Terminal carbido complexes of osmium: Synthesis, structure, and reactivity comparison to the ruthenium analogues

Article abstract of DOI:10.1021/om070208u

The first terminal carbide complex of osmium, O_s(≡C) (PCy₃)₂Cl₂ (4), was synthesized via S-atom abstraction from O_s(CS)(PCy₃)₂Cl₂ (4-S) by Ta(OSi-f-Bu₃)₃ (7). Compound 4 reacts with HO₃SCF₃ (HOTf) to form the first cationic osmium methylidyne complex [O_s(≡CH)(PCy₃) ₂Cl₂][OTf] (18). The analogous ruthenium complex [Ru(≡CH)(H₂IMeS)(PCy₃)Cl₂][OTf] is not observed upon protonation of Ru(≡C)-(H₂IMeS)(PCy ₃)Cl₂ (2) with HOTf. Substitution of the chloride ligands in 4 is surprisingly difficult compared to the case of 4-S, but Os(≡C)(PCy₃)₂I₂ can be obtained. Compound 4 also reacts with a variety of electrophiles to afford cationic five-coordinate and neutral six-coordinate carbyne complexes. In general, 4 reacts more readily with electrophiles than does 1, and cationic carbyne complexes formed from 4 are more resistant to degradation than are their Ru counterparts.

Full text of DOI:10.1021/om070208u

5102
Organometallics 2007, 26, 5102-5110
Terminal Carbido Complexes of Osmium: Synthesis, Structure, and
Reactivity Comparison to the Ruthenium Analogues
Michael H. Stewart, Marc J. A. Johnson,* and Jeff W. Kampf
Department of Chemistry, UniVersity of Michigan, 930 North UniVersity AVenue,
Ann Arbor, Michigan 48109-1055
ReceiVed March 6, 2007
The first terminal carbide complex of osmium, Os(tC)(PCy3)2Cl2 (4), was synthesized via S-atom
abstraction from Os(CS)(PCy3)2Cl2 (4-S) by Ta(OSi-t-Bu3)3 (7). Compound 4 reacts with HO3SCF3 (HOTf)
to form the first cationic osmium methylidyne complex [Os(tCH)(PCy3)2Cl2][OTf] (18). The analogous
ruthenium complex [Ru(tCH)(H2IMes)(PCy3)Cl2][OTf] is not observed upon protonation of Ru(tC)-
(H2IMes)(PCy3)Cl2 (2) with HOTf. Substitution of the chloride ligands in 4 is surprisingly difficult
compared to the case of 4-S, but Os(tC)(PCy3)2I2 can be obtained. Compound 4 also reacts with a
variety of electrophiles to afford cationic five-coordinate and neutral six-coordinate carbyne complexes.
In general, 4 reacts more readily with electrophiles than does 1, and cationic carbyne complexes formed
from 4 are more resistant to degradation than are their Ru counterparts.
Chart 1. Numbered Compounds
Introduction
The chemistry of carbide ligands is of interest for several
reasons. In the area of heterogeneous catalysis, surface-bound
carbides are thought to serve as critical intermediates in the
Fischer-Tropsch and related processes for catalytic formation
of hydrocarbons and “oxygenates” from synthesis gas.1-7
Carbides are also important to homogeneous catalysis, particu-
larly olefin metathesis catalyzed by ruthenium complexes. For
example, a bridging carbido complex is formed upon decom-
position of Ru(dCH2)(H2IMes)(PCy3)Cl2, a commonly used
catalyst for ring-closing metathesis (RCM) of olefins.8 In many
cases, the decomposition products of Grubbs-type catalysts are
not yet known, but in a growing number of examples the
terminal carbide complexes exemplified by Ru(tC)(L)(PCy3)-
Cl2 (L ) PCy3 [1], H2IMes [2]; see Chart 1) are formed
cleanly.9-14 The marked stability9,10,15 of 1 and 2 is surprising
given the general rarity of terminal carbide complexes.9,10,16-19
Compounds 1 and 2 are important not only as catalyst
* Corresponding author. Fax: (734) 647-4865. E-mail: mjaj@umich.edu.
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10.1021/om070208u CCC: $37.00 © 2007 American Chemical Society
Publication on Web 08/24/2007

Terminal Carbido Complexes of Osmium
Organometallics, Vol. 26, No. 20, 2007 5103
Scheme 1. Synthesis and Reactivity of 4 with Electrophiles
Figure 1. 50% thermal ellipsoid plot of 4.
metathesis of an alkylidene complex with Feist’s ester or a vinyl
ester. We circumvented this complication by employing des-
ulfurization of the thiocarbonyl analogue Os(CS)(PCy3)2Cl2
(4-S) to obtain 4 (Scheme 1). Complex 4-S is prepared in 53%
yield from known Os(CS)(PPh3)3Cl2 (5)24 upon phosphine
exchange using PCy3.
decomposition products to be avoided but also as precursors to
active olefin metathesis catalysts via protonation of the carbide
ligand and rearrangement to afford phosphoniocarbene com-
plexes that initiate metathesis of terminal olefins rapidly.19 As
four-coordinate 14-electron complexes, phosphoniocarbene 3
(Chart 1) and a closely related complex have been particularly
useful in establishing the structure and dynamics of the
ruthenacyclobutane intermediates in olefin cross-metathesis.20,21
In order to gain additional insight into the factors that govern
the stability and reactivity of terminal carbide complexes such
as 1 and 2, we sought to make the osmium analogue Os(tC)-
(PCy3)2Cl2 (4) for comparison to compounds based on ruthe-
nium. Herein we report the synthesis, structure, and reactions
of 4, including its protonation to form a terminal methylidyne
complex. Compound 4 is the first terminal carbide complex of
any metal other than Mo, W, and Ru and the first neutral
terminal carbide complex that does not contain Ru; the unstable
cationic methylidyne complex formed by protonation of 4 is
the first terminal methylidyne complex isolated for any metal
other than Mo and W.22
We next subjected 4-S to the conditions for S-atom abstraction
that effect the conversion of 1-S into 1.10 Reaction of 4-S with
3 equiv of Mo(H)(η2-Me2CNAr)(N[i-Pr]Ar)2 (Ar ) 3,5-
Me2C6H3) (6)25 for 5 h in C6D6 at 28 °C results in clean
conversion of 4-S into 4. The usual molybdenum-containing
1
byproduct, (µ-S)(Mo(N[i-Pr]Ar)3]2,10 is also observed by H
NMR spectroscopy. 13C{1H} NMR spectroscopy reveals the
signal for the terminal carbido ligand in 4 at 448 ppm, a shift
diagnostic of a terminal carbido species.9,10,16-19 Unlike 1,
however, 4 appears to decompose during workup. Accordingly,
we investigated other potential S-atom abstractors. We find that
Ta(OSi-t-Bu3)3 (7)26 reacts cleanly with 4-S in toluene over 49
h at room temperature to produce a 1:1 mixture of 4 and the
terminal sulfide complex SdTa(OSi-t-Bu3)3 (7-S),27 which is
readily separated from 4 by extraction with pentane following
removal of the toluene solvent (Scheme 1). This afforded pure
4 in 89% yield. As expected, addition of elemental sulfur to a
solution of 4 in C6D6 affords quantitative regeneration of 4-S.
The structure of 4 (Figure 1) was determined by single-crystal
X-ray diffraction in order to confirm its identity as a monomeric
terminal carbido complex and to establish its coordination
geometry. Crystals were grown by slow diffusion of pentane
into a dichloromethane solution of 4. Acquisition and refinement
data for 4, 4-S, and 15 are summarized in Table 1. Pertinent
bond lengths and angles for 4, 4-S, and 15 are listed in Table
2 for comparison to those of the ruthenium complexes 115 and
1-S.10 Compound 4 crystallizes in the space group P2(1)/c as a
discrete neutral species. As was the case for 1, the carbido ligand
occupies the apical position in what is best described as a square
pyramid (τ ) 0.1728). The Os-C interatomic distance of 1.689-
(5) Å is consistent with a short triple bond. For comparison,
the Os-C bond lengths in the carbyne complexes [Os(tCCHd
CMe2)(PCy3)2HCl2] (8) and [Os(tCCH2Ph)(PPh3)2Cl3] (9) are
Results and Discussion
We recently showed that 1 can be formed by S-atom
abstraction from its thiocarbonyl homologue.10 Complex 1 is
quite stable. It does not react with air, water, or benzoic acid.
