Cine-substitution reactions of metallabenzenes: An experimental and computational study

Article abstract of DOI:10.1002/chem.201301398

Alkali-resistant osmabenzene [(SCN)₂(PPh₃) ₂Os{CHC(PPh₃)CHCICH}] (2) can undergo nucleophilic aromatic substitution with MeOH or EtOH to give cine-substitution products [(SCN)₂(PPh₃)₂Os{CHC(PPh₃)CHCHCR}] (R=OMe (3), OEt(4)) in the presence of strong alkali. However, the reactions of compound 2 with various amines, such as n-butylamine and aniline, afford five-membered ring species, [(SCN)₂(PPh₃) ₂Os{CH=C(PPh₃)CH=C(CH=NHR′)}] (R′=nBu(8), Ph(9)), in addition to the desired cine-substitution products, [(SCN) ₂(PPh₃)₂Os{CHC(PPh₃) CHCHC(NHR′)}] (R′=nBu(6), Ph(7)), under similar reaction conditions. The mechanisms of these reactions have been investigated in detail with the aid of isotopic labeling experiments and density functional theory (DFT) calculations. The results reveal that the cine-substitution reactions occur through nucleophilic addition, dissociation of the leaving group, protonation, and deprotonation steps, which resemble the classical addition-of- nucleophile, ring-opening, ring-closure (ANRORC) mechanism. DFT calculations suggest that, in the reaction with MeOH, the formation of a five-membered metallacycle species is both kinetically and thermodynamically less favorable, which is consistent with the experimental results that only the cine-substitution product is observed. For the analogous reaction with n-butylamine, the pathway for the formation of the cine-substitution product is kinetically less favorable than the pathway for the formation of a five-membered ring species, but is much more thermodynamically favorable, again consistent with the experimental conversion of compound 8 into compound 6, which is observed in an in situ NMR experiment with an isolated pure sample of 8.

Full text of DOI:10.1002/chem.201301398

DOI: 10.1002/chem.201301398
cine-Substitution Reactions of Metallabenzenes: An Experimental and
Computational Study
Tongdao Wang,[a] Hong Zhang,[a, b] Feifei Han,[a] Lipeng Long,[a] Zhenyang Lin,*[b] and
Haiping Xia*[a]
Abstract: Alkali-resistant osmabenzene
[(SCN)2A(PPh3)2Os{CHC(PPh3)CHCI-
CH}] (2) can undergo nucleophilic aro-
matic substitution with MeOH or
EtOH to give cine-substitution prod-
tions have been investigated in detail
with the aid of isotopic labeling experi-
ments and density functional theory
(DFT) calculations. The results reveal
that the cine-substitution reactions
occur through nucleophilic addition,
dissociation of the leaving group, pro-
tonation, and deprotonation steps,
which resemble the classical “addition-
of-nucleophile, ring-opening, ring-clo-
sure” (ANRORC) mechanism. DFT
calculations suggest that, in the reac-
tion with MeOH, the formation of a
five-membered metallacycle species is
both kinetically and thermodynamical-
ly less favorable, which is consistent
with the experimental results that only
the cine-substitution product is ob-
served. For the analogous reaction with
n-butylamine, the pathway for the for-
mation of the cine-substitution product
is kinetically less favorable than the
pathway for the formation of a five-
membered ring species, but is much
more thermodynamically favorable,
again consistent with the experimental
conversion of compound 8 into com-
pound 6, which is observed in an in situ
NMR experiment with an isolated pure
sample of 8.
G
E
ACHTUNGTRENNUNG
ucts [(SCN)
2ACHTUNGTRENNUNG(PPh3)2OsACHUTNGTREG{NNUN CHCACHTUNGTREN(NUGN PPh3)CH-
ACHTUNGTRENNUNG
presence of strong alkali. However, the
reactions of compound 2 with various
amines, such as n-butylamine and ani-
line, afford five-membered ring species,
[(SCN)
(CH=NHR’)}] (R’=nBu(8), Ph(9)), in
addition to the desired cine-substitu-
tion products, [(SCN)2A(PPh3)2Os{CHC-
(PPh3)CHCHC(NHR’)}] (R’=nBu(6),
2ACHTUNGTRENNUNG(PPh3)2OsACHTUNGTRENNUNG{CH=CACHTGUNTREN(UNGN PPh3)CH=C-
ACHTUNGTRENNUNG
Keywords: aromaticity · cine-sub-
stitution · metallacycles · nucleo-
philic substitution · synthetic meth-
ods
C
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Ph(7)), under similar reaction condi-
tions. The mechanisms of these reac-
Introduction
Aromatic substitution reactions are among the most widely
and frequently used transformations in organic synthesis.[1]
Most studies in this field have concerned ipso-substitution,
in which a new substituent is introduced at the same ring
position as the departing leaving group (Scheme 1). In com-
parison with ipso-substitution, other patterns of aromatic
substitution, for example, the cine-substitution of aromatic
compounds is much less common.[2] In cine-substitution re-
Scheme 1. Examples of substitution reactions in aromatic systems.
[a] T. Wang,+ Dr. H. Zhang,+ F. Han, L. Long, Prof. Dr. H. Xia
State Key Laboratory of Physical Chemistry of
Solid Surfaces, Collaborative Innovation Center of
Chemistry for Energy Materials, and
actions, the newly entering group takes up a position adja-
cent to that previously occupied by the leaving group.
As new aromatic heterocycles, metalla-aromatic com-
pounds are currently attracting considerable attention,
owing to their unique properties and promising applica-
tions.[3] Extensive studies have been carried out on charac-
teristic chemical reactions of metalla-aromatic compounds,
such as electrophilic aromatic substitution (SEAr)[4] and nu-
cleophilic aromatic substitution (SNAr)[5] reactions, which
have provided strong evidence for the aromaticity of these
aromatic heterocycles and have allowed us to obtain new in-
teresting organometallic complexes. Until now, the reported
College of Chemistry and Chemical Engineering
Xiamen University, Xiamen, 361005 (P.R. China)
E-mail: hpxia@xmu.edu.cn
[b] Dr. H. Zhang,+ Prof. Dr. Z. Lin
Department of Chemistry
The Hong Kong University of Science and Technology
Clear Water Bay, Kowloon (Hong Kong)
E-mail: chzlin@ust.hk
[+] These authors contributed equally to this work.
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201301398.
10982
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 10982 – 10991

FULL PAPER
Table 1. Selected bond lengths and angles in compounds 2, 3, and 5.
substitution reactions of metalla-aromatic compounds have
been limited to ipso-substitution reactions. Given our long-
standing interest in metallabenzene chemistry,[5a–c,e,6] we in-
vestigated the nucleophilic reactions of metallabenzenes
that contained an electron-withdrawing substituent and ob-
served the first examples of cine-substitution for metalla-ar-
omatic compounds. Herein, we report our experimental
findings and, at the same time, provide our detailed DFT
calculations on the reaction mechanism.
