Osmium alkyl and silyl derivatives with cyclopentadienyl(phosphine) and pentamethylcyclopentadienyl(phosphine) ligand sets

Article abstract of DOI:10.1021/om9704197

The preparation and characterization of new osmium(II) and osmium(IV) silyl derivatives containing the cyclopentadienyl(phosphine) and pentamethylcyclopentadienyl(phosphine) ligand sets are described. The osmium silyl complexes are prepared by thermal reactions of hydrosilanes with osmium(II) alkyl complexes of the type Cp′(PR₃)₂OsCH₂SiMe₃ (Cp′ = Cp, R = Ph (4), Me (5); Cp′ = η⁵-C₅Me₅, R = Me (7)), which in turn are available via alkylation of the corresponding bromo complexes. The synthesis of alkyl derivatives of Cp(PR₃)₂Os (R = Ph, Me) requires the use of dialkylmagnesium reagents, while alkylation of the more electron-rich Cp*(PMe₃)₂Os system can be achieved using Grignard reagents. Additionally, reaction of Cp(PPh₃)₂OsBr with AgOTf (Tf = SO₂CF₃) affords the osmium(II) triflate complex Cp(PPh₃)₂OsOTf (2), which possesses a labile triflate group. The structure of complex 2 was determined by X-ray crystallography. Similar to their ruthenium analogs, the osmium-(II) alkyl complexes 4, 5, and 7 thermally activate arene C-H bonds. Reaction of 7 with HSiR₂[S(p-Tol)] (R = S(p-Tol), Me) provides metallacycle complexes of the type Cp*(PMe₃)-(H)Os[C₆H₃(S-Me)(G-S)SiR ₂] (R = S(p-Tol) (11), Me (13)) via activation of both the Si-H and arene C-H bonds in the silanes. The X-ray structure of 13 is described. Alkyl complexes 4, 5, and 7 react with HSiR₂Cl (R = Ph, Me) to give osmium(II) silyl and/or osmium(IV) bis(silyl) hydride species, depending on the reaction conditions and the strength of the Os-P bond. Reaction of 7 with HSiMeCl₂ or HSiCl₃ affords, exclusively, the osmium(II) silyl derivatives. Exchange reactions at silicon are used to synthesize Cp*(PMe₃)₂OsSiMe₂OTf (24) and Cp*(PMe₃)₂OsSiMe[S(p-Tol)]₂ (25) from the corresponding chloro(silyl) complexes Cp*(PMe₃)₂OsSiMe₂Cl (17) and Cp*(PMe₃)₂OsSiMeCl₂ (18). The solution behavior and solid-state structure of 24 indicate that the compound may be described as a base-stabilized silylene complex.

Full text of DOI:10.1021/om9704197

Organometallics 1997, 16, 4299-4313
4299
Osm iu m Alk yl a n d Silyl Der iva tives w ith
Cyclop en ta d ien yl(p h osp h in e) a n d
P en ta m eth ylcyclop en ta d ien yl(p h osp h in e) Liga n d Sets
Paulus W. Wanandi and T. Don Tilley*
Department of Chemistry, University of California, Berkeley, Berkeley, California 94720-1460
Received May 20, 1997X
The preparation and characterization of new osmium(II) and osmium(IV) silyl derivatives
containing the cyclopentadienyl(phosphine) and pentamethylcyclopentadienyl(phosphine)
ligand sets are described. The osmium silyl complexes are prepared by thermal reactions
of hydrosilanes with osmium(II) alkyl complexes of the type Cp′(PR3)2OsCH2SiMe3 (Cp′ )
Cp, R ) Ph (4), Me (5); Cp′ ) η5-C5Me5, R ) Me (7)), which in turn are available via alkylation
of the corresponding bromo complexes. The synthesis of alkyl derivatives of Cp(PR3)2Os (R
) Ph, Me) requires the use of dialkylmagnesium reagents, while alkylation of the more
electron-rich Cp*(PMe3)2Os system can be achieved using Grignard reagents. Additionally,
reaction of Cp(PPh3)2OsBr with AgOTf (Tf ) SO2CF3) affords the osmium(II) triflate complex
Cp(PPh3)2OsOTf (2), which possesses a labile triflate group. The structure of complex 2
was determined by X-ray crystallography. Similar to their ruthenium analogs, the osmium-
(II) alkyl complexes 4, 5, and 7 thermally activate arene C-H bonds. Reaction of 7 with
HSiR2[S(p-Tol)] (R ) S(p-Tol), Me) provides metallacycle complexes of the type Cp*(PMe3)-
(H)Os[C6H3(3-Me)(6-S)SiR2] (R ) S(p-Tol) (11), Me (13)) via activation of both the Si-H
and arene C-H bonds in the silanes. The X-ray structure of 13 is described. Alkyl complexes
4, 5, and 7 react with HSiR2Cl (R ) Ph, Me) to give osmium(II) silyl and/or osmium(IV)
bis(silyl) hydride species, depending on the reaction conditions and the strength of the Os-P
bond. Reaction of 7 with HSiMeCl2 or HSiCl3 affords, exclusively, the osmium(II) silyl
derivatives. Exchange reactions at silicon are used to synthesize Cp*(PMe3)2OsSiMe2OTf
(24) and Cp*(PMe3)2OsSiMe[S(p-Tol)]2 (25) from the corresponding chloro(silyl) complexes
Cp*(PMe3)2OsSiMe2Cl (17) and Cp*(PMe3)2OsSiMeCl2 (18). The solution behavior and solid-
state structure of 24 indicate that the compound may be described as a base-stabilized silylene
complex.
In tr od u ction
compounds has been further stimulated by the discovery
of complexes containing reactive silicon species (e.g.,
silylenes, SiR2; silenes, R2CdSiR′2; etc.) as ligands,
especially since such complexes have often been invoked
as key intermediates in numerous stoichiometric and
catalytic reactions of organosilanes.1,3c,4,5 In previous
work, we demonstrated that a variety of ruthenium silyl
complexes of the type Cp*(PMe3)2Ru(SiXX′X′′) (Cp* )
η5-C5Me5) are versatile precursors to ruthenium si-
lylene6 and base-stabilized silylyne7 complexes.
The burgeoning area of transition-metal silicon chem-
istry continues to generate considerable interest,1 mainly
due to the prominent role of metal-silicon bonded
species in various catalytic processes, such as hydrosi-
lation,2 dehydrogenative coupling of hydrosilanes to
polysilanes,3 and the redistribution of silanes.4 This
growing interest in transition-metal-silicon bonded
* To whom correspondence should be addressed.
X Abstract published in Advance ACS Abstracts, September 1, 1997.
(1) For reviews of metal-silicon compounds, see: (a) Tilley, T. D.
In The Silicon-Heteroatom Bond; Patai, S., Rappoport, Z., Eds.;
Wiley: New York, 1991; Chapters 9, 10, pp 245, 309. (b) Tilley, T. D.
In The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport,
Z., Eds.; Wiley: New York, 1989; Chapter 24, p 1415. (c) Mackay, K.
M.; Nicholson, B. K. In Comprehensive Organometallic Chemistry;
Wilkinson, G. , Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
Oxford, 1982; Vol. 6, p 1043. (d) Aylett, B. J . Adv. Inorg. Chem.
Radiochem. 1982, 25, 1. (e) Pannell, K. H.; Sharma, H. K. Chem. Rev.
1995, 95, 1351. (f) Schubert, U. Angew. Chem., Int. Ed. Engl. 1994,
33, 419.
On the basis of our previous work with ruthenium,
we sought to develop the analogous silicon chemistry
of osmium. Like ruthenium, osmium is an electron-rich
metal that can serve as a strong π-donor, as evidenced
by the wealth of osmium carbene and carbyne species
(5) (a) Zybill, C. Top. Curr. Chem. 1991, 160, 1. (b) Zybill, C.;
Handwerker, H.; Friedrich, H. Adv. Organomet. Chem. 1994, 36, 229.
(c) Lickiss, P. D. Chem. Soc. Rev. 1992, 271. (d) Procopio, L. J .; Berry,
D. H. J . Am. Chem. Soc. 1991, 113, 4039.
(6) (a) Straus, D. A.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J . J .
Am. Chem. Soc. 1987, 109, 5872. (b) Straus, D. A.; Zhang, C.; Quimbita,
G. E.; Grumbine, S. D.; Heyn, R. H.; Tilley, T. D.; Rheingold, A. L.;
Geib, S. J . J . Am. Chem. Soc. 1990, 112, 2673. (c) Grumbine, S. K.;
Straus, D. A.; Tilley, T. D.; Rheingold, A. L. Polyhedron 1995, 14, 127.
(d) Straus, D. A.; Grumbine, S. D.; Tilley, T. D. J . Am. Chem. Soc.
1990, 112, 7801. (e) Grumbine, S. K.; Tilley, T. D.; Arnold, F. P.;
Rheingold, A. L. J . Am. Chem. Soc. 1994, 116, 5495. (f) Grumbine, S.
K.; Tilley, T. D. J . Am. Chem. Soc. 1994, 116, 6951.
(2) For a review of hydrosilation, see: Ojima, I. In The Chemistry
of Organic Silicon Compounds; Patai, S., Rappoport, Z., Eds.; Wiley:
New York, 1989; Chapter 25, p 1479.
(3) (a) Harrod, J . F.; Mu, Y.; Samuel, E. Polyhedron 1991, 10, 1239.
(b) Harrod, J . F. In Inorganic and Organometallic Polymers; Zeldin,
M., Wynne, K. J ., Allcock, H. R., Eds.; ACS Symposium Series 360;
American Chemical Society: Washington, DC, 1988; Chapter 7. (c)
Tilley, T. D. Comm. Inorg. Chem. 1990, 10, 37. (d) Tilley, T. D. Acc.
Chem. Res. 1993, 26, 22. (e) Corey, J . In Advances in Silicon Chemistry;
Larson, G., Ed.; J AI Press, Inc.: Greenwich, CT, 1991; Vol. 1, p 327.
(4) Curtis, M. D.; Epstein, P. S. Adv. Organomet. Chem. 1981, 19,
213.
(7) Grumbine, S. D.; Chadha, R. K.; Tilley, T. D. J . Am. Chem. Soc.
1992, 114, 1518.
S0276-7333(97)00419-6 CCC: $14.00 © 1997 American Chemical Society

4300 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
that have been reported.8 This, coupled with the fact
that 5d transition metals inherently form strong bonds
to ligands,9 led us to expect that many silicon-based
ligands might be stabilized by osmium. In addition,
recent reports indicate that homogeneous catalysis by
osmium silyl complexes may be a field with promising
potential.10
While osmium silyl complexes have been known since
the 1970s, very little reaction chemistry for Os-Si bonds
has been developed. In a recent study, Esteruelas and
co-workers showed that the hydrosilation of phenyl-
acetylene, as catalyzed by OsHCl(CO)(PiPr3)2, proceeds
via the silyl dihydrogen intermediate Os(SiEt3)Cl(η2-
H2)(CO)(PiPr3)2.10a Of the known osmium silyl com-
plexes, the majority are derived from osmium carbonyl
clusters (primarily Os3(CO)12)1,11 and contain carbonyl
ligands. The primary method of synthesis for mono-
meric osmium silyl complexes, such as Os(SiMe3)(Cl)-
(CO)(PPh3)2,12a Os(SiEt3)(H)(CO)2(PPh3)2,12b and OsH3-
(CO)(SiHPh2)(PiPr3)2,13 involves oxidative addition of
hydrosilanes to unsaturated metal centers.
In this report, we describe synthetic routes to new
osmium(II) and osmium(IV) silyl complexes containing
cyclopentadienyl(phosphine) and pentamethylcyclopen-
tadienyl(phosphine) ligand sets. These syntheses are
modeled after our previously reported route to Cp*-
(PMe3)2RuSiX3 complexes, based on reactions of silanes
with the corresponding ruthenium alkyls Cp*(PMe3)2-
RuR.6b This strategy, therefore, required alkyl com-
plexes of the type Cp′(PR3)2OsR′ (Cp′ ) Cp, Cp*; R′ )
alkyl), which we anticipated might be accessible via
alkylation of the corresponding halide derivatives. To
our knowledge, there have been no published reports
on the synthesis of osmium alkyl complexes of this type,
although the 187Os NMR spectra of Cp(PPh3)2OsMe and
Cp(PMe3)2OsR (R ) Me, Et, CH2CMe3, Ph) have been
reported.14
were not detected. We found that the red solid could
be efficiently converted to 1 by its reaction with cyclo-
pentadiene in refluxing 95% ethanol. Apparently, the
presence of water is essential for the formation of 1,
which involves the red solid as an intermediate. Sub-
sequently, we obtained an improved procedure which
gives 1 in 97% yield (see Experimental Section).16
Recently, J ia et al. reported a modified synthesis of 1
using Zn as a reagent, but the yield of product is rather
low (17%).17
Initial attempts to alkylate 1 with common alkylating
agents met with little success. Thus, in contrast to the
ruthenium alkyl complexes Cp(PPh3)2RuR (R ) Me,
CH2SiMe3, CH2Ph, etc.), which can be synthesized from
Cp(PPh3)2RuCl and an organolithium or Grignard re-
agent at room temperature,18 1 did not react with
RMgCl (R ) CH2SiMe3, CH2CMe3, Ph, CH2Ph) or RLi
(R ) Me, Ph, CH2CMe3), even in refluxing toluene over
a few days. Prolonged heating of these reaction mix-
tures led only to the decomposition of 1.
We speculated that exchanging the bromide in 1 with
a better leaving group might lead to a complex with
greater reactivity toward alkylating agents. Treatment
of 1 with AgOTf (Tf ) SO2CF3) in arene solvents
quantitatively produced the red-orange triflate complex
Cp(PPh3)2OsOTf (2) (by NMR spectroscopy). This com-
pound crystallized from benzene or toluene as the arene
solvate (1 equiv), as confirmed by 1H NMR spectroscopy,
elemental analysis, and X-ray crystallography (vide
infra). The arene was not removed by prolonged
exposure of 2 to a vacuum. The solid-state infrared
spectrum of 2 contains a peak at 1311 cm-1, which falls
between the ν(SO3) values normally associated with
ionic (1280-1270 cm-1) and covalently bound (1395-
1365 cm-1) triflates.19 The lability of the triflate group
in 2 was indicated by the facile isomerization of 2 to a
new complex 2a , both in solution and in the solid state
(by NMR spectroscopy; eq 1). While solutions of 2 in
Resu lts a n d Discu ssion
Syn th esis of η5-Cp a n d η5-Cp * Osm iu m (II) Alk yl
Com p lexes. Our interest initially focused on the
starting material Cp(PPh3)2OsBr (1), which was re-
ported by Bruce et al. in 1977 as being available in high
yield from reaction of hexabromoosmic acid (H2OsBr6),
PPh3, and cyclopentadiene in refluxing ethanol.15 Initial
attempts to repeat this synthesis using anhydrous
ethanol gave mostly an insoluble red solid and only a
very low yield (<10%) of the desired orange product 1.
NMR spectra of the red solid were consistent with a
mixture of PPh3-containing compounds, but Cp ligands
arene solvents are indefinitely stable, a dichloromethane
solution of 2 underwent orthometalation within a few
hours at room temperature. Also, orthometalation of 2
occurred at room temperature in the solid state under
nitrogen (t1/2 ≈ 1 month).
On the basis of its 1H, 31P{1H}, and 19F{1H} NMR
spectra, the new complex 2a was formulated as an
orthometalated osmium hydride cation with a triflate
(8) (a) Gallop, M. A.; Roper, W. R. Adv. Organomet. Chem. 1986,
25, 121. (b) Roper, W. R. J . Organomet. Chem. 1986, 300, 167.
(9) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Applications of Organotransition Metal Chemistry, 2nd
ed.; USB: Mill Valley, CA, 1987.
(10) (a) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics
1991, 10, 462. (b) Esteruelas, M. A.; Lo´pez, A. M.; Oro, L. A.; Tolosa,
J . I. J . Mol. Catal. A: Chem. 1995, 96, 21. (c) Sa´nchez-Delgado, R. A.;
Rosales, M.; Esteruelas, M. A.; Oro, L. A. J . Mol. Catal. A: Chem. 1995,
96, 231.
1
counterion. The H NMR spectrum contains a doublet
of doublets at δ -11.18 (2J PH ) 26, 34 Hz) corresponding
to an osmium hydride coupled to two inequivalent
phosphorus atoms. The cis arrangement of the hydride
(11) Bonny, A. Coord. Chem. Rev. 1978, 25, 229.
(12) (a) Clark, G. R.; Rickard, C. E. F.; Roper, W. R.; Salter, D. M.;
Wright, L. J . Pure Appl. Chem. 1990, 62, 1039. (b) Clark, G. R.; Flower,
K. R.; Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright, L. J . J .
Organomet. Chem. 1993, 462, 331.
(13) Buil, M. L.; Espinet, P.; Esteruelas, M. A.; Lahoz, F. J .; Lledo´s,
A.; Mart´ınez-Ilarduya, J . M.; Maseras, F.; Modrego, J .; On˜ate, E.; Oro,
L. A.; Sola, E.; Valero, C. Inorg. Chem. 1996, 35, 1250.
(14) Benn, R.; Brenneke, H.; J oussen, E.; Lehmkuhl, H.; Ortiz, F.
L. Organometallics 1990, 9, 756.
(16) Angelici, R. J .; Rottink, M. K. Personal communication.
(17) J ia, G.; Ng, W. S.; Yao, J .; Lau, C.-P.; Chen, Y. Organometallics
1996, 15, 5039.
(18) (a) Bruce, M. I.; Gardner, R. C. F.; Stone, F. G. J . Chem. Soc.,
Dalton Trans. 1979, 906. (b) Blackmore, T.; Bruce, M. I.; Stone, F. G.
J . Chem. Soc. A 1971, 2376. (c) Lehmkuhl, H.; Mavermann, H.; Benn,
R. Liebigs Ann. Chem. 1980, 754. (d) Lehmkuhl, H.; Grundke, J .;
Mynott, R. Chem. Ber. 1983, 116, 159. (e) Lehmkuhl, H.; Grundke, J .;
Mynott, R. Chem. Ber. 1983, 116, 176.
(15) Bruce, M. I.; Windsor, N. J . Aust. J . Chem. 1977, 30, 1601.
(19) Lawrance, G. A. Chem. Rev. 1986, 86, 17.

