Sterically Congested 5‑Diphenylphosphinoacenaphth-6-yl-silanes and -silanols

The synthesis and characterization
of the 5-diphenylphosphinoacenaphth-6-yl-silanes
5-Ph2P-Ace-6-SiMe2H (1), 5-Ph2P­(S)-Ace-6-SiMe2H (1S), 5-Ph2P­(Se)-Ace-6-SiMe2H (1Se), and 5-Ph2P-Ace-6-SiMe2Cl (2) as well as of the 5-diphenylphosphinoacenaphth-6-yl-silanols
5-Ph2P-Ace-6-SiMe2OH (3), 5-Ph2P­(O)-Ace-6-SiMe2OH (3O), 5-Ph2P­(S)-Ace-6-SiMe2OH (3S), and 5-Ph2P­(Se)-Ace-6-SiMe2OH (3Se) are reported.
Due to steric congestion in the bay area, the substituents in peri-positions are affected by repulsion, out-of-plane deflection,
and distortion of the spatial arrangement to various extents. The peri-interaction energy associated with the steric congestion
of these and a number of previously known reference compounds was
computationally estimated with a set of isodesmic reactions. The organo-H-silanes 1, 1S, and 1Se possess very weak
intramolecular hydrogen bridges of the types Si–H···P
and Si–H···EP (E = S, Se), whereas the
organosilanols 3O, 3S, and 3Se contain medium-strength hydrogen bonds of the type Si–OH···EP
(E = O, S, Se). These hydrogen bonds and those of related model complexes
H3SiOH···(E)­PH3 were analyzed
applying real-space bonding indicators derived from the electron and
pair densities using the atoms-in-molecules and electron localizability
indicator space-partitioning schemes as well as natural population
analysis and natural bond orbital analyses.