Preparation of tris(trimethylsilyl)methyl (“trisyl”) derivatives of silicon

Treatment of (Me₃Si)₃CLi (“trisyl”lithium, TsiLi) with appropriate silicon halides has given a range of compounds of the type (Me₃Si)₃CSiRR′X; e.g., TsiSiCl₃, TsiSiMeCl₂, TsiSiMe₂X (X = Cl, OMe), TsiSiPh₂X (X = F, Cl, OMe), and TsiSiPhMeH. The trisyl group causes very large steric hindrance to nucleophilic displacements at the silicon to which it is attached, so that (unless one or more hydride ligands are present) most of the common displacements at silicon do not occur. However, halides can be reduced to hydrides by LiAlH₄, and the hydrides can be converted into halides in electrophilic displacements by hallogens. The presence of even one hydride ligand markedly reduces the hindrance, so that, for example, TsiSiPhHI reacts with refluxing methanol to give TsiSiPhH(OMe).     

One-pot, novel chemical modification of glycidyl methacrylate copolymers with very bulky organosilicon side chain substituents

Glycidyl methacrylate (GM) random copolymers with styrene and methylstyrene (in a 1:1 and 1:3 mole ratio) were synthesized by solution free radical polymerizations at 70 ± 1 °C using α,α′-azoisobutyronitrile as an initiator. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). Both types of polymer could be modified by incorporation of the highly sterically demanding tris(trimethylsilyl)methyl substituent (Me₃Si)₃C-(Tsi = trisyl) through the ring opening reaction of the epoxy groups in copolymers. Chemical modification was determined by ¹H NMR and infrared spectroscopies. The glass transition temperature T_g of all copolymers was determined by differential scanning calorimetry (DSC). The T_g value of the copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in the polymer side chain created new macromolecules with novel modified properties and potential use as membranes for fluid separation.     

Das unterschiedliche Reaktionsverhalten von basefreiem Tris(trimethylsilyl)methyl‐Lithium gegenüber den Trihalogeniden der Erdmetalle und des Eisens

The Variable Reaction Behaviour of Base‐free Tris(trimethylsilyl)methyl Lithium with Trihalogenides of Earth‐Metals and Iron Base‐free tris(trimethylsilyl)methyl Lithium, Tsi–Li, reacts with the earth‐metal trihalogenides (MHal₃ with M = Al, Ga, In and Hal = Cl, Br, I) primarily to give the metallates [Tsi–MHal₃]Li. Simultaneous to this simple metathesis a methylation also takes place, mainly with heavier halogenides of Ga and In with excess Tsi–Li, forming the mono and dimethyl compounds Tsi–M(Me)Hal (M = Ga, In; Hal = I), Tsi–MMe₂ (M = Ga), and the bis(trisyl)derivative (Tsi)₂InMe, respectively and the main by‐product 1,3‐disilacyclobutane. Representatives of each type of compound have been isolated by fractionating crystallizations or sublimations and characterized by spectroscopic methods (¹H, ¹³C, ²⁹Si NMR, IR, Raman) and X‐ray elucidations. Reduction takes place, when FeCl₃ reacts with Tsi–Li (1 : 3 ratio) in toluene at 55–60 °C, yielding red‐violet Fe(Tsi)₂, 1,1,1‐tris(trimethylsilyl)‐2‐phenyl ethane and low amounts of Tsi–Cl. Fe(Tsi)₂ is monomeric, crystallizes in the monoclinic space group C2/c and consists of a linear C–Fe–C skeleton with d(Fe–C) of 204,5(4) pm.     