2
3
5
Bond length [ꢁ]
ꢀ
Os1 C1
1.982(6)
1.939(8)
1.980(7)
1.953(9)
2.031(6)
2.202(6)
2.037(6)
1.365(7)
1.466(8)
1.344(8)
1.400(8)
ꢀ
Os1 C5
ꢀ
Os1 C4
ꢀ
C1 C2
1.377(9)
1.395(12)
1.421(13)
1.325(14)
1.411(15)
ꢀ
C2 C3
1.426(10)
1.369(10)
1.406(11)
ꢀ
C3 C4
ꢀ
C4 C5
Bond angle [8]
C5-Os1-C1
C1-Os1-C4
C2-C1-Os1
C1-C2-C3
89.9(3)
90.3(4)
111.0(2)
72.7(2)
Results and Discussion
128.1(5)
123.9(6)
123.8(7)
124.8(7)
128.4(5)
127.7(6)
121.9(8)
128.1(11)
123.0(11)
128.5(9)
122.0(4)
112.0(5)
108.8(5)
158.2(6)
64.5(3)
C4-C3-C2
C3-C4-C5
C4-C5-Os1
C3-C4-Os1
Reactions
of
osmabenzene
complex
[OsACTHNGUTRENNU{G CHC-
A
R
CHTUNGTRENNUNG
ously, we reported the synthesis of osmabenzene complex
1.[6t] Although osmabenzene complex 1 is stable in the solid
state, it slowly decomposes in solution in the presence of
alkali. Hence, we first modified this less-alkali-resistant os-
mabenzene complex through a ligand-substitution reaction.
The treatment of compound 1 with six equivalents of
sodium thiocyanate in CH2Cl2 led to the formation of the
corresponding osmabenzene complex (2, Scheme 2). Osma-
124.6(5)
Figure 1. Molecular structure of compound 2. Ellipsoids set at 50% prob-
ability. The hydrogen atoms of the PPh3 groups are omitted for clarity.
range 1.369(10)–1.426(10) ꢁ and the lack of significant alter-
ꢀ
nations in the C C bond lengths suggests that compound 2
has a delocalized structure.
Scheme 2. Preparation of osmabenzene 2 and the reactions of compound
2 with alcohols.
Osmabenzene complex 2 can tolerate strong bases in solu-
tion. When an excess of sodium methoxide was added as a
solution in MeOH to the solution of compound 2 in CH2Cl2,
the reaction yielded a new osmabenzene complex (3), which
was a product of a cine-substitution reaction, within 2 h at
room temperature (Scheme 2). This new osmabenzene com-
plex (3) was isolated as greenish solid in 93% yield. The
crystal structure of compound 3 has been determined and its
molecular structure is shown in Figure 2, which confirms
that the methoxy group is attached onto the C5 atom of the
essentially planar osmabenzene ring. All of the bond lengths
of the metallacycle fall within the observed range for other
benzene complex 2 has been characterized by using multinu-
clear NMR spectroscopy and by single-crystal X-ray diffrac-
tion analysis, as well as by high-resolution mass spectrosco-
1
py. In the H NMR spectrum, the two downfield signals of
the OsCH protons appear at d=19.5 and 17.5 ppm. The
31P{1H} NMR spectrum shows two singlet peaks at d=ꢀ2.3
(OsPPh3) and 19.0 ppm (CPPh3). On the basis of
13C{1H} NMR, 1H,13C HMQC, and 13C dept-135 NMR ex-
periments, the five carbon signals of the metallacycle are
identified at d=229.4 (C1), 112.7 (C2), 154.0 (C3), 97.4
(C4), and 261.5 ppm (C5).
The crystallographic details of osmabenzene complex 2
are listed in Table 3; selected bond lengths and angles are
listed in Table 1. As shown in Figure 1, osmabenzene com-
plex 2 contains an essentially planar metallabenzene unit.
typical metallabenzenes.[3] The two Os C bond lengths are
ꢀ
ꢀ
ꢀ
almost equal (Os C1 1.980(7) and Os C5 1.953(9) ꢁ) and
ꢀ
the ring C C distances are consistent with delocalization
ꢀ
ꢀ
ꢀ
(C1 C2 1.395(12), C2 C3 1.421(13), C3 C4 1.325(14), and
ꢀ
C4 C5 1.411(15) ꢁ). The change in the substituents on the
metallacyclic ring is also clearly evident by NMR spectro-
1
ꢀ
The C C bond lengths in the C1–C5 chain are within the
scopy. In particular, the H NMR (CDCl3) spectrum shows
Chem. Eur. J. 2013, 19, 10982 – 10991
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10983

Z. Lin, H. Xia et al.
Figure 3. Molecular structure of compound 5. Ellipsoids set at 50% prob-
Figure 2. Molecular structure of compound 3. Ellipsoids set at 50% prob-
ability. The hydrogen atoms of the PPh3 groups are omitted for clarity.
ability. The hydrogen atoms of the PPh3 groups are omitted for clarity.
three 1H signals of the metallabenzene ring at d=16.0
(C1H), 7.1 (C3H), and 5.5 ppm (C4H). With the aid of
1H,13C HSQC and 13C dept-135 NMR experiments, the five
carbon signals of the metallabenzene ring are observed at
d=234.4 (C1), 102.2 (C2), 146.1 (C3), 114.6 (C4), and
249.7 ppm (C5) in the 13C{1H} NMR spectrum. The presence
of a methoxy substituent is evident by the chemical shifts in
the 1H NMR (d=2.8 ppm) and 13C{1H} NMR spectra (d=
57.5 ppm).
(C1H), 7.0 (C3H), and 3.8 ppm (C5H). In the 31P{1H} NMR
spectrum, the signal of the CPPh3 atom appears at d=
9.3 ppm and the signals of the two phosphine ligands are ob-
served at d=16.0 (OsPPh
2A
(OsPPh3). In the 13C{1H} NMR spectrum, the signals of the
C1 and C2 atoms appear at d=207.3 and 116.1 ppm, where-
as the three carbon signals of the coordinated allene back-
bone appear at d=126.0 (C3), 199.7 (C4), and 49.9 ppm
(C5).
The reactions of osmabenzene complex 2 with other alco-
hol nucleophiles were also investigated. Compound 2 react-
ed with EtOH to produce cine-substitution product 4 in the
presence of sodium ethoxide (Scheme 2). Compound 4 was
characterized by NMR spectroscopy and by high-resolution
mass spectroscopy. The structure of compound 4 can be
easily deduced, because its NMR data are similar to those
of osmabenzene complex 3. The resonances of the osmaben-
Reactions of osmabenzene complex 2 with amines: To study
the scope of these cine-substitution reactions, the reaction of
osmabenzene complex 2 with n-butylamine was first investi-
gated. The reaction was monitored by in situ NMR spectro-
scopy. When a solution of sodium methoxide in MeOH was
added to a solution of compound 2 and excess n-butylamine
in CH2Cl2, compound 2 was completely consumed to give a
2:3 mixture of complexes 6 and 8 within 30 min (Scheme 3).
