Study of the Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid

Article abstract of DOI:10.1002/ejic.200300337

Evaluation of the reactivity of eight tridentate ligands derived from amino alcohols and salicylaldehyde, 2-hydroxyacetophenone, or 2-hydroxybenzophenone with ferrocenyl boronic acid has shown that the reaction leads to both monomeric and dimeric ferrocen

Full text of DOI:10.1002/ejic.200300337

FULL PAPER
Study of the Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid
[a]
[b]
[b]
[b]
´
´
Victor Barba,* Rubı Xochipa, Rosa Santillan, and Norberto Farfan
Keywords: Cyclizations / Boron / Tridentate ligands / Ferrocene
Evaluation of the reactivity of eight tridentate ligands de-
rived from amino alcohols and salicylaldehyde, 2-hydroxya- troscopic data. Furthermore, the structures of the dimeric (2a)
cetophenone, or 2-hydroxybenzophenone with ferrocenyl and monomeric (5b) boron complexes were established by
boronic acid has shown that the reaction leads to both mono- X-ray diffraction analyses. The dimeric compound contains a
ical and multinuclear (1H, 11B, 13C) magnetic resonance spec-
meric and dimeric ferrocenyl boronates. A coordinative N−B
bond is essential to give the tetrahedral boron atoms that are
responsible for the formation of heterobicyclic structures con-
taining six, seven and ten members. The purity and identity
of all compounds were unequivocally established by analyt-
ten-membered ring in a boat−chair−boat conformation, while
the monomeric compound has a seven-membered ring with
a chair conformation.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
Recently, ferrocenyl boron macrocycles have been pre-
pared by the reaction of 1,1Ј diborylated ferrocene [1,1Ј-
The synthesis and study of ferrocenyl boron derivatives {C5H4[B(R)Br]}2] with tetrafunctional Lewis bases such as
has generated considerable interest due to their interesting 2,5-di(pyrazol-1-yl)hydroquinone and quaterpyridine.[17,18]
properties and potential applications.[1Ϫ6] The boryl group Here, formation of the dative NϪB bond facilitates cycliza-
attached to the Cp fragment exerts an interesting influence, tion leading to cyclic oligomers. However, the reaction of
attributed to pπϪpπ interactions between the cyclopen- difunctional Lewis bases such as pyrazine or 4,4Ј-bipyridine
tadienyl system and the boron pz orbital. Additionally, the with 1,1-diborylated ferrocene led to polymeric materials
through-space FeϪB interaction seen in (dibromoboryl)fer- only.[19]
rocenes and (bispentafluorophenyl)boryl ferrocenes is fav-
Relatively few detailed studies have been performed on
ored because the occupied d orbitals on the iron center have the coordination chemistry of ferrocenyl boronic acid. Pre-
the appropriate symmetry to interact with the empty p or- viously, we reported the synthesis of monomeric,[20,21] di-
bital of the boron center.[6b,7] Borylated ferrocenes are isoe- meric,[21,22] trimeric,[23] and tetrameric[24] boron com-
lectronic with stable ferrocenyl carbocations.[7,8] Due to pounds by reaction of boronic acids with Schiff bases where
possible applications of their unusual properties to elec- the formation of dative NϪB bonds is very important in
tronic materials, boron compounds containing ferrocenyl their cyclization.[25] Here we describe the reactivity of ferro-
units have recently been examined as charge-transfer cenyl boronic acids with different tridentate ligands using
complexes.[9Ϫ12]
simple condensation reactions.
Moreover, boronic acids are potentially useful for selec-
tive recognition of sugars as they can form strong boronic
acidϪdiol interactions.[10,13,14] In addition, the com-
plexation of boronic acids with sugars affords a fluor-
escence intensity that is affected by complexation.[15] Ferro-
Results and Discussion
We have investigated the reaction of boronic acids with
cenyl boronic acid derivatives have also been used in the different ligands to establish the factors involved in the for-
electrochemical detection of saccharides[13,14] and the selec- mation of macrocyclic structures. To further evaluate elec-
tive recognition of fluoride, whereby the boron atom acts tronic and steric factors we selected CpFeC5H4B(OH)2, as
as a hard acid and fluoride as the hard base.[16]
the ferrocenyl group is bulkier and more electrophilic than
a phenyl group.[22] Thus, we discuss here the reactivity of
various tridentate ligands with ferrocenyl boronic acid in
order to prepare new macrocyclic boron compounds.
