Rearrangement of metallabenzynes to chlorocyclopentadienyl complexes

Article abstract of DOI:10.1021/om501181u

Treatment of the osmabenzyne complex Os{≡C-C(SiMe₃)=C(CH₃)-C(SiMe₃)=CH-}Cl₂(PPh₃)₂ with Mo(CO)₆ in refluxing benzene produced the η⁵-chlorocyclopentadienyl complex Os{

Full text of DOI:10.1021/om501181u

Article
pubs.acs.org/Organometallics
Rearrangement of Metallabenzynes to Chlorocyclopentadienyl
Complexes
Jiangxi Chen,†,‡ Ka-Ho Lee,† Tingbin Wen,† Feng Gao,† 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
‡Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen, China, 361005
S
* Supporting Information
ABSTRACT: Treatment of the osmabenzyne complex Os{C-
C(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PPh3)2 with Mo-
(CO)6 in refluxing benzene produced the η5-chlorocyclopenta-
dienyl complex Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3)
and Mo(CO)5(PPh3). A computational study suggests that the
chlorocyclopentadienyl complex is most likely produced via the
carbene intermediate Os{C(C(SiMe3)C(CH3)-C(SiMe3)CH−)}Cl2(CO)(PPh3) formed by a migratory insertion
reaction of the osmabenzyne complex Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(CO)(PPh3). DFT calculations show
that the relative thermal stability of metallabenzynes Os(C-CHCHCHCH)Cl2(L)2 and the corresponding isomeric
carbene complexes Os{C(−CHCHCHCH−)}Cl2(L)2 as well as the chlorocyclopentadienyl complexes Os(η5-
C5ClH4)Cl(L)2 (L = CO, phosphine, pyridine, amine) is strongly dependent on ligand L.
reactions of metallabenzenes to give cyclopentadienyl com-
plexes are well-documented.10 A theoretical study suggests that
steric effects involving the substituents (t-butyl, 1-adamantyl)
on the metallacycle play an important role in inducing the
conversion of osmabenzyne complexes Os{C-CHC(R)-
CHCH}Cl2(PPh3)2 (R = t-butyl, 1-adamantyl) to the
carbenes Os{C(−CHC(R)-CHCH−)}Cl2(PPh3)2.
It is known that migratory insertion reactions of carbyne
complexes Ln(R′)MCR to give carbene complexes LnM
CRR′ are also affected by both metals and ligands.11−14 Thus, it
would be of interest to study a similar effect for metallabenzyne
systems. However, experimental work in this direction is still
lacking, although, recently, Zhu and his co-workers have carried
out a theoretical study of ligand effects on the conversion of
metallanaphthalynes to indenylidene complexes.9b In our effort
to study the ligand effect on the conversion of osmabenzyne
complexes to carbene complexes, we have carried out ligand
substitution reactions of the osmabenzyne complex Os{C-
C(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PPh3)2 (1) with
PCy3, a strong σ-donating ligand, and CO, a strong π-accepting
ligand.
INTRODUCTION
■
There has been much interest in the chemistry of transition-
metal-containing metallaaromatic compounds. Transition-
metal-containing metallabenzenes,1,2 in particular, have at-
tracted considerable recent attention. These complexes are
interesting because they can display properties of both aromatic
organic compounds and organometallic compounds. A class of
metallaaromatics that are structurally closely related to
metallabenzenes are metallabenzynes,3 organometallic com-
pounds derived from formal replacement of a carbon atom in
benzyne by an isolobal transition-metal fragment. Compared
with that of metallabenzenes, the chemistry of metallabenzynes
is less developed. One of the major issues in the development
of metallabenzyne chemistry is to explore the chemical
properties of this interesting class of metallaaromatics. Previous
studies have shown that metallabenzynes can undergo electro-
philic substitution reactions to give new metallabenzynes,4,5
nucleophilic addition reactions to give metallabenzenes6 or
isometallabenzenes,7 and migratory insertion reactions to give
carbene complexes.8,9 In this work, we report a new
transformation of metallabenzynes, namely, the conversion of
metallabenzynes into chlorocyclopentadienyl complexes.
The reaction of 1 with PCy3 was first examined. Heating of a
mixture of osmabenzyne 115 and excess PCy3 in benzene at 80
°C for 12 h produced the osmabenzyne complex Os{C-
C(SiMe3)C(CH3)-C(SiMe3)CH−}Cl2(PCy3)2 (2), which
was isolated as a blue solid in 61% yield (Scheme 1). The
structure of 2 can be readily assigned based on its NMR
spectroscopic data. The 31P{1H} NMR spectrum (in CD2Cl2)
showed a singlet at −0.1 ppm. The 13C{1H} NMR spectrum
RESULTS AND DISCUSSION
■
Experimental Observations. We have recently shown that
the osmabenzyne complexes Os{C-CHC(R)-CHCH}-
Cl2(PPh3)2 (R = t-butyl, 1-adamantyl) could undergo migratory
insertion reactions to give the corresponding carbenes Os{
C(−CHC(R)-CHCH−)}Cl2(PPh3)2.8 These reactions
are interesting as they represent the only experimentally
observed examples of rearrangement of metallabenzynes to
carbene complexes. In contrast, analogous migratory insertion
Received: December 7, 2014
© XXXX American Chemical Society
A
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Treatment of the osmabenzyne complex Os{C-C-
(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) with Mo-
(CO)6 in refluxing benzene produced a mixture of species, from
which the unexpected η5-chlorocyclopentadienyl complex
Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) (3) and the
known complex Mo(CO)5(PPh3) (4)17 were isolated in
50.2% and 32.5% yields, respectively, based on osmium
(Scheme 1). The in situ 31P{1H} spectrum indicates that the
reaction also produced minor phosphorus-containing species
with chemical shifts of 25.4, 11.3, and 12.8 ppm. Unfortunately,
we have failed to identify the minor species.