Complex 6 can be isolated as a green solid from the reaction
mixture because of its good solubility in Et2O (complex 8 is
insoluble in Et2O. Similar to those of compounds 3 and 4,
the 1H NMR (d=15.2 (C1H), 6.8 (C3H), and 5.4 ppm
(C4H)) and 13C{1H} NMR spectra (d=212.7 (C1), 101.4
(C2), 143.4 (C3), 112.1 (C4), and 229.7 ppm (C5)) for the
1
zene ring in the H NMR (d=16.1 (C1H), 7.2 (C3H), and
5.6 ppm (C4H)) and 13C{1H} NMR spectra (d=234.7 (C1),
102.1 (C2), 146.3 (C3), 113.8 (C4), and 248.8 ppm (C5)) are
very close to those that were observed for osmabenzene
complex 3. The ethoxy substituent is readily distinguished in
the 1H NMR (d=3.0 (C6H) and 0.7 ppm (C7H)) and
13C{1H} NMR spectra (d=65.6 (C6) and 14.8 ppm (C7)).
Notably, the reaction of osmabenzene complex 2 with the
bulky tert-butanol in the presence of sodium tert-butoxide
did not give the desired cine-substitution product. Instead,
as shown in Scheme 2, allene-coordinated complex 5 was
isolated from the reaction. The structure of compound 5 has
been determined by using X-ray crystallography, as shown
in Figure 3. The X-ray diffraction study confirmed that the
complex contained a conjugated osmacycle, as well as a ter-
minal double bond from an allene that was coordinated to
the metal center. As a consequence of its coordination to
the metal center and because one of its substituents is part
of a phosphine ligand, the allene unit is strongly bent, with a
C3-C4-C5 angle of 158.2(6)8. In addition, the characteristic
spectroscopic data of compound 5 are also consistent with
an allene-coordinated osmacyclic structure. The 1H NMR
spectrum shows the signals of the metallacycle at d=11.2
Scheme 3. Reactions of osmabenzene 2 with amines.
10984
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Chem. Eur. J. 2013, 19, 10982 – 10991

cine-Substitution Reactions of Metallabenzenes
FULL PAPER
Table 2. Selected bond lengths and angles in compound 10.
metallacycle atoms of complex 6 confirm that complex 6 is a
cine-substitution product and that substitution occurs at the
C5 position. The resonances of the n-butylamine group are
observed in the 1H NMR (d=2.0 (C6H), 0.6 (C7H), 0.9
(C8H), and 0.6 ppm (C9H)) and 13C{1H} NMR spectra (d=
45.5 (C6), 30.9 (C7), 20.4 (C8), and 14.2 ppm (C9)).
Bond length [ꢁ]
ꢀ
ꢀ
Os1 C1
1.977(2)
2.082(2)
1.395(3)
1.423(3)
1.390(3)
1.413(3)
C5 N1
1.306(3)
1.467(3)
1.518(4)
1.519(4)
1.518(5)
ꢀ
ꢀ
Os1 C4
N1 C6
ꢀ
ꢀ
C1 C2
C6 C7
ꢀ
ꢀ
C2 C3
C7 C8
ꢀ
ꢀ
C3 C4
C8 C9
Owing to its high sensitivity to air and its poor solubility
in ordinary organic solvents, our attempts to perform a full
NMR spectroscopic characterization of complex 8 failed.
However, the structure of compound 8 could still be de-
ꢀ
C4 C5
Bond angle [8]
C4-Os1-C1
C2-C1-Os1
C1-C2-C3
77.96(9)
119.37(16)
112.8(2)
C4-C3-C2
C3-C4-Os1
115.1(2)
114.69(16)
1
duced from its H NMR and 31P{1H} NMR spectra. In addi-
tion, high-resolution mass spectroscopy of complex
8
showed a peak at m/z 1229.2903, which was consistent with
the supposed formula. Besides, we obtained the oxidation
product of compound 8, a complex that was structurally sim-
ilar to complex 8 (see below).
By using different amines, such as aniline, as the nucleo-
phile, we carried out analogous reactions and observed simi-
lar results. The reaction produced the expected cine-substi-
tution product (7) and the five-membered ring product (9)
in a molar ratio of 5:6. These complexes have also been
characterized by using NMR spectroscopy and by high-reso-
lution mass spectroscopy. For compound 7, the resonances
of the ring atoms in the 1H NMR (d=15.3 (OsCH), 6.9
(C3H), and 6.0 ppm (C4H)) and 13C{1H} NMR spectra (d=
217.3 (C1), 102.4 (C2), 143.2 (C3), 115.2 (C4), and
228.9 ppm (C5)) are comparable to those for compounds 3,
4 and 6, which are all in accord with the osmabenzene struc-
ture with a phenylamino substituent that is attached onto
the C5 position. There are only a few examples of metalla-
benzenes that contain electron-donating groups on the met-
allacycle.[4e,5d,6q,7] Thus, complexes 6 and 7 represent unpre-
cedented amino-substituted metallabenzenes.
We noted that only cine-substitution products were ob-
tained from the reactions of compound 2 with alcohols in
the presence of sodium methoxide. However, the reactions
of compound 2 with amines in presence of sodium methox-
ide not only produced cine-substitution products but also
the five-membered ring products. Because amines are typi-
cally more nucleophilic/basic than their alcohol equivalents,
we postulated that the five-membered ring products may be
formed through the direct reactions between compound 2
and amines without the aid of a strong alkali. To test this
idea, we performed the reaction of compound 2 with n-bu-
tylamine in the absence of sodium methoxide. Indeed, when
excess n-butylamine was added to the solution of compound
2 in CH2Cl2, it was completely converted into complex 8
within five minutes (Scheme 3).
Figure 4. Molecular structure of compound 10. Ellipsoids set at 50%
probability. The hydrogen atoms of the PPh3 groups are omitted for clari-
ty.
cyclopentadiene ring with an exocyclic imino group. Com-
plexes 8 and 10 have similar overall structural features, de-
spite the fact that they have different electron counts. Clear-
ly, complex 8 is easily oxidized in air to generate the oxida-
tion product (10). Similar results were observed when
aniline was allowed to react with osmabenzene complex 2 in
the absence of sodium methoxide (Scheme 3).
Mechanistic investigation of the reactions of compound 2
with various nucleophiles: To understand the mechanistic as-
pects of the reactions of compound 2 with various nucleo-
philes, we initially performed the same experiments starting
from deuterium-labeled MeOH. As shown in Scheme 4, the
experiments suggest that the hydrogen atom at the C4 posi-
tion in the cine-substitution product comes from the MeOH
proton. Interestingly, with CD3OD/MeONa, CD3O (instead
of MeO) and D were found at the C5 and C4 positions, re-
When a solution of complex 8 was stirred at room temper-
ature in air for one hour, it was cleanly converted into para-
magnetic complex 10 (Scheme 3). Complex 10 was isolated
as green solid and characterized by single-crystal X-ray dif-
fraction analysis and by high-resolution mass spectroscopy.
