Formation of a new ring system: Tetrazolo[5,1-f][1,2]azaborinin

Article abstract of DOI:10.1016/j.jorganchem.2010.08.049

Phenothiazinyldienes obtained from tetrazolopyridinium salts and phenothiazine derivatives were subjected to reduction by borane-dimethyl sulfide in THF. Structure elucidation of the products revealed that one of the olefinic bond underwent reduction and, furthermore, borane addition at the double bond took place to yield derivatives of tetrazolo[5,1-f][1,2]azaborinin as a new fused ring system involving a bridge-head nitrogen atom. The new products have been synthesized and characterized by X-ray analysis, solution and solid-state NMR.

Full text of DOI:10.1016/j.jorganchem.2010.08.049

Journal of Organometallic Chemistry 695 (2010) 2673e2678
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Formation of a new ring system: Tetrazolo[5,1-f][1,2]azaborinin
Daniella Takács a, Péter Király b, Ildikó Nagy a, Petra Bombicz b, Orsolya Egyed b,
,
Zsuzsanna Riedl a, György Hajós a
*
a Institute of Biomolecular Chemistry, Chemical Research Center of Hungarian Academy of Sciences, H-1025 Pusztaszeri út 59-67, Budapest, Hungary
b Institute of Structural Chemistry, Chemical Research Center of Hungarian Academy of Sciences, H-1025 Pusztaszeri út 59-67, Budapest, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
Phenothiazinyldienes obtained from tetrazolopyridinium salts and phenothiazine derivatives were
subjected to reduction by boraneedimethyl sulfide in THF. Structure elucidation of the products revealed
that one of the olefinic bond underwent reduction and, furthermore, borane addition at the double bond
took place to yield derivatives of tetrazolo[5,1-f][1,2]azaborinin as a new fused ring system involving
a bridge-head nitrogen atom. The new products have been synthesized and characterized by X-ray
analysis, solution and solid-state NMR.
Received 26 March 2010
Received in revised form
11 August 2010
Accepted 13 August 2010
Available online 1 October 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Phenothiazine
Cyclization
Azaborinin
Solid-state NMR
Single crystal
X-ray
1. Introduction
was isolated by chromatography and was obtained in moderate
(22e33%) yield. Mass spectroscopy and elemental analysis
Earlier we have reported that reaction of the easily accessible
tetrazolo[1,5-a]pyridinium salts [1] (1) with phenothiazine (2)
affords N-dienylphenothiazines bearing substituted tetrazole
moiety at the end of the diene chain (3, Scheme 1) [2]. Because of
valuable biological properties of some related phenothiazines
substituted by saturated carbon chains on the thiazine-nitrogen
atom [3], we have now decided to reduce the dienyl moieties of
these derivatives in order to seek for novel biologically active
compounds. Because of the presence of the sulfur atom, catalytic
hydrogenation had to be ruled out and, thus, the transformation
was tried by the use of boraneedimethyl sulfide complex as the
reducing agent [4]. This reagent has recently been applied
successfully for hydrogenation of enamines [5].
revealed, interestingly, that the product molecules contain a boron
atom. The stability of these crystalline products suggested that the
boron content was incorporated highly probably by covalent bonds.
In the possession of appropriate single crystals of the reduction
product obtained from 3b, X-ray diffraction analysis was carried out
in order to elucidate the structure: it has shown that in the course
of this transformation a BH2 group was attached to C2 of the carbon
chain followed by formation of a BeN s-bond with participation of
the adjacent ring-nitrogen atom of the tetrazole ring. Thus,
a zwitterionic derivative of a bridge-head nitrogen containing new
heterocyclic ring system: tetrazolo[5,1-f][1,2]azaborinin (4b) was
formed (Scheme 2).
The reaction obviously proceeds via formation of a boron-con-
taining intermediate (A) which is formed by borane addition to the
double bond C1eC2. The easy formation of 4 is due to the proximity
of the BH2 group and the N atom of the tetrazole ring. In the course
of this reaction the olefinic C3eC4 bond was also reduced.
The single crystal X-ray diffraction analysis proved that there is
one molecule in the asymmetric unit of 4b (Fig. 1.). It crystallises in
the monoclinic crystal system, space group P21/n. Although the
2. Results and discussion
When dienylphenothiazines (3aed) were treated with the
borane reagent under mild conditions (0 ꢀC) in tetrahydrofurane,
total disappearance of the starting compound was monitored by tlc
after 3 h. Formation of one main product was experienced which
lattice parameters feature higher symmetry as
b angle is close to
90ꢀ indicating the possibility of orthorhombic crystal system, it is
not supported by the content of the unit cell. There is one chiral
atom in the molecule, it is the carbon bonded toward the
* Corresponding author.