Glass transition temperature modification of acrylic and dienic type copolymers of 4-chloromethyl styrene with incorporation of (Me3Si)3C- groups

The new functional styrenic monomer, 4-trisylmethyl styrene (TsiMS) [Tsi=trisyl=tris(trimethylsilyl)methyl], was synthesized by reacting 4-chloromethyl styrene (CMS) with trisyllithium (TsiLi) in tetrahydrofuran (THF) solvent in the presence of copper chloride (CuCl). Attempt for the free radical polymerization of TsiMS by α,α^′-azobis(isobutyronitrile) (AIBN) as an initiator at 70 ± 1 °C failed for several periods of times. This result showed that the trisyl group is a highly sterically hindered substituent and, subsequently, TsiMS becomes resistant for polymerization. Therefore, for preparation of new methacrylic, acrylic and dienic copolymers of TsiMS, we firstly synthesized the copolymers of CMS with different monomers such as methyl methacrylate (MMA), ethyl methacrylate (EMA), methyl acrylate (MA), ethyl acrylate (EA), n-butyl acrylate (BA) and isoprene (IP) by free radical polymerization method in toluene solution at 70 ± 1 °C using AIBN initiator to give the copolymers I-VI in good yields. The copolymer compositions were obtained using related ¹H NMR spectra and the polydispersity indices of the copolymers determined using gel permeation chromatography (GPC). The trisyl groups were then covalently attached to the obtained copolymers as side chains by reaction between excess of TsiLi and benzyl chloride bonds of CMS units, to give the copolymers - in 80-92% yields. All the resulted polymers were characterized by FT-IR, ¹H NMR and ¹³C NMR spectroscopic techniques. The solubility of all the copolymers was examined in various polar and non-polar solvents. The glass transition temperature (T_g) of all copolymers was determined by differential scanning calorimetry (DSC) apparatus. The T_g value of copolymers containing bulky trisyl groups was found to increase with incorporation of trisyl groups in polymer structures. The presence of trisyl groups in polymer side chains, create new macromolecules with novel modified properties.     

Benzyl-tris(trimethylsilyl)methylzinndihalogenide, {(CH3)3Si}3C(C6H5–CH2)SnHal2 mit Hal = Cl,Br, I

Benzyl-tris(trimethylsilyl)methyl Tin Dihalides, {(CH₃)₃Si}₃C(C₆H₅–CH₂)SnHal₂ with Hal = Cl, Br, I The tin tetrahalides SnHal₄ (Hal = Cl, Br, I) react with base-free tris(trimethylsilyl)methyllithium (Tsi–Li) solved in toluene to form the trihalides Tsi–SnHal₃. But when the reaction is carried out in a 1 : 2 molar ratio at 60 °C in toluene, Tsi–H, Tsi–Hal and benzyl-trisyl tin-dihalides are formed in good yields, respectively. The nmr (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn) and the Raman spectra are discussed, the X-ray structure analyses of the dibromide as well as the diiodide have been measured.     

[{(CH3)3Si}3C–Li–C{Si(CH3)3}3][Li · 3(OC4H8)] und {(CH3)3Si}3C–Li · O=C(Si(CH3)3)2, zwei neue Addukte des Lithium‐trisylmethanids

[{(CH₃)₃Si}₃C–Li–C{Si(CH₃)₃}₃][Li · 3(OC₄H₈)] and {(CH₃)₃Si}₃C–Li · O=C(Si(CH₃)₃)₂, two New Adducts of Lithium Trisylmethanide Sublimation of (Tsi–Li) · 2 THF (Tsi = –C(Si(CH₃)₃)₃) at 180 °C and 10^–4 hPa gives (Tsi–Li) · 1.5 THF in very low yield. The X‐ray structure determination shows an almost linear [Tsi–Li–Tsi]^– anion connected by short agostic Li…C contacts with the threefold THF‐coordinated Li‐cation. Base‐free Tsi–Li, solved in toluene is decomposed by oxygen, forming the strawberry‐colored ketone O=C(SiMe₃)₂, which forms an 1 : 1 adduct with undecomposed Tsi–Li. The X‐ray structure elucidation of this compound is also discussed.     

