Synthesis and structure of a bimetallic hybrid inorganic/organic layered coordination polymer with an octamolybdate cluster variant trapped between the α and δ isomeric forms

Hydrothermal combination of CuSO 4, MoO 3, and 4-phenylpyridine (4-phpyr) in a 1:4:4.5 ratio under basic conditions afforded purple crystals of {[Cu(4-phpyr) 4] 2(Mo 8O 26)·4-phpyr} ( 1), which were analyzed by spectroscopy and single crystal X-ray diffraction. The asymmetric octamolybdate clusters in 1 adopt an intermediate structural variant between the known α and δ isomeric forms, with four octahedral and three tetrahedral molybdenum coordination spheres, along with one molybdenum atom in a highly distorted square pyramidal environment. Paddle-wheel shaped [Cu(4-phpyr) 4] 2+ cations link adjacent {α/δ-Mo 8O 26} 4− clusters into a 2-D layered rhomboid grid coordination polymer. Uncoordinated 4-phpyr molecules lie in incipient voids in the interlamellar regions. The structure of 1 illustrates the utility of sterically bulky coordination complexes in the stabilization of intermediate conformations during energetically facile polyoxometallate isomer interconversion. Crystallographic data: triclinic, P1, a = 13.717(3) Å, b = 13.728(3) Å, c = 14.809(3) Å, α = 109.251(4)°, β = 107.670(4)°, γ = 92.005(4)°, V = 2480.0(9) Å 3, R 1 = 0.0637, wR 2 = 0.1054. [Display omitted] Hydrothermal combination of CuSO 4, MoO 3, and 4-phenylpyridine (4-phpyr) under basic conditions afforded purple crystals of {[Cu(4-phpyr) 4] 2(Mo 8O 26)·4-phpyr}, in which the octamolybdate clusters adopt an asymmetric α/δ intermediate structural variant. Paddle-wheel shaped [Cu(4-phpyr) 4] 2+ cations link adjacent clusters into a 2-D rhomboid grid pattern. Uncoordinated 4-phpyr molecules lie in incipient voids in the interlamellar regions.