E-mail address: ghajos@chemres.hu (G. Hajós).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.08.049

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D. Takács et al. / Journal of Organometallic Chemistry 695 (2010) 2673e2678
close similarity of the proton (ESI Figs. S2 and S3), carbon (ESI Figs.
S
S4eS7) and boron NMR spectra (ESI Figs. S8 and S9) of 4a,c,d to
those of the fully characterized 4b clearly shows that all these
derivatives have related structures both in solution and in solid
state.
N
H
2
S
N
N
2
4
N
N
NaH, abs. THF
N
N
N
An interesting feature of the solid-state 13C-CP/MAS spectra of
the new products (4aed) is that certain resonances are doubled in
the aromatic region as compared to the solution spectra (ESI Figs.
S4eS7).
3
N
1
rt, 2-3 days
N
BF4
1a-d
3a-d
R= Cl, Br, OCH3, CH3
R
In the case of 4b the single resonance at 146.2 ppm represents
both nitrogen attached quaternary carbons of the phenothiazine
ring (C-9a00/C-10a00) in CDCl3. This, however, splits into two clearly
non-equivalent carbon sites (diso ¼ 149.0 and 144.0 ppm) in the
solid-state 13C-CP/MAS spectrum. As a consequence of the asym-
metric structure, the two sets of aromatic carbons in the pheno-
thiazine moiety experience different magnetic shielding. This, in
turn, remains hidden behind rapid chemical exchange processes in
solution due to the conformational flexibility of the phenothiazine
moiety.
R
Scheme 1.
phenothiazine in the ring containing the B. Both enantiomers can
be found in the centrosymmetric cell.
The diffraction measurement was performed at low tempera-
ture, ꢁ180 ꢀC. The structure was ordered. All hydrogen atoms were
found on difference Fourier maps. It was possible to refine the
structure to R ¼ 2.87%. Packing diagrams with the view from the a,
b and c crystallographic axis are shown in ESI Fig. S1.
There are no classic hydrogen bonds in the crystal structure. There
is one shorter centroidecentroid distance only: between C2e
C3eC4eC5eC6eC7 rings with the intermolecular [1 ꢁ X,1 ꢁ Y,1 ꢁ Z]
distance of 3.7716(11) Å. All other ring distances are over 4 Å.
Exploration of reactivity of the new zwitterionic azaborinin
derivative as well as extension of reductive transformations of
phenothiazinyldienes is in progress.
3. Experimental
Furthermore, two CeH.p interactions can be found in the crystal
3.1. General
structure: C4eH4.C8eC9eC10eC11eC12eC13 ring [1 ꢁ X,1 ꢁ
Y,1 ꢁ Z] 2.95 Å 134ꢀ and C32eH32.C2eC3eC4eeC6eC5C7
[ꢁX,ꢁY,1 ꢁ Z].
Melting Points were determined on a Büchi apparatus and are
uncorrected. The IR spectra were recorded on a Thermo Nicolet
Avatar 320 FT-IR spectrometer. The elemental analysis has been
carried out with an Elementar Vario EL III apparatus (at the
Analytical Laboratory for Organic Chemistry, Chemical Research
Center, Hungarian Academy of Sciences, H-1025 Budapest, Pusz-
taszeri út 59e67). All the chemicals and solvents were used as
supplied.
Our literature survey revealed that very few azaborinins related
to 4 have been described in the literature [7,8] and, furthermore, no
fused azaborinin with bridge-head nitrogen atom has been repor-
ted. Thus, these zwitterionic tetrazolo[5,1-f][1,2]azaborinin deriv-
atives (4) represent a new unprecedented ring system.
The comparison of solution and solid-state NMR data was useful
to confirm the formation of the new heterocyclic ring system 4aed.