Oxo(trisyl)boran (Me3Si)3C?BO als Zwischenstufe

Oxo(trisyl)borane (Me₃Si)₃C? B?O as an Intermediate The acyclic trisylboranes R? B(OSiMe₃)? Cl ( 4 a ) and R? B(OH)? H ( 5 a ) and the cyclic boranes (? RB? O? CO? CO? O? ) ( 1 a ) and (? RB? O? RB? O? SO₂? O? ) ( 6 a ) [R = (Me₃Si)₃C, “Trisyl”] are thermolyzed in the gasphase to give well-defined products. The tris(trisyl)boroxine (? RB? O? )₃ ( 2 a ) is formed from 4 a and 5 a at 140 and 160°C, respectively, besides Me₃SiCl and H₂, respectively, whereas the six-membered ring [? BMe? CH(SiMe₃)? SiMe₂? O? SiMe₂? CH₂? ] ( 8 ) is the product from 1 a and 6 a at 600 and 700°C, respectively, besides CO/CO₂ and SO₃, respectively. The oxoborane R? B?O is presumably a common intermediate. It is stabilized at the lower temperature by cyclotrimerization to give 2 and at the higher temperature by a sequence of several intramolecular steps: a 1,3-silyl shift along the chain C? B? O, an exchange of Me and Me₃SiO along the chain Si? C? B, and a C? H addition to the B?C double bond; the steps can be rationalized by analogous known reactions. The gas-phase thermolysis at 600°C of the dioxaboracyclohexenes (? BR? O? CR′ = CH? CRR′? O? ) ( 7 b? d ; R = Me, iPr, tBu; R′ = Me) yields the boroxines (RBO)₃ and the enones Me? CO? CH?CHR? Me; the cyclohexene 7 e (R = Me; R′ = CF₃) is not decomposed at 600°C.     

Synthesis and properties of polycarbosilanes with the meta-linkage bending unit by hydrosilylation polymerization

The polycarbosilanes (PCS) with meta-linkage bending unit ((SINGLE BOND)Me₂Si(SINGLE BOND)m(SINGLE BOND)C₆H₄(SINGLE BOND)Me₂Si(SINGLE BOND)CH₂CH₂(SINGLE BOND)) were successfully synthesized in mild conditions by hydrosilylation in the presence of [Pt{(CH₂(DOUBLE BOND)CHSiMe₂)₂O}₂]. The PCS obtained were soluble in various solvents owing to the lowering of the crystallinity. These properties are well compared with those of the PCS [(SINGLE BOND)Me₂Si(SINGLE BOND)p(SINGLE BOND)C₆H₄(SINGLE BOND)Me₂Si(SINGLE BOND)CH₂CH₂(SINGLE BOND)]_n. © 1996 John Wiley & Sons, Inc.     

New hyperbranched carbosiloxane–carbosilane polymers with aromatic units in the backbone

New hyperbranched polymers based on a carbosiloxane–carbosilane skeleton with aromatic units in the backbone have been prepared via one-pot hydrosilylation reaction using HSi(Me)₂–O–CH₂–C₆H₄–OSiMe–(CH₂)₄(C₃H₅)₂ as a novel AB₂ monomer. These polymers are easy to prepare, have narrow polydispersity values and present allyl groups on the surface which can be used as synthetic platforms for the introduction of different terminal groups like amine groups through hydrosilylation reactions, opening the door to functionalized polymers. The polymerization process was monitored using real-time ¹H NMR spectroscopy and the resulting hyperbranched polymers were characterized using ¹H NMR, ¹³C NMR, ²⁹Si NMR and SEC/MALLS. The degree of branching in these polymers was determined by quantitative ²⁹Si NMR spectroscopy and found to be very close to the theoretical value of 0.50 for AB₂ systems. The hydrolytic degradation of these polymers in protic solvents has been studied by ²⁹Si NMR.     

