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Interpretation of chemical shifts in antimony compounds
Volume 20, number
1
INTERPRETATION
CHEMICAL PHYSICS LETTERS
1 May 1973
OF CHEMICAL SHIFTS IN ANTIMONY COMPOUNDS
D.I. BALTRUNAS, S.P. IONOV, A.Yu. ALEKSANDROV and E.F. MAKAROV Institute of ChemicalPhysics, USSR Academy of Sciences, Aioscorv, USSR Received 8 January
1973
The value of (6RIR) c& = -(9.8 with semi-empirical approximation
* 0.4) x 104 tzas been obtained by combining atomic Hartree-Fock caIcuIations of the.mcthod of molecular orbit& The scale calibration of chemical shifts of antimon)! compounds has been carried out on the basis of the value 6RIR.
At present much experimental material is available concerning hlossbauer effect studies in antimony compounds and especially a wide variety of semiconducting compounds. In this connection systematization and interpretation of chemical shifts in terms of quantum-chemical calculations are of extreme importance. This task consists first in calculating populations of valence states of antimony ions in some selected compounds; then in comparing the obtained I $(0)12 values with chemical shifts, thus determining the 6R/R nuclear parameters, hence, calibrating the scale of chemical shifts for all the remaining compounds. Thus, in ref. [l] Hartree-Fock calculations of I $(Oj12 have been made for different contigurations of valence electrons in Sb ions. Assuming 5s1 5p3 valence configuration for the InSb compound and Ss”5p3 valence configuration for KSbF6 and using the corresponding chemical shifts, the value of tiR/R = -(8.5 +- 3.0) X 10s4 has been obtained [ 1] giving a calibrated scale for chemical shifts in antimony compounds. This calibrated scale, however, does not allow the classification of all the currently known antimony compounds (for example, for Co(NH3)6SbC16 6 = -20.2 mm/set). In ref. [2] the method of molecular orbitals (MO) has been used to estimate the population of electron valence states in InSb and KSbFs compounds as well. The .!~sl*715p1*6~and 5~05~2 electron configurations were determined in InSb and KSbF6 compounds, respectively. More recently the authors [2] have come to the conclusion that the 5s1e715p1-67 configuration
is not real; to determine 6R/R, use was again made of the value of 5s15p3 for antimony in 1nSb. Unfortunately, neither the work [2] itself, nor the references in it, give information about the nature of approximations made by the authors when cdcuInting the population of antimony in InSb and KSbF6 by the hf0 method. The present work deals with calibrating the scale of chemical shifts for a large class of antimony compounds and is based on calculating by the hI0 method the populations of electron valence states in five complexes which are “reference points” and differ sharply from each other by their chemical shifts. The correctness of such calculations is proved by the consistency of the 8R/R values when compared with the obtained populations, and the I $(0)/I values (we use I $(U)12 values from ref. [ 11) when compared with the chemical shifts of the corresponding compounds. It should be noted that such a comparison on the basis of only two compounds, as has been done in refs. [I, 2 J , is not sufficient since there are rather many poorly tested approximations in the MO method; simple assumptions concerning integer-valuepopuIations according to hybridization are not substantiated enough either. The latter is pnrticuladycharacteristic of compounds of the InSb type which do not possess an island-like structure and for which the calculations are complicated. Quantum-chemical calculations of moIecular wavefunctions are made for SbH; and SbCIz- (H = Cl, F) as well as for SbF3 and SW, whose structures are 55
