Intramolecularly Coordinated (6-(Diphenylphosphino)acenaphth-5-yl)stannanes. Repulsion vs Attraction of P- and Sn-Containing Substituents in the <i>peri</i> Positions

The intramolecularly coordinated (6-(diphenylphosphino)­acenaphth-5-yl)­stannanes ArSnBu₃ (<b>1</b>), ArSnPh₃ (<b>2</b>), ArSnPh₂Cl (<b>3</b>), ArSnPhCl₂ (<b>4</b>), ArSnCl₃ (<b>5</b>), Ar₂SnCl₂ (<b>6</b>), ArSnPh₂O₃SCF₃ (<b>7</b>), and ArSnPh₂F (<b>8</b>) were synthesized and fully characterized by multinuclear NMR spectroscopy (¹¹⁹Sn, ³¹P, ¹⁹F, ¹³C, ¹H) and X-ray crystallography (Ar = 6-Ph₂P-Ace-5-). Due to the different substituents, the Lewis acidities of the Sn atoms of <b>1</b>–<b>8</b> vary substantially, which is reflected in the different P–Sn <i>peri</i> distances lying in the range from 2.7032(9) to 3.332(2) Å. In MeCN, <b>7</b> undergoes electrolytic dissociation into solvated triarylstannyl cations and triflate anions. The gas-phase structures of <b>2</b>–<b>5</b>, <b>8</b>, and the triarylstannyl cations ArPh₂Sn⁺ (<b>7a</b>) and [ArPh₂Sn·NCMe]⁺ (<b>7b</b>) were obtained by geometry optimization at the B3PW91/TZ level of theory. A detailed analysis of a set of real-space bonding indicators (RSBI) derived from the electron and pair densities following the atoms in molecules (AIM) and electron localizability indicator (ELI-D) topological approaches, respectively, uncovers the Sn–P <i>peri</i> interaction in <b>2</b> to be in the border regime between nonbonding and weakly ionic. With an increasing number of Cl atoms attached to the Sn atom, the Sn–P bond becomes considerably shorter and exhibits a decreasingly polar covalent interaction. As expected, this trend is significantly enhanced for the Sn–P interactions in the charged compounds <b>7a</b>,<b>b</b>. The Sn–P bond properties of <b>8</b>, however, very much resemble those of <b>3</b>, which means that the electronic impact of the F atom in the axial position is comparable to that of the axial Cl atom