Polyfluoroorganoboron-oxygen compounds. 2 [1]: Base-catalysed hydrodeboration of polyfluorophenyl(dihydroxy)boranes

Article abstract of DOI:10.1002/1521-3749(200213)628:13<2834::AID-ZAAC2834>3.0.CO;2-2

Polyfluorinated phenyl(dihydroxy)boranes C₆H_5-nF_nB(OH)₂ (n = 3 - 5) underwent hydrodeboration (formal replacement of the (dihydroxy)boryl group by hydrogen) in the presence of bases (MeOH, 33% H₂O-MeO

Full text of DOI:10.1002/1521-3749(200213)628:13<2834::AID-ZAAC2834>3.0.CO;2-2

Polyfluoroorganoboron-Oxygen Compounds. 2 [1]
Base-catalysed Hydrodeboration of Polyfluorophenyl(dihydroxy)boranes
H.-J. Frohna,*, N. Y. Adoninb, V. V. Bardinb, and V. F. Starichenkob
a Duisburg, Fachgebiet Anorganische Chemie, Gerhard-Mercator-Universität
b Novosibirsk/Russia, N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Sibirian Branch of Russian Academy of Sciences
Received February 11th, 2002; revised May 30th, 2002.
Dedicated to Professor Rüdiger Mews on the Occasion of his 60th Birthday
Abstract. Polyfluorinated phenyl(dihydroxy)boranes C6H5-nFnB-
(OH)2 (n ϭ 3 Ϫ 5) underwent hydrodeboration (formal replace-
ment of the (dihydroxy)boryl group by hydrogen) in the presence
of bases (MeOH, 33 % H2OϪMeOH, KOH (1 equiv.)/33 %
H2OϪMeOH, pyridine and 9 % D2OϪpyridine) and formed the
fluoroaromatic compounds ArH or ArD, respectively. The rate of
reaction depends on the number of fluorine atoms in the phenyl
group and on the position of the fluorine atoms, relative to the
B(OH)2 substituent.
Keywords: Polyfluorophenyl(dihydroxy)boranes (Polyfluorophenyl-
boronic acids); Hydrodeboration; NMR spectroscopy
Polyfluororganische Bor-Sauerstoff Verbindungen. 2 [1]
Die Hydrodeborierung von Polyfluorphenyl(dihydroxy)boranen unter basischen
Bedingungen.
Inhaltsübersicht. Polyfluorierte Phenyl(dihydroxy)borane C6H5-nFnB-
(OH)2 (n ϭ 3 Ϫ 5) unterliegen in Gegenwart von Basen (MeOH,
33 % H2OϪMeOH, KOH (1 Äquiv.)/33 % H2OϪMeOH, Pyridin
und 9 % D2OϪPyridin) einer Hydrodeborierungsreaktion (forma-
ler Ersatz der (Dihydroxy)borylgruppe durch Wasserstoff) und bil-
den die entsprechenden Fluoraromaten ArH oder ArD. Die Reak-
tionsgeschwindigkeit hängt dabei von der Anzahl der Fluoratome
in der Arylgruppe und der relativen Stellung der Fluoratome zum
B(OH)2-Substituenten ab.
Introduction
and decomposed quickly in aqueous ethanol (45 min. at
20 °C). C6F5B(OH)2 was more stable in aqueous acetone
(several hours at 20 °C) and no decomposition was found
in an acidic solution with 2 N HCl/ethanol (20 °C, 1 h). The
oxidation of C6F5B(OH)2 with 85 % H2O2 at 20 to 50 °C
gave pentafluorophenol in 91 % yield [3]. Fluorine-contain-
ing aryl(dihydroxy)boranes formed the corresponding
potassium aryltrifluoroborates after treatment with K [HF2]
in aqueous methanol [4, 5]. To our knowledge, no infor-
mation exists about the reactivity of tri- and tetrafluoro-
phenyl(dihydroxy)boranes.
