Cuproussiloxane as two self-assemblies, Cu20O20Si10Me10R10 and Cu24O24Si12Me12R12, with catalytic property.

Cuproussiloxane (1) was prepared from the reaction of silanediol R(Me)Si(OH)2 (R = N(SiMe3)(2,6-iPr2C6H3)) and (CuMes)4 (Mes = 2,4,6-Me3C6H2). The prepared compound crystalizes into two self-assemblies: Cu24O24Si12Me12R12 ([(CuO)2Si(Me)R]12, 1a) and Cu20O20Si10Me10R10 ([(CuO)2Si(Me)R]10, 1b). 1a and 1b feature dodecagonal and decagonal prism X-ray structures, respectively. 1 was found to exhibit good to excellent activity for catalyzing the aerobic C-P cross-coupling reaction of terminal alkynes with H-phosphonates to form alkynylphosphonates (70-99% yields).

Homocoupling of Isocyanide at the Si(II) Center of Borylaminoamidinatosilylene.

Two borylaminoamidinatosilylenes (L)[(1,5-C8H14)B(Ar)N]Si (L = PhC(NtBu)2, Ar = 2,6-iPr2C6H3 (1)) and (L)[(1,5-C8H14)B(Ar')N]Si (Ar' = 2,4,6-Me3C6H2 (2)) have been prepared and utilized to investigate the reaction toward isocyanide. Reactions of 1 with the respective CN-2,6-Me2C6H3 and CNCy (Cy = cyclo-C6H11) produced compounds (L)Si(NAr)C(N-2,6-Me2C6H3)B(1,5-C8H14)(CN-2,6-Me2C6H3) (3) and (L)Si(NAr)C(NCy)C(NCy)B(1,5-C8H14)(CNCy) (4). Reactions of 2 with the respective CNCy and CN-2,6-Me2C6H3 yielded compounds cyclo-(L)SiN(Ar')C(NCy)B(1,5-C8H14)C(NCy) (5) and cyclo-(L)[(1,5-C8H14)B(Ar')N]SiC(CN-2,6-Me2C6H3)N(2,6-Me2C6H3)C(N-2,6-Me2C6H3) (6). Compounds 3-6 have different compositions and structures from each other. Density functional theory (DFT) calculations suggest initial formation of (L)[(1,5-C8H14)B(←:CN-2,6-Me2C6H3)(Ar)N]Si (A), (L)[(1,5-C8H14)B(←:CNCy)(Ar)N]Si (A'), (L)[(1,5-C8H14)B(←:CNCy)-(Ar')N]Si (A″), and (L)[(1,5-C8H14)B(←:CN-2,6-Me2C6H3)(Ar')N]Si (A‴) as the respective intermediates. The as-followed transition states TS, TS1', TS1″, and TS‴ all feature probable Si:→C(═N):→B bonding with different Gibbs energies of 7.24, 2.46, 3.86, and 6.59 kcal/mol, respectively, due to variation among the Ar, Ar', 2,6-Me2C6H3, and Cy groups in these species, and reacted in different ways.

One- and Two-Electron Transfer Oxidation of 1,4-Disilabenzene with Formation of Stable Radical Cations and Dications.

Electron-transferable oxidants such as B(C6 F5 )3 /nBuLi, B(C6 F5 )3 /LiB(C6 F5 )4 , B(C6 F5 )3 /LiHBEt3 , Al(C6 F5 )3 /(o-RC6 H4 )AlH2 (R=N(CMe2 CH2 )2 CH2 ), B(C6 F5 )3 /AlEt3 , Al(C6 F5 )3 , Al(C6 F5 )3 /nBuLi, Al(C6 F5 )3 /AlMe3 , (CuC6 F5 )4 , and Ag2 SO4 , respectively were employed for reactions with (L)2 Si2 C4 (SiMe3 )2 (C2 SiMe3 )2 (L=PhC(NtBu)2 , 1). The stable radical cation [1]+. was formed and paired with the anions [nBuB(C6 F5 )3 ]- (in 2), [B(C6 F5 )4 ]- (in 3), [HB(C6 F5 )3 ]- (in 4), [EtB(C6 F5 )3 ]- (in 5), {[(C6 F5 )3 Al]2 (µ-F)]- (in 6), [nBuAl(C6 F5 )3 ]- (in 7), and [Cu(C6 F5 )2 ]- (in 8), respectively. The stable dication [1]2+ was also generated with the anions [EtB(C6 F5 )3 ]- (9) and [MeAl(C6 F5 )3 ]- (10), respectively. In addition, the neutral compound [(L)2 Si2 C4 (SiMe3 )2 (C2 SiMe3 )2 ][µ-O2 S(O)2 ] (11) was obtained. Compounds 2-11 are characterized by UV-vis absorption spectroscopy, X-ray crystallography, and elemental analysis. Compounds 2-8 are analyzed by EPR spectroscopy and compounds 9-11 by NMR spectroscopy. The structure features are discussed on the central Si2 C4 -rings of 1, [1]+. , [1]2+ , and 11, respectively.

One-Shot Synthesis and Melt Self-Assembly of Bottlebrush Copolymers with a Gradient Compositional Profile.

Morphological control plays a central role in soft materials design. Herein, we report the synthesis of a gradient bottlebrush architecture and its role in directing molecular packing in the solid state. Bottlebrush copolymers with gradient interfaces were prepared via one-shot ring-opening metathesis polymerization of exo- and endo-norbornene-capped macromonomers. Kinetic studies revealed a gradient compositional profile separating the two blocks along the backbone. Side-chain symmetric gradient bottlebrush copolymers exhibited a strong tendency to assemble into cylindrical microstructures, in contrast to their block copolymer analogs with sharp interfaces. Such exquisite architectural control of the interfacial composition affords a delicate handle to direct macromolecular assembly.

A Germylene/Borane Lewis Pair and the Remarkable C=O Bond Cleavage Reaction toward Isocyanate and Ketone Molecules.

A germylene/borane Lewis pair (2) was prepared from a 1,1-carboboration of amidinato phenylethynylgermylene (1) by B(C6 F5 )3 . Compound 2 reacted with iPrNCO and (4-MeOC6 H4 )C(O)Me, respectively, with cleavage of the C=O double bond. In the first instance, O and iPrNC insert separately into the Ge-B bond to yield a GeBC2 O-heterocycle (3) and a GeBC3 -heterocycle (4). In the second case (4-MeOC6 H4 )(Me)C inserts into the Ge-N bond of 2 while O is incorporated in the Ge-B bond to form a Ge-centered spiroheterocycle (5). The reaction of 2 with tBuNC to give 6, which has almost the same structure as 4, proved the formation of the isonitrile during transformation from 2 and iPrNCO to 3 and 4. The kinetic study of the reaction of 2 and iPrNCO gave evidence of proceeding through a GeBC3 O-heterocycle intermediate. In addition, a DFT study was performed to elucidate the reaction mechanism.

Folding-promoted TBACl-mediated chemo- and regioselective demethylations of methoxybenzene-based macrocyclic pentamers.

Tetrabutylammonium chloride (TBACl) salt alone has not been shown previously to be capable of removing methoxy groups. It is demonstrated here that the use of TBACl achieves efficient folding-promoted chemo- and regioselective demethylations, eliminating up to two out of five methyl groups situated in similar macrocyclic chemical microenvironments.