The monometallic pseudo-octahedral complex, [Co(H2O)2(CH3COO)2(C5H5N)2], is shown to exhibit slow magnetic relaxation under an applied field of 1500 Oe. The compound is examined by
a combination of experimental and computational techniques in order to elucidate the nature of its electronic structure and slow magnetic relaxation. We demonstrate that any sensible model of the electronic structure must include a proper treatment of the first-order orbital angular momentum,
and we find that the slow magnetic relaxation can be well described by a two-phonon Raman process dominating at high temperature, with a temperature independent quantum tunnelling pathway being most efficient at low temperature.