spectra and structure of sulfonium c-dinitro ylides

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  • along the entire C I~ anionoid f ragment and, due to this, an increase in the order of the CN bond (PCN) and a decrease in the order of the NO bond (PNO), although the ratio PNO > PCN, wh ich is characteristic for non- ionized nitro compounds , should be retained here.

    To ascertain the characterist ics of the electronic structure of the CNY molecu le we made a quantum- + chemica l calculation by the SC F MO LCAO method as the C NDO/2 approx imat ion of the molecu les of (CH3)2S- CNO 2 (CN)(I), CH3NO2, CH2(NO2)CN, and their anions (Table 3). For (1) the geometr i c parameterswere aver - aged f rom the x - ray structure analysis data for the molecu les of (CH3)2S-C(CN) 2 [8] and (CGHs)2S-C(NO2) 2 [9]: CNbond =1.4 , NO=1.24A, (ONO=124 ~ .

    The calculated dipole moment of the (1) mo lecu le is high (10.32 D), wh ich is in agreement with the data for the dipole moments of su l fon ium C-yl ides [5]. In the NO 2 group the order of the CN bond is greater than one, but PCN < PNO, wh ich is in agreement with the assumpt ion , * made on the basis of studying the vibrational spectra (see Tab le 3), that in its electronic parameters the NO 2 group in CNY is c loser to the NO 2 group of co- valent nitro compounds , and not their salts.


    Based on the data of the vibrational spectra and quantum-chemica l calculation, in its electronic struc- ture the nitro g roup in su l fon ium C-n i t ro ylides is c loser to the nitro groups in nonionized nitro compounds than in their salts.


    i. K . I . Rezch ikov, O. P. Shitov, A. P. Seleznev, and V. A. Tartakovski i , Izv. Akad . Nauk SSSR, Set. Kh im. , 1129 (1979).

    2. G .F . Whif ield and M. 8. Beilan, Tet rahedron Lett., 3545 (1970). 3. A. McKi l lop , E. A. Sedor, B. M . Culbertson, and S. Wawzonek , Chem. Rev. , 7__3 , No. 2, 278 (1973). 4. K. Wallenfells, K. Fr iedrich, J. R ieser , W. Ertel, and H. Th ieme, Angew. Chem. , 8_88, 311 (1976). 5. B. T ros t and L. Melv in, Chemis t ry of Sulfur Yl ides, Academic P ress , New York (1975). 6. S .S . Novikov, G. A. Shvekhge imer , V. V. Sevost 'yanova, and V. A. Shlyapochnikov, Chemis t ry of

    Aliphatic and Alicyclic Nitro Compounds [in Russian], Kh imiya , Moscow (1974). 7. J .R . Murdoch , A. Streitweiser, and S. Gabriel , J. Am. Chem. Soe., i00, 6338 (1978). 8. A .T . Chr i s tensen and W. G. Wi tmore , Ac ta Cryst . , B25, 73 (1969). 9. V .V . Semenov , L. O. A tovmyan, N. I. Golovina, G. A. Mukh ina , K. Ya. Burshtein, and S. A. She-

    velev, Izv. Akad . Nauk SSSR, Ser. Kh im. , 801 (1981).

    9 Th is assumpt ion is conf i rmed by a pr ior calculation of the f requencies and fo rm of the normal vibrations of n i tro yl ide molecu les .



    K . I. Rezch ikova , 0 . P . Sh i tov , UDC 543.422:541.6:541.49:547.414..547.279.53 V . A . Tar takovsk i i , and V . A . Sh lyapochn ikov

    As a continuation of studying the structure of su l fon ium C-ni t ro ylides employ ing spectroscopLc methods [i] we studied the vibrational spectra of C-dinitro ylides (DNY} of type

    Rl ~+ _

    8--C(N02)2 1~ 1 = R z = CHs, C2H~, CaH~, C~H~, CsH s . /

    R= The exper iment was run the same as in [1]. Our object ive was to in terpret a number of the pr ine ipa l

    v ibrat ion f requencies of DNY molecu les , employing isotopic subst i tut ion, a compar i son of the IR and Raman spect ra (with measurement of the degree of depo lar izat ion of the l ines) , and also the exper imenta l data on the spect ra of the C -monon i t ro yl ides [1] and the l i te ra ture data [2, 3].

    N. D. Zelinskii Institute of Organ ic Chemis t ry , Academy of Sc iences of the USSR, Moscow. Trans lated f rom Izvestiya Akademi i Nauk SSSR, Ser iya Kh imicheskaya , No. 6, pp. 1407-1409, June, 1981. Original ar- ticle submitted August 4, 1980.

    0568-5230/81/3006- 1129 $07.50 9 1982 P lenum Publ ish ing Corporat ion 1129

  • TABLE i. F requenc ies of St retch ing V ibrat ions of NO 2 Group in V ibrat ional Spect ra of Su l fon ium C-D in i t ro Y l ides (Solids, u, cm -i)

    VasNO-' in spectra ~sNO~ in spectra vGN in spectra Compound )

    IR Raman IR { Raman IR Raman !