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4301
Me SiCH MgCl8
3
2
2Cp(PPh3)2OsOTf
-Mg(OTf)2
2
Cp(PPh3)2OsCH2SiMe3 + Cp(PPh3)2OsCl (2)
3
Me3CCH2Li, 2 reacted to give an inseparable mixture
of the corresponding alkyl complex, a number of ortho-
metalated species, and Cp(PPh3)2OsCl (<10%, presum-
ably from trace amounts of halide present in the
organolithium reagents).
Clean alkylation was finally accomplished using a
dialkylmagnesium reagent (eq 3). While the reaction
1
Cp(PPh ) OsBr
+ /2Mg(CH2EMe3)2 f
3 2
1
F igu r e 1. ORTEP drawing of Cp(PPh3)2OsOSO2CF3 (2)
with 40% probability thermal ellipsoids. Selected bond
lengths (Å) and angles (deg): Os(1)-Cp 1.833; Os(1)-O(1)
2.221(2); Os(1)-P(1) 2.3206(7); Os(1)-P(2) 2.3424(7); P(1)-
Os(1)-O(1) 92.64(5); P(2)-Os(1)-O(1) 84.79(5); P(1)-Os-
(1)-P(2) 101.80(2); Os(1)-O(1)-S(1) 126.7(1).
Cp(PPh3)2OsCH2EMe3
(3)
3, E ) C
4, E ) Si
of 2 with such reagents produced complex mixtures, 1
reacted cleanly to give the osmium alkyl derivative in
high yield. Compound 1 reacts with bis(neopentyl)-
magnesium in benzene-d6 at room temperature to give
Cp(PPh3)2OsCH2CMe3 (3) in >90% yield (by NMR
spectroscopy). The trimethylsilylmethyl complex Cp-
(PPh3)2OsCH2SiMe3 (4), prepared analogously, proved
easier to isolate. Complex 4 is soluble in saturated
hydrocarbons, from which it can be crystallized at -35
°C to give a bright-yellow, high-melting (225-226 °C)
solid in 79% yield.
The complex Cp(PMe3)2OsBr, synthesized from 1 by
phosphine exchange at high temperature (190-200
°C),24 was found to react analogously to 1. Thus, while
Cp(PMe3)2OsBr is inert toward Grignard and alkyl-
lithium reagents, it reacts with Mg(CH2SiMe3)2 to form
Cp(PMe3)2OsCH2SiMe3 (5). This complex is quite soluble
in hydrocarbons and can be crystallized from diethyl
ether at -35 °C to give a low-melting (72-73 °C), pale-
yellow solid in moderate (60%) yield. Compound 5 may
also be sublimed at 50-65 °C under vacuum.
2
and phosphine ligands is suggested by the large J PH
2
coupling constants, since trans J PH coupling constants
in such four-legged piano-stool complexes are normally
less than 10 Hz.20 The two phosphines in 2a are
chemically inequivalent, as shown by the two doublet
resonances in the 31P{1H} NMR spectrum at δ 6.34 and
-71.33 (2J PP ) 21 Hz). In addition, the sharp triflate
resonance at δ -14.3 in the 19F{1H} NMR spectrum of
2 was replaced in the spectrum of 2a by a very broad
resonance at δ -100. The ν(SO3) band in the infrared
spectrum of 2a at 1275 cm-1 is consistent with an ionic
triflate group.19
An ORTEP view of the molecular structure of 2 is
shown in Figure 1. The three-legged piano-stool geom-
etry about osmium and many of the corresponding
distances and angles in 2 are similar to those found for
the analogous halide complexes Cp(PPh3)2OsX (X ) Cl,
Br).21 The Os-O(1) distance (2.221(2) Å) is shorter than
the corresponding distances in two other structurally
characterized complexes containing an Os-OTf bond,
Given our success with preparing (pentamethylcyclo-
pentadienyl)ruthenium silyl complexes, it was of inter-
est to extend this work to the analogous osmium
t
Os(NAr)(CH2 Bu)2(OSiMe3)(OTf) (2.326(6) Å)22 and [Os-
(tN)(terpy)(Cl)(OTf)]+ (2.289(7) Å; terpy ) 2,2′:6′,2′′-
terpyridine).23 As expected from the analytical and
spectroscopic data, each molecule of the compound in
the unit cell is accompanied by one molecule of benzene.
However, there is no chemically significant contact
between the complex and benzene.
systems. Recently, Girolami et al. reported the synthe-
20a
sis of [Cp*OsBr2]2
which, like the ruthenium dimer
[Cp*RuCl2]2,25 is a versatile starting material for the
preparation of new complexes. Reaction of a dichlo-
romethane solution of [Cp*OsBr2]2 with excess PMe3 at
room temperature afforded the osmium(II) species
Cp*(PMe3)2OsBr (6) as orange plates in 54% isolated
As expected, the triflate complex 2 is more reactive
than its bromide precursor 1 toward alkylation. How-
ever, 2 readily exchanges its triflate group with the
halide present in Grignard reagents. Thus, 2 reacted
with Me3SiCH2MgCl in toluene at room temperature to
give the corresponding alkyl and chloro complexes, Cp-
(PPh3)2OsCH2SiMe3 (3) and Cp(PPh3)2OsCl,21a in equimo-
lar amounts (by NMR spectroscopy; eq 2). Upon treat-
ment with organolithium reagents such as MeLi and
1
yield. The H NMR spectrum of 6 consists of a triplet
4
for the C5Me5 ligand (δ 1.65, J PH ) 1.0 Hz), as well as
the filled-in doublet (“virtual triplet”) for the PMe3
protons (at δ 1.37) expected for such compounds.
similar synthesis of 6 was recently reported by Giro-
A
lami.26
Unlike Cp(PPh3)2OsBr and Cp(PMe3)2OsBr, the bro-
mide complex 6 reacts cleanly with Me3SiCH2MgCl in
toluene at room temperature to form the alkyl complex
Cp*(PMe3)2OsCH2SiMe3 (7) as a pale-yellow, high-
melting (220-222 °C) solid in high yield (98%, eq 4).
(20) (a) Gross, C. L.; Wilson, S. R.; Girolami, G. S. J . Am. Chem.
Soc. 1994, 116, 10294. (b) Heinekey, D. M.; Payne, N. G.; Sofield, C.
D. Organometallics 1990, 9, 2643.
(21) (a) Bruce, M. I.; Williams, M. L.; Patrick, J . M.; White, A. H.
Aust. J . Chem. 1983, 36, 1353. (b) Bruce, M. I.; Low, P. J .; Skelton, B.
W.; Tiekink, E. R. T.; Werth, A.; White, A. H. Aust. J . Chem. 1995, 48,
1887.
(24) Rottink, M. K.; Angelici, R. J . J . Am. Chem. Soc. 1993, 115,
7267.
(22) LaPointe, A. M.; Schrock, R. R.; Davis, W. M. Organometallics
1995, 14, 2699.
(23) Chin, K.-F.; Cheung, K.-K.; Yip, H.-K.; Mak, T. C. W.; Che, C.
M. J . Chem. Soc., Dalton Trans. 1995, 657.
(25) (a) Tilley, T. D.; Grubbs, R. H.; Bercaw, J . E. Organometallics
1984, 3, 274. (b) Oshima, N.; Suzuki, H.; Moro-oka, Y. Chem. Lett. 1984,
1161.
(26) Gross, C. L.; Girolami, G. S. Organometallics 1996, 15, 5359.