Chloroform solution of 4b was investigated to determine the
boron-containing six-membered ring in solution. The J-coupling
patterns of the diastereotopic methylene protons attached to C7
and C8 carbons suggested the intramolecular ring formation
(Fig. 2). The homonuclear couplings of the boron-attached protons
NMR experiments were carried out on 400 MHz (for 1H) and
600 MHz (for 1H) Varian NMR SYSTEM spectrometers by using 5 mm
direct detection 15Ne31P/{1He19F} probes equipped with Z pulse field
gradient. The assignments of the resonances of 4aed followed the
regular procedure: collection and analysis of selective 1D TOCSY,
selective 1D NOESY and heteronuclear through-bond correlations
(1He13CegHSQC and 1He13CegHMBC). Measurements were per-
formed at þ25 ꢀC in CDCl3. 1H and 13C NMR spectra are referenced to
residual solvent signal (dH ¼ 7.24 ppm; dC ¼ 77.0 ppm). Et2OxBF3 in
CDCl3 was used as external reference for 10B{1H} NMR spectra. The
direct detection of 10B instead of the commonly used 11B was chosen
to avoid the strong background of the latter. The rapid relaxation of
the boron nuclei in the asymmetric environment (4aed) leads to
extremely broad resonances (see ESI Fig. S8), which are difficult to
detect. 1H{11B} NMR spectra were recorded by using broadband
3
(3JBHax-H6 ¼ 6.0 Hz and JBHeq-H6 ¼ 4.0 Hz) are also characteristic of
the six-membered ring system (ESI Fig. S3). In addition, solid-state
NMR spectroscopy was applied to provide a link between the
structure of 4b determined by single crystal X-ray diffraction and
the solution NMR data. The isotropic chemical shifts (diso) obtained
from 11B-MAS (Fig. 3.) and 13C-CP/MAS (ESI Fig. S4) are in good
agreement with the d10B and d13C chemical shifts measured in
CDCl3. Therefore, we conclude that the solution structure of 4b is
identical to that determined by single crystal X-ray diffraction. The
R
R
4'
3'
1'
2'
BH3xMe2S
7"
8"
2
3
abs. THF
3a-d
6"
5a"
N
N
N
N
N
N
1
4
9"
0°C
rt
N
5"
N
S
H2B
5
8a
8
9a"
N
S
BH2
2
10"
4a"
7
4"
N
4
6
10a"
1"
1
3
3"
4a-d
2"
A
Scheme 2.

D. Takács et al. / Journal of Organometallic Chemistry 695 (2010) 2673e2678
2675
Fig. 1. Molecular structure ORTEP [6] representation of 4b. The displacement ellipsoids are drawn at 50% probability level, hetero atoms are shaded.
decoupling [11]. Solid-state 11B-MAS and 13C-CP/MAS spectra were
recorded on 400 MHz (for 1H) Varian NMR SYSTEM spectrometer by
using a 4.0 mm HX Varian Chemagnetics MAS probe and on 600 MHz
(for 1H) Varian NMR SYSTEM spectrometer by using a 3.2 mm HXY
Varian Chemagnetics MAS probe. Chemical shifts in the solid state
were referenced to Et2OxBF3 in CDCl3 (d11B ¼ 0 ppm) for boron and to
adamantane (d13C ¼ 38.55, 29.50 ppm) for carbon. Recycle delays
600 s for 4aeb and 10 s for 4ced were used in the 13C-CP/MAS
experiments (1e2 ms contact time, 92 kHz TPPMproton decoupling).
11B-MAS experiments (92 kHz TPPM proton decoupling) were
recorded with 10e60 s recycle delays.
solvent was evaporated, the residue was washed with diethyl ether
then it was recrystallised from ethyl acetate to give 3aed.
3.2.1.1. 10-((1E,3E)-4-(2-(4-Chlorophenyl)-2H-tetrazol-5-yl)buta-1,3-
dien-1-yl)-10H-phenothiazine (3a). Starting from 3-(4-chloro-
phenyl)-3H-tetrazolo[1,5-a]pyridin-4-ium 1a (1.75 g, 5.51 mmol) to
give 3a (1.91 g, 81%) was filtered off as yellow crystals (mp
198e202 ꢀC); (Found: N, 16.29; C, 64.32; H, 3.40; C23H16ClN5S
requires N, 16.29; C, 64.25; H, 3.75%); nmax(KBr)/cmꢁ1 1622, 1500,
1257, 994 and 766; dH (300 MHz, CDCl3; Me4Si) 6.19 (1H, d,
J ¼ 11.4 Hz), 6.65 (1H, t, J ¼ 11.4 Hz), 7.18e7.24 (3H, m), 7.31e7.37
(4H, m), 7.48e7.57 (4H, m), 7.66 (1H, dd, J ¼ 13.8, 11.4 Hz), 7.989
(2H, m); dC (75 MHz, CDCl3; Me4Si) 103.5, 105.7, 120.7 (2C), 122.4
(2C), 125.6 (2C), 127.4 (2C), 128.1 (2C), 129.6 (2C), 130.6, 135.0, 136.7,
139.8, 141.2, 141.5, 164.8; m/z (EI) 429.0824 (C23H16ClN5S requires
429.0815), 401 (25%), 276 (52), 262 (68), 199 (86), 198 (100), 167
(30), 154 (10), 140 (8), 127 (16), 90 (8), 77 (5) and 63 (10).
