John F. HarrodMcGill University | McGill · Department of Chemistry
John F. Harrod
B.Sc.(Hons.)Cemistry;Ph.D. (Chemistry) Birmingham, U.K.
About
190
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Introduction
Additional affiliations
September 1960 - September 1966
General Electric Research Laboratory, Schenectady, N.Y.
Position
- Research Chemist
Description
- Basic research in polymer chemistry and organosilicon chemistry. Member of the Emergency Task Force: Gemini Fuel Cell Team.
Education
September 1952 - June 1958
University of Birmingham U.K.
Field of study
- Chemistry
Publications
Publications (190)
The homogeneous catalytic hydrosilation-hydrogenation of pyridines is observed in the presence of Cp2TiMe2 (Cp = η5-C5H5) and CpCp*TiMe2 (Cp* = η5-C5Me5) as catalysts and using PhSiH3 or PhMeSiH2 as the source of Si-H. Under appropriate conditions, and with appropriate ring-substitution, good yields of the N-silyl-dihydropyridine or N-silyltetrahyd...
A variety of acetamide derivatives are reduced in excellent yields to tertiary amines by PhMeSiH2 in the presence of Cp2TiX2 (X = F or Me) catalysts. The reactions are very clean at 80 °C. At room temperature a secondary reaction, hydrogenolysis of the C(O)N bond, intervenes and reduces the chemoselectivity. Nevertheless, this chemistry provides a...
The mass spectra of the substituted methylcyclosiloxanes where X = H (n = 4, 5 and 6), X = C6H5 (n = 3 and 4), X = Br (n = 3 and 4), X = Co(CO)4 (n = 4 and 5) have been measured. The compounds X = H fragment by the same kinds of substituent loss and ring contraction mechanisms as previously reported for the compounds X = CH3 but also by the loss of...
A family of complexes IrH(CO)(Ph3P)2(ol), where ol is a monosubstituted ethylene, has been synthesized. Under an inert atmosphere the acrylonitrile complex undergoes clean decomposition to produce C2H5CN, half of the necessary hydrogen for the ligand reduction apparently being furnished by the phosphine ligand. The first step in the hydrogénation i...
Dimethylzirconocene and dihydridozirconocene both catalyze the dehydrogenative coupling of primary and secondary organosilanes. Primary silanes give linear polysilanes and secondary silanes give tetraorganodisilanes. The reaction of dimethylzirconocene with a small excess of phenylsilane gives the unusual unsymmetrically substituted zirconocenesily...
The structures of some poly(organosilylenes), (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osm...
Dimethyltitanocene is an excellent catalyst for the redistribution of alkoxy- and siloxyhydrosilanes. The redistribution reactions of triethoxysilane, diethoxymethylsilane, 1,3,5,7-tetramethylcyclotetrasiloxane, pentamethyldisiloxane, and H—(SiMe2O)n—SiMe2H (n = 1 to 3) are described. The mechanism of these reactions is discussed in terms of TiH me...
In the presence of an amine, copper(I) chloride is an effective catalyst for the cross-dehycrocoupling of silanes with alkynes. The reactions proceed at useful rates above 100 °C, but rates drop dramatically on going from 1° to 2° to 3° organosilanes. Primary silanes, RSiH3 (R = Ph,n-hexyl), react in a stepwise fashion with phenylacetylene to give...
Bis(indenyl)dimethylzirconocene, 1, and [1,2-bis(indenyl)ethane]dimethylzirconocene, 2, both catalyze the dehydropolymerization of phenylsilane to a mixture of low molecular weight cyclic oligosilanes (PhSiH)n (n = 6–9). The limited number of sharp resonances in the 29Si and 1H NMR spectra of the polymer produced with 2 as catalyst indicates that t...
A systematic comparison between the dimethylzirconocene (DMZ) and dimethyltitanocene (DMT) catalyzed dehydrocoupling of organosilanes is reported. The polymerization rates of primary silanes are about ten times faster for DMZ than for DMT, but the characteristics of the polymers produced are essentially identical. Variations of molecular weight and...
