Reactivity of a Stable and Highly Electron-Rich (η-Diborabenzene)nickel(0) Synthon.

The reaction of the diborabenzene (DBB) nickel(0) pogo-stick complex [(η-DBB)Ni(CO)] () with a large excess of [Ni(CO)] yields the dark green, unstable dinickel(0) complex [(η-DBB)Ni(μ-CO)Ni(CO)] (), which loses one CO ligand to yield the purple, bimetallic Ni half-sandwich complex [(η-DBB)Ni(μ-CO)(η-CO)] (). The addition of the chromium aminoborylene complex [(OC)Cr{BN(TMS)}] (TMS = trimethylsilyl) to does not result in the expected borylene transfer but in the formation of the black Ni-Cr complex [(η-DBB)Ni(μ-CO)Cr(CO)] (), alongside the dimeric iminoborane [(TMS)BN(TMS)] (), which results from the rearrangement of the released BN(TMS) aminoborylene moiety. Furthermore, the oxidative addition of methyl triflate (MeOTf) to leaves the (η-DBB)Ni moiety intact and provides the ionic Ni half-sandwich complex [(η-DBB)NiMe(CO)]OTf (), while reaction with pentaphenylborole (PPB) yields the unique, dark-blue, unsymmetrical sandwich complex [(η-DBB)Ni(μ-CO)(η-PPB)] (). DFT calculations point toward being a dinickel(0) complex with a neutral aromatic DBB and a neutral antiaromatic PPB ligand.