Formation of carbyne complexes in reactions of laser-ablated Os atoms with halomethanes: Characterization by C-H(X) and Os-H(X) stretching absorptions and computed structures

Article abstract of DOI:10.1039/b811805a

Reactions of laser-ablated Os atoms with halomethanes have been investigated. Small carbyne complexes are produced in reactions of Os atoms with fluoromethanes and identified through matrix infrared spectra and vibrational frequencies computed by density

Full text of DOI:10.1039/b811805a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Formation of carbyne complexes in reactions of laser-ablated Os atoms with
halomethanes: characterization by C–H(X) and Os–H(X) stretching
absorptions and computed structures†
Han-Gook Choa and Lester Andrews*a,b
Received 10th July 2008, Accepted 15th September 2008
First published as an Advance Article on the web 6th November 2008
DOI: 10.1039/b811805a
Reactions of laser-ablated Os atoms with halomethanes have been investigated. Small carbyne
complexes are produced in reactions of Os atoms with fluoromethanes and identified through matrix
infrared spectra and vibrational frequencies computed by density functional theory. The preference for
the carbon–osmium triple bond is traced to the low energy of the Os carbyne products. The C–H and
C–X stretching absorptions of the carbyne complexes are observed on the high frequency sides of the
corresponding precursor bands, which result from the high s character in the C–H bond and interaction
between the C–X and C–Os stretching modes, respectively. The calculated Os complex structures show
a large variation with the ligands and electronic states, similar to the analogous Ru complex structures.
The present report also compares previous Fe, Ru, and Os results and supports the general trend that
the higher oxidation state complexes become more stable on going down the family group column.
character in the C–H bond has also been reported.10,11a,b The
Introduction
carbyne C–X stretching frequencies of the halogenated derivatives
Interest in carbene and carbyne complexes has grown remarkably
are exceptionally high (C–F and C–Cl stretching frequencies
since their first introduction in the 1970’s.1 Increasing applications
in various syntheses, particularly C–H insertion and metathesis
catalytic properties provide the driving force for the progress in
high oxidation state complex chemistry.2,3 Numerous synthetic
routes are also introduced to generate osmium high oxidation state
complexes,2–5 which often show distinctive structures and various
catalytic and ligand effects.6 Hydrogen transfer from carbon-
to-osmium atom is directly observed in a recent time-resolved
infrared study.7
More recently, simple Fe and Ru high oxidation state complexes
were produced in reactions of laser-ablated Fe and Ru atoms
with halomethanes, introducing a new way to effectively provide
the Fe and Ru derivatives and allowing for examination of
their structural and photochemical properties.8 Both methyli-
denes and methylidynes were observed with Ru, but no Fe
carbynes were identified from the reactions with small alkanes
and fluoroalkanes.8 Exclusive formation of Os methylidynes in
reactions ofOs withCH4, C2H6 and CH3Xhave also been reported,
showing a high preference for the triple bond between carbon
and the third row transition metal,9 parallel to the W and Re
systems.10,11
higher than 1500 and 1200 cm-1), resulting from X–C–M anti-
symmetric stretching character.10,11c The small group 8 metal
complexes also show unusual, low symmetry structures including
the highly distorted methylidynes8,9 similar to the structures of the
corresponding Re carbynes11 and unusual inclination of the C–Cl
bond toward the metal center in the Fe insertion complexes.8a
The non-bonding electrons evidently play an important role in
the distinct structures of the group 8 metal complexes,8,9 while the
distorted structures of the small Re methylidynes10 are traced to
the Jahn–Teller effect.13
Here, we report the IR spectra of isotopic products from
reactions of laser-ablated Os atoms with halomethanes. The
carbyne products, the only identified product from the reactions,
reaffirm the preference of the carbon–osmium triple bond, and
the interesting methylidyne C–H(X) stretching absorptions are
also observed on the blue sides of the corresponding precursor
bands. DFT computations substantiate the stability of the carbyne
products and reveal unique structures for the products along with
the structural effects of the lone electron pair on the metal center.
The elusive carbyne C–H stretching absorptions12 are clearly
observed at ~200 cm-1 on the blue side of the corresponding
precursor absorption from the Ru and Os carbynes8,9 as well
as the Re, W and Mo methylidynes.10,11 A general trend of
increasing methylidyne C–H stretching frequency with the s
Experimental computational methods
Laser ablated Os (Metallium, Inc.) atoms were reacted with
CH2F2, CD2F2,14 CH2FCl, CH2Cl2, CD2Cl2, 13CH2Cl2, CHCl3,
CDCl3, 13CHCl3, CF3Cl, 13CF3Cl,14 CF2Cl2, CFCl3, CCl4
(Dupont) and 13CCl4 in excess argon during condensation at
10 K using a closed-cycle refrigerator (Air Products HC-2).
These methods have been described in detail elsewhere.15 Reagent
gas mixtures ranged 0.5–1.0% in argon. After reaction, infrared
spectra were recorded at a resolution of 0.5 cm-1 using a Nicolet
550 spectrometer (lower limit near 410 cm-1) with an MCT-B
detector. Samples were later irradiated for 20 min periods by a
aDepartment of Chemistry, University of Incheon, 177 Dohwa-dong, Nam-ku,
Incheon, 402-749, South Korea
bDepartment of Chemistry, University of Virginia, P. O. Box 400319,
Charlottesville, Virginia, 22904-4319, USA. E-mail: lsa@virginia.edu
† Electronic supplementary information (ESI) available: Additional calcu-
lated and observed fundamental frequencies. See DOI: 10.1039/b811805a
5858 | Dalton Trans., 2009, 5858–5866
This journal is
The Royal Society of Chemistry 2009
©

mercury arc street lamp (175 W) with the globe removed and a
combination of optical filters, and subsequently annealed to allow
further reagent diffusion.15
In order to support the assignment of new experimental
frequencies and correlate with related work,8–11 density func-
tional theory (DFT) calculations were carried out using the
Gaussian 03 package,16 the B3LYP density functional,17 the 6–
311++G(3df,3pd) basis sets for C, H, F, Cl18 and SDD pseu-
dopotential and basis set19 for Os to provide a consistent set of
vibrational frequencies for the reaction products. Geometries were
fully relaxed during optimization, and the optimized geometry was
confirmed by vibrational analysis. The BPW9120 functional was
also employed to complement the B3LYP results. The vibrational
frequencies were calculated analytically, and the zero-point energy
is included in the calculation of the binding energies. Previous
investigations have shown the DFT calculated harmonic frequen-
cies are usually slightly higher than observed frequencies,8–11,21,22
depending on the mode anharmonicity, and they provide useful
predictions for the infrared spectra of new molecules.
