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The study represents new bioanalytical characterization of mainly organic components of the poorly investigated extracellular polymeric substances (EPS) of the enigmatic diatom Didymosphenia geminata, an invasive, worldwide expanding species endangering diverse ecosystems. This microalga attaches its siliceous cells to rocky substrates using fibrous stalks, which are made of an EPS-based matrix stabilized by crystalline calcite. The EPS were analyzed using selected methods, including microscopic, spectroscopic, and spectrometric techniques. We identified diverse types of biomolecules. The presence of lipids, condensed aromatics, and heteroaromatic compounds in the EPS has been confirmed using high-resolution mass spectrometry (HR-MS). Additionally, both sulfur-containing functionalities and carboxylic acids were determined too using infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. For the first time, lignin compounds have been detected as one of the components of the EPS of the D. geminata diatom, using HR-MS and fluorescence microscopy (FM) in combination with specific staining techniques. By increasing the understanding of the chemistry and structural features of the stalks, we aim to develop potential applications and methods for removing these stalks from affected regions in the future, or, alternatively, to use them as a large-scale source of sustainable biocomposite material. [ABSTRACT FROM AUTHOR]

Nitrilotris(methylenephenylphosphinic) acid (NTPAH3) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe3)3. From the latter, upon alcoholysis in chloroform, NTPAH3 could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH3 synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H⋅⋅⋅O H-bonded networks (NTPAH3P), in chloroform crystals in the space group R3c formed (NTPAH3M), the constituents of which are individual molecules with exclusively intramolecular O-H⋅⋅⋅O hydrogen bonds. Both solids, NTPAH3P and NTPAH3M, were characterized by single-crystal X-ray diffraction, multi-nuclear (1H, 13C, 31P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH3P and NTPAH3M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)3 H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and 1H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)3 H-bond trimers of NTPAH3M over those in NTPAH3P. [ABSTRACT FROM AUTHOR]

Copper ores and concentrates thereof feature an increasingly notable content of impurities such as arsenic and other hazardous elements. As an alternative to the state-of-the-art partial roasting process, arsenic could be removed by the alkaline sulfide leaching of the copper concentrates. In order to optimize and understand the processes, knowledge of the speciation and oxidation states is essential. In addition to methods such as UV/Vis spectroscopy, chromatography and ICP/MS methods, 75As NMR spectroscopy may be useful for the differentiation and quantification of the various species. Although arsenate(V) has been characterized by 75As NMR some time ago, to our knowledge, there are no data on tetrathioarsenate(V) AsS43− and the mixed oxygen/sulfur substituted mono-, di- and trithioarsenates(V) AsOxS4−x3−, x = 3, 2, 1, respectively. Therefore, we investigated several model solutions and samples from Cu-As leaching with 75As NMR. The strongly alkaline conditions of the leaching solution proved to be very advantageous for that purpose. Both the tetrathioarsenate(V) and the mixed species AsOxS4−x3− (x = 1–3) could be characterized and provide valuable data for the quantification of the material flows in the leaching process. [ABSTRACT FROM AUTHOR]

4-Azidopyridine (1) and SiCl4 react with the formation of the hexacoordinate silicon complex SiCl4(4-azidopyridine)2 (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl4 and forms back upon cooling. Depending on the cooling, two different crystalline modifications of 2 were obtained, which feature two different trans-conformers. Slow cooling to room temperature afforded conformer 2′, which features coplanar pyridine rings. Rapid cooling to −39 °C afforded crystals of conformer 2″, in which the planes of the pyridine ligands are nearly orthogonal to one another. Whereas 2′ resembles the molecular arrangement of various other known SiX4(pyridine)2 (X = halide) complexes, 2″ represents the first crystallographically confirmed example of a SiX4(pyridine)2 complex in this conformation. Conformers 2′ and 2″ were studied with 13C and 29Si solid state NMR spectroscopy. Their differences in 29Si chemical shift anisotropy, as well as energetic differences, were further investigated with computational analyses. In spite of the similar stabilities of the two conformers as isolated molecules, the crystal packing of 2″ is less stable, and its crystallization is interpreted as a kinetically controlled effect of seed formation. (3+2)-cycloaddition of 1 and phenylacetylene in toluene at 110 °C yields a mixture of 1-(4-pyridyl)-4-phenyl-1,2,3-triazole (1,4-3) and 1-(4-pyridyl)-5-phenyl-1,2,3-triazole (1,5-3) in approximate 1:2 molar ratio. The crystal structures of the two isomers were determined via X-ray diffraction. In chloroform (at 60 °C), this reaction is slow (less than 2% conversion within 4 h), but the presence of SiCl4 enhanced the rate of the reaction slightly, and it shifted the triazole isomer ratio to ca. 1:6 in favor of 1,5-3. [ABSTRACT FROM AUTHOR]