In the presence of cuprous chloride, hydrosilanes and primary amines react to give silazanes. Methylphenylsilane reacts with (R)-(+)-α-methylbenzylamine to give the two diastereomeric monosilazanes as the only products. Aniline and benzylamine react with methylphenyl- and diphenylsilanes to give primarily the monosilazane, disilazane, or diazasilan...
As previously described, organosilanes react with dimethyltitanocene (DMT) to give three reduced titanium intermediates, Cp2Ti(μ-SiRR′H)(μ-H)TiCp2, 1, [Cp2Ti(μ-SiRR′H)]2, 2, and [Cp2Ti(H)]2(μ-H), 3. When R = Me and R′ = n-Bu, the DMT is quantitatively converted to 1, which is persistent at room temperature. When R′ = H, DMT is initially converted q...
The reaction of Ph2Si(NHNHMe)2 (1) with MeI results in a mixture of two six-membered ring isomers, 1,2,4,5-tetraaza-1,4-dimethyl-3,3,6,6-tetraphenyl-3,6-disilacyclohexane (2), 45%, and 1,2,4,5-tetraaza-1,5-dimethyl-3,3,6,6-tetraphenyl-3,6-disilacyclohexane (3), 40%. The reaction of 1 with HCl or Ph2SiCl2 proceeds in a similar fashion. The thermolys...
S,S-[1,2-Bis(tetrahydroindenyl)ethane]titanium-based catalysts were used, in conjunction with either diphenyl- or methylphenylsilane, to effect the catalytic hydrosilation of a wide variety of dialkyl ketones. The highest enantioselectivity was observed with c-pentylethylketone (70%) and the selectivity was found to be very sensitive to the steric...
Except for t-butyl chloride, the 1- and 2-methyl substituted ethyl chlorides reacted at ambient temperatures with clean titanium surfaces to produce mixtures of the corresponding alkanes and alkenes; t-butyl chloride gave only isobutene. At elevated temperatures (80–150 °C depending on reactant) the branched alkyl chlorides underwent clean, catalyt...
The thermal decomposition of a series of phenoxo complexes of copper (II), in solution, containing either trichlorophenoxo or tribromophenoxo ligands and a variety of neutral ligands, has led to a rather unique method for the synthesis of μ4-oxo-hexa-μ-halotetracopper(II) complexes. The yield of this complex was found to increase considerably with...
The reactions of 1-chloropropane (1) and 1-chloro-2-methylpropane (2) with clean, polycrystalline films of the metals Ti through Cu were studied at ambient and elevated temperatures. At ambient temperature all of the metals exhibited a complex pattern of behavior. Titanium was uniquely different from other metals in that no catalytic hydrogenation...
The kinetics of the reactionshave been studied (M = Si, Ge, Sn). All three reactions proceed by predissociation of the iridium complex and concerted cis addition of Ph3MH to the square-planar intermediate. The relative rate of addition of Ph3MH increases in the order Si (1) < Ge (18) < Sn (70) and the difference in rate within experimental error is...
The reactions of several substituted cuprous phenoxides with CCl4 in acetonitrile were examined. Phenoxides without ortho-substituents usually gave high yields of tetraarylorthocarbonates. It is shown that the latter are also produced catalytically from sodium phenoxides and CCl4 in the presence of small amounts of cuprous chloride. Cuprous phenoxi...
The oxidation of 2,4,6-tritertbutylphenol and several other alkyl and halophenols by CrO2Cl2 and VOCl3 was studied. The products of CrO2Cl2 oxidation are mostly quinones and diphenoquinones, whilst those of VOCL3 oxidation also include major amounts of dealkylated phenols and C—C coupled dimers. The product distributions are interpreted in terms of...
