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The 1H, 13C, 15N and 29Si chemical shifts of three trimethylsilyl-1H-pyrazoles were calculated and compared with literature results; the calculations were carried out at the GIAO/B3LYP/6–311 + + G(d,p) level resulting in a very good agreement that allows to predict with confidence the missing experimental values. The prototropic barrier of 4-trimethylsilyl-1H-pyrazole (1) as well as the silylotropic barriers of 1-trimethylsilyl-1H-pyrazole (2) and 1-trimethylsilyl-4-methyl-1H-pyrazole (3) were also calculated and the mechanism was established, the accordance with the experimental values being satisfactory. [ABSTRACT FROM AUTHOR]

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy‐ and amino‐acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di‐ and trialkyl‐silyl derivatives, various substituted‐alkyldimethylsilyl derivatives such as the tert‐butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3‐pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1–107, 2019 [ABSTRACT FROM AUTHOR]

As an extension of the study on the Hudrlik–Peterson reaction of trans -TMS-epoxy alcohols with lithium acetylides, four cis -TMS-epoxy alcohols possessing different alkyl substituents were subjected to the reaction with TMS-acetylide. The reaction completed in 1 h at 0 °C to afford cis -enynyl alcohols in good yields. The results indicated that cis -TMS-epoxy alcohols had higher reactivity than the trans -isomers. Anions derived from 1-heptyne and phenylacetylene participated in the reaction as well. The reaction was applied to optically active cis -TMS-epoxy alcohols, and the resulting enynyl alcohols were transformed to the synthetic intermediates of protectin D1, maresin 1, resolvin E1, and leukotriene B4. [ABSTRACT FROM AUTHOR]

The concept of protecting groups and leaving groups in organic synthesis was applied to the synthesis of siloxane-based molecules. Alkoxy-functionalized siloxane oligomers composed of SiO4, RSiO3, or R2SiO2 units were chosen as targets (R: functional groups, such as Me and Ph). Herein we describe a novel synthesis of alkoxysiloxane oligomers based on the substitution reaction of trimethylsilyl (TMS) groups with alkoxysilyl groups. Oligosiloxanes possessing TMS groups were reacted with alkoxychlorosilane in the presence of BiCl3 as a catalyst. TMS groups were substituted with alkoxysilyl groups, leading to the synthesis of alkoxysiloxane oligomers. Siloxane oligomers composed of RSiO3 and R2SiO2 units were synthesized more efficiently than those composed of SiO4 units, suggesting that the steric hindrance around the TMS groups of the oligosiloxanes makes a difference in the degree of substitution. This reaction uses TMS groups as both protecting and leaving groups for SiOH/SiO− groups. [ABSTRACT FROM AUTHOR]

A convenient synthetic approach towards previously unknown N- and N,O-silylated α-iminophosphonates bearing fluoroalkyl groups at the imine C atom was developed. The synthetic potential of the compounds was demonstrated by their easy functionalization and the straightforward preparation of biorelevant aminophosphonates and free aminophosphonic acids with heterocyclic residues in the α-position. [ABSTRACT FROM AUTHOR]

We report the synthesis and structure of a series of tantalum(V) complexes having the trimethylsilylimide moiety and using as ancillary support the pincer ligand PNP (PNP − = N[2-P i Pr 2 -4-methylphenyl] 2 ). Via transmetallation of Li(PNP) with Cl 3 (py) 2 Ta N{SiMe 3 } (py = pyridine), the precursor complex (PNP)Ta N{SiMe 3 }Cl 2 ( 1 ) could be prepared in 94% isolated yield. Attempts to promote FSiMe 3 elimination when 1 was treated with FSnMe 3 resulted in mixtures from which the salt-like product [{(PNP)Ta N{SiMe 3 }} 2 (μ 2 -F) 3 ][Me 3 ClSn(μ 2 -X)SnClMe 3 ] ( 2 ) (X − = F or Cl) was structurally identified. However, conducting the reaction with NaOAr (Ar = 2,6- i Pr 2 C 6 H 3 ) resulted in clean formation to (PNP)Ta N{SiMe 3 }(OAr)Cl ( 3 ) in 79% isolated yield, and when 3 was mixed with FSnMe 3 , the fluoride-imide complex (PNP)Ta N{SiMe 3 }(OAr)F ( 4 ) and ClSnMe 3 were formed cleanly. Attempts to promote FSiMe 3 elimination in 4 thermally and photochemically did not yield the desired nitride (PNP)Ta N(OAr). Complexes 1 – 4 were characterized by single-crystal X-ray diffraction studies and in the case of complexes 1 , 3 and 4 a variety of multinuclear NMR studies are presented and discussed. [ABSTRACT FROM AUTHOR]

