I N V E S T I G A T I O N O F f l - S T Y R Y L A N D P H E N Y L

D E R I V A T I V E S O F P H O S P H O R U S BY T H E

M E T H O D S O F O P T I C A L S P E C T R O S C O P Y

R . R . S h a g i d u l l i n , A . V. C h e r n o v a , V. S. G a l e e v , a n d Y a . A. L e v i n

UDC 543.42:661.718.1

It is known that the methods of optical spec t roscopy are among the most sens i t ive to effects of con- jugation. The c h a r a c t e r i s t i c s of conjugation a r e an inc rease in the intensi t ies of the l ines of the c o r r e s - ponding c h a r a c t e r i s t i c v ib ra t ions in the Raman spec t r a [1] and a ba thochromic shift of the absorpt ion m a x i - mum in the UV spec t ra , f requent ly accompanied by an i nc rea se in the intensi ty of the band [2].

In the las t decade, the invest igat ion of organophosphorus compounds by t h e method of UV s p e c t r o - scopy has been conducted r a t h e r widely. However, the avai lable l i t e r a tu re data a r e somewhat con t rad ic - to ry . In ce r ta in invest igat ions, [3, 4], the authors indicate the absence of conjugation between the phospho- rus a tom and the benzene r ing bonded to it. We should emphas ize that they draw the i r conclusions on the bas i s of a study of the secondary band of benzene (1LB), which, as is we l l known, is l e ss sensi t ive to r e - sonance ef fec ts [5]. Actually, an invest igat ion of the p r i m a r y band of benzene (ILA) indicated the p r e sen ce of a modera te ly s t rong conjugation between the phosphorus a tom of the phosphoryl group and the benzene r ing [6-8]. In addition, the authors of [9], who studied the UV spec t r a of ce r t a in unsa tura ted organophos- phorus compounds containing a vinyl group, d i rec t ly adjoining the 3- and 4-coord ina ted phosphorus a toms, did not o b s e r v e a ba thochromic shift of the absorpt ion band.

No sys t ema t i c invest igat ion of organophosphorus compounds by the method of Raman spec t roscopy has been conducted. The individual studies avai lable in the l i t e r a tu re [9, 10], a re evidence of the absence of any s i g n s of conjugation in the Raman spec t r a . However, in an inves t igat ion of organophosphorus c o m - pounds containing a diene group toge ther with the phosphorus atom, we obse rved the expected optical s igns of conjugation [11]. Continuing this invest igat ion we studied the UV s p e c t r a and Raman s p e c t r a of f l -s tyryl and phenyl de r iva t ives of phosphorus .

In the Raman s p e c t r a of f i -s tyryl de r iva t ives of phosphorus, two lines a r e obse rved in the region of the va lence v ibra t ions of the double bond v C = C and VAt (Table 1 and Fig. 1). Table 1 p r e s e n t s t h e s u m - m a r y integral intensi ty of these l ines (IM), s ince t h e l ines over lap for ce r t a in compounds (2, 5, 7, and 13). A compar i son of the data obtained shows that as we go f r o m s tyrene to i t s phosphorus der iva t ives , r e g a r d - l e s s of the va lence s ta te of phosphorus , a 3 - 6 ' f o l d inc rease in the intensi ty of the indicated l ines is ob- se rved . The inc rease in the intensi ty in genera l is a l i t t le s m a l l e r than the effect produced by the acetyl group inthe spec t rum of benzalacetone (compound 13), but quite comparab l e with it. The degree of i nc rease in I M depends on the nature of the subst i tuent at the P atom. The introduction of Cl (compounds 6, 8, and 10) is accompanied by an i nc rea se in the intensi ty of the l ines v C c ' e spec ia l ly apprec iab le for compounds 8 and 10. T h i s ag r ee s with the conceptofd~r-p~r conjugation, s ihce-the e lec t ronega t ive Cl a tom should in- c r e a s e the accep to r p r o p e r t i e s of the d -o rb i t a l s of phosphorus [13]. T h e r a t h e r l a rge d i f ference be tween the spec t r a of compounds 6 and 8 can probably be explained by the fact that ~r-bondingin the P = S bond is a p p r e c i a - bly s m a l l e r than in P = O [14]. This p r o m o t e s conjugation of P withthe s ty rene group in the der iva t ive of thiophos- phonic acid (compound 8). The low intensi ty of the band v C = C of d i e thy l -~ - s ty ry l phosphonate (compound 1) may be a s soc ia t ed with the in terac t ion of the unshared pa i r s of e lec t rons of the e s t e r oxygen with the vacant d -orb i ta l s of phosphorus [15]. In a cco rd with this , a~ d e c r e a s e in the number of e s t e r groups: (compounds 2 and 3) or a