The organosilicon pyridine-2-olates 1a–1d (RSi(pyO)3, R = Me (a), Ph (b), Bn (c), Allyl (d); pyO = pyridine-2-olate) may serve as tripodal ligands toward CuCl with formation of complexes of the type RSi(μ2-pyO)3CuCl (2a–2d). In addition, for R = Allyl, formation of the more stable isomer 2d′ (κO-pyO)Si(μ2-pyO)2(μ2-Allyl)CuCl was observed. In the presence of dry air (as a source of oxygen), reactions of 1a–1d and CuCl afforded Cu(II) complexes RSi(μ2-pyO)4CuCl (3a–3d); 3a–3c in good yield, and 3d only as a side product. Reaction of Ph2Si(pyO)2 (4) and CuCl in equimolar ratio afforded, depending on reaction conditions, a series of (CuCl)n-ladder-type oligonuclear Cu(I) complexes Ph2Si(μ2-pyO)2(CuCl)n(μ2-pyO)2SiPh2 (n = 2 (52), 3 (53), 4 (54)). In all of the above compounds, the pyO group is Si–O bound and, in the case of μ2 coordination, Cu–N bound. All new compounds (1c, 1d, 2b, 2c, 2d, 2d′, 3b, 3c, 3d, 52, 53, 54) were characterized by single-crystal X-ray diffraction, and further characterization includes solution 1H, 13C, 29Si NMR spectroscopy (1c, 1d, 2b, 2c, 2d', 53, 54), solid-state 29Si (2b, 2c, 2d′, 53, 54) and 63Cu NMR spectroscopy (2c, 2d′) as well as computational analyses of the isomerization of the couple 2d, 2d′. [ABSTRACT FROM AUTHOR]

The phenyltetrel pyridine-2-olates PhE(pyO)3 (E = Si, Ge, Sn; pyO = pyridine-2-olate) were synthesized from the respective chlorides PhECl3 and 2-hydroxypyridine (2-pyridone) with the aid of a sacrificial base (triethylamine). Their solid-state structures were determined by single-crystal X-ray diffraction. PhSi(pyO)3 exhibits a three-fold capped tetrahedral Si coordination sphere ([4+3]-coordination, Si···N separations ca. 3.0 Å), in accordance with structures of previously reported silicon pyridine-2-olates. PhGe(pyO)3 adopts a related [4+3]-coordination mode, which differs in terms of the tetrahedral faces capped by the pyridine N atoms. Additionally, shorter Ge···N separations (2.8–2.9 Å) indicate a trend toward tetrel hypercoordination. PhSn(pyO)3 features heptacoordinate tin within a pentagonal bipyramidal Sn coordination sphere (Sn···N separations 2.2–2.4 Å). For the Si and Sn compounds, 29Si and 119Sn NMR spectroscopy indicates retention of their tetrel coordination number in chloroform solution. [ABSTRACT FROM AUTHOR]

Starting from [Ru(pyO)2(nbd)] 1 and a N,P,N-tridentate ligand (2a: PhP(pic)2, 2b: PhP(pyO)2) (nbd = 2,5-norbornadiene, pic = 2-picolyl = 2-pyridylmethyl, pyO = 2-pyridyloxy = pyridine-2-olate), the compounds [PhP(μ-pic)2(μ-pyO)Ru(κ2-pyO)] (3a) and [PhP(μ-pyO)3Ru(κ2-pyO)] (3b), respectively, were prepared. Reaction of compounds 3 with CO and CNtBu afforded the opening of the Ru(κ2-pyO) chelate motif with the formation of compounds [PhP(μ-pic)2(μ-pyO)Ru(κ-O-pyO)(CO)] (4a), [PhP(μ-pic)2(μ-pyO)2Ru(CNtBu)] (5a), [PhP(μ-pyO)4Ru(CO)] (4b) and [PhP(μ-pyO)4Ru(CNtBu)] (5b). In dichloromethane solution, 4a underwent a reaction with the solvent, i.e., substitution of the dangling pyO ligand by chloride with the formation of [PhP(μ-pic)2(μ-pyO)Ru(Cl)(CO)] (6a). The new complexes 3a, 4a, 5a, 5b and 6a were characterized by single-crystal X-ray diffraction analyses and multi-nuclear (1H, 13C, 31P) NMR spectroscopy. The different coordination behaviors of related pairs of molecules (i.e., pairs of 3, 4 and 5), which depend on the nature of the P–Ru-bridging ligand moieties (μ-pic vs. μ-pyO), were also studied via computational analyses using QTAIM (quantum theory of atoms in molecules) and NBO (natural bond orbital) approaches, as well as the NCI (non-covalent interactions descriptor) for weak intramolecular interactions. [ABSTRACT FROM AUTHOR]

