Excess Silane Research Articles

Si-H Bond Activation and Dehydrogenative Coupling of Silanes across the Iron-Amide Bond of a Bis(amido)bis(phosphine) Iron(II) Complex.

Despite the utility of Si-Si bonds, there are relatively few examples of Si-Si bond formation by base metals. In this work, a four-coordinate iron complex, (PNNP)FeII, is shown to strongly activate the Si-H bonds in primary silanes across the Fe-amide bonds in a metal-ligand cooperative fashion. Upon treatment with excess silane, Si-Si dehydrogenative homocoupling is shown to occur across the Fe-Namide bond without concomitant oxidation and spin state changes at the Fe center.

Activation of CS2 and CO2 by Silylium Cations.

The hydride‐bridged silylium cation [Et3Si−H−SiEt3]+, stabilized by the weakly coordinating [Me3NB12Cl11]− anion, undergoes, in the presence of excess silane, a series of unexpected consecutive reactions with the valence‐isoelectronic molecules CS2 and CO2. The final products of the reaction with CS2 are methane and the previously unknown [(Et3Si)3S]+ cation. To gain insight into the entire reaction cascade, numerous experiments with varying conditions were performed, intermediate products were intercepted, and their structures were determined by X‐ray crystallography. Besides the [(Et3Si)3S]+ cation as the final product, crystal structures of [(Et3Si)2SMe]+, [Et3SiS(H)Me]+, and [Et3SiOC(H)OSiEt3]+ were obtained. Experimental results combined with supporting quantum‐chemical calculations in the gas phase and solution allow a detailed understanding of the reaction cascade.

The Effect of Piranha and Silane Modifications on Boron Nitride Nanosheets (BNNSs) Thin Film Formation

In this study, the aim was to increase the adhesion between the two phases (glass substrate and BNNSs film). Surface treatment was provided by TEOS silane group and piranha solution. The retention times of the glass surfaces in the piranha solution and the adherence of different ratios of the silane solution to the glass surface were investigated. Surface characterization was carried out by Fourier Transform Infrared Spectrophotometer (FT-IR). Scanning Electron Microscopy (SEM) images were taken to characterize the surface morphology, the thickness of the thin films and the structure of boron nitride nanosheets. UV visible spectrophotometer was used to determine the efficiency of boron nitride nanosheets after the exfoliation process. Surface roughness tester (Time TR200) was used to determine surface roughness of the thin films. According to the results, it was observed that the piranha and silane solutions improved the adhesion of the glass surface. SEM images showed that the silane was coated on the glass surface and the coating material was retained on the silane. Excess silane loading caused the structure to deteriorate. Boron nitride yield was calculated and found to be 54.1% and 34.1% for different centrifugation rates after exfoliation.

Effect of excess silane on the viscoelastic behavior of epoxy under hygrothermal conditions

This study investigates the effects of excess organofunctional silane on the elastic and viscoelastic properties of an epoxy resin. Samples were prepared by adding 3–glycidoxypropyl trimethoxysilane (GPTMS) in varying amounts ranging from 0.5 to 8.0 wt% to diglycidyl ether of bisphenol–F (DGEBF) epoxy cured using an amine-based hardener. Prepared samples were subjected to hygrothermal conditioning by immersion in water at 21 °C and 50 °C. Subsequently, instrumented nanoindentation was used to determine the elastic modulus and creep compliance. A Fickian model fitted to moisture absorption data indicates that after 48 h specimens were fully saturated to a depth of approximately 150 µm, which is significantly higher than the maximum indentation depth of 1 µm. This implies that the indentation material response was determined from a fully saturated region. It was found that the addition of silane leads to a reduction in the elastic modulus. In the presence of hygrothermal degradation, this reduction still occurs but is less than the non-conditioned case, especially for exposure at 50 °C. For example, the addition of 8.0 wt% silane reduces the elastic modulus by an average of 70% as compared to the pristine sample, and conditioning at 21 °C and 50 °C results in reductions of elastic modulus by 73% and 52%, respectively. The overall reduction in the elastic modulus value is due to the inclusion of flexible silane into the epoxy resin. Under hygrothermal conditions, however, the hydrolysis of silane mitigates the reduction in elastic modulus, especially at higher temperature conditioning. The viscous response of the material is sensitive to the inclusion of silane and hygrothermal conditioning. However, at very low wt% of silane (less than 2%), the material becomes creep resistant and at higher wt%, the behavior is similar to the elastic modulus. Fourier transform infrared (FTIR) spectra indicates that Si–Si interaction becomes predominant at higher wt. fractions leading to softening of the material. Inclusion of silane also reduces the glass transition temperature, which supports the increase in flexibility of the polymer chain.

