Silylation of N2 Catalyzed by Cubic [Mo3S4Ni] Clusters Bearing Mo-Bound Cyclopentadienyl Ligands

Ni has been known as a relatively inert transition metal for N2 capturing and reduction. Based upon our recent report on N2 activation at the Fe site of cubic [CpR3Mo3S4Fe] clusters (CpR = C5Me5 (Cp*), C5Me4SiMe3 (CpL), C5Me4SiEt3 (CpXL)), we report herein a rare example of catalytic N2 silylation by the Ni congeners, [CpR3Mo3S4Ni] clusters. Even though the reduction of [CpR3Mo3S4Ni] precatalysts under a N2 atmosphere did not give stable and isolable N2-bound species, the clusters displayed up to 100 equiv. per cluster of N(SiMe3)3 formation from N2 in the presence of excess Na and ClSiMe3. This number is as high as four times the only previous report in lieu of molecular Ni catalyst. Computational studies on the potential N2-bound state of the [CpR3Mo3S4Ni] catalyst and its Fe analog gave quantitative insights into the role of the M(d) to N2(π*) π back-donation in the activation of the N-N bond.