GC–MS and GC–MS/MS of pentafluorobenzyl (PFB) ester trimethylsilyl (TMS) ether (PFB-TMS) derivatives of hydroxylated long-chain fatty acids including arachidonic acid metabolites, the eicosanoids, in the electron-capture negative-ion chemical ionization (ECNICI) mode are the most sensitive and accurate approaches to quantify carboxyl groups-containing compounds in complex biological fluids such as plasma and urine. Under ECNICI conditions, PFB-TMS derivatives of eicosanoids ionize to form very few ions, with the carboxylates [M–PFB] − being typically the most intense. Less intense ions may be additionally formed by consecutive neutral loss (NL) of trimethylsilanol (TMSOH, 90 Da) groups ([M–PFB–(TMSOH) n ] − ). By using [1,1- 18 O 2 ]- and [1,ω- 18 O 2 ]-eicosanoids, we studied ion processes following collisionally activated dissociation (CAD) of the precursor ions [M–PFB] − . We found that CAD resulted in formation of product ions due to NL of a TMS 18 OH (92 Da) group in monocarboxylic and of a PFB 18 OH (200 Da) group in dicarboxylic eicosanoids. TMS 18 OH NL implies an intra-molecular transfer of the TMS group from hydroxyl groups to their carboxylate anions [M–PFB] − . From a mechanistic point of view, this rearrangement may explain formation of unique product ions in GC–MS/MS of eicosanoids under ECNICI conditions. From the quantitative point of view, quantification by GC–MS/MS of product ions due to [M–PFB–(TMSOH) n ] − and [M–PFB–TMS 18 OH–(TMSOH) n-1 ] − would reveal incorrect data, if [1,1- 18 O 2 ]-eicosanoids are used as internal standards and if no correction for the 18 O-loss is performed. In 18 O-labelled dicarboxylic eicosanoids, such as the major urinary metabolite (MUM) of E prostaglandins, i.e., [1,ω- 18 O 2 ]-PGE-MUM), no TMS ester/TMS ether rearrangement was observed. Yet, 18 O-loss occurred upon CAD of [M–PFB] − due to NL of PFB 18 OH (200 Da). In both cases the extent of 18 O-loss needs to be determined and considered for accurate quantification of monocarboxylic acids such as 8-isoprostaglandin F 2α (8-iso-PGF 2α ) and dicarboxylic eicosanoids such as PGE-MUM. [ABSTRACT FROM AUTHOR]

Coupling reactions of epoxide linked to a secondary oxygen group with Gilman reagents were examined. The regiochemical direction depended on whether there is TMS or MOM as a protective group of the secondary alcohol. anti -Epoxy alcohol 6 tended to react with Me 2 CuLi at the C4 position to generate 1,2-diol 22 as a major component. Epoxide 7 linked to a trimethylsilyloxy group displayed selective formation of 1,3-diol 18 . On the other hand, the reactions of syn -epoxy alcohol 12 and the corresponding TMS ether 13 resulted in the selective formation of 1,2-diol 25 . [ABSTRACT FROM AUTHOR]

