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 center dot center dot center dot P and Si-H center dot center dot center dot E=P (E = S, Se), whereas the organosilanols 3O, 3S, and 3Se contain medium-strength hydrogen bonds of the type Si-OH center dot center dot center dot E=P (E = O, S, Se). These hydrogen bonds and those of related model complexes H3SiOH center dot center dot center dot(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.