In fact, the only reactions it is reported to undergo are its
transformation into Ru(CO)(PCy3)2Cl2 and Ru(CS)(PCy3)2Cl2
(1-S),10 its protonation to yield [Ru(dCHPCy3)(PCy3)Cl2][BX4]
(X ) F, C6F5),19 the formation of weak complexes with the
Mo(CO)5 and Pd(Cl)2(SMe2) fragments,15 and [2+1] cycload-
dition with activated alkynes to afford cyclopropenylidene
complexes.23
Unlike the case for ruthenium,10 the lack of a suitable
metathesis-active precursor prevented us from preparing 4 via
(18) Enriquez, A. E.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc.
2001, 123, 4992.
(19) Romero, P. E.; Piers, W. E.; McDonald, R. Angew. Chem., Int. Ed.
2004, 43, 6161.
(20) Romero, P. E.; Piers, W. E. J. Am. Chem. Soc. 2005, 127, 5032.
(21) Wenzel, A. G.; Grubbs, R. H. J. Am. Chem. Soc. 2006, 128, 16048.
(22) Eide, E. F. V.; Piers, W. E.; Parvez, M.; McDonald, R. Inorg. Chem.
2007, 46, 14.
(23) Caskey, S. R.; Stewart, M. H.; Johnson, M. J. A.; Kampf, J. W.
Angew. Chem., Int. Ed. 2006, 45, 7422.
(24) Elliott, G. P.; McAuley, N. M.; Roper, W. R.; Shapley, P. A. Inorg.
Synth. 1989, 26, 184.
(25) Tsai, Y. C.; Johnson, M. J. A.; Mindiola, D. J.; Cummins, C. C.;
Klooster, W. T.; Koetzle, T. F. J. Am. Chem. Soc. 1999, 121, 10426.
(26) LaPointe, R. E.; Wolczanski, P. T.; Mitchell, J. F. J. Am. Chem.
Soc. 1986, 108, 6382.
(27) Neithamer, D. R. Ph.D. Thesis, Cornell University, Ithaca, NY, 1989.
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C. J. Chem. Soc., Dalton Trans. 1984, 1349.

5104 Organometallics, Vol. 26, No. 20, 2007
Stewart et al.
Table 1. Crystallographic Data
4-S‚(CH2Cl2)2
4
15‚(CH2Cl2)
crystals grown by
cooling a conc CH2Cl2
solution to -35 °C
green, block
C39H70Cl6P2SOs
1035.85
slow diffusion of pentane
into a CH2Cl2 solution
orange, plates
C37H66Cl2P2Os
833.94
slow diffusion of pentane
into a CH2Cl2 solution
pale green, plates
C45H75BCl4F4P2Os
1096.80
cryst color, habit
formula
fw
cryst size (mm)
a (Å)
b (Å)
0.50 × 0.48 × 0.46
11.7573(6)
14.4579(7)
15.3416(8)
95.308(2)
112.333(2)
105.071(2)
2275.2(2)
0.18 × 0.10 × 0.10
13.1464(12)
23.313(2)
13.5957(12)
90
115.585(5)
90
3758.2(6)
0.44 × 0.24 × 0.12
12.268(3)
14.927(3)
14.950(3)
114.796(2)
105.238(3)
91.668(3)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
2367.4(9)
Z
2
4
2
D
µ
calcd (Mg m-3
)
1.512
3.297
triclinic
P1h
123(2)
1.474
3.645
monoclinic
P2(1)/n
123(2)
1.539
3.034
triclinic
P1h
123(2)
calcd (mm-1
)
cryst syst
space group
T (K)
θ range (deg)
1.90 e θ e 28.32
-15 e h e 14
-19 e k e 19
-20 e l e 20
1.75 e θ e 27.47
-16 e h e 15
-30 e k e 30
-17 e l e 17
1.96 e θ e 28.32
-16 e h e 16
-19 e k e 19
-19 e l e 19
hkl range
no. of reflections
collected
unique
74 381
11 287
129 783
8526
75 165
11 718
no. of params/restraints
GOF
442/0
1.078
379/0
1.127
514/0
1.089
final R indices [I > 2σ(I)]
R1 ) 0.0163
wR2 ) 0.0422
R1 ) 0.0337
wR2 ) 0.0716
R1 ) 0.0333
wR2 ) 0.0857
Table 2. Selected Bond Lengths (Å) and Angles (deg), Structural Comparison of 1, 1-S, 4, 4-S, and 15
115
1-S10
4
4-S
15
[M-C]
1.632(6)
2.427(2)
2.376(2)
160.66(5)
156.66(5)
1.7376(19)
2.418(1)
2.369(1)
165.789(18)
166.290(19)
1.689(5)
2.415(2)
2.372(2)
165.71(4)
155.46(4)
1.7579(17)
2.4097(6)
2.3734(6)
165.196(14)
163.823(15)
1.701(3)
2.452(1)
2.343(1)
161.68(3)
156.16(3)
[M-P]a
[M-Cl]a
[P-M-P]
[Cl-M-Cl]
a Average values.
1.715(4) and 1.734(3) Å, respectively.29,30 Benzylidyne com-
plexes display similar OstC bond lengths.31-36
complexes 4-S and 4 is also statistically insignificant. The same
trend is seen for Ru (Table 2).
Single-crystal X-ray diffraction reveals that 4-S has a structure
grossly similar to that of 4 (Figure 2, Tables 1, 2). Compound
4-S crystallizes from cooled dichloromethane as a monomer in
the space group P1h. Compared to 4, the Os-C bond in 4-S is
considerably longer. The P-Os-P bond angle in 4-S is
essentially unchanged from that in 4 (Table 2). In contrast, the
Cl-Os-Cl bond angle is over 8° larger in 4-S than in 4;
consequently, 4-S is even closer to the limiting square-pyramidal
structure (τ ) 0.0228). The thiocarbonyl ligand occupies the
apical site. In spite of the fact that halide exchange is more
rapid in 4-S than in 4, the difference in mean Os-Cl bond
lengths between these two complexes is statistically insignifi-
cant. The difference in mean Os-P bond lengths between
It is also instructive to compare these metrical parameters to
those of 115 and 1-S10 (Table 2). The mean Os-Cl bond length
in 4 is indistinguishable from that of its Ru counterpart, 1. The
mean Os-P bond length in 4 is slightly shorter than the mean
Ru-P internuclear distance in 1. Similarly, the mean M-Cl
and M-P bond lengths in 4-S are statistically indistinguishable
from those of its Ru analogue, 1-S. Unlike the case of the
osmium complexes (Vide supra), upon S-atom abstraction from
1-S, both the P-Ru-P and the Cl-Ru-Cl bond angles
decrease. The structures are otherwise very similar; the largest
differences in bond lengths occur for the M-C bonds in both
1/4 and 1-S/4-S. Although the Ru-C bond in 1-S is already
shorter than the Os-C bond in 4-S, upon desulfurization the
Ru-C internuclear separation decreases even more than does
the Os-C distance.
(29) Werner, H.; Jung, S.; Weberndorfer, B.; Wolf, J. Eur. J. Inorg.
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L. J. J. Organomet. Chem. 1986, 315, 211.
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Organometallics 2003, 22, 414.
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371.
Reactions with Alkylating Agents. Although 4 does not react
with air or water at room temperature, it is somewhat more
Lewis basic than is 1. Addition of MeOTf (Tf ) CF3SO2) to a
CD2Cl2 solution of 4 at -35 °C followed by warming to 28 °C
affords the cationic five-coordinate ethylidyne complex [Os(t
CMe)(PCy3)2Cl2][OTf] (10) cleanly in 20.5 h (Scheme 1). In
order to confirm the identity of this new compound, we
synthesized it independently from known Os(tCMe)(PPh3)2-
Cl3 (11)30 via phosphine exchange with 3.4 equiv of PCy3 in

Terminal Carbido Complexes of Osmium
Organometallics, Vol. 26, No. 20, 2007 5105
Scheme 2. Reactivity of 1 and 4 with Acylating Agents
Scheme 3. Protonation of 4
Figure 2. 50% thermal ellipsoid plot of 4-S.
ever, this compound is difficult to isolate in pure form because
it slowly decomposes in solution, affording [HPCy3]+ and
uncharacterized ruthenium product(s). Werner has similarly
noted the instability of cationic complexes of the form [Ru(t
CCH2R′)(PR3)2Cl2]+ (R′ ) Ph, t-Bu; R ) i-Pr, Cy) with respect
to formation of [HPR3]+ in solution.37 Related cationic carbyne-
hydride complexes29,39,49 can also decompose by deprotonation.
Both 4 and 1 react cleanly with [C7H7][BF4] to afford the
cationic alkylidyne complexes [M(tCCH2Ph)(PCy3)2Cl2][BF4]
(M ) Os [15], Ru [16]) following spontaneous ring contraction.