In Situ Generation of ArCu from CuF2 Makes Coupling of Bulky Aryl Silanes Feasible and Highly Efficient.

A bimetallic system of Pd/CuF2, catalytic in Pd and stoichiometric in Cu, is very efficient and selective for the coupling of fairly hindered aryl silanes with aryl, anisyl, phenylaldehyde, p-cyanophenyl, p-nitrophenyl, or pyridyl iodides of conventional size. The reaction involves the activation of the silane by Cu(II), followed by disproportionation and transmetalation from the Cu(I)(aryl) to Pd(II), upon which coupling takes place. Cu(III) formed during disproportionation is reduced to Cu(I)(aryl) by excess aryl silane, so that the CuF2 system is fully converted into Cu(I)(aryl) and used in the coupling. Moreover, no extra source of fluoride is needed. Interesting size selectivity towards coupling is found in competitive reactions of hindered aryl silanes. Easily accessible [PdCl2 (IDM)(AsPh3)] (IDM = 1,3-dimethylimidazol-2-ylidene) is by far the best catalyst, and the isolated products are essentially free from As or Pd (<1 ppm). The mechanistic aspects of the process have been experimentally examined and discussed.

Carbon dioxide hydrosilylation promoted by cobalt pincer complexes.

The addition of carbon dioxide to ((tBu)PNP)CoH [(tBu)PNP = 2,6-bis(di-tert-butylphosphinomethyl)pyridine] resulted in rapid insertion into the Co-H bond to form the corresponding κ(1)-formate complex, which has been structurally characterized. Treatment of ((tBu)PNP)CoH with PhSiH3 resulted in oxidative addition to form trans-((tBu)PNP)CoH2(SiH2Ph), which undergoes rapid exchange with excess free silane. With 0.5 mol % ((tBu)PNP)CoH, the catalytic hydrosilylation of CO2 with PhSiH3 to a mixture of oligomers containing silyl formate, bis(silyl)acetyl, and silyl ether subunits has been observed.

A New Side‐on End‐On Ditantalum Dinitrogen Complex and Its Reaction with BuSiH3

AbstractThe formation of the P‐cyclohexyl dinitrogen complex, (CyPh[NPN]Ta)2(μ‐η2:η1‐N2)(μ‐H)2 (CyPh[NPN] = [CyP(CH2SiMe2NPh)2], and Cy = C6H11) is described and its reaction with butylsilane (BuSiH3) explored. The reaction was monitored by multinuclear NMR spectroscopy and showed the formation of a number of intermediates. The final product is a hydride‐bridged imido‐amido silyated species that has the imido bridging between the two central tantalum atoms. The origin of the bridging hydrides in the product is likely to arise from the excess silane present, on the basis of labeling studies.

Insight into the mechanism of carbonyl hydrosilylation catalyzed by Brookhart's cationic iridium(III) pincer complex.

New experimental findings suggest partial revision of the currently accepted mechanism of the carbonyl hydrosilylation catalyzed by the iridium(III) pincer complex introduced by Brookhart. Employing silicon-stereogenic silanes as a stereochemical probe results in racemization rather than inversion of the configuration at the silicon atom. The degree of the racemization is, however, affected by the silane/carbonyl compound ratio, and inversion is seen with excess silane. Independently preparing the silylcarboxonium ion intermediate and testing its reactivity then helped to rationalize that effect. The stereochemical analysis together with these control experiments, rigorous multinuclear NMR analysis, and quantum-chemical calculations clearly prove that another silane molecule participates in the hydride transfer. The activating role of the silane is unexpected but, in fact, vital for the catalytic cycle to close.

SiSi and SiO Bond Activation at Platinum: Stepwise Formation of a SiH3Complex

The more, the better: Treatment of [Pt(H)2(dcpe)] (dcpe=1,2-bis(dicyclohexylphosphino)ethane) with stoichiometric amounts of silane leads to the bis(silyl) complex [Pt{Si(OMe)3}2(dcpe)], whereas the use of an excess silane results in hydrodealkoxylations by repetitive SiO bond activation and the formation of SiH3 ligands (see scheme; Cy=cyclohexyl).

