Synthesis and molecular structures of 1‐chloro‐1‐silacyclopent‐2‐enes. Combination of 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of alkyn‐1‐yl(chloro)(methyl)vinyl‐ and alkyn‐1‐yl(chloro)(phenyl)‐vinylsilane with 9‐borabicyclo[3.3.1]nonane (9‐BBN) afforded selectively 1‐silacyclopent‐2‐ene derivatives containing a Si? Cl function, as a result of consecutive 1,2‐hydroboration and 1,1‐organoboration. Protodeborylation with acetic acid left the Si? Cl functions in various 1‐silacyclopent‐2‐enes untouched, whereas acetic acid in the presence of dipropylamine led to conversion of the Si? Cl into the Si? OAc function. New starting materials and all products were characterized in solution by multinuclear NMR spectroscopy (¹H, ¹¹B, ¹³C and ²⁹Si NMR), and the molecular structures of two 1‐silacyclopent‐2‐ene derivatives were determined by X‐ray analysis. The gas phase geometries of 1‐silacyclopent‐2‐enes were optimized by DFT calculations [B3LYP/6‐311 + G(d,p) level of theory], found to be in reasonable agreement with the results of the crystal structure determination, and NMR parameters were calculated at the same level of theory. Copyright © 2009 John Wiley & Sons, Ltd.     

High magnetic field solid‐state NMR analyses by combining MAS,MQ‐MAS,homo‐nuclear and hetero‐nuclear correlation experiments

A general strategy of structural analysis of alumina silicate by combining various solid‐state NMR measurements such as single pulse, multi‐quantum magic angle spinning, double‐quantum homo‐nuclear correlation under magic angle spinning (DQ‐MAS), and cross‐polarization hetero‐nuclear correlation (CP‐HETCOR) was evaluated with the aid of high magnetic field NMR (800 MHz for ¹H Larmor frequency) by using anorthite as a model material. The high magnetic field greatly enhanced resolution of ²⁷Al in single pulse, DQ‐MAS, and even in triple‐quantum magic angle spinning NMR spectra. The spatial proximities through dipolar couplings were probed by the DQ‐MAS methods for homo‐nuclear correlations between both ²⁷Al–²⁷Al and ²⁹Si–²⁹Si and by CP‐HETCOR for hetero‐nuclear correlations between ²⁷Al–²⁹Si in the anorthite framework. By combining various NMR methodologies, we elucidated detailed spatial correlations among various aluminum and silicon species in anorthite that was hard to be determined using conventional analytical methods at low magnetic field. Moreover, the presented approach is applicable to analyze other alumina‐silicate minerals. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of 4,5‐Dihydro‐1H‐Pyrazole Derivatives by 13C NMR Spectroscopy

The ¹³ C NMR resonances of 19 1‐acyl‐3‐(2‐nitro‐5‐substitutedphenyl)‐4,5‐dihydro‐1H‐pyrazoles, and 19 1‐acyl‐3‐(2‐amino‐5‐substituted)‐4,5‐dihydro‐1H‐pyrazoles, were completely assigned using the concerted application of one‐ and two‐dimensional NMR experiments (DEPT, gs‐HSQC and gs‐HMBC). Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Base‐catalyzed Phenyl Modified PDMS/PHMS Copolymers

A series of phenyl modified polydimethylsiloxane (PDMS) / polyhydrogenmethylsiloxane (PHMS) random copolymers containing both internal Si‐H and terminal SiH₂ and T (MeSiO_3/2) units was synthesized in one step through n‐BuLi‐catalyzed ring‐opening polymerization of cyclic comonomers and characterized by GPC, IR and ¹H and ²⁹Si NMR. Sequential microstructures of these copolymers were determined by ²⁹Si‐NMR spectroscopy. Epoxy‐modified polysiloxanes were prepared and used as comparable standards for the assignment of the NMR spectra. A hydride‐transfer mechanism has been proposed to account for the formation of terminal Si‐H and T group. Detailed sequential analyses and chemical shifts of ²⁹Si‐NMR for various siloxane units are reported for the first time.     

