Radical coupling for directed C-C/C-S bond formation in the reaction of Cp*IrS2C2B10H10 with 1-azido-3-nitrobenzene

Article abstract of DOI:10.1039/c3dt52308j

Reactions of half-sandwich complex Cp*IrS₂C ₂B₁₀H₁₀ (1) with 1-azido-3-nitrobenzene (3-NO₂C₆H₄N₃, L) upon heating or under light led to new complexes 2-6. Complexes 2 and 3 contain a five-membered cyclometalated ligand arising from C(sp²)-H activation of the azide ligand L. Complex 4 is a 16 electron species containing a new-generated C-C bond between the azide ligand L and the Cp* unit where C(sp³)-H activation of the methyl unit occurred. Complexes 5 and 6 contain two types of the ligand which appear in complexes 2, 3 and 4. Further reactions of complexes 5 and 6 with L under more harsh conditions gave rise to the nucleophilic addition products 7 and 8, where ring expansion of the azide ligand at the imido site of complexes 5 and 6 happened. Complexes 2-8 were characterized by NMR, MS, IR, and elemental analysis, and X-ray structural analyses were performed for complexes 2-4 and 6-8. The radical mechanisms for the formation of complexes 2-6 were proposed on the basis of capture experiments by EPR and ESI-MS. And the formation mechanism of complexes 7 and 8 was also suggested.

Full text of DOI:10.1039/c3dt52308j

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Radical coupling for directed C–C/C–S bond
formation in the reaction of Cp*IrS2C2B10H10 with
1-azido-3-nitrobenzene†
Cite this: Dalton Trans., 2014, 43,
4962
Wei Zhong,a,b Qibai Jiang,a Qian Zhang,a Yi Shang,a Hong Yan*a and
Vladimir Bregadze*c
Reactions of half-sandwich complex Cp*IrS2C2B10H10 (1) with 1-azido-3-nitrobenzene (3-NO2C6H4N3, L)
upon heating or under light led to new complexes 2–6. Complexes 2 and 3 contain a five-membered
cyclometalated ligand arising from C(sp2)–H activation of the azide ligand L. Complex 4 is a 16 electron
species containing a new-generated C–C bond between the azide ligand L and the Cp* unit where
C(sp3)–H activation of the methyl unit occurred. Complexes 5 and 6 contain two types of the ligand
which appear in complexes 2, 3 and 4. Further reactions of complexes 5 and 6 with L under more harsh
conditions gave rise to the nucleophilic addition products 7 and 8, where ring expansion of the azide
ligand at the imido site of complexes 5 and 6 happened. Complexes 2–8 were characterized by NMR,
MS, IR, and elemental analysis, and X-ray structural analyses were performed for complexes 2–4 and 6–8.
The radical mechanisms for the formation of complexes 2–6 were proposed on the basis of capture
experiments by EPR and ESI-MS. And the formation mechanism of complexes 7 and 8 was also
suggested.
Received 22nd August 2013,
Accepted 23rd September 2013
DOI: 10.1039/c3dt52308j
www.rsc.org/dalton
study on the Co(por)-catalyzed amination of benzylic C–H
bonds by different organic azides, which proceed via a
Introduction
Aryl nitrenes, which are readily available from the photolysis multistep radical mechanism involving an unusual “nitrene
or thermolysis of aryl azides, are among the most thoroughly radical” intermediate (por)CoIII–N·Y;13 Peters reported facile
investigated reactive intermediates.1–4 Present studies of aryl catalytic N–N coupling of aryl azides to yield azoarenes
nitrenes are focused on the organic system, such as photo- mediated by the Ru(I) metalloradical [SiPiPr3]Ru(N2).14 On the
chemistry of phenyl azide.5–8 Comparatively, nitrene chemistry other hand, it is well-established that photolysis or thermolysis
in the organometallic field is much less explored, although of aryl azides initially yields singlet aryl nitrenes, which then
organic azides were used extensively for the preparation of either undergo intersystem crossing to the triplet ground
imido complexes and organoazido metal complexes.9–11 state or rearrange to didehydroazepines via bicyclic
Among a few reported examples, Abu-Omar and co-workers azirines.5,15–18 Among these sequential transformations, we
described a novel mechanism for the reactions of aryl azides assumed that addition of an appropriate metal complex may
with manganese corroles in which the metal captures triplet capture some reactive intermediates or lead to some
nitrene rather than form an organoazido complex;12 Bruin unexpected results. Bearing this in mind and considering
et al. presented EPR spectroscopic and detailed computational the activity of the 16-electron half-sandwich complex
Cp*IrS2C2B10H10 (1) with different substrates,19 our recent
study on the thermal and photochemical reactions of complex
aState Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical
1 with 2,6-disubstituted aryl azides showed C(sp3)–H activation
Engineering, Nanjing University, Nanjing, Jiangsu 210093, China.