The reaction of tridentate ligand 1a derived from salicyl-
aldehyde and ethanolamine with ferrocenyl boronic acid
was carried out under reflux of THF to yield, after 60 min,
a red solid that is stable to air (Scheme 1). The EI mass
[a]
´
Centro de Investigaciones Quımicas UAEM,
Av. Universidad 1001, C. P. 62210, Cuernavaca Morelos,
´
Mexico
E-mail: vbarba@ciq.uaem.mx
Departamento de Quımica, Centro de Investigacion y de
[b]
´
´
Estudios Avanzados del IPN
´
´
Apdo. Postal 14-740, 07000 Mexico, D. F., Mexico
E-mail: jfarfan@mail.cinvestav.mx
118
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200300337
Eur. J. Inorg. Chem. 2004, 118Ϫ124

Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid
FULL PAPER
Scheme 1. Dimeric boron compounds from tridentate ligands
spectrum has a highest peak at m/z ϭ 718, establishing the
dimeric composition of compound 2a.
To determine if a larger substituent could influence the
imine bond and alter the course of the reaction, we pre-
pared ligands derived from 2-hydroxyacetophenone (1b)
and 2-hydroxybenzophenone (1c); however, these ligands
react with ferrocenyl boronic acid to give dimeric boronates
2b and 2c in moderate yields (Scheme 1).
The dimeric composition of these compounds was estab-
lished by spectroscopic analyses whereby the EI mass spec-
tra have highest peaks at m/z ϭ 746 and 870, which corre-
spond to the molecular weight of 2b and 2c, respectively. In
all cases, the base peak corresponds to the loss of one ferro-
cenyl moiety. NMR analyses of 2a and 2c could not be ob-
tained due the compounds’ insolubility in common sol-
vents. In the NMR spectra of 2b only a single set of signals
is observed, owing to the C2 fold axis present in the mol-
ecule. The 11B NMR spectrum of 2b shows a singlet at δ ϭ
7.8 ppm, which is in the range expected for tetracoordinate
boron atoms containing a dative NϪB bond.[26]
Figure 1. Molecular structure of solid-state 2a
The stretching band for the CϭN group in the IR spectra
The tetrahedral geometry for the boron atom is evident
is shifted to 1640, 1610, and 1606 cmϪ1 for 2a, 2b, and 2c, from the bond angles, which are in the range
respectively. The lower shift showed by 2b and 2c can be 106.9(3)Ϫ111.5(3)°, the largest being O(1)ϪB(1)ϪC(10),
attributed to electronic and inductive effects of the methyl which in the boron-phenyl derivative[24] is 109.4(2)°. This
and phenyl groups present.
difference in bond angles may be attributed to the steric
The crystal structure of 2a confirms the dimeric nature effect of the bulkier ferrocene unit, compared to the phenyl
of this compound (Figure 1). Crystallographic data and group. As expected, the inverse effect is observed on com-
selected distances and bonds are listed in Tables 1 and 2, paring the N(1)Ϫ(B1)Ϫ(C10) angle, which is slightly
respectively. In analogy to the dimeric compounds pre- smaller [107.0(3)°] in the ferrocene derivative than in the
viously described,[22,24,25] the structure has an inversion phenyl [108.1(2)°] one.[24] The six-membered heterocycle is
center at the center of the ten-membered ring. Ferrocenyl nearly planar, as evidenced by the O(1)ϪB(1)ϪN(1)ϪC(7)
substituents on each boron atom are trans disposed with torsion angle (10.2°). The ten-membered heterocycle pre-
regard to the ten-membered macrocycle, which may be at- sents a boatϪchairϪboat conformation. The structure
tributed to the bulkiness of the ferrocenyl moieties. A dative shows a relatively short transannular H···O interaction
˚
NϪB bond, together with the required tetrahedral ge- (2.47 A) between the oxygen atom on one side of the ring
ometry of the boron atoms, is responsible for the dimeric with a hydrogen atom from the CH2 group on the op-
form of these compounds.
Thus, B(1)ϪN(1) [1.632(5) A] in 2a is very similar to that
posite side.
˚
In contrast, the reaction of ligands 1d and 1e, obtained
of the boron-phenyl derivative [1.624(3) A[24]] and accords from salicylaldehyde and 1-aminomethylcyclohexanol, with
˚
with analogous systems.[27] The C(10)ϪB(1) [1.595(6) A] is two equivalents of ferrocenyl boronic acid provided exclus-
˚
˚
slightly shorter than in the phenyl derivative [1.601(3) A] ively complexes 3a and 3b (Scheme 2). The different reactiv-
because the ferrocenyl group is a stronger electron donor ity, compared to 1a and 1c ligands, may be attributed to the
than the phenyl group.
