Aluminum Borate Nanowires from the Pyrolysis of Polyaminoborane Precursors

Polyaminoboranes [N(R)H-BH2]n (1: R = H, 2: R = Me) were pyrolyzed on a range of substrates: silicon, metal foils (stainless steel, nickel, and rhodium), and sapphire wafers, as well as on Al2O3 and AlN powders.</p

An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

<p>This paper presents a detailed analysis of the structure of the hexagonal phase of poly(ferrocenylsilane) (PFS)-based cylindrical micelles found at concentrations above ca. 5 wt. % in non-polar solvents such as decane. Small-angle X-ray scattering indicated that the hexagonal order is not long-range. In all samples, deviations in the lower order peak positions were observed with respect to those expected for a perfect hexagonal lattice, with the degree of deviation correlating with micelle length. Furthermore, analysis of the peak shapes and peak widths suggests that the phase possesses intermediate translational order similar. to the hexatic phase. The observed features can be reproduced by amending Hosemann’s paracrystal theory to include a distribution of lattice parameters to model well and poorly condensed regions. It is proposed that this distribution arises due to the bending and intertwining of individual micelles in a hexagonal lattice, resulting in a kinetically trapped phase that is initially neither perfectly hexagonal nor canonically hexatic but which anneals over time towards a perfect hexagonal lattice.</p

Polyferrocenylsilanes:synthesis, properties, and applications

This comprehensive review covers polyferrocenylsilanes (PFSs), a well-established, readily accessible class of main chain organosilicon metallopolymer. The focus is on the recent advances involving PFS homopolymers and block copolymers and the article covers the synthesis, properties, and applications of these fascinating materials.</p

Heavier alkaline‐earth catalyzed dehydrocoupling of silanes and alcohols for the synthesis of metallo‐polysilylethers

The dehydrocoupling of silanes and alcohols mediated by heavier alkaline-earth catalysts, [Ae{N(SiMe 3) 2} 2⋅(THF) 2] (I–III) and [Ae{CH(SiMe 3) 2} 2⋅(THF) 2], (IV–VI) (Ae=Ca, Sr, Ba) is described. Primary, secondary, and tertiary alcohols were coupled to phenylsilane or diphenylsilane, whereas tertiary silanes are less tolerant towards bulky substrates. Some control over reaction selectivity towards mono-, di-, or tri-substituted silylether products was achieved through alteration of reaction stoichiometry, conditions, and catalyst. The ferrocenyl silylether, FeCp(C 5H 4SiPh(OBn) 2) (2), was prepared and fully characterized from the ferrocenylsilane, FeCp(C 5H 4SiPhH 2) (1), and benzyl alcohol using barium catalysis. Stoichiometric experiments suggested a reaction manifold involving the formation of Ae–alkoxide and hydride species, and a series of dimeric Ae–alkoxides [(Ph 3CO)Ae(μ 2-OCPh 3)Ae(THF)] (3 a–c, Ae=Ca, Sr, Ba) were isolated and fully characterized. Mechanistic experiments suggested a complex reaction mechanism involving dimeric or polynuclear active species, whose kinetics are highly dependent on variables such as the identity and concentration of the precatalyst, silane, and alcohol. Turnover frequencies increase on descending Group 2 of the periodic table, with the barium precatalyst III displaying an apparent first-order dependence in both silane and alcohol, and an optimum catalyst loading of 3 mol % Ba, above which activity decreases. With precatalyst III in THF, ferrocene-containing poly- and oligosilylethers with ferrocene pendent to- (P1–P4) or as a constituent (P5, P6) of the main polymer chain were prepared from 1 or Fe(C 5H 4SiPhH 2) 2 (4) with diols 1,4-(HOCH 2) 2-(C 6H 4) and 1,4-(CH(CH 3)OH) 2-(C 6H 4), respectively. The resultant materials were characterized by NMR spectroscopy, gel permeation chromatography (GPC) and DOSY NMR spectroscopy, with estimated molecular weights in excess of 20,000 Da for P1 and P4. The iron centers display reversible redox behavior and thermal analysis showed P1 and P5 to be promising precursors to magnetic ceramic materials. </p

A Convenient Route to Monoalkyl-Substituted Phosphanylboranes (HRP–BH2–NMe3): Prospective Precursors to Poly[(alkylphosphino)boranes]

A simple method to access borylphosphonium iodides [RH2P-BH2 center dot NMe3]I (1a: R = Me; 1b: R = Et; 1c: R = nPr) by the addition of iodoalkanes to PH2-BH2 center dot NMe3 was developed. Complexes 1a-c were characterized by multinuclear NMR spectroscopy, and 1a and 1b additionally by single-crystal X-ray diffraction. It was possible to synthesize the Lewis-base-stabilized organosubstituted phosphanylborane MePH-BH2 center dot NMe3 (2) from [MePH2-BH2 center dot NMe3] I (1a). Thermolysis of 2 generated a soluble, low-molecular-mass poly(alkylphosphinoborane)consisting of at least 40 repeat units, as identified by ESI-MS. These results are promising for the future preparation of a wide range of Lewis-base-stabilized phosphanylboranes, which are of interest as precursors to poly[(alkylphosphino)boranes] and are otherwise difficult to access by conventional metal-catalyzed methods