and electron-withdrawing group migration.20 To further under-
E-mail: hyan1965@nju.edu.cn; Tel: +86-25-83686724
bCollege of Biological, Chemical Sciences and Engineering, Jiaxing University,
stand such transformations and explore the scope of organic
azides, we focus on the reactions of other aryl azides with
complex 1. In this paper, we report on the reaction of 1
and 1-azido-3-nitrobenzene (L) which has led to C–C and/or
C–S bond formation via radical coupling initiated by heat
or light.
Jiaxing, Zhejiang 314001, China. Tel: +86-573-83640303
cA. N. Nesmeyanov Institute of Organoelement Compounds (INEOS),
Russian Academy of Sciences, Vavilov Str. 28, Moscow, 119991, Russia.
E-mail: bre@ineos.ac.ru; Tel: +7-499-135-7405
†CCDC 936371–936376. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt52308j
4962 | Dalton Trans., 2014, 43, 4962–4968
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Results and discussion
Reaction of complex 1 and 3-NO2C6H4N3 (L)
Similar to the reactions of 1 with 2,6-disubstituted aryl azides
that we previously investigated,20 cyclometalated complexes 2
and 3 were formed as expected in the reaction of 1 with excess
L upon heating in toluene (80 °C) (Scheme 1). Two additional
products 5 and 6 were also isolated from this reaction in yields
of 14.5% and 15.8%, respectively. It is not surprising that two
ortho-positions in L have the same possibility for cyclometala-
tion and the results gave the two expected types of products 2
and 3 with a ratio of 2/3. But interestingly, another product 4
was obtained if treated with one equiv. or less L in the reac-
tion. If excess L was used, complex 4 could not be isolated as it
further reacted with ligand to produce 5 and 6 in moderate
yields. Note that the further reactions of complexes 2 and 3
with excess L did not lead to 5 and 6, but products 7 and 8,
respectively, under higher temperature or longer photolysis
(Scheme 1).
Fig. 1 Molecular structures of 2 and 3 with 30% displacement ellip-
soids. All H atoms are omitted for clarity.
the phenyl (ortho-position) ring. The C13–N1 lengths in 2 and
3 are 1.349 and 1.330 Å, respectively, demonstrating a feature
of a double bond, close to the cyclometallated amino-carbene
complexes.25 This is also consistent with the Ir1–N1–C13 bond
angle of 120–122°, indicative of sp2 hybridization of the N1
atom. The characteristic –NH signals in the 1H NMR spectra of
complexes 2 and 3 are assigned to the broad singlets at
4.30 ppm and 4.13 ppm, respectively. Three phenyl proton
resonances, which show two doublets and one triplet in 2 and
one singlet and two doublets in 3, are supportive of cyclometa-
lation in these complexes.
The molecular structure of 4 (Fig. 2) inherits the [IrS2C2B10H10]
moiety from the precursor 1, but with a new ancillary ligand
which is generated from the coupling of Cp* ligand with aryl
azide. Therein, the carbon atom between nitro and azido
groups connects with one methyl group of Cp* and the nitro-
gen is subsequently converted to the NH2 group via hydrogen
transfer after the loss of N2. In comparison to the formation of
complexes 2 and 3, it appears that complex 4 adopts a
different pathway from the 16-electron precursor 1 and azide.
