Synthesis of V/Fe/S Clusters Using Vanadium(III) Thiolate Complexes Bearing a Phenoxide-Based Tridentate Ligand

Vanadium­(III) thiolate complexes carrying a phenoxide-based tridentate ligand were prepared from the reactions of V­(NMe₂)₄ with the protonated forms of tridentate ligands (H₂­(O,P,O) = bis­(3,5-di-<i>tert</i>-butyl-2-hydroxy­phenyl)­phenylphosphine or H₂(O,O,O) = bis­(3,5-di-<i>tert</i>-butyl-2-hydroxy­phenyl)­phenyl­phosphine­oxide) and thiols (HSR; R = mesityl (Mes), 2,4,6-<i>ⁱ</i>Pr₃C₆H₂ (Tip)). The vanadium–thiolate complexes were subjected to the V/Fe/S cluster synthesis via treatment with an Fe­(II) thiolate complex [(TipS)­Fe]₂­(μ-SDmp)₂ (<b>4</b>, Dmp = 2,6-(mesityl)₂­C₆H₃) and elemental sulfur in toluene, leading to the formation of two new V/Fe/S clusters. One is an edge-bridged double-cubane-type [VFe₃S₄]-[VFe₃S₄] cluster [(O,P,O)­VFe₃S₄­(SDmp)­(HNMe₂)]₂ (<b>5</b>) having face-capping tridentate (O,P,O) ligands on vanadium atoms. The other is a [VFe₃S₄-Fe] cluster [(μ-O,O,O)­VFe₃S₄­(SDmp)­(STip)­Fe­(μ-SDmp)] (<b>6</b>), the core of which consists of a cubane-type [VFe₃S₄] unit and an external iron atom. The external iron is bound to an SDmp ligand and two oxygen atoms of the tridentate (O,O,O) ligand. Cluster <b>6</b> is structurally relevant to the active site of nickel-dependent CO dehydrogenase, and their common structural features include a cubane-type unit with a heterometal, one more iron atom besides the cubane unit, and a bridging ligand between the external iron and the heterometal of the cubane unit