Dinickela-bicyclo[4,4,0]-decadiene Complex with a Linear Heterometallic Mg–Ni–Ni–Mg Chain

Transition metal-diene complexes constitute a fundamental class of organometallic compounds, in which conjugated dienes typically behave as neutral π-donor ligands. While doubly reduced enediyl derivatives have been occasionally documented in the literatures, dinuclear transition metal complexes featuring such bonding motifs have not been explored. Herein, we report a heterometallic complex [(<b>L</b>Mg)₂Ni₂(C₄H₆)₂] (<b>L</b> = [(DIPPNCMe)₂CH]^-, DIPP = 2,6-^<i>i</i>Pr₂C₆H₃) featuring a linear Mg-Ni-Ni-Mg bonded chain, which was formed by the reaction of <b>L</b>MgBu·Et₂O with Ni(cod)₂ (cod: 1,5-cyclooctadiene). Experimental and computational studies reveal two <i>s-trans</i>-butadiene ligands bridging the Ni-Ni bond in a doubly reduced enediyl configuration. This unique bonding arrangement results in a dinickela-bicyclo[4,4,0]-decadiene framework containing a heterocyclic <i>trans</i>-cycloalkene moiety. Treatment of [(<b>L</b>Mg)₂Ni₂(C₄H₆)₂] with the additional butadiene afforded [(<b>L</b>Mg)₂Ni₂(C₄H₆)₃], involving three C₄H₆ ligands bound to nickel centers, in which they behave as two doubly reduced enediyl ligands and one neutral butadiene ligand. In contrast, upon exposure to carbon monoxide (CO), a ligand exchange reaction occurred, yielding [(<b>L</b>Mg)₂Ni₂(C₄H₆)(CO)₄] with one C₄H₆ ligand, which is considered as a dinickelacyclo-4-hexene supported by Mg-metalloligands.