A new strategy towards tridentate N-heterocyclic carbene ligands derived from benzimidazolium and mixed-azolium salt

Article abstract of DOI:10.1016/j.molstruc.2017.03.097

The tridentate N-heterocyclic carbenes (NHC) ligands derived from tris azolium salts by a new synthetic approach are described. The tris azolium salts have been obtained by reacting the initially synthesized precursor 3-(2-bromoethyl)-1-methylbenzimidazolium bromide (I) with benzimidazole/imidazole resulting in the tris azolium salts namely, 1 and 2. The ligand potential of the salts 1 and 2 was investigated by the formation of NHC-Ag(I) complexes 3 and 4, using Ag₂O. The most downfield resonances in ¹³C NMR around 180–190?ppm indicates the successful coordination of carbene with Ag(I).

Full text of DOI:10.1016/j.molstruc.2017.03.097

Accepted Manuscript
A New Strategy Towards Tridentate N-Heterocyclic Carbene Ligands Derived
From Benzimidazolium and Mixed-azolium Salt
Tabinda Fatima, Rosenani A. Haque, Mohd. R. Razali
PII:
S0022-2860(17)30386-1
10.1016/j.molstruc.2017.03.097
MOLSTR 23593
DOI:
Reference:
To appear in:
Journal of Molecular Structure
Received Date:
Revised Date:
Accepted Date:
14 December 2016
21 March 2017
26 March 2017
Please cite this article as: Tabinda Fatima, Rosenani A. Haque, Mohd. R. Razali, A New Strategy
Towards Tridentate N-Heterocyclic Carbene Ligands Derived From Benzimidazolium and Mixed-
azolium Salt, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.03.097
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ACCEPTED MANUSCRIPT
A New Strategy Towards Tridentate N-Heterocyclic Carbene Ligands Derived From
Benzimidazolium and Mixed-azolium Salt
Tabinda Fatima, Rosenani A. Haque and Mohd. R. Razali‡
School of Chemical Sciences, Universiti Sains Malaysia, Penang, 11800, Malaysia
‡Corresponding email: mohd.rizal@usm.my
ABSTRACT
The tridentate N-heterocyclic carbenes (NHC) ligands derived from tris azolium salts by a
new synthetic approach are described. The tris azolium salts have been obtained by reacting
the initially synthesized precursor 3-(2-bromoethyl)-1-methylbenzimidazolium bromide (I)
with benzimidazole/imidazole resulting in the tris azolium salts namely, 1 and 2. The ligand
potential of the salts 1 and 2 was investigated by the formation of NHC-Ag(I) complexes 3
and 4, using Ag2O. The most downfield resonances in 13C NMR around 180-190 ppm
indicates the successful coordination of carbene with Ag(I).
Keywords: Tri-N-heterocyclic carbene, Ag(I) complexes, Crystal structure, Azolium.
The N-heterocyclic carbenes ever since their discovery [1] are the intensively studied ligands
in organometallic chemistry owing to their ability to form complexes with virtually all the
elements of the periodic table in addition to their easy accessibility and structural diversity
[2]. Started with the mono NHC complexes with a variety structural motifs, this area has been
extended by the introduction of numerous complexes containing poly NHCs ligands that
include the bis-, tri-, tetra- and hexa-NHCs [3].
Among the different types of poly N-heterocyclic carbene systems featuring metal
complexes, the tri-NHC systems are relatively scarce. The first known tri-NHC ligand and
respective metal complexes were reported by Hu et al., that was synthesized by a simple
synthetic approach involving the quaternization of N-methylimidazole with 1,1,1-
tris(bromomethyl) ethane [4]. Meanwhile, Rit et al., have reported the preparation of
tricarbene ligand by the reaction of imidazole with 1,3,5-tribromobenzene followed by the
alkylation of the free imine [5]. Both strategies in obtaining these tri-NHC ligands involves
the uses of a tridentate linker that connects the three imidazolium units in a single step.

