Facile Synthesis and Structure of Heavy Alkali Metal Thiocarboxylates:  Structural Comparison with the Selenium and Tellurium Isologues

Abstract

Potassium, rubidium, and cesium thiocarboxylates were found to be synthesized by the reaction of thiocarboxylic acid or its O-trimethylsilyl esters with KF, RbF, and CsF. Tetramethylammonium thiocarboxylates were prepared in good yields by the reaction of sodium thiocarboxylates with tetramethylammonium chloride. The structures of potassium benzene-, 2-methoxybenzene-, and 4-methoxybenzenecarbothioates, rubidium 2-methoxybenzenecarbothioate, tetramethylammonium 2-methoxy- and 2-trifluoromethylbenzenecarbothioates, potassium 2-methoxybenzenecarboselenoate, and rubidium 2-methoxybenzenecarbotelluroate were characterized by X-ray structural analysis. All of these alkali metal salts exhibit a dimeric structure in which the oxygen and/or sulfur atom is associated with the metal of the opposite molecule, while the tetramethylammonium thiocarboxylates are monomeric. In potassium 2-methoxybenzenecarbothioate, the two thiocarboxylate groups chelate to the potassium atoms above and below the plane which involves the thiocarboxylate groups. In potassium 4-methoxybenzenecarbothioate, one thiocarboxylate group chelates to potassium. Without exception, the o-methoxy oxygen intermolecularly coordinates to the metal of the opposite molecule. The C-O bond lengths of the thiocarboxylate group are in the range 1.22-1.24 Å, which is slightly longer than those of common thioesters. The C(sp(2))-S distances are in the range 1.70-1.72 Å, which is close to that of a typical C-S single bond and suggests that the negative charge may be somewhat localized on the sulfur atom. The interaction number of the metals with oxygen and sulfur atoms was 7 for K and 8 for both Rb and Cs. The dihedral angle between the thiocarboxyl group and the phenyl ring is substantially increased by the introduction of the o-methoxy group. In these alkali metal thio-, seleno-, and tellurocarboxylates, only cesium 2-methoxybenzenecarbotelluroate showed an intermolecular nonbonding interaction between the cesium and the phenyl ring carbons.

First Isolation and Characterization of Sodium and Potassium Tellurocarboxylates: Structural Analysis of Te-Alkyl Telluroester

“…Our efforts, however, have achieved unsuccessful results, even under various conditions. As shown in the preceding paper, we have revealed the structures of heavy alkali metal thiocarboxylates 1 and potassium 1 and cesium selenocarboxylates, ,20b and rubidium 1 and cesium tellurocarboxylates are dimeric. , On the basis of these structural analyses and the similarity of the IR and 13 CO and 125 Te NMR spectra, the aromatic potassium salts ( 2 , R = aryl) may be dimeric structures ( a , b , or c , in Figure ) in which the oxygen and/or tellurium atom is associated with the metal of the opposite molecule.

1 Structural modes of potassium arenecarbotelluroates.

…”

“…In the cases of alkali metal thio- and selenocarboxylates, the effects of the alkali metal cations on the carbonyl carbon chemical shifts are very little. , …”

“…As mentioned in the preceding paper, there are 15 possible kinds of alkali metal chalcogenocarboxylates for each alkali metal in which one or two O atoms of the carboxyl group were replaced by S, Se, or Te . Although these alkali metal salts are the most important class of compounds for the synthesis of chalcogenocarboxylic acid derivatives and are considered to belong to the heteroallylic anion system I − III (Scheme ), much less is known about the chemistry of these chalcogenocarboxylic acid salts except for the thio and dithio salts .…”

Alkali Metal and Organo Group‐14 Element Ferrocenecarbo­selenoates: Synthesis and Structures

“…The rubidium 4 and cesium salts 5 appeared to be less reactive than the salts 2 and 3 , and under the same conditions they gave Se ‐methyl selenoester 6a in respective yields of 67 % and 57 % (entries 4, 5). A similar trend was observed for the methylation of rubidium and cesium carbothio‐ 8. and carbotelluroates 9.…”

The synthesis and characterisation of masked phosphonioalkyl selenoates: Potential ligands for the production of functionalised gold nanoparticles

“…Thus, for example, potassium 2-methoxybenzenecarboselonate has K-Se bond lengths in the range 3.309(1)-3.625(2) Å [20]. One of the two independent selenocyanate anions forms a slightly bent hydrogen bond (O1W-H1WÁ Á ÁN2 = 166°) to the OH anion; the other is involved in SeÁ Á ÁK interactions to the disordered potassium (the exact nature of these interactions is hard to assess due to the disorder).…”