J . Phys. Chem. 1989, 93, 2280-2284
2280
Charge Distribution on Benzene Determined from Infrared Band Intensities by a New Equation Minoru Akiyama,* Yukari Shimizu, Hisato Itaya, Department of Chemistry, Rikkyo (St. Paul's) University, Nishi Ikebukuro, Toshimaku, Tokyo 171, Japan
and Masato Kakihana Department of Chemistry, The National Defense Academy, Hashirimizu, Yokosuka 239, Japan (Received: April 20, 1988; I n Final Form: July 28, 1988)
When the absolute intensities of the infrared absorption bands are measured in condensed phases, the observed values must be corrected for the effect of the so-called internal electric field. For such correction, the Bakhshiev and Crawford (BC) equation has been commonly used, but recently, we derived a new equation by adapting the same Lorentz field used in the derivation of BC. In this study, the validity of our new equation was verified experimentally by measuring the nonplanar band intensities of benzene and its deuterium derivatives in the gas and solution states. The observed values were corrected in two ways according to our equation and the BC equation, and the effective charge on the hydrogen atom qH of benzene was evaluated from the corrected values. The qH value from our equation was in good agreement with the results calculated by the simple classical model on solute-solvent interactions.
Introduction
The infrared absorption spectra can provide information on several physical properties such as band frequencies, intensities, and band shapes; and from these properties we can determine several molecular parameters. In such a determination, however, the observed values must be corrected for the effect of the so-called internal electric field, because the internal field acting directly on molecules, the microscopic field, is different from the applied macroscopic electric field. An equation that makes this correction on the band intensity was first derived by Chako,' where the author adapted the Lorentz model* for the internal field. Polo and Wilson3 showed that Onsager's field4 also leads to the same equation for the relation between the intensities in the liquid and gas phases. However, their equation neglects the anomalous dispersion of the refractive index in the region of the absorption band, and therefore its usefulness is restricted to rather weak absorption bands. Then, Bakhshiev and co-workers5 rigorously took into account the frequency dependence of the refractive index. They introduced a complex refractive index, used the Lorentz internal field, and derived the equation that yields the corrected band intensity A,, from the observed intensity Aobsd. Crawford and co-workers6-* also derived the same equation (hereinafter called the BC equation) and then applied this BC equation for determination of the corrected optical constants of some liquids using the method of attenuated total reflection. The correction gave reasonable results for both band intensities and band shapes. The BC equation is identical with the Polo-Wilson equation when the refractive index is constant. It is commonly accepted that one must make a correction for the internal field effect according to the BC equation for the observed bands. However, recently we derived a different equation, although we used the same internal field (Lorentz model) The object as employed in the derivation of the BC
of the present study was to verify experimentally the validity of our new equation. We have already shown in ref 12 and 13 that for planar molecules, effective charge distributions can be determined accurately from their nonplanar band intensities, because the charge derivatives for the nonplanar modes vanish on account of the molecular symmetry. In the present study, the intensity measurements of the most intense nonplanar fundamental band arising from the umbrella mode (u band) were carried out for benzene and its deuterium derivatives in the gas phase and in dilute solutions of CS2 and n-hexane (C6H14). The Aobsd values were corrected in two ways, one according to our equation and the other according to the BC equation, and the effective charge on the hydrogen atom qH of benzene was evaluated from the A , values. Our equation and the BC equation gave different results for q H values. In order to judge which result was better, we carried out the calculation of solute-solvent interactions for qH determination based on the simple classical m0de1.l~ The result supported the validity of our equation. The difference in the band intensities observed in various phases is considered to arise from two effects.15 One is the change in the internal field, and the other the change in the molecular parameters, such as the force constants and effective charges. The first effect can be eliminated by the internal field correction. Then, the second effect can be determined from the A,, values. These molecular parameters are quite informative for understanding the intermolecular interactions in various phases. Therefore, it is very important to deal with the internal field effect correctly.