3.2. Experimental procedures and spectroscopic data
3.2.1. General procedure for preparation of tetrazolyldienylpheno-
thiazines (3aed)
To a mixture of sodium hydride (60%, 0.26 g, 6.67 mmol) and
phenothiazine 2 (1.21 g, 6.06 mmol) in abs. THF (50 cm3) was added
dropwise the appropriate 3H-tetrazolo[1,5-a]pyridin-4-ium 1aed
(5.51 mmol) over 20 min, and the mixture was stirred at room
temperature for 2 days. After evaporation of reaction mixture the
residue was dissolved with EtOAc:water ¼ 1:1 eluent (50 cm3) and
the solid product was filtered off. The aqueous mother liquor was
extracted with EtOAc (thrice) and the organic phase was dried over
anhydrous Na2SO4, filtered and evaporated. The combined organic
3.2.1.2. 10-((1E,3E)-4-(2-(4-Bromophenyl)-2H-tetrazol-5-yl)buta-1,3-
dien-1-yl)-10H-phenothiazine (3b). Starting from 3-(4-bromo-
phenyl)-3H-tetrazolo[1,5-a]pyridin-4-ium 1a (2.00 g, 5.51 mmol)
to give 3b (1.98 g, 76%) as yellow crystals (mp 200e204 ꢀC);
(Found: N, 14.55; C, 57.91; H, 3.11; C23H16BrN5S requires N, 14.76; C,
58.23; H, 3.40%); nmax(KBr)/cmꢁ1 1621, 1499, 1257, 994 and 765; dH
(300 MHz, CDCl3; Me4Si) 6.19 (1H, d, J ¼ 11.1 Hz), 6.65 (1H, t,
Fig. 2. Aliphatic region of the 1H and 1H{11B} NMR spectra of 4aed in CDCl3. The resonances of the boron-attached protons are indicated by arrows.

2676
D. Takács et al. / Journal of Organometallic Chemistry 695 (2010) 2673e2678
of BH3xMe2S, the mixture was stirred from 0 ꢀC to room temper-
ature for 3 h. During this time, the starting suspension turned to be
a clear solution. This mixture was cooled to 0 ꢀC and the excess of
BH3xMe2S was quenched with cold water (10 cm3). Then the
reaction mixture was made alkaline with sodium carbonate solu-
tion (10%) and extracted with DCM (15 cm3, thrice). The organic
phase was dried over anhydrous Na2SO4, filtered and evaporated
under reduced pressure at room temperature. The residue was
purified with flash chromatography on silica gel (gradient from
hexane:DCM ¼ 2:1). The solid product was recrystallised from
hexane and diethyl ether to give 4aed as yellow or yellow-white
crystals.
3.2.2.1. 6-((10H-Phenothiazin-10-yl)methyl)-2-(4-chlorophenyl)-
5,6,7,8-tetrahydro-2H-tetrazolo[5,1-f][1,2]azaborinin-4-ium-5-uide
(4a). Starting from 10-((1E,3E)-4-(2-(4-chlorophenyl)-2H-tetrazol-
5-yl)buta-1,3-dien-1-yl)-10H-phenothiazine (3a, 0.43 g, 1 mmol) to
give 4a (0.11 g, 25%) as yellow crystals (mp 166e168 ꢀC); (Found: N,
15.47; C, 61.86; H, 4.64; C23H21BClN5S requires N, 15.71; C, 61.97; H,
4.75%); nmax(KBr)/cmꢁ1 3440, 2352, 1452, 1109 and 755; NMR data
(þ25 ꢀC, CDCl3, 30 mM): d1H-{11B} (599.7 MHz) 1.65 (1H, dddd,
J ¼ 12.7, 10.5, 10.3, 4.8, 7ax-H), 1.74 (1H, br m, 6-H), 2.32 (1H, dddd,
J ¼ 12.7, 5.6, 4.9, 3.1, 7e-H), 2.44 (1H, dd, J ¼ 10.7, 5.7, BHax), 2.81 (1H,
ddd, J ¼ 17.6, 10.3, 5.6, 8ax-H), 2.83 (1H, dd, J ¼ 10.7, 4.2, BHeq), 3.07
(1H, ddd, J ¼ 17.6, 4.9, 4.8, 8e-H), 3.71 (1H, dd, J ¼ 14.0, 11.9, a1-H),
4.07 (1H, dd, J ¼ 14.0, 3.0, a2-H), 6.88 (2H, td, J ¼ 7.7, 1.1, 300-H þ 700-
H), 6.98 (2H, dd, J ¼ 8.1, 1.1, 100-H þ 900-H), 7.12 (2H, ddd, J ¼ 8.1, 7.7,
1.4, 200-H þ 800-H), 7.14 (2H, dd, J ¼ 7.7, 1.4, 400-H þ 600-H), 7.57 (2H, m,
30-H þ 50-H), 8.06 (2H, m, 20-H þ 60-H); dC (150.8 MHz) 21.8 (6-C),
Fig. 3. Solution and solid-state boron NMR spectra of 4b. (a) 10B{1H} in CDCl3
(b) 11B{1H}-MAS [9] at 192.4 MHz, 7 kHz (c) 11B{1H}-MAS at 128.3 MHz, 7 kHz. The
isotropic chemical shift was determined by using the SIMPSON package [10].