1,3‐Bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophanes

The 2‐tert‐butyl, 2‐phenoxy, and 2‐diethylamino derivatives of 1,3‐bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophane were prepared, and the molecular structure of the latter was determined by X‐ray diffraction. The phosphines could be oxidized by their slow reactions with sulfur or selenium, and the molecular structures of three sulfides and one selenide were determined. In contrast, the synthesis of oxides was less straightforward. All new compounds were characterized in solution by multinuclear magnetic resonance methods (1D and 2D ¹H, ¹³C, ¹⁵N, ²⁹Si, ³¹P, and ⁷⁷Se NMR spectroscopy).     

Synthesis and molecular structures of 1‐boracyclopent‐2‐enes

The reaction of 1‐silyl‐1‐borylalkenes with alkyn‐1‐yltin compounds affords borol‐2‐enes, organometallic‐substituted allenes, mixtures thereof or even more complex mixtures with buta‐1,3‐dienes, depending on the third substituent at the C?C bond (Bu or Ph), on the number of Si? Cl functions (two or three) and the nature of the alkyn‐1‐yltin compound. Six new borol‐2‐enes were isolated in pure state, and two of them were characterized by X‐ray structural analysis. The solution‐state structures of all major products were clearly established by multinuclear magnetic resonance methods (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2009 John Wiley & Sons, Ltd.     

Ammonolysis of 1,2‐Bis[dichloro(methyl)silyl]ethane. On the Structure of 1,3,6,8‐Tetramethyl‐2,7,11,12‐tetraaza‐1,3,6,8‐tetrasila‐tricyclo[6.2.1.13,6]‐dodecane

Ammonolysis of 1,2‐bis[dichloro(methyl)silyl]ethane afforded a crystalline tricyclic silazane along with polymeric material. The crystalline material could be isolated in pure state. It was analyzed by ¹H, ¹³C, ¹⁵N and ²⁹Si NMR spectroscopy in solution, by ¹³C, ¹⁵N and ²⁹Si MAS NMR spectroscopy in the solid state, as well as by single‐crystal and powder X‐ray diffraction. The title compound exists as a single isomer in solution, whereas in the solid state the presence of several modifications is indicated, in particular by the solid‐state MAS NMR spectra.     

Solid‐State NMR Characterization of Wilkinson’s Catalyst Immobilized in Mesoporous SBA‐3 Silica

The Wilkinson’s catalyst [RhCl(PPh₃)₃] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA‐3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid‐state NMR methods. The successful modification of the silica surface was confirmed by ²⁹Si CP‐MAS NMR experiments. The presence of the T_n peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. ³¹P‐³¹P J‐resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable ³¹P‐³¹P J‐coupling, well resolvable in 2D MAS NMR experiments. This J‐coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable ³¹P‐³¹P J‐coupling in off‐magic‐angle‐spinning experiments, as well as slow‐spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules.     

Self‐assembling directed synthesis of a novel terephthalamide‐bridged ladderlike polysiloxane

A novel, soluble terephthalamide‐bridged ladderlike polysiloxane ( L ) was synthesized successfully for the first time by stepwise coupling polymerization. The process involved the hydrogen‐bonding self‐assembly of amido groups, which resulted in the formation of a more highly ordered polymeric structure. A novel monomer, bis(3‐methyldimethoxysilylpropyl) terephthalamide ( M ), was prepared by a hydrosilylation reaction in the presence of dicyclopentadienyl platinum dichloride as a catalyst. The structures of the monomer ( M ) and the polymer ( L ) were characterized by Fourier transform infrared, ¹H NMR, ¹³C NMR, ²⁹Si NMR, mass spectrometry, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry. All the characterization data indicated that the synthesized polymer ( L ) possessed an ordered ladderlike structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3161–3170, 2002     

