Preparation, spectroscopy and reaction with oxygen of [Co(en)2]2+ on the surface of hectorite

Abstract

Planar low-spin [Co(en)₂]²⁺ is prepared by vacuum decomposition of [Co(en)₃]²⁺ on the surface of hectorite in the temperature range 423–500 K. The e.p.r. parameters of [Co(en)₂]²⁺ are: g_⊥= 2.579 ± 0.002, A_⊥= 0.0174 cm^–1, g_∥= 1.964 ± 0.002 and A_∥= 0.0149 cm^–1. The unpaired electron spin density is distributed as follows: 68% in Co(3d_z²), 13% in Co(4s) and 19% on ligand orbitals. The d–d reflectance spectrum is analysed in the strong ligand-field limit and in the angular-overlap model approximation with D_4h symmetry. The most probable parameters are: B= 455 cm^–1, 10D_q= 16709 cm^–1, E(d_x²–y²)–E(d_z²)= 17 800 cm^–1 and E(d_x²–y²)–E(d_xz, d_yz)= 22 909 cm^–1, l_σ= 8900 cm^–1, l_πx= 1896 cm^–1 and l_πy= 2498 cm^–1. The reaction of [Co(en)₂]²⁺ with O₂ is diffusion controlled on the surface of hectorite.