Bis- and tetrakis(organosilyl) decatungstosilicate, [gamma-SiW10O36(RSi)(2)O](4-) and [gamma-SiW10O36(RSiO)(4)](4-): Synthesis and structural determination by multinuclear NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The high propensity of organosilanes towards polycondensation and reaction with nucleophilic moieties has facilitated the formation of new organic - i norganic hybrids based on the lacunary divacant heteropolyanion [gamma-SiW1 0O36](8-). Depending on the experimental conditions two different types of derivatives were obtained with the general formula [gamma-SiW10O36(RSi)(2)O ](4-) (1) (> 90 % yield) and [gamma-SiW10O36(RSiO)(4)](4-) (2) (>85 % yield ) (R=H (1a, 2a), vinyl (1b), -C3H6OC(O)C-(Me)=CH2 (1c, 2c), phenyl (1d, 2d) ). The structures of the hybrid anions have been inferred from spectroscopi c data, in particular from multinuclear (Si-29 and W-183) NMR solution stud ies and from MALDI-TOF mass spectrometry. Both species correspond to the gr afting of an ore-bridged siloxane unit onto the surface of the lacunary pol yoxoanion.