E-H bond activation reactions (E = H, C, Si, Ge) at ruthenium: Terminal phosphides, silylenes, and germylenes

Article abstract of DOI:10.1021/om900216u

The placement of a strongly trans-influencing ligand on a ruthenium center opposite an anchoring silyl group of the tetradentate tripodal tris(phosphino)silyl ligand, [SiP^ph1₃]^- ([SiP^ph₃]^-=

Full text of DOI:10.1021/om900216u

3744 Organometallics 2009, 28, 3744–3753
DOI: 10.1021/om900216u
E-H Bond Activation Reactions (E = H, C, Si, Ge) at Ruthenium:
Terminal Phosphides, Silylenes, and Germylenes
Ayumi Takaoka,† Arjun Mendiratta,‡ and Jonas C. Peters*,†
†Department of Chemistry, Massachusetts Institute of Technology Cambridge, Massachusetts 02139, and
‡Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena,
California 91125
Received March 20, 2009
The placement of a strongly trans-influencing ligand on a ruthenium centeropposite an anchoring silyl
group of the tetradentate tripodal tris(phosphino)silyl ligand, [SiPPh3]- ([SiPPh3]-=tris(2-(diphenylpho-
sphino)phenyl)silyl), has been explored. Installation of alkyl or terminal phosphide ligands trans to the
anchoring silyl group affords the complexes [SiPPh3]RuR (R=Me (2), CH2Ph (4), PPh2 (5), PiPr2 (6)).
Complexes 2, 4, and 5 are thermally unstable. Complexes 2 and 4 decay to the cyclometalated complex
[SiPPh2P0Ph]Ru (3), whereas complex 5 decays to the cyclometalated phosphine adduct [SiPPh2P0Ph]Ru-
(PHPh2) (7). Complex 3 is found to effect E-H (E=H, C, Si, Ge) bond activation of substrates such as
secondary silanes and germanes to yield the structurally unusual silylene complexes [SiPPh3]Ru(H)
(SiRR0) (R=R0 =Ph (10a), R=Ph R0 =Me (10b)) and the germylene complex [SiPPh3]Ru(H)(GeR2)
(R = Ph) (11) via double E-H activation transformations. Both theory and experiments suggest
electrophilic character at the silylene moiety. Reaction of 3 with catecholborane, in contrast to silanes
and germanes, results in insertion of the B-H unit into the M-C bond of the cyclometalated species to
yield the borate complex [SiPPh2PPh-B(cat)]Ru(μ-H) (14). Complex 3 also reacts with bis(catecholato)
diboron to yield a similar complex, [SiPPh2PC6H3B(cat)-B(cat)]Ru(μ-H) (15), with selective borylation of
an ortho C-H bond.
Introduction
N(CH2CH2PR2)3 systems4 and Meyer’s more recently
developed tris(carbene)amine system,5 in which the apical
amine donor can be hemilabile as a function of the ligand
Tetradentate, tripodal ligands have a long-standing
history in inorganic chemistry and continue to be exploited
to prepare new types of coordination complexes and catalyst
that occupies the site opposite the N atom. This article
examines the properties of the [SiPPh
-
]
3
ligand by studying
auxiliaries.1 Recently, we reported the synthesis of the
a family of ruthenium complexes in which synthetic attempts
are made to place strongly trans-influencing donor ligands at
the site opposite the silyl anchor. Our studies have revealed
interesting E-H bond activation transformations (E=H, C,
Si, Ge). We also report the isolation and structural char-
acterization of unusual coordination complexes including
examples of terminal phosphide, silylene, and germylene
complexes. These functionalities occupy positions trans to
the silyl anchor and to our knowledge are structurally unique
in this context.
tripodal monoanionic tris(phosphino)silyl ligands [SiPR
]
-
3
([SiPR3] = [(2-R2PC6H4)3Si], R = Ph and Pr) and several
corresponding iron complexes, including a terminal N2
adduct of iron(I).2 A conspicuous feature of this ligand
scaffold is the presence of a strongly trans-influencing silyl
anchor,3 which is unlikely to be labile due to its anionic
nature. This feature contrasts that of several topologically
related ligands such as Sacconi’s tris(phosphino)amine
i
*Corresponding author. E-mail: jcpeters@mit.edu.
(1) (a) Macbeth, C. E.; Golombek, A. P.; Young, V. G. Jr.; Yang, C.;
Kuczera, K.; Hendrich, M. P.; Borovik, A. S. Science 2000, 289, 938.
(b) Lim, M. H.; Rohde, J.; Stubna, A.; Bukowski, M. R.; Costas, M.;
Results and Discussion
Alkyl and phosphide ligands were initially targeted as
candidates for the trans-influencing ligands opposite the silyl
anchor. Heating [SiPPh3]H, Ru(PPh3)4Cl2, and excess
triethylamine at 60 °C affords purple crystals of [SiPP3h]RuCl
(1) in 95% yield after workup (Scheme 1). The solid-state
structure of 1 reveals a structure midway between a square
pyramid and a trigonal bipyramid (τ=0.47; Figure 1)6 with
a Si-Ru-Cl angle of 174.35(3)o. At room temperature the
€
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(3) Joslin et al. have previously reported a similar scaffold. See: Joslin,
F. L.; Stobart, S. R. Chem. Commun. 1989, 504.
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r
2009 American Chemical Society
pubs.acs.org/Organometallics
Published on Web 06/16/2009

Article
Organometallics, Vol. 28, No. 13, 2009 3745
Scheme 1
which is in accordance with the absence of a trans ligand
opposite the silyl anchor in 3. The 31P{1H} NMR spectrum of 3
features three sets of peaks, with the resonance of the phos-
phine in the metallacycle shifted significantly upfield at δ=-
11.3 ppm relative to the others at δ = 64.9 and 62.0 ppm.
Upfield shifts for the 31P{1H} NMR spectrum of cyclometa-
lated phosphine complexes are well precedented.7
The reaction between benzyl magnesium chloride and
1 results in the corresponding benzyl complex [SiPPh3]Ru-
(CH2Ph) (4). NMR spectroscopy suggests that the benzyl
moiety is not bound in an η1 fashion. At room tempera-
ture complex 4 exhibits two broad resonances at δ=81.4 and
58.3 ppm in a 1:2 ratio in the 31P{1H} spectrum in addition to
Figure 1. Left: Solid-state structure of 1. Right: Solid-state
structure of 3. Thermal ellipsoids are set at 50% probability,
and solvent molecules and hydrogen atoms have been removed
for clarity. Selected bond lengths (A) and angles (deg): 1: Ru-Si
2.3222(11), Ru-P(1) 2.3284(11), Ru-P(2) 2.2027(11), Ru-P(3)
2.3214(12), Ru-Cl 2.5117(10), Si-Ru-Cl 174.35(3). 3: Ru-
Si 2.2592(6), Ru-C(49) 2.137(2), Ru-P(1) 2.3447(6), Ru-P(2)
2.3240(6), Ru-P(3) 2.3186(6).
-
1
several broad [SiPPh
]
resonances in the H and 13C{1H}
3
spectra. An η3 assignment of the benzyl ligand in 4 is
suggested by the large 1JCH value of 145 Hz at the benzylic
carbon in the 13C spectrum of 4, though η2 coordination
cannot be rigorously excluded from the NMR data avail-
able.8 The upfield resonance of the ortho hydrogens of the
benzyl ligand in the 1H NMR spectrum, which appears as a
doublet at δ=5.97 (J=7.6 Hz) in d8-THF, provides strong
evidence against η1 coordination.8 Although broadening of
the ortho hydrogen resonance is observed upon cooling,
decoalescence is not observed at temperatures as low as -
90 °C. Decoalescence of the ortho carbons on the benzyl
ligand is likewise not attained in the 13C{1H} spectrum at -
90 °C. The benzyl species shows thermal instability akin to 2
and decays to 3 via loss of toluene over several days at 22 °C.
The addition of lithium diphenylphosphide to 1 at -78 °C
immediately leads to a dark green solution of the phosphide
phosphines are equivalent on the 31P NMR time scale.
Addition of methyllithium at -78 °C to a THF solution of
1, followed by warming to room temperature, leads to an
orange solution of the thermally unstable methyl complex
1
[SiPPh3]RuMe (2). A H NMR spectrum of the solution at
room temperature, taken shortly after addition of methyl-
lithium at -78 °C, features a quartet at δ = -0.98 ppm
corresponding to the methyl protons coupled to three
equivalent phosphines on the NMR time scale. The corre-
sponding 31P{1H} NMR spectrum shows a singlet at δ=63.7
ppm. Both spectra indicate 3-fold symmetry for dissolved 2
on the NMR time scale, whereas its diamagnetism suggests
a structure similar to 1.
