ROLFE. B ~ H L E R
3220 also see the formation of an appreciable amount of an (R;I 3. 145)’- ion. which presumably arises from the addition of two alkyl siliconium moieties.
Gonclusiions The brief survey of compounds discussed above shows that tetramethylsilane, when used as a chemical ionization reagent gas, exhibits the advantageous properties of a high reactivity coupled with a low-energy release upon reaction. This-low-energy release is evident in the similarity of spectra of compounds with different functional groups which are dominated by an abundant (M i .73) * quasimolecular ion. On the other hand in the absence of 8 well-defined reaction site the spectra obtained in tetramethylsilane are very similar to those obtained in methane or isobutane. It is significant to note here that it has been reported12that tetramethylsilane has been used successfully to study the chemical
ionization mass spectra of trimethylsilyl derivatives of prostaglandins whereas neither ammonia or methane produced useable spectra. One disadvantage of tetramethylsilane is the large number of intense reagent ion peaks up to approximately mass 200. While this may effectively limit the sample molecular weight range which can be investigated, it may also be utilized to an advantage by serving as an internal mass marker which is in contrast to the difficulty of counting when using a reagent gas such as ammonia. Acknowledgments. Financial assistance by the National Institutes of Health (Grants No. GM-13901, GM-16216, and GM-02055) is gratefully acknowledged. (12) P.A. Leclercq, K. Hagele, E. Middleditch, R. Thompson, and D . M. Desiderio, 20th Annual Conference on Mass Spectrometry and Allied Topics, Dallas, Tex., June 1972, paper K4.
Correlation of Spectral Data for Halogen Atom Complexes with the Electron Donors Involved by Rolf E. Buhler Labolatory for Physical Chemistry, Swiss Federal Institute of Technology, 8006 Ziirich, Switzerland (Received December $8,1071)
With the known data for transient charge-transfer complexes (CT complexes) with chlorine, bromine, and iodine atoms, the correlation of the CT energy (EcT)with the ionization potential, ID,of the electron donors is studied. It is shown that the pseudolinear dependency with slopes much less than one can be explained by the nonlinear, general solution for the simple resonance structure model ECT= P YO ID^ - TIID YZ)’’~. With an estimated value for the overlap integral &I this correlation can be fitted t o experimental data by the least-squares method, which then permits calculation of the resonance integral PO and a n energy term CI, which contains the electron affinity. From these three values (Sol,Po,and C,) ID dependency of characteristic data for the ground state and excited state of the complexes can be derived. The resonance energies, the enbut the derived thalpy of formation, the ionic character, and the dipole moments show strong dependences on ID, transition moments, the oscillator strengths, and the extinction coefficients emax have little correlation with ID. The calculated emax is compared to experimental values. It is found that the rather small differences are mast likely due t o the neglected environmental and structural effects.
+
1
e
Introduction
In recent years CI, large number of transient absorptions detected by pulse radiolysis and flash photolysis were interpreted as being due to charge-transfer complexes (CT complexes) with halogen at0ms.I These absorption bands are quite broad and without structure (e.g., ref 2-4). Their lifetimes cover the range from milliseconds to microseconds. To confirm these band assignments it was common to test the energy of sorption (CT energy) for a linear depenThe Journal of Physical: Chemistry, Vol. 76, No. 22, 1972
dence on the ionization potential 11,of the presumptive donor^.^-^ This test was derived from a two-structure resonance model calculated by second-order pertur(1) R. E. Btthler, Radiat. Res. Rev.,4, 233 (1972). (2) T. A. Gover and G. Porter, Proc. Roy. Soc., Ser. A , 262, 476 (1961). (3) R. E. Btlhler, Helv. Chim. Acta, 51, 1558 (1968). (4) J. M . Bossy, R . E. Btthler, and M. Ebert, J . Amer. Ch,em. SOC., 92, 1099 (1970). (5) R. E. Btthler and M. Ebert, Nature (London), 214, 1220 (1967).
