New perspectives for boronic esters in macrocyclic chemistry

Article abstract of DOI:10.1016/S0022-328X(99)00054-6

In the present contribution a tetrameric macrocyclic compound derived from 2,6-pyridinedimethanol and 3-nitrophenyl boronic acid, as well as 10 new dimeric boronates prepared from 2-salicylideneaminoethanol and different aryl boronic acids such as a 2-met

Full text of DOI:10.1016/S0022-328X(99)00054-6

Journal of Organometallic Chemistry 581 (1999) 70–81
New perspectives for boronic esters in macrocyclic chemistry
Norberto Farfa´n a,*, Herbert Ho¨pfl b, Victor Barba a, Ma. Eugenia Ochoa a,
Rosa Santillan a, Elizabeth Go´mez a, Atilano Gutie´rrez c
a Depto. de Qu´ımica, Centro de In6estigacio´n y de Estudios A6anzados del IPN, Apdo. postal 14-740, 07000, Me´xico D.F., Mexico
b Uni6ersidad Auto´noma del Estado de Morelos, Centro de In6estigaciones Qu´ımicas, A6. Uni6ersidad 1001, C. P. 62210, Cuerna6aca,
Morelos, Mexico
c Laboratorio de Resonancia Magne´tica Nuclear, Uni6ersidad Auto´noma Metropolitana, Unidad Ixtapalapa, A6. Michoaca´n y la Pur´ısima s/n,
Col. Vicentina, 09340, Ixtapalapa, Mexico
Received 30 June 1998; received in revised form 14 December 1998
Abstract
In the present contribution a tetrameric macrocyclic compound derived from 2,6-pyridinedimethanol and 3-nitrophenyl boronic
acid, as well as 10 new dimeric boronates prepared from 2-salicylideneaminoethanol and different aryl boronic acids such as a
2-methylphenyl-, 3-methylphenyl-, 4-methylphenyl-, 3-methoxyphenyl-, 4-methoxyphenyl-, 3-chlorophenyl-, 4-chlorophenyl-, 3-ni-
trophenyl-, 3-trifluoromethylphenyl- and 4-fluorophenylboronic acid are described. The tetrameric and three of the dimeric
structures have been analyzed by X-ray crystallography, and a series of parameters such as bond length, bond angles, deviation
of the boron atom from the boronate mean plane and intermolecular interactions are discussed. © 1999 Elsevier Science S.A. All
rights reserved.
Keywords: Boron; Boronic esters; Macrocyclic chemistry; X-ray crystallography; 2,6-Pyridinedimethanol, 2-salicylideneaminoethanol
1. Introduction
Other interesting macrocyclic boron compounds are
the bis(dimethylglyoximato)diphenylboron chelate (3)
[8–10], the very original boroncryptand (4), which has
been designed for the complexation of alkali metal
cations [11], the cyclotetrakis(triazolylborane) (5) [12–
14], cyclotetrakis(aminoborazine) derivatives (6) [15–
17] and the heterocycle B8S16 (7), which is composed of
four five-membered B2S3 rings that are linked through
the boron atoms by sulfur atom bridges to form a
planar inorganic porphine analog [18–20].
A review of the literature shows that a number of
macrocyclic boron compounds are known. Among the
simplest structure types are doubly bridged diboronate
esters (1) [1,2] and triply bridged diborate esters (2)
[3–7].
* Corresponding author. Tel.: +52-5-7473800, ext. 4031; fax: +
52-5-7477113.
E-mail address: jfarfan@mail.cinvestav.mx (N. Farfa´n)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00054-6

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
71
paraquat. The host–guest complexation is due to the
presence of a strong dipolarization directed along the
N–B bond [25].
In previous studies of compounds containing nitro-
gen–boron co-ordination, we have described the prepa-
ration of borane complexes with 8-hydroxyquinoline,
pyridinealcohols [26,27] and pyridine [28], as well as
diphenyl borinates derived from aminoacids [29],
ephedrine derivatives [30], pyridinealcohols [31] and
piperidine alcohols [32]. These studies were performed
to investigate by (dynamic) NMR and X-ray diffraction
analyses electronic and steric aspects that influence the
nitrogen–boron bond stability. The results obtained
were completed by ab initio calculations of different
substituted 2-aminoethylborinates at the HF/6-31G**
level of theory [33].
In the last few years, we have been also interested in
the reaction of phenylboronic acid with tridentate lig-
ands such as phenolethanolamines [34], diethanolamines
[35,36], diphenolamines [37], iminodiacetic acid [38] and
N-alkyl-N-(2-hydroxyethyl)glycine [39]. We reported
that, in all cases, [3.3.0] heterobicyclic compounds with
an intra-molecular nitrogen–boron bond are obtained.
Similarly, most salicylideneaminoalcohols were found to
react with phenylboronic acid to produce [5.4.0], [4.4.0]
and [4.3.0] heterobicyclic structures [40].
A somewhat uncommon macrocyclic dimer has been
isolated during the synthesis and characterization of
1,6-dioxa-2-sila-5-bora-3-cycloalkenes (8), where it has
been observed that actually the dimeric structure (9) is
the correct one [21–23].
Since we have developed a new strategy of synthesis
for the preparation of macrocyclic di- and tetrameric
boronates [41,42] from iminodialcohols and boronic
acids (13), we now direct our efforts to the preparation
of new macrocyclic boronates. It is thereby important to
note that the boronate units are connected by co6alent
BꢀO bonds and that the hydrolytic stability of these
molecules is enhanced by co-ordinative N–B bonds.
More recently, the synthesis of macrocyclic di-
boronate esters has received much attention. Com-
pound types 10 and 11 represent the complexation of
cyclic saccharides by diboronic acids, whereby the sec-
ond option of boron stabilization is preferred [24].
Applying the same synthetic principle there have been
also synthesized allosteric devices in order to study the
saccharide transport through membranes [24].
The cyclic diboronate ester 12 represents a similar
structure and has been designed as neutral receptor for