The substitution of boron in the C-B bond by hydrogen,
either under acid- or base-catalysis (electrophilic and nuc-
leophilic hydrodeboration), is one of the fundamental
properties of aryl(dihydroxy)boranes [6, 7]. In 1930 Ainley
and Challenger reported that phenyl(dihydroxy)borane was
unreactive in 5 % boiling aqueous NaOH (20 h) but formed
benzene slowly when heated with a concentrated aqueous
solution of NaOH or with water under pressure (140 Ϫ
150 °C, 40 h) [8]. Kuivila et al. have studied the kinetics of
the base-catalysed hydrodeboration of several aryl(dihy-
droxy)boranes ArB(OH)2 [Ar ϭ C6H5, 2-, 3- and 4-C6H4X
(X ϭ F, Cl, CH3, OCH3)] (90 °C, preferentially at pH
6.70) [9].
Recently, we have reported a general preparative procedure
for polyfluorinated aryl(dihydroxy)boranes C6H5-nFnB-
(OH)2 and tri(aryl)boroxins (C6H5-nFnBO)3 (n ϭ 3 Ϫ 5)
[1]. The latter were obtained by thermal dehydration of the
corresponding aryl(dihydroxy)boranes (often named aryl-
boronic acids) ArB(OH)2 at 100 °C or by treatment of the
acids with SOCl2 in ether at 20 °C. Despite the fact that
some of these compounds [2,4-, 2,5-, 2,6-, 3,4-, 3,5-
C6H3F2B(OH)2, and C6F5B(OH)2] are now commercially
available [2], their basic reactivity has not been investigated.
Chambers and Chivers have found that pentafluorophenyl-
(dihydroxy)borane underwent a slow hydrodeboration in
aqueous solution (20 % conversion at 20 °C within 2 days)
* Prof. Dr. H.-J. Frohn
Fachgebiet Anorganische Chemie
Gerhard-Mercator-Universität Duisburg
Lotharstr. 1
D-47048 Duisburg
Fax: (ϩ49) 2 03-3 79 22 31
e-mail: frohn@uni-duisburg.de
2834
 2002 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim 0044Ϫ2313/02/628/2834Ϫ2838 $ 20.00ϩ.50/0 Z. Anorg. Allg. Chem. 2002, 628, 2834Ϫ2838

Polyfluoroorganoboron-Oxygen Compounds. 2
In the present work we investigate the hydrodeboration
of pentafluorophenyl- (1), 2,3,4,5-tetrafluorophenyl- (2),
2,3,4,6-tetrafluorophenyl- (3), 2,3,5,6-tetrafluorophenyl-
(4), 2,4,6-trifluorophenyl- (5), 3,4,5-trifluorophenyl- (6),
2,4-difluorophenyl- (7) and 2,6-difluorophenyl- (8) (di-
hydroxy)boranes in the presence of bases (MeOH, 33 %
H2OϪMeOH, KOH (1 equiv.)/33 % H2OϪMeOH, pyridine
and 9 % D2OϪpyridine).
specific substitution of the boron-containing substituent by
deuterium (quantitative yield) in all cases. Pentafluoro-
phenyl(dihydroxy)borane was the most reactive acid in this
group and yielded deuteropentafluorobenzene (9b). The
marked differences in reactivity within the series of isomers
of C6H3F2B(OH)2 (7, 8), C6H2F3B(OH)2 (5, 6) and
C6HF4B(OH)2 (2, 3, 4) are reflected in the data presented
in Table 1.
D2OϪPy
C6H5-nFnB(OH)2
Ǟ C6H5ϪnFnD
Results and Discussion
The aryl(dihydroxy)boranes 1 Ϫ 8 dissolve in aprotic polar
solvents (acetonitrile, acetone) and form stable solutions.
The comparison of the 19F NMR spectra of solutions of
1 in MeCN (basic solvent) and in CH2Cl2 (neutral, “non-
coordinating” solvent) suggested a donorϪacceptor mole-
cular interaction of 1 with a base [1]. However, the disso-
lution of 1 in methanol (protic polar solvent) at 20 Ϫ 30 °C
caused the appearance of pentafluorobenzene (9a) (ca. 5 %
conversion within 15 minutes). The rate of hydrodeboration
was substantially increased in 33 % H2OϪMeOH or after
addition of water to a solution of 1 in CH2Cl2. For instance,
the hydrodeboration of 1 in 33 % H2OϪMeOH was 81 %
after 20 minutes and completed after 2 h hours. The ad-
dition of KOH (1 equivalent) shortened the time of com-
plete hydrodeboration of 1 in aqueous methanol to 10 Ϫ 15
minutes. The reaction of 1 with anhydrous pyridine pro-
ceeded exothermally and resulted in the immediate forma-
tion of pentafluorobenzene (9a).