A. E. Arbuzov Ins t i tu te of Organic and Phys ica l Chemis t ry , Academy of Sciences of the USSR. T rans l a t ed f r o m Izves t iya Akademii Nauk SSSR, Ser iya Khimicheskaya, No. 6, pp. 1168-1172, June, 1971. Or ig inal a r t i c l e submit ted August 21, 1969.

�9 1971 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00.

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TABLE 1. Spectral P a r a m e t e r s of T r a n s - 3 - s t y r y [ Derivatives of Phosphorus and Model Compounds C6H~CH= C H - R

o

d Z

3 /, 5 6 7 8 9 i0 t1 12 t3

R--

P (O)(0C2H,)2 PH (0)(0C2H~) P (0)(C=H~)(00,H0 P (0)(0CH=CH~)(0C,HD P (0)(0CH=CG]=)(0C,H~) P (O)Cl, P (S)(0C~H~)~ P (S)Cl~ P (OC~H0,

CH, [12] C (0)CH=

Raman spectra

" v C = C , . ~ v~*cm -I U~

VAr'Cm ~(I~176 X t0-9 X 10 ~ )

1621 1602(245) 968 (19) 1616 1602 (282) i6o2 (22) 16t3 t600 (29t) i002 (37) 16i6 t600(304) i6o3 (32) t6t8 1604 (328) 1006 (25) 1604 1569 (385) 1006 (30) 1618 1606 (264) 1002 (t8) 1600 t570 (660) 998 (34) 16t4 1578 (32~) 16o2 (30) 1600 t572 (616) 1003 (35) t63t t600 (89) 994 (20)

1628 t6t2 (592) 1660

UVspectra, kma x, mn (ig e)

'B XLA

211 (4,63) z~Y (a.~l~ 212(4,66) z~l(~ ~1) I 2t i (4.66~ 269 (4'66) 212 (4.70) 259 (4'69) 211 (4.80) 260 (4~70~

211 (&fi3) I Z~U (~,~'I) 2i6 (4 56) I 272 (4 50) 2~ (4'54) I 259 (4:46) 2i6 (4'.~5} I 27i (4_52~ 207 (~,74) I ~t~ (a.qm

2i9 (4,58) 2an (~160~ J

*L B

294 (3,54) 295 (3 56) 294 (3~) 295 (3,54) 295 (6,74) 298 (3,85) 294 (3,99) 301 (4 t4) 29~ (4'03) 298 (3'97) 29t (3'12) 288 (a',oi)

* Notation of the vibration according to [13].

/00

@" 60

I

500 600

Fig. i,

l l E i I �9 r l l~i i i i 7go 8go MgO iqoo /6"00 3oog r cm

Raman spectra: s o l i d - C6HsCH= CHPH(O)(OC2H5); dot- ted - C6HsCH = CH 2.

switching of the unshared pai r of e lectrons of the es ter oxygen to resonance with the vinyl group (compounds 4 and 5) leads to an increase in the intensity of the investigated bands.

