Phenyl(iodo)platinum complexes having a 2,2′-bipyridine (bpy) or 1,2-bis(diphenylphosphino)ethane (dppe) ligand react with incompletely condensed silsesquioxane (c-C5H9)7Si7O9(OH)3 in the presence of Ag2O to yield platinasilsesquioxane complexes [Pt{(c-C5H9)7Si7O10(OH)2}(C6H5)(L)] (1, L = bpy; 2, L = dppe). NMR spectroscopy revealed their square-planar structures with an O-coordinated silsesquioxanate ligand and O−H···O hydrogen bonds within the ligand. Both complexes undergo transmetalation of p-methoxyphenylboronic acid to afford unsymmetrical diarylplatinum complexes [Pt(C6H4OCH3-p)(C6H5)(L)] (3, L = bpy; 4, L = dppe).