SPECTRAL DATAFOR HALOQEN ATOMCOMPLEXES
3221
bation.6-8 Although the correlations for the halogen atom complexes were close t o linear, their slopes were as low as 0.51, 0.37, and 0.29 for the iodine, bromine, and chlorine atom complexes, r e s p e c t i ~ e l y , ~in- ~contrast to the expected slope of one. Similar but less dramatic deviations are known for molecular complexes. It will be shown for the halogen atom complexes that the simple two-structure resonance model is still capable of explaining the apparent weaker dependency on I D if the general solution of the secular determinant is used.*s9 Since the quantum chemical terms involved correspond to estimated values, several ID dependencies of complex properties were deduced: resonance energy, ionic character, dipole and transition moments, and extinction coefficients. The latter corresponds surprisingly well with the experimental values. The validity of such data will be discussed.
cases it is acceptable to arbitrarily assume So as constant. The following correlation formula then results
Em2 = Y d D 2 - YIID d- YZ with yo =
Yz =
- So12)-*
(6)
-k 4pdoi)Yo
(7)
(ci2-k 4p02 -k 4floSoiCi)Yo
(8)
The square of the CT energy therefore should be quadratically dependent on ID. Table I : LeastrSquares Adjustment of Eq 5 to the CT Energy of Halogen Complexes
I-*,RX,ROH Brmr 12-H
Iz-nb Estimated error
Po
I
CI,
sot
RV
eV
0.1 0.1 0.1 0.1 0.1 0.1 0.3 jzo. 1
-1.04 -0.94 -1.02 -1.12 -1.17 -0.78 -2.14 I t O . 03
7.7 7.8 8.0 8.6 5.7 5.2 8.2 It0.3
Complexes
I-*.
The simdified resonance model for a 1:l comdex originally introduced by Mullikens describes the ground and excited electronic state (+N and +E) of a CT complex as a linear combination of a no-bond wave func$N = tion (+o) and :t dative wave function “” $- a’h and +E = - bl$‘o’ Calculation by the second-order perturbation method yields the following, well-known COrrelatiOn for the C T energy ( E m = Et: - EN) with the ionization potential of the donor
(1
Y i = (2ci
c1-* Br-r
2. Correlation Formula from the Resonance Structure Theory
(5)
Persons found similar data: Sol = 0.2 i 0.1, po = -1.0 f 8.0 f 0.5 ev. b The values from Person9,lO (sol= o,3, = -2.5 eV, and cI = 6.9 eV) differ from these values and do not fit the data by Yada, et ~ 1 . 2 1 a
0.1 eV, and Cl
In7,8,10
+
C1 -- E A - Hllr 4-HOO‘and Cz = Po2 pi2 l 1 are assumed to be constant for a given electron acceptor, irrespective of the choice of donors. The condition for near linearity is C, .=( (ID - CI)~
(2)
This implies a slope of one. Apparent linear dependency with slopes substantially smaller than one cannot be explained by cq 1. For some molecular complexes such deviations were explained by the general solution of the secular determinant*
ECT’ = (EE - EN)^
=
Sot is the overlap integral. The resonance integrals and are related through
Po
For the halogen atom complexes they differ at most by about 20% (calculated from the values in Table I).lZa They therefore ea11no.t be set equal. But for most
If it is possible to fit a curve as given by (5) t o the experimental data, then the three values 801,PO, and CI derived from such optimized curves will allow calculation of some chara,cteristic properties of the complexes.* (a,) The resonance energies X o for the ground state and Xi for the excited state are given by X0,l
=
1 {(ID 2(1 - Sol2)
--
- Cl) =f
(b) The ionic character of t,he C T band in the ground (6) R. S. Mulliken, J . Amer. Chem. SOC.,7 4 , 811 (1952). (7) .G. Briegleb, “Elektronen-Donator-Akzeptor Komplexe,” Springer-Verlag, West Berlin, 1961. (8) W. B. Person and R. S. Mulliken, “Molecular Complexes: A Lecture and Reprint Volume,” Wiley, New Yorlr, N. Y., 1970. (9) W. B. Person, J. Chem. Phgs., 38, 109 (1963). (10) R. S. Mulliken and W. B. Person, Ann. Rm. Phys. Chem., 13, 107 (1962). (11) Hoo’, and Hti’, are the bond energies of the hypothetical no-bond and dative structure, respectively; BO and PI are the corresponding resonance integrals; E A = electron affinity of the electron acceptor. (12) (a) R. E. Btlhler, “Halogenatom-Charge-Transfer Komplexe, Vergleichende und theoretische Diskussion Pulsradiolytischer Resultate,” Habilitationsschrift, Eidgenoss. Technische Hochschule, Zurich, 1970. (b) R. Foster, “Organic Charge-Transfer Complexes,” Academic Press, New York, N. Y., 1969. The Journal of Physical Chemistry, Vol. 76, N o . 22, 1976
3222
+
state (& -. a12/(ao2 Q ~ ) )and excited state (b = bo2/(602 can be calculated from the coefficient ratios of the linear combination of the wave functions $0 and $1.