J ¼ 11.1 Hz), 7.17e7.23 (3H, m), 7.30e7.37 (4H, m), 7.55 (2H, d,
J ¼ 7.2 Hz), 7.61e7.66 (3H, m), 7.92 (2H, m); dC (75 MHz, CDCl3;
Me4Si) 103.5, 105.6, 120.9 (2C), 122.4 (2C), 125.6 (2C), 127.4 (2C),
128.1 (2C), 130.6, 132.6 (2C), 136.8, 137.7, 139.8, 141.2, 141.5, 164.8;
m/z (EI) 473.0314 (C23H16BrN5S requires 473.0310), 447 (8%), 276
(16), 262 (23), 248 (15), 199 (100), 167 (40), 154 (9), 99 (5), 77 (6)
and 63 (9).
22.2 (8-C), 25.1 (7-C), 51.6 (
a
-C), 116.3 (100-C þ 900-C), 121.4 (20-
3.2.1.3. 10-((1E,3E)-4-(2-(4-Methoxyphenyl)-2H-tetrazol-5-yl)buta-
1,3-dien-1-yl)-10H-phenothiazine (3c). Starting from 3-(4-methoxy-
phenyl)-3H-tetrazolo[1,5-a]pyridin-4-ium 1c (1.73 g, 5.51 mmol) to
give 3c (1.73 g, 74%) as yellow-brown crystals (mp 194e199 ꢀC);
(Found: N, 16.30; C, 67.60; H, 4.32; C24H19N5OS requires N, 16.46; C,
67.74; H, 4.50%); nmax(KBr)/cmꢁ1 2360, 1620, 1514, 1257 and 762; dH
(300 MHz, CDCl3; Me4Si) 3.90 (3H, s), 6.19 (1H, d, J ¼ 11.1 Hz), 6.61
(1H, t, J ¼ 11.4 Hz), 7.02 (2H, m), 7.15e7.21 (3H, m), 7.31e7.36 (4H, m),
7.54 (2H, m), 7.69 (1H, dd, J ¼ 13.8,11.1 Hz), 7.96 (2H, m); dC (75 MHz,
CDCl3; Me4Si) 55.7, 103.7, 106.2, 114.5 (2C), 121.1 (2C), 122.1, 122.4
(2C), 125.5 (2C), 127.5 (2C), 128.1 (2C), 130.5, 136.1, 140.7, 141.6, 160.2,
164.5; m/z (EI) 425.1320 (C24H19N5OS requires 425.1310) 397 (30%),
276 (78), 262 (51), 227 (70), 198 (100), 167 (16), 121 (51), 106 (17), 91
(8), 78 (13) and 55 (11).
C þ 60-C), 122.0 (300-C þ 700-C), 125.3 (4a00-C þ 5a00-C), 127.1 (200-
C þ 800-C), 127.3 (400-C þ 600-C), 130.3 (30-C þ 50-C), 134.1 (10-C), 137.7
(40-C), 146.2 (9a00-C þ 10a00-C), 162.4 (8a-C); d10B (64.4 MHz) ꢁ11.6
(br s, BH2); dC,iso (
13C{1H}-CP/MAS; 100.6 MHz; 7 kHz) 22.5, 26.1,
51.5, 117.9, 120.7, 122.5, 123.8, 126.9, 128.4, 133.5, 143.4, 148.9, 162.9;
m/z (ESIþ) [M þ Na]þ: 468.2, [M þ H]þ: 446.2 (C23H21BClN5S
requires 445.78).
3.2.2.2. 6-((10H-Phenothiazin-10-yl)methyl)-2-(4-bromophenyl)-
5,6,7,8-tetrahydro-2H-tetrazolo[5,1-f][1,2]azaborinin-4-ium-5-uide
(4b). Starting from 10-((1E,3E)-4-(2-(4-bromophenyl)-2H-tetra-
zol-5-yl)buta-1,3-dien-1-yl)-10H-phenothiazine (3b) (0.474 g,
1 mmol) to give 4b (0.160 g, 33%) as yellow crystals (mp
155e157 ꢀC); (Found: N, 14.03; C, 56.30; H, 4.18; C23H21BBrN5S
requires N, 14.29; C, 56.35; H, 4.33%); nmax(KBr)/cmꢁ1 3446, 2354,
1451, 1109 and 755; NMR data (þ25 ꢀC, CDCl3, 30 mM): d1H-{11B}
(599.7 MHz; þ25 ꢀC; CDCl3; 20 mM) 1.64 (1H, dddd, J ¼ 13.0, 10.5,
