DFT challenge of intermetallic interactions: From metallophilicity and metallaromaticity to sextuple bonding

In this review, I have tried to summarize the current state of research related to metal-metal bonding modes under the perspectives of DFT computational techniques. I have deliberately devoted considerable attention on the theoretical bonding characterization toolbox that includes a variety of computational techniques. The most recent advances in the chemistry of coordination compounds of the d- and f-block elements that contain d-d, f-f or d-f metal-metal bonds are outlined. There seems little doubt that the chemistry of metal-metal bonded species and clusters will continue to throw up surprises that challenge theory and that will, ultimately, give us a deeper understanding of the nature of the chemical bond that fall anywhere upon a continuum ranging from weak magnetic coupling, metallophilicity and metallaromaticity to multiple (single up to sextuple) metal-metal bonding.