Chalcogen versus Dative Bonding in [SF3]+ Lewis Acid-Base Adducts: [SF3(NCCH3)2]+, [SF3(NC5H5)2]+, and [SF3(phen)]+ (phen = 1,10-phenanthroline).

The Lewis-acid behavior of [SF3][MF6] (M = Sb, As) salts toward mono- and bidentate nitrogen bases was explored. Reactions of [SF3][MF6] with excesses of CH3CN and C5H5N yielded [SF3(L)2]+ (L = CH3CN, C5H5N) salts, whereas the reaction of [SF3][SbF6] with equimolar 1,10-phenanthroline (phen) in CH3CN afforded [SF3(phen)][SbF6]·2CH3CN. Salts of these cations were characterized by low-temperature X-ray crystallography and Raman spectroscopy in the solid state as well as by 19F NMR spectroscopy in solution. In the solid state, the geometries of [SF3(NC5H5)2]+ and [SF3(phen)]+ are square pyramids with negligible cation-anion contacts, whereas the coordination of CH3CN and [SbF6]- to [SF3]+ in [SF3(NCCH3)2][SbF6] results in a distorted octahedral coordination sphere with a minimal perturbation of the trigonal-pyramidal SF3 moiety. 19F NMR spectroscopy revealed that [SF3(L)2]+ is fluxional in excess L at -30 °C, whereas [SF3(phen)]+ is rigid in CH2Cl2 at -40 °C. Density functional theory (DFT-B3LYP) calculations suggest that the S-N bonds in [SF3(NC5H5)2]+ and [SF3(phen)]+ possess substantial covalent character and result in a regular AX5E VSEPR geometry, whereas those in [SF3(NCCH3)2]+ are best described as S···N chalcogen-bonding interactions via σ-holes on [SF3]+, which is consistent with the crystallographic data.

Reactions of Molybdenum and Tungsten Oxide Tetrafluoride with Sulfur(IV) Lewis Bases: Structure and Bonding in [WOF4]4, MOF4(OSO), and [SF3][M2O2F9] (M = Mo, W).

The structure of [WOF4]4 has been reinvestigated by low-temperature X-ray crystallography and DFT (MN15/def2-SVPD) studies. Whereas the W4F4 ring of the tetramer is planar and disordered in the solid state, the optimized gas-phase geometry prefers a disphenoidally puckered W4F4 ring and demonstrates asymmetric fluorine bridging. Dissolution of MOF4 (M = Mo, W) in SO2 and SF4 results in the formation of MOF4(OSO) and [SF3][M2O2F9], respectively. Both SO2 adducts and [SF3][Mo2O2F9] have been characterized by X-ray crystallography. The crystal structure of [SF3][Mo2O2F9] reveals dimerization of the ion pair that results in a rare heptacoordinate sulfur center. Optimization of the {[SF3][M2O2F9]}2 dimers in the gas phase, however, results in the elongation of one contact such that the sulfur centers are effectively hexacoordinate. Meanwhile, the crystal structure of [SF3][W2O2F9]·HF instead demonstrates hexacoordinate sulfur centers and a highly unusual coordination to [SF3]+ from [W2O2F9]- through an oxido ligand. While [SF3][W2O2F9] does not decompose at ambient temperature, MOF4(OSO) and [SF3][Mo2O2F9] are unstable toward evolution of SO2 or SF4. Computational studies reveal that the monomerization of [WOF4]4 in the gas phase at 25 °C is thermodynamically unfavorable using SO2, but favorable using SF4, consistent with the relative thermal stabilities of WOF4(OSO) and [SF3][W2O2F9].

Application of Chromosomal Microarray for Evaluation of Idiopathic Short Stature in Asian Indian Children: A Pilot Study.

BACKGROUND: Human height is a classic polygenic trait and currently available data explains only 10% of the phenotypic variation in height. Almost 60%-80% of the children coming to pediatric and endocrinology outpatient department for the evaluation of short stature are still labeled as idiopathic. OBJECTIVES: The aim of this study is to identify various chromosomal alterations causing idiopathic short stature (ISS) and short stature with dysmorphic features not pertaining to known genetic syndromes. MATERIALS AND METHODS: After exclusion of all nutritional, systemic, endocrine, and syndromic causes of short stature, 19 patients with height <2 standard deviation scores were subjected to chromosomal microarray (CMA) study using Affymetrix CytoScan 750K array and CMA Scanner 3000 platform. RESULTS: We identified total 61 copy-number variant (CNV) and polymorphs (33 gains, 11 loss, and 17 gain-mosaics) not described as normal variants in database of genomic variations. We identified SHOX haploinsufficiency as a cause of short stature in two patients, whereas one patient was gain-mosaic for SHOX. All three had normal conventional karyotype. One of these patients also had deletion of PAX3, which could be the cause of both short stature and associated mild intellectual impairment in this patient. We also found a long noncoding RNA, namely, KIAA0125 and a pseudogene ADAM6 in 18 out of our 19 patients which might have a regulatory role. CONCLUSION: This study shows that CMA is a very promising tool for the identification of pathogenic CNVs in patients with ISS. It can also help to identify novel genes controlling height and can open up new insight into pathophysiologic mechanisms underlying ISS, and thus may help to unfold new therapeutic targets for treatment of this condition. The association of CNV having genes for long noncoding RNAs, such as KIAA0125 and pseudogene such as ADAM6 with ISS suggest that they may play a role in controlling the expression of height-related genes and it needs further investigations.