Multiple Si–H Bond Activations in a Bis(diethylphosphino)methane-Bridged Complex of Rhodium and Iridium: Synthesis of an Unusual Bis(silyl)/μ-Silylene Complex

The reaction of 1 equiv of a primary silane (PhSiH3 or MesSiH3; Mes = mesityl) with the bis(diethylphosphino)methane-bridged complex [RhIr(CO)3(depm)2] (1; depm = Et2PCH2PEt2) yields the silylene-bridged dihydride complexes [RhIr(H)2(CO)2(μ-SiHR)(depm)2] (2, R = Ph; 3, R = Mes) by double Si–H bond activation. Complex 2 reacts further with excess phenylsilane to yield a bis(silylene)-bridged product, [RhIr(CO)2(μ-SiHPh)2(depm)2] (4), while complex 3 reacts with CO to produce a silylene- and carbonyl-bridged product, [RhIr(CO)2(μ-CO)(μ-SiHMes)(depm)2] (5). The reaction of 1 with 1 equiv of diphenylsilane leads to a silylene-bridged dihydride, [RhIr(H)2(CO)2(μ-SiPh2)(depm)2] (6), while reaction with 2 equiv of diphenylsilane at 60 °C in the presence of CO yields the silyl/μ-silylene complex [RhIr(H)(SiPh2H)(CO)3(κ1-depm)(μ-SiPh2)(depm)] (7). The reactions of 1, 6, and 7 with excess silane at 80 °C under a CO purge yield a novel bis(silyl)/μ-silylene complex, [RhIr(SiPh2H)2(CO)4(μ-SiPh2)(depm)] (8), with accompanying loss of a depm ligand.

Deposition of Dense Siloxane Monolayers from Water and Trimethoxyorganosilane Vapor

A convenient, laboratory-scale method for the vapor deposition of dense siloxane monolayers onto oxide substrates was demonstrated. This method was studied and optimized at 110 °C under reduced pressure with the vapor of tetradecyltris(deuteromethoxy)silane, (CD(3)O)(3)Si(CH(2))(13)CH(3), and water from the dehydration of MgSO(4)·7H(2)O. Ellipsometric thicknesses, water contact angles, Fourier transform infrared (FTIR) spectroscopy, and electrochemical capacitance measurements were used to probe monolayer densification. The CD(3) stretching mode in the FTIR spectrum was monitored as a function of the deposition time and amounts of silane and water reactants. This method probed the unhydrolyzed methoxy groups on adsorbed silanes. Excess silane and water were necessary to achieve dense, completely hydrolyzed monolayers. In the presence of sufficient silane, an excess of water above the calculated stoichiometric amount was necessary to hydrolyze all methoxy groups and achieve dense monolayers. The excess water was partially attributed to the reversibility of the hydrolysis of the methoxy groups.

Multiple Silicon−Hydrogen Bond Activations at Adjacent Rhodium and Iridium Centers

