Thermal and photochemical dimer formation in (n-Bu4N)3[Co(CN)5Cl] and (n-Bu4N)3[Co(CN)5NCS]

Abstract The thermal and the photochemical reactivity of (n-Bu 4 N) 3 )[Co(CN) 5 Cl] and(n- Bu 4 N) 3 )[Co(CN) 5 NCS] have been investigated in CH 2 Cl 2 solution. Experimental evidence is found for the formation of CN bridged binuclear Co(III) complexes. (n-Bu 4 N) 3 )[Co(CN) 5 Cl] reacts thermally to give a reaction product which can be identified from its infrared spectrum as (n-Bu 4 N)[(NC) 5 CoNCCo(CN) 4 Cl]. Its identification and the kinetics of its formation are discussed. Irradiation at 405 nm yields the same product (Π ⩽ 10 −3 at 273 K). (n-Bu 4 N) 3 [Co(CN) 5 NCS] is thermally stable in CH 2 Cl 2 solutions at room temperature. Irradiation at 405 nm causes the formation of the dimer product (n-Bu 4 N) 5 [Co 2 (CN) 10 NCS]. The quantum yield at room temperature is found to be 0.30.