4302 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
Me SiCH MgCl8
time (10 days). In contrast, thermolysis of Cp(PPh3)2-
OsCH2SiMe3 (4) in benzene-d6 proceeded at much lower
temperatures (60-67 °C) in 48 h to cleanly give SiMe4
3
2
Cp*(PMe3)2OsBr
-MgClBr
6
and a species whose H and 31P{1H} NMR spectra are
Cp*(PMe3)2OsCH2SiMe3 (4)
1
7
consistent with the orthometalated complex Cp(PPh3)-
Compound 7 is very soluble in common organic solvents
and is stable at room temperature for long periods in
both the solid state and in solution under nitrogen.
Interestingly, the 31P{1H} NMR spectra of the bromo
and alkyl osmium complexes contain low-intensity
satellites resulting from coupling to 187Os in natural
Os(2-C6H4PPh2) (10, eq 6). The behavior of 4 upon
1
abundance (I ) 1/2, 1.64% abundance), with J OsP
coupling constants ranging from 300 to 313 Hz. This
observation is unusual because its low natural abun-
dance makes 187Os one of the most insensitive nuclei in
NMR spectroscopy.27 Similar coupling has been ob-
served in osmium carbonyl cluster complexes28 and
more recently has been measured by indirect hetero-
nuclear 2D NMR spectroscopy for a number of Cp(PR3)2-
OsL14 and (η6-arene)Os(II)29 complexes.
C-H Activa tion s by Osm iu m (II) Alk yl Com -
p lexes. Ruthenium(II) alkyl complexes of the type Cp*-
(PMe3)2RuR react with arene C-H or Si-H bonds at
elevated temperatures.6bc,30 For example, Cp*(PMe3)2-
RuCH2SiMe3 reacts cleanly over 3 h with benzene at
100 °C to give Cp*(PMe3)2RuPh and SiMe4.30 The rate-
determining step for this process was shown to be initial
phosphine loss to generate the coordinatively unsatur-
ated, 16-electron intermediate Cp*(PMe3)RuR, which
oxidatively adds arene C-H bonds. In the presence of
a large excess of arene, this 16-electron intermediate is
selectively intercepted by near-stoichiometric quantities
of hydrosilane. To analyze the behavior of the analo-
gous osmium complexes under these conditions, we
examined the reactions of the alkyl complexes 4, 5, and
7 with arenes.
thermolysis is not surprising given the tendency of PPh3
ligands to orthometallate.31 A proposed mechanism for
the observed C-H activation reactions, as illustrated
for the intermolecular process, is given in Scheme 1.
We assume that phosphine loss from the alkyl com-
plexes is rate determining, as shown in the analogous
ruthenium systems6b,30,32,33 and in the thermolysis of cis-
(PMe3)4Os(H)R (R ) CH2CMe3, CH2SiMe3, Me).34 Pre-
sumably, the large range of reaction temperatures
reflects differences in the Os-P bond strengths for
complexes 4, 5, and 7; that is, the Os-PMe3 bond in 5
is stronger than that in 7, and the Os-PMe3 bond is
stronger than the Os-PPh3 bond. Nolan et al. have
recently determined the enthalpies of formation for a
series of Cp′(PR3)2RuCl (Cp′ ) Cp, Cp*) complexes from
the corresponding cyclooctadiene complexes.35 Their
results indicate that the Ru-PMe3 bond is stronger than
the Ru-PPh3 bond by 7-8 kcal/mol and that replacing
a Cp group with a Cp* group decreases the strength of
the Ru-PMe3 bond by 2-3 kcal/mol. Our results
suggest that the same trend exists in the analogous
osmium compounds.
Syn th esis of Osm iu m Silyl Com p lexes. Ruthe-
nium(II) silyl complexes of the type Cp′(PR3)2RuSiX3
(Cp′ ) Cp, Cp*; R ) Ph, Me) were synthesized by
heating the corresponding alkyl complexes Cp′(PR3)2-
RuCH2SiMe3 with the appropriate hydrosilane in tolu-
ene at 100 °C.6b,c,33 Under certain conditions, ruthenium-
(IV) bis(silyl) hydride complexes are obtained along with
the mono(silyl) products. However, the Ru(IV) products
are readily converted to the corresponding bis(phos-
phine) Ru(II) complexes by reaction with excess phos-
phine at elevated temperatures. The proposed mecha-
nism for the formation of the ruthenium silyl complexes
is analogous to that by which the ruthenium and
osmium alkyl complexes activate arenes (Scheme 2).
Initial attempts to synthesize osmium silyl complexes
from Cp*(PMe3)2OsCH2SiMe3 (7) and various silanes,
using the same conditions employed in the ruthenium
system, were unsuccessful. For example, reaction of 7
with HSi(SEt)3 or HSi(OEt)3 at 115 °C in benzene-d6
gave an intractable mixture of products, the major one
being Cp*(PMe3)2OsC6D5 (8-d5), which resulted from
Complex 7 was cleanly converted to Cp*(PMe3)2-
OsC6D5 (8-d5) and Me3SiCH2D in benzene-d6 at 115 °C
over 10 h, as monitored by 1H and 31P{1H} NMR
spectroscopy (eq 5). An authentic sample of the phenyl
∆, C6D6
Cp*(PMe3)2OsCH2SiMe3
8
7
Cp*(PMe3)2OsC6D5
+ Me3SiCH2D (5)
8-d5
derivative Cp*(PMe3)2OsC6H5 (8) was prepared from
Cp*(PMe3)2OsBr (6) and PhMgBr. The conversion of 7
to 8 required a higher temperature and a longer reaction
time than for the analogous ruthenium complexes, as
might be expected from periodic trends in reaction
rates.9
On the basis of the 1H and 31P{1H} NMR spectroscopy,
Cp(PMe3)2OsCH2SiMe3 (5) also reacts with benzene-d6
to form the deuterated phenyl derivative Cp(PMe3)2-
OsC6D5 (9-d5). However, this reaction requires higher
temperatures (160-170 °C) and a much longer reaction
(31) For reviews on orthometalation, see: (a) Hartley, F. R. In
Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G.
A., Abel, E. W., Eds.; Pergamon Press: London, 1982; Vol. 6, Chapter
39, p 592. (b) Ryabov, A. D. Chem. Rev. 1990, 90, 403.
(32) Davies, S. G.; McNally, J . P.; Smallridge, A. J . Adv. Organomet.
Chem. 1990, 30, 1.
(27) (a) Multinuclear NMR; Mason, J ., Ed.; Plenum Press: New
York, 1987. (b) Mason, J . Chem. Rev. 1987, 87, 1299.
(28) Gallop, M. A.; J ohnson, B. F. G.; Lewis, J . J . Chem. Soc., Chem.
Commun. 1987, 1831.
(29) Bell, A. G.; Kozminski, W.; Linden, A.; von Philipsborn, W.
Organometallics 1996, 15, 3124.
(30) (a) Tilley, T. D.; Togni, A.; Paciello, R. A.; Bercaw, J . E.; Grubbs,
R. H. Unpublished results. (b) Bryndza, H. E.; Domaille, P. J .; Paciello,
R. A.; Bercaw, J . E. Organometallics 1989, 8, 379. (c) Lehmkuhl, H.;
Bellenbaum, M.; Grundke, J .; Mauermann, H.; Kru¨ger, C. Chem. Ber.
1988, 121, 1719.
(33) Lemke, F. R.; Chaitheerapapkul, C. Polyhedron 1996, 15, 2559.
(34) (a) Desrosiers, P. J .; Shinomoto, R. S.; Flood, T. C. J . Am. Chem.
Soc. 1986, 108, 7964. (b) Shinomoto, R. S.; Desrosiers, P. J .; Harper,
T. G. P.; Flood, T. C. J . Am. Chem. Soc. 1990, 112, 704.
(35) (a) Cucullu, M. E.; Luo, L.; Nolan, S. P.; Fagan, P. J .; J ones, N.
L.; Calabrese, J . C. Organometallics 1995, 14, 289. (b) Luo, L.; Nolan,
S. P.; Fagan, P. J . Organometallics 1993, 12, 4305.

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4303
Sch em e 1
Sch em e 2
activation of the solvent. In cyclohexane, these reac-
tions gave multiple uncharacterized products. In the
analogous ruthenium system, activation of the solvent
was not observed unless a very bulky silane (e.g., HSi-
(SMes)3 or HSi(SCy)3) was used.36
The ruthenium alkyl Cp*(PR3)2RuCH2SiMe3 reacts
with HSi[S(p-Tol)]3 and HSiMe2[S(p-Tol)] in toluene at
100 °C to cleanly give Cp*(PR3)2RuSi[S(p-Tol)]3 and
Cp*(PR3)2RuSiMe2[S(p-Tol)], respectively.6c However,
reaction of 7 with HSi[S(p-Tol)]3 at 115 °C in benzene-
d6 gave three products: 8-d5, 11, and 12, in a 10:9:1
ratio (eq 7). In cyclohexane, only 11 and 12 were
(prepared from Cp*(PMe3)2OsBr (6) and LiS(p-Tol)).
Similarly, 7 reacted with HSiMe2[S(p-Tol)] in cyclohex-
ane at 115 °C to give the analogous metallacycle Cp*-
(PMe3)(H)Os{C6H3(3-Me)(6-S)SiMe2} (13) and 12 in an
8:1 ratio.
1
The H NMR spectra of the cyclometalated hydrido
silyl complexes 11 and 13 feature OsH resonances as
doublets at δ -13.38 (2J PH ) 32.0 Hz) and -15.10 (2J PH
2
) 32.0 Hz), respectively. The large J PH coupling
constants are consistent with a cis arrangement of the
hydride and phosphine ligands. Similar observations
2
have been reported for Cp*Os(PPh3)H3, where the J PH
coupling is larger for the cis hydrides (2J PH ) 33.5 Hz)
as compared to the trans hydride (2J PH ) 8 Hz).20a The
1H and 13C NMR data also showed that the two R groups
on silicon in 11 and 13 are diastereotopic, as expected
for the structures drawn in Scheme 3.
The formation of metallacycle complexes 11 and 13
can be rationalized by two different mechanisms (path-
ways a and b in Scheme 3), depending on the relative
ordering of the Si-H and C-H bond activations. In the
mechanism represented by path a, intermolecular Si-H
bond activation by Cp*(PMe3)OsCH2SiMe3 occurs before
an intramolecular arene C-H bond activation in the
intermediate Cp*(PMe3)OsSiR2S(p-Tol). In the alterna-
tive mechanism of path b, arene C-H bond activation
occurs first and the cyclometalated product results from
intramolecular oxidative addition of the Si-H bond. The
intermolecular arene C-H activation in the second
mechanism would presumably be promoted by the
ortho-directing, activating thiolate group. However,
pathway b seems somewhat unlikely given the fact that
Cp*(PMe3)2OsPh is not an intermediate in the reaction
of 7 with silanes in benzene (vide infra). Although the
formed, in a 3:2 mixture. Complex 11 was formulated
as the metallacycle species Cp*(PMe3)(H)Os{C6H3(3-
1
Me)(6-S)Si[S(p-Tol)]2} from its H NMR spectrum (vide
infra). The other product, Cp*(PMe3)2OsS(p-Tol) (12),
was identified by comparison to an authentic sample
(36) Grumbine, S. K. Ph.D. Thesis, University of California, San
Diego, CA, 1993.

4304 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
Sch em e 3
two mechanisms should give rise to different isomers
of the product (D and E), a Berry-type isomerization
would probably allow conversion to the more thermo-
dynamically favored isomer.37 Thus, the mechanism
cannot be identified simply from the regiochemistry of
the isolated product, which was confirmed by an X-ray
diffraction study (vide infra).
The cyclometalated complex 13 was separated from
the reaction mixture by taking advantage of the differ-
ent solubility properties for 13 and the decomposition
product 12. While 12 is readily soluble in most common
organic solvents, 13 is soluble only in dichloromethane
and aromatic hydrocarbons. Thus, washing the crude
solid mixture with pentane followed by crystallization
from a dichloromethane/ether mixture afforded pure 13
as colorless crystals in 77% yield.
was located and refined at a distance of 1.59(5) Å from
Os, and the Os-Si bond length of 2.382(2) Å is quite
normal.38 Interestingly, the hydride ligand is quite close
to the Si center (2.06(5) Å), and the Si-Os-H bond
angle (59(2)°) is rather acute. Although these param-
eters might suggest η2-silane character, the Si-H
interaction is rather weak, as evidenced by the low
2J SiOsH coupling constant (15 Hz). In complexes exhibit-
ing strong M-H-Si interactions, the Si-H distances
2
are shorter than 2.00 Å and the J SiMH coupling con-
stants are usually well above 20 Hz.39 Thus, the
proximity of the hydride ligand to the silicon atom in
13 might simply be due to steric crowding in the
molecule.
The reaction of alkyl complex 7 with excess HSiR2Cl
(R ) Ph, Me) in toluene at 115 °C gave a mixture of the
osmium(IV) bis(silyl)hydride complex Cp*(PMe3)Os(H)-
(SiR2Cl)2 (R ) Ph (14) or Me (16)) and the osmium(II)
mono(silyl) complex Cp*(PMe3)2OsSiR2Cl (R ) Ph (15)
To investigate the regiochemistry of the product, the
molecular structure of 13 was determined by X-ray
crystallography. The structure is shown in Figure 2,
and selected bond distances and angles are summarized
in Table 1. The structure shows the configuration of
the molecule to be that of isomer E in Scheme 3. As
2
expected from the large J PH coupling constant, the
hydride and phosphine ligands are in a cis arrangement.
The five-membered metallacycle ring has an “open-
envelope” conformation; the plane of the Si-Os-C(14)
flap is 40.8° out of the approximate plane of the other
four atoms (C(14)-C(19)-S-Si; root-mean-square de-
viation from planarity ) 0.086 Å). The hydride ligand
(37) Isomers D and E can be interconverted by two cycles of a
combined Berry-turnstile mechanism, see: Smith, J . M.; Coville, N.
J . Organometallics 1996, 15, 3388.
(38) A search of the Cambridge Structural Database revealed a
mean Os-Si single bond length of 2.40(2) Å.
(39) (a) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151. (b)
Colomer, E.; Corriu, R. J . P.; Marzin, C.; Vioux, A. Inorg. Chem. 1982,
21, 368. (c) Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32,
789. (d) Luo, X.-L.; Kubas, G. J .; Bryan, J . C.; Burns, C. J .; Unkefer,
C. J . J . Am. Chem. Soc. 1994, 116, 10312. (e) Luo, X.-L.; Kubas, G. J .;
Burns, C. J .; Bryan, J . C.; Unkefer, C. J . J . Am. Chem. Soc. 1995, 117,
1159.
F igu r e 2. ORTEP drawing of Cp*(PMe3)(H)Os{C6H3(3-
Me)(6-S)SiMe2} (13) with 40% probability thermal el-
lipsoids.

