Cyclometalation of 2-vinylpyridine with MCl2(PPh 3)3 and MHCl(PPh3)3 (M = Ru, Os)

Article abstract of DOI:10.1021/om0611305

Treatment of RuCl₃(PPh₃)₃ in benzene at room temperature with 2-vinylpyridine produces the vinylpyridine complex RuCl₂(2-CH₂=CHC₅H₄N)(PPh ₃)₃. In the presen

Full text of DOI:10.1021/om0611305

Organometallics 2007, 26, 2849-2860
2849
Cyclometalation of 2-Vinylpyridine with MCl2(PPh3)3 and
MHCl(PPh3)3 (M ) Ru, Os)
Li Zhang, Li Dang, Ting Bin Wen, Herman H.-Y. Sung, Ian D. Williams,
Zhenyang Lin,* and Guochen Jia*
Department of Chemistry, The Hong Kong UniVersity of Science and Technology, Clear Water Bay,
Kowloon, Hong Kong
ReceiVed December 14, 2006
Treatment of RuCl2(PPh3)3 in benzene at room temperature with 2-vinylpyridine produces the
vinylpyridine complex RuCl2(2-CH2dCHC5H4N)(PPh3)2. In the presence of Cs2CO3, RuCl2(PPh3)3 reacts
with 2-vinylpyridine at room temperature to give the cyclometalated complex RuCl(CHdCHC5H4N)-
(CH2dCHC5H4N)(PPh3), which is also produced from the reaction of RuHCl(PPh3)3 with 2-vinylpyridine.
OsCl2(PPh3)3 reacts with 2-vinylpyridine/Cs2CO3 at room temperature to give the analogous cyclometalated
complex OsCl(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3). In the presence of NaBF4, the reaction produces
[Os(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3)2]BF4. The dihydrogen complex Os(H2)Cl(CHdCHC5H4N)-
(PPh3)2 is produced from the reaction of OsHCl(PPh3)3 with 2-vinylpyridine. The mechanism of the
cyclometalation reactions has been investigated by computational chemistry.
or olefins,7 arylation of aromatic ketones with arylboronates,8
carbonylation of arenes9 and alkenes,10 and allylation of
2-pyridylarenes with allyl acetates.11 In view of the increasing
interest in catalytic reactions involving cyclometalated ruthenium
species, it is of interest to see how the ligand environment
around ruthenium may affect the cyclometalation process. To
this end, we have studied the cyclometalation reactions of
2-vinylpyridine with RuCl2(PPh3)3 and RuHCl(PPh3)3. For
comparison, the reactions of 2-vinylpyridine with OsCl2(PPh3)3
and OsHCl(PPh3)3 have also been investigated.
Introduction
Cyclometalation through C-H bond activation is a very
important process, due to its relevance to selective activation
and functionalization of hydrocarbons.1 Cyclometalated com-
plexes have also found increasing applications in catalysis,2
organometallic chemistry, and materials sciences.3
Like many other transition-metal complexes, ruthenium
complexes4 can also effect cyclometalation reactions involving
C-H bond activation. Recently, there have been much activity
in the development of catalytic reactions involving cyclometa-
lation on ruthenium. These studies have led to the discovery of
a number of interesting reactions involving cyclometalation of
C-H bonds on the ruthenium center. These include additions
of the C-H bonds of aromatics and olefins to unsaturated
substrates,5 coupling reactions of aryl halides with aromatics6
Cyclometalation reactions of 2-vinylpyridine have been
reported previously with metal complexes of Pd,12 Pt,13 Ir,14
Rh,15-17 Co,18 Re,19,20 Ru21-23 and Os.21,24-28 In the cases of
ruthenium and osmium, cyclometalation of 2-vinylpyridine has
(6) See for example,: (a) Ackermann, L. Org. Lett. 2005, 7, 3132. (b)
Oi, S.; Aizawa, E.; Ogino, Y.; Inoue, Y. J. Org. Chem. 2005, 70, 3113. (c)
Oi, S.; Ogino, Y.; Fukita, S.; Inoue, Y. Org. Lett. 2002, 4, 1783. (d) Oi, S.;
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S. J. Am. Chem. Soc. 2003, 125, 1698.
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Matsuo, T.; Fukuyama, T.; Muri, S. J. Org. Chem. 2003, 68, 7538. (c)
Chatani, N.; Yorimitsu, S.; Asaumi, T.; Kakiuchi, F.; Murai, S. J. Org.
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10.1021/om0611305 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 04/28/2007

2850 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
Scheme 1
Figure 1. Molecular structure of RuCl2(2-CH2dCHC5H3N)
(PPh3)2 (2).
Scheme 2
been observed in the reactions of 2-vinylpyridine with com-
plexes such as RuH4(PhP(CH2CH2CH2PCy2)2),22 [RuHCl(P-
iPr3)2]2,23 Ru(R)Cl(CO)(PiPr3)2 (R ) Ph, CHdCHPh),21 Os-
(R)Cl(CO)(PiPr3)2 (R ) Ph, CHdCHPh),21 Os3(CO)10(MeCN)2,24
OsH6(PiPr3)2,25 OsH2Cl2(PiPr3)2,26and OsH3(SnPh2Cl)(CH2dCHP-
iPr2)(PiPr3).27 However, the reactions of MCl2(PPh3)3 and MHCl-
(PPh3)3 (M ) Ru, Os) with 2-vinylpyridine have not been
reported, despite the fact that RuCl2(PPh3)3 is known to promote
the coupling reactions of 2-alkenylpyridines with aryl bromides
(the Heck reaction), for which cyclometalation of C-H bonds
Figure 2. Molecular structure of RuCl(2-CHdCHC5H3N)(2-CH2d
CHC5H3N)(PPh3) (3A).
of alkenylpyridines on a Ru(II) or Ru(0) center has been
suggested as one of the key steps.7
Results and Discussion
Reaction with RuCl2(PPh3)3. Treatment of RuCl2(PPh3)3 (1)
in benzene at room temperature with 2-vinylpyridine produced
a brownish yellow solution along with a yellow precipitate, from
which the vinylpyridine complex RuCl2(2-CH2dCHC5H4N)-
(PPh3)2 (2) can be isolated as a yellow solid in 81% (Scheme
1). Complex 2 is also produced if the reaction is carried out in
dichloromethane.
The structure of 2 has been confirmed by an X-ray diffraction
study. The crystallographic details, selected bond distances and
angles are given in Tables 1 and 2, respectively. The X-ray
structure shown in Figure 1 clearly reveals that the complex is
a neutral molecule with two trans PPh3 ligands, two cis
chlorides, and an η3-vinylpyridine ligand coordinated to ruthe-
nium through both the N atom and the olefinic double bond.
The complex adopts a distorted-octahedral structure with the
two chlorides, N, and the olefinic double bond in the same plane.
The CH2dCH vector is essentially perpendicular to the equato-
rial plane: i.e., parallel with the Ru-P bonds. The Ru-C (2.181-
(4) and 2.188(4) Å) and C-C bond distances associated with
(20) Ozerov, O. V.; Pink, M.; Walson, L. A.; Caulton, K. G. J. Am.
Chem. Soc. 2004, 126, 2105.
(21) Buil, M. L.; Esteruelas, M. A.; Goni, E.; Oliva´n, M.; On˜ate, E.
Organometallics 2006, 25, 3076.
(22) Jia, G.; Meek, D. W.; Gallucci, J. C. Organometallics 1990, 9, 2549.
(23) Coalter, J. N., III; Streib, W. E.; Caulton, K. G. Inorg. Chem. 2000,
39, 3749.
(24) (a) Wong, W.-Y.; Wong, W.-T. J. Organomet. Chem. 1996, 513,
27. (b) Burgess, K.; Holden, H. D.; Johnson, B. F. G.; Lewis, J.; Hursthouse,
M. B.; Walker, N. P. C.; Deeming, A. J.; Manning, P. J.; Peters, R. J.
Chem. Soc., Dalton Trans. 1985, 85.
(25) Barrio, P.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004, 23,
3627.
(26) Esteruelas, M. A.; Ferna´ndez-Alvarez, F. J.; Oliva´n, M.; On˜ate, E.
J. Am. Chem. Soc. 2006, 128, 4596.
(27) Eguillor, B.; Esteruelas, M. A.; Oliva´n, M.; On˜ate, E. Organome-
tallics 2005, 24, 1428.
(28) Examples of cyclometalation on osmium with other substrates: (a)
Esteruelas, M. A.; Herna´ndez, Y. A.; Lo´pez, A. M.; Oliva´n, M.; On˜ate, E.
Organometallics 2005, 24, 5989 and references therein. (b) Esteruelas, M.
A.; Lo´pez, A. M. Organometallics 2005, 24, 3584. (c) Esteruelas, M. A.;
Lledos, A.; Oliva´n, M.; On˜ate, E.; Tajada, M. A.; Ujaque, G. Organome-
tallics 2003, 22, 3753.

