Quintuple bond reactivity toward group 16 and 17 elements: Addition vs insertion

Article abstract of DOI:10.1021/ic3020805

The low valent, coordinatively unsaturated, and formally quintuply bonded bimetallic aminopyridinato chromium complex 1 was investigated regarding its reactivity toward group 16 and 17 elements. Reaction of 1 with O₂ yielded a dimeric Cr oxo complex 2, a compound with a high formal oxidation state carrying both bridging and terminal oxo ligands. Reactions with the higher homologues of the group lead to the formation of dimeric Cr^II complexes in which E₂^2- ligands were formed [E = S (3), Se (4), and Te (5)]. Here the quintuply bonded dichromium unit formally undergoes an addition reaction. Reaction of 1 with the homo diatomic molecules of the group 17 elements leads to products in which the Cr-Cr quintuple bond is inserted into the corresponding X₂ molecule [X = Cl (6), Br (7), and I (8)]. Complex 1 was also found to insert into the S-S and Se-Se bonds of 1,2-diphenyldisulfane or the corresponding selenium compound (complexes 9 and 10, respectively). All the compounds have been characterized by NMR and elemental analysis. Additionally, eight of the complexes have been characterized by X-ray analysis. The bimetallic Cr^II complexes feature metal-metal distances between 1.8369(18) and 1.918(12) A.

Full text of DOI:10.1021/ic3020805

Article
pubs.acs.org/IC
Quintuple Bond Reactivity toward Group 16 and 17 Elements:
Addition vs Insertion
Emmanuel Sobgwi Tamne, Awal Noor, Sadaf Qayyum, Tobias Bauer, and Rhett Kempe*
Lehrstuhl Anorganische Chemie II, Universitat Bayreuth, 95440 Bayreuth, Germany
̈
ABSTRACT: The low valent, coordinatively unsaturated, and
formally quintuply bonded bimetallic aminopyridinato chro-
mium complex 1 was investigated regarding its reactivity
toward group 16 and 17 elements. Reaction of 1 with O2
yielded a dimeric Cr oxo complex 2, a compound with a high
formal oxidation state carrying both bridging and terminal oxo
ligands. Reactions with the higher homologues of the group
lead to the formation of dimeric CrII complexes in which E2 ligands were formed [E = S (3), Se (4), and Te (5)]. Here the
2−
quintuply bonded dichromium unit formally undergoes an addition reaction. Reaction of 1 with the homo diatomic molecules of
the group 17 elements leads to products in which the Cr−Cr quintuple bond is inserted into the corresponding X2 molecule [X =
Cl (6), Br (7), and I (8)]. Complex 1 was also found to insert into the S−S and Se−Se bonds of 1,2-diphenyldisulfane or the
corresponding selenium compound (complexes 9 and 10, respectively). All the compounds have been characterized by NMR
and elemental analysis. Additionally, eight of the complexes have been characterized by X-ray analysis. The bimetallic CrII
complexes feature metal−metal distances between 1.8369(18) and 1.918(12) Å.
Scheme 1. Carboalumination and Oxidation of a
Chromium−Chromium Quintuple Bond
INTRODUCTION
■
Bond orders are of fundamental interest in chemistry.1 Looking
at the simple hydrocarbons ethane, ethylene, and acetylene we
see a drastic increase in reactivity with an increasing bond
order. Formally, we store electrons in the C−C linkage and can
use them for additional bond formations. Of course, it is not
that simple. For the related dinitrogen compounds the triply
bonded molecule, rich in electrons too, is stable like a rock and
the other two, diazene and hydrazine, are the more reactive.
Very high bond orders, namely quintuple and sextuple bonds
can be observed between transition metals.2 Molecules having
such high bond orders are known for decades,3 the transient
diatomic molecules M2 (M = V, Nb, Cr, Mo) being prominent
examples.4 Unfortunately, their instability and highly demand-
ing and partially highly unselective synthesis restricts their use
in (for instance) inorganic synthesis, small molecule activation,
or catalysis. In 2005, the group of Power reported a
breakthrough in this field, the synthesis of the first stable
molecule having a quintuple bond.5 Shortly after and inspired
by that compound the groups of Theopold, Tsai, and us
reported on N-ligand stabilized dichromium complexes having
a quintuple bond.6 Ultrashort metal−metal bond distances have
been observed for these compounds.1,7 The record is right now
at 1.73 Å.8 Meanwhile, a considerable number of quintuply
bonded dichromium complexes have been reported.9 Fur-
thermore, related dimolybdenum compounds were synthe-
sized.10 With these stable compounds in hand we are enabled
to study their reactivity and by doing so we may understand
quintuple bonds chemically. We have previously shown that
quintuply bonded complexes can provide from two to eight
electrons and observed the carboalumination of a quintuple
bond as well as its oxidation with O2, during which CrI has been
oxidized to CrV (Scheme 1).11a
At the same time, Power et al. have shown that the ligand
role is crucial in quintuple bond reactivity by observing
complete cleavage of the quintuple bond for complexes of the
type ArCrCrAr (Ar = substituted terphenyl) if reacted with
N2O and azides (Scheme 2).12
Cycloaddition reactions were observed by Theopold et al.
