CRYSTAL AND MOLECULAR-STRUCTURES OF COMPLEXES OF 2 ISOMERIC 18-MEMBERED TETRAAZA MACROCYLIC LIGANDS HAVING THE EMPIRICAL-FORMULA [CUC20H40N4](CLO4)2 - EFFECTS OF CHELATE RING SIZE AND DOUBLE-BOND PLACEMENT ON COORDINATION GEOMETRY ABOUT COPPER(II)
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abstract
Crystal and molecular structures are reported for two isomeric compounds, {[5S(R), 10R(S)]-2, 4, 4, ll, ll, 13-hexamethyl- 1, 5, 10, 14-tetraazacyclooctadeca-l, 13-diene]copper(II) perchlorate, [Cu(cis-[18]dieneN4)](C104)2, I, and {[5R-(S), 14R(S)] -2, 4, 4, 11, 13, 13-hexamethyl-1, 5, 10, 14-tetraazacyclooctadeca-1, 10-dienejcopper(II) perchlorate, [Cu(trans-[18]dieneN4)](C104)2, II, having the empirical formula [CuC20H40N4](ClO4)2. This is the first reported structural characterization of an 18-membered tetraazamacrocyclic ligand complex and only the second structural characterization of cis/trans isomerism in tetraazamacrocyclic complexes. Compound I forms purple monoclinic crystals, space group C2/c (No. 15): a = 29.132 (16), b = 14.021 (8), c = 14.838 (9) A; = 113.89 Z = 8; Dcalcd = 1.44Dobsd = 1.45 (2) g/cm3. The nitrogens coordinate copper(II) in a pseudotetrahedral manner, with a dihedral angle of 36.6 between the N(l)CuN(2) and N(3)CuN(4) planes. Compound II forms orange-red orthorhombic crystals, space group P21212 (No. 18): a = 14.720 (2), b = 12.308 (2), c = 7.982 (1) A; Z = 2;Dcalcd = 1.38, Dobsd = 1.39 (2) g/cm3. The tetrahedral distortion in this complex is rather small, with a dihedral angle between the N(l)CuN(2) and N(l)'CuN(2)' planes of 11.5. The extent of tetrahedral distortion about Cu(II) and the amount of strain in the macrocyclic ligand (as determined by deviation of bond angles and torsional angles from ideal values) depend on both the chelate ring size and the C-N double-bond placement. It appears that a variety of tetrahedral distortions about Cu(II) may be obtained if these features of the ligand are modified. 1980, American Chemical Society. All rights reserved.
