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The crystal structure of Sc3Ir4Si13+x (x = 0.22) [space group P m 3 ‾ n $Pm\bar{3}n$ , a = 8.4651(1) Å] is found to be a new disordered variant of the primitive cubic Yb3Rh4Sn13 Remeika prototype. The silicide is stable in the narrow temperature range of 1283–1397 °C and reveals metallic properties. The crystal structure of Sc4Ir7Ge6 [U4Re7Si6 type, space group I m 3 ‾ m $Im\bar{3}m$ , a = 8.1397(8) Å] is refined for the first time. The electronic band structure calculations reveal that the properties of this germanide can be explained based on the free electron gas model. Both compounds reveal close structural relationships to the simple perovskite structure.

The compounds Pn(pyS)3 (Pn = P, As, Sb, Bi) were synthesized from the respective chloride (Pn = P, As, Sb) or nitrate (Bi), pyridine-2-thiol (pySH) and triethylamine (NEt3) as a supporting base in THF (P, Sb), CHCl3 (As) or methanol (Bi). Sb(pyS)3 was also obtained from the reaction of SbCl3 with LipyS (prepared in situ) in methanol. The compounds Sb(pyS)2Ph and Sb(pyS)Ph2 were prepared in a one-pot reaction starting from SbCl3 and SbPh3 (1:1 ratio). Upon Cl/pyS substitution, the resulting reaction mixture allows for a facile separation of the products in hot hexane. P(pyS)3 and As(pyS)3 crystallize isostructurally to the reported structure of Sb(pyS)3 with κ-S-bound pyS ligands. These crystal structures feature close Pn···Pn contacts which are most pronounced for the arsenic derivative. Bi(pyS)3 adopts a different molecular structure in the solid state, which features two chelating (κ 2-S,N-pyS) ligands and a κ-S-bound ligand. The presence of N→Bi interactions between the nitrogen atom of the κ-S-pyS ligand and the Bi atom of another molecule renders this structure a polymer chain along the crystallographic b axis with Bi⋅⋅⋅Bi van-der-Waals contacts. The structures of this set of Pn(pyS)3 compounds were also studied in solution using 1H NMR spectroscopy, revealing equivalent pyS ligands in discrete Pn(pyS)3 molecules. The molecular structure of Sb(pyS)Ph2 was optimized by quantum chemical methods, and a comparison with the structures reported for the other Sb/pyS/Ph combinations reveals Sb(pyS)2Ph to feature the strongest Sb···N interactions with the κ-S-pyS ligand. The results of 1H NMR spectroscopic investigations of the compounds Sb(pyS) x Ph3–x (x = 3–0) suggest the Ph protons in ortho position to be incorporated into intramolecular C–H···S contacts for x = 2 and 1. Natural localized molecular orbital (NLMO) calculations were employed in order to gain insights into the electronic situations of the Pn atoms and Pn–R bonds (R = S, C), especially for the effects caused by formal substitution of Pn in the compounds Pn(pyS)3 and the ligand patterns in the compounds Sb(pyS) x Ph3–x (x = 3–0). For the latter series of compounds, the electronic situation of the Sb atom was further studied by 121Sb Mössbauer spectroscopy, providing a correlation between the calculated electron density at Sb [ρ(0)] and the experimentally observed isomer shift δ. The missing link between group 15 and group 13 metal compounds of the type M(pyS)3, compound Al(pyS)3, was synthesized in this work. In the solid state (confirmed crystallographically), the mer isomer of this tris-chelate complex with distorted octahedral Al coordination sphere was found. This coordination mode was confirmed for the solution state (CDCl3) by 1H and 13C NMR spectroscopy at T = −40 °C.