Scheme 1
Complex 3 has been characterized by multinuclear NMR and
elemental analysis. In the 31P{1H} NMR spectrum, the complex
showed a sharp singlet for the phosphine ligand at 5.5 ppm.
1
1
The H NMR spectrum showed the characteristic H signal of
the Cp ring at 4.23 ppm and that of the methyl at 2.08 ppm.
The 13C{1H} NMR spectrum showed the characteristic CO
signal at 184.3 ppm. The single-crystal X-ray structure of 3
confirmed it to be a chlorocyclopentadienyl complex (Figure
2).
displayed the OsC signal at 301.2 ppm, the Os-CH signal at
224.8 ppm, the CCH3 signal at 180.0 ppm, and the C(SiMe3)
signals at 134.0 and 113.7 ppm. In the H NMR spectrum (in
1
CD2Cl2), the OsCH and the CH3 signals were observed at
14.80 and 2.79 ppm, respectively. The structure of 2 has also
been confirmed by an X-ray diffraction analysis (Figure 1).
Figure 2. ORTEP drawing of 3 with thermal ellipsoids at 35%
probability level. The hydrogen atoms on the PPh3 ligand and TMS
groups are omitted for clarity. Selected bond lengths [Å] and angles
[deg]: Os(1)−C(1) 2.176(4), Os(1)−C(2) 2.253(4), Os(1)−C(3)
2.320(4), Os(1)−C(4) 2.323(4), Os(1)−C(5) 2.184(4), Os(1)−
C(10) 1.858(5); C(10)−Os(1)−C(1) 91.39(17), P(1)−Os(1)−C(5)
101.59(11), Cl(2)−Os(1)−C(3) 90.22(10).
Figure 1. ORTEP drawing of Os{C-C(SiMe3)C(CH3)-C-
(SiMe3)CH}Cl2(PCy3)2 (2) with thermal ellipsoids at 35%
probability level. The hydrogen atoms on the PCy3 ligands and
TMS groups are omitted for clarity. Selected bond lengths [Å] and
angles [deg]: Os(1)−C(1) 1.767(6), C(1)−C(2) 1.376(8), C(2)−
C(3) 1.412(8), C(3)−C(4) 1.430(8), C(4)−C(5) 1.387(8), Os(1)−
C(5) 2.011(6); C(5)−Os(1)−C(1) 77.8(2), Os(1)−C(1)−C(2)
153.2(5), C(1)−C(2)−C(3) 111.7(5), C(2)−C(3)−C(4) 123.1(5),
C(3)−C(4)−C(5) 120.3(5), C(4)−C(5)−Os(1) 134.0(4).
Proposed Reaction Mechanisms. Scheme 2 shows two
plausible pathways for the formation of complex 3. As
Mo(CO)6 can act as the source of carbon monoxide, we
assume that the key intermediate of the reaction is the
osmabenzyne 5, which can be formed by an initial ligand
exchange reaction of 1 with Mo(CO)6. From osmabenzyne 5,
complex 3 could be formed via a carbene intermediate (path
A), or a metallabenzene intermediate (path B). In path A, the
osmabenzyne 5 or its isomers undergo migratory insertion
reactions involving the two metal-bonded carbons to give the
carbene complex 6. Migratory insertion of the carbene into the
Os−Cl bond in 6 with a change to η5 coordination would give
complex 3. In path B, the osmabenzyne 5 or its isomers
undergo migratory insertion involving one of the chloride
ligands and the carbyne carbon of 5 to give the metallabenzene
complex Os{CCl-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl-
Overall, the structural features associated with the metallacycle
are very similar to those of 1.15 Considering the reaction
conditions, we can conclude that complex 2, like 1, is thermally
stable, and does not rearrange to the corresponding carbene
complex.
We next attempted to prepare a CO-supported osmabenzyne
complex. It is known that Mo(CO)6 can be used as a source of
carbon monoxide.16 Therefore, the reaction of osmabenzyne 1
with Mo(CO)6 was carried out with the intention of obtaining
a CO-containing osmabenzyne through a ligand exchange
reaction of 1 with Mo(CO)6.
B
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
migratory insertion process is thermodynamically favored by
6.2 kcal/mol, but with a substantially high barrier of 33.9 kcal/
mol. The barrier for the carbene formation is significantly
lowered if 8 first isomerizes to 8_iso1, which then undergoes
migratory insertion. The isomer 8_iso1, in which a chloride
ligand is trans to the carbyne carbon and PPh3 is trans to the
vinyl carbon, can be generated from 8 via dissociation of PPh3
to give the five-coordinated intermediate 8_pro (with a barrier
of 23.0 kcal), followed by association of PPh3 with 8_pro (with
a barrier of 10.4 kcal/mol). Migratory insertion of 8_iso1
involving the two osmium-bonded carbon atoms gives the
square pyramidal carbene complex 9_iso1, in which two
chloride ligands are cis to each other, the carbene ligand is at
the axial position with the carbocylic ring of the carbene ligand
parallel to the Cl-Os-CO axis, and the SiH3 group at the carbon
α to the carbene carbon is on the same side of the CO ligand.
