Correlation among the Gas-Phase, Solution, and Solid-Phase Geometrical and NMR Parameters of Dative Bonds in the Pentacoordinate Silicon Compounds. 1-Substituted Silatranes

Abstract

Silatranes XSi(OCH2CH2)3N exhibit a good linear relationship between their experimental and calculated (IGLO and GIAO) values of the NMR chemical shifts of (15)N, δN, and the lengths of dative bonds Si←N, dSiN, determined in the gas phase (ED, CCSD), solutions (COSMO PBE0, B3PW91), and crystals (X-ray). An aggregate of the obtained data provides strong evidence that the gas-phase value of dSiN in MeSi(OCH2CH2)3N should be greater by ∼0.05 Å than that determined in the electron diffraction (ED) experiment (2.45 Å). Given this condition, a long-standing contradiction between the data of the structural (X-ray, ED) and NMR (15)N experiments for the molecules of 1-methyl- and 1-fluorosilatrane regarding the sensitivity of their coordination contact Si←N to the medium effect is resolved.

Assignment of photoelectron spectra of silatranes: first ionization energies and the nature of the dative Si←N contact

“…30 for the neutral molecule I, is observed also for their open-shell structures I + . 30 for the neutral molecule I, is observed also for their open-shell structures I + .…”

“…30 The information on the ED experimental gas phase structure of ethoxysilatrane 2 is absent in the literature. 30 The information on the ED experimental gas phase structure of ethoxysilatrane 2 is absent in the literature.…”

Electrochemical Oxidation and Radical Cations of Structurally Non‐rigid Hypervalent Silatranes: Theoretical and Experimental Studies

“…Obviously,t he procedure of separation of the gas phase and solvation contributions to DG 0 ox within the approaches (2) and (3) is not appropriate for the silatranes with high sensitivity of the geometry to the media effects. [8][9][10][11] In line with what was mentioned earlier, [3] the proper (that is, affecting the N s )o xidationo f1 3s ilatranes (1a-1c, 1e-1l, 1o,a nd 1r)o ccurs at remarkably more positive potentials (E p = 1.43-2.031 V; Ta ble 3), than that of the model amines in which nitrogeni sn ot involved in the dative N!Si bonding (for example for N(CH 2 CH 2 OH) 3 E p = 0.90 B [3] ). Note that p-H 2 N-C 6 H 4 -silatrane 1m (E p = 0.76 V) should be considered as asilylated anilinew here silatranyl moiety is not concerned by ET and only acts as as ubstituent.…”

“…[32] As am easureo fs trength of the dative N!Si bond in silatranes,a long with the above-mentioned geometrical, energet-ic, electronic, and orbital characteristics, its NMR parameters, particularly,t he values of isotropic 15 Nc hemical shifts (d N )o f the donor nitrogen atom may also be used. [8,9,36] Moreover,t he good linear relationship [9] d N = À252.41À47.07 d SiN (R = 0.99) is common for crystals, gases,a nd solutions of silatranes XSi(OCH 2 CH 2 ) 3 Na ta ny substituent X. [9] This equation allows, using the solution experimentalv alues d N for 1,t oo btain the solution d SiN values and, as shown above,r elativelys urely predict the values of properoxidation potentials of silatranes.…”

“…[8,9,36] Moreover,t he good linear relationship [9] d N = À252.41À47.07 d SiN (R = 0.99) is common for crystals, gases,a nd solutions of silatranes XSi(OCH 2 CH 2 ) 3 Na ta ny substituent X. [9] This equation allows, using the solution experimentalv alues d N for 1,t oo btain the solution d SiN values and, as shown above,r elativelys urely predict the values of properoxidation potentials of silatranes.…”