Synthesis and reactivity of silyl and silylene ligands in the coordination sphere of the 14-electron fragment Cp*(iPr3P)Os +

Article abstract of DOI:10.1021/om040062o

Oxidative addition reactions of the 16-electron half-sandwich osmium complex Cp*(ⁱPr₃P)-OsBr (2) with SiH₄ and primary and secondary hydrosilanes were examined. Compared to the previously studied ruthenium complex Cp(ⁱPr₃P)RuCl (1), 2 exhibits a greater tendency to add hydrosilanes to afford stable, isolable silyl complexes. Using an abstraction-migration methodology, in which abstraction of a labile metal halide ligand is followed by 1,2-H migration from silicon to the metal center, new osmium silylene complexes were prepared. Thus, silyl complexes derived from 2 were combined with LiB(C₆F₅)₄ to afford cationic osmium silylene complexes of the type [Cp*( ⁱPr₃P)(H₂Os-SiRR][B(C₆F ₅)₄](R = aryl, silyl; R′ = aryl, H). The silylene complexes exhibit downfield ²⁹Si chemical shifts ranging from 316 ppm (R = 2,4,6-ⁱPr₃C₆H₂, R′ = H; 18) to 417 ppm (R = Si(SiMe₃)₃, R′ = H; 19). Complexes with a hydride substituent at silicon feature downfield shifts for this proton (e.g., 12.06 ppm for 19). The reaction of Cp*( ⁱPr₃P)Os(H)(Br)SiH₂SiPh₃ (11) with LiB(C₆F₅)₄ provided the unexpected rearrangement product [Cp*(ⁱPr₃P)(H) ₂Os=Si(Ph)SiPh₂H][B(C₆F₅) ₄] (22). Reaction of 2 with KB(C₆F₅) ₄ produced the metalated complex {Cp*[ⁱPr ₂P(η²-MeC=CH₂)]OsH₂}-[B(C ₆F₅)₄] (24), which was shown to act as a synthon for the 14-electron species Cp*(ⁱPr₃P)- Os⁺. Thus, 24 reacted with Ph₂SiH₂ to afford [Cp*(ⁱPr₃P)(H)₂Os=SiPh ₂][B(C₆F₅)₄] (14).

Full text of DOI:10.1021/om040062o

Organometallics 2004, 23, 5799-5812
5799
Synthesis and Reactivity of Silyl and Silylene Ligands in
the Coordination Sphere of the 14-Electron Fragment
Cp*(iPr3P)Os+
Paul B. Glaser† and T. Don Tilley*
Department of Chemistry and Center for New Directions in Organic Synthesis (CNDOS),
University of California, Berkeley, Berkeley, California 94720-1460
Received April 29, 2004
Oxidative addition reactions of the 16-electron half-sandwich osmium complex Cp*(iPr3P)-
OsBr (2) with SiH4 and primary and secondary hydrosilanes were examined. Compared to
the previously studied ruthenium complex Cp(iPr3P)RuCl (1), 2 exhibits a greater tendency
to add hydrosilanes to afford stable, isolable silyl complexes. Using an abstraction-migration
methodology, in which abstraction of a labile metal halide ligand is followed by 1,2-H
migration from silicon to the metal center, new osmium silylene complexes were prepared.
Thus, silyl complexes derived from 2 were combined with LiB(C6F5)4 to afford cationic osmium
silylene complexes of the type [Cp*(iPr3P)(H)2OsdSiRR′][B(C6F5)4] (R ) aryl, silyl; R′ ) aryl,
H). The silylene complexes exhibit downfield 29Si chemical shifts ranging from 316 ppm (R
) 2,4,6-iPr3C6H2, R′ ) H; 18) to 417 ppm (R ) Si(SiMe3)3, R′ ) H; 19). Complexes with a
hydride substituent at silicon feature downfield shifts for this proton (e.g., 12.06 ppm for
19). The reaction of Cp*(iPr3P)Os(H)(Br)SiH2SiPh3 (11) with LiB(C6F5)4 provided the
unexpected rearrangement product [Cp*(iPr3P)(H)2OsdSi(Ph)SiPh2H][B(C6F5)4] (22). Reaction
of 2 with KB(C6F5)4 produced the metalated complex {Cp*[iPr2P(η2-MeCdCH2)]OsH2}-
[B(C6F5)4] (24), which was shown to act as a synthon for the 14-electron species Cp*(iPr3P)-
Os+. Thus, 24 reacted with Ph2SiH2 to afford [Cp*(iPr3P)(H)2OsdSiPh2][B(C6F5)4] (14).
Introduction
action of organosilicon compounds with reactive transi-
tion metal centers.
Many important reactions of organosilanes, such as
the hydrosilylation of olefins,1,2 the Direct Process for
the synthesis of chlorosilanes,3 and Si-H/O-H cou-
pling,4,5 are promoted by transition metals. In the
future, it is expected that transition metal silicon
chemistry will play an even greater role in providing
useful routes to silicon-based compounds and materials.
Undoubtedly, this will require a better understanding
of possible reaction pathways resulting from the inter-
A primary mode of initial silane activation by a
transition metal complex involves the oxidative addition
of an Si-H bond to a coordinatively unsaturated metal
center to give a silyl hydride complex.6 Subsequent
reactions of the silyl hydride complexes with additional
substrates, or further rearrangements of the new silicon
ligand, may provide pathways to new products. In
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† Current address: General Electric Global Research, Niskayuna,
NY.
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10.1021/om040062o CCC: $27.50 © 2004 American Chemical Society
Publication on Web 10/29/2004

5800 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
studies on transition metal-mediated reactions of orga-
nosilanes, considerable speculation has centered on the
possible role of transition metal silylene complexes in
observed reactivity. Such silylene species have been
proposed as intermediates in processes such as the
redistribution of substituents on silicon,7 transfer of
silylene fragments to an unsaturated carbon-carbon
bond,8 and the Direct Process.3 Consequently, studies
with isolated silylene complexes should contribute
important information regarding their possible roles in
observed, metal-mediated transformations.
For the conversion of silyl to silylene complexes, two
reaction pathways have been observed. These are anion
metathesis, in which a labile substituent on silicon, such
as a halide, triflate, or thiolate, is replaced with a
noncoordinating anion (eq 1),9 and 1,2-migration of a
substituent, such a hydride, silyl, or alkyl group, from
silicon to an unsaturated metal center (eq 2).10,11
platinum complex (κ2-iPr2PCH2CH2PiPr2)Pt(Me)SiHMes2
afforded the cationic silylene complex [(κ2-iPr2PCH2-
CH2PiPr2)(H)PtdSiMes2][MeB(C6F5)3] via a 1,2 hy-
dride migration from silicon to the unsaturated metal
center.10a
While the synthesis of silylene complexes via multi-
step routes involving silyl complexes has provided
important data concerning the nature of these species,
synthesis of silylene complexes directly from silanes
remains an important goal. Furthermore, transforma-
tions of the latter type may play a role in the develop-
ment of new catalytic cycles involving silicon. In prin-
ciple, the activation of two Si-H bonds at a metal center
would seem to require a 14-electron metal fragment or
its synthetic equivalent (eq 3). Along these lines,
unsaturated iridium complexes have been employed in
the conversion of secondary silanes to silylene ligands
via two sequential Si-H bond activations.10b,c The future
development of this reactivity and its use in new
catalytic pathways is likely to hinge upon the avail-
ability of a range of metal species capable of activating
silanes in this manner.
Previous studies involving the coordinatively unsat-
urated ruthenium species Cp*(R3P)RuCl (R ) cyclo-
i
hexyl, Pr (1)) demonstrated that these complexes are
useful precursors to a variety of electron-rich silyl and
silene complexes.12 Similarly, preliminary investigations
with the related osmium complex Cp*(iPr3P)OsBr (2)
demonstrated that it also oxidatively adds small mol-
ecules such as H2 and PhSiH3 to form stable Os(IV)
species.13 The presence of a potentially labile bromide
substituent in complexes derived from 2 suggested the
use of the abstraction-migration route outlined above
for the generation of new osmium silylene complexes.
In particular, it seemed that the established ability of
electron-rich osmium fragments to stabilize unsaturated
ligands14-19 might facilitate the isolation of stable
silylene complexes. For this reason, we have begun to
explore the oxidative addition reactions of 2 with various
hydrosilanes and have investigated conversions of the
resulting osmium silyl derivatives to silylene complexes.
Generation of a 14-electron fragment of the type
Cp*(iPr3P)Os+, as a means to effect the direct conversion
of silanes to silylene ligands (eq 3), was also targeted.
The open coordination site required for the latter
pathway may be created by abstraction of an anionic
group from the metal center (path a),10a reductive C-H
bond elimination (path b),10b-e or ligand dissociation.11
For example, abstraction of the methyl ligand from the
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Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5801
Table 1. NMR Spectroscopic Data for Silyl Complexes 3-11
RSiH3
product
δ 1H (Si-H)
δ 29Si (Os-Si)
SiH4
Cp*(iPr3P)Os(H)(Br)SiH3
(3)
3.59
-73.0
-26.0
-49.9
-53.1
-53.0
-62.2
-30.5
-83.5
-78.3
PhSiH3
Cp*(iPr3P)Os(H)(Br)SiH2Ph
Cp*(iPr3P)Os(H)(Br)SiH2Mes
Cp*(iPr3P)Os(H)(Br)SiH2dipp
Cp*(iPr3P)Os(H)(Br)SiH2trip
Cp*(iPr3P)Os(H)(Br)SiH2(C6F5)
Cp*(iPr3P)Os(H)(Br)SiH2Hex
Cp*(iPr3P)Os(H)(Br)SiH2Si(SiMe3)3
Cp*(iPr3P)Os(H)(Br)SiH2SiPh3
(4)
6.60, 4.71
4.90, 4.90
5.05, 4.91
4.96, 4.83
5.49, 3.98
5.38, 4.39
5.12, 3.62
4.84, 3.19
MesSiH3
dippSiH3
tripSiH3
(C6F5)SiH3
HexSiH3
(Me3Si)3SiSiH3
Ph3SiSiH3
(5)
(6)
(7)
(8)
(9)
(10)
(11)
Results and Discussion
doublets (1JSiH ) 176 Hz, 2JSiH ) 10 Hz, 2JPSi ) 10 Hz)
conclusively demonstrated the presence of three intact
Si-H bonds in 3. The presence of diastereotopic methyl
groups on the PiPr3 ligand indicated that the complex
is stereochemically rigid on the NMR time scale at room
temperature. The osmium-bound hydride ligand exhib-
As described below, oxidative additions of hydrosi-
lanes to 2 are substantially more general in scope than
corresponding reactions of hydrosilanes with related
ruthenium species such as Cp*(iPr3P)RuCl (1). While
intermolecular oxidative addition reactions of hydrosi-
lanes with 1 are limited to primary silanes such as
PhSiH3 and MesSiH3,12 secondary silanes such as
Me2SiH2 and Ph2SiH2 add to 2 to form stable silyl
complexes (vida infra). The underlying reasons for this
observed difference in reactivity may include a higher
metal-silicon bond strength for the osmium complexes
and the greater stability of osmium(IV) versus analo-
gous ruthenium(IV) complexes.20
Reactions of 2 with Hydrosilanes. Despite being
the simplest hydrosilane, SiH4 has been employed in
few syntheses of transition metal silyl complexes.6a,21
The paucity of such reports may be attributed to the
difficulty in safely handling this pyrophorric reagent
and to the instability of the resulting products toward
further reactions.6a
2
its a JSiH coupling constant of 6.2 Hz, suggesting that
oxidative addition of the Si-H bond to osmium is
complete in 3 and that there are no “nonclassical”
interactions present.
Reactions of 2 with the primary silanes PhSiH3,
MesSiH3, dippSiH3 (dipp ) 2,4-iPr2C6H3), tripSiH3 (trip
) 2,4,6-iPr3C6H2), (C6F5)SiH3, HexSiH3, (Me3Si)3SiSiH3,
and Ph3SiSiH3 proceeded smoothly to afford the corre-
sponding Os(IV) silyl complexes 4-11 (eq 4, Table 1).
Exposure of a solution of 2 to an atmosphere of 15%
SiH4 in N2 resulted in immediate formation of the bright
yellow silyl complex Cp*(iPr3P)Os(H)(Br)SiH3 (3), which
was isolated as a yellow microcrystalline solid. When 2
was treated with excess SiH4 in an NMR tube at room
temperature, only 3 and unreacted SiH4 were observed.
The stability of the Si-H bonds in 3 to further oxidative
addition may be attributed to the steric protection
afforded by the Cp* and PiPr3 ligands. The bimetallic
complex Cp*(iPr3P)(H)(Br)Os(SiH2)Os(Br)(H)(PiPr3)Cp*,
in which two osmium centers are bridged by a single
silicon atom, would presumably be too sterically crowded.
A 1H-coupled 29Si INEPT NMR spectrum in which the
29Si resonance appeared as a quartet of doublets of
The complexes were isolated as moderately air-sensitive
yellow to yellow-orange microcrystalline solids. As
determined by NMR spectroscopy, yields were es-
sentially quantitative (>95%) in all cases. The most
important spectroscopic data for these complexes were
1
obtained from H and 29Si NMR spectroscopy. In each
case, the two silicon hydrides are rendered diaste-
reotopic by the chiral osmium center. Each complex
exhibits a single, upfield-shifted, 31P-coupled resonance
for the osmium hydride ligand. For silyl hydride com-
plexes of this type, the possibility exists for “nonclassi-
cal” hydrogen-silicon interactions. Species featuring
such interactions, including η2 silane complexes, often
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2
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Chem. Radiochem. 1982, 25, 1. (m) Lebuis, A. M.; Harrod, J. F. J.
Chem. Soc., Chem. Commun. 1998, 1089.
(15) (a) Bleeke, J. R. Chem. Rev. 2001, 101, 1205. (b) Elliott, G. P.;
Roper, W. R.; Waters, J. M. Chem. Commun. 1982, 811.
(16) (a) Bin Wen, T.; Zhou, Z. Y.; Jia, G. C. Angew. Chem., Int. Ed.
2001, 40, 1951. (b) Roper, W. R. Angew. Chem., Int. Ed. 2001, 40, 2440.
(17) (a) Baya, M.; Crochet, P.; Esteruelas, M. A.; Lopez, A. M.;
Modrego, J. Organometallics 2001, 20, 4291. (b) Puerta, M. C.; Valerga,
P. Coord. Chem. Rev. 1999, 195, 977. (c) Bin Wen, T.; Yang, S. Y.; Zhou,
Z. Y.; Lin, Z. Y.; Lau, C. P.; Jia, G. C. Organometallics 2000, 19, 3757.
(18) (a) Collins, T. J.; Roper, W. R.; Town, K. G. J. Organomet. Chem.
1976, 121, C41. (b) Clark, G. R.; Marsden, K.; Roper, W. R.; Wright,
L. J. J. Am. Chem. Soc. 1980, 102, 1206.
(19) (a) Collins, T. J.; Roper, W. R. Chem. Commun. 1976, 1044. (b)
Collins, T. J.; Roper, W. R. J. Organomet. Chem 1978, 159, 73.
(20) (a) Cotton, F. A.; Wilkinson, G. Advanced Inorganic Chemistry;
Wiley-Interscience: New York, 1980. (b) Sa´nchez-Delgado, R. A.;
Rosales, M.; Esteruelas, M. A.; Oro, L. A. J. Mol. Catal. A 1995, 96,
231.