and us, when alkynes and dienes were reacted with quintuply
bonded dichromium complexes (Scheme 3).11b,13 While
extending our understanding of quintuple bond reactivity we
have shown that molecules like phosphorus, yellow arsenic, and
AsP3 can be activated under mild conditions and in a highly
selective manner.11c
Tsai et al. have shown that amidinate ligands stabilized
complexes with a Cr−Cr bond length of 1.7404(8) Å6e show
weak coordination of tetrahydrofuran (THF) and 2-MeTHF
(2-MeTHF = 2-methyltetrahydrofuran) with long Cr−O
distances of 2.579(4) and 2.305(7) Å, respectively (Scheme
4).9 The ligated THF and 2-MeTHF ligands are labile and
Received: September 25, 2012
© XXXX American Chemical Society
A
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Scheme 2. Cleavage of a Quintuple Bond by N2O and Admantyl Azide (AdN3)
red brown solid in reasonable isolated yield of 72% (Scheme
6).11a
Scheme 3. Cycloaddition and Addition Reactions of
Quintuply Bonded Cr Complexes
1H NMR shows 2 to be a diamagnetic compound with sharp
signals between 0 and 8 ppm. We observe two doublets for the
isopropyl groups, two singlets for the CH3 protons, and two
septets for the CH proton of the isopropyl-groups. Crystals
suitable for X-ray analysis were grown from hexane solution.
The solid state structure shows 2 to be a dimeric Cr(V) oxo
complex, in which two oxo ligands are bridging and two oxo
ligands coordinate terminally (Figure 1). Chromium oxo
complexes of this type are rare15 and were first reported by
Herberhold and co-workers.16 The bridging Cr−O bond
distances of 1.791(2) Å is similar to the respective 1.817(4)
Å distance in the Cr(V) complex [CpCr(O)(μ-O)]2.16 The
terminal Cr−O bond length of 1.563(2) Å is considerably
shorter than the bridging Cr−O distances and indicates a
strong double bond character. It is also shorter than the CrV
complex of Herberhold (1.594(3) Å).16 The long Cr−Cr
distance of 2.5314(10) Å corresponds to a single bond between
the two metal centers.
Impressed by the highly selective oxidation of the quintuple
bond by O2 we became interested in exploring the higher
homologues of that group. Complex 1 reacts with S8 at room
temperature and with Se8 and Te at 60 °C in toluene to afford
3, 4, and 5, respectively, in high yields (Scheme 6). Complexes
3−5 are diamagnetic and have been characterized by solution
NMR spectroscopy and elemental analysis. The 1H NMR
spectra of 3−5 in C6D6 are as expected for diamagnetic
complexes, featuring slight shifting for a multitude of sharp
resonances between 0 and 8 ppm. We observe four doublets for
the non-equivalent isopropyl CH3 protons, two singlets for the
methyl CH3 protons and two septets for the isopropyl CH
protons of the aminopyridinato ligands. Additionally, 3 and 5
have also been characterized by X-ray analysis. The solid state
structure shows the oxidation of Cr2 moiety to give structurally
similar bimetallic μ,η2-disulfide (3) and μ,η2-ditelluride (5)
complexes (Figure 2). Quintuply bonded diatomic molecules
can provide from two to ten electrons if activated with small
molecules and can thus show a large disparity in the formal
oxidation states of chromium. It can be seen that for dimeric
oxo complex 2, CrI has been oxidized to CrV and for 3−5 to
CrII. In 3 the S−S distance of 2.058(4) Å is shorter than
expected for disulfur ligands,17 but it lies close to other known
bimetallic chromium complexes [2.028(2) Å].18 The averaged
Cr−S bond distance, 2.3885(3) Å, is longer than those known
for relevant μ,η2-disulfide bimetallic chromium complexes.17−20
In comparison to μ,η2-disulfide ligands, μ,η2-ditelluride ligands
on diatomic transition metals platform are rare and unknown
for chromium; thus 5 represents the first example of such Cr
complexes. The Te−Te bond distance of 2.6878(8) Å is
comparable to a closely known ditellurido vanadium(IV)
result in comprehensive elongation of the Cr−Cr bond to
1.8115(12) and 1.7636(5) Å, respectively.
