SILVER MACROCYCLIC COMPLEXES - SYNTHESIS, CRYSTAL-STRUCTURES AND REDOX PROPERTIES OF [AG([18]ANEN2S4)]PF6 AND [AG(ME2[18]ANEN2S4)]BPH4([18]ANEN2S4=1,4,10,13-TETRATHIA-7,16-DIAZACYCLOOCTADECANE, ME2[18]ANEN2S4=7,16-DIMETHYL-1,4,10,13-TETRATHIA-7,16-DIAZACYCLOOCTADECANE)

Reaction of AgNO3 with one molar equivalent of [18]aneN2S4 (1,4,10,13-tetrathia-7,16-diazacyclooctadecane) or Me2[18]aneN2S4 (7,16-dimethyl analogue) in refluxing MeOH-H2O affords the complex cations [Ag([18]aneN2S4)]+ and [Ag(Me2[18]aneN2S4)]+ respectively. [Ag([18]aneN2S4)]PF6 crystallises in the orthorhombic space group Pcab with a = 16.7327(25), b = 17.5023(11), c = 14.7031(6) angstrom and Z = 8. The metal ion is bound to a highly distorted octahedral arrangement of the six macrocyclic donor atoms [Ag-S 2.630(4), 2.664(4), 2.719(4), 2.774(4) angstrom; Ag-N 2.533(10), 2.817(15) angstrom]. The complex cation adopts a rac configuration in which the two S-N-S linkages are bound meridionally to the metal ion. [Ag(Me2[18]aneN2S4)]BPh4 crystallises in the monoclinic space group P2(1)/n with a = 10.7529(15), b = 19.0571(28), c = 18.9360(22) angstrom, beta = 106.035(10)degrees and Z = 4. The cation is disordered and shows two different configurations. The major [70.8(8)%] component shows an unusual kite-based pyramidal geometry with Ag(I) bound via a periplanar arrangement of four S-donor atoms [Ag-S(1) 2.583(4), Ag-S(4) 2.819(3), Ag-S(10) 2.663(4), Ag-S(13) 2.673(4) angstrom] and one apical N-donor atom [Ag-N(7) 2.517(11) angstrom]. The second N-donor atom does not interact with the metal centre [Ag ... N(16) 3.684(11) angstrom]. In view of the asymmetric bond length distribution, the overall stereochemistry may alternatively be described as tetrahedral through S(1), N(7), S(10) and S(13), with S(4) interacting more weakly at long range. Although this complex is severely distorted, it is clear that unlike in [Ag([18]aneN2S4)]+, the S(4)-N(7)-S(10) linkage in [Ag(Me2[18]aneN2S4)]+ binds facially to the Ag(I) centre to give a distorted meso isomer. The minor [29.2(8)%] component differs only in the orientation of the S(1), N(16') and S(13) linkage. Although the C-C and C-S bond lengths in this region were constrained, it is clear that N(16') is directed towards, and is co-ordinated to the Ag(I) centre [Ag-N(16') 2.778(10) angstrom], giving an octahedral complex in a genuine meso configuration. [Ag([18]aneN2S4)]+ shows a reversible Ag(I)-Ag(II) couple at E1/2 = + 0.65 V and a quasi-reversible Ag(I)-Ag0 couple at E1/2 = -0.74 V while [Ag(Me2[18]aneN2S4)]+ shows an irreversible Ag(I)-Ag(II) couple at E(pa) = +0.78 V and an irreversible Ag(I)-Ag(0) couple at E(pc) = -0.78 V (all potentials vs. ferrocene-ferrocenium).