72
N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
In this context, we recently reported the synthesis of
2. Results and discussion
macrocyclic compounds, that consist of a dimeric (14a–
e) and tetrameric (15) boronate ring system of 10 and
20 members, respectively [41,42]. Both types of
molecules are air-stable and are obtained in high yields
by one step syntheses from the corresponding imino
dialcohol and phenylboronic acid. The molecular struc-
tures of these compounds have been established by
X-ray diffraction studies [41,42].
Compound 16 is obtained by condensation of 2,6-
pyridinedimethanol with 3-nitrophenylboronic acid in
chloroform (Scheme 1). The reaction is finished within
30 min to give a yield of 80%. Crystals suitable for
X-ray crystallography have been obtained when the
reaction was performed at room temperature without
stirring. Experimental data, selected bond lengths and
selected bond angles are resumed in Tables 1 and 2.
Normally, 2,6-pyridinedimethanol acts as a tridentate
monochelating ligand as it has been shown for a series
of complexes with metal ions and organometallic com-
pounds [43–45]. In the case of the smaller boron atom,
only one five-membered chelate ring is formed so that
the second methyleneoxy group binds to another boron
atom. As in the case of compound 15 [41], the forma-
tion of a cyclic structure instead of a polymeric one
seems to be highly favored owing to the tetrahedral
stereochemistry around the boron atom (Fig. 1). The
tetrahedral environment of the boron atom and the
planarity of the ligand with the collinearity of its pri-
mary bonds (the mean deviation of the aliphatic carbon
Based on the strategy developed to obtain these
macrocyclic compounds, it can be expected that te-
trameric and dimeric structures are also obtained, when
different substituents are introduced in the phenyl ring
of the boronic acid. Therefore, macrocycles with a
nitro-, methyl-, methoxy,- chloro-, trifluoromethyl- or
fluoro substituent in ortho, meta or para position of the
phenylboryl group were prepared with the result that in
all cases the reaction proceeded to give the expected
dimeric or tetrameric structure.
,
atoms from the mean planes is 0.026 A in compound
16) dictate the tetrameric macrocyclic structure forma-
tion. The dihedral angles between the four boronate
moieties are nearly perpendicular to each other (84.6
and 84.9°, respectively), but they are smaller than in
compound 15 with a mean value of 90.7°. The configu-
ration of the boron atoms is alternate so that S4
symmetry could be expected for the macrocycles 15 and
16. Actually, in both cases the point group is only
Scheme 1. Preparation of compound 16.

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
73
Table 1
Experimental crystallographic data of compounds 16, 17c, 17i and 17j
16
17ca,b
17i
17j
Crystal Data
Chemical formula
Crystal size (mm)
C52H44B4N8O16, 4 CHCl3
0.3×0.5×0.5
1080.20
C32H32B2N2O4, 2 H2O
0.30×0.18×0.18
530.32
P1
C32H26B2F6N2O4
0.48×0.48×0.54
638.18
C30H26B2F2N2O4
0.39×0.36×0.24
538.17
MW (g mol−1
Space group
)
C2/c
P21/c
P1
Cell parameters
,
a (A)
16.617(1)
18.395(1)
22.766(2)
90
93.336(9)
90
6947.6(9)
4
0.55
11.043(2)
11.287(2)
12.506(3)
83.87(3)
74.69(2)
80.89(3)
1481.0(5)
2
11.210(1)
6.420(1)
20.952(1)
90
100.76(1)
90
1481.30(2)
2
0.11
8.001(1)
9.355(1)
10.467(1)
113.084(8)
97.680(1)
111.21(1)
604.65(2)
1
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
v (mm−1
)
0.086
1.27
0.100
1.47
z (Calc.) (Mg m−3
)
1.49
1.43
Data collectionc
Scan range (°)
q limits (°)
No. of collected reflections
No. of independent reflections
No. of observed reflectionsd
0.50+0.51 tg u
2BqB26
7228
6814
2523
1.03+1.43 tg u
2BqB23
4443
0.98+0.84 tg u
2BqB26
2331
2185
1276
0.98+0.79 tg u
2BqB22
1549
1445
1169
4102
1744e
Refinementf
Rg
Rw
Goof
No. of variables
0.058
0.050
3.13
0.050
0.130i
1.009
379
0.045
0.039
1.59
0.036
0.034
1.85
h
452
237
222
Maximum D/|
0.001
−0.35
0.46
0.002
−0.24
0.26
0.08
−0.17
0.17
0.02
−0.13
0.13
−3
,
Dzmin (e A
)
−3
,
Dzmax (e A
)
a Program used Shelxs (Sheldrick 1993, version 1.8).
b T=193 K.
c ꢀ–2q scan; T=293 K, uMo–Ka =0.71069 A.
,
d (Fo)2\3|(Fo)2.
e F\4|(F).
f w=1/|2.
g R=ꢀ(ꢁFoꢂ−ꢂFcꢁ)/ꢀꢂFoꢂ).
h Rw=[ꢀw(ꢂFoꢂ−ꢂFcꢂ)2/ꢀw F2o]1/2
.
i wR2={ꢀ[w(Fo2−Fc2)2]/ꢀ[w(F2o)2}1/2
.
pseudo S4, whereby the molecular structure of 16 has
higher symmetry (C2-axis) than the one of 15 (no
symmetry element). The average distance between two
The sum of bond angles in the five-membered
boronate heterocycles with a mean value of 107.9 (7)°
for the five bond angles in both molecules indicates a
certain ring strain, that would still be higher in a
monomeric species: the NꢀBꢀCaryl bond angles with
average values of 111.9 (5)° for 16 and 111.9 (5)° for 15
are significantly smaller than 120°.
The ring strain is also expressed by the mean devia-
tion of the boron and oxygen atoms from the boronate
mean planes. This average deviation is smaller in com-
,
,
neighboring boron atoms is 5.36 A for 16 and 5.42 A
for 15. If all van der Waals interactions are considered,
the void in the center of the molecule has a diameter of
,
about 1.37 A, but the B-aryl groups close the outside of
the macrocycle, so that only a channel with a diameter
,
of about 0.60 A remains open for entrance. The cave
should be therefore ideal for the lodging of small atoms
or ions like Li+ or Be2+
The mean N–B bond length in 16 is 1.650(9) A and
not significantly different from the one in 15 (1.667(9)
.
pound 16 (0.089 A for the boron atoms and 0.040 A for
the oxygen atoms in the heterocyclic ring) when com-
,
,
,
,
pared to compound 15 (0.065 A for the boron atoms
,
,
A), a fact that is also true for the rest of the bond
and 0.204 A for the oxygen atoms), the boronate units
lengths and bond angles.
are more planar.

