Hydrocarbon-Soluble Nanocatalysts with No Bulk Phase: Coplanar, Two-Coordinate Arrays of the Base Metals

A structurally unique class of hydrocarbon-soluble,
ancillary-ligand-free,
tetrametallic Co­(I) and Ni­(I) clusters is reported. The highly unsaturated
complexes are supported by simple, sterically bulky phosphoranimide
ligands, one per metal. The electron-rich nitrogen centers are strongly
bridging but sterically limited to bimetallic interactions. The hydrocarbon-soluble
clusters consist of four coplanar metal centers, mutually bridged
by single nitrogen atoms. Each metal center is monovalent, rigorously
linear, and two-coordinate. The clusters are in essence two-dimensional
atomic-scale “molecular squares,” a structural motif
adapted from supramolecular chemistry. Both clusters exhibit high
solution-phase magnetic susceptibility at room temperature, suggesting
the potential for applications in molecular electronics. Designed
to be catalyst precursors, both clusters exhibit high activity for
catalytic hydrogenation of unsaturated hydrocarbons at low pressure
and temperature.