wkll .known. ‘?he compounds of the M2SbH6 type (h! = Rb, Cs; H = Cl, Br), containing SbH, and SbHi&ions, are isostructural with K,PtCl, 133 and have .‘the fo~owingp_arameters: R,,_,(SbCI,) = 2.4 ‘4, ) = 2.6 8, RSb_F(SbF;) = 1.9 8. R,,_,,(SbCI, The SbF, molecules are trigond pyramids with Sb atoms at the vertices: RSb_F = 2.00 A, LFSbF = 81.9’ and 2 LFSbF = 104.3” [4]. The SbCI, crystals are molecular compounds with trigonal bipyramidal molecules [4J whose Sb-CI distances are not equal; the bonds with Cl atoms in the molecular equatorial plane ,are stronger than those with Cl atoms in the axial plane;R!$“f& = 2.29 A and Ri$_,-, = 2.34 A. To calculate molecular orbitals use is made of the Wolfsberg-Hehnholz approximation [5] with the following initial parameters: RSb _ @r,d is an equilibrium internuclear distance, H fs a-diagonal matrix element (in ev) [6], c is a Slater orbital exponent: H&, = -15.8O;Hb = -24.60;H; = -37.85;Hk = -9.07; = - 17.46; &&Sb) = 1.78; &&Cl) = H& = -13.08;H; 2.03; c,(F) = 2.06. Coulomb integrals Hpp (taken with the negative sign) are assumed to be eqilaI to ionization,.potentials of a free atom in the conesponding valence state. To derive the secular equation IHp -Sp4 E[ = 0 external sand p orbitals of Sb atoms an 8-hgands are taken into consideration. Population values, ps and pp, on some atomic orbit& are calculated according to Mulliken [ 7J and are shotin in table 1. In table 1 the values of p(O)ai are taken from ref. [I] together With the obtained values of ps and pp; 6 is a chemical shift related to the source in the chemical form 121mSnOX according to the data of refs. [l, 8,9], the asterisk denotes compounds for which Hpp parameters are varied to test consistency of the results of the calculation (Hib = -15.80; Hgf) = - 16.95; Hib = -9.07; Hg*) = -8.46). Calculations are made for SbF;, SbC1; and SbF3 compounds where ligand s-orbit& ire not taken into account. {See fig. 1 and table 2.) The expression for the chemical shift in antimony compounds is written in the form .’6 = KS’(Sb)lAp(O)l6RlR
1
CHEMICAL PHYSICS LETTERS
Vohime 20, number 1
,
where K = 4n?e2R2c]5E7 = 525 cm4/sec 10m26. .S’(Sb) iS a.relativistic factor = 2.4 [lo] ; Ap(0) = p,(O) f pi(O) [i I] : Using the data from tibIe 1 we obtain : the plot I $(O)l 2cza= f(S), fig. 1, As can be seen this
May
1973
Table 1 Compound
P,hlO
P,MO
p(O)az
& (mm/set)
SbFa SbClj
1.4 0.8
0.9 0.9
31.4 19.0
-14.6 -3.1
SbClj !&FE SbCI:SbCI: SbF;
0.7 0.4 2.0 0.7. 1.3
1.0 0.3 1.4 1.1 1.1
17.3 11.5 38.3 16.5 28.0
-3.2 +2.5 -19.5 -3.1 -14.6
\!
I
I
-2c
-15
‘.
,
-10
-5
0
;
F
6 (nm/sec)
Fig. 1. Dependence of experimental chemical shift on calculated values of the electron density on antimony nucleus.
Compound
P$O
PpMO
pan
6
SbF; SbCIZ SbF;
0.77 1.17 1.96
0.6 1.5 0.4
19.4 25.5 42.6
+2.5 -3.2 -14.6
(mm/set)
relationship is linear, i.e., the 6RIR value obtained from the analysis of “reference point” compounds remains constant. It should be noted that similar analysis carried out without taking ligand >orbitals into account also gives linear relationship between I$$O)12a~ and 6 with approximately the same slope (se? fig. 1 - dotted line). Thus, the 8RiR value is practically unaffected if ligand s-orbitals are taken into account when carrying out calculations - whilst these latter do influence the values of the population
Volume 20, number 1
_--I
CHEMICAL PHYSICS LETTERS
2
n
Fig. 2. Dependence of the electron density on antimony nucleus and the chemical shift on the populations of Q(m)
and Sp(n).orbitals. of Sb electron valence states, so they cannot be neglected. The value obtained is 6R/R = -(9.8k 0.4)