+
bO/bL =
-
[(ID- C I ) ~ 4PoP11”~) (2P1)-’$ - (ID - C,) [(ID- Ci)’ + POP^]^")
udao = (2PJ-q
(ID
&‘I>
(loa) (lob)
(e) The dipole moment of the CT complex in the ground state (pN) and excited state (WE) and the transition moment (vEN) can be calculated from y.0 (the dipole moment of the no-bond structure) and (the dipole moment of the dative structure). (ai2 4-aoai8oi)gi
VN = WE
=I
PEN =
(bo2 -
[%bo
+ (ao2 + aoai8or)Vo + (biz - bobi8w)Po
+ (SOl/2)(adO -
Figure 1. Brwr complexes. The following donors, taken from Table XI1 in ref 7 and listed with increasing ID, were used: naphthalene, p-, 0-, and, m-xylene, iodobenzene, toluene, bromobenzene, chlorobenzene, and benzene.
(11) (12)
- PO) (13)
alb1)1(~1
with 6*1
= 2”o
+
t 14)
eorAD
(d) Assuming that the oscillator strength7>lzb fth =
( ~ T ~ ~ ~ / ~l 3 ~is ~identical ~ ) E with c T the ~ Eoptically N ~ defined one, the maximum extinction coefficient of the CT band can be calculated from the transition moment’
ER - EL denotes the full half-width of the absorption band, which must be taken from the experiment.
3. CT Data The correlation formula 5 was tested with all published C T energies on halogen atom n complexes in Table 11: Experimental Data for Chlorine Atom CT Complexes in CCla Solution Donor
=
Solute
Benzene C hlorobenzene o-Dichlorobenzene Bromobenzene Toluene Cumene tert-Butylbenxene o-Xylene Bipheny: Naphthalene I-Methylnaphthalene Anthracene Naphthacene a
ID, eV
9.25 9.07 9.06 8.98 8.82 8.69 8.68 8.56 8.31 8.12
7.96 7.38 6.88
b”, nm
490 490 485 510
475 480 480 505 540 540 550
605 620
ECT, eV
Method’”
2.53 2.53 2.56 2.43 2.61 2.58 2.58 2.46 2.30 2.30 2.26 2.05 2.00
PR PR PR PR PR PR PR PR PR PR PR PR PR
PR = pulse radiolysis, see ref 3 and 5
The Journal of Physieal Chemistry, Val. 76, No. 22, 19Y8
t / Figure 2. 1 z - r complexes. The following donors, taken from Table XI in ref 7 and listed with increasing ID,were used: anthracene, pyrene, chrysene, hexamethylbenzene, triphenylene, 1-methylnaphthalene, phenenantrene, durene, naphthalene, biphenyl, mesitylene, p-, 0-, and m-xylene, toluene, styrene, bromobenzene, chlorobenzene, and benzene.
liquid systems. The data used are given in Tables II-IV.14-20 For the purpose of comparison the following additional sets of data were analyzed in exactly the same way: (a) iodine atom complexes with mixed donors, including T donors, alkyl halides, and alcohols (Table 11, this is based on the fact that for nzoZecular iodine complexes these additional donors are found t o (13) eo and me are the charge and mass of an electron. (14) (a) R. L. Strong, J . Phys. Chem., 66, 2423 (1962); (b) J. S. Bartlett, “Flash Photolysis of Bromine in Benzene,” Thesis, Rensselaer Polytechnic Institute, 1962. (15) J. M. Bossy, “Die Radiolyse von Brombeneol,” Thesis No. 4490 Eidgenoss. Technische Hochschule, Zurich, manuscript in preparation. (16) N. Yamamato, T. Kajikawa, H. Sato, and 13. Tsubomura, J . Ame?. Chem. Sac., 91, 265 (1969). (17) V. I . Vedeneyev, L. V. Gurvich, V. N. Kondrat’yev, V. A. Medvedev, and Ye. L. Frankevich, “Bond Enerpiss, Ionization Potentials, and Electron Affinities,” E. Arnold, London, 1966. (18) S. J. Rand and R. L. Strong, J . Amer. Chem. Soc., 82, 5 (1960). (19) R. L . Strong, 9. J. Rand, and J. A. Britt, ibid., 82, 5053 (1960). (20) R. L. Strong and J. Perano, ibid., 89, 2535 (1967).
