A complex having the structure of formula (I) is disclosed. L1, L2, L3, L4, and L5 may be or include independently metal-coordinating ligands selected from the group consisting of neutral ligands, anionic ligands, and mixed ligands, and combinations thereof. In a non-limiting embodiment, the complex is an N-heterocyclic carbene (NHC) Re(I) complex having an unsubstituted or substituted benzimidazol-2-ylidene ligand. The complex may be included in a pharmaceutical composition for treating gram (+) bacterial infections.