cyclohexyl group at the β position relative to the nitrogen
Eur. J. Inorg. Chem. 2004, 118Ϫ124
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
119

´
V. Barba, R. Xochipa, R. Santillan, N. Farfan
FULL PAPER
Table 1. Crystal data and structure refinement for 2a and 5b
2a
5b
Empirical formula
Molecular mass
Crystal size [mm3]
Temperature [K]
Crystal system
C19H18BNFeO2
359.01
0.20 ϫ 0.24 ϫ 0.50
293
C22H24BNFeO2
410.08
0.48 ϫ 0.30 ϫ 0.21
293
monoclinic
P21/c
triclinic
¯
Space group
P1
Unit cell dimensions
˚
a [A]
7.7230(10)
10.5580(10)
10.7290(10)
103.660(10)
95.000(10)
109.610(10)
787.44 (15)
2
1.51
0.968
Ϫ8/9, Ϫ12/0, Ϫ12/13
3117
2951
8.5644(6)
11.3609(7)
19.1696(12)
90.00
91.5850(10)
90.00
1864.5(2)
4
1.429
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
3
˚
V [A ]
Z
Density (calculated) [g/cm3]
Absorption coefficient [mmϪ1
Index ranges
]
0.826
Ϫ10/10, Ϫ13/13, 0/23
17467
3283
Reflections collected
Independent reflections
parameters
217
246
Final R indices [IϾ2σ(I)]
R indices (all data)
GOOF
0.049
wR2 ϭ 0.1597
1.005
0.0487
wR2 ϭ 0.1058
1.219
3
˚
Largest diff. peak and hole [e/A ]
0.437/ Ϫ0.309
0.302 / Ϫ0.297
˚
tempts to form the dimeric compound from this ligand by
using different reaction conditions as well as other boronic
acids were unsuccessful.
Table 2. Selected bond lengths [A] and angles [°] for 2a and 5b
2a
5b
Bicyclic structures for 3a and 3b were established by MS,
where the molecular peaks appear at m/z ϭ 639 and 653,
respectively. 11B NMR spectra show two signals at δ ϭ 34.8
and 8.2 ppm for 3a and 38.3 and 7.2 ppm for 3b, corre-
sponding to trigonal and tetrahedral boron atoms, respec-
tively. 1H NMR shows an AB system for the NCH2C group,
due to the formation of the seven-membered heterocycle.
˚
Bond lengths [A]
O(1)ϪB(1)
O(1)ϪC(1)
1.491(5)
1.324(5)
1.432(6)
1.413(5)
1.632(5)
1.595(6)
1.286(5)
1.459(5)
1.481(4)
1.333(3)
1.426(4)
1.424(3)
1.641(3)
1.596(4)
1.290(4)
1.473(3)
O(2)ϪB(1)
O(2)ϪC(9)[a]
B(1)ϪN(1)
B(1)ϪC(10)[b]
N(1)ϪC(7)
N(1)ϪC(8)[c]
We then examined the ligand containing three carbon
atoms between the OH and CϭN groups to evaluate the
effect upon ring closure. 1f reacted with ferrocenyl boronic
Bond angles [°]
B(1)ϪO(1)ϪC(1)
B(1)ϪO(2)ϪC(9)[a]
O(1)ϪB(1)ϪO(2)
O(1)ϪB(1)ϪN(1)
O(2)ϪB(1)ϪN(1)
O(1)ϪB(1)ϪC(10)[b]
O(2)ϪB(1)ϪC(10)[b]
N(1)ϪB(1)ϪC(10)[b]
B(1)ϪN(1)ϪC(7)
B(1)ϪN(1)ϪC(8)[c]
C(7)ϪN(1)ϪC(8)[c]
125.9(4)
119.0(3)
111.5(4)
106.9(3)
109.1(3)
111.5(3)
110.6(4)
107.0(3)
121.8(3)
119.2(3)
119.0(4)
119.6(2)
119.0(2)
111.1(2) acid under reflux in THF (40 min) to yield a red solid that
105.0(2)
107.8(2)
111.1(2)
111.8(2)
107.5(2)
122.7(2)
115.0(2)
122.3(2)
was characterized as monomeric compound 4 (Scheme 3).
In accordance with previous reports,[20,28] the six-membered
ring is favored (monomer) over a twelve-membered ring (di-
mer) in this type of ligands. The 11B NMR spectrum shows
a signal significantly up-field (δ ϭ 5.0 ppm) with respect to
ferrocenyl boronic acid, due to the formation of a tetra-
1
hedral boron atom. In H NMR, an AB system appears at
[a]
[b]
[c]
δ ϭ 4.82 and 4.89 ppm, corresponding to the CH2 group.
