Organosilicon Radical Cations

Infrared Spectrum of the Si3H8+ Cation: Evidence for a Bridged Isomer with an Asymmetric Three‐Center Two‐Electron SiHSi Bond

“…The IRPD spectrum of Si 2 H 6 + confirms that ionization from the HOMO of oligosilanes is achieved by removal of an electron from the bonding s SiSi orbital, [22] as evidenced by photoelectron spectra of Si x H 2x + 2 . [16] However, in addition to the most stable H 3 SiÀSiH 3 + structure with D 3d symmetry, a bridged structure with a 3c-2e bond of the type [H 2 Si À H À SiH 3 ] + was predicted to be only around 15 kJ mol À1 less stable. [22] The most stable structure of protonated disilane, Si 2 H 7 + , indeed features such a nonlinear 3c-2e bond, which is generated either by addition of SiH 4 to SiH 3 + or by proton insertion into the SiÀSi bond of Si 2 H 6 .…”

“…Despite their importance, little spectroscopic data has been reported so far for Si x H y (AE) , mainly due to the limited availability of suitable stable precursors. Early low-resolution photoelectron spectra of the smallest oligosilanes, Si x H 2x + 2 with x = 1-5, [16] do not provide any structural information. Until recently, the only structure-sensitive spectroscopic data available for Si x H y + has come from IR spectra of cations with a single Si atom (x = 1), including SiH 3 + , [17] SiH 5 + , [18] SiH 7 + , [19] SiRA C H T U N G T R E N N U N G (CH 3 ) 2 + with R = H/CH 3 , [20] and protonated phenylsilane.…”

First ionization potentials and conjugation in molecules of ethylene derivatives containing organoelemental substituents of Group IV elements

“…The experimental li cxp values for compounds 1--8 and 9--10 were taken from Refs. 28 The ~,I I differences considered as an indicator of nonadditivit3' of the effect of two X substituents on the li values of trans-XHC=CHX molecules can be either negative (if cv+(X) < O, i.e., if the substituent exhibits an overall donor electron effect) or positive (if c,* > 0).…”

Paramagnetic intermediates in the photoinduced reaction between dodecamethylcyclohexasilane and 9,10-phenanthraquinone: Time-resolved CIDNP study

“…In recent decades, many research groups have explored this area, and a vast pool of the experimental data obtained have been summarized and analyzed in the detailed results with the discussion of the possible investigation prospects (see, e.g., [1][2][3][4]). Different methods used to generate and to investigate short-lived silicon-centered radical cations and radical anions include ESR [5], cyclic voltammetry [6], preparative electrolysis [7], electron impact [8], c-irradiation [9], photolysis in highly polar media [10], etc.…”

“…Photoinduced reactions of cyclic oligosilanes and quinone 2 have been earlier studied in the polar and nonpolar media -acetonitrile and benzene [18]. In both solvents, the formation of 2,2 0 -dimethylphenanthro [9,10-d] [1,3,2]dioxasilole 4 has been observed -formal product of the transfer reaction of dimethylsilylene Me 2 Si: 3. It was assumed [18] that the first step of the photoinitiated reaction in both polar and nonpolar media is the triplet excitation of quinone 2.…”