New cyclic and spirocyclic aminosilanes were synthesised using ethylenediamine, 2-aminobenzylamine, 1,8-diaminonaphthalene, o-phenylenediamine, andtrans-cyclohexane-1,2-diamine as starting material. These diamines were converted into aminosilanes using silicon tetrachloride and dimethyldichlorosilane directly and via theN,N’-bis(trimethylsilylated) amino derivatives. 15 new compounds of the type (diamino)(SiMe3)2, (diamino)2Si, (diamino)SiMe2, and (diamino)SiCl2have been prepared. The formation of two cyclotrisilazane derivatives was observed starting from (N,N’-2-aminobenzylamino)dichlorosilane by trimerisation. All synthesised compounds have been characterised with NMR-, Raman-, or IR-spectroscopy, mass-spectrometry, and boiling or melting point. Single-crystal X-ray structure analyses of several derivatives have been performed.The degree of substitution with trimethylsilyl groups in the final compounds depends on the ring size of the spirocycles. It was shown with quantum chemical calculations on the M062X/6-31G(d) level that trimethylsilyl groups have a stabilising effect on 5-membered ring systems and a destabilising effect on 6-membered rings in these compounds.

Reactions of SiCl4 with R2 PO(OH) (R=Me, Cl) yield compounds with six-fold coordinated silicon atoms. Whereas R=Me afforded the hexacoordinated tetra-cationic silicon complex [Si(Me2 PO(OH))6 ]4+ with chloride counter-ions, R=Cl caused release of HCl with formation of a cyclic dimeric silicon complex [Si(Cl2 PO(OH))(Cl2 PO2 )3 (μ-Cl2 PO2 )]2 with bridging bidentate dichlorophosphates.

Neutral bi-, tri-, and tetradentate ligands of the type Ph3–xSb(L)x [x = 1 (1), 2 (2), and 3 (3). L = La = phthalimidinyl (1a, 2a, and 3a), Lb = 2-pyridyloxy (1b, 2b, and 3b)] have been synthesized...

Amine treatment is commonly used to capture CO2 from exhaust gases and from ambient air. The Si−N bond in aminosilanes is capable of reacting with CO2 more readily than amines. In the current study we have synthesized trimethylsilylated ethanolamines, diethanolamines and piperazines and investigated their reaction toward CO2. All products were characterized by 1H, 13C, and 29Si NMR, RAMAN spectroscopy as well as mass spectrometry. The product of a twofold CO2‐insertion into bis‐trimethylsilylated piperazine was analysed by single‐crystal X‐ray diffraction. Furthermore, quantum chemical calculations (DFT) were used to supplement the experimental results. Geometry optimizations and NBO calculations for each starting material were carried out at the B3LYP level with different basis sets. DFT calculations at the B3LYP, WB97XD and M062x level were conducted for geometry optimization and frequency calculations to examine the thermochemical data. The calculations were carried out both for the gas phase and in solvent environment. The calculated reaction enthalpies varied between −37 and −107 kJ mol−1, while experimental values around −100 kJ mol−1 were determined., The insertion reaction of CO2 into the Si−N‐bond of silylated ethanolamines and piperazines yields products that were analysed by 1H, 13C and 29Si NMR and RAMAN spectroscopy as well as mass spectrometry. The experimental results are compared with these of quantumchemical calulations. The calculated reaction enthalpies varied between −37 and −107 kJ mol−1, while experimental values around −100 kJ mol−1 were determined.

The insertion of carbon dioxide into the Si-N bonds of aminodisilanes ((RR'N)

Inspired by the known complex [PhP(μ-PyO)4Ru(CO)] (PyO = 2-pyridyloxy), the family of group 15 paddle-wheel complexes has been expanded to [PhPn(μ-PyO)4Ru(L)] (Pn = P, As, Sb; L = NCMe, CO). Solvent-dependent reversible switching between [PhAs(μ-PyO)4Ru(NCMe)] and [PhAs(μ-PyO)3Ru(κ2-PyO)] was detected. Electrochemical investigations of the [PhPn(μ-PyO)4Ru(L)] complexes showed reversible oxidation of the complexes with L = NCMe and back-formation of the complexes with L = NCMe upon oxidation of the complexes with L = CO in NCMe. In the series of [PhPn(μ-PyO)4Ru(L)] complexes, the Pn→Ru bonding mode is shifted from L-type Pn to X-type upon going from Pn = P and As to Pn = Sb, resulting in a pronounced electron-rich Ru site in the latter case. The easily accessible complex [PhSb(μ-PyO)4RuCl] exhibits reversible electrochemical and coordinative exchange with its reduced analogue [PhSb(μ-PyO)4Ru(NCMe)] under retention of the paddle-wheel motif and Sb-Ru bond properties.