The data obtained for derivat ives of t r ivalent phosphorus are interesting. The substantial increase in I M of f l -s tyryldichlorophosphine (compound 10) in compar ison with diethyl-f i -s tyryl phosphonite (com- oo

pound 9), supports a dTr - p ~ - m e c h a n i s m of conjugation. If the unshared pair of e lect rons of the P atom part icipated in conjugation [16], the introduction of electronegat ive C1 should hinder the interaction and lower the intensity of the lines under discussion. The available l i terature data, obtained by the method of corre la t ion analysis [16], agree with this conclusion. It is unexpected that I M for derivatives of t r ivalent phosphorus lies at the upper limit of the measured values. According to [16] we should have expected that t r ivalent phosphorus should show the least ability for conjugation. From Table 1, which also presents I M of the pulsational vibrations of the phenyl r ing u 1 ~ 1000 cm -t, it is evident that this quantity exhibits con- s iderably less sensi t ivi ty to changes in the s t ructure .

In the UV spect ra of the compounds under discussion, three bands are observed, !B, 1LA, and 1L B. The band 1B has a vibrational s t ructure; ),max, cited in Table 1 denotes the approximate center of the group of bands. The most convenient for observation, both with respect to position in the spec t rum and with r e s - pect to intensity, is the band 1L A. Resonance effects play the predominant role in changes in this band [5]. As we go f rom styrene and t r ans - f l -me thy l s ty r ene (compounds 11 and 12) to its phosphorus-containing de- r ivatives, a bathochromic shift of the band ILA, reaching a maximum value for dichlorides of f i - s tyry lphos- phonic (compound 6) and thiophosphonic (compound 8) acids and f i-s tyryldichlorophosphine (compound 10), is observed. The same interrelat ionship is observed between the bathochromic shift and the nature of the substituent as in the Raman spectra : the bathochromic shift Xma x in the ser ies of phospho derivatives in- c reases in the same sequence: 1 ~ 2, 3, 4, 5, 9, 7 - - 6 - - 10, 8 (see Table 1).

Table 2 presents the frequencies and integral intensities of the most shor t -wave band of the valence vibrations of the benzene r ing in the Raman spec t rum and Xmax of the K-band (or ILA) in the UV spectrum for a number of phenyl derivat ives of phosphorus. A compar ison of the data obtained shows that as we go

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TABLE 2. Spectral P a r a m e t e r s of Toluene and PhenyI Der iva- tives of Phosphorus CsHsR

R--

P(O)(OC~Hs)~ P(O)(OC~Hs)(C~Hs) P(O)CI~ P(OCsHs)~ PCls CeHsPCI CHs

,Ar,Cm"

1600. 1593 1592 1608 1585 1586 1605

UV spectra, Raman spectra [<.-band

/~.10 -4 %, cm _1

t002 100t 1004 t008

t6 t003 t004 t004

/~.10-4 ~.max,nIn (lg ~)

12 13 17 14 2o

~210 (4,29) ~2i0 (4,28)

222 (4,29} ~2i5 (4,30}

234 (4,38} 230 (4,53) 207 (4,26}

f rom toluene to phosphorus-containing derivatives, an increase in the intensities of the lines in the Raman spec t rum is observed, accompanied by an increase in the baLhechromic shift in the UV spect rum in the same sequence as for derivat ives of f i -s tyrene: 1, 2, 4 ~ 3, 5, 6. The intensity of the pulsational v ibra - tions of the benzene ring (see Table 2), just as for f i -s tyryl derivat ives of phosphorus, is considerably less sensit ive to the influence of substituents at the P atom. In this case, its changes obey the same principles as the other pa ramete r s .

E X P E R I M E N T A L M E T H O D

1"he Raman spec t ra were obtained on an ISP-51 instrument with a F]~P-1 photoelectric attachment (width of the entrance slit 0.06-0.03 mm and exit slit 0.070-0.040 mm). The integral intensities of the lines were obtained in a scale of cyclohexane and calculated per mole [10]. The relat ive e r r o r in the de termina- tion of the intensity is ~15%. The UV spect ra were obtained on an SF-8 instrument. The solutions were prepared in n-hexane with a concentrat ion N5 �9 10 -2 M. On account of the s trong oxidizability of derivat ives of t r ivalent phosphorus, the preparat ion of the solutions and filling of the cuvettes were per formed in a chamber filled with dry argon.