Single-crystal X-ray diffraction was employed in order to
confirm the identity of 15 (Tables 1, 2). A thermal ellipsoid
plot (Figure 3) of the cation evinces the expected connectivity,
a square-pyramidal coordination geometry about Os, and an
OstC triple bond. The OstC bond length of 1.701(3) Å in 15
is similar to those found in 4, 8, and 9. Unlike 14, crude 16
was initially isolated without significant decomposition to
[HPCy3]+. However, crude 16 partially decomposed under the
conditions of attempted recrystallization, yielding [HPCy3]+ and
uncharacterized ruthenium products.
Reactions with Acylating Agents. In analogous fashion to
its reactions with alkylating agents, 4 reacts cleanly with benzoyl
chloride, forming the six-coordinate acylcarbyne complex Os-
(tCC(O)Ph)(PCy3)2Cl3 (17) in 88% isolated yield (Scheme 2).
Complex 4 does not react at all with pivaloyl chloride under
these conditions, probably for steric reasons. Unlike 4, com-
pound 1 does not react with either of these acylating agents
under these conditions. This highlights a small but important
difference in the Lewis base strengths of 1 and 4.
-
Figure 3. 50% thermal ellipsoid plot of 15 (BF4 counterion not
shown).
refluxing THF for 1.2 h, followed by treatment with 1 equiv of
AgOTf in CH2Cl2. The intermediate complex Os(tCMe)-
(PCy3)2Cl3 (12) was isolated in 64% yield after recrystallization
from dichloromethane. Following the reaction with AgOTf, pure
10 was isolated in 67% yield from 12 by this route. Like similar
complexes,29,37-41 12 is readily deprotonated to form the
analogous vinylidene42-48 complex. Treatment of 12 with 1.1
equiv of LiO-t-Bu in THF afforded vinylidene 13 in 59% yield
after recrystallization (Scheme 1). In contrast, reaction of 1 with
MeOTf affords an unstable intermediate that appears by
multinuclear NMR spectroscopy to be the corresponding cationic
ethylidyne complex, [Ru(tCMe)(PCy3)2Cl2][OTf] (14). How-
(37) Gonzalez-Herrero, P.; Weberndorfer, B.; Ilg, K.; Wolf, J.; Werner,
H. Organometallics 2001, 20, 3672.
(38) Gonzalez-Herrero, P.; Weberndorfer, B.; Ilg, K.; Wolf, J.; Werner,
H. Angew. Chem., Int. Ed. 2000, 39, 3266.
(39) Stu¨er, W.; Wolf, J.; Werner, H.; Schwab, P.; Schulz, M. Angew.
Chem., Int. Ed. 1998, 37, 3421.
(40) Bourgault, M.; Castillo, A.; Esteruelas, M. A.; Onate, E.; Ruiz, N.
Organometallics 1997, 16, 636.
Reaction with Strong Acids. As noted earlier, 1 and 2 react
with the strong acids HBX4 (X ) F, C6F5) to afford cationic
phosphoniomethylidene complexes via an apparent 1,2-migra-
tion of the PCy3 ligand following protonation of the carbide
ligand. The mechanism of this transformation has not yet been
determined. Protonation of 4 with these acids has to date failed
to yield tractable products. However, reaction of 4 with
trifluoromethanesulfonic acid (HOTf) in toluene at -35 °C
produced [Os(tCH)(PCy3)2Cl2][OTf] (18) as an insoluble pale
tan compound that decomposes slowly when dissolved in CH2-
Cl2 (Scheme 3). Over a period of 8 h at room temperature, 97%
(41) Wen, T. B.; Hung, W. Y.; Zhou, Z. Y.; Lo, M. F.; Williams, I. D.;
Jia, G. C. Eur. J. Inorg. Chem. 2004, 2837.
(42) Bruneau, C.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2006, 45, 2176.
(43) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311.
(44) Puerta, M. C.; Valerga, P. Coord. Chem. ReV. 1999, 195, 977.
(45) Bruce, M. I. Chem. ReV. 1991, 91, 197.
(46) Stu¨er, W.; Wolf, J.; Werner, H. J. Organomet. Chem. 2002, 641,
203.
(47) Wen, T. B.; Cheung, Y. K.; Yao, J. Z.; Wong, W. T.; Zhou, Z. Y.;
Jia, G. C. Organometallics 2000, 19, 3803.
(48) Gusev, D. G.; Maxwell, T.; Dolgushin, F. N.; Lyssenko, M.; Lough,
A. J. Organometallics 2002, 21, 1095.
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H. Angew. Chem., Int. Ed. 2000, 39, 3266.

5106 Organometallics, Vol. 26, No. 20, 2007
Stewart et al.
Scheme 4. Synthetic Routes to 20
Comparison of Ta(III) and Mo(III) Complexes as Chal-
cogen Atom Abstractors. Neither 6 nor 7 emerged as a
generally superior S-atom abstractor in these studies. Instead,
each is preferred under certain circumstances. Nevertheless, the
intermetal chalcogen atom-transfer reactions shown in Scheme
5 confirm the expectation that 7 is thermodynamically superior
to 21 (which should be comparable to 6)53 as a S-/Se-atom
abstractor.
Conclusions
In summary, we have prepared a unique terminal osmium
carbide complex, 4, via S-atom abstraction from the thiocarbonyl
analogue 4-S using a Ta(III) reagent, 7. Compound 7 is
thermodynamically superior to the masked Mo(III) compound
6 that had previously been used to generate carbide complexes
via S-atom abstraction. However, 6 is more tolerant of heavier
halides in the ancillary ligand set than is 7. Single-crystal X-ray
diffraction reveals that molecular 4 adopts an approximately
square-pyramidal core geometry, with the carbido ligand oc-
cupying the apical position and a short OstC bond. Air-stable
4 is somewhat more Lewis basic than its Ru homologue 1,
forming stable alkylidyne complexes upon reaction with a
variety of electrophiles; the corresponding cationic carbyne
complexes are more persistent for Os than for Ru. We are
currently investigating the reactivity of 4 and some analogues
prepared from it by substitution of the ancillary ligand set toward
a number of other electrophiles, oxidants, and reductants. We
are also exploring the further reactions of the unstable cationic
terminal methylidyne complex (18) that is formed upon proto-
nation of 4 by trifluoromethanesulfonic acid. The formation of
cationic 18 illustrates a key divergence in the chemistry of the
ruthenium carbide 1 from that of the osmium carbide 4 upon
protonation.
Scheme 5. Intermetal Atom Transfer
decomposition of 18 to form multiple products was observed.
This is in contrast to the case of protonation of related 2 by
HOTf, which yields the phosphoniocarbene complex 19 cleanly
without observation of any intermediate even at -80 °C.14 The
greater osmium-ligand bond strength compared to the ruthe-
nium-ligand bond strength in homologous complexes likely
accounts for the observed preference for a structure with more
metal-ligand bonds in the case of Os.
Substitution of Ancillary Halide Ligands. Substitution of
the chloride ligands in 1 is notoriously difficult compared to
halide substitution in its precursors.10,50,51 This is also the case
for 4. As we desired the diiodide analogue of 4, Os(tC)-
(PCy3)2I2 (20), for ongoing reactivity studies, we examined its
synthesis by several routes. Although the process is slow, direct
conversion of 4 into 20 can be achieved in low isolated yield
(28%) by heating a toluene solution of 4 and 10 equiv of Me3-
SiI to 120 °C for 10 h in a sealed vessel (Scheme 4). The low
yield results primarily from difficulty in separating an impurity,
not poor conversion. Nevertheless, this is the preferred method
for generating 20, rather than S-atom abstraction from Os(CS)-
(PCy3)2I2 (20-S), as explained next. Crude 20-S can be prepared
in 85% yield from 4-S by reaction with 10 equiv of NaI in
THF for 24 h at 30 °C and subsequently purified by two
consecutive crystallizations from dichloromethane at -35 °C.
Unfortunately, reaction of 20-S with 7 in C6D6 results in double
iodine-atom abstraction, affording Ta(OSi-t-Bu3)3I2 (7-I2)52 as
the principal Ta-containing product. Although reaction of 20-S
with 6 in C6D6 produces 20, the reaction is not clean, and several
unidentified P-containing products are also formed. Furthermore,
we were unable to separate 20 from the Mo-containing byprod-
uct, (µ-S)(Mo(N[i-Pr]Ar)3]2, because of their very similar
solubilities.
Experimental Section
General Procedures. All reactions were carried out using
standard Schlenk techniques under an atmosphere of nitrogen or
in a nitrogen-filled MBraun Labmaster 130 glovebox, unless
otherwise specified. 1H, 13C, 31P, and 19F NMR spectra were
recorded on a Varian Inova 300 MHz or 400 MHz spectrometer.