Table 1 Total conversion of aryldihydroxyboranes ArB(OH)2 into
deuteropolyfluorobenzenes ArD in 9 % D2O-pyridine (v/v)
Aryl group
Temperature, °C
Time of conversion, min.
C6F5
1
2
3
3
4
5
6
7
8
25
100
32
100
32
100
100
100
100
< 3 Ϫ 5
2,3,4,5-C6HF4
2,3,4,6-C6HF4
2,3,4,6-C6HF4
2,3,5,6-C6HF4
2,4,6-C6H2F3
3,4,5-C6H2F3
2,4-C6H3F2
2,6-C6H3F2
50
210
a)
15
60
90
180, no reaction
19 hours
150
b)
a) Conversion 82 %.
b) Conversion 53 %.
Based on the product analysis by 19F NMR spectroscopy
we estimated the rates of disappearance of ArB(OH)2 (2 Ϫ
5, 7 and 8) in 9 % D2OϪpyridine at 32 °C and 100 °C (Fig-
ures 1 and 2) and calculated k (the observed rate constant).
Compounds 1 and 6 were not examined because of the reac-
tivity of the former being to high whereas the latter was too
unreactive. The pseudo-first-order values of k were calcu-
lated taking into account an excess of the base.
Base
C6F5B(OH)2
Ǟ C6F5H
1
Base ϭ MeOH, aqueous MeOH, H2O in CH2Cl2, KOH in aque-
ous MeOH
In the series of the three isomeric acids C6HF4B(OH)2
the influence of the position of the hydrogen atom relative
to the B(OH)2 group becomes obvious (Figure 1).There is
a significant decrease in the hydrodeboration reaction from
The solutions of tetrafluorophenyl(dihydroxy)boranes
(2 Ϫ 4) in MeOH were more stable than that of 1 and
showed no notable decomposition within 1 h. The hydrode-
boration of 2,3,4,6-tetrafluorophenyl(dihydroxy)borane (3)
in anhydrous pyridine also proceeded more slowly with re-
spect to 1. After 20 min. the molar ratio of borane 3 to
1,2,3,5-tetrafluorobenzene (10) was 4 : 1 (19F NMR).
p-H [4, k(32 °C ϭ (6.0
[3, k(32 °C) ϭ (0.83
0.6) x 10Ϫ2 min.Ϫ1] over m-H
0.1) x 10Ϫ2 min.Ϫ1] to o-H
[2, k(32 °C) ϭ 0.009 x 10Ϫ2 min.Ϫ1, calculated from the ex-
perimental results at 100 °C]. The higher importance of the
position of fluorine atoms over the number of fluorine
atoms is best demonstrated by the comparison of 2,4,6-
Py
C6H2F3B(OH)2 [5, k(100 °C) ϭ (6.8 0.2) x 10Ϫ2 min.Ϫ1
]
5-XC6F4B(OH)2
Ǟ 5-XC6F4H
and 2,3,4,5-C6HF4B(OH)2 [2, k(100 °C) ϭ (4.2
0.1) ϫ
10Ϫ2 min.Ϫ1] (Figure 2). The presence of only one fluorine
atom in the o-position in 2 is responsible for this result.
Principally, it seems reasonable that the hydrodeboration
of fluorinated aryl(dihydroxy)boranes proceeds under base-
catalysis via an intermediate species involving four-coordi-
nate boron. Based on his kinetic measurements, Kuivila et
al. proposed a two-step mechanism of hydrodeboration for
monosubstituted aryl(dihydroxy)boranes RC6H4B(OH)2 in
water (90 °C, pH 6.0 Ϫ 6.7) [9]. (Scheme 1).