Complexes stabilized by diamidopyridine ligands undergo
two electron oxidation if reacted with AgOTf and thus
completely cleave the Cr−Cr bond.9 Similar cleavage of the
quintuple bond has been observed when the diamidopyridine
ligand stabilized Cr complexes were reacted with [18] crown-6
ether (Scheme 5).9
Very recently, Tsai et al. have extended the reactivity studies
of quintuply bonded complexes toward Mo and have observed
[2+2+2] cycloaddition reactions with alkynes.14
Here we report our results involving reactions between a
chromium−chromium quintuple bond and chalcogens (S, Se,
and Te), halogens, and cleavage of single bonds between
chalcogenides (PhSSPh and PhSeSePh).
RESULTS AND DISCUSSION
■
Complex 1 was readily prepared following the published
procedure.11a Reacting 1 with excess of oxygen afforded 2 as
Scheme 4. Weak Coordination of THF and 2-MeTHF to
Quintuply Bonded Cr Complexes
B
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Scheme 5. Quintuple Bond Reactivity of Diamidopyridine Stabilized Cr Complexes
Scheme 6. Synthesis of 2−5
Figure 2. Molecular structure of 5, ORTEP representation on the 50%
probability level for all non-carbon atoms. Hydrogen atoms have been
deleted for clarity.
Table 1. Selected Bond Lengths [Å] and Angles [deg] for
a
Complexes 3 and 5
3 (E = S)
5 (E = Te)
Cr−Cr
NAm−Cr
NPy−Cr
E−E
E−Cr
E−E−Cr
Cr−E−Cr
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
Cr−Cr−E
1.847(2)
2.004(8)
2.004(8)
2.058(4)
2.388(3)
64.48(11)
45.48(7)
95.5(2)
Cr−Cr
NAm−Cr
NPy−Cr
E−E
E−Cr
E−E−Cr
Cr−E−Cr
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
Cr−Cr−E
1.8369(18)
2.030(7)
2.030(7)
2.6878(18)
2.7351(13)
60.57(3)
39.24(4)
95.13(19)
97.79(19)
106.2(3)
70.36(6)
58.85(3)
97.4(3)
104.7(3)
67.66(9)
51.03(10)
E−Cr−E
E−Cr−E
a
NAm = NAmido, NPy = NPyridine
.
Figure 1. Molecular structure of 2. ORTEP representation on the 50%
probability level for all non-carbon atoms. Hydrogen atoms have been
deleted for clarity. Selected bond lengths [Å] and angles [deg]: Cr1−
N1 2.053(2), Cr1−N2 1.946(2), O1−Cr1 1.563(2), O2−Cr1
1.791(2), Cr1−Cr1A 2.5314(10); Cr1−Cr1A−O1A 121.69(9),
Cr1−Cr1A−O2 45.02(7), N2−Cr1−N1 65.20(10).
X2 molecule yielded complexes 6−8 in good yields (6: X = Cl;
7: X = Br; 8: X = I) (Scheme 7). Compounds 6−8 are
1
diamagnetic, and their H NMR spectra in solution show a
characteristic peak pattern of two doublets for the non-
complex [2.6961(5) Å]21 and ditellurido iron complexes
[2.700−2.719(4) Å],22 and are normal for a ditelluride single
bond. The Cr−Te distances lie in the range of 2.7231(14) to
2.7511(13) Å. The Cr−Cr bond distances of 1.847(2) Å in 3
and 1.8369(18) Å in 5 lie in the range known for quadruply
bonded complexes (Table 1).
Scheme 7. Synthesis of 6−8
Furthermore, we were interested to study the reactivity of 1
toward homo diatomic group 17 molecules, especially in
comparison to the activation of sulfur, selenium, and tellurium.
Stirring toluene/benzene solution of 1 with the corresponding
C
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equivalent CH3 protons of the isopropyl groups, one singlet for
the CH3 protons, and one septet for the CH proton of the
isopropyl groups. A single set of signals was observed for the
aromatic protons. Solid state structure analyses show halogen
bridged bimetallic CrII complexes. We observed selective
oxidative addition even if an excess of Cl2, Br2, or I2 was
used. In similar reactions Power et al. have observed not only
complete cleavage of the quintuple bond but also excess of I2
led to form [CrI2(thf)2] species.23 Structurally characterized
chromium complexes with bridging iodides are also rare and
only a few examples are known.24 The halogen-bridged
complexes 6−8 are structurally similar and feature Cr atoms
coordinated to five other atoms thus forming a distorted
trigonal bipyramidal geometry (Figure 3). The Cr−Cr distances
Å] (Table 2). The longer Cr−Npy distances compared to Cr−
Nam bond distances show the localization of the anionic
function on the amido N-atom which is typical of an
amidopyridine mode of coordination of the ligands.25 Details
of the X-ray crystal structure analyses are summarized in Table
2.
The reaction of diphenyldiselenide and diphenyldisulfide
with 1 at room temperature in toluene resulted in the
formation of complexes 9 and 10, respectively (Scheme 8).
