Group 15 complexes with α-hydroxy carboxylic acids:: 7 -: The preparation and structure determination of sodium (+)-tartrato arsenate(III), [Na8As10(C4H2O6)8(C4H3O6)2(H2O)19]n; Silver(I) (+)-tartrato arsenate(III), [Ag9As10(C4H2O6)9(C4H3O6)(H4As2O5)(H2O)10]n and rubidium citrato antimonate(III), [Rb2Sb4(C6H5O7)2(C6H6O7)2(C6H7O7)4 (H2O)2]

The structures of sodium (+)-tartrato arsenate( III), [Na8As10(C4H2O6)(8)(C4H3O6)(2)(H2O)(19)](n) (1), silver (+)-tartrato arsenate( III), [Ag9As10(C4H2O6)(9)(C4H3O6)(H4As2O5)(H2O)(10)] (2) and rubidium citrato antimonate( III) [Rb2Sb4 (C6H6O7)(6)(C6H7O7)(2)(H2O)(2)] (3) have been determined by X-ray methods and refined to residuals of 0.085 (1), 0.072 (2) and 0.065 (3) for 5018, 4487 and 8207 observed reflections, respectively. The (+)-tartrato complexes (1) and (2) are similar in structure to the two known isomorphous silver( I) (+)-tartrato arsenate( III) complexes in that independent anionic [As 2 (tartrate) 2] dimeric cages are linked to the sodium or silver counter-cations, respectively, through free carboxyl oxygen atoms. However, the structures are made more complex by the presence of labile water molecules in the lattice, resulting in some disorder. Furthermore, charge balance in both (1) and (2) requires the presence of two and one tri-negative tartrato units, respectively, among the ten independent tartrate units in each structure, an unusual feature for As and Sb complexes with this ligand species. Bond distances within the five arsenic( III)-(+)- tartrate dimers in each structure are: As-O (hydroxy), 1.75(2)-1.84(2) Angstrom (1); 1.75(3)-1.83(2) Angstrom (2) and As-O (carboxy), 1.94(2)-2.13(3) Angstrom (1); 1.95(2)-2.14(2) Angstrom (2). In addition, the structure of (2) has two short Ag-As bonds [2.500, 2.524(3) Angstrom] in the terminal sites of two of the five independent dimers, as well as an additional Ag-As bond [2.613(4) Angstrom] to an unusual dimeric arsenious acid residue (H4As2O5), part of an As2AgO3 hetero-ring forming the polymeric network structure. The antimony( III) citrate complex (3) is isomorphous and isostructural with the previously reported potassium analogue which involves mixed-valence citrato ligands in conventional bischelate four-coordination about the antimony centres, linked by both seven- and eight-coordinate rubidium ions [Rb-O, 2.743(10)-3.102(9) Angstrom]. The arsenic and antimony atoms in all compounds have typical distorted pseudotrigonal bipyramidal stereochemistry.