Full text of DOI:10.1007/BF02659523

L I T E 1 1 A T U 1 1 E C I T E D
1.
2.
3.
A . N . Vereshchagin, S. G. Vul'fson, A . I. Donskova, and V. I. Savtn, Dokl. Akad. Nauk SSSB, 215,
339 (1974).
S.G. Vul'fson, A . I. Donskova, A. N. Vereshchagin, and V. I. Savin, Izv. Akad. Nauk SSS11, Ser.
Khim., 76 (1975).
B . A . Arbuzov, A. I. Donskova, S. G. Vul'fson, and A . N. Vereshchagin, Izv. Akad. Nauk SSS11,
Set. Khim., 1498 (1975).
4.
5.
6.
7.
8.
A . H . Cowley and T. O. Furth, J. Am. Chem. Soc., 91, 39 (1969).
L. S. Bartell, 11. L. Carrol, and J. P. Gullory, Tetrahedron Lett., 705 (1964).
L. S. Bartell and J. P. GuUory, J. Chem. Phys., 43, 647 (1965).
J . P . Pi e rre and P. Arnoud, Bull. Soc. Chtm. France, 1690 (1966).
M . J . Aronsy, K. E. Calderbank, and H. J. Stootman, J. Chem. Soc. P e r k i n Trans., 2 (1973), 1365.
A. de MeiJere and W . Iuttke, Tetrahedron Lett., 2047 (1969).
9.
10.
11.
12.
13.
14.
15.
16.
L. S. BarteIl, J. P. Gullory, and A. T. Parks, J. Phys. Chem., 69, 3043 (1965).
M . T . Rogers and J. D. Roberts, J. Am. Chem. Soc., 68, 843 (1946).
W . H . Flygare, A. Narath, and W. D. Gwinn, J. Chem. Phys., 36, 200 (1962).
A . N . Vereshchagin and S. G. Vul'fson, T e o r . Eksp. Khim., 4, 548 (1968).
C. -Y. Chen and 1t. J. W. LeFewre, J. Chem. Soc., B, 40 (1966).
O. E x n s r and V. Jehli~ka, Collect. Czech. Chem. Commun., 30, 639 (1965).
L . A . Yanovskaya, V. A . Dombrovskii, G. V. Kryshtal', L. G. Vorontsova, M . O. Dekarptlevtch, and
I. P. Yakovlev, Application of Conformationsl Analysis to the Synthesis of New Organic Compounds [in
Russian], Izd. Odessk. Univ. (1975), p. 167.
17.
18.
M . J . Aroney, M. G. Corfleld, and 1t. J . W . LeFevre, J. Chem. Soc., 1964, 648.
P . H . Gore, P. A . Hopkins, 1t. J. W . LeFevre, L. Random, and G. L. 111tchie, J. Chem. Soc., B,
120 (1971).
19.
I.G. Tishchenko, O. G. Kultnkovtch, and Yu. V. Glazkov, Zh. OrE. Khim., 11, 581 (1975).
C O N F O R M A T I O N S O F C E R T A I N
D I A L K Y L A 1 1 Y L P H O S P H I N E S
A N D T H E I R O X I D E S
O. A . 1 1 a e v s k i i , A . N. V e r e s h c h a g i n ,
Y u . A . D o n s k a y a , I. G. M a l a k h o v a ,
Y u . I. S u k h o r u k o ¢ , E. N. T s v e t k o v ,
and M. I. K a b a c h n i k
UDC 541.63:547.1'i18
The energy of p-- ~" coupling in 112EAr aromatic compounds containing an unshared electron pair CUSP) is
determined by two geometrical factors: 1) the valence angles at the hetero atom, which, in turn, are fixed by
the unshared pair hybridization and the energy of pair interaction with the aromatic ring • system [1], and 2)
the spatial ortentstion of the aryl r i n g .
In the course of a study of the dimethyl- and di(tert-butyl)-p-tolylphosphinss
[3], we have shown that both
the f i r s t and the second of t h e s e factors are unfavorable for p-- • coupling in the dialkylarylphosphines, the
situation here being different from that met with the aromatic amines. In fact the unshared pair of the phos-
phorous is coplansr with the benzcyl ring, and accordingly orthogonal to the r system of the latter, a situation
in which the second-power cosine law predicts zero possibility of p-- • interaction.