The reaction of 1 equiv of primary silanes, SiH(3)R (R = Ph, Mes), with [RhIr(CO)(3)(dppm)(2)] yields mono(silylene)-bridged complexes of the type [RhIr(H)(2)(CO)(2)(μ-SiHR)(dppm)(2)] (R = Ph or Mes), while for R = Ph the addition of 2 equiv yields the bis(silylene)-bridged complexes, [RhIr(CO)(2)(μ-SiHPh)(2)(dppm)(2)]. The kinetic isomer of this bis(silylene)-bridged product has the phenyl substituent axial on one silylene unit and equatorial on the other, and in the presence of excess silane this rearranges to the thermodynamically preferred "axial-axial" isomer, in which the phenyl substituents on each bridging silylene unit are axial and parallel to one another. The reaction of 1 equiv of diphenylsilane with [RhIr(CO)(3)(dppm)(2)] produces the mono(silylene)-bridged product, [RhIr(H)(2)(CO)(2)(μ-SiPh(2))(dppm)(2)], and the subsequent addition of silane in the presence of CO yields the silyl/silylene product [RhIr(H)(SiPh(2)H)(CO)(3)(κ(1)-dppm)(μ-SiPh(2))(dppm)]. The reaction of [RhIr(CO)(3)(dppm)(2)] with 2 equiv of SiH(2)Me(2) yields the analogous product [RhIr(H)(SiMe(2)H)(CO)(3)(κ(1)-dppm)(μ-SiMe(2))(dppm)]. Low-temperature NMR spectroscopic observation of some key intermediates, such as [RhIr(H)(SiH(2)Ph)(CO)(2)(μ-CO)(dppm)(2)], formed during the formation of the mono(silylene)-bridged species provides evidence for a mechanism involving initial Si-H bond activation at Rh, followed by the subsequent Si-H bond activation at Ir. The Si-H bond activation of a second equivalent of silane seems to be initiated by dissociation of the Rh-bound end of one diphosphine. The reaction of diphenylsilane with the cationic complex [RhIr(CH(3))(CO)(2)(dppm)(2)][CF(3)SO(3)] gives rise to a different reactivity pattern in which Si-H bond activation is initiated at Ir. In this case, the cationic silyl-bridged species, [RhIr(CH(3))(CO)(2)(κ(1):η(2)-SiHPh(2))(dppm)(2)][CF(3)SO(3)], contains an agostic Si-H interaction with Rh. In solution, at ambient temperature, this complex converts to two species, [RhIr(H)(COCH(3))(CO)(μ-H)(μ-SiPh(2))(dppm)(2)][CF(3)SO(3)] and [RhIr(CO)(2)(μ-H)(μ-SiPh(2))(dppm)(2)] [CF(3)SO(3)], formed by the competing methyl migration to CO and reductive elimination of methane, respectively. In the diphenylsilylene dihydride product, a weak interaction between the bridging silicon and the terminal Ir-bound hydride is proposed on the basis of NMR evidence.

Silyl and σ-silane ruthenium complexes: Chloride substituent effects on the catalysed silylation of ethylene

Silylation of ethylene by the chlorosilanes HSiMe(2)Cl and HSiMeCl(2) was catalysed by the bis(dihydrogen) complex RuH(2)(eta(2)-H(2))(2)(PCy(3))(2) (1). Dehydrogenative silylation leading to the formation of the corresponding vinylsilanes was in competition with hydrosilylation. The rate and selectivity of the reactions were influenced by the number of chloro substituents and the ethylene pressure. A comparative mechanistic study was performed in toluene-d(8) with the two chlorosilanes. Reaction of 1 with an excess of HSiMe(2)Cl (10 equiv.) produced the sigma-silane complexes RuH(2)(eta(2)-H(2))(eta(2)-HSiMe(2)Cl)(PCy(3))(2) (2Me(2)Cl), RuH(2)(eta(2)-HSiMe(2)Cl)(2)(PCy(3))(2) (3Me(2)Cl) and the silyl complex RuCl(SiMe(2)Cl)(eta(2)-H(2))(PCy(3))(2) (4Me(2)Cl), all characterised by multinuclear NMR spectroscopy. Complexes 2Me(2)Cl and 3Me(2)Cl adopt a cis configuration for the two bulky phosphine ligands as a result of stabilising SISHA (Secondary Interactions between Silicon and Hydrogen Atoms) interactions. Complex 4Me(2)Cl resulted from the stoichiometric reaction of HSiMe(2)Cl with 1 producing RuHCl(eta(2)-H(2))(PCy(3))(2)in situ which further reacted with evolution of H(2) and formation of 4Me(2)Cl. When reacting 1 with 10 equiv. of HSiMeCl(2), the corresponding complexes 3MeCl(2) and 4MeCl(2) were detected as well as traces of 2MeCl(2). The reactivity toward ethylene was then examined. Under catalytic conditions (excess silane in toluene-d(8), ethylene atmosphere) only two compounds could be characterised: free PCy(3) and the new (eta(6)-aryl)(disilyl) complexes of the general formula Ru(eta(6)-C(6)D(5)CD(3))(SiMe(3-n)Cl(n))(2)(PCy(3)) (6Me(3-n)Cl(n)-d(8), n = 1,2). The X-ray structure of 6MeCl(2) was obtained on a single-crystal at 160 K. When only 2 equiv. of HSiMe(2)Cl were added, the ethylene(silyl) complex RuH(SiMe(2)Cl)(C(2)H(4))(PCy(3))(2) (7Me(2)Cl) was obtained in addition to the organic products resulting from catalytic hydrogenation, hydrosilylation and dehydrogenative silylation, i.e. C(2)H(6) (major one), C(2)H(3)SiMe(2)Cl and C(2)H(5)SiMe(2)Cl. In the case of 2 equiv. of HSiMeCl(2), upon ethylene addition, 7MeCl(2) was formed in minority compared to a new disilyl complex Ru(SiMeCl(2))(2)(PCy(3))(2) (8MeCl(2)) characterised by NMR spectroscopy and X-ray diffraction on a single crystal at 160 K. In 8MeCl(2), a formal 14-electron species, stabilisation through two agostic C-H bonds of the cyclohexyl groups was ascertained by DFT calculations.