Results and discussion
Reactions of osmium with halomethane isotopic modifications
were carried out, and the matrix infrared spectra of new products
will be compared with frequencies calculated by density functional
theory.
Fig. 1 IR spectra in the selected regions of 3130–3090 and 630–500 cm-1
for laser-ablated Os atoms co-deposited with CH2F2 isotopomers and
CH2FCl in excess argon at 10 K and their variation. (a) Os + 0.5% CH2F2
in Ar co-deposited for 1 h. (b) As (a) after visible (l > 420 nm) photolysis.
(c) As (b) after UV (240 < l < 380 nm) photolysis. (d) As (c) after visible
photolysis. (e) As (d) after UV photolysis. (f) As (e) after annealing to 28 K.
(g) Os + 0.5% CD2F2 in Ar co-deposited for 1 h. (h) As (g) after visible
photolysis. (i) As (h) after UV photolysis. (j) As (i) after visible photolysis.
(k) As (j) after UV photolysis. (l) As (k) after annealing to 28 K. (m) Os +
0.5% CH2FCl in Ar co-deposited for 1 h. (n) As (m) after visible photolysis.
(o) As (n) after UV photolysis. (p) As (o) after visible photolysis. (q) As
(p) after UV photolysis. (r) As (q) after annealing to 28 K, “y” denotes
the product absorption. P and c designate the precursor and absorptions
common to this precursor with different metal atoms, respectively.
Os + CH2X2
Previous studies show that reactions of metal atoms with small
alkanes and halomethanes generate small metal complexes (in-
sertion, carbene, and carbyne products) as primary reaction
products.8,22 Fig. 1 shows the CH2F2, CD2F2 and CH2FCl reaction
product spectra in the C–H stretching and low frequency regions.
The much stronger product absorptions in the CH2FCl spectra
indicate that substitution of F with Cl increases the reaction
yield considerably. Only one group of absorptions marked “y”
(y for methylidyne) are observed, which decrease and increase
reversibly on visible (l > 420 nm) and UV (240 < l < 380 nm)
irradiations. No significant changes were observed on annealing.
The observed frequencies are listed in Table 1 and compared with
DFT computed frequencies for the simple carbyne products in
Tables S1 and S2.†
The experimental evidence favours 1 : 1 metal–precursor
reaction products. In the case of similar experiments with Mo,
natural Mo isotopic splittings were resolved, which indicates a
single Mo atom contribution to the important Mo–C stretching
mode in question.10 Since Os is more difficult to evaporate than
Mo, it is straightforward to conclude that a single Os atom
contributes to these primary reaction products. Relatively dilute,
0.2 and 0.5%, reagent concentrations were employed here, and
doubling the reagent concentration only increased the product
absorptions by one third. Furthermore, no significant absorption
growth was observed on annealing. Hence, we also conclude that
a single reagent molecule is involved in these primary reaction
products. Higher stoichiometry products have been limited to the
CH4 and CH3X reagents and favoured in group 4 metal reactions,
Table 1 Frequencies of product absorptions observed from reactions of CH2X2 isotopomers with Os in excess argona
Group
y
CH2F2
CD2F2
CH2FCl
CD2FCl
13CH2FCl
CH2Cl2
CD2Cl2
13CH2Cl2
Description
3113.7
—
605.9
521.5
—
—
601.5
—
3107.3
666.9
612.1
568.7
2351.6
—
610.6
—
3095.9
—
611.8
565.0
3101.3
657.7
—
2335.7
—
—
3090.1
655.8
—
C–H stretch
HCOsH bend
Os–F stretch
HCOs bend
580.9, 577.7
—
577.5, 574.5
a All frequencies are in cm-1. Stronger absorptions in a set are bold. Description gives major coordinate and “y” stands for carbyne (methylidyne) products.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 5858–5866 | 5859
©

and such absorptions increase substantially on annealing,22 in
contrast to the osmium reaction products observed here.
The sharp y absorption in the C–H stretching region at
3113.7 cm-1 in the CH2F2 spectra has its counterpart at 3107.3 cm-1
in the CH2FCl spectra while its D counterpart is covered by
residual CO2 absorptions. The C–H stretching absorptions whose
frequencies are about 200 cm-1 higher than the corresponding
precursor bands strongly suggest that the products contain a
C–Os triple bond, which in turn increases the s character in
the C–H bond, parallel to the previous results of carbyne C–H
stretching bands.8–12 The y absorption at 605.9 cm-1 has its D and
CH2FCl counterparts at 601.5 and 612.1 cm-1 and is assigned to
the OsF2 anti-symmetric stretching mode of the carbyne complex
≡
(HC OsHF2) on the basis of the frequency and small shifts. The
OsF2 symmetric stretching absorption, expected at about 10 cm-1
on the blue side, is believed to be covered by a common feature in
the spectra. We are not aware of infrared spectra of binary osmium
fluorides, but the matrix-isolated OsO3F2 molecule exhibits Os–F
stretching modes in this region at 619 and 646 cm-1.23
Another y absorption at 521.5 cm-1 has its CH2FCl counterpart
at 568.7 cm-1, but its D counterpart is unfortunately beyond our
observation range. It is assigned to the HCOs bending mode due to
the frequency and sizable shifts (Tables S1 and S2†). Other absorp-
tions are computed to be much weaker. The good agreement with
the strongest DFT predicted frequencies substantiates formation
Fig. 2 IR spectra in selected regions of 3125–3075, 2360–2310, and
670–560 cm-1 for laser-ablated Os atoms co-deposited with methylene
chloride isotopomers in excess argon at 10 K and their variations. (a) Os +
0.5% CH2Cl2 in Ar co-deposited for 1 h. (b) As (a) after visible photolysis.
