DFT investigations of the redox transmetallation reaction of the diorganomercurial (Hg(C6F5)2) with Yb metal, yielding Yb(C6F5)2, allowed us to define a very low energy reaction mechanism. This involves formation of a metal-metal bonded, formally Yb(I)-Hg(I), intermediate valence complex, (C6F5)Yb-Hg(C6F5). The subsequent reactivity of the divalent ytterbium complex with pyrazole was also computationally investigated, indicating that σ-bond metathesis occurs at divalent ytterbium.