Hydrogen‐bonding‐aided synthesis of novel ladderlike organobridged polysiloxane containing side‐chain naphthyl groups

With a hydrogen‐bonding template, a novel soluble aryl amide‐bridged ladderlike polysiloxane, containing naphthyl as the side‐chain group, has been successfully synthesized via a stepwise coupling polymerization. It is proposed that the monomer, N,N′‐di(3‐naphthyldiethoxylsilyl‐propyl)‐[4,4′‐oxybis(benzyl amide)], prepared by Grignard and hydrosilylation reactions, undergoes self‐assembly first via amido hydrogen bonding and then via hydrolysis, followed by condensation under controlled reaction conditions to yield a high molecular weight, soluble, dark yellow polymer. The analytical results (Fourier transform infrared, ¹H NMR, ²⁹Si NMR, X‐ray diffraction, differential scanning calorimetry, and vapor pressure osmometry) show that the polymer possesses an ordered ladderlike architecture. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 636–644, 2003     

Synthesis and structure of novel spirosilanes. Combination of 1,2‐hydroboration and 1,1‐organoboration

The reaction of tetra(alkyn‐1‐yl)silanes Si(C?C‐R¹)₄ 1 [R¹ = ^tBu ( a ), Ph ( b ), C₆H₄‐4‐Me ( c )] with 9‐borabicyclo[3.3.1]nonane (9‐BBN) in a 1:2 ratio affords the spirosilane derivatives 5a – c as a result of twofold intermolecular 1,2‐hydroboration, followed by twofold intramolecular 1,1‐organoboration. Intermediates 3a–c , in which two alkenyl‐ and two alkyn‐1‐yl groups are linked to silicon, were identified by NMR spectroscopy. The molecular structure of the spiro compound 5c was determined by X‐ray analysis, and the solution‐state structures of products and intermediates follow conclusively from the consistent NMR spectroscopic data sets (¹H, ¹¹B, ¹³C and ²⁹Si NMR). Copyright © 2008 John Wiley & Sons, Ltd.     

A novel 4‐methylene‐3‐borahomoadamantane: 1,1‐organoboration of an alkyn‐1‐ylsilane using 1‐boraadamantane

1,1‐Dibromo‐2,2‐bis(trimethylsilylethynyl)ethene ( 2 ) reacts with two equivalents of 1‐boraadamantane ( 1 ) by 1,1‐organoboration of both trimethylsilylethynyl groups to give a triene 3 bearing two 4‐methylene‐3‐borahomoadamantane moieties in terminal positions. The triene was characterized by one‐ and two‐dimensional ¹H, ¹¹B, ¹³C and ²⁹Si NMR spectroscopy in solution and X‐ray structural analysis in the solid state. The planes of the C double bond are strongly twisted against each other as a result of the bulky substituents, and the surroundings of the boron atoms deviate from the ideal trigonal planar geometry owing to the tension in the tricyclic frameworks. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis of 1‐silacyclopent‐2‐ene derivatives using 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of di(alkyn‐1‐yl)vinylsilanes R¹(H₂C═CH)Si(C≡C―R)₂ (R¹ = Me ( 1 ), Ph ( 2 ); R = Bu (a), Ph (b), Me₂HSi (c)) at 25°C with 1 equiv. of 9‐borabicyclo[3.3.1]nonane (9‐BBN) affords 1‐silacyclopent‐2‐ene derivatives ( 3a , 3b , 3c , 4a , 4b ), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2‐hydroboration followed by intramolecular 1,1‐carboboration. Treated with a further equivalent of 9‐BBN in benzene they are converted at relatively high temperature (80–100°C) into 1‐alkenyl‐1‐silacyclopent‐2‐ene derivatives ( 5a , 5b 6a , 6b ) as a result of 1,2‐hydroboration of the Si―C≡C―R function. Protodeborylation of the 9‐BBN‐substituted 1‐silacyclopent‐2‐ene derivatives 3 , 4 , 5 , 6 , using acetic acid in excess, proceeds smoothly to give the novel 1‐silacyclopent‐2‐ene ( 7 , 8 , 9 , 10 ). The solution‐state structural assignment of all new compounds, i.e. di(alkyn‐1‐yl)vinylsilanes and 1‐silacyclopent‐2‐ene derivatives, was carried out using multinuclear magnetic resonance techniques (¹H, ¹³C, ¹¹B, ²⁹Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6‐311+G/(d,p) level of theory), and ²⁹Si NMR parameters were calculated (chemical shifts δ²⁹Si and coupling constants ⁿJ(²⁹Si,¹³C)). Copyright © 2014 John Wiley & Sons, Ltd.     