The present paper will report the results of a study of.~he geometrical structures of dimethylphenylphos-
phine 6), digert-butyl)phenylphosphine (II), dimethyt-p-cyanophenylphosphine C[II), dimethyl-p-tolytphosphine
A . E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Branch of the Academy of Sciences of
the USSR. Translated from Izvestiya Akademit Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2243-2246,
October, 1976. Origiml article submitted August 7, 1975.
o[ this i ~ b ~ t ~
~
be ee~Woduced, stored tn • eetvf~NI xyUem, or mms~itted, in cny [orm or by any magns, ¢~¢¢~mc, mecn~aau, photocopying, I
txavc~bicfrom the publlxt~.for $7.30.
enJoofllveu~ e ~ , ~ l n for otkcewt~, without ~ t t m p~m~lon of'thel~bli~w. A ¢o1~ of th~
~
]
2092

T A B L E 1.
Experimentally Determined Dipole MO-
ments and Double Refractions of the Dialkylaryphos-
phines
Compound
]
Solvent
A,IA~,
aB:B,A~
:~. D
t,2
5,9
6,2
7o6
1.5
4,4
(II)
C,Hxz
0,906
1
I ,,o
(ill)
Dioxane
t4,374
TABLE 2. Dipole M o m e n t s and Double Refractions
of Dialkylarylphosphine Oxides
CornpoundlSolvent
[ ~*IA~ -.~)I"'~ AS#B,A~ p.D
I
(IV)
(V)
(VI)
[
CCI4
14,997
0,628
259
241
t27
4,39
4,85
cc~ ] 27,730 0,485
0,357
DiOxal~ I t5,347
4.6,~
I
oxide (IV), di~ert-butyl)-p-tolylphosphine oxide (V), and dimethyl-p-cyanophenylphosphine oxide NI) based
on measurement of dipole m o m e n t s (DM) and Kerr constants (KC).
The fact that the arylphosphines {/)-(HI) readily oxidize in solution meant that the measured values of
DM's and KC, s of these compounds were less accurate than those of the compounds (IV)-(VI). Dipole m o m e n t s
(table 1) were determined from the coneentrattonal variation of the solution dielectric constant (A~/A#2),
calculation being through a modified Higashi equation [A, 5]; the KC's were determined from the A e l A #z
values and the concentrational variation of the specific K C (AB/Aoz).
in treating the data for (IV)- (VI).
The equations derived in [6] were used
Values of the parameters required for developing the relation between the molar K C and the angle of
aryl group rotation with respect tot h e U S P direction were obtained in the following manner. The C s H s P group
m o m e n t (0.76 D) was determined from the experimentally measured D M for (I), following the method described
in [3]. The m o m e n t of (Ill) was used to determine the polarity of the PC6H4CN- p group. Calculations based on
an additive vector s c h e m e gave the value 3.91 D, while the difference between the m o m e n t s of the C 6 H s P and
benzonltrile (4.04 D) groups was 3.28 D. The interaction m o m e n t of 0.63 D was directed toward the C N group,
thus indicating a certain redistribution of the electron density of the PCsHsCn- p system.* The calculated
values of the KC's for the arylphosphtnss could be sensitive to the orientation of the molecular dipole moment.
The K C for (IV) was therefore calculated by two methods, the one assuming the experimental D M (of. Table 2)
to be directed along the phosphoryl group (A) (a procedure justified by the fact that the radical group m o m e n t s
were essentially identical in value) and the other working from a D M based on the s u m of m o m e n t s of the cor-
responding phosphine [3] and the value m ( P = O ) = 2.98 D [7] (B). Since the results obtained from such calcula-
tions were consistent with the experimental data in both cases (Table 3), work on the other arylphosphine
oxides was carried out by method (A). The A r C N group m o m e n t was set equal to the D M of benzonitrile for
the calculations on (VI). Calculations on the components of the polarizability ellipsoid were based on bond and
group parameters, some of which have been given earlier in [3]. Using the data on the benzonitrile molecular
ellipsoid [8] with correction for the Isotropic polarizability of the C -- H bond, the following va_lues were ob-
tained for the C 6 H 4 C N group polarizability:
~ = 0.65 A~): bi = 15.51; bz --- 10.95; th = 7.50 A 3. Parameter
values for the P = O b o n d were taken from [9].
Calculations were carried out for two positions of the benzene ring, one in which in the dihedral angle
between the bisector of the Csp~-- P-- Csps angle and the plane of the phenyl ring is zero = 0) and the other
~
in which this angle is 90° (~0 ffi 90"). Cbserved and calculated values of the K C are s h o w n in Table 3. C o m p a r -
ison indicates the value of the angle q for the (i) and (II) conformations to be close to 0". The fact that the K C
of (ill) was relatively insensitive to the angle of aryl rotation made it impossible to reach any decision con-
cerning the conformation of this compound. The experimentally determined constant was higher than the
*Decision as to whether this interaction proceeds through direct polar coupling or through competetive coup-
ling from two acceptor groups would require additional experimental data on the D M's of various substituted
arylphosphtnss.