74
N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
1
Table 2
complex. The H-NMR spectrum shows only one pat-
tern of signals for the four boronate units of the
tetrameric species so that the already proposed S4
symmetry of the macrocycle in solution is most likely.
The two –OCH2 groups of each boronate unit appear
,
Selected bond lengths (A) and bond angles (°) of compound 16
Ring B(7)
Ring B(27)
,
Bond lengths (A)
NꢀB
1
at different chemical shifts in both the H- and 13C-
1.646(9)
1.454(8)
1.444(8)
1.391(8)
1.408(6)
1.479(9)
1.338(7)
1.653(8)
1.466(7)
1.433(8)
1.398(7)
1.415(7)
1.508(8)
1.343(7)
BꢀOcycle
BꢀOchain
CꢀOcycle
CꢀOchain
CꢀCcycle
CꢀNcycle
NMR spectra (Fig. 2) and give rise to AB systems
(2J=18 Hz, Dl=0.30 ppm and Dl=0.67 ppm, respec-
tively). The high field shift of the bridging methyle-
neoxy group is due to a protection by the neighboring
pyridine ring as can be seen from the molecular struc-
ture (Fig. 1). The most striking difference is the extreme
Bond angles (°)
NꢀBꢀOcycle
NꢀBꢀOchain
BꢀOꢀCcycle
BꢀOꢀCchain
OꢀCꢀCcycle
NꢀCꢀCcycle
BꢀNꢀCcycle
NꢀBꢀCaryl
1
98.3(5)
98.8(5)
low field shift of H-5 in the H-NMR spectrum (l=
109.3(5)
114.3(5)
118.2(5)
108.0(6)
109.1(6)
109.9(5)
112.2(5)
112.6(5)
109.3(6)
114.7(5)
109.1(5)
114.8(5)
114.9(5)
107.0(5)
109.7(6)
109.7(5)
111.6(5)
111.1(5)
111.6(5)
114.0(5)
7.99 ppm for H-5 and l=7.45 ppm for H-3) that may
be explained by an interaction with the O-19 atom
,
(H-5···O-19 2.46 A) [46].
The H-NMR signals of the 3-nitrophenyl group are
1
shielded due to the N–B coordination, since this bond
diminishes the electron withdrawing effect of the tri-co-
ordinated boron atom.
CarylꢀBꢀOcycle
C
arylꢀBꢀOchain
In accordance to the preparation of compounds 14a–
e [41,42], a series of arylboronic acids that include
2-methylphenyl-, 3-methylphenyl-, 4-methylphenyl-, 3-
methoxyphenyl-, 4-methoxyphenyl-, 3-chlorophenyl-, 4-
chlorophenyl-, 3-nitrophenyl-, 3-trifluoromethylphenyl-
and 4-fluorophenylboronic acid were reacted with 2-
(salicylideneamino)-1-hydroxyethane, whereupon the
dimeric boronates 17a–j were obtained (Scheme 2).
OchainꢀBꢀOcycle
Compound 16 is nearly insoluble in all common
solvents, and spectra could only be recorded from
DMSO-d6. However, the water present in the solvent
decomposed part of the small amount of dissolved
Fig. 1. Molecular structure of compound 16.

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
75
Thereby, the dimeric dication structure can be ex-
cluded on the basis of the isotopic abundance (10B
19.6%, 11B 80.4%) that would lead to a different rela-
tionship of the isotope peaks in a compound with two
boron atoms [53].
The IR spectra show that the wavenumber of the
CꢁN bond in the dimers with substituents in para
position are shifted to higher energy by 2–6 cm−1. In
all cases the corresponding wavenumbers are between
1634 and 1640 cm−1
.
The dimeric compounds 17a–j are nearly insoluble in
all common solvents, and NMR spectra could only be
recorded in the case of compounds 17b, 17f and 17g. A
1
comparison of the H-NMR data between the ligand
and the dimeric compounds 17b, 17f and 17g shows
that the signal of the azomethine hydrogen atom is
shifted downfield (Dl=0.48, 0.52 and 0.49 ppm, re-
spectively) with formation of the co-ordinative N–B
bond. The signals of the methylene hydrogens atoms
are split in diastereotopic signals (Dl=0.08–0.14 ppm
for H-8 and Dl=0.28–0.35 ppm for H-9). In compari-
son to the ligand the 13C-NMR signals of the azome-
thine, the C-1, the C-2 and C-6 carbon atoms are
shifted upfield, while the ones of C-3, C-4 and C-5 are
shifted downfield. The –OCH2 group its shifted upfield
(Dl=1.6, 1.4 and 1.7 ppm) and the –NCH2 group is
shifted downfield (Dl=0.4, 0.7 and 0.3 ppm) in 17b,
17f and 17g, respectively, with respect to the ligand.
The tetracoordination of the boron atom can be seen
from the 11B-NMR spectra of compounds 17b, 17f and
17g, where values of l=3.0 ppm (h1/2=390 Hz), 6.6
ppm (h1/2=600 Hz) and 2.1 ppm (h1/2=1126 Hz),
respectively, have been measured. These shifts can be
compared to those of diphenylboron chelates that have
been synthesized from different amino-substituted sali-
cylaldehyde azomethines [47,48].
One of the aims of the present investigation was to
analyze, if the dimeric structures are also formed in the
presence of substituents with different electronic and
steric effects at the B-phenyl group. Owing to the
insolubility of compounds 17a–j (only 17b, 17f and 17g
dissolve slightly in chloroform) an X-ray crystallo-
graphic study had to be undertaken in order to obtain
more detailed information. Crystals could be grown for
the complexes 17c, 17i and 17j and their molecular
structures are presented in Figs. 3–5. The asymmetric
unit of 17c consists of a water molecule and two half
dimers. Experimental data are summarized in Table 1
and selected bond lengths and bond angles are pre-
sented in Tables 2 and 3.
Fig. 2. 1H-NMR spectrum of compound 16 in DMSO-d6: (a)
aliphatic region; (b) aromatic region. The signals of the starting
materials are marked with % for the 2,6-pyridinedimethanol and ¦ for
the 3-nitrophenylboronic acid. The signal of H2O results from an
impurity in DMSO-d6. CHCl3 is forming part of the crystal lattice of
compound 16.
The reaction provides the highest yields (82–97%) in
benzene or tetrahydrofuran, if a Dean–Stark trap is
used to separate the water formed during the
condensation.
The dimeric structures of compounds 17a–j could be
established by mass spectrometry, although in all cases
only the [MꢀAr]+ ion was detected owing to the easy
loss of the corresponding aryl radical [47–52]. At the
same time the presence of different substituents at the
B-phenyl group confirms the fragmentation pattern
proposed for compounds 14a–e. It is interesting to note
that the highly dominating base peaks correspond to
the cation 18, where the ring strain is lowered due to
the sp2 hybridization of the boron atom.
As in the case of compounds 14a–b and 14d–e, in all
four crystal structures the dimeric molecules are located
at an inversion center and belong therefore to the Ci
point group.
A comparison of the bond lengths and bond angles
in Table 3 with the data of compound 14a [41,42]

