Inorganic clusters as metalloligands: ligand effects on the synthesis and properties of ternary nanopropeller clusters

Abstract

Redox-active multimetallic platforms with synthetically addressable and hemilabile active sites are attractive synthetic targets for mimicking the reactivity of enzymatic co-factors toward multielectron transformations. To this end, a family of ternary clusters featuring three edge metal sites anchored on a [Co₆Se₈] multimetallic support via amidophosphine ligands are a promising platform. In this report, we explore how small changes in the stereoelectronic properties of these ligands alter [Co₆Se₈] metalloligand formation, but also substrate binding affinity and strength of the edge/support interaction in two new ternary clusters, M₃Co₆Se₈L₆ (M = Zn, Fe; L⁽⁻⁾ = Ph₂PN⁽⁻⁾ⁱPr). These clusters are characterized extensively using a range of methods, including single crystal X-ray diffraction, electronic absorption spectroscopy and cyclic voltammetry. Substrate binding studies reveal that Fe₃Co₆Se₈L₆ resists coordination of larger ligands like pyridine or tetrahydrofuran, but binds the smaller ligand CN^tBu. Additionally, investigations into the synthesis of new [Co₆Se₈] metalloligands using two aminophosphines, Ph₂PN(H)ⁱPr (L^H) and ⁱPr₂PN(H)ⁱPr, led to the synthesis and characterization of Co₆Se₈L^H₆, as well as the smaller clusters Co₄Se₂(CO)₆L^H₄, Co₃Se(μ₂-PPh₂)(CO)₄L^H₃, and [Co(CO)₃(ⁱPr₂PN(H)ⁱPr)]₂. Cumulatively, this study expands our understanding on the effect of the stereoelectronic properties of aminophosphine ligands in the synthesis of cobalt chalcogenide clusters, and, importantly on modulating the push–pull dynamic between the [Co₆Se₈] support, the edge metals and incoming coordinating ligands in ternary M₃Co₆Se₈L₆ clusters.