(c) As (b) after UV photolysis. (d) As (c) after visible photolysis. (e) As
(d) after UV photolysis. (f) As (e) after annealing to 28 K. (g) Os + 0.5%
CD2Cl2 in Ar co-deposited for 1 h. (h) As (g) after visible photolysis. (i) As
(h) after UV photolysis. (j) As (i) after annealing to 28 K. (k) Os + 0.5%
13CH2Cl2 in Ar co-deposited for 1 h. (l) As (k) after visible photolysis.
(m) As (l) after UV photolysis. (n) As (m) after annealing to 28 K, “y”
denotes a product absorption. CO2 and c designate the residual CO2 and
absorptions common with different metals.
≡
≡
of the Os carbynes, HC OsHF2 and HC OsHFCl. Analogous
reversible photochemistry was observed for the Ru analogues and
their methylidene partners,8b but the Os methylidene complexes
were not detected here most likely owing to masking by common
absorptions in the precursor. It is of course possible for this
reversible photochemistry to involve another transient species that
is not observed here.
≡
present HC OsHF2 observation suggests that the C–H stretching
≡
frequency for HC RuHF2 should be higher even than the osmium
Fig. 2 shows the methylene chloride spectra in the C–H and
C–D stretching and low frequency regions. Only y absorptions are
observed again, which are almost depleted and recover reversibly
in the alternating cycles of visible and UV irradiations. The sharp
y absorption at 3101.3 cm-1 shows D and 13C shifts of -765.6 and
-11.2 cm-1 (H : D and 12 : 13 ratios of 1.328 and 1.004). The C–H
stretching absorptions at about 200 cm-1 on the blue side of the
corresponding precursor absorption is again strong evidence that
counterpart.
The reversible photochemistry described above for the
≡
HC OsHCl2 product is parallel to that observed for the
CH2 RuCl2 and HC RuHCl2 counterparts,8b but the 6 kcal
mol-1 higher energy photochemical partner methylidene complex
=
≡
=
CH2 OsCl2 is not detected here because its strongest chro-
mophore, the anti-symmetric OsCl2 stretching mode (Table S2
continued†), falls below our instrumental limit of about 410 cm-1.
We are however, confident that the analogous photochemical
reactions take place with Os and Ru, but the relative yield of
the highest oxidation state product is probably higher with Os.
≡
the carbyne complex (HC OsHCl2) is formed (Table S3†). The
y absorption at 657.7 cm-1 has its 13C counterparts at 655.8 cm-1
(12 : 13 ratios of 1.003) and is assigned to the HCOsH symmetric
in-plane bending mode without observation of the D counterpart.
Another y absorption at 577.7 cm-1 with its 13C counterpart at
574.5 cm-1 (12 : 13 ratio of 1.006 compared with the calculated
ratio of 1.006) is assigned to the HCOs bending mode without
observation of the D counterpart.
=
≡
Os + CH2Cl2 → CH2Cl-OsCl* → CH2 OsCl2 ↔ HC OsHCl2
Os + CHCl3
It is interesting to compare the trend in C–H stretching frequen-
cies in the above methylidyne complex series. These frequencies
increase from 3101.3 to 3107.3 to 3113.7 cm-1 with increasing
fluorine substitution, which parallels an increase in s character
in the C–H bond calculated by NBO analysis, as described
previously,10,16 namely 48.19, 48.61 and 49.46%, respectively. Such
correlations were also found in Re and group 6 methylidyne
complexes.10,11 Lower C–H stretching frequencies and smaller s
Fig. 3 illustrates the CHCl3 spectra in the C–H and C–D
stretching and HCOs bending regions, and Table 2 lists the
observed frequencies. The product absorptions (all labelled y)
increase about 40% on visible irradiation, are almost depleted
on UV irradiation, and partly recover on the following visible
irradiation. The y absorption at 3091.5 cm-1 has its D and 13C
counterparts at 2326.8 and 3080.7 cm-1 (H : D and 12 : 13 ratios
of 1.329 and 1.0035), whose high frequency and isotopic shifts
strongly suggest formation of a complex with a carbon–osmium
≡
≡
characters were reported for the HC RuHFCl and HC RuHCl2
counterparts,8b but the HC RuHF2 counterpart had higher s
≡
≡
character (49.95%) and a lower frequency, which is out of line. The
triple bond (HC OsCl3). (The c absorptions are common to
5860 | Dalton Trans., 2009, 5858–5866
This journal is
The Royal Society of Chemistry 2009
©

Table 2 Frequencies of product absorptions observed from reactions of
Again, a reversible photochemical process with the methylidene is
implicated, analogous to the Ru case,8b but we cannot detect the
likely methyidene partner.
CHCl3 isotopomers with Os in excess argona
Group
y
CHCl3
CDCl3
13CHCl3
Description
3091.5
596.3
2326.8
—
3080.7
591.3
A¢ C–H stretch
A¢ HCOs bend
Os + CX4 (X = F or Cl)
Fig. 4 shows the CF3Cl spectra in the C–F and OsFCl2 stretching
regions, and Table 3 gives the observed absorptions. The y
absorptions increase slightly, 50%, and 50% upon visible, UV, and
full arc (l > 220 nm) irradiations, respectively. The y absorption at
1580.9 cm-1 with the 13C counterpart at 1532.7 cm-1 (12 : 13 ratio
a All frequencies are in cm-1. Description gives major coordinate, “y”
stands for carbyne (methylidyne) products.
