Organic-inorganic hybrids based on polyoxometalates.: 6.: Syntheses, structure, and reactivity of the bis(tert-butylsilyl)decatungstophosphate [(γ-PW10O36) (t-BuSiOH)2]3

Bis(tert-butylsilyl)decatungstophosphate (n-Bu4N)(3)[(gamma -PW10O36)(t-BuSiOH)(2)] (1) has been synthesized through phase-transfer conditions, by reaction of t-BuSiCl3 with Cs-7[(gamma -PW10O36)]. xH(2)O. This new hybrid anion has been characterized by elemental analysis, X-ray crystallography, multinuclear solution and solid-state NMR, and infrared spectroscopy. Crystals of 1 are monoclinic, space group C2/c, with lattice constants a = 44.762(10) Angstrom, b = 19.032(4) Angstrom, c = 22.079(8) Angstrom, beta = 98.9(2)degrees, and Z = 8. Anion 1 has nominal C-s symmetry and displays an "open structure" with two t-BuSiOH;groups anchored to the (gamma -PW10O36) framework. The two t-BuSiOH units are nonequivalent as confirmed by Si-29 CP-MAS NMR and by diffuse reflection infrared spectroscopy. The two OH groups are linked through one H-bond (d(O-O) = 2.63 Angstrom). According to Si-29 and W-183 NMR, 1 adopts a more symmetrical conformation (C-2v) in solution. Anion 1 reacts cleanly in homogeneous conditions with Me2SiCl2 to yield (n-Bu4N)(3)[(gamma -PW10O36)(t-BuSiO)(2)(SiMe2)] (2). The structure of 2 has been inferred from multinuclear NMR and infrared spectroscopy. The hybrid "closed-structure" anion 2 consists of the (gamma -PW10O36) framework on which is grafted a heterosilylated network composed of a capping fragment, Si(CH3)(2), Linked to the t-BuSi groups through two siloxane bridges.