Unstable intermediates. Part 169. Electron-gain and -loss centres in irradiated potassium dicyanoargentate(I)

Abstract

Exposure of K[Ag(CN)₂] to ⁶⁰Co γ-rays at 77 K gives two paramagnetic species, A and B. Species A, having g_∥ 2.001, g_⊥ 2.006. A_∥(¹⁰⁹Ag) 60 G, and A_⊥(¹⁰⁹Ag) 30 G, is identified as an electron-gain centre, [Ag(CN)₂]^2–, with the extra electron in a σ* orbital with 4d_z²+ 5s character on silver and considerable density on the ligands. Species B, having g_x 2.091, g_y 2.051, g_z 2.008. A_x(¹⁰⁹Ag) 42 G, A_y 34 G, and A_z⩽ 65 G, is thought to be the electron-loss centre, Ag[CN]₂ with the hole largely localised in silver (again, 4d_z²± 5s); on annealing above 77 K, centre B, acquired axial symmetry (g_⊥ 2.078, A_⊥ 29 G). Solutions in methanol give a poorly defined centre similar to A at 77 K. On annealing, a new species having A_iso.(¹⁰⁹Ag) 155 G and A(¹⁴N)(one) 17.3 G with g_av. 2.002 is obtained. This is tentatively identified as [Ag(CN)]^– and reasons for the large hyperfine coupling to ¹⁴N are discussed.