Scheme 8. Synthesis of 9 and 10
Complexes 9 and 10 show very little solubility in organic
solvents once precipitated which excludes detailed character-
ization by NMR spectroscopy. Crystals of 9 suitable for X-ray
analysis were grown from THF-d8 solution and of 10 from
toluene solution. Complexes 9 and 10 are isostructural
dinuclear complexes in which the Cr−Cr bond is inserted
into the S−S and Se−Se bonds, respectively (Figure 4). The
two Cr atoms are joined by two bridging phenylthio or
phenylselenato groups. The average Cr−S distance in 9 is 2.44
Å and in 10 the Cr−Se bond distance lies at 2.570 Å. The
difference between the Cr−S and Cr−Se bond distances
reflects the difference in covalent radii of S and Se (Table 4).
The Cr-ligand distances in 9 and 10 are almost identical to each
other. The Cr−Cr distances of 1.8486(19) Å (9) and
1.8635(16) Å (10) fall into the range of “supershort”
chromium−chromium quadruple bonds (Cr−Cr 2.0 Å).26
Details of the X-ray crystal structure analyses are summarized in
Table 3.
Figure 3. Molecular structure of 6. ORTEP representation on the 50%
probability level for all non-carbon atoms. Hydrogen atoms have been
deleted for clarity.
of 1.918(12) Å for 6, 1.868(18) Å for 7, and 1.874(4) Å for 8
are typical for quadruple bonds. The average Cr−X bond
length could be classified as Cr−Cl (2.438 Å) < Cr−Br (2.575
Å) < Cr−I (2.758 Å). The short Cr−Cl bond could be due to
the more electronegative nature of chlorine than bromine and
iodine. This has also an impact on the values of the Cr−X−Cr
angles which amount to 46.32(3), 42.54(4), and 39.74(7)° for
6, 7, and 8, respectively. It is also in accordance with the values
of the Cr−Cr bond distance which is longest in 6 [1.918(12)
CONCLUSION
■
In summary, reactivity studies on a quintuply bonded, low
valent dichromium complex have been extended to a variety of
small inorganic compounds of group 16 and 17 elements. It has
a
Table 2. Selected Bond Lengths [Å] and Angles [deg] for Complexes 6, 7, and 8
6 (X = Cl)
7 (X = Br)
8 (X = I)
Cr−Cr
NAm−Cr
NPy−Cr
Cr−X
Cr−Cr−X
Cr−X−Cr
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
NAm−Cr−X
NPy−Cr−X
X−Cr−X
1.918(12)
2.010(12)
2.023(2)
2.438(13)
67.61(3)
46.32(5)
97.91(7)
92.55(8)
169.54(19)
91.76(7)
92.28(7)
133.68(3)
Cr−Cr
NAm−Cr
NPy−Cr
Cr−X
Cr−Cr−X
Cr−X−Cr
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
NAm−Cr−X
NPy−Cr−X
X−Cr−X
1.868(18)
1.997(5)
Cr−Cr
NAm−Cr
NPy−Cr
Cr−X
Cr−Cr−X
Cr−X−Cr
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
NAm−Cr−X
NPy−Cr−X
X−Cr−X
1.874(4)
2.004(8)
2.028(9)
2.757(2)
69.81(11)
39.71(3)
97.5(3)
2.003(5)
2.574(12)
69.73(6)
42.54(4)
98.64(14)
93.25(14)
168.11(19)
91.22(14)
89.22(13)
142.54(4)
94.2(3)
168.3(4)
93.4(2)
90.7(3)
140.26(7)
a
NAm = NAmido, NPy = NPyridine
.
D
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been shown that the dichromium platform can provide from
two to eight electrons to give dinuclear complexes, in which Cr
exists in +II and +V oxidation states. Preferentially, two
electrons are donated. For the group 16 elements, O2 leads to a
dimeric CrV species. Other chalcogens undergo addition
reactions in which an E2 moiety binds to the CrII -unit (E
2−
2
= S, Se, and Te). For homo diatomic molecules of group 17
insertion of the quintuple bond into the corresponding X−X
bond (X = Cl, Br and I) was observed. Complex 1 was also
found to cleave the single bonds of dichalcogenides Ph2S2 and
Ph2Se2 forming the corresponding oxidative addition products.
EXPERIMENTAL SECTION
■
General Considerations. All manipulations were performed with
rigorous exclusion of oxygen and moisture in Schlenk-type glassware
on a dual manifold Schlenk line or in a N2 filled glovebox (mBraun
120-G) with a high-capacity recirculator (<0.1 ppm O2). Solvents were
dried by distillation from sodium wire/benzophenone. Complex 1 was
prepared according to the published procedure.11a Commercial CrCl2,
S8, Se8, Te, PhSSPh, and PhSeSePh were used as received. Deuterated
solvents were obtained from Cambridge Isotope Laboratories and
were degassed, dried, and distilled prior to use. NMR spectra were
recorded on Bruker 250 MHz, Varian 300 MHz, and Varian 400 MHz
spectrometers at ambient temperature. The chemical shifts are
reported in ppm relative to the internal TMS. Elemental analyses
(CHN) were determined using a Vario EL III instrument. X-ray crystal
structure analyses were performed by using a STOE-IPDS II equipped
with an Oxford Cryostream low-temperature unit. Structure solution
and refinement were accomplished using SIR97,27 SHELXL97,28 and
WinGX.29 Crystallographic details are summarized in Tables 4 and 5.