1H and 13C NMR spectra were referenced to solvent signals.54 19
F
NMR spectra were referenced to external CFCl3 in CDCl3 (δ )
0). 31P NMR spectra were referenced to external 85% aqueous H3-
PO4 (δ ) 0).
Materials. All solvents were dried by passage through solvent
purification columns according to the method of Grubbs.55 Deu-
terated solvents were dried over 4 Å molecular sieves. Silver
trifluoromethanesulfonate, iodomethane, trifluoromethanesulfonic
acid, methyl trifluoromethanesulfonate, sodium iodide, iodotrim-
ethylsilane, and pivaloyl chloride were purchased from Acros. Sulfur
was purchased from Mallinckrodt. Tricyclohexylphosphine was
purchased from Organometallics Inc. Tropylium tetrafluoroborate
was purchased from Matrix Scientific. Lithium tert-butoxide was
purchased from Strem. Benzoyl chloride was purchased from Alfa
Aesar. Selenium powder (∼100 mesh) was purchased from
Aldrich. Solid and liquid reagents were used as received. Ta(OSi-
t-Bu3)3 (7),26 Os(CS)(PPh3)3Cl2 (5),24 Os(tCMe)(PPh3)2Cl3 (11),30
(53) Stephens, F. H.; Figueroa, J. S.; Cummins, C. C.; Kryatova, O. P.;
Kryatov, S. V.; Rybak-Akimova, E. V.; McDonough, J. E.; Hoff, C. D.
Organometallics 2004, 23, 3126.
(54) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997,
62, 7512.
(50) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996,
118, 100.
(51) Dias, E. L.; Nguyen, S. T.; Grubbs, R. H. J. Am. Chem. Soc. 1997,
119, 3887.
(52) Chamberlain, R. L.; Chambers, M.; Chadeayne, A. R.; Wolczanski,
P. T. Unpublished results.
(55) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.

Terminal Carbido Complexes of Osmium
Organometallics, Vol. 26, No. 20, 2007 5107
Mo(H)(η2-Me2CNAr)(N[i-Pr]Ar)2 (6),25 SdMo(N[t-Bu]Ar)3,56 and
SedMo(N[t-Bu]Ar)3 were synthesized according to published
procedures.
28.29 (virtual t, 2JPC ) 5 Hz, P(C6H11)3), 27.12 (s, P(C6H11)3). 31P-
{1H} NMR (C6D6): 23.39 (s). Anal. Calcd for C37H66Cl2P2Os: C,
53.28; H, 7.98. Found: C, 53.38; H, 7.95.
56
Synthetic Procedures. [Os(CS)(PCy3)2Cl2] (4-S). Method A
(preparative scale). The crude residue from a preparation of 5 (3.03
g, 2.77 mmol) was dissolved without purification in dichlo-
romethane (230 mL). Tricyclohexylphosphine (3.89 g, 13.9 mmol,
5.02 equiv) was added to the dichloromethane solution. The mixture
was stirred for 1.2 h at 30 °C, and then the solvent was removed
under vacuum. The resulting brown solid was slurried in a mixture
of diethyl ether (5 mL) and pentane (25 mL), stirred for 20 min,
filtered, washed with pentane (20 mL), and then washed with diethyl
ether (3 × 10 mL). The brown powder was dissolved in minimal
dichloromethane (60 mL), and tricyclohexylphosphine (2.19 g, 7.81
mmol) was added to the solution. The mixture was stirred for 30
min at 30 °C, and then the solvent was removed under vacuum.
The resulting brown powder was slurried in pentane (20 mL) and
diethyl ether (10 mL), stirred for 30 min, filtered, washed with
pentane (3 × 10 mL), washed with diethyl ether (3 × 10 mL), and
then dried in Vacuo. Crude brown 4-S was dissolved in dichlo-
romethane (26 mL) and placed in the freezer overnight at -35 °C,
whereupon green crystals of [4-S‚(CH2Cl2)2] formed. The crystals
were filtered, washed with cold dichloromethane (3 × 5 mL), and
dried under vacuum. The crystals rapidly converted to a green
powder upon drying. A second crop was recovered from the filtrate
in a similar manner, resulting in 1.27 g (1.47 mmol, 53.1%) of
green 4-S. This green powder was lyophilized from benzene to
remove residual dichloromethane to yield pure 4-S. 1H NMR (CD2-
Cl2): δ 2.97 (m, 6H, P(C6H11)3), 2.11 (pseudo-d, 12H, P(C6H11)3),
1.84 (m, 12H, P(C6H11)3), 1.74 (br s, 6H, P(C6H11)3), 1.55 (pseudo-
q, 12H, P(C6H11)3), 1.26 (m, 18H, P(C6H11)3). 13C{1H} NMR (CD2-
Method B. 4 was synthesized from 4-S and 6. Compound 4-S
(0.323 g, 0.373 mmol) was dissolved in benzene (50 mL). Solid 6
(0.611 g, 1.05 mmol, 2.82 equiv) was added to the benzene solution
with stirring, and the reaction mixture was sealed under vacuum.
The reaction was monitored by 31P NMR spectroscopy. The mixture
was stirred for 2 h at 30 °C, and then more 6 (0.130 g, 0.223 mmol,
0.598 equiv) was added. After 14 h, 31P NMR spectroscopy showed
complete consumption of the starting material and one peak
corresponding to the carbido product 4 (δ 23.5). The mixture was
frozen in benzene at -35 °C and lyophilized, affording a black-
brown residue. The remaining residue was washed with cold
pentane (2 × 20 mL, then 4 × 5 mL). The filtrate was analyzed by
31P NMR spectroscopy and showed three peaks: δ 36.4 (unas-
signed, 8.0%), 23.5 (4, 38.5%), and 10.6 (PCy3, 53.5%). The
remaining solid was washed with cold diethyl ether (4 × 5 mL).
The filtrate was analyzed by 31P NMR spectroscopy and showed
one peak corresponding to 4; the mass was small and not quantified.
No 31P NMR signal was observed in the 31P NMR spectrum of the
1
remaining solid. The H NMR spectrum identified the remaining
material as a mixture of (µ-N)[Mo(N[i-Pr]Ar)3]2 and (µ-S)[Mo-
(N[i-Pr]Ar)3]2.
[SedTa(OSi-t-Bu3)3] (7-Se). Selenium (9.7 mg, 0.12 mmol, 1.0
equiv) was added to a stirred, blue solution of compound 7 (101
mg, 0.122 mmol) in diethyl ether (5 mL) at 30 °C. The blue solution
bleached within 1 min, leaving a nearly colorless solution with a
faint yellow tint. The mixture was stirred for 30 min and filtered,
and then the solvent was removed under reduced pressure. The
white residue was dissolved in minimal pentane and cooled to
-35 °C overnight. The fine white needles that formed were filtered
on a cold frit, washed with cold pentane (3 × 2 mL), and dried in
Vacuo. A second crop was collected in a similar manner, yielding
2
1
Cl2): δ 239.68 (t, JPC ) 6 Hz, Os(CS)), 33.80 (virtual t, JPC
)
2
12 Hz, P(C6H11)3), 30.42 (s, P(C6H11)3), 28.38 (virtual t, JPC ) 5
Hz, P(C6H11)3), 27.05 (s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): 18.3
(s). Anal. Calcd for C37H66Cl2P2SOs: C, 51.31; H, 7.68. Found:
C, 51.43; H, 7.39.
1
7-Se (22 mg, 0.024 mmol, 20%). H NMR (C6D6): δ 1.32 (s).
13C{1H} NMR (C6D6): δ 30.66 (s, C(CH3)3), 24.03 (s, C(CH3)3).
Anal. Calcd for C36H81O3SeSi3Ta: C, 47.71; H, 9.01. Found: C,
48.09; H, 9.34.
Method B (NMR scale). Compound 4 (0.0083 g, 0.010 mmol)
and S8 (0.0014 g, 0.0055 mmol) were dissolved in C6D6 (0.8 mL)
and stirred at 30 °C. Reaction progress was monitored for the
disappearance of starting material (δ 23.3) and the appearance of
product (δ 18.3) by 31P NMR spectroscopy. Clean conversion to
product required 24 h.