The iminic proton is shifted to down field (9.21 ppm) in
comparison with the ligand (8.57 ppm) due to formation of
the dative NϪB bond. All boron compounds described her-
ein shown diastereotopic signals for the C5H4 moiety at-
tached to the boron atoms, in accordance with the litera-
ture data.[2]
For 5b is C(12). For 5b is C(13). For 5b is C(9).
atom in ligands 1d and 1e, which could cause strong intra-
molecular interactions upon formation of either a dimeric
structure or a monomeric compound containing five- and
six-membered rings. Consequently, bicyclic structures are
preferred. The six- and seven-membered rings contain two
boron atoms, one tetrahedral and the other tricoordinate.
We also prepared ligands 1g and 1h from 4-aminobutanol
When only one equivalent of ferrocenyl boronic acid is and salicylaldehyde or 2-hydroxyacetophenone, respectively.
used, 3a and 3b are also formed, but in lower yields. At- 1g and 1h reacted with ferrocenyl boronic acid to give the
120
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Eur. J. Inorg. Chem. 2004, 118Ϫ124

Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid
FULL PAPER
Scheme 2. Boron complexes having two boron atoms with different geometry
Scheme 3. Monomeric boron compound from an aromatic tridentate ligand
monomeric compounds 5a and 5b with six- and seven- in the seven-membered ring [107.8(2)°] as a result of the
membered-rings (Scheme 4). Only a monomeric product annular tension and planarity of the ring. The seven-mem-
was isolated, in contrast to using phenylboronic acid,[30] bered ring has a chair conformation in the solid state (Fig-
where both monomeric and dimeric compounds were iso- ure 2).
lated; a possible explanation is that the bulky ferrocenyl
group prevents formation of the dimeric compound. Tetra-
coordination of the boron atom is evident in the 11B NMR
spectra, with signals at δ ϭ 9.6 ppm and 8.7 ppm for 5a and
5b, respectively, as a result of dative NϪB bond formation.
Compound 5b was characterized by X-ray crystal struc-
Conclusions
Ferrocenyl boronic acid reacts with different tridentate
ture analysis (Figure 2). Selected bond lengths and angles ONO ligands to provide, in one step, novel dimeric and
are summarized in Table 2. The corresponding bond lengths monomeric structures depending on the ligand used. Ne-
and angles in the six-membered rings of 2a and 5b are indis- ither different groups in the imine position nor a bulky
tinguishable within experimental error. Insignificant varia- group such as ferrocenyl influence the formation of the
tions were found in the dative bond, for 5b NϪB bond is structure. The new chemistry reported here may be useful in
˚
˚
1.641(3) A and is very similar to 2a [1.632(5) A]. In 5b, macrocyclic syntheses, and ferrocene derivatives could find
˚
BϪO is longer in the six-membered [1.481(4) A] than in the interesting applications for molecular recognition. Current
seven-membered [1.426(4) A] heterocycle, and the OϪBϪN work in our laboratory involves the reactivity of anal-
˚
bond angle is smaller in the six-membered [105.0(2)°] than ogous compounds.
Scheme 4. Monomeric boron compounds from tridentate ligands derived from 4-aminobutanol
Eur. J. Inorg. Chem. 2004, 118Ϫ124
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121

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V. Barba, R. Xochipa, R. Santillan, N. Farfan
FULL PAPER
the solvent was then removed with a DeanϪStark trap so as to
favor precipitation. The product was then filtered off and washed
with small amounts of the same solvent.
Complex 2a: Compound 2a was prepared from 1a (0.50 g,
3.02 mmol) and ferrocenyl boronic acid (0.70 g, 3.02 mmol). A red
solid was obtained, in 72% yield (0.78 g, 1.08 mmol), that is insol-
uble in all common solvents, m.p. 280Ϫ282 °C. IR ν˜ ϭ (KBr):
3412, 2930, 2850, 1640 (CϭN), 1608, 1560, 1480, 1438, 1316, 1308,
1234, 1214, 1148, 1126, 1110, 1104, 1054, 1044, 1026, 1010, 970,
794, 752 cmϪ1. EM (15 eV): m/z (%) ϭ 718 (1) [Mϩ] 570 (2), 361
(25), 359 (100), 358 (35), 357 (10), 356 (3), 334 (4), 333 (2), 330 (2),
294 (6), 293 (6), 292 (4), 291 (8), 290 (3), 255 (3), 187 (7), 186 (51),
184 (4), 175 (7), 174 (50), 173 (20), 121 (2). C38H36B2Fe2N2O4:
calcd. C 63.06, H 4.97, N 3.87; found C 63.38, H 5.33, N 3.84 (%).