Abstract: The oxidative addition of I2, PhCH2Br and MeI with [Pt(CH2SiMe3)2(DPK)], 1, DPK=di-2-pyridyl ketone, occurred with trans stereochemistry to give [PtI2(CH2SiMe3)2(DPK)], [PtBr(CH2Ph)(CH2SiMe3)2(DPK)] and [PtIMe(CH2SiMe3)2(DPK)], respectively. Complex 1 reacted with acids HX (X=Cl or CF3CO2) to give initially the hydridoplatinum complexes [PtHX(CH2SiMe3)2(DPK)], but these complexes were thermally unstable and decomposed largely by α-silyl migration to give compounds such as [PtX(SiMe3)Me2(DPK)], as determined by monitoring the reactions by NMR at low temperature. With excess acid, HX, at room temperature, the products were largely [PtX2(DPK)], CH4 and Me3SiX with Me4Si as a minor product only. The mechanism of the easy Si–CH2 bond cleavage is discussed. [Copyright &y& Elsevier]

Abstract: Complexes of three related 1-azapentadienyl ligands [N(SiMe2R1)C(But)(CH)3SiMe2R]−, abbreviated as L (R=But, R1 =Me), L′ (R=Me=R1), and L″ (R=But =R1), are described. The crystalline compounds Sn(L)2 (1), Sn(L′)2 (2), [Sn(L′)(μ-Cl)]2 (3) and [Sn(L″)(μ-Cl)]2 (4) were prepared from SnCl2 and 2 K(L), 2 K(L′), K(L′) and K(L″), respectively, in thf. Treatment of the appropriate lithium 1-azapentadienyl with Si(Cl)Me3 yielded the yellow crystalline Me3Si(L) (5) and the volatile liquid Me3Si(L′) (6) and Me3Si(L″) (7), each being an N,N,C-trisilyldieneamine. The red, crystalline Fe(L)2 (8) and Co(L′)2 (9) were obtained from thf solutions of FeCl2 with 2 Li(L)(tmeda) and CoCl2 with 2 K(L′), respectively. Each of 1–9 gave satisfactory C, H, N analyses; 6 and 7 (GC–MS) and 1, 2, 8 and 9 (MS) showed molecular cations and appropriate fragments (also 3 and 4). The 1H, 13C and 119Sn NMR (1–4) and IR spectra support the assignment of 1–4 as containing Sn–N(SiMe2R1)-C(But)(CH)3SiMe2R moieties and 5–7 as N(SiMe3)(SiMe2R1)C(But)(CH)3SiMe2R molecules; for 1–4 this is confirmed by their X-ray structures. The magnetic moments for 8 (5.56 μB) and 9 (2.75 μB) are remarkably close to the appropriate Fe and Co complex [M{η3-N(SiMe3)C(But)C(H)SiMe3}2]; hence it is proposed that 8 and 9 have similar metal-centred, centrosymmetric, distorted octahedral structures. [Copyright &y& Elsevier]

Abstract: New multilayer composite membranes for gas separation with enhanced performance were prepared. Membranes consist of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) as the gutter layer deposited on a poly(acrylonitrile) porous support and partially crosslinked Matrimid® 5218 selective top-layer. Matrimid® 5218 is an attractive soluble polyimide known for its excellent thermal and mechanical resistance and high selectivities for some gas pairs, e.g. O2/N2 or H2/CH4. A partial crosslinking of Matrimid® 5218 using 1,4-xylylenediamine was performed to obtain high-viscous coating solutions exhibiting significantly lower penetration into support pores in comparison with composite membranes where neat commercial Matrimid® 5218 was used. Because PTMSP is soluble in most organic solvents, including chloroform used for coating of Matrimid® 5218, a procedure for crosslinking of the PTMSP gutter layer using bis(2-azidophenyl) sulfone was developed. The influence of crosslinking time and crosslinking agent concentration on gas transport properties was determined. The effect of the PTMSP gutter layer on gas transport properties was compared with that of the PDMS sealing layer. It was demonstrated that the gutter layer enhances both gas permeances and selectivities whereas the sealing layer increases selectivities but with a small gas permeance decrease. Long-term performance of prepared multilayer composite membranes showed about 20% reduction of single gas permeances, whereas selectivities remained almost unchanged. [Copyright &y& Elsevier]