[Os(tCMe)(PCy3)2Cl2][OTf] (10). Method A (preparative
scale). Compound 12 (0.121 g, 0.137 mmol) was dissolved in
dichloromethane (10 mL) in a vial covered with black electrical
tape. Silver trifluoromethanesulfonate (36 mg, 0.14 mmol, 1.0
equiv) was added to the dichloromethane solution of 12. The mix-
ture was stirred for 30 min and then filtered through a bed of Celite
with dichloromethane. The solvent was removed under vacuum,
and the residue was dried in Vacuo overnight. The orange-brown
residue was suspended in diethyl ether (5 mL), stirred for 5 min,
filtered, washed with diethyl ether (2 × 3 mL), and dried in Vacuo,
[Os(tC)(PCy3)2Cl2] (4). Method A. Green-yellow, powdery 4-S
(1.18 g, 1.36 mmol) was dissolved in toluene (40 mL). Separately,
blue, crystalline Ta(OSi-t-Bu3)3 (1.28 g, 1.55 mmol, 1.14 equiv)
was dissolved in toluene (40 mL), poured into the solution of 4-S,
and rinsed in with an additional 10 mL of fresh toluene. The flask
was evacuated, sealed, and stirred overnight at 30 °C. Reaction
progress was monitored for disappearance of starting material (δ
18.4) relative to appearance of 4 (δ 23.4) by 31P NMR spectroscopy.
After stirring for 24 h, a 31P NMR spectrum showed 95% conversion
to 4. Compound 7 (71 mg, 0.086 mmol, 0.063 equiv) was added
to the toluene solution, stirred for 3 h, and analyzed by 31P NMR
spectroscopy. No change was observed by NMR spectroscopy.
Additional 7 (71 mg, 0.086 mmol, 0.063 equiv) was added to the
toluene solution and stirred for 22 h at 30 °C. 31P NMR spectroscopy
showed complete conversion of 4-S to 4. The solvent was removed
under vacuum, and the resulting brown solid was slurried in pentane
(20 mL), filtered, washed with 10 mL of pentane, washed with
additional pentane (4 × 5 mL), and then dried in Vacuo, affording
1
affording pure light tan 10 (91 mg, 0.091 mmol, 67%). H NMR
(CD2Cl2): δ 3.02 (m, 6H, P(C6H11)3), 2.22 (s, 3H, CH3), 1.93 (m,
24H, P(C6H11)3), 1.79 (m, 6H, P(C6H11)3), 1.57 (pseudo-q, 12H,
P(C6H11)3), 1.28 (m, 18H, P(C6H11)3). 13C{1H} NMR (CD2Cl2):
1
δ 279.55 (m, OsCCH3), 42.26 (s, OsCCH3), 33.70 (virtual t, JPC
2
) 12 Hz, P(C6H11)3), 30.65 (s, P(C6H11)3), 28.20 (virtual t, JPC
) 6 Hz, P(C6H11)3), 26.51 (s, P(C6H11)3). 31P{1H} NMR (CD2-
Cl2): 43.49 (s). 19F NMR (CD2Cl2): -79.41 (s). Anal. Calcd for
C39H69Cl2F3O3P2SOs: C, 46.93; H, 6.97. Found: C, 46.76;
H, 6.90.
Method B (NMR scale). Compound 4 (8.6 mg, 0.010 mmol)
was dissolved in CD2Cl2 (0.8 mL) and cooled to -35 °C. Methyl
trifluoromethanesulfonate (1.2 µL, 0.011 mmol) was added to the
dichloromethane solution, and the mixture was stirred at 30 °C.
Reaction progress was monitored by 1H and 31P NMR spectroscopy.
After 2.5 h, a 31P NMR spectrum showed the following. 31P(121.5
MHz, CD2Cl2): δ 43.4 (10, 90.2%) and 36.0 (unassigned, 9.8%).
Complete conversion to the product was observed after stirring for
20.5 h.
1
pure 4 as a pale yellow powder (1.01 g, 1.21 mmol, 89.4%). H
NMR (C6D6): δ 2.91 (m, 6H, P(C6H11)3), 2.41 (pseudo-d, 12H,
P(C6H11)3), 1.72 (m, 24H, P(C6H11)3), 1.59 (m, 6H, P(C6H11)3), 1.20
(m, 18H, P(C6H11)3). 13C{1H} NMR (C6D6): δ 448.45 (s, Os(C)),
1
31.51 (virtual t, JPC ) 12 Hz, P(C6H11)3), 30.09 (s, P(C6H11)3),
(56) Johnson, A. R.; Davis, W. M.; Cummins, C. C.; Serron, S.; Nolan,
S. P.; Musaev, D. G.; Morokuma, K. J. Am. Chem. Soc. 1998, 120, 2071.

5108 Organometallics, Vol. 26, No. 20, 2007
Stewart et al.
[Os(tCMe)(PCy3)2Cl3] (12). The crude residue from the
preparation of 11 (0.347 g, 0.409 mmol) was suspended in
tetrahydrofuran (100 mL). Tricyclohexylphosphine (0.390 g, 1.39
mmol, 3.40 equiv) was added to the tetrahydrofuran solution. The
mixture was refluxed for 1.2 h and then cooled to room temperature.
The solvent was removed under vacuum, leaving a pale yellow
residue, which was slurried in pentane (25 mL) and diethyl ether
(10 mL), stirred for 10 min, and then filtered. The resulting yellow
powder was washed with pentane (2 × 5 mL), followed by diethyl
ether (3 × 5 mL), and was then dried under vacuum. Crude 12
was dissolved in minimal dichloromethane and placed in the freezer
at -35 °C overnight to afford a yellow microcrystalline solid, which
was filtered and washed with cold dichloromethane (2 × 3 mL).
Two more crops were collected in a similar manner, resulting in
0.232 g (0.262 mmol, 64.1%) of yellow 12. Pure 12 was obtained
after crystallizing crude 12 twice from minimal dichloromethane
diethyl ether (5 mL). The crystals were separated by hand for NMR
analysis. The colorless crystals were identified as [HPCy3]+, and
the orange-brown crystals were identified as crude 14. H NMR
1
(CD2Cl2): δ 3.17 (virtual t, 3H, CH3), 2.87 (m, 6H, P(C6H11)3),
1.79 (m, P(C6H11)3), 1.60 (pseudo-q, P(C6H11)3), 1.32 (m, P(C6H11)3).
13C{1H} NMR (CD2Cl2): δ not observed (m, RuCCH3), 46.47
1
(s, RuCCH3), 34.30 (virtual t, JPC ) 10 Hz, P(C6H11)3), 30.88
2
(s, P(C6H11)3), 28.15 (virtual t, JPC ) 5 Hz, P(C6H11)3), 26.48
(s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): 53.56 (s). 19F NMR
(CD2Cl2): δ -79.30 (s).
[Os(tCCH2Ph)(PCy3)2Cl2][BF4] (15). Tropylium tetrafluo-
roborate (64 mg, 0.36 mmol, 1.9 equiv) was added to a stirred
solution of compound 4 (0.160 g, 0.192 mmol) in dichloromethane
(10 mL). The mixture was stirred for 4 h, and the solvent was
removed under vacuum. The residue was suspended in 10 mL of
dichloromethane and filtered through Celite. The solvent was
removed under vacuum, and the residue was suspended in pentane
(10 mL), filtered, washed with pentane (10 mL), washed with
diethyl ether (5 × 3 mL), washed with cold tetrahydrofuran (3 ×
1 mL), and then dried in Vacuo, affording crude 15 (0.122 g, 0.121
mmol, 63.2%) contaminated with a small quantity of tropylium
1
at -35 °C. H NMR (CD2Cl2): δ 2.80 (m, 6H, P(C6H11)3), 2.11
(pseudo-d, 12H, P(C6H11)3), 1.84 (m, 24H, P(C6H11)3), 1.56 (m,
4
6H, P(C6H11)3), 1.56 (t, JPH ) 2 Hz, OsCCH3), 1.28 (m, 18H,
2
P(C6H11)3). 13C{1H} NMR (CD2Cl2): δ 274.98 (t, JPC ) 12 Hz,
1
OsCCH3), 42.38 (s, OsCCH3), 34.81 (virtual t, JPC ) 11 Hz,
2
1
1
P(C6H11)3), 29.52 (s, P(C6H11)3), 28.52 (virtual t, JPC ) 5 Hz,
tetrafluoroborate (0.06 C7H7BF4/15 by H NMR integration). H
NMR (CD2Cl2): δ 7.41 (m, 3H, Ph), 7.12 (d, 2H, Ph), 3.83 (br s,
2H, OsCCH2Ph), 3.01 (m, 6H, P(C6H11)3), 1.90-1.75 (m, 30H,
P(C6H11)3), 1.48 (pseudo-q, 12H, P(C6H11)3), 1.23 (m, 18H,
P(C6H11)3). 13C{1H} NMR (CD2Cl2): δ 277.21 (m, OsCCH2Ph),
130.34 (s, Ph), 129.74 (s, Ph), 129.21 (s, Ph), 127.57 (s, Ph), 59.46
P(C6H11)3), 26.99 (s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ -10.24
(s). Anal. Calcd for C38H69Cl3P2Os: C, 51.60; H, 7.86. Found: C,
51.55; H, 7.83.