Complex 2b: Compound 2b was prepared from 1b (0.50 g,
2.79 mmol) and ferrocenyl boronic acid (0.64 g, 2.79 mmol) as an
orange solid, in 77% yield (0.80 g, 1.06 mmol) that is slightly sol-
uble in chloroform, m.p. 204Ϫ206 °C. IR ν˜ ϭ (KBr): 2918, 2850,
1610 (CϭN), 1550, 1456, 1444, 1332, 1276, 1214, 1144, 1134, 1118,
1106, 1004, 814, 758 cmϪ1. MS (15 eV): m/z (%) ϭ 746 (5) [Mϩ],
745 (2), 585 (3), 584 (1), 399 (3), 398 (2), 375 (3), 374 (18), 373 (74),
372 (20), 371 (5), 370 (2), 359 (2), 358 (9), 357 (2), 308 (2), 296 (2),
212 (1), 189 (11), 188 (100), 187 (43), 186 (75), 185 (5), 184 (4), 174
(5), 121 (2), 72 (4), 71 (5), 43 (3), 42 (11), 41 (4). 1H NMR
(300 MHz, CDCl3): δ ϭ 2.84 (s, 3 H, Me), 4.10Ϫ3.93 (m, 4 H, 8-,
9-H), 4.22 (s, 5 H, Cp-H), 4.36 (m, 2 H, 12-, 13-H), 4.44 (m, 2 H,
11-, 14-H), 6.92 (t, J ϭ 7.7 Hz, 1 H, 5-H), 7.08 (d, J ϭ 7.7 Hz, 1
H, 3-H), 7.54 (t, J ϭ 7.7 Hz, 1 H, 4-H), 7.76 (d, J ϭ 7.7 Hz, 1 H,
6-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 16.7 (Me), 51.1 (C-
8), 61.4 (C-9), 71.9 (C-Cp), 77.2 (C-11, 14), 77.6 (C-12, 13), 118.7
(C-1, 5), 120.5 (C-3), 128.5 (C-6), 136.7 (C-4), 161.4 (C-2), 175.3
Figure 2. Molecular structure of solid-state 5b
Experimental Section
Materials and Methods: All reagents were purchased from Aldrich
and were used without further purification. NMR spectra were re-
corded at room temperature using the following spectrometers: Jeol
GSX 270, Bruker 300, and Jeol eclipseϩ400. Chemical shifts are
given in ppm. Infrared spectra were recorded on a PerkinϪElmer
16F-PC FT-IR spectrophotometer. Mass spectra were obtained
with a HP 5989-A mass spectrometer operating in electron impact
mode. Melting points were determined with a Gallenkamp MFB-
595 apparatus. Elemental microanalyses were performed by Oneida
Research Services (Whitesboro, NY. 13492).
(C-7) ppm. 11B NMR (96 MHz, CDCl3): δ ϭ 7.8 ppm (h1/2
ϭ
Crystal Structure Determination: Single Crystals of 2a suitable for
X-ray diffraction were obtained when the reaction was performed
in THF at 25 °C without stirring; crystals of 5b suitable for X-ray
structure analysis were grown by slow evaporation of a THF/
CH2Cl2 solution of the complex. Intensity data were collected at
293 K with an EnrafϪNonius CAD4 diffractometer for compound
2a and a Bruker-AXS APEX diffractometer with a CCD area de-
228 Hz). C40H40B2Fe2N2O4: calcd. C 63.91, H 5.32, N 3.72; found
C 63.96, H 5.78, N 3.54 (%).
Complex 2c: 2c was prepared from 1c (0.50 g, 2.07 mmol) and
ferrocenyl boronic acid (0.48 g, 2.07 mmol). A red solid was ob-
tained, in 83% yield (0.74 g, 0.84 mmol), that is insoluble in all
common solvents, m.p. 288Ϫ298 °C. IR ν˜ ϭ (KBr): 3094, 3066,
2934, 2916, 1606 (CϭN), 1548, 1474, 1456, 1444, 1338, 1214, 1148,
1118, 1112, 1102, 1026, 1012, 1002, 802, 752 cmϪ1. MS (15 eV):
m/z (%) ϭ 870 (15) [Mϩ], 435 (24), 311 (17), 239 (13), 368 (20), 296
(16), 250 (100), 236 (24), 186 (21), 148 (15), 98 (27), 84 (32), 44
(79). C50H44B2Fe2N2O4: calcd. C 68.56, H 5.02, N 3.20; found C
68.89, H 5.29; N 3.20 (%).
˚
tector for 5b; Mo-Kα-radiation, λ ϭ 0.71073 A, graphite mono-
chromator, ω ϭ 2θ scan. Empirical absorption corrections (DI-
FABS) were applied. The structures were solved by direct methods
(SHELXS-86)[30] and refined using SHLXS-97.[31] All non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were
placed in geometrically calculated positions using a riding model.
Crystallographic data for the structures have been deposited at the
Cambridge Crystallographic Data Center as supplementary mate-
rial No. 211441 for complex 2a and 210542 for 5b. Copies of the
data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB2 1EZ, UK. E-mail: deposit@ccdc.ca-
m.ac.uk.