Solutions of 2 cleanly convert over approximately 30 min at
room temperature to the new species [SiPPh2P0Ph]Ru (3) via
cyclometalation of an ortho phenyl C-H bond with concomi-
tant loss of methane. The solid-state structure of 3, shown in
Figure 1, shows a square-pyramidal geometry (τ=0.07) with
the silicon atom occupying the apical position and an open
coordination site trans to the silyl anchor. The Ru-Si bond
length in 3 is shorter than that in 1 (2.2592(6) vs 2.3222(11) A),
(7) (a) Cole-Hamilton, D. J.; Wilkinson, G. J. J. Chem. Soc., Dalton
Trans. 1977, 797. (b) Pez, G. P.; Grey, R. A.; Corsi, J. J. Am. Chem. Soc.
1981, 103, 7528.
ꢀ
ꢀ
(8) (a) Campora, J.; Lopez, J. A.; Palma, P.; Ruız, C.; Carmona, E.
´
Organometallics 1997, 16, 2709. (b) Brookhart, M.; Buck, R. C.;
Danielson, E. III J. Am. Chem. Soc. 1989, 111, 567. (c) Winter, M. J.;
Woodward, S. J. Chem. Soc., Chem. Commun. 1989, 457. (d) Braun, T.;
€
Munch, G.; Windmuller, B.; Gevert, O.; Laubender, M.; Werner, H.
Chem.;Eur. J. 2003, 9, 2516. (e) Boardman, B. M.; Valderrama, J. M.;
€
~
Munoz, F.; Wu, G.; Bazan, B. C.; Rojas, R. Organometallics 2008, 27,
1671. (f) Gielens, E. E. C. G.; Tiesnitsch, J. Y.; Hessen, B.; Teuben, J. H.
Organometallics 1998, 17, 1652.

3746 Organometallics, Vol. 28, No. 13, 2009
Takaoka et al.
Scheme 2
the coordinated PPh2H. Complex 7 is also accessible via
addition of diphenylphosphine to 3.
Figure 2. Left: Solid-state structure of 5. Right: Solid-state
structure of 6. Thermal ellipsoids are set at 50% probability,
and solvent molecules and hydrogen atoms have been removed
for clarity. Only one molecule in the asymmetric unit for 5 is
shown. Selected bond lengths (A) and angles (deg): 5: Ru(1)-Si
(1): 2.3783(3), Ru(1)-P(4) 2.2700(3), Ru(1)-P(1) 2.3522(3), Ru
(1)-P(2) 2.3404(3), Ru(1)-P(3) 2.2567(3), Si(1)-Ru(1)-P(4)
176.42(1), P(1)-Ru(1)-P(2) 130.47(1), P(2)-Ru(1)-P(3)
109.54(1), P(1)-Ru(1)-P(3) 108.87(1). 6: Ru-Si 2.3690(4),
Ru-P(4) 2.2592(4), Ru-P(1) 2.3354(4), Ru-P(2) 2.3368(4),
Ru-P(3) 2.2827(4), Si(1)-Ru-P(4) 161.88(2), P(1)-Ru-P(2)
142.46(2), P(2)-Ru-P(3) 102.64(2), P(1)-Ru-P(3) 104.55(2).
The decay of 5 follows clean first-order kinetics with
activation parameters of ΔHq =20(2) kcal/mol and ΔSq =
16(4) eu. A kinetic isotope effect was obtained by the use of a
deuterated ligand, d30-[SiPPh3]H, in which the phenyl sub-
stituents on the phosphine arms are fully deuterated. The
synthesis of d30-[SiPPh3]H is outlined in Scheme 2 and
is accomplished in four steps in an overall yield of 42%.
d10-PPh2H,11 prepared in 81% yield by lithium metal reduc-
tion of d15-PPh3 followed by acidic workup, is coupled with
2-iodobromobenzene through a palladium-catalyzed reac-
tion to yield d10-[2-(diphenylphosphino)phenylbromide] in
95% yield. Lithiation of d10-[2-(diphenylphosphino)phenyl-
bromide], followed by addition of trichlorosilane, yields the
desired deuterated product in 85% yield. The 1H NMR
spectrum of the prepared d30-[SiPPh3]H shows resonances
attributable to the protons on the ligand backbone with
complex [SiPPh3]RuPPh2 (5). The 31P{1H} spectrum exhibits
one species with resonances at δ = 214.1 and 75.0 ppm
corresponding to the phosphide and phosphine P nuclei,
respectively. The highly downfield chemical shift of the
phosphide P nucleus indicates the presence of a terminal
phosphide ligand with a planar geometry about the phos-
phorus atom,9 a rare feature for ruthenium phosphide com-
plexes; there is only one other structurally characterized
example.10 The solid-state structure (Figure 2) contains
two molecules in the asymmetric unit and shows that the
angles about the terminal phosphide ligand sum to average
values of 357°. In contrast to 1, the geometry of 5 more
closely approximates a trigonal bipyramid, with an average
τ value of 0.74. Notably, the Ru-P (phosphide) bond lengths
of 2.2700(3) and 2.2525(3) A are significantly shorter than
the Ru-P (phosphine) bond lengths that average to 2.32 A,
despite the presence of the trans-silyl group. This observation
points to multiple-bond character between the phosphide
ligand and the ruthenium center, especially in light of the
planar geometry about the phosphide P atom. Complex 5 is
also structurally distinctive in that the terminal phosphide
and silyl ligands are trans disposed in the solid state with Si-
Ru-P angles of 176° and 174° for the two molecules in the
asymmetric unit. The diisopropyl phosphide complex,
[SiPPh3]RuPiPr2 (6), is prepared analogously to 5 and ex-
hibits similar spectroscopic characteristics but different
structural parameters, with a geometry closer to that of
1 (Figure 2). The Ru-Si bond in 6 is appreciably longer
than in 1 (2.369 vs 2.322 A), reflecting the stronger trans
influence of the phosphide ligand. Similarly to solutions of
2 and 4, solutions of 5 decay to an isolable cyclometala-
ted phosphine adduct complex, 7 (Scheme 1). The identity of
7 is confirmed by elemental analysis, an (νP-H) IR stretch at
2288 cm-1, and a JPH of 302 Hz in the 31P NMR spectrum for
1
very little (<3%) incorporation of H nuclei in the phenyl
substituents of the phosphine. d30-[SiPPh3]Ru(PPh2) was
prepared analogously to 5, and its thermal decay behavior
at 35 °C shows a kinetic isotope effect of 5.5(3). Collectively,
the kinetic data suggest a highly ordered transition state with
significant C-H bond cleavage.
The clean conversion of 2 to 3 and 5 to 7 via C-H
activation of a phenyl ring inspired us to examine the
installation of a silyl ligand trans to the [SiPPh3]- silyl anchor.
Structurally characterized mononuclear complexes with
trans silyl ligands are not known for group 8 metals, with a
small number reported for the earlier metals12 and the rest
comprised of group 10 or later metals.13 The first approach
we examined involved addition of silanes to the dinitrogen
hydride complex [SiPPh3]Ru(H)(N2) (8). Complex 8 is readily
prepared by addition of sodium triethylborohydride to 1.
Our assignment of 8 is based upon the presence of a hydride
resonance at δ=-7.95 ppm in the 1H NMR spectrum and an
(νN-N) IR stretch at 2167 cm-1, which shifts to 2095 cm-1
upon use of 15N2 (calcd: 2093 cm-1). The Ru-H stretch is
not observed in the IR spectrum. In accordance with the
high-frequency N2 stretch, the N2 ligand is appreciably
labile. Solutions of 8 change color from yellow to orange
under reduced pressure, and the 15N NMR spectrum of an
ꢀ
(11) Gulyas, H.; Benet-Buchholz, J.; Escudero-Adan, E. C.; Freixa,
Z.; van Leeuwen, P. W. N. M. Chem.;Eur. J. 2007, 13, 3424.
(12) (a) Wu, Z.; Diminnie, J. B.; Xue, Z. J. Am. Chem. Soc. 1999, 121,
4300. (b) Qiu, H.; Woods, J. B.; Wu, Z.; Chen, T.; Yu, X.; Xue, Z.
Organometallics 2005, 24, 4190.
(13) Selected examples: (a) Ilsley, W. H.; Sadurski, E. A.; Schaaf, T.
F.; Albright, M. J.; Anderson, T. J.; Glick, M. D.; Oliver, J. P. J.