Yb

29Si enrichment would be advantageous for many NMR studies of the structural properties of sol-gel derived materials. The required starting materials (29Si enriched alkoxysilanes), however, are expensive and difficult to provide. Here we present a scalable, reliable synthesis of 29Si enriched tetraethoxysilane starting from silicon dioxide or elemental silicon with a total yield up to 75%.

We report the successful synthesis of up to millimeter-size single crystals of the pyrochlore rare earth element (RE) germanates Dy2Ge2O7 and Ho2Ge2O7. Crystals were grown from oxide starting mater...

In the present work an azomethinic pincer ( P ) possessing an ONNNO donor set was prepared via condensation reaction of diethylenetriamine and o -hydroxyacetophenone followed by silyl-functionalization (introduction of a triethoxysilylpropyl or silatranylpropyl group via urea linker) to afford P-Sil and P-Silt , respectively. The resulting products were characterized by various spectroscopic techniques, elemental analysis and single-crystal X-ray diffraction. They were further utilized for the fabrication of post-synthesis functionalized mesoporous silica nanoparticles (MSNs) using similar reaction conditions. The obtained hybrid materials (P-Sil@MSNs and P-Silt@MSNs) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetry (TGA), nitrogen gas adsorption-desorption measurements and C,H,N microanalysis. The corresponding results revealed particularly high loading of organic moieties for the P-Silt functionalized particles. In addition, adsorption behavior of both materials towards the anionic dye eriochrome black T (EBT) was evaluated by examining the effect of pH, solution temperature, time and dye concentration. The maximum adsorption capacity of P-Silt@MSNs and P-Sil@MSNs at pH = 3 was found to be 101 mg g −1 and 69.9 mg g −1 , respectively (calculated on the basis of Langmuir model). The characterization and adsorption studies revealed better loading of organic moieties in P-Silt@MSNs with respect to P-Sil@MSNs. Furthermore, P-Silt@MSNs was used to adsorb the cationic dye methylene blue (MB) at pH = 8. Its maximum adsorption capacity reached 28 mg g −1 .

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.

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.

29Si enrichment would be advantageous for many NMR studies of the structural properties of sol-gel derived materials. The required starting materials (29Si enriched alkoxysilanes), however, are expensive and difficult to provide. Here we present a scalable, reliable synthesis of 29Si enriched tetraethoxysilane starting from silicon dioxide or elemental silicon with a total yield up to 75%.