x 10-4. Fig. 2 shows the scale of chemical shifts obtained in this work (6 values are taken from refs. [l, 2, 8,9, 12-151) together with the data obtained in ref. [l] by atomic Hartree-Fock calculations. In the light of the above discussion we shall now consider chemic&shifts in semiconducting compounds of the SbSJ and M,SbCL, type [ 14,9] as examples. The smallest values of isomeric shifts in compounds of the SbSJ Pjpe, in SbSJ and Sb2Se3, are -14.2 mm/sac and -14.4 mm/set. Assuming the bond antimony-ligand to be formed at the expense of p2 Sb electrons, the population of s-orbitals in the Sb atom for these two compounds will equal ~1.6. For SbSeJ (6 = -17.4 mmlsec) the population of antimony s-orbitals will be ~2. If we take the selectron density on Sb nucleus to be unchanged, the variation in populations of p-orbitals between the terminal (according to isomeric shift) compounds
1 aray 1973
SbSJ and SbSeJ will be ~1.3. Thus, increasing the popuiation of p states by lp electron leads to the same chemical shift as removal of 0.3 of 5s etectron. The chemical shifts of SbCli- in compounds of the M2SbHg type have large values, 6 = -( 18.5-2 1) mm/set, that indicate a great density of 5s electrons on the Sb nucleus in SbCIz-. Comparison with fig. 2 gives the value ~(5s) = 1.5-2. It can be seen from fig.-2 that the value of a chemical shift in the region of extreme positive and negative values depends on the cation type, for example KSbF6 and NaSbF6, Cs2SbC16 and Co(NH3)6SbC16, whiie in the region of intermediate values, according to the same scale, such a relationshi? is not observed (for KSbSe?, CsSbSe,, RbSbSe2 the chemical shifts are similar [ 161). In connection with this fact average values of chemical shifts are shown for SbF; and SbClz- in fig. 1. It is necessary to note here that according to our scale of chemical shifts 0.93 < 5s < 1.3 with 0 < Sp < 3 for compounds of AISb, GaSb, tnSb type; these values are beyond those for populations of 5s and 5p states obtained [2] for InSb, AlSb, GaSb compounds in +he example of antimony. Our values do not disagree with the conclusion that the lnSb compound is the most covalent one in the series AI%. GaSb and InSb, since little rearrangement of s and p populations leads to decreasing the ionic character of compounds in this series. Thus, the results of this work together with the results of those dealing with Sn and Te compounds [I 1, 171 indicate that combining the MO method with the results of atomic Hartree-Fock calcu!ations allows one to obtain 6R/R values and to compare the chemical shifts of Te, Sn and Sb compounds with their electron valence configuration. The authors thank G.V. Ionova for helpful discussion.
References [I] S.L. Ruby+G.hI. Kalvius, S.B. Beard and R.E. Snyder, Phys. Rev. 159 (1967) 239. [Z] R.A. Pruitt, S.W. hhr&aU and CM.O’Donell, Phys. Rev. 28 (1970) 1383. [ 31 M.B. Robin and P. Day, Advan. Inog. Chem. Radiothem. 10 (1967) 247. [4] T.N. Polynova and hf.A. Poraj-Koshic, zh. Strukt. Khim. T(1966) 146,642;
57
CHEMICAL PHYSICS LETTERS
Volume 20, number 1
151 _ _ M. Wolfsberg, H. Brennan and Jf. Helrnholz, J. Chem. Phys. 23 $55) 840. [6] C.E. Moore, Atomic energy levels. Natl. Bur. Std., Circular, Washington (1949, 1952). [ 71 R.S. Mulliken, J. Chem. Phys. 23 (1955) 1833. [8] L;H. Bowen, J.G. Stevens and G.G. Long, J. Chem. Phys 51 (1969) 2010. 191 A.Yu. Aleksandrov, S.P. Ionov, A.M. Pritchard.and V.I. Goldanskij, Pis’ma Zh. Eksperim. i Teor. Fiz. 13 (1971)
[lo] &.
Shirley, Rev. Mod. Phys 36 (1964) 339. S.P. lonov, D.K. Kaipov and L.M. Dautnv, Izv. Akad. Nauk Kaz. SSR Ser. Fiz.-Mat. Nauk 4 (1970) 44. [ 121 V.A. Bryukhanov, B.Z. Iofa, V. Kothekar, I.S. Semenov
..-
: .‘,
: ,.
. .
‘.’
1 hiay 1973
and V.S. Shpinel, Zh. Eksperim. i Tear. Fix. 53 (1967) 1582. 1131 G.G. Long, J.G. Stevens, R.J. Tulbane and L.H. Bowen, J. Am. Chem. Sot. 92 (1970) 4230. iI41A.Yu. Aleksandrov, D.I. Baltrunas, L.hl. Beliajev, 1-S. . Liubutin and V.A. Liakhovickaja, Kristallogratiya 17 (1972) 332. 1151 J.D. Donaldson, M.J. Tricker and B.W. Della, J. Chem. Sot. Dalton Trans. 8/9 (1972) 893. 1161 B.W. Veic, S.I. Bcrul, V.J. Grigalis and Yu.D. Lisin, IZV. Akad. Nauk l&v. SSR, Ser. Fiz.-Tekh. Nauk. No. 1 (1971) 48. 1171 S.P. Ionov, E.F. Makarov and D.1. Baltrunas, Zh. Strukt. Khim., to be published.
