Atomically Defined Nano-Propeller Fe₃Co₆Se₈(Ph₂PNTol)₆: Functional Model for the Electronic Metal-Support Interaction Effect, and High Catalytic Activity for Carbodiimide Formation

Abstract

Atomically defined interfaces that maximize the density of active sites and harness the electronic metal−support interaction are desirable to facilitate challenging multielectron transformations, but their synthesis remains a considerable challenge. We report the rational synthesis of the atomically defined metal chalcogenide nanopropeller Fe 3 Co 6 Se 8 L 6 (L = Ph 2 PNTol) featuring three Fe edge sites, and its ensuing catalytic activity for carbodiimide formation. The complex interaction between the Fe edges and Co 6 Se 8 support, including the interplay between oxidation state, substrate coordination, and metal−support interaction, is probed in detail using chemical and electrochemical methods, extensive single crystal X-ray diffraction, and electronic absorption and Mossbauer spectroscopy.

Hierarchical nanosheets built from superatomic clusters: properties, exfoliation and single-crystal-to-single-crystal intercalation

“…We illustrate the versatility of our synthetic strategy to program nanoclusters through the facile synthesis of the tricobalt variant, prepared similarly to Fe 3 Co 6 Se 8 L 6 . 35 With increased affinity of the edge sites for external ligands, the tricobalt nanopropeller is isolated exclusively as the tris-pyridine adduct Co 3 (py) 3 Co 6 Se 8 L 6 (1, 81% yield, Scheme 1). In nanocluster 1, each Co edge is anchored k 3 to the cluster core via two amides, and one surface selenium (Fig.…”

“…One is the intrinsic helicity of 1, isolated as a (D/L) racemic pair, stemming from the propeller geometry of its inorganic core. 35 The other is the stereogenic nature of the Co edge sites. The stereoisomerism of 1 is easiest understood by analogy to isomerism in 1,2,3-trisubstituted cyclopropanes, where the three substituents are either all oriented on the same face of the ring, or one points to the opposite side from the other two.…”

“…43,44 In 1, the Co 6 Se 8 support behaves as an electron reservoir, donating electron density to the Lewis-acidic edge sites through Co-Se interactions. 35 In turn, these core-edge contacts induce steric distortions and electron density redistribution within the Co 6 Se 8 core. As Se lone pairs engage in bonding interactions with the edge Co sites, their corresponding bonds to the core Co elongate from an average of 2.33 A to 2.38 A.…”

“…Specically, we recently introduced the synthesis of the helically chiral nanocluster, Fe 3 Co 6 Se 8 L 6 (L ¼ Ph 2 PN(Tol), Ph ¼ phenyl, Tol ¼ 4-tolyl), obtained by functionalizing the surface of the Chevreltype cluster Co 6 Se 8 L H 6 (L H ¼ Ph 2 PNHTol) with three Fe edges. 35 Oriented at the vertices of a triangle, the iron sites are poised to function as linker-attachment points that would impose 2D growth upon assembly with linear linkers. A quick evaluation of Fe 3 Co 6 Se 8 L 6 as a building block for self-assembly reveals a critical limitation: the Fe edges have very low affinities for external ligands.…”

Heavy chalcogenide-transition metal clusters as coordination polymer nodes

“…Here too, a similar strategy with molecular clusters has recently been reported with Fe edge sites supported by a Co 6 Se 8 cluster. 86 In addition to the unique binding sites provided by these clusters, the rich properties of metal-chalcogenides, such as photo-activity and redox-activity, can potentially enhance catalysis with cooperative effects. 87…”