10.3, 4.9, 7ax-H), 1.74 (1H, br m, 6-H), 2.33 (1H, dddd, J ¼ 13.0, 5.7,
4.9, 3.7, 7e-H), 2.44 (1H, dd, J ¼ 10.7, 6.0, BHax), 2.81 (1H, ddd,
J ¼ 17.6, 10.3, 5.7, 8ax-H), 2.83 (1H, dd, J ¼ 10.7, 4.0, BHeq), 3.08 (1H,
dt, J ¼ 17.6, 4.9, 8e-H), 3.71 (1H, dd, J ¼ 13.8, 11.7, a1-H), 4.07 (1H,
dd, J ¼ 13.8, 3.0, a2-H), 6.88 (2H, td, J ¼ 7.1, 1.2, 300-H þ 700-H), 6.97
(2H, dd, J ¼ 8.0, 1.2, 100-H þ 900-H), 7.12 (2H, ddd, J ¼ 8.0, 7.1, 1.3, 200-
H þ 800-H), 7.14 (2H, dd, J ¼ 7.1, 1.3, 400-H þ 600-H), 7.73 (2H, m, 30-
H þ 50-H), 8.0 (2H, m, 20-H þ 60-H); dC (150.8 MHz; þ25 ꢀC; CDCl3;
3.2.1.4. 10-((1E,3E)-4-(2-(p-Tolyl)-2H-tetrazol-5-yl)buta-1,3-dien-1-
yl)-10H-phenothiazine (3d). Starting from 3-(p-tolyl)-3H-tetrazolo
[1,5-a]pyridin-4-ium 1d (1.64 g, 5.51 mmol) to give 3d (1.83 g, 81%)
as yellow crystals (mp 203e209 ꢀC); (Found: N, 16.90; C, 70.16; H,
4.55; C24H19N5S requires N, 17.10; C, 70.39; H, 4.68%); nmax(KBr)/
cmꢁ1 1622, 1584, 1463, 1258 and 763; dH (300 MHz, CDCl3; Me4Si)
2.45 (3H, s), 6.20 (1H, d, J ¼ 11.1 Hz), 6.62 (1H, t, J ¼ 11.1 Hz),
7.16e7.22 (4H, m), 7.29e7.36 (5H, m), 7.53e7.57 (2H, m), 7.69 (1H,
dd, J ¼ 13.8, 11.1 Hz), 7.92 (2H, m); dC (75 MHz, CDCl3; Me4Si) 21.2,
103.6, 106.1, 119.4 (2C), 122.4 (2C), 125.5 (2C), 127.4 (2C), 128.0 (2C),
129.9 (2C), 130.5, 134.7, 136.2, 139.4, 140.8, 141.5, 164.5; m/z (EI)
409.1352 (C24H19N5S requires 409.1361) 381 (22%), 276 (56), 275
(13), 262 (56), 211 (60), 198 (100), 182 (15), 167 (21), 154 (8), 105 (9),
77 (9) and 69 (10).
20 mM) 21.7 (6-C), 22.2 (8-C), 25.1 (7-C), 51.6 (a
-C), 116.3 (100-
C þ 900-C), 121.5 (20-C þ 60-C), 122.0 (300-C þ 700-C), 125.3 (4a00-
C þ 5a00-C), 125.9 (40-C), 127.1 (200-C þ 800-C), 127.3 (400-C þ 600-C),
133.3 (30-C þ 50-C), 134.6 (10-C), 146.2 (9a00-C þ 10a00-C), 162.4 (8a-
C); d10B (64.4 MHz; þ25 ꢀC; CDCl3; 20 mM) ꢁ11.3 (BH2 br s); dC
3.2.2. General procedure for preparation of 5,6,7,8-tetrahydro-2H-
tetrazolo[5,1-f][1,2]azaborinin-4-ium-5-uides (4aed)
(
13C{1H}-CP/MAS; 100.6 MHz; 7 kHz) 22.9, 26.4, 51.8, 116.7, 118.1,
121.0, 122.8, 124.2, 127.3, 129.0, 134.0, 144.0, 149.0, 163.1; d11B,iso
In an inert atmosphere at 0 ꢀC, BH3xMe2S (0.4 cm3, 4 mmol) was
added to the suspension of the appropriate tetrazolyldienylphe-
nothiazines (3aed, 1 mmol) and abs. THF (10 cm3). After injection
(
11B{1H}-MAS; 192.4 MHz; 11 kHz and 11B{1H}-MAS; 128.3 MHz;
7 kHz) diso ¼ ꢁ12 ppm (Qcc ¼ 2.0 MHz and
h
¼ 0); m/z (ESIþ)
[M þ Na]þ: 514.0 (C23H21BBrN5S requires 490.23).