The kinetics of the reduction of ferric chloride by molecular hydrogen in aqueous solution, in the presence of chloropalladate(II), were examined. The latter acts as a homogeneous catalyst for the reaction. The rate-law was found to be,whereThe mechanism of the reaction is discussed.
Ruthenium(III) chloride, in aqueous HCl solution, was found to activate H2 homogeneously and to catalyze the reduction by H2 of Ru(IV)and Fe(III). The kinetics of these reactions were examined and, in each case, the rate law was found to be −d[H2]/dt = k1[H2][RuIII] where k1 = 4.0 × 1014 exp [−23,800/RT] M−1 sec−1. The mechanisms of these reactions...
A series of phenoxo complexes of copper(II) containing a variety of halophenoxo ligands and a variety of amine ligands has been prepared. The thermal stability of the complexes with regard to the decomposition reaction:was found to be lower with those ligands, L, which increase the oxidizing power of the copper(II) and vice versa.The intense absorp...
The dehydrochlorination of dihydridochlorocarbonylbis(triphenylphosphine)iridium(III) by organic and inorganic bases is described. The manner in which this reaction provides a formal link between the homolytic activation of hydrogen at a single metal center and the heterolytic activation of hydrogen is discussed.
Complexes have been prepared by oxidation of hydridocarbonyltris(triphenylphosphine)iridium(I) with a variety of silicon hydrides. The complexes were very stable with respect to thermal loss of either silicon hydride or molecular hydrogen.An unequivocal assignment of stereochemistry of the complexes was obtained from a combination of infrared and p...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
group 4B;uncatalyzed reaction;homolysis;silicon hydrides;hydrosilation reaction
insertion reaction;metal centers;unsaturated molecules;hydride compound;unsaturated substrate
main group hydrides;auto-oxidation;carbon-hydrogen bonds;oxidative degradation;electron-delocalizing substituents
hydrogen-germanium bonds;catalytic semihydrogenation;nucleophilic attack;free radical catalyst;aryl thiolets
fischer tropsch synthesis;thermodynamic factors;saturated complex;formyl cmplexes;kinetics of insertion reaction
catalytic hydrosilation;hydrogenation;tautomerization;oxidative addition;reverse insertion
group 6B, 7B;radical catalyzed addition;transition metals;organometallic synthesis;ziegler natta polymerization
transition metal hydride complexes;regioselectivity;protonation;stereochemistry;isomerization
nitrogen compounds;insertion reactions;single insertion;isonitriles;hydrometallation
hydrogen-germanium bonds;hydrogen-tin bonds;reductive elimination;oxidative addition;recrystallization
group 5B;reactivity trends;hydrophosphinatyion;pholytic conditions;olefin isomerization
insertion reaction;hydrolysis;exothermic reaction;palladium complex;triosmium cluster
Tri-μ-chloro-chloro(thiocarbonyl)tetrakis(triphenylphosphine) diruthenium(II)-acetone(1:1) Carbonyltri-μ-chloro-chlorotetrakis(triphenylphosphine)diruthenium(II)-acetone(1:2)
A variety of acetamide derivatives are reduced in excellent yields to tertiary amines by PhMeSiH2 in the presence of Cp2TiX2 (X = F or Me) catalysts. The reactions are very clean at 80 °C. At room temperature a secondary reaction, hydrogenolysis of the C(O)—N bond, intervenes and reduces the chemoselectivity. Nevertheless, this chemistry provides a...
Preceramic polymers offer exceptional potential for low-temperature processing of both oxide and non-oxide ceramics. In addition, shapes such as fibers, films, and membranes that are not commonly available using standard processing techniques are readity available using preceramic polymers. In non-oxide ceramics, the ceramic products generally avai...
The title reaction has been surveyed for a number of substrates with differing substitution patterns. With a few exceptions, the methodology provides a one-pot synthesis of the 1,2-diamines from widely available and inexpensive starting materials, and in high yields. In addition, the coupling of 1,4- and 1,3-bis-(N,N,N',N'-tetraalkyl)arylenediamide...