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N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
Scheme 2. Preparation of compounds 17a–j.
Fig. 3. Molecular structure of compound 17c.
Fig. 4. Molecular structure of compound 17i.

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
77
ciation of different components to form a complex,
highly ordered macromolecular or supramolecular
building that is favored thermodynamically [55].
The substituents at the aryl group allow us to confirm
that the fragmentation pattern in mass spectrometry in-
volves the initial loss of the aryl substituent at the boron
atom and that the base peak corresponds to a mono-
meric structure with a sigma boron–nitrogen bond.
4. Perspectives
Our interest in the synthesis of the macrocyclic
boronates presented in this and other contributions
[41,42] becomes clear, if one thinks of possible applica-
tions in host–guest chemistry. The advantage of these
macrocycles lies in their easy, one step syntheses from
readily available starting materials and there should be
no doubt that it is possible to obtain other structures
with 12, 14, 16, 18 etc. members forming the macrocyclic
ring.
Once a series of compounds is known, one can start
to introduce functional groups in the macrocycles that
can enhance the complexing ability of these boronates or
one can try to rupture the coordinative N–B bond in
order to enhance the ring size of the macrocycle and to
liberate the Lewis acid boron atom as co-ordination site
for Lewis bases or anions.
We entered this field only recently and problems we
have to deal with actually are related to low solubility,
small cage radius and relatively strong N–B bonds in
our complexes. In order to start the next millenium well
prepared in boron chemistry, we hope to find solutions
to some of these problems soon.
Fig. 5. Molecular structure of compound 17j.
shows no significant differences, so that the electronic
and/or steric effects of the substituents in meta or para
positions of the B-phenyl moiety should be relatively
small. In the case of electron withdrawing substituents,
we would have expected a stronger effect on the N–B
bond strength that could lead to its rupture by heating
and enhancement of the ring size from 10 to 18 members.
A variable temperature 1H-NMR experiment of the
slightly soluble compound 17b has shown that this does
not happen in the range of 25–110°C in DMSO-d6. At
higher temperatures the macrocycle starts to decompose.
5. Experimental
1H- and 13C-NMR spectra were recorded on Jeol GSX
270, Jeol Eclipse +400 and Bruker DMX-500 spectrom-
eters. Special techniques (COSY, HETCOR, NOESY)
were applied when necessary to assign the spectra ade-
quately. Chemical shifts (ppm) are relative to (CH3)4Si
(1H and 13C) and BF3·OEt2. Coupling constants are
quoted in Hz. Infrared spectra were recorded on a
Perkin–Elmer 16F-PC FT-IR spectrophotometer. Melt-
ing points were obtained on a Gallenkamp MFB-595
apparatus and are uncorrected.
A selected monocrystal was set upon an automatic
diffractometer, unit cell dimensions with estimated
standard deviations were obtained from least-squares
refinements of the setting angles of 24 well centered
reflections. Two standard reflections were monitored
periodically; they showed no change during data collec-
tion. Corrections were made for Lorentz and polariza-
tion effects. Absorption corrections were not applied.
3. Conclusions
The present contribution shows that dimeric com-
pounds are the preferred reaction product of 2-salicyli-
deneaminoethanol with arylboronic acids. Thereby, the
presence of electron donating or withdrawing groups in
ortho, meta or para positions does not alter the course
of the reaction. The tetrameric compound with 3-nitro-
phenyl boronic acid presents the same behavior. We can
conclude that the determining factor in the synthesis of
these boron macrocycles is the ligand structure. The
crystal structure analyses of 16, 17c, 17i and 17j show
that the boron atom prefers an alternate configuration
in the macrocyclic ring systems.
Together with the fact that condensation reactions are
based on equilibria, a self assembly mechanism can be
proposed [14,54]. Self assembly is the spontaneous asso-