X ϭ F (1) (few min.), H (3) (2 Ϫ 3 hours)
We undertook a detailed investigation of the hydrodebor-
ation of polyfluoroaryl(dihydroxy)boranes (1 Ϫ 8) using
9 % D2O in pyridine. The essential results were (a) the clear
dependence of the reaction rate on the number of fluorine
atoms on the aryl group and on the position of the fluorine
atoms, relative to the B(OH)2 substituent and (b) the regio-
Z. Anorg. Allg. Chem. 2002, 628, 2834Ϫ2838
2835

H.-J. Frohn, N. Y. Adonin, V. V. Bardin, V. F. Starichenko
Scheme 1
slow
[RC6H4B(OH)3]ϪϩH2O
Ǟ RC6H4Hϩ[HO]ϪϩB(OH)3
Although no direct evidence for the formation of the
aryl(trihydroxy)borate anion was presented, this assump-
tion is reasonable, even for relatively weak Lewis acids. Fur-
thermore, the 19F NMR spectra of the para-fluorinated
aryl(dihydroxy)boranes 4-FC6H4B(OH)2 and 3-Cl-4-
FC6H3B(OH)2 showed a significant low-frequency shift of
the fluorine resonance in aqueous alkaline solution with re-
spect to that in aqueous solution which illustrated the
change of the B(OH)2 group into a strongly electron-donat-
ing substituent [10]. However, the replacement of several
hydrogen atoms in the phenyl group by fluorine atoms in-
creases both the Lewis, as well as the Brønsted acidity of
aryl(dihydroxy)boranes. This circumstance allows, in ad-
dition to the acid-base adduct formation, to propose the
deprotonation of polyfluorophenyl(dihydroxy)boranes by a
strong base (OHϪ, pyridine) and the generation of aryl(hyd-
roxy)oxyborate anions [ArB(OH)O]Ϫ with a three-coordi-
nated boron atom or the strong polarization of the
BϪOϪH bond by a hydrogen-bridge interaction with the
base: BϪOδϪ···Hδϩ···Base. For example, the hydrodebor-
ation of 1 with the sterically hindered 2,6-di(tert-butyl)pyri-
dine (neat, in excess or in toluene solution) should proceed
more likely via deprotonation of 1 than via the formation
of the adduct C6F5B(OH)2 · Base. Also, the heterogeneous
reaction of 1 with anhydrous K2CO3 in toluene can include
a deprotonation step.
Figure 1 Deuterodeboration of penta- and tetrafluorophenyl(di-
hydroxy)boranes (1؊4) in 10 % D2O - pyridine at 32 °C
Base, 20 °C
C6F5B(OH)2
Ǟ C6F5H
Base ϭ 2,6-(tert-Bu)2C5H3N (neat or in toluene solution, 3 Ϫ
5 min.); K2CO3 in toluene (24 h)
In general, the intermediate formation of the anions
[ArB(OH)3]Ϫ or [ArB(OH)O]Ϫ is expected to influence the
19F NMR spectroscopic characteristics of the fluorinated
aryl group Ar. The position of the resonances of the poly-
fluorinated aryl(trihydroxy)borate salts should not be sig-
nificantly distinguished from those of the known polyfluo-
roaryl(trifluoro)borates [5] or -(trialkoxy)borates [11]. How-
ever, we did not observe any remarkable difference in the
19F NMR spectra of fluorinated phenyl(dihydroxy)boranes
in different basic solvents, either in acetonitrile, acetone or
ether [1], or in protic media (MeOH, 33 % H2OϪMeOH or
in 9 % D2OϪpyridine) or in anhydrous pyridine (Table 2).
This spectroscopic result can be caused by a low equilib-
rium concentration of the [ArB(OH)3]Ϫ anion (Scheme 1)
or of the acid-base adduct ArB(OH)2 · base or by a fast
reaction of the deprotonated form of the acid
[ArB(OH)O]Ϫ or its polarized form (Scheme 2).
