70832-93-8Relevant academic research and scientific papers
Organochromium(III) macrocyclic complexes. Factors controlling homolytic vs heterolytic cleavage of the chromium-carbon bond
Shi, Shu,Espenson, James H.,Bakac, Andreja
, p. 4318 - 4322 (2008/10/08)
Kinetics studies were done of the homolytic and heterolytic cleavage reactions of the chromium-carbon bonds in the complexes RCr(L)An+ (where L = [15]aneN4 = 1,4,8,12-tetraazacyclopentadecane; A = H2O, OH-). Activation parameters (ΔH?/kJ mol-1, ΔS?/J mol-1 K-1) for homolysis of RCrL(H2O)2+ are as follows: 111 ± 2, 54 ± 6 (R = p-CH3C6H4CH2); 103 ± 2, 28 ± 5 (C6H5CH2); 101 ± 3, 22 ± 9 (p-BrC6H4CH2); 110 ± 3, 62 ± 6 (i-C3H7). The ΔH? and ΔS? parameters are considerably smaller than those for homolysis of (H2O)5CrR2+ analogues. Primary alkyl macrocyclic complexes do not undergo homolysis. The complexes RCrL(OH)+ slowly hydrolyze for R = n-C3H7 and i-C3H7 whereas those for which R = ArCH2 do not. The activation parameters for hydrolysis are 78 ± 1, -53 ± 2 (R = i-C3H7) and 83 ± 3, -46 ± 9 (n-C3H7). This pathway shows no solvent deuterium isotope effect. The complexes RCrL(H2O)2+ are not subject to acidolysis by H3O+ or H2O, unlike their (H2O)5CrR2+ analogues.
