title: Polyoxometalate (POM)-based, multi-functional, inorganic-organic, hybrid compounds: syntheses and molecular structures of silanol- and/or siloxane bond-containing species grafted on mono- and tri-lacunary Keggin POMs.
abstract: Using 3-mercaptopropyltrimethoxysilane (HS(CH₂)₃Si(OMe)₃) as a silane-coupling agent (SCA), mono- and tri-lacunary Keggin polyoxometalate (POM)-based, multi-functional, inorganic-organic, hybrid compounds, (Et₄N)₃[α-PW₁₁O₃₉{(HS(CH₂)₃Si)₂O}] EtN-1 (the 1 : 2 complex of a POM unit and organosilyl groups), (Bu₄N)₃[A-PW₉O₃₄(HS(CH₂)₃SiOH)₃] BuN-2 (the 1 : 3 complex) and (Bu₄N)₃[A-α-PW₉O₃₄(HS(CH₂)₃SiO)₃(Si(CH₂)₃SH)] BuN-3 (the 1 : 4 complex) were synthesized and unequivocally characterized by elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solid-state (²⁹Si and ³¹P) CPMAS NMR, solution (²⁹Si, ³¹P, ¹H and ¹³C) NMR, and X-ray crystallography. [Note: The moieties of their polyoxoanions are abbreviated simply as 1-3, respectively.] The X-ray molecular structures of EtN-1 and BuN-3 were determined. In EtN-1, two organic groups connected through a siloxane bond (-Si-O-Si- bond) were grafted on a mono-lacunary site of a Keggin POM, whereas in BuN-3 four organic groups connected through siloxane bonds were grafted on a tri-lacunary site of a Keggin POM. In BuN-2, three organic groups were grafted in the form of silanol (-SiOH) on a tri-lacunary site, i.e., in BuN-2 there was no siloxane bond. BuN-3 was synthesized as BuN-3a and BuN-3b by two methods, respectively; (1) BuN-3a was obtained by a 1 : 1 molar-ratio reaction of BuN-2 and an SCA in CH₃CN, and (2) BuN-3b was prepared by a direct 1 : 4 molar-ratio reaction of a tri-lacunary Keggin POM and SCA in water-CH₃CN. X-Ray crystallography revealed that BuN-3a is the same as BuN-3b. It is probable that BuN-2 is an intermediate in the formation of BuN-3. Terminal -SH groups in 1-3, as well as -OH groups in 2, can be utilized for immobilization of POMs and, also, as building blocks for the formation of novel hybrid compounds.
authors.affiliation: Department of Materials Science (present name Department of Chemistry), Faculty of Science, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Shotaro
authors.initials: S
authors.lastname: Aoki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kurashina
authors.forename: Yuhki
authors.initials: Y
authors.lastname: Kasahara
authors.forename: Tadashi
authors.initials: T
authors.lastname: Nishijima
authors.forename: Kenji
authors.initials: K
authors.lastname: Nomiya
mesh_terms: D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D017646:Organosilicon Compounds; D012821:Silanes / Q000737:chemistry*; D012833:Siloxanes / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D017973:Tungsten Compounds / Q000737:chemistry*; D000099294:Polyoxometalates
chemical_list: D017646:Organosilicon Compounds; D012821:Silanes; D012833:Siloxanes; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates; C102833:(3-mercaptopropyl)trimethoxysilane