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Calculation of the УOptical ElectronegativityФ of Transition Metal Ions from NQR Coupling Constants.

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ports the structure 2 H3P04 . HzO. In the case of an oxonium salt H3O’HzP04- . H3P04, however, two short and
two long bonds should be observed in the anionic PO4 tetrahedron.
Calculation of the “Optical Electronegativity”
of Transition Metal Ions from NQR
Coupling Constants
Similar arguments applied t o the structure of ( 2 j . which has
been determined much morc accurately, indicate the presence of oxonium ions. Compound ( 2 ) crystallizes monoclinically in the space group P21/c with two centrosymmetric
formula units in the unit cell. With 746 independent photographic data (Cu radiation) an R factor of 0.059 was obtained.
The three S - 0 bonds are of equal length (Fig. 2, standard
deviation 0.003 A), thus clearly indicating the transfer of the
acidic proton to the water molecule since the difference in
length between an S 0 and an S-OH bond is very large; in
the case of oxonium hydrogen sulfate, H3O+HS04, it is
0.11 .&[el. The difference Fourier synthesis of (21 was not so
unambiguous regarding the hydrogen atoms of the oxonium
By P. Machnicr1*1
The “optical electronegativity” ;(opt( M) of the central ions
of octahedral complexes has previously been determined
from the wave number E of the first intense charge transfer
band. With the aid of equation (1) [I]
the relevant U V spectroscopic data afforded the values of
xopt(M) listed in Table 1. [xopt(L) denotes the “optical
electronegativity” of the ligands L].
In conjunction with the examination of the nuclear quadrupole resonance (NQR) spectra [2-5J of inorganic compounds,
it can be shown that characteristic electronegativity values
can also be derived from the NQR coupling constants of
solids. The effectiveness of this technique, which is independent of solvent effects, will now be demonstrated for octahedral chloro complexes of a number of transition metal ions.
The electronegativity values x(Mnf) of the central ions
(Table 1) were calculated according to equation (2)
from 3sCl-NQR coupling constants (values of e2Qqmole/h
for the 35C1 ligands were taken from the Iiterature[6-121; the
dimensions of the proportionality factor 0.38 are MHz-Vz.
Fig. 2. The anion in the crystal structure of 2 H,0+[03SCHZCH2S0,1Z( 2 ) . The bond lengths are given in A.
Table 1. Electronegativities calculated from NQR coupling constants
of transition metal ions in chloro complexes compared with the optical
Relatively short hydrogen bonds occur in both crystal structures. Compound (1) shows four bridges of the type
P-OH..-O-P having O-.-O distances between 2.510 and
2.550A, and two of the type P-OH-..OHz of 2.620 and
2.638 A. Those bridges having the water molecule as proton
donor are longer and cannot be assigned unequivocally
without knowledge of the positions of the protons (five O...O
distances between 2.897 and 3.013 A). In (2) the oxonium
ion is coordinated pyramidally and acts as proton donor for
three short hydrogen bonds t o independent oxygen atoms in
different anions. The 0 . ..O distances lie between 2.549 and
2.578 A.
Received: October 10, 1968
IZ 912 IE]
German version: Angew. Chem. 8 1 , 116 (1969)
~. ..
[*I Doz.
Dr. D. Mootz, Dip(.-Chem. J. Goldmann, and
Dip1.-Phys. H . Wunderlich
Institut fur Anorganische Chemie
der Technischen Universitat
33 Braunschweig, Pockelsstrasse 4 (Germany)
and Abteilung fur Rontgenstrukturanalyse
im Institut fur Molekulare Biologie, Biophysik und Biochemie
3301 Stockheim iiber Braunschweig, Mascheroder Weg 1
[I] A . Blaschette and H. Biirger, Inorg. nuclear Chem. Letters 3,
339 (1967). We wish to thank Dr. Blaschette for crystals of compound (2).
[21 J . P . Smith, W . E. Brown, and J . R . Lehr, .I.Amer. chem. SOC.
77, 2728 (I 955).
[31 H . Worzalu, Acta crystallogr. B 24, 987 (1968).
[41 F. E. Cole, Dissertat. Abstr. B 27, 1850 (1966).
I51 We are grateful to Dr. D . Panke and Dr. R. D. Rosensteiu,
Pittsburgh, for carrying out the calculations on which the diagrams are based with the ORTEP program written by C. K .
[6] I . Taesler and I . Olovsson, Actd crystallogr. B 24, 299 (1968).
Angew. Chem. internat. Edit.
I VoI.8 (1969) / No. 2
~+ 4
1.67 [I31
2.4 [I41
The relationship between the electronegativity x(Mn+) of the
central ion and the NQR coupling constants of the 79Br
ligands can also be formulated quantitatively for the analogous bromo complexes(proportiona1ity factor 0.1 34 MHz-%).
0.134 x
Table 2. NQR coupling constants of the halogen ligands
35CI and 7981 calculated from equations ( 2 ) and ( 3 ) .
