STRUCTURAL ISOMERISM IN SILVER THIOETHER MACROCYCLIC CHEMISTRY - THE SYNTHESIS, REDOX PROPERTIES AND CRYSTAL-STRUCTURES OF [AGN([15]ANES5)N][PF6]N, [AG2([15]ANES5)2][BPH4]2 AND [AG([15]ANES5)][B(C6F5)4] ([15]ANES5=1,4,7,10,13-PENTATHIACYCLOPENTADECANE)

Reaction of AgNO3 with 1 molar equivalent of [15]aneS5 (1,4,7,10,13-pentathiacyclopentadecane) in refluxing MeOH-water gives a colourless solution. Addition of excess of counter ion [PF6-, BPh4- or B(C6F5)4-] affords the colourless complexes [Ag(n)([15]aneS5)n][PF6]n, [Ag2([15]aneS5)2][BPh4], and [Ag([15]aneS5)][B(C6F5)4] respectively in high yield. Single-crystal X-ray structural studies on these systems have revealed different cation stereochemistries as the counter ion is altered. Thus, [Ag(n)([15]aneS5)n] [PF6]n crystallises in the orthorhombic space group Iba2 with a = 25.713(3), b = 25.749(3), c = 11.6989(19) angstrom and Z = 16. The two independent infinite chains of cations in the structure are antiparallel. The stereochemistry at Ag(I) is severely distorted octahedral through an [S4 + S2] donor set, Ag(1) ... S(1) 3.219(5), Ag(1)-S(4) 2.659(5), Ag(l )-S(7) 2.651 (6), Ag(1) ... S(10) 3.075(7), Ag(1)-S(13) 2.564(6) angstrom, with one thioether donor from an adjacent [Ag([15]aneS5)]+ fragment asymmetrically bridging two metal centres, Ag(1)-S(l B) 2.742(5) angstrom. A similar geometry is observed at the second Ag ion, Ag(2) ... S(1') 3.263(5), Ag(2)-S(4') 2.605(5), Ag(2) ... S (7') 2.964(8), Ag(2)-S(10') 2.713(7), Ag(2)-S(13') 2.637(6), Ag(2)-S(1D) 2.714(5) A. The complex (Ag2([l 5]aneS5)2] [BPh4]2 crystallises in the triclinic space group P1BAR with a = 11.462(3), b = 11.895(3), c = 27.019(10) angstrom, alpha = 78.503(18), beta = 84.729(13), gamma = 67.118(18)-degrees, and Z = 2. The structure of the [Ag2([l 5]aneS5)2]2+ cation shows an unusual binuclear stereochemistry with (4 + 1 ] thioether donation to one silver(I) centre, Ag(2)-S(7') 2.558(4), Ag(2)-S(10') 2.623(5), Ag(2)-S(13') 2.716(5), Ag(2)-S(1) 2.486(3), Ag(2) ... S(1') 3.131 (3) angstrom, and [3 + 1 ] thioether donation to the other, Ag(1)-S(7) 2.529(3), Ag(1)-S(10) 2.608(4), Ag(1)-S(1') 2.537(3), Ag(1) ... S(1) 2.907(3) angstrom. Thus, one S-donor [S(1) and S(1')] of each macrocycle bridges asymmetrically between the two metal centres. The complex [Ag([l 5]aneS5)] [B(C6F5)4] crystallises in the triclinic space group P1BAR with a = 12.476(5), b = 13.658(7), c = 15.608(6) angstrom, alpha = 108.300(22), beta = 108.467(17), gamma = 100.518(21)-degrees and Z = 2. The structure contains discrete mononuclear [Ag([15]aneS5)]+ cations and [B(C6F5)4]- anions. The geometry at Ag(I) is asymmetric with all five thioether donors of the macrocycle interacting with the metal centre: Ag-S(1) 2.4712(19), Ag ... S(4) 2.7262(20), Ag-S(7) 2.6847(21), Ag-S(10) 2.5621(19), Ag ... S(13) 2.8813(19) angstrom. In MeCN solution [Ag ([15]aneS5)]+ shows a chemically reversible Ag(I)-Ag(II) redox couple at E1/2 = 0.76 V and a quasi-reversible Ag(I)-Ag0 couple at -0.37 V vs. ferrocene-ferrocenium. The intensely coloured d9 silver(II) oxidation product has been observed by X- and Q-band ESR spectroscopy and the oxidation of Ag(I)to Ag(II) monitored spectroelectrochemically.