Group 15 complexes with alpha-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)(C 4H3O6)(2)(H2O)(19)](n) (1), silver (+)-tartrato arsenate( III), [Ag9As10(C4 H2O6)(9)(C4H3O6)(H4As2O5)(H2O)(10)] (2) and rubidium citrato antimonate( II I) [Rb2Sb4 (C6H6O7)(6)(C6H7O7)(2)(H2O)(2)] (3) have been determined by X-ra y methods and refined to residuals of 0.085 (1), 0.072 (2) and 0.065 (3) fo r 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 anion ic [As 2 (tartrate) 2] dimeric cages are linked to the sodium or silver cou nter-cations, respectively, through free carboxyl oxygen atoms. However, th e structures are made more complex by the presence of labile water molecule s in the lattice, resulting in some disorder. Furthermore, charge balance i n both (1) and (2) requires the presence of two and one tri-negative tartra to units, respectively, among the ten independent tartrate units in each st ructure, an unusual feature for As and Sb complexes with this ligand specie s. Bond distances within the five arsenic( III)-(+)- tartrate dimers in eac h 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) ci trate complex (3) is isomorphous and isostructural with the previously repo rted potassium analogue which involves mixed-valence citrato ligands in con ventional bischelate four-coordination about the antimony centres, linked b y 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 dis torted pseudotrigonal bipyramidal stereochemistry.