1.71 [a]
[a1 From Table
If Xopt (M) is known with sufficient accuracy, it is also possible to estimate the NQR coupling constants ezQqmole/h on
the basis of equations (2) and (3). Values thus obtained for
the NQR coupling constants of complexes whose N Q R
spectra have not yet been recorded are given in Table 2
(estimated error 3= 5 %). The validity range of the considerations sketched out in this communication remains to be
Received: August 26, 1968
IZ 914 IE]
German version: Angew. Chem. 81, 117 (1969)
connected to the pressure generator and the storage autoclaves via steel capillaries by means of the pressure coupling
shown in Fig. lbC41. The pressure generator with manometer
is filled with pentane as pressure-transmitting fluid and can
be closed to the remaining apparatus at valve 1. The storage
autoclaves contain in glass vessels (i) the solution to be investigated (this autoclave can be cooled to -80 "C) and (ii)
pure solvent used to clean the apparatus. The quartz capillaries (i. d., 1 mm; 0.d., 5 mm) withstand pressures of up to
500 atm.
[*I Dr. P. Machmer
Department of Chemistry
The University
Leicester LE 1 7 RH (England)
[I] C. K. Jergensen: Inorganic Complexes. Academic Press,
London-New York 1963, p. 5.
121 P. Machmer, M. Read, and P. Cornil, C.R. hebd. Seances
Acad. Sci. 262, 650 (1966).
[3] P. Machmer, Z. Naturforsch. 216, 1025 (1966).
141 P. Machmer, 2. Naturforsch. 23b, 295 (1968); see also P.
Machmer, Nature (London) 217, 165 (1968).
151 P . Machmer, I. inorg. nuclear Chem. 30, 2627 (1968).
161 M. Kubo and D . Nakamura, Advances inorg. Chem. Radiochem. 8, 257 (1966).
171 D. Nakamura, Kagaku To Kogyo (Tokyo) 19, 816 (1966).
181 K . Ito, D . Nakamura, K. Ito, and M . Kubo, Inorg. Chem. 2,
691 (1963).
[9] R. Ikedu, D . Nukamura, and M . Kubo, J. physic. Chem. 69,
2102 (1965).
[lo] D. Nakamura, Y. Kuritu, K. Ito, and M . Kubo, J. Amer.
chem. SOC.82, 5785 (1960).
1111 K . Iro, D. Nukamura, Y. Kurita, K . Iro, and M . Kubo,
J. Amer. chem. SOC.83,4526 (1961).
[12] E. P. Marram, E . J . McNiff, and J . L. Ragle, J. physic.
Chem. 67, 1719 (1963).
1131 R. A. Walfon and P. C. Crouch, Spectrochim. Acta 24 A,
609 (1968).
1141 C . K. Jsrgensen, Solid State Physics 13, 433 (1962).
[151 C. K. Jsrgensen: Orbitals in Atoms and Molecules. Academic Press, London-New York 1962, p. 95.
ESR Measurements under Pressure: Effect of
Pressure on Chemical Equilibria involving
Solvated Electrons
Fig. 1 . a) Experimental arrangement for ESR measurements under
pressure. A: pressure generator with manometer; B: sample cell with
pressure coupling; C, D: storage autoclaves for solution and pure
solvent; 1-3: valves; magnet and microwave guide of the ESR spectrometer are indicated by dotted lines.
b) Pressure coupling with Teflon packings connecting the quartz
To study the equilibrium (1). a 1 M solution of potassium
amide in ammonia was saturated, at room temperature, with
100 atm of hydrogen in the storage autoclave and was transferred into the sample cell under this pressure. The intensity
of the ESR signal of the solvated electrons, which is proportional to their equilibrium concentration (< 10-4 M [31),
decreases by a factor of 2.3 as the pressure is raised by 300
atm (Fig. 2).
By K . W. Boddeker, G . Lang, and U. Schindewolf[*l
The physical properties of solvated electrons in liquid ammonia are highly pressure dependent 111. As will be shown in
this communication by considering various equilibria involving solvated eIectrons, the chemical properties of electrons dissolved in ammonia or in methylamine-ammonia
mixtures (amine system) also are strongly affected by pressure.
The experiments were carried out ESR-spectrometrically
since the solvated electrons, and in many instances the products of their reactions as well, exhibit characteristic ESR
signals permitting a quantitative detection. We have investigated the reversible formation of solvated electrons by the
reaction of amide ions with hydrogen129 31
and equilibria between solvated electrons and arene radical
anions, e.g.
The experimental arrangement is shown in Fig. la. The
sample cell, a length of quartz capillary extending through
the temperature-controlled cavity of the ESR spectrometer, is
Fig. 2. ESR signal of the solvated electrons in a hydrogen-saturated
(100atm) solution of potassium amide (1 M) in ammonia at varying
pressures at room temperature.
For the investigation of equilibrium (2) a solution of potassium (10-2 M) and benzene (10-1 M) in methylamine-ammonia (2:l) was prepared at -78 O C in the storage autoclave and
was forced into the pre-cooled sample cell by inert gas under
pressure (e.g., nitrogen, 30 atm). The ESR spectrum of this
system shows both the single-line signal of the solvated
electrons and the spectrum of the benzene radical anions
consisting of 7 lines of binomial intensity distribution (Fig.
3) 151. On raising the pressure by 300 atm at -120 OC the concentration of solvated electrons decreases by a factor of 2.6
while that of the benzene radical anions increases by a factor
of 3.2. - A corresponding pressure dependence was observed
with other simple aromatic radical anions.
Angew. Chem. internut. Edit. Vol. 8 (1969) J No. 2
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constantin, nqr, metali, calculations, couplings, transitional, ions, уoptical, electronegativityф
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