Al‐ion batteries employing natural graphite cathodes have been proposed as a valid alternative to Li‐ion systems due to their low‐cost and sustainability, as well as a stable long‐term cycle life. In contrast to commonly used but typically expensive ionic‐liquid‐based electrolytes, our reported Al‐graphite batteries use AlCl3/urea and AlCl3/acetamide deep eutectic solvents (DES, also known as ionic liquid analogues) as low‐cost alternative. By carefully selecting amide composition, Al speciation in the DES electrolyte can be modified, as confirmed by Raman, NMR and IR spectroscopy. We correlate the speciation changes to resulting battery performance by systematic electrochemical investigations of Al‐graphite batteries employing urea and acetamide eutectics of different compositions. The practical applicability was demonstrated using long‐term cycling experiments with >8000 cycles, exhibiting a specific capacity of around 50 mAh/g at a current rate of 2 A/g. [ABSTRACT FROM AUTHOR]

The reversible hydrogenation of aminoalanes employing activated aluminium and piperidine has been explored. A selection of transition metal (TM) compounds have been investigated as additives for producing TM-activated aluminium (TM = Ti, Zr, Hf and Y). The effect of these additives on the activation of aluminium with respect to hydrogenation of an aluminium/piperidinoalane system has been studied. It has been shown that Ti, Zr and Hf can efficiently promote the activation of aluminium for its hydrogenation. The experiments performed showed that the TM activity for the piperidinoalane formation decreases in the order Zr > Hf > Ti > Y. Using multinuclear NMR spectroscopy, the reversibility of this piperidinoalane-based hydrogenation system has been evidenced, demonstrating a potential pathway for hydrogen storage in aminoalanes. The syntheses of piperidinoalanes as well as their structural and spectroscopic characterisation are described. Single-crystal X-ray diffraction analyses of [pip2AlH]2 and [pip3Al]2 (pip = 1-piperidinyl, C5H10N) revealed dimers containing a central [AlN]2 unit. [ABSTRACT FROM AUTHOR]

Reactions of SiCl4 with R2PO(OH) (R=Me, Cl) yield compounds with six‐fold coordinated silicon atoms. Whereas R=Me afforded the hexacoordinated tetra‐cationic silicon complex [Si(Me2PO(OH))6]4+ with chloride counter‐ions, R=Cl caused release of HCl with formation of a cyclic dimeric silicon complex [Si(Cl2PO(OH))(Cl2PO2)3(μ‐Cl2PO2)]2 with bridging bidentate dichlorophosphates. [ABSTRACT FROM AUTHOR]

The structure of amorphous silicodiphosphonates made from diphosphonic acids and tetraethoxysilane was investigated by 1H, 13C, 29Si, and 31P single pulse and cross polarization (CP) MAS NMR spectroscopy as well as 1H–31P{29Si} REDOR, 1H–31P–29Si and 1H–29Si–13C double CP MAS experiments. The combination of these solid-state NMR techniques leads to a structural understanding of the short range order. The structure is dominated by [Si(OP)6] units. Besides a few [SiO4] groups, we noticed that HEDP based silicodiphosphonate possesses further five- and sixfold coordinated silicon moieties. Another synthesis route to obtain Si–O–P compounds with higher coordinated silicon species is the reaction of trimethylsilyl-substituted diphosphates and diphosphonates with tetramethoxysilane. The 29Si CP NMR spectra also demonstrate polymeric structures with different [SiO4] units in the solids. Both silyl-substituted phosphorus precursors show a surprising triplet signal in the 29Si INEPT NMR spectra that we interpret using higher order coupling patterns. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of di- and trisiloxanes with 3,5-dimethylpyrazolyl (pz*) moieties are presented. Disiloxanes of the type O(SiMe3- npz* n)2 ( n = 1, 2, and 3 in 2, 3, and 4, respectively) are easily accessible through a trans-silylation approach. Crystal structure analyses of compound 4 and the two side products 5 and 6 illustrate different coordination motifs of pz* (terminal vs. bridging) in the disiloxane system. The reaction of O2Si3Cl8 with Me3Sipz* led to the unsymmetrically substituted trisiloxane pz*3SiO-Sipz*2O-SiCl2pz* ( 7) with bridging pz* units and tetra- and pentacoordinate silicon atoms and the fully pyrazolyl-substituted trisiloxane O2Si3pz*8 ( 8), depending on the choice of the reaction conditions. The 29Si NMR properties of 7 were investigated by 29Si CP/MAS NMR spectroscopy and supporting quantum chemical calculations analyzing the principal components of the chemical-shift tensor for all three silicon atoms in this molecule. [ABSTRACT FROM AUTHOR]