2093

T A B L E 3. Experimental and Calculated Values
of,~he Kerr Constan~ (mK • 1011)
Calculated
Compound[Measured
t i n 0
e
~ m g 0~
3
6
--4
-4
96
9o
-73~^); -.so,2~ )
-...~,7
~,0
44,4
24,9
-.85,9
calculated in this case. The nonadditivity of the KC exaltation indicated interaction between the phosphorous
atoms and the CNgroup, the situation here being s i m i l a r to that pointed out above in the c a s e of the DM's.
Generalizing the data of the present work and that already given in [3], it can be concluded that the spatial
position of the aromatic ring in the dialkyiarylphosphines is such as to eliminate the possibility of interaction
between the unshared electron pair of the phosphorus and the ring • electrons. The data presently available
do not permit a decision concerning the conformation of dimethyl-p-cyanophenylphosphine.
In the four-coor-
dinated analogs of the latter compound, the bisector of the CPC angle is also directed along the plane of the
l:~nzcsrt r i n g .
E X P E R I M E N T A
L
All operations with P(IH) compounds were carried out in an atmosphere of argon. The procedures for
determining the DM's and KC's have been s h o w n earlier in [3].
Dimethylphenylphosphine (I). This compound was prepared from phenylchlorophosphine and CHsMgI;
bp 70-71°C (15 ram); nDZ°l.5650; d42° 0.9662; cf. [10].
Di(tert-butyl)phenylphosphine
(II). To 16.7 g of di(tert-butyl)chlorophosphine [11] dissolved in 50 ml abs.
ether at 20°C there was added a phenyllithium solution prepared by dissolving 2.3 g Lt and 21.8 g CeHsBr in
250 ml ether. This mixture was boiled for 1 h, and 75 ml of a saturated NH4CI solution and 200 ml benzene
then added to it. The organic layer was evaporated downto 100 ml and extracted with concer~ated HCI (3 x
30 ml). The combined extract was then washed with 50 ml benzene,neutralized with a 40~ KOH solution, and
the precipitated oil extracted with benzene (2 ~ 100 ml). The combined extract was washed with water 50 ml
w a t e r , and dried over Na2S04. The solvent was evaporated off in vacuum and the residue distilled. The r e -
suiting mass was held at 90~C for 4 h and once more distilled. Yield of (II) 15.0 g (73%), bp 113-114°C (6 ram);
nD2° 1.5350; d42° 0.9333; found MR 74.15; calculated MR 73.49; cf. [12].
Dlmethyl-p-carbox~phenylphosphine
Oxide. A Grigrmrd reagent was prepared by adding 21.6 g Mg and
154.0 g p-BrCeH4CH ~ to 700 ml ether; to this 72.5 g (CH3)2P(O)C1 dissolved in 250 m[ THF was added dropwise
at 0-2°C. After boiling for 2 h, the mixture was broken down with a saturated NH4CL solution and then acidified
with HCL (1:1). The aqueous solution was neutralized with a saturated NazCC~ solution and extracted with
CHCI s (5 x 50 ml). The combined extract was dried over Na~SO4, the solvent evaporated off in vacuum, and
the residue distiUed. The fraction boiling at 130-1450C (2 ram) was treated with 250 mI water, the insoluble
residue (4.0 g) filtered off, and the filtrate extracted with heptane (2 x 20 rot). The aqueous layer was mixed
with 250 mt pyridine and 248.0 g finely pulverized KMnO4 added, the rate of additionbeing adjusted s o as to
maintain the m i n u t e at the boiling point. Alter additional boiling for 5 h, the pyridine was driven off with
water vapor, and the MnO: filtered off. The result was 43.0 g of a substance with 241-242.5°C rap. After r e -
crystaUization from alcohol--benzene soLution the yield was 37.0 g (28,~); mp 244.5-245°C, cf. [13].
Dlmethyl-F-carbamoylphenylphosphine
Oxide. A mixture of 10.3 g dimethyi-p-carboxyphenylphosphtne
and 12 ml SOCIz in 70 ml THF was boiled for 1.5 h and then allowed to evaporate. The residue was dissolved
in 30 ml THF, and the resulting solution slowly poured into a continuously agitated conce~a~rated NH4OH solu-
tion. The precipitated crystals were filtered off and washed with alcohol. The result was 6.7 g of a substance
with 280-283"C rap. Recrystatlization from methanol solution gave a yield of 4.5 g (44~), mp 288-290°C.
Found: C 54.7; H 6.2; P 1 5 . 5 ~ . C~I120:P. Calculated: C 54.8; H 6.1; P 1 5 . 7 ~ .