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4305
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 13
(in addition to 14 and 15). Attempts to separate the
solid mixture of 14 and 15 by fractional recrystallization
also met with little success. These results imply that
the rate of addition of a second silane to the intermedi-
ate [Cp*(PMe3)OsSiPh2Cl] (kSi in Scheme 2) is faster
than the rate of phosphine coordination (kP) and that
the bis(silyl) hydride complex 14 is quite inert.
Bond Distances
Os-Cp*a
Os-Si
1.921
Si-C(21)
Si-C(22)
Si-S
1.872(6)
1.893(6)
2.187(2)
1.788(6)
2.382(2)
2.298(2)
1.59(5)
2.157(6)
Os-P
Os-H(1)
Os-C(14)
S-C(19)
The reaction conditions also governed the distribution
of products from the reaction of 7 with excess HSiMe2-
Cl. Highest yields for the mono(silyl) complex 17 were
obtained by heating a closed flask containing 7 and a
large excess (>100 equiv) of neat silane. The flask was
heated by partially submerging it in an oil bath at 115
°C. However, under certain conditions, the bis(silyl)
hydride 16 was formed along with 17. For example,
when 7 and HSiMe2Cl (e20 equiv) were heated in
toluene at 115 °C for 20 h, a 1:3 mixture of 16 and 17
resulted. When the same reaction was carried out in
hexane or without solvent, only the bis(silyl) 16 was
observed. Like 14, the Os(IV) complex 16 cannot be
converted to the corresponding mono(silyl) derivative 17
by heating (150 °C, 1 week) in the presence of excess
PMe3. However, the two products can be separated
from the solid mixture by careful fractional recrystal-
lization from a dichloromethane/ether mixture. Cur-
rently, we do not understand the observed concentration
effects on the relative yields of 16 and 17, but these
results suggest that a mechanism other than that
described in Scheme 2 might be in operation.
Bond Angles
P-Os-Si
103.17(5)
87.8(2)
75(2)
77.7(1)
59(2)
127(2)
93.0(2)
120.6(4)
Os-Si-C(21)
Os-Si-C(22)
C(21)-Si-C(22)
S-Si-C(21)
S-Si-C(22)
Os-C(14)-C(19)
Os-Si-S
120.9(2)
119.1(2)
102.8(3)
104.7(2)
103.6(2)
125.4(4)
103.62(7)
P-Os-C(14)
P-Os-H(1)
Si-Os-C(14)
Si-Os-H(1)
C(14)-Os-H(1)
Si-S-C(19)
S-C(19)-C(14)
a
Cp* ) Cp* ring plane.
or Me (17); eq 8). The reaction with HSiPh2Cl produced
+
Cp*(PMe3)2OsCH2SiMe3
7
∆, -SiMe4
-xPMe3
(2x + y)HSiR2Cl
8
xCp*(PMe3)Os(H)(SiR2Cl)2
+
14, R ) Ph
16, R ) Me
yCp*(PMe3)2OsSiR2Cl
(8)
15, R ) Ph
17, R ) Me
Both bis(silyl) hydride complexes 14 and 16 were
1
mostly the white, crystalline Os(IV) complex 14, while
the reaction with HSiMe2Cl yielded primarily the mono-
(silyl) complex 17. However, the product distributions
for these reactions are strongly influenced by the
reaction conditions.
isolated as the trans isomers, as indicated by H and
29Si NMR spectroscopy. The OsH resonances display
2
low J PH coupling constants (8 Hz for 14; 12 Hz for 16),
which indicate a trans arrangement for the phosphine
ligands. The 29Si{1H} NMR spectrum of 16 contained
only one resonance for the two silyl ligands (a doublet
at δ 28.44), which further supports a trans geometry
for the complex.
We considered the possibility that formation of the
osmium silyl derivatives in arene solvents occurs via
initial C-H activation of the solvent to form the aryl
complex. However, since Cp*(PMe3)2OsPh (8) does not
react with silanes (HSiPh2Cl or HSiMe2[S(p-Tol)]) even
at 150 °C over 3 days, this does not seem likely.
Osmium(II) silyl complexes Cp*(PMe3)2OsSiR3 (SiR3
) SiMeCl2 (18), SiCl3 (19)) can be obtained cleanly from
reaction of the alkyl complex 7 with the corresponding
hydrosilanes (neat, excess) at 115 °C (eq 9). In contrast
The reaction with HSiPh2Cl can be driven exclusively
to the bis(silyl) hydride complex 14 by periodic exposure
of the reaction mixture to a vacuum to remove PMe3.
On the other hand, attempts to obtain pure mono(silyl)
complex 15 were unsuccessful. Unlike its ruthenium
analog Cp*(PMe3)Ru(H)(SiPh2Cl)2, which can be driven
cleanly to Cp*(PMe3)2RuSiPh2Cl by heating to 100-110
°C for 36 h with excess PMe3,6b 14 did not react with
PMe3 (g100 equiv), even after heating to 150 °C for 3
days in a closed vessel. This presumably reflects the
greater tendency of osmium toward higher oxidation
states and/or the more kinetically inert character of
osmium vs ruthenium.
In theory, reaction of 7 with 1 equiv of HSiPh2Cl
should give only the osmium(II) silyl 15. In practice,
however, heating an equimolar mixture of HSiPh2Cl and
7 in cyclohexane resulted in a 2:1 mixture of 14 and
15, as well as unreacted starting material and a
decomposition product, Cp*(PMe3)2OsCl. It was also
hoped that the addition of free PMe3 at the beginning
of the reaction would favor formation of mono(silyl) 15
over 14. However, carrying out the reaction under
varying concentrations of silane and free phosphine, as
well as varying the reaction time, had little effect on
the product ratio. For example, heating a 10:5:1 mix-
ture or a 5:10:1 mixture of HSiPh2Cl, PMe3, and 7 at
115 °C for 18 h or 2 days (in a closed vessel) yielded the
same ratio of 14 to 15 (2:1). Increasing the temperature
of the reaction to 155 °C (above the boiling point of the
silane) changed the product ratio to favor the mono(silyl)
15 (5:1 ratio of 15 to 14), but at higher temperatures
(g160 °C) many decomposition products were produced
+ HSiR3 9
∆8
Cp*(PMe3)2OsCH2SiMe3
7
Cp*(PMe3)2OsSiR3 + SiMe4 (9)
18, SiR3 ) SiMeCl2
19, SiR3 ) SiCl3
to the reactions with HSiPh2Cl and HSiMe2Cl, no bis-
(silyl) hydride species were observed.
We, therefore, observe that the electronic properties
of the hydrosilanes play a strong role in influencing the
rate and course of the osmium silylation reactions.
Qualitatively, the presence of more electronegative
substituents leads to slower reactions. Thus, while the
reaction with HSiMe2Cl is complete in less than 24 h,
the reaction involving HSiMeCl2 requires 2 days and
the one with HSiCl3 takes at least 14 days. This trend
is opposite to that found for reactions of Cp(PMe3)2-

4306 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
RuCH2SiMe3, which follow the reactivity ordering
HSiCl3 > HSiMeCl2 > HSiMe2Cl.33 It seems likely that
the rates of these reactions are determined by the series
of steps leading to complete oxidative addition of the
silane (see Scheme 2), since the subsequent alkane
reductive elimination step is expected to be fast.9 Note
also that an intermediate η2-silane complex of the type
Cp′(PMe3)M(η2-HSiX3)(CH2SiMe3) (Cp′ ) Cp or Cp*)
may immediately precede the oxidative addition step.
For ruthenium, the observed trend may reflect a large
contribution by the oxidative addition step. In this case,
formation of the M-Si bond may provide a significant
thermodynamic driving force for the reaction, with
silanes that result in a stronger M-Si bond reacting
faster.33 Silyl groups with greater π-acceptor ability
(SiCl3 > SiMeCl2 > SiMe2Cl)40 should provide more
stabilization for an electron-rich metal fragment. For
the osmium system, the oxidative addition should be
highly favored and the ligand substitution kinetics may
play a greater role in defining the relative rates. If in
this case the rate of silylation is influenced heavily by
the ability of the reacting silane to compete with
phosphine for the empty site at osmium, then the more
electron-rich silanes will react more rapidly and the
reactivity ordering observed for the osmium system
would be expected. Determination of the true origin of
these trends, however, must await further mechanistic
studies.
The formation of Os(IV) bis(silyl) hydride complexes
is also heavily influenced by the nature of the silane
reactant, such that more electropositive substituents on
the hydrosilane favor this reaction pathway. This
observation may be analyzed in terms of the mechanism
in Scheme 2 and the competition between silane and
phosphine for trapping of an intermediate C which
already has one silyl group bound to osmium. Lich-
tenberger et al., using valence photoelectron spectros-
copy, have shown that the SiCl3 ligand has considerable
π-acceptor ability, while the SiMe3 ligand has negligible
π-acceptor character and binds to the metal primarily
as a σ-donor.40 This is consistent with the observed
trend in our system: as the groups on silicon become
more electronegative, the silyl ligand becomes a better
π-acceptor, thus favoring addition of σ-donating PMe3
to intermediate C. On the other hand, silyl ligands with
significant σ-donor properties appear to promote silane
addition to form the less electron-rich Os(IV) bis(silyl)
hydride complex.
80 °C) than those required for silylation of 7. The
preferred formation of bis(silyl) hydride complexes in
these reactions may be attributed to the relatively labile
phosphine ligand. Unfortunately, attempts to separate
20 and 21 from free PPh3 were unsuccessful. Like the
Cp* analogs 14 and 16, both 20 and 21 are formed solely
as the trans isomers, as indicated by their 1H NMR
spectra. Interestingly, while the OsH resonance for 21
2
(doublet at δ -11.70, J PH ) 8.0 Hz) is similar to those
found for 14 and 16, the OsH resonance for 20 appears
as a singlet at δ -10.65. The gated 31P NMR spectrum
2
of 20 also confirmed the unusually low trans J PH
coupling constant, in that the phosphorus signal was
observed as a singlet.
The Cp analog of 7, Cp(PMe3)2OsCH2SiMe3 (5), re-
acted with HSiPh2Cl (2 equiv) in toluene to give the
osmium(II) silyl derivative Cp(PMe3)2OsSiPh2Cl (22) as
the major product (by NMR spectroscopy; eq 11). The
+ HSiPh2Cl 9
∆8
Cp(PMe3)2OsCH2SiMe3
5
+ SiMe (11)
Cp(PMe3)2OsSiPh2Cl
4
22
reaction required a higher temperature (150-165 °C)
and a longer time (4 days) than the analogous reaction
in the Cp* system, as expected. Also, unlike the Cp*
derivative, no bis(silyl) hydride complex was observed
in the product mixture. This is presumably due to the
higher Os-PMe3 bond strength in the Cp (vs the Cp*)
complexes, which favors the addition of phosphine over
silane to intermediate C (Scheme 2). Unfortunately,
complex 22 could not be obtained in analytically pure
form either by recrystallization under various conditions
or by sublimation at 100 °C under vacuum, which did
not separate the complex from small quantities of
impurities.
The reaction of 5 with excess HSiMe2Cl (ca. 20 equiv)
in toluene at 150-165 °C did not give the expected silyl
complex Cp(PMe3)2OsSiMe2Cl. The 1H and 31P{1H}
NMR spectra of the resulting residue in dichloromethane-
d2 revealed the presence of two major products in
roughly equal amounts. These compounds were readily
separated by the addition of toluene, which dissolved
one product and left the other as a white solid, which
gave a 1H NMR spectrum that is consistent with a
cationic dihydride [Cp(PMe3)2OsH2]+X-. In particular,
a triplet resonance at δ -13.95, which integrated as two
hydrogens, was observed in the spectrum. The hydride
The alkyl complex Cp(PPh3)2OsCH2SiMe3 (4) was
observed to react with excess HSiR2Cl (R ) Ph, Me; neat
or in benzene) to give the corresponding osmium(IV)
species Cp(PPh3)Os(H)(SiR2Cl)2 (R ) Ph (20) or Me (21))
as the major products in solution (by NMR spectroscopy;
eq 10). Consistent with earlier observations, these
2
ligands in this cation are probably trans, since the J PH
coupling constant of 33.1 Hz is very similar to those
observed for trans-[Cp(PR3)2Os(H)2]+ ((PR3)2 ) (PPh3)2,
(Ph2PMe)2, (PPh3)(P(OEt)3), dppm, dppe, dppp).17,24,41 At
this point, the identity of the anion X- remains unclear,
as does the mechanism of formation for this complex.
However, note that Lemke has shown that Cp(PMe3)2-
RuH reacts with chlorosilanes ClSiR3 to produce
[Cp(PMe3)2RuH2]+Cl- and Cp(PMe3)2RuSiR3, probably
via nucleophilic attack of ruthenium onto the chlorosi-
lane.42 Concentration of the toluene extract gave a
white solid, which analyzed by NMR and mass spec-
troscopy as Cp(PMe3)2OsSiMeCl2 (23). The redistribu-
tion chemistry leading to the formation of 23 is pre-
sumably promoted by the high temperature. Redis-
∆
Cp(PPh3)2OsCH2SiMe3
+ 2HSiR2Cl
8
-PPh3
4
Cp(PPh3)Os(H)(SiR2Cl)2 + SiMe4 (10)
R ) Ph (20)
R ) Me (21)
reactions proceeded at much lower temperatures (65-
(40) (a) Lichtenberger, D. L.; Rai-Chaudhuri, A. J . Am. Chem. Soc.
1991, 113, 2923. (b) Lichtenberger, D. L.; Rai-Chaudhuri, A. J . Am.
Chem. Soc. 1990, 2492. (c) Lichtenberger, D. L.; Rai-Chaudhuri, A. J .
Am. Chem. Soc. 1989, 111, 3583.
(41) Wilczewski, T. J . Organomet. Chem. 1986, 317, 307.
(42) Lemke, F. R. J . Am. Chem. Soc. 1994, 116, 11183.

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4307
tributions of this sort may proceed via intermolecular
exchanges involving silylene intermediates, as observed
in the Cp*(PMe3)2Ru system.6f
The derivatization of a metal-bound silyl group rep-
resents an important synthetic pathway to new metal-
silicon species. For example, chloride/triflate exchanges
have been used to provide Cp*(PMe3)2RuSiR2OTf de-
rivatives, which are precursors to silylene complexes.6
Since the silylation reactions described above proved to
be rather limited in scope, we developed alternative
routes to osmium(II) silyl complexes based on substitu-
tion at silicon.
The chloride in 17 is readily exchanged for the more
labile triflate group, via reaction with Me3SiOTf in
dichloromethane at room temperature (eq 12). The light
CH2Cl2
Cp*(PMe ) OsSiMe Cl
+ Me3SiOTf -Me SiCl8
3 2
2
3
17
Cp*(PMe3)2OsSiMe2OTf
(12)
24
F igu r e 3. ORTEP drawing of Cp*(PMe3)2OsSiMe2OTf (24)
yellow, crystalline complex Cp*(PMe3)2OsSiMe2OTf (24)
appeared to possess a covalent Si-O bond, as judged
by its solubility in nonpolar aromatic solvents and from
infrared data. Compound 24 displays an infrared band
close to the typical range for covalent triflates19 in both
the solid state (Nujol mull, ν(SO3) ) 1352 cm-1) and
dichloromethane solution (ν(SO3) ) 1352 cm-1). How-
ever, in acetonitrile, only ionic triflate (ν(SO3) ) 1269
cm-1) was detected by infrared spectroscopy. Thus, 24
is extensively dissociated in acetonitrile solution and is
presumed to exist as the base-stabilized silylene adduct
[Cp*(PMe3)2OsSiMe2(NCMe)]OTf, which is probably
best represented by the “silyl” resonance form in eq 13.
with 40% probability thermal ellipsoids.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for 24
Bond Distances
Os(1)-Cp*a
Os(1)-Si(1)
Os(1)-P(1)
Os(1)-P(2)
1.950
Si(1)-O(1)
Si(1)-C(17)
Si(1)-C(18)
1.866(5)
1.886(8)
1.901(8)
2.334(2)
2.285(2)
2.282(2)
Bond Angles
P(1)-Os(1)-Si(1)
P(2)-Os(1)-Si(1)
P(1)-Os(1)-P(2)
O(1)-Si(1)-C(17)
O(1)-Si(1)-C(18)
91.01(7)
90.68(7)
94.17(8)
96.6(3)
Os(1)-Si(1)-O(1)
Os(1)-Si(1)-C(17)
Os(1)-Si(1)-C(18)
C(17)-Si(1)-C(18)
115.3(2)
119.1(3)
120.8(3)
103.6(4)
96.9(3)
a
Cp* ) Cp* ring plane.
tetrahedral environment. The staggered conformation
about the Os-Si bond is similar to those observed for
Cp*(PMe3)2RuSiR2OTf (R ) Ph,6b S(p-Tol)6c), in that the
triflate group is in a position anti to the Cp* ligand.
Several features of the structure seem to support the
presence of some multiple bonding between Os and Si.
The Os-Si bond length of 2.334(2) Å is comparable to
the corresponding value in the base-stabilized osmium
silylene complex (TTP)OsSiEt2‚2THF (2.325(8) Å; TTP
) tetraphenylporphyrin)44 and is shorter than a typical
Os-Si single bond.38 Silylene character in 24 is also
supported by the relatively long Si-O bond length of
1.866(5) Å. Typical Si-O bonds in four-coordinate
silicon compounds are in the range 1.63-1.66 Å,45
whereas metal-silylene complexes stabilized by oxygen
bases have Si-O distances between 1.68 and 1.85
Å.1,5b,6b,c,44,46 In fact, the Si-O bond length in 24 is
longer than reported Si-O distances in silylene com-
plexes containing coordinated oxygen donors.47 The
Si-O distance in 24 is significantly longer than the
Si-O distances in base-stabilized silylene complexes of
the type (CO)nMdSiX2(HMPA) (n ) 5, M ) Cr; n ) 4,
Similar observations have been made for analogous
ruthenium complexes.6b,c
The 29Si{1H} NMR spectrum of 24 exhibits a triplet
at δ 83.43 (2J SiP ) 23 Hz; benzene-d6 solution). This
chemical shift lies downfield from that for the corre-
2
sponding chloro(silyl) complex 14 (δ 46.76, J SiP ) 20
Hz). For comparison, the ruthenium complex Cp*-
(PMe3)2RuSiMe2OTf has a 29Si NMR shift of δ 133.3
(2J SiP ) 33 Hz).6c Downfield 29Si shifts for compounds
containing sp2-hybridized silicon43 and arguments based
on correlations between 13C and 29Si NMR data43a
suggest that 24 might possess a slight amount of
silylene (MdSi) character. However, since the 29Si
NMR resonance for 24 is significantly lower than those
found for base-free silylene complexes (251-276
ppm),6d,e,36 it is best to regard 24 as a tetravalent silicon
species.
The solid-state structure of 24 was determined by
single-crystal X-ray crystallography. An ORTEP draw-
ing of the molecule is shown in Figure 3, and relevant
bond distances and angles are listed in Table 2. Mol-
ecules of 24 adopt a three-legged piano-stool coordina-
tion geometry, and the silicon atom exists in a distorted
(44) Woo, L. K.; Smith, D. A.; Young, V. G., J r. Organometallics
1991, 10, 3977.
(45) Wiberg, N.; Wagner, G.; Mu¨ller, G.; Riede, J . J . Organomet.
Chem. 1984, 271, 381.
(46) Zybill, C.; Mu¨ller, G. Angew. Chem., Int. Ed. Engl. 1987, 26,
669.
(47) The longest Si-O distance in
a “base-stabilized” silylene
complex previously reported (1.856(5) Å) is in Cp*(PMe3)2RuSi[S(p-
(43) (a) Olah, G. A.; Field, L. D. Organometallics 1982, 1, 1485. (b)
Raabe, G.; Michl, J . Chem. Rev. 1985, 85, 419.
Tol)]2OTf (ref 6c).