The Effect of Second Filler on Cure Characteristic and Mechanical Properties of Si-69 Treated Precipitate Silica/NR Composite

Silica has been widely used as non-black reinforcing filler, however, the filler-filler interaction has been an important issue. Cure characteristic and mechanical properties of the rubber compound and rubber vulcanizate were affected both by filler-rubber interaction and filler-filler interaction. There have been, presently, a number of natural fillers which are also used as fillers for the rubber, i.e. fly ash, sawdust and zeolite. This work therefore will study the effect of second filler added into the 13% Si-69 treated precipitate silica (PSi) filled natural rubber compounds. It was revealed that the scorch and cure time of the rubber compound increased with the content of treated PSi. This was the effect of excess of the silane treated onto PSi which would agglomerate and form the cluster of polysiloxane and would then be able to absorb vulcanizing accelerator resulting in extending the scorch and cure time of the rubber compounds. However, this effect was over ruled with the reinforcing effect as could be seen by the increasing, with the contents of PSi, of maximum torque and mechanical properties of the vulcanizates. The NR compounded with treated PSi content of 20 phr selected to study the effect of excess silane on the cure characteristic of hybrid fillers NR composite. The addition of sawdust led to longer scorch time and cure time but not much change of the maximum torque. As expected, the modulus of the rubber vulcanizate increased with the sawdust content whereas the tensile strength and elongation at break decreased with the sawdust content. The incorporation of zeolite could accelerate the cure reaction therefore both scorch time and cure time decreased. The maximum torque also increased with the content of zeolite. Both modulus and tensile strength increased with the content of the zeolite whereas elongation at break tended to be unchanged. In the case of using fly ash as the second filler, the cure time tended to be unchanged. However, the maximum torque tended to be increased with the content of fly ash. It was found that the modulus, tensile strength increased but elongation at break decreased. Interestingly, the excess of Si-69 used effect pronouncedly for the addition of zeolite and fly ash cases as the excess silane could promote the interaction between fillers surface and rubber molecule accept for sawdust

Oxidation of Tertiary Silanes by Osmium Tetroxide

In the presence of an excess of pyridine ligand L, osmium tetroxide oxidizes tertiary silanes (Et(3)SiH, (i)Pr(3)SiH, Ph(3)SiH, or PhMe(2)SiH) to the corresponding silanols. With L = 4-tert-butylpyridine ((t)Bupy), OsO(4)((t)Bupy) oxidizes Et(3)SiH and PhMe(2)SiH to yield 100 +/- 2% of silanol and the structurally characterized osmium(VI) mu-oxo dimer [OsO(2)((t)Bupy)(2)](2)(mu-O)(2) (1a). With L = pyridine (py), only 40-60% yields of R(3)SiOH are obtained, apparently because of coprecipitation of osmium(VIII) with [Os(O)(2)py(2)](2)(mu-O)(2) (1b). Excess silane in these reactions causes further reduction of the OsVI products, and similar osmium "over-reduction" is observed with PhSiH(3), Bu(3)SnH, and boranes. The pathway for OsO(4)(L) + R(3)SiH involves an intermediate, which forms rapidly at 200 K and decays more slowly to products. NMR and IR spectra indicate that the intermediate is a monomeric Os(VI)-hydroxo-siloxo complex, trans-cis-cis-Os(O)(2)L(2)(OH)(OSiR(3)). Mechanistic studies and density functional theory calculations indicate that the intermediate is formed by the [3 + 2] addition of an Si-H bond across an O=Os=O fragment. This is the first direct observation of a [3 + 2] intermediate in a sigma-bond oxidation, though such species have previously been implicated in reactions of H-H and C-H bonds with OsO(4)(L) and RuO(4).