D. Takács et al. / Journal of Organometallic Chemistry 695 (2010) 2673e2678
2677
3.2.2.3. 6-((10H-Phenothiazin-10-yl)methyl)-2-(4-methoxyphenyl)-
5,6,7,8-tetrahydro-2H-tetrazolo[5,1-f][1,2]azaborinin-4-ium-5-uide
(4c). Starting from 10-((1E,3E)-4-(2-(4-methoxyphenyl)-2H-tetra-
I > 2
s
(I). Completeness to 2
q
¼ 0.998. A multi-scan absorption
correction was applied to the data (the minimum and maximum
transmission factors were 0.744 and 1.000). The structure was solved
by directmethods (SHELXS-97) [12]. Neutralatomic scatteringfactors
and anomalous scattering factors are taken from International Tables
for X-ray Crystallography [13]. Anisotropic full-matrix least-squares
refinement (SHELXL-97) [14,15] on F2 for all non-hydrogen atoms
zol-5-yl)buta-1,3-dien-1-yl)-10H-phenothiazine
(3c,
0.425 g,
1 mmol) to give 4c (0.096 g, 22%) as yellow-white crystals (mp
155e162 ꢀC); (Found: N, 15.56; C, 65.17; H, 5.37; C24H24BN5OS
requires N, 15.87; C, 65.31; H, 5.48%); nmax(KBr)/cmꢁ1 3344, 2354,
1454, 1264 and 755; NMR data (þ25 ꢀC, CDCl3, 30 mM): d1H-{11B}
(399.9 MHz) 1.64 (1H, dddd, J ¼ 13.0, 10.2, 9.8, 5.0, 7ax-H), 1.74 (1H,
br m, 6-H), 2.30 (1H, dddd, J ¼ 13.0, 5.6, 5.0, 2.5, 7e-H), 2.43 (1H, dd,
J ¼ 10.6, 5.9, BHax), 2.77 (1H, ddd, J ¼ 17.7, 9.8, 5.6, 8ax-H), 2.82 (1H,
dd, J ¼ 10.6, 4.0, BHeq), 3.05 (1H, dt, J ¼ 17.7, 5.0, 8e-H), 3.71 (1H, dd,
J ¼ 14.2, 11.6, a1-H), 3.91 (3H, s, 40-OCH3), 4.07 (1H, dd, J ¼ 14.2, 3.1,
a2-H), 6.87 (2H, td, J ¼ 7.5,1.0, 300-H þ 700-H), 6.99 (2H, dd, J ¼ 7.9,1.0,
100-H þ 900-H), 7.04 (2H, m, 30-H þ 50-H), 7.12 (2H, ddd, J ¼ 7.9, 7.5,
1.5, 200-H þ 800-H), 7.13 (2H, dd, J ¼ 7.5, 1.5, 400-H þ 600-H), 8.02 (2H, m,
20-H þ 60-H); dC (100.6 MHz) 21.7 (6-C), 22.2 (8-C), 25.1 (7-C), 51.6
yielded R1 ¼0.0287 and wR2 ¼ 0.0715 for 4698 [I > 2
s(I)] and
R1 ¼0.0315 and wR2 ¼ 0.0731 forall(5052)intensitydata(goodness-
of-fit ¼ 1.035 the maximum and mean shift/esd 0.001 and 0.000).
Number of parameters ¼ 284. The maximum and minimum residual
electron density in the final difference map was 0.575 and
ꢁ0.460 e Åꢁ3. The weighting scheme applied was
h
ꢀ
ꢁ
i
w ¼ 1= s2 Fo2 þ ð0:0364PÞ2þ1:8626P
P ¼ Fo2 þ 2Fc2
where
ꢀ
ꢁ.
3
(
a
-C), 55.8 (40-OCH3), 115.0 (30-C þ 50-C), 116.3 (100-C þ 900-C), 121.7
Hydrogen atomic positions were located in difference maps.
Hydrogen atoms were included in structure factor calculations but
they were not refined. The isotropic displacement parameters of
the hydrogen atoms were approximated from the U(eq) value of the
atom they were bonded.
(20-C þ 60-C), 121.9 (300-C þ 700-C), 125.3 (4a00-C þ 5a00-C), 127.1 (200-
C þ 800-C), 127.3 (400-C þ 600-C), 129.0 (10-C), 146.2 (9a00-C þ 10a00-C),
161.8 (8a-C), 161.9 (40-C); d10B (43.0 MHz) ꢁ11.5 (br s, BH2); dC,iso
(
13C{1H}-CP/MAS; 150.8 MHz; 10 kHz) 21.0, 23.9, 25.8, 51.6, 54.3,
61.9, 114.7, 116.0, 118.5, 119.7, 123.0, 126.2, 128.1, 145.0, 150.2, 162.2;
m/z (ESIþ) [M þ Na]þ: 464.4, [M þ H]þ: 442.3 (C24H24BN5OS
requires 441.36).