SI?ECTRAL
DATAFOR
ALOGEN
ATOMCOMPLEXES
3223
Table I11 : ~ x p e r ~ ~Data e ~ tfora Bromine ~ Atom CT Complexes ID,
Donor
eV
Solvent
Benzene Benzene Benzene Benzene Benzene Benzene Bromobenzene Bromobenzene Toluene Biphenyl Naphthalene
9.25 9.25 9.25 9.25 9.25 9.25 8.98 8.98 8.82 8.31 8.12
Benzene Benzene Benzene Benzene Benzene Benzene Bromobenzene Bromobenzene Toluene CHBr, CHBra
Bromocyclohexane
9.9b
Bromocyclohexane
a
Xmas,
ECT,
nm
eV
560 560 555 550 540 535 560 560 575 640 680
2.21 2.21 2.24 2.25 2.30 2.32 2.21 2.21 2.15 1.94 1.82
480
2.58
Solute
Brz Brz Brz CBr4 CHBrs CClaBr Brz Brz Biphenyl Naphthalene
Method"
PRdJ
PR
14.
d
= pulse radiolysis; FP = flash photolysis. b Estimated value by analogy to 1-bromobicyclo[2.2.1]hexane.~~ c Reference Reference 15. e Reference 16. Reference 4.
-
_._
Table 1%' : Experimental Data for Iodine Atom CT Complexes
a
10.85 10.50 10.29 9.33 9.33
FP = flash photolysis.
Referenee 2.
---
Solute
Benzene Benzene Benzene Toluene Toluene a-X ylene p-Xylene Mesitylene
9.25 9.25 9.25 8.82 8.82 8.56 8.44 8.39
Methanol Ethanol Ethyl bromide Ethyl iodide Ethyl iodide
-
Solvent
@V
Benzene Benzene Benzene Toluene Toluene a-Xylene p-X ylene Mesitylene
nm
ECT, eV
500 495 465 520 515 570 520 590
2.48 2.50 2.67 2.39 2.41 2.18 2.39 2.10
390 390 395 490 475
3.18 3.18 3.14 2.54 2.60
Amax,
ID,
Donor
I2 I2 I2
I2
Iz I2 12 I2
Methanol Ethanol Ethyl bromide Ethyl iodide Cyclohexane c
12 IZ I2
I2 IZ ethyl iodide
+
References 14a and 19.
fit the w dependency') ; (b) Brz-n complexes, a selection of data taken from Table 12 in ref 7 (see Figure 1); (c) 1,-T complexes, a selection of data taken from Table 11 in ref 7 (see Figure 2 ) ; (d) Is-n complexes, a set of primary, secondary, and tertiary amines as n donors from ref 21 (see Figure 2). For all complexes the resulting values for 801, Po, and CI were used t o calculate the characteristic complex data (eq 9-15).
4. Resultsand 4.1 GT Energy. I n principle the correlation formula 5 should be fitted So the data by the least-squares method. Because the data are close t o a linear dependeme, the calculation of a quadratic regression involves small differences of very large numbers. The optimisled values for -io,yl, and yztherefore have very large errors, and it is impoadde t o give a reasonable interpre-
d
Reference 18.
e
Reference 16.
f
Method5
FP6 FPb J?P
FP* FP
Reference 20.
tation. Instead, the overlap integral Sol (and yo) was estimated by simple quantum chemical method, and the problem of determining the best fit of eq 5 is reduced t o a least-squares fit with two coefficients only. The resultant values for y1and y2 then allow calculation of the energy term C1 and the resonance integral PO for the various sets of data, with errors of a few per cent only (see below). Person estimated the overlap integrsl 801to be 0.1 for weak CT complexes (e.g., Izn complexes) and 0.3 for strong complexes (I, complexes with amines) . 9 , 2 2 I n the present calculation for halogen atom complexes it was found that the fit t o eq 5 is better for smaller values of Sol. The overlap integral was therefore (21) H. Yada, J. Tanaka, and S. Nagakura,, Bull. Chem. Soc. Jap., 33, 1660 (1960). (22) R. S. Mulliken, C. A . Rieke, D. Orloff, and E. Orloff, J . Chem. Phys., 17, 1248 (1949).