5802 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
Scheme 1
observable, was found to be below 6 Hz. For example,
the value for 2JSiH is 5.3 Hz for 5 and is too small to be
resolved in 10.23 These low values are inconsistent with
a significant Si-H interaction.
Figure 1. ORTEP drawing of 4 with thermal ellipsoids
at the 50% probability level. Non-silicon-bound hydrogen
atoms are omitted for clarity. Selected bond lengths (Å)
and angles (deg) (Cp* ) C5Me5 centroid): Os-P 2.368(3),
Os-Br 2.568(1), Os-Si 2.398(3), Os-Cp* 1.9369(4)
Br-Os-P 86.51(7), Br-Os-Si 79.56(7), P-Os-Si
101.0(1), Si-Os-Cp* 120.58(8), P-Os-Cp* 136.29(7),
Br-Os-Cp* 112.15(3).
As previously reported,12b the reaction of 1 and
MesSiH3 afforded the chlorosilyl complex Cp*(iPr3P)(H)2-
RuSi(H)(Cl)Mes instead of a dihydridosilyl complex
analogous to 5. In this reaction, it appears that the
initial product Cp*(iPr3P)Ru(H)(Cl)RuSiH2Mes reduc-
tively eliminates MesSiH2Cl, which then adds to
Cp*(iPr3P)RuH to afford the observed product (Scheme
1). The observed difference in reactivity between 1 and
2 may be attributed to the inherently greater lability
of ruthenium complexes compared to analogous osmium
species and to the greater thermodynamic driving force
for the formation of a Si-Cl versus a Si-Br bond.
Reaction of (C6F5)SiH3 with 5 (2-fold molar excess,
CD2Cl2 solution) quantitatively afforded 8 after 7 h at
room temperature. This indicates that the oxidative
addition of MesSiH3 to 2 is reversible and that 8 is
thermodynamically more stable than 5.
Reactions of secondary silanes with 1 have so far not
provided isolable silyl complexes.12 For example, in the
presence of a large excess of Me2SiH2, 1 was found to
exist in rapid equilibrium with the corresponding oxida-
tive addition product, precluding isolation of the product
in this case.24
Figure 2. ORTEP drawing of 8 with thermal ellipsoids
at the 50% probability level. Non-silicon-bound hydrogen
atoms are omitted for clarity. Selected bond lengths (Å)
and angles (deg) (Cp* ) C5Me5 centroid): Cp*-Os
1.9379(1), Os-Si 2.389(2), Os-P 2.393(2), Os-Br 2.562-
(7), Cp*-Os-Br 112.87(2), Cp*-Os-Si 122.93(5),
Cp*-Os-P 134.41(4), P-Os-Si 101.46(6), P-Os-Br
85.47(4), Br-Os-Si 76.24(5).
In contrast to the behavior of 1 toward secondary
silanes, 2 reacts with Me2SiH2 and Ph2SiH2 to afford
Cp*(iPr3P)Os(H)(Br)SiMe2H (12) and Cp*(iPr3P)Os(H)-
(Br)SiPh2H (13), respectively, as isolable, crystalline
compounds. It is reasonable to assume that greater
Os-H and Os-Si bond strengths, as well as the stability
of the Os(IV) oxidation state, are responsible for this
pronounced difference in reactivity. The spectroscopic
properties of these complexes are similar to those
resulting from the oxidative additions of primary si-
lanes. In both 12 and 13, the two organic groups bound
to silicon are diastereotopic (by NMR spectroscopy).
The steric limitations of this oxidative addition are
reached with more bulky secondary silanes such as
with 2 to afford isolable silyl complexes. Consistent with
a steric explanation for this lack of reactivity, 2 was also
found to be unreactive toward tertiary hydrosilanes such
as Me3SiH and Et3SiH. Esteruelas and co-workers have
previously shown that upon loss of a phosphine ligand,
Cp(iPr3P)2OsCl adds Et3SiH and Ph3SiH, an observation
consistent with the smaller steric impact of the Cp
ligand versus Cp*.25
t
iPr2SiH2, Mes2SiH2, and Bu2SiH2, which do not react
X-ray Structures of Osmium Silyl Complexes.
Complexes 4, 8, 11, 12, and 13 were characterized by
X-ray crystallography (Figures 1-5). In each case, the
complex was found to adopt a geometry in which the
(22) (a) Schubert, U. Adv. Organomet. Chem. 1990, 30, 151. (b)
Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 35, 789. (c)
Dubberley, S. R.; Ignatov, S. K.; Rees, N. H.; Razuvaev, A. G.;
Mountford, P.; Nikonov, G. I. J. Am. Chem. Soc. 2003, 125, 642.
(23) A 29Si filtered 1H NMR spectrum showed that the coupling
present in this complex was on the order of the Os-H line width of 2
Hz.
(25) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.;
Ruiz, N. Organometallics 1999, 18, 5034.
(24) Glaser, P. B.; Tilley, T. D. Unpublished results.

Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5803
Figure 5. ORTEP drawing of one of the two similar
molecules of 13 in the asymmetric unit with thermal
ellipsoids at the 50% probability level. Non-silicon-bound
hydrogen atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg) (Cp* ) C5Me5 centroid): Cp*-
Os 1.9409(3), Os-Si 2.414(2), Os-P 2.382(2), Os-Br
2.5655(8), Cp*-Os-Si 111.63(2), Cp*-Os-Br 127.21(5),
Cp*-Os-P 135.56(5), P-Os-Si 94.78(7), P-Os-Br 85.83-
(5), Br-Os-Si 81.25(5).
Figure 3. ORTEP drawing of 11 with thermal ellipsoids
at the 50% probability level. Non-silicon-bound hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg) (Cp* ) C5Me5 centroid): Cp*-Os 1.9414(3),
Os-Si(1) 2.406(3), Os-P 2.382(3), Os-Br 2.567(1), Si(1)-
Si(2) 2.378(4), Cp*-Os-Si 110.26(3), Cp*-Os-Br 112.19-
(7), Cp*-Os-P 136.43(7), Os-Si(1)-Si(2) 126.1(1), P-Os-
Si 100.00(9), P-Os-Br 85.60(7), Br-Os-Si 80.01(7).
Osmium Silylene Complexes via 1,2-Hydrogen
Migrations. It was reasoned that abstraction of the
bromide substituent of an osmium silyl species might
promote a hydride migration process and allow access
to cationic osmium silylene complexes (Scheme 2).
Treatment of 13 with the anion metathesis reagent
LiB(C6F5)4‚3Et2O in CD2Cl2 afforded a product having
Cs symmetry (on the NMR time scale) and formulated
as the osmium dihydride silylene complex [Cp*(iPr3P)(H)2-
OsSiPh2][B(C6F5)4], as determined by 1H and 13C NMR
spectroscopy. A 29Si resonance could not be detected for
this species (23 °C, CD2Cl2 solution), possibly because
of a dynamic interaction with Et2O or LiBr in solution.
Such a process could dramatically broaden the 29Si
resonance of the silylene complex. Unfortunately, at-
tempts to separate the organometallic product from LiBr
and Et2O by crystallization or precipitation were unsuc-
cessful and resulted in either the recovery of starting
material or decomposition (apparently, small amounts
of Et2O efficiently solubilize LiBr in CH2Cl2 and fluo-
robenzene). Removal of volatile materials from reaction
mixtures containing Et2O under high vacuum and
subsequent workup afforded only impure products that
retained Et2O. This behavior contrasts with that of the
previously described bis-phosphine silylene complexes
[Cp*(Me3P)2MSiR2][B(C6F5)4] (M ) Ru, Os), which can
be recrystallized as base-free complexes from solutions
containing ethereal solvents.9h-j,l,m
Figure 4. ORTEP drawing of 12 with thermal ellipsoids
at the 50% probability level. Non-silicon-bound hydrogen
atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg) (Cp* ) C5Me5 centroid): Cp*-Os 1.9471(8),
Os-Si 2.431(6), Os-P 2.379(5), Os-Br 2.574(2), Cp*-Os-
Si 115.15(6), Cp*-Os-Br 126.7(1), Cp*-Os-P 130.6(1),
P-Os-Si 99.8(2), P-Os-Br 87.1(1), Br-Os-Si 78.6(2).
phosphine, hydride, bromide, and silyl substituents form
the “legs” of a “four-legged piano stool”, in which the
triisopropylphosphine and the silyl substituents are in
mutually transoid positions.26 Whereas the silyl groups
derived from primary silanes and small secondary
silanes can adopt a conformation in which steric inter-
actions with the Cp* and PiPr3 ligands are minimized,
this is not possible for large secondary or tertiary silyl
groups.
The bond lengths and angles for this series of com-
plexes are all relatively similar (Table 2). The Os-Si
bond lengths range from 2.389(2) Å in 8 to 2.431(6) Å
in 12.
Use of the ether-free borate reagent LiB(C6F5)4 fa-
cilitated preparation of the pure silylene complex
[Cp*(iPr3P)(H)2OsdSiPh2][B(C6F5)4] (14). In the ab-
sence of Et2O, LiBr precipitates from CH2Cl2 solution
and can be removed by filtration. The resulting complex
has effective Cs symmetry on the NMR time scale and
exhibits a single set of resonances for the triisopropyl-
phosphine methyl groups, one upfield resonance inte-
grating to two protons for two mutually transoid os-
mium hydrides, and a sharp, 31P-coupled 29Si resonance
2
at 313 ppm. The observed value for JSiH (5.5 Hz) is
inconsistent with a significant silicon-hydrogen inter-
action in 14.
Exhaustive attempts to crystallize 14 and the other
osmium silylene complexes described below were unsuc-
(26) The position of the osmium hydride ligand in these complexes
could not be reliably located by X-ray crystallography and is inferred
from the positions of the other ligands on osmium and by spectroscopic
measurements.