( I ) Chako, N. Q . J . Chem. Phys. 1934, 2, 644. (2) Lorentz, H. A. The Theory of Electrons; Dover: New York, 1952; p
Derivation of the New Equation Since the complete derivation of the new equation has already been described in ref 9-1 1, only the outline is given here. When an electromagnetic wave of the infrared frequency v traverses a dielectric material, the infrared polarization Po and the optical polarization PI will occur in the dielectric. Since these two polarizations superpose linearly without perturbing each other, the total polarization P is the sum of Po and PI.The polarization
303. (3) Polo, S . R.; Wilson, M. K. J . Chem. Phys. 1955, 23, 2376. (4) Onsager, L. J . Am. Chem. Sot. 1936, 58, 1486. (5) Mikhailov, B. A,; Zolotarev, V. M.; Bakhshiev, N. 6 . Opt. Spectrosc. 1973, 34, 627. (6) Clifford, A. A,; Crawford, B., Jr. J . Phys. Chem. 1966, 70, 1536. (7) Favelukes, C. E.; Clifford, A. A,; Crawford, B., Jr. J . Phys. Chem. 1968, 72, 962. ( 8 ) Fujiyama, T.; Crawford, B . , Jr. J . Phys. Chem. 1969, 7 3 , 4040.
(9) Akiyama, M. J . Chem. Phys. 1984, 81, 5229. ( I O ) Akiyama, M. J . Chem. Phys. 1986, 84, 631. ( 1 1 ) Akiyama, M. J . Chem. Phys. 1986,85, 7. (12) Akiyama, M. J . Mol. Spectrosc. 1980, 84, 49. (1 3) Akiyama, M. Spectrochim. Acta, Part A 1984, 40, 78 1. (14) Frood, D. G.; Dekker, A. J. J . Chem. Phys. 1952, 20, 1030. (1 5) Kakimoto, M.; Fujiyama, T. Bull. Chem. Sot. Jpn. 1975, 48, 2258.
0022-3654/89/2093-2280$01.50/0
0 1989 American Chemical Society
The Journal of Physical Chemistry, Vol. 93, No. 6, 1989 2281
Charge Distribution on Benzene
Poshows a lag in phase from the internal electric field F acting directly on themolecules. We define their ratio as Co (=Cd+ iC/), that is, Co = Po/F. The other polarization PI,on the other hand, is in phase with the applied macroscopic electric field E. Substituting the Lorentz field, F = E ( 4 ~ / 3 ) Pinto , the definition, one obtains
+
+
where P = ?E (2 = x’ ix”) and PI = glE (jil = xl’ +, ixl”) are used. The real and imaginary parts of ji are related with the refractive index n and the extinction coefficient k: x’ = (n2- k2 - 1 ) / 4 ~and x” = n k / 2 ~respectively. , Similar relations hold for g l , but its imaginary part equals zero, because PI is in phase with E. The real part, on the other hand, can be taken as xl’ = (nD2 - 1 ) / 4 ~in the infrared region, because P, is entirely due to the displacement of electrons. Here nD is the refractive index for the N a D line. By substitution of these relations into eq 1, the imaginary part of Co becomes (C/)obsd
nK(nD2 + 2 )
3c =-
(n2 - k2
8ir2u
+ 2)2 + 4n2k2
(2)
where c is the velocity of light and K is the absorption coefficient: K = 4 m k / c . When the probability of a fundamental transition by a harmonic oscillator is calculated quantum-mechanically, the following relation is obtained: (3)
where N is the number of absorbing molecules per unit volume, and ( ~ 9 p / d Q is) ~the dipole moment derivative. Thus, by inserting eq 2 into eq 3 , we obtain a new equation for the band intensity corrected for the internal field effect, Aar: du=z(2) 2 3nK(nD2 2 ) (4) Acor (n2 - k2 2)2 4n2k2 3~ aQ
+ + +
For dilute solutions, since n 4 can be written as
=
nD of the solvent, and n >> k, eq 3nD
4 0 ,
=Aobsd nD2 + 2
(5)
with AoM
=
-1. du 1 N
In the present study, the validity of eq 5 was checked. The derivation due to Clifford and Crawford6 is as follows. They define C by C =P/F. Substituting the Lorentz field into the definitio; yiel$s C = 32/(47rji + 3 ) . Here they use the relationship C = C, + K , where K is a constant real quantity. Thus, the imaginary part of Co is given by (C/)OM =
3c
3nK
-
8x2u (n2 - k2
‘s
+ 2)2 + 4n2k2
(6)
Substituting eq 9 into eq 3 , they obtain A,, =
N
9nK (n2 - k2 +2)2
+ 4n2k2du
(7)
and for dilute solutions eq 7 becomes
=
9nD (nD2 +
2)2Aobsd
Equation 8 corresponds to the Polo-Wilson equation3 and was compared with eq 5. Here we can point out the contradiction in the derivation of eq 6-8. The real quantity K in their derivation is equal to the
cell
’
Path Length
Figure 1. Cell used for gas band intensities.
