POLYMERIZATION BY PHASE TRANSFER CATALYSIS. 25. SYNTHESIS OF POLYCARBONATES AND POLYTHIOCARBONATES DERIVED FROM DIPHENOLS CONTAINING GERMANIUM AND SILICON IN THE MAIN CHAIN†

Polycarbonates and polythiocarbonates derived from diphenols containing Si or Ge, bis(4-hydroxyphenyl)-dimethyl-germane (I), bis(4-hydroxyphenyl)-diphenyl-germane (II), bis(4-hydroxy-phenyl)-dimethyl-silane (III), and bis(4-hydroxyphenyl)-diphenyl-silane (IV), and phosgene (a) or thiophosgene (b), respectively, were synthesized under phase transfer conditions using several phase transfer catalysts. The results were evaluated by the yields and η_inh values, showing that this technique was effective for the synthesis of this kind of polymers. The yields were low compared with those obtained with other diphenols, due probably to the use in this work of stoichiometric amounts of NaOH to avoid the decomposition of the diphenol, which hindered a salting out effect of the diphenolate to the organic phase.

     

Reaction rate studies of atomic germanium (3P0,1) and silicon (3PJ) with various oxidizers

The gas phase reactions of Ge(³P_0,1) and Si(³P_J) with O₂, NO and N₂O have been studied in a flow tube system at 350 K. Atomic Ge and Si were produced by flowing GeH₄ and SiH₄ through a hollow cathode discharge. The subsequent disappearance of the Ge and Si atoms was followed with atomic absorption spectroscopy. Rate constants were determined for the reactions at 4 and 5 torr pressures.     

B-site substitutions in LaNb1−xMxO4−δ materials in the search for potential proton conductors (M=Ga, Ge, Si, B, Ti, Zr, P, Al)

The solid solubilities of potential B-site dopants in LaNb_1-xM_xO_4−δ, materials, M=Ga, Ge, Si, Al, B, P, Zr or Ti, have been investigated in the search for possible novel proton conductors. In general, the solubility levels of these cations were found to be very low (x≤0.03). At the maximum value x=0.03, only compositions containing Ti, Ge, Ga and Si appeared pure at the limit of resolution of XRD. The literature phase diagram, La₂O₃-Nb₂O₅-ZrO₂, has been re-analysed for compositions of low Zr-content around the composition LaNbO₄. The electrical properties of phase pure Ti-doped compositions have been studied. Higher bulk and total conductivities were observed in wet than dry conditions, suggesting a significant protonic contribution to total conductivity. In wet conditions, the activation energy for bulk conductivity of LaNb_0.98Ti_0.02O_4-δ was found to be much higher than that of an A-site, Sr-doped material, Sr_0.02La_0.98NbO_4-δ, of similar acceptor dopant concentration. The Sr-doped composition offered higher conductivities than the Ti-doped composition up to approximately 900°C.     

Diverse Reactivity of bis(Silylene) and bis(Germylene) [LE−EL (E=Si and Ge: L=PhC(NtBu)2)] in the Oxidative Activation of C−F Bond: Si−Si Bond is Retained While the Ge−Ge Bond Is Cleaved

Herein we report the reactions of 3,4,5,6-tetrafluoroterephthalonitrile ( 1 ) with bis(silylene) and bis(germylene) LE−EL [E=Si ( 2 ) and Ge( 3 ): L=PhC(N^tBu)₂)]. The reaction of LSi−SiL (L=PhC(N^tBu)₂) ( 2 ) with two equivalents of 1 resulted in an unprecedented oxidative addition of a C−F bond of 1 leading to disilicon(III) fluoride {L(4-C₈F₃N)FSi−SiF(4-C₈F₃N)L}( 4 ), wherein the Si−Si single bond was retained. In contrast, the reaction of LGe−GeL (L=PhC(N^tBu)₂) ( 3 ) with one equivalent of 1 resulted in the oxidative cleavage of Ge−Ge bond leading to L(4-C₈F₃N₂)Ge ( 5 ) and LGeF ( 6 ). All three compounds ( 4 – 6 ) were characterized by NMR spectroscopy, EI-MS spectrometry, and elemental analysis. X-ray single-crystal structure determination of compound 4 unequivocally established that the Si^III−Si^III bond remains uncleaved.     