The crystallographic details are given in Table 3 and selected
bond lengths and angles are given in Table 2. The molecular
structure of the complex is shown in Figure 4. X-ray diffrac-
tion analysis indicates that compound 10 contains a metalla-
Scheme 4. Reactions of osmabenzene 2 with deuterium-labeled MeOH.
Chem. Eur. J. 2013, 19, 10982 – 10991
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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10985

Z. Lin, H. Xia et al.
Table 3. Crystal data and structure refinement for compounds 2, 3, 5, and 10.
2·2.5CHCl3 3·CH2Cl2 5·2CH2Cl2
C63.50H50.50N2S2P3ICl7.50Os C63H53N2S2P3Cl2OOs C63H51N2S2P3Cl4Os C67H61N3S2P3Cl4Os
derivatives. However, our at-
tempts to trap the possible met-
allabenzyne intermediate by
performing a [4+2] cycloaddi-
tion reaction with furan or pyr-
role failed. Successful trapping
is generally believed to be
strong supporting evidence for
the existence of a benzyne-type
intermediate.
10·2CHCl2
formula
Mw
1581.56
173
1272.20
173
1325.09
123
1397.22
173
T [K]
l [ꢁ] (MoKa or
CuKa radiation)
crystal system
space group
a [ꢁ]
b [ꢁ]
c [ꢁ]
a [8]
0.71073
0.71073
0.71073
1.54178
monoclinic
P21/c
23.123(3)
12.8492(17)
25.086(3)
90
monoclinic
P21/n
12.739(2)
19.773(4)
22.575(4)
90
orthorhombic
Pbca
14.9224(4)
17.7297(6)
43.1777(15)
90
monoclinic
P21/c
21.91400(10)
12.38410(10)
23.4976(2)
90
As mentioned above, cine-
substitution does not occur for
the reactions of osmabenzene
b [8]
117.423(2)
90
6615.8(15)
4
1.588
2.873
96.992(3)
90
5644.2(17)
4
1.497
2.557
90
90
103.8430(10)
90
6191.68(8)
4
1.499
7.179
g [8]
V [ꢁ3]
11423.5(6)
8
1.541
2.619
5312
0.20ꢂ0.20ꢂ0.10
2.73–25.00
27875
complex
2 with alcohols or
Z
amines in the absence of strong
alkali. Furthermore, the direct
reactions of compound 2 with
amines only afford five-mem-
bered ring products 8 or 9.
Taking these observations into
1calcd [gcmꢀ3
]
m [mmꢀ1
(000)
]
F
A
3116
2560
2820
crystal size [mm3]
q range [8]
0.20ꢂ0.20ꢂ0.10
0.99–25.00
33015
0.30ꢂ0.20ꢂ0.20
1.37–25.00
28388
0.20ꢂ0.10ꢂ0.04
3.87–60.16
34268
total reflns
unique reflns
observed reflns
[Iꢁ2s(I)]
11655
9805
9912
9190
10050
6066
9218
8759
account, we can consider
a
plausible mechanism
data/restraints/pa-
rameters
11655/135/776
9912/54/655
10050/0/676
9218/0/721
(Scheme 6) that is supported by
our DFT calculations (see
below). The nucleophilic addi-
tion of a molecule of MeOH
(or n-butylamine) at the C5 po-
sition results in the formation
of sH adduct A (or E). Then,
dissociation of the halide anion
affords allene-coordinated in-
GOF on F2
1.000
1.000
0.867
1.000
R1/wR2 [Iꢁ2s(I)]
R1/wR2 (all data)
largest peak/hole
0.0507/0.1476
0.0606/0.1531
2.219/ꢀ1.280
0.0663/0.1858
0.0719/0.1915
2.144/ꢀ2.159
0.0437/0.0767
0.0866/0.0833
1.084/ꢀ2.480
0.0201/0.0491
0.0217/0.0500
0.694/ꢀ0.884
[eꢁꢀ3
]
CCDC No.[a]
920029
920030
920031
920028
[a] These files 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.
spectively, in the cine-substitution product. The isotopic-la-
beling experiments suggest that the nucleophilic attack of
MeOH, not MeONa, on the metallabenzene ring initiates
the reaction, owing to the poor solubility of sodium methox-
ide in the reaction mixture and to the relatively dominant
amount of MeOH (about 60 equiv with respect to MeONa).
For more details on the isotope-labeling experiments, see
the Supporting Information.
Thus, we first attempted to see whether we could find fur-
ther support for the mechanism of this cine-substitution re-
action, which was proposed to involve an elimination/addi-
tion process through
a
metallabenzyne intermediate
(Scheme 5). The proposed elimination/addition mechanism
is similar to the classical examples of cine-substitution,
which proceed through benzyne intermediates in homoarene
Scheme 6. Proposed mechanism for the reactions of osmabenzene 2 with
nucleophiles.
termediate B (or F). The attack of a proton from another
nucleophile onto the central carbon atom of the allene
moiety of structure B (or F) induces redistribution of the p-
conjugation system and produces alkene-coordinated inter-
mediate C (or G). Subsequent replacement of the counter-
anion by sodium methoxide and the dissociation of a mole-
cule of MeOH or n-butylamine may produce intermediate
Scheme 5. Proposed elimination-addition mechanism for the reaction of
ꢀ
osmabenzene 2 with MeOH.
D (or H). Finally, deprotonation of the C5 H bond yields
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cine-Substitution Reactions of Metallabenzenes
FULL PAPER
step process (Figure 5). As shown in Figure 5, allene-coordi-
nated complex B’ is directly formed from compound 2 and
MeOH through transition state TSB, with a barrier of
27.2 kcalmolꢀ1. From structure B’, there are two possible
paths, that is, paths a and b, which lead to the formation of
the expected cine-substitution product and the five-mem-
bered ring species (which are only observed in the reactions
with amines), respectively. In path a, the electrophilic addi-
tion of another molecule of MeOH through the attack of a
proton onto the central carbon of the allene moiety of struc-
ture B’ proceeds through six-membered transition state
TSC1 to give intermediate C’. This addition step is a fast
process with a small barrier (3.2 kcalmolꢀ1). Structure C’ is
an ion-pair species that can mix well with the base
(MeONa) in solution and facilitate further reaction. Then,
ion exchange of MeOꢀ for Iꢀ take place, followed by depro-
tonation at the C5 position, thereby giving intermediate D1’
with a barrier of 14.9 kcalmolꢀ1. Finally, the formation of a
bond between the C5 position and the metal center, accom-
panied with aromatization, generates cine-substitution prod-
uct 3’. The rate-determining step for the whole reaction cor-
responds to the first addition of MeOH, followed by iodide
dissociation, with a calculated barrier of 27.2 kcalmolꢀ1.