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In our attempt to obtain tri-NHC compound, the benzimidazole was firstly N-
substituted and then followed by quaternized with 1,2-dibromoethane that facilitate the
formation of 3-(2-bromoethyl)-1-methylbenzimidazolium bromide (I) (Scheme 1) [6]. The
synthesis of the key reactant (I) was carried out by different strategy which involves the neat
reaction of N-substituted benzimidazole with 1,2-dibromoethane on a reflux at 80°C for 8
hours. This then resulted the formation of white precipitates that were collected and washed
with DCM, somewhat different with reported synthesis procedure that involves this type of
reaction however using diethy ether as solvent and several days of stirring at room
temperature [7,8]. Subsequently the salt (I) was reacted with unsubstituted benzimidazole in a
solvent mixture of 1,4-dioxane and methanol, in which after 32 hrs of reflux the tri-NHC
precursor was precipitated out (Scheme 2) [9]. The reaction of salt (I) with benzimidazole
without the uses of any strong base required for deprotonation of 1H proton indicates that this
synthetic route is unique compared to the reported single step methods of substitution and
addition on the nitrogens (N1 & N3) of imidazole which involve the use of strong bases [10].
This direct alkylation has been carried out taking advantage of the reactivity of
benzimidazole/imidazole with alkyl halides which under vigorous conditions resulted in the
formation of 1,3-dialkylbenzimidazolium halides [11].
We thereafter extended our approach to synthesize the tri-NHC ligand precursor of
mixed azolium salts. This was achieved by the introduction of the benzimidazolium and
imidazolium units in one tri-NHC system, by following the aforementioned strategy [12]
(Scheme 2). To the best of our knowledge such NHC systems are unprecedented and can
serve as a new class of NHC ligands. Further the potential of the salts 1 and 2 as ligands was
investigated by the formation of respective Ag(I) complexes (Scheme 3) [13]. The
complexation with Ag(I) was preferred as NHC-Ag(I) complexes are most suitable
candidates for transmetallation [14] and biological studies [15] in addition to catalysis [16]
for the purpose of future studies.

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DMSO,KOH
Br
N
N
RT, 3hrs stirring
N
NH
Br
8 hrs reflux
N
N
Br
neat
N
N
Br
Br
I
Scheme 1: Synthesis of 3-(2-bromoethyl)-1-benzylbenzimidazolium bromide salt I.
Dioxane & methanol
Br
N
N
32 hrs reflux
N
Bn
N
N
NH
N
N
Bn
N
Bn
N
Br
Br
Br
Br
1
Dioxane & methanol
32 hrs reflux
Br
N
N
N
Bn
N
N
NH
N
N
Bn
N
Bn
N
Br
Br
Br
Br
2
Scheme 2: Synthesis of tris benzimidazolium bromide salts 1 and 2, respectively.

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N
N
N
N
Bn
N
Bn
N
Br
(1 or 2)
Br
Br
a. Ag2O
methanol
48 hrs
b. metathesis
using KPF6
RT, stirring
3
3PF6
N
N
N
Bn
Bn
N
N
N
Bn
Ag
Ag
Ag
N
N
N
N
Bn
N
N
(3 or 4)
Scheme 3: Synthesis of tri NHC-Ag(I) complexes 3 and 4, respectively.
Spectroscopic investigation at each step of synthesis supported the formation of
desired salts along with the confirmation of the designed structures (I, 1 and 2) through single
crystal X-ray diffraction data. The N, N’-substitution and addition of benzimidazole with
precursor I in a single step without the use of any base was evidenced by the disappearance
of the absorption band of medium intensity for N-H vibrations of benzimidazole/ imidazole
around 3400 cm-1. This was further supported by the disappearance of the 1-H acidic proton
resonance at ca. 12.6 ppm. In these tris azolium salts, there are three pre-carbenic centres
under two different chemical environments. Hence as expected, two resonance signals
appeared in the form of two singlets in the most downfield region at 10.1-10.3 ppm in the
salts 1, which is a characteristic feature for the two types of acidic protons (NCHN) of
benzimidazolium salts [17]. For salt 2, these acidic protons show resonances in the region of