New Stable Germylenes,Stannylenes, and Related Compounds II. Bis(butylthio)tin(II) and ate-Complexes [(Me3Si)3CE(μ-SBu)2Li(THF)2] (E = Ge,Sn). Synthesis and Structure

By reaction of Me₃SiSBu with anhydrous tin(II) chloride bis(butylthio)tin was obtained that exemplified a coordination polymer [Sn(SBu)₂] _n , whose elementary unit contained according to X-ray diffraction study three independent four-membered rings Sn₂S₂ of unusual geometry. It was demonstrated that polymeric thiolates [E(SBu)₂] _n (E = Ge, Sn) readily reacted with TsiLi (Tsi = C(SiMe₃)₃) in a mixed solvent ether THF affording in a good yield ate-complexes [(Me₃Si)₃CE(-SBu)₂Li(THF)₂]. Both complexes contain a four-membered ring in a butterfly conformation where the lithium atom is symmetrically bonded to both sulfur atoms, and the coordination polyhedra of Ge and Sn atoms may be regarded as distorted tetrahedra AB₃X, where one of coordination places is occupied by unshared electron pair. The structure of the ate-complexes observed in a crystal is conserved also in solution of nonpolar solvents.     

Solubility of carbon dioxide,methane, and propane in silicone polymers. Effect of polymer backbone chains

The solubility of carbon dioxide, methane, and propane in poly(dimethyl silmethylene) [(CH₃)₂SiCH₂]_x and poly(tetramethyl silhexylene siloxane) [(CH₃)₂Si (CH₂)₆Si (CH₃)₂O]_x was measured in the temperature range from 10.0 to 55.0°C and at elevated pressures. The present results are compared with similar measurements made with other silicone polymers. At a given temperature and pressure, the solubility of the above three gases is highest in poly(dimethyl siloxane) (Me₂SiO)_x. The gas solubility is decreased by either backbone-chain or side-chain substitutions of functional groups in (Me₂SiO)_x which increase the stiffness of the polymer chains and decrease the specific or fractional free volume of the polymers. It is conjectured that a decrease in the free volume of silicone polymers has a greater effect in decreasing the gas solubility than differences in gas/polymer interactions [with the exception of specific interactions (e.g., between CO₂ and polar groups in the polymer)]. © 1993 John Wiley & Sons, Inc.     

Functionalization and further crosslinking of the nicalon polycarbosilane based on its metalation with the n-butyllithium—postassium t-butoxide reagent

Reaction of the Nicalon polycarbosilane with the n-BuLi/Me₃COK reagent resulted in metalation of approximately one CH₂ group in four. Reaction of the metalated polymer with Me₂ (CH₂ = CH)SiCl gave a Me₂(CH₂ = CH)Si-substitued Nicalon polycarbosilane. The polymer was heated with different amounts of the [(MeSiH)_～0.8(MeSi)_～0.2]_n polysilane in the presence of azobisisobutyronitrile in refluxing benezene. Hydrosilylation by the Si? H-containing polysilane of the CH₂?CH groups of the Me₂(CH₂?CH) Si-substituted Nicalon polycarbosilane gave a new hybrid polymer (when appropriate quantities of reactant polymers were used) whose pyrolyis in a stream of argon to 1000°C left a ceramic residue in 77% yield whose elemental analysis indicated a nominal composition of 91% by weight SiC and 9% C.     

A new class of silicon-phosphorus heterocycles: 4-silaphosphorinanes

Radical reactions of Me₃SiPH₂ with Me₂Si(CHCH₂)₂ or Si(CHCH₂)₄ yield the 4-silaphosphorinanes Me₂Si(CH₂CH₂)₂PSiMe₃, (CH₂CH)₂Si(CH₂CH₂)₂PSiMe₃, or [Me₃SiP(CH₂CH₂)₂]₂Si; methanolysis of these produces quantitatively the secondary phosphorinanes Me₂Si(CH₂CH₂)₂PH, (CH₂CH)₂Si(CH₂CH₂)₂PH, or [HP(CH₂CH₂)₂]₂Si. Me₂Si(CH₂CH₂)₂PSiMe₃ with O₂/H₂O yields the phosphinic acid Me₂Si(CH₂CH₂)₂P(O)OH. All compounds are characterized by spectral data; an X-ray crystal analysis confirms the structure of Me₂Si(CH₂CH₂)₂P(O)OH.     