    (cu , )~ (N02)~ w 8~ v. s

    4- - -

    (CD3) ~S-G (NQ) 2

    + - -

    (C2H5) 28-C (NO2).,

    + - -

    (C3H0 2S-C (NO~) 2

    4- __

    (C~Hg) 28-C (N02)

    4- - -

    (CsH~) 28-C(N02) 2

    t490 s. br 1460 sh

    t485 s 1460 sh

    t486 s


    t494 s

    1502 s

    1492 v. w 1476 v. w

    1492 v. w 1476 v. w

    1498 w t486 w

    1494 w t480 w

    t490 v.w

    1492 w t472 w

    t348 w t275 s. br t265 s. br 1245s, br

    t330w 1285s. br t275s, br 12552. br

    t33,0 w t272 s t258 s t23t s

    t327 w t260 w t24t w t229 s t2 t0 s

    t322 v. w i246 s t226 s t200 w

    t330m t275 s t252 w r


    830 v. w

    835 w

    828 s

    838 V.s

    832 v .s

    822 v.s

    828 s

    TABLE 2. Ranges in the F requenc ies of the St retch ing V ibrat ions of the NO 2 Group of D in i t ro Y l ides , D in i t ro Compounds , and The i r Salts (u, cm -I)

    Compound VasNO2 'vsNOz vCN

    R~R~C (NO2) 2 '[4] RHC(NO2h [41

    / R~ RC(N02) 2 [41


    t500- t460

    1300- t200 t200- t t20

    1400-t380 t340- t330


    t200- t040 t005-818



    1500-1440 t370- t320

    Ana logous to the monon i t ro yl ides, in the spect ra of the DNY the v ibrat ion f requenc ies of the NO 2 group are changed substant ia l ly when compared with the spect ra of var ious nitro compounds and their salts. The ass ignment of the latter is shown in Tab le I.

    In Tab le 2 is compared the ranges in the f requenc ies of the s t retch ing v ibrat ions of the NO 2 group in the DNY with the cor respond ing ranges for the dinitro compounds and their salts.

    As can be seen, accord ing to the proposed interpretat ion (see Tab le i), the ar rangement o rder of the Uas NO 2 and u s NO 2 f requenc ies in the spect ra of the DNY is the same as for the dinitro compounds , but is in the reverse order to these f requenc ies in the salts of the gem-d in i t roa lkanes [4], a l though definite d i f ferences exist between the u NO 2 f requenc ies of the non ion ized dinitro compounds and the DNY. Thus , the Uas bands of the v ibrat ions of the NO 2 group are shifted toward lower f requenc ies when compared wi th the dinitro compounds [4] (see Tab les 1 and 2), wh i le the u s a re not shifted as much.

    S ince the ar rangement o rder of the Uas NO 2 and v s NO 2 f requenc ies is a quite r igorous cr i ter ion of the iomc or cova lent s t ructure for var ious c lasses of nitro compounds [4], then on the basis of interpret ing the f requenc ies of the st retch ing v ibrat ions of the NO 2 group it may be assumed that in the DNY, ana logous to the C -monon i t ro yl ides, the e lectronic s t ructure of the NO 2 group is c loser to that of the NO 2 group in dinitro compounds , and not their salts. However , the effects of a partial delocal izat ion of the negat ive charge of the C a tom and an increase in the order of the CN bond in the DNY are apparent ly substant ia l ly weaker than in the monon i t ro ylides.


  • TABLE 3. Charges on Atoms, Groups, and Bond Orders of Mole- cules of (CH3)2~-C(NO2)2, Dinitromethane, and Its Anion*


    CH2 (NO2) z

    + - (CHa) ~S'-C(NO~)a

    CI~(NQ) 2 0,337

    Charges on atoms

    Cylide N

    0,009 0,497

    --0,t99 0,5t5 --0,055 0,349

    o f


    -0,414 -0,442

    C o mpound

    CH2(N02)2 + --

    (CH3)2S--C(NO~)a CH(N02)2

    l harges on atoms

    NO. ,


    -0,237 -0,477

    C (NO~)


    -0,673 -l,Oi

    Bond order





    t,i37 1,384

    N- -O




    * The obta ined ca lcu la t ion resu l t s a re in agreement w i th the l i ter- a ture data [5].

    Max imum charge on outer O a tom of NO 2 group .

    For a detailed elucidation of the character ist ics of the electronic structure of the DNY we used the SCF MO LCAO method as the CNDO/2 approximation to make a quantum-chemical calculation of the molecules of

    + - -

    (CH3)2S-C(NO2) 2 (I), dinitromethane (DNM), and its anion (Table 3).

    For (I) the geometric parameters corresponded to the averaged data of the x - ray structure analys is of + - -

    the (CH3)2~-C(CN)2 [6] and (C6Hs)2S-C(NO2} 2 [2] molecules: CN bond 1.4, NO 1.22 /k, (ONO = 122 ~ and the SC(NO2) 2 fragment was taken as being planar. The geometric parameters of DNM were averaged from the data on the structure of CH3NO2, CH(NO2)3, and C(NO2) 4 [7]: CN bond 1.495, NO 1.220 A, < ONO = 127 ~ The geo- metry of the DNM anion corresponded to the x- ray structure analysis data for its K salt [8], with the condition that the NO 2 groups are equivalent.

    According to the calculations, the dipole moment value for (I) (1043 D) is in good agreement with the ex- perimental value [2], which permits assuming that the obtained distribution of the charges in the (I) molecule truly reflects the picture of the electron cloud.

    In the DNM, its anion, and (I) ser ies the greatest changes in the charge occur on the C atom. In the ylide molecule it is substantially higher than the corresponding change


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