Substituent Effects in the Hydrosilylation of Coordinated Dinitrogen in a Ditantalum Complex: Cleavage and Functionalization of N2

The dinitrogen complex ([NPN]Ta)2(mu-eta1:eta2-N2)(mu-H)2, 1, (where [NPN] = (PhNSiMe2CH2)2PPh) undergoes hydrosilylation with primary and secondary alkyl- and arylsilanes, giving a new N-Si bond and a new terminal tantalum hydride derived from one Si-H unit. Various primary silanes can be employed to give isolable complexes of the general formula ([NPN]TaH)(mu-N-N-SiH(n)R(3-n))(mu-H)2(Ta[NPN]) (5, R=Bu, n = 2; 9, R=Ph, n = 2). Analogous complexes featuring secondary silanes are not isolable, because these products, and 5 and 9, are uniformly unstable toward reductive elimination of bridging hydrides as H2, followed by cleavage of the N-N bond to give ([NPN]TaH)(mu-N)(mu-N-SiH(n)R(3-n))(Ta[NPN]) (6, R=Bu, n = 2; 10, R=Ph, n = 2; 15, R=Ph, n = 1; 16, R=Ph and Me, n = 1). The bridging nitrido ligand in these complexes is itself a substrate for a second hydrosilylation when n = 2, and schemes leading to Ta(IV) complexes of the general formula ([NPN]Ta)2(mu-N-SiH2R)(mu-N-SiH2R') via elimination of H2 are reported (4, R=R'=Bu; 12, R=Bu, R' = Ph; 13, R=Bu, R' = CH2CH2SiH3). At this point, the general reaction manifold for these compounds ramifies, with distinct outcomes occurring for different R groups-[NPN] ligand amide migration from Ta to RSi affords 11, whereas stable complex 6 rearranges to give 7, in the presence of excess silane. Ethanediylbissilane reacts with 1 to give 14, isostructural to 7.

Three-Coordinate Co(I) Provides Access to Unsaturated Dihydrido-Co(III) and Seven-Coordinate Co(V)

The three-coordinate, T-shaped Co(I) complex, PNPCo (PNP = [(tBu2PCH2SiMe2)2N-], is readily synthesized by magnesium reduction of divalent PNPCoCl. Triplet (S = 1) PNPCo is coordinatively and electronically unsaturated and undergoes a thermally reversible oxidative addition reaction with H2, producing trivalent PNPCo(H)2. In contrast, the reaction with excess primary silane PhSiH3 quantitatively generates the base-stabilized silylene Co(V) compound {kappa2-tBu2PCH2Me2SiNSiMe2CH2tBu2P(H)Si=}Co(H)3(SiH2Ph)2.

Quantifying the Specific Binding between West Nile Virus Envelope Domain III Protein and the Cellular Receptor αVβ3 Integrin

A previous study has illustrated that the alphaVbeta3 integrin served as the functional receptor for West Nile virus (WNV) entry into cells. Domain III (DIII) of WNV envelope protein (E) was postulated to mediate virus binding to the cellular receptor. In this study, the specificity and affinity binding of WNV E DIII protein to alphaVbeta3 integrin was confirmed with co-immunoprecipitation and receptor competition assay. Binding of WNV E DIII protein to alphaVbeta3 integrin induced the phosphorylation of focal adhesion kinase that is required to mediate ligand-receptor internalization into cells. A novel platform was then developed using the atomic force microscopy to measure this specific binding force between WNV E DIII protein and the cellular receptor, alphaVbeta3 integrin. The single protein pair-interacting force measured was in the range of 45 +/- 5 piconewtons. This interacting force was highly specific as minimal force was measured in the WNV E DIII protein interaction with alphaVbeta5 integrin molecules and heparan sulfate. These experiments provided an insight to quantitate virus-receptor interaction. Force measurement using atomic force microscopy can serve to quantitatively analyze the effect of candidate drugs that modulate virus-host receptor affinity.