Abstract: Seven group 14 element(IV) compounds 2–7 have been prepared, derived either (2–5) from the potassium β-diketiminate K(L) [L ={N(Ar)C(Me)}2CH, Ar=C6H3Pr i 2-2,6] (1) or the known lithium β-dialdiminate Li(L′)] [L′ ={N(Ar)C(H)}2CPh, Ar=C6H3Pr i 2-2,6]. Treatment of 1 with Bu t C(O)Cl, Me3SiCl, Ph3SnCl, or Me3SnCl afforded {N(Ar)C(Me)}2C(H)C(O)Bu t (2), [ArNC(Me)C(H)C(Me)N(Ar)SiMe3] (3), [HN(Ar)C(Me)C(H)C(CH2SnPh3)N(Ar)] (4), or ▪ (5), respectively. Compounds 4 and 5 are remarkable as they have arisen from a tautomer of 1; crystalline centrosymmetric 5 has a fused tricyclic structure, a central eight-membered ring flanked by two six-membered rings. The compounds [GeCl2(L′)(OGeCl3)] (6) or [SnCl(L′)Me2] (7), the first group 14 metal β-dialdiminates, were obtained from Li(L′) and (GeCl3)2O or Me2SnCl2, respectively. The Sn(II) compound SnCl(L′) (8) was prepared from SnCl2 and K(L′). The molecular structures of the crystalline compounds 3–8 are reported. [Copyright &y& Elsevier]

Fe[C(SiMe3)3]2 compound, in which iron is coordinated by two carbons, was prepared using the reaction of FeCl2 with (Me3Si)3CLi, and investigated by XRD, 57Fe Mössbauer spectroscopy and DFT calculations. 157.5 T hyperfine magnetic field was found at the site of the iron nucleus of this compound at 20 K. DFT calculations predict the quintet states to be clearly favored energetically over the lower spin states. The population analysis reveals considerable 4 s as well as large unpaired 3 d electron contributions, which can be responsible for the extremely high hyperfine field. [ABSTRACT FROM AUTHOR]

Abstract: Solid-phase analytical derivatization (SPAD) with bis(trimethylsilyl)trifluoroacetamide (BSTFA) has successfully been used as a sample preparation method for determination of (APs) in fish bile treated with β-glucuronidase and sulfatase. Derivatized APs were analysed by gas chromatography–mass spectrometry in the electron ionization mode (GC–EI-MS). Overall limits of detection (LODs) ranged from 5 to 18ng/g bile for 19 out of 21 investigated compounds. LODs were not determined for 4-methylphenol and 4-tert-octylphenol due to high background levels in control bile. Recoveries ranged from 83 to 109%. The analysed APs vary in degree of alkylation from methyl (C1) to nonyl (C9), and represent various pollution sources, including produced water (PW) discharge from the offshore oil industry. The applicability and sensitivity of the method has been demonstrated by analysis of bile taken from Atlantic cod (Gadus morhua L.) exposed to two dilutions of PW (1:500 and 1:1500) in a continuous flow system. [Copyright &y& Elsevier]

series of N-allyl, N-ethylmethacrylate and N-phenylmethacrylatenaphthalimide monomers have been prepared with -C=CFc, -C≡CFc and -C≡CSiMe substituents at the 4-position of the naphthalimide ring. All have been characterised by elemental analysis and spectroscopy; the X-ray structure of N-allyl-4-ethenylferrocenylnapththalimide is also reported. Free-radical polymerisation of these monomers gave homopolymers, random co- and terpolymers with polydispersities ranging from 1.7 to 3.2. Incorporation into a polymer matrix has no effect on the spectroscopic and electrochemical properties of the naphthalimide or ferrocenyl components. The ferrocenyl polymers are electrochromic and when oxidised give naphthalimide $${\rightarrow \hbox{Fc}^{+}}$$ charge-transfer bands in the NIR; this electrochromism was examined by OTTLE techniques. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of Bi[N(SiMe3)2]3 from BiCl3 and KN(SiMe3)2 generates an unusual amido bismuth imide by-product, {[(Me3Si)2N]Bi[μ-N(SiMe3)]}2, evidently formed via Sieavage. X-ray diffraction shows that the complex contains a planar Bi2N2 ring with tetrahedral bismuth and trigonal planar imido nitrogen atoms. [Copyright &y& Elsevier]