In the course of our investigations of the coordination chemistry of trivalent antimony (Sb) compounds, we studied heteronuclear complexes formed in reactions of the compounds RSb(pyS)2 (R = pyS, Ph; pyS- = pyridine-2-thiolate) with [Pt(PPh3)4], i.e., complexes [(R)Sb(μ-pyS)2Pt(PPh3)] (R = pyS, 1; R = Ph, 2). The reaction of 1 with o-chloranil proceeds cleanly with elimination of 2,2'-dipyridyl disulfide and formation of the salt [(PPh3)Pt(μ-pyS)2Sb(μ-pyS)2Pt(PPh3)]+[Sb(C6Cl4O2)2]- (3III), which features the cation 3+. The charge-neutral, unsymmetrically substituted compound [(PPh3)Pt(μ-pyS)2Sb(μ-pyS)2Pt(κS-pyS)] (4) can be accessed by the reaction of 3+ with LipyS. The oxidation of 2 with o-chloranil furnishes the complex [(κ-O,O-C6Cl4O2)PhSb(μ-pyS)2Pt(PPh3)] (5). The oxidation of 1 with PhICl2 afforded the paddlewheel-shaped complex [Sb(μ-pyS)4PtCl] (6). Moreover, compound 6 was obtained by the reaction of Sb(pyS)3 with [PtCl(pyS)(PPh3)]. The polarization of Pt-Sb bonds of compounds 1-6 was investigated by natural localized molecular orbital (NLMO) calculations, which suggest X-type ligand character (covalent Pt-Sb bonds) for 1 and 2, whereas the Sb ligand of 6 reflects Z-type character (dative Pt→Sb bonds). In 3+, 4, and 5, high contributions of the reverse, i.e., L-type (dative Pt←Sb bonds), were observed. In conjunction with the results of NLMO analyses, 121Sb Mossbauer spectroscopy proves that complexes 1-6 represent essentially trivalent Sb complexes with either a free lone pair (LP) at the Sb atom (1, 2, and 6) or LP character involved in L-type Pt←Sb coordination (3+, 4, and 5).

Invited for this month's cover is the group of Marcus Herbig from the TU Bergakademie in Freiberg. The cover picture shows the reaction of CO(2) with a silyl derivative of the biogenic amine ethanolamine. The role of CO(2) as a contributor to climate change makes “carbon capture” a desirable goal. However, in addition to simply capture CO(2), aminosilanes form silylcarbamates, which represent starting materials for a variety of crucial chemicals. Thus, the entrapped CO(2) represents a useful C(1) building block. The ESF‐funded Junior Research Group CO(2)‐Sil at the TU Bergakademie Freiberg (represented by their Logo and location) pursues that kind of goals. CO(2)‐Sil studies these key reactions of CO(2) insertion in depth by syntheses, quantum chemical calculations and calorimetric experiments. CO(2) brought to the ground by our method shall be feedstock for various branches in chemistry. Read the full text of their Full Paper at 10.1002/open.201900269.

The Front Cover shows the reaction of CO(2) with a silyl derivative of the biogenic amine ethanolamine. The role of CO(2) as a contributor to climate change makes “carbon capture” a desirable goal. However, in addition to simply capture CO(2), aminosilanes form silylcarbamates, which represent starting materials for a variety of crucial chemicals. Thus, the entrapped CO(2) represents a useful C(1) building block. The ESF‐funded Junior Research Group CO(2)‐Sil at the TU Bergakademie Freiberg (represented by their Logo and location) pursues that kind of goals. More information can be found in the Full Paper by Marcus Herbig et al.[Image: see text]

Neutral inherently tri- and tetradentate ligands of the type Ph3-xAs(PyO)x (x = 2 (1), 3 (2)) have been synthesized and characterized. Reaction of 1 with [RuCl2(PPh3)3] affords complex [PhAs(μ-PyO)2RuCl2(PPh3)] (3), whereas 2 and [RuCl2(PPh3)3] react with formation of [As(μ-PyO)2RuCl(PPh3)2] (5) and [Ph3P(PyO)]Cl (6). Treatment of complex 5 with [AuCl(tht)] (tht = tetrahydrothiophene) results in liberation of tht and formation of [AuCl(As(PyO)2)RuCl(PPh3)2] (7), featuring an (Au-As-Ru) core. For compounds 3, 5, and 7 the As-Ru and As-Au bond situation has been investigated using NBO, AIM and ELF analysis, allowing the assignment of pronounced canonical forms of σ-(AsIII→RuII) to 3, σ-(AsII-RuI) to 5 and σ-(AuI←AsI→RuII) to 7.

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., Ionic dissociation of SiCl4: The first example of a structurally characterized tetra‐cationic hexacoordinated silicon tetrachloride is reported. It was obtained by reaction of dimethylphosphinic acid with SiCl4 under ambient conditions. Additionally, the structure of a cyclic dimeric hexacoordinated silicon complex was determined by single‐crystal X‐ray diffraction and verified by solid‐state NMR spectroscopy.