Ferrocene-Containing Polycarbosilazanes via the Alkaline-Earth-Catalyzed Dehydrocoupling of Silanes and Amines

We report the use of the alkaline-earth (Ae) metal-catalyzed dehydrocoupling of silanes and amines for the synthesis of ferrocene-containing polycarbosilazanes. The barium complex [Ba(N(SiMe 3) 2) 2·(THF) 2] catalyzed the dehydrocoupling of the hydrosilane FeCp(CpSiPhH 2) (1) with 1,4-(H 2NCH 2) 2C 6H 4 under mild conditions to give a polycarbosilazane with pendant ferrocene groups. The polymer could be readily cross-linked by the addition of phenylsilane to the unquenched reaction mixture. Well-defined polycarbosilazanes with ferrocene in the main chain were also obtained from the dehydrocoupling of hydrosilanes Fe(Cp(SiPhH 2)) 2 (3) and Fe(Cp(SiMe 2H)) 2 (IX) with 1,4-(H(Me)NCH 2) 2C 6H 4 and 1,4-(H 2NCH 2) 2C 6H 4, respectively. Crystalline monomeric analogues, FeCp(Cp(SiPh(NHBn) 2)) (2, Bn = CH 2(C 6H 5)), and Fe(Cp(SiPh(NHBn) 2)) 2 (4), were also obtained via the dehydrocoupling benzylamine with 1 and 3, respectively. The barium-catalyzed dehydrocoupling of diaminoferrocene with Ph 2SiH 2 or Ph(Rc)SiH 2 (6, Rc = (C 5H 4)Ru(C 5H 5)) did not result in polymer, but instead in the formation of the silazane-bridged ansa-[3]ferrocenophanes (Fe(ν-C 5H 4NH) 2SiPh 2) (5) and (Fe(ν-C 5H 4NH) 2SiPh(Rc)) (7), respectively. Both polymeric and molecular products were electrochemically investigated, and the polymers proved to be promising precursors to magnetic iron-containing ceramics in yields of up to 64%. </p

Ferrocene-Containing Polycarbosilazanes via the Alkaline-Earth-Catalyzed Dehydrocoupling of Silanes and Amines

We report the use of the alkaline-earth (Ae) metal-catalyzed dehydrocoupling of silanes and amines for the synthesis of ferrocene-containing polycarbosilazanes. The barium complex [Ba(N(SiMe 3) 2) 2·(THF) 2] catalyzed the dehydrocoupling of the hydrosilane FeCp(CpSiPhH 2) (1) with 1,4-(H 2NCH 2) 2C 6H 4 under mild conditions to give a polycarbosilazane with pendant ferrocene groups. The polymer could be readily cross-linked by the addition of phenylsilane to the unquenched reaction mixture. Well-defined polycarbosilazanes with ferrocene in the main chain were also obtained from the dehydrocoupling of hydrosilanes Fe(Cp(SiPhH 2)) 2 (3) and Fe(Cp(SiMe 2H)) 2 (IX) with 1,4-(H(Me)NCH 2) 2C 6H 4 and 1,4-(H 2NCH 2) 2C 6H 4, respectively. Crystalline monomeric analogues, FeCp(Cp(SiPh(NHBn) 2)) (2, Bn = CH 2(C 6H 5)), and Fe(Cp(SiPh(NHBn) 2)) 2 (4), were also obtained via the dehydrocoupling benzylamine with 1 and 3, respectively. The barium-catalyzed dehydrocoupling of diaminoferrocene with Ph 2SiH 2 or Ph(Rc)SiH 2 (6, Rc = (C 5H 4)Ru(C 5H 5)) did not result in polymer, but instead in the formation of the silazane-bridged ansa-[3]ferrocenophanes (Fe(ν-C 5H 4NH) 2SiPh 2) (5) and (Fe(ν-C 5H 4NH) 2SiPh(Rc)) (7), respectively. Both polymeric and molecular products were electrochemically investigated, and the polymers proved to be promising precursors to magnetic iron-containing ceramics in yields of up to 64%. </p

Synthesis, thin-film self-assembly, and pyrolysis of ruthenium-containing polyferrocenylsilane block copolymers

The self-assembly of a ruthenium-containing polyferrocenylsilane in bulk and thin films yielded spherical or cylindrical domains in a PS matrix; pyrolysis provided a route to bimetallic Fe/Ru NPs for potential catalytic applications.</p