New C2-symmetric chiral phosphinite ligands based on amino alcohol scaffolds and their use in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic ketones

Asymmetric transfer hydrogenation processes of ketones with chiral molecular catalysts are attracting increasing interest from synthetic chemists due to their operational simplicity. C₂-symmetric catalysts have also received much attention and been used in many reactions. A series of new chiral C₂-symmetric bis(phosphinite) ligands has been prepared from corresponding amino acid derivated amino alcohols or (R)-2-amino-1-butanol through a three- or four-step procedure. Their structures have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. ¹H-³¹P NMR, DEPT, ¹H-¹³C HETCOR or ¹H-¹H COSY correlation experiments were used to confirm the spectral assignments. In situ prepared ruthenium catalytic systems were successfully applied to ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives by iso-PrOH. Under optimized conditions, these chiral ruthenium catalyst systems serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as good catalysts, giving the corresponding optical secondary alcohols in 99% yield and up to 79% ee.     

Catalytic asymmetric hydrosilylation of ketones by rhodium(I) complexes containing the enantiomers of (R1, R1)-(±)-1,2-phenylenebis(methylphenylarsine) and their phosphorus isosteres

Soluble (bicyclo[2.2.1]hepta-2,5-diene)rhodium(I) complexes containing the enantiomers of (R¹,R¹-(±)-1,2-phenylenebis(methylphenyl-arsine) or its phosphorus isosteres have been found to be highly efficient catalysts for the asymmetric hydrosilylation of prochiral ketones. The rates of reaction for both the bis(tertiary arsine)- and the bis(tertiary phosphine)-containing catalysts appear to be amongst the fastest of their type hitherto reported, with both catalysts giving comparable optical yields of asymmetric silyl ethers. This is the first successful use of a tertiary arsine-containing complex for catalytic asymmetric hydrosilylation. The optical yields varied between 18 – 41% for C₆H₅COCH₃ and CH₃COC(CH₃)₃, depending upon conditions and catalyst, but with o-MeOC₆H₄COCH₃ as substrate, the optical yield dropped to 1 – 2% for both catalysts.     

Design of Binaphthyl‐Modified Symmetrical Chiral Phase‐Transfer Catalysts: Substituent Effect of 4,4′,6,6′‐Positions of Binaphthyl Rings in the Asymmetric Alkylation of a Glycine Derivative

A series of symmetrical chiral phase‐transfer catalysts with 4,4′,6,6′‐tetrasubstituted binaphthyl units have been designed, and these aryl‐ and trialkylsilyl‐substituted phase‐transfer catalysts, which included a highly fluorinated catalyst, were prepared. The chiral efficiency of these chiral phase‐transfer catalysts was investigated in the asymmetric alkylation of tert‐butylglycinate–benzophenone Schiff base under mild phase‐transfer conditions, and the eminent substituent effect of the 4,4′,6,6′‐positions of the binaphthyl units on enantioselection was observed. In particular, the OctMe₂Si‐substituted catalyst was found to be highly efficient for the phase‐transfer alkylation of tert‐butylglycinate–benzophenone Schiff base with various alkyl halides, including sec‐alkyl halides. The highly fluorinated catalyst was also utilized as a recyclable chiral phase‐transfer catalyst by simple extraction with fluorous solvents.     

Tris(trichlorosilyl)tetrelide Anions and a Comparative Study of Their Donor Qualities

Trichlorosilylated tetrelides [(Cl₃Si)₃E]⁻ have been prepared by adding 1 equiv of a soluble Cl⁻ salt to (Cl₃Si)₄Si (E=Si) or 4 Si₂Cl₆/GeCl₄ (E=Ge). To assess their donor qualities, the anions [(Cl₃Si)₃E]⁻ (E=C, Si, Ge) have been treated with BCl₃, AlCl₃, and GaCl₃. Both BCl₃ and GaCl₃ give 1:1 adducts with the anionic centers. AlCl₃ leads to Cl⁻ abstraction from [(Cl₃Si)₃E]⁻ with formation of (Cl₃Si)₄E (E=Si or Ge). (Cl₃Si)₄Ge is cleanly converted to the perhydrogenated (H₃Si)₄Ge by use of Li[AlH₄]. Another case of Cl⁻ abstraction was observed for [(Cl₃Si)₃Ge ⋅ GaCl₃]⁻, which reacts with GaCl₃ to afford the neutral dimer [(Cl₃Si)₃Ge−GaCl₂]₂.     

On the distribution of tetrelide atoms (Si, Ge) in Gd5(SixGe1−x)4

A crystallographic study of the Si/Ge site preferences in the Si-rich regime of Gd₅(Si_xGe_1−x)₄ and a crystal chemical analysis of these site preferences for the entire range is presented. The room temperature crystal structure of Gd₅Si₄ as well as four pseudobinary phases, Gd₅(Si_xGe_1−x)₄ for x?0.6, is reported. All structures are orthorhombic (space group Pnma), Gd₅Si₄-type and show decreasing volume as the Si concentration increases. Refinements of the site occupancies for the three crystallographic sites for Si/Ge atoms in the asymmetric unit reveal a nonrandom, but still incompletely ordered arrangement of Si and Ge atoms. The distribution of Si and Ge atoms at each site impacts the fractions of possible homonuclear and heteronuclear Si-Si, Si-Ge and Ge-Ge dimers in the various structures. This distribution correlates with the observed room temperature crystal structures for the entire series of Gd₅(Si_xGe_1−x)₄.     