Bis(trimethylsilyl)carbodiimide (BTSC), so-called “pseudo water” because of some analogies such as similar (group)electronegativities of Me3Si– vs. H– and –N=C=N– vs. –O–, may form two different kinds of “pseudo hydrates” of metals (M), i.e. M–N(SiMe3)=C=N(SiMe3) and M–N≡C–N(SiMe3)2, derived from its carbodiimide and cyanamide isomeric forms, respectively. With anhydrous AlCl3 in Me3SiCl solution BTSC was shown to be capable of forming both kinds of solvates, i.e. Cl3Al–N(SiMe3)–C≡N(SiMe3) (1) and ((Cl3Al)(Me3Si)NCN)3–Al–(N≡C–N(SiMe3)2)3 (2). Both compounds were isolated as crystalline solids, which undergo condensation reactions upon storage. By single-crystal X-ray diffraction analysis the constitution of 1 was confirmed unambiguously, and quantum chemical calculations (B3LYP/6-311++g(d,p)) confirmed that compound 1 is 6 kcal mol−1 more stable than its hypothetical N,N-bis(trimethylsilyl)cyanamide isomer Cl3Al–N≡C–N(SiMe3)2. Compound 1 represents the first crystallographically confirmed disilylcarbodiimide complex of a metal salt. The molecules of compound 2 are heavily disordered in the solid state (positional disorder of N≡C–N(SiMe3)2 vs. N≡C–N(SiMe3)(AlCl3) and positional disorder of SiMe3 vs. AlCl3 groups in the latter). Therefore, the identity of 2 was additionally confirmed by 13C, 15N, 27Al and 29Si CP/MAS NMR spectroscopy.

Herein, biologically crucial amino acids have been explored for the synthesis of fluorescent organotin compounds. One-pot reaction of dimethyltin oxide, 2-hydroxy-4-methoxybenzophenone and α-amino acids, i.e., glycine, L-isoleucine and L-methionine, afforded respective organotin compounds with biogenic Schiff base skeletons 1–3. Although all the compounds were constituted from similar ONO type Schiff base units, only compound 1 (derived from glycine) crystallized as a hexacoordinated organotin compound of the type (ONO)SnMe2(MeOH) with a tridentate chelating Schiff base ligand. Analogous syntheses with L-isoleucine and L-methionine did not afford the related Schiff base compounds 2 and 3. Instead, some kind of precursors, namely 2′ and 3′, crystallized as solvent mediated Sn4O4 ladders and two Schiff base ligand moieties bound to the terminal Sn atoms via carboxylate moiety only. Interestingly, solution NMR spectroscopy (1H, 13C, 119Sn) of 1 unambiguously complied with its solid state structure while for 2′ and 3′ the behaviour was entirely different suggesting their transformation to mononuclear compounds 2 and 3 in solution phase. The distinctive structural aspects of 2′/2 and 3′/3 in solid and solution phase were also supported by solid state 119Sn CP/MAS NMR studies. All the compounds were found to be fluorescent when excited at 365 nm and the solutions of compound 3′ experienced quenching in the presence of paramagnetic metal ions due to chelation enhanced quenching.

Reaction of dichlorodimethylsilane and L-valin in molar ratio 1:2 (with addition of a supporting base, Et3N) afforded a complex mixture of products, from which the pentacoordinate silicon complex (val-val)SiMe2 (1) could be isolated and identified by single-crystal X-ray diffraction analysis. This complex features the di-anion of dipeptide valinylvalin as a tridentate (N,N‘,O)-ligand. Using a stochiometric ratio of starting materials adjusted to the formation of 1 (the use of dichlorodimethylsilane and L-valin in molar ratio 1:1, the additional silane serving as a water trap to foster peptide condensation) allowed for the preparation of this compound in moderate yield. Using 1,1,3,3,5,5-hexamethylcyclotrisilazane, which may serve both as a source of SiMe2 moieties and deprotonator for valin, afforded another pentacoordinate Si-complex, i.e., (val)SiMe2(NH3) (2). In addition to the chelating di-anion of valin its Si atom carries an ammonia molecule as an axial ligand within a trigonal-bipyramidal coordination sphere, as confirmed by single-crystal XRD. For both solids 1 and 2 29Si CP/MAS NMR spectra were recorded and the chemical shift anisotropy tensors were determined therefrom.