ACCEPTED MANUSCRIPT
9.3-9.9 ppm [18]. All the bridging dimethylene protons in salt 1 appear as singlet at around
5.2 ppm, whereas in salt 2 as the two methylene are similar, thus show two triplets in the
region of 4.8-5.1 ppm. The benzylic protons present in the salts 1 and 2 appear as singlets
around 5.8 ppm implying the conformational flexibility of these salts in the solution, as in
case of rigid molecules, the benzylic protons have been reported to appear as sharp doublets
[19].
13
In the C NMR spectra, the pre-carbenic carbons (NCHN) exhibit resonances at
ca. 143 and 144 ppm for salt 1, while for salt 2 are around 134 and 143 ppm, respectively.
The formation of tri-NHC-Ag(I) complexes demonstrated by disappearance of resonance
signals for the two sets of acidic protons around 10 ppm which supports the generation of
carbene. The resonances for the other protons underwent broadening of signals, somewhat
similar to that reported for poly NHC-Ag(I) complexes which indicates that the complexes
have a highly flexible structure [20]. The signals remain the same even by undertaking low
temperature NMR studies. The successful complexation was further supported by the
appearance of two sets of doublets attributed to two types of carbenoid centres coordinating
with Ag107 and Ag109 as clearly observed in complex 3 (Figure 1). For the doublets of
doublets set, the carbene-silver coupling could be observed with the coupling constants of
180.6 Hz for C-107Ag and 209.0 Hz for C-109Ag. This splitting pattern is consistent with the
literature reports on the carbene-Ag(I) coupling constants [21]. The other set of doublets
remained unresolved appearing at 188 ppm [22]. For complex 4 two unresolved doublets
were observed at 188.5 and 190.1 ppm.

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Figure 1: Selected part of 13C NMR spectrum of NHC-Ag(I) complex 3 (d3-acetonitrile)
highlighting the appearance of the resonance signal for the two types of carbene-Ag bonds
which is an indication of a successful synthesis of the tri NHC-Ag(I) complex.
Single crystal X-ray crystallography studies of the precursor shows that the compound
I crystallizes in triclinic space group P-1 with two anion units (Figure 2), two bromide
cations and one water molecule in the asymmetric unit [23]. The water molecule behaves as
hydrogen bonds donor to two independence bromide ions in the lattice.
Figure 2: Structure of anion unit in I with an ellipsoids shown at 50% probability. Molecules
in the lattice omitted for clarity.
Both of the salts 1 and 2 crystallise in monoclinic space group C2/c with one and the
half of the molecule in the asymmetric unit [24]. The presences of the bromide cations in the
lattice thus balance the entire charge of the molecule. The crystal of 2 contains as well three
water molecules in the lattice. The crystal structure clearly depicts the three azolium units
connected via dimethylene linker having their planes parallel to each other, while the benzyl
rings are projecting perpendicular to the planes of benzimidazolium rings (Figure 3). The
nitrogen to the precarbene carbon bond distance of benzimidazolium unit ranges from
1.328(6)-1.333(6) Å, while for imidazole ring it ranges from 1.296(10)-1.314(10) Å. The
internal ring angles at the precarbenic centre (N-C-N) of benzimidazole and imidazole are in
the range of 109.5°-110.4°, both in salts 1 and 2. The face-to-face π-π stacking of the
aromatic rings being a dominance supramolecular interaction in 1 while hydrogen bonds
interactions between water molecule and bromide ions in the lattice being the main
supramolecular interactions in stabilizing compound 2.