[II)
:
.
.-.
: .,
,:
1
INTERPRETATION
CHEMICAL PHYSICS LETTERS
1 May 1973
OF CHEMICAL SHIFTS IN ANTIMONY COMPOUNDS
D.I. BALTRUNAS, S.P. IONOV, A.Yu. ALEKSANDROV and E.F. MAKAROV Institute of ChemicalPhysics, USSR Academy of Sciences, Aioscorv, USSR Received 8 January
1973
The value of (6RIR) c& = -(9.8 with semi-empirical approximation
* 0.4) x 104 tzas been obtained by combining atomic Hartree-Fock caIcuIations of the.mcthod of molecular orbit& The scale calibration of chemical shifts of antimon)! compounds has been carried out on the basis of the value 6RIR.
At present much experimental material is available concerning hlossbauer effect studies in antimony compounds and especially a wide variety of semiconducting compounds. In this connection systematization and interpretation of chemical shifts in terms of quantum-chemical calculations are of extreme importance. This task consists first in calculating populations of valence states of antimony ions in some selected compounds; then in comparing the obtained I $(0)12 values with chemical shifts, thus determining the 6R/R nuclear parameters, hence, calibrating the scale of chemical shifts for all the remaining compounds. Thus, in ref. [l] Hartree-Fock calculations of I $(Oj12 have been made for different contigurations of valence electrons in Sb ions. Assuming 5s1 5p3 valence configuration for the InSb compound and Ss”5p3 valence configuration for KSbF6 and using the corresponding chemical shifts, the value of tiR/R = -(8.5 +- 3.0) X 10s4 has been obtained [ 1] giving a calibrated scale for chemical shifts in antimony compounds. This calibrated scale, however, does not allow the classification of all the currently known antimony compounds (for example, for Co(NH3)6SbC16 6 = -20.2 mm/set). In ref. [2] the method of molecular orbitals (MO) has been used to estimate the population of electron valence states in InSb and KSbFs compounds as well. The .!~sl*715p1*6~and 5~05~2 electron configurations were determined in InSb and KSbF6 compounds, respectively. More recently the authors [2] have come to the conclusion that the 5s1e715p1-67 configuration
is not real; to determine 6R/R, use was again made of the value of 5s15p3 for antimony in 1nSb. Unfortunately, neither the work [2] itself, nor the references in it, give information about the nature of approximations made by the authors when cdcuInting the population of antimony in InSb and KSbF6 by the hf0 method. The present work deals with calibrating the scale of chemical shifts for a large class of antimony compounds and is based on calculating by the hI0 method the populations of electron valence states in five complexes which are “reference points” and differ sharply from each other by their chemical shifts. The correctness of such calculations is proved by the consistency of the 8R/R values when compared with the obtained populations, and the I $(0)/I values (we use I $(U)12 values from ref. [ 11) when compared with the chemical shifts of the corresponding compounds. It should be noted that such a comparison on the basis of only two compounds, as has been done in refs. [I, 2 J , is not sufficient since there are rather many poorly tested approximations in the MO method; simple assumptions concerning integer-valuepopuIations according to hybridization are not substantiated enough either. The latter is pnrticuladycharacteristic of compounds of the InSb type which do not possess an island-like structure and for which the calculations are complicated. Quantum-chemical calculations of moIecular wavefunctions are made for SbH; and SbCIz- (H = Cl, F) as well as for SbF3 and SW, whose structures are 55
