1,2-diaminobenzene Adducts of Nickel(II) 1,3-diketonates: Their Role in Dibenzotetraaza[14]annulence Macrocycle Formation


The attempted preparation of the macrocyclic ligand,6,8,15,17-tetraphenyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine from 1,2-diaminobenzene, 1,3-diphenyl-1,3-propanedione, and nickel(II)acetate via a template condensation is unsuccessful because of severe steric interactions in the desired product. The product isolated from this reaction, in high yield, is the bis(1,2-diaminobenzene) adduct of bis(1,3-diphenyl-1,3-propanedionato) nickel(II). Crystals of the adduct are monoclinic with a = 7.425(1), b = 12.221(3), c = 19.194(3) Å, β = 97.01°, Z = 2, V = 1728.7 Å 3, and space group P2 1/n. The structure was solved by the heavy atom method and difference Fourier techniques, and refined by the block-diagonal least-squares method to a final R of 0.0379 for 2218 reflections with I>2σ(I). An empirical absorption correction was made via ψ-scan of 5 reflections with 2θ-values between 5 and 90°, and χ close to 90°. The compound consists of a square planar Ni(II)O 4 array with two molecules of axially coordinated diamine. The monodentate trans arrangement of a diamine molecules gives the compound the overall pseudo-octahedral geometry that is common to adducts of metal 1,3-diketonates. The 6,8,15,17-tetramethyl macrocycle is readily formed via template condensation when the diketone employed is 2,4-pentanedione. The bis(1,2-diaminobenzene) adduct of bis(2,4-pentanedionato)nickel(II) has also been prepared. A small amount of macrocycle can be detected by refluxing this latter adduct in alcohol. The principal product is (1,2-diaminobenzene) tetrakis(2,4-pentanedionato)dinickel(II). © 1987.



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