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 [(LMg)₂Ni₂(C₄H₆)₂] (L = [(DIPPNCMe)₂CH]^-, DIPP = 2,6-ⁱPr₂C₆H₃) featuring a linear Mg-Ni-Ni-Mg bonded chain, which was formed by the reaction of LMgBu·Et₂O with Ni(cod)₂ (cod: 1,5-cyclooctadiene). Experimental and computational studies reveal two s-trans-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 trans-cycloalkene moiety. Treatment of [(LMg)₂Ni₂(C₄H₆)₂] with the additional butadiene afforded [(LMg)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 [(LMg)₂Ni₂(C₄H₆)(CO)₄] with one C₄H₆ ligand, which is considered as a dinickelacyclo-4-hexene supported by Mg-metalloligands.