The aminosilanes MenSi(NRR′)4−n (n=2,3) with NRR′=ethylamino (NHEt), n-propylamino (NH n Pr), sec-butylamino (NH s Bu), n-octylamino (NH n Oct), n-dodecylamino (NH n Dodec), allylamino (NHAll), tert-butylamino (NH t Bu), diethylamino (NEt2), and anilino (NHPh) were synthesized and their reactions with phenyl isocyanate were studied. In all cases of these silanes Me3SiNRR′ and Me2Si(NRR′)2 formal insertion of the –NCO group into their Si–N bonds was observed, i.e. formation of products with Si–N (rather than Si–O) bonds was found. In some cases, the products could be crystallized and their molecular structures have been elucidated with single-crystal X-ray diffraction analyses.

In contrast to numerous thio- and selenocyanuric acid derivatives, sulfur- or selenium-containing s-heptazines have not been reported so far. Thio- and selenocyameluric acid esters were obtained by substitution reactions of s-heptazine chloride C6 N7 Cl3 with aromatic thiols and selenophenol; the resultant white or yellow solids were stable in air. They were comprehensively characterized by elemental analysis, 1 H, 13 C NMR, and IR spectroscopy. The thiocyameluric acid phenyl ester (1, C6 N7 (S(C6 H5 ))3 ) and the corresponding selenium compound (7) formed co-crystals with mesitylene, which were analyzed by single-crystal X-ray diffraction. Both structures showed unusually large channels of ≈12 A diameter. The thermal stability was measured by TGA (thermogravimetric analysis), and the flame retardancy of compound 1 was tested in PP by carrying out limiting oxygen index (LOI) measurements, which gave promising results. Quantum chemical calculations of the title compounds were performed to explain the observed properties and structural characteristics.

Exploration of an aminotrisphenol ligand (H3L) to synthesise heterocyclic tin derivatives led to the unexpected formation of a stannatrane-like [4.4.4.01,6] heterotricyclic stannate anion [LSnCl2]− (1). Further, its metathesis reaction with ammonium thiocyanate provided access to its thiocyanate derivative [LSn(NCS)2]− (2), which proved to be a chromophoric probe. The characterization methods applied, such as elemental analysis, various spectroscopic methods (FT-IR, NMR (1H, 13C, 119Sn), UV–Vis, Mass) and X-ray crystallography (for 2) are in accord with the formation of these ionic compounds. The rhodanide functionalized stannatrane-like compound (2) was isolated as triethylammonium salt with distorted octahedral environment around Sn generated by the tripodal O3N donor system and the N atoms of two cis configured thiocyanates. This particular organization of rhodanides imparted chelator and chromophoric character to 2 and enhanced its colorimetric and optical response towards some metal ions (such as Fe3+, Cu2+ and Co2+ ions) as compared to the free tripodal ligand (H3L) and ammonium thiocyanate. The role of 2 as a bidentate ligand for the chelation of metal ions may be responsible for the enhanced stability of metal complexes as well as the observed spectral behaviour.

The molecular structures of the transition metal cyclohexasilyl complexes M(CO) 5 Si 6 Me 11 * 0.5 n -C 5 H 12 (M = Mn, Re) were determined by single crystal X-ray diffraction. The two compounds are isomorphous. Their silicon-silicon bond lengths are compared with those of the parent cyclohexasilane and of other cyclohexasilyl complexes (comprising group 6, 7, 8, and 10 as well as row 3, 4, and 5 transition metals) with respect to silicon-silicon bond activation.