Figure
2 Deuterodeboration of fluoro-containing phenyl(di-
hydroxy)boranes 2. 5, 7 and 8 in D2O -pyridine at 100 °C
2836
Z. Anorg. Allg. Chem. 2002, 628, 2834Ϫ2838

Polyfluoroorganoboron-Oxygen Compounds. 2
Table 2 19F NMR spectroscopic data of fluorinated phenyl(dihydroxy)boranes ArB(OH)2
Chemical shifts, ppm
Aryl group
Solvent
F-2
F-3
F-4
F-5
F-6
a)
C6F5
C6F5
C6F5
1
1
1
2
2
2
3
3
3
3
4
4
4
5
5
6
6
7
7
8
8
Acetone-d6
MeOH
33 % H2OϪMeOH
Acetone-d6
9 % D2OϪPy
MeOH
CD3CN
9 % D2OϪPy
MeOH
Ϫ132.61
Ϫ132.44
Ϫ132.14
Ϫ131.69
Ϫ130.66
Ϫ131.71
Ϫ125.56
Ϫ125.32
Ϫ126.13
Ϫ124.59
Ϫ133.70
Ϫ133.48
Ϫ133.59
Ϫ99.95
Ϫ163.50
Ϫ162.75
Ϫ162.30
Ϫ158.17
Ϫ156.80
Ϫ157.60
Ϫ167.16
Ϫ166.79
Ϫ167.44
Ϫ166.31
Ϫ140.34
Ϫ140.30
Ϫ139.30
Ϫ154.72
Ϫ154.11
Ϫ153.69
Ϫ155.27
Ϫ154.64
Ϫ155.43
Ϫ131.51
Ϫ132.41
Ϫ131.61
Ϫ131.98
Ϫ163.50
Ϫ162.75
Ϫ162.30
Ϫ141.14
Ϫ139.50
Ϫ140.14
Ϫ132.61
Ϫ132.44
Ϫ132.14
a)
a)
2,3,4,5-C6HF4
2,3,4,5-C6HF4
2,3,4,5-C6HF4
2,3,4,6-C6HF4
2,3,4,6-C6HF4
2,3,4,6-C6HF4
2,3,4,6-C6HF4
2,3,5,6-C6HF4
2,3,5,6-C6HF4
2,3,5,6-C6HF4a)
2,4,6-C6H2F3
2,4,6-C6H2F3
3,4,5-C6H2F3
3,4,5-C6H2F3
Ϫ105.80
Ϫ105.20
Ϫ106.20
Ϫ104.65
Ϫ133.70
Ϫ133.48
Ϫ133.59
Ϫ99.95
Py
a)
Acetone-d6
9 % D2OϪPy
MeOH
Ϫ140.34
Ϫ140.30
Ϫ139.30
Acetone-d6
9 % D2OϪPy
Acetone-d6
9 % D2OϪPy
Acetone-d6
9 % D2OϪPy
Acetone-d6
9 % D2OϪPy
Ϫ107.67
Ϫ109.01
Ϫ159.65
Ϫ162.46
Ϫ100.79
Ϫ100.79
a)
Ϫ136.41
Ϫ139.08
Ϫ136.41
Ϫ139.08
a)
2,6-C6H3F2
2,6-C6H3F2
2,4-C6H3F2
2,4-C6H3F2
Ϫ103.16
Ϫ103.65
Ϫ101.37
Ϫ101.64
Ϫ103.16
Ϫ103.65
a)
Ϫ107.65
Ϫ109.19
a) Reference [1].
Scheme 2
Hydrodeboration of 1 in aqueous methanol
Aryl(dihydroxy)borane 1 (30 mg, 0.14 mmol) was dissolved in
methanol (0.20 ml) and water (0.10 ml) at 20 °C and the progress
of the reaction was monitored by 19F NMR spectroscopy over
several hours until the hydrodeboration was completed.
Hydrodeboration of 1 with KOH in aqueous methanol
A 2 M solution of KOH in methanol (0.12 mmol KOH, 0.062 ml
CH3OH) was added to the mixture of methanol (0.139 ml) and
water (0.100 ml) before aryl(dihydroxy)borane
1
(26 mg,
0.12 mmol) was dissolved. The solution was periodically examined
second step:
by 19F NMR spectroscopy during several hours.
H2O
[ArB(OH)O]Ϫ or ArB(OH)OδϪ
Ǟ ArH
Hydrodeboration of aryl(dihydroxy)boranes (arylboronic acids)
with pyridine or 2,6-di(tert-butyl)pyridine
alternatively
[ArB(OH)O]Ϫ or ArB(OH)OδϪ
A. Aryl(dihydroxy)borane 1 (21 Ϫ 27 mg, 0.10Ϫ 0.12 mmol) was
added to anhydrous pyridine or 2,6-di(tert-butyl)pyridine (0.2 Ϫ
0.3 ml) at 20 °C. An exothermic reaction proceeded immediately
and after 3 Ϫ 5 min. the quantitative formation of pentafluoroben-
zene was detected (19F NMR).