≡
of 1.031) is designated to the C–F stretching mode of FC OsCl3
on the basis of the unusually high frequency and sizable 13C shift.
Mode analysis shows that the unusually high frequency is due to
the fact that the C–F stretching mode is essentially the F–C–Os
anti-symmetric stretching mode with considerable carbon motion,
parallel to the previous results.8,10,11 The strong coupling between
the C–F and C–Os motions is another evidence for formation of
the carbyne tetrahalide: the frequency of a C–Os single or double
bond would be too low to yield meaningful coupling with the C–F
stretching mode. In the low frequency region, the y absorption and
its 13C counterpart at 615.6 and 615.4 cm-1 are assigned to the anti-
symmetric OsFCl2 stretching modes on the basis of the frequencies
and negligible 13C shift. A weak y absorption is observed at
Fig.
3
IR spectra in the regions of 3110–3050, 2335–2315, and
605–585 cm-1 for laser-ablated Os atoms co-deposited with chloroform
isotopomers in excess argon at 10 K and their variations. (a) Os + 0.5%
CHCl3 in Ar co-deposited for 1 h. (b) As (a) after visible photolysis. (c)
As (b) after UV photolysis. (d) As (c) after visible photolysis. (e) As (d)
after annealing to 28 K. (f) Os + 0.5% CDCl3 in Ar co-deposited for 1 h.
(g) As (f) after visible photolysis. (h) As (g) after UV photolysis. (i) As
(h) after annealing to 28 K. (j) Os + 0.5% 13CHCl3 in Ar co-deposited
for 1 h. (k) As (j) after visible photolysis. (l) As (k) after UV photolysis.
(m) as (l) after visible photolysis. (n) As (m) after annealing to 28 K, “y”
denotes a product absorption. P and c indicate the precursor and common
absorptions, respectively.
Fig.
4
IR spectra in the regions of 1620–1500, 1235–1215, and
625–575 cm-1 for laser-ablated Os atoms co-deposited with CF3Cl and
13CF3Cl in excess argon at 10 K and their variations. (a) Os + 0.5% CF3Cl
in Ar co-deposited for 1 h. (b) As (a) after visible photolysis. (c) As (b)
after UV photolysis. (d) As (c) after full arc (l > 220 nm) photolysis. (e)
As (d) after annealing to 28 K. (f) Os + 0.5% 13CF3Cl in Ar co-deposited
for 1 h. (g) As (f) after visible photolysis. (h) As (g) after UV photolysis.
(i) As (h) after full arc photolysis. (j) As (i) after annealing to 28 K, “y”
denotes a product absorption and P indicates a product absorption.
CHCl3 experiments with other metals). Another y absorption
at 595.6 cm-1 has its 13C counterpart at 591.3 cm-1 and is
assigned to the in-plane HCOs bending mode. Other absorptions
≡
from HC OsCl3 are either too weak to observe, covered by
precursor bands, or beyond our observation range (Table S4†).
Table 3 Frequencies of product absorptions observed from reactions of CX4 isotopomers with Os in excess argona
13CF3Cl
Group CF3Cl
CF2Cl2
CFCl3
CCl4
—
13
≡
≡
≡
≡
y
1580.9 FC OsF2Cl(T) 1532.7 F C OsF2Cl(T)
1571.6 FC OsFCl2(T)
1551.2 FC OsCl3(T)
13
≡
≡
≡
≡
—
—
1231.0, 1224.2 Cl C OsF3(T) 1279.2, 1271.3 ClC OsF2Cl(T) 1283.0 ClC OsFCl2(T) 1345.9 ClC OsCl3(S)
≡
—
—
—
—
—
1295.6 ClC OsCl3(T)
≡
≡
≡
615.6 FC OsF2Cl(T)
615.4 FC OsF2Cl(T)
597.9 FC OsFCl2(T)
—
—
—
≡
—
—
606.5 ClC OsF2Cl(T)
≡
≡
≡
585.7 FC OsF2Cl(T)
—
621.3 ClC OsF2Cl(T)
608.2 ClC OsFCl2(T)
a All frequencies are in cm-1. Description gives major coordinate, “y” stands for carbyne (methylidyne) products.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 5858–5866 | 5861
©

585.7 cm-1, but the 13C counterpart is believed to be overlapped by
a common band. It is assigned to the OsFCl2 symmetric stretching
mode. The good agreement with DFT frequencies (Table S5†)
intensity. The y¢ absorptions at 621.3 and 606.5 cm-1 are assigned
to the A¢¢ and A¢ OsF2 stretching modes (Table S6†). The isomers
-1
≡
are again energetically comparable: FC OsFCl2 is 5.6 kcal mol
≡
≡
substantiates the formation of FC OsF2Cl.
more stable than ClC OsF2Cl.
Another product absorption marked “y¢”, which is much
The y absorptions in the CFCl3 spectra increase about 10, 50
and 10% on visible, UV, and full arc irradiations, whereas the
y¢ absorptions increase about 20, 200 and 30% on the series
of irradiations. Parallel to the case of CF2Cl2, The y and y¢
absorptions at 1551.2 and 1283.0 cm-1 in the CFCl3 spectra are
≡
weaker than the C–F stretching absorptions of FC OsF2Cl, is
observed at 1224.2 cm-1 in the 13CF3Cl spectra. Assuming that
its 12C counterpart expected at about 1272 cm-1 is covered by a
precursor band, it is tentatively assigned to the 13C–Cl stretching
13
≡
≡
≡
mode of Cl C OsF3, a structural isomer of FC OsF2Cl. While
assigned to the C–F and C–Cl stretching modes of FC OsCl3
-1
≡
≡
FC OsF2Cl is only slightly (4.3 kcal mol ) more stable than
ClC OsF3, the small energy difference only is seemingly not
enough to explain primary formation of FC OsF2Cl. This, there-
fore, suggests that the C–Cl insertion followed by Cl migration
is easier than the F counterpart, and it is also consistent with
the considerable increase in reaction yield by substitution of F
with Cl.
and ClC OsFCl2 on the basis of the high frequencies similar to
those of the halogenated carbyne complexes8,10,11 and consistency
with the DFT values. Another y¢ absorption at 608.2 cm-1 is
assigned to the Os–F stretching mode of ClC OsFCl2. The
FC OsCl3(S) product is only 2.6 kcal mol lower in energy than
≡
≡
≡
-1
≡
≡
ClC OsFCl2(T).