Cyclometalation of 2-Vinylpyridine
Organometallics, Vol. 26, No. 11, 2007 2851
Table 1. Crystallographic Data and Structure Refinement Details for RuCl2(2-CH2dCHC5H3N)(PPh3)2 (2),
RuCl(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3) (3A), OsCl(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3) (7B), and
[Os(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3)2]BF4 (8)
2
3A
7B
8
formula
mol wt
symmetry
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C44H39Cl4NP2Ru
886.57
monoclinic
P21/n
13.4753(8)
13.1464(8)
21.8713(13)
90
91.0610(10)
90
3873.9(4)
4
1.520
0.797
3.5-50
19 444
C32H28ClN2PRu
608.05
triclinic
P1h
9.3139(11)
14.6492(18)
19.876(2)
99.525(2)
97.661(2)
91.188(2)
2648.1(6)
4
1.525
0.778
3.2-52
27 552
10367
667/0
0.953
0.0447
C39H36ClN2OsP
789.32
triclinic
P1h
9.9664(12)
10.2744(13)
16.463(2)
82.292(2)
82.888(2)
74.077(2)
1599.8(3)
2
1.639
4.150
4.6-50
10 585
5553
398/0
1.040
0.0381
C52H47BCl4F4N2OsP2
1180.67
triclinic
P1h
11.4371(7)
13.5518(8)
16.7303(10)
73.1180(10)
78.7380(10)
74.7740(10)
2374.3(2)
2
Z
D
calcd, g cm-3
1.652
3.033
3.2-50
15 016
8184
595/0
1.004
0.0339
µ, mm-1
2θ range, deg
no. of data collected
no. of unique data
no. of params/restraints
goodness of fit on F2
R1 (I > 2σ(I))
6795
469/18
1.085
0.0568
0.1192
0.987/-0.805
wR2 (all data)
0.0982
1.008/-0.680
0.0777
2.082/-1.385
0.0783
2.679/-1.094
peak/hole, e Å-3
Table 2. Selected Bond Distances (Å) and Angles (deg) for
the Ru(CH2dCH) unit are normal compared with those of
reported ruthenium-olefin complexes29 and show little asym-
metry in the binding of the olefin.
RuCl2(2-CH2dCHC5H3N)(PPh3)2 (2)
Bond Distances
Ru(1)-C(7)
Ru(1)-N(1)
Ru(1)-Cl(2)
Ru(1)-P(2)
2.181(4)
2.056(3)
2.436(1)
2.377(1)
Ru(1)-C(8)
Ru(1)-Cl(1)
Ru(1)-P(1)
C(7)-C(8)
2.188 (4)
2.427(1)
2.426(1)
1.385(5)
The solid-state structure is supported by the solution NMR
spectroscopic data. In particular, the 1H NMR spectrum in CD2-
Cl2 shows the 1H signals of coordinated CHdCH2 at 3.47 (CH2),
3.73 (CH2), and 4.59 ppm (CH). In the 13C{1H} NMR spectrum
(in CD2Cl2), the signals of coordinated CHdCH2 were observed
at 53.3 (CH2) and 64.8 ppm (CH). The 31P{1H} NMR spectrum
shows two doublets at 37.0 and 22.2 ppm with a J(PP) coupling
of 347.5 Hz. Observation of two 31P signals for 2 is expected,
due to the unsymmetric nature of the olefinic ligand.
Bond Angles
C(7)-Ru(1)-C(8)
C(7)-Ru(1)-N(1)
C(7)-Ru(1)-P(1)
C(7)-Ru(1)-P(2)
C(7)-Ru(1)-Cl(2)
C(8)-Ru(1)-N(1)
C(8)-Ru(1)-P(1)
C(8)-Ru(1)-P(2)
P(1)-Ru(1)-P(2)
36.9(1)
64.2(1)
110.6(1)
78.8(1)
111.3(1)
85.5(1)
81.0(1)
N(1)-Ru(1)-Cl(1)
N(1)-Ru(1)-P(1)
N(1)-Ru(1)-P(2)
Cl(1)-Ru(1)-Cl(2)
Cl(1)-Ru(1)-P(1)
Cl(1)-Ru(1)-P(2)
Cl(2)-Ru(1)-P(1)
Cl(2)-Ru(1)-P(2)
89.09(9)
91.16(9)
93.74(9)
95.50(3)
86.45(3)
85.53(3)
89.72(3)
86.04(3)
When the reaction was carried out in CH2Cl2 in the presence
of Cs2CO3 and NaBF4 at room temperature (Scheme 1), HCl
was eliminated and cyclometalation of 2-vinylpyridine occurred
to give RuCl(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3) (3). Ini-
tially, we thought that the NaBF4 might facilitate the cyclom-
etalation through formation of NaCl. However, further study
shows that the base Cs2CO3 is required, while NaBF4 is not
necessary for the cyclometalation reaction. In situ NMR
experiments indicate that the reaction of 1 with 2-vinylpyridine
in the presence of Cs2CO3 initially produces complex 2 as the
dominant product, then a mixture of 2 and 3, and eventually 3
only. The observation implies that complex 3 is formed from
complex 2. Indeed, isolated 2 can be converted to 3 when treated
with CsCO3 and additional 2-vinylpyridine (Scheme 1).
The cyclometalated product 3 is found as a mixture of two
isomers in a 1:1 ratio, as indicated by its NMR data (in
dichloromethane). The presence of both 2-vinylpyridine and a
cyclometalated vinylpyridine in complex 3 as ligands is sup-
107.5(1)
170.53(4)
Table 3. Selected Bond Distances (Å) and Angles (deg) for
RuCl(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3) (3A)
Bond Distances
Ru(1)-C(18)
Ru(1)-N(2)
Ru(1)-C(28)
Ru(1)-P(1)
C(27)-C(28)
2.018(4) Ru(1)-N(1)
2.108(3) Ru(1)-C(27)
2.171(4) Ru(1)-Cl(1)
2.291(1) C(17)-C(18)
1.376(5)
2.129(3)
2.151(4)
2.533(1)
1.335(5)
Bond Angles
C(18)-Ru(1)-N(1)
C(18)-Ru(1)-N(2)
C(18)-Ru(1)-P(1)
C(18)-Ru(1)-C(27)
N(1)-Ru(1)-N(2)
N(1)-Ru(1)-Cl(1)
N(1)-Ru(1)-P(1)
N(2)-Ru(1)-P(1)
N(2)-Ru(1)-Cl(1)
77.1(1)
89.8(1)
86.0(1)
80.6(2)
96.3(1)
87.30(8)
95.02(8)
166.70(9)
82.24(8)
C(27)-Ru(1)-C(28)
37.1(1)
64.3(1)
102.5(1)
C(27)-Ru(1)-N(2)
C(27)-Ru(1)-P(1)
C(27)-Ru(1)-Cl(1) 110.3(1)
C(28)-Ru(1)-N(2)
C(28)-Ru(1)-P(1)
C(28)-Ru(1)-Cl(1)
Cl(1)-Ru(1)-P(1)
82.9(1)
87.2(1)
82.4(1)
105.26(3)
1
ported by the H and 13C NMR data. The existence of two
isomers is clearly indicated by the observations of two singlet
3A is a pseudo-octahedral complex with Cl trans to the η1-
Ru-C(vinyl) group, the η2-olefin of the neutral 2-vinylpyridine
trans to N of the vinylpyridine anion, and PPh3 trans to N of
2-vinylpyridine. The olefinic group CHdCH2 is oriented in such
a way that the CH2 is closer to the chloride ligand. The structural
data associated with Ru(η2-CH2dCH) are similar to those of 2,
and the structural data associated with Ru(η1-CHdCH) are
similar to those of RuCl(CHdCHC6H4N)(PiPr3)2.23
31P signals at 48.5 and 47.7 ppm in the 31P{1H} NMR spectrum
1
and two sets of H and 13C signals of Ru(CHdCH) and Ru-
(η2-CH2dCH) in the 1H and 13C{1H} NMR spectra. The
structure of one of the isomers, isomer 3A, has been determined
by X-ray diffraction (see Table 1). A view of the molecular
structure of 3A is shown in Figure 2, and selected bond distances
and angles are given in Table 3. As shown in Figure 2, isomer
In view of the similarity of the NMR data of 3A and 3B, it
is reasonable to assume that isomer 3B has a coordination sphere
(29) Jazzar, R. F. R.; Mahon, M. F.; Whittlesey, M. K. Organometallics
2001, 20, 3745.

