The document discusses the molecular orbital (MO) theory of coordination complexes. It explains that in MO theory, the symmetry of combining atomic orbitals must be the same to allow maximum orbital overlap. When forming molecular orbitals, lower energy atomic orbitals contribute more to bonding orbitals, while higher energy ones contribute more to antibonding orbitals. For an octahedral complex, the d-orbitals split into lower energy eg and higher energy t2g sets, and the document provides an example electronic configuration of the [Co(NH3)6]3+ complex.