wkll .known. ‘?he compounds of the M2SbH6 type (h! = Rb, Cs; H = Cl, Br), containing SbH, and SbHi&ions, are isostructural with K,PtCl, 133 and have .‘the fo~owingp_arameters: R,,_,(SbCI,) = 2.4 ‘4, ) = 2.6 8, RSb_F(SbF;) = 1.9 8. R,,_,,(SbCI, The SbF, molecules are trigond pyramids with Sb atoms at the vertices: RSb_F = 2.00 A, LFSbF = 81.9’ and 2 LFSbF = 104.3” [4]. The SbCI, crystals are molecular compounds with trigonal bipyramidal molecules [4J whose Sb-CI distances are not equal; the bonds with Cl atoms in the molecular equatorial plane ,are stronger than those with Cl atoms in the axial plane;R!$“f& = 2.29 A and Ri$_,-, = 2.34 A. To calculate molecular orbitals use is made of the Wolfsberg-Hehnholz approximation [5] with the following initial parameters: RSb _ @r,d is an equilibrium internuclear distance, H fs a-diagonal matrix element (in ev) [6], c is a Slater orbital exponent: H&, = -15.8O;Hb = -24.60;H; = -37.85;Hk = -9.07; = - 17.46; &&Sb) = 1.78; &&Cl) = H& = -13.08;H; 2.03; c,(F) = 2.06. Coulomb integrals Hpp (taken with the negative sign) are assumed to be eqilaI to ionization,.potentials of a free atom in the conesponding valence state. To derive the secular equation IHp -Sp4 E[ = 0 external sand p orbitals of Sb atoms an 8-hgands are taken into consideration. Population values, ps and pp, on some atomic orbit& are calculated according to Mulliken [ 7J and are shotin in table 1. In table 1 the values of p(O)ai are taken from ref. [I] together With the obtained values of ps and pp; 6 is a chemical shift related to the source in the chemical form 121mSnOX according to the data of refs. [l, 8,9], the asterisk denotes compounds for which Hpp parameters are varied to test consistency of the results of the calculation (Hib = -15.80; Hgf) = - 16.95; Hib = -9.07; Hg*) = -8.46). Calculations are made for SbF;, SbC1; and SbF3 compounds where ligand s-orbit& ire not taken into account. {See fig. 1 and table 2.) The expression for the chemical shift in antimony compounds is written in the form .’6 = KS’(Sb)lAp(O)l6RlR
1
CHEMICAL PHYSICS LETTERS
Vohime 20, number 1
,
where K = 4n?e2R2c]5E7 = 525 cm4/sec 10m26. .S’(Sb) iS a.relativistic factor = 2.4 [lo] ; Ap(0) = p,(O) f pi(O) [i I] : Using the data from tibIe 1 we obtain : the plot I $(O)l 2cza= f(S), fig. 1, As can be seen this
May
1973
Table 1 Compound
P,hlO
P,MO
p(O)az
& (mm/set)
SbFa SbClj
1.4 0.8
0.9 0.9
31.4 19.0
-14.6 -3.1
SbClj !&FE SbCI:SbCI: SbF;
0.7 0.4 2.0 0.7. 1.3
1.0 0.3 1.4 1.1 1.1
17.3 11.5 38.3 16.5 28.0
-3.2 +2.5 -19.5 -3.1 -14.6
\!
I
I
-2c
-15
‘.
,
-10
-5
0
;
F
6 (nm/sec)
Fig. 1. Dependence of experimental chemical shift on calculated values of the electron density on antimony nucleus.
Compound
P$O
PpMO
pan
6
SbF; SbCIZ SbF;
0.77 1.17 1.96
0.6 1.5 0.4
19.4 25.5 42.6
+2.5 -3.2 -14.6
(mm/set)
relationship is linear, i.e., the 6RIR value obtained from the analysis of “reference point” compounds remains constant. It should be noted that similar analysis carried out without taking ligand >orbitals into account also gives linear relationship between I$$O)12a~ and 6 with approximately the same slope (se? fig. 1 - dotted line). Thus, the 8RiR value is practically unaffected if ligand s-orbitals are taken into account when carrying out calculations - whilst these latter do influence the values of the population
Volume 20, number 1
_--I
CHEMICAL PHYSICS LETTERS
2
n
Fig. 2. Dependence of the electron density on antimony nucleus and the chemical shift on the populations of Q(m)
and Sp(n).orbitals. of Sb electron valence states, so they cannot be neglected. The value obtained is 6R/R = -(9.8k 0.4)
x 10-4. Fig. 2 shows the scale of chemical shifts obtained in this work (6 values are taken from refs. [l, 2, 8,9, 12-151) together with the data obtained in ref. [l] by atomic Hartree-Fock calculations. In the light of the above discussion we shall now consider chemic&shifts in semiconducting compounds of the SbSJ and M,SbCL, type [ 14,9] as examples. The smallest values of isomeric shifts in compounds of the SbSJ Pjpe, in SbSJ and Sb2Se3, are -14.2 mm/sac and -14.4 mm/set. Assuming the bond antimony-ligand to be formed at the expense of p2 Sb electrons, the population of s-orbitals in the Sb atom for these two compounds will equal ~1.6. For SbSeJ (6 = -17.4 mmlsec) the population of antimony s-orbitals will be ~2. If we take the selectron density on Sb nucleus to be unchanged, the variation in populations of p-orbitals between the terminal (according to isomeric shift) compounds