Organomet. Chem. 1980, 190, 257. (b) Biershenk, T. R.; Guerra, M. A.;
Juhlke, T. J.; Larson, S. B.; Lagow, R. J. J. Am. Chem. Soc. 1987, 109,
4855. (c) Arnold, J.; Tilley, T. D.; Rheingold, A. L.; Geib, S. J. Inorg.
Chem. 1987, 26, 2106. (d) Suginome, M.; Oike, H.; Shuff, P. H.; Ito, Y.
J. Organomet. Chem. 1996, 521, 405.
(9) (a) Baker, R. T.; Whitney, J. F.; Breford, S. S. Organometallics
1983, 2, 1049. (b) Rocklage, S. M.; Schrock, R. R.; Churchill, M. R.;
Wasserman, H. J. Organometallics 1982, 1, 1332.
(10) Derrah, E. J.; Pantazis, D. A.; McDonald, R.; Rosenberg, L.
Organometallics 2007, 26, 1473.

Article
Organometallics, Vol. 28, No. 13, 2009 3747
Scheme 3
dihydride/silyl complex. While 9 is six-coordinate, the
31P{1H} NMR spectrum features a single resonance even
at -80 °C, indicative of fluxional behavior and potential
scrambling of the hydride and silane hydrogen atoms.
1
Scrambling in 9 was examined through H NMR analysis
of a deuterated analogue synthesized by the addition of
D2SiPh2 to a solution of d30-[SiPPh3]Ru(H)(N2).16 The pre-
sence of a single exchangeable 1H nucleus enables facile
examination of scrambling. The 1H NMR spectrum at -20
°C indeed shows resonances at both 5.46 and -7.18 ppm in a
1:2.8 ratio, pointing to facile scrambling between the three
hydrogen atoms in 9 (Scheme 3) and to the slight preference
for deuterium to occupy the position on the silane that is not
interacting with the metal.17
To explore related Si-H bond activation processes, the
reaction between diphenylsilane and the cyclometalated
species 3 was examined. While many cyclometalated com-
plexes are stable to ring-opening under a variety of condi-
tions, several systems have been found to ring open upon
addition of substrates.18 Accordingly, the addition of diphe-
nylsilane to 3 at -78 °C quantitatively produces a single
product according to the 1H NMR spectrum. The spectrum
features an upfield singlet resonance at δ = -8.97 ppm.
Moreover, the 29Si{1H} spectrum shows a singlet resonance
at δ=374 ppm, which is significantly downfield of known
isotopically enriched sample features a single broad reso-
nance centered at δ=-65 ppm (ref to MeNO2) with no signal
for free N2, indicating facile exchange. Judging from the 2JPH
values of 60 and 28 Hz, the structure of 8 is most consistent
with a pseudooctahedral complex featuring a dinitrogen
ligand trans disposed to the silyl anchor. Such an arrange-
ment is rare and renders the N2 ligand labile, as has been
observed by our group for the iron complex [SiPPh3]Fe(N2).2
As outlined in Scheme 3, the addition of diphenylsilane to
8 cleanly leads to one species by 1H NMR spectroscopy. The
solid-state structure of the product14 reveals Ru-Si bond
silyl complexes,19 in addition to the quartet resonance for
-
the [SiPPh
]
3
ligand at δ=104 ppm (2JSiP=15 Hz). Taken
together, the spectra support the formulation of the silylene
complex [SiPPh3]Ru(H)(SiPh2) (10a). The solid-state struc-
ture, shown in Figure 3, corroborates this assignment and
reveals a terminal silylene ligand trans disposed to the silyl
-
anchor of the [SiPPh
]
ligand, providing a Si1-Ru-Si2
3
angle of 175.58(2)°. As for the case of the phosphide complex
5, this arrangement of ligands is to our knowledge unprece-
dented.20 The angles about the silylene silicon sum to 359.9
(1)°, confirming sp2 hybridization at the Si atom. The
hydride ligand can be located in the difference map and
resides at a position that is nearly coplanar with the plane
defined by the silylene moiety, providing evidence against
direct Si-H interactions. The Ru-Si bond length between
the metal and the silylene moiety is 2.2842(5) A and is slightly
longer than other base-free ruthenium silylene complexes,21
manifesting the trans influence of the silyl donor. The addi-
tion of methylphenylsilane to 3 similarly results in the facile
conversion to the silylene complex [SiPPh3]Ru(H)(SiMePh)
(10b), featuring 29Si{1H} resonances at δ=359 and 101 ppm
(2JSiP = 18 Hz). As in 10a, the hydride resonance at δ =
-9.21 ppm in the 1H spectrum shows no coupling with the
phosphines. Both 10a and 10b exhibit a single resonance in
the 31P{1H} NMR spectrum at 22 °C despite being six
coordinate, as in 9. We presume that complexes 10a and
lengths of 2.4808(4) and 2.4103(4) A for the silicon derived
-
from diphenylsilane and that from the [SiPPh
]
ligand,
3
respectively. Although a signature resonance in the hydride
region of the 1H NMR spectrum is easily discerned, hydro-
gen atom(s) bound to the ruthenium center could not be
assigned from the XRD data (see Supporting Information).
At -20 °C, a resonance at δ = 5.46 ppm is observed that
integrates in a 1:2 ratio against the hydridic resonance at
δ=-7.18 ppm. The former resonance appears close to the
silicon hydride resonance of diphenylsilane in the same
solvent (δ=4.88 ppm, d8-THF) and is assigned to a terminal
silicon hydride. The latter resonance could be assigned
to two hydride ligands, giving a dihydride/silyl formulation
for the product 9, or alternatively to a resonance arising from
a terminal Ru hydride and a bridging Ru-H-Si hydride
in rapid exchange. Further cooling of 9 to -80 °C does not
lead to decoalescence of this resonance. To establish the
possibility of a direct hydride interaction with the new
silicon-containing ligand, a 1H-29Si HSQC experiment
was undertaken. The spectrum at -20 °C reveals coupling
(16) d30-[SiPPh3]Ru(H)(N2) is prepared analogously to 8.
(17) A small amount of free diphenylsilane is also observed in the
spectrum. This indicates that free diphenylsilane can exchange with the
η2-coordinated silane.
(18) Selected examples: (a) Leucke, H. F.; Bergman, R. G. J. Am.
Chem. Soc. 1997, 119, 11538. (b) Mork, B. V.; Tilley, T. D. J. Am. Chem.
Soc. 2001, 123, 9702.
(19) Corey, J. Y.; Braddock-Wilking, J. Chem. Rev. 1999, 99, 175.
(20) Okazaki et al. have reported a complex in which a base-stabilized
silylene and a silyl ligand are at an angle of 160.34(2)° and 159.89(3)°
from each other. See: Okazaki, M.; Minglana, J. J. G.; Yamahira, N.;
Tobita, H.; Ogino, H. Can. J. Chem. 2003, 81, 1350.
(21) (a) Ochiai, M.; Hashimoto, H.; Tobita, H. Angew. Chem. 2007,
119, 8340; Angew. Chem., Int. Ed. 2007, 46, 8192. (b) Grumbine, S. K.;
Tilley, T. D. J. Am. Chem. Soc. 1994, 116, 5495.
1
1
constants of JSiH=80 Hz at δ=-7.18 ppm15 and JSiH
=
210 Hz at δ=5.46 ppm at -20 °C. These data suggest the
most reliable assignment to be a terminal hydride/η2-silane
adduct complex, [SiP3]Ru(H)(η2-H2SiPh2) (9), instead of a
(14) See Supporting Information.
(15) JSiH =40 Hz from the spectrum, but this value is doubled to
account for the rapid exchange with the hydride, which is assumed to
have a JSi-H=0 Hz. The reader is referred to Taw, F. L.; Bergman, R. G.
Brookhart, M. Organometallics 2004, 23, 886 for further details.

3748 Organometallics, Vol. 28, No. 13, 2009
Takaoka et al.
Figure 3. Left: Solid-state structure of 10a. Right: LUMO of 10a. Thermal ellipsoids are set at 50% probability, and hydrogens on
phenyl rings and solvent molecules have been removed for clarity. Selected bond lengths (A) and angles (deg): 10a: Ru-Si(2) 2.2842(5),
Ru-P(1) 2.3698(5), Ru-P(2) 2.2920(5), Ru-P(3) 2.3130(5), Si(1)-Ru-Si(2) 175.58(2).
Scheme 4
Figure 4. Solid-state structure of 11. Thermal ellipsoids are set
at 50% probability, and hydrogens on phenyl rings and solvent
10b result from R-hydrogen migration from a five-coordi-
molecules are removed for clarity. Selected bond lengths (A) and
angles (deg): Ru-Ge 2.3579(3), Ru-P(1) 2.3709(5), Ru-P(2)
nate silyl intermediate, [SiPPh3]Ru(SiHR2), by analogy with
2.2955(5), Ru-P(3) 2.3136(5), Si-Ru-Ge 176.25(1).
the proposed manner by which several other silylenes derived
from silanes are thought to be formed.22
moiety are quite rare25 and may be expected to be unstable.
Typical examples of complexes featuring a strong donor
trans to a silylene ligand possess two heteroatom-stabilized
cyclic silylenes opposite one another.26 Accordingly, solu-
tions of 10a and 10b decompose slowly to unknown
products at room temperature over a few days but are
stable in the solid state at -35 °C. For comparison, the
The germylene analogue of 10a is similarly obtained
through the addition of diphenylgermane to 3 (Scheme 4).
Such a reaction cleanly affords [SiPPh3]Ru(H)(GePh2) (11).
As expected, complex 11 exhibits spectroscopic character-
istics closely resembling that of 10a, and an XRD study
establishes that it is nearly isostructural. The only significant
difference arises from the Ru-Ge bond length of 2.3579(3)
A. This bond length is difficult to compare with other
systems due to the dearth of ruthenium germylene com-
plexes, but is similar to the reported bond length of 2.339
(1) A in the related iridium complex, [PhB(CH2PPh2)3]Ir-
(H)2(GeMes2).23
related six-coordinate iridium silylene complexes [PhBPPh
]
3
Ir(H)2(SiR2) (R = Mes, Ph, Et, Me)22,23 are prepared at
elevated temperatures and are appreciably more stable
([PhBPPh3]=[PhB(CH2PPh2)3]-).
The addition of excess H2 gas to 10a affords two products,
with the silane adduct 9 being the major species present. The
minor product is obtained quantitatively via an independent
route through the addition of excess H2 gas to 3 and is
While bona fide examples of terminal silylene complexes
have gained increasing prominence in the literature,24 those
that feature a strongly donating ligand trans to the silylene
(25) An example of a base-stabilized silylene complex with a trans
hydride ligand has been reported. The reader is referred to: Grumbine,
S. D.; Tilley, T. D.; Arnold, F. P.; Rheingold, A. L. J. Am. Chem. Soc.
1993, 115, 7884.
(22) Peters, J. C.; Feldman, J. D.; Tilley, T. D. J. Am. Chem. Soc.
1999, 121, 9871.
(23) Feldman, J. D.; Peters, J. C.; Tilley, T. D. Organometallics 2002,
21, 4065.
(24) Waterman, R.; Hayes, P. G.; Tilley, T. D. Acc. Chem. Res. 2007,
40, 712.
(26) (a) Haaf, M.; Schmedake, T. A.; West, R. Acc. Chem. Res. 2000,
33, 704. (b) Gehrhus, B.; Hitchcock, P. B.; Lappert, M. F.; Maciejewski,
H. Organometallics 1998, 17, 5599.

Article
Organometallics, Vol. 28, No. 13, 2009 3749
1
1
Figure 5. Left: H NMR (300 MHz) of the hydride resonance of 8 at RT. Right: H NMR (500 MHz) of 13 in the hydride region
at -90 °C.
Scheme 5
assigned as the dihydrogen hydride complex [SiP3]Ru(H)-
(H2) (12). Complex 12 features a broad upfield resonance at
δ = -4.3 ppm that exhibits coalescence even at -80 °C,
making a specific structural assignment difficult. However,
the short T1 min value of 33 ms recorded at 0 °C (500 MHz
1H NMR) is consistent with a dihydrogen/hydride formula-
tion.27,28 The dihydrogen ligand is labile, and 12 can hence be
converted to 8 upon prolonged exposure to dinitrogen. The
formation of 12 likely results from silane displacement by
dihydrogen, as exposure of excess H2 gas to 9 results in
partial conversion of 9 to 12 with loss of free silane. Further,
addition of approximately 1 equiv of H2 gas to 10a results in
formation of 9 with very little concomitant generation of 12.
The addition of methyllithium to 10a at -78 °C was
examined to try to generate a species exhibiting trans dis-
position of silyl ligands. The LUMO of 10a, obtained from a
single-point DFT calculation and shown in Figure 3, reveals
significant contribution from the p orbital on the silicon of
the silylene moiety,29 which suggests it should have electro-
philic character. Our data for the addition of methyllithium
to 10a is consistent with nucleophilic attack at the silylene to
generate a MePh2Si- ligand, as opposed to deprotonation of
brief comment. Addition of catecholborane at -78 °C to 3
followed by warming gives rise to a light orange solution
(Scheme 5). Its 1H NMR spectrum shows clean formation of
one product featuring a broad resonance at δ=-6.24 ppm,
and a broad resonance at δ=12 ppm is observed in the 11B
{1H} spectrum. The solid-state structure for complex 14,
shown in Figure 6, depicts formal insertion of the B-H bond
into the M-C bond of the metallacycle, revealing a bridging
B-(μ-H)-Ru hydride.30 The Ru-B distance of 2.468(2) A
indicates very little, if any, direct interaction between the
boron atom with the metal. One of the oxygen atoms from
the catecholborane is coordinated to the metal, with a Ru-O
distance of 2.376(2) A, completing the coordination sphere.
The above reaction suggested to us that replacement of the
bridging hydride unit with a boryl ligand might be possible
through addition of bis(catecholato)diboron. However, such
a reaction instead affords a product with a 1H NMR
spectrum closely resembling 14. The solid-state structure of
the product, 15, indeed reveals an analogous structure to 14,
but moreover shows that a phenyl ring has been selectively
borylated at the ortho position. A number of mechanisms are
conceivable for this transformation,31 and a plausible inter-
mediate might be the intended boryl complex, which subse-
quently activates the aryl C-H bond.
1
the metal-bound hydride. The H NMR spectrum of the
product formed shows a singlet hydride resonance at δ =
-9.77 ppm, which exhibits no coupling to the phosphine P
atoms as in 10a and 10b, and a resonance at δ=0.21 that is
assigned to the methyl group. The absence of satellites at the
upfield resonance indicates little interaction between the
hydride and either silyl Si atom, suggesting the hydride silyl
product {[SiPPh3]Ru(H)(SiMePh2)}{Li(THF)x} (13). The
structure of 13 is presumed to feature the silyl ligand trans
-
to the [SiPPh
]
3
silyl anchor on the basis of variable-tem-
perature NMR analysis. As shown in Figure 5, upon cooling
to -90 °C, partial decoalescence of the hydride resonance to
a broad five-line pattern with a coupling constant of JHP=28
Hz is observed. This splitting pattern is reminiscent of that
observed for the hydride resonance in 8, with 2JHP=60 Hz,
28 Hz due to coupling with the cis and trans phosphines,
respectively. We rationalize the broad five-line pattern of 13
as resulting from the superposition of a doublet of triplets
with similar coupling constants.
We have also attempted the installation of a boryl ligand
opposite the silyl anchor. While unsuccessful, the reac-
tion products (Scheme 5) are interesting and worthy of
Concluding Remarks
(27) (a) Hamilton, D. G.; Crabtree, R. H. J. Am. Chem. Soc. 1988,
110, 4126. (b) Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J.
J. Am. Chem. Soc. 1991, 113, 4173.
(28) A partial deuteration experiment of 12 using HD has been
performed to try to obtain the H-D coupling constant according, but
overlap of the H3 and H2D isotopomer resonances at 0 °C complicates
the determination. Further cooling results in the gradual merging of the
resonances until at -50 °C a single broad resonance is observed. This
method of analysis follows: Oldham, W. J. Jr; Hinkle, A. S.; Heinekey,
D. M. J. Am. Chem. Soc. 1997, 119, 11028.
-
The tetradentate [SiPPh
the preparation of a family of new ruthenium complexes.
]
ligand has been exploited in
3
(30) Such an insertion has been observed previously. The reader is
referred to: Baker, R. T.; Calabrese, J. C.; Westcott, S. A.; Marder, T. B.
J. Am. Chem. Soc. 1995, 117, 8777.
(31) (a) Hartwig, J. F.; Cook, K. S.; Hapke, M.; Incarvito, C. D.; Fan,
Y.; Webster, C. E.; Hall, M. B. J. Am. Chem. Soc. 2005, 127, 2538.
(b) Wan, X.; Wang, X.; Luo, Y.; Takami, S.; Kubo, M.; Miyamoto, A.
Organometallics 2002, 21, 3703. (c) Ishiyama, T.; Miyaura, N.
J. Organomet. Chem. 2003, 680, 3. (d) Tamura, H.; Yamazaki, H.; Sato,
H.; Sakaki, S. J. Am. Chem. Soc. 2003, 125, 16114.
(29) Tilley and co-workers have reported related results: (a) Hayes, P.
G.; Beddie, C.; Hall, M. B.; Waterman, R.; Tilley, T. D. J. Am. Chem.
Soc. 2006, 128, 428. (b) Calimano, E.; Tilley, T. D. J. Am. Chem. Soc.
2008, 130, 9226.

3750 Organometallics, Vol. 28, No. 13, 2009
Takaoka et al.
Figure 6. Left: Solid-state structure of 14. Right: Solid-state structure of 15. Thermal ellipsoids are set at 50% probability, and
hydrogens on phenyl rings and solvent molecules have been removed for clarity. The bridging hydride was not found in 15. Selected
bond lengths (A) and angles (deg): 14: Ru-Si 2.2913(6), Ru-P(1) 2.3288(5), Ru-P(2) 2.3250(5), Ru-P(3) 2.3382(6), Ru-O(1) 2.3757
(15), Ru-B 2.4684(2), Si-Ru-O(1) 167.47(4). 15: Ru-Si 2.2952(3), Ru-P(1) 2.3400(3), Ru-P(2) 2.3108(3), Ru-P(3) 2.3497(3), Ru-
O(1) 2.3265(6), Ru-B 2.449(1), Si-Ru-O(1) 167.65(2).
Most notably, the cyclometalated derivative 3 is a reactive
synthon that activates E-H bonds, allowing the preparation
of structurally distinctive silylene and germylene complexes.
In addition, phosphide/silyl and disilyl complexes can be
prepared using the [SiPPh3]Ru scaffold. All of these com-
plexes are unusual by virtue of the placement of two strongly
trans-influencing ligands in approximate trans positions to
one another. As such, these species are thermally unstable, as
is manifest in the thermal conversion of phosphide 5 to
phosphine 7. Studies in our lab continue to map the reactivity
patterns of this [SiP3]Ru system and to exploit its properties
in the context of homogeneous catalysis.
phosphine. LiPPh2 Et2O was synthesized by the addition of
3
butyllithium to a diethyl ether solution of diphenylphosphine.
Triethylamine was dried over calcium hydride and distilled.
Deuterated solvents were purchased from Cambridge Isotope
Laboratories, Inc., degassed, and stored over 3 A molecular
sieves prior to use. Elemental analyses were performed by Desert
Analytics, Tuscon, AZ, and by Columbia Analytical Services,
Tuscon, AZ (formerly Desert Analytics).
X-ray Crystallography Procedures. X-ray diffraction studies
were carried out at the Beckman Institute Crystallography
Facility and at the MIT Department of Chemistry X-ray
Diffraction Facility on a Bruker Smart 1000 CCD diffract-
ometer or Bruker three-circle Platform diffractometer, equipped
with a CCD detector. Data was collected at 100 K using Mo KR
(λ=0.710 73 A) radiation for all structures except for 6 and Cu
KR (λ=1.541 78 A) for 6 and solved using SHELXL.35 X-ray
quality crystals were grown as described in the experimental
procedures. The crystals were mounted on a glass fiber or nylon
loop with Paratone N oil.
Experimental Section
General Considerations. All manipulations were carried out
using standard Schlenk or glovebox techniques under an atmo-
sphere of dinitrogen. Unless otherwise noted, solvents were
degassed and dried by thoroughly sparging with N2 gas followed
by passage through an activated alumina column. Pentane,
benzene, toluene, tetrahydrofuran, and diethyl ether were tested
with a standard purple solution of sodium benzophenone ketyl
in tetrahydrofuran. All reagents were purchased from commer-
cial vendors and used without further purification unless other-
wise noted. Celite (Celite 545) was dried at 150 °C overnight
before use. Methyllithium was purchased in a solution form and
concentrated, redissolved in tetrahydrofuran, and titrated. Ru-
(PPh3)4Cl2,32 tris(2-(diphenylphosphino)phenyl)silane ([SiPPh3]-
H),2 and diphenylphosphine were synthesized according to
literature procedures.11 d15-Triphenylphosphine was prepared
by a modification of a literature procedure33 in which purifica-
tion was attained by column chromatography (eluent 1:1 hex-
ane/EtOAc). d10-Diphenylphosphine was prepared analogously
to diphenylphosphine. d30-[SiPPh3]H was synthesized analo-
gously to [SiPPh3]H using d10-[2-(diphenylphosphino)phenyl
bromide] (prepared analogously to 2-(diphenylphosphino)
Spectroscopic Measurements. Varian Mercury-300, Bruker
Avance-400, and Varian Inova-500 were used to collect 1H,
11B, 13C, 29Si, and 31P spectra at room temperature unless
1
otherwise noted. H and 13C spectra were referenced to resi-
dual solvent resonances. 11B spectra were referenced to ex-
ternal boron trifluoride etherate (δ=0 ppm), 15N spectra were
referenced to external neat nitromethane (δ = 0 ppm), 29Si
spectra were referenced to external tetramethylsilane (δ =
0 ppm), and 31P spectra were referenced to external 85%
phosphoric acid (δ=0 ppm).
Kinetic Measurements. In a typical experiment, 0.5 mL of a
solution of 5 (approximately 50 mM) was added to a J. Young
tube containing a sealed internal integration standard (PPh3),
and the sealed tube was heated on a temperature-equilibrated
hot plate, which was kept to within 0.5 °C at all times. The
reaction was followed by 31P NMR, and the ratio of 5 to PPh3
was obtained through comparison of the peak height of 5
(peak at 75.0 ppm) to that of PPh3. The resulting data were fit to
first-order decay. The rate constants reported are the average of
two experiments, and the error reported is the standard devia-
tion of the two rate constants obtained. A kinetic isotope
effect was obtained by performing an analogous reaction at
35 °C using d30-[SiPPh3]Ru(PPh2) (prepared similarly to 5) and
phenyl bromide34). LiPiPr2 THF was synthesized by the addi-
3
tion of lithium pellets to a THF solution of chlorodiisopropyl-
(32) Hallman, P. S.; Stephenson, T. A.; Wilkinson, G. Inorg. Synth.
1970, 12, 237.
(33) Baldwin, J. E.; Barden, T. C.; Pugh, R. L.; Widdison, W. C.
J. Org. Chem. 1987, 52, 3303.
(34) Whited, M. T.; Rivard, E.; Peters, J. C. Chem. Commun. 2006,
1613.
(35) Sheldrick, G. M. Acta Crystallogr. A 2008, 64, 112.

Article
Organometallics, Vol. 28, No. 13, 2009 3751
comparing the rate constants of the decay of 5 and d30-[SiPPh3]-
Ru(PPh2).
DFT Calculations. A single-point calculation on 10a was run
on the Gaussian0336 suite of programs with the B3LYP37 level of
theory with the LANL2DZ basis set for Ru,38 Si, and P with
diffuse and polarization functions for Si and P.39 The 6-31G-
(d,p) basis set was used for C and H.
8.03 (d, J=6.6 Hz, 1H), 7.73 (m, 3H), 7.53 (t, J=7.5 Hz, 1H),
7.27-6.38 (m, 31H), 6.22 (td, J=13.0 Hz, 1.8 Hz, 2H). 13C{1H}
NMR (THF-d8, δ): 167.8, 167.2, 157.0, 156.6, 153.8, 153.3,
151.6, 151.3, 149.7, 149.3, 146.8, 146.5, 146.4, 146.3, 145.9,
140.0, 139.8, 137.6, 136.5, 136.4, 135.7, 135.6, 135.0, 134.9,
132.3, 132.1, 131.3, 131.3, 131.2, 131.1, 131.1, 130.8, 129.9,
128.8, 129.7, 128.4, 128.2, 127.8, 127.6, 127.5, 127.2, 127.0,
126.8, 126.7, 126.4, 126.2, 126.0, 125.9, 125.7, 125.6, 125.4,
125.2, 124.7, 124.3, 124.2, 122.5, 119.7. 29Si{1H} NMR (THF-
d8, δ): 71.4. 31P{1H} NMR (C6D6, δ): 64.9 (dd, J = 19 Hz, 14
Hz), 62.0 (dd, J=235 Hz, 14 Hz), -11.3 (dd, J=235 Hz, 19 Hz).
Anal. Calcd for C58H51OSiP3Ru: C, 70.65; H, 5.21. Found: C,
70.77; H, 5.40.