5804 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
Table 2. Selected Bond Lengths (Å) and Angles (deg) of Crystallographically Characterized Osmium Silyl
Complexes Derived from 1
4
8
11
12
13b
15
Cp*-Osa
1.9369(4)
2.398(3)
2.368(3)
2.568(1)
112.15(3)
120.58(8)
136.29(7)
101.0(1)
86.51(7)
79.56(7)
120.3(3)
1.9378(1)
2.389(2)
2.393(2)
2.5627(7)
112.87(2)
122.93(5)
134.41(4)
101.46(6)
85.47(4)
76.24(5)
118.3(2)
1.9414(3)
2.406(3)
2.382(3)
2.567(1)
110.26(3)
112.19(7)
136.43(7)
100.00(9)
85.60(7)
80.01(7)
126.1(1)c
1.9471(8)
2.431(6)
2.379(5)
2.574(2)
115.15(6)
126.7(1)
130.6(1)
99.8(2)
1.9409(3)
2.414(2)
2.382(2)
2.5655(8)
111.63(2)
127.21(5)
135.56(5)
94.78(7)
85.83(5)
81.25(5)
118.1(3)
116.7(3)
104.4(4)
1.9534(3)
2.412(2)
2.382(2)
2.5723(8)
111.45(2)
127.92(5)
134.76(5)
94.98(7)
86.34(5)
80.71(6)
118.7(3)
116.7(3)
103.2(4)
1.9348(3)
2.355(2)
2.358(2)
Os-Si
Os-P
Os-Br
Cp*-Os-Br
Cp*-Os-Si
Cp*-Os-P
P-Os-Si
P-Os-Br
Br-Os-Si
Os-Si-C
123.98(5)
131.72(4)
104.24(6)
87.1(1)
78.6(2)
116.6(7)
117.7(8)
103(1)
121.2(2)
119.9(2)
105.2(3)
C-Si-C
a Cp* ) C5Me5 centroid. b Two crystallographically independent molecules in the unit cell. c Os-Si-Si.
Scheme 2
cessful. Cooling concentrated CH2Cl2 or C6H5F solutions
failed to afford solid products, and various hydrocar-
bon-halocarbon and fluoroether-halocarbon solvent
mixtures led primarily to phase separation and pre-
cipitation of the products as viscous orange oils. Dif-
ficulties in crystallizing ionic species containing large,
-
very weakly coordinating anions such as B(C6F5)4
are often attributed to the low lattice energies of
such substances.27 Attempts to increase the crystallinity
of the silylene complexes by employing the {B[3,5-
(CF3)2C6H3]4}- anion were unsuccessful and led to
Figure 6. ORTEP drawing of 15 with thermal ellipsoids
at the 50% probability level. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg) (Cp*
) C5Me5 centroid): Cp*-Os 1.9348(3), Os-Si 2.355(2),
Os-P 2.358(2), Si-O(1) 1.847(5), Cp*-Os-Si 123.98(5),
Cp*-Os-P 131.72(4), P-Os-Si 104.24(6), Os-Si-O(1)
107.6(2).
decomposition. This anion is known to be more suscep-
-
tible than B(C6F5)4 to electrophilic attack by a Lewis
acidic silicon species.28
Removal of solvent from solutions of the silylene
complexes described here, including 14, afforded dark
yellow oils which solidified as foams after prolonged
exposure to vacuum. These foams tenaciously retained
small quantities of solvent, making combustion analyses
unreliable. The silylene complexes decomposed over the
course of days in the solid state to afford complicated
mixtures of products. For these reasons, the silylene
complexes (other than 18) were characterized in solution
using multinuclear NMR spectroscopy.
dinated to the silicon center both in CD2Cl2 solution,
as determined by NMR spectroscopy, and in the solid
state, as determined by X-ray crystallography (Figure
6). The Os-Si bond in 15 is significantly shorter than
the corresponding bond in 13 (Table 2), and the sum of
the Os-Si-C and the C-Si-C bond angles in 15 is
346.3° (for comparison, this sum is 339.2° for 13). These
observations are consistent with a greater amount of
silylene character at the silicon center of 15.
The reaction of 13 with AgOTf gave the silyltriflate
complex Cp*(iPr3P)(H)2OsSiPh2OTf (15; eq 5).
Silylene Complexes of the Type [Cp*(iPr3P)-
(H)2OsdSi(H)R]+. Silylene complexes derived from
dihydrosilyl derivatives, LnM-SiH2R, are of particular
interest, as silylene complexes possessing an Si-H bond
represent a very rare structure type with relatively
unexplored reactivity and spectroscopic properties.10b,29
In an attempt to synthesize a cationic silylene com-
plex of the type [LnMdSiH2]+, 3 was treated with
LiB(C6F5)4 in CD2Cl2. This reaction afforded a single
major product that featured resonances in the 1H NMR
spectrum consistent with a highly fluxional structure.
In contrast to the silylene complex [Cp*(Me3P)(H)-
IrSiMes2][OTf],9j the triflate group in 15 remains coor-
(27) (a) Bond, D. R.; Jackson, G. E.; Joao, H. C.; Hofmeyer, M. N.;
Modro, T. A.; Nassimbein, L. R. J. Chem. Soc., Chem. Commun. 1989,
1910. (b) Hunter, R.; Haueisan, R. H.; Irving, A. Angew. Chem., Int.
Ed. Engl. 1994, 33, 566. (c) Dioumaev, V. K.; Harrod, J. F. Organo-
metallics 1996, 15, 3859. (d) Lambert, J. B.; Zhao, Y.; Wu, H.; Tse, W.
C.; Kuhlmann, B. J. Am. Chem. Soc. 1999, 121, 5001.
(29) (a) Simons, R. S.; Gallucci, J. C.; Tessier, C. A.; Youngs, W. J.
J. Organomet. Chem. 2002, 654, 224. (b) Watanabe, T.; Hashimoto,
H.; Tobita, H. Angew. Chem., Int. Ed. 2004, 43, 218. (c) Mork, B. V.;
Tilley, T. D.; Schultz, A. J.; Cowan, J. A. J. Am. Chem. Soc. 2004, 126,
10428.
(28) (a) Kira, M.; Hino, T.; Sakurai, H. J. Am. Chem. Soc. 1992,
114, 6697. (b) Reed, C. A. Acc. Chem. Res. 1998, 31, 325.

Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5805
1
In the H NMR spectrum, the Cp* and PiPr3 peaks of
three resonances for the cation in 20, but the ortho-F
resonances are significantly broader than the meta and
para resonances. Fluorocarbons are known to be ex-
ceedingly poor hydrogen bond acceptors,31 but the close
proximity of the C6F5 group to the silicon-bound hydro-
gen, the relatively organized structure of 20, and the
inductive effect of the electrophilic silylene center on the
Si-H bond could favor an unusual interaction between
an ortho-fluorine and the silicon-bound hydrogen in 20.
Treatment of Cp*(iPr3P)Os(H)(Br)SiH2SiPh3 (11) with
LiB(C6F5)4 in CD2Cl2 afforded a single product display-
ing two equivalent osmium hydride resonances and a
single Si-H resonance having a chemical shift of 5.78
ppm, a value that would seem to be inconsistent with
an OsdSi(H)R+ structure. Furthermore, the 13C{1H}
NMR spectrum indicates that the SiPh3 group of the
starting material is not intact in the presumed silylene
product. A 29Si-1H HMQC NMR experiment demon-
strated that the hydrogen resonating at 5.78 ppm is
bound to the â-silicon in the product, instead of the
metal-bound silicon. It was therefore concluded that a
nascent silylene complex formulated as [Cp*(iPr3P)-
(H)2OsdSi(H)(SiPh3)][B(C6F5)4] (21) undergoes an isomer-
ization involving the exchange of a phenyl group with
the silylene hydrogen to afford [Cp*(iPr3P)(H)2Osd
Si(Ph)(SiPh2H)][B(C6F5)4] (22). Related 1,2-migrations
between silicon and electrophilic centers have been
previously observed and studied with theoretical meth-
ods.32 Reaction of 11 with LiB(C6F5)4 in the presence of
the strongly coordinating base 4-(dimethylamino)pyri-
dine (DMAP) afforded a single product that contained
an intact SiPh3 group and a single Si-H bond, as
determined by multinuclear NMR spectroscopy. This
new product was formulated as the “intercepted” si-
lylene complex [Cp*(iPr3P)(H)2OsdSi(H)(SiPh3)‚(DMAP)]-
[B(C6F5)4] (21‚DMAP) (Scheme 3). This product is not
formed upon reaction of 22 with DMAP.
the product are sharp, but the resonances associated
with the presumed SiH2 silylene group (δ(1H) ) 6.2
ppm) and the metal-bound hydride (δ(1H) ) -14.8 ppm)
were broad and featureless. A 29Si resonance could not
be detected for this species. The identities of the species
in solution are unclear, but low-temperature NMR data
are consistent with reversible aggregation to a low-sym-
metry complex tentatively formulated as {[Cp*(iPr3P)-
(H)2OsdSiH2][B(C6F5)4]}n (16).
Various reactions of LiB(C6F5)4 with Cp*(iPr3P)-
Os(H)(Br)SiH2R did not cleanly generate silylene com-
plexes when R ) Ph (4), Mes (5), or Hex (9). However,
reaction of LiB(C6F5)4 with silyl complexes possessing
more sterically demanding substituents on silicon af-
forded cationic osmium silylene species of the type
[Cp*(iPr3P)(H)2OsdSi(H)R][B(C6F5)4]. These silylene com-
plexes are distinguished by Cs symmetry on the NMR
time scale and downfield 29Si and 1H shifts for the
silylene center and the silicon-bound proton, respec-
tively. For example, for R ) trip (17), the Si-H
resonance appears at 11.56, and δ (29Si) ) 315 ppm.
These values parallel the downfield 13C and 1H chemical
shifts observed in metal carbene complexes of the type
MdC(H)R30 and reflect sp2 hybridization at silicon. As
demonstrated by 13C{1H} NMR spectroscopy, the large
aryl groups in 16 (R ) dipp) and 17 rotate freely about
their Si-C bonds, rendering the ortho-isopropyl methyl
groups equivalent on the NMR time scale.
The silylene complex derived from 9, [Cp*(iPr3P)-
(H)2OsdSi(H)Si(SiMe3)3][B(C6F5)4] (19; eq 6),
Upon monitoring the reaction of 11 with LiB(C6F5)4
in CD2Cl2 at low temperature by NMR spectroscopy, an
intermediate (23) was observed. This intermediate
reached a maximum concentration of approximately
70% after 2 min at 0 °C. Thereafter, the intensities of
the resonances associated with this species rapidly
decreased as the concentration of 22 increased. The
intermediate exhibited two inequivalent osmium hy-
dride resonances (δ(1Η) ) -13.97 and -14.37 ppm) and
exhibits a downfield 1H chemical shift for the Si-H
group at 12.05 ppm and a very downfield-shifted 29Si
resonance at 417.5 ppm. Surprisingly, the 1JSiH coupling
constant for 19 is 147 Hz, a value approximately 30 Hz
lower than the 1JSiH values in 9. The steric demands of
the Si(SiMe3)3 group bound to silicon should favor a
large Os-Si-Si angle in 19, which would, in turn,
decrease the amount of s-character in the Si-H bond,
causing a decreased value for 1JSiH. For comparison, the
1
a single broad Si-H peak at 5.98 ppm in its H NMR
spectrum. The observation of two inequivalent hydride
ligands in 23 suggests the presence of a chiral silicon
center bound to osmium. Thus, the conversion of 21 to
22 appears to proceed by the 1,2-migration of a phenyl
group from the â-silicon atom of 21 its silylene center
to generate 23. A 1,2 hydrogen migration would then
complete the formation of 22 (Scheme 3).
1
values for JSiH in 17 (188 Hz) and 18 (184 Hz) are
essentially identical to those in the corresponding silyl
complexes. It is interesting to note that the â-silicon
atom in 19 has a 29Si chemical shift of -74.9 ppm.
Consequently, 29Si chemical shifts spanning nearly 500
ppm are found in a single molecule.
Reaction of 8 with LiB(C6F5)4 in CD2Cl2 afforded
[Cp*(iPr3P)(H)2OsdSi(H)(C6F5)] [B(C6F5)4] (20), as de-
termined by NMR spectroscopy. While the 29Si reso-
nance of 20 appears at 318 ppm, the silicon-bound hy-
dride appears at only 6.75 ppm. The origin of the dis-
parity between the chemical shifts of the Si-H reso-
nances in 17-19 and that of 20 is not entirely clear.
The 29Si chemical shift of 20 is inconsistent with a four-
coordinate silicon center that might result from intra-
molecular donation by an aryl C-F group to the silylene
silicon center. The 19F NMR spectrum of 20 exhibits
A Metalated Triisopropylphosphine Complex
as a Formal Synthon for the 14-Electron Cation
(30) Crabtree, R. H. The Organometallic Chemistry of the Transition
Metals; Wiley: New York, 2001
(31) Plenio, H.; Diodone, R. Chem. Ber. 1997, 130, 633. (b) Plenio,
H.; Hermann, J.; Diodone, R. Inorg. Chem. 1997, 36, 5722. (c)
Takemura, H. J. Synth. Org. Chem., Jpn. 2002, 60, 963. (d) Mele, A.;
Vergani, B.; Viani, F.; Meille, S. V.; Farina, A.; Bravo, P. Eur. J. Org.
Chem. 1999, 187.
(32) (a) Apeloig, Y.; Stanger, A. J. Am. Chem. Soc. 1987, 109, 272.
(b) Cho, S. G. J. Organomet. Chem. 1996, 510, 25. (c) Lickiss, P. D In
The Chemistry of Organic Silicon Compounds; Patai, S., Rappoport,
Z., Eds.; J. Wiley and Sons: New York, 1998; Vol. 2, Chapter 11.