Solid catalysts, prepared by treating alkyl or aryl magnesium halides with titanium tetrachloride or butyl o‐titanate, polymerize styrene rapidly to amorphous low molecular weight (10 ⁴ –10 ⁵ ) polymer. The energy of activation for the process is approximately 20 kcal/mole for all active catalysts. Kinetic evidence indicates that initiation and pro...
PhMeSiH2 reduces ethyl benzoate in the presence of a Cp2TiMe2 (Cp = eta(5)-cyclopentadienyl) catalyst to give PhMeSi(OEt)(OCH2Ph) (1). Small to moderate amounts of toluene are also produced, depending on the reaction conditions. Under 40 psi of H-2 the same reaction gives quantitative reduction of the ester to toluene. PhCHO is reduced, under the s...
Symmetrische vicinale Diamine entstehen bei einer Reaktionssequenz aus Reduktions-, Desoxygenierungs- und Kupplungsschritten ausgehend von aromatischen Amiden in Gegenwart von PhMeSiH2 und einem Titanocen-Katalysator (siehe Schema).
Thin layers of a-Si3N4 were synthesized by the pyrolysis of thin films of poly(methylsilane) (PMS) and poly(dimethylsilane) (PDMS) spin-coated on silicon single-crystal wafers and via deposition of the volatile species resulting from the thermal cracking of the bulk precursor in the presence of ammonia. The process was monitored by FT-IR spectrosco...
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
This review describes the remarkable ability of titanocene derivatives to catalyze reactions of SiH compounds. These reactions involve addition of SiH to unsaturated molecules, dehydrocoupling of SiH with SiH and with a variety of other EH bonds, and redistribution of compounds containing the ROSiH bond system. The characterization of the ma...
A kinetic study of the photochemical reaction of [Cp2Zr(mu-SiH2Ph)](2)(2+)2[BBun(C6F5)(4-n)](-) (1) with PhCH2SiH3 to give the analogous PhCH2SiH2 complex 2 was carried out using a combination of NMR and EPR spectroscopy to follow the rates of disappearance of reactants and the appearance of intermediates and products. The paramagnetic intermediate...
Phenylsilane was polymerized with a number of group 4 metallocene precatalysts, including (S,S)-[1,2-bis(η5-tetrahydroindenyl)ethane]titanium binaphtholate (1)/2BuLi, Cp2HfCl2 (2)/2BuLi/B(C6F5)3, and CpCp*ZrCl2 (3)/2BuLi/B(C6F5)3. With 1, polymerization proceeds extremely slowly and it is possible to observe the stepwise oligomerization to Si2, Si3...
The titanocene(III) complexes Cp2TiX(PMe3) (X=F, Cl, Br, I, Me, SMe) are readily synthesized by comproportionation reactions of Cp2Ti(PMe3)2 and Cp2TiX2. The products are characterized by EPR spectroscopy.
The color change from yellow to violet allows the formation of the intermediate [Cp2Ti(SiHMePh)(pyridine)] to be monitored in the reaction of PhMeSiH2 with a pyridine in the presence of the precatalyst [Cp2TiMe2] [Eq. (a)]; the hydride [Cp2TiH] is postulated to be the key intermediate in the catalytic cycle. The regioselective hydrosilylation of py...
The color change from yellow to violet allows the formation of the intermediate [Cp2 Ti(SiHMePh)(pyridine)] to be monitored in the reaction of PhMeSiH2 with a pyridine in the presence of the precatalyst [Cp2 TiMe2 ] [Eq. (a)]; the hydride [Cp2 TiH] is postulated to be the key intermediate in the catalytic cycle. The regioselective hydrosilylation o...
The complex Cp2Ti[2-SiMe2(C5H4N)] 1, the first example of a chelating silyl, and a tertiary silyl complex of Cp2Ti(III), is prepared by reaction of 2-SiHMe2(C5H4N) with Cp2TiMe2, and its X-ray structure, EPR spectrum and reactions with C5H5N and PMe3 are reported.
