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The particular reactivity of the recently discovered class of the main group element polyhedral clusters, pyramidanes, remains largely unexplored. In this communication, we report the reaction of the germapyramidane with tert‐butyllithium leading to the rather unusual organogermanium compound [Li+(thf)2]⋅2−, as the product of the formal insertion of a Ge‐apex into the C−Li bond. This reactivity mode exemplifies unusual electrophilic behaviour of a pyramidane, which is a priori considered as a nucleophilic reagent. Being highly reactive, [Li+(thf)2]⋅2− readily undergoes reactions with electrophiles (MeI, EtBr), initially forming intermediate germahousenes, which isomerize to the thermodynamically more favourable germoles. [ABSTRACT FROM AUTHOR]

In this study, compounds with phenylethynyl (PE) groups introduced at all of the possible positions of the methylene‐bridged structure of the 1,1′‐bi‐2‐naphthol backbone (3‐PE to 8‐PE) were synthesized. Compounds with four or six phenylethynyl groups (3,6‐PE, 4,6‐PE, 5,6‐PE, 6,7‐PE, and 3,4,6‐PE) were also synthesized. The key reaction for the synthesis of these compounds was the Sonogashira reaction using halogen scaffolds. The new transformation methods include (1) selective bromination of the 5‐position of the binaphthyl skeleton and (2) bromination of the 6‐position and then iodination of the 4‐position, followed by the Sonogashira reaction of iodine at the 4‐position and lithiation and protonation of bromine at the 6‐position. The optical properties of the compounds were evaluated. The extension of the π system greatly differed depending on the position of the phenylethynyl group. 4‐PE, 4,6‐PE, and 3,4,6‐PE, in which the phenylethynyl groups were introduced in the extended direction of the naphthalene linkage axis, showed longer absorption and emission wavelengths and higher fluorescence quantum yields than the other compounds. In circularly polarized luminescence measurements, 7‐PE showed a relatively large glum value, an interesting finding that reverses the sense. [ABSTRACT FROM AUTHOR]

A bis(ferrocenyl)stannylene, whose ferrocenyl ligands contain sterically demanding substituents, Fc*2Sn (1; Fc*=2,5‐bis(3,5‐di‐t‐butylphenyl)‐1‐ferrocenyl), has been synthesized as a monomeric diorganostannylene. Stannylene 1 undergoes a ligand‐redistribution reaction with SnCl2 to give the corresponding chloro(ferrocenyl)stannylene, Fc*(Cl)Sn:. [ABSTRACT FROM AUTHOR]

To establish some steric protection at the P center of a tricyclic 1,4‐dihydro‐1,4‐phosphasiline, the potassium salt of a tricyclic 1,4‐dihydro‐1,4‐phosphasilin‐1‐ide was treated with triphenylmethyl chloride. Subsequently, the two Si‐bound diethylamino groups, were converted to give the SiCl2 derivative using HCl. The Si‐functionality could be used in substitution reactions thus giving Si‐dimethyl and Si‐dimethoxy derivatives. Reduction of the SiCl2 derivative at low temperature gave transient tricyclic silylene which could not be detected by NMR spectroscopy but successfully trapped by 1,3‐butadiene to give a P‐containing spiro‐silolene derivative. DFT studies provide insight into reduction and the silylene formation. [ABSTRACT FROM AUTHOR]

Dual chalcogen‐bonding interactions is proposed as a novel means for the conformational control of urea derivatives. The formation of a chalcogen‐bonding interaction at both sides of the urea carbonyl group was unambiguously confirmed by X‐ray diffraction as well as computational studies including non‐covalent interaction (NCI) plot index analysis, quantum theory of atoms in molecules (QTAIM) analysis, and natural bond orbital (NBO) analysis via DFT calculations. By virtue of this dual interaction, urea derivatives that bear chalcogen atoms (X=S and Se) adopt a planar structure via the carbonyl oxygen (O) with an X⋅⋅⋅O⋅⋅⋅X arrangement on the same side of the molecule. The rigidity of the conformational lock was evaluated using the molecular arrangement in the crystal and the rotational barrier of benzochalcogenophene ring, which indicated a stronger conformational lock in benzoselenophene than in benzothiophene urea derivatives. Furthermore, the acidity of the urea derivatives increases according to the Lewis‐acidic properties of the chalcogen‐bonding interactions, whereby benzoselenophene urea is more acidic than benzothiophene urea. Tweezer‐shaped urea derivatives were prepared, and their stereostructure proved the viability of the conformational control for defining the location of the substituents on the urea framework. [ABSTRACT FROM AUTHOR]

While analogues of allenes with heavier main-group elements (group 14–16) have been extensively studied, 2-heteraallenes are rare chemical species whose properties are mostly unknown. It is also notable that the synthesis and isolation of allene-type molecules are not widespread, despite the extensive study of two-coordinated low-valent chemical species. [ABSTRACT FROM AUTHOR]