Marina S. Dronova

Cage‐like Copper(II) Silsesquioxanes: Transmetalation Reactions and Structural, Quantum Chemical, and Catalytic Studies

The transmetalation of bimetallic copper-sodium silsesquioxane cages, namely, [(PhSiO1.5 )10 (CuO)2 (NaO0.5 )2 ] (Cooling Tower; 1), [(PhSiO1.5 )12 (CuO)4 (NaO0.5 )4 ] (Globule; 2), and [(PhSiO1.5 )6 (CuO)4 (NaO0.5 )4 (PhSiO1.5 )6 ] (Sandwich; 3), resulted in the generation of three types of hexanuclear cylinder-like copper silsesqui- oxanes, [(PhSiO1.5 )12 (CuO)6 (C4 H9 OH)2 (C2 H5 OH)6 ] (4), [(PhSiO1.5 )12 (CuO)6 (C4 H8 O2 )4 (PhCN)2 (MeOH)4 ] (5), and [(PhSiO1.5 )12 (CuO)6 (NaCl)(C4 H8 O2 )12 (H2 O)2 ] (6). The products show a prominent solvating system-structure dependency, as determined by X-ray diffraction. Topological analysis of cages 1-6 was also performed. In addition, DFT theory was used to examine the structures of the Cooling Tower and Cylinder compounds, as well as the spin density distributions. Compounds 1, 2, and 5 were applied as catalysts for the direct oxidation of alcohols and amines into the corresponding amides. Compound 6 is an excellent catalyst in the oxidation reactions of benzene and alcohols.

Family of Polynuclear Nickel Cagelike Phenylsilsesquioxanes; Features of Periodic Networks and Magnetic Properties

A new family of bi-, tetra-, penta-, and hexanickel cagelike phenylsilsesquioxanes 1-6 was obtained by self-assembly and transmetalation procedures. Their crystal structures were established by single-crystal X-ray analysis, and features of crystal packing relevant to the network formation were studied by a topological analysis. Compounds 1, 2, and 4 are isolated architectures, while 3, 5, and 6 present extended 1D and 3D networks. The investigation of magnetic properties revealed the presence of ferro- (1 and 3-5) or antiferromagnetic (2 and 6) interactions between Ni(II) ions, giving rise in the most cases (1, 2, and 4-6) to the presence of a slow relaxation of the magnetization, which can originate from the spin frustration.

Quantum chemical study of the template synthesis of cage-like metallasiloxanes

The template synthesis of cage-like metallasiloxanes from oligomeric metallasiloxanes and alkaline metal silanolates was simulated by the DFT/B3PW91/6–31g(d,p) quantum chemical calculation using the Gaussian 09 program. Three possible directions of the reaction were considered. The structural parameters of the formed compounds were compared to the experimental results. The enthalpies of the processes in different solvents were estimated. The possibility of the transition of solvate molecules in the course of the synthesis from the transition metal ion to the alkaline metal ion was shown. The factors governing the formation of six-membered coordination cycles as the main structural units of arising cage-like metallasiloxanes were revealed.

Competing ferro- and antiferromagnetic interactions in (manganese,sodium)phenylsilsesquioxane with metal oxide fragments

Magnetic measurements of individual (manganese,sodium)phenylsilsesquioxane containing eight MnII ions were performed. The magnetic arrangement of manganese ions in this cage-like compound was investigated. The magnetic moment of the cage molecule equals 21 μB (at 300 K), that is a consequence of the mutual antiferromagnetic compensation of four MnII ions, whereas the other four MnII ions have aligned spins. Hence, this metallasiloxane is a promising compound for the chemical design of molecular nanomagnets. At low temperatures, the antiferromagnetic coupling causes a decrease in the effective magnetic moment (to 16 μB at 40 K).