X-ray crystallographic data for compounds 2 (CCDC 713546), 3
(CCDC 901063), 5 (CCDC 901062), 6 (CCDC 901066), 7 (CCDC
901061), 8 (CCDC 901060), 9 (CCDC 901064), and 10 (CCDC
901065) contain 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.
Figure 4. Molecular structure of 10. ORTEP representation on the
50% probability level for all non-carbon atoms. Hydrogen atoms have
been omitted for clarity.
Table 3. Selected Bond Lengths [Å] and Angles [deg] for
a
Complexes 9 and 10
9 (E = S)
10 (E = Se)
Cr−Cr
1.8486(14)
1.992(5)
Cr−Cr
1.8635(16)
2.012(5)
NAm−Cr
NPy−Cr
E−Cr
Cr−Cr−E
Cr−E−Cr
NAm−Cr
NPy−Cr
E−Cr
Cr−Cr−E
Cr−E−Cr
2.030(5)
2.030(5)
2.444(19)
64.54(7)
2.5608(10)
69.06(5)
44.45(5)
42.53(4)
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
NAm−Cr−E
NPy−Cr−E
E−Cr−E
97.64(14)
95.09(14)
167.27(19)
86.47(15)
98.28(10)
135.55(5)
Cr−Cr−NAm
Cr−Cr−NPy
NAm−Cr−NPy
NAm−Cr−E
NPy−Cr−E
E−Cr−E
98.61(14)
93.67(12)
167.72(17)
88.44(14)
96.03(13)
137.46(4)
Syntheses of the Metal Complexes. Synthesis of 2.11a O2 (1
bar) was introduced into a solution of 1 (0.1 g, 0.12 mmol) in hexane
(10 mL) at room temperature with continuous stirring. A color change
a
NAm = NAmido, NPy = NPyridine
.
Table 4. Data of the X-ray Crystal Structure Analyses for Complexes 2, 3, 5, and 6
211a
3
5
6. 2×C7H8
formula
C25H29CrN2O2
441.50
C50H58Cr2N4S2
883.12
C50H58Cr2N4Te2
1074.23
C64H74Cl2Cr2N4
1074.17
Mr g mol−1
crystal system
space group
a [Å]
monoclinic
P2(1)/c
triclinic
triclinic
triclinic
P1
̅
P1
P1
̅
12.6130(10)
14.6670(12)
13.6720(12)
10.342(1)
12.5140(14)
18.550(2)
99.296(9)
104.196(8)
105.977(8)
2168.9(4)
0.29 × 0.11 × 0.08
1.352
10.3990 (6)
11.4990 (7)
14.5830 (11)
107.170 (5)
90.903(5)
107.541(5)
1578.09(18)
0.26 × 0.13 × 0.11
1.130
10.584(6)
11.856(6)
13.473(7)
65.461(4)
88.144(4)
67.808(4)
1408.38(13)
0.5 × 0.34 × 0.29
1.266
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
116.302(6)
V [Å−3
crystal size [mm3]
ρcalcd. [g.cm−3
]
2267.4(3)
0.37 × 0.32 × 0.23
1.293
]
μ [mm−1] (Mo−Kα)
T [K]
0.527
0.638
1.278
0.524
133(2)
133(2)
133(2)
133(2)
θ range [deg]
1.80−25.79
4289
1.17−25.74
8203
1.47−25.71
11305
1.68−25.63
5307
no. unique refl.
