Hydrothermal synthesis and structures of three new copper complexes: [{Cu(2,2′-bipy}2(β-Mo8O26)], [{Cu(py)3}2{Cu(py)2}2(α-Mo8O26)] and [Cu(py)2]4[(SO4)Mo12O36]

TLDR: Two interesting organic-inorganic hybrid solids [{Cu(2,2′-bipy)2}2(β-Mo8O26)] and [Cu(py)2]4[Mo12O36(SO4)] were synthesized by hydrothermal methods and structurally characterized by X-ray diffraction.

Abstract: Two interesting organic–inorganic hybrid solids [{Cu(2,2′-bipy)2}2(β-Mo8O26)] (1), [{Cu(py)3}2{Cu(py)2}2(α-Mo8O26)] (2), and a new two-electron-reduced Keggin-core compound [Cu(py)2]4[Mo12O36(SO4)] (3), were synthesized by hydrothermal methods and structurally characterized by X-ray diffraction. The structure of 1 consists of discrete [{Cu(2,2′-bipy)2}2(β-Mo8O26)] clusters, constructed from β-[Mo8O26]4− subunits covalently bonded to two [Cu(2,2′-bipy)2]2+ coordination cations via bridging oxo groups that connect two adjacent molybdenum sites. The structure of 2 consists of heterometallic dodecanuclear clusters, [{Cu(py)3}2{Cu(py)2}2(α-Mo8O26)], connected via π–π stacking contacts into an extended 1-D chain. Each [α-Mo8O26]4− anion forms weak covalent interactions to two [Cu(py)3]+ and two [Cu(py)2]+ units through terminal oxo groups of the octamolybdate cluster. A new compound [Cu(py)2]4[MoV2Mo10O36(SO4)] (3), with two-electron-reduced Keggin anions, was unexpectedly obtained from the similar hydrothermal treatment of 2. Compounds 1–3 are of interest due to their unusual Cu-coordination geometries; trigonal bipyramidal Cu(II), distorted tetrahedral, T-shaped trigonal, and linear Cu(I) are observed, and in 2, two distinct Cu(I)-coordination geometries are observed in the same structure!