Fig. 6 shows the CCl4 and 13CCl4 spectra in the C–Cl stretching
region. The y absorptions increase about 5, 15 and 5% in
visible, UV, and full arc irradiations, whereas the y* absorptions
increase distinctly less on the same irradiation sequence. The y
absorption at 1346.3 cm-1 has 13C counterpart at 1298.4 cm-1
(12 : 13 ratio of 1.037) is assigned to the C–Cl stretching
Fig. 5 illustrates the CF2Cl2 and CFCl3 spectra in the C–F and
C–Cl stretching and low frequency regions, where two groups
of absorptions “y” and “y¢” are observed. The y absorptions
in the CF2Cl2 spectra increase about 10%, 30% and 10% upon
visible, UV, and full arc irradiations, whereas the y¢ absorptions
increase about 30% and slightly more on visible and full arc
irradiations but stay almost the same on UV irradiation. The y
absorptions at 1571.6 cm-1 most probably arise from the C–F
≡
mode of ClC OsCl3(S) on the basis of the characteristic high
frequency and sizable 13C shift, which are consistent with the
DFT values (Table S7†). The large 13C shift is due to the anti-
≡
stretching mode of FC OsFCl2 on the basis of the unusually high
symmetric Cl–C–Os stretching nature of this normal mode. As
frequency and intensity, and the one at 597.9 cm-1 is believed
from the Os–F stretching mode (Table S6†). The y¢ absorptions
at 1279.2 and 1271.3 cm-1 are assigned to the C–Cl stretching
reported for the analogous ClC WCl3 molecule, the Cl 35–37
10
≡
isotopic splitting for a single Cl atom is small (1.7 cm-1) and not
resolved from the major bands although there is an unresolved red
shoulder that could contain this isotopic splitting. Unfortunately,
≡
≡
mode of ClC OsF2Cl, the structural isomer of FC OsFCl2, on
the basis of the exceptionally high frequency and high absorption
Fig. 5 IR spectra in the regions 1600–1525, 1300–1260 and 630–590 cm-1
for laser-ablated Os atoms co-deposited with CFCl3 and CF2Cl2 in excess
argon at 10 K and their variations. (a) Os + 0.5% HFCl3 in Ar co-deposited
for 1 h. (b) As (a) after visible photolysis. (c) As (b) after UV photolysis. (d)
As (c) after full arc photolysis. (e) As (d) after annealing to 28 K. (f) Os +
0.5% CF2Cl2 in Ar co-deposited for 1 h. (g) As (f) after visible photolysis.
(h) As (g) after UV photolysis. (i) As (h) after full arc photolysis. (j) As
(i) after annealing to 28 K, “y” and “y¢” denote the product absorption
groups and w and c designate the residual water and common absorptions.
Fig. 6 IR spectra in the region 1450–1150 cm-1 for laser-ablated Os atoms
co-deposited with CCl4 and 13CCl4 in excess argon at 10 K and their
variations. (a) Os + 0.5% CCl4 in Ar co-deposited for 1 h. (b) As (a) after
visible photolysis. (c) As (b) after UV photolysis. (d) As (c) after full arc
photolysis. (e) As (d) after annealing to 28 K. (f) Os + 0.5% 13CCl4 in Ar
co-deposited for 1 h. (g) As (f) after visible photolysis. (h) As (g) after UV
photolysis. (i) As (h) after full arc photolysis. (j) as (i) after annealing to
28 K, “y” and “y*” denote the product absorption groups and c designates
a common absorption.
5862 | Dalton Trans., 2009, 5858–5866
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©

≡
the strongest other ClC OsCl3 band is beyond our observation
range.
two Cl atoms are farther from one another (<ClOsCl = 138.8◦
˚
and r(Cl–Cl) = 4.290 A). In consideration of the van der Waals
The y* absorption at 1295.6 cm-1 (50.7 cm-1 lower than the y
absorption) in the CCl4 spectra shows a 13C shift of -46.2 cm-1 (12 :
13 ratio of 1.039). While the C–Cl stretching frequency is unusually
high like those of other small transition metal carbynes,8,10,11 the
large frequency differences between the y and y* absorptions in
the isotopomer spectra (different 12 : 13 frequency ratios) virtually
preclude the possibility that the weaker y* absorptions arise from
radius of Ar (1.88 A), it is possible that an argon atom can be
˚
trapped between the two chlorine atoms. Therefore, the difference
in the molecular structures with the Os–Cl bonds long enough to
hold an Ar atom in between may be preserved in the matrix cages,
resulting in the observed y and y* absorptions from the two close
lying singlet and triplet electronic states.
≡
ClC OsCl3(S) in a different matrix site. Other plausible products
Os carbyne structures
=
(e.g. CCl3–OsCl and CCl2 OsCl2) would not show an absorption
in this high frequency region: normally the C–Cl, Os–Cl, and C–Os
stretching frequencies are much lower (<900 cm-1). Therefore, we
cautiously suggest the possibility that the y* absorption arises from
Fig. 7 reveals that the Os carbyne structure varies significantly
≡
with the ligands and electronic states. HC OsHX2 (X = F or Cl)
in its singlet ground state shows a highly distorted structure. The
H, C, Os and two halogen atoms form a near planar structure and
the remaining hydrogen atom bonded to the Os atom is located
ClC OsCl3 in the triplet state, which is only 1.7 kcal mol-1 higher
≡
in energy than the singlet ground state. The observed frequency
and its 13C shift are in excellent agreement with the predicted values
of 1311.7 and -47.5 cm-1 for the triplet state as shown in Table S7.†
≡
straight above it. HC OsCl3 has a Cs structure with one long Os–
Cl bond and two short Os–Cl bonds, instead of a C3v structure,
9
≡
≡
The structures of ClC OsCl3 in the singlet and triplet states are
similar to the structure of HC OsH3 reported previously. The
carbyne tetra halides (XC OsX3) also show distorted structures.