no. of obsd. refl. [I > 2σ (I)]
no. of parameters
wR2 (all data)
3181
2474
6549
3642
273
524
535
325
0.1333
0.2318
0.1063
0.1096
R value [I > 2σ(I)]
0.0528
0.0893
0.0505
0.0443
E
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Table 5. Data of the X-ray Crystal Structure Analyses for Complexes 7, 8, 9, and 10
7. 2×C7H8
8. 2×C6H6
9. 2×C4D8O
10
formula
C64H74Cr2Br2N4
1163.09
C62H70Cr2I2N4
1229.02
C70H84Cr2N4O2S2
1181.55
C62H68Cr2N4Se2
1131.12
Mr g mol−1
crystal system
space group
a [Å]
triclinic
triclinic
triclinic
triclinic
P1
̅
P1
P1
̅
P1
̅
̅
10.474(8)
11.937(9)
13.549(9)
65.290(5)
88.590(6)
68.247(5)
1412.16(18)
0.27 × 0.12 × 0.1
1.368
13.6265(13)
13.6621(12)
16.0303(13)
97.156(7)
97.922(7)
110.392(7)
2722.3(4)
0.16 × 0.16 × 0.14
1.499
11.5330(8)
12.2980(10)
12.9370(10)
102.624(6)
107.411(6)
110.733(6)
1525.4(2)
0.29 × 0.24 × 0.07
1.286
11.3100(8)
11.4090(9)
11.8050(9)
100.458(6)
98.588(6)
111.989(6)
1348.98(18)
0.20 × 0.17 × 0.13
1.392
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å−3
]
crystal size [mm3]
ρcalcd. [g.cm−3
]
μ [mm−1] (Mo−Kα)
T [K]
1.843
1.576
0.474
1.795
133(2)
133(2)
133(2)
133(2)
θ range [deg]
1.67−25.68
5328
1.31−26.17
10275
1.77−24.59
5105
1.81−25.81
4518
no. unique refl.
no. of obsd. refl. [I > 2σ(I)]
no. of parameters
wR2 (all data)
3341
5433
2110
3012
328
635
367
322
0.1754
0.1961
0.1672
0.1341
R value [I > 2σ(I)]
0.0641
0.0609
0.0680
0.0569
from purple to brown was observed within 5 min. The reaction
solution was further stirred at ≈300 rpm for 4 h and then filtered using
glass fiber filters. The filtrate was kept at −30 °C to afford brown
crystals overnight. Yield: 0.079 g (73%). C50H58Cr2N4O4 (883.00):
H
10/18), 7.19 (m, 2H, H9/11/17/19) ppm. 13C NMR (75 MHz, C6D6): δ
= 18.9 (C13,14), 22.1 (C13,14), 23.6 (C 22/23/25/26), 24.7 (C22/23/25/26),
24.9 (C22,23,/25,26), 25.4 (C22,23/25,26), 27.9 (C21,24), 29.6 (C21,24), 108.9
(C3), 109.8 (C5), 124.0 (C10), 125.7 (C17,19), 125.9 (C17,19), 127.2
(C18), 127.8 (C18), 128.5 (C4), 135.5 (C9,11), 135.8 (C8,12), 137.1
(C4), 138.5 (C7), 143.9 (C16,20), 144.4 (C16,20), 144.9 (C15), 157.8
(C6), 171.9 (C2) ppm.
1
calcd. C 68.01, H 6.62, N 6.34; found C 67.71, H 6.88, N 6.10. H
NMR (400 MHz, C6D6): δ = 1.40 (d, 12H, J = 6.8 Hz, H22,23,25,26),
1.41 (d, 12H, J = 6.8 Hz, H22,23,25,26), 1.80 (s, 6H, H13,14), 2.24 (s, 6H,
H
H
13,14), 2.46 (sept, 2H, J = 6.8 Hz, H21,24), 4.76 (sept, 2H, J = 6.8 Hz,
21,24), 5.40 (d, 2H, J = 8.4 Hz, H3), 5.85 (d, 2H, J = 6.8 Hz, H5),
Synthesis of 4. Toluene (5 mL) was added to a mixture of 1 (246
mg, 0.3 mmol) and Se (48 mg, 0.6 mmol) at room temperature. The
reaction mixture was stirred at ≈300 rpm at 60 °C for 2 h as color
changed to brown green. Red needles were obtained by cooling a hot
toluene solution to room temperature overnight. Yield 0.180 g (61%)
C50H58Cr2N4Se2 (978.18): calcd. C 61.47, H 5.98, N 5.73; found C
61.48, H 5.76, N 5.72. 1H NMR (300 MHz, C6D6): δ = 0.39 (d, 6H, J
= 6.8 Hz, H22/23/25/26), 1.03−1.06 (m, 12H, H13,14,22,23,25,26), 1.11 (d,
6H, J = 6.8 Hz, H22/23/25/26), 1.39 (d, 6H, J = 6.8 Hz, H22/23/25/26), 2.18
(s, 6H, H13,14), 3.09 (sept, 2H, J = 6.8 Hz, H21/24), 3.53 (sept, 2H, J =
6.8 Hz, H21/24), 5.74 (d, 2H, J = 6.7 Hz, H3), 6.27 (d, 2H, J = 6.7 Hz,
H5), 6.32 (d, 2H, J = 9.1 Hz, H17/19), 6.64−6.77 (m, 5H, H4,9,11/17,19),
7.02−7.05 (m, 2H, H10/18), 7.19 (m, 4H, H9/11/17/19) ppm. 13C NMR
(75 MHz, C6D6): δ = 18.8 (C13,14), 22.6 (C13,14), 23.7 (C 22/23/25/26),
24.9 (C22/23/25/26), 25.1 (C22,23,/25,26), 25.3 (C22,23/25,26), 27.9 (C21,24),
29.6 (C21,24), 109.1 (C3), 110.0 (C5), 124.2 (C10), 125.7 (C17,19), 126.1
(C17,19), 127.1 (C18), 128.5 (C4), 134.0 (C10), 135.5 (C9,11), 135.2
(C8,12), 135.7 (C8,12), 137.3 (C4), 138.6 (C7), 144.3 (C16,20), 144.4
(C16,20), 145.2 (C15), 157.8 (C6), 172.6 (C2) ppm.