The Journal of Physical Chemistry, Vol. 76, No. $9, 1972
ROLFE. B ~ ~ H L E R
3224
3
2
7
8
9
Figure 3. Chlorine atom CT complexes.
I
ct
chosen to be 0.1 (aO.1). The terms C1and PO are not very sensitive to 801: the error limit of k0.1 affects the values for POand C1 by a few per cent only (Table V) .
Table V : Sensitivity of Po and C1 for Variations of Sol
PO
Ci a
Effect' of A801 = 0.1 for c1 Br a1,oms atoms
0.02 0.23
1, (ev)
I
11
ECT
(ev)
10
9
Figure 4. Bromine atom CT complexes. (The effect from the difference with and without bromocyclohexane, a non-r donor (A),is negligible on the curve fitting.)
Energy term affected
I
10
Figure 5. Iodine atom CT complexes. (0 denotes the A donors).
ECT (eV)
8
I
9
T
complexes with I atoms
0.02 0.22
0.03 0.27
Measured in eV.
The results of the least-squares calculations are given in Table I. The corresponding curves for the halogen atom-CT complexes are shown in Figures 3-5 and for the halogen molecule complexes in Figures 1, 2 , and 6. It is seen that the correlation formula 5 is able to explain the low ID dependency of the experimental data. The scatter of points relative to the theoretical curve is roughly comparable to the results with molecular complexes (see Figures 1 and 2 and also ref 7). For the weak molecular. complexes (Figures 1 and 2 ) the optiThe Journal of Physical Chemistry, Val. 76,N o . 22, 1978
Figure 6. In-amine complexes. The following donors, taken from ref 21 and listed with increasing ID, were used: tri-npropylamine, triethylamine, trimethylamine, diethylamine, dimethylamine, n-butylamine, ethylamine, methylamine, pyridine, and ammonia.
mized curve (eq 5 ) corresponds exactly t o the usual linear relationship based on eq 1. The three curves for halogen atom 7~ complexes (Figures 3-5) are almost parallel. For a fixed donor the CT energy is decreasing from C1 complexes to I complexes to Br complexes. This unexpected sequence is primarily due to the low value of P O for bromine atom complexes.12" Often the resonance integral PO is considered representative of the complex strength. Consequently the Br complexes should be weaker than the C1 and I complexes. Such conclusions are based on the experience that the enthalpy of formation ( A H * ) is often paralleled by the value of Rut since A H * is dependent on the donor (Table VI), contrary to PO, the statement is relatively weak. From Table I and the definition of C1 it can be seen that there are two main reasons for large values of C1: (1) the electron affinity is large (as for the halogen atom complexes) or (2) strong complexes are involved, where the much smaller mean distance between the complex charge centers produces a large Coulomb term for -Hll' (e.g., 12-n complexes). It is possible to estimate the value of CI by analogy to a
SPECTRALDATAFQE MALOGENATOXCOMPLEXES
3225
discusZion by Pemon9 by calculating the basic terms which define CI (el- Table VII). The electron affinities are taken from the l i t e r a t ~ r e . ~The ~ , ~energy ~ Hoo' must be derived from (16)
Known values for t h e enthalpy of formation are summarized in Table together with calculated values for X o (see Section 4.2). The mean values for Hoe' from Table VI, are assumed t o be valid for all similar complexes (see Table VII). The term -Hn' is the sum of the Goulonib energy EC and the valence energy EV in the dative structure. EV is estimated on the base that it must be sixaller than the equivalent covalent bond energy by a fraction related to the differences between the covalent bond length and the complex distance T A D (see Table VII). Ec can be calculated if the mean charge separn,tion TAD is known. TAD was evaluated from the van. der Waals distance and the few knownvalues for solid-state complexes (TableVIII).26-29 The average value for \Teak complexes was used to calculate Ec. If nc solid-state values are known, a correction from the van der Waals distance of about - 5% was chosen. For the strong complexes, where TAD for the solid-state complexes is much smaller than the van der Waals value, a -+5% correction was applied to the solid-state value. Table VIII lists the values used to calculate Ec. The s x n of all the energy terms discussed so far yields the calculated values C l , o a ~ c d = E A Ec ET $- Hoc'. I n Table VI1 they are com-
+ -+
Table VI : Noo' from Experimental AHf and Calculated Xo (see Section 4.2) ~
Complexes
ANf
xu,
e 17
eV
Hoe', eV
Hoo', eV
I,-a Benzene Chlorobenzene Toluene pXylene Naphthalene Hexamethylbenzene
--0.06b --0.05' -0.08' --0.09b -0.08' -0. lfjb
Ammonia Pyridine Ethylamine Dimethylamine Dliethylamine Triethylamine
-0.226 -0.35' -0.33' -0.43'
-0.14 -0.14 -0.15
0.09 0.07
-0.17 -0.18 -0.20
0.10 0.04
It-n
-0.43' -0.53b
o.861
- 1.08 -1.31 - 1.41
0.96 1.081 1.20
-1.63 - 1.45 -1.17
1 . 0 i 0.2
0.64 l.O21
-0.09' -0.10~
a Estimated error. ence 20.