Para‐hydrogen induced polarization of Si‐29 NMR resonances as a potentially useful tool for analytical applications

Para‐hydrogen–induced polarization effects have been observed in the ²⁹Si NMR spectra of trimethylsilyl para‐hydrogenated molecules. The high signal enhancements and the long T₁ values observed for the ²⁹Si hyperpolarized resonances point toward the possibility of using ²⁹Si for hyperpolarization applications. A method for the discrimination of multiple compounds and/or complex mixtures of hydroxylic compounds (such as steroids), consisting of the silylization of alcoholic functionalities with an unsaturated silylalkyl moiety and subsequent reaction with para‐H₂, is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Ring‐Opening and polymerization of 1‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotrisiloxane

1‐[2′‐(Heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotetrasiloxane ( II ) was prepared from 1‐[2′‐(methyldichlorosilyl)ethyl]‐1,3,3,5,5,7,7‐heptaphenylcyclotetrasiloxane ( I ) and tetramethyldisiloxane‐1,3‐diol. Acid‐catalyzed ring‐opening of II in the presence of tetramethyldisiloxane gave 1,9‐dihydrido‐5‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( III ) and 1,9‐dihydrido‐3‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( IV ). Both acid‐ and base‐catalyzed ring‐opening polymerization of II gives highly viscous, transparent polymers. The structures of I – IV and polymers were determined by UV, IR, ¹H, ¹³C, and ²⁹Si NMR spectroscopy. In addition, molecular weights obtained by GPC and NMR end group analysis were confirmed with mass spectrometry. On the basis of ²⁹Si NMR spectroscopy, the polymers appear to result exclusively from ring‐opening of the cyclotrisiloxane ring. No evidence for ring‐opening of the cyclotetrasiloxane ring was observed. Polymer properties were determined by DSC and TGA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 137–146, 2006     

Synthesis,Solid‐State NMR Characterization,and Application for Hydrogenation Reactions of a Novel Wilkinson’s‐Type Immobilized Catalyst

Silica nanoparticles (SiNPs) were chosen as a solid support material for the immobilization of a new Wilkinson’s‐type catalyst. In a first step, polymer molecules (poly(triphenylphosphine)ethylene (PTPPE); 4‐diphenylphosphine styrene as monomer) were grafted onto the silica nanoparticles by surface‐initiated photoinferter‐mediated polymerization (SI‐PIMP). The catalyst was then created by binding rhodium (Rh) to the polymer side chains, with RhCl₃ ? x H₂O as a precursor. The triphenylphosphine units and rhodium as Rh^I provide an environment to form Wilkinson’s catalyst‐like structures. Employing multinuclear (³¹P, ²⁹Si, and ¹³C) solid‐state NMR spectroscopy (SSNMR), the structure of the catalyst bound to the polymer and the intermediates of the grafting reaction have been characterized. Finally, first applications of this catalyst in hydrogenation reactions employing para‐enriched hydrogen gas (PHIP experiments) and an assessment of its leaching properties are presented.     