In path b, which leads to the formation of the five-mem-
bered metallacyclic species, the elimination of HI from
structure B’ occurs to first give structure B2’. Then, structur-
al rearrangement generates five-membered metallacycle
species C2’. Figure 5 shows that path b is less favorable than
path a. Furthermore, osmacyclopentadiene complex C2’ is
relatively unstable. The instability of structure C2’ can be at-
tributed to its highly reactive oxonium structure. Therefore,
the formation of the five-membered metallacycle species in
the reaction with MeOH is kinetically and thermodynami-
cally less favorable, consistent with the experimental results
for the reaction of compound 2 with MeOH in the presence
of sodium methoxide, which affords the net cine-substitution
product.
Scheme 7. Amination of pyrimidine derivatives (ANRORC mechanism).
osmabenzene 3 (or 6). The whole process, as presented in
Scheme 6, resembles the classical ANRORC mechanism
(Scheme 7), which has been thoroughly investigated by van
de Plas and co-workers,[8] thereby proceeding through a se-
quence that comprises three key steps: 1) the addition of the
nucleophile, 2) ring opening, and 3) ring closure. In the ab-
sence of strong alkali, five-membered ring product 8 is ex-
clusively formed (2!E!F!8).
DFT studies: As mentioned above, our DFT calculations
support the mechanisms proposed in Scheme 6. In this sec-
tion, the results of the DFT calculations will be given and
discussed in detail. From these DFT results, we also want to
understand the experimental observations that the reactions
of compound 2 with amines also produced five-membered
ring products with the desired cine-substitution product,
whereas the cine-substitution products were exclusively
formed from the reactions of compound 2 with alcohols.
Figure 5 shows the calculated energy profile based on the
mechanism shown in Scheme 6, which leads to the formation
of experimentally observed cine-substitution product 3. In
Figure 5, the labels of the model compounds are followed
by the prime (’) symbol to differentiate them from their cor-
responding experimental compounds.
Scheme 6 shows that the nucleophilic attack of a molecule
of MeOH onto the C5 position of compound 2 is followed
by the dissociation of iodide, which initiates the reaction to
lead to the formation of allene-coordinated complex B. In-
terestingly, the calculations indicate that this event is a one-
Figure 5. Calculated energy profile for the formation of structure 3’, based on the reaction mechanism shown in Scheme 6. The relative electronic ener-
gies are given in kcalmolꢀ1
.
Chem. Eur. J. 2013, 19, 10982 – 10991
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10987

Z. Lin, H. Xia et al.
Figure 6. Calculated electronic energy profile for the formation of structures 6’ and 8’, based on the reaction mechanism shown in Scheme 6. The relative
electronic energies are given in kcalmolꢀ1
.
We also calculated the reaction of metallabenzene com-
plex 2 with n-butylamine. Figure 6 shows the calculated
energy profile for the mechanism presented in Scheme 6.
Nucleophilic addition of an amine molecule and dissociation
of the halide anion afford allene-coordinated intermediate
F’. Unlike the reaction with MeOH, the event that leads to
the formation of allene-coordinated intermediate F’ is a
two-step process, which may be attributed to the higher sta-
bility of iminium ion intermediate E’ compared to that of
the analogous oxonium ion intermediate. In addition, the
barrier to the addition is much lower than the corresponding
one in the reaction with MeOH, in agreement with the ex-
perimental observations that the reaction time with n-butyl-
amine is significantly shorter than that with MeOH. All of
these results indicate that n-butylamine is a much-stronger
nucleophile than MeOH in these reactions.
From structure F’, there are again two paths, that is,
paths a and b, thus leading to the formation of the cine-sub-
stitution product and the five-membered ring product, re-
spectively. Because of the greater nucleophilicity of n-butyl-
amine, path b, which involves the elimination of HI and a
structural rearrangement to give five-membered ring prod-
uct 8’, is kinetically very favorable. In addition, five-mem-
bered ring product 8ꢀ is more stable than intermediate F’.
Consistent with this theoretical result, five-membered ring
product 8 was observed (and characterized) experimentally.
The calculated energy profile (Figure 6) for path a, which
leads to the formation of the cine-substitution product, is
similar to the profile for the reaction with MeOH
(Figure 5). The results of the calculations (Figure 6) indicate
that this pathway is kinetically less favorable than path b,
but is much more thermodynamically favorable.
Prompted by the results of the calculations discussed
above, we isolated a pure sample of compound 8 and, by
performing in situ NMR experiments, we observed that it
could be converted into cine-substitution product 6 in solu-
tion in the presence of excess n-butylamine, hydriodic acid,
and sodium methoxide.
Conclusion
In summary, the first examples of cine-substitution reactions
of metalla-aromatic compounds have been observed experi-
mentally and studied computationally. The net cine-substitu-
tion products can be obtained from the reactions of osma-
benzene with alcohols in the presence of strong alkali. For
the reactions with amines, the desired cine-substitution
products can also be achieved, together with the five-mem-
bered ring species under similar reaction conditions. All of
our investigations (i.e., in situ NMR experiments and isotop-
ic labeling experiments) support the conclusion that cine-
substitution reactions involve a sequence of three key steps:
the addition of a nucleophile, ring opening, and ring closure,
which resemble the classical ANRORC mechanism. These
findings were corroborated by using DFT calculations and
demonstrate that the nucleophilicity of the nucleophiles and
the basicity of the reaction conditions are crucial for cine-
substitution reactions.
Experimental Section
General comments: All manipulations were carried out at room tempera-
ture under a nitrogen atmosphere by using standard Schlenk techniques,
unless otherwise stated. Solvents were distilled under a nitrogen atmos-
phere from sodium benzophenone (Et2O, n-hexane) or calcium hydride
(CH2Cl2). Column chromatography was performed on neutral alumina
Comparing the calculated energy profiles for the two
pathways, we can conclude that structure 8’ is a kinetic prod-
uct whilst structure 6’ is the thermodynamic product and
that structure 8’ can be converted into structure 6’ because
the barrier for the conversion is accessible (27.8 kcalmolꢀ1,
which corresponds to the energy difference between struc-
ture 8’ and TSG1; Figure 6).
gel (200–300 mesh). The starting material [I2ACHUTNGTRNENUG(PPh3)2OsACHTUNGTRENNUNG{CHC-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
dure.[6t] NMR experiments were performed on Bruker AV-500 (1H:
500.2 MHz, 13C: 125.8 MHz, 31P: 202.5 MHz) or Bruker AV-400 spec-
trometers (1H: 400.1 MHz, 13C: 100.6 MHz, 31P: 162.0 MHz). 1H and
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cine-Substitution Reactions of Metallabenzenes
FULL PAPER
13C NMR chemical shifts are reported relative to TMS; 31P NMR chemi-
cal shifts are reported relative to 85% H3PO4. High-resolution mass spec-
tra (HRMS) were recorded on a Bruker En Apex Ultra 7.0T FTMS mass
spectrometer.