b
-0.53 -0.71
Reference 7 .
'
1.0
'
0.5
.
0
\
V)
Figure 7. IDdependence of the resonance energies for the halogen atom complexes in comparison with halogen molpcule complexes: (*) denotes the dependence for iodine atom complexes with mixed donors ( s , RX, and ROII), estimated relative error i 1 0 7 0 .
pared with the values C1, expt from the fit t o the experimental data. It is seen that correspondence is within estimated error limits. 4.2. Resonance Energy a i d Enthalpy of Formation. The resonance energies X o and X1 as calculated by eq 9 are shown in Figure 7. They have an estimated relative error of +lo%. The resonance energies for all halogen atom complexes are strongly dependent on ID. They are intermediate between the weak x complexes of the halogen molecules and the strong complexes of I s with the amines (12-n). A comparison of the curves for (I-z) and (I-z, RX, ROH) demonstrate that it is not acceptable to relate different classes of donors. The same is true for the ionic character (Figuse 8). The enthalpy of formation, A H f , is related to the resonance energy X o by eq 16. Eloo' was calculated from number of known AHf in Table VI. If onc assumes that Woo' is not (or very little) dependent on I D (see Table VI), then the mean values Woo'from Table 6 can be used to estimate AHt through eq 16 and X o . The results in Table IX denionstrate that the halogen atom complexes with donors of higher I D (e.g., benzene) do form weak (23) B. L. Moiseiwitsch, Advun. At. Mol. Phys., 1, 61 (1965). (24) J. J, DeCorpo and J. L. Franklin, J. Chem. Phys., 54, I885 (1971). (25) G. Porter and J. A . Smith, Proc. Roy. Soc., Ser. A , 261, 28 (1961).
I-S Renzene 0-X ylene
-
1.5
0.52 0'44] c
0.48 i 0.20
Reference 25.
Refer-
(26) 0. Hassel and Chr. Rimming, Quart. f l e a . , Chem. Soc.. 16, 1 (1962). (27) 0. Hassel and K. 0. Strdmme, Acta Chem. Scund., 13, 1782 (1959). (28) 0. I-Iassel and K. 0. Strimme, ibid., 12, 1146 (1958). (29) H . A . Bent, Chem. Rev., 68, 587 (1968). The Journal of Phy.rica1 Chemistry, Vol. Y6,Ivo. E?,197.2
RQLFE. BUHLER
3226 Table VI1 : Comparison of Calculated and Experimental Values for CI (All Data in eV) Eo EA
Complex
61-7r Br-rr 1-1 It-amine
c1,expt
EV
Nan'
(zt0.5)
(JrO.3)
4.2 4.0 3.7 3.9 2.8 3.0
0.2 0.2 0.2 1.0 0.2 0.2
0.4 f0.2 0.4 It 0 . 2 0 . 4 i0 . 2 1 . O f 0.2 0 . 1 i 0.02 0.1 4 0.02
8.4 8.0 7.4 8.5 5.7 6.2
7.7 7.8 8.0 8.2 5.2 5.7
3.613 i 0 . 0 0 3 " 3.363 i 0.003" 3.06340.003a 2.62~0.1~ 2 . 6 ?c O . l b 2 . 9 i 0.1*
12-7r r2-r a
C1,oalod
(40.1)
Reference 23.
Reference 24.
Table IX: Enthalpy of Formation ( A H f )
Table VI11 : Mean Distance between Charge Centers of the Dative Structure riin
(solid state)
Complex
61-7f Br-s I-r Br2-n
3. 2Sdme 3.3Wf 3.78 4.57d' 5 1d'Q 3.7d
11-n
TAD, b (liquid phase)
3.65 3.80 4.0 4.94 5.3 5.0 3 80/3.60* 3.80/3. 7