Complexes of Sn(II), Sn(IV), Ge(IV), and Si(IV) with the ambidentate pyridine-2-thiolato ligand (PyS-) were synthesized and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffractometry. Comparison of the structures of E(PyS)2Cl2 (E=Sn, Ge, Si) and E(PyS)4 (E=Sn, Si) allows for insights into the group 14 coordination chemistry of this ambidentate chelator in dependence of the thiophilicity of the central atom of the corresponding complex. Furthermore, the crystal structure of Sn(PyS)2 reveals two different coordination modes of its constituents, i.e., the crystal packing features cyclic dimers and polymeric chains of Sn(PyS)2. This compound was shown to undergo oxidative addition of 2,2′-dipyridyldisulfide and sulfur with the formation of Sn(PyS)4and (PyS)2Sn(μ-S)2Sn(PyS)2, respectively. [ABSTRACT FROM AUTHOR]

The reaction of 1-methyl-3-trimethylsilylimidazoline-2-thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N, S-bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel-shaped complexes of the type ClSi(μ-mt)4SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN4)SiSi(S4Cl), (ClN3S)SiSi(S3NCl), and (ClN2S2)SiSi(S2N2Cl) skeletons as so-called (4,0), (3,1), and cis-(2,2) paddlewheels) were detected in solution by using 29Si NMR spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X-ray diffraction studies. In accord with time-dependent NMR spectroscopy, computational analyses proved the cis-(2,2) isomer with a (ClN2S2)SiSi(S2N2Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two SiSi-bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms. [ABSTRACT FROM AUTHOR]

Bridged bis(trialkoxysilylalkyl)pyromellitic diimides 3–6 were prepared as single-source precursors for sol–gel derived organic–inorganic hybrid materials. The synthesis route starts with the formation pyromellit diimide 1 from pyromellitic dianhydride and hexamethyldisilazane (HMDS), followed by metallation of the NH groups to give the dipotassium salt 2. The four molecular hybrid precursors 3–6 were obtained according to the first step of the Gabriel synthesis. The reaction rates were studied as a function of the alkyl chain length and the nature of the halide (Cl vs. I). All products 1–6 were comprehensively analysed using FT-IR, 1H and 13C NMR spectroscopy as well as elemental analysis, and – in the case of 3–6– also with 29Si NMR spectroscopy. For compounds 3 (with propylene groups and methoxy substituents) and 6 (with methylene groups and ethoxy substituents) single crystal X-ray structures were determined and discussed. Hydrolysis and condensation of the alkoxides 3–6 were carefully monitored with solution 29Si and 1H NMR spectroscopy providing a basis for further studies on the formation of silica-pyromellit organic–inorganic hybrids from precursors 3–6. Finally the formation of flexible and transparent hydride films using precursors 4 and 6 was proved. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and characterization of sulfoethyl cellulose (SEC) exhibiting low degrees of substitution ascribed to sulfoethyl groups (DSSE) were reported. The effects of reaction temperature, duration, reaction mediums as well as sulfoethylating agents on DSSE were investigated. The total DSSE was determined via elemental analysis and the structure of SEC was elucidated by FT Raman, one- (1D-) and two-dimensional (2D-) NMR spectroscopy. Based on the characterization, SEC with diverse total DSSE up to 0.65 were obtained and the primary hydroxyl groups were found to be preferably substituted. Finally, the feasibility of using FT Raman spectroscopy with the band at 1044, 811 or 747cm−1 as marker band to determine total DSSE of SEC was presented. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis and spectroscopic characterisation of cellulose sulfate (CS) were reported. Various CS exhibiting diverse degrees of sulfation (DSS) were prepared through acetosulfation or direct sulfation of cellulose. During the acetosulfation, intermediate product – cellulose acetate sulfate (CAS) – was formed after the comparative esterification and subsequent deacetylation of CAS led to CS. The direct sulfation proceeded quasi-homogeneously and heterogeneously in N,N-dimethylformamide (DMF) or homogeneously in N,N-dimethylacetamide (DMAc)/LiCl mixture. The total DSS between 0.21–2.59 and partial DSS6 as well as DSS2 of up to 1 were determined via elemental analysis and 13C NMR spectroscopy. Besides, solid-state CP/MAS 13C NMR could characterise CS regarding the sulfation. Subsequently, FT Raman investigation of obtained CS was conducted with the aim to establish analysis methods quantifying the total DSS. The intensities of Raman bands ascribed to the vibrations of Oh name="dbnd" />O and C–O–S groups were used as analysis parameters, yielding calibration curves with high correlation coefficients of more than 0.96. [ABSTRACT FROM AUTHOR]