Consistent with the solid structure, the 1H NMR spectrum
showed one broad signal at 4.55 ppm ascribed to the –NH2
group, one singlet at 3.51 ppm assigned to the methylene
group and two singlets at 1.87 and 1.76 ppm assigned to four
methyl groups. The 13C NMR signal for methylene appears at
25.77 ppm whereas the methyl signals appear as two close
singlets at 9.83 and 10.13 ppm.
Characterization of complexes 2–8
All these complexes were fully characterized by NMR spec-
troscopy, mass spectrometry, and elemental analysis. Addition-
ally, the solid state structures of these complexes were solved
by X-ray crystallography with the exception of complex 5.
Crystal structures of 2 and 3 are shown in Fig. 1. As two iso-
meric examples, the common feature of both is the covalent
combination of one sulfur atom with an ortho-position carbon
atom of the phenyl ring to construct a five-membered Ir–N–C–C–S
metallacyclic ring, which shares one Ir–S bond with the origi-
nal five-membered ring in complex 1 (Ir–S–C–C–S). In each
case the new “SSN” pincer ligand derived from the azide and
carboranyl dithiolate, is coordinated to the iridium center via
Ir–S/Ir←S/Ir–N bonding. Although structurally similar to reported
alkyne-inserted 18-electron adducts,21–24 the formation of the
Ir–N–C–C–S ring within 2 and 3 can be inferred as a different
pathway because of the necessary activation of a C–H bond of
A perspective view of complex 6 is shown in Fig. 2. The
structure of 6 can be considered as the combination of 3 and
Scheme 1 The synthesis of complexes 2–8. Reaction conditions: (i)
toluene, 80 °C, 3 hours or hν, RT, 30 minutes; (ii) toluene, reflux, 24 hours
or hν, RT, 3 hours.
Fig. 2 Molecular structures of 4 and 6 with 30% displacement ellip-
soids. All H atoms are omitted for clarity.
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Fig. 3 Molecular structures of 7 and 8 with 30% displacement ellip-
soids. All H atoms are omitted for clarity.
4, with the same cyclometalation in 3 and C–H activation of
the Cp* ligand in 4. But its 1H NMR spectrum shows some
differences from 4, with two doublets at 3.59 and 3.70 ppm
(J = 17 Hz) due to the diastereotopic protons of the methylene
group and four singlets in the range of 1.51–1.84 ppm for the
inequivalent methyl groups. The NMR spectra of 5 are similar
to those of 6, with the main difference in the phenyl signals of
cyclometalation, thus supporting the proposed structure.
The molecular structures of 7 and 8 are shown in Fig. 3.
Both complexes 7 and 8 demonstrate that the nitrogen atom in
the five-membered Ir–N–C–C–S metallacyclic ring is bound to
a distorted seven-membered heterocycle, which is named as
4-nitro-3H-azepine. Complexes 7 and 8 can be thought of as the
nucleophilic addition of 2 and 3 with L after the loss of N2 and
ring expansion. With the same skeleton of the Ir–N–C–C–S
metallacyclic ring sharing one Ir–S bond with the original five-
membered ring Ir–S–C–C–S in 2 and 3, the Ir1–N1 and N1–C13
lengths in 7 and 8 are 0.09 Å and 0.05 Å longer than those in
2 and 3 on average. All other distances and angles are in the
Fig. 4 EPR spectra (X band, 9.7 GHz, room temperature) for reaction
mixtures in the different periods of irradiation: the radical trap agent
DMPO (100 mM), 1 (100 mM) and L (100 mM).