When compared with the direct reduction process, this process
via 8_iso1 to 9_iso1 is thermodynamically favored by −9.8
kcal/mol with a moderate barrier of 23.6 kcal/mol.18
Scheme 2
(CO)(PPh3) (7), which undergoes a further migratory
insertion and rearrangement to give complex 3.
Migratory insertion of the carbene complex 9_iso1 to give
the final η5-chlorocyclopentadienyl product 11 can proceed
exothermically via a transition state lying 20.4 kcal/mol in
energy above complex 8 (see the Supporting Information). The
barrier for the formation of 11 is lowered if 9_iso1 first
isomerizes, by rotation about the OsC bond via
TS9_iso1‑9_iso2, to isomer 9_iso2 in which the SiH3 group at
the carbon α to the carbene carbon is on the same side of the
Cl ligand. The isomerization process has a barrier of 15.5 kcal/
mol. Migratory insertion of 9_iso2 produces the k2-C,Cl-
chlorocyclopentadienyl complex 10, which rearranges to the
final η5-chlorocyclopentadienyl product 11 exothermically via
TS10‑11, which lies 17.0 kcal/mol in energy above complex 8.
Formation of the chlorocyclopentadienyl complex 11 from
819 involving metallabenzene intermediates (path B) is less
favored, as indicated by the energy profile shown in Figure 4.
Migratory insertion of 8 involving one of the chloride ligands
Theoretical Studies. As described below, our computa-
tional study suggests that path A is the preferred pathway for
the formation of the η5-chlorocyclopentadienyl complex. The
reaction of Os{C-C(SiH3)C(CH3)C(SiH3)CH}-
Cl2(PPh3)2 (1A, a model complex for 1) with Mo(CO)6 to
give Os{C-C(SiH3)C(CH3)-C(SiH3)CH}Cl2(CO)-
(PPh3) (8) (a model complex for 5) and Mo(CO)5(PPh3)
was found to be feasible with a free energy change of −0.9 kcal/
mol. Figure 3 shows the energy profile calculated for the
formation of the chlorocyclopentadienyl complex Os{η5-
C5HCl(CH3)(SiH3)2}Cl(CO)(PPh3) (11) (a model for
complex 3) from Os{C-C(SiH3)C(CH3)-C(SiH3)
CH}Cl2(CO)(PPh3) (8) (a model for complex 5) via path
A. Direct migratory insertion reaction of 8 involving the two
osmium-bonded carbon atoms gives the square pyramidal
carbene complex 9 with the carbene ligand at the axial position
and the two trans-chloride ligands at the base. This direct
Figure 3. Energy profiles for the rearrangement of 8 to the chlorocyclopentadienyl complex 11 involving carbene intermediates (Path A). The
relative Gibbs free energies and electronic energies (in parentheses) at 298 K are given in kcal/mol.
C
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Figure 4. Energy profiles for the rearrangement of 8 to the cyclopentadienyl complex 11 involving metallabenzene intermediates (Path B). The
relative Gibbs free energies and electronic energies (in parentheses) at 298 K are given in kcal/mol.
and the carbyne carbon gives the pseudo trigonal bipyramidal
metallabenzene complex 12 with CO and PPh3 ligands at the
axial positions. The process is slightly unfavorable thermody-
namically (by 0.9 kcal/mol) with a barrier of 20.2 kcal/mol.
Further migratory insertion of 12 to give the final product
chlorocyclopentadienyl complex 11 has a substantially higher
barrier of 37.2 kcal/mol. The barrier for the formation of 11 is
lowered if 12 first isomerizes to isomer 12_iso1, a square
pyramidal metallabenzene complex which contains the CCl-
(vinyl) carbon at the apical position and PPh3 trans to the CH
carbon. This isomer is 2.5 kcal/mol less stable than 12, and can
be generated from 12 with a barrier of 14.5 kcal/mol.
Rearrangement of isomer 12_iso1 to the final product
chlorocyclopentadienyl complex 11 can proceed via
TS12_iso1‑11, which lies 26.6 kcal/mol in energy above complex
8.20 Since the overall barrier for path B (26.6 kcal/mol, Figure
4) is higher than that for path A (23.1 kcal/mol, Figure 3) and
the metal carbene complexes 9_iso1 and 9_iso2 (in path A)
are thermodynamically more stable than the metallabenzenes
12 and 12_iso1 (in path B), formation of the metal carbene
complexes 9_iso1 and 9_iso2 is likely to be preferred over the
metallabenzenes 12 and 12_iso1, and the reaction pathway
involving metallabenzene intermediate (path B) is, therefore,
probably less important for the formation of the cyclo-
pentadienyl complex 11.
rather than a chloride ligand is transferred to the carbene
carbon.
Scheme 3
One may ask why the PPh3-containing osmabenzyne 1 and
the PCy3-containing osmabenzyne 2 do not rearrange to the
corresponding carbene or cyclopentadienyl complexes, and
whether osmabenzynes supported by other ligands would
undergo similar transformation. To answer these questions, we
have calculated the relative energies of metallabenzynes of the
type Os(C-CHCHCHCH)Cl2(L)2 (16) and the
corresponding isomeric carbene complexes Os{C(−CH
CHCHCH−)}Cl2(L)2 (17) and chlorocyclopentadienyl
complexes Os(η5-C5ClH4)Cl(L)2 (18). The results are
presented in Figure 5.