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N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
Table 3
,
Selected bond lengths (A) and bond angles (°) of compounds 14a, 17c, 17i and 17j
14a
17c
17i
17j
,
Bond lengths (A)
B–Ocycle
B–Ochain
B–N
Cph–Ocycle
CꢁN
C–N
Caliph–Ochain
Caliph–Caliph
B–Caryl
1.492(3)
1.433(3)
1.624(3)
1.332(3)
1.291(3)
1.477(3)
1.412(3)
1.512(3)
1.601(3)
1.500(7) / 1.493(6)
1.431(7) / 1 434(6)
1.639(7) / 1.606(6)
1.335(6) / 1.347(5)
1.275(7) / 1.294(5)
1.467(6) / 1.460(5)
1.411(6) / 1.408(5)
1.498(7) / 1.527(6)
1.579(8) / 1.583(6)
1.473(5)
1.469(5)
1.619(6)
1.341(5)
1.295(5)
1.484(5)
1.419(4)
1.517(6)
1.593(6)
1.492(4)
1.432(4)
1.613(4)
1.333(3)
1.292(4)
1.482(4)
1.415(4)
1.512(5)
1.601(5)
Bond angles (°)
Ocycle–B–N
Ocycle–B–C
Ocycle–B–O
N–B–Caryl
N–B–Ochain
C–B–Ochain
B–N–Ccycle
B–O–Ccycle
106.5(3)
109.4(2)
111.6(2)
108.1(2)
109.0(2)
111.9(2)
121.6(4)
126.5(2)
118.7(2)
122.8(2)
113.0(2)
118.2(2)
120.4(2)
119.4(2)
105.9(4) / 106.3(3)
110.1 (4) / 110.2(4)
110.6(4) / 111.4(4)
108.3(4) / 110.7(4)
109.0(4) / 109.3(4)
112.8(5) / 108.8(4)
122.8(5) / 122.3(4)
126.3(4) / 123.1(4)
119.2(4) / 121.0(3)
122.8(5) / 121.9(4)
113.3(4) / 112.0(3)
118.1(4) / 118.5(5)
120.1(6) / 120.4(4)
119.7(6) / 119.4(4)
107.6(4)
110.4(4)
110.9(4)
108.4(3)
107.6(4)
110.4(4)
121.5(4)
125.2(4)
119.0(3)
122.6(4)
112.3(3)
118.5(4)
119.7(5)
120.3(4)
106.7(3)
109.2(3)
111.9(3)
108.8(3)
109.1(3)
111.1(3)
122.7(3)
125.7(3)
118.7(2)
122.1(3)
112.5(3)
120.7(3)
120.7(3)
119.6(3)
B–O–Cchain
N–Ccycle–Ccycle
N–Cchain–Cchain
Ccycle–N–Cchain
Ocycle–Ccycle–Ccycle
Ccycle–Ccycle–Ccycle
,
De6iation from the boronate mean plane (A)
B
O
C
−0.129
0.070
−0.233 /
0.047 / 0.072
−0.023 / 0.018
−0.170
0.055
0.096
−0.169
0.070
0.032
0.037
,
Intramolecular interactions (A)
C–H···O
2.43
2.46 / 2.52a
2.52a
2.43
a H atoms have been calculated.
Computations were performed by using CRYSTALS [56]
adapted on a Micro Vax II. Atomic form factors for
neutral B, C, N, O, and H were taken from lit. [57].
The structures were solved by direct methods using the
SHELXS86 program [58]. Hydrogen atoms were calculated
and refined with an overall isotropic temperature factor.
Anisotropic temperature factors were introduced for all
non-hydrogen atoms and least-squares refinements were
carried out by minimizing Sw(ꢁFoꢂ−ꢂFcꢁ)2, where Fo and
Fc are the observed and calculated structure factors.
Models reached convergence with R=S(ꢁFoꢂ−ꢂFcꢁ)/
SꢂFoꢂ and Rw=[Sw(ꢂFoꢂ−ꢂFcꢂ)2/Sw(Fo)2]1/2. Criteria for
a satisfactory complete analysis were the ratios of rms
shift to standard deviation being less than 0.1 and no
significant features in the final difference map. In all cases
only reflections on the basis of Friedel’s law have been
collected and a reflections to parameter ratio \5 has
been considered sufficient for the kind of studies per-
formed in here.
have been deposited at the Cambridge Crystallographic
Data Center.
Elemental microanalyses were performed by Oneida
Research Services, Whitesboro, NY 13492.
All starting materials were commercial. Solvents were
used without further purification, but single crystals were
grown from spectrophotometric grade solvents.
5.1. Preparation of 4,14,24,34-tetra(3-nitrophenyl)
[3,5,13,15,23,25,33,35]octaoxa[41,42,43,44]tetraaza-
[4,14,24,34]tetraborapentacyclo[31.3.1.17,11.117,21.127,31]-
dotriaconta-1(41),7,9,11(42),17,19,21(43),27,
29,31(44),37,39-dodecaene (16)
Compound 16 was prepared from 0.10 g (0.72 mmol)
of 2,6-pyridinedimethanol and 0.12 g (0.72 mmol) of
3-nitrophenylboronic acid in chloroform. The product
obtained is a colorless solid (0.16 g, 0.14 mmol), that is
slightly soluble in DMSO. m.p. (dec.) 284–286°C, yield
80%.1H-NMR (500 MHz, DMSO-d6) l (ppm): 3.37–3.67
(8H, AB, J 18 Hz, H-20), 4.61–5.28 (8H, AX, J 18 Hz,
H-9), 7.45 (4H, d, H-3), 7.51 (8H, d, H-13, H-15), 7.95
Supplementary material available: tables of atomic
coordinates, thermal parameters, bond lengths and an-
gles as well as observed and calculated structure factors