5806 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
Scheme 3
Figure 7. ORTEP drawing of 24 with thermal ellipsoids
at the 50% probability level. Hydrogen atoms and the
B(C6F5) counterion are omitted for clarity. Selected bond
lengths (Å) and angles (deg) (Cp* ) C5Me5 centroid, CC )
midpoint of C(17) and C(18)): Os-P 2.320(2), Os-Cp*
1.8958(3), Os-CC 2.0680(3), C(17)-C(18) 1.43(1), C(17)-
C(19) 1.49(1). Cp*-Os-P 134.02(5), Cp*-Os-CC 136.59-
(2), P-Os-CC 67.09(5), P-C(17)-C(18) 109.9(5), P-C(17)-
C(19) 126.0(6), C(18)-C(17)-C(19) 124.1(7).
Scheme 4
Cp*(iPr3P)Os+. As demonstrated by the studies de-
scribed above, coordinatively unsaturated osmium com-
plexes are potentially very useful in the synthesis of
silylene complexes. From the 16-electron complex 2,
silylene complexes are obtained in two steps involving
oxidative addition of a silane followed by a bromide
abstraction. In principle, the formally 14-electron com-
plex Cp*(iPr3P)Os+ could serve as a more direct precur-
sor to cationic [Cp*(iPr3P)(H)2OsdSiRR′]+ silylene com-
plexes via the double Si-H bond activation of a
hydrosilane (eq 3). To investigate a possible route to
Cp*(iPr3P)Os+ (or a synthon thereof), the metathesis of
the bromide in 2 with the noncoordinating B(C6F5)4
anion was attempted.
Reaction of 2 with 1 equiv of KB(C6F5)4 in THF/
CH2Cl2 afforded the unexpected cationic species
{Cp*[iPr2P(η2-MeCdCH2)]OsH2}[B(C6F5)4] (24; eq 7).
reported examples of metalated triisopropylphosphine
ligands have also been described as chelating R-al-
1
kenylphosphine ligands. The H NMR spectrum of 24
is consistent with its solid-state structure and features
two distinct osmium hydride resonances and five intact
and magnetically inequivalent isopropyl methyl groups.
Complex 24 was deprotonated with KN(SiMe3)2 to
afford the neutral, hydrocarbon-soluble species
Cp*[iPr2P(η2-MeCdCH2)]OsH (25; eq 8).
-
This reaction is conveniently carried out in benzene, a
solvent in which 24 forms a dense, insoluble oil and
KB(C6F5)4 is insoluble. Complex 25 is a viscous oil that
is exceedingly soluble in common solvents such as
hydrocarbons and Et2O, and for this reason, it could not
be crystallized. Thus, this compound was only charac-
terized by multinuclear NMR spectroscopy.
Although complexes 24 and 25 are both coordinatively
saturated 18-electron complexes, it was thought that
they might function as synthons for 14-electron
Cp*(iPr3P)Os+ via reductive elimination processes
(Scheme 4). In fact, the reaction of 24 with Ph2SiH2 in
CD2Cl2 at 80 °C in a sealed NMR tube for 48 h afforded
the diphenylsilylene complex 14 as the major component
of a mixture of products, as determined by NMR
spectroscopy (eq 9). Although the generation of 14 from
24 is a demonstration of double Si-H activation by a
Presumably, exchange of the bromide substituent with
the noncoordinating B(C6F5)4- anion affords a transient,
formally 14-electron intermediate Cp*(iPr3P)Os+, which
then activates two of the C-H bonds in the triisopro-
pylphosphine ligand (Scheme 4).33 The solid-state struc-
ture of 24 is shown in Figure 7. The metalated isopropyl
group is planar within error, indicating sp2 hybridiza-
tion of the phosphorus-bound carbon atom. Recently
(33) (a) Edwards, A. J.; Esteruelas, M. A.; Lahoz, F. J.; Lopez, A.
M.; Onate, E.; Oro, L. A.; Tolosa, J. I. Organometallics 1997, 16, 1316.
(b) Esteruelas, M. A.; Lopez, A. M.; Ruiz, N.; Tolosa, J. I. Organome-
tallics 1997, 16, 4657. (c) Esteruelas, M. A.; Lledo´s, A.; Maseras, F.;
Oliva´n, M.; On˜ate, E.; Tajada, M. A.; Toma`s, J. Organometallics 2003,
22, 2087. (d) Esteruelas, M. A.; Lledo´s, A.; Oliva´n, M.; On˜ate, E.;
Tajada, M. A.; Ujaque, G. Organometallics 2003, 22, 3753. (e) Baya,
M.; Buil, M. L.; Esteruelas, M. A.; On˜ate, E. Organometallics 2004,
23, 1416.

Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5807
Cp*(iPr3P)Os+ surrogate, the synthesis of 14 is ac-
complished more rapidly and with fewer byproducts
from the reaction of the isolable silyl complex 13 with
LiB(C6F5)4.
N2 atmosphere or in a Braun Uni-Lab drybox. Nondeuterated
solvents were distilled under N2 from appropriate drying
agents and stored in PTFE-valved flasks. Deuterated solvents
(Cambridge Isotopes) were dried with appropriate drying
agents, vacuum-transferred before use, and stored over mo-
lecular sieves.
Previously described methods were used to prepare
Cp*(iPr3P)OsBr,13 Li[B(C6F5)4]‚3Et2O,35 Cp*(iPr3P)Os(H)(Br)-
(SiH2Ph),13 (C6F5)SiH3,36 and KN(SiMe3)2.37 Both Li[B(C6F5)4]
and K[B(C6F5)4] were generous gifts of Boulder Scientific Co.
The silanes (Me3Si)3SiSiH3, Ph3SiSiH3, PhSiH3, dippSiH3, and
tripSiH3 were prepared by the LiAlH4 reduction of the corre-
sponding silyl chlorides.38 Liquid silanes were fractionally
distilled under N2 and stored over molecular sieves. Solid
silanes were recrystallized from Et2O and dried in vacuo.
Hexylsilane and Ph2SiH2 were purchased from Gelest Co.,
degassed, and stored over molecular sieves. Dimethylsilane
and 15% SiH4 in N2 were purchased from Gelest Co. and used
as received.
NMR spectra were acquired on a Bruker DRX-500 spec-
trometer equipped with a 5 mm BBI probe or a Bruker AVB-
400 spectrometer equipped with a 5 mm gradient BB probe.
Spectra were recorded at room temperature and were refer-
enced to protio-impurities in the deuterated solvent for 1H,
solvent peaks for 13C, CFCl3 for 19F, SiMe4 for 29Si, and 85%
H3PO4 for 31P. Multiplets that appear as virtual triplets or
quartets are denoted as “vt” or “vq”, respectively. Resonances
assignable to the B(C6F5)4 anion are not reported. When
necessary, DEPT and 1H-13C gHMQC detection schemes were
employed in the assignment of 13C and 1H resonances. The
gHMBC experiment used for 29Si detection has a nominal
resolution of approximately 1 ppm under standard conditions.
Combustion analyses were performed by the University of
California, Berkeley College of Chemistry Microanalytical
Facility.
Concluding Remarks
The 16-electron complex 2 is a useful starting precur-
sor to a series of stable osmium silyl complexes derived
from hydrosilanes. Compared to the similar ruthenium
complex 1, 2 reacts with a wider variety of silanes,
including secondary silanes such as Ph2SiH2 and
Me2SiH2. This enhanced reactivity is attributed to the
greater strength of bonds to osmium and the stability
of Os(IV) versus Ru(IV) in analogous complexes.
The successful reactions of LiB(C6F5)4 with these silyl
complexes to afford silylene complexes under relatively
mild conditions are examples of the utility of the
abstraction-migration route to silylene complexes. Since
the silyl complexes used in this method are derived from
relatively simple hydrosilanes, the abstraction-migra-
tion route for the synthesis of silylene complexes may
have greater versatility than previously employed routes
to silylenes that require more complex silicon starting
materials, such as alkylchlorohydridosilanes or thiola-
tosilanes. The successful preparation of a series of
complexes featuring the MdSi(H)R structural motif
should provide greater insight into the reactivity modes
of this class of silylene complexes.
Attempted generation of the 14-electron complex
Cp*(iPr3P)Os+ via reaction of KB(C6F5)4 with 2 in-
stead afforded the 18-electron complex {Cp*[iPr2P(η2-
MeCdCH2)]OsH2}[B(C6F5)4]. This complex features an
unusual orthometalated alkylphosphine ligand resulting
from the double C-H activation of an isopropyl group.
The complex was shown to slowly react with Ph2SiH2
to afford the diphenylsilylene complex 14, demonstrat-
ing the ability of a 14-electron synthon to convert
hydrosilanes directly to silylene ligands through double
Si-H activation. Improved understanding of the con-
version of hydrosilanes to silylenes may contribute to
the understanding of previously observed reactions
believed to operate through mechanisms including si-
lylene intermediates.
Cp*(iPr3P)Os(H)(Br)SiH3 (3). WARNING: At concentra-
tions of 15% in N2, SiH4 is pyrophoric and should only be
handled by qualified individuals with adequate safety precau-
tions in place. A heavy-walled 100 mL reaction vessel equipped
with an 8 mm PTFE valve and a 24/40 ground glass joint was
charged 312 mg of 2 and a small magnetic stirbar. The solid
was dissolved in approximately 15 mL of Et2O to afford a
purple solution. The vessel was attached directly to a Schlenk
line, and the solution was degassed through a series of freeze-
pump-thaw cycles. The vessel was then cooled to -78 °C and
charged with 1 atm of SiH4 (15% in N2). The color of the
vigorously stirred solution rapidly changed from purple to
orange. The cooling bath was removed, and the solution was
allowed to warm to room temperature. Stirring was continued
until the solution had become a uniform banana-yellow color
and a fine yellow precipitate had formed. Unreacted SiH4 was
then vented to the atmosphere with a N2 cross-purge and
allowed to inflame. The solution was stirred under an atmo-
sphere of N2 for an additional 10 min, and solvent was then
removed in vacuo. The powdery yellow residue was extracted
with two 5 mL portions of 3:1 Et2O/CH2Cl2. The combined
filtrates were cooled slowly to -80 °C over 16 h to afford well-
formed orange-yellow crystals (192 mg). Removing the solvents
from the filtrates afforded an additional 61 mg of analytically
pure 3 as a fine yellow powder. Yield: 253 mg (76%). 1H NMR
We are currently exploring the potential utility of
cationic silylene complexes of the type LnMdSi(H)R+ for
use as catalysts in a variety of organic transformations.
Initial results have shown that such silylene complexes
catalyze the selective hydrosilylation of alkenes by an
unexpected mechanism.34 It is hoped that new systems
can be identified in which double Si-H activation
processes are rapid enough for incorporation into useful
catalytic cycles.
1
(CD2Cl2, δ): 3.59 (s, 3 H, JSiH ) 174.6 Hz, OsSiH3), 2.51 (m,
3 H, P(CHMe2)3), 1.74 (d, 15 H, JPH ) 1.5 Hz, C5Me5), 1.12-
(35) Massey, A. G.; Park, A. J. J. Organomet. Chem. 1964, 2, 245.
(36) Molander, G. F.; Corrette, C. P. Organometallics 1998, 17, 5504.
(37) (a) Barash, E. H.; Coan, P. S.; Lobkovsky, E. B.; Streib, W. E.;
Caulton, K. G. Inorg. Chem. 1993, 32, 497. (b) Drouiche, Y.; Lickiss,
P. D. J. Organomet. Chem.1991, 407, 41.
Experimental Section
(38) Smit, C. N.; Bickelhaupt, F. Organometallics 1987, 6, 1156. (b)
Gutekunst, G.; Brook, A. G. J. Organomet. Chem. 1980, 225, 1. (c)
Campion, B. K.; Heyn, R. H.; Tilley, T. D. Organometallics 1993, 12,
2584. (d) Woo, H. G.; Freeman, W. P.; Tilley, T. D. Organometallics
1992, 11, 2198.
Manipulations involving air-sensitive compounds were con-
ducted using standard Schlenk techniques under a purified
(34) Glaser, P. B.; Tilley, T. D. J. Am. Chem. Soc. 2003, 125, 13640.