Synthesis of [SiPPh3]RuCl (1). H[SiPPh3] (1.90 g, 2.34 mmol)
and Ru(PPh3)4Cl2 (2.86 g, 2.34 mmol) were charged into a flask,
and benzene (120 mL) was added. Triethylamine (1.01 mL,
7.26 mmol) was added, and the flask was heated at 60 °C for
18 h. The mixture was filtered through Celite, and the volatiles
were removed in vacuo. Layering diethyl ether over a concen-
trated CH2Cl2 solution resulted in large purple blocks. The crys-
tals were dissolved in benzene, and lyophilization yielded an
analytically pure, red-purple solid (2.12 g, 95.6%). Crystals
suitable for X-ray diffraction were grown by vapor diffusion
of pentane into a concentrated benzene solution. 1H NMR
(C6D6, δ): 8.38 (d, J=7.5 Hz, 3H), 7.38 (m, 11H), 7.24 (t, 3H),
7.15 (m, 7H), 6.87 (t, 3H), 6.77 (t, 5H), 6.66 (t, 10H). 13C{1H}
NMR (C6D6, δ): 155.0, 154.9, 147.9, 135.7, 134.2, 132.7, 132.5,
129.8, 129.2, 128.8. 31P{1H} NMR (C6D6, δ): 68.1 (s). 29Si{1H}
NMR (CDCl3, δ): 77.6 (q, J = 16 Hz). Anal. Calcd for
C54H42SiP3ClRu: C, 68.38; H, 4.46. Found: C, 68.44; H, 4.23.
Synthesis of [SiPPh3]RuMe (2). [SiPPh3]RuCl (10 mg, 0.011
mmol) was charged into a J-Young tube and dissolved in d8-
THF. The tube was cooled to -78 °C, and MeLi (11 μL, 0.011
mmol) was syringed in. The tube was quickly capped, and a
NMR spectrum of the sample was taken immediately after-
ward. 1H NMR (THF-d8, δ): 8.34 (d, J=7.2 Hz, 3H), 7.36-6.71
(m, 39H), -0.98 (q, J = 4.8 Hz, 3H, Ru-CH3). 31P NMR
(THF-d8, δ): 63.7
Synthesis of [SiPPh3]Ru(η3-CH2Ph) (4). [SiPPh3]RuCl (50 mg,
0.053 mmol) was dissolved in THF (5 mL) and cooled to -78 °C.
BnMgCl (27 μL, 0.053 mmol) was added by syringe, and the
resulting solution was allowed to warm to room temperature.
The solvent was removed in vacuo, the residue was redissolved
in benzene, and the resulting solution was filtered through
Celite. Pentane was added to a concentrated solution to pre-
cipitate out the product, which was pure by NMR (48 mg, 91%).
1H NMR (d8-THF, δ): 7.8-6.5 (br, overlapping peaks), 6.96 (t,
J=7.2 Hz, 1H), 6.63 (t, J=7.6 Hz, 2H), 5.97 (d, J=7.6 Hz, 2H),
2.52 (q, J=4.4 Hz, 2H). 1H NMR (d8-THF, δ, -20 °C): 7.93 (d,
J=7.2 Hz, 2H), 7.63 (s, 4H), 7.45-7.12 (m, 12H), 6.97-6.85 (m,
10H), 6.72-6.6 (m, 8H), 6.41 (s, 4H), 6.40 (d, J=8.4 Hz, 4H),
5.88 (d, J=8 Hz, 2H), 2.49 (br, 2H). 13C NMR (C6D6, δ): 152.1
(br), 139.3 (br), 134.4, 132.5, 131.1 (br), 129.2, 127.7, 126.1,
121.3, 38.4. 13C NMR (d8-THF, δ, -20 °C): 157.9, 157.4, 152.4
(m), 147.0, 146.7, 140.0 (br), 139.4 (br), 136.9, 135.6, 134.4,
134.3, 133.8, 132.8, 132.6, 132.4, 130.7, 129.8, 128.9, 128.6,
128.5, 128.3, 128.2, 128.0, 127.9, 127.7, 125.7, 38.2 (m). 31P
NMR (C6D6, δ): 81.4 (br), 58.3 (br).
Synthesis of [SiPPh2P0Ph]Ru (3). [SiPPh3]RuCl (0.93 g,
0.98 mmol) was dissolved in THF (60 mL) in a flask and cooled
to -78 °C. MeLi (0.95 mL, 0.98 mmol) was added dropwise via
syringe. The red solution was warmed to room temperature,
yielding an orange solution. The solvent was removed in vacuo,
and benzene (50 mL) was added to the resulting orange solid.
The resulting solution was stirred for 1 h, and the mixture was
filtered through Celite and concentrated. Recrystallization from
layering diethyl ether over a concentrated THF solution yielded
Synthesis of [SiPPh3]Ru(PPh2) (5). [SiPPh3]RuCl (0.30 g, 0.32
mmol) was dissolved in THF (5 mL) and cooled to -78 °C.
LiPPh2 Et2O (84 mg, 0.32 mmol) was added in one portion,
3
resulting in an immediate color change to dark green. Solvent
was removed, and the resulting solid was redissolved in benzene,
followed by filtration through Celite. The dark green solution
was lyophilized to yield a green solid (0.34 g, 97%). Crystals
suitable for X-ray diffraction were grown from layering diethyl
ether over a concentrated solution of dichloromethane at
orange needles that analyzed for [SiPPh2P0Ph]Ru Et2O. These
3
1
crystals were suitable for X-ray diffraction, and the solid-state
structure includes one molecule of diethyl ether, consistent with
the elemental analysis. The diethyl ether could be removed by
prolonged exposure of the crushed crystals to vacuum (0.76 g,
85%). 1H NMR (C6D6, δ): 8.32 (m, 2H), 8.16 (d, J=7.5 Hz, 1H),
-35 °C. H NMR (C6D6, δ): 8.48 (d, J=7.2 Hz, 3H), 7.25-
6.67 (m, 52H). 13C NMR (C6D6, δ): 156.0 (m), 151.6, 150.9 (m),
143.2 (m), 133.6, 132.8, 132.5, 132.3 (m), 129.4, 128.9, 128.7,
128.5, 128.3, 128.1, 128.0, 128.0, 127.9, 126.9. 31P NMR (C6D6,
δ): 214.1 (q, J=15 Hz, 1P), 75.0 (d, J=15 Hz).
Synthesis of [SiPPh3]Ru(PiPr2) (6). [SiPPh3]RuCl (0.20 g, 0.21
mmol) was suspended in benzene (10 mL), and an excess of
LiPiPr2 THF (0.082 g, 0.42 mmol) was added in one portion.
(36) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; , Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Hasegawa, J.;
Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li,
X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.;
Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.;
Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.;
Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.;
Keith, T.; M. A. Al-Laham, Peng C. Y.; Nanayakkara, A.; Challacombe,
M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.;
Pople, J. A. Gaussian 03, Revision C.02; Gaussian, Inc.: Wallingford, CT,
2004.
3
The resulting mixture was stirred for 7 h, at which time the color
of the solution had turned from purple to dark green. The
mixture was filtered through Celite, and pentane was layered
over a concentrated solution to yield green crystals that ana-
lyzed for [SiPPh3]Ru(PiPr2) 1.5C6H6 (0.17 g, 71%). These crys-
3
tals were suitable for X-ray diffraction and showed the correct
number of benzene molecules, as indicated by the elemental
analysis. 1H NMR (C6D6, δ): 8.36 (d, J=6.9 Hz, 3H), 7.24-7.20
(m, 15H), 6.96 (m, 3H), 6.82 (q, J =7.5 Hz, 21H), 3.04 (2H,
J=7.2 Hz, 2H), 1.18 (d, J=7.2 Hz, 6H), 1.15 (d, J=7.2 Hz, 6H).
13C NMR (C6D6, δ): 155.6 (m), 151.2 (m), 143.7 (m), 133.5,
133.3(m), 132.1, 129.0, 128.9, 128.7, 128.5, 128.3, 128.0, 127.9,
46.3 (d, J=8.0 Hz), 21.7, 21.6. 31P NMR (C6D6, δ): 295.0 (q,
J = 18 Hz, Ru-PiPr2), 77.0 (d, J = 18 Hz). Anal. Calcd for
C69H65SiP4Ru: C, 72.23; H, 5.71. Found: C, 72.45; H, 5.72.
Synthesis of [SiPPh2P0Ph]Ru(PHPh2) (7). [SiPPh2P0Ph]Ru
(0.025 g, 0.027 mmol) was dissolved in THF (4 mL) and cooled
to -78 °C. To the stirring solution was added diphenylpho-
sphine via syringe. The resulting yellow solution was warmed
to room temperature, and the solvent was removed to yield
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3752 Organometallics, Vol. 28, No. 13, 2009
Takaoka et al.
a yellow solid. Analytically pure material was obtained by
recrystallization from layering pentane over a concentrated
THF solution to yield yellow microcrystals (0.023 g, 76%). 1H
NMR (C6D6, δ): 8.44 (d, J=7.0 Hz, 1H), 8.26 (d, J=7.0 H, 1H),
8.10 (m, 3H), 7.65 (t, J=7.5 Hz, 1H), 7.59 (t, J=7.5 Hz, 2H), 7.56
(dt, J=303 Hz, 9.5 Hz, 1H, PHPh2), 7.40 (t, J=8.0 Hz, 2H),
7.33-6.39 (m, 38H), 5.65 (t, J=8.0 Hz, 2H). 13C NMR (C6D6,
δ): 161.3, 160.8, 158.0, 157.6, 154.9, 154.5, 152.2, 151.8, 151.5,
150.8, 150.5, 150.3, 149.9, 145.7, 145.3, 142.4, 142.1, 141.5,
140.1, 139.4, 139.3, 137.6, 137.4, 135.4, 135.3, 135.1, 134.9,
134.2, 134.0, 133.9, 133.4, 133.3, 132.6, 132.5, 130.5, 130.3,
129.7, 129.4, 129.3, 129.3, 129.2, 128.9, 128.0, 127.9, 127.8,
127.5, 127.4, 127.1, 127.0, 126.4, 126.3. 31P NMR (C6D6, δ):
67.6 (dm, J=226 Hz), 62.3 (m), 8.4 (q, J=21 Hz), -13.0 (dm,
J = 226 Hz). IR (KBr, cm-1): 3046, 2956, 2924, 2869, 2288
(ν[P-H]), 1954, 1558, 1479, 1434, 1309, 1273, 1183, 1156, 1090.
Anal. Calcd for C66H52SiP4Ru: C, 72,18; H, 4.77. Found: C,
71.59; H, 4.82.
Synthesis of [SiPPh3]Ru(H)(SiMePh) (10b). [SiPPh2P0Ph]Ru-
(0.040 g, 0.044 mmol) was dissolved in THF (5 mL) and cooled
to -78 °C. Methylphenylsilane (6.0 μL, 0.044 mmol) was added
via syringe, and the resulting orange solution was allowed to
warm to room temperature. The solvent was removed, and
lyophilization of a benzene solution resulted in an orange solid
1
(0.043 g, 95%). H NMR (C6D6, δ): 8.51 (d, J=7.0 Hz, 3H),
7.29-7.09 (m, 20H), 6.98 (t, J=7.5 Hz, 3H), 6.90 (t, J=7.5 Hz,
3H), 6.80 (t, J=7.5 Hz, 6H), 6.68 (t, J=7.5 Hz, 12H), 1.04 (s, Ru-
SiCH3Ph, 3H), -9.21 (s, Ru-H, 1H). 13C NMR (C6D6, δ): 154.5
(m), 153.3 (m), 152.3, 142.8 (m), 134.3, 132.8, 132.3 (m), 132.0,
129.1, 128.3, 127.6, 127.4, 127.3, 19.4 (Ru-SiCH3Ph). 29Si NMR
(THF-d8, δ): 359.5 (s, Ru-SiMePh), 101.7 (q, J=18 Hz). 31P
NMR (C6D6, δ): 73.2.
Synthesis of [SiPPh3]Ru(H)(GePh2) (11). [SiPPh2P0Ph]Ru-
(0.10 g, 0.11 mmol) was dissolved in THF (7 mL) and cooled
to -78 °C. Diphenylgermane (21 μL, 0.11 mmol) was added via
syringe, and the resulting dark red solution was warmed to room
temperature. The solvent was removed, and recrystallization
from layering pentane over a concentrated benzene solution
yielded red crystals suitable for X-ray diffraction. The crystals
were washed with pentane, crushed, and dried under vacuum to
yield an analytically pure solid (0.93 g, 74%). 1H NMR (C6D6,
δ): 8.60 (d, J=7.5 Hz, 3H), 7.3-6.9(m, 31H), 6.73 (t, J=7.5 Hz,
7H), 6.58 (t, J=7.5 Hz, 11H), -8.95 (s, 1H, Ru-H). 13C NMR
(THF-d8, δ): 163.0, 155.1, 154.7, 152.3, 151.9, 142.6 (br), 133.5
(br), 132.5, 128.7, 128.3, 127.9, 127.6 (br), 127.5, 127.4. 31P
NMR (C6D6, δ): 76.2 (br). Anal. Calcd for C66H53SiP3GeRu:
C, 69.49; H, 4.68. Found: C, 69.23; H, 4.53.
Alternatively, a solution of [SiPPh3]Ru(PPh2) can be left
standing at room temperature for several days and cleanly
decays to 7.
Synthesis of [SiPPh3]Ru(H)(N2) (8). [SiPPh3]RuCl (0.60 g, 0.63
mmol) was dissolved in THF (60 mL) and cooled to -78 °C.
Sodium triethylborohydride (1 M in THF, 0.63 mL, 0.63 mmol)
was added dropwise to the solution, and the resulting solution
was warmed to room temperature. The solvent was removed,
and the resulting solid was redissolved in benzene, followed by
filtration through Celite. Pentane was layered over a concen-
trated benzene solution to yield white needles (0.53 g, 88%). 1H
NMR (C6D6, δ): 8.59 (d, J=7.2 Hz, 2H), 8.32 (d, J=7.5 Hz, 1H),
7.87 (m, 4H), 7.44 (m, 2H), 7.31 (td, J=6.0 Hz, 1.2 Hz, 2H),
7.20-6.46 (m, 32H), -7.95 (dt, J=60.9 Hz, 27.6 Hz, 1H, Ru-H).
13C NMR (C6D6, δ): 156.8, 156.2, 155.8, 155.4, 155.0, 150.8,
150.5, 150.1, 149.1, 148.5, 147.4, 142.1, 141.8, 141.5, 140.3,
140.0, 137.5 (t), 134.4 (t), 133.7, 133.2, 133.1 (d), 132.9, 132.5,
132.3, 129.3 (d), 129.2, 127.7, 127.4 (d). 15N NMR (C6D6, δ): -
65.1. 31P NMR (C6D6, δ): 67.5 (d, J=12 Hz, 2P), 59.4 (t, J=
12 Hz, 1P). IR (KBr, cm-1): 3050, 2929, 2869, 2167 (ν[N2]), 1896,
1482, 1436, 1118.
Synthesis of [SiPPh3]Ru(H)(H2) (12). [SiPPh2P0Ph]Ru was
charged into a J. Young tube and freeze-pump-thawed three
times. Excess H2 gas (1 atm) was introduced. Analysis by NMR
indicated clean conversion to product. 1H NMR (C6D6, δ): 8.58
(d, J=7.5 Hz, 3H), 7.31-7.24 (m, 18H), 6.96 (t, J=7.5 Hz, 3H),
6.77 (t, J=7.5 Hz, 6H), 6.63 (t, J=7.5 Hz, 12H), -4.23 (s, 3H,
Ru-(H)(H2)). 13C NMR (C6D6, δ): 155.6 (m), 150.3 (m), 140.7
(m), 133.2, 133.2, 133.1, 132.9, 129.1, 128.9, 128.7, 128.1, 127.9,
127.8. 31P NMR (C6D6, δ): 71.2.
Synthesis of {[SiPPh3]Ru(H)(SiMePh2)}Li(THF)n (13).
[SiPPh3]Ru(H)(SiPh2) (0.040 g, 0.037 mmol) was dissolved
in THF (4 mL) and cooled to -78 °C. MeLi (0.035 mL, 0.037
mmol) was added dropwise and allowed warm to room tem-
perature. The resulting red solution was lyophilized to give an
orange-red solid that was pure by 1H NMR. 1H NMR (THF-d8,
δ): 8.18 (d, J=7.0 Hz, 3H), 7.02 (t, J=7.0 Hz, 3H), 6.88 (d, J=7.0
Hz, 4H), 6.80-6.48 (m, 32H), 0.21 (s, 3H, Si-CH3), -9.77
(s, 1H, Ru-H). 13C NMR (THF-d8, δ): 158.4, 155.6 (m), 154.8
(m), 144.0, 134.9, 131.7, 129.5, 127.8, 124.2, 123.9, 123.6, 123.5,
121.1, 7.2. 29Si NMR (THF-d8, δ): 102.4 (q, J=19.8 Hz), 9.6 (q,
J=12.2 Hz). 31P NMR (THF-d8, δ): 70.4
Synthesis of [SiPPh3]Ru(H)(η2-H2SiPh2) (9). [SiPPh3]Ru(H)-
(N2) (0.15 g, 0.16 mmol) was dissolved in benzene (7 mL), and
diphenylsilane (0.030 mL, 0.16 mmol) was added dropwise to
the stirring solution. The mixture was stirred for 5 min, and the
solvent was removed. Layering pentane over a concentrated
benzene solution yielded yellow crystals suitable for X-ray
1
diffraction (0.15 g, 85%). H NMR (THF-d8, δ): 8.43 (d, J=
7.0 Hz, 3H), 7.33 (t, J=7.0 Hz, 3H), 7.03-6.70 (m, 46H), 5.49
(br, 1H, Ru-SiHPh2), -7.18 (br, 2H, Ru(H)(HSiHPh2). 13C
NMR (C6D6, δ): 153.9 (m), 150.7 (m), 143.3, 143.1, 143.0, 135.5,
133.6, 133.4, 132.8, 132.8, 132.7, 132.5, 128.8, 128.7, 128.1,
127.9, 127.7, 127.6, 127.4. 29Si NMR (C6D6, δ): 90.3, -5.4.
