A facile synthetic procedure to prepare π-extended seven-membered phosphorus heterocycles, both symmetric and asymmetric, is reported. The prepared molecules present a persistent nonplanar framework and are soluble in a wide variety of solvents. The seven-membered phosphorus heterocycles can be electrochemically reduced and oxidized, and photoluminesce with a blue color.

Calix[4]pyrroles are readily synthesized in one step from pyrroles and ketones. For several decades, these macrocycles have been exploited as powerful anion receptors or ligands for transition and rare-earth metals....

Anionic, metal‐centered nucleophiles are emerging compounds with unique reactivities. Here, we describe the isolation and full characterization of the first tetraamido tin(II) dianion, its behavior as ligand towards transition metals, and its reactivity as a tin‐centered nucleophile. Experimental values such as the Tolman electronic parameter (TEP) and computations attest tin‐located σ‐donor ability exceeding that of carbenes or electron‐rich phosphines. Against transition metals, the stannate(II) can act as η1‐ or η5‐type ligand. With aldehydes, it reacts by hydride substitution to give valuable acyl stannates. The reductive dehalogenation of iodobenzene indicates facile redox pathways mediated by halogen bond interaction. Calix[4]pyrrolato stannate(II) represents the first example of this macrocyclic ligand in low‐valent p‐block element chemistry.

Previously reported Lewis superacids are colorless and do not exhibit visual changes upon adduct formation. Herein, we combine the features of near Lewis superacidity with light absorption and emission in the visible range. Detailed (TD-)­DFT considerations lead to the design of bis­(alizarinato)­silane 1 as a powerful chromogenic Lewis acid, that responds to one or two fluoride ions with different optical outputs. Lewis adducts of 1 are synthesized, and the coordination-state-dependent absorption and emission maxima verified experimentally. Reaction with, for example, sodium fluoride, reveals the simultaneous participation of the Lewis acidic silicon center and the Lewis basic alizarin carbonyl functions, promising its additional use as a salt-selective molecular receptor. Although the poor solubility and moisture intolerance of 1 for the moment hinder real practical applications, this study paves the way for dual-gated fluoride ion sensing.

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