Novel surface-functionalized metal oxo clusters were obtained using an in situ surface-modification method based on the sol−gel process. A reaction of 2-bromoisobutyric acid with Zr(OPr)4 or Ti(OiPr)4 resulted in the compounds Zr5O4(BrC(CH3)2COO)10(OnPr)2(nPrOH)4 and Ti6O4(BrC(CH3)2COO)8(OiPr)8. The reaction of 2-bromopropionic acid with VO(OiPr)3 resulted in the cluster V3O3(BrC(CH3)COO)6(HOiPr). All obtained compounds have in common that the organic functionalities are exclusively located on the surface of the well-defined sub-nanometer metal oxo clusters. The prepared compounds were successfully used as macroinitiators in atom transfer radical polymerizations (ATRP) and produced inorganic−organic core−shell nanoparticles.

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Modified cubic spherosilicate cages of the type [Si8O20]8− were used as rigid, inorganic cores for the synthesis of macroinitiators for thermal and photoinduced free radical and controlled radical polymerizations. Two different routes to these macroinitiators were investigated: the direct modification of the octaanion with chlorosilane‐functionalized initiators and the hydrosilation of SiH‐substituted cages. The latter synthesis of the macroinitiators resulted in more defined reaction products. With these compounds, the polymerizations of styrene and methyl methacrylate were carried out. The free radical polymerizations showed broad polydispersities based on coupling reactions, whereas the copper‐mediated atom transfer radical polymerizations (ATRP) revealed that good polymerization control could be achieved with the prepared initiators. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3858–3872, 2002