1
expected range. The H NMR spectra show the signals of Cp*,
phenyl and 4-nitro-3H-azepine in rational regions. The reson-
ances at δ = 1.27 ppm are attributed to the CH2 groups in the
4-nitro-3H-azepine of both complexes 7 and 8, whose corres-
ponding 13C NMR signals appear at δ = 32.99 and 32.19 ppm,
respectively.
Fig. 5 ESI-MS spectra of the mixture of DMPO (100 mM), 1 (100 mM)
and L (100 mM) after irradiation for two minutes without any workup.
782.83 corresponds to [1 + L-N2 + DMPO] species, and the peak
at m/z 982.25 matches the formula [1 + 2L-2N2 + DMPO + Na +
Mechanistic considerations
Generally, the interaction between transition metal com- MeCN + H+]. Nevertheless, the results of EPR signal change
plexes and organic azides usually undergoes two plausible with irradiation time indicate that the DMPO/radical adducts
pathways: one proceeds in an ionic reaction via dipolar can survive within 40 minutes (Fig. 4), thus the DMPO/radical
addition to the substrates; the other forms nitrene species adducts are hard to be isolated and further characterized. The
and then reacts further to give a variety of products, which lower percentages of the peaks at m/z 782.83 and 982.25 in
in some cases involve radical intermediates and undergo a ESI-MS spectra also reflect the instability of the DMPO/radical
radical mechanism. As shown above, the reactions demon- adducts (Fig. 5). For comparison, the reaction was also con-
strate unusual C–H activation in phenyl/methyl to form ducted under photolytic conditions, lower yields of expected
C–S and C–C bonds. This inspired us to consider a radical compounds were isolated than under thermal conditions.
mechanism. For mechanistic elucidation, EPR experiments
Based on the above experiments, a plausible mechanism
were carried out. In situ irradiation of the solution of 1, L and involving radical species for the formation of compounds 2–6
the radical capture reagent, 5,5-dimethyl-1-pyrroline N-oxide is proposed in Scheme 2. In the first step, azide ligand L inter-
(DMPO), strong EPR signals were observed (Fig. 4). More than acting with 16-electron species 1 to generate metal–imido
this, the DMPO/radical adducts could be detected by ESI-MS complex I is suggested. This species can transform into diradical
after irradiation for two minutes (Fig. 5). The peak at m/z II, then to IIIA–IIIC by hydrogen abstraction and radical
4964 | Dalton Trans., 2014, 43, 4962–4968
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activation undergoing a radical mechanism. The unsaturated
characterization of complex 1 together with the nature of
azide ligand L is responsible for such interesting chemical
transformation. We also found that the –NH group in metal
complexes can act as a nucleophile to trap the seven-mem-
bered ring keteneimine in nitrene chemistry. The preliminary
results have shown application potential in organometallic or
organic synthesis.
Experimental
Compounds were prepared and handled by standard Schlenk
techniques. Toluene was predried over molecular sieves
and distilled over CaH2 under nitrogen prior to use.
Cp*IrS2C2B10H10 (1)27 and 1-azido-3-nitrobenzene28 were pre-
pared by literature procedures. The NMR measurements were
performed using a Bruker DRX 500 spectrometer. Chemical
shifts were given with respect to CHCl3/CDCl3 (δ 1H =
7.24 ppm; δ 13C = 77.0 ppm) and external Et2O·BF3 (δ 11B =
0 ppm). The IR spectra were recorded using a Bruker Vector 22
spectrophotometer with KBr pellets in the region of
4000–400 cm−1. The C, H and N microanalyses were carried
out with an Elementar Vario EL III elemental analyzer.
Mass data were determined with the LCQ (ESI-MS, Thermo
Finnigan) mass spectrometer.
Scheme 2 Proposed mechanisms for the formation of complexes 2–6.
Scheme 3 The formation of complexes 7 and 8.
Preparation of complexes 2–6
migration.26 After these processes intramolecular radical coup-
ling happens to lead to products 2 and 3. Similarly, intermedi-
ate IV, which is supported and evidenced by the analogous
product in our previous report,20 is formed by intramolecular
radical coupling of IIIC in the same way. In this case, IV may
be thermodynamically unstable and may rearrange to amino-
coordinated species V, which can easily transform to com-
pound 4 due to the weak coordination of the amino group.
