Short Communication: Cobalt(III) Complexes of Monobenzyl-Cyclam Macrocycle Derivatives

Abstract

Two dichlorocobalt(III) complexes of ligands L1 and L3 in which 4-R-benzyl moieties (R = NO₂, NH₂) are either N-bonded (1-position) or C-bonded (6-position) to the 1,4,8,11-tetraazacyclotetradecane (cyclam) macrocycle have been prepared and characterized: L1 = 1-(4-nitrobenzyl)cyclam; L3 = 6-(4-aminobenzyl)cyclam. The X-ray crystal structure of trans-[Co(L1)Cl₂]ClO₄ {M 564.73, monoclinic P2₁/c (No. 14); a 13.1987(14), b 11.7701(11), c 14.9305(14) Å, β 97.692(9)˚; V 2298.6(4) ų. Z 4. D_c 1.632 g cm^–3; final R1 0.0282, wR2 0.0671 (3438 refls F_o > 4σFo), [for all 4022 unique data R1 0.0366, wR2 0.0717]} shows a distorted octahedral stereochemistry at Co, with a Cl–Co–Cl angle of 174˚. The X-ray crystal structure of trans-[Co(L3)Cl₂]Cl·H₂O {M 488.77; monoclinic P2₁/n (No. 14); a 10.5781(12), b 13.536(2), c 15.065(3) Å, β 101.027(13)˚; V 2117.3(6) ų. Z 4. D_c 1.207 g cm^–3; final R1 0.0284, wR2 0.0727 (5296 refls F_o > 4σF_o), [for all 7928 data R1 0.0345, wR2 0.0762]} shows a less distorted octahedral stereochemistry. The Cl–Co–Cl angle is essentially linear, 179.80(14)˚. The cyclam moieties in both structures display the trans-III conformation.

Manuscript received: 11 April 2001.