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
79
(4H, d, H-11), 7.99 (4H, d, H-5), 8.11 (4H, m, H-14), 8.63
(4H, t, H-4); 13C-NMR (125.8 MHz, DMSO-d6) l (ppm):
57.4 (C-20), 68.8 (C-9), 118.4 (C-5), 120.3 (C-3), 122.0
(C-14), 125.6 (C-11), 128.6 (C-13), 138.7 (C-15), 143.9
(C-4), 147.2 (C-12), 147.8 (C-10), 155.2, 158.2 (C-2, C-6);
IR (KBr) w (cm−1): 3068 (C–Harom.), 2928 (CꢀHaliph.),
2850, 1654, 1648 (CꢁN), 1636, 1622 (CꢁN, CꢁC), 1252,
1198, 1092 (BꢀC, BꢀO, CꢀO), 808, 792, 732, 710
(CꢀHarom.). Elemental analysis Anal. Calc.: C, 57.82, H,
4.11, N, 10.37%. Found: C, 57.94, H, 4.13, N, 9.86%.
[M+ꢀC7H7, 13], 440 (4), 438 (6), 266 (2), 264 (2), 175 (10)
174 (100), 173 (27) 132 (2), 91 (3). IR (KBr) w (cm−1):
3040 (w), 3022 (w), 2944 (w), 2914 (w), 2850 (w), 1638
(CꢁN, s), 1160 (s), 1482 (s), 1310 (s), 1170 (s), 1150 (s),
1
970 (s), 770 (s), 756 (s). H-NMR (400 MHz, CDCl3) l
(ppm): 8.49 (1H, s, H-7), 7.51 (1H, dt, J 7.7, 1.5 Hz, H-4),
7.47 (1H, dd, J 7.7, 1.5 Hz, H-6), 7.34 (1H, s, H-11), 7.32
(1H, d, J 7.3, Hz, H-15), 7.14 (1H, t, J 7.3 Hz, H-14),
7.03 (1H, d, J 7.7 Hz, H-3), 7.02 (1H, d, J 7.3, Hz, H-13),
6.94 (1H, dt, J 7.7, 1.46 Hz, H-5), 3.64 (1H, dt, J 10.1,
3.1 Hz, H-9), 3.50 (1H, dt, J 11.8, 3.6 Hz, H-8), 3.42 (1H,
dd, J 11.8, 3.6 Hz, H-8%), 3.29 (1H, dd, J 10.1, 3.1 Hz,
H-9%), 2.28 (3H, s, Me); 13C-NMR (100 MHz, CDCl3) l
(ppm): 164.4 (C-7), 160.8 (C-2), 137.5 (C-4), 136.3 (C-12)
132.9 (C-11), 131.0 (C-6), 129.1 (C-15), 127.8 (C-13),
127.3 (C-14), 119.0 (C-3), 118.7 (C-5), 115.9 (C-1), 60.6
(C-8), 59.8 (C-9), 21.7 (Me); 11B-NMR (128 MHz,
CDCl3) l (ppm): 3.5 (h1/2=399 Hz); Elemental analysis
Calc.: C, 72.48, H, 6.08, N, 5.29%. Found: C, 72.34, H,
5.98, N, 5.35%.
5.2. Preparation of 2-(salicylideneamino)-1-
hydroxyethane
2-(Salicylideneamino)-1-hydroxyethane (H2SAE) was
prepared from equimolar quantities of 2-aminoethanol
and salicylaldehyde under reflux in benzene for 30 min.
The solvent and the water formed during the reaction
were removed by a Dean–Stark trap to obtain a yellow
oil (2.98 g, 18.04 mmol), yield 95%.
5.3.3. 2,11-Di-(4%-methylphenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
6,15-diene (17c)
5.3. Preparation of the boronates: general procedure
for the preparation of compounds 17a–j
Compound 17c was prepared from 0.50 g (3.00 mmol)
of H2SAE and 0.41 g (3.00 mmol) of 4-methylphenyl-
boronic acid. The product obtained is a white solid (0.72
g, 1.35 mmol) that is insoluble in all common solvents.
Crystals suitable for X-ray diffraction were obtained,
when the reaction was performed in THF at room
temperature without stirring, m.p. 291–293°C, yield
91%. MS (EI, 70 eV) m/z: 439 [M+ꢀC7H7, 13], 440 (4),
438 (6), 266 (9), 175 (10) 174 (100), 173 (26), 132 (2),
91(2). IR (KBr) w (cm−1): 3060 (w), 2940 (w), 2916 (w),
2848 (w), 1640 (CꢁN, s), 1606 (s), 1560 (s), 1482 (s), 1450
(s), 1440 (s), 1388 (s), 1308 (s), 1234 (s) 1218 (s), 1194 (s),
1180 (s), 1150 (s), 1138 (s), 1128 (s), 1110 (s), 1026 (s),
1018 (s), 962 (s) 928 (s), 778 (s), 754 (s), 738 (s); Elemental
analysis (C32H32B2N2O4·H2O) Calc.: C, 70.01, H, 6.20,
N, 5.10%. Found: C, 69.58, H, 5.77, N, 4.96%.
The following procedure is representative for the
preparation of all dimeric compounds described in this
study.
Equimolar quantities of the corresponding arylboronic
acid and H2SAE were refluxed in 10 ml benzene for 30
min. The solvent and water formed during the reaction
were removed by a Dean–Stark trap. The product was
filtered, washed and dried.
5.3.1. 2,11-Di-(2%-methylphenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooc-
tadeca-6,15-diene (17a)
Compound 17a was prepared from 0.50 g (3.00 mmol)
of H2SAE and 0.41 g (3.00 mmol) of 2-methylphenyl-
boronic acid. The product obtained is a white solid (0.70
g 1.31 mmol), m.p. 293–294°C, yield 88%. MS (EI, 70
eV) m/z: 439 [M+ –C7H7, 7], 440 (2), 438 (3), 266 (1.5),
175 (10), 174 (100), 173 (26), 132 (2). IR (KBr) w (cm−1):
3058 (w), 3012 (w), 2970 (w), 2936 (w), 2858 (w), 1638
(CꢁN, s), 1560 (s), 1606 (s), 1464 (s), 1448 (s), 1310 (s),
1234 (s), 1202 (s), 1186 (s), 1150 (s), 1114 (s), 1016 (s),
966 (s), 746 (s), 740 (s). Elemental analysis Calc.: C, 72.48,
H, 6.08, N, 5.29%. found: C, 72.16, H, 6.04, N, 5.21%.
5.3.4. 2,11-Di-(3%-methoxyphenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
6,15-diene (17d)
Compound 17d was prepared from 0.50 g (3.00 mmol)
of H2SAE and 0.45 g (3.00 mmol) of 3-methoxyphenyl-
boronic acid. The product obtained is a yellow solid (0.78
g, 1.42 mmol) that is insoluble in all common solvents,
m.p. 278–280°C, yield 92%. MS (EI, 70 eV) m/z: 455
[M+ꢀC7H7O, 4], 456 (1), 454 (2), 281 (3), 175 (16), 174
(100), 173 (40), 148 (18), 132 (4), 77 (7). IR (KBr) w
(cm−1) 3008 (w), 2956 (w), 2934 (w), 2910 (w), 2854 (w),
2832 (w), 1634 (CꢁN, s), 1606 (s), 1578 (s), 1560 (s), 1480
(s), 1408 (s), 1308 (s), 1254 (s), 1238 (s), 1174 (s), 1150
(s), 1138 (s), 1122 (s), 1026 (s), 1008 (s), 986 (s), 786 (s),
778 (s), 752 (s); Elemental analysis Anal. Calc.: C, 68.35,
H, 5.73, N, 4.98%. Found: C, 67.48, H, 5.70, N, 4.87%.
5.3.2. 2,11-Di-(3%-methylphenyl)dibenzo[h,q]-6,15-
diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
7,16-diene (17b)
Compound 17b was prepared from 0.50 g (3.00 mmol)
of H2SAE and 0.41 g (3.00 mmol) of 3-methylphenyl-
boronic acid. The product obtained is a white solid (0.65
g, 1.22 mmol) that is slightly soluble in chloroform, m.p.
287–289°C, yield 82%. MS (EI, 70 eV) m/z: 439