The formation of compounds 5 and 6 repeat the same pathway
as the formation of complexes 2 and 3 from 1 and L.
On the other hand, photolysis or thermolysis of phenyl
azide has been studied extensively5,16,17 and it is well conceiv-
able that such processes yield phenylnitrene, which acts as a
singlet species and undergoes ring expansion. The first step is
to form a bicyclic azepine intermediate, then further rearrange
to a seven-membered ring keteneimine product, which may be
trapped by nucleophiles (e.g. Et2NH). In our case, the for-
mation of 7 and 8 can be regarded as the –NH group in 2 and
3 acting as a nucleophile to add to the seven-membered hetero-
cycle 4-nitro-3H-azepine, which is formed from ring expansion
and rearrangement of initial azide ligand L (Scheme 3).
The mixture of complex 1 (106.8 mg, 0.2 mmol) and 1-azido-
3-nitrobenzene (0.2 or 1.0 mmol) was heated at 80 °C in dried
toluene for 3 hours. The solvent was removed and the crude
product was purified by chromatography using silica gel.
(Note: complex 4 was obtained when one equivalent 1-azido-
3-nitrobenzene was used.)
2 (16.8 mg, 12.5%). Purple solid. 1H NMR: 7.06 (d, J = 7.0 Hz,
1H, ArH), 6.97 (t, J = 7.5 Hz, 1H, ArH), 6.86 (d, J = 7.0 Hz,
1H, ArH), 4.30 (s, 1H, NH), 1.80 (s, 15H, CH3, Cp*). 11B{1H}
NMR: −1.7 (2B), −3.1 (2B), −4.4 (2B), −6.9 (2B), −8.1 (1B), −8.8
(1B). 13C NMR: 8.59 (CH3, Cp*), 90.02 (carborane), 93.27
(C, Cp*), 103.05 (C, Ph), 108.85 (carborane), 110.16 (CH, Ph),
123.38 (CH, Ph), 132.54 (CH, Ph), 149.69 (C, Ph), 167.30
(C, Ph). ESI-MS (m/z): 669.17 (100%) [M]−. IR (KBr, cm−1):
2565.8 (νB–H). Anal. Found: C, 32.03; H, 4.49; N, 4.03. Calcd for
C18H29B10IrN2O2S2: C, 32.27; H, 4.36; N, 4.18.
3 (26.3 mg, 19.6%). Purple solid. 1H NMR: 7.38 (s, 1H, ArH),
7.30 (d, J = 8.5 Hz, 1H, ArH), 6.93 (d, J = 8.5 Hz, 1H, ArH), 4.13
(s, 1H, NH), 1.79 (s, 15H, CH3, Cp*). 11B{1H} NMR: −1.4 (2B),
−2.7 (2B), −4.9 (2B), −6.9 (2B), −8.0 (1B), −9.7 (1B). 13C NMR:
8.61 (CH3, Cp*), 89.17 (carborane), 93.19 (C, Cp*), 105.08 (CH,
Ph), 106.78 (carborane), 110.49 (CH, Ph), 116.62 (C, Ph),
134.42 (CH, Ph), 151.83 (C, Ph), 164.34 (C, Ph). ESI-MS (m/z):
669.33 (100%) [M]−. IR (KBr, cm−1): 2586.7 (νB–H). Anal.