Photochemical reactions of [CH2(η5-C5H4)2][Rh(C2H4)2]2with silanes: evidence for Si–C and C–H activation pathways

Photochemical reaction of [CH2(eta5-C5H4)2][Rh(C2H4)2]2 1 with dmso led to the stepwise formation of [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(dmso)] 2a and [CH2(eta5-C5H4)2][Rh(C2H4)(dmso)]2 2b. Photolysis of 1 with vinyltrimethylsilane ultimately yields three isomeric products of [CH2(eta5-C5H4)2][Rh(CH2=CHSiMe3)2]2, 3a, 3b and 3c which are differentiated by the relative orientations of the vinylsilane. When this reaction is undertaken in d6-benzene, H/D exchange between the solvent and the alpha-proton of the vinylsilane is revealed. In addition evidence for two isomers of the solvent complex [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(eta2-toluene)] was obtained in these and related experiments when the photolysis was completed at low temperature without substrate, although no evidence for H/D exchange was observed. Photolysis of 1 with Et3SiH yielded the sequential substitution products [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiEt3)H] 4a, [CH2(eta5-C5H4)2][Rh(C2H4)(SiEt3)H]2 4b, [CH2(eta5-C5H4)2][Rh(C2H4)(SiEt3)H][Rh(SiEt3)2(H)2] 4c and [CH2(eta5-C5H4)2][Rh(SiEt3)2(H)2]2 4d; deuteration of the alpha-ring proton sites, and all the silyl protons, of 4d was demonstrated in d6-benzene. This reaction is further complicated by the formation of two Si-C bond activation products, [CH2(eta5-C5H4)2][RhH(mu-SiEt2)]2 5 and [CH2(eta5-C5H4)2][(RhEt)(RhH)(mu-SiEt2)2] 6. Complex 5 was also produced when 1 was photolysed with Et2SiH2. When the photochemical reactions with Et3SiH were repeated at low temperatures, two isomers of the unstable C-H activation products, the vinyl hydrides [CH2(eta5-C5H4)2][{Rh(SiEt3)H}{Rh(SiEt3)}(mu-eta1,eta2-CH=CH2)] 7a and 7b, were obtained. Thermally, 4c was shown to form the ring substituted silyl migration products [(eta5-C5H4)CH2(C5H3SiEt3)][Rh(SiEt3)2(H)2]2 8 while 4b formed [CH2(C5H3SiEt3)2][Rh(SiEt3)2(H)2]2 (9a and 9b) upon reaction with excess silane. The corresponding photochemical reaction with Me3SiH yielded the expected products [CH2(eta5-C5H4)2][Rh(C2H4)2][Rh(C2H4)(SiMe3)H] 10a, [CH2(eta5-C5H4)2][Rh(C2H4)(SiMe3)H]2 10b, [CH2(eta5-C5H4)2][Rh(C2H4)(SiMe3)H][Rh(SiMe3)2(H)2] 10c and [CH2(eta5-C5H4)2][Rh(SiMe3)2(H)2]2 10d. However, three Si-C bond activation products, [CH2(eta5-C5H4)2][(RhMe)(RhH)(mu-SiMe2)2] 11, [CH2(eta5-C5H4)2][(Rh{SiMe3})(RhMe)(mu-SiMe2)2] 12 and [CH2(eta5-C5H4)2][(Rh{SiMe3})(RhH)(mu-SiMe2)2] 13 were also obtained in these reactions.

表面修飾されたカーボンブラック粒子を用いた分散系レオロジーの非線形性

表面処理状態の異なったカーボンブラック分散系の定常流粘度、動的粘弾性を円錐円板型のレオメータで測定した。カーボンブラック表面処理はシランカップリング剤にて行った。表面修飾の程度とレオロジー的性質との関係をカーボンブラック粒子の形成する凝集網目構造の変遷を考慮しながら検討した。粒子の表面処理が進行するに従い分散系の見かけ粘度は減少し、シアーシンニングの傾向が少なくなった。また動的粘弾性においては粒子の表面処理の進行にともない貯蔵弾性率の値は減少し、その周波数依存性が増加した。これらの現象は凝集構造の減少と関係がある。つまり表面修飾が進行するにともないシランカップリング剤中のフェニル基が粒子表面を覆い粒子間凝集を阻害し、かつ粒子表面の微細孔が閉塞されたことを示す。この結果として凝集網目構造は表面修飾と共に減少し、粒子の比表面積も減少する事となるが、余剰のシランカップリング剤は逆に粒子問の結合と構造形成とを促すため表面処理時間と粘弾性挙動との関係は不明瞭になる。