under vacuum and the residue was extracted with CH2Cl2 (3ꢂ2 mL). The
volume of the filtrate was concentrated to about 2 mL under vacuum;
the addition of n-hexane (20 mL) to the solution produced a yellow solid
that was collected by filtration, washed with n-hexane (3ꢂ2 mL), and
dried under vacuum. Yield: 151 mg, 82%; 1H NMR (500.2 MHz,
Synthesis of [(SCN)
2ACHTUNGTRENNUNG(PPh3)2OsACHUTNRTGEG{NUNN CHCACHTNUGRTEN(NUGN PPh3)CHCICH}] (2): A mixture of
CD2Cl2): 11.2 (d, JACHTUNGRTENNGU CAHTUNTGNER(NUGN P,H)=6.9 Hz, 1H;
(P,H)=16.9 Hz, 1H; C1H), 7.0 (d, J
compound (460 mg, 0.32 mmol) and sodium thiocyanate (158 mg,
1
1
C3H, obscured by the phenyl signals but confirmed by H,13C HMQC ex-
1.95 mmol) in CH2Cl2 (35 mL) was stirred at 08C for about 6 h to give a
green suspension. The solvent was removed under vacuum and the resi-
due was extracted with CH2Cl2 (3ꢂ5 mL). The volume of the filtrate was
concentrated to about 5 mL under vacuum; the addition of Et2O (50 mL)
to the solution produced a green solid, which was collected by filtration,
washed with Et2O (3ꢂ5 mL), and dried under vacuum. Yield: 370 mg,
89%; 1H NMR (500.2 MHz, CDCl3): d=19.5 (s, 1H; C5H), 17.5 (d, J-
periments), 6.7–7.7 (m, 44H; Ph), 3.8 ppm (s, 1H; C5H); 31P{1H} NMR
(202.5 MHz, CD2Cl2): d=9.3 (s; CPPh3), 16.0 (d,
OsPPh2A(C6H5)CH), (d, (P,P)=302.5 Hz;
ꢀ3.5 ppm
13C{1H} NMR (125.8 MHz, CD2Cl2): d=207.3 (br; C1), 199.7 (d, J
23.7 Hz; C4), 157.3 and 138.2 (s; C7 and C6), 126.0 (d, J
(P,C)=27.0 Hz;
JACHTUNGTRENNUNG
C
JACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACTHNUTRGNEUNG
C3), 116.1 (d, J(P,C)=72.5 Hz; C2), 116.1–157.4 (m; Ph), 49.9 ppm (s; C5);
HRMS (ESI): m/z calcd for C61H47N2S2P3Os: 1156.2008 [M]+; found:
ACHTUNGTRENNUNG ACHTUNGTRENNUGN
(P,H)=21.6, 1H; C1H), 8.0 (d, J(P,H)=12.2 Hz, 1H; C3H), 6.8–7.7 ppm
(m, 45H; Ph); 31P{1H} NMR (202.5 MHz, CDCl3): d=19.0 (s; CPPh3),
ꢀ2.3 ppm (s; OsPPh3); 13C{1H} NMR (125.8 MHz, CDCl3, with
1H,13C HSQC and 13C dept-135 NMR experiments): d=229.4 (br; C1),
1156.1996.
Synthesis of [(SCN)2CATHUNGTRENU(NNG PPh3)2OsACHUTTNGRENNUG{CHCACHUTNGTNER(NUG PPh3)CHCHCACHTUNGERTNNUG(NHnBu)}] (6): A
suspension of sodium methoxide (59 mg, 1.1 mmol) in MeOH (1 mL,
24.71 mmol) was added to a solution of compound 2 (260 mg, 0.20 mmol)
in CH2Cl2 (10 mL). The mixture was stirred at RT for about 1 min and
then n-butylamine (0.20 mL, 2.0 mmol) was added. The mixture was stir-
red for a further 30 min to give a deep-green suspension. The solvent was
removed under vacuum and the residue was extracted with CH2Cl2 (3ꢂ
2 mL). The volume of the filtrate was concentrated to about 2 mL under
vacuum. Et2O (20 mL) was slowly added with stirring to give a deep-
green precipitate and a yellow-green solution, which were separated by
filtration. The solvent of the yellow-green filtrate was removed under
vacuum, which produced a green solid that was collected by filtration
and washed with n-hexane (3ꢂ2 mL). Yield: 87 mg, 35%. As indicated
by in situ NMR spectroscopy, compounds 6 (Yield (by NMR spectrosco-
py): 40%) and 8 (Yield (by NMR spectroscopy): 60%) were both con-
tained in the deep-green solution. Disappointingly, our attempts to iso-
late compound 8 were not successful. 1H NMR (400.1 MHz, CDCl3): d=
261.5 (br; C5), 154.0 (d, J
(NCS)2), 134.4–120.6 (m; Ph), 112.7 (d, J
(d, J
(P,C)=14.1 Hz; C4); HRMS (ESI): m/z calcd for C61H48N2S2P3IOs:
1284.1126 [M]+; found: 1284.1108.
Synthesis of [(SCN)2A(PPh3)2Os{CHC
ACHTUNGTRENNUNG
G
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
E
G
ACHUTGTNERN(NGU PPh3)CHCHCAHCTUNGTREN(NUNG OMe)}] (3): A sus-
pension of sodium methoxide (16 mg, 0.30 mmol) in MeOH (1 mL,
24.71 mmol) was added to a solution of compound 2 (120 mg, 0.09 mmol)
in CH2Cl2 (10 mL). The mixture was stirred at RT for about 2 h to give a
green suspension. The solvent was removed under vacuum and the resi-
due was extracted with CH2Cl2 (3ꢂ2 mL). The volume of the filtrate was
concentrated to about 2 mL under vacuum; the addition of n-hexane
(30 mL) to the solution produced a green solid that was collected by fil-
tration, washed with n-hexane (3ꢂ2 mL), and dried under vacuum.
Yield: 103 mg, 93%; 1H NMR (500.2 MHz, CDCl3): d=16.0 (d, J
22.5 Hz, 1H; C1H), 6.8–7.8 ppm (m, 45H; Ph), 7.1 (t, J
(P,H)=10.3 Hz, J-
(H,H)=10.3 Hz, 1H; C3H, obscured by the phenyl signals but confirmed
ACHTUNGTRNE(NUNG P,H)=
AHCTUNGTRENNUNG
A
(P,H)=23.6 Hz, 1H; C1H), 6.8 (t, J
15.2 (d, JACHTUNGTERNUNGN AHCTUNRTGEGUNN(N P,H)=10.1 Hz, JACHTUNGTRENNUNG(H,H)=
by 1H,13C HMQC experiments), 5.5 (d, J
E
10.1 Hz, 1H; C3H, obscured by the phenyl signals but confirmed by
1H,13C HMQC experiments), 6.6–7.7 ppm (m, 46H; Ph and NH), 5.4 (d,
2.8 ppm (s, 3H; OCH3); 31P{1H} NMR (202.5 MHz, CDCl3): d=17.0 (s;
CPPh3), ꢀ5.4 ppm (s; OsPPh3); 13C{1H} NMR (125.8 MHz, CDCl3, with
1H,13C HSQC and 13C dept-135 NMR experiments): d=234.4 (br; C1),
JACTHNUTRGNEUNG
(P,H)=10.1 Hz, 1H; C4H), 2.0 (br, 2H; NHCH2CH2CH2CH3), 0.6 (m,
2H; NHCH2CH2CH2CH3), 0.9 (m, 2H, NHCH2CH2CH2CH3), 0.6 ppm (t,
249.7 (br; C5), 146.1 (d, J
(NCS)2), 139.9–114.5 (m; Ph), 114.6 (d, J
(P,C)=78.2 Hz; C2), 57.5 ppm (s; OCH3); HRMS (ESI): m/z calcd for
C62H51N2S2P3OOs: 1188.2265 [M]+; found: 1188.2264.