Dimethyi-p-cyanophen~lphosphtne
Qxide (HI). To 3.9 g dimethyl-p-carbamoylphenylphosphine oxide 3
ml PCCI3 were added. This mixture was heated for 1 h at 60-70°C, dissolved in 20 mI water, made alkaline
with dry NaOH, and extracted with CHCIs (5 x 10 ml). The combined extract was dried over Na~SO4, and the
2094

solvent evaporated off in vacuum. The yield of (II) was 2.0 g (57%), mp 159-160.5°C (alcohol--benzene)..
Found: C 60.4; H 5.8; N 7.7; P 17.3%. CsHx0ONP. Calculated: C 60.3; H 5.6; N 7.8; P 17.3%.
Dimethyl-p-cyanophen~rlphosphine.
A solution containing 6.9 g dimethyl-p-cyanophenylphosphlne oxide
and 11 ml SfHC 13 dissolved in 100 ml benzene was boiled for 2 h and then cooled; to it there was then added
9 ml SiHC13 and boiling contiraled for another hour. The resulting mixture was broken down with a 40% KOH
solution, the organic layer separated off, washed with water, and dried over NapqO4. The solvent was eva-
porated off in vacuum, and the residue distilled. The yield was 4.2 g (65%), bp 104°C (3 mm) (mp 36-37"C,
thermometer in mass). Found: C 66.3; H 6.2; P 19.0%. CgH10NP. Calculated: C 66.4; H 6.2; p 1 9 . ( ~ .
The syntheses of Q'V) and (V) have been described in [13,14].
C O N C L U S I O N S
It is characteristic of the conformations of the dialkylphenylphosphines and their oxides that the bisector
of the C P C angle lies in the plane of the benzoyl ring.
L I T E R A T U R E C I T E D
I.
E . N . Tsvetkov and D. I. Lobanov, Chemistry and Applications of Phosphorganic Compounds [in Rus-
sian], Nauka (1972), p. 160; E. N. Tsvetkov, D. I. Bochvar, and M. I. Kabachnik, Teor Eksp. Khlm.,
3, 3 (1967); E. N. Tsvetkov and M. I. Kabachnik, Usp. Khim., 40, 177 (1971).
E . N . Tsvetkov, Zh. Obshch. Khim., 45, 490 (1975).
2.
3.
O . A . Raevskii, A. N. Vereshchagin, Yu. A. Donskaya, F. G. Klmlitov, I. G. IV[alakhova, and E. N.
Tsvetkov, Izv. Akad. Nauk SSSR, Ser. Id~im., 453 (1974).
4.
5.
K. Higashi, Bull. Inst. C h e m . Res. Kyoto Univ., 22, 805 (1943).
R.S. Armstrong, M. J. Aroney, R. W. LeFevre, R. K. Pierens, J. D. Saxby, and C. J. Wilkins,
J. C h e m . Soc., A, 2735 (1969).
6.
7.
E . A . Guggenheim and J. E. Prue, Physicochemical Calculations [Russlantranslation], Inostr. Lit.
(1958), p. I00.
C . G . LeFevre, and R. J. W . LeFevre, Physical Methods of Organic Chemistry, Vol. I, Interscience
(1960), l~rt 3, p. 2459; E. A. Ishmaeva, A. N. Vereshchag~n, N. A. Bondarenko, G. E. Yastrebova,
and A. N. Pudovfk, Izv. Akad. Nauk SSSR, Ser. Khlm., 2695 (1970).
8.
9.
R . J . W . LeFevre, Advances Phys. Org. Chem., 3, I (1965).
B . A . Arbuzov, R. P. Arshinova, A. N. Vereshchagin, and S. G. Vul'ison, Izv. Aired. Nauk SSSR,
Set. Khim., 1964 (1973).
10.
E . A . Yakovleva(Jakoleva), E. N. Tsvetkov, D. I. Lobanov, M. I. Kabachnik, and A. I. Shatenstein,
Tetrahedron Lett., 4161 (1966).
11.
12.
13.
14.
W. Voskuil and G. F. Arena, Rec. T r a y . Chim., 82, 302 (1963).
B . E . Mann, B. L. Shaw, and R. M. Slade, J. Chem. Soe., A, 2976 (1971).
I.G. Malakhova, E. N. Tsvetkov, and M. I. Kabachnik, Izv. Akad. Nauk SSSR, Ser. Khim., 1842 (1974).
I.G. Malakhova, E. N. Tsvetkov, and M. I. Kabachnik, Izv. Akad. Nauk SSSR, Ser. Khim., 174 (1975).
2095