The synthesis of the investigated compounds was described in [17, 18], the constants corresponded to the l i te ra ture data. The t r a n s - s t r u c t u r e of f l -s tyryl derivatives is shown in [19].

C O N C L U S I O N S

1. In f l - s tyry l and phenyl derivatives of phosphorus, the intensities of the lines of the Raman spec- t rum a r e increased, while the maxima of the UV bands are shifted bathochromical ly in compar ison with s tyrene and toluene, respect ively .

2. The increase in the intensities and shifts of the bands depend on the nature of the substituents at the phosphorus atom and agree with the conception of dlr-pTr-conjugation.

L I T E R A T U R E C I T E D

1. P . P . Shorygin, Uspekhi Khimii, 19, 419 (1950). 2. A. Giliem and E. Stern, Electronic--Absorption Spectra of Organic Compounds [Russian translation],

IL (1957), p. 96. 3. H . H . Jaffe and L. D. Fredman, J. Amer . Chem. Sot . , 74, 1069, 2930 (1952). 4. M. Arshad and A. Beg, Samiuzzaman, Tetrahedron, 24, 191 (1968). 5. Yu. A. Zhdanov and V. I. Minkin, Correla t ion Analysis in Organic Chemis t ry [in Russian], Izd-vo

Rostovsk. Un-ta (1966), p. 411. 6. H . H . Hsich, PhD Thesis , Universi ty of Pi t tsburgh (1964). 7. J . H . Monagle, J. V. Mengenhanser, and D. A. Jones, J. Organ. Chem., 32, 2477 (1967). 8. C . E . Griffin and R. A. Polsky, J. Organ. Chem., 26, 4772 (1961). 9. E . M . Popov, E. N. Tsvetkov , Chang Jung-yu, and T. Ya. Medved, Zh. Obshch. Khim., 32, 3255

(1962). 10. Ya. S. Bobovich and V. V. Perekalin, Dokl. Akad. Nauk SSSR, 127, 1239 (1959). 11. R . R . Shagidullin, A. V. Chernova, E. A. Ishmaeva, and A. N. Pudovik, Dok[. Akad. Nauk SSSR,

175, 135 (1967); Izv. Akad. Nauk SSSR, Ser. Khim., 1123 (1966).

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12. C . G . Oberberger, D. Tanner, and E. M. Pearce, J. Amer. Chem. Soc., 35, 4566 {1958). 13. H .A . Szymanski, Interpretation of Infrared Spectra, New York, Vol. 1 (1964), p. 81. 14. R. Hudson, The Structure and Mechanism of the Reactions of Organophosphorus Compounds [Russian

T(ranslation], Mir (1967), pp. 74, 94, 102. 15. C . N . Rao, J. Ramachandran, and M. S. C. Jan, Nature, 183, 1475 (1959); M. A~ Weiner and G.

Pasternak, J. Organ. Chem., 32, 3707 {1967); H. Goetz, F. Nerdel, and W. A. Wiechil, Liebigs, Ann. Chem., 665, I (1963); H, Schindlbauer, Monatsh. Chem., 105 (1963); H. Schindlbauer and V. H[ezensauer, Monatsch. Chem., 1196 (1967).

16. E . N . Tsvetkov, M. M. Makhamatkhanov, and M. I. Kabachnik, Teoret. i l~ksperim. Khimiya, 3, 824 (1967); E. N. Tsvetkov, D. I. Labanov, and M. I. Kabachnik, Teoret. i ]~ksperim. Khimiya,-1, 729 (1965); 2, 458 (1966).

17. Ya. A. LevFn and V. S. Gaieev, Zh. Obshch. Khim., 37, 1327, 1872, 2736 (1967). 18. Methoden der Organishen Chemie Bd. XIt/1, Teiel, Georg. Thieme Verlag, Stutgart (1963). 19. T . N . Timofeeva, B. I. Ionia, Yu. L. Kleiman, N. V. Morkovich, and A. .4. Petrov, Zh. Obshch.

Khim., 38, 1255 (1968).

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