Showing papers by "Gillian Reid published in 1991"

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)

Abstract: 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)A 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)A; Ag–N 2.533(10), 2.817(15)A]. 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 P21/n with a= 10.7529(15), b= 19.0571(28), c= 18.9360(22)A, β= 106.035(10)° 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 AgI bound via a periplanar arrangement of four S-donor atoms [Ag–S(1) 2.583(4), Ag–S(4), Ag–S(4) 2.819(3), Ag–S(10) 2.663(4), Ag–S(13) 2.673(4)A] and one apical N-donor atom [Ag–N(7) 2.517(11)A]. The second N-donor atom does not interact with the metal centre [Ag ⋯ N(16) 3.684(11)A]. 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 facilally to the AgI 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 Ag1 centre [Ag–N(16′) 2.778(10)A], giving an octahedral complex in a genuine meso configuration. [Ag([18]aneN2S4)]+ shows a reversible AgI–AgII couple at E½=+0.65 V and a quasi-reversible AgI–Ag0 couple at E½=–0.74 V while [Ag(Me2[18]aneN2S4)]+ shows an irreversible AgI–AgII couple at Epa=+0.78 V and an irreversible AgI–Ag0 couple at Epc=–0.78 V (all potentials vs. ferrocene–ferrocenium).