Organic-inorganic hybrid nano-building blocks of aromatic nitro-, aldehyde-, and bromo-functionalized polyhedral oligomeric silsesquioxanes were easily prepared through nucleophilic substitutions, starting from the reactions between octakis(3-chloropropyl)octasilsesquioxane and phenoxide derivatives. These phenoxide anions not only supply the substitution functions to a silsesquioxane cage, but can also induce a cage-rearrangement leading to the formation of octa-, deca-, and dodecahedral silsesquioxane cages.

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Silsesquioxane formation competing with the deprotonation of alcohol solvents in the presence of a strong base to form alkoxides is reported for the first time. Evidently, sodium isopropoxide is formed during the synthesis of the sodium salt of a double‐decker octaphenylsilsesquioxane tetrasilanolate in 2‐propanol as the solvent, which leads to the formation of unexpected cis‐ and trans‐di[(3‐chloropropyl)isopropoxysilyl]‐bridged double‐decker octaphenylsilsesquioxanes after in situ coupling with 3‐chloropropyltrichlorosilane. The desired products were characterized by 1H NMR, 13C NMR, and 29Si NMR spectroscopy; ESI‐MS; and single‐crystal X‐ray diffraction.

We describe a novel and green synthetic methodology for the fabrication of polyhedral oligomeric silsesquioxane-supported N-heterocyclic carbenes/imidazolium salts on palladium(II) complexes; Pd(II)-MPIm-POSS (1) composite by solid-state annealing between Pd(OAc) 2 and octakis(3-(1-methylimidazolium)propyl) octasilsesquioxane without added base. Subsequently, arylboronic acid based in situ or ex situ reduction of 1 in aqueous ethanol produces polyhedral oligomeric silsesquioxane-supported N-heterocyclic carbenes/imidazolium salts on palladium nanoparticles; Pd(0)-nano-POSS (2) composite, consisting of monodispersed and N-heterocyclic carbene (NHC) stabilized Pd nanoparticles of very small size (3.0 AE 1.5 nm). Nanocatalyst 2 is a highly efficient and easily recyclable homogeneous catalyst for Suzuki-Miyaura cross-coupling reactions with TOF up to 1670 h À1 .Palladium nanoparticles stabilized on solid supports have been used in various applications including chemical sensor and catalysis, particularly for reduction and C-C coupling reactions. [1] Over the past decades, development of an efficient and environmentally friendly method to fabricate monodispersed metal nanoparticles with definite size and shape, high catalytic activity, exceptional stability, and multiple recyclability is highly desirable for practical applications. In particular, novel methods for the fabrication of palladium nanocomposites on a non-toxic support and stabilizer have been actively pursued. [2] In this context due to strong s donating properties and coordinating ability to the metal center, the N-heterocyclic carbene (NHC) has shown to be an excellent ligand for transition metals as well as metal nanoparticles. [3] Despite many examples of NHC ligands in homogeneous metal-catalyzed chemical transformations and polymer synthesis, fewer reports involving carbene stabilized d block metal nanoparticles are known with limited applications. [4]