Found: C, 31.92; H, 4.21; N, 4.27. Calcd for C18H29B10IrN2O2S2:
Conclusions
We have shown that thermal and photolytic reaction of half- C, 32.27; H, 4.36; N, 4.18.
sandwich complex 1 and 1-azido-3-nitrobenzene led to new
4 (23.6 mg, 17.6%). Bluish green solid. 1H NMR: 7.34 (d, J =
products involving C–C and C–S bond formation via C–H 8.0 Hz, 1H, ArH), 7.26 (t, J = 8 Hz, 1H, ArH), 6.98 (d, J = 8 Hz,
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1H, ArH), 4.45 (s, 2H, NH2), 3.51 (s, 2H, CH2, Cp*), 1.87 (s, 6H, 8.87 (CH3, Cp*), 8.97 (CH3, Cp*), 9.18 (CH3, Cp*), 22.07 (CH2,
2 × CH3, Cp*), 1.76 (s, 6H, 2 × CH3, Cp*). 11B{1H} NMR: −3.5 Cp*), 88.20 (carborane), 92.44 (C, Cp*), 92.73 (C, Cp*), 93.48
(1B), −4.7 (3B), −5.5 (3B), −6.9 (3B). 13C NMR: 9.83 (2 × CH3, Cp*), (C, Cp*), 94.30 (C, Cp*), 95.53 (C, Cp*), 105.55 (CH, Ph),
10.13 (2 × CH3, Cp*), 25.77 (CH2, Cp*), 91.22 (CCH2, Cp*), 106.17 (carborane), 110.56 (CH, Ph), 113.96 (C, Ph), 114.55
92.02 (carborane), 92.35 (2 × CCH3, Cp*), 93.24 (2 × CCH3, (CH, Ph), 116.73 (C, Ph), 120.33 (CH, Ph), 128.67 (CH, Ph),
Cp*), 113.53 (C, Ph), 114.63 (CH, Ph), 120.88 (CH, Ph), 129.01 134.43 (CH, Ph), 147.25 (C, Ph), 151.16 (C, Ph), 151.87 (C, Ph),
(CH, Ph), 147.40 (C, Ph), 151.37 (C, Ph). ESI-MS (m/z): 671.67 164.30 (C, Ph). ESI-MS (m/z): 807.25 (46%) [M + H+]+. IR
(100%) [M + H+]+. IR (KBr, cm−1): 2579.2 (νB–H). Anal. Found: (KBr, cm−1): 2586.3 (νB–H). Anal. Found: C, 35.54; H, 4.01;
C, 32.10; H, 4.25; N, 3.97. Calcd for C18H29B10IrN2O2S2: N, 7.11. Calcd for C24H33B10IrN4O4S2: C, 35.76; H, 4.13; N, 6.95.
C, 32.27; H, 4.36; N, 4.18.
1
Preparation of complexes 7 and 8
5 (23.4 mg, 14.5%). Light brown solid. H NMR: 7.30 (d, J =
7.5 Hz, 1H, ArH), 7.22 (t, J = 8.0 Hz, 1H, ArH), 7.11 (d, J =
7.5 Hz, 1H, ArH), 7.02 (t, J = 8.0 Hz, 1H, ArH), 6.92 (d, J =
7.5 Hz, 1H, ArH), 6.90 (d, J = 7.5 Hz, 1H, ArH), 4.42 (s, 2H,
NH2), 4.34 (s, 1H, NH), 3.73 (d, J = 17.0 Hz, 1H, CHH), 3.62 (d,
J = 17.0 Hz, 1H, CHH), 1.84 (s, 3H, CH3, Cp*), 1.77 (s, 3H, CH3,
Cp*), 1.71 (s, 3H, CH3, Cp*), 1.56 (s, 3H, CH3, Cp*). 11B{1H}
NMR: −1.6 (2B), −2.8 (2B), −4.3 (3B), −6.8 (2B), −8.3 (1B).