2852 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
Scheme 3
Scheme 4
similar to that of isomer 3A. A structure in which the olefinic
group is oriented in such a way that the CH is closer to the
chloride ligand can be proposed for 3B. As will be discussed
below, the structure of an osmium complex with a structure
similar to that of 3B has been confirmed by an X-ray study.
During the course of this work, Esteruelas et al. reported the
synthesis of the osmium complex OsCl(CHdCHC5H4N)(CH2d
CHC5H4N)(PiPr3), an analogue of complex 3, from the reaction
of OsH2Cl2(PiPr3)2 with 2-vinylpyridine.26 The complex OsCl-
(CHdCHC5H4N)(CH2dCHC5H4N)(PiPr3) also shows similar
isomerism. Consistent with the proposed structures, NOE effects
were observed for one of the 1H signals of CH2 in complex 3B
possible outcomes for the reaction. For example, RuHCl(PPh3)3
may react with 2-vinylpyridine to give a cyclometalated complex
by elimination of H2 or HCl. Since the complex RuHCl(CO)-
(PPh3)3 is known to undergo insertion reaction with 2-vinylpy-
ridine,30 reaction of RuHCl(PPh3)3 with 2-vinylpyridine may
also give an insertion product. Treatment of RuHCl(PPh3)3 (4)
in benzene with 2-vinylpyridine produced 2-ethylpyridine and
complex 3 (Scheme 3), which was also produced from the
reaction of RuCl2(PPh3)3 with 2-vinylpyridine in the presence
of Cs2CO3 (see preceding subsection).
As mentioned previously, elimination of HCl was observed
in the reactions of RuCl2(PPh3)3 with 2-vinylpyridine in the
presence of the base Cs2CO3. In order to see if a similar reaction
may also occur for the reactions of RuHCl(PPh3)3 with
2-vinylpyridine, we have carried out the reaction of RuHCl-
(PPh3)3 with 2-vinylpyridine in the presence of Cs2CO3 and Cs2-
CO3/NaBF4. In both cases, the reaction also produced complex
3 and 2-ethylpyridine, suggesting that the base has no effect on
the course of the reaction.
A plausible mechanism for the formation of 3 and 2-eth-
ylpyridine from the reaction of RuHCl(PPh3)3 (4) with 2-vi-
nylpyridine is shown in Scheme 4. The reaction may initially
produce the olefin complex D. Complex D could undergo a
cyclometalation reaction to give the dihydrogen complex E,
which loses the dihydrogen ligand to generate intermediate B,
which reacts further with 2-vinylpyridine to give complex 3.
Intermediate B is structurally related to the cyclometalated
complex RuCl(CHdCHC6H4N)(PiPr3)2, which has been previ-
1
and for the H signal of CHdCH2 in complex 3A when the
RuCH signals in 3B and 3A were irradiated.
Scheme 2 shows a plausible mechanism for the formation of
3. Complex 2 can undergo a C-H oxidative addition reaction
to give intermediate A, which could eliminate HCl with the
help of the base Cs2CO3 to give intermediate B. Complex 3
can then be generated by an addition and substitution reaction
of 2-vinylpyridine with intermediate B. Alternatively, complex
3 may be formed by initial formation of the cationic species
[RuCl(CH2dCHC5H4N)2(PPh3)2]+ (C) followed by direct depro-
tonation of the coordinated olefin ligand. However, we feel that
the direct deprotonation process is unlikely, because the reaction
rate is not significantly different in either the presence or absence
of NaBF4. If the direct deprotonation process is involved, one
would expect that the reaction should proceed more quickly in
the presence of NaBF4, because NaBF4 can help to form cationic
species.
Reaction of RuHCl(PPh3)3. The reaction of RuHCl(PPh3)3
with 2-vinylpyridine is interesting, because there are several
(30) Hiraki, K.; Ochi, N.; Sasada, Y.; Hayashida, H.; Fuchita, Y.;
Yamanaka, S. J. Chem. Soc., Dalton Trans. 1985, 873.

Cyclometalation of 2-Vinylpyridine
Organometallics, Vol. 26, No. 11, 2007 2853
Table 4. Selected Bond Distances (Å) and Angles (deg) for
OsCl(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3) (7B)
Bond Distances
Os(1)-C(8)
Os(1)-C(18)
Os(1)-N(11)
Os(1)-P(1)
C(7)-C(8)
2.040(6) Os(1)-C(17)
2.129(6) Os(1)-N(1)
2.098(4) Os(1)-Cl(1)
2.298(1) C(17)-C(18)
1.339(9)
2.166(6)
2.149(5)
2.510(1)
1.395(9)
Bond Angles
C(8)-Os(1)-N(1)
C(8)-Os(1)-C(18)
C(8)-Os(1)-Cl(1)
C(17)-Os(1)-N(11)
C(17)-Os(1)-Cl(1)
75.9(2)
81.7(3)
160.9(2)
64.7(2)
79.8(2)
C(8)-Os(1)-N(11)
89.9(2)
113.5(2)
96.4(2)
37.9(2)
105.6(2)
157.6(2)
95.9(2)
93.1(1)
170.1(1)
C(8)-Os(1)-C(17)
C(8)-Os(1)-P(1)
C(17)-Os(1)-C(18)
C(17)-Os(1)-P(1)
C(18)-Os(1)-N(1)
N(1)-Os(1)-N(11)
N(1)-Os(1)-P(1)
N(11)-Os(1)-P(1)
C(18)-Os(1)-Cl(1) 115.1(2)
C(18)-Os(1)-P(1)
N(1)-Os(1)-Cl(1)
Cl(1)-Os(1)-P(1)
89.9(2)
87.0(1)
92.95(5)
ously isolated by Caulton et al. from the reaction of [RuHCl-
(PiPr3)2)]2 with 2-vinylpyridine.23
Figure 3. Molecular structure of OsCl(2-CHdCHC5H3N)(2-CH2d
CHC5H3N)(PPh3) (7B).
Intermediate D can also undergo an insertion reaction to give
the alkyl complex F, which may react with H2 (released from
the formation of B from E) to give the dihydrogen complex G.
G can undergo intramolecular hydrogen transfer reaction to give
H, which can react with 2-vinylpyridine to yield 2-ethylpyridine
and regenerate D. Dihydrogen complexes E and G are reason-
able species, as we have isolated the related dihydrogen complex
OsCl(H2)(2-CHdCHC5H4N)(PPh3)2 from the reaction of OsH-
Cl(PPh3)3 with 2-vinylpyridine (see below). Intramolecular
hydrogen transfer from H2 to a cis-alkyl ligand has been
proposed previously in the mechanisms of catalytic hydrogena-
tion reactions of olefins and alkynes.31 Unfortunately, we have
failed to identify any of the intermediates proposed in
Scheme 4.
Reaction with OsCl2(PPh3)3. To gain more insight into the
cyclometalation reactions of ruthenium complexes, we have
investigated the reactions of 2-vinylpyridine with OsCl2(PPh3)3
and OsHCl(PPh3)3, with a view to detecting or isolating some
osmium complexes structurally related to the intermediates
proposed for the ruthenium-mediated reactions.
Figure 4. Molecular structure of the cation [Os(CHdCHC5H3N)-
(2-CH2dCHC5H3N)(PPh3)2]+ of complex 8.
The course of the reaction of 2-vinylpyridine with OsCl2-
(PPh3)3 (5) in the presence of Cs2CO3 was monitored by 31P-
{1H} NMR. The reaction of OsCl2(PPh3)3 with excess 2-vi-
nylpyridine in the presence of Cs2CO3 initially generated free
PPh3 and several other phosphorus-containing species having
doublet 31P{1H} signals, which could not be separated or
identified. After 4 h, the in situ 31P NMR spectrum mainly
showed a singlet signal at -6 ppm for PPh3, two doublet signals
at -7.9 (d, J(PP) ) 15.2 Hz) and -11.7 (d, J(PP) ) 15.2 Hz)
ppm, and a singlet signal at -22.6 ppm. After 8 h, the doublet
signals at -7.9 (d, J(PP) ) 15.2 Hz) and -11.7 ppm (d, J(PP)
) 15.2 Hz) disappeared and the singlet signal at -22.6 ppm
remained. At this time, two singlets at 0.3 and -4.9 ppm
appeared. After 24 h, the singlet signal at -22.6 ppm also
disappeared, and only the two singlet signals at 0.3 and -4.9
ppm remained. These observations suggest that the complex
with a 31P chemical shift of -22.6 ppm is an intermediate for
the formation of complexes with the 31P shifts of 0.3 and -4.9
ppm.
The compounds with 31P signals at 0.3 and -4.9 ppm were
isolated from a preparative-scale reaction and identified by NMR
and MS to be the two isomers of the cyclometalated complex
7, an osmium analogue of the ruthenium complex 3. The
structure of 7B has been confirmed by X-ray diffraction.
Selected bond distances and angles are given in Table 4. As
shown in Figure 3, the coordination sphere of osmium in 7B is
similar to that of ruthenium in 3A, except that the olefinic group
CHdCH2 is oriented in such a way that the CH2 is closer to
the chloride ligand in 3A, while the olefinic group is oriented
in such a way that the CH is closer to the chloride ligand in
7B. Determination of the X-ray structures of 3A and 7B provide
strong support for the proposition that the two isomers observed
for 3 and 7 are due to the difference in the orientation of the
olefinic group CHdCH2. Complex 7 is closely related to
Esteruelas’ complex OsX(CHdCHC5H4N)(CH2dCHC5H4N)(Pi-
Pr3) (X ) Cl, OTf).26 The two isomers of 7 are produced in a
(31) (a) Liu, S. H.; Lo, S. T.; Wen, T. B.; Zhou, Z. Y.; Lau, C. P.; Jia,
G. Organometallics 2001, 20, 667. (b) Tenorio, M. J.; Puerta, M. C.;
Valerga, P. J. Chem. Soc., Chem. Commun. 1993, 1750. (c) Espuelas, J.;
Esteruelas, M. A.; Lahoz, F. J.; Oro, L. A.; Valero, C. Organometallics
1993, 12, 663. (d) Bianchini, C.; Meli, A.; Peruzzini, M.; Frediani, P.;
Bohanna, C.; Esteruelas, M. A.; Oro, L. A. Organometallics 1992, 11, 138.
(e) Bianchini, C.; Bohanna, C.; Esteruelas, M. A.; Frediani, P.; Meli, A.;
Oro, L. A.; Peruzzini, M. Organometallics 1992, 11, 3837. (f) Andriollo,
A.; Esteruelas, M. A.; Meyer, U.; Oro, L. A.; Sanchez-Delgado, R. A.;
Sola, E.; Valero, C.; Werner, H. J. Am. Chem. Soc. 1989, 111, 7431. (g)
Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics 1992 ,11, 3362.
(h) Crabtree, R. H. The Organometallic Chemistry of the Transition Metals,
3rd ed.; Wiley: New York, 2001; pp 237-238. (i) Chan, W. C.; Lau, C.
P.; Chen, Y. Z.; Fang, Y. Q.; Ng, S. M.; Jia, G. Organometallics 1997, 16,
34.