Complex 3a: 3a was prepared from 1d (0.30 g, 1.28 mmol) and
ferrocenyl boronic acid (0.30 g, 1.28 mmol) as a red solid, in 73%
yield (0.60 g, 0.93 mmol), that is slightly soluble in chloroform,
m.p. 228 °C. IR ν˜ ϭ (KBr): 3504, 2928, 2850, 1638 (CϭN), 1552,
1474, 1458, 1446, 1406, 1390, 1382, 1270, 1260, 1214, 1176, 1148,
766 cmϪ1. MS (15 eV): m/z (%) ϭ 639 (100) [Mϩ], 595 (1), 478 (2),
427 (17), 362 (5), 320 (11), 242 (81), 212 (27), 186 (44), 148 (30),
General Method for the Preparation of Tridentate Ligands 1a؊1h:
The ligands were obtained by condensation of an aldehyde or ke-
tone with the corresponding amino alcohol under reflux in meth-
anol for 45 min. The water formed and part of the solvent was
removed using a DeanϪStark trap and the product was then dried
under high vacuum. Ligands 1a,[24] 1b,[29] 1f,[20] and 1g[30] have been
described previously.
1
121 (21), 95 (8), 67 (9), 56 (9). H NMR (300 MHz, CDCl3): δ ϭ
1.81Ϫ1.17 (m, 10 H, 10-, 10Ј-, 11-, 11Ј-, 12-H), 3.24 (d, J ϭ 12.9
Hz, 1 H, 8b-H), 3.68 (m, 1 H, 16-H), 4.01 (m, 1 H, 15-H), 4.12 (m,
1 H, 17-H), 4.18 (s, 5 H, Cp-H Btetra), 4.19 (d, J ϭ 12.9 Hz, 1 H,
8a-H), 4.29 (s, 5 H, Cp-H Btri), 4.33 (m, 1 H, 14-H), 4.37 (m, 1 H,
21-H), 4.42 (m, 1 H, 20-H), 4.54 (m, 1 H, 22-H), 4.61 (m, 1 H, 19-
H), 6.86 (t, J ϭ 8.6 Hz, 1 H, 5-H), 7.13 (d, J ϭ 8.6 Hz, 1 H, 3-H),
7.27 (d, J ϭ 8.6 Hz, 1 H, 6-H), 7.56 (t, J ϭ 8.6 Hz, 1 H, 4-H), 7.85
(s, 1 H, 7-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 21.8 (C-11Ј),
General Syntheses for Boron Complexes: An equimolar solution of
1aϪ1h and ferrocenyl boronic acid in THF (60 mL) was prepared
and then boiled under reflux for 60 min (two equivalents of the
boronic acid were used to prepare 3a and 3b complexes). Part of 21.9 (C-11), 26.0 (C-12), 34.8 (C-10Ј), 38.4 (C-10), 66.5 (C-8), 68.3
122  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjic.org
Eur. J. Inorg. Chem. 2004, 118Ϫ124

Reaction of Tridentate Ligands with Ferrocenyl Boronic Acid
(C-Cp Btetra), 68.5 (C-Cp Btri), 68.7 (C-16), 69.4 (C-15), 70.3 (C-
FULL PAPER
H, 9-, 10-H), 3.69 (t, J ϭ 9.0 Hz, 2 H, 8-H), 3.87 (m, 1 H, 16-H),
21), 71.2 (C-17), 71.4 (C-14), 72.4 (C-20), 73.9 (C-9), 74.1 (C-22), 3.99 (t, J ϭ 9.0 Hz, 2 H, 11-H), 4.10 (s, 5 H, Cp-H), 4.12 (m, 1 H,
74.8 (C-19), 115.9 (C-1), 118.6 (C-5), 119.8 (C-3), 131.5 (C-6), 138.2 14-H), 4.17 (m, 1 H, 15-H), 4.20 (m, 1 H, 13-H), 6.83 (td, J ϭ 8.5,
(C-4), 161.3 (C-2), 161.6 (C-7) ppm. 11B NMR (96 MHz, CDCl3):
1.8 Hz, 1 H, 5-H), 7.11 (d, J ϭ 8.5 Hz, 1 H, 3-H), 7.26 (dd, J ϭ
8.5, 1.8 Hz, 1 H, 6-H), 7.57 (td, J ϭ 8.5, 1.8 Hz, 1 H, 4-H), 8.03
δ: Btri ϭ 34.8 ppm (h1/2 ϭ 260.3 Hz), Btetra ϭ 8.2 ppm (h1/2
ϭ
130.3 Hz). C34H35B2Fe2NO3: calcd. C 63.34, H 5.43, N 2.17; found (s, 1 H, 7-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 27.6 (C-10),
C 63.07, H 5.85, N 2.20 (%).