Acknowledgments
3.2.2.4. 6-((10H-Phenothiazin-10-yl)methyl)-2-(p-tolyl)-5,6,7,8-tetra-
hydro-2H-tetrazolo[5,1-f][1,2]azaborinin-4-ium-5-uide (4d). Starting
from 10-((1E,3E)-4-(2-(p-tolyl)-2H-tetrazol-5-yl)buta-1,3-dien-1-
yl)-10H-phenothiazine (3d, 0.410 g, 1 mmol) to give 4d (0.134 g,
32%) as yellow-white crystals (mp 167e172 ꢀC); (Found: N, 16.19; C,
67.76; H, 5.70; C24H24BN5S requires N, 16.46; C, 67.77; H, 5.69%);
nmax(KBr)/cmꢁ1 3369, 2352, 1459, 1108 and 754; NMR data (þ25 ꢀC,
CDCl3, 30 mM): d1H-{11B} (399.9 MHz) 1.63 (1H, dddd, J ¼ 12.0, 11.0,
10.0, 4.7, 7ax-H),1.73 (1H, br m, 6-H), 2.31 (1H, dddd, J ¼ 12.0, 5.3, 5.0,
2.7, 7e-H), 2.44 (1H, dd, J ¼ 10.6, 5.3, BHax), 2.45 (3H, s, 40-CH3) 2.79
(1H, ddd, J ¼ 17.7, 10.0, 5.3, 8ax-H), 2.83 (1H, dd, J ¼ 10.6, 3.9, BHeq),
3.06 (1H, ddd, J ¼ 17.7, 5.0, 4.7, 8e-H), 3.71 (1H, dd, J ¼ 14.1,11.6, a1-H),
4.07 (1H, dd, J ¼ 14.1, 3.1, a2-H), 6.87 (2H, td, J ¼ 7.5,1.0, 300-H þ 700-H),
6.98 (2H, dd, J ¼ 8.2, 1.0, 100-H þ 900-H), 7.12 (2H, ddd, J ¼ 8.2, 7.5, 1.5,
200-H þ 800-H), 7.13 (2H, dd, J ¼ 7.5, 1.5, 400-H þ 600-H), 7.36 (2H, m, 30-
H þ 50-H), 7.97 (2H, m, 20-H þ 60-H); dC (100.6 MHz) 21.3 (40-CH3)
The support of the OTKA 77784 and Hungarian GVOP-3.2.1.-
2004-04-0210/3.0 projects as well as the National Science and
Technology Office for an X-ray diffractometer purchase grant (MU-
00338/2003) are gratefully acknowledged.
Appendix. Supplementary data
CCDC 757953 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.jorganchem.
2010.08.049.
References
21.7 (6-C), 22.2 (8-C), 25.1 (7-C), 51.6 (
a
-C),116.3 (100-C þ 900-C),120.0
(20-C þ 60-C), 121.9 (300-C þ 700-C), 125.3 (4a00-C þ 5a00-C), 127.1 (200-
C þ 800-C), 127.3 (400-C þ 600-C), 130.5 (30-C þ 50-C), 133.5 (10-C), 142.2
(40-C), 146.2 (9a00-C þ 10a00-C), 161.9 (8a-C); d10B (43.0 MHz) ꢁ12.0
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13C{1H}-CP/MAS; 150.8 MHz; 10 kHz) 22.6, 26.5,
53.4, 117.1, 120.8, 124.7, 126.6, 127.9, 130.0, 133.6, 142.3, 144.3, 148.8,
162.3; m/z (ESIþ) [M þ Na]þ: 448.4, [M þ H]þ: 426.2 (C24H24BN5S
requires 425.36).
3.3. X-ray crystallography
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X-ray structure: Crystal data: C23H21BBrN5S, Fwt.: 490.23, yellow,
block, size: 0.50 ꢂ 0.40 ꢂ 0.32 mm, monoclinic, space group P21/n
(No14),
a ¼ 12.547(2) Å,
b ¼ 9.8202(13) Å,
c ¼ 17.879(3) Å,
a
¼
g
¼ 90ꢀ,
b
¼ 90.011(7)ꢀ, V ¼ 2203.1(6) Å3, T ¼ 93(2) K, Z ¼ 4,
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F(000) ¼ 1000, Dx ¼ 1.478 Mg mꢁ3
,
m
¼ 1.98 mmꢁ1. Acrystalof4bwas
mounted on a MiTeGen loop. Cell parameters were determined by
least-squares of the setting angles of 77,979 (3.08 ꢃ
q
ꢃ 27.49ꢀ)
reflections. Intensity data were collected on a Rigaku RAxis Rapid
diffractometer (graphite monochromator; Mo-K
a
radiation,
l
¼ 0.71073 Å) at 93(2) K in the range 3.08 ꢃ
q
ꢃ 27.48ꢀ using dtpro-
fit.ref scans. A total of 93,290 reflections were collected of which 5052
[8] (a) D. Hoffmann, H. Reinke, H. Oehme, J. Organomet. Chem. 585 (1999)
189e197;
were unique [Rint ¼ 0.0353, R( ) ¼ 0.0123]; 4698 reflections were
s

2678
D. Takács et al. / Journal of Organometallic Chemistry 695 (2010) 2673e2678
ꢀ
ꢁ
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