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(a)
(b)
Figure 3: Structure of 1 and 2 with an ellipsoids shown at 50% probability. Molecules in the
lattice omitted for clarity.
The structures of tri NHC-Ag(I) complexes 3 and 4 could not be further supported by
single crystal X-ray diffraction data as all the efforts to obtain single crystals remain
13
unsuccessful. However, the evidence of successful complexation with Ag(I) by C-NMR
studies along with elemental analysis supported the formation of tri-NHC trinuclear Ag(I)
complexes with the stoichiometry of [Ag3L2]·3PF6 (where L = 1 or 2) which signifies the
formation of the expected complexes.
In conclusion, a new approach for the synthesis of tris azolium salts has been explored
that represents a new class of NHC ligands. The transmetallation and anticancer study of such
compounds are underway.

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Acknowledgments
This work was supported by RUI grant 1001/PKIMIA/811346.
Appendix A. Supplementary material
Spectroscopic data are presented as supporting information and CCDC 1520347-1520349
contains the crystallographic data for I, 1 and 2, respectively. Copy of this material can be
obtained from the Director, CCDC, 12 union Road, Cambridge CB2 1EZ, UK (Fax: +44
1223 336033; Email: deposit@ccdc.cam.ac.uk/deposit).
References
[1] A.J. Arduengo, R.L. Harlow, M. Kline, J. Am. Chem. Soc. 113 (1991) 361-363.
[2] (a) P.L. Arnold, I.J. Casely, Chem. Rev. 109 (2009) 3599-3611.
(b) M.N. Hopkinson, C. Richter, M. Schedler, F. Glorius, Nature 510 (2014) 485-496.
[3] (a) J.C. Garrison and W.J. Youngs, Chem. Rev. 105 (2005) 3978-4008.
(b) M. Poyatos, J.A. Mata, E. Peris, Chem. Rev. 109 (2009) 3677-3707.
(c) C. Segarra, G.G. Barrios, F.E. Hahn, E. Peris, Organometallics 33 (2014) 5077-
5080.
[4] X. Hu, Y. Tang, P. Gantzel, K. Meyer, Organometallics 22 (2003) 612-614.
[5] A. Rit, T. Pape, F.E. Hahn, J. Am. Chem. Soc. 132 (2010) 4572-4573.
[6]
3-(2-bromoethyl)-1-benzyl benzimidazolium bromide (I): N-benzyl benzimidazole
was synthesized according to the literature procedure. The N-benzyl benzimidazole
(1.00 g, 4.80 mmol) was reacted with 1,2-dibromoethane (4 ml, 46 mmol) in neat. The
reaction mixture was refluxed at 80°C for 8 hours. After completion of reaction time
the product appeared as white crystalline salt. The excess 1,2-dibromoethane was
rotary evaporated, dichloromethane was added to the solid residue and was filtered.
The filtrate was left to evaporate in the fume cupboard and after evaporation of
solvent the product was collected in crystalline form. Salt I was collected as colorless

