Univalent metal ion α-hydroxy and interactions: Part 9. Preparation and crystal structures of lithium hydrogen (+)-tartrate monohydrate, potassium (+)-tartrate hemihydride and thallium(I) (+)-tartrate

The univalent metal ion compounds of (+)-tartaric acid, lithium hydrogen (+)-tartrate monohydrate (1), potassium (+)-tartrate hemihydrate (2) and thallium (+)-tartrate (3) have been prepared and their structures determined by X-ray diffraction methods. All form network polymer structures similar to the other group one metal tartrates. However, (1) is based on a dimeric repeating unit, with two independent but different five-coordinate square pyramidal lithium centres, [LiO, 1.971-2.322(8) Å]. Although both centres involve (+)-tartrate residues in α-hydroxycarboxyl bis-coordinate interactions, one centre has two, the other has one and is also coordinated to both waters (one bridging). The protonated carboxylic acid groups are uncoordinated but hydrogen bonded in both inter- and intra-dimer associations. Potassium (+)-tartrate hemihydrate (2) has two independent and different distorted octahedral potassium centres. About the first, there are five oxygens from (+)-tartrate residues and one from a water which bridges to another symmetry generated potassium. The second potassium has six bonds to (+)-tartrate oxygens, including a β-hydroxycarboxyl chelate ring, with a KO range of 2.711(2)-2.988(3) Å. An unusual feature is a carboxyl oxygen giving a three-centre bonding system to three separate potassium ions. The polymeric structure of thallium(I) (+)-tartrate (3) is based upon two different five-coordinate thallium centres [TlO range, 2.59(3)-2.96(2) Å]. About one, bonds are to three oxygens from one (+)-tartrate residue (one carboxyl, two hydroxyl), and two from a symmetric bidentate-carboxylato-(O,O′) group of a bridging (+)-tartrate. The bonded hydroxyl also bridges to the second Tl [Tl⋯Tl, 3.519(2) Å]. Completing the bonding to this second Tl are oxygens from four different tartrate residues. Crystallographic and analytical data are also provided for silver(I) (+)-tartrate (4)