Diverse reactions of a fluorostannylenoid towards ethynes

Fluoro(dialkyl)stannylenoid 2 exhibits unique reactivity towards ethynes with acetylenic hydrogen and those with trimethylsilyl groups, though the corresponding free dialkylstannylene 1 is inactive against those ethynes. Stannylenoid 2 reacts smoothly with gaseous ethyne and phenylethyne at room temperature, giving the corresponding diethynylstannanes, di(phenylethynyl)stannane 3 and diethynylstannane 6, respectively, in good yields with the concomitant evolution of H₂. Trimethylsilyl-substituted ethynes such as 1-trimethylsilyl-(2-phenyl)ethyne and 1,2-bis(trimethylsilyl)ethyne react similarly to give 3 and bis(trimethylsilylethynyl)stannane 8, respectively. Rather unexpectedly, the reaction of 2 with (trimethylsilyl)ethyne affords 1,2-bis(ethenylstannyl)ethyne 7 in a good yield. The reactions of 2 with methyl and ethyl propynoates give the same products 4 and 5 as those obtained during the reaction of dialkylstannylene 1 without CsF. Pathways involving the nucleophilic attack of cesium acetylide to an ethyne-complexed stannylene were proposed, while the detailed mechanisms remain unknown. The structure of 7 was studied by single crystal X-ray diffraction analysis.

Novel diaminopropyl substituted organotin compounds

A novel synthetic pathway involving the desilylation of a tin trimethylsilyl species (Ph2Sn(SiMe3)2) towards nonprotected di(3-aminopropyl)tin dichloride ((H2N(CH2)3)2SnCl2) is described. Di(3-aminopropyl)tin dichloride is then converted to the respective dicarboxylates species (H2N(CH2)3)2Sn(OCOR)2 containing carboxylic acids of different lengths (R = –CH3, –(CH2)10CH3). Depending on the nature of R, discrete packing effects are observed in the solid state of di(3-aminopropyl)tin dicarboxylate derivatives. All the synthesized substances were characterized by 1H, 13C, and 119Sn nuclear magnetic resonance data and also single crystal X-ray analysis. These compounds are a promising class of substances for biological, pharmaceutical, and technical applications.

Close contacts involving germanium and tin in crystal structures: experimental evidence of tetrel bonds

Modeling indicates the presence of a region of low electronic density (a "σ-hole") on group 14 elements, and this offers an explanation for the ability of these elements to act as electrophilic sites and to form attractive interactions with nucleophiles. While many papers have described theoretical investigations of interactions involving carbon and silicon, such investigations of the heavier group 14 elements are relatively scarce. The purpose of this review is to rectify, to some extent, the current lack of experimental data on interactions formed by germanium and tin with nucleophiles. A survey of crystal structures in the Cambridge Structural Database is reported. This survey reveals that close contacts between Ge or Sn and lone-pair-possessing atoms are quite common, they can be either intra- or intermolecular contacts, and they are usually oriented along the extension of the covalent bond formed by the tetrel with the most electron-withdrawing substituent. Several examples are discussed in which germanium and tin atoms bear four carbon residues or in which halogen, oxygen, sulfur, or nitrogen substituents replace one, two, or three of those carbon residues. These close contacts are assumed to be the result of attractive interactions between the involved atoms and afford experimental evidence of the ability of germanium and tin to act as electrophilic sites, namely tetrel bond (TB) donors. This ability can govern the conformations and the packing of organic derivatives in the solid state. TBs can therefore be considered a promising and robust tool for crystal engineering. Graphical abstract Intra- and intermolecular tetrel bonds involving organogermanium and -tin derivatives in crystalline solids.

Stabilizing, non-covalent interactions in the solid state structure of novel aryltin hydrides and halogenides

A group of novel aryltin chlorides, bromides and hydrides (ArnSnY4-n) (Ar = o-tolyl, 2,6-xylyl, 1-naphthyl, 2-naphthyl, p-n-butylphenyl; Y = Cl, Br, H) have been synthesized and structurally characterized via X-ray diffraction. These compounds display noncovalent intermolecular interactions in the form of edge to face, π–π stacking and C–H···π interactions resulting in discrete arrangements in the solid state. The strength of these interactions and their effect on resulting structural parameters, as well as the consequence of the aromatic substituent on the type of interactions present, will be highlighted and discussed.