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crystals. Yield: 1.05 g (53%). M.p.: 205-207°C. Anal.Calc.for C16H16Br2N2: C, 48.48;
H, 4.04; N, 7.07. Found: C, 48.24; H, 3.94; N, 6.77. FTIR (KBr) ʋ (cm-1): 3136, 3025
(Carom-H); 2966, 2884 (Caliph-H), 1610, 1492, 1458 (Carom=Carom), 1561 (Carom-N),
1263 (Caliph-N). 1H NMR (500 MHz, DMSO-d6) δ ppm: 3.85 (2H, -CH2-Br, t, J = 5.0
Hz), 4.62 (2H, N-CH2-, t, J = 5.0 Hz), 5.85 (2H, N-CH2-Ar, s), 7.35-8.13 (9H, Ar-H,
13
m), 10.01 (1H, NCHN, s). C NMR (125 MHz, DMSO-d6) δ ppm: 49.6 (CH2-Br),
49.7 (N-CH2), 58.5 (Ar-CH2); 114.1, 126.5, 128.2, 128.9, 130.7, 131.5, 134.0 (Ar-C);
142.8 (NCHN).
[7] L.D. Field, B.A. Messerle, K.Q. Vuong, P. Turner, Organometallics 24 (2005) 4241-
4250.
[8] T.A.P. Paulose, J.A. Olson, J.W. Quail, S.R. Foley, J. Org. Chem. 693 (2008) 3405-
3410.
[9]
Benzyl substituted tris benzimidazolium bromide salt (1): The synthesis was carried
out by reacting (I) (1.00 g, 2.50 mmol) with benzimidazole (0.15 g, 1.26 mmol) in a
solvent mixture of 1,4-dioxane (20ml) and methanol (2 ml). The reaction was carried
out on reflux for 32 hours. The tris benzimidazolium bromide salt appeared in the
form of white precipitates which was filtered, washed with fresh 1,4-dioxane and
dichloromethane and left to dry in the fume cupboard. Salt 1 was collected as white
powder. Yield: 0.63 g (60%). M.p.: 263-267°C. Anal.Calc.for C39H37Br3N6: C, 56.45;
H, 4.46; N, 10.13. Found: C, 56.74; H, 4.63; N, 10.41. FTIR (KBr) ʋ (cm-1): 3124
(Carom-H); 2995 (Caliph-H), 1614, 1485, 1435 (Carom=Carom), 1557 (Carom-N), 1286
1
(Caliph-N). H NMR (500 MHz, DMSO-d6) δ ppm: 5.23 (8H, 2 × -CH2-CH2-, s), 5.77
(4H, 2 × -CH2-Ar, s), 7.38-7.45 (14H, Ar-H, m), 7.46-7.65 (4H, Ar-H, m), 7.78-8.18
13
(4H, Ar-H, m), 10.13 (2H, NCHN, s), 10.27 (1H, NCHN, s). C NMR (125 MHz,
DMSO-d6) δ ppm: 44.8, 45.6, 49.9, 50.1 (CH2), 111.7, 113.2, 116.2, 125.3, 126.9,
128.2, 130.7, 131.5, 133.6 (Ar-C); 143.0, 144.2 (NCHN).
[10] (a) R.A. Haque, H.Z. Zulikha, M.Z. Ghdhayeb, S. Budagumpi, A.W. Salman,
Heteroatom Chem. 23 (2012) 486-497.
(b) U. F. M. Haziz, R. A. Haque, A. A. Amirul, N. Shaheeda and M. R. Razali,
Polyhedron, 117 (2016) 775.
[11]
J.B. Wright, Chem. Rev. 48 (1951) 397-541.