[Os(dCCH2)(PCy3)2Cl2] (13). Compound 12 (0.243 g, 0.274
mmol) was partially dissolved in tetrahydrofuran (28 mL). Sepa-
rately, lithium tert-butoxide (25 mg, 0.31 mmol, 1.1 equiv) was
partially dissolved in tetrahydrofuran (5 mL). The lithium tert-
butoxide solution was added by pipet to the stirred flask containing
12. The mixture slowly turned burgundy and was stirred for 2 min,
at which time benzene (10 mL) was added. The resulting reaction
mixture was stirred for 30 min at 30 °C and filtered, and then the
solvent was removed under reduced pressure. The crude residue
was filtered through Celite with toluene until the filtrate was
colorless, and then the solvent was removed from the combined
filtrate and washings under vacuum. The residue was triturated with
pentane (10 mL) and then dissolved in minimal dichloromethane,
layered with an equal volume of diethyl ether, and placed in the
freezer at -35 °C overnight. The reddish-brown crystals were
filtered on a cold frit, washed with cold dichloromethane (3 × 4
mL), and then dried in Vacuo. Another crop was collected in a
similar manner, yielding 13 (137 mg, 0.162 mmol, 58.9%). 1H NMR
(CD2Cl2): δ 2.83 (m, 6H, P(C6H11)3), 2.07 (pseudo-d, 12H,
P(C6H11)3), 1.80-1.57 (m, 30H, P(C6H11)3), 1.24 (m, 18H, P(C6H11)3),
0.65 (vt, Japp ) 2 Hz, 2H, CCH2). 13C{1H} NMR (CD2Cl2): δ
1
(s, OsCCH2Ph), 33.60 (virtual t, JPC ) 12 Hz, P(C6H11)3), 30.58
2
(s, P(C6H11)3), 28.18 (virtual t, JPC ) 6 Hz, P(C6H11)3), 26.48
(s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ 44.03 (s).
[Ru(tCCH2Ph)(PCy3)2Cl2][BF4] (16). Tropylium tetrafluo-
roborate (23 mg, 0.13 mmol, 0.94 equiv) was added to a stirred
dichloromethane (8 mL) solution of Ru(tC)(PCy3)2Cl2 (101 mg,
0.136 mmol) at 30 °C. The mixture turned dark orange within 1
min and was stirred for 19 h. The reaction mixture was filtered,
and the solvent was removed from the filtrate under reduced
pressure. The resulting dark residue was suspended in pentane (10
mL), filtered, washed with pentane (10 mL), and then washed with
additional pentane (3 × 5 mL). The dark solid was washed with
diethyl ether (3 × 5 mL) and then washed with toluene (4 × 5
mL). The resulting yellow powder was dried in Vacuo, yielding
crude [Ru(tCCH2Ph)(PCy3)2Cl2][BF4] (42 mg, 0.13 mmol, 35%).
The 31P NMR spectrum showed one peak at 55.5 ppm. The crude
product was recrystallized by vapor diffusion of pentane into a
concentrated dichloromethane solution at 30 °C overnight. The
filtrate was decanted from the yellow and orange crystals, which
were then rinsed three times with 2 mL of the surrounding vapor
diffusion solvent and then dried in Vacuo. The crystals were
separated by hand for NMR analysis. The orange crystals were
identified as crude 16, and the yellow-tinted crystals were identified
2
274.56 (vt, JPC ) 9 Hz, OsCCH2), 90.36 (m, OsCCH2), 34.06
(pseudo-t, Japp ) 11 Hz, P(C6H11)3), 30.41 (s, P(C6H11)3), 28.46
(pseudo-t, Japp ) 5 Hz, P(C6H11)3), 27.18 (s, P(C6H11)3). 31P{1H}
NMR (CD2Cl2): 2.56 (s). Anal. Calcd for C38H68Cl2P2Os: C, 53.82;
H, 8.08. Found: C, 53.57; H, 8.47.
1
as crude [HPCy3]+. H NMR (CD2Cl2): δ 7.44 (m, 3H, Ph), 7.19
(m, 2H, Ph), 4.66 (br s, 2H, RuCCH2Ph), 2.87 (m, 6H, P(C6H11)3),
1.90-1.75 (m, P(C6H11)3), 1.50 (pseudo-q, P(C6H11)3), 1.26 (m,
P(C6H11)3). 13C{1H} NMR (CD2Cl2): δ 312.00 (m, RuCCH2Ph),
130.57 (s, Ph), 130.28 (s, Ph), 129.65 (s, Ph), 127.60 (s, Ph), 63.27
[Ru(tCMe)(PCy3)2Cl2][OTf] (14). Methyl trifluoromethane-
sulfonate (16.2 µL, 0.143 mmol, 1.00 equiv) was added by syringe
to a thawing dichloromethane (9 mL) solution of 1 (107 mg, 0.142
mmol). The mixture was stirred at 30 °C and slowly turned orange.
After 5 h, an aliquot was removed and was analyzed by 31P NMR
spectroscopy. The spectrum showed a new peak at 53.6 ppm (85%)
and starting material at 38.9 ppm (15%). The reaction mixture was
stirred overnight at 30 °C, which resulted in a dark orange solution.
31P NMR spectrum showed a peak at 53.6 ppm (14, 74%) and a
peak at 28.9 ppm ([HPCy3]+, 26%). The mixture was filtered, and
the dichloromethane was removed from the filtrate under reduced
pressure. The resulting residue was dissolved in minimal dichlo-
romethane, layered with pentane, and cooled to -35 °C. The
resulting mixture of orange-brown crystals and colorless needles
was filtered on a cold frit and washed four times with 5 mL of a
cold dichloromethane/pentane mixture (1:6) followed by cold
1
(s, RuCCH2Ph), 34.20 (virtual t, JPC ) 10 Hz, P(C6H11)3), 30.79
2
(s, P(C6H11)3), 28.12 (virtual t, JPC ) 6 Hz, P(C6H11)3), 26.44
(s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ 55.38 (s). 19F NMR
(CD2Cl2): δ -153.27 (br s).
[Os(tCC(O)Ph)(PCy3)2Cl3] (17). Benzoyl chloride (16.6 µL,
0.144 mmol, 1.20 equiv) was added by syringe to a stirred
dichloromethane (13 mL) solution of 4 (100 mg, 0.120 mmol). The
yellow solution was stirred overnight at 30 °C for 18.5 h, yielding
an orange solution. 31P NMR spectroscopy showed partial conver-
sion of the starting material (23.35 ppm, 21%) to the desired product
(-7.85 ppm, 79%). Benzoyl chloride (33.2 µL, 0.288 mmol, 2.40
equiv) was added to the reaction mixture, which was stirred

Terminal Carbido Complexes of Osmium
Organometallics, Vol. 26, No. 20, 2007 5109
overnight for 20 h. A 31P NMR spectrum of the orange solution
showed only the desired product. The solvent was removed under
vacuum, leaving a yellow powder, which was suspended and stirred
in pentane (6 mL) for 2 h, filtered, washed with pentane (5 × 4
mL), and then dried in Vacuo, affording analytically pure 17 (103
mg, 0.106 mmol, 88.0%). 1H NMR (CD2Cl2): δ 8.31 (d, 3JHH ) 7
[Os(tC)(PCy3)2I2] (20). A pressure vessel was charged with 4
(209 mg, 0.251 mmol) dissolved in toluene (14 mL). Iodotrimeth-
ylsilane (360 µL, 2.5 mmol, 10 equiv) was added to the vessel,
which was then sealed under nitrogen. The stirred reaction mixture
was heated to 120 °C for 10 h, which resulted in a dark orange
solution. The solvent was removed, and the residue was suspended
in pentane (7 mL), filtered, washed with pentane (3 mL), washed
with diethyl ether (2 mL), and then dried in Vacuo, yielding brown
powder containing crude 20 (159 mg, 0.157 mmol, 62.4%). The
brown powder was dissolved in minimal dichloromethane and
placed in the freezer at -35 °C overnight. The resulting orange
crystals were filtered, washed with cold dichloromethane (2 × 4
mL), and dried in Vacuo. A second crop was obtained in a similar
manner, yielding analytically pure 20 (70 mg, 0.069 mmol, 28%).