6.74−7.38 (m, 14H, H4,9,10,11,17,18,19) ppm. 13C NMR (100 MHz,
C6D6): δ = 19.8 (C13,14), 20.2 (C13,14), 24.4 (C22,23,25,26), 24.7
(C22,23,25,26), 25.0 (C22,23,25,26), 28.1 (C21,24), 28.7 (C21,24), 101.0 (C3),
111.8 (C5), 123.9 (C9,11), 124.3 (C9,11), 127.2 (C18), 127.5 (C17,19),
136.2 (C10), 136.5 (C4), 136.7 (C8,12), 140.2 (C7), 142.6 (C8,12), 145.3
(C16,20), 147.4 (C15), 157.9 (C6), 173.5 (C2) ppm (see Figure 5 for the
labeling).
Synthesis of 5. Toluene (5 mL) was added to a mixture of 1 (41
mg, 0.05 mmol) and Te (25 mg, 0.2 mmol) at room temperature, and
the reaction mixture was then heated at 60 °C and stirred at ≈300 rpm
for 3 h as color changed to brown green. The solution was filtered
using glass fiber filters, and the volume of the filtrate was reduced to
about 1 mL to afford red crystals overnight at low temperature. Yield
0.025 g (47%). C50H58Cr2N4Te2·C7H8 (1074.21): calcd: C 58.70, H
Figure 5. Labeling of the NMR signals.
Synthesis of 3. Toluene (5 mL) was added to a mixture of 1 (82
mg, 0.1 mmol) and S (7 mg, 0.2 mmol) at room temperature. The
reaction mixture was stirred at ≈300 rpm for 2 h at room temperature
as color changed to brown green. Red needles were obtained by
cooling a hot toluene solution to room temperature overnight. Yield
0.052 g (58%). C50H58Cr2N4S2 (882.29): calcd. C 68.00, H 6.62, N
6.34; found C 67.21, H 6.23, N 6.17. 1H NMR (250 MHz, C6D6): δ =
0.31 (d, 6H, J = 6.7 Hz, H22/23/25/26), 1.06 (d, 6H, J = 6.7 Hz,
1
5.70, N 4.80; found C 58.46, H 6.09, N 5.35. H NMR (250 MHz,
C6D6): δ = 0.49 (d, 6H, J = 6.7 Hz, H22/23/25/26), 0.96 (s, 6H, H13,14),
1.01−1.06 (m, 12H, H22/23/25/26), 1.42 (d, 6H, J = 6.7 Hz, H22/23/25/26),
2.11 (s, 12H, H13,14), 3.47 (sept, 2H, J = 6.7 Hz, H21/24), 3.59 (sept,
2H, J = 6.7 Hz, H21/24), 5.79 (d, 2H, J = 4.9 Hz, H3), 6.25 (d, 2H, J =
6.5 Hz, H5), 6.33 (d, 2H, J = 8.9 Hz, H17/19), 6.66−6.77 (m, 5H,
H
22/23/25/26), 1.11 (s, 6H, H13,14), 1.14 (d, 6H, J = 6.7 Hz, H22/23/25/26),
1.38 (d, 6H, J = 6.7 Hz, H22/23/25/26), 2.24 (s, 6H, H13,14), 2.84 (sept,
2H, J = 6.7 Hz, H21/24), 3.51 (sept, 2H, J = 6.7 Hz, H21/24), 5.73 (d,
2H, J = 6.5 Hz, H3), 6.27 (d, 2H, J = 6.5 Hz, H5), 6.33 (d, 2H, J = 8.9
Hz, H17/19), 6.64−6.79 (m, 5H, H4,9,11/17,19), 7.00−7.05 (m, 4H,
H
4/10), 7.03−7.18 (m, 6H, H10/18,9/11/17/19) ppm.
Synthesis of 6. Cl2 (ca. 0.2 bar) was introduced into a solution of 1
(0.4 g, 0.48 mmol) in toluene (10 mL) at room temperature with
F
dx.doi.org/10.1021/ic3020805 | Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
continuous stirring. A color change from purple to red-brown was
observed within 10 min. The mixture was stirred at ≈300 rpm under
Cl2 atmosphere overnight after which some dark precipitate had
formed. Then the solution was filtered using glass fiber filters, and the
filtrate was kept at −30 °C to afford brown crystals. Yield 0.032g
(33%). C50H58Cr2N4Cl2·C7H8 (980.3): calcd. C 69.71, H 6.77, N 5.71;
found C 69.95, H 6.81, N 5.26. 1H NMR (400 MHz, C6D6, 298 K): δ
= 1.09 (d, 12H, J = 7.5 Hz, H22/23/25/26), 1.40 (d, 12H, J = 7.5 Hz,
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: Kempe@uni-bayreuth.de.