1,1‐Organoboration of bis(trimethylstannyl)ethyne with trimethylsilyl‐ and dimethylsilyl‐dialkylboryl‐substituted alkenes: organometallic‐substituted allenes

The reactions of bis(trimethylstannyl)ethyne, Me₃Sn–C?C–SnMe₃ ( 4 ), with trimethylsilyl‐ or dimethylsilyl‐dialkylboryl‐substituted alkenes 1 – 3 afford organometallic‐substituted allenes 5 , 6 and 8 , 9 in high yield. In the case of (E)‐2‐trimethylsilyl‐3‐diethylboryl‐2‐pentene ( 1) , a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by ²⁹Si and ¹¹⁹Sn NMR, and the products were characterized by an extensive NMR data set (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd.     

Synthesis and Rearrangement of Stable NHC→Silylene Adducts and Their Unique Reactivity towards Cyclohexylisocyanide

The syntheses and reactivity of the two N‐heterocyclic carbene (NHC)→ silylene complexes 2 and 4 have been investigated. The latter are easily accessible by reaction of the zwitterionic, N‐heterocyclic silylene LSi: 1 [L=Ar‐N‐C(=CH₂)CH?C(Me)‐N‐Ar, Ar=2,6‐iPr₂C₆H₃] with 1,3,4,5‐tetramethylimidazol‐2‐ylidene and 1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene, respectively. While compound 2 undergoes facile rearrangement above ?20 °C to give the unsymmetrical N‐heterocyclic silylcarbene 3 , the derivative 4 remains unchanged even after boiling in benzene. The remarkable reactivity of 3 and 4 towards cyclohexylisocyanide has been examined which leads in a unique series of C? H, Si? H, and C? N bond activations to the new triaminosilanes 5 and 6 , respectively. The novel compounds 3 , 4 , 5 , and 6 were fully characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy, EI‐MS, elemental analysis, and single‐crystal X‐ray diffraction.     

The Preparation of a New Kind of Carbosilane Dendrimer with 4‐(Naphthalen‐1‐yl)phenyl Core‐An Application of Suzuki Coupling Reaction

Using the divergent method, carbosilane dendrimers with p‐bromophenyl core were synthesized by using alternating Grignard and hydrosilylation reactions. And then, α‐naphthalenyl was connected to the core by using Suzuki coupling reaction. This gave a new carbosilane dendrimer with a 4‐(naphthalen‐1‐yl)phenyl core. All the products were characterized by IR, ¹H NMR, ¹³C NMR, ²⁹Si NMR, and MS. The study shows that Suzuki Coupling reaction is an effective and powerful core‐functionalization method and a satisfactory result can be achieved through prolonging the reaction time.     

1‐Silacyclopent‐2‐enes and 1‐silacyclohex‐2‐enes bearing functionally substituted silyl groups in 2‐positions. Novel electron‐deficient Si?H?B bridges

The reactions of alkyn‐1‐yl(vinyl)silanes R₂Si[C?C‐Si(H)Me₂]CH?CH₂ [R = Me (1a), Ph (1b)], Me₂Si[C?C‐Si(Br)Me₂]CH?CH₂ (2a), and of alkyn‐1‐yl(allyl)silanes R₂Si[C?C‐Si(H)Me₂]CH₂CH?CH₂ (R = Me (3a), R = Ph (3b)] with 9‐borabicyclo[3.3.1]nonane in a 1:1 ratio afford in high yield the 1‐silacyclopent‐2‐ene derivatives 4a, b and 5a, and the 1‐silacyclohex‐2‐ene derivatives 6a, b, respectively, all of which bear a functionally substituted silyl group in 2‐position and the boryl group in 3‐position. This is the result of selective intermolecular 1,2‐hydroboration of the vinyl or allyl group, followed by intramolecular 1,1‐organoboration of the alkynyl group. In the cases of 4a, b, potential electron‐deficient Si? H? B bridges are absent or extremely weak, whereas in 6a,b the existence of Si? H? B bridges is evident from the NMR spectroscopic data (¹H, ¹¹B, ¹³C and ²⁹Si NMR). The molecular structure of 4b was determined by X‐ray analysis. Copyright © 2005 John Wiley & Sons, Ltd.