≡
significantly different as shown in Fig. 7. While both structures
have Cs symmetry, the singlet structure has one short and two
long Os–Cl bonds and t◦he two Cl atoms are relatively close to each
For the carbynes with a OsCl3 or OsF3 group, one Os–X bond is
shorter than the remaining two Os–X bonds in the singlet state,
which are relatively close to each other. On the other hand, in the
triplet state one Os–X bond is longer than the other two Os–X
bonds, which are farther apart than those in the singlet state.
While the Re carbynes, whose low symmetry structures are
traced to the Jahn–Teller effect due to the unpaired electron,11
the Ru and Os carbynes in the singlet ground state also have
similarly distorted structures. The lone electron pair on the
˚
other (<ClOsCl = 85.2 and r(Cl–Cl) = 3.116 A). In contrast, the
triplet structure has one long and two short Os–Cl bonds and the
metal center apparently plays a crucial role in determining the
1
structure.8,9 Fig. 8 illustrates the HOMO’s of HC OsHF2( A¢),
≡
1
3
≡
≡
ClC OsCl3( A¢), and ClC OsCl3( A¢¢). Clearly there is a nodal
plane between the two F atoms in HC OsHF2, pushing them
apart and thereby forming a near planar structure with H, C and
≡
≡
Os atoms. In the ClC OsCl3 singlet state, the lone electron pair
provides bonding character between the two chlorine atoms and
anti-bonding character between the remaining chlorine atom and
two chlorine atoms, resulting in the small Cl–Os–Cl bond angle.
In the triplet state, on the other hand, the anti-bonding character
between the two chlorine atoms pushes them apart.
Comparison of Fe, Ru and Os complexes
The previous1–3 and present results reveal that the primary
products of group 8 metal reactions with small alkanes and
halomethanes vary greatly with going down the family group
column. Parallel to the previous early transition metal studies,1,2
the tendency that the higher oxidation state complexes are more
favoured in reactions of heavier metals with small alkanes and
halomethanes is evident with group 8 metals.3 Fe forms both
the insertion and carbene products with di-, tri-, and tetra-
halomethanes, whereas it provides only the insertion products
in reactions of small alkanes and methyl fluoride. Ru generates
carbynes along with carbene or insertion complexes in reactions
with halomethanes while it still produces an insertion product
in reactions with small alkanes. On the other hand, only carbyne
products are identified from the reactions of Os with small alkanes
and halomethanes, showing the high preference of carbon–
osmium triple bond.
Fig.
7
Optimized molecular structures of Os carbyne complexes
in the ground electronic states. The structures are calculated with
B3LYP/6–311++G(3df,3pd) and the SDD core potential and basis set
are used for Os. In HC OsHX2, C, Os and two halogen atoms form a near
≡
planar structure and the hydrogen atom is located above it. Also notice
≡
≡
that FC OsF2Cl and ClC OsFCl2 have C1 structures. The bond lengths
and angles are in A and ◦, respectively.
˚
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©

1
1
3
≡
≡
≡
Fig. 8 The HOMO’s of HC OsHF2( A¢), ClC OsCl3( A¢), and ClC OsCl3( A¢¢). Notice the anti-bonding character between the two F atoms in
≡
≡
HC OsHF2, spreading them apart. The significant difference between the singlet and triplet structures of ClC OsCl3 can also be traced to the HOMO’s.
The nodal planes bisecting the two Os–Cl bonds in the triplet state spread the two Cl atoms apart, but the two Cl atoms are much closer in the singlet
state.
Fig. 9 illustrates, as an example, the energies of the plausible
group 8 metal reaction products with methylene chloride in the
ground electronic states relative to the reactant (M + CH2Cl2)
energies. Attempts to locate a stable Fe carbyne species result
in the Fe insertion or methylidene structure depending on the
electronic state: we were unable to locate a stable methylidyne on
the singlet or triplet potential energy surface for this system. This
indicates that the Fe methylidyne complex is not a stable energy
minimum. In contrast, the Ru carbene and carbyne complexes are
more stable than the insertion product, and the Os carbyne product
has the lowest energy among the three probable complexes. The
previous studies also suggest that a higher oxidation state complex
is perhaps more stable in the matrix than predicted, due to the
more polarized bonds (particularly the carbon–metal bond).8,10,11,22
Finally, our experimental and computational results with group
8 metal atoms are consistent with those from analogous group 6
and 7 studies.10,11,22
Fig. 10 Optimized molecular structures with B3LYP/6–311++G-
(3df,3pd)/SDD for the plausible products from group 8 transition metals
and CH2Cl2. Notice their unusual structures, particularly the C–Cl
=
distortion in CH2Cl–FeCl, allene-type structure of CH2 FeCl2, and near
planar structure of the carbyne complexes with a hydrogen atom placed
right above (see ref. 8a).
from the interaction between the lone electron pair of the
electron-rich chlorine atom and the metal center. The allene-
type carbene structures and the near planar carbyne structure
with the hydrogen atom right above is believed to be related
to the non-bonding extra electrons on the metal center. Fig. 11
Fig. 9 The energies of the plausible reaction products from reactions
of group 8 metals with CH2Cl2. Attempts to optimize the Fe carbyne
shows the MO’s believed responsible for the distorted molecular
structures. While the unpaired electrons in CH2Cl–FeCl(Q) occupy
the Fe d orbitals, one of the lone electron pairs on the Cl atom
bonded to the carbon atom interacts with the metal center,
leading to inclination of the C–Cl bond toward the Fe atom.8a
The carbene complex HOMO’s reveal that the planar structure
of the CMCl2 moiety results from the anti-bonding character
between the two chlorine atoms. Similarly the near planar structure
structure gave the insertion or methylidene structure depending on the
electronic state (see ref. 8a).