ratio of P1/F, but this ratio becomes a complex quantity when the Lorentz field is introduced; that is
where R1 in the infrared region is a real quantity as described above. Therefore, to make the ratio of PI/Freal is inconsistent. In our derivation, however, we take into account only Po/F in order to avoid such contradiction. Experimental Section The C6H6 (H6), CS2, and n-hexane (C6HI4)used were commercially available. The deuterium species of C6H$ (D,), m-, p-D2), C6H3D3(sym-, uic-D3), C6H2D4(0-, m-, C6H4D2(0-, p-D4), and C6D6 (D6) were all supplied from Merck Sharp & Dohme. The C6HD5(D5) was prepared from the corresponding bromide by Grignard reactions. The gas chromatography data showed that some of these compounds contained impurities other than deuterated benzenes, and these were eliminated completely by fractional distillation. The amounts of undesired isotopic species determined from intensities of the infrared spectra are listed in Table I. All observed intensities were corrected to a basis of 100% purity. Infrared spectra were measured on a JASCO DS-701G dispersion spectrometer at room temperature, while the whole optical path was flushed with dry nitrogen. A Bruker I F S - 1 1 3 ~FT-IR spectrometer was also used for the measurements of C6H6 and C6D6 in the gas phase. The scanning speed was about 3 cm-I min-I over the entire frequency region concerned. The wavenumber ratio scale was calibrated by the standard bands of ND3 and H 2 0 . For the measurements of the gas phase, a special cell with a short path length was made, but both sides were expanded in order tohold sufficient volume of the sample (see Figure 1). The volume of the cell was determined by measuring the weight of the water that filled the cell, whereas the path length could be measured accurately with slide calipers. The thickness of a typical liquid type cell was precisely determined by the interference method. In the gas-phase measurements, an accurately weighed sample of the liquid (- 3 mg) in a microsyringe was injected into a gas cell, which had been previously filled with pure helium at a pressure of about 1 atm. Previous ~tudies’~J’ had shown that this pressure was enough for the pressure broadening of the rotation-vibration bands of benzene under the spectral slit width used: 0.35 cm-’ for DS-701G and 0.06 cm-’ for Bruker IFS. After the complete vaporization of the sample, the spectrum for a given band was recorded by using the absorbance scale, and the numerical integration of the absorbance curve over the whole band was carried out by a trapezoid method. The base line was referenced (16) Spedding, H.; Whiffen, D. H. Proc. R . SOC.London,A 1956, A238, 245. (17) Dows, D.A,; Pratt, A. L.Spectrochim. Acta, Part A 1962, 18, 433.
2282 The Journal of Physical Chemistry, Vol. 93, No. 6, 1989
Akiyama et al.
TABLE I: Freauencies and Band Intensities for u Bands
99.9 97 97 93 97 93 97 95 98 96 96 99
H6
Dl 0-D2 m-D2 P-D2 sym-D, uic-D, 0-D4 m-D, P-D4 D5 D6
613.9 607.0 575.9 566.7 596.1 530.9 543.4 529.9 523.3 545.2 512.2 495.8
674.2 607.0 576.4 567.1 596.6 531.4 544.2 530.9 524.1 545.7 513.2 496.2
674.7 607.0 576.4 567.7 596.6 53 1.7 544.4 530.9 524.3 545.4 5 13.2 496.7
Error in parentheses.
in Sas
/l \ r; P
in n-Hexane
3
1 l
643
660
6&;
705
Figure 2. Spectra for the u band of benzene.
-~
. U^
723
2.L
I
WAVENUMBER [ cm"]
WEIGHT OF BENZENE (mg) Figure 3. Beer's law plots for the u band of gaseous benzene.
to the line recorded for the gas cell with helium only. Both wings of the band fortunately overlapped the base line in the region of 40 cm-', which is distant from the band maximum for all the bands concerned. Figure 2 shows the u band of CsH6observed by the Bruker IFS, and Figure 3 gives a graph of the integrated band area against concentration N , where the slope is equal to the AoM value. The band intensities obtained are listed in Table I, together with the peak positions of the Q branches, designated as v,hd. A similar method was used for the determination of Aow in solution. The spectral slit width was about 0.8 cm-I, which was sufficiently narrow relative to the half-bandwidth. The base line was recorded by using the sample cell filled with the solvent, and the two wings of the u band were in the same region as those in the gas phase as shown in Figure 2. The AoM and uOM values are given in Table
Y
x
I. Calculations and Results The dipole moment derivative with respect to the Ith out-ofplane normal coordinate QI of a planar molecule becomes ( C ? ~ , / C ~where Q ~ ) ~p z, is the z component of the molecular dipole moment, z is perpendicular to the molecular plane (Figure 4), and the subscript zero indicates the equilibrium state of the vibrating system. Since it is an accepted fact that the band intensities can be successfully interpreted in terms of an effective atomic charge model,'* this model leads to the relation p z = Ciq(i)zl, where q ( i ) is the effective charge located on the ith atom; and since the values of z I are linearly related to the Qcvalues through the L-matrix (18) Gussoni, M.; Castiglioni, C.; Zerbi, G.J. Phys. Chem. 1984, 88, 600.
0 :7 0 : -4
Figure 4. Reaction field
ER within the benzene molecule
elements Lil = C?zi/C?QI, the absolute band intensity A,,, arising from the Ith normal mode can be expressed as
The parameter qo(i), which is the equilibrium value of q(i), is a constant common to all isotopically exchanged homologues. Under the conditions of neutrality and symmetry such as qO(Hor D) = -qo(C) = q H , the independent parameter is merely the effective charge on the hydrogen atom, qH.
The Journal of Physical Chemistry, Vol. 93, No. 6, 1989 2283
Charge Distribution on Benzene
TABLE II: Effective Charge on the Hydrogen Atom of Benzene (e) this work, eq 5 sample 9H(gas) %l(C6Hll) h(Cs2)
HA
BC, eq 8 qH(CSH14)
dCs2)
D6
0.129 0.135 0.135 0.136 0.131 0.136 0.134 0.136 0.137 0.138 0.135 0.139
0.158 0.162 0.158 0.165 0.161 0.162 0.164 0.160 0.158 0.161 0.167 0.158
0.164 0.162 0.163 0.164 0.162 0.164 0.164 0.165 0.165 0.168 0.168 0.165
0.139 0.142 0.139 0.145 0.142 0.142 0.144 0.141 0.139 0.141 0.147 0.139
0.132 0.130 0.131 0.132 0.131 0.132 0.132 0.133 0.133 0.135 0.135 0.133
av
0.135 f 0.003
0.161 f 0.003
0.165 f 0.003
0.142 f 0.003
0.132 f 0.002
D; o-D~ m-D2 P-D2 sym-D3 uic-D3 0-D4 m-D4 PD4 D5
In the gas phase, since A,, = AoWrqH is directly calculated from Aobd of each band listed in Table I, by using eq 9. The L-matrix data were obtained from the nonplanar force field of benzene in the gas phase.12 Table 11gives the results for qH taken to be positive as in ref 12. In dilute solutions, A o w must be corrected with our equation or the BC equation, and A , thus obtained gives the qH values listed in Table 11. The refractive indices of CSz and n-hexane were taken as 1.62409 and 1.37226, re~pective1y.l~As shown in Table 11, eq 5 and 8 lead to different results; with experimental errors taken into account, our equation gives qH(gas)
< qH(CSH14 Or
csZ)
(10)
while the BC equation results in
negative -4) on the y axis with y+ and y-, respectively, was calculated. According to Frood and Dekker,I4 the potential inside the sphere becomes m
V=-
B,PP,(cos
6')
m=O
with B, =
- l)(m + l)cV+" - Y-"'1 (t(m + 1) m]aZm+l