32.2 (C-9), 56.2 (C-11), 62.4 (C-8), 68.6 (C-Cp), 68.8 (C-15), 69.1
(C-14), 70.9 (C-16), 72.1 (C-13), 117.3 (C-1), 118.8 (C-5), 119.8 (C-
3), 131.4 (C-6), 137.8 (C-4), 161.9 (C-2), 162.4 (C-7) ppm. 11B
Complex 3b: 3b was prepared from 1e (0.30 g, 1.21 mmol) and
ferrocenyl boronic acid (28 g, 1.21 mmol) as an orange solid in 78%
yield (0.62 g, 0.94 mmol), m.p. 219 °C. IR ν˜ ϭ (KBr): 2922, 1612
(CϭN), 1550, 1458, 1438, 1420, 1380, 1348, 1330, 1270, 1208, 1192,
1178, 1154, 1104, 762 cmϪ1. MS (15 eV): m/z (%) ϭ 653 (97) [Mϩ],
639 (2), 467 (38), 441 (11), 426 (4), 398 (7), 376 (2), 257 (17), 256
(100), 240 (3), 212 (6), 186 (18), 162 (2). 1H NMR (300 MHz,
CDCl3): δ ϭ 1.80Ϫ1.10 (m, 10 H, 10-, 10Ј-, 11-, 11Ј-, 12-H), 2.50
(s, 3 H, Me), 3.52 (d, J ϭ 14.9 Hz, 1 H, 8b-H), 3.75 (s, 1 H, 16-H),
3.93 (s, 1 H, 15-H), 4.10 (s, 1 H, 17-H), 4.20 (s, 5 H, Cp-H Btetra),
4.24 (s, 1 H, 14-H), 4.25 (d, J ϭ 14.9 Hz, 1 H, 8a-H), 4.29 (s, 5 H,
Cp-H Btri), 4.33 (s, 1 H, 21-H), 4.36 (s, 1 H, 20-H), 4.56 (s, 1 H,
22-H), 4.63 (s, 1 H, 19-H), 6.89 (td, J ϭ 7.8, 1.5 Hz, 1 H, 5-H),
7.00 (dd, J ϭ 7.8, 1.5 Hz, 1 H, 3-H), 7.55 (td, J ϭ 7.8, 1.5 Hz, 1
H, 4-H), 7.76 (dd, J ϭ 7.8, 1.5 Hz, 1 H, 6-H) ppm. 13C NMR
(75 MHz, CDCl3): δ ϭ 17.3 (Me), 21.8 (C-11), 22.1 (C-11Ј), 26.0
(C-12), 35.3 (C-10Ј), 36.1 (C-10), 59.3 (C-8), 68.3 (C-16), 68.4 (C-
15), 68.5 (C-21), 68.6 (C-20), 68.7 (C-Cp Btetra), 68.9 (C-Cp Btri),
71.4 (C-17), 71.6 (C-14), 74.2 (C-22), 74.7 (C-19), 74.9 (C-9), 118.6
(C-1), 118.8 (C-5), 119.3 (C-3), 131.1 (C-6), 136.9 (C-4), 160.7 (C-
2), 168.9 (C-7) ppm. 11B NMR (96 MHz, CDCl3): δ: Btri ϭ 38.3
NMR (96 MHz, CDCl3):
δ ϭ 9.6 ppm (h1/2 ϭ 154.8 Hz).
C21H22B1Fe1N1O2: calcd. C 64.69, H 5.64, N 3.59; found C 64.99,
H 5.59, N 3.95 (%).