Synthesis of [(SCN)2A(PPh3)2Os{CHC(PPh3)CHCHC
ACHTUNGTRENNUNG
JACTHNUTRGNEUNG
(H,H)=7.2 Hz, 3H; NHCH2CH2CH2CH3); 31P{1H} NMR (162.0 MHz,
CDCl3): d=16.9 (s; CPPh3), 0.5 ppm (s; OsPPh3); 13C{1H} NMR
A
ACHTUNGTRENNUNG
(125.8 MHz, CD2Cl2, with 1H,13C HSQC and 13C dept-135 NMR experi-
ACHTUNGTRENNUNG
ments): d=212.7 (br; C1), 229.7 (br; C5), 143.4 (d, J
ACHTUNGTRENNUNG
142.7 and 137.6 (s; Os
12.3 Hz; 101.4
G
ACHTUNGTRENNUNG
C
E
G
ACHTUNGTREN(NUGN OEt)}] (4): A sus-
C4),
JACHTUNGTRENNUNG
pension of sodium ethoxide (21 mg, 0.31 mmol) in EtOH (1 mL,
17.13 mmol) was added to a solution of compound 2 (130 mg, 0.10 mmol)
in CH2Cl2 (10 mL). The mixture was stirred at RT for about 2 h to give a
green suspension. The solvent was removed under vacuum and the resi-
due was extracted with CH2Cl2 (3ꢂ2 mL). The volume of the filtrate was
concentrated to about 2 mL under vacuum; the addition of n-hexane
(30 mL) to the solution produced a green solid that was collected by fil-
tration, washed with n-hexane (3ꢂ2 mL), and dried under vacuum.
NHCH2CH2CH2CH3), 30.9 (s; NHCH2CH2CH2CH3), 20.4 (s;
NHCH2CH2CH2CH3), 14.2 ppm (s; NHCH2CH2CH2CH3); HRMS (ESI):
m/z calcd for C65H58N3S2P3Os: 1229.2900 [M]+; found: 1229.2903.
Synthesis of [(SCN)2ACHTNUGETRN(UNNG PPh3)2OsACHUTGTNREN{NUG CHCACHTUNEGRTNN(GUN PPh3)CHCHCCAHTNUGTREN(NUNG NHPh)}] (7): A sus-
pension of sodium methoxide (70 mg, 1.3 mmol) in MeOH (1.3 mL,
32.13 mmol) was added to a solution of compound 2 (280 mg, 0.22 mmol)
in CH2Cl2 (10 mL). The mixture was stirred at ER for about 1 min, then
aniline (0.21 mL, 2.3 mmol) was added. The mixture was stirred for a fur-
ther 30 min to give a deep-green suspension. The solid suspension was re-
moved by filtration and the volume of the filtrate was concentrated to
about 2 mL under vacuum. The residue was purified by column chroma-
tography on neutral alumina (acetone/CH2Cl2, 1:20) to give compound 7
as a green solid. Yield: 104 mg, 38%. As indicated by in situ NMR spec-
troscopy, compounds 7 (Yield (by NMR spectroscopy): 44%) and 9
(Yield (by NMR spectroscopy): 56%) were both contained in the deep-
green reaction solution. Disappointingly, our attempts to isolate com-
pound 9 were not successful. 1H NMR (500.2 MHz, CD2Cl2): d=15.3 (d,
Yield: 117 mg, 96%; 1H NMR (500.2 MHz, CDCl3): d=16.1 (d, J
22.5 Hz, 1H; C1H), 6.8–7.8 ppm (m, 45H; Ph), 7.2 (t, J
(P,H)=10.2 Hz, J-
(H,H)=10.2 Hz, 1H; C3H, obscured by the phenyl signals but confirmed
by 1H,13C HMQC experiments), 5.6 (d, J(H,H)=10.2 Hz, 1H; C4H), 3.0
(q, J(H,H)=6.5 Hz, 2H; OCH2CH3), 0.7 ppm (t, J(H,H)=6.4 Hz, 3H;
ACHTUNGTRNE(NUNG P,H)=
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
OCH2CH3); 31P{1H} NMR (202.5 MHz, CDCl3): d=17.3 (s; CPPh3),
ꢀ4.9 ppm (s; OsPPh3); 13C{1H} NMR (125.8 MHz, CDCl3, with
1H,13C HSQC and 13C dept-135 NMR experiments): d=234.7 (br; C1),
248.8 (br; C5), 146.3 (d, J
(NCS)2), 140.0–113.8 (m; Ph), 113.8 (d, JACTHUNGTRENNUNG
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
(P,C)=78.0 Hz; C2), 65.6 (s; OCH2CH3), 14.8 ppm (s; OCH2CH3);
J
N
ACHTUNGTREN(NGNU P,H)=10.3 Hz, J-
HRMS (ESI): m/z calcd for C63H53N2S2P3OOs: 1202.2427 [M]+; found:
1
by H,13C HMQC experiments), 6.2–7.8 ppm (m, 50H; Ph), 6.0 ppm (d, J-
1202.2453.
AHCTUNGTRENNUNG
(P,H)=10.3 Hz, 1H; C4H). 31P{1H} NMR (202.5 MHz, CD2Cl2): d=
Synthesis of [(SCN)2PPh
(5): A suspension of sodium tert-butoxide (82 mg, 0.85 mmol) in tert-buta-
nol (1.5 mL, 15.68 mmol) was added to solution of compound
(205 mg, 0.16 mmol) in CH2Cl2 (15 mL). The mixture was stirred at RT
for about 1 h to give a yellow suspension. The solvent was removed
(h2-CCH)}]
3CATHNUGTRNE(NUG PPh2ACUTHNTGRENNGU(N C6H4))OsACHNUTRTGEG{NNUN CHCAHTCUGNTERN(NUNG PPh3)CHACHTUNTGRNUEGN
16.7 ppm (s; CPPh3), ꢀ1.4 (s; OsPPh3); 13C{1H} NMR (125.8 MHz,
a
2
CD2Cl2, with 1H,13C HSQC and 13C dept-135 NMR experiments): d=
217.3 (br; C1), 228.9 (br; C5), 143.2 (d, J
ACHTUNGTRENNUNG
139.4 (s; OsACTHNUGRTEN(NUNG NCS)2), 140.7–118.8 (m; Ph), 115.2 (d, JACHTGNUTRENNUNG
Chem. Eur. J. 2013, 19, 10982 – 10991
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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10989

Z. Lin, H. Xia et al.
102.4 ppm (d,
C67H54N3S2P3Os: 1249.2587 [M]+; found: 1249.2572.