Optimizing Cs-exchange in titanosilicate with the mineral pharmacosiderite topology: framework substitution of Nb and Ge

Titanosilicates with complete or partial substitution of Ge or Nb in the framework and having the mineral pharmacosiderite topology were hydrothermally prepared and their ion-exchange properties towards Cs were studied for Ti/Ge/Si, Ti/Si, Nb/Ti/Si and pure Ge phases. The basis for the differences in the ion exchange properties measured as distribution coefficients (K_d) for these materials are detailed via structural characterization using the Rietveld refinement technique on the X-ray powder diffraction data. The differences in affinity towards Cs⁺ result either from the degree of hydration of the exchanger resulting in different coordination environments or the position of cesium ion in the eight-ring channel.     

Cyclische Diazastannylene. XIX. Zur Reaktion eines Bis(amino)germylens, -stannylens und -plumbylens mit Phosphortrichlorid und 2, 3-Dimethyl-1, 3-butadien

Cyclic Diazastannylenes. XIX. Reaction of a Bis(amino)germylene, -stannylene, and -plumbylene with Phosphorus Trichloride and 2, 3-Dimethyl-1, 3-butadiene The cyclic bis(amino)germylene 1 reacts with PCl₃ by a threefold insertion into the P? Cl bonds and forms [Me₂Si(N^tBu)₂Ge(Cl)]₃P( 4 ). 4 crystallizes in the triclinic space group P1 with cell dimensions: a = 1955.2(9), b = 1378.3(6), c = 1074.3(5) pm, α = 90.4(1), β = 121.6(1), γ = 97.9(1)° and Z = 2. X-ray structure analysis was used to show, that the molecule 4 has approximately C_3h point symmetry. All germanium, chlorine, and silicon atoms are quite accurately situated in a plane, perpendicular to which the GeN₂Si-rings are erected. The only heavy atom which disturbs the mirror symmetry is the phosphorus, which is on the top of a flat pyramide (Ge? P? Ge = 115.0°). Important bond lengths (mean values) are: Ge? P = 231.0(4), Ge? N = 182.4(7), Ge? Cl = 217.9(2) and Si? N = 173.6(7) pm. The unusual nearly planar coordination of the phosphorus atom can be explained by the particular steric requirements of the substituents. PCl₃ oxidizes the tin atom in the bis(amino)stannylene 2 by the formation of Me₂Si(N^tBu)₂SnCl₂ ( 5 ); as additional product originates an amorphous solid of analytical composition (PCl)_n. In contrast to 1 and 2 the lead atom     

New method for the synthesis of trialkyl(triorganylsilylalkylthio)silanes and trialkyl(triorganylsilylalkylthio)germanes

Conclusions A new method was developed for the synthesis of trialkyl(triorganylsilylalkylthio)silanes and trialkyl(triorganylsilylalkylthio)germanes with the general formula R₃MS(CH₂)_nSiR₃ ' (M=Si or Ge) by the reaction of the corresponding triorganylsilylalkenethiols with bis(trialkylsilyl)mercury or bis(trialkylgermyl)mercury.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2401–2402, October, 1984.     

Investigations on aromatic polyesters with polynaphthalene systems in the main chain—IX. Influence of the chain structure of aromatic copolyesters on their glass transition temperatures

Glass transition temperatures of terephthalic copolyesters of 4,4′dihydroxydinaphthyl 1,1′ and 2,2 bis(4-hydroxyphenyl)propane with various mole ratios of the comonomers and different chain structures have been measured. A relationship has been found between T_g and the chain structure of aromatic copolyesters with polynaphthalene rings in the chain.     

The reaction of methyl diazoacetate with 4,4-dimethyl-2-pentyn-1-al and related compounds

Methyl 2-diazo-3-hydroxy-6,6-dimethyl-4-heptynoate was prepared by treating 4,4-dimethyl-2-pentyn-1-al with methyl diazoacetate at room temperature in the absence of catalysts. In the case of related aldehydes, RCCCHO (R = n-Bu, Me₃Si, Et₃Si, Et₃Ge), this unusual reaction is partially or completely suppressed by a competing 1,3-cycloaddition process. The latter leads to a mixture of isomeric 3- and 4-formylpyrazole, one of which cyalodimerizes to form tricyclic hemiaminal.     