4308 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
1
M ) Fe), which vary from 1.68 to 1.78 Å,5b and longer
than those found in (TTP)OsdSiEt2‚2THF (1.82(2) Å)44
and ruthenium triflato(silyl) complexes of the type Cp*-
(PMe3)2RuSiR2OTf (R2 ) [S(p-Tol)]2, (SMes)(Cl), Ph2)
(1.82-1.85 Å).36
alkyl complexes (300-313 Hz), since values of J (M,P)
coupling are dependent on a number of contributing
factors, such as M-P bond strength, metal oxidation
state, and structural effects.27a,49
The summation of angles at silicon, ignoring the Si-
OTf bond, may also be used to evaluate the hybridiza-
tion at silicon.5b,6c These values range widely (336-
353°) in the base-stabilized silylene complexes
characterized crystallographically,1a,b,6a-c,44,48 with the
mean value (345°) falling exactly between the ideal
values for sp2 (360°) and sp3 hybridization (329°).
Summation of the angles Os-Si-C(17), Os-Si-C(18),
and C(17)-Si-C(18) in 24 gives a value (343.5°) which
might be interpreted in terms of partial sp2 character
at silicon. The bond angles around the silicon also
reflect considerable distortion from a tetrahedral ge-
ometry. The Os-Si-C angles of 119.1(3)° and 120.8-
(3)° are larger than the Os-Si-O angle of 115.3(2)°, and
the C-Si-O angles of 96.6(3)° and 96.9(3)° are rather
acute.
Although complex 24 appears to have some silylene
character, as evidenced by its solid-state structure and
its lability in acetonitrile, the structural and spectro-
scopic data are much more consistent with an sp3-
hybridized (and silyl-like) silicon center. The short Os-
Si bond and the long Si-O(triflate) distance may be
alternatively rationalized as resulting from significant
dπ-σ* π-donation from the metal center to the silyl
ligand.1a,b,40 Such dπ-σ* donation should be heavily
favored by the high electronegativity of the triflate
group, which contributes to greater dπ-σ* overlap by
concentrating much of the σ* orbital in the vicinity of
the metal atom.
Initial attempts to substitute the chloride groups in
Cp*(PMe3)2OsSiMeCl2 (18) were unsuccessful. For
example, reaction of 18 with equimolar or excess
amounts of Me3SiOTf at room temperature gave only a
complex mixture of products. Similarly, 18 did not react
with nucleophilic reagents such as MesLi, LiSCy, or
NaOMe, even after prolonged heating. Clean substitu-
tion was finally achieved using LiS(p-Tol). Thus, heat-
ing a mixture of 18 and LiS(p-Tol) (3 equiv) in toluene
overnight at 40-50 °C gave Cp*(PMe3)2OsSiMe[S(p-
Tol)]2 (25) in 90% yield (by NMR spectroscopy). Com-
plex 25 can be isolated as colorless crystals in 67% yield
after recrystallization from a dichloromethane/diethyl
ether mixture.
Con clu sion s
The synthesis of new osmium alkyl and silyl com-
plexes have been developed. The preparation of alkyl
complexes of the type Cp(PR3)2OsCH2EMe3 (R ) Ph,
Me; E ) C, Si) required the use of dialkylmagnesium
reagents. We have also isolated and structurally char-
acterized an osmium(II) triflate complex Cp(PPh3)2-
OsOTf (2), which possesses a chemically labile triflate
group and may, therefore, prove useful in synthetic
applications, as has the ruthenium analog Cp(PPh3)2-
RuOTf.50 Convenient synthetic routes to complexes
containing the electron-rich Cp*(PMe3)2Os fragment
have been developed, and the alkyl derivatives, like the
corresponding ruthenium alkyls, thermally activate
arene C-H and Si-H bonds.
Reactions of osmium alkyl complexes toward hydrosi-
lanes were found to differ significantly from those of
analogous ruthenium compounds. For example, reac-
tions of Cp*(PMe3)2OsCH2SiMe3 (7) with (arylthio)-
silanes did not give the expected Os(II) silyl complexes;
instead, activation of both the Si-H and arene C-H
bonds of the silanes took place, giving Os(IV) metalla-
cycles. This reactivity may be attributed to the stronger
basicity of Cp*Os(II), compared to Cp*Ru(II), com-
plexes.26 The rates and product distributions for reac-
tions of osmium alkyl complexes with hydrosilanes were
found to be very sensitive to reaction conditions, the
electronic nature of the hydrosilanes, and the lability
of the Os-P bonds. In general, it appears that Os(II)
silyl complexes are favored in reactions involving com-
plexes with strong Os-P bonds and silanes with elec-
tronegative substituents. Unlike the Cp*(PMe3)Ru(H)-
(SiX3)2 complexes, the Os(IV) bis(silyl) hydrides are
kinetically stable and are not readily converted to mono-
(silyl) bis(phosphine) complexes of the type Cp*(PMe3)2-
OsSiX3. The chloro(silyl) complex Cp*(PMe3)2OsSiMe2-
Cl (17) is easily converted to the triflato(silyl) complex
Cp*(PMe3)2OsSiMe2(OTf) (24), which is currently being
examined as a precursor to the base-free silylene
+
complex Cp*(PMe3)2OsdSiMe2
.
Exp er im en ta l Section
Like their bromo and alkyl precursors, most of the
osmium silyl complexes show low-intensity osmium
Gen er a l Con sid er a tion s. Unless otherwise noted, all
manipulations were performed under an atmosphere of nitro-
gen using standard Schlenk techniques and/or in a Vacuum
Atmospheres glovebox. Dry, oxygen-free solvents were em-
ployed throughout. Diethyl ether (Et2O), pentane, hexane, and
toluene were distilled from sodium benzophenone ketyl and
stored under N2 prior to use. Dichloromethane was distilled
from CaH2. Benzene-d6 was purified by vacuum distillation
from Na/K alloy. Dichloromethane-d2 was distilled from CaH2
and degassed with two freeze-pump-thaw cycles prior to use.
Unless otherwise specified, all reagents were purchased from
commercial suppliers and used without further purification.
The silanes HSiPh2Cl, HSiMe2Cl, HSiMeCl2, and HSiCl3 were
distilled under N2 and degassed before use. The compounds
1
satellites in the 31P{1H} NMR spectra and J (187Os,31P)
coupling constants ranging from 260 to 280 Hz. It is
not entirely clear why the coupling constants for the
silyl derivatives are lower than those for the bromo and
(48) (a) Ueno, K.; Tobita, H.; Shimoi, M.; Ogino, H. J . Am. Chem.
Soc. 1988, 110, 4092. (b) Tobita, H.; Ueno, K.; Shimoi, M.; Ogino, H.
J . Am. Chem. Soc. 1990, 112, 3415. (c) Takeuchi, T.; Tobita, H.; Ogino,
H. Organometallics 1991, 10, 835. (d) Koe, J .; Tobita, H.; Ogino, H.
Organometallics 1992, 11, 2479. (e) Ueno, K.; Tobita, H.; Ogino, H. J .
Organomet. Chem. 1992, 430, 93. (f) Ueno, K.; Tobita, H.; Seki, S.;
Ogino, H. Chem. Lett. 1993, 1723. (g) Kobayashi, H.; Ueno, K.; Ogino,
H. Organometallics 1995, 14, 5490. (h) Corriu, R.; Lanneau, G. F.;
Priou, C. Angew. Chem., Int. Ed. Engl. 1991, 9, 1130. (i) Corriu, R. J .;
Lanneau, G. F.; Chauhan, P. S. Organometallics 1993, 12, 2001. (j)
Corriu, R. J . P.; Chauhan, B. P. S.; Lanneau, G. F. Organometallics
1995, 14, 1646. (k) J utzi, P.; Mo¨hrke, A. Angew. Chem., Int. Ed. Engl.
1990, 29, 893. (l) Lee, K. L.; Arif, A. M.; Gladysz, J . A. Chem. Ber.
1991, 124, 309. (m) Auner, N.; Wagner, C.; Herdtweck, E.; Heckel, M.;
Hiller, W. Bull. Soc. Chim. Fr. 1995, 132, 599. (n) Chen, W.; Edwards,
A. J .; Esteruelas, M. A.; Lahoz, F. J .; Oliva´n, M.; Oro, L. A. Organo-
metallics 1996, 15, 2185.
(49) Pregosin, P. S.; Kunz, R. W. 31P and 13C NMR of Transition
Metal Phosphine Complexes; Springer-Verlag: Berlin, 1979.
(50) (a) Amarasekera, J .; Rauchfuss, T. B.; Wilson, S. R. J . Am.
Chem. Soc. 1988, 110, 2332. (b) Amarasekera, J .; Rauchfuss, T. B.
Inorg. Chem. 1989, 28, 3875. (c) Amarasekera, J .; Houser, E. J .;
Rauchfuss, T. B.; Stern, C. L. Inorg. Chem. 1992, 31, 1614.