Abstract: o-Quinone methides are formed from the reaction of nucleophiles with trimethylsilyl(methyl)-1,4-benzoquinones. These reactive intermediates are trapped by excess nucleophile to form substituted quinones following oxidation. In addition, varying amounts of a symmetrical dimer and a xanthen derivative were observed. The influence of different nucleophiles and ring substituents on the rate of reaction have been studied, and are consistent with rate-limiting formation of a vinylogous enolate initiated by attack of the nucleophile on the silyl group. [Copyright &y& Elsevier]

A new method for determination of ascorbic acid using gas chromatography was developed and compared to the high-performance liquid chromatography (HPLC) one. The analysis was performed after simple clean up techniques and a freeze drying step. Total ascorbic acid was analyzed after reduction of dehydroascorbic acid by dithiothreitol as in some HPLC methods. These conditions can be employed only for ascorbic acid or for multi-compound assay. [Copyright &y& Elsevier]

A simple and rapid analysis of sugars and organic acids by gas chromatography (GC) has been developed. Fructose, glucose, sucrose, citric and malic acid in citric fruits were quantitatively derivatized in two reactions. The total derivatization time was 5 min using a domestic microwave oven at 180 W radiation power. Average analytical recoveries were above 97%. The method demonstrate be 20 times faster than others found in the literature and ideal for routine analysis. [Copyright &y& Elsevier]

Trimethylsilyl (TMS) groups were chemically introduced on to the phenylene group of bisphenol-A polysulfone (PSf) at sites ortho to ether (EM3) or to sulfone (SM3) linkages. Gas permeabilities increased by substitution of TMS and especially oxygen permeability increased from 1.1 barrer for PSf to 4.2 barrer for SM3 and to 7.1 barrer for EM3. Perm-selectivity of oxygen to nitrogen decreased from 5.8 to 5.5 and therefore substitution of TMS on polysulfone resulted in improved gas transport properties. In addition, it was found that EM3 is more effective in enhancing the gas transport properties than SM3. In order to interpret the effect substitution site on gas transport, d-spacing was investigated in terms of interchain packing. Furthermore, the effect of substitution site on chain motion was investigated through dynamic mechanical analyzer (DMA), dielectric analyzer (DEA), and solid-state NMR. DMA and DEA experiments showed that motions of unsubstituted phenylene and sulfonyl linkage are much more hindered in SM3 than in EM3. NMR experiments showed that motion of TMS is more mobile in EM3 than in SM3. These results revealed that chain motions of SM3 are more hindered than those of EM3 and substitution site affects chain motions. Therefore, we can conclude that these changes in chain motion also gas transport in modified polysulfones with silyl side group. [Copyright &y& Elsevier]

π-Electron systems of silicon have attracted attention because of their narrow HOMO-LUMO gap and high reactivity, but the structural diversity remains limited. Herein, new dialkylboryl-substituted disilenes were synthesized by the selective desilylation-borylation of the corresponding trimethylsilyl-substituted disilenes. The dialkylboryl-substituted disilenes were fully characterized by a combination of NMR spectroscopy, MS spectrometry, single-crystal X-ray diffraction analysis, and theoretical calculations. The longest-wavelength absorption bands of boryldisilenes were bathochromically shifted compared to the corresponding silyl-substituted disilenes, indicating a substantial conjugation between π(Si=Si) and vacant 2p(B) orbitals. In the presence of 4-(dimethylamino)pyridine (DMAP), the dialkylboryl groups in the boryl-substituted disilenes were easily converted to trimethylsilyl groups, suggesting the dialkylboryl-substituted disilenes in the presence of a base serve as the surrogates of disilenyl anions (disilenides). [ABSTRACT FROM AUTHOR]