80
N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
5.3.5. 2,11-Di-(4%-methoxyphenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooc-
tadeca-6,15-diene (17e)
chlorophenylboronic acid. The product obtained is a
yellow solid (0.82 g 1.35 mmol) that is slightly soluble
in chloroform, m.p. 292–294°C, yield 95%. MS (EI, 70
eV) m/z: 459 [M+ꢀC6H4Cl, 7], 460 (3), 461 (2), 255 (2),
254 (4), 175 (11), 174 (100), 173 (28), 148 (9); IR (KBr)
w (cm−1): 2944 (w), 2856 (w), 1640 (CꢁN, s), 1636
(s),1560 (s), 1480 (s), 1308 (s), 1216 (s), 1198 (s), 1150
(s), 1138 (s), 1126 (s) 1150 (s), 1110 (s), 1086 (s), 1022
(s), 1014 (s), 966 (s), 754 (s); 1H-NMR (270 MHz,
CDCl3) l (ppm): 8.49 (1H, s, H-7), 7.53 (1H, dt, J 7.8,
1.7 Hz, H-4), 7.46 (1H, dd, J 8.1, 1.7 Hz, H-6), 7.43
(2H, d, J 8.4 Hz, H-11), 7.20 (2H, d, J 8.4 Hz, H-12),
7.01 (1H, d, J 7.8 Hz, H-3), 6.96 (1H, t, J 8.1, Hz, H-5),
3.58 (1H, dt, J 9.15, 1.98 Hz, H-9), 3.48 (1H, dt, J 11.6,
3.7 Hz, H-8), 3.34 (1H, dd, J 11.2, 3.7 Hz, H-8%), 3.28
(1H, dd, J 10.2, 2.96 Hz, H-9%); 13C-NMR (68 MHz,
CDCl3) l (ppm): 164.7 (C-7), 160.7 (C-2), 138.0 (C-4)
133.5 (C-12) 133.2 (C-11), 131.1 (C-6), 127.5 (C-13),
119.2 (C-3), 119.0 (C-5), 115.8 (C-1), 60.5 (C-8), 59.7
(C-9); 11B-NMR (87 MHz, CDCl3) l (ppm): 2.14 (h1/
2=1126 Hz); Elemental analysis Anal. Calc.: C, 63.04,
H, 4.59, N, 4.90%. Found: C, 62.64, H, 4.54, N, 4.70%.
Compound 17e was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.45 g (3.00 mmol) of 4-
methoxyphenylboronic acid. The product obtained is a
yellow solid (0.75 g, 1.33 mmol) that is insoluble in all
common solvents, m.p. 283–285°C, yield 89%. MS (EI,
70 eV) m/z: 455 [M+ꢀC7H7O, 11], 456 (3), 454 (49),
281 (3), 280 (3), 175 (20), 174 (100), 173 (51), 148 (18).
IR (KBr) w (cm−1) 3024 (w), 2962 (w), 2928 (w), 2870
(w), 2836 (w), 2748 (w), 1640 (CꢁN, s), 1600 (s), 1558
(s), 1504 (s), 1450 (s), 1440 (s), 1388 (s), 1308 (s), 1234
(s), 1218 (s), 1194 (s), 1234 (s), 1218 (s), 1200 (s), 1170
(s), 1148 (s), 1138 (s), 1124 (s), 1110 (s), 1024 (s), 1014
(s), 994 (s), 928 (s), 814 (s), 784 (s), 750 (s), 584 (s);
Elemental analysis (C32H32B2N2O6·H2O) Calc.: C,
66.17, H, 5.89, N, 4.82%. Found: C, 66.66, H, 5.34, N,
4.89%.
5.3.6. 2,11-Di-(3%-chlorophenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooc-
tadeca-6,15-diene (17f)
Compound 17f was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.47 g (3.00 mmol) of 3-
chlorophenylboronic acid. The product obtained is a
yellow solid (0.77 g, 1.35 mmol) that is slightly soluble
in chloroform, m.p. 288–290°C, yield 90%. MS (EI, 70
eV) m/z: 459 [M+ꢀC6H4Cl, 10], 460 (4), 461 (3), 175
(13), 174 (100), 173 (34), 148 (10). IR (KBr) w (cm−1):
3046 (w), 2936 (w), 2864 (w), 1636 (CꢁN, s), 1608 (s),
1560 (s), 1480 (s), 1462 (s), 1448 (s), 1396 (s), 1304 (s),
1234 (s) 1194 (s), 1152 (s), 1140 (s), 1112 (s), 1090 (s)
1022 (s), 772 (s), 752 (s), 742 (s), 722 (s), 698 (s);
1H-NMR (300 MHz, CDCl3) l (ppm): 8.52 (1H, s,
H-7), 7.59 (1H, dt, J 7.5, 1.5 Hz, H-4), 7.57 (1H, dd, J
7.7, 1.5 Hz, H-6), 7.54 (1H, d, J 1, Hz, H-11), 7.20 (1H,
dd, J 8.4, 1.4 Hz, H-15), 7.19 (1H, dd, J 8.4, 1.4 Hz,
H-13), 7.17 (1H, dt, J 8.4, 1.4 Hz, H-14), 7.05 (1H, d,
J 8.1 Hz, H-3), 7.00 (1H, dt, J 7.7, 1.5 Hz, H-5), 3.60
(1H, dt, J 10.7, 2.9 Hz, H-9), 3.50 (1H, dt, J 10.5, 2.7
Hz, H-8), 3.40 (1H, dd, J 10.4, 2.3 Hz, H-8%), 3.32 (1H,
dd, J 10.2, 2.3 Hz, H-9%); 13C-NMR (75.47 MHz,
CDCl3) l (ppm): 165.2 (C-7), 160.9 (C-2), 138.3 (C-4)
134.0 (C-12) 132.5 (C-11), 131.7 (C-6), 129.3 (C-15),
127.6 (C-13), 130.4 (C-14), 119.6 (C-3), 119.3 (C-5),
116.2 (C-1), 60.8 (C-8), 60.1 (C-9); 11B-NMR (96.3
MHz, CDCl3) l (ppm): 6.6 (h1/2=600 Hz); Elemental
analysis Calc.: C, 63.04, H, 4.59, N, 4.90%. Found: C,
63.58, H, 4.83, N, 5.35%.
5.3.8. 2,11-Di-(3-nitrophenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
6,15-diene (17h)
Compound 17h was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.501 g (3.00 mmol) of 3%-nitro-
phenylboronic acid. The product obtained is a white
solid (0.83 g, 1.40 mmol) that is insoluble in all com-
mon solvents, m.p. 300–302°C, yield 93%; MS (EI, 70
eV) m/z: 470 [M+ꢀC6H4NO2, 3], 471 (1), 469 (2), 351
(1), 297 (2), 296 (3), 175 (10), 174 (100), 173 (26), 148
(6); IR (KBr) w (cm−1): 3060 (w), 2972 (w), 2932 (w),
2918 (w), 2872 (w), 2856 (w), 1636 (CꢁN, s), 1616 (s),
1558 (s), 1516 (s), 1480 (s), 1462 (s), 1448 (s), 1344 (s),
1304 (s) 1234 (s), 1150 (s), 1140 (s), 1132 (s), 1010 (s)
1094 (s), 1028 (s), 984 (s), 968 (s), 762 (s), 732 (s), 708
(s); Elemental analysis Calc.: C, 60.84, H, 4.42, N,
9.45%. Found: C, 60.31, H, 4.24, N, 9.41%.
5.3.9. 2,11-Di-(3%-trifluoromethylphenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
6,15-diene (17i)
Compound 17i was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.56 g (3.00 mmol) of 3%-trifl-
uoromethylphenylboronic acid. The product obtained
is a yellow solid (0.92 g, 1.44 mmol) that is insoluble in
all common solvents. Crystals suitable for X-ray dif-
fraction were obtained, when the reaction was per-
formed in THF at r.t. without stirring, m.p.
290–292°C, yield 96%. MS (EI, 70 eV) m/z: 493
[M+ꢀC7H4F3, 4], 494 (1), 492 (2), 288 (7), 175 (11),
174 (100), 173 (27), 148 (6); IR (KBr) w (cm−1): 3064
(w), 3034 (w), 2946 (w), 2876 (w), 1640 (CꢁN, s), 1608
5.3.7. 2,11-Di-(4%-chlorophenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooctadeca-
6,15-diene (17g)
Compound 17g was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.47 g (3.00 mmol) of 4-