13C NMR: 8.32 (CH3, Cp*), 8.82 (CH3, Cp*), 9.02 (CH3, Cp*),
9.17 (CH3, Cp*), 21.99 (CH2, Cp*), 89.15 (carborane), 92.68
(C, Cp*), 92.93 (C, Cp*), 93.25 (C, Cp*), 94.08 (C, Cp*), 95.63
(C, Cp*), 103.02 (C, Ph), 108.18 (carborane), 110.57 (CH, Ph),
114.12 (C, Ph), 114.57 (CH, Ph), 120.30 (CH, Ph), 123.47 (CH,
Ph), 128.63 (CH, Ph), 132.79 (CH, Ph), 147.24 (C, Ph), 149.62
(C, Ph), 151.13 (C, Ph), 167.25 (C, Ph). ESI-MS (m/z): 805.25
(100%) [M]−. IR (KBr, cm−1): 2587.6 (νB–H). Anal. Found:
C, 35.42; H, 4.25; N, 6.81. Calcd for C24H33B10IrN4O4S2:
C, 35.76; H, 4.13; N, 6.95.
The mixture of complex 2 (20.0 mg, 0.03 mmol) or 3 (20.0 mg,
0.03 mmol) and 1-azido-3-nitrobenzene (49.2 mg, 0.3 mmol)
was heated in refluxing toluene for 24 hours. The solvent was
removed and the crude product was purified by chromato-
graphy using silica gel to give a yellowish-brown solid 7 or 8.
7 (8.6 mg, 35.6%). Yellowish-brown solid. 1H NMR: 7.98
(d, J = 7.5 Hz, 1H, ArH), 7.64 (d, J = 7.5 Hz, 1H, ArH), 7.50 (t, J =
8.0 Hz, 1H, ArH), 7.38 (d, J = 7.5 Hz, 1H, ArH), 7.36 (d, J =
7.5 Hz, 1H, ArH), 5.79 (t, J = 7.5 Hz, 1H, ArH), 1.78 (s, 15H,
CH3, Cp*), 1.27 (s, 2H, CH2). 11B{1H} NMR: −1.4 (2B), −2.6
(2B), −3.8 (2B), −7.0 (3B), −8.8 (1B). 13C NMR: 9.05 (CH3, Cp*),
32.99 (CH2), 93.44 (carborane), 94.84 (C, Cp*), 97.21 (carbor-
ane), 103.43 (C, Ph), 107.62 (CH, Ph), 118.13 (CH, Ph), 119.87
(C, 4-nitro-3H-azepine), 128.84 (CH, 4-nitro-3H-azepine), 129.72
(C, 4-nitro-3H-azepine), 131.75 (CH, Ph), 133.19 (CH, 4-nitro-
3H-azepine), 146.42 (CH, 4-nitro-3H-azepine), 148.94 (C, Ph),
162.89 (C, Ph). ESI-MS (m/z): 805.25 (100%) [M]−. IR (KBr,
cm−1): 2574.2 (νB–H). Anal. Found: C, 35.59; H, 4.28; N, 6.72.
Calcd for C24H33B10IrN4O4S2: C, 35.76; H, 4.13; N, 6.95.
6 (25.5 mg, 15.8%). Brown solid. 1H NMR: 7.41 (s, 1H, ArH),
7.30 (d, J = 8.5 Hz, 1H, ArH), 7.28 (t, J = 8.0 Hz, 1H, ArH), 7.22
(t, J = 8.0 Hz, 1H, ArH), 6.98 (d, J = 7.5 Hz, 1H, ArH), 6.93 (d, J =
7.5 Hz, 1H, ArH), 4.39 (s, 2H, NH2), 4.24 (s, 1H, NH), 3.70
(d, J = 17.0 Hz, 1H, CHH), 3.59 (d, J = 17.0 Hz, 1H, CHH), 1.84
(s, 3H, CH3, Cp*), 1.78 (s, 3H, CH3, Cp*), 1.70 (s, 3H, CH3,
Cp*), 1.51 (s, 3H, CH3, Cp*). 11B{1H} NMR: −1.6 (2B), −2.6
(2B), −4.8 (3B), −6.5 (2B), −8.2 (1B). 13C NMR: 8.36 (CH3, Cp*),
8 (8.0 mg, 32.9%). Yellowish-brown solid. 1H NMR: 8.01
(s, 1H, ArH), 7.98 (d, J = 7.5 Hz, 1H, ArH), 7.69 (d, J = 8.5 Hz,
1H, ArH), 7.64 (d, J = 8.5 Hz, 1H, ArH), 7.38 (d, J = 7.5 Hz, 1H,