1H NMR (CD2Cl2): δ 3.24 (m, 6H, P(C6H11)3), 2.22 (pseudo-d,
12H, P(C6H11)3), 1.83 (pseudo-d, 12H, P(C6H11)3), 1.71 (pseudo-
d, 6H, P(C6H11)3), 1.55 (pseudo-q, 12H, P(C6H11)3), 1.26 (m, 18H,
P(C6H11)3). 13C{1H} NMR (CD2Cl2): δ 446.14 (s, Os(C)), 34.71
(pseudo-t, Japp ) 13 Hz, P(C6H11)3), 31.42 (s, P(C6H11)3), 28.61
(pseudo-t, Jzpp ) 5 Hz, P(C6H11)3), 27.47 (s, P(C6H11)3). 31P{1H}
NMR (CD2Cl2): δ 16.70 (s). Anal. Cacld for C37H66I2P2Os: C,
43.70; H, 6.54. Found: C, 43.70; H, 6.64.
3
3
Hz, 2H, Ph), 7.71 (t, JHH ) 7 Hz, 1H, Ph), 7.57 (t, JHH ) 8 Hz,
2H, Ph), 2.75 (m, 6H, P(C6H11)3), 2.08 (m, 12H, P(C6H11)3), 1.83-
1.62 (m, 30H, P(C6H11)3), 1.29-1.07 (m, 18H, P(C6H11)3). 13C-
2
{1H} NMR (CD2Cl2): δ 255.33 (vt, JPC ) 11 Hz; OsCC(O)Ph),
192.3 (s, OsCC(O)Ph), 136.50 (s, Ph), 133.72 (s, Ph), 131.40
(s, Ph), 129.77 (s, Ph), 36.32 (pseudo-t, Japp ) 11 Hz, P(C6H11)3),
29.50 (s, P(C6H11)3), 28.34 (pseudo-t, 2JPC ) 5 Hz, P(C6H11)3), 26.90
(s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ -7.90 (s). Anal. Cacld
for C44H71Cl3OP2Os: C, 54.23; H, 7.34. Found: C, 54.08; H, 7.21.
[Os(tCH)(PCy3)2Cl2][OTf] (18). Compound 4 (34 mg, 0.041
mmol) was dissolved in toluene (2 mL) and cooled to -35 °C.
Trifluoromethanesulfonic acid (3.7 µL, 0.042 mmol, 1.0 equiv) was
added to the stirred solution of Os(tC)(PCy3)2Cl2. After 10 min,
the suspension was filtered and the pale tan colored solid was
washed with toluene (2 × 2 mL) and pentane (2 × 2 mL). The
resulting solid was dried under vacuum, yielding 18 (30 mg, 0.030
1
Control reaction of PCy3 with HOTf. Trifluoromethanesulfonic
acid (7.0 µL, 0.079 mmol, 1.0 equiv) was added to a stirred CD2-
Cl2 (0.7 mL) solution of tricyclohexylphosphine (22 mg, 0.077
mmol) at 30 °C. The mixture was stirred for 27 min, yielding
mmol, 77%). H NMR (CD2Cl2): δ 11.02 (s, 1H, OsCH), 2.90
(m, 6H, P(C6H11)3), 1.94 (m, 24H, P(C6H11)3), 1.78 (m, 6H,
P(C6H11)3), 1.55 (pseudo-q, 12H, P(C6H11)3), 1.28 (m, 18H,
P(C6H11)3). 13C{1H} NMR (CD2Cl2) at -19 °C: δ 285.66
(s, OsCH), 31.71 (pseudo-t, Japp ) 12 Hz, P(C6H11)3), 30.09 (s,
m-C of P(C6H11)3), 28.00 (pseudo-t, Japp ) 6 Hz, P(C6H11)3), 26.39
(s, P(C6H11)3). 31P{1H} NMR (CD2Cl2): 50.55 (s). 19F NMR (CD2-
Cl2): -79.34 (s). Anal. Calcd for C38H67Cl2F3O3P2SOs: C, 46.38;
H, 6.86. Found: C, 45.67; H, 6.40.
1
1
[HPCy3][OTf]. H NMR (CD2Cl2): δ 5.78 (dq, JHP ) 466 Hz,
3JHH ) 4 Hz, 1 H, HP(C6H11)3), 2.49 (m, 3H, P(C6H11)3), 2.00 (m,
P(C6H11)3), 1.93 (m, P(C6H11)3), 1.79 (m, P(C6H11)3), 1.57 (m,
P(C6H11)3), 1.47-1.26 (m, P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ
29.5 (s). 19F NMR (CD2Cl2): δ -79.3 (s).
Decomposition of [Os(tCH)(PCy3)2Cl2][OTf] (18) with an
Internal Standard. Compound 18 (7.1 mg, 0.0072 mmol) was
dissolved in CD2Cl2 (0.7 mL) and placed in a J. Young NMR tube
at 30 °C with an insert containing P(OCH3)3 diluted in C6D6. The
[Os(CS)(PCy3)2I2] (20-S). Method A. Green, microcrystalline
4-S (301 mg, 0.348 mmol) was dissolved in 30 mL of tetrayhy-
drofuran in a 100 mL round-bottom covered with foil. Sodium
iodide (523 mg, 3.49 mmol, 10.0 equiv) was added, and the mixture
was stirred 24 h at 30 °C. A 31P NMR spectrum of the reaction
mixture showed one resonance corresponding to 20-S at δ 12.16.
The solvent was removed, and the green residue was filtered through
Celite with toluene. The Celite was washed with toluene until the
filtrate was colorless. The toluene was removed, and the green
residue was suspended in 20 mL of pentane, filtered, washed with
pentane (2 × 5 mL), and dried in Vacuo, yielding crude 20-S (308
mg, 0.294 mmol, 84.6%). Elementally pure material was obtained
by recrystallizing crude 20-S twice from minimal dichloromethane
1
sample was analyzed by H and 31P NMR spectroscopy, and the
resonances were integrated relative to the internal standard set at 6
and 10, respectively. For example, a singlet at 10 ppm that integrates
to 5 relative to the internal standard will be described as δ 10
(s, 5). The initial NMR spectrum showed that the sample had
decomposed in the solid state while stored at 30 °C under nitrogen.
31P NMR spectroscopy showed resonances at δ 50.48 (s, 18, 29.14),
46.43 (s, 0.38), 30.44 (s, [HPCy3]+, 1.84), 12.22 (s, 2.68). After 2
h, the 31P NMR spectrum showed resonances at δ 50.48 (s, 18,
18.02), 46.43 (s, 4.09), 30.44 (s, [HPCy3]+, 6.76), and 12.22
1
at -35 °C. H NMR (CD2Cl2): δ 3.54 (m, 6H, P(C6H11)3), 2.08
1
(s, 7.81). The H NMR spectrum showed resonances at δ 24.64
(pseudo-d, 12H, P(C6H11)3), 1.81 (pseudo-d, 12H, P(C6H11)3), 1.73
(pseudo-d, 6H, P(C6H11)3), 1.52 (pseudo-q, 12H, P(C6H11)3), 1.30
(d, J ) 32 Hz, 0.04), 22.50 (d, J ) 37 Hz, 0.22), 11.06 (s, Os-
(CH), 0.52), and [HPCy3]+ (0.32). After an additional 2 h, the 31
P
2
(m, 18H, P(C6H11)3). 13C{1H} NMR (CD2Cl2): δ 241.06 (vt, JPC
NMR spectrum showed resonances at δ 50.48 (s, 18, 9.02), 46.43
) 7 Hz; CS), 37.0 (pseudo-t, Japp ) 13 Hz, P(C6H11)3), 31.32
(s, P(C6H11)3), 28.21 (pseudo-t, Japp ) 5 Hz, P(C6H11)3), 27.07 (s,
P(C6H11)3). 31P{1H} NMR (CD2Cl2): δ 11.80 (s). Anal. Cacld for
C37H66I2P2OsS: C, 42.36; H, 6.34. Found: C, 42.04; H, 6.39.