The tin(IV) compounds MexSn(2-C6F4PPh2)4-x (1, x = 1; 2, x = 2) and ClSn(2-C6F4PPh2)3 (3) were obtained from the reactions of 2-LiC6F4PPh2 with MeSnCl3 (3:1), Me2SnCl2 (2:1), or SnCl4 (3:1), respectively. The reactions of 2-LiC6F4PPh2 with SnCl4 in different stoichiometric ratios (4:1-1:1) gave 3 as the main product. Compound Cl2Sn(2-C6F4PPh2)2 (4) was formed in the transmetalation reaction of 3 and [AuCl(tht)] but could not be isolated. 1 and 2 react with palladium(0) sources {[Pd(PPh3)4] and [Pd(allyl)Cp]} by the oxidative addition of one of their Sn-CAryl bonds to palladium(0) with formation of the heterobimetallic complexes [MeSn(μ-2-C6F4PPh2)2Pd(κC-2-C6F4PPh2)] (5) and [Me2Sn(μ-2-C6F4PPh2)Pd(κ2-2-C6F4PPh2)] (6) featuring Sn-Pd bonds. The reaction of 3 with palladium(0) proceeds via the oxidative addition of the Sn-Cl bond to palladium(0), thus furnishing the complex [Sn(μ-2-C6F4PPh2)3PdCl] (7) featuring a Sn-Pd bond and a pentacoordinate Pd atom. Transmetalation of MexSn(2-C6F4PPh2)4-x (x = 1-3) with [Pd(allyl)Cl]2 gave MexClSn(2-C6F4PPh2)3-x and [Pd(allyl)(μ-2-C6F4PPh2)]2. For x = 1, the compound MeClSn(2-C6F4PPh2)2 (generated in situ) reacted with another 1 equiv of [Pd(allyl)Cl]2 by the oxidative addition of the Sn-Cl bond to palladium(0) and the reductive elimination of allyl chloride, thus leading to [MeSn(μ-2-C6F4PPh2)2PdCl] (8). The reductive elimination of allyl chloride was also observed in the reaction of 3 with [Pd(allyl)Cl]2, giving [Sn(μ-2-C6F4PPh2)3PdCl] (7). All compounds have been characterized by means of multinuclear NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and selected compounds by 119Sn Mossbauer spectroscopy. Computational analyses (natural localized molecular orbital calculations) have provided insight into the Sn-Pd bonding of 5-8.

An azo-azomethine host has been synthesized and incorporated onto sol-gel derived silica via hydrolysis of its tricyclic silanizing unit (i.e., a silatrane moiety). The azo-azomethine functionalized silatrane (the “host”) was studied by various spectroscopic techniques, elemental analysis, single crystal X-ray diffraction and thermogravimetric analysis. Upon application to silica, significant change in surface area, pore diameter and pore volume of the product confirmed the incorporation of azo-azomethine pendants in the channels of the silica gel. Scanning electron microscopy and high resolution-transmission electron microscopy were used to analyse the surface morphology and porous nature of the sorbent. The azo-azomethine functionalized silica was further utilized for the uptake of picric acid (PA) assisted by proton transfer. PA (the “guest”) being highly acidic interacts with the electron rich site of the host via proton transfer. As a consequence electrostatic interactions between host and guest molecules result in the fast uptake of PA onto the sorbent. Formation of the host-guest complex was studied by NMR spectroscopy of the host/guest solutions and host solutions with related dummy guest molecules. The maximum adsorption capacity of the sorbent for PA was found to be 68.5 mg g−1 calculated on the basis of a Langmuir model.