31P NMR (C6D6, δ): 66.0. IR (KBr, cm-1): 3055, 2086 (ν[Si-H])
1961, 1891, 1813, 1479, 1307, 1250, 1187, 1102. Anal. Calcd for
C66H55Si2P3Ru: C, 72.18; H, 5.04. Found: C, 72.79; H, 5.01.
Synthesis of [SiPPh3]Ru(H)(SiPh2) (10a). [SiPPh2P0Ph]Ru-
(0.20 g, 0.22 mmol) was dissolved in THF (10 mL) and cooled
to -78 °C. Diphenylsilane (40 μL, 0.22 mmol) was added via
syringe, and the resulting red solution was allowed to warm to
room temperature. The solvent was removed, and lyophilization
of a benzene solution resulted in an analytically pure red solid
(0.22 g, 91%). Crystals suitable for X-ray diffraction were grown
from layering pentane over a concentrated benzene solution. 1H
NMR (THF-d8, δ): 8.66 (d, J=7.0 Hz, 3H), 7.32 (t, J=7.2 Hz,
3H), 7.26-6.57 (m, 46H), -8.97 (s, 1H, Ru-H). 13C NMR
(THF-d8, δ): 154.9 (m), 153.9 (m), 143.3, 143.1, 143.0, 135.5,
133.6, 133.4, 132.8, 132.8, 132.7, 132.5, 128.8, 128.7, 128.1,
127.9, 127.7, 127.6, 127.4. 29Si NMR (C6D6, δ): 373.9 (s, Ru-
SiPh2), 103.5 (q, J=15 Hz). 31P NMR (C6D6, δ): 73.6. Anal.
Calcd for C66H55Si2P3Ru: C, 72.31; H, 4.87. Found: C, 72.29;
H, 4.97.
Synthesis of [SiPPh2PPh-B(cat)]Ru(μ-H) (14). [SiPPh2P0Ph]Ru-
(0.12 g, 0.13 mmol) was dissolved in THF (7 mL) and cooled to
-78 °C. Catecholborane (14 μL, 0.13 mmol) was added via
syringe, and the resulting orange solution was allowed to warm
to room temperature. The solvent was removed, and crystals
suitable for X-ray diffraction were grown from layering pentane
over a concentrated benzene solution to yield orange crystals
that analyzed as [SiPPh2PPh-BH(O2C6H4)]Ru 1.5C6H6 (0.10 g,
3
69%). These crystals were suitable for X-ray diffraction, and
the solid-state structure shows the correct number of solvent
molecules. 1H NMR (C6D6, δ): 8.43 (d, J=7.5 Hz, 1H), 8.28 (d,
J=7.2 Hz, 1H), 8.14 (m, 2H), 7.98 (m, 2H), 7.72-7.60 (m, 2H),
7.21-6.00 (m, 38H), -6.24 (br, 1H, Ru-H-B). 11B NMR (THF-
d8, δ): 12 (br). 13C NMR (THF-d8, δ): 157.8, 157.5, 157.;1, 156.8,
156.1, 154.6, 151.2, 150.9, 150.3, 149.9, 147.8, 147.4, 144.7,
144.5, 141.6, 141.3, 139.6, 139.3, 136.6, 136.5, 136.2 (d, J=3.4
Hz), 136.1, 135.8, 134.8 (d, J=3.0 Hz), 134.2 (d, J=4.3 Hz),
134.0 (d, J=3.9 Hz), 133.8 (d, J=20.8), 133.5 (m), 133.2, 132.8
(d, J=10.4 Hz), 132.7, 132.5 (d, J=15.3 Hz), 132.2, 131.6 (d,
J=3.4 Hz), 130.7, 130.5, 130.4, 130.3 (d, J=3.4 Hz), 129.8, 129.1

Article
Organometallics, Vol. 28, No. 13, 2009 3753
(d, J=21.5 Hz), 128.9, 128.8, 128.7, 128.6, 128.5, 128.5, 128.4,
128.3, 128.2, 128.0, 128.0, 127.9, 127.8, 127.5 (d, J=8.9 Hz),
121.8, 119.0, 117.6, 113.5, 112.1, 108.6. 29Si NMR (C6D6, δ):
75.7. 31P NMR (C6D6, δ): 72.7 (dd, J=20.0, 15.7 Hz), 63.8 (dd,
J=233.0, 20.0 Hz), 54.1 (dd, J=233.0, 15.7 Hz). Anal. Calcd for
C69H54BO2SiP3Ru: C, 72.12; H, 4.74. Found: C, 72.48; H, 4.65.
Synthesis of [SiPPh2PC6H3B(cat)-B(cat)]Ru(μ-H) (15). [Si-
PPh2P0Ph]Ru (0.10 g, 0.11 mmol) was dissolved in toluene (30
mL) and cooled to -78 °C. Biscatecholatodiboron (0.026 g, 0.11
mmol) was added in one portion, and the resulting orange
solution was allowed to warm to room temperature. The solvent
was removed, and the residue was recrystallized twice from
layering pentane over a concentrated benzene solution to yield
yellow crystals suitable for X-ray diffraction (0.081 g, 64%). 1H
NMR (THF-d8, δ): 8.50 (d, J=7.5 Hz, 1H), 8.22 (d, J=7.0 Hz,
1H), 8.10 (t, J=8.5 Hz, 2H), 8.00-7.95 (m, 2H), 7.76 (d, J=7.5
Hz, 1H), 7.71 (d, J=6 Hz, 1H), 7.43-5.81 (m, 40H), -6.25 (br,
1H). 11B NMR (THF-d8, δ): 30 (br), 11(br). 13C NMR (THF-d8,
δ): 156.5,156.2, 155.8, 155.6, 154.7, 151.1, 150.7, 149.9, 149.5,
149.2, 149.0, 148.5, 148.1, 144.7, 144.4, 144.7, 144.4, 142.4,
142.2, 141.8, 137.2, 137.1, 136.6, 136.5, 136.1, 135.8, 135.5,
135.4, 134.8, 134.5, 134.3, 134.2, 134.0, 133.7, 133.6, 133.4,
133.3, 133.2, 133.0, 132.9, 132.8, 132.2, 132.1, 130.8, 130.6,
130.5, 129.7, 129.5, 129.3, 128.9, 128.9, 128.8, 128.7, 128.5,
128.4, 128.3, 128.0, 128.0, 127.9, 127.6, 127.6, 127.4, 127.1,
127.0. 31P NMR (THF-d8, δ): 72.6 (dd, J=19.5 Hz, 16.1 Hz),
68.8 (dd, J=232.8 Hz, 19.5 Hz), 54.8 (dd, J=232.7 Hz, 16.1 Hz).
Anal. Calcd for C66H49B2O4SiP3Ru: C, 68.94; H, 4.30. Found:
C, 69.02; H, 3.84.
Acknowledgment. This work was supported by the
NSF (CHE-0750234). Dr. Jeffrey H. Simpson is acknowl-
€
edged for assistance with NMR studies. Dr. Peter Muller,
Neal Mankad, and Samantha MacMillan are acknowl-
edged for crystallographic assistance, and Paul Oblad is
acknowledged for a preliminary reaction study. The NSF
is acknowledged for its support of the DCIF at MIT
(CHE-9808061 and DBI-9729592). We also acknowle-
dge a reviewer for a helpful suggestion regarding the η3
formulation for complex 4.
Supporting Information Available: X-ray crystallographic
data, kinetic data, and NMR spectra for 4, 5, 8, 9, 10b, 12,
and 13. This material is available free of charge via the Internet
at http://pubs.acs.org.