Intramolecular P–H···H–Si Dihydrogen Bonding in the 5-Dimethylsilyl-9,9-dimethylxanthen-4-yl-diphenylphosphonium Cation

Abstract

The synthesis of 4-bromo-5-diphenylphosphino-9,9-dimethylxanthene (1a), 4-bromo-6-diphenylphosphinodibenzofuran (1b), 4-diphenylphosphino-5-dimethylsilyl-9,9-dimethylxanthene (2a), 4-diphenylphosphino-6-dimethylsilyldibenzofuran (2b), 5-dimethylsilyl-9,9-dimethylxanthen-4-yl-diphenylphosphonium tetrakis­(pentafluorophenyl)­borate [3a]­[B­(C6F5)4], and 6-dimethylsilyldibenzofuran-4-yl-diphenylphosphonium tetrakis­(pentafluorophenyl)­borate [3b]­[B­(C6F5)4] was reported. Unlike the benzofuran derivate [3b]+, the xanthene derivative [3a]+ shows an intramolecular dihydrogen bond of the type P–H···H–Si, which was studied by DFT calculation using a set of real-space bond indicators (RSBIs) derived from the Atoms-In-Molecules (AIM), Non-Covalent Interactions (NCI) indicator, and Electron Localizability Indicator (ELI-D) methods. Neither [3a]+ nor [3b]+ shows any propensity to release dihydrogen to give the 4-diphenylphosphino-9,9-dimethylxanthen-5-yl-dimethylsilyl cation [4a]+ or the 4-diphenylphosphino-dibenzofuran-5-yl-dimethylsilyl cation [4b]+, respectively.

The Effect of Donor Additives on the Stability and Structure of 5‐Diphenylphosphinoacenaphth‐6‐yllithium

“…AIM topology typically “detects” all kinds of interactions from covalent to ionic and from strong to weak, however, is known to fail in decent cases of low electron density (ED) gradients, e.g. in cage structures, or H ··· H contacts . Minor alternations in the ED were computed with NCIplot (grid step size of 0.1 au), using the non‐covalent interactions (NCI) index, which is derived from the ED gradient according to: s( r ) = [1/2(3π 2 ) 1/3 ]|∇ ρ |/ ρ 4/3 .…”

In silico activation of dinitrogen with a light atom molecule

“…The compounds chosen in the present density functional theory (DFT) study are thus derived from and related to a variety of published peri-substituted compounds comprising intramolecular interactions. [63][64][65][66][67][68][69][70] Peri-substituted compounds were initially synthesized to enforce direct atom-atom contacts and investigate the basic bonding characteristics. 71 The structures typically employ naphthalene or acenaphthalene as spacer groups, but xanthene, dibenzofuran, biphenylene and others are also used to modulate the peri-distance.…”

Excited state dynamics of P-H···H-B and P-H···H-Si hydride-hydride interactions and potential dehydrogenation reactions in frustrated lewis pair

“…interactions and cleaved dihydrogen at room temperature after adjusting the thermodynamics of activation and the degree of preorganization [46]. Unlike the previous report, Beckmann and coworkers reported the P-H (δ−) •••H (δ−) -B and P−H (δ−) •••H (δ−) −Si unconventional dihydrogen bonds in 4-bis(pentafluorophenyl)-borane-5-dimesitylphosphino-9,9-dimethylxanthine (FMB-MP-MX) and 5-dimethylsilyl-9,9-dimethylxanthen-4-yl-diphenylphosphonium cation (MSi-PP-MX) molecules, and proposed that the two dihydrogen interactions were very similar and were of inverse homopolar type H (δ−) •••H (δ−) [47]. This novel hydride-hydride interaction attracts much attention for is further study.…”

“…Previous studies on H (δ−) •••H (δ−) hydride-hydride interaction mainly focused on the activation of small molecules and the bond characteristics (homopolar or inverse homopolar) in FPB-MP-MX and MSi-PP-MX [46,47]. Nevertheless, there are few reports on the photophysical and photochemical dynamics of P-H•••H-B and P−H•••H−Si hydride-hydride interaction upon photoexcitation, and their effects on the possible dehydrogenation reaction.…”