5808 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
1.20 (2 overlapping vq, 18 H, P(CHMe2)3), -15.35 (d, 1 H, 2JPH
) 32 Hz, OsH). 13C{1H} NMR (CD2Cl2, δ): 94.11 (d, JPH ) 2
Hz, C5Me5), 28.03 (d, 2JPH ) 27.1, P(CHMeMe)3), 20.28, 19.86
(P(CHMe2)3), 10.19 (C5Me5). 31P{1H} NMR (CD2Cl2, δ): 12.19.
NMR (CD2Cl2,δ): 4.0. Anal. Calcd for C34H62BrOsPSi: C,
51.04; H, 7.81. Found: C, 51.17; H, 7.70.
Cp*(iPr3P)Os(H)(Br)SiH2(C6F5) (8). To a stirred solution
of 2 (253 mg, 0.440 mmol) in CH2Cl2 (10 mL) was added 100
mg (0.505 mmol) of (C6F5)SiH3 in CH2Cl2 (approximately 5 mL)
by cannula, causing a rapid color change from purple to yellow-
orange. The volume of the solution was reduced by half, and
the flask was slowly cooled to -80 °C. After 24 h, well-formed
orange crystals of 8 had formed. These crystals were isolated
by filtration. Yield: 260 mg (77%). 1H NMR (CD2Cl2, δ): 5.48
1
29Si NMR (coupled INEPT, δ): -72.97 (qdd, JSiH ) 176 Hz,
2
2JSiH ) 10 Hz, JPSi ) 10 Hz). Anal. Calcd: C, 38.18; H; 6.75.
Found: C, 38.51; H, 6.98.
Cp*(iPr3P)Os(H)(Br)SiH2Mes (5). To a stirred solution of
500 mg (0.881 mmol) of 2 in approximately 25 mL of Et2O was
added slowly by cannula at room temperature 145 mg (0.97
mmol) of MesSiH3 in 10 mL of Et2O. The mixture’s color
quickly turned from purple to golden yellow-orange. The
solution was concentrated in vacuo to approximately 15 mL
and slowly cooled to -80 °C. After 1 day, a microcrystalline
precipitate had formed. The product was isolated by filtra-
tion and dried in vacuo. Yield: 475 mg (75%). 1H NMR
(CD2Cl2, δ): 6.78 (s, 2 H, aryl), 4.9 (br s, 2 H, 1JSiH ) 176 Hz,
SiH2Mes), 2.68 (s, 3 H, 4-Me), 2.52 (s, 6 H, 2,6-Me), 2.44 (m, 3
H, P(CHMe2)3), 1.63 (s, 15 H, C5Me5), 1.11-1.16 (vq, 9 H,
P(CHMeMe)3), 1.07-1.11 (vq, 9 H, P(CHMeMe)3), -15.04 (d,
1
(dd, 1 H, J ) 5 Hz, JSiH ) 200 Hz), 3.98 (dd, 1 H, J ) 5 Hz,
1JSiH ) 201 Hz), 2.06 (m, 3 H, P(CHMe2)3), 1.71 (s, 15 H,
C5Me5), 1.22-1.15 (2 overlapping vq, 18 H, P(CHMe2)3), -15.05
2
2
(d, 2 H, JPH ) 31.7 Hz, JSiH ) 5 Hz) Os(H)). 13C{1H} NMR
1
(CD2Cl2, δ): 95.1 (d, JPC ) 1 Hz, C5Me5), 27.9 (d, JPC
)
26.0 Hz, P(CHMe2)3), 20.21, 19.95 (P(CHMe2)3), 10.42 (C5Me5).
19F{1H} NMR (CD2Cl2, δ): -125.00 (m, o-C6F5), -155.85 (t,
p-C6F5), -62.89 (m, m-C6F5). 29Si{1H} NMR (INEPT, CD2Cl2,
δ): -62.2 (d, 2JPSi ) 13.5 Hz). 31P{1H} NMR (CD2Cl2, δ): 6.68.
Anal. Calcd for C25H39BrF5OsPSi: C, 39.31; H 5.15. Found:
C, 39.16; H, 5.20.
2
1 H, JPH ) 29.4 Hz, OsH). 13C{1H} NMR (CD2Cl2, δ): 144.5,
1
Cp*(iPr3P)Os(H)(Br)SiH2Hex (9). To a stirred solution of
2 (210 mg, 0.370 mmol) in C5H12 (10 mL) was added 52 mg
(0.447 mmol) of HexSiH3 in 20 mL of pentane. The solution
immediately became a golden yellow. The volume of the
solution was reduced to approximately 5 mL in vacuo, and the
reaction vessel was slowly cooled to -80 °C. After 24 h at -80
°C, a fine, yellow, microcrystalline precipitate had formed. This
product was isolated by filtration and dried in vacuo. Yield:
136.8, 136.5, 127.5 (aryl), 94.2 (C5Me5), 28.2 (d, JCP ) 25.8
2
Hz, P(CHMe2)3) 23.9, 20.7 (C6H2Me3), 19.8 (d, JCP ) 3.1 Hz,
P(CHMeMe)3), 19.7 (P(CHMeMe)3), 10.2 (C5Me5). 31P{1H} NMR
(CD2Cl2, δ): 3.9. 29Si{1H} NMR (CD2Cl2, HMBC, δ): -49.9 (d,
2JSiP ) 9.8 Hz). Anal. Calcd for C28H50BrOsPSi: C, 46.98; H,
7.04. Found: C, 47.29; H, 7.24.
Cp*(iPr3P)Os(H)(Br)SiH2dipp (6). To a stirred solution
of 175 mg (308 mmol) of 2 in approximately 25 mL of pentane
was added slowly by cannula at room temperature 61 mg (0.32
mmol) of dippSiH3 in 10 mL of pentane. The mixture’s color
quickly turned from purple to golden yellow-orange. The
solution was concentrated in vacuo to approximately 10 mL
and slowly cooled to -80 °C. After 1 day, a microcrystalline
precipitate had formed. The product was isolated by filtration,
washed with two 10 mL portions of pentane at -78 °C, and
dried in vacuo. Yield: 131 mg (56%). 1H NMR (CD2Cl2, δ): 7.20
(t, 1 H, 3JHH ) 8 Hz, p-aryl), 7.09 (d, 2 H, 3JHH ) 8 Hz, m-aryl),
1
1
148 mg (58%). H NMR (C6D6, δ): 5.38 (m, 1 H, JSiH ) 183
Hz, OsSiHH), 4.39 (m, 1 H, 1JSiH ) 167 Hz, OsSiHH), 2.48 (m,
3 H, P(CHMe2)3), 1.90 (m, 2 H, CH2), 1.69-1.58 (m, over-
lapping, 2 H, CH2), 1.42-1.36 (2 overlapping m, 4 H, CH2),
1.38-1.35 (overlapping m, 1 H, Si(H)2CHH), 1.18 (m, 1 H,
Si(H)2CHH), 1.09-1.02 (2 overlapping vq, P(CHMe2)3), 0.91
(t, 3JHH ) 7 Hz, CH2CH3), -15.36 (d, 2JPH ) 32.4 Hz, 1 H, OsH).
13C{1H} NMR (C6D6, δ): 93.64 (d, JCP ) 1.8 Hz, C5Me5), 33.69,
32.36, 31.27 (CH2), 28.01 (d, 1JCP ) 26.8 Hz, P(CHMe2)3), 23.18
(CH2), 20.36, 21.17, (P(CHMe2)3), 17.73 (SiH2CH2), 14.45,
(CH2Me), 10.44 (C5Me5). 31P{1H} NMR (CD2Cl2, δ): 8.50.
29Si{1H} NMR (CD2Cl2, δ): -30.49 (d, 2JPSi ) 9 Hz). Anal. Calcd
for C25H52BrOsPSi: C, 44.04; H, 7.69. Found: C, 44.17; H, 7.90.
Cp*(iPr3P)Os(H)(Br)SiH2Si(SiMe3)3 (10). To a solution
of 479 mg of 2 (0.844 mmol) in Et2O (15 mL) was added 239
mg (0.86 mmol) of (Me3Si)3SiSiH3 in 20 mL of Et2O by cannula,
causing a rapid color change from purple to yellow and the
precipitation of a microcrystalline solid. The heterogeneous
mixture was stirred for an additional 5 min and then allowed
to settle. The solid was collected by filtration and dried in
2
1
5.05 (d, 1 H, JHH) 4.8 Hz, JSiH ) 178 Hz, SiHH), 4.91 (d, 1
H, 2JHH ) 4.8 Hz, 1JSiH ) 181 Hz SiHH), 3.73 (sept, 2 H, 3JHH
) 7 Hz, m-CHMe2), 2.52 (m, 3 H, P(CHMe2)3, 1.68 (s, 15 H,
C5Me5), 1.26 (d, 12 H, 7 Hz, m-CHMe2), 1.21 (vq, 9 H,
P(CHMeMe)3, 1.09 (vq, 9 H, P(CHMeMe)3), -15.00 (d, 1 H,
2JPH ) 29.3 Hz, Os-H). 13C{1H} NMR (CD2Cl2, δ): 156.1
(m-aryl) 138.1, (ipso-aryl), 128.5, 122.0 (aryl), 94.6 (C5Me5),
33.4 (o-CHMe2), 28.7 (d, 1JPC ) 27 Hz, P(CHMe2)3) 25.3, 24.8
(o-CHMe2), 20.2, 20.0 (P(CHMe2)3), 10.8 (C5Me5). 29Si{1H} NMR
(CD2Cl2, δ): -53.1. 31P{1H} NMR (CD2Cl2, δ): 4.31. Anal. Calcd
for C31H56BrOsPSi: C, 49.12; H, 7.45. Found: C, 49.33; H, 7.65.
1
vacuo. Yield: 581 mg (81%). H NMR (C6D6, δ): 5.12 (s, 1 H,
Cp*(iPr3P)Os(Br)(H)SiH2trip (7). To a stirred solution of
600 mg (1.06 mmol) of 1 in approximately 25 mL of pentane
was added slowly by cannula at room temperature 367 mg
(1.48 mmol) of tripSiH3 in 10 mL of pentane. The mixture’s
color quickly turned from purple to golden yellow-orange. The
solution was concentrated in vacuo to approximately 10 mL
and slowly cooled to -80 °C. After 1 day, a microcrystalline
precipitate had formed. The product was isolated by filtration,
washed with two 10 mL portions of pentane at -78 °C, and
1
1JSiH ) 179 Hz, SiHH), 3.62 (s, 1 H, JSiH ) 171 Hz, SiHH),
2.41 (m, 3 H, P(CHMe2)3) 1.62 (s, 15 H, C5Me5), 1.05 (vq, 9 H,
P(CHMeMe)3), 0.98 (vq, 9 H, P(CHMeMe)3), 0.49 (s, 27 H,
2
Si(SiMe3)3, -14.91 (d, 1 H JPH ) 30.8 Hz). 13C{1H} NMR:
1
94.04 (C5Me5), 28.48 (d, JCP ) 28.1 Hz, P(CHMe2)3), 20.48,
20.34, (P(CHMe2)3), 11.08 (C5Me5), 3.49 (Si(SiMe3)3). 29Si NMR
2
(gHMBC, C6D6, δ): -8.3 (SiH2Si(SiMe3)3), -83.5 (d, JSiP
)
12 Hz, SiH2Si(SiMe3)3), -134.0 (SiH2Si(SiMe3)3). 31P{1H} NMR
(C6D6, δ): 8.81.
1
Cp*(iPr3P)Os(H)(Br)SiH2SiPh3 (11). To a solution of 143
mg of 2 (0.252 mmol) in toluene (10 mL) was added 75 mg
(0.253 mmol) of Ph3SiSiH3 in toluene (5 mL) by pipet, causing
a rapid color change from purple to yellow. The mixture was
concentrated in vacuo to a volume of approximately 10 mL,
layered with pentane (15 mL), and cooled to -80 °C, affording
a microcrystalline precipitate (60 mg), which was isolated by
filtration and dried in vacuo. Solvent was removed in vacuo
from the filtrate, affording an additional 60 mg of 11 as an
analytically pure, fine yellow powder. Yield: 120 mg (55%).
1H NMR (CD2Cl2, δ): 7.64 (m, 6 H, o-Ph), 7.32 (m, 9 H, p- and
dried in vacuo. Yield: 715 mg (85.1%). H NMR (CD2Cl2, δ):
6.92 (s, 2 H, aryl H), 4.96 (d, 1 H, 2JHH ) 4 Hz, 1JSiH ) 178 Hz,
Os-SiH), 4.83 (d, 1 H 2JHH ) 4 Hz, 1JSiH ) 179 Hz, Os-SiH),
3.70 (sept, 2 H, 3JHH ) 7 Hz, CHMe2), 2.82 (sept, 1 H, 3JHH
7 Hz, CHMe2), 2.46 (m, 3 H, P(CHMe2)3), 1.64 (d, 15 H, JPH
)
)
0.8 Hz, C5Me5), 1.23 (d, 12 H, 3JHH ) 7 Hz, CHMe2), 1.21 (d, 6
3
H, JHH ) 7 Hz, CHMe2), 1.16 (vq, 9 H, P(CHMeMe)3) 1.03
(vq, 9 H, P(CHMeMe)3), -15.07 (d, 1 H, 2JPH ) 29.4 Hz, OsH).
13C{1H} NMR: 155.6, 148.5, 134.4, 119.7 (Ar), 94.1 (d, C5Me5,
1
2JPC ) 2.5 Hz), 34.19, 32.98, (CHMe2) 28.32 (d, JC-P ) 23.5
Hz, P(CHMe2)3), 24.90, 24.39, 23.79, 23.70, 19.73, 19.50
(CHMe2), 10.29 (C5Me5). 29Si NMR (CD2Cl2,δ): -53.0. 31P{1H}
m-Ph), 4.84 (s, 1 H, JSiH ) 178 Hz, SiHH), 3.19 (s, 1 H, JSiH
1
1

Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5809
) 164 Hz, SiHH), 2.31 (m, 3 H, P(CHMe2)3), 1.59 (d, 15 H,
JPH ) 0.5 Hz, C5Me5), 1.06 (vq, 9 H, P(CHMeMe)3), 0.94 (vq,
solution. Volatile components of the mixture were removed in
vacuo to afford a yellow-orange foam. NMR spectroscopy
showed that the desired product was consistently contami-
nated with varying amounts (5-20%) of a second, unidentified
species and unreacted starting material that was not removed
by crystallization from pentane/Et2O. Employing a molar
excess of AgOTf (1.25 equiv) in the reaction did not in-
crease the proportion of 15 in the product mixture. 1H
2
9 H, P(CHMeMe)3), -14.66 (d, 1 H, JPH ) 31 Hz, Os-H).
13C{1H} NMR (CD2Cl2, δ): 138.9 (ipso-C), 136.4, 128.3, 127.4
1
(aryl), 94.53 (C5Me5), 28.73 (d, JCP ) 26.7 Hz, P(CHMe2)3),
19.82, 19.64 (P(CHMe2)3), 9.92 (C5Me5). 29Si NMR (gHMBC,
2
CD2Cl2, δ): -78.3 (d, JSiP ) 9 Hz, Os-SiH2SiPh3), -21.0
(Os-SiH2SiPh3). 31P{1H} NMR (CD2Cl2, δ): 10.10. Anal.
Calcd: C, 51.91; H, 6.36. Found: C, 52.63; H, 6.46.
3
NMR (C6D6, δ): 8.17 (d, 4 H, JHH ) 7 Hz, o-aryl), 7.29 (m,
3
Cp*(iPr3P)Os(H)(Br)SiMe2H (12). A solution of 113 mg
(0.199 mmol) of 2 in Et2O (15 mL) was degassed with a freeze-
pump-thaw cycle. An atmosphere of Me2SiH2 was admitted
to the reaction flask, causing the stirred solution to change
immediately from a purple to a yellow color. The volatile
components of the mixture were removed in vacuo to afford
12 as an analytically pure yellow-orange foam. Yield: 125 mg
4 H, JHH ) 7 Hz, m-aryl), 7.16 (m, 2 H, p-aryl), 1.61 (m,
3 H, P(CHMe2)3) 1.59 (s, 15 H, C5Me5), 0.87 (vq, 18 H,
2
P(CHMe2)3), -14.34 (d, 2 H, JPH ) 28 Hz, OsH). 31P{1H}
NMR (C6D6, δ): 30.0. 29Si{1H} NMR (CD2Cl2, δ): 64.1 (d, 2JPSi
) 24.6 Hz).
{[Cp*(iPr3P)(H)2OsdSiH2][B(C6F5)4]}n (16). To a CD2Cl2
solution (1 mL) of 3 (20 mg, 33 µmol) was added 1.1 equiv of
LiB(C6F5)4 (25 mg, 36 µmol) in CD2Cl2 by pipet, causing a color
change from golden yellow to lemon yellow and the formation
of a fine white precipitate. The mixture was allowed to stand
for 30 min and was filtered through a fine glass fiber, affording
a clear yellow solution. 1H NMR spectroscopy showed 16 to
be the major (>95%) product in solution. NMR (1H, CD2Cl2,
δ): 6.2 (br s, LW ) 500 Hz, fwhh), 1.79 (m, 3 H, P(CHMe2)3),
1.77 (s, 15 H, C5Me5), 0.87 (vq, 18 H, P(CHMe2)3), -14.77 (br
s, LW ) 100 Hz, fwhh, 2 H, OsH). 31P{1H} (CD2Cl2, δ): 32.5
(LW ) 150 Hz, fwhh).
1
1
(92%). H NMR (C6D6, δ): 6.16 (m, 1 H, JSiH ) 178 Hz, SiH)
2.41 (m, 3 H, P(CHMe2)3), 1.56 (d, 15 H, J ) 1 Hz, C5Me5),
1.03 (vq, 9 H, P(CHMeMe)3), 1.07 (vq, 9 H, P(CHMeMe)3), 0.93
3
3
(d, 3 H, JHH ) 4 Hz, Si(H)MeMe), 0.91 (d, 3 H, JHH ) 4 Hz,
Si(H)MeMe), -15.23 (d, 1 H, 2JPH ) 31.9 Hz, Os-H). 1H NMR
(CD2Cl2, δ): 5.50 (m, 1 H, 1JSiH ) 178 Hz, SiH), 2,48 (m, 3 H,
P(CHMe2)3), 1.74 (d, 15 H, J ) 1 Hz, C5Me5), 1.22-1.16, (2
overlapping vq, 18 H, (P(CHMe2)3). 0.49 (d, 3 H, 3JHH ) 4 Hz,
3
Si(H)MeMe), 0.39 (d, 3 H, JHH ) 4 Hz, Si(H)MeMe), -15.24
(d, 1 H, 2JPH ) 31.7 Hz, OsH). 13C{1H} NMR (CD2Cl2, δ): 94.06
1
[Cp*(iPr3P)(H)2OsdSi(H)dipp][B(C6F5)4] (17). To
a
(C5Me5), 28.16 (d, JPC ) 26.5 Hz), 20.74, 20.48 (P(CHMe2)3),
10.94 (C5Me5), 4.26, 0.94 (SiMe2). 31P{1H} NMR (CD2Cl2, δ):
5.66. 29Si{1H} NMR (CD2Cl2, HMBC, δ): -23.9. Anal. Calcd:
C, 40.31, H 7.09. Found: C 40.44; H, 7.24
CD2Cl2 solution (1 mL) of 6 (31 mg, 40 µmol) was added
LiB(C6F5)4 (30 mg, 44 µmol) in 0.75 mL of CD2Cl2 by pipet,
causing a color change from golden yellow to lemon yellow and
the formation of a fine white precipitate. The mixture was
allowed to stand for 30 min and was then filtered through a
fine glass fiber, affording a clear yellow solution. NMR
spectroscopy showed 17 to be the major (>95%) product in
Cp*(iPr3P)Os(H)(Br)SiPh2H (13). To a stirred solution of
452 mg of 2 in pentane (40 mL) was added 157 mg (0.853
mmol) of Ph2SiH2 in pentane (5 mL) by cannula, causing a
rapid color change from purple to yellow. The solution was
filtered, concentrated to 2/3 its original volume, and cooled to
-80 °C, affording a microcrystalline solid. Yield: 375 mg
(78%). IR: νSiH 2080 cm-1, νOsH 2199 cm-1. 1H NMR (C6D6, δ):
1
1
solution. H NMR (CD2Cl2, δ): 11.61 (s, 1 H, JSiH ) 188 Hz
OsSi(H)), 7.35 (t, 1 H, 3JHH ) 8 Hz, p-aryl), 7.26 (d, 2 H, 3JHH
) 8 Hz, m-aryl), 2.73 (sept, 2 H, JHH ) 6.4 Hz, m-CHMe2),
3
3
3
8.11 (d, 2 H, JHH ) 7.8 Hz, o-Ph), 8.07 (d, 2 H, JHH ) 7.8
Hz, o-Ph), 7.31-7.17 (m, overlapping, 9 H, aryl, SiH), 2.38 (m,
3 H, P(CHMe2)3), 1.47 (s, 15 H, C5Me5), 1.04 (vq, 9 H,
P(CHMeMe)3), 0.87 (vq, 9 H, P(CHMeMe)3), -14.15 (d, 1 H,
2JPH ) 32 Hz, OsH). 13C{1H} NMR (CD2Cl2, δ): 145.7, 144.6,
137.4, 137.2, 127.4, 127.3, 127.0, 126.6 (aryl), 94.96 (C5Me5)
28.28 (d, 1JPC ) 26.6 Hz, P(CHMe2)3), 20.48, 20.33 (P(CHMe2)3),
10.76 (C5Me5). 31P{1H} NMR (CD2Cl2, δ): 3.79. 29Si{1H} NMR
2.07 (m, 3H, P(CHMe2)3), 2.04 (s, 15 H, C5Me5), 1.34 (d, 12 H,
3JHH ) 6.4 Hz, m-CHMe2), 1.14 (vq, 18 H, P(CHMe2)3), -12.72
(d, 2 H, 2JPH ) 27.9 Hz, Os-H). 13C{1H} NMR (CD2Cl2, δ):
151.2, 136.5, 133.1 123.3 (aryl), 97.4 (C5Me5), 37.4 (m-CHMe2),
1
28.3 (d, JCP ) 29 Hz, P(CHMe2)3), 24.1 (m-CHMe2), 18.6
((P(CHMe2)3), 10.89 (C5Me5). 29Si{1H} NMR (CD2Cl2, δ): 314
2
(d, JSiP ) 15 Hz). 31P{1H} NMR (CD2Cl2, δ): 32.4.
[Cp*(iPr3P)(H)2OsdSi(H)trip][B(C6F5)4] (18). To a solu-
tion of 310 mg (0.387 mmol) of 7 in 10 mL of fluorobenzene
was added a solution of 275 mg (0.401 mmol) of Li[B(C6F5)4]
in 10 mL of fluorobenzene. The solution immediately turned
from golden yellow-orange to pale lemon yellow. A fine white
precipitate formed at the same time. The mixture was filtered
and the volatile material was removed in vacuo to afford a
pale yellow foam, which was then dried in vacuo. Yield: 373
mg (73%). 1H NMR (CD2Cl2, δ): 11.56 (s, 1 H, 1JSiH ) 183 Hz,
OsdSi(H)trip), 7.06 (s, 2 H, Ar), 2.92 (sept, 1 H, 3JHH ) 7 Hz,
CHMe2), 2.72 (sept, 2 H, 3JHH ) 7 Hz, CHMe2), 2.0-2.1 (m, 3
2
(CD2Cl2, δ): -10.65 (d, JSiP ) 9 Hz). Anal. Calcd: C, 49.65;
H, 6.45. Found: C, 49.47; H, 6.48.
[Cp*(iPr3P)(H)2OsdSiPh2][B(C6F5)4] (14). To a CD2Cl2
solution (1 mL) of 13 (25 mg, 33 µmol) was added 1.1 equiv of
LiB(C6F5)4 (26 mg, 38 µmol) in CD2Cl2 (0.75 mL) by pipet,
causing a color change from golden yellow to lemon yellow and
the formation of a fine white precipitate. The mixture was
allowed to stand for 30 min and was then filtered through a
fine glass fiber, affording a clear yellow solution. NMR
spectroscopy showed 14 to be the major (>95%) product in
3
3
solution. 1H NMR (CD2Cl2, δ): 7.86 (d, 4 H, o-Ph, JHH ) 7
H, P(CHMe2)3), 2.04 (s, 15 H, C5Me5), 1.34 (d, 12 H, JHH ) 7
Hz), 7.67 (t, 2 H, p-Ph, 3JHH ) 8 Hz), 7.61 (m, 4 H, m-Ph), 2.07
(s, 15 H, C5Me5), 1.88 (m, 3 H, P(CHMe2)3), 1.05 (vq, 18 H,
Hz, CHMe2), 1.25 (d, 6 H, JHH ) 7 Hz, CHMe2), 1.13 (vq, 18
3
2
2
H, P(CHMe2)3), -12.74 (d, 2 H, JPH ) 27 Hz, JSiH ) 5.5 Hz
2
P(CHMe2)3) -11.65 (d, 2 H, JPH ) 28.4 Hz, Os(H)2). 13C{1H}
Os-H). 13C{1H} NMR (CD2Cl2, δ): 155.3, 151.8, 134.2, 121.9
2
NMR: 143.0, 136.2, 133.8, 128.7 (aryl), 96.1 (C5Me5), 28.8 (d,
(Ar), 97.81 (d, C5Me5, JPC ) 2.5 Hz), 37.86, 35.06 (CHMe2),
1JCP ) 30 Hz, (P(CHMe2)3), 19.33 (P(CHMe2)3, 11.34 (C5Me5).
28.79 (d, JCP ) 30.0 Hz, P(CHMe2)3), 24.57, 23.94, 19.08
1
2
29Si NMR (INEPT, CD2Cl2, δ): 313.6 (d, JSiP ) 7 Hz).
(CHMe2), 11.31 (C5Me5). 29Si (HMBC expt, CD2Cl2, δ): 315 (dd,
2JSiP ) 13.6 Hz, 2JSiH ) 5.5 Hz). 31P{1H} NMR (CD2Cl2, δ): 32.5.
Anal. Calcd for C58H62BF20OsPSi: C, 49.79; H, 4.47. Found:
C, 50.04; H, 4.31.
31P{1H} NMR (CD2Cl2, δ): 39.6.
Cp*(iPr3P)Os(H)2SiPh2OTf (15). To a stirred pentane
solution of 324 mg (0.394 mmol) of 13 cooled in a CO2/iPrOH
bath was added slowly an Et2O (25 mL) solution of 114 mg
(0.445 mmol) of AgOTf by cannula. The reaction vessel was
protected from light and allowed to slowly come to room
temperature. After 3 h, a dark, extremely fine precipitate had
formed. The solution was filtered through a combination of
Whatman #50 paper and glass fiber to afford an orange
[Cp*(iPr3P)(H)2OsdSi(H)Si(SiMe3)3][B(C6F5)4] (19). To a
CD2Cl2 solution (0.75 mL) of 10 (28 mg, 33 µmol) was added
LiB(C6F5)4 (25 mg, 36 µmol) in CD2Cl2 (0.75 mL) by pipet,
causing a color change from golden yellow to lemon yellow and
the formation of a fine white precipitate. The mixture was
allowed to stand for 30 min and was then filtered through a