Neutral bi- and tripodal ligands of the type PhxP(L)3−x (x = 1 (for 1), 0 (for 2); L = N-methylbenzamidyl (La, 1a, 2a), phthalimidyl (Lb, 1b, 2b), 2-pyridyloxy (Lc, 1c, 2c)) have been synthesized to act as P,O (1a, 1b, 2a, 2b) or P,N (1c, 2c) chelating ligands in the ruthenium coordination sphere. Reactions of the ruthenium source [RuCl2(PPh3)3] with 1a,b,c and 2b,c result in the formation of all-cis bis-chelate complexes [RuCl2(PPh3)κ-P,O,O- or κ-P,N,N-(PhxP(L)3−x)] 3a,b,c (x = 1) and 4b,c (x = 0), respectively. Surprisingly, during the reaction of [RuCl2(PPh3)3] with 2a a P–N bond cleavage in favor of P O bond formation takes place with formation of complex 5a [RuCl(PPh3)2κ-P,O,O-(O P(La)2)]. Treatment of the reaction mixture with TlPF6 afforded the phosphonium salt 6 [Ph3P(Ph)C NMe]PF6. Attempts to form similar compounds to 5a with Lb or Lc (driven by chloride abstraction upon addition of TlPF6) only afforded the cationic complexes of the type [RuCl(PPh3)2κ-P,O,O- or κ-P,N,N-(P(L)3)]PF6 (L = Lb (7b), Lc (7c)). All isolated compounds were characterized with multi-nuclear NMR spectroscopy, single-crystal X-ray diffraction (except 4c) and elemental analysis.

The carboxylic amides N-methylbenzamide (HLa), phthalimidine (HLb) and pyridine-2-one (HLc) were diphenylphosphino-functionalized (with ClPPh2 and a base, n-BuLi for HLa, triethylamine for HLb and HLc) to yield the N-PPh2 derivatives of N-methylbenzamide (1a) and of phthalimidine (1b) as well as the O-PPh2 derivative 2-diphenylphosphinoxypyridine (1c). Thus, 1a and 1b represent P,O-chelate ligands, whereas 1c is a P,N-chelate ligand. Both P,O-ligands (1a, 1b) react with [RuCl2(PPh3)3] in a two-step fashion to form mono-chelates with trans-situated Cl atoms (2a, 2b) upon using a 1:1 stoichiometric ratio or Cl-trans bis-chelates (3aII, 3bII) upon using two equivalents of the chelator. In contrast, reaction of [RuCl2(PPh3)3] and the P,N-chelator 1c in 1:1 molar ratio immediately produced a bis-chelate (3cI) with an all-cis orientation of the ligands (while 50% of the [RuCl2(PPh3)3] starting material remained unreacted). Compound 3cI slowly isomerizes to the Cl-trans isomer (3cII). All isolated compounds were characterized with multi-nuclear NMR spectroscopy, single-crystal X-ray diffraction and elemental analysis.

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.

Three novel atrane-like pentacoordinate silicon and hexa- and mixed penta- and hexacoordinate tin compounds containing [4.4.3.0]tridecane cages have been synthesized. In the present work, the bis-phenol amine tetradentate ligand, N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-2-aminoethanol (H3L), was treated with phenyltrichlorosilane, butyltrichlorostannane and phenyltrichlorostannane to give the mononuclear pseudo-silatrane 1, dinuclear pseudo-stannatrane 2 and tetranuclear pseudo-stannatrane 3, respectively. These compounds were characterized by spectroscopic techniques (1H, 13C and 119Sn NMR, FTIR and MS). Single-crystal X-ray diffraction studies revealed 1 to be a discrete molecule and 2 to be a non-centrosymmetric dimer, whereas compound 3 is a “ladder”-like architecture bearing two types of Sn coordination spheres arranged in a centrosymmetric fashion. Thus, a broad range of molecular architectures are accessible with this tripodal ligand H3L. Pseudo-atranes 1–3 are structurally characterized representatives of the hitherto very scarcely explored class of tricyclic group 14 metal compounds bearing mixed ring systems in an atrane cage.