ArH), 5.78 (t, J = 7.5 Hz, 1H, ArH), 1.78 (s, 15H, CH3, Cp*), 1.27
(s, 2H, CH2). 11B{1H} NMR: −1.2 (2B), −2.5 (2B), −4.4 (2B),
−7.0 (3B), −9.8 (1B). 13C NMR: 9.16 (CH3, Cp*), 32.19 (CH2),
Table 1 Selected bond lengths (Å) and angles (°) for 2–4 and 6–8
2
3
4
6
7
8
Ir1–S1
Ir1–S2
Ir1–N1
N1–C13
C1–C2
S1–C1
S2–C2
S2–C14
S1–Ir1–S2
S1–Ir1–N1
S2–Ir1–N1
Ir1–S1–C1
Ir1–S2–C2
Ir1–S2–C14
Ir1–N1–C13
C2–S2–C14
S1–C1–C2
S2–C2–C1
N1–C13–C14
S2–C14–C13
2.364(2)
2.311(2)
2.045(8)
1.349(13)
1.649(12)
1.786(10)
1.847(8)
1.766(10)
91.55(8)
87.3(2)
2.3706(14)
2.3087(13)
2.066(3)
1.330(6)
1.680(6)
1.777(4)
1.821(4)
1.764(4)
91.91(4)
89.14(10)
81.72(10)
105.24(13)
106.28(14)
100.00(15)
120.2(3)
104.7(2)
118.7(3)
117.1(3)
120.2(4)
115.3(3)
2.2596(16)
2.2667(13)
2.3708(17)
2.3139(13)
2.051(4)
1.343(7)
1.669(8)
1.771(4)
1.830(6)
1.730(4)
91.49(5)
87.69(14)
82.46(12)
104.6(2)
106.16(17)
99.87(16)
121.1(4)
104.1(2)
119.6(4)
116.2(3)
118.1(5)
116.9(4)
2.3724(15)
2.2769(14)
2.168(4)
1.393(5)
1.693(10)
1.783(6)
1.824(6)
1.784(3)
91.79(5)
88.07(12)
81.44(12)
105.3(2)
108.5(2)
100.69(11)
113.3(3)
103.0(2)
119.3(4)
115.0(4)
119.9(3)
115.9(2)
2.3622(12)
2.2953(11)
2.125(4)
1.395(4)
1.667(5)
1.769(5)
1.824(5)
1.776(4)
91.75(4)
87.08(10)
82.10(11)
105.06(12)
107.28(15)
99.31(14)
115.9(3)
104.20(19)
120.0(3)
115.6(3)
118.4(4)
117.6(3)
1.631(7)
1.793(5)
1.800(5)
92.35(5)
82.3(2)
104.2(3)
105.2(3)
100.7(3)
121.8(6)
103.8(4)
119.2(6)
116.7(6)
119.1(9)
115.4(7)
107.16(17)
106.34(16)
116.6(3)
117.5(3)
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92.72 (carborane), 94.87 (C, Cp*), 96.02 (carborane), 107.78
(CH, Ph), 115.09 (CH, Ph), 117.17 (CH, 4-nitro-3H-azepine),
117.32 (C, Ph), 119.15 (C, 4-nitro-3H-azepine), 129.32 (C, 4-nitro-
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Hydrogen atoms were included in calculated positions and
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data collection and structure refinements of complexes 2–4
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Acknowledgements
This work was supported by the National Basic Research
Program of China (2010CB923303 and 2013CB922101), the
National Science Foundation of China (20925104, 21271102
and 21021062) and NSFC-RFBR joint grant (21110143 and
12-03-91165).
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4968 | Dalton Trans., 2014, 43, 4962–4968
This journal is © The Royal Society of Chemistry 2014