Substituted thioureas. Part II. Trimethylthiourea and its complexes with cobalt(II) and halogens

Abstract

The proton magnetic resonance spectra of such complexes provide therefore a very sensitive test for the steric arrangement of the ligand. We have used this method to establish the conformation of trimethylthiourea (tmtu) in its complexes with cobalt(n), EXPERIMENTAL Prepamtions.-TlieComplexes of general formula Co-(tmtu),X, (X = C1, Br, or I) have been prepared by literature methods 49 and recrystallized from ethanollight petroleum mixtures.The ligand was deuteriated a t the nitrogen by dissolving it in D,O and drying it under vacuum several times. The degree of deuteriation was checked by n.m.r.: the N H signal had completely disappeared and the methyl attached to i t appeared as a sharp singlet.

Medium Effect on the Rotational Barrier of N,N,N′-Trimethylurea and N,N,N′-Trimethylthiourea: Experimental and Theoretical Study

“…The rotational barriers measured in this work for TMT are very close to those reported earlier in other solvents. For instance, Gattegno and Giuliani determined a value of Δ G ‡ = 10.7 ± 0.2 kcal/mol in CDCl 3 , very similar to the result of Isaksson and Sandstrom for the same solvent, Δ G ‡ = 10.6 kcal/mol. In both cases, entropy contributions could not be determined.…”

“…On the other hand, N,N,N′-trimethylthiourea (TMT) has a rotational barrier of 10.7 ( 0.2 kcal/mol in CDCl 3 . 24 Modeling the solution behavior of molecules represents a special challenge from the theoretical point of view, especially when strong interactions such as hydrogen bonding are present. Previously, we used liquid simulations combined with quantum mechanical calculations to model the solvent effect on a series of amidelike systems.…”

“…Haushalter et al found that thiourea presents a barrier of 13.5 kcal/mol, which is above that of urea (11.0 kcal/mol in DMF/DMSO). On the other hand, N , N , N ′-trimethylthiourea (TMT) has a rotational barrier of 10.7 ± 0.2 kcal/mol in CDCl 3 …”