5810 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
fine glass fiber, affording a clear yellow solution. NMR
slowly to -80 °C, affording a crop of well-formed taupe crystals.
1
spectroscopy showed 19 to be the major (>95%) product in
Yield: 540 mg (46%). H NMR (CD2Cl2, δ): 3.12 (d, 1 H, JPH
1
2
solution. H NMR (CD2Cl2, δ): 12.05 (t, 1 H, JHH ) 2.5 Hz,
) 35 Hz, MeCdCHH), 2.54 (d, 3 H, JPH ) 8 Hz, MeCdCHH),
2.37 (m, 1 H, P(CHMe2)), 2.24 (s, 15 H, C5Me5), 2.24 (d,
overlapping, 1 H, JPH ) 12 Hz, MeCdCHH), 1.60-1.53 (3
overlapping vq, 9 H, P(CHMeMe)), 1.55-1.52 (m, overlapping,
1 H, P(CHMe2), 1.41 (vq, 3 H, P(CHMeMe), -13.74 (d, 1 H,
1JSiH ) 147.6 Hz, OsSiH), 2.18 (s, 15 H, C5Me5) 1.76 (m, 3 H,
2
P(CHMe2)3), 1.22 (vq, 18 H, P(CHMe2)3) 0.40 (s, JSiH ) 5.9
2
Hz, 27 H, Si(SiMe3)3), -9.90 (d, JPH ) 27.5 Hz, OsH).
13C{1H} NMR (CD2Cl2, δ): 96.43 (C5Me5), 31.07 (d, JPH ) 29
1
2
2
Hz, P(CHMe2)3), 19.45 (P(CHMe2)3), 12.17 (C5Me5), 3.20 (SiMe3).
29Si NMR (HMBC): 417.5 (d, 2JPSi ) 9 Hz, OsSi(H)Si(SiMe3)3),
-5.9 (OsSi(H)Si(SiMe3)3), -74.9 (OsSi(H)Si(SiMe3)3). 31P{1H}
NMR (CD2Cl2): 40.88.
OsH, JPH ) 23.1 Hz), -15.10 (d, 1 H, OsH, JPH ) 20.6 Hz).
13C{1H} NMR (CD2Cl2, δ): 98.28 (C5Me5), 57.79 (d, 2JPH ) 20.3
Hz, MeCdCH2), 33.42 (d, 2JPH ) 37.5 Hz, P(CHMe2), 32.70 (s,
MeCdCH2), 26.55 (s, MeCdCH2 ), 24.92, 22.55 (s, P(CHMeMe),
2
[Cp*(iPr3P)(H)2OsdSi(H)(C6F5)][B(C6F5)4] (20). To a
CD2Cl2 solution (0.75 mL) of 8 (22 mg, 29 µmol) was added
LiB(C6F5)4 (22 mg, 32 µmol) in CD2Cl2 (0.75 mL) by pipet,
causing a color change from golden yellow to lemon yellow and
the formation of a fine white precipitate. The mixture was
allowed to stand for 30 min and filtered through a fine glass
fiber, affording a clear yellow solution. NMR spectroscopy
showed 20 to be the major (>95%) product in solution. 1H
22.08 (d, JPH ) 22.3 Hz, P(CHMe2)), 19.81, 18.73 (s,
P(CHMeMe), 11.73 (s, C5Me5). 31P{1H} NMR (CD2Cl2, δ):
-4.62. Anal. Calcd: C, 44.34; H, 3.12. Found: C, 44.06; H,
3.29.
Cp*[iPr2P(η2-MeCdCH2)]OsH (25). A 468 mg (0.377
mmol) sample of 9 was treated with 10 mL of C6H6, affording
a dense, mobile oil at the bottom of the vessel. The mixture
was stirred, forming a heterogeneous suspension. This suspen-
sion was treated with KN(SiMe3)2 (80 mg, 0.40 mmol) in C6H6
(30 mL). The solution rapidly became homogeneous as the
cationic species reacted, and a white precipitate, presumably
KB(C6F5)4, formed. The solution was allowed to settle and was
filtered to afford a pale yellow solution. Removal of solvent
from the filtrate afforded a dense, gelatinous oil that did not
solidify upon prolonged exposure to vacuum or treatment with
pentane. Attempts to isolate this compound as a solid suitable
for elemental analysis were unsuccessful. NMR tube reactions
and spectroscopy of the viscous oil both demonstrated that 25
is formed in greater than 95% yield from 24 in C6D6. 1H NMR
(C6D6, δ): 2.27 (m, 1 H, MeCdCHH), 2.05 (s, 15 H C5Me5),
1.98 (m, 1 H, MeCdCHH), 1.71 (m, 1 H, P(CHMe2)), 1.56 (m,
1
NMR (CD2Cl2, δ): 6.75 (br s, 1 H, JSiH ) 185 Hz), 1.92-2.20
(m, 3 H, P(CHMe2)3), 2.05 (s, 15 H, C5Me5), 1.08-1.18 (vq, 18
2
H, P(CHMe2)3), -14.09 (d, JPH ) 27.9 Hz). 13C{1H} NMR:
1
95.50 (C5Me5), 28.95 (d, JPC ) 27.7 Hz, P(CHMe2)3), 18.92
(P(CHMe2)3), 11.20 (C5Me5). 19F{1H} NMR: -128.8 (br, o-C6F5),
-150.9, 160.8, (C6F5). 29Si NMR (HMBC expt, CD2Cl2, δ): 318
br. 31P{1H} NMR (CD2Cl2, δ): 29.9.
[Cp*(iPr3P)(H)2OsdSi(H)SiPh3‚DMAP][B(C6F5)4] (21‚
DMAP). To a CD2Cl2 solution (1 mL) of 11 (19 mg, 22 µmol)
and DMAP (3 mg, 25 µmol) was added a CD2Cl2 solution (0.75
mL) of LiB(C6F5)4 (17 mg, 25 µmol) by pipet, causing a color
change from golden yellow to very pale yellow and the
formation of a fine white precipitate. The mixture was allowed
to stand for 30 min and was then filtered through a fine glass
fiber, affording a clear yellow solution. NMR spectroscopy
showed 21‚DMAP to be the major (>95%) product in solution
3
3 H, P(CHMe2)), 1.52 (d, 3 H, JPH ) 6 Hz, MeCdCHH), 1.19
(vq, 3 H, P(CHMeMe)), 1.11 (vq, 1 H, P(CHMeMe)), 0.91-0.85
(2 overlapping vq, 6 H, P(CHMeMe), -16.18 (dd, 1 H JHH ) 8
with excess DMAP. 1H NMR (CD2Cl2, δ): 7.81 (d, 2 H, 3JHH
)
2
Hz, JPH ) 26 Hz, OsH). 13C{1H} NMR (C6D6, δ): 88.11 (d,
1
7.5 Hz, DMAP) 7.46 (m, 6 H, aryl), 7.40 (m, 3 H, aryl), 7.32
(m, 6 H, aryl), 6.47 (d, 1 H, J ) 2.5 Hz, 1JSiH ) 169 Hz, Si-H),
6.35 (d, 2 H, 3JHH ) 7.5 Hz, DMAP), 3.10 (s, 6 H, NMe2), 2.09
(m, 3 H, P(CHMe2)3), 1.84 (s, 15 H, C5Me5), 1.02 (vq, 9 H,
P(CHMeMe)3), 0.93 (vq, 9 H, P(CHMeMe)3), -14.65 (d, 1 H,
JPH ) 0.8 Hz, C5Me5), 27.08 (d, JPH ) 31 Hz, P(CHMe2)),
23.10 (d, 2JPH ) 6.7 Hz, P(CHMeMe)), 20.84 (d, 2JPH ) 21 Hz,
MeCdCH2), 20.62 (d, 2JPH ) 4 Hz, P(CHMeMe)), 20.39 (d, 2JPH
) 6.7 Hz, P(CHMeMe)), 19.84 (d, 2JPH ) 2.4 Hz, P(CHMeMe)),
2
3
18.88 (d, JPH ) 4.5 Hz, P(CHMeMe)), 16.95 (d, JPH ) 21.2
2
2JPH ) 29 Hz, Os-H), -14.71 (d, 1 H, JPH ) 28 Hz, Os-H).
2
Hz, P(CHMe2)), 12.30 (C5Me5), 12.15 (d, JPH ) 15 Hz,
13C{1H} NMR (CD2Cl2, δ): 145.8 (DMAP aryl), 136.4, 136.3,
129.7, 128.4 (aryl), 106.8 (DMAP aryl), 94.4 (C5Me5), 39.9
(NMe2), 26.8 (d, 1JPC ) 29.7 Hz, P(CHMe2)3), 18.8 (P(CHMe2)3),
11.62 (C5Me5).
MeCdCH2). 31P{1H} NMR (C6D6, δ): 4.82.
X-ray Crystallography. General Considerations. Crys-
tallographic analyses were carried out at the University of
California, Berkeley CHEXRAY crystallographic facility.39 All
measurements were made on a Bruker SMART CCD area
detector with graphite-monochromated Mo KR radiation (λ )
0.71069 Å). Crystals were mounted on capillaries with Para-
tone-N hydrocarbon oil and held in a low-temperature N2
stream during data collection. Frames were collected using ω
scans at 0.3° increments, using exposures of 10 s (4, 8, 11, 15,
and 24) or 20 s (12 and 13). Data were integrated with the
program SAINT,40 corrected for Lorentz and polarization
effects, and analyzed for agreement and possible absorption
using XPREP.41 Empirical absorption corrections were made
with either SADABS42 or XPREP. A p-factor of 0.030 was
employed to downweight intense reflections. Structures were
solved by direct methods and expanded using Fourier tech-
niques.43 The quantity minimized by the least-squares program
was ∑w(|Fo| - |Fc|), where w is the weight of a given
observation. The analytical forms of the scattering factor tables
for the neutral atoms were used, and all scattering factors were
[Cp*(iPr3P)(H)2OsdSi(Ph)SiPh2H][B(C6F5)4] (22). To a
CD2Cl2 solution (1 mL) of 11 (26 mg, 30 µmol), a CD2Cl2
solution (0.75 mL) of LiB(C6F5)4 (23 mg, 34 µmol) was added
by pipet, causing a color change from golden yellow to pale
lemon yellow and the formation of a fine white precipitate.
The mixture was allowed to stand for 30 min and filtered
through a fine glass fiber. NMR spectroscopy showed 22 to be
the major (>95%) product in solution. 1H NMR (CD2Cl2, δ):
3
8.24 (d, 2 H, o-PH, JHH ) 8 Hz), 7.72-7.44 (overlapping m,
1
2
13 H, aryl), 5.79 (s, 1 H, JSiH ) 198 Hz, JSiH ) 7 Hz, SiH),
1.99 (s, 15 H, C5Me5), 1.70 (m, 3 H, P(CHMe2)3), 0.94 (vq, 18H,
2
2
P(CHMe2)3), -10.58 (d, 2 H, JPH ) 28.2 Hz, JSiH ) 13.5 Hz,
Os-H). 13C{1H} NMR (CD2Cl2, δ): 136.3, 135.9, 135.7, 134.0,
130.4, 129.8, 128.8, 128.5 (aryl), 95.7 (d, JPC ) 1 Hz, C5Me5),
1
28.5 (d, JPC ) 29.8 Hz, P(CHMe2)3), 18.8 (P(CHMe2)3), 11.0
(C5Me5). 29Si NMR (HMBC, CD2Cl2, δ): 379, -18. 31P{1H}
NMR (CD2Cl2, δ): 41.4.
{Cp*[iPr2P(η2-MeCdCH2)]OsH2}[B(C6F5)4] (24). Solid 2
(545 mg, 0.94 mmol) and solid KB(C6F5)4 (750 mg, 1.04 mmol)
were combined in a Schlenk tube and cooled to -78 °C with a
dry ice/iPrOH bath. THF (10 mL) was added, and the mixture
was stirred for 5 min at -78 °C and then allowed to come to
room temperature. After 1 h at room temperature, solvent was
removed in vacuo. The dark residue was extracted with 3 ×
10 mL of 1:1 CH2Cl/Et2O. The combined filtrates were cooled
(39) http://xray.cchem.berkeley.edu.
(40) SAINT: SAX Area-Detector Integration Program, version 4.024;
Bruker, Inc.: Madison, WI, 1995.
(41) XPREP v. 5.03, Part of the SHELXTL Crystal Structure
Determination Package; Siemens Industrial Automation, Inc.: Madi-
son, WI, 1995.
(42) Sheldrick, G. M. SADABS, Siemens Area Detector Absorption
Correction Program; 1996. Advance copy, private communication.