2854 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
Scheme 5
Table 5. Selected Bond Distances (Å) and Angles (deg) for
[Os(2-CHdCHC5H3N)(2-CH2dCHC5H3N)(PPh3)2]BF4 (8)
Scheme 6
Bond Distances
Os(1)-C(17)
Os(1)-C(27)
Os(1)-N(2)
Os(1)-P(2)
C(26)-C(27)
2.045(4) Os(1)-N(1)
2.205(4) Os(1)-C(26)
2.163(4) Os(1)-P(1)
2.419(1) C(16)-C(17)
1.427(6)
2.111(4)
2.212(4)
2.367(1)
1.357(6)
provide Na+, an electrophile that can remove the Cl- ligand
from the osmium center of 6 to give the cationic complex 8. It
should be noted that NaBF4 is not required for the cyclometa-
lation reaction to proceed to give 7. It is also interesting to note
that the analogous cationic ruthenium complex was not gener-
ated from the reaction of RuCl2(PPh3)3 with 2-vinylpyridine in
the presence of Cs2CO3/NaBF4. Apparently, Os has a higher
affinity for PPh3. Isolation of the cationic complex 8 from the
reaction of OsCl2(PPh3)3 with 2-vinylpyridine in the presence
of CsCO3 and NaBF4 supports the idea that cyclometalation
does not proceed through direct deprotonation.
Reaction of OsHCl(PPh3)3. In the reaction of RuHCl(PPh3)3
with 2-vinylpyridine, we assume that the reaction proceeds
through the dihydrogen intermediate RuCl(H2)(CHdCHC5H4N)-
(PPh3)2 (E) (Scheme 4). However, we have failed to isolate or
observe the intermediate. It is known that osmium dihydrogen
complexes could have higher thermal stability than analogous
ruthenium dihydrogen complexes. Thus, we have studied the
reaction of 2-vinylpyridine with OsHCl(PPh3)3 (9) with a hope
to isolate the dihydrogen complex OsCl(H2)(CHdCHC5H4N)-
(PPh3)2 (10).
Indeed, complex 10 was isolated in 63% yield as a yellow
solid by treatment of OsHCl(PPh3)3 (9) or OsH3Cl(PPh3)3 with
2-vinylpyridine (Scheme 6). Its structure can be readily assigned
on the basis of NMR spectroscopic data. The presence of the
dihydrogen ligand is confirmed by the observation of a hydride
signal at -6.96 ppm, which has a T1(min) value of 41.2 ms at
230 K and 300 MHz. The T1(min) value suggests that complex
10 can be classified as an elongated dihydrogen complex (or a
compressed dihydride complex).32 Reported osmium alkyl
dihydrogen complexes closely related to 10 include Os(H2)Cl-
Bond Angles
C(17)-Os(1)-N(1)
C(17)-Os(1)-C(27)
76.9(2)
94.7(2)
C(26)-Os(1)-N(2)
62.7(2)
37.7(2)
76.3(1)
110.2(1)
103.9(1)
94.18(9)
88.43(9)
105.0(1)
84.4(2)
C(26)-Os(1)-C(27)
C(26)-Os(1)-P(1)
C(26)-Os(1)-P(2)
N(1)-Os(1)-N(2)
N(2)-Os(1)-P(1)
N(2)-Os(1)-P(2)
C(27)-Os(1)-P(1)
C(27)-Os(1)-N(2)
C(17)-Os(1)-C(26) 117.0(2)
C(17)-Os(1)-P(1)
C(17)-Os(1)-P(2)
N(1)-Os(1)-P(1)
N(1)-Os(1)-P(2)
P(1)-Os(1)-P(2)
C(27)-Os(1)-P(2)
87.0(1)
90.5(1)
84.97(9)
84.60(9)
173.48(4)
81.2(1)
ratio of 63/37. NOE experiments suggest that the major isomer
is complex 7B.
We have also tried to isolate and identify the complex with
the 31P shift of -22.6 ppm. However, a pure sample of the
compound could not be obtained. We have only been able to
obtain a sample of the compound contaminated with ca. 22 mol
% of 7. The MS showed a peak with m/z 855.15, corresponding
1
to a formula of OsCl(CHdCHC5H4N)(PPh3)2. The H NMR
spectrum showed two characteristic signals at 11.14 and 6.84
ppm assignable to OsCHdCH and OsCHdCH, respectively.
On the basis of its MS and NMR data and the fact that it can
be converted to 7 in the presence of 2-vinylpyridine, we
tentatively assign the compound to the structure shown as 6.
This compound can be related to intermediate B proposed for
the ruthenium-mediated reactions.
When a mixture of OsCl2(PPh3)3 and 2-vinylpyridine in CH2-
Cl2 was stirred at room temperature in the presence of CsCO3
and NaBF4 for 24 h, the predominant product of the reaction is
the cationic complex 8 (Scheme 5). As indicated by an in situ
NMR experiment, a small amount of complex 7 was produced
from the reaction. Complex 8 was isolated as a yellow solid.
Its structure has also been confirmed by single-crystal X-ray
diffraction (Figure 4). Selected bond distances and angles are
given in Table 5. As shown in Figure 4, the complex has two
trans PPh3 ligands, two trans pyridines, and the η2-olefin is trans
to η1-vinyl. The solution NMR spectroscopic data are in
agreement with the solid-state structure.
(32) Reviews on dihydrogen complexes: (a) Crabtree, R. H. Angew.
Chem., Int. Ed. Engl. 1993, 32, 789. (b) Heinekey, D. M.; Oldham, W. J.,
Jr. Chem. ReV. 1993, 93, 913. (c) Jessop, P. G.; Morris, R. H. Coord. Chem.
ReV. 1992, 121, 155. (d) Esteruelas, M. A.; Oro, L. A. Chem. ReV. 1998,
98, 577. (e) Kubas, G. J. Dihydrogen and s-Bond Complexes; Kluwer
Academic/Plenum Press: New York, 2001. (f) Peruzzini, M.; Poli, R. Recent
AdVances in Hydride Chemistry; Elsevier: Amsterdam, 2001.
The cationic complex 8 is likely formed via substitution of
the chloride in 6 by 2-vinylpyridine. Obviously, NaBF4 can

Cyclometalation of 2-Vinylpyridine
Organometallics, Vol. 26, No. 11, 2007 2855
Figure 5. Energy profiles calculated for the reactions of the model complex RuHCl(CH2dCHC5H4N)(PH3)2 (D′): (a) cyclometalation
reaction to give the dihydrogen complex E′; (b) insertion reaction to generate the alkyl complex F′. The calculated relative free energies
and zero point energy corrected electronic energies (in parentheses) are given in kcal/mol. The relative electronic energies (kcal/mol) in
brackets were obtained on the basis of the ONIOM calculations, which consider the steric effect of the realistic PPh3 ligands.
(CHdCHC5H4N)(PiPr3)2,25 Os(H2)(SnClPh2)(CHdCHC5H4N)(Pi-
Pr3)2,27 Os(H2)ClH(PPh3)3,33 Os(H2)X(C6H4COMe)(PiPr3)2 (X
) Cl, F)34 and Os(H2)Cl(PPh3)(PCP).35
Theoretical Studies. Reaction of RuHCl(PPh3)3 with 2-vi-
nylpyridine in benzene produces both ethylpyridine and complex
3 (Scheme 3). Mechanistically, we believe that the reaction
initially produces the intermediate olefin complex D (Scheme
4). In order to generate both ethylpyridine, a hydrogenated
product, and complex 3, the intermediate complex D should
undergo simultaneously an insertion reaction to give the alkyl
complex F and a cyclometalation reaction to generate the
dihydrogen complex E (Scheme 4). In other words, only if both
of the two reactions occurred could ethylpyridine and complex
3 be produced. Energetically, the two reactions should be
comparable in their reaction barriers. To see if this is the case,
we carried out density functional calculations based on the model
complex RuHCl(CH2dCHC5H4N)(PH3)2 (D′). Figure 5 shows
the relevant energy profiles calculated for the two reactions.
Figure 6 gives the optimized structures with selected structural
parameters for the species involved in these two reactions. It
can be clearly seen from Figure 5 that the barrier difference
between the two reactions is within 3.0 kcal/mol, supporting
the mechanistic proposal shown in Scheme 4. The steric effect
(33) Yousufuddin, M.; Wen, T. B.; Mason, S. A.; McIntyre, G. J.; Jia,
G.; Bau, R. Angew. Chem., Int. Ed. 2005, 44, 7227.
(34) Barrio, P.; Esteruelas, M. A.; Lledos, A.; Onate, E.; Tomas, J.
Organometallics 2004, 23, 3008.
(35) Liu, S. H.; Lo, S. T.; Wen, T. B.; Williams, I. D.; Zhou, Z. Y.;
Lau, C. P.; Jia, G. Inorg. Chim. Acta 2002, 334, 122.

2856 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
Figure 6. Selected structural parameters (Å) calculated for the species shown in paths a and b of Figure 5.
missed from the small model PH3 calculations was studied with
two-layer ONIOM calculations using the real PPh3 ligand for
several selected species (see those data in brackets in Figure 5
for the relative electronic energies derived from the ONIOM
calculations and the Experimental Section for the computational
details). The results show that the use of PPh3 in the models
does not significantly alter the reaction barriers. More discussion
on the ONIOM results will be given below.
In Figure 5, path a gives the energy profile for the cyclom-
etalation reaction. Interestingly, the cyclometalation reaction is
a one-step process and the transition-state structure (TS(D′-E′)
)
corresponds to an oxidatively added species having a formal
Ru(IV) metal center. In this transition-state structure, the CR-
H1 and H2-H1 distances are 1.49 and 1.85 Å, respectively
(see Figure 6 for the atom-labeling scheme). Transition-state
structures that correspond to a Ru(IV) oxidatively added species

Cyclometalation of 2-Vinylpyridine
Organometallics, Vol. 26, No. 11, 2007 2857
Figure 7. Energy profile calculated for the conversion of 2′ to A′.
The calculated relative free energies and zero point energy corrected
electronic energies (in parentheses) are given in kcal/mol.
Scheme 7
have been found in many other Ru systems.36 Path b of Figure
5 gives the energy profile for the insertion reaction. Path b starts
with a trans-to-cis isomerization from D′ to D′′. The cis isomer
D′′ is slightly more stable than the trans isomer D′ when the
PH3 models were considered. It becomes slightly less stable
when the PPh3 models were considered. From D′′, olefin
insertion into the Ru-H bond occurs to give F′. We were unable
to locate a transition state directly linking D′ and F′. The failure
to locate a transition state directly linking D′ and F′ is
understandable because the hydride ligand and the η2-olefin
ligand are approximately perpendicular to each other, not in an
optimal (coplanar) arrangement for olefin insertion. In the cis
isomer D′′, the hydride ligand and the η2-olefin ligand are
approximately coplanar (Figure 6), facilitating the insertion
process.
Figure 8. Selected structural parameters (Å) calculated for the
species involved in the conversion of 2′ to A′.
give D2′. The intermediates D1′ and D2′ are both only slightly
less stable than D′. The high stability of the five-coordinate
intermediates can be understood as follows. In D′, the vinylpy-
ridine ligand is highly strained to secure that both the N atom
and the vinyl group are coordinated to the metal center. The
strained geometry of the vinylpyridine ligand can be clearly
seen in the calculated structure of D′ (Figure 6) and the X-ray
structure of 2 (Figure 1). In D1′ and D2′, there is no strain in
the ligand and the strength of the strong trans-influencing
metal-hydride bond is enhanced. From D2′, a ligand recoor-
dination occurs to give the cis isomer D′′.
In the trans to cis isomerization (D′ f D′′) (Figure 5b), a
ligand dissociation occurs to form the five-coordinate intermedi-
ate D1′ followed by a rotation of the vinylpyridine ligand to
(36) (a) Toner, A. J.; Grundemann, S.; Clot, E.; Limbach, H.-H.;
Donnadieu, B.; Sabo-Etienne, S.; Chaudret, B. J. Am. Chem. Soc. 2000,
122, 6777. (b) Ng, S. M.; Lam, W. H.; Mak, C. C.; Tsang, C. W.; Jia, G.;
Lin, Z.; Lau, C. P. Organomeatllics 2003, 22, 641. (c) Lam, W. H.; Jia,
G.; Lin, Z.; Lau, C. P.; Eisenstein, O. Chem. Eur. J. 2003, 9, 2775. (d)
Oxgaard, J.; Goddard, W. A., III. J. Am. Chem. Soc. 2004, 126, 442. (e)
Oxgaard, J.; Periana, R. A.; Goddard, W. A., III. J. Am. Chem. Soc. 2004,
126, 11658.
It is of interest to make a few comments on the ONIOM
results that consider the effect of PPh3. Comparing the data in
the parentheses with those in the brackets in Figure 5, we have
the following findings. In the PPh3 models, both the TS(D′-E′)

2858 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
and TS(D2′-D′′) transition states are relatively stabilized with
respect to the PH3 models. E′ is also stabilized, but to a less
significant extent. Interestingly, D′′ is relatively destabilized.
These results suggest that the steric effect from the PPh3 ligands
in both D′ and D′′ is more significant than that in other species
and that the steric effect in D′′ is the most significant.
Explanations of these unexpected results can be given as follows.
When both the N atom and the vinyl group are coordinated
with the metal center, the strained geometry of the vinylpyridine
ligands creates the most steric crowdedness in the coordination
sphere of the ligands, leading to the observation that D′ and
D′′ experience the most steric crowdedness. In D′′, the cis
arrangement of the two phosphine ligands further increases the
crowdedness in comparison with D′.
cyclometalatedcomplexRuCl(CHdCHC5H4N)(CH2dCHC5H4N)-
(PPh3), which is also produced from the reaction of RuHCl-
(PPh3)3 with 2-vinylpyridine. The reaction with RuHCl(PPh3)3
is kinetically more favorable than RuCl2(PPh3)3. OsCl2(PPh3)3
reacts with 2-vinylpyridine/Cs2CO3 at room temperature to give
the analogous cyclometalated complex OsCl(CHdCHC5H4N)-
(CH2dCHC5H4N)(PPh3). In the presence of NaBF4, the reaction
produces [Os(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3)2]BF4.
The dihydrogen complex Os(H2)Cl(CHdCHC5H4N)(PPh3)2 is
produced from the reaction of OsHCl(PPh3)3 with 2-vinylpy-
ridine. All of the cyclometalation reactions proceed through
initial oxidative addition of the cis C-H bond of vinylpyridine.
In the case of RuHCl(PPh3)3, both cyclometalation and insertion
reaction were found to have very similar reaction barriers.
Scheme 2 shows that the vinylpyridine dichloro complex
RuCl2(2-CH2dCHC5H4N)(PPh3)2 (2) can eliminate HCl in the
presence of a base. 2 is an analogue of D but does not contain
a hydride ligand. Therefore, we expect that the elimination of
HCl from 2 should follow a pathway similar to the conversion
of D to E, generating an intermediate having hydrochloride as
a ligand. Figure 7 shows the energy profile calculated for the
formation of the hydrochloride intermediate (A′) from the model
complex RuCl2(CH2dCHC5H4N)(PH3)2 (2′). Figure 8 gives the
optimized structures with selected structural parameters for the
species involved. Indeed, we see that the formation of the
intermediate (A′) having HCl as a ligand also corresponds to a
one-step process with a reaction barrier of 20.3 kcal/mol and
the transition-state structure (TS(2′-A′)) is an oxidatively added
species having a formal Ru(IV) metal center, similar to what
we found for the conversion of D to E (Figure 5). The
intermediate A′, which contains HCl as a ligand, is less stable
than 2′ by ca. 19.8 kcal/mol. Therefore, the presence of a base
is absolutely necessary to make the HCl elimination feasible.
In comparison to the conversion of D to E, the formation of A′
from 2′ has a much higher reaction barrier. The difference is
understandable in view of the fact that hydrochloride complexes
are rarely found while dihydrogen complexes are prevalent.37
It is also interesting to see that in the experiment E, which is
a dihydrogen complex, is ready to dissociate the dihydrogen
ligand to generate B (Scheme 4). However, elimination of HCl
from E does not occur, even in the presence of a base. To
understand the difference between the two processes, we
calculated the reaction energies of the H2 dissociation from E′
and the metathetical conversion of E′ to E′′, a species containing
HCl as a ligand (Scheme 7). From Scheme 7, we can conclude
that H2 can easily dissociate from E′, with a reaction free energy
of -6.6 kcal/mol. In E′, the H2 ligand is only weakly
coordinated to the metal center. The 16e species B′, which is
formed after the H2 dissociation, is relatively stable, due to the
presence of the π-donor chloride ligand. From Scheme 7, we
can also conclude that the formation of E′′ is not possible. E′′
is less stable than E′ by ca. 27 kcal/mol. It is therefore expected
that, even in the presence of a base, it is not possible to eliminate
HCl from E′ because the relevant precursor complex E′′ is very
unstable compared with E′.
Experimental Section
All manipulations were carried out under a nitrogen atmosphere
using standard Schlenk techniques, unless otherwise stated. Solvents
were distilled under nitrogen from sodium benzophenone (hexane,
ether, THF), sodium (benzene), or calcium hydride (CH2Cl2). The
starting materials RuCl2(PPh3)3,38 OsCl2(PPh3)3,39 RuHCl(PPh3)3,40
41
and OsH3Cl(PPh3)3 and OsHCl(PPh3)3 were prepared following
the procedures described in the literature. All other reagents were
used as purchased from Aldrich Chemical Co. Microanalyses were
performed by M-H-W Laboratories (Phoenix, AZ). H, 13C{1H},
and 31P{1H} NMR spectra were collected on a JEOL EX-400
spectrometer (400 MHz) or a Bruker ARX-300 spectrometer (300
MHz). 1H and 13C NMR shifts are relative to TMS, and 31P chemical
shifts are relative to 85% H3PO4. MS spectra were recorded on a
Finnigan TSQ7000 spectrometer.
1
RuCl2(CH2dCHC5H4N)(PPh3)2 (2). To a solution of RuCl2-
(PPh3)3 (0.40 g, 0.42 mmol) in benzene was added 2-vinylpyridine
(0.18 mL, 1.68 mmol). The reaction mixture was stirred at room
temperature for 30 min to give a brownish yellow solution with a
yellow precipitate. The volume of the mixture was reduced to half,
and the solid was collected by filtration, washed with diethyl ether
(10 mL), and dried under vacuum (0.19 g). The filtrate was
concentrated to ca. 1 mL under reduced pressure, and diethyl ether
(20 mL) was added to the residue with stirring to give additional
yellow solid, which was collected by filtration, washed with diethyl
ether (10 mL × 2), and dried under vacuum (84 mg). Total yield:
81%. Anal. Calcd for C43H37Cl2NRuP2: C, 64.42; H, 4.65; N, 1.75.
Found: C, 64.65; H, 4.80; N, 1.63. 31P{1H} NMR (121.5 MHz,
CD2Cl2): AB pattern, δ 37.0 (d), 22.2 (d), J(PP) ) 347.5 Hz). 1H
NMR (300.13 MHz, CD2Cl2): δ 8.25 (br, 6 H, PPh3), 7.23-7.36
(br m, 24 H, PPh3), 6.74 (t, J(HH) ) 7.4 Hz, 1 H, CH, py), 6.21
(d, J(HH) ) 5.2 Hz, 1 H, CH, py), 5.94 (t, J(HH) ) 6.4 Hz, 1 H,
CH, py), 5.64 (d, J(HH) ) 7.6 Hz, 1 H, CH, py), 4.59 (m, 1 H,
CHdCH2), 3.73 (m, 1 H, CHdCH2), 3.47 (d, J(HH) ) 7.3 Hz, 1
H, CHdCH2). 13C{1H} NMR (75.47 MHz, CD2Cl2): δ 163.87 (s,
C(ipso-py)), 147.32 (s, CH, py), 134.82-127.96 (m, PPh3), 133.58
(s, CH, py), 121.80 (s, CH, py), 119.39 (s, CH, py), 64.75 (s, CHd
CH2), 53.28 (s, CHdCH2, obscured by the CD2Cl2 resonance and
confirmed by H-13C COSY and DEPT-135).
1
RuCl(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3) (3A and 3B).
To a suspension of RuHCl(PPh3)3 (0.45 g, 0.48 mmol) in benzene
(20 mL) was added 2-vinylpyridine (0.31 mL, 2.87 mmol). The
reaction mixture was stirred at room temperature for 3 h to give a
clear yellow solution. The volume of the solution was concentrated
to ca. 1 mL under reduced pressure. Hexane (30 mL) was added
Conclusion
We have found that cyclometalation of 2-vinylpyridine with
MCl2(PPh3)3 and MHCl(PPh3)3 (M ) Ru, Os) can proceed at
room temperature. In the presence of Cs2CO3, RuCl2(PPh3)3
reacts with 2-vinylpyridine at room temperature to give the
(38) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth. 1970,
12, 237.
(39) Hoffmann, P. R.; Caulton, K. G. J. Am. Chem. Soc. 1975, 97, 4221.
(40) Hallman, R. S.; McGarvey, B. R.; Wilkinson, G. J. Chem. Soc. A
1968, 3143.
(37) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes; Kluwer
Academic/Plenum Publishers: New York, 2000.
(41) Ferrando, G.; Caulton, K. G. Inorg. Chem. 1999, 38, 4168.

Cyclometalation of 2-Vinylpyridine
Organometallics, Vol. 26, No. 11, 2007 2859
slowly with stirring to give a yellow solid, which was collected by
filtration. The solid was then stirred in 20 mL of diethyl ether cooled
with an ice bath for 10 min, collected on a filter frit, and dried
under vacuum, to give a mixture of isomers 3A and 3B in about a
1:1 ratio. Yield: 0.21 g, 71%. Anal. Calcd for C32H28ClN2RuP:
C, 63.21; H, 4.64; N 4.61; Found: C, 63.22; H, 4.43; N, 4.71.
31P{1H} NMR (121.5 MHz, CD2Cl2): δ 48.48 (s), 47.68 (s) (in
about 1:1 ratio). 1H NMR (300.13 MHz, CD2Cl2): δ 9.75 (d, J(HH)
) 7.8 Hz, 1 H, RuCHdCH of 3B), 9.49 (br s, 2 H, W1/2 ) 13.2
Hz, py), 8.98 (dd, J(HH) ) 7.6 Hz, J(PH) ) 3.2 Hz, 1 H, RuCHd
CH of 3A), 7.52-6.92 (m, 40 H, PPh3, py), 6.86-6.76 (m, 4 H,
py, RuCHdCH of 3 (the resonance of RuCHdCH of 3A appears
at ca. 6.77 and that of RuCHdCH of 3B at ca. 6.82, as confirmed
by 1H-1H COSY)), 6.67 (t, J(HH) ) 6.3 Hz, 2 H, py), 4.60-4.53
(m, 2 H, a doublet at ca. 4.58 ppm (CH2dCH of 3A) partially
overlapped with a triplet at ca. 4.55 ppm (CH2dCH of 3B), 4.12
(t, J(HH) ) 9.3 Hz, 1 H, CH2dCH of 3A), 3.92 (dd, J(HH) ) 8.1
Hz, J(PH) ) 4.8 Hz, 1 H, CH2dCH of 3A), 3.77 (dd, J(HH) )
8.5 Hz, J(PH) ) 5.3 Hz, 1 H, CH2dCH of 3B), 3.49 (d, J(HH) )
10.4 Hz, 1 H, CH2dCH of 3B). 13C{1H} NMR (75.47 MHz, CD2-
Cl2): δ 204.17 (d, J(PC) ) 10.9 Hz, RuCHdCH of 3B), 198.24
(d, J(PC) ) 15.2 Hz, RuCHdCH of 3A), 167.02, 166.47, 166.40,
165.75 (s, 4 C(ipso-py)), 152.65, 151.97 (s, 2 CH, py), 146.46,
145.94 (s, 2 CH, py), 136.05 (s, CH, py), 135.73 (s, 2 CH, py),
135.32 (s, CH, py), 134.89-127.26 (m, PPh3), 132.78, 129.58 (s,
2 CH, py), 122.53 (s, RuCHdCH of 3B), 121.71 (s, RuCHdCH
of 3A), 120.64, 119.98, 119.66, 118.54, 117.23, 117.18 (s, 6 CH,
py), 68.03 (s, CH2dCH), 67.48 (s, CH2dCH), 66.40 (s, CH2d
CH), 65.57 (s, CH2dCH).
mL to give a crystalline brick red precipitate. The crystalline brick
red precipitate was collected, washed with hexane (15 mL) twice,
and dried under vacuum. The NMR data shows that it is a mixture
of 7A and 7B in a ratio of 37/63. Yield: 249 mg (47%). Anal.
Calcd for C32H28N2ClPOs: C, 55.13; H, 4.05; N, 4.02. Found: C,
1
55.97; H, 4.41; N, 3.67. As indicated by H NMR, the sample
contains a small amount of hexane. Anal. Calcd for C32H28N2ClPOs‚
0.25C6H14: C, 56.35; H, 4.38; N, 3.87. MS (FAB): m/z 698 (M+),
663([M - Cl]+). 31P{1H} NMR (121.5 MHz, C6D6): δ 0.3 (s, 7B),
1
-4.9 (s, 7A). H NMR of 7 (300.13 MHz, C6D6; the number of
protons is not specified, because 7A and 7B are not present in
equimolar amounts): δ 10.51 (d, J(HH) ) 8.7 Hz, OsCHdCH of
7B), 10.08 (m, ortho CH of py of 7A and 7B), 9.90 (dd, J(HH) )
8.6 Hz, J(HP) ) 1.5 Hz, OsCHdCH of 7A), 7.61-7.60 (m, phenyl
and py), 7.30 (d, J(HH) ) 8.7 Hz, OsCHdCH of 7B), 7.11-6.89
(m, phenyl and py, OsCHdCH of 7A), 6.74-6.62 (m, py), 6.48
(d, J(HH) ) 7.8 Hz, py), 6.33-6.22 (m, py), 5.96 (m, py), 4.62 (d,
J(HH) ) 8.1 Hz, CH2dCH of 7A), 4.42 (m, CH2dCH of 7A and
7B), 3.98 (m, CH2dCH of 7A and 7B) and 3.54 (d, J(HH) ) 8.1
Hz, CH2dCH of 7B).
[Os(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3)2]BF4 (8). A mix-
ture of OsCl2(PPh3)3 (0.585 g, 0.558 mmol), NaBF4 (0.766 g, 6.98
mmol), Cs2CO3 (0.567 g, 1.74 mmol), and vinylpyridine (0.602
mL, 5.58 mmol) in DCM (30 mL) was stirred at room temperature.
The reaction mixture turned from green to brick red. After 24 h,
the inorganic solid was removed by filtration and the solvent was
removed under vacuum. The residue was extracted with methanol
(10 mL). The flask containing the methanol solution was stored in
an ice bath. After 3 h, a yellow powder precipitated from the
solution. The methanol was evaporated to half its original volume
to give more yellow powder. The yellow powder was collected by
filtration, washed with diethyl ether, and dried under vacuum. Yield,
0.26 g, 46%. Anal. Calcd for C50H43BF4N2P2Os: C, 59.41; H, 4.29;
N, 2.77. Found: C, 59.26; H, 4.66; N, 2.75. 31P{1H} NMR (121.5
MHz, CD2Cl2): δ 8.3 (d, J(PP) ) 234.5 Hz), 0.6 (d, J(PP) ) 234.6
Observation of 6. A mixture of OsCl2(PPh3)3 (0.798 g, 0.762
mmol), Cs2CO3 (0.620 g, 1.90 mmol), and 2-vinylpyridine (0.310
mL, 2.87 mmol) in DCM (50 mL) was stirred at room temperature.
The reaction mixture turned from green to brick red. After 4 h, the
31P{1H} signal of 6 appeared as a singlet at -22.6 ppm, together
with two doublet signals at -7.9 (d, J(PP) ) 15.2 Hz) and -11.7
ppm (d, J(PP) ) 15.2 Hz) and a singlet signal at -6.0 ppm for
PPh3 in the 31P NMR spectrum. After 8 h, the doublet signals at
-7.9 (d, J(PP) ) 15.2 Hz) and -11.7 ppm (d, J(PP) ) 15.2 Hz)
disappeared and the singlet signal at -22.6 ppm for 6 remained.
At this time, two singlet signals at 0.3 and -4.9 ppm also appeared.
The reaction was stopped by the removal of inorganic salts by
filtration and most of the solvent of DCM, at which point the 31P-
{1H} NMR spectrum showed five major peaks: a singlet signal at
-22.6 ppm for 6, a singlet signal at -6.0 ppm for PPh3, two singlet
signals at 0.3 and -4.9 ppm for 7, and a singlet signal at 24.8 ppm
for OdPPh3. To the filtrate was added a small amount of diethyl
ether to give a small amount of brown precipitate. The obtained
precipitate was a 82/18 mixture of 6 and 7. (The ratio varies
depending on when the reaction was stopped. The product might
be contaminated with other unknown byproducts, if the reaction
was stopped too early.) Spectroscopic data for 6 are as follows.
MS (FAB): m/z 855 (M+). 31P{1H} NMR (121.5 MHz, CDCl3):
δ -22.6. 1H NMR(300.13 MHz, CDCl3): δ 11.36 (br d, J(HH) )
8.1 Hz, 1 H, OsCHdCH), 8.55 (d, J(HH) ) 6.3 Hz, 1 H, py),
7.88-7.102 (m, PPh3 and py), 6.84 (d, J(HH) ) 7.8 Hz, 1 H,
OsCHdCH), 6.12 (t, J(HH) ) 6.9 Hz, 1 H, py).
OsCl(CHdCHC5H4N)(CH2dCHC5H4N)(PPh3) (7A and 7B).
A mixture of OsCl2(PPh3)3 (0.798 g, 0.762 mmol), Cs2CO3 (0.620
g, 1.90 mmol), and 2-vinylpyridine (0.310 mL, 2.87 mmol) in DCM
(50 mL) was stirred at room temperature. The color of the reaction
mixture turned from green to brick red. After 24 h, the inorganic
solid was removed by filtration and the volume of the mixture was
concentrated to ca. 5 mL under vacuum. To the filtrate was added
diethyl ether (30 mL) to give a brown precipitate. The brown
precipitate was filtered off. Addition of hexane (30 mL) to the
filtrate gave a brick red precipitate. The brick red precipitate was
removed by filtration, and the filtrate was concentrated to ca. 5
1
Hz). H NMR (300.13 MHz, CD2Cl2): δ 9.85 (d, 1 H, J(HH) )
8.3 Hz, 1 H, OsCHdCH), 8.48 (d, 1 H, J(HH) ) 5.5 Hz, 1 H, py),
8.07 (d, 1 H, J(HH) ) 5.1 Hz, 1 H, py), 7.07-7.55 (m, 33 H,
PPh3, py), 6.82 (m, 2 H, OsCHdCH, and py), 6.31 (d, 1 H, J(HH)
) 7.9 Hz, 1 H, py), 6.13 (d, 1 H, J(HH) ) 7.8 Hz, 1 H, py), 3.87
- 3.97 (m, 2 H, CH2dCH), 3.53-3.62 (m, 1 H, CH2dCH). 13C-
{1H} NMR (75.47 MHz, CD2Cl2): δ 169.9 (t, J(PC) ) 10.0 Hz,
OsCHdCH), 169.6 (s, C(ipso-py), 165.4, (s, C(ipso-py)), 150.4-
119.9 (m, PPh3, OsCHdCH, and other CH signals of py), 44.3 (d,
J(PC) ) 6.3 Hz, CH2dCH), 43.3 (d, J(PC) ) 4.3 Hz, CH2dCH).
OsCl(H2)(CHdCHC5H4N)(PPh3)2 (10). To a suspension of
OsH3Cl(PPh3)3 (0.60 g, 0.59 mmol) in benzene (10 mL) and CH2-
Cl2 (2 mL) was added 2-vinylpyridine (0.26 mL, 2.41 mmol) with
stirring. The reaction mixture turned to an orange solution after
ca. 2 min, which produced a yellow precipitate after stirring at room
temperature for 2 h. The solution was then concentrated to ca. 5
mL, and the yellow solid was collected on a filter frit, washed with
benzene (3 mL × 2), and dried under vacuum overnight (0.18 g).
The orange filtrate and the washing solution were combined and
concentrated to ca. 2 mL. Hexane (20 mL) was added to the residue
slowly with stirring to give a pale yellow precipitate. The solid
was collected by filtration, washed with diethyl ether (15 mL ×
2), and dried under vacuum to give additional yellow product (0.14
g). Total yield: 0.32 g, 63%. The complex could also be obtained
by reacting OsHCl(PPh3)3 with excess 2-vinylpyridine at room
temperature in benzene. Anal. Calcd for C43H38NClP2Os: C, 60.31;
H, 4.47; N, 1.64. Found: C, 60.11; H, 4.66; N, 1.61. 31P{1H} NMR
1
(121.5 MHz, CD2Cl2): δ 11.2 (s). H NMR (300.13 MHz, CD2-
Cl2): δ 9.14 (dt, J(HH) ) 8.9 Hz, J(PH) ) 3.9 Hz, 1 H, OsCHd
CH), 8.39 (d, J(HH) ) 6.1 Hz, 1 H, py), 7.40-7.46 (m, 12 H,
PPh3), 7.14-7.24 (m, 18 H, PPh3), 7.00 (t, J(HH) ) 7.4 Hz, 1 H,
py), 6.68 (d, J(HH) ) 8.9 Hz, 1 H, OsCHdCH), 6.62 (d, J(HH) )

2860 Organometallics, Vol. 26, No. 11, 2007
Zhang et al.
7.9 Hz, 1 H, py), 6.04 (t, J(HH) ) 6.4 Hz, 1 H, py), -6.96 (td,
J(PH) ) 11.9 Hz, J(HH) ) 3.9 Hz, 2 H, OsH2). 13C{1H} NMR
(75.47 MHz, CD2Cl2): δ 174.06 (t, J(PC) ) 8.2 Hz, OsCHdCH),
165.56 (s, C(ipso py)), 148.77 (s, CH, ortho py), 134.86 (s, CH,
para py), 134.45 (t, J(PC) ) 5.7 Hz) and 128.26 (t, J(PC) ) 4.6
Hz, CH of ortho and meta PPh3), 134.5 ppm (t, J(PC) ) 23.8 Hz,
the ipso carbon signal of the PPh3), 129.77 (s, para PPh3), 127.24
(s, OsCHdCH), 119.04 (s) and 116.83 (s, CH, meta-py). T1 (ms,
Os(H2), 300.13 MHz, CD2Cl2): 90.1 (298 K), 61.2 (273 K), 52.8
(262 K), 47.2 (252 K), 43.3 (241 K), 41.2 (230 K), 49.9 (220 K).
center.46 The 6-31G basis set was used for all of the other atoms.47
All of the calculations were performed with the Gaussian 0348
software package.
In most of our DFT calculations, we used PH3 as a model for
PPh3. To study the steric effect missed from the small-model
calculations, we performed two-layer ONIOM (B3LYP/BSI:HF/
Lanl2MB)49 calculations with the real PPh3 ligand for several
selected species. In the ONIOM calculations, the phenyl groups
on the phosphine ligand were treated as the second layer, while
the rest were treated as the first layer. BSI represents the basis set
described above.
Crystallographic Analysis of 2, 3A, 7B, and 8. All compounds
are sufficiently air stable to be mounted on glass fibers with epoxy
adhesive. The diffraction intensity data were collected with a Bruker
Smart APEX CCD diffractometer with graphite-monochromated
Mo KR radiation (λ ) 0.710 73 Å) at 100 K under a cold N2 stream.
Lattice determination and data collection were carried out using
SMART v.5.625 software. Data reduction and absorption correction
by empirical methods were performed using SAINT v 6.26 and
SADABS v 2.03, respectively. Structure solution and refinement
were performed using the SHELXTL v.6.10 software package. The
structures were all solved by direct methods. All of the structures
were refined smoothly, with the exception of 2, which showed
extensive phenyl ring disorder that was modeled with restraints.
Otherwise, all non-hydrogen atoms were refined anisotropically by
full-matrix least squares, with a riding model for the hydrogen
atoms.
Acknowledgment. This work was supported by the Hong
Kong Research Grant Council (Project No. 601505), National
Natural Science Foundation of China through the Outstanding
Young Investigator Award Fund (Project No. 20429201).
Supporting Information Available: CIF files giving X-ray
crystallographic data. This material is available free of charge via
the Internet at http://pubs.acs.org.
OM0611305
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Computational Details. Full geometry optimizations of all the
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density functional theory (DFT).42 Frequency calculations had also
been performed at the same level of theory to identify all the
stationary points as minima (zero imaginary frequency) or transition
states (one imaginary frequency) and to provide free energy at
298.15 K which includes entropic contributions by taking into
account the vibrational, rotational, and translational motions of the
species under consideration. Transition states were located using
the Berny algorithm. Intrinsic reaction coordinates (IRC)43 were
calculated for the transition states to confirm that such structures
are indeed connecting two relevant minima. The effective core
potentials (ECPs) of Hay and Wadt with double-ú valence basis
sets (LanL2DZ)44 were used to describe Ru, Cl, and P. Polarization
functions were also added for Ru (úf ) 1.235), Cl (úd ) 0.640),
and P (úd ) 0.387).45 The 6-311G(d,p) Pople basis set was used
for those C and H atoms that were directly bonded to the metal
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(c) Ananikov, V. P.; Szilagyi, R.; Morokuma, K.; Musaev, D. G.
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