+
(12)
where r and 6' are the spherical coordinates (Figure 4), and P, represents Legendre polynomial$. Next, the potential on t h e y axis, VR,produced by all the charges was calculated by adding eq 12 for each pair of charges. The result was
Discussion Recently, Ermler et al. reported ab initio S C F calculations on the charge distribution of benzene. According to their results, the atomic charge on the hydrogen atom of benzene is 0.138 ezO and 0.173 eeZ1 These values are in good agreement with the present value of qH in the gas phase. This consistency supports both our observed intensities in the gas phase and our L-matrix elements used. The observed frequencies in the gas phase agree well with those in solutions as shown in Table I, and from this excellent agreement, "solvent effect" on the out-of-plane force field seems to be very small. It is, therefore, reasonable to use the same L-matrix elements derived from the force field in the gas phase for the liquid solutions. Several authors have already reported the gas band intensities of benzene and its isotope^.'^*'^^" The present results are about 10% larger than the previous ones. The three points of improvement in this study are as follows: (1) The slit width was set so narrow that the effect of a finite slit width could be neglected, (2) the purity of the sample was determined accurately, and the concentration was corrected, and (3) the specially made gas cell could hold a sufficient volume of the sample. All of these factors led to higher intensity values. In order to compare the results of eq 10 and 11, the calculations were carried out for the effects of the solvents on the charge distribution of benzene. We assumed a benzene molecule to be a spherical cavity of radius a surrounded by a homogeneous solvent with dielectric constant e, and we calculated the reaction field E R as follows. The x,y,z axis system was chosen in such way that its origin was a t the center of the cavity. Two kinds of charges, q and -q, were distributed in the benzene-like arrangement in the xy plane, as illustrated in Figure 4. At first, the potential of the reaction field V produced by only two charges (positive q and (19) Riddick, J. A,; Bunger, W. B. Organic Soluents; Why-Interscience: New York, 1970; p 107. (20) Ermler, W. C.; Kern, C. W. J . Chem. Phys. 1973, 58, 3458. (21) Ermler, W. C.; Mulliken, R. S.;Clementi, E. J. A m . Chem. SOC. 1976, 98, 388.
with P,' = P,(l)
+ 2Pm(1/2) + 2P,(-1/2) + Pm(-1)
(13)
where r is the magnitude of the position vector r on t h e y axis, and each P, respectively corresponds to the following charge pairs: 6' = 0 0,axis); 6' = a/3 (ortho); 6' = 2a/3 (meta);B = a (para). According to the symmetry of the charge distribution, the reaction field on t h e y axis, ER, is directed along t h e y axis and is given by ER
=-
(-)
~ V R r dr
Substituting eq 13 into eq 14, we finally obtain
Since B, and P,' are always positive, E R has the same direction as r, Le., the same direction as the C-H bond moment. This means that the electron clouds on the C-H bond move toward the center of the molecule. Therefore, the charge on the hydrogen atom should be more positive in the solution than in the gas phase. This result strongly indicates a preference for the charge distribution proposed in eq 10 obtained by us over that obtained from the BC equation (8). In practice, the value of qH(solution) was evaluated as 1.2qH(gas), where the following valuCs were used: a(radius), 3 A; C-H bond polarizability, 0.79 A3.22 This result is in good agreement with our qH values in Table 11. Finally, it is very important to consider whether molecular interactions other than the above exist between benzene and the solvent molecules. Cole and Michellz3 already indicated exper(22) Denbigh, K.G. Trans. Faraday SOC.1940, 36, 936. (23) Cole, A. R. H.; Michell, A. J. Spectrochim. Acta, Part A 1964, 20, 747.
