Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

Egorochkin, A. N.; Skobeleva, S. E.; Bogoradovsky, E.T.; Zubova, T. P.

doi:10.1007/bf01558061

Cited by 3 publications

(3 citation statements)

References 11 publications

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“…Hence, the Koopmans approximation (4) is too rough for these compounds. However, it is likely that the conjugation in M § is satisfactorily described by na + constants taking into account the resonance component of R and C contributions in formula (3). Therefore, cr !…”

Section: Resultsmentioning

confidence: 95%

Conjugation in radical cations of benzene, ethylene, and acetylene derivatives. Nonuniversality of the resonance parameters of group 14 organoelement substituents

1998

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The first vertical ionization potentials I t of molecules R~X (X = Ph, H2C=CH , and HC~-C) depend on the joint influence of the inductive, resonance, and polarizability effects of substituents X, which are characterized by parameters al, ~R +, and aa, respectively. The mechanism of conjugation in radical cations formed upon ionization of I~X is changed as compared to neutral R~X molecules, while the substituent X becomes polarized. The conjugation and polarizability effects are strenthened in the sequence Ph < H2C=CH < HC~C as I~ changes from Ph to H2C=CH and HC-~C. The a~. + parameters of Si-, Ge-, and Sn-containing substituents X are dependent on the type of R, but are connected by linear dependences in the series of benzene, ethylene, and acetylene derivatives.Key words: ionization potential, radical cations, conjugation, polarizability, group 14 substituents, non-universality of resonance parameters.The mechanism of conjugation of organoelement substituents MR 3 (M = Si, Ge, Sn, and Pb; R are organic radicals) with indicator centers Rn (Ph, H2C=CH, HC=C, furyl, thienyl, etc.) in compounds R~MR 3 is more complex than that in organic derivatives R,tR. t The substituent MR 3 exhibits simultaneously acceptor (d,Tt-conjugation, i.e., the interaction of nd orbitals of M and a*-orbitals of the M--C bond with 1~) and donor (a,rt-conjugation, Le., the interaction of a-orbitals of the M--C bond with R~) properties toward the R.~ fragment. Only a,n-conjugation occurs in coml~ounds R~CH2M R3. tThe quantitative characteristics of conjugation, i.e., parameters ~R ofsubstituents MR 3 and CH2MR3,1'2 are not universal al~d depend on both the type of fragment R~ and charges on its a(oms, hi the case of a small charge on R~ (0.01e; H-complexes of R~MR 3 and R~CHaMR 3 with phenol) and a large charge (>0.9e; the excited state of R~MR 3 complexes with iodine and tetmcyanoethylene), the degree of conjugation in isolated neutral molecules is characterized by parameters aK ~ erR, and erp+, respectively, which can differ in both magnitude and sign. The main reason for these distinctions is the dependence of a,~-conjugation on the charge on R~. I-6 These problems were studied in detail for benzene derivatives (R~ = Rh) t-7 and only fragmentarily for compounds with other type of R~ 1.3-s,s because of scarce information on the experimental values of aR ~ erR, and aR +. Recently, s we have shown that information on the aR + parameters of substituents can be obtained from the first vertical ionization pote~tials /~ of organoeleme~at compounds.

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Section: Resultsmentioning

confidence: 95%

Conjugation in radical cations of benzene, ethylene, and acetylene derivatives. Nonuniversality of the resonance parameters of group 14 organoelement substituents

1998

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“…(9) and (10) for the compounds studied allows us to consider the change in the energy of the HOMO formed from the eig orbitats of the unsubstituted benzene as a result of both the indue-tive and the resonance effects of the substitttents. (9) and (10) for the compounds studied allows us to consider the change in the energy of the HOMO formed from the eig orbitats of the unsubstituted benzene as a result of both the indue-tive and the resonance effects of the substitttents.…”

Section: Resultsmentioning

confidence: 99%

The first ionization potentials and conjugation in benzene derivatives containing organosilicon, organogermanium, organotin, and organolead substituents

Egorochkin

Skobeleva²,

Mushtina³

1997

Russ Chem Bull

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The inductive and resonance effects of silicon-, germanium-, tin-. and lead-containing and some organic substituents on the HOMO energies (EHoMO) for 43 monosubstituted and p-disubstituted benzene derivatives were analyzed in the Koopmans approximation. A linear dependence between the perturbation energy 6E and the resonance err § parameters of the substituents was established. The Koopmans approximation is a rough approximation for the compounds studied, since to provide for its rigorous fulfilment, the 6E values must depend on the ~R ~ parameters of the sulgstituents. The principal regularities of increasing the or,n-conjugation between the organoelement substituents and the n-system caused by a positive charge on the benzene ring were established.