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4309
1
(Me3SiCH2)2Mg,51 PMe3,52 Cp(PMe3)2OsBr,24 Cp*2Os2Br4,20a
HSi[S(p-Tol)]3,53 and HSiMe2[S(p-Tol)]53 were prepared by
literature methods.
from red-orange to yellow. The H and 31P{1H} NMR spectra
showed that complete conversion of 2 to 2a had taken place.
Crystals of 2 also decomposed to 2a upon standing at room
temperature under N2 (drybox) over 1 month. Spectral data
for 2a : 1H NMR (CD2Cl2): δ 7.55-6.59 (br m, ArH), 5.29 (s, 5
NMR spectra were recorded at 400.13 MHz (1H), 100.62
MHz (13C), 161.98 MHz (31P), and 59.6 MHz (29Si). The spectra
were obtained at room temperature in benzene-d6, unless
H, Cp), -11.18 (dd, J PH ) 34 Hz, 26 Hz, 1 H, OsH). 31P{1H}
2
2
2
1
NMR (CD2Cl2): δ 6.34 (d, J PP ) 21 Hz), -71.33 (d, J PP ) 21
Hz). 13C{1H} NMR (CD2Cl2): δ 149.15, 133.85, 133.75, 131.68,
129.62, 129.55, 129.05, 128.94 (Ph), 87.86 (Cp). IR (CH2Cl2):
1986 (m, ν(Os-H)), 1484 (m), 1438 (m), 1275 (s, ν(SO3)), 1220
(m), 1155 (s), 1099 (m), 1030 (s), 881 (w).
otherwise noted. The H resonances for the PMe3 ligands in
complexes of the type Cp′(PMe3)2OsX (Cp′ ) Cp, Cp*) appear
as a A9XX′A′9 pattern, the appearance of which is a “filled-in
doublet” (fd) with the separation of the outer lines N ) 2J PH
+
54
4J PH
.
In the 13C{1H} NMR spectra, the PMe3 resonances
appear as a virtual triplet (vt) with the separation of the outer
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 2‚C6H6. Red
blocklike crystals of 2‚C6H6 were obtained from slow evapora-
tion of a benzene solution at room temperature. A single
crystal was mounted on a glass capillary using Paratone-N
hydrocarbon oil, centered in the beam, and cooled to -104 °C
by a nitrogen-flow low-temperature apparatus which had been
previously calibrated by a thermocouple placed at the sample
position. All measurements were made on a Siemens SMART
1
3
54
lines N ) J PC + J PC
.
Melting points were measured on a
Mel-Temp II apparatus in sealed capillaries under nitrogen
and are uncorrected. Elemental analyses were performed by
the UC Berkeley College of Chemistry Microanalytical Labora-
tory. IR spectra were obtained on a Mattson Galaxy Series
FTIR 3000 spectrometer as Nujol mulls on NaCl plates, unless
otherwise specified, and all absorptions are reported in cm-1
.
Mass spectroscopic (MS) analysis were obtained at the UC
Berkeley mass spectrometry facility on AEI MS-12 mass
spectrometers. X-ray diffraction studies were performed in the
UCB X-ray Diffraction facility (CHEXRAY).
diffractometer with
a CCD area detector using graphite
monochromated Mo KR radiation (λ ) 0.710 69 Å). Collection
of 60 10-s frames, followed by spot integration and least-
squares refinement, gave a preliminary orientation matrix and
cell constants. A hemisphere of data was collected using ω
scans of width 0.3°. The raw data were integrated (XY spot
spread ) 1.60°; Z spot spread ) 0.60°) using SAINT (SAX
Area-Detector Integration Program, v. 4.024; Siemens Indus-
trial Automation, Inc.: Madison, WI, 1995). Data analysis was
performed using Siemens XPREP (part of the SHELXTK
Crystal Structure Determination Package; Siemens Industrial
Automation, Inc.: Madison, WI, 1995). The 8822 reflections
measured were averaged, yielding 5876 unique reflections (Rint
) 2.0%). The data were corrected for Lorentz and polarization
effects. No correction for crystal decay was necessary, but a
Cp (P P h 3)2OsBr (1).15,21b An ampule of OsO4 (1.0 g, 3.93
mmol) was broken in a flask containing 48% HBr (37 mL),
and the red solution was heated at reflux for 2 h in air. Water
and excess HBr were removed from the mixture by distillation
at 50 °C under vacuum, leaving a dark red residue. The
residue was dissolved in absolute ethanol (20 mL) and added
to a stirred, boiling solution of triphenylphosphine (6.30 g, 24.0
mmol) in ethanol (180 mL), followed immediately by a solution
of freshly distilled cyclopentadiene (10 mL) in ethanol (20 mL).
Water (25 mL)55 was then added to the mixture via syringe,
and the crimson suspension was heated at reflux for 2 h,
resulting in a color change to orange. After the reaction
mixture was cooled to room temperature, the resulting orange-
yellow powder was filtered, washed with ethanol (2 × 10 mL)
and hexane (2 × 10 mL), and dried under vacuum to give pure
1, mp 180-182 °C dec (lit.21b 180-181 °C dec). The orange
filtrate was concentrated to 40 mL and cooled to -35 °C to
obtain the remaining product. Overall yield: 97% (3.25 g)
(lit.21b 89%). 1H NMR: δ 7.55 (br m, 12H, Ph), 6.93 (br m,
semiempirical absorption correction (Tmax ) 0.264, Tmin
)
0.200) was applied. The space group P1h was confirmed by the
refinement.
The structure was solved using the teXsan software package
(Crystal Structure Analysis Package; Molecular Structure
Corporation, 1992) by direct methods (SIR92) and refined by
full-matrix least-squares methods. The non-hydrogen atoms
were refined anisotropically. All hydrogen atoms were as-
signed idealized positions and were included in the structure
factor calculations but were not refined. The final residuals
for the 523 variables refined against the 5696 accepted data
for which I > 3σ(I) were R ) 1.8%, Rw ) 2.9%, and GOF )
1.41. Using all 5877 unique data (including systematic
absences), R ) 1.9% and Rw ) 2.9%. The maximum and
minimum peaks in the final difference Fourier map had
electron densities of 0.61 and -0.63 e-/Å3, respectively. The
weighting scheme was based on counting statistics and
included a factor (p ) 0.030) to downweight the intense
reflections. The analytical forms of the scattering factor tables
for the neutral atoms were used, and all scattering factors were
corrected for both the real and imaginary components of
anomalous dispersion. The crystal and data collection param-
eters for this data set are given in Table 3.
18H, Ph), 4.35 (s, 5H, Cp). 31P{1H} NMR: δ -5.67 (1J OsP
312 Hz).
)
Cp (P P h 3)2OsOSO2CF 3 (2). To a mixture of 1 (150 mg, 0.17
mmol) and AgOSO2CF3 (47 mg, 0.18 mmol) was added 5 mL
of toluene at room temperature. The resulting mixture was
stirred for 30 min and then filtered to remove the AgBr salt.
Removal of solvent from the bright red-orange solution gave
2 as a red solid (0.12 g, 72%, mp 118-120 °C) in >95% purity
1
by H NMR. 1H NMR: δ 7.28 (br m, 12 H, Ph), 6.93 (br m, 18
H, Ph), 4.63 (s, 5 H, Cp). 31P{1H} NMR: δ 5.51. 19F{1H} NMR
(376.48 MHz): δ -14.3. 13C{1H} NMR: δ 140.4, 140.0, 134.4,
128.6, 127.3 (Ph). The analytically pure toluene adduct
2‚C6H5CH3 was obtained by recrystallization from toluene.
Anal. Calcd for C49H43F3O3OsP2S: C, 57.64; H, 4.24. Found:
C, 57.46; H, 4.14. IR (KBr): 1481 (m), 1434 (m), 1313 (s,
ν(SO3)), 1263 (w), 1228 (m), 1201 (s), 1091 (m), 1001 (s).
Or th om eta la tion of Cp (P P h 3)2OsOTf (2) to Cp (P P h 3)-
Rea ction of Cp (P P h 3)2OsOTf (2) w ith Me3SiCH2MgCl.
To a cooled (-35 °C), stirred solution of 2 (51 mg, 0.055 mmol)
in toluene (5 mL) was added via syringe 0.04 mL (0.07 mmol)
of a 1.7 M solution of Me3SiCH2MgCl in Et2O. An immediate
color change to bright yellow was observed. The reaction
mixture was allowed to warm to room temperature and was
then stirred for 16 h. Removal of solvent from the yellow
mixture gave a yellow solid, which was shown by 1H and
31P{1H} NMR to be a 1:1 mixture of Cp(PPh3)2OsCH2SiMe3
(4; compared with spectral data of a pure sample synthesized
as described below) and Cp(PPh3)2OsCl.22a The two compounds
can be separated by extraction with hexane (the yellow alkyl
complex 4 is hexane-soluble while the orange chloro complex
is not).
(H)Os(2-C6H4P P h 2) (2a ). Allowing a solution of 2 in CH2Cl2
to stand at room temperature for 8 h resulted in a color change
(51) Andersen, R. A.; Wilkinson, G. J . Chem. Soc., Dalton Trans.
1977, 809.
(52) Luetkens, M. L.; Sattelberger, A. P.; Murray, H. H.; Basil, J .
D.; Fackler, J . P. Inorg. Synth. 1990, 28, 305.
(53) Birkofer, L.; Stuhl, O. In The Chemistry of Organic Silicon
Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New York, 1989;
Chapter 10, p 655.
(54) (a) Harris, R. K. Can. J . Chem. 1964, 42, 2275. (b) Harris, R.
K.; Hayter, R. G. Can. J . Chem. 1964, 42, 2282.
(55) The reaction will not work with complete exclusion of water,
and a much longer reaction time is required (with lower yield of
product) when less than 25 mL of water is added to the reaction
mixture.
R ea ct ion of Cp (P P h 3)2OsBr (1) w it h Mg(CH2CMe3)2.
Mixing an orange solution of 1 (30 mg, 0.035 mmol) in benzene-

4310 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
Ta ble 3. Cr ysta l a n d Da ta Collection P a r a m eter s for Com p lexes 2‚C6H6, 13, a n d 24a
2‚C6H6
13
24
empirical formula
fw
C48H41F3O3OsP2S
1007.05
C22H37OsPSSi
582.85
C19H39F3O3OsP2SSi
684.80
cryst color, habit
cryst size, mm
cryst syst
space group
a, Å
red, block
0.30 × 0.31 × 0.27
triclinic
P1h
12.2274(1)
12.7827(2)
13.6433(2)
93.227(1)
94.503(1)
100.970(1)
2081.47(5)
2
colorless, plate
0.13 × 0.10 × 0.08
triclinic
P1h
8.9271(3)
9.5732(3)
16.0925(5)
74.883(1)
86.281(1)
63.136(1)
1182.16(6)
2
yellow, block
0.20 × 0.10 × 0.20
monoclinic
P21/c
9.4152(1)
16.6655(3)
17.3217(3)
90.0
‘04.329(1)
90.0
2633.38(7)
4
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, g cm-3
1.607
32.44
1.637
56.01
1.727
51.24
µ(Mo KR), cm-1
temp, °C
-104 ( 1
-124 ( 2
-111 ( 1
scan type
ω
ω
ω
2θ range, deg
no. of rflns measd
total
3-47
3-47
3-52
8822
4997
12608
unique
min/Tmax
5876 (Rint ) 2.0%)
0.200/0.264
5696
3326 (Rint ) 2.7%)
0.477/0.589
3034
5830 (Rint ) 5.4%)
0.234/0.365
4297
T
no. of observations (I > 3.00σ(I))
no. of params
523
235
271
residuals R; Rw, %
Rall R; Rw, %
goodness of fit
1.8; 2.9
1.9; 2.9
1.41
0.61
-0.63
0.03
2.4; 3.2
2.9; 3.5
1.24
0.52
-0.67
0.03
4.0; 5.0
5.5; 5.5
1.50
0.63
-1.83
0.03
max peak in final diff map, e-/Å3
min peak in final diff map, e-/Å3
p factor
a
General information: diffractometer, Siemens SMART; radiation, Mo KR radiation (λ ) 0.710 69 Å); monochromator, graphite.
d6 with (Me3CCH2)2Mg (6 mg, 0.04 mmol) at room temperature
resulted in an instant color change to yellow and formation of
a white precipitate. 1H and 31P{1H} NMR spectroscopy showed
the major product (>90%) in solution to be Cp(PPh3)2OsCH2-
CMe3 (3). 1H NMR: δ 7.18 (br m, 12 H, Ph), 6.99 (br m, 18 H,
(w), 2665 (w), 1277 (m), 1236 (m), 1097 (w), 953 (s), 933 (s),
854 (s), 821 (m), 794 (w), 671 (w).
Cp *(P Me3)2OsBr (6). To a stirred, brown-black solution
of Cp*2Os2Br4 (1.20 g, 1.24 mmol) in CH2Cl2 (20 mL) was added
via syringe 0.84 mL (8.1 mmol) of neat PMe3. A color change
to yellow-brown took place immediately after the addition, and
the mixture was stirred in a closed flask at room temperature
for 11 h. The volatile materials were then removed under
vacuum, and the residue was extracted 3 times with hot (50
°C) hexane to give 100 mL of combined extracts. The resulting
orange solution was concentrated to ca. 15 mL and cooled to
-80 °C. Dark orange plates of 6 were collected and dried (mp
196-197 °C dec). Yield: 0.82 g (59%). 1H NMR: δ 1.65 (t,
4J PH ) 1.0 Hz, 15 H, C5Me5), 1.37 (fd, N ) 8.5 Hz, 18 H, PMe3).
31P{1H} NMR: δ -47.5 (1J OsP ) 301 Hz). 13C{1H} NMR: δ
3
Ph), 4.67 (s, 5 H, Cp), 2.21 (t, J PH ) 8.9 Hz, 2 H, OsCH2),
1.15 (s, 9 H, CMe3). 31P{1H} NMR: δ 1.25.
Cp (P P h 3)2OsCH2SiMe3 (4). To a mixture of 1 (150 mg,
0.17 mmol) and (Me3SiCH2)2Mg (35 mg, 0.18 mmol) was added
5 mL of cold (-35 °C) toluene. The resulting suspension was
allowed to warm to room temperature and was then stirred
for 15 h, during which time a color change from orange to
bright yellow was observed. After removal of the solvent under
vacuum, the yellow residue was extracted with hexane (2 ×
10 mL). The combined extracts were concentrated to ca. 3 mL
and cooled to -35 °C for 12 h, giving pure 4 (mp 225-226 °C)
as bright yellow crystals (120 mg, 79%). 1H NMR: δ 7.24 (br
m, 12 H, Ph), 6.96 (br m, 18 H, Ph), 4.50 (s, 5 H, Cp), 0.61 (t,
3J PH ) 8.0 Hz, 2 H, OsCH2), 0.35 (s, 9 H, SiMe3). 31P{1H}
NMR: δ 1.93 (1J OsP ) 313 Hz). 13C{1H} NMR (CD2Cl2): δ
140.4, 140.0, 134.4, 128.6, 127.3 (Ph), 77.37 (s, Cp), 4.31 (s,
2
83.84 (t, J PC ) 2.4 Hz, C5Me5), 21.5 (vt, N ) 45.3 Hz, PMe3),
11.31 (s, C5Me5). Anal. Calcd for C16H33BrOsP2: C, 34.47; H,
5.97. Found: C, 34.45; H, 6.04. IR: 2723 (m), 2669 (m), 1923
(m), 1911 (m), 1296 (m), 1277 (s), 1261 (s), 1155 (w), 1093 (m),
1024 (s), 937 (s), 848 (w), 798 (s), 665 (s).
2
Cp *(P Me3)2OsCH2SiMe3 (7). To a cold (-35 °C), stirred
solution of 4 (0.654 g, 1.17 mmol) in toluene (20 mL) was added
0.75 mL (1.3 mmol) of a 1.7 M solution of Me3SiCH2MgCl in
Et2O via syringe. The reaction mixture was allowed to warm
to room temperature and was then stirred for 13 h. After
removal of the volatile components in vacuo, the residue was
extracted with hexane (2 × 20 mL). The combined extracts
were concentrated to dryness, leaving a pale yellow solid of 7
SiMe3), -0.42 (t, J PC ) 8.0 Hz, OsCH2). Anal. Calcd for
C
45H46OsP2Si: C, 62.33; H, 5.35. Found: C, 62.53; H, 5.38.
IR: 2727 (w), 2667 (w), 1583 (w), 1236 (m), 1182 (w), 1155
(w), 1086 (m), 995 (w), 854 (m), 821 (m), 744 (m), 694 s (m).
Cp (P Me3)2OsCH2SiMe3 (5). A mixture of Cp(PMe3)2OsBr
(100 mg, 0.20 mmol), (Me3SiCH2)2Mg (61 mg, 0.31 mmol), and
toluene (3 mL) was stirred for 2 h at room temperature, until
the orange mixture turned pale yellow. The solvent was then
removed in vacuo, and the residue was extracted with hexane
(2 × 5 mL). Removal of the hexane left a pale yellow solid,
which was crystallized from Et2O at -35 °C to give 60 mg
(60%) of 5 as pale yellow prisms (mp 72-73 °C). The complex
can also be sublimed at 50-65 °C under vacuum. 1H NMR:
δ 4.41 (s, 5 H, Cp), 1.22 (fd, N ) 8.4 Hz, 18 H, PMe3), 0.29 (s,
1
(0.65 g, 98%) in >95% purity by H NMR. Analytically pure
7 (mp 220-222 °C) was obtained by recrystallization from
pentane. Anal. Calcd for C20H44OsP2Si: C, 42.53; H, 7.85.
Found: C, 42.62; H, 7.76. 1H NMR: δ 1.72 (s, 15 H, C5Me5),
1.26 (fd, N ) 7.6 Hz, 18 H, PMe3), 0.37 (s, 9 H, SiMe3), -0.27
3
(t, 2H, J PH ) 6.2 Hz, OsCH2). 31P{1H} NMR: δ -50.5 (1J OsP
2
) 303 Hz). 13C{1H} NMR: δ 85.36 (t, J PC ) 2.7 Hz, C5Me5),
3
9 H, SiMe3), -0.14 (t, J PH ) 7.9 Hz, 2 H, OsCH2). 31P{1H}
NMR: δ -46.39 (1J OsP ) 305 Hz). 13C{1H} NMR: δ 73.34 (t,
2J PC ) 2.5 Hz, Cp), 22.6 (vt, N ) 47.3 Hz, PMe3), 4.30 (s, SiMe3),
-44.21 (t, 2J PC ) 7.4 Hz, OsCH2). Anal. Calcd for C15H34OsP2-
Si: C, 36.42; H, 6.93. Found: C, 36.48; H, 7.07. IR: 2723
21.8 (vt, N ) 43.7 Hz, PMe3), 11.74 (s, C5Me5), 5.33 (s, SiMe3),
-0.88 (t, 2J PC ) 6.4 Hz, OsCH2). IR: 1884 (w), 1292 (w), 1275
(m), 1261 (m), 1234 (w), 1090 (w), 1026 (m), 951 (s), 933 (s),
848 (s), 820 (m), 800 (m), 696 (w), 671 (w).