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[12] Salt 2 was prepared following the same procedure as that for salt 1 except that and
benzimidazole was replaced by imidazole (0.12 g, 1.8 mmol). Salt 23 was collected as
white powder. Yield: 0.71 g (51%). M.p.: 173-177°C. Anal.Calc.for C35H35Br3N6: C,
53.93; H, 4.49; N, 10.78. Found: C, 54.28; H, 4.21; N, 10.45. FTIR (KBr) ʋ (cm-1):
3127 (Carom-H); 2964 (Caliph-H), 1620, 1465 (Carom=Carom), 1557 (Carom-N), 1260
1
(Caliph-N). H NMR (500 MHz, DMSO-d6) δ ppm: 5.23 (8H, 2 × -CH2-CH2-, s), 5.80
(4H, 2 × -CH2-Ar, s), 7.38-7.75 (16H, Ar-H, m), 7.97-8.08 (4H, Ar-H, m), 9.37 (1H,
13
NCHN, s), 9.97 (2H, NCHN, s). C NMR (125 MHz, DMSO-d6) δ ppm: 46.7, 48.2,
50.5 (CH2), 113.9, 114.5, 123.4, 127.4, 128.8, 131.3 (Ar-C); 134.1, 143.2 (NCHN).
[13]
Tri NHC-Ag(I) complex (3): Salt 1 (0.27 g, 0.34 mmol) was dissolved in 50 ml of
methanol and silver oxide (0.24 g, 1.00 mmol) was added to it. The reaction mixture
was stirred at room temperature for 2 days. The reaction was carried out in a round
bottom flask wrapped with aluminium foil in order to exclude light. After completion
of reaction time the product was separated from the insolubles like AgBr and
unreacted Ag2O by filtering through a column of celite. The resulted silver complex in
bromide form was subjected to metathesis using potassium hexafluorophosphate (0.18
g, 1 mmol). The mixture was stirred for 2 hours and the resulting precipitates were
filtered, washed with distilled water and left to dry at room temperature. The silver
complex 3 was collected as white powder. Yield: 0.37 g (57%). M.p.: 246-250°C.
Anal.Calc.for C78H68Ag3F18N12P3: C, 48.49; H, 3.52; N, 8.70. Found: C, 48.79; H,
3.87; N, 8.57. FTIR (KBr) ʋ (cm-1): 3110, 3062 (Carom-H), 2949 (Caliph-H), 1607,
13
1477, 1446 (Carom=Carom), 1267 (Caliph-N). C NMR (125 MHz, Acetonitrile-d3) δ
ppm: 43.6, 46.2, 50.6(CH2); 111.5, 123.6, 124.3, 126.5, 128.2, 129.1, 132.6, 133.3,
1
1
134.8(Ar-C); 183.9 & 185.6 [d, J(C-107Ag) = 180.6 Hz & J(C-109Ag) = 209 Hz), 187.6
(C-Ag, br d), 189.3 (C-Ag, br d).
Tri NHC-Ag(I) complex (4): Complex 4 was prepared following the same procedure
as that for complex 3 except that salt 1 was replaced by salt 2 (0.23 g, 0.30 mmol).
The silver complex 4 was collected as white powder. Yield: 0.37 g (57%). M.p.: 251-
255°C. Anal.Calc.for C70H64Ag3F18N12P3: C, 45.88; H, 3.49; N, 9.17. Found: C,
45.62; H, 3.58; N, 9.03. FTIR (KBr) ʋ (cm-1): 3129 (Carom-H), 2948 (Caliph-H), 1615,
13
1452, 1476 (Carom=Carom), 1240 (Caliph-N). C NMR (125 MHz, Acetonitrile-d3) δ
ppm: 46.4, 50.2, 51.5(CH2); 112.5, 124.3, 126.2, 128.6, 132.9, 136.3, 138.9(Ar-C);
188.5 & 190.1 (C-Ag, br d).