N. Farfa´n et al. / Journal of Organometallic Chemistry 581 (1999) 70–81
81
[15] A. Meller, H.J. Fu¨llgrabe, Chem. Ber. 111 (1978) 819.
[16] A. Meller, H.J. Fu¨llgrabe, Z. Naturforsch. 33B (1978) 156.
[17] A. Meller, H.J. Fu¨llgrabe, C.D. Habben, Chem. Ber. 112 (1979)
1252.
[18] B. Krebs, H.-U. Hu¨rter, Angew. Chem. Int. Ed. Engl. 19 (1980)
481.
[19] B.M. Gimarc, N. Trinajstic, Inorg. Chem. 21 (1982) 21.
[20] B.M. Gimarc, J.K. Zhu, Inorg. Chem. 22 (1983) 479.
[21] R. Ko¨ster, G. Seidel, R. Boese, B. Wrackmeyer, Chem. Ber. 123
(1990) 1013.
(s), 1560 (s), 1482 (s), 1330 (s), 1308 (s), 1234 (s), 1190
(s), 1176 (s) 1162 (s), 1138 (s), 1118 (s), 1090 (s), 1018
(s) 980 (s), 970 (s), 786 (s), 762 (s), 708(s), 686 (s), 680
(s); Elemental analysis Anal. Calc.: C, 60.24, H, 4.10,
N, 4.38%. Found: C, 60.01, H, 4.00, N, 4.35%.
5.3.10. 2,11-Di-(4%-fluorophenyl)dibenzo[h,q]-
7,16-diaza-1,3,10,12-tetraoxa-2,11-diboracyclooc-
[22] R. Ko¨ster, G. Seidel, R. Boese, Chem. Ber. 123 (1990) 2109.
[23] R. Ko¨ster, G. Seidel, B. Wrackmeyer, Chem. Ber. 123 (1990) 2287.
[24] T.D. James, K.R.A. Samankumara Sandanayake, S. Shinkai,
Angew. Chem. Int. Ed. Engl. 35 (1996) 1910.
tadeca-6,15-diene (17j)
Compound 17j was prepared from 0.50 g (3.00
mmol) of H2SAE and 0.42 g (3.00 mmol) of 4%-
fluorophenylboronic acid. The product obtained is a
yellow solid (0.78 g, 1.45 mmol) that is insoluble in all
common solvents. Crystals suitable for X-ray diffrac-
tion were obtained, when the reaction was performed in
dichloromethane at r.t. without stirring, m.p. 283–
285°C, yield 97%; MS (EI, 70 eV) m/z: 443
[M+ꢀC6H4F, 6], 444 (1), 442 (3), 238 (7), 175 (10), 174
(100), 173 (26), 132 (2); IR (KBr) w (cm−1): 3040 (w),
2976 (w), 2932 (w), 2872 (w), 1640 (CꢁN, s), 1606 (s),
1588 (s), 1558 (s), 1310 (s), 1234 (s), 1208 (s), 1192 (s),
1152 (s), 1138 (s), 1124 (s), 1110 (s), 1038 (s), 1024 (s),
964 (s), 930 (s), 820 (s), 752 (s). Elemental analysis
(C30H26B2F2N2O4·H2O) Calc.: C, 64.49, H, 5.06, N,
5.03%. Found: C, 64.49, H, 4.74, N, 4.99%.
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