Templated Synthesis of Heterobimetallic Nd─Co Clusters.

Heterometallic clusters are typically realized through the design of metal site-specific coordination environments. Their unusual metal-metal interactions and potentially synergistic effects toward small-molecule activation and catalysis are two of the many attributes of fundamental importance. Synthetic heterometallic clusters containing f- and d-block metals are challenging to design and synthesize, and lag far behind those only containing transition metals. To this end, we used compound LH5Nd (1), where LH8 = cyclen(1,4,7,10-tetra-o-NH2C6H4)4, and subjected it to metalation with Co2(HMDS)4 (HMDS = hexamethyldisilazide) resulting in LH3NdCo2(HMDS)2 (2). Cluster 2 displays a Nd─Co distance of 3.276(12) Å, which is under the shortest distance previously reported for a Nd─Co interaction (3.294(4) Å). Exposing 2 to dry dioxygen results in a dimeric species containing a single oxygen atom in a pseudo-planar geometry across two Nd and two Co atoms, (LH3)2Nd2Co2(µ4-O) (5). The Nd─Co distance in 5 shortens significantly to 2.993(6) Å. X-ray photoelectron spectroscopic studies reveal 5 to be best described as [NdIII 2CoIII 2], where the Co(III) centers remain high spin based on local structural metrics (davg (Co─N) = 2.02(4) Å and davg (Co─O) = 1.920(2) Å). Overall, we report the design and synthesis of well-defined heterobimetallic Nd─Co clusters and their metal-metal interaction synergy to activate dioxygen.