The title compound, the first example of a structurally fully characterized, unsubstituted silyl complex of a group 4 element, has been synthesized and showed unusual thermal stability compared to its analog Cp2Ti(SiH2Me)(PMe3).
The hydrosilation of prochiral ketones using catalysts prepared by alkylation of [1,2-bis(tetrahydroindenyl)ethane]titaniumIV(1,1′-binaphth-2,2′-diolate) with MeLi and n-BuLi, and (EtO)3SiH, Me(EtO)2SiH, [MeSi(H)O]4, Me3SiO[MeSi(H)O]nSiMe3 and MeSiH3 as the hydrosilane is described. The rates obtained with the MeLi based catalyst are one to two ord...
The structure of a complex previously assigned as [Cp2Ti(µ- SiH2)]2 is shown to be [Cp2Ti(µ-H–SiH2)]2.
Reactions and intermediates leading to zirconocene complexes [Cp‘2Zr(μ-H)(SiHR)]22+[BR‘n(C6F5)4-n]22- (Cp‘ = Cp, MeCp, Me5Cp; R = Ph, PhCH2; R‘ = Bu or H; 1a−e) were investigated in situ by NMR and EPR studies and by trapping unstable intermediates with PMe3. Two novel ZrIII complexes, [Cp2ZrIII]+[BBun(C6F5)4-n]- (5) and [Cp2ZrIII(PMe3)2]+[BBun(C6F...
The reaction of dimethyltitanocene (Cp2TiMe2) with PhSiH3 in hexane in the presence of Cy2PH (Cy = cyclohexyl) is photoinitiated to give paramagnetic Cp2Ti(SiH2Ph)(PHCy2), characterized in solution by EPR spectroscopy (a(H) of phosphine = 4.8 G, a(P) = 26.9 G, giso = 1.9950). Under the same conditions, a similar reaction with Ph2SiH2 gives a crysta...
The thermal decomposition of dibutylzirconocene (1) at room temperature affords paramagnetic butylzirconocene(III) (11), zirconocene(III) hydride (12), the diamagnetic butenylzirconocene(IV) hydride dimer 5a, and the 1,1-bis(cyclopentadienyl)-2-methyl-3-(zirconocenyl hydride)-1-zirconacyclobutane(IV) dimer 9. Initially, decomposition furnishes crot...
The novel zirconocene complexes [Cp‘2Zr(μ-H)(SiHR)]22+[BR‘n(C6F5)4-n]22- (Cp‘ = Cp, MeCp, Me5Cp; R = Ph or PhCH2; R‘ = Bu or H) were isolated from silane dehydropolymerization reaction mixtures catalyzed by Cp‘2ZrCl2/2BuLi/B(C6F5)3 or by [Cp‘2Zr(μ-H)H]2/2B(C6F5)3 combination catalysts. A total structure analysis of these compounds, performed by mul...
The use of ‘cation-like’ metallocene combination catalysts (Cp′2MCl22BuLiB(C6F5)3; Cp′ = η5-cyclopentadienyl, or substituted η5-cyclopentadienyl; M = Ti, Zr, Hf, U) for dehydropolymerization of silanes significantly improves the polymer molecular weight. For example, under the same conditions a Cp(C5Me5)ZrCl22BuLi catalyst gives Mn = 1890, while...
Poly(methylsiladiazane) (PMSDZ) is synthesized by the copolymerization of MeHSiClâ with HâNNHâ in 1:1.4 molar ratio. The structure of the polymer is shown by NMR and IR spectroscopies to consist of tetraazadisiliacyclohexane rings bridged by MeHSi groups. The polymer gives a mixture of silicon nitride and silicon carbonitride when heated above 1,10...
A preliminary study of the dimethyltitanocene, 7, and rac-[ethylene-1,2-bis(η5-4,5,6,7-tetrahydroindenyl)]TiMe2, 8, catalyzed reactions of silanes with allylic and homoallylic alcohols is described. In the presence of catalysts 7 or 8, tertiary silanes bearing at least one phenyl group react with 2-methyl-but-1-ene-4-ol, 2a, to produce the 4-siloxy...
