Final answer:
MLCT is likely to occur in complexes with transition metals having low oxidation states and vacant orbitals, ligands capable of accepting electrons, and a suitable electronic structure that permits the necessary energy transitions as elucidated by Crystal Field Theory.
Step-by-step explanation:
The characteristics of a complex that make a Metal-to-Ligand Charge Transfer (MLCT) likely to occur include the nature of the transition metal, the type of ligands attached to the metal, and the overall electronic structure of the complex.
Transition metals with low oxidation states and the presence of empty d or p orbitals can facilitate MLCT because they allow the transfer of electrons from the metal to the ligands. Ligands that are capable of accepting electrons, often characterized by having π*-orbitals such as unsaturated organic molecules, enhance the likelihood of MLCT. Furthermore, the presence of strong field ligands can split the d-orbital energy levels of the metal, making MLCT transitions more probable when light is absorbed, which is often observed as vivid colors.
Crystal Field Theory (CFT) plays a significant role in explaining these interactions, although it considers metal-ligand bonds as electrostatic, which might not always accurately describe the nature of bonding in all complexes.