Fluorination of dimethylmercury,tetramethylsilane and tetramethylgermanium. Synthesis and characterization of polyfluorotetramethylsilanes,polyfluorotetramethylgermanes,bis(trifluoromethyl)mercury and tetrakis(trifluoromethyl)germanium

It has been found possible to preserve metal—carbon and metalloid—carbon bonds during direct fluorination. The reaction of dimethylmercury with fluorine gives bis(trifluoromethyl)mercury in 6.5% yield. Fluorination of tetramethylsilane has led to the isolation of the new polyfluorotetramethylsilanes of the following type, Si(CH₃)_x(CH₂F)_y(CHF₂)_z, x + y + z = 4. Also characterized were compounds containing SiCF₃. It has been possible to synthesize tetrakis(trifluoromethyl)germanium in 63.5% yield from the reaction of fluorine with tetramethylgermanium. Also characterized were many polyfluorotetramethylgermanes of the following type, Ge(CF₃)_x(CF₂H)_y(CFH₂)_z (x + y + z = 4).     

Organometallic derivatives of diphenyl-N-methylamine

The lithium-halogen exchange reaction in two-different solvents has been used to prepare bis(4-lithiophenyl)-N-methylamine in high yields. Bis(4-bromophenyl)-N-methylamine underwent quantitative halogen-metal exchange with n-butyllithium in tetrahydrofuran/diethylether at −78°. An 83% conversion was accomplished in refluxing benzene. Subsequently a series of para-disubstituted organometallic derivatives of diphenyl-N-methylamine was synthesized using the reaction of the dilithio intermediate with various organometallic monohalides of Si, Ge, Sn, Pb and As. Exchange reactions were carried out between bis[4-(trimethylstannyl)-phenyl]-N-methylamine and mercury compounds.     

Metallorganische diazoalkane : XVI. Synthese von silyldiazoalkanen Me3Si(LnM)CN2

Silyldiazoalkanes Me₃Si(L_nM)CN₂ (L_nM = Me₃Si, Me₃Ge, Me₃Sn, Me₃Pb; Me₃As, Me₃Sb, Me₃Bi) have been synthesized by three different routes: (a) reactions of the Me₃SiCHN₂ with metal amides L_nMNR¹R² of Group IVB and VB elements, using Me₃SnCl as catalyst; (b) reactions of the in situ prepared organolithium compound Me₃SiC(Li)N₂ with organometallic chlorides Me₃MCl (M = Si, Ge); (c) tincarbon bond cleavage reaction of (Me₃Sn)₂CN₂ with Me₃SiN₃, affording Me₃SnN₃, traces of bis(trimethylsilyl)diazomethane (Me₃Si)CN₂, trimethylsilyl(trimethylstannyl)diazomethane Me₃Si(Me₃Sn)CN₂ and bis(trimethylsilyl)aminoisocyanide (Me₃Si)₂NNC as the major reaction products. IR and NMR data (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ²⁰⁷Pb) of the new heterometal-diazoalkanes are reported and discussed in comparison to relevant compounds of the organometallic diazoalkane series.     

Etude systématique des relations entre les structures wadéite et tétragermanate

Systematic study of solid solutions with general formula A_2?xA_x′(B_1?zB_z′)Ge_3?ySi_yO₉ (A, A′ = K, Rb, Cs, Tl; B, B′ = Ge, Ti, Sn) has been carried out. These results allow us to propose a tridimensional diagram of existence of wadeite and tetragermanate structures, as a function of the sizes of A, B, Ge, and Si elements. Condition of stability based upon differences of sizes between A and M elements and B and M elements (M = Ge, Si) were found. The variation of compactness of wadeite and tetragermanate structures shows up the particular role of M element (Ge, Si).     

Efficient alkene hydrosilation with bis(8-quinolyl)phosphine (NPN) nickel catalysts. The dominant role of silyl-over hydrido-nickel catalytic intermediates

A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]⁺, is a precursor to efficient catalysts for the hydrosilation of alkenes with a variety of hydrosilanes under mild conditions and low catalyst loadings. DFT studies reveal the presence of two coupled catalytic cycles based on [(NPN)NiH]⁺ and [(NPN)NiSiR₃]⁺ active species, with the latter being more efficient for producing the product. The preferred silyl-based catalysis is not due to a more facile insertion of alkene into the Ni–Si (vs. Ni–H) bond, but by consistent and efficient conversions of the hydride to the silyl complex.

A cationic nickel complex of the bis(8-quinolyl)(3,5-di-tert-butylphenoxy)phosphine (NPN) ligand, [(NPN)NiCl]⁺, is a precursor to efficient catalysts for the hydrosilation of alkenes with hydrosilanes under mild conditions and low catalyst loadings.