Unusual Tri‑, Hexa‑, and Nonanuclear Cu(II) Cage Methylsilsesquioxanes: Synthesis, Structures, and Catalytic Activity in Oxidations with Peroxides

Three
types of unusual cagelike copper­(II) methylsilsesquioxanes, namely,
nona- [(MeSiO1.5)18(CuO)9] 1, hexa- [(MeSiO1.5)10(HO0.5)2(CuO)6­​(C12H8N2)2­(MeSiO1.5)10(HO0.5)1.33­​(CH3COO0.5)0.67(CuO)6­(C12H8N2)2] 2, [(MeSiO1.5)10(CuO)6­​(MeO0.5)2­(C10H8N2)2] 3, and trinuclear [(MeSiO1.5)8­​(CuO)3(C10H8N2)2] 4, were obtained in 44%,
27%, 20%, and 16% yields, respectively. Nuclearity and structural
fashion of products was controlled by the choice of solvent system
and ligand, specifically assisting the assembling of cage. Structures
of 1–4 were determined by single-crystal
X-ray diffraction analysis. Compounds 1 and 4 are the first cage metallasilsesquioxanes, containing nine and three
Cu ions, respectively. Product 1 is the first observation
of nonanuclear metallasilsesquioxane ever. Unique architecture of 4 represents early unknown type of molecular geometry, based
on two condensed pentamembered siloxane cycles. Topological analysis
of metal clusters in products 1–4 is provided. Complex 1 efficiently catalyzes oxidation
of alcohols with tert-butylhydroperoxide TBHP to
ketones or alkanes with H2O2 to alkyl hydroperoxides
in acetonitrile.