The computed group 8 metal complex structures show unusual
distortions as illustrated in Fig. 10. The C–Cl bond in the Fe
insertion complex is inclined to the metal center while the C–H
and C–F bonds of the corresponding products do not show
similar distortion.8a Most probably, the inclination originates
5864 | Dalton Trans., 2009, 5858–5866
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©

=
Fig. 12 Molecular structures for the methylidene complexes CH2 MHF
computed with B3LYP/6–311++G(3df,3pd) and SDD for Ru and Os.
Conclusions
The matrix IR spectra show that the Os carbyne products are pre-
dominantly formed in reactions with di-, tri-, tetra-halomethanes,
in line with the previous results of Os reactions with methane,
methyl halides, and ethane,9 re-confirming the high preference
for the carbon–osmium triple bond. The carbyne C–H stretching
frequencies are observed at about 200 cm-1 on the blue side of the
corresponding precursor absorption, due to the higher s character
in the bond. Vibrational analyses show that the carbyne C–X
≡
stretching mode coupled with the C Os stretching mode, resulting
in the unusually high frequencies. DFT calculations reveal low
symmetry structures for the small Os carbynes, and the extra
electrons evidently play an important role in the structures, in line
with the previously investigated Fe and Ru products.8 The two sets
of product absorptions in the Os + CCl4 spectra suggest that both
≡
singlet and triplet ClC OsCl3 with similar energies are trapped in
an argon matrix, due to the large differences in structure and long
Os–Cl bonds.
Fig. 11 MO’s responsible for the distinct structures of the group 8
transition metal complexes. The MO (31st a-spin) of CH2Cl–FeCl(Q)
corresponds to the lone electron pair on the Cl atom showing the
interaction between the chlorine and iron atoms, distorting the C–Cl
bond. The HOMO’s of the carbene and carbyne complexes reveal that
the non-bonding electrons provide anti-bonding character between the
chlorine atoms.
The dominant formation of the Os carbynes, along with
the previous results of group 8 metals,8,9 reveal the tendency
that higher oxidation state complex is more favoured on going
down the column,25 parallel to the previously investigated early
transition metal systems.10,22 DFT calculations also reproduce
the tendency that stability of the carbyne product relative to the
corresponding insertion and methylidene complexes increases with
going down the column. The present and previous results lead
to a conclusion that Re and Os, the group 7 and 8 third row
elements, have the highest preference to form a carbyne complex in
reaction with small alkanes and halomethanes. The group 8 metal
complexes also show interesting photochemistry including photo-
reversibility and highly distorted structures including unusual
inclination of the C–Cl bond in the Fe insertion complexes.
consisting of the C, Ru and two Cl atoms in the carbyne complex
is also caused by the extra lone electron pair on the metal
center.8b
Our recent studies show that groups 9–12 transition metals
do not form a carbyne complex in reactions with small alkanes
and halomethanes,24 which is consistent with the computational
results that the high oxidation state complexes become gradually
less favoured on moving from group 8–12. Previous investi-
gations have also shown that higher oxidation-state complexes
are more favoured with moving from group 3–6.22 Only the
carbyne products are identified from reactions of Re and Os
with small alkanes and halomethanes, revealing the stability
of the carbyne product relative to the insertion and carbene
complexes.9,11 All of these previous and the present results8–10,11,22
lead to a conclusion that Re and Os are indeed at the apex in
terms of the preference for the high oxidation-state complexes
in reactions of transition-metal atoms and small alkanes and
halomethanes.
Acknowledgements
We gratefully acknowledge financial support from National
Science Foundation (U. S.) Grant CHE 03–52487 to L. A.,
and support from Korea Institute of Science and Technology
Information (KISTI) by Grant No. KSC-2006-S00–2014.
References
=
This trend is also illustrated in the CH2 MHF methylidene
1 (a) E. O. Fischer, G. Kreis, C. G. Kreiter, J. Mu¨ller, G. Huttner and H.
Lorenz, Angew. Chem., Int. Ed. Engl., 1973, 12, 564; (b) S. J. McLain,
C. D. Wood, L. W. Messerle, R. R. Schrock, F. J. Hollander, W. J.
Youngs and M. R. Churchill, J. Am. Chem. Soc., 1978, 100, 5962.
2 (a) R. R. Schrock, Chem. Rev., 2002, 102, 145; (b) J. W. Herndon,
Coord. Chem. Rev., 2007, 251, 1158; (c) J. W. Herndon, Coord. Chem.
Rev., 2006, 250, 1889; (d) J. W. Herndon, Coord. Chem. Rev., 2005, 249,
999; (e) J. W. Herndon, Coord. Chem. Rev., 2004, 248, 3.
structures calculated for the group 8 metals and illustrated in
Fig. 12. Although these intermediate molecules are not observed
in our spectra, they are physically stable and their computed
structures illustrate the trend of increased a-H-transfer from the
carbon to the metal center, which accompanies formation of the
higher oxidation state complexes.
This journal is
The Royal Society of Chemistry 2009
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©

3 (a) S. K. Ritter, Handbook of Metathesis, ed. R. H. Grubbs, Wiley-
VCH, Weinheim, Germany, 2003, vol. 1–3; (b) U. H. F. Bunz, Chem.
Rev., 2000, 100, 1605; (c) W. A. Nugent and J. M. Mayer, Metal–
Ligand Multiple Bonds, John Wiley and Sons, New York, 1988; (d) For
a discussion of the explosive growth in the use of iron as a catalyst, see:
C. & E. News, July 28, 2008, p. 53.
4 (a) C. L. Gross, S. R. Wilson and G. S. Girolami, J. Am. Chem. Soc.,
1994, 116, 10294; (b) T. Bolan˜o, R. Castarlenas, M. A. Esteruelas, F. J.