Experimental and Theoretical Studies on Some Energetic Functionalized Trimethylamine Derivatives

The synthesis and structural properties (from X‐ray diffraction or B3LYP/6‐31G(d) calculations) of three energetic compounds derived from tris(chloromethyl)amine and of tris(chloromethyl)amine itself were investigated and compared to those of compounds with similar structures. The compounds have almost planar NC₃ units at their amine center, and the substituents bound to the CH₂ groups tend to be reactive towards further substitution. Multiple hyperconjugation was used to explain these observations.     

Intramolecular O → Si donor-acceptor interaction in R2P(=O)CH2CH2SiF3 molecules: Synthesis of dialkyl [2-(trifluorosilyl)ethyl]phosphonate and bis[(chloromethyl)dimethylsilyl] styrylphosphonate

The reaction of diethyl [2-(triethoxysilyl)ethyl]phosphonate with boron trifluoride etherate was used to synthesize diethyl [2-(trifluorosilyl)ethyl]phosphonate. The reaction of bis(trimethylsilyl) styrylphosphonate with chloro(chloromethyl)dimethylsilane gave bis[(chloromethyl)dimethylsilyl] styrylphosphonate. Multinuclear ¹H, ¹³C, ¹⁹F, ²⁹Si, and ³¹P NMR spectroscopy established the absence of a P=O → Si coordination bond in these compounds and the four-coordinate state of the silicon atom. Evidence for this finding was obtained by B3LYP/6-31G(d) quantum-chemical calculations. However, the same calculations for R₂P(=O)· CH₂CH₂SiF₃ (R = Me, Me₂N) showed the presence in such molecules of an O → Si coordination bond both in the gas phase and in CHCl₃ solution. The distance between the O and Si atoms in this series molecules decreases with R in the order: MeO > Me > Me₂N. The axial Si-F bond length increases in the same order and parallels the order of the Hammet σ ₀ ^m constants of these substituents, relating to their interaction with π-electron systems.     

Stabilization of a Silaaldehyde by its η2 Coordination to Tungsten

Treatment of pyridine‐stabilized silylene complexes [(η⁵‐C₅Me₄R)(CO)₂(H)W?SiH(py)(Tsi)] (R=Me, Et; py=pyridine; Tsi=C(SiMe₃)₃) with an N‐heterocyclic carbene ^MeIⁱPr (1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) caused deprotonation to afford anionic silylene complexes [(η⁵‐C₅Me₄R)(CO)₂W?SiH(Tsi)][H^MeIⁱPr] (R=Me ( 1‐Me ); R=Et ( 1‐Et )). Subsequent oxidation of 1‐Me and 1‐Et with pyridine‐N‐oxide (1 equiv) gave anionic η²‐silaaldehydetungsten complexes [(η⁵‐C₅Me₄R)(CO)₂W{η²‐O?SiH(Tsi)}][H^MeIⁱPr] (R=Me ( 2‐Me ); R=Et ( 2‐Et )). The formation of an unprecedented W‐Si‐O three‐membered ring was confirmed by X‐ray crystal structure analysis.     

