Crystal structure of dipotassiumN-carbodithioato-L-prolinate trihydrate

Abstract

The molecular and crystal structure of the l-proline-derived dithiocarbamatecarboxylate compound poly[tri--aqua-( -2-carboxylatopyrrolidine-1-carbodithioato)dipotassium], [K 2 (C 6 H 7 NO 2 S 2 )(H 2 O) 3 ] n or K 2 (SSC-NC 4 H 7 -COO)Á3H 2 O, has been determined. The dithiocarbamate moiety displays a unique coordination mode, comprising a 'side-on' -coordinated K + cation besides a commonly -chelated K + cation. By bridging coordination of the CSS group, COO group and water molecules, the K + cations are linked into a two-dimensional coordination polymer extending parallel to the ab plane. These layers are again interconnected by O-HÁ Á ÁS hydrogen bonds. Chemical contextNatural amino acids react readily with carbon disulfide in an alkaline environment to give dithiocarbamate-functionalized carboxylates. Since the first report on a series of barium salts in the 1950s (Zahradnik, 1956), numerous transition metal complexes have been explored. More recently, various late transition metal complexes of this family have been investigated due to their biological activity (e.g. Giovagnini et al., 2005;Cachapa et al., 2006;Nagy et al., 2012). In most cases, the dithiocarbamate moiety acts as a classical small-bite chelate ligand, while the carboxylate group (often esterified) does not contribute to metal coordination. The structural chemistry of main group derivatives of dithiocarbamate-derived amino acids is much less explored, even though alkali metal and alkaline earth metal salts are frequently used as precursors for other metal complexes. A key intermediate in our ongoing reasearch on coordination polymers with dithiocarbamatecarboxylates is the l-proline-derived potassium salt K 2 (SSC-NC 4 H 7 -COO). This compound crystallizes from aqueous solution as a trihydrate, which has been structurally characterized in the course of this work. Structural commentaryThe title compound, K 2 (SSC-NC 4 H 7 -COO)Á3H 2 O, crystallized as colourless plates in the orthorhombic space group ISSN 2056-9890 P2 1 2 1 2 1 , with one formula moiety in the asymmetric unit ( Fig. 1). One K atom (K2) is bonded in a typical chelating fashion by the CSS group, while K1 is coordinated 'side-on' to the CSS group, certainly under participation of the delocalized electrons. This rather uncommon coordination mode might be supported by additional coordination of a carboxylate O atom (O1) to K1. K1 adopts a low-symmetric seven-coordination by four carboxylate O atoms, two H 2 O molecules and the -coordinating CSS group. K2 is eight-coordinated by three S atoms and five H 2 O molecules (Fig. 2). Consequently, the full coordination mode of the carboxylate group is 3 -4 O,O 0 :O:O 0 , and the dithiocarbamate group adopts a 3 -6 S,S 0 ,C:S,S 0 :S coordination. One H 2 O molecule displays a 3 -coordination (O3) and the remaining two H 2 O molecules are coordinating in a -bridging mode (O4 and O5). The K-S distances at the -chelated K + cation (K2) are 3.2176 (8) and 3.2650 (9) Å , while the K-S separations at the -coordinated K + cation (K1) are signif...

Alkali Metal Dithiocarbamato Carboxylates (DTCCs) – Synthesis, Properties, and Crystal Structures

“…Similarly, for the K-S separations no systematic dependency on the coordination mode of the ligating group was observed, as the intervals of interatomic distances are comparable for σ-coordinated (318.1(1)-358.7(1) pm) and πcoordinated (329.6(1)-346.8(1) pm) sulfur groups. Similar values of K-O and K-S distances have been observed in the previously reported 6-K ⋅ 3H 2 O, [17] as well as in related potassium compounds deposited in the CSD. [36]…”

“…It is worth mentioning that the enantiopure compound 6-K, whose solidstate structure has been reported previously, crystallized as a trihydrate. [17] In compounds 6' ⋅ 4H 2 O, for one of the two metal atoms in the asymmetric unit (Na1 or K1) a distorted octahedral six-coordination is realized by one S atom, two carboxylate O atoms, and three H 2 O ligands. For Na2 or K2, respectively, the coordination is increased to an irregular seven-coordination, formed by two S atoms, two carboxylate O atoms, and three H 2 O ligands.…”

“…Among alkali metal DTCCs, the vast majority of known compounds are sodium and potassium derivatives, which have been isolated and characterized by NMR spectroscopy in only few studies. [4,[16][17][18] Lithium DTCCs have been mentioned only very briefly in the previous literature. [7] With the exception of the sodium, potassium, rubidium, and cesium salts of N-dithioato-lprolinate, none of these compounds has been structurally characterized in the solid state to the best of our knowledge.…”

Formation and structural characterization of a potassium amidinoguanidinate

“…4) (Giesbrecht et al, 1999;Benndorf et al, 2011). A similar mixed -/-coordination to that in the title compound has been recently observed by us in a potassium dithiocarbamate (Liebing, 2017).…”

The Alkali Metal Salts of Methyl Xanthic Acid

“…The bonding situation of the latter two K atoms can be described by π-coordination of the CSS fragment, as it has been previously seen with Mo(III) xanthates [11] and with a related potassium dithiocarbamate. [29] In addition to κ 2 S,S′-coordination, single-and/or dual-chelation of metal centers is also realized by κ 2 S,O-modes (Scheme 5, c and d). Contribution of the oxygen donor group in xanthates to metal coordination is rare and has been reported for few compounds of Na, [30,31] K, [16][17][18][19]27,32,33] Ba, [20] Hg(II), [34] and Tl(III).…”