Ǟ <ArϪ>
<ArϪ> ϩ H-A Ǟ ArH ϩ AϪ (H-A ϭ H2O, [Base-H]ϩ, HO-B<)
B. Aryl(dihydroxy)borane 3 (16 mg, 0.08 mmol) was dissolved in
anhydrous pyridine (0.2 ml) at 20 °C. After 20 min. the 19F NMR
spectrum showed the resonances of 3 (Table 2) and of 1,2,3,5-tetra-
fluorobenzene in the molar ratio of 4 : 1. 6 hours later only the
polyfluoroaromatic product was present.
C. For kinetic measurements each of the fluorinated aryl(dihydroxy)-
boranes (1 Ϫ 8) (20 mg) was dissolved in pyridine (0.300 ml) and
D2O (0.030 ml) at 0 °C and placed into the probehead of the NMR
spectrometer within 1 Ϫ 2 min. The measurements proceeded at
32 °C. For the high temperature series the NMR tube with the
solution was kept at 100 2 °C for the appropriate time, cooled
immediately to 32 °C and the composition of the reaction mixture
was determined by 19F NMR spectroscopy. The reaction rates were
determined with an accuracy of 25 Ϫ 35 %.
Our present experimental data do not allow us to decide
between the aryl(trihydroxy)borate and aryl(hydroxy)oxy-
borate anion or the hydrogen-bridged species as the reactive
key intermediate and precursor to ArH. Further investi-
gations in this field are in progress.
Experimental
The NMR spectra were recorded on the BRUKER spectrometer
WP 80 SY (19F at 75.39 MHz) at 32 °C. The chemical shifts are
referenced to CCl3F (19F) (with C6F6 as secondary reference, δ ϭ
Ϫ162.9 ppm). The yields of the reaction products were determined
by 19F NMR spectroscopy using the internal quantitative refe-
rence C6H5CF3.
D. Acid 1 (7 mg, 0.03 mmol) was dissolved in toluene (0.074 ml)
and 2,6-di(tert-butyl)pyridine (63 mg, 0.33 mmol) was added to the
solution at 20 °C. After 3 Ϫ 5 min. pentafluorobenzene was formed
in quantitative yield (19F NMR).
Pyridine, 2,6-di(tert-butyl)pyridine, methanol and toluene were
purified by standard procedures. Toluene was stored over molecular
˚
sieve (4 A) before use.
Z. Anorg. Allg. Chem. 2002, 628, 2834Ϫ2838
2837

H.-J. Frohn, N. Y. Adonin, V. V. Bardin, V. F. Starichenko
Interaction of pentafluorophenyl(dihydroxy)borane (pentafluoro-
phenylboronic acid) with K2CO3 in toluene.
[2] Aldrich Katalog, Handbuch Feinchemikalien (Deutschland),
2000 Ϫ 2001, 674, 675 and 1488.
Acid 1 (380 mg, 1.79 mmol) was stirred with K2CO3 (1 g) in tolu-
ene (2.5 ml) at 20 °C. After 18 h the conversion of 1 into penta-
fluorobenzene was 86 % and after 24 h 100 %.
[3] R. D. Chambers, T. Chivers, J. Chem. Soc. 1965, 3933.
[4] E. Vedejs, R. W. Chapman, S. C. Fields, S. Lin, M. R.
Schrimpf, J. Org. Chem. 1995, 60, 3020.
[5] H.-J. Frohn, H. Franke, P. Fritzen, V. V. Bardin, J. Organomet.
Chem. 2000, 598, 127.
We gratefully acknowledge financial support by the Deutsche For-
schungsgemeinschaft, the Russian Foundation for Basic Research,
and the Fonds der Chemischen Industrie.
[6] B. M. Mikhailov, Y. U. Bubnov, Organoboron compounds in
organic synthesis. /; Bell Bain, Glasgow, 1984.
[7] Methoden der organischen Chemie (Houben-Weyl). Bd 13/3b.
Organobor-Verbindungen II; Thieme, Stuttgart, 1983.
[8] A. D. Ainley, F. Challenger, J. Chem. Soc. 1930, 2171.
[9] H. G. Kuivila, J. F. Reuwer, J. A. Mangravite, Can. J. Chem.
1963, 41, 3081.
References
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[11] H.-J. Frohn, N. Y. Adonin, V. V. Bardin, Main Group Metal
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[1] H.-J. Frohn, N. Y. Adonin, V. V. Bardin, V. F. Starichenko, Z.
Anorg. Allg. Chem. submitted for publication.
2838
Z. Anorg. Allg. Chem. 2002, 628, 2834Ϫ2838