Notes
The authors declare no competing financial interest.
H
22/23/25/26), 2.80 (s, 6H, H13/14), 4.71 (sept, 2H, J = 7.5 Hz, H21/24),
ACKNOWLEDGMENTS
■
5.20 (d, 2H, J = 7.5 Hz, H3), 6.17 (d, 2H, J = 5.2 Hz, H5), 6.38 (t, 2H,
J = 5.2 Hz, H4), 6.98−7.37 (m, 12H, H9/10/11,17/18/19) ppm. 13C NMR
(C6D6, 298 K): δ = 20.5 (C13/14), 23.8 (C22/23/25/26), 28.7 (C21/24),
103.7 (C3), 114.5 (C5), 124.2 (C9/11), 125.6 (C17/19), 127.7 (C18),
128.0 (C10), 134.1 (C8/12), 135.9 (C8/12), 137.9 (C4), 142.0 (C7),
148.1 (C16/20), 154.3 (C15), 159.5(C6), 160.0 (C2) ppm.
Financial support from the Deutsche Forschungsgemeinschaft
(DFG KE 756/20-1) is gratefully acknowledged. E.S.T. thanks
the Deutscher Akademischer Austausch Dienst (DAAD) for a
Ph.D. scholarship.
Synthesis of 7. Br2 (7 μL, 0.1 mmol) was added to a solution of 1
(82 mg, 0.1 mmol) in toluene (10 mL) at room temperature with
continuous stirring at ≈300 rpm. A color change from purple to brown
was observed. The reaction solution was filtered using glass fiber filters,
and the filtrate was kept at −30 °C to afford brown crystals. Yield
0.052g (48%). C50H58Cr2N4Br2·C7H8 (1070.7): calcd. C 63.92, H
REFERENCES
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6.21, N 5.23; found C 64.17, H 5.39, N 5.35. H NMR (400 MHz,
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C50H58Cr2N4I2 (1072.16): Calc. C 55.98, H 5.45, N 5.22; found. C
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1
55.99, H 5.88, N 4.78. H NMR (400 MHz, C6D6): δ = 1.14 (br d,
12H, H22,23,25,26), 1.24 (br d, 12H, H22,23,25,26), 2.19 (s, 6H, H13,14), 3.97
(br sept, 2H, H21,24), 5.74 (d, 2H, J = 6.8 Hz, H3), 6.15 (d, 2H, J = 6.5
Hz, H5), 6.28 (t, 2H, J = 6.5 Hz, H4), 6.49 (m, 6H, H17,18,19), 6.96−
7.36 (m, 12H, H9,10,11) ppm. 13C NMR (C6D6, 298 K): δ = 19.8
(C13,14), 20.5 (C13,14), 23.7 (C22,23,25,26), 24.6 (C22,23,25,26), 25.7
(C22,23,25,26), 28.7 (C21,24), 103.7 (C3), 108.1 (C5), 124.2 (C9,11),
124.9 (C17,19), 125.6 (C18), 127.7 (C10), 134.7 (C8,12), 135.8 (C8,12),
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Synthesis of 9. Toluene (20 mL) was added to a mixture of 1 (82
mg, 0.1 mmol) and Ph2SSPh2 (22 mg, 0.1 mmol) at room
temperature, and the resulting green reaction mixture was stirred at
≈300 rpm at room temperature for 6 h. Standing of the solution at
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0.072 g (69%). C62H68Cr2N4S2 (1037.36): calcd. C 71.79, H 6.61, N
5.40; found C 71.94, H 6.60, N 5.54. 1H NMR (300 MHz, C6D6, 298
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2.19 (s, 12H, H13/14), 3.80 (br sept, 4H, H21/24), 5.95 (d, 2H, J = 6.3
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4.95; found C 64.65, H 5.90, N 4.77. 1H NMR (300 MHz, C6D6, 298
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(br d, 6H, H22/23/25/26), 1.96 (s, 6H, H13/14), 2.40 (s, 6H, H13/14), 2.96
(sept, 2H, J = 7.5 Hz, H21/24), 4.71 (sept, 2H, J = 7.5 Hz, H21/24), 5.95
(d, 2H, J = 7.5 Hz, H3), 6.42 (t, 2H, J = 6.9 Hz, H4), 6.52 (d, 2H, J =
8.7 Hz, H5), 6.65−7.05 (m, 16H, H9/10/11,17/18/19/Ph) ppm.
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