Related Experiment Video
Updated: Oct 3, 2026

Hot Biological Catalysis: Isothermal Titration Calorimetry to Characterize Enzymatic Reactions
Published on: April 4, 2014
Synthesis, Characterization, and Reactivity of Urea Derivatives Coordinated to Cobalt(III). Possible Relevance to
Lee Roecker1, Janet Akande, L. Nelson Elam
1The Department of Chemistry, Berea College, Berea, Kentucky 40404, The Research School of Chemistry, Australian National University, Canberra, A.C.T. 0200 Australia, and The School of Pharmaceutical and Medicinal Chemistry, University of Kentucky, Lexington, Kentucky.
Abstract:
The syntheses of a cobalt(III) complex, 2, containing N-(2-pyridylmethyl)urea and of six complexes, 3, containing phenyl-substituted N-2-pyridylmethyl-N'-(X)phenylureas (where X = 4-H, 4-CH(3), 4-Br, 3-Cl, 4-CF(3), and 4-NO(2)), have been accomplished by reaction of [(en)(2)Co(OSO(2)CF(3))(2)](CF(3)SO(3)) with the urea ligands in tetramethylene sulfone. The complexes have been characterized by UV-vis, FTIR, (1)H NMR, and (13)C NMR spectra along with elemental analysis. Also, X-ray crystallographic analysis of 2 confirms that the urea ligand chelates as a bidentate through the pyridyl nitrogen atom and the endo deprotonated, urea nitrogen atom to form a stable five-membered ring. Crystals of the perchlorate salt of 2 were monoclinic, space group P2(1)/c with a = 9.743(1) Å, b = 13.924(3) Å, c = 15.006(4) Å, beta = 97.07(1) degrees, and Z = 4. Reflection data (3454) with I = 3sigma(I) were refined to conventional R factors of 0.037 and 0.051. In acidic solution (0.05-1.00 M HCl at 55 degrees C), the phenyl-substituted complexes undergo hydrolysis to form the bis(ethylenediamine)(2-picolylamine-N,N')cobalt(III) ion, 4, aniline, and CO(2). The hydrolysis kinetics of the phenyl-substituted complexes were studied by UV-vis spectroscopy (I = 1.00 M HCl/LiCl). At 55 degrees C the observed rate constants fit the rate law k(obsd) = kK[H(+)]/(1 + K[H(+)]). It is proposed that the protonated urea eliminates aniline to give a coordinated isocyanate intermediate that hydrolyzes rapidly to the pyridyl methylamine complex and CO(2) via the carbamate complex. Since all of the studies of this kind to date appear to involve the NCO intermediate, it raises the prospect that urease also functions by a similar path and that urease should be tested with NCO(-) as a substrate.
Related Concept Videos
Structural Isomerism
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Aldehydes and Ketones with Amines: Imine and Enamine Formation Overview
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
Aldehydes and Ketones with Amines: Imine Formation Mechanism
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Coordination Compounds and Nomenclature
Valence Bond Theory