Consistent with experimental observations, complexes
supported with PPh3 (a) and PMe3 (b) ligands have the
following trend in their relative energies: osmabenzyne (16) <
carbene complex (17) < chlorocyclopentadienyl complex (18).
Complexes supported with the amine ligand NMe3 (g) have the
same trend. The three isomers have very similar stability when
L = PH3 (d). Complexes supported with π accepting ligands
P(OMe)3 (c), PCl3 (e), and CO (f) have the opposite trend in
their relative energies: osmabenzyne (16) > carbene complex
(17) > chlorocyclopentadienyl complex (18). Interestingly,
pyridine-supported complexes (h) have the following trend in
their relative energies: carbene complex (17) < osmabenzyne
(16) < chlorocyclopentadienyl complex (18).
Formation of the η5-chlorocyclopentadienyl complexes from
the dichloro osmium carbene complexes is interesting as several
dichloro osmium carbene complexes Os(CRR′)Cl2Ln have
been isolated, but migratory insertion reactions of these
complexes involving chloride and carbene carbon appear to
be unknown.21 As a closely related transformation, we noted
that the cyclopentadienyl complex 15 was produced when the
ruthenium indenylidene complex 13 was refluxed in EtOH in
the presence of NEt3, which was proposed to proceed through
intermediate 14 (Scheme 3).22 However, in this case, a hydride
D
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
AZ). H, 13C{1H}, and 31P{1H} spectra were collected on a Bruker
ARX-400 spectrometer (400 MHz). 1H and 13C NMR shifts are
relative to TMS, and 31P chemical shifts relative to 85% H3PO4.
Reactions of 1 with PCy3. A benzene (10 mL) solution of Os{
C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) (0.30 g, 0.30
mmol) and PCy3 (1.26 g, 4.50 mmol) was heated at 80 °C for 12 h to
give a blue solution. The solvent was pumped away under vacuum, and
the residue was extracted with diethyl ether (3 mL). Hexane (20 mL)
was added to the extract with stirring. The solution was concentrated
to ca. 8 mL and cooled with an ice bath for 30 min to give a blue
precipitate. The blue solid was collected by filtration, washed with
cooled hexane (2 × 3 mL), and dried under vacuum, and was
identified to be 2. Yield: 0.19 g, 61%. 31P {1H} NMR (161.98 MHz,
CD2Cl2): δ −0.1 (s). 1H NMR (400.13 MHz, CD2Cl2): δ 0.35 (s, 9 H,
Si(CH3)3), 0.42 (s, 9 H, Si(CH3)3), 1.05−2.46 (m, 66 H, PCy3), 2.79
(s, 3 H, CH3), 14.80 (s, 1 H, OsCH). 13C {1H} NMR (100.40 MHz,
CD2Cl2): δ 301.2 (t, 2JP,C = 10.0 Hz, OsC), 224.8 (t, 2JP,C = 5.6 Hz,
OsCH), 180.0 (s, CCH3), 134.0 (s, OsCHC(SiMe3)), 113.7 (s,
OsCC(SiMe3)), 33.2 (t, JP,C = 11.7 Hz, PCy3), 29.3 (s, PCy3), 28.3
(s, PCy3), 27.1 (t, JP,C = 5.0 Hz, PCy3), 26.8 (t, JP,C = 5.6 Hz, PCy3),
25.9 (s, CH3), 25.8 (s, PCy3), 0.9 (s, SiMe3), 0.1 (s, SiMe3). Anal. Calcd
for C48H88Cl2OsP2Si2: C 55.20, H 8.49; Found: C 55.12; H 8.25.
Reactions of 1 with Mo(CO)6. A mixture of Os{C-C(SiMe3)
C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1) (327 mg, 0.32 mmol) and
Mo(CO)6 (440 mg, 1.67 mmol) in benzene (8 mL) was stirred at 80
°C for 12 h to give a brown solution. The mixture was concentrated to
ca. 1 mL and was loaded onto a silica gel column. The column was
flashed with hexane to remove excess Mo(CO)6 and then eluted with
hexane/dichloromethane (3/1) to give a yellow solution, which gives
the known complex Mo(CO)5(PPh3) (4) after the solvent was
removed under vacuum. Yield: 52 mg, 32.5% (based on Os) or 6.2%
(based on Mo(CO)6). 31P{1H} NMR (161.98 MHz, C6D6): δ 37.9
(s). The column was then eluted with hexane/dichloromethane (1/1)
to give a yellow solution. The solvent was removed under vacuum to
give complex 3 as a yellow solid, which was dried under vacuum. Yield:
1
Figure 5. Relative energies of osmabenzynes Os(C-CHCHCH
CH)Cl2(L)2 (16, 0.0 kcal/mol) and their corresponding isomeric
carbene (17) and chlorocyclopentadienyl (18) complexes. The relative
Gibbs free energies and electronic energies (in parentheses) at 298 K
are given in kcal/mol.