Complex 5b: 5b was obtained from 1h (0.50 g, 2.41 mmol) and
ferrocenyl boronic acid (0.55 g, 2.41 mmol) as a red solid, in 84.7%
yield (0.82 g, 2.03 mmol), that is soluble in chloroform, m.p. 196
°C. IR ν˜ ϭ (KBr): 2914, 2894, 2364, 1624 (CϭN), 1558, 1458, 1434,
1370, 1348, 1328, 1280, 1210, 1126, 1110, 996, 960, 760 cmϪ1. MS
(15 eV): m/z (%) ϭ 401 (100) [Mϩ], 400 (29), 386 (5), 336 (1), 217
(11), 216 (80), 215 (22), 186 (57), 162 (4), 146 (2). 1H NMR
(300 MHz, CDCl3): δ ϭ 2.00Ϫ1.30 (m, 4 H, 9-, 10-H), 2.47 (s, 3
H, Me), 3.56 (m, 1 H, 15-H), 3.63 (t, J ϭ 9.0 Hz, 2 H, 8-H), 3.91
(m, 1 H, 14-H), 3.93 (t, J ϭ 9.0 Hz, 2 H, 11-H), 4.06 (m, 1 H, 16-
H), 4.07 (s, 5 H, Cp-H), 4.19 (m, 1 H, 13-H), 6.83 (t, J ϭ 7.8 Hz,
1 H, 5-H), 7.08 (d, J ϭ 7.8 Hz, 1 H, 3-H), 7.45 (d, J ϭ 7.8 Hz, 1
H, 6-H), 7.46 (t, J ϭ 7.8 Hz, 1 H, 4-H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 15.9 (Me), 28.8 (C-10), 30.6 (C-9), 48.4 (C-11), 61.8
(C-8), 68.3 (C-Cp), 68.4 (C-15), 68.7 (C-14), 70.2 (C-16), 72.1 (C-
13), 118.3 (C-5), 118.9 (C-1), 120.3 (C-3), 128.2 (C-6), 136.2 (C-4),
160.8 (C-2), 168.1 (C-7) ppm. 11B NMR (96 MHz, CDCl3): δ ϭ
8.7 ppm (h1/2 ϭ 159 Hz). C22H24B1Fe1N1O2: calcd. C 65.42, H 5.94,
N 3.47; found C 65.69, H 6.11, N 3.61 (%).
(h1/2
ϭ
905 Hz), Btetra
ϭ
7.2 ppm (h1/2
ϭ
148 Hz).
C35H37B2Fe2NO3: calcd. C 63.80, H 5.62, N 2.13; found C 64.10,
H 6.08, N 2.91 (%).
Complex 4: 4 was prepared from 1f (0.30 g, 1.32 mmol) and ferro-
cenyl boronic acid (0.30 g, 1.32 mmol) as a red solid in 75.5% yield
(0.42 g, 1.00 mmol), m.p. 236Ϫ238 °C. IR ν˜ ϭ (KBr): 3080, 3056,
2916, 1618 (CϭN), 1548, 1474, 1452, 1438, 1388, 1302, 1240, 1210,
1192, 1104, 1094, 1008, 952, 938, 816, 762 cmϪ1. MS (15 eV): m/z
(%) ϭ 421 (100) [Mϩ], 420 (44), 419 (12), 418 (4), 357 (1), 356 (6),
355 (4), 354 (3), 353 (5), 352 (1), 317 (1), 312 (2), 300 (4), 299 (2),
298 (2), 297 (4), 296 (2), 290 (2), 238 (2), 237 (20), 236 (84), 235
(55), 234 (9), 225 (2), 187 (2), 186 (20), 184 (2). 1H NMR
(300 MHz, CDCl3): δ ϭ 3.75 (s, 5 H, Cp-H), 3.79 (m, 1 H, 18-H),
3.88 (m, 1 H, 17-H), 3.93 (m, 1 H, 19-H), 4.05 (m, 1 H, 16-H), 4.82
(d, J ϭ 15.5 Hz, 1 H, 14b-H), 4.89 (d, J ϭ 15.5 Hz, 1 H, 14a-H),
6.96 (t, J ϭ 7.9 Hz, 1 H, 5-H), 7.01 (d, J ϭ 7.9 Hz, 1 H, 3-H), 7.28
(d, J ϭ 7.5 Hz, 1 H, 10-H), 7.40 (t, J ϭ 7.5 Hz, 1 H, 11-H), 7.46
(t, J ϭ 7.5 Hz, 1 H, 12-H), 7.60 (t, J ϭ 7.9 Hz, 1 H, 4-H), 7.68 (d,
J ϭ 7.9 Hz, 1 H, 6-H), 7.97 (d, J ϭ 7.5 Hz, 1 H, 13-H), 9.21 (s, 1
H, 7-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 62.3 (C-14), 67.6
(C-Cp), 67.9 (C-18), 68.0 (C-17), 70.6 (C-19), 71.0 (C-16), 117.9
(C-1), 118.9 (C-13), 119.1 (C-3), 119.6 (C-5), 125.8 (C-11), 127.8
(C-12), 128.4 (C-10), 132.9 (C-6), 134.9 (C-9), 137.9 (C-4), 138.2
(C-8), 156.8 (C-7), 160.2 (C-2) ppm. 11B NMR (96 MHz, CDCl3):
δ ϭ 5.0 ppm (h1/2 ϭ 555 Hz). C24H20B1Fe1N1O2: calcd. C 67.99, H
4.72, N 3.30; found C 67.69, H 4.70, N 3.42 (%).
Acknowledgments
Financial support from CONACyT (Mexico) is gratefully acknowl-
edged. The authors thank Ing. G. Cuellar for mass spectra and Q.
I. G. Uribe for NMR spectra.
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124
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2004, 118Ϫ124