Multiple‐Oxidation‐State Tungsten‐Oxide Clusters on a Carbon Surface as an Intersection between Molecular and Bulk Oxides

Bulk tungsten oxides exhibit a wide range of oxidation states, whereas the oxidation states available in molecular oxides such as polyoxometalates (POMs) is limited. In this paper, tungsten oxide clusters with diameters of 1.2±0.4 ( W 60 O x /C ), 1.1±0.4 ( W 28 O x /C ), and 0.9±0.3 nm ( W 12 O x /C ) were produced in a size‐selective manner on graphitic carbon by using a phenyl‐azomethine‐type dendrimer as a template and applying hydrogen reduction after fixing the dendrimers on a support. X‐ray photoelectron spectroscopy revealed that the W atoms in the clusters exhibited multiple oxidation states, i. e., W δ + , W 4+ , W 5+ , and W 6+ . Moreover, X‐ray absorption fine structure measurements indicated the W−W bond length of 2.84–2.85±0.01 Å in these clusters. Auto‐oxidation with adventitious oxygen after hydrogen reduction is proposed as a reasonable mechanism for the formation of these clusters on the carbon surface.