We have also calculated the relative energies of the related
CO-containing metallabenzynes of the type Os(C-CH
CHCHCH)Cl2(CO)(PR3) (19) and the corresponding
isomeric carbene (20) and chlorocyclopentadienyl (21)
complexes where PR3 = PPh3 (a), PMe3 (b). For both cases,
the three isomers are in the following trend in their relative
energies: osmabenzyne > carbene complex > chlorocyclopenta-
dienyl complex (see the Supporting Information for details).
1
126 mg, 50.2%. 31P{1H} NMR (161.98 MHz, C6D6): δ 5.5 (s). H
NMR (400.13 MHz, C6D6): δ 7.87−7.90 (m, 6H, PPh), 7.05−7.17
(m, 9H, PPh), 4.23 (d, JP,H = 1.94 Hz, 1H, η5-C5H), 2.09 (d, JP,H
=
1.50 Hz, 3H, CH3), 0.64 (s, 9H, Si(CH3)3), 0.11 (s, 9H, Si(CH3)3).
2
13C{1H} NMR (100.62 MHz, CD2Cl2): δ 184.3 (d, JP,C = 14.9 Hz,
CO), 134.3 (d, 1JP,C = 55.2 Hz, PPh3), 133.4 (d, JP,C = 10.8 Hz, PPh3),
129.6 (d, JP,C = 2.3 Hz, PPh3), 127.3 (d, JP,C = 11.1 Hz, PPh3), 123.5
(d, JP,C = 3.1 Hz, η5-C5CH3), 95.6 (s, η5-C5Cl), 88.5 (s, η5-C5H), 83.6
(d, JP,C = 7.6 Hz, η5-C5SiMe3), 83.4 (s, η5-C5SiMe3), 13.5 (s, CH3)),
0.5 (s, Si(CH3)3), −0.5 (s, Si(CH3)3). Anal. Calcd for C31H37-
Cl2OOsPSi2: C, 48.11; H, 4.82. Found: C, 47.87; H, 5.02.
CONCLUSION
■
Treatment of the osmabenzyne complex Os{C-C(SiMe3)
C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 with Mo(CO)6 in reflux-
ing benzene produced the η5-chlorocyclopentadienyl complex
Os{η5-C5HCl(CH3)(SiMe3)2}Cl(CO)(PPh3) and Mo(CO)5-
(PPh3). A computational study suggests that the chlorocyclo-
pentadienyl complex is most likely formed via the carbene
intermediate Os{C(C(SiMe3)C(CH3)-C(SiMe3)
CH−}Cl2(CO)(PPh3) formed by a migratory insertion
reaction of the osmabenzyne complex Os{C-C(SiMe3)
C(CH3)-C(SiMe3)CH}Cl2(CO)(PPh3). DFT calculations
show that the relative thermal stability of metallabenzynes
Os(C-CHCHCHCH)Cl2(L)2 and the corresponding
isomeric carbene complexes Os{C(−CHCHCH
CH−)}Cl2(L)2 as well as the chlorocyclopentadienyl com-
plexes Os(η5-C5ClH4)Cl(L)2 (L = CO, phosphine, pyridine,
amine) varies with ligand L.
Crystal Structure Analyses. Crystals of 2 and 3 suitable for X-ray
diffraction were grown from CH2Cl2 solutions layered with hexane.
The crystals were mounted on glass fibers with epoxy glue. The
diffraction intensity data of 2 were collected with a Bruker APEX CCD
diffractometer using Mo−Kα radiation (λ = 0.71073 Å) at 293 K.
Lattice determination and data collection were carried out using
SMART v.5.625 software. Data reduction and absorption correction
were performed using SAINT v 6.26 and SADABS v 2.03, respectively.
The diffraction intensity data of 3 were collected with an Oxford
Diffraction Gemini S Ultra X-ray diffractometer with monochromat-
ized Cu−Kα radiation (λ = 1.54178 Å). Lattice determination, data
collection and reduction were carried out using CrysAlisPro 171.33.46.
Empirical absorption correction using spherical harmonics, was
implemented with the SCALE3 ABSPACK scaling algorithm in the
CrysAlisPro program suite. Structure solution and refinement for all
compounds were performed using the Olex2 software23 package
(which embedded SHELXTL24). All the structures were solved by
direct methods, expanded by difference Fourier syntheses, and refined
by full-matrix least-squares on F2. All non-hydrogen atoms were
refined anisotropically with a riding model for the hydrogen atoms,
except noted separately. Further details on crystal data, data collection,
and refinements are summarized in Table S1 (Supporting
Information).
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 (benzene, diethyl
ether, hexane), or calcium hydride (CH2Cl2). The starting material
Os{C-C(SiMe3)C(CH3)-C(SiMe3)CH}Cl2(PPh3)2 (1)15 was
prepared following the procedure described in the literature. All other
reagents were used as purchased from Aldrich Chemical Co.
Microanalyses were performed by M-H-W Laboratories (Phoenix,
E
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Computational Details. The Becke3LYP (B3LYP) level25 of
density functional theory was used to optimize (without any
constraint) all the structures studied in this work. The SDD effective
core potentials and basis sets were used to describe Os, Cl, P, and Si
atoms.26 Polarization functions were added for Os(ζ(f) = 0.707),
Cl(ζ(d) = 0.514), P(ζ(d) = 0.340) and Si(ζ(d) = 0.262).27 The 6-
31G* basis set was used for carbons involved in the metallabenzyne
ring, and 6-31G basis set for all other atoms.28 Frequency calculations
were also performed to identify all the stationary points as minima
(zero imaginary frequency) or transition states (one imaginary
frequency), and to provide Gibbs free energies at 298.15 K. All of
the calculations were performed with the Gaussian 03 package.29
567. (q) Dalebrook, A. F.; Wright, L. J. Organometallics 2009, 28,
5536.
(3) (a) Roper, W. R. Angew. Chem., Int. Ed. 2001, 40, 2440. (b) Jia, G.
Organometallics 2013, 32, 6852.
(4) Wen, T. B.; Ng, S. M.; Hung, W. Y.; Zhou, Z. Y.; Lo, M. F.; Shek,
L. Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2003, 125, 884.
(5) Hung, W. Y.; Liu, B.; Shou, W.; Wen, T. B.; Shi, C.; Sung, H. H.
Y.; Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2011, 133, 18350.
(6) Hung, W. Y.; Zhu, J.; Wen, T. B.; Yu, K. P.; Sung, H. H. Y.;
Williams, I. D.; Lin, Z.; Jia, G. J. Am. Chem. Soc. 2006, 128, 13742.
(7) Zhao, Q.; Zhu, J.; Huang, Z. A.; Cao, X. Y.; Xia, H. Chem.Eur.
J. 2012, 18, 11597.
(8) Chen, J.; Shi, C.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.; Jia, G.
Angew. Chem., Int. Ed. 2011, 50, 7295.
ASSOCIATED CONTENT
■
(9) For theoretical studies, see: (a) Anusha, C.; De, S.;
Parameswaran, P. Dalton Trans. 2013, 42, 14733. (b) Fan, J.; An,
K.; Wang, X.; Zhu, J. Organometallics 2013, 32, 6271.
(10) See, for example: (a) Johns, P. M.; Roper, W. R.; Woodgate, S.
D.; Wright, L. J. Organometallics 2010, 29, 5358. (b) Wu, H. P.; Lanza,
S.; Weakley, T. J. R.; Haley, M. M. Organometallics 2002, 21, 2824.
(c) Wu, H. P.; Weakley, T. J. R.; Haley, M. M. Chem.Eur. J. 2005,
11, 1191. (d) Wu, H. P.; Ess, D. H.; Lanza, S.; Weakley, T. J. R.; Houk,
K. N.; Baldridge, K. K.; Haley, M. M. Organometallics 2007, 26, 3957.
(e) Yang, J.; Jones, W. M.; Dixon, J. K.; Allison, N. T. J. Am. Chem. Soc.
1995, 117, 9776.
S
* Supporting Information
Detailed computational results; tables giving Cartesian
coordinates and electronic energies for all the calculated
structures; and X-ray crystallographic files (CIF) for complexes
2 and 3. This material is available free of charge via the Internet
at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: chwill@ust.hk (I.D.W.).
*E-mail: chzlin@ust.hk (Z.L.).
*E-mail: chjiag@ust.hk (G.J.).
́
(11) (a) Spivak, G. J.; Coalter, J. N.; Olivan, M.; Eisenstein, O.;
Caulton, K. G. Organometallics 1998, 17, 999. (b) Spivak, G. J.;
Caulton, K. G. Organometallics 1998, 17, 5260. (c) Caulton, K. G. J.
Organomet. Chem. 2001, 617−618, 56. (d) Jacobsen, J. J. Organomet.
Chem. 2003, 674, 50. (e) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.;
Notes
The authors declare no competing financial interest.
Modrego, F. J.; Onate, E. J. Am. Chem. Soc. 2005, 127, 11184.
̃
(f) Bolano, T.; Esteruelas, M. A.; Onate, E. J. Organomet. Chem. 2011,
696, 3911.
̃
̃
ACKNOWLEDGMENTS
■
This work was supported by the Hong Kong Research Grants
Council (Project Nos.: 602611, 601812, CUHK7/CRF/12G-
2).
(12) For additional examples of conversion of Os(R′)CR
complexes to OsCRR′ complexes, see: (a) Esteruelas, M. A.;
García-Yebra, C.; Olivan
2000, 19, 5098. (b) Barrio, P.; Esteruelas, M. A.; Onate, E. J. Am.
Chem. Soc. 2004, 126, 1946. (c) Lee, J. H.; Pink, M.; Caulton, K. G.
Organometallics 2006, 25, 802. (d) Bolano, T.; Castarlenas, R.;
́
, M.; Onate, E.; Tajada, M. A. Organometallics
̃
̃
REFERENCES
■
(1) Reviews of metallabenzene chemistry: (a) Cao, X. Y.; Zhao, Q.;
Lin, Z.; Xia, H. Acc. Chem. Res. 2014, 47, 341. (b) Dalebrook, A. F.;
Wright, L. J. Adv. Organomet. Chem. 2012, 60, 93. (c) Paneque, M.;
Esteruelas, M. A.; Onate, E. J. Am. Chem. Soc. 2007, 129, 8850.
̃
(e) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Onate, E.
̃
Organometallics 2007, 26, 2037. (f) Castro-Rodrigo, R.; Esteruelas,
́
Poveda, M. L.; Rendon, N. Eur. J. Inorg. Chem. 2011, 19. (d) Landorf,
M. A.; Lop
́
ez, A. M.; Onate, E. Organometallics 2008, 27, 3547.
̃
C. W.; Haley, M. M. Angew. Chem., Int. Ed. 2006, 45, 3914. (e) Wright,
L. J. Dalton Trans. 2006, 1821. (f) Bleeke, J. R. Chem. Rev. 2001, 101,
1205.
(g) Bolano, T.; Castarlenas, R.; Esteruelas, M. A.; Onate, E.
Organometallics 2008, 27, 6367. (h) Buil, M.; Esteruelas, M. A.;
̃
Garces, K.; Onate, E. Organometallics 2009, 28, 5691. (i) Liu, B.; Xie,
̃
(2) Examples of recent work: (a) Han, F.; Wang, T.; Li, J.; Zhang, H.;
Xia, H. Chem.Eur. J. 2014, 20, 4363. (b) Vivancos, A.; Paneque, M.;
Poveda, M. L.; Alvarez, E. Angew. Chem., Int. Ed. 2013, 52, 10068.
(c) Wang, T.; Zhang, H.; Han, F.; Long, L.; Lin, Z.; Xia, H. Angew.
Chem., Int. Ed. 2013, 52, 9251. (d) Wang, T.; Zhang, H.; Han, F.;
Long, L.; Lin, Z.; Xia, H. Chem.Eur. J. 2013, 19, 10982. (e) Chen, J.;
Zhang, C.; Xie, T.; Wen, T. B.; Zhang, H.; Xia, H. Organometallics
2013, 32, 3993. (f) Wang, T.; Zhang, H.; Han, F.; Lin, R.; Lin, Z.; Xia,
H. Angew. Chem., Int. Ed. 2012, 51, 9838. (g) Lin, R.; Zhao, J.; Chen,
H.; Wang, H.; Wu, L.; Zhao, Q.; Chen, J.; Wen, T. B.; Cao, Z.; Xia, H.
Angew. Chem., Int. Ed. 2009, 48, 5461.
(13) For examples of conversion of OsCHR complexes to
Os(H)CR complexes, see: (a) Esteruelas, M. A.; Olivan
́
, M.; Onate,
̃
E.; Ruiz, N.; Tajada, M. A. Organometallics 1999, 18, 2953. (b) Buil, M.
L.; Eisenstein, O.; Esteruelas, M. A.; García-Yebra, G.; Gutierrez-
Puebla, E.; Olivan
Organometallics 1999, 18, 4949. (c) Buil, M. L.; Esteruelas, M. A.;
García-Yebra, C.; Gutierrez-Puebla, E.; Olivan, M. Organometallics
́
, M.; Onate, E.; Ruiz, N.; Tajada, M. A.
̃
́
́
H.; Zhang, H.; Xia, H. Chem.Asian J. 2012, 7, 1915. (h) Hernan
Juarez, M.; Salazar, V.; García-Baez, E. V.; Padilla-Martínez, I. I.; Hopfl,
H.; Rosales-Hoz, M. J. Organometallics 2012, 31, 5438. (i) Clark, G. R.;
́
dez-
̈
2000, 19, 2184. (d) Baya, M.; Esteruelas, M. A.; Onate, E.
̃
́
́
Organometallics 2001, 20, 4875. (e) Barrio, P.; Esteruelas, M. A.;
Onate, E. Organometallics 2002, 21, 2491. (f) Esteruelas, M. A.;
̃
Johns, P. M.; Roper, W. R.; Sohnel, T.; Wright, L. J. Organometallics
̈
Gonzal
(g) Esteruelas, M. A.; Gonzal
Organometallics 2004, 23, 4858. (h) Castarlenas, R.; Esteruelas, M. A.;
Onate, E. Organometallics 2007, 26, 2129. (i) Castarlenas, R.;
́
ez, A. I.; Lopez, A. M.; Onate, E. Organometallics 2003, 22, 414.
́
̃
2011, 30, 129. (j) Lin, R.; Zhang, H.; Li, S.; Chen, L.; Zhang, W.; Wen,
T. B.; Zhang, H.; Xia, H. Chem.Eur. J. 2011, 17, 2420. (k) Lin, R.;
Zhang, H.; Li, S.; Chen, L.; Zhang, W.; Wen, T. B.; Zhang, H.; Xia, H.
Chem.Eur. J. 2011, 17, 2420. (l) Clark, G. R.; Ferguson, L. A.;
́
́
ez, A. I.; Lopez, A. M.; Onate, E.
̃
̃
Esteruelas, M. A.; Lalrempuia, R.; Olivan
metallics 2008, 27, 795.
́
, M.; Onate, E. Organo-
̃
Mclntosh, A. E.; Sohnel, T.; Wright, L. J. J. Am. Chem. Soc. 2010, 132,
̈
13443. (m) Zhang, H.; Lin, R.; Hong, G.; Wang, T.; Wen, T. B.; Xia,
H. Chem.Eur. J. 2010, 16, 6999. (n) Jacob, V.; Landorf, C. W.;
Zakharov, L. N.; Weakley, T. J. R.; Haley, M. M. Organometallics 2009,
28, 5183. (o) Gong, L.; Chen, Z.; Lin, Y.; He, X.; Wen, T. B.; Xu, X.;
Xia, H. Chem.Eur. J. 2009, 15, 6258. (p) Clark, G. R.; O’Neale, T.
R.; Roper, W. R.; Tonei, D. M.; Wright, L. J. Organometallics 2009, 28,
(14) For additional examples of conversion of M(R′)CR
complexes to MCRR′ complexes with metals other than osmium,
see: (a) M = W: Bannwart, E.; Jacobsen, H.; Furno, F.; Berke, H.
Organometallics 2000, 19, 3605. (b) M = Ru: Boone, M. P.; Brown,
C. C.; Ancelet, T. A.; Stephan, D. W. Organometallics 2010, 29, 4369.
F
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(c) M = Re: Chen, J.; Shi, C.; Sung, H. H. Y.; Williams, I. D.; Lin, Z.;
Jia, G. Organometallics 2012, 31, 1817.
(15) Wen, T. B.; Zhou, Z. Y.; Jia, G. Angew. Chem., Int. Ed. 2001, 40,
Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J.
J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.;
Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman,
J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.;
Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen,
W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, Revision
E.01; Gaussian, Inc.: Wallingford, CT, 2004.
1951.
(16) Nordeman, P.; Odell, L. R.; Larhed, M. J. Org. Chem. 2012, 77,
11393.
(17) (a) Magee, T. A.; Matthews, C. N.; Wang, T. S.; Wotiz, J. H. J.
Am. Chem. Soc. 1961, 83, 3200. (b) Cotton, F. A.; Darensburg, D. J.;
Ilsley, W. H. Inorg. Chem. 1981, 20, 518.
(18) We have also considered the reaction involving another isomer,
isomer 8_iso2, in which a chloride ligand is trans to the vinyl carbon
and PPh3 is trans to the carbyne carbon. This isomer is 6.2 kcal/mol
less stable than the isomer 8 and can be generated from 8 via
dissociation of PPh3 to give the five-coordinated intermediate 8_pro,
followed by association of PPh3 with 8_pro (with a barrier of 10.4
kcal/mol). Migratory insertion of 8_iso2 to give a carbene complex
has a reaction barrier of 27.1 kcal/mol, which is higher than that for
the reaction of 8_iso1 (see the Supporting Information).
(19) In principle, metallabenzene intermediate could be formed from
8_iso2. Our calculations show that the reaction involving 8_iso2 to
give the metallabenzene intermediate has a higher barrier than that
involving 8_iso1 and, therefore, is unlikely to occur (see the
Supporting Information).
(20) We have also considered formation of 11 from PPh3 adduct of
12, namely, the 18e osmabenzene complex Os(CCl-C(SiH3)
C(CH3)-C(SiH3)CH)Cl(CO)(PPh3)2. The process was found to
be much less favorable than that involving 12_iso1 (see the
Supporting Information). The result is not surprising, as it has been
reported that direct reductive elimination from six-coordinate
complexes L2PtMe4 is kinetically less feasible than that from five-
coordinate complexes LPtMe4; see:. Ariafard, A.; Ejehi, Z.; Sadrara, H.;
Mehrabi, T.; Etaati, S.; Moradzadeh, A.; Moshtaghi, M.; Nosrati, H.;
Brookes, N. J.; Yates, B. F. Organometallics 2011, 30, 422.
(21) Esteruelas, M. A.; Lop
2007, 251, 795.
́ ́
ez, A. M.; Olivan, M. Coord. Chem. Rev.
(22) (a) Manzini, S.; Urbina-Blanco, C. A.; Poater, A.; Slawin, A. M.;
Cavallo, L.; Nolan, S. P. Angew. Chem., Int. Ed. 2012, 51, 1042.
(b) Manzini, S.; Poater, A.; Nelson, D. J.; Cavallo, L.; Slawin, A. M.;
Nolan, S. P. Angew. Chem., Int. Ed. 2014, 53, 8995. (c) Manzini, S.;
Nelson, D. J.; Lebl, T.; Poater, A.; Cavallo, L.; Slawin, A. M.; Nolan, S.
P. Chem. Commun. 2014, 50, 2205.
(23) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.;
Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339−341.
(24) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112−122.
(25) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Miehlich, B.;
Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989, 157, 200.
(c) Lee, C.; Yang, W.; Parr, G. Phys. Rev. B 1988, 37, 785.
(d) Stephens, P. J.; Devlin, F. J.; Chabalowski, C. F. J. Phys. Chem.
1994, 98, 11623.
(26) (a) Fuentealba, P.; Preuss, H.; Stoll, H.; Szentpaly, L. V. Chem.
Phys. Lett. 1989, 89, 418. (b) Andrae, D.; Hauβermann, U.; Dolg, M.;
̈
Stoll, H.; Preuβ, H. Theor. Chem. Acc. 1990, 77, 123.
(27) (a) Huzinaga, S.; Andzelm, J.; Klobukowski, M.; Radzio-
Andzelm, E.; Sakai, Y.; Tatewaki, H. Gaussian Basis Sets for Molecular
Calculations; Elsevier: Amsterdam, 1984. (b) Iron, M. A.; Lucassen, A.
C. B.; Cohen, H.; van der Boom, M. E.; Martin, J. M. L. J. Am. Chem.
Soc. 2004, 126, 11699.
(28) Hollwarth, A.; Bohme, M.; Dapprich, S.; Ehlers, A. W.; Gobbi,
A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 237.
(29) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, Jr., J. A.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.;
Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.;
Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao,
O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J.
B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R.
E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.;
G
DOI: 10.1021/om501181u
Organometallics XXXX, XXX, XXX−XXX