Structural Isomerism in Silver Thioether Macrocyclic Chemistry: the Synthesis, Redox Properties and Crystal Structures of n(aneS5)n>n, aneS5)2>2 and aneS5)>(B(C6F5)4> (aneS5 = 1,4,7,10,13-pentathiacyclopentadecane)

Article abstract of DOI:10.1039/DT9930000521

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 -, BPh4^- or B(C6F5)4^-> affords the colourless complexes n(<15>aneS5)_n>_n, aneS5)2>2 and aneS5)> 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, n(<15>aneS5)_n>_n crystallises in the orthorhombic space group Iba2 with a = 25.713(3), b = 25.749(3), c = 11.6989(19) Angstroem 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 donor set, Ag(1)...S(1) 3.219(5), Ag(1)-S(4) 2.659(5), Ag(1)-S(7) 2.651(6), Ag(1)...S(10) 3.075(7), Ag(1)-S(13) 2.564(6) Angstroem, with one thioether donor from an adjacent aneS5)>⁺ fragment asymmetrically bridging two metal centres, Ag(1)-S(1B) 2.742(5) Angstroem.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) Angstroem.The complex aneS5)2>2 crystallises in the triclinic space group P1/ with a = 11.462(3), b = 11.895(3), c = 27.019(10) Angstroem, α = 78.503(18), β = 84.729(13), γ = 67.118(18) deg, and Z = 2.The structure of the 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) Angstroem, 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) Angstroem.Thus, one S-donor of each macrocycle bridges asymmetrically between the two metal centres.The complex aneS5)> crystallises in the triclinic space group P1/ with a = 12.476(5), b = 13.658(7), c = 15.608(6) Angstroem, α = 108.300(22), β = 108.467(17), γ = 100.518(21) deg and Z = 2.The structure contains discrete mononuclear aneS5)>⁺ cations and ^- anions.The geometry at Ag^I is asymmetric wih 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) Angstroem.In MeCN solution aneS5)>⁺ shows a chemically reversible Ag^I-Ag^II redox couple at E_1/2 = 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.