Modrego and E. On˜ate, J. Am. Chem. Soc., 2005, 127, 11184; (c) T.
Bolan˜o, R. Castarlenas, M. A. Esteruelas and E. On˜ate, J. Am. Chem.
Soc., 2006, 128, 3965; (d) L. M. Hodges, M. Sabat and W. D. Harman,
Inorg. Chem., 1993, 32, 371; (e) L.-J. Baker, G. R. Clark, C. E. F.
Rickard, W. R. Roper, S. D. Woodgate and L. J. Wright, J. Organomet.
Chem., 1998, 551, 247. (Os carbynes).
5 (a) H. Fischer, P. Hofmann, F. R. Kreissl, R. R. Schrock, U. Schubert
and K. Weiss, Carbyne Complexes, VCH, New York, 1988; (b) M. A.
Gallop and W. R. Roper, Adv. Organomet. Chem., 1986, 25, 121; (c) P. F.
Engel and M. Pfeffer, Chem. Rev., 1995, 95, 2281.
6 (a) T.-F. Mao and G. L. Rempel, J. Mol. Catal. A: Chem., 2000, 153,
63; (b) A. K. Hughes, K. L. Peat and K. Wade, J. Chem. Soc., Dalton
Trans., 1997, 2139; (c) C. E. F. Rickard, W. R. Roper, G. R. Whittell
and L. J. Wright, J. Organomet. Chem., 2004, 689, 605. (Os complexes).
7 (a) J. Zhang, D. C. Grills, K.-W. Huang, E. Fujita and R. M. Bullock,
J. Am. Chem. Soc., 2005, 127, 15684; (b) J. Zhang, K. W. Huang, D. J.
Szalda and R. M. Bullock, Organometallics, 2006, 25, 2209.
8 (a) H.-G. Cho, J. T. Lyton and L. Andrews, Organometallics, 2008, 27,
5241 (Fe + halomethanes); (b) H.-G. Cho and L. Andrews, Eur. J. Inorg.
Chem., 2008, 2537. (Ru + halomethanes).
13 (a) H. A. Jahn and E. Teller, Proc. R. Soc. London, Ser. A, 1937, 161, 220;
(b) E. Teller, A historical note, in The Jahn–Teller Effect in Molecules
and Crystals, ed. R. Engelman, Wiley-Interscience, London, 1972.
14 L. Andrews, H. Willner and F. T. Prochaska, J. Fluorine Chem., 1979,
13, 273, isotopic modifications synthesized.
15 (a) L. Andrews and A. Citra, Chem. Rev., 2002, 102, 885, and references
therein; (b) L. Andrews, Chem. Soc. Rev., 2004, 33, 123, and references
therein.
16 K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V.
Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson,
H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X.
Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi,
C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth,
P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D.
Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.
Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y.
Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson,
W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, Gaussian, 03,
Revision B.04, Gaussian, Inc., Pittsburgh, PA, 2003.
17 (a) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; (b) C. Lee, Y. Yang
and R. G. Parr, Phys. Rev. B: Condens. Matter Mater. Phys., 1988, 37,
785.
18 K. Raghavachari and G. W. Trucks, J. Chem. Phys., 1989, 91,
1062.
9 H.-G. Cho and L. Andrews, Organometallics, 2008, 27, 1786. (Os +
CH4, C2H6, CH3X).
19 D. Andrae, U. Haeussermann, M. Dolg, H. Stoll and H. Preuss, Theor.
Chim. Acta, 1990, 77, 123.
20 K. Burke, J. P. Perdew, Y. Wang, in Electronic Density Functional
Theory: Recent Progress and New Directions, ed. J. F. Dobson,
G. Vignale and M. P. Das, Plenum, 1998.
21 (a) A. P. Scott and L. Radom, J. Phys. Chem., 1996, 100, 16502; (b) M. P.
Andersson and P. L. Uvdal, J. Phys. Chem. A, 2005, 109, 3937.
22 L. Andrews and H.-G. Cho, Organometallics, 2006, 25, 4040, and
references therein (review article). See also: H.-G. Cho and L. Andrews,
J. Phys. Chem. A, 2004, 108, 6294, (Ti + CH3F).
23 I. R. Beattie, H. E. Blaydon, R. A. Crocombe, P. J. Jones and J. S.
Ogden, J. Raman Spectrosc., 1976, 4, 313.
10 J. T. Lyon, H.-G. Cho and L. Andrews, Organometallics, 2007, 26,
6373(Cr, Mo, W + CHX3, CX4).
11 (a) H.-G. Cho and L. Andrews, Organometallics, 2007, 26, 4098; (b) H.-
G. Cho and L. Andrews, Inorg. Chem., 2008, 47, 1653. (Re + alkanes);
(c) J. T. Lyon, H.-G. Cho, L. Andrews, H.-S. Hu and J. Li, Inorg. Chem.,
2007, 46, 8728. (Re + CHX3, CX4).
12 (a) J. Manna, R. F. Dallinger, V. M. Miskowski and M. D. Hopkins,
≡
J. Phys. Chem. B, 2000, 104, 10928, (H-C W group freq); (b) M.
Barnes, A. J. Merer and G. F. Metha, J. Mol. Spectrosc., 1997, 181, 168,
≡
(Ti CH); (c) L. Sari, Y. Yamaguchi and H. F. Schaefer, III, J. Chem.
≡
Phys., 2001, 115, 5932, (Ge CH); (d) A. Kalemos, T. H. Dunning,
24 H.-G. Cho, L. Andrews, unpublished data. (Group 9–12 metals +
halomethanes).
25 Pyykko, P. Adv. Quantum Chem., 1978, 11, 353.
Jr., J. F. Harrison and A. Mavridis, J. Chem. Phys., 2003, 119, 3745,
≡
(Ti CH).
5866 | Dalton Trans., 2009, 5858–5866
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©