coordination chemistry of 11 has been studied with the "hard" metal ions NiII and CoII. Reaction of NiCl2&#183;6H2O with one molar equivalent of 11 in refluxing methanol followed by addition of NH4PF6 affords NiII complex 14. The assignment of an octahedral geometry to 14 follows from its paramagnetism (&#956;eff=2.50 &#956;B) and UV/Vis spectrum and was further confirmed by single-crystal X-ray diffraction studies. The crystal structure of 14 consists of a distorted octahedral nickel center coordinated by two selenium and four nitrogen atoms. Complex 14: hexagonal, space group P61, a=17.0747(16), b=17.0747(16), c=29.958(4) &#197;, Z=6. CoII complexes 15 and 16 of selenaaza macrocycles were prepared by the reaction of Co(ClO4)2&#183;6H2O with 11 and 3, respectively. Complex 16: monoclinic, space group C2, a=17.160(2), b=10.9660(14), c=9.4941(12) &#197;, Z=2. The cyclic voltammograms of 15 and 16 in MeCN solution show well-behaved quasi-reversible couples