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[14] (a) I.J.B. Lin, C.S. Vasam, Coord. Chem. Rev. 251 (2007) 642-670.
(b) C. Cesari, S. Conti, S. Zacchini, V. Zanotti, MC. Cassani, R. Mazzoni, Dalton
Trans. 43 (2014) 17240-17243.
(c) M.Z. Ghdhayeb, R.A. Haque, S. Budagumpi, M.B.K. Ahamed, A.M.S. Majid,
Polyhedron 121 (2017) 222-230.
[15] (a) S. Budagumpi, R.A. Haque, S. Endud, G.U. Rehman, A.W. Salman, Eur. J. Inorg.
Chem. 2013(2013) 4367-4388.
(b) W. Liu, R. Gust, Coord. Chem. Rev. 329(2016) 191-213.
[16]
(a) I.J. Talisman, V. Kumar, J.R. Deschamps, M. Frisch, S.V. Malhotra,
Carbohydrate Research 346 (2011) 2337-2341.
(b) H. Yoshida, I. Kageyuki, K. Takaki, Org. Letters 16 (2014) 3512-3515.
(c) S. Li, Z. Zhang, R. Xie, X. Fang, M. Zhou, Dalton Trans. 45 (2016) 10577-10584.
[17] (a) M.A. Iqbal, R.A. Haque, S. Budagumpi, M.B.K. Ahamed, A.M.S. Majid, Inorg.
Chem. Comm. 28 (2013) 64-69.
(b) M. A. Iqbal, R. A. Haque, W. C. Ng, L. E. H. Hassan, A. M. S. A. Majid and M.
R. Razali, J. Organometallic Chem. 801 (2016) 130.
[18]
[19]
R.A. Haque, P.O. Asekunowo, S. Budagumpi, Inorg. Chem. Comm. 47 (2014) 56-59.
M.V. Baker, D.H. Brown, R.A. Haque, B.W. Skelton, A.H. White, Dalton Trans. 21
(2004) 3756-3764.
[20]
(a) D. T. Weiss, S. Haslinger, C. Jandl, A. Pöthig, M. Cokoja, F. E. Kühn, Inorg.
Chem. 54 (2014) 415-417.
(b) D. T. Weiss, P. J. Altmann, S. Haslinger, C. Jandl, A. Pöthig, M. Cokoja, F. E.
Kühn, Dalton Trans. 44 (2015) 18329-18339.
[21]
[22]
(a) B. Bildstein, M. Malaun, H. Kopacka, K. Wurst, M. Mitterback, K.H.
Organia, G. Opromolla, P. Zanello, Organometallics 18 (1999) 4325-4336.
(b) J.C. Garrison and W.J. Youngs, Chem. Rev. 105 (2005) 3978-4008.
X. Hu, I.C. Rodriguez, K. Olsen, K. Meyer, Organometallics 23 (2004) 755-764.

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[23]
Crystal structure details of I: Formula C32H32N4Br2·2Br·H2O. Fw = 810.23,
Triclinic, space group P-1 , a = 9.1159(7) Å , b = 10.3486(8) Å, c = 18.0330(13) Å, α
= 90.499(1)°, β = 97.554(1)°, γ = 98.025(1)°, V = 1669.3(2) Å3, Z = 2, D(calc) = 1.612
g cm-3, F(000) = 804, Crystal size 0.12 x 0.24 x 0.27 , T = 100 K, θmin = 1.1°, θmax
=
30.0°, Tot = 67209, Uniq. Data = 9750, R(int) = 0.052, R = 0.0591, wR2 = 0.1175, S =
1.06.
[24] Crystal structure details of 1: Formula C39H37N6·3Br. Fw = 829.45, Monoclinic, space
group C2/c, a = 45.472(3) Å, b = 11.4437(7) Å, c = 21.6836(14) Å, α = γ = 90°, β =
99.8532(14)°, V = 11117.0(12) Å3, Z = 12, D(calc) = 1.487 g cm-3, F(000) = 5016, Crystal
size 0.14 x 0.14 x 0.34 , T = 100 K, θmin = 1.8°, θmax = 28.0°, Tot = 83757, Uniq. Data =
13427, R(int) = 0.050, R = 0.0637, wR2 = 0.2011, S = 1.04. The crystal contained
significant pores (556 Å3) containing disordered solvent that could not be satisfactorily
refined. The data was therefore treated with the SQUEEZE routine of PLATON and
accounted for 88 electrons per unit cell. R1(obs) and wR2(obs) before SQUEEZE = 0.1305
and 0.2489 respectively.
Crystal structure details of 2: Formula C35H35N6·3Br·3H2O. Fw = 833.44, Monoclinic,
space group C2/c, a = 45.5050(17) Å, b = 11.5567(4) Å, c = 22.0400(8) Å, α = γ = 90°,
β =113.6650(13)°, V = 1616.6(7) Å3, Z = 12, D(calc) = 1.564 g cm-3, F(000) = 5064,
Crystal size 0.09 x 0.17 x 0.26 , T = 100 K, θmin = 1.0°, θmax = 25.5°, Tot = 133318,
Uniq. Data = 9890, R(int) = 0.102, R = 0.0634, wR2 = 0.1868, S = 1.12. Two of the
bromide anions in the lattice are disordered over two positions and were refined with
half occupancies.