Toward Charge-neutral ‘soft scorpionates’: Coordination Chemistry and Lewis Acid Promoted Isomerization of tris(1-organo-imidazol-2-ylthio)methanes

Authors

Chengeto Gwengo, Marquette University
Rosalice M. Silva, Marquette University
Mark D. Smith, University of South CarolinaFollow
Sergey V. Lindeman, Marquette UniversityFollow
James R. Gardinier, Marquette UniversityFollow

Document Type

Article

Language

eng

Publication Date

8-15-2009

Publisher

Elsevier

Source Publication

Inorganica Chimica Acta

Source ISSN

0020-1693

Abstract

Two tris(1-organo-imidazol-2-ylthio)methanes, HC(S-tim^R)₃ (R = organo = methyl, tert-butyl), have been prepared by a triphasic reaction between chloroform, the appropriate heterocycle, and saturated aqueous solutions of Na₂CO₃, in the presence of a phase transfer agent, (NBu₄)(Br). These ligands have been characterized both spectroscopically and by single crystal X-ray diffraction. The reaction chemistry of these potentially N,N,N-tripodal ligands with AgBF₄ was also explored where simple 1:1 coordination complexes could be isolated from reactions performed in THF solution at room temperature. The derivative {Ag[HC(S-tim^Me)₃]}(BF₄) was structurally characterized which showed that the ligand binds in a μ–κ²N,κ¹N-mode to give a coordination polymer with an interesting layered supramolecular structure. Surprisingly, heating CH₃CN solutions of the silver complexes at reflux resulted in decomposition of the complex and concomitant isomerization of the ligands to give metal-free tris(3-organo-1-imidazole-2-thione)methane, HC(N-imt^R)₃; the heretofore elusive charge-neutral analogues of the well-studied ‘soft scorpionate’ Tm^R− anions. The solution isomerization of HC(S-tim^R)₃ to HC(N-imt^R)₃ was found to be general, occurring in a variety of solvents with any of a host of different Lewis acids [para-toluenesulfonic acid, KPF₆, and M(CO)₅Br (M = Mn, Re)] but did not occur by heating in the absence of Lewis acid. The compound HC(N-imt^Me)₃ exhibited unusually low solubility in common organic solvents. Single crystal X-ray diffraction of HC(N-imt^Me)₃ revealed a remarkable honeycomb supramolecular structure with ca. 5 Å channels filled with solvent. The robust nature of this solid is a result of strong dipolar stacking interactions of molecules into polymer chains bolstered by concerted π–π and CH–π interactions involving the heterocycles, holding the chains together in the remaining two dimensions.

Comments

Accepted version. Inorganica Chimica Acta, Vol. 362, No. 11 (August 15, 2009): 4127-4136. DOI. © 2009 Elsevier. Used with permission.

Recommended Citation

Gwengo, Chengeto; Silva, Rosalice M.; Smith, Mark D.; Lindeman, Sergey V.; and Gardinier, James R., "Toward Charge-neutral ‘soft scorpionates’: Coordination Chemistry and Lewis Acid Promoted Isomerization of tris(1-organo-imidazol-2-ylthio)methanes" (2009). Chemistry Faculty Research and Publications. 605.
https://epublications.marquette.edu/chem_fac/605