J . Phys. Chem. 1989, 93, 2284-2291
2284
imentally that both solvents used in the present study are not strongly perturbing solvents. Marcus24also has classified these as inert solvents. This classification is strongly supported by the experimental data on the total dipole moment of a toluene molecule having a similar electronic structure as benzene: 0.37 D in the gas phase and 0.43 D in inert solvents.2s The ratio of the observed moments coincides with that calculated by eq 15. This means (24) Marcus, Y . Introduction to Liquid State Chemistry; Wiley-Interscience: New York, 1977; Chapter 3. (25) McClellan, A. L. Tables of Experimental Dipole Moments; W. H. Freeman and Company: San Francisco, 1963; p 251
there exist no specific interactions between toluene (benzene) and inert solvents. Thus, it can be concluded that the validity of our new equation is confirmed in dilute solution. Further work is of course necessary, and we are now attempting to test our equation in the liquid phase.
Acknowledgment. We express our deepest appreciation to Emeritus Professor Yuzo Kakiuti for making this study possible. Thanks are also due to Mr. Hiroshi Saito for his kind advice. We also thank Professor Gene S. Lehman for his kindness in reading the original manuscript. Registry No. C6H6, 71-43-2.
Crystal and Molecular Structure of the 2: 1 Charge-Transfer Salt of Decamethylferrocene and Perfluoro-7,7,8,8-tetracyano-p-quinodlmethane: f[Fe(C,Me,)2]*+~2[TCNQF4]2-. Electronic Structure of [TCNQF,]" ( n = 0, 1-, 2-)+ David A. Dixon,* Joseph C. Calabrese, and Joel S. Miller* Central Research and Development Department, E . I . du Pont de Nemours & Co., Inc., Wilmington, Delaware I9898 (Received: April 20, 1988; In Final Form: August 4, 1988)
The reaction of decamethylferrocene, Fe(CSMeS),,and perfluoro-7,7,8,8-tetracyano-p-quinodimethane, TCNQF,, leads to the isolation of two phases of 1:l and 2:1 stoichiometry. The crystal and molecular structure of the black 2:l substance has been determined by single-crystal X-ray analysis at -70 OC: Pi space group (no. 2), a = 9.604 (1) A, b = 9.789 (1) A, c = 12.203 (1) A, (Y = 91.33 ( I ) O , p = 92.05 (1)O, and y = 93.61 (l)", V = 1143.9 A3, and Z = 1. The cation is ordered and shows no unusual bond lengths or angles. The average Fe-C, C-C, and C-Me distances are 2.097, 1.428, and 1.495 A, respectively. The dianion is nonplanar with the -C(CN), groups forming a plane and the c6 ring forming a second plane with a dihedral angle of 33.3'. The ring C-C distances range from 1.373 (3) to 1.401 (3) A and are essentially equal to each other and the 1:389-A distance accepted for an aromatic bond distance. The exocyclic C-C(CN),, C-CN, and C=N average distances are 1.457, 1.403, and 1.155 A, respectively. This structure is comprised of .-DADDAD-. chains (D = [Fe(CSMeS),]'+; A = [TCNQF,I2-). The DAD repeat unit possesses inversion symmetry. The [TCNQF4I2-ion has been characterized by infrared, Raman, and UV-vis spectroscopic techniques, and the data are compared experimentally and theoretically to [TCNQF4]'- and TCNQF,. Ab initio molecular orbital theory with the STO-3G basis set was used for the theoretical calculations. The geometries were gradient optimized for [TCNQF,]" (n = 0, 1-, 2-). Force fields were calculated analytically for n = 0 and 2-. The 1:l Fe (as well as the Co and Cr analogues) phases belong to the P 2 J c monoclinic space group and are amorphous to the previously reported dimer phase of [Fe(CSMes)z]2[TCNQ]2 and contain the S = 0 [TCNQF,]?anion.