1 aray 1973
SbSJ and SbSeJ will be ~1.3. Thus, increasing the popuiation of p states by lp electron leads to the same chemical shift as removal of 0.3 of 5s etectron. The chemical shifts of SbCli- in compounds of the M2SbHg type have large values, 6 = -( 18.5-2 1) mm/set, that indicate a great density of 5s electrons on the Sb nucleus in SbCIz-. Comparison with fig. 2 gives the value ~(5s) = 1.5-2. It can be seen from fig.-2 that the value of a chemical shift in the region of extreme positive and negative values depends on the cation type, for example KSbF6 and NaSbF6, Cs2SbC16 and Co(NH3)6SbC16, whiie in the region of intermediate values, according to the same scale, such a relationshi? is not observed (for KSbSe?, CsSbSe,, RbSbSe2 the chemical shifts are similar [ 161). In connection with this fact average values of chemical shifts are shown for SbF; and SbClz- in fig. 1. It is necessary to note here that according to our scale of chemical shifts 0.93 < 5s < 1.3 with 0 < Sp < 3 for compounds of AISb, GaSb, tnSb type; these values are beyond those for populations of 5s and 5p states obtained [2] for InSb, AlSb, GaSb compounds in +he example of antimony. Our values do not disagree with the conclusion that the lnSb compound is the most covalent one in the series AI%. GaSb and InSb, since little rearrangement of s and p populations leads to decreasing the ionic character of compounds in this series. Thus, the results of this work together with the results of those dealing with Sn and Te compounds [I 1, 171 indicate that combining the MO method with the results of atomic Hartree-Fock calcu!ations allows one to obtain 6R/R values and to compare the chemical shifts of Te, Sn and Sb compounds with their electron valence configuration. The authors thank G.V. Ionova for helpful discussion.
References [I] S.L. Ruby+G.hI. Kalvius, S.B. Beard and R.E. Snyder, Phys. Rev. 159 (1967) 239. [Z] R.A. Pruitt, S.W. hhr&aU and CM.O’Donell, Phys. Rev. 28 (1970) 1383. [ 31 M.B. Robin and P. Day, Advan. Inog. Chem. Radiothem. 10 (1967) 247. [4] T.N. Polynova and hf.A. Poraj-Koshic, zh. Strukt. Khim. T(1966) 146,642;
57
CHEMICAL PHYSICS LETTERS
Volume 20, number 1
151 _ _ M. Wolfsberg, H. Brennan and Jf. Helrnholz, J. Chem. Phys. 23 $55) 840. [6] C.E. Moore, Atomic energy levels. Natl. Bur. Std., Circular, Washington (1949, 1952). [ 71 R.S. Mulliken, J. Chem. Phys. 23 (1955) 1833. [8] L;H. Bowen, J.G. Stevens and G.G. Long, J. Chem. Phys 51 (1969) 2010. 191 A.Yu. Aleksandrov, S.P. Ionov, A.M. Pritchard.and V.I. Goldanskij, Pis’ma Zh. Eksperim. i Teor. Fiz. 13 (1971)
[lo] &.
Shirley, Rev. Mod. Phys 36 (1964) 339. S.P. lonov, D.K. Kaipov and L.M. Dautnv, Izv. Akad. Nauk Kaz. SSR Ser. Fiz.-Mat. Nauk 4 (1970) 44. [ 121 V.A. Bryukhanov, B.Z. Iofa, V. Kothekar, I.S. Semenov
..-
: .‘,
: ,.
. .
‘.’
1 hiay 1973
and V.S. Shpinel, Zh. Eksperim. i Tear. Fix. 53 (1967) 1582. 1131 G.G. Long, J.G. Stevens, R.J. Tulbane and L.H. Bowen, J. Am. Chem. Sot. 92 (1970) 4230. iI41A.Yu. Aleksandrov, D.I. Baltrunas, L.hl. Beliajev, 1-S. . Liubutin and V.A. Liakhovickaja, Kristallogratiya 17 (1972) 332. 1151 J.D. Donaldson, M.J. Tricker and B.W. Della, J. Chem. Sot. Dalton Trans. 8/9 (1972) 893. 1161 B.W. Veic, S.I. Bcrul, V.J. Grigalis and Yu.D. Lisin, IZV. Akad. Nauk l&v. SSR, Ser. Fiz.-Tekh. Nauk. No. 1 (1971) 48. 1171 S.P. Ionov, E.F. Makarov and D.1. Baltrunas, Zh. Strukt. Khim., to be published.
[II)
:
.
.-.
: .,
,: