Thermal rearrangement of osmabenzenes to osmium cyclopentadienyl complexes

Article abstract of DOI:10.1021/om1003754

The purple osmabenzene complex Os(C₅H₄{SMe-1}) (CF₃SO₃)(CO)(PPh₃)₂ (1) is formed in high yield through reaction between Os(C₅H₄{S-1})(CO) (PPh₃)₂ and methyl triflate. The neutral blue osmabenzenes Os(C₅H₄{SMe-1})(cis-X)(CO)(PPh₃)₂ (X = I (2a), Cl (2b), SCN (2c), CF₃CO₂ (2d)) are readily obtained through treatment of 1 with the appropriate anion X^-. In these complexes the geometry about osmium is approximately octahedral, with the two PPh₃ ligands being mutually trans and X being cis to the SMe-substituted carbon of the metallabenzene ring. When solutions of 2a in benzene are heated under reflux, the I and CO ligands interchange positions and the brown isomeric osmabenzene Os(C₅H₄{SMe-1})(trans-I) (CO)(PPh₃)₂ (3a) is formed. However, if a solution of either 2a or 3a is heated under reflux in toluene, the metal-bound carbon atoms of the osmabenzene fragment couple and a mixture of the two cyclopentadienyl complexes [Os(η⁵-C₅H₄SMe)(CO)(PPh ₃)₂]I (4a) and Os(η⁵-C₅H ₄SMe)I(CO)(PPh₃) (5a) is formed. Heating solutions of 2b-d is not a viable route to the corresponding brown isomers of these compounds, because cyclopentadienyl products are formed directly. In the case of 2b a mixture of the cyclopentadienyl complexes [Os(η⁵-C ₅H₄SMe)(CO)(PPh₃)₂]Cl (4b) and Os(η⁵-C₅H₄SMe)Cl(CO)(PPh₃) (5b) is formed, while in the case of 2c [Os(η⁵-C₅H ₄SMe)(CO)(PPh₃)₂]SCN (4c) and Os(η⁵-C₅H₄SMe)(SCN)(CO)(PPh₃) (5c) are formed. In contrast, [Os(η⁵-C₅H ₄SMe)(CO)(PPh₃)₂](CF₃CO ₂) (4d) is the only cyclopentadienyl complex formed on heating solutions of 2d. The brown osmabenzene isomers Os(C₅H ₄{SMe-1})(trans-X)(CO)(PPh₃)₂ (X = Cl (3b), SCN (3c), CF₃CO₂ (3d)) are accessible through treatment of 3a with AgCF₃SO₃, followed by addition of the appropriate anion X^-. Heating the brown isomers 3a,b under the same conditions gives the same mixture of cyclopentadienyl complexes that are formed when 2a,b, respectively, are heated. However, 3c,d are resistant to thermal rearrangement and remain unchanged when heated under reflux in toluene. The crystal structures of 2c, 3c, 4d, and 5a have been obtained.

Full text of DOI:10.1021/om1003754

5358 Organometallics 2010, 29, 5358–5365
DOI: 10.1021/om1003754
Thermal Rearrangement of Osmabenzenes to Osmium
Cyclopentadienyl Complexes†
Paul M. Johns, Warren R. Roper, Scott D. Woodgate, and L. James Wright*
Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand
Received April 30, 2010
The purple osmabenzene complex Os(C5H4{SMe-1})(CF3SO3)(CO)(PPh3)2 (1) is formed in high yield
through reaction between Os(C5H4{S-1})(CO)(PPh3)2 and methyl triflate. The neutral blue osmabenzenes
Os(C5H4{SMe-1})(cis-X)(CO)(PPh3)2 (X = I (2a), Cl (2b), SCN (2c), CF3CO2 (2d)) are readily obtained
through treatment of 1 with the appropriate anion X-. In these complexes the geometry about osmium is
approximately octahedral, with the two PPh3 ligands being mutually trans and X being cis to the SMe-
substituted carbon of the metallabenzene ring. When solutions of 2a in benzene are heated under reflux, the
I and CO ligands interchange positions and the brown isomeric osmabenzene Os(C5H4{SMe-1})(trans-
I)(CO)(PPh3)2 (3a) is formed. However, if a solution of either 2a or 3a is heated under reflux in toluene, the
metal-bound carbon atoms of the osmabenzene fragment couple and a mixture of the two cyclopenta-
dienyl complexes [Os(η5-C5H4SMe)(CO)(PPh3)2]I (4a) and Os(η5-C5H4SMe)I(CO)(PPh3) (5a) is formed.
Heating solutions of 2b-d is not a viable route to the corresponding brown isomers of these compounds,
because cyclopentadienyl products are formed directly. In the case of 2b a mixture of the cyclopentadienyl
complexes [Os(η5-C5H4SMe)(CO)(PPh3)2]Cl (4b) and Os(η5-C5H4SMe)Cl(CO)(PPh3) (5b) is formed,
while in the case of 2c [Os(η5-C5H4SMe)(CO)(PPh3)2]SCN (4c) and Os(η5-C5H4SMe)(SCN)(CO)(PPh3)
(5c) are formed. In contrast, [Os(η5-C5H4SMe)(CO)(PPh3)2](CF3CO2) (4d) is the only cyclopentadienyl
complex formed on heating solutions of 2d. The brown osmabenzene isomers Os(C5H4{SMe-1})(trans-X)-
(CO)(PPh3)2 (X = Cl (3b), SCN (3c), CF3CO2 (3d)) are accessible through treatment of 3a with
AgCF3SO3, followed by addition of the appropriate anion X-. Heating the brown isomers 3a,b under
the same conditions gives the same mixture of cyclopentadienyl complexes that are formed when 2a,b,
respectively, are heated. However, 3c,d are resistant to thermal rearrangement and remain unchanged
when heated under reflux in toluene. The crystal structures of 2c, 3c, 4d, and 5a have been obtained.
Introduction
development of rational syntheses of kinetically stable metalla-
benzenes. Although undetected metallabenzenes have often been
proposed as intermediates in the formation of cyclopentadienyl
complexes,6-16 examples that involve the well-defined trans-
formation of isolated metallabenzenes into the corresponding
Metallabenzenes are now a well established class of metalla-
aromatic compounds. Although a considerable number of
papers have appeared that address the reaction chemistry of
these species, this is still a relatively underdeveloped area.1-3
One of the fundamental reactions of metallabenzenes is the
process whereby the two metal-bound carbon atoms couple to
form a cyclopentadienyl ligand. This has been identified as
a key decomposition route for metallabenzenes, and calcula-
tions suggest that most metallabenzenes are thermodynami-
cally unstable with respect to this rearrangement.4,5 A deeper
understanding of this process is therefore essential for the
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Williams, I. D.; Lin, Z.; Jia, G. Angew. Chem., Int. Ed. 2007, 46, 9065–
9068.
† Part of the Dietmar Seyferth Festschrift. Dedicated to Dietmar Seyferth in
recognition of his outstanding contributions to the advancement of organo-
metallic chemistry, particularly as Editor of Organometallics.
*To whom correspondence should be addressed. E-mail: lj.wright@
auckland.ac.nz.
(12) Clark, G. R.; Lu, G.-L.; Roper, W. R.; Wright, L. J. Organo-
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r
pubs.acs.org/Organometallics
Published on Web 07/28/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 21, 2010 5359
cyclopentadienyl complexes are surprisingly rare. The best
example is provided by the iridabenzene Ir(C5H3{Ph-1}{t-Bu-
2})(CO)(PPh3)2, which in solution at 50 °C is smoothly con-
verted into the corresponding cyclopentadienyl complex Ir-
(η5-C5H3{Ph-1}{t-Bu-2})(CO)(PPh3) over 15 h.17 The closely
related trimethylsilyl-substituted iridabenzenes (in mixtures
with the corresponding precursor iridabenzvalenes) are also
slowly converted in solution to the corresponding iridium
cyclopentadienyl complexes, and these reactions have been
monitored by NMR spectroscopy.18,19 In addition to these
examples a reactive ruthenabenzene intermediate has been
detected by NMR spectroscopy in solution at low temperature
and shown to rearrange to the corresponding cyclopentadienyl
complex on warming to 0 °C.20 In a related reaction it has been
reported that on heating solid samples of the ruthenaben-
zene [Ru(C5H3{PPh3-2}{PPh3-4})Cl2(PPh3)2]Cl the free cyclo-
pentadienyl derivative [C5H3{PPh3-1}{PPh3-3}]Cl is formed.21
Herein we report (i) the synthesis of the set of blue osmaben-
zenes Os(C5H4{SMe-1})(cis-X)(CO)(PPh3)2 (X = I (2a), Cl
(2b), SCN (2c), CF3CO2 (2d); PPh3 ligands mutually trans, X
and the SMe-substituted carbon mutually cis) through treat-
ment of purple Os(C5H4{SMe-1})(cis-CF3SO3)(CO)(PPh3)2
(1) with the appropriate anion X-, (ii) the conversion of 2a
into the corresponding brown isomeric osmabenzene Os-
(C5H4{SMe-1})(trans-I)(CO)(PPh3)2 (3a; where CO and I
have interchanged positions and the I and the SMe-substituted
carbon are mutually trans) through heating 2a under reflux in
benzene and the formation of the remaining brown osmaben-
zene isomers Os(C5H4{SMe-1})(trans-X)(CO)(PPh3)2 (X=Cl
(3b), SCN (3c), CF3CO2 (3d)) through sequential treatment of
3a with AgCF3SO3 and X-, (iii) heating toluene solutions of
2a-c under reflux gives mixtures of the two corresponding
cyclopentadienyl complexes [Os(η5-C5H4SMe)(CO)(PPh3)2]X
(4a-c) and Os(η5-C5H4SMe)X(CO)(PPh3) (5a-c), while 2d
gives [Os(η5-C5H4SMe)(CO)(PPh3)2]CF3CO2 (4d) exclusively,
(iv) heating toluene solutions of the brown isomers 3a,b under
reflux also gives mixtures of the two corresponding cyclopen-
tadienyl complexes (4a,b and 5a,b), although 3c,d are unreac-
tive under these conditions, and (v) the crystal structures of 2c,
3c, 4d, and 5a.
Scheme 1. Syntheses of the Blue Osmabenzenes 2a-d and the
Corresponding Isomeric Brown Osmabenzenes 3a-d
and 243.36 ppm, while the remaining ring carbon atoms appear
in the normal aromatic region (C2 122.58 ppm, C4 126.87 ppm,
and C3 146.09 ppm). The proton on C5 (H5) also has a
characteristically low-field signal (at 13.93 ppm) and the remain-
ing ring protons (H2 6.50 ppm, H3 7.04 ppm, and H4 6.94 ppm)
have regular aromatic shifts. The single resonance observed for
the two PPh3 ligands in the 31P NMR spectrum and the coupling
to phosphorus observed for the phenyl carbon atoms in the 13C
NMR spectrum indicates the two PPh3 ligands are mutually
-
trans. We have represented the structure of 1 with the CF3SO3
anion coordinated to osmium in the position cis to the SMe-
substituted metallabenzene carbon (C1) because of the similarity
between the IR and NMR spectral properties of 1and the closely
related osmabenzenes 2a-c. The structure of 2b has been
reported previously,23 and the X-ray crystal structure determina-
tion of 2c is discussed below. However, the possibility that the
Results and Discussion
22
Treatment of the osambenzene Os(C5H4{S-1})(CO)(PPh3)2
-
CF3SO3 anion is present as an uncoordinated counteranion,
with methyl triflate is a high-yielding and direct route to the
purple osmabenzene Os(C5H4{SMe-1})(cis-CF3SO3)(CO)-
(PPh3)2 (1) (Scheme 1). Characterization data for 1 and all the
other new compounds are given in the Experimental Section.
The ring-numbering system used for discussion of the NMR
spectra is indicated in Scheme 1. The 1H and 13C NMR spectra
for 1 are entirely consistent with a metallabenzene formula-
tion.1,2 The metallabenzene metal-bound carbon atoms C1 and
C5 have characteristically downfield-shifted signals at 224.63
with either a water molecule or the sulfur atom of the methane-
thiolate group coordinated to osmium, cannot be ruled out.
Osmabenzene 1 is a convenient starting material for the
synthesis of the set of closely related blue osmabenzenes
Os(C5H4{SMe-1})(cis-X)(CO)(PPh3)2 (X = I (2a), Cl (2b),
SCN (2c), CF3CO2 (2d)) through simple anion metathesis
reactions (Scheme 1). In each of these cases the ligand X is cis
to the SMe-substituted carbon of the metallabenzene ring.
We have previously reported an alternative synthesis of 2a
that involves treatment of Os(C5H4{S-1})(CO)(PPh3)2 with
methyl iodide.22 Furthermore, 2b can also be prepared by
treating 2a first with AgCF3SO3 and then LiCl, although this
is a less efficient route than that depicted in Scheme 1. As
might be expected, the 1H and 13C NMR spectra of each of
the blue compounds 2a-d are all very similar and are
consistent with osmabenzene formulations. As an example,
(17) Wu, H.-P.; Weakley, T. J. R.; Haley, M. M. Chem. Eur. J. 2005,
11, 1191–1200.
(18) Wu, H.-P.; Ess, D. H.; Lanza, S.; Weakley, T. J. R.; Houk, K. N.;
Baldridge, K. K.; Haley, M. M. Organometallics 2007, 26, 3957–3968.
(19) Wu, H.-P.; Lanza, S.; Weakley, T. J. R.; Haley, M. M. Organo-
metallics 2002, 21, 2824–2826.
(20) Yang, J.; Jones, W. M.; Dixon, J. K.; Allison, N. T. J. Am. Chem.
Soc. 1995, 117, 9776–9777.
(21) Zhang, H.; Feng, L.; Gong, L.; Wu, L.; He, G.; Wen, T.; Yang,
F.; Xia, H. Organometallics 2007, 26, 2705–2713.
(22) Elliott, G. P.; Roper, W. R.; Waters, J. M. J. Chem. Soc., Chem.
Commun. 1982, 811–13.
(23) Johns, P. M.; Roper, W. R.; Woodgate, S. D.; Wright, L. J. Acta
Crystallogr., Sect. E 2009, E65, m1319.

5360 Organometallics, Vol. 29, No. 21, 2010
Johns et al.
Figure 2. Molecular structure of 3c with thermal ellipsoids at
the 50% probability level. Hydrogen atoms have been omitted
for clarity.
Figure 1. Molecular structure of 2c with thermal ellipsoids at
the 50% probability level. Hydrogen atoms have been omitted
for clarity.
the resonances of the ring protons of 2c are observed at
6.36 (H2), 7.03 (H3), 6.38 (H4), and 13.17 ppm (H5) and
the ring carbon atoms appear at 244.70 (C1), 120.00 (C2),
146.72 (C3), 125.98 (C4), and 225.32 ppm (C5). The crystal
structure of 2c has been determined, and there are two
molecules in the asymmetric unit. The molecular structure
of one of these is shown in Figure 1, and for simplicity the
discussion of the bond lengths and angles below refers to
only one of these molecules. The crystal data and refinement
details for 2c and for the other crystal structures reported in
this paper are available in the Supporting Information.
The overall geometry is approximately octahedral with the
two triphenylphosphine ligands arranged mutually trans.
The cis disposition of the SCN- ligand and the SMe-sub-
stituted carbon atom is confirmed. The SCN- ligand is
bonded through nitrogen in an approximately linear geo-
metry with the angle Os-N1-C8 = 168(1)°. The two osma-
12.40 ppm (H5). Subtle changes are also apparent in the 13C
NMR spectrum of 3a (244.18 (C1), 120.48 (C2), 146.07 (C3),
128.22 (C4), and 219.34 ppm (C5)), with the largest change
(6.7 ppm) occurring for C1. Although we have not been able
to obtain crystals of 3a that are suitable for an X-ray crystal
structure determination, we have obtained the crystal struc-
ture of the thiocyanate analogue 3c (see below), and this
confirms the geometry depicted in Scheme1.
In contrast to the thermal isomerization process that
transforms blue 2a to brown 3a, heating benzene solutions
of 2b-d does not lead cleanly to the corresponding brown
isomers Os(C5H4{SMe-1})(trans-X)(CO)(PPh3)2 (X = Cl
(3b), SCN (3c), CF3CO2 (3d)). Instead, conversion to cyclo-
pentadienyl complexes of osmium very slowly ensues (see
below). Nevertheless, 3b-d can be conveniently prepared by
the treatment of 3a with AgCF3SO3, removal of the AgI
precipitate, and then addition of the appropriate anion X-
(Scheme 1). As might be expected, the resonances of the
metallabenzene ring atoms in the 1H and 13C NMR spectra
of 3a-d are all very similar. The crystal structure of 3c has
been obtained, and the molecular structure is shown in
Figure 2. The structure confirms that the CO and SCN
ligands have exchanged positions compared with the case
for 2c and the thiocyanate ligand is now trans to the SMe-
substituted carbon of the metallabenzene ring.
˚
benzene Os-C distances (Os-C1=2.112(8) A, Os-C5 =
˚
2.025(8) A) are not equivalent but are consistent with there
being some multiple character to each of these bonds. The
longest of these two distances (Os-C1) involves the carbon
trans to the CO ligand. The C-C bond distances within the
planar osmabenzene ring are entirely appropriate for a metal-
˚
˚
labenzene (C1-C2 = 1.428(11) A, C2-C3 = 1.375(12) A,
˚
˚
C3-C4 = 1.384(12) A, C4-C5 = 1.393(11) A).
During investigations into the thermal stability of the
metallabenzenes 2a-d it was found that, on heating a
benzene solution of 2a under reflux for a period of 10 min,
the color changes from blue to brown. The brown product
isolated in good yield from solution is the isomeric osma-
benzene Os(C5H4{SMe-1})(trans-I)(CO)(PPh3)2 (3a), which
differs from 2a in that the iodide and carbonyl ligands have
interchanged positions so that the iodide is now trans to the
SMe-substituted carbon atom (Scheme 1). This different
geometry gives rise to small changes in the resonances of
the osmabenzene ring protons in the 1H NMR spectrum of
3a. These are observed at 5.67 (H2), 6.90 (H3), 7.28 (H4), and
As in 2c, the SCN ligand in 3c is bound through nitrogen
and has an approximately linear geometry (Os-N-C8 =
176.2(3)°). The two osmabenzene Os-C distances are in-
˚
˚
equivalent (Os-C1 = 2.029(4) A, Os-C5 = 2.091(4) A),
and again it is the bond trans to the CO ligand (in this case
Os-C5) that is the longest. The bond distances within the
˚
planar osmabenzene ring (C1-C2 = 1.434(6) A, C2-C3 =
˚
˚
˚
1.369(6) A, C3-C4 = 1.425(6) A, C4-C5 = 1.366(6) A) all
fall within the range observed for other metallabenzenes but
clearly show some alternation in length. Unfortunately
the relatively high esd values obtained for the correspon-
ding distances in 2c means that no significant differences

Article
Organometallics, Vol. 29, No. 21, 2010 5361
Scheme 2. Rearrangement of the Blue Osmabenzenes 1 and 2a-d
and the Isomeric Brown Osmabenzenes 3a,b to the Corresponding
Cyclopentadienyl Osmium Complexes 4a-e and 5a-c
Figure 3. Molecular structure of 5a with thermal ellipsoids at
the 50% probability level. Hydrogen atoms have been omitted
for clarity.
The transformation of the isolated and fully characterized
osmabenzene 2a into the cyclopentadienyl complexes 4a and
5a provides a very rare example of this important metalla-
benzene decomposition route. Therefore the behavior of the
other closely related metallabenzenes 2b-d and 3a-d in
boiling toluene was also explored in an attempt to learn
more about the influence that the nature of the ancillary
ligands and the coordination geometry has on this reaction.
It was found that on heating under reflux toluene solutions of
the blue osmabenzenes 2b-d for 1 h conversion into osmium
cyclopentadienyl products also occurred. The products
formed are presented in Table 1. Osmabenzenes 2b and
2c form the chloride and thiocyanate analogues of 4a and
5a, respectively. The cyclopentadienyl products 4b-c and
5b-c have been characterized by high resolution ESI-MS
between these two sets of metallabenzene C-C distances can
be discerned.
With the establishment of convenient routes to the two sets
of isomeric osmabenzenes 2a-d and 3a-d, the possibility
that these osmabenzenes might undergo rearrangement to
cyclopentadienyl compounds under more vigorous thermal
conditions was investigated. It was found that if 2a is heated
under reflux in the higher boiling solvent toluene for 1 h the
initial blue color first changes to brown and then fades as the
colorless cationic cyclopentadienyl complex [Os(η5-C5H4SMe)-
(CO)(PPh3)2]I (4a) precipitates from solution. This material
is obtained in about 45% yield after isolation and purifica-
tion. In addition, the neutral cyclopentadienyl complex
Os(η5-C5H4SMe)I(CO)(PPh3) (5a) can be recovered from
this reaction in about 42% yield (Scheme 2).
1
as well as H and 31P NMR spectroscopy. As expected,
Two sets of equivalent protons for the cyclopentadienyl
ligand of 4a are observed in the 1H NMR spectrum at 4.91
and 5.03 ppm, while the SMe group appears at 2.55 ppm.
In the 13C NMR spectrum the carbon atoms of the cyclo-
pentadienyl ligand appear at 81.53, 90.85, and 113.09 ppm
(C-SMe). The X-ray crystal structure of the trifluoroacetate
analogue of 4a has been determined (see below), and this
confirms the geometry depicted in Scheme 2. The neutral
cyclopentadienyl complex 5a is chiral, and multiplet signals
are observed for the four cyclopentadienyl protons at 4.71
(2H, overlapping signals), 4.78 (1H), and 5.00 ppm (1H). The
five inequivalent carbon atoms of the cyclopentadienyl
ligand are observed in the 13C NMR spectrum at 74.66,
77.99, 81.07, 83.88, and 110.69 (C-SMe) ppm. The X-ray
crystal structure of 5a has been determined, and the mole-
cular structure is shown in Figure 3.
the NMR spectra of these species are very similar to
the spectra of the corresponding compounds 4a and 5a,
respectively.
In contrast to these results, heating under reflux a toluene
solution of 2d results in the rapid (<10 min) and exclusive
formation of [Os(η5-C5H4SMe)(CO)(PPh3)2](CF3CO2) (4d).
1
The H, 13C, and 31P NMR spectra of 4d are essentially
identical with those obtained for 4a-c. The X-ray crystal
structure of 4d has been determined, and the molecular
structure is shown in Figure 4. The distances between the
osmium atom and the five carbon atoms of the η5-cyclopen-
˚
˚
tadienyl ligand are Os-C1 = 2.326(6) A, Os-C2 = 2.296(6) A,
˚
˚
Os-C3 = 2.266(6) A, Os-C4 = 2.245(6) A, and Os-C5=
2.276(6) A. In this case the longest distance is to the carbon
˚
atom that bears the SMe substituent (C1) which is oriented
approximately opposite one of the PPh3 ligands. The other
structural features of 4d are unremarkable. Unlike the other
osmabenzenes, 1 is insoluble in toluene but also undergoes
rapid (<3 min) conversion solely to the corresponding
cationic cyclopentadienyl complex [Os(η5-C5H4SMe)(CO)-
(PPh3)2](CF3SO3) (4e) when heated under reflux in the sol-
vent 1,2-dichloroethane.
The distances between osmium and the carbon atoms of the
˚
cyclopentadienyl ligand are Os-C1 = 2.258(8) A, Os-C2 =
˚
˚
˚
2.305(10) A, Os-C3 = 2.307(8) A, Os-C4 = 2.215(8) A, and
˚
Os-C5 = 2.221(8) A. The longest distances are Os-C2 and
Os-C3, which are positioned nearly opposite the CO ligand.
The other structural parameters associated with 5a are normal.

5362 Organometallics, Vol. 29, No. 21, 2010
Johns et al.
Table 1. Relative Amounts of the Two Cyclopentadienyl Complexes That Are Formed on Heating under Reflux for 1 h Toluene Solutions of
the Osmabenzenes 2a-d and 3a-d and 1,2-Dichloroethane Solutions of 1 (L = PPh3)a
a Complete conversion of 1 and 2d occurs in <3 min.
products (4a and 5a) and in the same ratio that was
obtained from 2a (Table 1). Similarly 3b produced 4b
and 5b also in the same ratio that was obtained starting
from 2b. Unexpectedly, the brown osmabenzenes 3c,d
resisted rearrangement to cyclopentadienyl derivatives
and remained unchanged when heated under reflux in
toluene for 1 h.
The data collected in Table 1 clearly illustrate that, for the
rearrangement reactions of the osmabenzenes 1-3 to the
corresponding osmium cyclopentadienyl complexes 4 and 5,
the rates of the reactions and the ratios of the products
formed are dependent on both the nature of the ancillary
ligands and the arrangement of these ligands about the metal
center. Although we have very little data concerning the
mechanisms of these reactions, we have observed that when
3a is heated in toluene in the presence of 10 equiv of PPh3, the
ratio of the two cyclopentadienyl products formed changes
considerably in favor of 4a (90%) over 5a (10%). The
reduction in the relative amount of 5a formed under these
conditions suggests that PPh3 dissociation is involved in the
rate-determining step of the pathway to this particular
product. In addition we have observed that the cyclopenta-
dienyl osmium products 4a and 5a do not interconvert under
the conditions used for the rearrangements. Thus, 5a does
Figure 4. Molecular structure of the cation of 4d with thermal
ellipsoids at the 50% probability level. Hydrogen atoms and the
CF3CO2 anion have been omitted for clarity.
The behavior of the isomeric brown osmabenzenes
3a-d on heating in toluene was also investigated. 3a was
transformed over 1 h into the same cyclopentadienyl
not convert into 4a on heating in toluene in the presence of
excess PPh3, and similarly 4a does not convert into 5a, even
when heated in 2-methoxyethanol (bp 124 °C), in which the

Article
Organometallics, Vol. 29, No. 21, 2010 5363
Table 2. X-ray Structure Summary for 2c, 3c, 4d, and 5a
2c
3c CH2Cl2
3
4d 1/2C7H8
5a
3
formula
mol wt
C
912.01
triclinic
P1
11.88460(10)
18.036
18.61300(10)
101.73
101.78
44H37NOOsP2S2
C45H39Cl2NOOsP2S2 CH2Cl2
3
C45H37F3O3OsP2S 1/2C7H8
3
C25H22IOOsPS
718.56
orthorhombic
P21nb
7.8046(3)
16.4655(5)
18.1317(6)
90.0
90.0000(10)
90.0
996.93
triclinic
P1
1008.98
monoclinic
P21/n
cryst syst
space group
˚
a, A
11.33480(10)
12.1545(2)
16.1521(2)
71.0440(10)
81.92
82.8800(10)
2076.40(5)
84(2)
10.33680(10)
30.8905(3)
13.78020(10)
90.0
100.7210(10)
90.0
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
95.0630(10)
3788.91(4)
84(2)
3
˚
V, A
T, K
4323.33(7)
200(2)
2330.04(14)
84(2)
Z
4
1.599
1816
3.596
2
1.595
992
3.413
4
1.550
2004
3.126
4
2.048
1360
6.971
d(calcd), g cm-3
F(000)
μ, mm-1
cryst size, mm
2θ (min, max), deg
no. of rflns collected
no. of indep rflns
T (min, max)
goodness of fit on F2
R1, wR2 (obsd data)a
R1, wR2 (all data)
P
0.26 ꢀ 0.20 ꢀ 0.18
1.15, 25.69
14 692
14 251
0.594 172, 0.502 233
1.07
0.22 ꢀ 0.12 ꢀ 0.05
1.86, 26.35
20 080
8349
0.681 708, 0.565 278
1.06
0.21 ꢀ 0.10 ꢀ 0.10
2.00, 26.00
8438
8438
0.795 483, 0.643 484
1.07
0.22 ꢀ 0.12 ꢀ 0.05
1.12, 27.17
5290
5042
0.772 845, 0.483 445
1.02
0.0438, 0.0972
0.0636, 0.1078
P
0.0293, 0.0756
0.0333, 0.0779
P
0.0428, 0.0761
0.0670, 0.0836
0.0339, 0.0835
0.0386, 0.0863
P
a R1= ||Fo| - |Fc||/ |Fo|; wR2 = { [w(Fo2 - Fc2)2]/ [w(Fo2)2]}1/2
.
salt 4a is completely soluble. These observations strongly
suggest that the cyclopentadienyl products 4a-d and
5a-c are probably formed independently via two diffe-
rent pathways. We are currently in the process of carrying
out high-level DFT calculations to establish the most
likely pathways and the key transition states involved in
the transformation of the osmabenzenes 1-3 into the
corresponding cyclopentadienyl osmium products and
also to explain the reluctance of 3c,d to undergo similar
rearrangements. The results of these studies will be re-
ported separately.
With regard to the key step in which the cyclopenta-
dienyl ligand is formed, one possibility is that the C1-C5
coupling process proceeds through a transition state that
has the same basic features as those identified in a recent
DFT study of 18 different model metallabenzenes.4,5 All
the model compounds in this study were found to pass
through a similar transition state that was independent of
the metal and ligand environment. In these transition
states the two metal-bound carbon atoms of the metalla-
benzene are pinched toward each other, there is a distinct
alternation of short and long bonds within the ring, and
the ring planarity is lost. Accordingly it was proposed that
the C-C bond formation step can be viewed as a carbene
migratory insertion.
In conclusion, all the blue osmabenzenes (1, 2a-d) but
only two of the isomeric brown osmabenzenes (3a,b)
undergo thermally induced rearrangements to the corres-
ponding osmium cyclopentadienyl products 4 and 5. The
ratios of the osmium cyclopentadienyl products formed
and the rates at which the reactions proceed are very
dependent on both the nature of the ancillary ligands
and the geometry of these ligands about the metal center.
These well-defined reactions provide very rare examples
of this important metallabenzene decomposition route.
The unexplained observation that the brown osmaben-
zene isomers 3c,d do not undergo thermal rearrange-
ment to cyclopentadienyl complexes may have interesting
mechanistic implications.
Experimental Section
General Comments. Standard laboratory procedures were
followed, as have been described previously.24 The compounds
Os(C5H4{SMe-1})(cis-I)(CO)(PPh3)2 (2a)25 and Os(C5H4{SMe-
1})(cis-Cl)(CO)(PPh3)2 (2b)23 have been reported previously.
Infrared spectra (4000-400 cm-1) of solid samples were
recorded on a Perkin-Elmer Spectrum 400 spectrometer using
an ATR accessory. NMR spectra were obtained on a Bruker
Avance 300 at 25 °C. 1H, 13C, 31P, and 19F NMR spectra were
obtained operating at 300.13 (1H), 75.48 (13C), 121.50 (31P), and
282.4 MHz (19F), respectively. Resonances are quoted in ppm
and 1H NMR spectra referenced to either tetramethylsilane
(0.00 ppm) or the protio impurity in the solvent (7.25 ppm
for CHCl3). 13C NMR spectra were referenced to CDCl3
(77.00 ppm), 31P NMR spectra to 85% orthophosphoric acid
(0.00 ppm) as an external standard, and 19F NMR spectra to
CFCl3 (0.00 ppm) as an external standard. Mass spectra were
recorded using the fast atom bombardment technique with a
Varian VG 70-SE mass spectrometer or electrospray ionization
using a Bruker Daltronics MicrOTOF instrument. X-ray in-
tensities were recorded on a Siemens SMART diffractometer
with a CCD area detector using graphite-monochromated Mo
˚
KR radiation (λ = 0.710 73 A) at 87 K. A summary of the X-ray
crystal structure data is provided in Table 2. Elemental analyses
were obtained from the Microanalytical Laboratory, University
of Otago.
Synthesis of Os(C5H4{SMe-1})(CF3SO3)(CO)(PPh3)2 (1).
Methyl triflate (519 mg) was added to a solution of Os(C5H4-
{S-1})(CO)(PPh3)2 (241 mg) in toluene (5 mL) and the mixture
stirred for 1 h. The purple crystalline solid that formed was
collected by filtration and washed with toluene and n-hexane to
give pure 1 (254 mg, 88%). Anal. Calcd for C44H37O4F3OsP2S2
H2O: C, 51.76; H, 3.85. Found: C, 51.47; H, 3.82. MS (FABþ):
3
found m/z 855.166 63, C43H37O192OsP2S [M]þ requires 855.165 53.
IR (cm-1): 1945 s ν(CO). 1H NMR (CDCl3, δ): 1.98 (s, SCH3, 3H),
=
6.50 (d, H2, 3JHH = 8.3 Hz, 1H), 6.94 (apparent t, H4, JHH
3
3
8.2 Hz, 1H), 7.04 (apparent t, H3, JHH = 8.2, 1H), 7.24-7.39
(24) Maddock, S. M.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J.
Organometallics 1996, 15, 1793–803.
(25) Rickard, C. E. F.; Roper, W. R.; Woodgate, S. D.; Wright, L. J.
Angew. Chem., Int. Ed. 2000, 39, 750–752.

5364 Organometallics, Vol. 29, No. 21, 2010
Johns et al.
3
(m, PPh3, 30H), 13.93 (d, H5, JHH = 8.6 Hz, 1H). 13C NMR
added and the solution was stirred for a further 10 min. The
solvent was removed from the reaction mixture; the resulting
product was dissolved in the minimum amount of dichloro-
methane and then purified by column chromatography on silica
gel using dichloromethane as eluant. The yellow-brown band
was collected, ethanol added, and the dichloromethane removed
under reduced pressure. Recrystallization of the brown material
that formed from dichloromethane/ethanol gave pure 3b as
brown crystals (38 mg, 86%). Anal. Calcd for C43H37OClOsP2S:
C, 58.07; H, 4.19. Found: C, 57.86; H, 4.13. IR (cm-1): 1933 s
(CDCl3, δ): 18.44 (s, SCH3), 122.58 (s, C2), 126.87 (s, C4), 128.19
(t0,24 o-PPh3,2,4JCP = 10.3 Hz), 129.98 (t0,i-PPh3,1,3JCP = 53.2 Hz),
130.68 (s, p-PPh3), 133.83 (t0, m-PPh3, 3,5JCP = 10.6 Hz), 146.09 (s,
C3), 189.49 (t, CO, 2JCP = 10.2 Hz), 224.63 (br s, C5), 243.36 (t, C1,
2JCP = 8.2 Hz) (SO3CF3 not observed). 31P NMR (CDCl3, δ):
10.89. 19F NMR (CDCl3, δ): -79.26.
Synthesis of Os(C5H4{SMe-1})(SCN)(CO)(PPh3)2 (2c).
Potassium thiocyanate (35 mg) was added to a solution of 1
(36 mg) in ethanol (5 mL), and a blue precipitate formed
instantly. The suspension was stirred for 40 min and then
filtered to collect the blue solid, which was recrystallized
from dichloromethane/ethanol to yield pure 2c as blue crys-
1
ν(CO). H NMR (CDCl3, δ): 1.62 (s, SCH3, 3H), 5.64 (d, H2,
3JHH = 9.6 Hz, 1H), 6.84 (m, H3, 1H), 7.13 (m, H4, 7.22-7.28
(m, PPh3, 18H), 7.54-7.59 (m, PPh3, 12H), 11.76 (ddt, H5,
4
3
3JHH = 11.1, JHH = 2.2, JHP = 2.0 Hz, 1H). 13C NMR
tals (25 mg, 76%). Anal. Calcd for C44H37NOOsP2S2 H2O:
3
(CDCl3, δ): 23.35 (s, SCH3), 120.48 (s, C2), 127.13 (t0, o-PPh3,
C, 56.82; H, 4.23; N, 1.51. Found: C, 57.12; H, 4.30; N, 1.61.
MS (FABþ): found m/z 885.146 22; C43H37N192OsP2S2 [M -
CO]þ requires 855.145 76. IR (cm-1): 1937 s ν(CO), 2095 s
ν(CN). 1H NMR (CDCl3, δ): 1.70 (s, SCH3, 3H), 6.36 (d, H2,
2,4
J
= 9.1 Hz), 128.22 (s, C4), 129.40 (s, p-PPh3), 132.55 (t0,
CP
i-PPh3, 1,3JCP = 51.3 Hz), 134.40 (t0, m-PPh3, 3,5JCP = 9.1 Hz),
146.07 (s, C3), 189.92 (t, CO, JCP = 9.3 Hz), 219.34 (t, C5,
2
2JCP = 12.3 Hz), 244.18 (t, C1, JCP = 5.1 Hz). 31P NMR
2
3JHH = 8.9 Hz, 1H), 6.38 (apparent t, H4, JHH = 8.8 Hz,
3
(CDCl3, δ): -6.42.
1H), 7.03 (m, H3, 1H), 7.28-7.40 (m, PPh3, 30H), 13.17 (d,
H5, 3JHH = 9.6, 1H). 13C NMR (CDCl3, δ): 19.95 (s, SCH3),
120.00 (s, C2), 125.98 (s, C4), 127.66 (t0, o-PPh3, 2,4JCP = 10.3
Synthesis of Os(C5H4{SMe-1})(SCN)(CO)(PPh3)2 (3c). Silver
trifluoromethanesulfonate (14 mg) was added to a solution of 3a
(50 mg) in dichloromethane (5 mL) and ethanol (0.5 mL). A
floccular yellow solid (AgI) formed within 1 min. The solution was
stirred for 15 min at which time the AgI was removed by filtration,
sodium thiocyanate (50 mg) was added to the filtrate, and the
solution was stirred for a further 10 min. The solvent was removed
under reduced pressure; the resulting residue was dissolved in the
minimum amount of dichloromethane and then purified by col-
umn chromatography on silica gel using dichloromethane as
eluant. The yellow-brown band was collected, ethanol added,
and the dichloromethane removed under reduced pressure. Re-
crystallization of the brown material that formed from dichloro-
methane/ethanol gave pure 3c as reddish brown crystals (31.7 mg,
Hz), 129.94 (s, p-PPh3), 131.72 (t0, i-PPh3, 1,3JCP = 52.6 Hz),
3,5
134.14 (t0, m-PPh3,
J
=10.6 Hz), 146.72 (s, C3), 189.61
CP
(t, CO, 2JCP=10.5 Hz), 225.32 (t, C5, 2JCP=6.5 Hz), 244.70
(t, C1, JCP = 8.3 Hz) (SCN not observed). 31P NMR
2
(CDCl3, δ): 5.03.
Synthesis of Os(C5H4{SMe-1})(CO2CF3)(CO)(PPh3)2 (2d).
A solution of sodium trifluoroacetate (123 mg) in ethanol (2 mL)
was added to a solution of 1 (52 mg) in ethanol (5 mL). The
solution was stirred for 1 h and then filtered to collect a blue
solid, which was washed with a small amount of a 1:1 ethanol/
n-hexane mixture followed by n-hexane to yield pure 2d (29.9 mg,
44%). Anal. Calcd for C45H37O3F3OsP2S: C, 55.89; H, 3.86.
Found: C, 55.53; H, 4.08. MS (FABþ): found m/z 940.159 98;
C44H37O2F3192OsP2S [M - CO]þ requires 940.155 65. IR (cm-1):
1940 s ν(CO), 1707 w, 1678 s ν(CO2CF3). 1H NMR (CDCl3, δ):
68%). Anal. Calcd for C44H37ONOsP2S2 1/2CH2Cl2: C, 56.00; H,
3
4.01; N, 1.47. Found: C, 55.62; H, 4.15; N, 1.53.MS (FABþ):
found m/z 914.148 08; C44H38ON192OsP2S2 [MH]þ requires
914.148 50. IR (cm-1): 2095 s ν(CN); 1937 s, 1925 s ν(CO). H
1
3
1.80 (s, SCH3, 3H), 6.03 (d, H2, JHH = 8.7 Hz, 1H), 6.90
(apparent t, H3, JHH = 8.4 Hz, 1H), 7.13 (m, H4, 1H),
NMR (CDCl3, δ): 1.70 (s, SCH3, 3H), 5.83 (d, H2, 3JHH = 9.6 Hz,
1H), 6.88 (m, H3, 1H), 6.99 (m, H4, 1H), 7.29-7.34 (m, PPh3,
3
7.21-7.38 (m, PPh3, 30H), 14.38 (d, H5, 3JHH = 8.5 Hz, 1H).
3
13C NMR (CDCl3, δ): 18.28 (s, SCH3), 121.77 (s, C2), 127.43 (t0,
18H), 7.39-7.46 (m, PPh3, 12H), 11.18 (ddt, H5, JHH = 11.1,
4JHH = 2.0, 3JHP = 2.0 Hz, 1H). 13C NMR (CDCl3, δ): 23.24 (s,
SCH3), 120.94 (s, C2), 127.67 (t0, o-PPh3, 2,4JCP = 10.0 Hz), 128.02
2,4
o-PPh3,
J
CP
= 9.4 Hz), 127.85 (s, C4), 129.71 (s, p-PPh3),
= 51.8 Hz), 133.94 (t0, m-PPh3,
CP
1,3
131.76 (t0, i-PPh3,
J
= 10.0 Hz), 145.36 (s, C3), 191.81 (t, CO, JCP = 10.1
(s, C4), 129.86 (s, p-PPh3), 131.85 (t0, i-PPh3, 1,3JCP = 52.5 Hz),
3,5
2
J
CP
Hz), 230.00 (br s, C5), 244.19 (t, C1, 2JCP = 8.8 Hz) (CO2CF3
3,5
133.99 (t0, m-PPh3,
J
CP
= 10.5 Hz), 147.04 (s, C3), 187.33 (t,
not observed). 31P NMR (CDCl3, δ): 7.18.
CO, 2JCP = 11.6 Hz), 215.88 (t, C5, 2JCP = 9.2 Hz), 248.71 (t, C1,
2JCP = 5.2 Hz) (SCN not observed). 31P NMR (CDCl3, δ): -2.33.
Synthesis of Os(C5H4{SMe-1})(CO2CF3)(CO)(PPh3)2 (3d).
Silver trifluoromethanesulfonate (13 mg) was added to a solu-
tion of 3a (49.4 mg) in dichloromethane (5 mL) and ethanol
(0.5 mL). A floccular yellow solid (AgI) formed within 1 min.
The solution was stirred for 10 min, the AgI was removed by
filtration, sodium trifluoroacetate (90 mg) was added, and the
solution was then stirred for a further 20 min. The solvent was
removed under reduced pressure and the resultant residue
dissolved in a minimum amount of dichloromethane and
then purified by column chromatography on silica gel using
dichloromethane as eluant. The red band was collected,
ethanol added, and the dichloromethane removed under
reduced pressure. Recrystallization of the bronze material
that formed from dichloromethane/ethanol gave pure 3d as
Synthesis of Os(C5H4{SMe-1})I(CO)(PPh3)2 (3a). 2a (200
mg, 0.203 mmol) was heated under reflux in benzene for
10 min, during which time the initial dark blue color changed
to black. The benzene was removed under vacuum to give a
brown solid, which was recrystallized from dichloromethane/
ethanol to yield pure 3a as shiny black crystals (180 mg, 90%).
Anal. Calcd for C43H37IOOsP2S CH3CH2OH: C, 52.63; H,
4.22. Found: C, 51.93; H, 4.29. MS (ESI): found m/z 855.1694;
3
C43H37OOsP2S [M - I]þ requires 855.1655. IR (cm-1): 1939
1
ν(CO). H NMR (CDCl3, δ): 1.72 (s, SCH3, 3H), 5.67 (d, H2,
3JHH = 9.5 Hz, 1H), 6.90 (m, H3, 1H), 7.3 (H4, position
determined by COSY experiment, 1H), 12.40 (dd, H5, 3JHH
=
4
11.2 Hz, JHH = 1.9 Hz, 1H), 7.33-7.60 (m, PPh3, 30H). 13C
NMR (CDCl3, δ): 23.35 (s, SCH3), 120.18 (s, C2), 129.02 (s, C4),
146.31 (s, C3), 188.71 (t, CO, JCP = 9.1 Hz), 212.48 (t, C5,
2
2
2JCP = 12.0 Hz), 242.13 (t, C1, JCP = 6.0 Hz), 126.91 (t0,
bronze-gold crystals (23 mg, 47%). Anal. Calcd for C45H37-
o-PPh3, 2,4JCP = 10.1 Hz), 129.42 (s, p-PPh3), 132.78 (t0, i-PPh3,
O3F3OsP2S: C, 55.89; H, 3.86. Found: C, 55.98; H, 4.08.
MS (FABþ): found m/z 940.156 29; C44H37O2F3192OsP2S
[M - CO]þ requires 940.155 65. IR (cm-1): 1943 s ν(CO),
1714 w, 1688 s ν(CO2CF3). 1H NMR (CDCl3, δ): 1.95 (s,
SCH3, 3H), 5.89 (d, H2, JHH = 9.5 Hz, 1H), 6.65 (m, H3,
1H), 7.02 (m, H4, 1H), 7.23-7.32 (m, PPh3, 18H), 7.39-7.44
(m, PPh3, 12H), 11.78 (ddt, H5, JHH = 11.1, JHH = 1.8,
3JHP = 1.8 Hz, 1H). 13C NMR (CDCl3, δ): 23.45 (s, SCH3),
1,3
J
CP
= 52.3 Hz), 134.74 (t0, m-PPh3, 3,5JCP = 11.1 Hz).
Synthesis of Os(C5H4{SMe-1})Cl(CO)(PPh3)2 (3b). Silver
trifluoromethanesulfonate (14 mg) was added to a solution of
Os(C5H4{SMe-1})I(CO)(PPh3)2 (3a; 49 mg) in dichloromethane
(5 mL) and ethanol (0.5 mL). A floccular yellow solid (AgI)
formed within 1 min. The solution was stirred for 15 min, the
AgI was removed by filtration, and then LiCl (21.2 mg) was
3
3
4

Article
Organometallics, Vol. 29, No. 21, 2010 5365
121.74 (s, C2), 127.33 (t0, o-PPh3, 2,4JCP = 10.12 Hz), 128.91 (t, C4,
3JCP = 2.2 Hz), 129.75 (s, p-PPh3), 131.39 (t0, i-PPh3, 1,3JCP = 51.6
Hz), 134.14 (t0, m-PPh3, 3,5JCP = 10.6 Hz), 146.45 (s, C3), 190.93 (t,
CO, 2JCP = 9.2 Hz), 221.28 (t, C5, 2JCP = 12.0 Hz), 246.22 (t, C1,
2JCP = 5.4 Hz) (CO2CF3 not observed). 31P NMR (CDCl3, δ):
3.14. 19F NMR (CDCl3, δ): -76.18.
Synthesis of [Os(η5-C5H4SMe)(CO)(PPh3)2]CF3SO3 (4e). A
solution of 1 (32 mg) in 1,2-dichloroethane (4 mL) under
nitrogen was heated under reflux for 20 min. The solvent was
removed in vacuo to give 4e as an off-white solid (31.6 mg, 99%).
The analytical sample was recrystallized from 1,2-dichloro-
ethane/heptane. Anal. Calcd for C44H37F3O4OsP2S2 C2H4Cl2:
3
Synthesis of [Os(η5-C5H4SMe)(CO)(PPh3)2]I (4a). A solution
of 2a (100 mg) in dry toluene (6 mL) under nitrogen was heated
to reflux for 1 h, by which time the blue solution had turned
colorless and a white solid was formed. The mixture was cooled
to room temperature and then filtered to collect the white solid,
which was washed with a small amount of toluene followed by n-
hexane, yielding pure 4a (46 mg, 46%). Anal. Calcd for C43H37-
OIOsP2S: C, 52.65; H, 3.80. Found: C, 52.53; H, 3.69. MS
(FABþ): found m/z 855.165 59; C43H37O192OsP2S [M]þ re-
quires 855.165 53. IR (cm-1): 1950 s ν(CO). 1H NMR (CDCl3,
δ): 2.55 (s, SCH3, 3H), 4.91 (br s, Cp, 2H), 5.03 (br s, Cp, 2H),
7.07-7.44 (m, PPh3, 30H). 13C NMR (CDCl3, δ): 17.15 (s,
SCH3), 81.53 (br s, Cp), 90.85 (s, Cp), 113.09 (br s, C-SMe),
128.71 (apparent t, o-PPh3, JCP = 5.3 Hz), 131.10 (s, p-PPh3),
133.03 (apparent t, m-PPh3, JCP = 5.2 Hz), 133.52 (dd, i-PPh3,
C, 50.13; H, 3.75. Found: C, 50.24; H, 3.48% (1H NMR shows 1
equiv of C2H4Cl2 present in analytical sample). MS (ESI): m/z
calcd for C43H37OOsP2S [M - CF3SO3]þ 855.1650; found
855.1667. IR (cm-1): 1947 s ν(CO). 1H NMR (CDCl3, δ): 2.51
(s, SCH3, 3H), 4.86 (br s, Cp, 2H), 4.97 (br s, Cp, 2H), 7.07-7.60
(m, PPh3, 30H). 13C NMR (CDCl3, δ): 16.88 (s, SCH3), 81.48 (br
s, Cp), 90.89 (s, Cp), 113.18 (br s, C-SMe), 128.70 (apparent t,
o-PPh3, JCP = 5.2 Hz), 131.16 (s, p-PPh3), 133.11 (apparent t,
m-PPh3, JCP = 5.1 Hz), 133.64 (dd, i-PPh3, 1JCP = 60.7, 3JCP
=
2.5 Hz), 183.56 (t, CO, 2JCP = 11.2 Hz) (SO3CF3 not observed).
31P NMR (CDCl3, δ): -0.50.
Synthesis of Os(η5-C5H4SMe)I(CO)(PPh3) (5a). A solution
of 2a (48 mg) in dry toluene (6 mL) under nitrogen was heated to
reflux for 1 h, by which time the blue solution had turned
colorless and a white solid was formed. The solvent was removed
from the reaction mixture under vacuum and the residue
purified by column chromatography on silica gel using dichloro-
methane as the eluent. The yellow band was collected, ethanol
added, and the dichloromethane removed under reduced pres-
sure to give pure 5a as yellow crystals (14.6 mg, 41.5%). Anal.
Calcd for C25H22OIOsPS: C, 41.79; H, 3.09. Found: C, 41.94; H,
2.84. MS (FABþ): found m/z 719.979 35; C25H22IO192OsPS
1JCP = 59.6, 3JCP = 2.6 Hz), 183.42 (t, CO, 2JCP = 11.3 Hz). 31
NMR (CDCl3, δ): -0.52.
P
General Procedure for Monitoring the Formation of 4b,c and
5b,c by NMR Spectroscopy and High-Resolution ESI-MS. The
osmabenzene (5 mg) was added to toluene (2 mL) and the
solution heated under reflux for 1 h. The solution was cooled
and a small sample removed for analysis by high resolution
ESI-MS. The toluene was removed under vacuum from the
remaining solution and the resulting solid dissolved in CDCl3
and the NMR spectra recorded.
1
[M]þ requires 719.978 86. IR (cm-1): 1922 s ν(CO). H NMR
(CDCl3, δ): 2.35 (s, SCH3, 3H), 4.71 (m, Cp, 2H), 4.78 (m, Cp,
1H), 5.00 (m, Cp, 1H), 7.36-7.52 (m, PPh3, 30H). 13C NMR
(CDCl3, δ): 17.67 (s, SCH3), 74.66 (d, Cp, 2JCP = 4.3 Hz), 77.99
(s, Cp), 81.07 (d, Cp, 2JCP = 2.7 Hz), 83.88 (s, Cp), 110.69 (d, C-
SMe, 2JCP = 2.1 Hz), 128.06 (d, o-PPh3, 2JCP = 10.5 Hz), 130.27
(d, p-PPh3, 4JCP = 2.4 Hz), 133.89 (d, m-PPh3, 3JCP = 10.4 Hz),
Data for [Os(η5-C5H4SMe)(CO)(PPh3)2]Cl (4b). MS (ESI):
m/z calcd for C43H37OOsP2S [M - Cl]þ 855.1650, found 855.1653.
1H NMR (CDCl3, δ): 2.56 (s, SCH3, 3H), 4.98 (br s, Cp, 2H), 5.23
(br s, Cp, 2H), 7.07-7.44 (m, PPh3, 30H). 31P NMR (CDCl3, δ):
-0.43.
1
2
135.95 (d, i-PPh3, JCP = 56.4 Hz), 183.17 (d, CO, JCP
12.3 Hz). 31P NMR (CDCl3, δ): 8.24.
=
Data for [Os(η5-C5H4SMe)(CO)(PPh3)2]SCN (4c). MS (ESI):
m/z calcd for C43H37OOsP2S [M - SCN]þ, 855.1650, found
Data for Os(η5-C5H4SMe)Cl(CO)(PPh3) (5b). MS (ESI): m/z
calcd for C25H22OOsPS [M - Cl]þ 593.0737, found 593.0740.
1H NMR (CDCl3, δ): 2.35 (s, SCH3, 3H), 4.53 (m, Cp, 1H), 4.60
(m, Cp, 1H), 4.84 (m, Cp, 1H), 5.12 (m, Cp, 1H), 7.10-7.52 (m,
PPh3, 30H). 31P NMR (CDCl3, δ): 11.67.
1
855.1640. H NMR (CDCl3, δ): 2.52 (s, SCH3, 3H), 4.90 (br s,
Cp, 2H), 5.24 (br s, Cp, 2H), 7.07-7.44 (m, PPh3, 30H). 31P NMR
(CDCl3, δ): -0.35.
Synthesis of [Os(η5-C5H4SMe)(CO)(PPh3)2](CF3CO2) (4d).
A solution of 2d (42 mg) in dry toluene (4 mL) under nitrogen
was heated to reflux for 10 min, by which time the blue solution
had turned colorless and a white solid was formed. The mixture
was cooled to room temperature and then filtered to collect the
white solid, which was washed with a small amount of toluene
followed by n-hexane to give pure 4d (38 mg, 90%). Anal. Calcd
Data for Os(η5-C5H4SMe)(SCN)(CO)(PPh3) (5c). MS (ESI):
m/z calcd for C26H23NOOsPS2 [M þ H]þ 652.0565, found
1
652.0574. H NMR (CDCl3, δ): 2.39 (s, SCH3, 3H), 4.54 (m,
Cp, 2H), 4.90 (m, Cp, 1H), 5.25 (m, Cp, 1H), 7.05-7.50 (m,
PPh3, 30H). 31P NMR (CDCl3, δ): 10.99.
for C45H37O3F3OsP2S 1/2C7H8: C, 57.50; H, 4.08. Found: C,
3
Acknowledgment. We thank the Marsden Fund and
The University of Auckland for providing support for
this work.
57.28; H, 3.97. MS (FABþ): found m/z 855.167 34; C43H37O192
-
OsP2S [M]þ requires 855.165 53. IR (cm-1): 1933 s ν(CO), 1689 s
ν(CO2CF3). 1H NMR (CDCl3, δ): 2.52 (s, SCH3, 3H), 4.90 (br s,
Cp, 2H), 4.97 (br s, Cp, 2H), 7.06-7.43 (m, PPh3, 30H). 13C
NMR (CDCl3, δ): 16.89 (s, SCH3), 81.58 (br s, Cp), 90.83
(s, Cp), 113.16 (br s, C-SMe), 128.70 (apparent t, o-PPh3,
Supporting Information Available: The crystal data and re-
finement details in CIF format for complexes for 2c (CCDC
782227), 3c (CCDC 782228), 4d (CCDC 782229), and 5a (CCDC
782230) are available free of charge via the Internet at http://pubs.
acs.org.
J
CP = 5.3 Hz), 131.17 (s, p-PPh3), 133.08 (apparent t, m-PPh3,
J
CP = 5.2 Hz), 133.64 (dd, i-PPh3, 1JCP = 60.7, 3JCP = 2.5 Hz),
183.51 (t, CO, 2JCP = 11.2 Hz). 31P NMR (CDCl3, δ): -0.47.