1
(s, 6.75), 30.44 (s, [HPCy3]+, 9.94), and 12.22 (s, 13.56). The H
NMR spectrum showed resonances at δ 24.64 (d, J ) 32 Hz, 0.08),
22.50 (d, J ) 37 Hz, 0.31), 11.06 (s, Os(CH), 0.26), and [HPCy3]+
(0.44). After an additional 4 h, the 31P NMR spectrum showed
resonances at δ 204.00 (s, 0.72), 50.48 (s, 18, 2.76), 49.38 (s, 1.23),
46.43 (s, 5.80), 30.44 (s, [HPCy3]+, 10.72), 14.19 (s, 1.35), 12.22
Method B. A pressure vessel was charged with the crude residue
from a preparation of 5 (796 mg, 0.729 mmol), tricyclohexylphos-
phine (650 mg, 2.32 mmol, 3.18 equiv), and 50 mL of tetrahydro-
furan, respectively in that order. The mixture was heated to 60 °C
for 1.5 h, which resulted in a brown solution. The reaction vessel
was wrapped with foil, charged with sodium iodide (932 mg, 6.22
mmol, 8.53 equiv), and stirred for 21.5 h. The solvent was removed,
and the green residue was dissolved in toluene (70 mL) and filtered
through Celite. The Celite was washed with toluene until the filtrate
was colorless. The solvent was removed, and the green residue was
suspended in pentane (25 mL), stirred for 10 min, filtered, washed
with pentane (2 × 10 mL), washed with diethyl ether (3 × 7 mL),
and dried in Vacuo, yielding crude 20-S (552 mg, 0.525 mmol,
72.1%). Crude 20-S can be recrystallized as described in
method A.
1
(s, 12.24), and 11.02 (s, 1.13). The H NMR spectrum showed
resonances at δ 24.64 (d, J ) 32 Hz, 0.11), 22.50 (d, J ) 37 Hz,
0.37), 11.06 (s, Os(CH), 0.07), and [HPCy3]+ (0.58).
Attempted Reaction of [Os(tC)(PCy3)2Cl2] (4) with ClC(O)t-
Bu. Pivaloyl chloride (0.8 µL, 0.007 mmol, 1 equiv) was added by
syringe to an NMR tube containing compound 4 (5.2 mg, 0.0062
mmol) dissolved in CD2Cl2 (0.7 mL). The NMR tube was inverted
several times and stored at room temperature overnight. A 31P NMR
spectrum of the yellow solution showed only starting material
(δ ) 23.2).
Attempted Reaction of [Ru(tC)(PCy3)2Cl2] (1) with ClC(O)-
Ph. Benzoyl chloride (1.5 µL, 0.013 mmol, 1.0 equiv) was added

5110 Organometallics, Vol. 26, No. 20, 2007
Stewart et al.
by syringe to an NMR tube containing compound 1 (9.8 mg, 0.013
mmol) dissolved in CD2Cl2 (0.8 mL). The NMR tube was inverted
several times and stored at room temperature overnight. A 31P NMR
spectrum of the yellow solution showed only starting material
(δ ) 38.7).
Attempted Reaction of [Ru(tC)(PCy3)2Cl2] (1) with ClC(O)t-
Bu. Pivaloyl chloride (1.7 µL, 0.014 mmol, 1.1 equiv) was added
by syringe to an NMR tube containing compound 1 (10 mg, 0.013
mmol) dissolved in CD2Cl2 (0.8 mL). The NMR tube was inverted
several times and stored at room temperature overnight. A 31P NMR
spectrum of the yellow solution showed only starting material
(δ ) 38.7).
NMR spectrum and the singlet at δ 51.32 in the 31P NMR spectrum
are consistent with [Os(tCH)(PCy3)2Cl2][BF4]. After mixing
overnight at 30 °C, the 31P NMR spectrum showed mostly [HPCy3]+
at δ 30.0 (52%) along with resonances at δ 49.21 (15%), 15.47
(5%), 14.07 (10%), 11.05 (12%), and 9.66 (6%). A 1H NMR
spectrum showed the doublet at δ 24.63 and [HPCy3]+ in a 0.4:1
ratio.
Reaction of [Os(tC)(PCy3)2Cl2] (4) with [H(OEt2)2][B(C6F5)4].
Compound 4 (10 mg, 0.013 mmol) and [H(OEt2)2][B(C6F5)4] (10
mg, 0.012 mmol, 0.92 equiv) were separately dissolved in CD2Cl2
(0.4 mL) and cooled to -35 °C. The [H(OEt2)2][B(C6F5)4] solution
was slowly added by pipet to the stirred solution of 4. The reaction
mixture was warmed to 30 °C while stirring for 30 min. 31P NMR
spectroscopy showed a broad resonance at δ 28.5 (60%) and a
singlet at δ 34.5 (26%) as well as multiple smaller signals. 1H NMR
spectroscopy did not show resonances corresponding to the Os
analogue of [Ru(dCHPCy3)(PCy3)Cl2][B(C6F5)4]. Instead, singlets
were observed at δ 21.8, 19.2, 17.5, 12.0, and 9.9. The 31P NMR
spectra and 1H NMR spectra were equally complex after the solution
was mixed for an additional 2 h at 30 °C.
X-ray Analysis of 4, 4-S, and 15. Crystals were mounted on a
standard Bruker SMART CCD-based X-ray diffractometer equipped
with a LT-2 low-temperature device and normal focus Mo-target
X-ray tube (λ ) 0.71073 Å) operated at 2000 W power (50 kV, 40
mA). Analysis of the data showed negligible decay during data
collection; the data were processed with SADABS and corrected
for absorption. The structures were solved and refined with the
Bruker SHELXTL (version 6.12) software package. All non-
hydrogen atoms were refined anisotropically with the hydrogen
atoms placed in idealized positions. Additional details are presented
in Table 1 and are given as Supporting Information in a CIF file.
Reaction of [SedMo(N[t-Bu]Ar)3] with [Ta(OSi-t-Bu3)3] (7).
Compound 7 (20 mg, 0.024 mmol, 1.0 equiv) was dissolved in
C6D6 (0.7 mL) and added by pipet to a stirred solution of Sed
Mo(N[t-Bu]Ar)3 (17 mg, 0.024 mmol) dissolved in C6D6 (0.7 mL).
The solution immediately turned orange and was stirred for 30 min
1
at 30 °C. A H NMR spectrum showed complete conversion to
Mo(N[t-Bu]Ar)3 and 7-Se.
Reaction of [SdMo(N[t-Bu]Ar)3] with [Ta(OSi-t-Bu3)3] (7).
Compound 7 (22 mg, 0.026 mmol, 1.0 equiv) was dissolved in
C6D6 (0.6 mL) and added by pipet to a stirred solution of SdMo-
(N[t-Bu]Ar)3 (17 mg, 0.026 mmol) dissolved in C6D6 (0.6 mL).
The solution immediately turned dark red-orange and was stirred
for 30 min at 30 °C. A 1H NMR spectrum showed complete
conversion to Mo(N[t-Bu]Ar)3 and 7-S27 (δ ) 1.31).
Reaction of [Os(CS)(PCy3)2I2] (20-S) with [Ta(OSi-t-Bu3)3]
(7). Compound 7 (8.4 mg, 0.010 mmol, 1.0 equiv) was dissolved
in C6D6 (0.4 mL) and added by pipet to a stirred, partially dissolved
solution of 20-S (10 mg, 0.010 mmol) in C6D6 (0.6 mL). The
mixture slowly turned brown. After 10 min the 1H NMR spectrum
showed a broad peak at 1.66 ppm and a few other t-Bu-containing
products (δ ) 1.39, 1.35, 1.31, 1.29). The mixture was stirred
Acknowledgment. This material is based upon work sup-
ported by the National Science Foundation under Grant No.
CHE-0449459 and by an award from Research Corporation.
We also thank the University of Michigan and the Camille and
Henry Dreyfus Foundation for support. We thank Peter T.
Wolczanski for sharing characterization data for unpublished
derivatives of Ta(OSi-t-Bu3)3.
1
overnight at 30 °C. A H NMR spectrum revealed a sharp peak
corresponding to Ta(OSi-t-Bu3)3I2 (δ ) 1.43), the major product,
and several other t-Bu-containing products.52
Reaction of [Os(tC)(PCy3)2Cl2] (4) with HBF4. Compound 4
(9.9 mg, 0.012 mmol) was dissolved in CD2Cl2 (0.6 mL). A 52 wt
% (d ) 1.19) solution of HBF4 in diethyl ether (2.0 µL, 0.014 mmol,
1.2 equiv) was added to the stirred solution of 4 by syringe. The
solution turned dark brown and was stirred at 30 °C for 45 min.
31P NMR spectroscopy showed five phosphorus resonances at δ
51.32 (51%), 49.27 (16%), 30.08 (23%), 14.08 (4%), and 11.06
Supporting Information Available: Synthesis and character-
ization data for all new compounds, conditions for their reactions,
and crystallographic data for 4, 4-S, and 15. This material is
available free of charge via the Internet at http://pubs.acs.org.
1
(6%). H NMR spectroscopy showed a doublet at δ 24.63 (J )
32.7 Hz), a broad singlet at δ 10.41, and [HPCy3]+ in the ratio
1
0.38:1.65:1, respectively. The broad singlet at δ 10.41 in the H
OM070208U