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4311
Th er m olysis of Cp *(P Me3)2OsCH2SiMe3 (7) in C6D6. A
solution of 7 (10 mg, 0.018 mmol) in benzene-d6 (0.5 mL) was
sealed in a J . Young Valve NMR tube and heated to 115 °C.
The reaction was monitored by 1H and 31P{1H} NMR spec-
troscopy. After 10 h, all of 7 was consumed to give Cp*(PMe3)2-
OsC6D5 (8-d5; identified by comparisons to the spectra of 8)
and Me3SiCH2D in quantitative yield (by NMR).
Found: C, 47.04; H, 6.75. IR: 2727 (w), 1591 (w), 1275 (m),
1169 (w), 1076 (m), 1026 (w), 924 (s), 847 (w), 802 (m), 665
(m), 488 (s).
Cp *(P Me3)(H)Os{C6H3(3-Me)(6-S)SiMe2} (13). A flask
containing 7 (150 mg, 0.27 mmol), HSiMe2[S(p-Tol)] (49 mg,
0.27 mmol), and cyclohexane (2 mL) was closed (Teflon
stopcock), and the contents were heated to 115 °C with stirring
for 15 h. The volatile materials were then removed, giving a
yellow-white solid whose spectral data are consistent with a
1:9 mixture of 12 and 13. The crude solid was extracted with
pentane (2 × 5 mL) to give a yellow solution and an undis-
solved white solid. The yellow solution was filtered, concen-
trated, and cooled to -35 °C to give yellow crystals of 12. The
remaining white solid was recrystallized from CH2Cl2/Et2O at
-35 °C to give 13 (118 mg, 77%) as white crystals, mp 149-
150 °C dec. Anal. Calcd for C22H37OsPSSi: C, 45.34; H, 6.40.
Found: C, 45.10; H, 6.19. 1H NMR: δ 7.79 (d, J ) 7.7 Hz, 1
H, OsC6H3(3-Me)(6-S)Si), 7.01 (s, 1 H, OsC6H3(3-Me)(6-S)Si),
Cp *(P Me3)2OsP h (8). To a solution of 5 (50 mg, 0.09 mmol)
in toluene (2 mL) was added 0.05 mL (0.1 mmol) of a 2.0 M
solution of PhMgBr in THF via syringe. The mixture was
heated to 70 °C and then stirred for 6 h. After removal of the
solvent, the residue was extracted with 10 mL of hexane and
the extract was concentrated to dryness. The dark yellow solid
was recrystallized from Et2O at -35 °C to give 8 as pale yellow
crystals (27 mg, 54%), mp 318-320 °C. 1H NMR: δ 7.57 (d, J
) 6.5 Hz, 2 H, o-ArH), 7.08 (m, 2 H, m-ArH), 7.01 (m, 1 H,
4
p-ArH), 1.61 (t, J PH ) 1.0 Hz, 15 H, C5Me5), 1.32 (fd, N ) 8.0
Hz, 18 H, PMe3). 31P{1H} NMR: δ -47.7 (1J OsP ) 313 Hz).
2
13C{1H} NMR: δ 145.65 (t, J PC ) 5.0 Hz, ipso-ArC), 128.53,
6.67 (d, J ) 7.7 Hz, 1 H, OsC6H3(3-Me)(6-S)Si), 2.20 (s, 3 H,
2
126.40, 119.24 (Ph), 87.62 (t, J PC ) 2.8 Hz, C5Me5), 22.1 (vt,
2
OsC6H3(3-Me)(6-S)Si), 1.57 (s, 15 H, C5Me5), 1.15 (d, J PH
)
N ) 35.3 Hz, PMe3), 11.18 (s, C5Me5). Anal. Calcd for C22H38
-
9.2 Hz, 9 H, PMe3), 0.94 (s, 3 H, SiMe2), 0.82 (s, 3 H, SiMe2),
OsP2: C, 47.64; H, 6.90. Found: C, 48.11; H, 6.96. IR: 1562
(m), 1292 (w), 1274 (m), 1057 (w), 1016 (m), 948 sh, 935 (s),
848 (m), 702 (m), 663 (m), 642 (w).
2
1
2
-15.10 (d, J PH ) 32.0 Hz, J OsH ) 83 Hz, J SiOsH ) 15 Hz, 1
H, OsH). 31P{1H} NMR: δ -48.5. 13C{1H} NMR: δ 155.86
(s), 146.10 (d, 2J PC ) 9.6 Hz, OsC), 130.04 (s), 127.30 (s), 125.43
(s), 124.68 (s, SC6H4Me), 93.88 (s, C5Me5), 22.17 (d, 1J PC ) 36.5
Hz, PMe3), 20.78 (s, SC6H4Me), 16.72 (s, SiMe), 10.41 (s,
C5Me5), 8.03 (s, SiMe). 29Si{1H} NMR: δ 30.55 (d, 2J SiP ) 12.2
Hz). IR (CH2Cl2): 3934 (m), 3053 (s), 2983 (m), 2684 (w), 2303
(m), 1442 (m), 1421 (m), 1041 (w), 897 (m), 702 (s).
Th er m olysis of Cp (P Me3)2OsCH2SiMe3 (5) in C6D6. A
sealed NMR tube containing a solution of 5 (10 mg, 0.020
mmol) in benzene-d6 was heated to 170 °C. A slow conversion
of 5 to Me3SiCH2D and Cp(PMe3)2OsC6D5 (9-d5) was monitored
by 1H and 31P{1H} NMR spectroscopy. The reaction was
complete (by NMR) after 10 days of heating at 160-170 °C.
9-d5: 1H NMR δ 4.40 (s, 5 H, Cp), 1.26 (fd, N ) 8.4 Hz, 18 H,
PMe3). 31P{1H} NMR: δ -43.7.
Th er m olysis of Cp (P P h 3)2OsCH2SiMe3 (4) in C6D6. A
solution of 4 (10 mg, 0.011 mmol) in benzene-d6 (0.5 mL) in a
sealed J . Young valve NMR tube was heated to 60-67 °C. The
reaction was monitored by 1H and 31P{1H} NMR spectroscopy.
After 48 h, all of 4 was converted into SiMe4 and a complex
formed whose spectral data are consistent with Cp(PPh3)Os(2-
C6H4PPh2) (10). 10: 1H NMR δ 7.31 (br m, 9 H, ArH), 6.91 (br
m, 20 H, ArH), 4.41 (s, 5 H, Cp). 31P{1H} NMR: δ 2.58 (d, J
) 14 Hz), 1.97 (d, J ) 14 Hz). 13C{1H} NMR (CD2Cl2): δ
134.43, 134.33, 134.23, 128.72, 127.37, 127.17, 127.07 (Ph),
82.35 (Cp).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 13. Colorless
platelike crystals of 13 were obtained from a CH2Cl2/Et2O
solution at -35 °C. A single crystal was mounted on a glass
capillary using Paratone N hydrocarbon oil. The data collec-
tion, reduction, and refinement were carried out as described
for 2‚C6H6, except that the hydride position was located in the
difference Fourier map and was refined isotropically. The
crystal and data collection parameters are given in Table 3.
Cp *(P Me3)Os(H )(SiP h 2Cl)2 (14) a n d Cp *(P Me3)2Os-
SiP h 2Cl (15). (a) A flask charged with 7 (81 mg, 0.14 mmol)
and neat HSiPh2Cl (0.2 g, 0.9 mmol) was sealed with a Teflon
stopcock, and the contents were heated to 115 °C with stirring
for 18 h, during which time a white solid precipitated from
the yellow solution. The volatile components were removed
under vacuum, pentane (5 mL) was added, and the superna-
tant was filtered. The remaining white microcrystals were
washed with cold (-35 °C) pentane (5 mL) and dried in vacuo
to give pure 14 (mp 283-285 °C) in 48% yield (28 mg). Cooling
the yellow supernatant to -35 °C gave a white solid, shown
by NMR to be a 2:1 mixture of 14 and 15. Attempts to
separate pure 15 from the mixture were unsuccessful. 15: 1H
NMR δ 7.94 (m, 4 H, Ph), 7.61 (m, 2 H, Ph), 7.25 (t, J ) 7.2
Hz, 4 H, Ph), 1.55 (s, 15 H, C5Me5), 1.35 (fd, N ) 8.0 Hz, 18 H,
PMe3). 31P{1H} NMR: δ -52.8.
Rea ction of Cp *(P Me3)2OsCH2SiMe3 (7) w ith HSi[S(p-
Tol)]3. A flask containing 7 (10 mg, 0.018 mmol), HSi[S(p-
Tol)]3 (7.0 mg, 0.018 mmol), and cyclohexane (2 mL) was sealed
with a Teflon stopcock and heated to 115 °C for 36 h. Removal
of the volatile materials gave a yellow oil, whose spectroscopic
characteristics (1H and 31P NMR) are consistent with Cp*-
(PMe3)(H)Os{C6H3(3-Me)(6-S)Si[S(p-Tol)]2} (11) and Cp*-
1
(PMe3)2OsS(p-Tol) (12) in a 3:2 mixture. 11: H NMR δ 7.79
(d, J ) 7.9 Hz, 2 H, SC6H4Me), 7.76 (d, J ) 8.0 Hz, 2 H, SC6H4-
Me), 7.67 (d, J ) 7.8 Hz, 1 H, OsC6H3(3-Me)(6-S)Si), 7.00 (s, 1
H, OsC6H3(3-Me)(6-S)Si), 6.93 (d, J ) 7.9 Hz, 2 H, SC6H4Me),
6.89 (d, J ) 8.0 Hz, 2 H, SC6H4Me), 6.68 (d, J ) 7.8 Hz, 1 H,
OsC6H3(3-Me)(6-S)Si), 2.16 (s, 3 H, OsC6H3(3-Me)(6-S)Si), 2.05
(s, 3 H, SC6H4Me), 2.03 (s, 3 H, SC6H4Me), 1.62 (s, 15 H,
(b) Alternatively, 14 can be synthesized in pure form by
heating 7 and excess HSiPh2Cl to 115 °C in a closed flask for
12 h, with brief, periodic (ca. 3 times) exposure to vacuum to
remove PMe3. Removal of the volatile materials, addition of
a 1:1 mixture of CH2Cl2 and Et2O to the resulting mixture,
and cooling (-35 °C) gave white crystals of 14 in 60-84% yield.
Anal. Calcd for C37H45Cl2OsPSi2: C, 53.03; H, 5.41. Found:
C, 52.73; H, 5.69. 1H NMR: δ 8.35 (d, J ) 6.96 Hz, 4 H, Ph),
8.00 (d, J ) 6.9 Hz, 4 H, Ph), 7.35 (t, J ) 7.6 Hz, 4 H, Ph),
2
2
C5Me5), 1.26 (d, J PH ) 9.6 Hz, 9 H, PMe3), -13.38 (d, J PH
)
32.0 Hz, 1 H, OsH). 31P{1H} NMR: δ -49.4.
In d ep en d en t Syn th esis of Cp *(P Me3)2OsS(p-Tol) (12).
A flask charged with 6 (50 mg, 0.09 mmol), LiS(p-Tol) (25 mg,
0.16 mmol), and toluene (3 mL) was heated with stirring to
80 °C for 10 h. Removal of the volatile components under
vacuum, extraction with hexane (10 mL), and concentration
to dryness gave a yellow solid. Recrystallization from Et2O
afforded 12 as bright yellow plates (30 mg, 55%), mp 211-
213 °C. 1H NMR: δ 7.56 (d, J ) 8.1 Hz, 2 H, SC6H4Me), 6.93
(m, J ) 8.1 Hz, 2 H, SC6H4Me), 2.24 (s, 3 H, SC6H4Me), 1.71
(s, 15 H, C5Me5), 1.32 (fd, N ) 8.2 Hz, 18 H, PMe3). 31P{1H}
NMR: δ -49.1 (1J OsP ) 300 Hz). 13C{1H} NMR: δ 131.19,
130.04, 129.02, 128.45 (SC6H4Me), 87.13 (t, 2J PC ) 2.3 Hz, C5-
Me5), 20.85 (s, SC6H4Me), 20.5 (vt, N ) 43.3 Hz, PMe3), 11.18
(s, C5Me5). Anal. Calcd for C23H40OsP2S: C, 45.98; H, 6.71.
7.16 (t, J ) 7.4 Hz, 2 H, Ph), 6.96 (t, J ) 7.2 Hz, 4 H, Ph), 6.86
2
(t, J ) 7.3 Hz, 2 H, Ph), 1.42 (s, 15 H, C5Me5), 1.09 (d, J PH
)
9.5 Hz, 9 H, PMe3), -13.08 (d, J PH ) 8.0 Hz, 1 H, OsH). 31P-
2
{1H} NMR: δ -57.3 (1J OsP ) 260 Hz). 13C{1H} NMR: δ 146.86
3
(d, J PC ) 3.9 Hz, ipso-ArC), 135.29, 134.97, 128.47, 128.13,
2
127.42, 127.34 (Ph), 97.18 (d, J PC ) 2.0 Hz, C5Me5), 22.03 (d,
1J PC ) 39.2 Hz, PMe3), 10.41 (s, C5Me5). IR: 2725 (w), 2673
(w), 2017 (m, ν(Os-H)), 1306 (m), 1155 (w), 1088 (m), 1028
(w), 953 (s), 933 (m), 852 (w), 735 (s), 700 (m), 685 (w).
Cp *(P Me3)(H)Os(SiMe2Cl)2 (16). A closed flask contain-
ing 7 (500 mg, 0.90 mmol) and excess HSiMe2Cl (2.0 mL, 18