Silyl and Silylene Ligands
Organometallics, Vol. 23, No. 24, 2004 5811
Table 3. Experimental Details for X-ray Crystallography
4
8
11‚C6H6
12‚(C6H5F)0.5
empirical formula
C
25H44BrOsSiP
C25H39F5SiPOsBr
763.74
C43H60OsPSi2Br
934.20
yellow plate
0.15 × 0.10 × 0.07
monoclinic
C-centered
Cc (#9)
9.364(2)
28.9855(5)
15.5909(3)
90
104.671(1)
90
C24H43OsSiBrPF0.50
670.27
fw
673.79
cryst color and habit
yellow blade
0.29 × 0.1 × 0.02
monoclinic
primitive
P21/n (#14)
9.242(1)
17.895(2)
16.121(2)
90
orange shard
0.20 × 0.09 × 0.05
monoclinic
primitive
P21/n (#14)
15.5293(1)
9.1041(1)
19.8726(3)
90
yellow block
0.11 × 0.09 × 0.07
monoclinic
primitive
P21/n (#14)
9.0114(1)
20.7564(9)
14.876(3)
90
cryst size (mm)
cryst syst
lattice type
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
95.507
90
99.319(1)
90
91.25(1)
90
γ (deg)
volume (Å3)
2653.9(4)
3.4-51.3
4
2772.51(5)
3.4-50.9
4
4093.7(5)
3.4-51.2
4
2781.9(3)
3.4-51.2
4
orientation refln, 2θ range (deg)
Z
Dcalc (g/cm3)
1.69
1.830
1.516
1.600
F000
1336
1496
1888
1326
µ(Mo KR) (cm-1
)
64.38
61.89
42.18
61.39
temperature (°C)
-112
-109
-119
-105
data collected, 2θmax (deg)
no. of reflns measd, total
no. of reflns measd, unique
Rint
51.3
50.9
51.1
50.9
11 889
12 218
10 796
5495
4531
4874
5115
4074
0.057
0.036
0.035
.034
transmn factors, Tmin/Tmax
no. of obsd data I > 3σ
no. of params refined
refln/param ratio
0.15/0.88
2911
0.41/0.65
3608
0.50/0.72
4540
0.50/0.61
2925
262
307
431
242
11.11
0.042, 0.049, 0.065
1.20
0.01
2.91; -3.78
11.75
0.034; 0.041; 0.044
1.34
0.00
1.35; -2.63
10.53
0.038; 0.044; 0.043
1.51
0.01
1.72; -2.31
12.09
0.064; 0.096; 0.078
3.16
0.03
2.64; 4.46
a
final residuals R; Rw; Rall
goodness of fit indicatorb
max. shift/error in final LS cycle
max.; min. peaks (e-/Å3)
13‚(C5H12
)
15
24
2
empirical formula
Os2Si2P2Br2C74H100
1647.93
yellow plate
0.19 × 0.17 × 0.07
monoclinic
primitive
P21/n (#14)
13.5150(3)
39.3983(9)
14.3453(3)
90
OsPC35.5F3SSiO3H48Br0.05
865.08
yellow prism
0.26 × 0.23 × 0.16
triclinic
primitive
P1h (#2)
C43F24POsH36B
fw
1240.70
cryst color and habit
amber block
cryst size (mm)
0.13 × 0.11 × 0.08
monoclinic
primitive
P21/c (#14)
17.1214(6)
14.1558(6)
19.3014(6)
90
cryst syst
lattice type
space group
a (Å)
9.1510(2)
11.9720(3)
18.1370(1)
81.930(1)
77.270(1)
76.040(1)
1872.92(6)
3.5-45.0
2
b (Å)
c (Å)
R (deg)
â (deg)
98.738(1)
90
114.089(1)
90
γ (deg)
volume (Å3)
7549.8(3)
3.4-51.4
4
4270.6(2)
3.4-49.4
4
orientation reflns, 2θ range (deg)
Z
Dcalc (g/cm3)
1.450
1.534
1.930
F000
3296
869.5
2424
µ(Mo KR) (cm-1
)
45.28
36.33
31.61
temperature (°C)
-113
-127
-132
data collected, 2θmax (deg)
no. of reflns measd, total
no. of reflns measd, unique
Rint
51.5
50.8
49.4
39 351
9183
18 809
13 103
5884
7343
0.058
0.036
0.055
transmn factors, Tmin/Tmax
no. of obsd data I > 3σ
no. of params refined
refln/param ratio
0.43/0.67
8826
0.20/0.59
4986
0.52/0.78
4487
723
400
475
12.21
0.037; 0.045; 0.064
1.17
0.04
2.74; 1.92
12.46
0.038; 0.046; 0.042
1.43
0.02
1.86; -2.78
9.45
a
final residuals R; Rw; Rall
0.034; 0.038; 0.065
1.06
goodness of fit indicatorb
max. shift/error in final LS cycle
0.03
0.92; -1.66
max.; min. peaks in (e-/Å3)
2
1/2
a R ) ∑||Fo| - |Fc||/∑|Fo|. Rw) [∑w(|Fo| - |Fc|)2/∑wFo
]
.
b GOF ) [∑w(|Fo| - |Fc|)2/(Nobs - Nparam)]1/2
.
corrected for both the real and the imaginary components of
anomalous dispersion. Calculations were performed using the
teXsan crystallographic software package.44 In each case, the
calculated centroid of the Cp* ring was placed in a fixed
position as a carbon atom with a partial occupancy of 0.0001
and a fixed Biso of 0.2 and included in the final cycles of least-
squares refinement. Osmium hydride ligands could not be
reliably located in the Fourier difference maps and were not
included in the refinement. Unless stated otherwise, non-
hydrogen atoms were allowed to refine anisotropically, and
carbon-bound hydrogen atoms were placed at calculated posi-
tions and not refined.
Selected experimental parameters for data collection and
refinement are presented above in Table 3. Atomic coordinates,

5812 Organometallics, Vol. 23, No. 24, 2004
Glaser and Tilley
anisotropic thermal parameters, and selected bond lengths and
angles are collected in the Supporting Information.
sizable channel-shaped voids that are filled with disordered
pentane. This disordered solvent was successfully modeled as
a series of half-occupancy carbon atoms. The largest peaks in
the Fourier map were located close to osmium.
For 15. Crystals were grown by layering a toluene solution
containing 15 as the major constituent with pentane. The
asymmetric unit contains half of a molecule of toluene on an
inversion center. A large peak close to osmium was at the
appropriate distance for an osmium-bound bromine atom and
was modeled as such at 5% occupancy. The partial occupancy
of bromine at this location can be attributed to cocrystallization
of a small amount of the precursor material 13. Other large
peaks in the Fourier map were located close to osmium.
For 24. Crystals were grown by slow cooling of a CH2Cl2/
Et2O solution. The 24 carbon atoms of the B(C6F5)4 anion were
allowed to refine isotropically to maintain a high data/
parameter ratio. A model in which these carbons were refined
anisotropically did not provide significantly different metric
parameters. Hydrogen atoms bound to the sp2 carbon atom in
the metalated PiPr3 ligand were located in the Fourier map
and fixed in the final stages of refinement. The largest residual
peaks in the Fourier difference map were close to osmium.
For 4. Crystals were grown by slow diffusion of pentane
into a benzene solution. The relatively large residual peaks
in the Fourier density map are a symptom of an imperfect
absorption correction due to the bladelike morphology of the
crystals. The largest peaks in the Fourier map are sym-
metrically disposed about osmium.
For 8. Crystals were grown by slow cooling of a concentrated
CH2Cl2/Et2O solution. The structure is of high quality, and no
problems were encountered in the refinement. The largest
peaks in the Fourier map were located close to osmium.
For 11. Crystals were grown by layering a concentrated
C6D6 solution with pentane. There is one well-ordered molecule
of benzene per molecule of 11. The structure is of high quality,
and no problems were encountered in the refinement. The
correct choice of enantiomorph was verified by refinement to
a low R value and a successful Bijvoet analysis. The largest
peaks in the Fourier map were located close to osmium.
For 12. Crystals were grown from a concentrated fluoroben-
zene/pentane solution at -30 °C. After collection of the data
set, careful inspection of the data showed that the crystal had
fractured in the cold stream midway through collection. Data
collected after this event were discarded, significantly reducing
the redundancy of the data (total/unique data ) 1.34). Despite
this difficulty, the model refined to an acceptable R value, and
bond lengths and angles were reasonable. The asymmetric unit
contains half of a molecule of fluorobenzene located on an
inversion center. This solvent molecule was refined isotropi-
cally. The largest peaks in the Fourier map were located close
to osmium.
Acknowledgment. This work was supported by the
National Science Foundation. CNDOS is supported by
Bristol-Meyers Squibb as a Sponsoring Member and
Novartis Pharama as a Supporting Member. The au-
thors wish to thank Alan Oliver and Fred Hollander of
the UC Berkeley CHEXRAY facility for assistance with
X-ray crystallography, Urs Burckhardt and Herman van
Halbeek for implementation of 29Si NMR experiments,
and Terry Krafft, Robert Bergman, and Richard Ander-
sen for valuable discussions.
For 13. Crystals were grown by layering a concentrated
C6D6 solution with pentane. The asymmetric unit contains two
crystallographically independent molecules of 13 which have
essentially identical metric parameters. The unit cell has
(43) (a) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.;
Giacovazzo, C.; Guagliardi, A.; Polidori, G. SIR92. J. Appl. Crystallogr.
1993, 26, 343. (b) Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.;
Smykalla, C. DIRDIF92: The DIRDIF Program System, Technical
Report of the Crystallography Laboratory; University of Nijmegen: The
Netherlands, 1992.
Supporting Information Available: Tables of atomic
coordinates, thermal displacement parameters, and selected
bond lengths and angles for 4, 8, 11, 12, 13, 15, and 24. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(44) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corporation, 1985 and 1992.
OM040062O