“Constrained geometry” catalysts of the rare-earth metals for the hydrosilylation of olefins

A series of yttrium and lutetium alkyl complexes [Ln(η⁵-C₅Me₄ZNR′-κN)(CH₂SiMe₃)(THF)_n] (Ln = Y, Lu) was prepared by reacting the tris(trimethylsilylmethyl) precursor [Ln(CH₂SiMe₃)₃(THF)₂] with different linked amino-cyclopentadienes of the type (C₅Me₄H)ZNHR′ (Z = SiMe₂, CH₂SiMe₂; R′ = tBu, Ph, C₆H₄-tBu-4, C₆H₄-nBu-4). The catalytic activity of these alkyl complexes in the hydrosilylation of 1-decene and styrene using PhSiH₃ as reagent was examined under standard conditions. A significant influence of the ligand structure on the catalytic property (turnover frequency, regioselectivity) was observed with the yttrium complex [Y(η⁵-C₅Me₄CH₂SiMe₂NtBu-κN)(CH₂SiMe₃)(THF)] being the most active for 1-decene hydrosilylation.     

Chloromethylsilane functionalised dendrimers: synthesis and reactivity

Tetraallylsilane was functionalised using (chloromethyl)dimethylsilane to give the first generation chloromethyl terminated dendrimer 1. The resulting dendrimer was successfully reacted with K[CpM(CO)₂] (Cp=η⁵-C₅H₅; M=Fe, Ru) to give Si[(CH₂)₃SiMe₂CH₂MCp(CO)₂]₄ functionalised dendrimers in satisfactory yield. Reaction of dendrimer 1 with NaI in acetone gave the -SiMe₂CH₂I functionalised dendrimer, while reactions of 1 with K[CpM(CO)₃] (M=Mo, W, Re), Li[C₅Me₄H], Na[C₅Me₄H], the cobaloxime nucleophile or tert-BuLi were not successful.     

Some highly sterically hindered organo-silanols and -siloxanes

Reaction of the iodides TsiSiMe₂I and TsiSiPh₂I, (Tsi  (Me₃Si)₃C) with AgClO₄ in t-BuOH provides a route to the silanols TsiSiMe₂OH and (Me₃Si)₂-C(SiPh₂Me)(SiMe₂OH), respectively. TsiSiMe₂OH gives the disiloxane TsiSiMe₂OSiMe₃ when treated with either (a) Me₃SiOClO₃ (prepared in situ from AgClO₄ and Me₃SiCl) in benzene, (b) Me₃SiI (in the presence of a little (Me₃Si)₂-NH), (c) O,N-bis(trimethylsilyl)acetamide, or (d) MeLi followed by Me₃SiCl. It does not react with Me₃SiCl, but with Me₂SiCl₂ gives TsiSiMe₂OSiMe₂Cl, and with CH₃COCl gives TsiSiMe₂OCOCH₃. The disiloxane is stable to methanolic acid or base, but reacts with KOH in H₂O/Me₂SO and with CF₃COOH to give TsiSiMe₂OH. The disiloxane (Me₃Si)₂C(SiPh₂Me)(SiMe₂OSiMe₃) is formed by treatment of (Me₃Si)₂C(SiPh₂Me)(SiMe₂OH) with Me₃SiI/(Me₃Si)₂NH. Treatment of TsiSiPhMeI with AgClO₄ in t-BuOH gives the silanols TsiSiPhMeOH and (Me₃Si)₂C(SiPhMe₂)(SiMe₂OH) (which with Me₃SiI/(Me₃Si)₂NH give the corresponding disiloxanes) along with some of the t-butoxide (Me₃Si)₂C(SiPhMe₂)(SiMe₂OBu^t).     

Dendronized polystyrene supports for new catalytic systems

New catalytic systems based on tris(dimethylvinyl)methyl substituted polystyrene were prepared. Dendronized polystyrenes were obtained by modification of poly(styrene-co-chloromethylstyrene) precursors with LiC(SiMe₂CHCH₂)₃. Platinum was attached to the polymers via coordination to vinyl groups located on carbosilane moieties. Such the catalytic system makes an interesting alternative for heterogenous platinum catalysts (Pt/charcoal, Pt/C_act and Pt/Al₂O₃) and also to Karstedt’s catalyst, when used in hydrosilylation of vinylsilanes.