A novel sandwich-type polyoxometalate incorporating a unique hybrid hexanuclear copper cluster, [Cu(enMe)(2)](2){[Cu(enMe)(2)(H2O)](2)[Cu-6(enMe)(2)(B-a-SiW9O34)(2)]}ce nter dot 4H(2)O (1, enMe = 1,2-diaminopropane), has been hydrothermally synthesized and structurally characterized by the elemental analyses, IR spectroscopy, TG analysis, magnetic properties, and single-crystal X-ray diffraction analysis. Crystal data for 1 triclinic, P (1) over bar; a = 12.5105(2), b = 14.3710(2), c = 17.2687(2) A; alpha = 98.834(1), beta = 110.744(1), gamma = 104.711(1)degrees; V = 2704.57(7) A(3); rho = 3.646 g/cm(3); Z = 1. X-ray crystallographic study shows that the molecular structure of 1 contains 10 copper ions: Six of them form an unprecedented inorganic-organic hybrid Cu-6 cluster via edge-sharing combination of two CuO6 octahedra, two CuO5, and two CuO3N2 square pyramids and are encapsulfated between two {B-a-SiW9O34} units. Two of them form two [Cu(enMe)(2)(H2O)](2+) complexes and further attach to the two {B-a-SiW9O34} units via two Cu-OW bridges, acting as a decorated role. The remaining two form isolated [Cu(enMe)(2)](2+) complexes playing roles of charge-compensation and space-fillers. Magnetization measurement reveals that the hexanuclear copper cluster exhibits overall ferromagnetic interactions.