The structure of trimethyltin fluoride.

The solid-state structure of (CH3)3SnF was reinvestigated by X-ray diffraction techniques as well as by multi-nuclear solid-state NMR spectroscopy. Trimethyltin fluoride crystallizes from hot ethanol in the orthorhombic space group Pnma at room temperature and changes to a low-temperature orthorhombic phase (space group: Cmcm) below -70 °C. In both modifications, trimethyltin fluoride adopts a linear chain structure with symmetric fluorine bridges, in contrast to previous reports. During its synthesis, (CH3)3SnF precipitates in another, poorly crystalline modification, as shown by powder X-ray diffraction. Solid-state MAS NMR experiments of both room-temperature phases of (CH3)3SnF (non-recrystallized and recrystallized) were carried out for the (1)H, (13)C, (19)F, and (119)Sn nuclei. The (119)Sn{(19)F, (1)H} and (19)F{(1)H} NMR spectra offer unambiguous determination for the (19)F and (119)Sn shielding tensors. The (119)Sn{(1)H} solid-state NMR spectra are in agreement with pentacoordination of Sn in this compound for the non-recrystallized and the recrystallized modifications. Based on the solid-state NMR results, the non-recrystallized modification of (CH3)3SnF also consists of linear, symmetrically fluorine-bridged chains, and differs from the recrystallized orthorhombic phase only in packing of the chains.

Lewis acid behavior of SF4 : synthesis, characterization, and computational study of adducts of SF4 with pyridine and pyridine derivatives.

Sulfur tetrafluoride was shown to act as a Lewis acid towards organic nitrogen bases, such as pyridine, 2,6-dimethylpyridine, 4-methylpyridine, and 4-dimethylaminopyridine. The SF4 ⋅NC5 H5 , SF4 ⋅2,6-NC5 H3 (CH3 )2 , SF4 ⋅4-NC5 H4 (CH3 ), and SF4 ⋅4-NC5 H4 N(CH3 )2 adducts can be isolated as solids that are stable below -45 °C. The Lewis acid-base adducts were characterized by low-temperature Raman spectroscopy and the vibrational bands were fully assigned with the aid of density functional theory (DFT) calculations. The electronic structures obtained from the DFT calculations were analyzed by the quantum theory of atoms in molecules (QTAIM). The crystal structures of SF4 ⋅NC5 H5 , SF4 ⋅4-NC5 H4 (CH3 ), and SF4 ⋅4-NC5 H4 N(CH3 )2 revealed weak SN dative bonds with nitrogen coordinating in the equatorial position of SF4 . Based on the QTAIM analysis, the non-bonded valence shell charge concentration on sulfur, which represents the lone pair, is only slightly distorted by the weak dative SN bond. No evidence for adducts between quinoline or isoquinoline with SF4 was found by low-temperature Raman spectroscopy.

SF4·N(C2H5)3: the first conclusively characterized SF4 adduct with an organic base.

Sulfur tetrafluoride and triethylamine react at low temperatures to form a 1:1 adduct. The unambiguous characterization of the SF(4)·N(C(2)H(5))(3), which is only stable at low temperature, proves the Lewis acid property of SF(4) towards organic Lewis bases. The S-N bond has a length of 2.384(2) Å and is an archetypical example of a dative S(IV) ← N bonding modality.

Hydrogen-bonding interactions in T-2 toxin studied using solution and solid-state NMR.

The structure of T-2 toxin in the solid-state is limited to X-ray crystallographic studies, which lack sufficient resolution to provide direct evidence for hydrogen-bonding interactions. Furthermore, its solution-structure, despite extensive Nuclear Magnetic Resonance (NMR) studies, has provided little insight into its hydrogen-bonding behavior, thus far. Hydrogen-bonding interactions are often an important part of biological activity. In order to study these interactions, the structure of T-2 toxin was compared in both the solution- and solid-state using NMR Spectroscopy. It was determined that the solution- and solid-state structure differ dramatically, as indicated by differences in their carbon chemical shifts, these observations are further supported by solution proton spectral parameters and exchange behavior. The slow chemical exchange process and cross-relaxation dynamics with water observed between the hydroxyl hydrogen on C-3 and water supports the existence of a preferential hydrogen bonding interaction on the opposite side of the molecule from the epoxide ring, which is known to be essential for trichothecene toxicity. This result implies that these hydrogen-bonding interactions could play an important role in the biological function of T-2 toxin and posits towards a possible interaction for the trichothecene class of toxins and the ribosome. These findings clearly illustrate the importance of utilizing solid-state NMR for the study of biological compounds, and suggest that a more detailed study of this whole class of toxins, namely trichothecenes, should be pursued using this methodology.