Poly(methylsilane) (PMS), produced by the (eta(5)-C5H5)(2)Zr(CH3)(2)-catalyzed dehydrocoupling of CH3SiHCl2, can be pyrolyzed into silicon carbide (SiC) and deposited as thin films on silicon single-crystal wafers to form SiC/Si heterojunctions. Two procedures have been developed for in situ doping the SiC layers in such heterojunctions with nitrog...
Quadrupolar effects transferred from N-14 to Si-29 have been observed in the magic-angle spinning NMR spectra of the cyclic polysilazanes octamethylcyclotetrasilazane, [(CH3)(2)SiNH](4), and hexamethylcyclotrisilazane, [(CH3)(2)SiNH](3). For the latter compound, three silicon and six carbon chemical shifts were observed, and the residual dipole-qua...
Polymethylsilane (PMS) is an excellent precursor for the preparation of thin films of amorphous SiC on useful substrates, such as silicon wafers, quartz plates and polycrystalline alumina plates. The progress of pyrolysis chemistry can be easily monitored by FTIR on films supported on silicon, down to thicknesses as low as 10- 20 nm. The reactivity...
In the ten years since the scientific rationale for the design, synthesis and application of inorganic and organometallic polymers (IOPs) was first conceptualised, we have witnessed the first tentative exploration of IOPs as precursors to new materials, with efforts focusing on the design and synthesis of novel ceramic precursors. Developing expert...
Dimethyltitanocene, in conjunction with a wide variety of compounds containing SiH bonds, is an excellent catalyst for the polymerization of acetylene to give free standing films. Polymerizations of acetylene in a variety of siloxane and silane matrices using this catalyst system are described. The polyacetylenes produced with a [(MeSiHO)3(Me2Si)17...
Several tetraazadisilacyclohexanes, with general formula R2Si(NHNR')2SiR2 (R = Me or Ph, R' = H or Me), have been synthesized by a dehydrocoupling methodology. Structural study showed that planar and pyramidal coordinations about nitrogen atoms exist in these molecules.
The use of pol(methylsilane) (PMS) as a pyrolytic precursor to thin layers of silicon carbide (SiC) on silicon single-crystal wafers has been examined. The enhanced IR signals resulting from the multiple internal reflections that occur within the thin layers deposited on the chemically polished Si surfaces have been used to monitor the oxidation an...
Bis(2-methythydrazino)tetraphenyldisiloxane, 1, is prepared by the controlled hydrolysis of bis(2-methythydrazino)diphenylsilane, 2. Crystals of 1 are monoclinic, space group P2(1)/n, with a = 10.3200(19) angstrom, b = 7.3343(20) angstrom, c = 16.6.58(3) angstrom, beta = 94.013(15)-degrees, and Z = 2. The molecule is centrosymmetric, with a linear...
Reaction of Ph2Si(NHNHMe)2 (1) with n-BuLi and Ph2SiCl2 in 1 : 2 : 1 ratio afforded 54% of 1,2,4-triaza-1-methyl-4-methylamino-3,3, 5, 5-tetraphenyl-3,5-disilacylopentane (2). In the presence of a catalytic amount of n-BuLi, 2 is rearranged to two isomers, 1,2,4,5-tetraaza-1,4-dimethyl-3,3,6,6-tetraphenyl-3,6-disilacyclohexane (3) and 1,2,4,5-tetra...
The use of tris(pentafluorophenyl)borane, (C6F5)3B, as a cocatalyst in the dehydrocoupling of phenylsilane, in the presence of zirconocene-derived catalysts, leads to suppression of chain scission reactions and to an increase in polysilane chain length (M(n) > 7000). An exhaustive multinuclear NMR study of the catalytic species leads to the conclus...
