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

Abstract

The intramolecularly coordinated (6-(diphenylphosphino)acenaphth-5-yl)stannanes ArSnBu3 (1), ArSnPh3 (2), ArSnPh2Cl (3), ArSnPhCl2 (4), ArSnCl3 (5), Ar2SnCl2 (6), ArSnPh2O3SCF3 (7), and ArSnPh2F (8) 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 1–8 vary substantially, which is reflected in the different P–Sn peri distances lying in the range from 2.7032(9) to 3.332(2) Å. In MeCN, 7 undergoes electrolytic dissociation into solvated triarylstannyl cations and triflate anions. The gas-phase structures of 2–5, 8, and the triarylstannyl cations ArPh2Sn+ (7a) and [ArPh2Sn·NCMe]+ (7b) 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 peri interaction in 2 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 7a,b. The Sn–P bond properties of 8, however, very much resemble those of 3, which means that the electronic impact of the F atom in the axial position is comparable to that of the axial Cl atom.