The reaction between 2,3-dimercaptopropane-1-sulfonate (DMPS, unithiol) and four phenylarsonic(V) acids, i.e. phenylarsonic acid (PAA), 4-hydroxy-3-nitrophenylarsonic acid (HNPAA), 2-aminophenylarsonic acid (o -APAA) and 4-aminophenylarsonic acid (p -APAA), is investigated in aqueous solution. The pentavalent arsenic compounds are reduced by DMPS to their trivalent analogs and instantly chelated by the vicinal dithiol, forming covalent As–S bonds within a five-membered chelate ring. The different types and positions of polar substituents at the aromatic ring of the arsonic acids influence the reaction rates in the same way as observed for reaction with glutathione (GSH), as well as the syn/anti molar ratio of the diastereomeric products, which was analyzed using time- and temperature-dependent nuclear magnetic resonance (NMR) spectroscopy. Addition of DMPS to the conjugate formed by a phenylarsonic(V) acid and the biologically relevant tripeptide GSH showed the immediate replacement of GSH by chelating DMPS, underlining the importance of dithiols as detoxifying agent. Sequestering Phenylarsonic Acids with the Vicinal Dithiol DMPS: The rate determining reduction of the differently substituted aromatic As(V) compounds (with different types and positions of polar substituents at the aromatic ring) by DMPS and instantaneous chelation of the formed As(III) intermediates yields arsadithiolane compounds. The molecular structures in solution and the single crystal structures–are discussed considering the formation of diastereomers. Interconversion of the latter requires free DMPS as shown by time-dependent NMR spectra. DPMS replaces GSH immediately in arylarsenic(III)-GSH conjugates. [Display omitted] • Reaction kinetics proved to be essential for understanding the detoxification with DMPS. • The redox reaction of phenylarsonic(V) acids with DMPS is the rate determining step. • In phenylarsinic(III)–GSH conjugates the latter is replaced immediately by DMPS. • Interconversion between diastereomers is slow and requires free DMPS. • The most toxic phenylarsonic(V) derivatives show fastest reaction with DMPS! [ABSTRACT FROM AUTHOR]

Front Cover: A Low-Cost Al-Graphite Battery with Urea and Acetamide-Based Electrolytes (11/2021) Aluminium batteries, deep eutectic solvent, energy storage, Raman spectroscopy, NMR spectroscopy Keywords: aluminium batteries; deep eutectic solvent; energy storage; Raman spectroscopy; NMR spectroscopy EN aluminium batteries deep eutectic solvent energy storage Raman spectroscopy NMR spectroscopy 1925 1925 1 06/24/21 20210601 NES 210601 B The Front Cover b shows the investigation of deep eutectic solvent electrolytes for Al-graphite batteries by spectroscopic methods. [Extracted from the article]

Alkali aluminosilicates are potential materials for high temperature applications under alkali load. This study investigated the corrosion behaviour of potassium aluminosilicates of the nominal compositions of KAlSi 2 O 6 and KAlSiO 4 synthesized at different temperatures and dwell times and exposed to alkali load at 1100 °C. For understanding the corrosion behaviour depending on the synthesizing parameters, the produced materials and corroded samples were investigated by XRD and NMR spectroscopy (29Si, 27Al). The combination of both analytical techniques showed that characteristics of the synthesized materials on a structural level played an important role for the corrosion behaviour. It was shown that amorphous and disordered components in the samples occurred which were not registered by XRD. The application of 29Si and 27Al NMR spectroscopy yielded that materials having already after synthesis a structural arrangement similar to the equilibrium target phase of the batch showed a high structural stability under alkali load and gave positive results in the applied corrosion test. Materials with large structural rearrangements during alkali load exhibited volume changes and therefore failed the corrosion test. Based on these observations it should therefore be possible to design materials with high chemical and mechanical stability suitable as furnace linings and to evaluate end-of-life aluminosilicates for an application as alkali corrosion resistant recyclates. [ABSTRACT FROM AUTHOR]