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“…Equation (9) can be used to assess the /(Si--Si) values for the X3Si--SiX 3 compounds with known values of c~ 1 and G a constants of substituents X. We used dependence (9) in the foml /(Si--Si) = I 0 + In + P (10) for calculating the inductive and polarizability contributions (In = 0.86Z~ I and P = 0.70Z%~, respectively) to the changes in the /(Si--Si) values of molecules l--Z0.…”

Section: Ref 23)mentioning

confidence: 99%

Substituent effects in radical cations of linear oligosilanes

et al. 2000

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The dependence was analyzed of the firsl ionization potential l(Si--Si) corresponding to detachment of an electron from the ~(Si--Si) highest occupied molecular orbital on the parameters of organic (X = *%, Et. Bu t . Ph, CH=CH~), inorganic (X = F, CI, Br), and organosilicon (X = SIR.:; R is organic radical) substit~ents in eli-, tri-, and tetrasilanes X:~SiSiX 3. It was fotmd by correlation analysis that out of the tl~ree possible effects of substiments X (the inductive, polarizability, and resonance effects), only the first two of them affect the /(Si--Si) values. This means that no conjugation between the substituent X and the radical cation center occurs in X3Si "e-SiX 3.Key words: linear oligosilanes, ionization potential, radical cations, substituent effi:cts.The electronic structure of linear polysilanes R--(SIR2) --R (n > 2) that currently find a wide field of application has been studied in detail, t-6 Theoretical studies of these compounds are of great importance for re~ealing the peculiarities of the Si--Si chemical bond and tbr sol~ing actual problems of the chemistry, of organoelement compounds (in particular, for development of the modem concept of conjugation in the compounds of the silicon subgroup eiemcntsL According to the current concept, 7 organoelement substituents M R 3 (M = Si, Ge, Sn, Pb: R is organic radical) in R.,MR 3 molecules exhibit simultaneously resonance donor and resonance acceptor properties toward the =-electron centers R= (C6H s, I-I.,C=CH, HC~:C. etc.). The resonance acceptor effect (d-,~-conjugation) is due to the interaction of the vacant nd-orbitals of the M atom and antibonding cs*-orbitals of the M--R bonds with the orbitals of the R, fragment. This effect decreases as the atomic number of the M atom increases, i.e., in the series Si > Ge > Sn > Pb_ The resonance donor effect (o.r~-conjugation), which is due to the interaction of the cs-orbitals of the M--R bonds with the orbitals of the R,. fragment, increases as the number of the M atom increases (Si < Ge < Sn < Pb). In the RxCH2MR 3 molecules, d,~-conjugation is absent, while ~,=-conjugation with R involves the r of the C--M bond of the CHuM fragment. Both resonance effects are present in R SiR2SiR 3 compounds, namely, d,a-conjugation with the ~-electron system <3t" R~, involves the orbitals of the SiR, fragment, while ~,rt-conjugation occurs involving the r of the Si--Si bond. These regularities are characteristic of the abovementioned neutral systems in the ground electron state.At small perturbations, e.g., in the case of the fommtion of a H-complex of the ~-donor center R with an acceptor molecule ('phenol, pyrrole, etc_), the effective negative charge of the R fragment is somewhat decreased (by n = 0.01e), which increases o,=-conjugation. Appreciable decrease (n = O. le) in the negative charge on the R~ substituent (e.g., in tile excited state of rt,r,-type charge-transfer complexes of R~MR 3 and R,CH2M R 3 molecules with tetracyanoethylene) leads to a sharp increase in ~.a-conjugation. v-t~We have developed a ne...

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Charge control in the formation of complexes of phenol with unsaturated compounds containing organometallic substituents from group IV

Cited by 3 publications

References 11 publications

Conjugation in radical cations of benzene, ethylene, and acetylene derivatives. Nonuniversality of the resonance parameters of group 14 organoelement substituents

Conjugation in radical cations of benzene, ethylene, and acetylene derivatives. Nonuniversality of the resonance parameters of group 14 organoelement substituents

The first ionization potentials and conjugation in benzene derivatives containing organosilicon, organogermanium, organotin, and organolead substituents

Substituent effects in radical cations of linear oligosilanes

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