Introduction The observation of metamagnetisml for the one-dimensional (1-D) phase of [Fe(CSMes),]*+[TCNQ]'- (TCNQ = 7,7,8,8tetracyano-p-quinodimethane), as well as the observation of ferromagnetism for various phases of polycyanoanionic acceptors24 and decamethylferrocene, has led us to undertake the systematic study of the structurefunction relationship between planar strong acceptors and metallocenium donors. As a result of these studies we have discovered a series of D2A (D = donor; A = acceptor) complexes enabling the structural and spectroscopic characterization of d i a n i o q S e.g., [TCNQF4I2-, [TCNE]2-,6 [TCNQI2-,' [c6(cN)6]2-,8C4(CN)6]2-,9and [DDQI2-., Herein we report the results of our structural, spectroscopic, and theoretical studies of [TCNQF412-and compare these results with [TCNQF,]'-'O and TCNQF, as well as [TCNQ]" ( n = 0, 1-, 2-).' Experimental Section Synthesis. [Fe(CSMes),],[ TCNQF,] was prepared from Fe(C,Me,), (Organometallics, Inc., E. Hampsted, NH; Strem Chemical Co., Newburyport, N H ) and TCNQF, in an inert atmosphere glovebox. Decamethylferrocene (1 50 mg; 0.46 mmol) dissolved in 30 mL of hot acetonitrile was added to a warm solution 'Contribution No. 4720.
of 63 mg (0.23 mmol) TCNQF411dissolved in 3 mL of MeCN. Upon cooling to room temperature and vacuum filtration, 170 mg of the dark green-black crystalline product (80%) was col( 1 ) Candela, G.A.; Swartzendruber, L. J.; Miller, J. S.; Rice, M. J. J . Am. Chem. SOC.1979, 101, 2755. (2) Miller, J . S.; Epstein, A. J.; Reiff, W. M. Isr. J . Chem. 1987, 27, 363. Miller, J. S.; Epstein, A. J.; Reiff, W. M. Science 1988, 240, 40-47. Miller, J. S.;Epstein, A. J.; Reiff, W. M. Acc. Chem. Res. 1988,21, 114-120. Miller, J . S.; Epstein, A. J.; Reiff, W. M. Chem. Reu. 1988, 88,201-200. (3) (a) Miller, J. S.; Calabrese, J. C.; Epstein, A. J.; Bigelow, R. W.; Zhang, J. H.; Reiff, W. M. J . Chem. Soc., Chem. Commun. 1986, 1026. (b) Miller, J. S.; Calabrese, J. C.; Chittapeddi, S.; Zhang, J. H.; Reiff, W. H.; Epstein, A. J . J. Am. Chem. SOC.1987, 109, 769. (4) Miller, J. S.;Zhang, J. H.; Reiff, W. M. J . Am. Chem. SOC.1987, 109, 4584. (5) Miller, J. S.; Dixon, D. A. Science 1987, 235, 871. (6) Dixon, D. A.; Miller, J. S. J . Am. Chem. SOC.1987, 109, 3656. (7) Miller, J. S.; Zhang, J. H.; Reiff, W. M.; Dixon, D. A,; Preston, L. D.; Reis, A. H., Jr.; Gebert, E.; Extene, M.; Troup, J.; Epstein, A. J.; Ward, M. D. J . Phys. Chem. 1987, 91, 4344. (8) Miller, J. S.; Ward, M. D.; Dixon, D. A,; Reiff, W. M.; Zhang, J. H. Manuscript in preparation. (9) Miller, J . S.;Dixon, D. A.; Calabrese, J. C. Manuscript in preparation. (10) Miller, J. S.; Zhang, J. H.; Reiff, W. M. Inorg. Chem. 1987, 26, 600. ( 1 1) TCNQF4 was prepared by: Wheland, R. C . ; Martin, E. L. J . Org. Chem. 1975, 40, 3101.
0022-3654/89/2093-2284$01.50/0 0 1989 American Chemical Society