N -(2-hydroxy-1-naphthylidene)- l -valine 1 , N -(2-hydroxy-1-naphthylidene)- l -phenylalanine 2 , and N -(2-hydroxy-1-naphthylidene)- l -threonine 3 were prepared and characterized with spectroscopic methods, elemental analyses, and values of optical rotation. Compound 1 undergoes a solid state order-disorder phase transition at 231 K. The X-ray structures of the high and low temperature phase of 1 have been determined. Single crystal X-ray structures of 2 and 3 have been determined as well. The tautomerism of N -(2-hydroxy-1-naphthylidene)amino acid derivatives is discussed controversial in the literature. A bond lengths statistical analysis shows that all three compounds exist uniformly in the keto-amine form in the solid state. Quantum chemical calculations, NMR, and UV–Vis spectroscopy were used to obtain further insight into the existence of phenol-imine and keto-amine structures in this class of compounds. [ABSTRACT FROM AUTHOR]

The reaction between phenyltrichlorosilane and the tetradentate ligands o-HO-C6H4–C(CH3)＝N(CH2) n –N＝C(CH3)-o-C6H4-OH (n =2, 3, 4), supported by an amine base, yields pentacoordinate silicon complexes (C6H5)Si-[o-O-C6H4–C(CH3)(CH2) n –N–C(＝CH2)-o-C6H4-O] with enamine functionalized ligands. This reaction pattern can be transferred onto various ligands of 2-iminomethylphenolate-type. The resulting pentacoordinate silicon complexes react with a variety of Brønsted acids HY to yield hexacoordinate salen silicon complexes (C6H5)(Y)Si-[o-O-C6H4–C(CH3)(CH2) n –N＝C(CH3)-o-C6H4-O] (Y=benzoate, picrate, 8-oxyquinolinate, 2-oxy-1,4-naphthoquinonate, p-tert-butylphenolate, (5-phenyltetrazol)-2-ide, fluoride, tetrafluoroborate). Hexacoordination of their Si-atoms was confirmed by 29Si NMR spectroscopy and, in some cases, by X-ray crystal structure analysis. Examples for similarities and differences in the coordination behavior of the silicon atom and its heavier congeners (Ge, Sn) in the salen-type coordination sphere as well as data regarding the nucleophilicity of some of these novel enamine complexes are presented. [Copyright &y& Elsevier]

Stable in the solid state and isolable in high yields are adducts of H2SiCl2, HSiCl3, and RSiCl3 (R = Me, Ph) with the N,N′-chelating ligands 1,10-phenanthroline (phen; 1c), 2,2′-bipyridine (bipy; 1b), and (to a limited extent) N,N,N′,N′-tetramethylethylenediamine (tmeda; 1a). The products were comprehensively characterized via multinuclear solution and solid-state NMR spectroscopy, including analysis of the 29Si NMR chemical shift anisotropy tensors, Raman spectroscopy, elemental analyses, and, for SiCl4(phen) (2c), HSiCl3(bipy) (3b), H2SiCl2(bipy) (4b), MeSiCl3(phen) (5c), and PhSiCl3(phen) (6c), single-crystal X-ray structure analyses. The latter revealed that the nonchlorine substituents (i.e., H, Me, and Ph) are exclusively trans-disposed to the N-donor atoms of the chelating ligands. A dismutation of the complexes HXSiCl2(bipy) and HXSiCl2(tmeda) (X = H or Cl) was observed in polar solvents at elevated temperatures. This reaction is more pronounced when phen is used instead of bipy or tmeda. For MeHSiCl2(phen), in addition to undergoing H-Cl redistribution accompanied by the formation of 5c, an unexpected 1,4-hydrosilylation was observed. The latter was proven NMR-spectroscopically and by a single-crystal X-ray structure analysis of the product MeSiCl2(4H-phen) (7), a pentacoordinated silicon compound with a trigonal-bipyramidal arrangement of the subsituents and the methyl group located in an equatorial position. [ABSTRACT FROM AUTHOR]