Poly(methylsilanes) produced by sodium coupling of methyldichlorosilane (2:1 molar ratio) contain residual chlorine which can be removed by reduction with LiAlH4 at low temperature. Following this reduction, the polymers contain catalytically active centers (presumed to be silyl anions) which, in THF solution, further polymerize and crosslink the p...
Infrared and Raman spectra have been recorded with the aid of diamond anvil cells for all-trans-hexaphenylcyclohexasilane, [Si(H)Ph](6) (I), at various pressures up to similar to 40 kbar. The pressure dependences (d nu/dP) and relative pressure dependences (d In nu/dP) of the internal vibrations (nu(SiH),nu(SiSi),nu(SiC),nu(CH),etc.) have been dete...
The reaction of Cp2MMe2 (M = Zr, Hf) with Ph2Si(OH)2 yields the eight-membered ring [Cp2M(mu-OSiPh2O)]2 (M = Zr (1), Hf (2)). 1 crystallizes in the space group P1BAR with a = 10.410(9) angstrom, b = 12.140(6) angstrom, c = 16.318(5) angstrom, alpha = 94.26(3)degrees, beta = 103.42(5)degrees, gamma = 93.16(6)degrees, and Z = 2. The crystal structure...
Phenylsilane reacts spontaneously with hydrazine to give a soluble oligomer, [PhSi(NHNH)2SiPhNHNH]n, 1, while in the presence of dimethyltitanocene (DMT) as catalyst, rapid coupling took place to give an insoluble gel. The dehydrocoupling reactions of phenylsilane with methylhydrazines (1-methyl-, 1,1-dimethyl-, and 1,2-dimethylhydrazine) are effec...
The reaction of Cp[sub 2]MMe[sub 2](M = Zr, Hf) with Ph[sub 2]Si(OH)[sub 2] yields the eight-membered ring [Cp[sub 2]M([mu]-OSiPh[sub 2]O)][sub 2] (m = Zr (1), Hf (2)). 1 crystallizes in the space group P[bar 1] with a = 10.410(9) [angstrom], b = 12.140(6) [angstrom], c = 16.318(5) [angstrom], [alpha] = 94.36(3)[degrees], [beta] = 103.42(5)[degrees...
Pre-ceramic block or graft copolymers may offer entrée into nanocomposite ceramics provided the two homopolymers are immiscible and one can carefully control the size of the blocks or grafts. We are exploring the possibility of making copolymers from methylsilsesquioxane, [MeSi(O)1.5]x, (SiO), a precursor to ‘black glass’ and the polysilazane, [MeH...
Hexabenzylcyclohexasilane, [Si(H)CH2Ph]6 (1), has been synthesized in moderate yield (approximately 35%) by dehydrocoupling benzylsilane in the presence of dimethyltitanocene (Cp2TiMe2,CP = eta5-C5H5) catalyst. Compound 1 crystallizes in the trigonal R3BAR (C3i2) space group [a = 25.077-(2), c = 5.7031(6) angstrom; V = 3105.9(4) angstrom3; D(calcd)...
Infrared and Raman spectra have been recorded at room temperature for the following four cyclohexasilanes: dodecamethylcyclohexasilane, (SiMe2)6 (I); all-trans-hexabenzylcyclohexasilane, [Si(H)CH2Ph]6 (II); all-trans-hexaphenylcyclohexasilane, [Si(H)Ph]6(III); and dodecaphenylcyclohexasilane, (SiPh2)6 (IV). Vibrational assignments have been propose...
EPR spectroscopy shows that reactions of organosilanes with dimethyltitanocene in the presence of the phosphines PMe(n)Ph3-n (n = 1-3) lead to a rich variety of products, including Cp2TiH(PMe(n)Ph3-n), Cp2TiSiRR'H(PMe(n)Ph3-n), Cp2Ti[(SiRR')nSiRR'H]-(PMe(n)Ph3-n), and CP2Ti(eta2-CH2PMexPh2-x) (x = 1, 2).