4312 Organometallics, Vol. 16, No. 20, 1997
Wanandi and Tilley
mmol) was heated to 120 °C for 15 h. Removal of the volatiles
and recrystallization of the residue from CH2Cl2/Et2O gave 350
mg (66%) of 16 as colorless blocks, mp 265 °C dec. Anal. Calcd
for C17H36Cl2OsP2Si: C, 34.51; H, 6.13. Found: C, 34.33; H,
6.12. 1H NMR: δ 1.64 (s, 15 H, C5Me5), 1.35 (d, N ) 9.2 Hz,
9 H, PMe3), 0.943 and 0.939 (2 overlapping singlets, 6H,
H, Cp), 0.95 (s, 6 H, SiMe2), 0.60 (s, 6 H, SiMe2), -11.70 (d,
2J PH ) 8.0 Hz, OsH). 31P{1H} NMR: δ 9.33.
Rea ction of Cp (P Me3)2OsCH2SiMe3 (5) w ith HSiR2Cl
(R ) P h , Me). (a) A mixture of 5 (20 mg, 0.040 mmol) and
HSiPh2Cl (18 mg, 0.082 mmol) in toluene (3 mL) was heated
in a Teflon-stoppered flask with stirring at 150-165 °C for 4
days. The volatile materials were removed, leaving a yellow-
white residue. The residue was extracted with hexane (2 × 2
mL) to remove the excess silane and leave a white solid, shown
by NMR to be mostly Cp(PMe3)2OsSiPh2Cl (22). 1H NMR: δ
7.82 (d, J ) 7.0 Hz, 4 H, Ph), 7.61 (d, J ) 6.0 Hz, 2 H, Ph),
7.28 (t, J ) 7.0 Hz, 4 H, Ph), 4.36 (s, 5 H, Cp), 1.27 (fd, N )
8.9 Hz, 18 H, PMe3). 31P{1H} NMR: δ -46.7 (1J OsP ) 280 Hz).
13C{1H} NMR (CD2Cl2): δ 135.00, 134.94, 134.75, 128.87,
2
SiMe2), -15.27 (d, J PH ) 12.0 Hz, 1 H, OsH). 31P{1H} NMR:
2
δ -53.4. 13C{1H} NMR: δ 96.01 (t, J PC ) 2.2 Hz, C5Me5),
23.26 (d, 1J PC ) 38.1 Hz, PMe3), 17.55 (s, SiMe), 17.35 (s, SiMe),
2
10.85 (s, C5Me5). 29Si{1H} NMR: δ 28.44 (d, J SiP ) 19.8 Hz).
IR: 3839 (m), 3745 (s), 2360 (s), 2318 (m), 2087 (m, ν(Os-H)),
1280 (m), 1234 (m), 1030 (m), 951 (s).
Cp *(P Me3)2OsSiMe2Cl (17). A flask containing 7 (190 mg,
0.34 mmol) and excess HSiMe2Cl (ca. 3 mL) was sealed with
a Teflon stopcock. The flask was partially submerged in a 115
°C oil bath, and the mixture was heated with stirring for 20
h, until the solution turned colorless. All volatile materials
were then removed in vacuo to give a yellow-white solid, shown
2
127.25, 127.14 (SiPh2Cl), 77.70 (t, J PC ) 2.2 Hz, C5H5), 25.94
(vt, N ) 53.4 Hz, PMe3). MS (EI): m/ z 626 [M+]. Repeated
attempts to obtain satisfactory microanalysis data on this
material after recrystallization or sublimation at 100 °C in
vacuo were unsuccessful.
1
by H NMR and 31P{1H} NMR to be a 10:1 mixture of 17 and
(b) A mixture of 5 (20 mg, 0.040 mmol) and HSiMe2Cl (0.1
mL, 0.9 mmol) in toluene (3 mL) was heated in a Teflon-
stoppered flask at 150-165 °C for 4 days, with stirring. The
volatile materials were removed, leaving a white residue. The
residue was extracted with toluene (2 × 5 mL). The toluene
extract was concentrated to dryness in vacuo, giving a white
solid whose spectroscopic characteristics are consistent with
Cp(PMe3)2OsSiMeCl2 (23). 1H NMR: δ 4.36 (s, 5 H, Cp), 1.30
(fd, N ) 8.8 Hz, 18 H, PMe3), 0.99 (s, 3 H, SiMe). 31P{1H}
16. A minimum amount of CH2Cl2 was added to dissolve the
solid, the solution was filtered, and Et2O was added dropwise
until cloudiness appeared. Cooling the CH2Cl2/Et2O solution
to -35 °C afforded pure 17 as white crystals (mp >360 °C dec).
Further concentration and cooling resulted in crystallization
of more product and an overall yield of 88% (0.17 g). Anal.
Calcd for C18H39ClOsP2Si: C, 37.85; H, 6.88. Found: C, 37.81;
H, 6.93. 1H NMR: δ 1.66 (t, 4J PH ) 1.2 Hz, 15 H, C5Me5), 1.35
(fd, N ) 8.3 Hz, 18 H, PMe3), 1.03 (s, 6 H, SiMe2). 31P{1H}
NMR: δ -48.7 (1J OsP ) 280 Hz). 13C{1H} NMR: δ 90.25 (t,
2J PC ) 2.5 Hz, C5Me5), 24.4 (vt, N ) 46.2 Hz, PMe3), 16.37 (s,
SiMe2), 11.73 (s, C5Me5). 29Si{1H} NMR: δ 46.76 (t, 2J SiP ) 20
Hz). IR: 2721 (w), 2669 (w), 1298 (w), 1277 (m), 1223 (w),
1155 (w), 1066 (w), 1030 (m), 955 (s), 935 (s), 850 (m), 827
(m), 791 (m).
2
NMR: δ -45.0. 13C{1H} NMR: δ 77.22 (t, J PC ) 2.2 Hz,
C5H5), 26.28 (vt, N ) 52.3 Hz, PMe3), 17.01 (s, SiMe). MS
(EI): m/ z 522 [M+]. The undissolved white solid remaining
after the extraction was dissolved in CD2Cl2; its spectral data
+
is consistent with trans-Cp(PMe3)2Os(H)2
:
1H NMR (CD2Cl2)
δ 5.48 (s, 5 H, Cp), 1.84 (fd, N ) 6.5 Hz, 18 H, PMe3), -13.95
2
(t, J PH ) 33.1 Hz, 2 H, OsH2).
Cp *(P Me3)2OsSiMeCl2 (18). A flask charged with 7 (100
mg, 0.18 mmol) and excess HSiMeCl2 (ca. 3 mL) was sealed
with a Teflon stopcock and heated with stirring at 115 °C for
36 h, until the solution turned colorless. Removal of the
volatiles in vacuo and recrystallization of the resulting white
solid from CH2Cl2/Et2O at -35 °C gave white crystals of 18
(85 mg, 80%), mp >360 °C. Anal. Calcd for C17H36Cl2OsP2Si:
C, 34.51; H, 6.13. Found: C, 34.33; H, 6.12. 1H NMR: δ 1.64
(s, 15 H, C5Me5), 1.39 (s, 3 H, SiMe), 1.35 (fd, N ) 8.6 Hz, 18
Cp *(P Me3)2OsSiMe2OTf (24). To a cold (-35 °C), stirred
solution of 17 (150 mg, 0.26 mmol) in CH2Cl2 (3 mL) was added
Me3SiOTf (120 mg, 0.54 mmol). The mixture was allowed to
warm to room temperature and was then stirred for 2 h, during
which time the colorless solution turned light yellow. The
volatile components were removed, and the resulting residue
was recrystallized from a 1:1 mixture of CH2Cl2 and Et2O at
-35 °C to afford pure 24 as light yellow crystals (mp 190-
192 °C) in 81% yield (145 mg). Anal. Calcd for C19H39F3-
O3OsP2SSi: C, 33.32; H, 5.74. Found: C, 33.32; H, 5.75. 1H
NMR: δ 1.52 (s, 15 H, C5Me5), 1.22 (fd, N ) 8.2 Hz, 18 H,
2
H, PMe3). 31P{1H} NMR: δ -48.5 (1J OsP ) 272 Hz, J SiP ) 21
2
Hz). 13C{1H} NMR: δ 91.16 (t, J PC ) 1.6 Hz, C5Me5), 23.87
29
(vt, N ) 46.2 Hz, PMe3), 22.04 (s, SiMe), 11.47 (s, C5Me5).
-
PMe3), 0.98 (s, 6 H, SiMe2). 31P{1H} NMR: δ -49.6 (1J OsP
)
Si{1H} NMR: δ 41.19 (t, 2J SiP ) 24.4 Hz). IR: 2731 (m), 2719
(m), 1300 (m), 1280 (s), 1236 (w), 1028 (m), 848 (m), 789 (s),
719 (m), 669 (m).
2
267 Hz). 13C{1H} NMR: δ 90.29 (t, J PC ) 2.2 Hz, C5Me5),
24.22 (vt, N ) 46.5 Hz, PMe3), 13.12 (s, SiMe2), 11.36 (s,
2
C5Me5). 29Si{1H} NMR: δ 83.43 (t, J SiP ) 23 Hz). 19F{1H}
Cp *(P Me3)2OsSiCl3 (19). To a solution of 7 (48 mg, 0.085
mmol) in benzene (1 mL) was added excess HSiCl3 (0.2 mL,
2.0 mmol). The resulting mixture was heated in a closed
system (Teflon stopcock) at 110-115 °C for 16 days. The white
solid that precipitated out of the solution was filtered and dried
in vacuo. Recrystallization by slow diffusion of Et2O into a
concentrated CH2Cl2 solution at room temperature gave 20 mg
(38%) of pure 19 as white plates, mp >360 °C. Anal. Calcd
for C16H33Cl3OsP2Si: C, 31.40; H, 5.43. Found: C, 31.78; H,
5.36. 1H NMR: δ 1.61 (s, 15 H, C5Me5), 1.32 (fd, N ) 8.7 Hz,
18 H, PMe3). 31P{1H} NMR: δ -49.3. 13C{1H} NMR: δ 91.96
(s, C5Me5), 23.37 (vt, N ) 50.1 Hz, PMe3), 11.70 (s, C5Me5).
NMR (376.48 MHz): δ -14.8. IR: 2725 (w), 2675 (w), 1352
(s, ν(SO3)), 1300 (w), 1282 (m), 1236 (m), 1194 (s), 1151 (m),
1130 (w), 968 (s), 941 (s), 833 (m), 781 (w), 739 (w), 712 (m),
669 (m), 644 (m), 629 (s), 511 (w). IR (CH2Cl2): ν(SO3) 1352
(s). IR (CH3CN): ν(SO3) 1269 (s).
X-r a y Cr ysta l Str u ctu r e Deter m in a tion of 24. Yellow
blocklike crystals of 24 were obtained from a CH2Cl2/Et2O
solution at -35 °C. A single crystal was mounted on a glass
capillary using Paratone-N hydrocarbon oil. The data collec-
tion, reduction, and refinement were carried out as described
for 2‚C6H6. The cell parameters and data collection param-
eters are given in Table 3.
Cp *(P Me3)2OsSiMe[S(p-Tol)]2 (25). A mixture of 18 (58
mg, 0.098 mmol) and LiS(p-Tol) (40 mg, 0.31 mmol) in toluene
(2 mL) was heated with stirring at 50-55 °C for 8 h. Filtration
of the resulting mixture and removal of the volatiles in vacuo
left a yellow-white solid. Recrystallization of the solid by slow
diffusion of Et2O into a saturated CH2Cl2 solution gave
colorless crystals of 25 (50 mg, 67%), mp 185 °C dec. Anal.
Calcd for C31H50OsP2S2Si: C, 48.54; H, 6.57. Found: C, 48.13;
H, 6.55. 1H NMR: δ 7.38 (d, J ) 7.8 Hz, 4 H, ArH), 6.88 (d,
J ) 7.8 Hz, 4 H, ArH), 2.09 (s, 6 H, SC6H4Me), 1.92 (s, 15 H,
C5Me5), 1.45 (fd, N ) 7.7 Hz, 18 H, PMe3), 0.83 (s, 3 H, SiMe).
2
29Si{1H} NMR: δ -15.92 (t, J SiP ) 27.5 Hz). IR (CH2Cl2):
3801 (m), 2915 (m), 2073 (w), 1479 (w), 1375 (w), 1298 (m),
1030 (m), 958 (s), 944 (s), 858 (m), 673 (m).
Rea ction of Cp (P P h 3)2OsCH2SiMe3 (4) w ith HSiR2Cl
(R ) P h , Me). A mixture of 4 (20 mg, 0.023 mmol) and excess
silane (ca. 0.1 mL) in a Teflon-stoppered flask was heated at
80-85 °C for 12 h. Removal of the volatiles gave a pale-yellow
waxy solid. Cp(PPh3)Os(H)(SiPh2Cl)2 (20): 1H NMR δ 7.91
(m, 4 H, Ph), 7.44 (m, 5 H, Ph), 7.38 (m, 5 H, Ph), 7.23 (m, 6
H, Ph), 4.86 (s, 5 H, Cp), -10.65 (s, OsH). 31P{1H} NMR: δ
-2.16. Cp(PPh3)Os(H)(SiMe2Cl)2 (21): 1H NMR δ 4.76 (s, 5

Osmium Alkyl and Silyl Derivatives
Organometallics, Vol. 16, No. 20, 1997 4313
31P{1H} NMR: δ -51.0 (1J OsP ) 278 Hz). 13C{1H} NMR (CD2-
Cl2): δ 135.60, 135.43, 134.90, 128.81 (SC6H4Me), 91.75 (s, C5-
thank Prof. R. J . Angelici and Dr. Mary K. Rottink for
advice concerning the preparation of 1.
Me5), 24.43 (vt, N ) 47.9 Hz, PMe3), 21.07 (s, SC6H4Me), 12.20
2
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, collection, and refinement parameters, positional and
anisotropic displacement parameters, bond distances and
angles, and least-squares planes for 2‚C6H6, 13, and 24 (28
pages). Ordering information is given on any current mast-
head page.
(s, C5Me5), 10.29 (s, SiMe). 29Si{1H} NMR: δ 18.86 (t, J SiP
)
18.3 Hz). IR: 1294 (m), 1280 (m), 1234 (w), 1088 (w), 1018
(w), 854 (m), 841 (m), 806 (s), 779 (s), 763 (s), 708 (m), 667
(m).
Ack n ow led gm en t is made to the National Science
Foundation for their generous support of this work. We
OM9704197