Synthesis of [(SCN)2A(PPh3)2Os{CHC(PPh3)CHCACTHGUNTER(UNNG CHNHR)}]: In an
J
G
(CPCM).[14] CH2Cl2 was used as the solvent, according to the experimen-
tal reaction conditions.
NMR tube, the primary amine (R’NH2, about 3 equiv) was added to a
solution of compound 2 (9.0 mg, 7.0ꢂ103 mmol) in CD2Cl2 (0.4 mL),
which afforded a color change from green to deep green. The reaction
was complete after 5 min at RT and the NMR spectra were collected.
Acknowledgements
1
We thank the 973 Program (2012CB821600), the National Natural Sci-
ence Foundation of China (20925208, 21174115, 21272193), the Research
Grants Council of Hong Kong (HKUST603711), and the Mingang Post-
doctoral Science Foundation of China.
R=nBu (8): Yield (by NMR spectroscopy): 100%; H NMR (500.2 MHz,
CD2Cl2): d=13.3 (d, JACHTUNGTRENNUNG
(P,H)=14.7 Hz, 1H; C1H), 6.5–7.4 ppm (m, 48H;
Ph, NH, C5H, and C3H), 2.2 (br, 2H; NHCH2CH2CH2CH3), 0.5–1.0 ppm
(m, 7H; NHCH2CH2CH2CH3); 31P{1H} NMR (202.5 MHz, CD2Cl2): d=
10.3 (s; CPPh3), ꢀ2.2 ppm (s; OsPPh3). Disappointingly, the poor solubil-
ity of compound 8 prevented its 13C{1H} NMR characterization. HRMS
(ESI): m/z calcd for C65H58N3S2P3Os: 1229.2900 [M]+; found: 1229.2903.
[1] a) H.-J. Arpe, Industrial Organic Chemistry, Wiley-VCH, Weinheim,
2010; b) H.-G. Franck, J. W. Stadelhofer, Industrial Aromatic Chem-
istry, Springer-Verlag, Berlin and New York, 1987; c) F. Effenberger,
Angew. Chem. 1980, 92, 147; Angew. Chem. Int. Ed. Engl. 1980, 19,
151; d) D. E. Pearson, C. A. Buehler, Synthesis 1972, 533.
R=Ph (9): Yield (by NMR spectroscopy): 100%; 1H NMR (500.2 MHz,
CD2Cl2): d=14.5 (d,
13.4 Hz, 1H; NH), 9.2 (d, JAHCTNUGTRENNNUG
JACHTUNGTRENNUNG JACHTUNGTRENNUNG
(P,H)=15.3 Hz, 1H; C1H), 11.0 (d,
51H; Ph and C3H); 31P{1H} NMR (202.5 MHz, CD2Cl2): d=10.7 (s;
CPPh3), ꢀ3.1 ppm (s; OsPPh3). Disappointingly, the poor solubility of
compound 9 prevented its 13C{1H} NMR characterization. HRMS (ESI):
m/z calcd for C67H54N3S2P3Os: 1249.2587 [M]+; found: 1249.2592.
´
[2] For a review of cine-substitution reactions, see: J. Suwinski, K.
´
Swierczek, Tetrahedron 2001, 57, 1639.
[3] For recent reviews, see: a) M. Paneque, M. L. Poveda, N. Rendꢃn,
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Synthesis of [(SCN)2CATHUNGTRENU(NNG PPh3)2OsACHUTTNGRENNUG{CHCACHUTNGERTG(NNUN PPh3)CHCACHTNUGTREN(GUNN CHNnBu)}] (10):
nBuNH2 (30 ml, 0.30 mmol) was added to a solution of compound 2
(115 mg, 0.09 mmol) in CH2Cl2 (5 mL). The reaction solution was stirred
at RT for about 5 min under a nitrogen atmosphere, then under an
oxygen atmosphere or in air for a further 50 min. The solvent was re-
moved under vacuum and washed with n-hexane (3ꢂ2 mL). A paramag-
netic complex was collected as a green solid. Yield: 102 mg, 91%; HRMS
(ESI): m/z calcd for C65H57N3S2P3Os: 1229.2900 [M+H]+; found:
1229.2888.
Crystallographic analysis: Crystals of compounds 3, 5, and 10 that were
suitable for X-ray diffraction were grown from their solutions in CH2Cl2
that were layered with n-hexane; crystals of compound 2 that were suita-
ble for X-ray diffraction were grown from its solution in CHCl3 that was
layered withn-hexane. Selected crystals of compounds 2, 3, 5, and 10
were mounted on top of a glass fiber and transferred into a cold stream
of nitrogen. Single-crystal X-ray diffraction data were collected on an
Oxford Gemini S Ultra CCD Area Detector or a Bruker Apex CCD
area detector with graphite-monochromated MoKa radiation (l=
0.71073 ꢁ) or CuKa radiation (l=1.54178 ꢁ). All of the data were cor-
rected for absorption effects by using the multi-scan technique. The struc-
tures were solved by using direct methods, expanded by difference Fouri-
er syntheses, and refined by using full-matrix least-squares on F2 with the
Bruker SHELXTL (Version 6.10) program package. Non-H atoms were
refined anisotropically, unless otherwise stated. Hydrogen atoms were in-
troduced at their geometric positions and refined as riding atoms, unless
otherwise stated. For further details on the crystal data, data collection,
and refinements, see Table 3.
Computational details: The molecular geometries of the reactants, inter-
mediates, transition states, and products were optimized by using density
functional theory (DFT) calculations with the hybrid Becke3LYP
(B3LYP) method.[9] The 6–31 g** basis set was used for the C, O, N, and
H atoms, whilst the effective core potentials (ECPs) of Hay and Wadt
with the double-z valance basis set (LanL2DZ)[10] were chosen to de-
scribe the Os, S, P, and I atoms. In addition, polarization functions were
added for Os(zf)=0.886, I(zd)=0.266, P(zd)=0.340, S(zd)=0.421.[11] Fre-
quency analyses were performed to obtain the zero-point energies (ZPE)
and to identify all of the stationary point as minima (zero imaginary fre-
quencies) or transition states (one imaginary frequency) on the potential-
energy surfaces (PES). Intrinsic reaction coordinate (IRC) calculations
were also calculated for the transition states to confirm that such struc-
tures indeed connected two relevant minima.[12] To cut the computational
cost, the Ph3P group was modeled as PH3. All calculations were per-
formed with the Gaussian 03 software package.[13]
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10990
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Chem. Eur. J. 2013, 19, 10982 – 10991

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Received: April 12, 2013
Published online: July 10, 2013
Chem. Eur. J. 2013, 19, 10982 – 10991
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10991