[Ru(xantsil)(CO)(η6-toluene)]: Synthon for a highly unsaturated ruthenium(II) complex through facile dissociation of the toluene ligand [xantsil = (9,9-dimethyIxanthene-4,5-diyl)bis(dimethylsilyl)]

Article abstract of DOI:10.1021/om701194e

The reactions of [Ru(xantsil)(CO)(η⁶-C₆H ₅CH₃)] [la, xantsil = (9,9-dimethylxanthene-4,5-diyl) bis(dimethylsilyl))] with some electron-donating molecules were reported. When la was dissolved in benzene, benzene replaced the η⁶-toluene ligand easily at room temperature to give [Ru(xantsil)(CO)(η⁶- C₆H₆)] (lb). The η⁶-toluene ligand was also substituted by sterically less demanding two-electron donors smoothly at room temperature to afford [Ru(xantsil)(CO)L₃] (L = CH₃CN (2), BuNC (3), and PMe₃ (4)). The X-ray diffraction studies revealed that they take a typical octahedral geometry, in which the xantsil ligand is coordinated to the Ru(II) center in k²(Si,Si) fashion. Reactions of la with sterically demanding phosphines gave [Ru(xantsil)(CO)(PR₃)] (R = ⁱPr (5) and Cy (6)). According to the X-ray diffraction study, complex 6 takes a square-pyramidal geometry, in which the xantsil ligand is bound to the Ru(II) center in k³(Si1Si1O) fashion and one of the silyl groups occupies the apical position. The coordinatively unsaturated Ru(II) center is slightly stabilized by the agostic interaction by the C-H bonds in PCy₃ [RuH: 2.89 and 3.06 A]. The highly coordinatively unsaturated nature in 6 was indicated by the reaction with carbon monoxide molecules to give [Ru(xantsil)(CO)₃(PCy₃)] (7) at room temperature. The typical octahedral geometry with the K²(Si,Si)- xantsil ligand was established by the X-ray diffraction study.

Full text of DOI:10.1021/om701194e

918
Organometallics 2008, 27, 918–926
[Ru(xantsil)(CO)(η6-toluene)]: Synthon for a Highly Unsaturated
Ruthenium(II) Complex through Facile Dissociation of the Toluene
Ligand [xantsil ) (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)]
Masaaki Okazaki,† Nobukazu Yamahira, Jim Josephus Gabrillo Minglana,‡
Takashi Komuro, Hiroshi Ogino,§ and Hiromi Tobita*
Department of Chemistry, Graduate School of Science, Tohoku UniVersity, Sendai 980-8578, Japan
ReceiVed NoVember 28, 2007
The reactions of [Ru(xantsil)(CO)(η6-C6H5CH3)] [1a, xantsil ) (9,9-dimethylxanthene-4,5-diyl)bis-
(dimethylsilyl))] with some electron-donating molecules were reported. When 1a was dissolved in benzene,
benzene replaced the η6-toluene ligand easily at room temperature to give [Ru(xantsil)(CO)(η6-C6H6)]
(1b). The η6-toluene ligand was also substituted by sterically less demanding two-electron donors smoothly
t
at room temperature to afford [Ru(xantsil)(CO)L3] (L ) CH3CN (2), BuNC (3), and PMe3 (4)). The
X-ray diffraction studies revealed that they take a typical octahedral geometry, in which the xantsil ligand
is coordinated to the Ru(II) center in κ2(Si,Si) fashion. Reactions of 1a with sterically demanding phosphines
gave [Ru(xantsil)(CO)(PR3)] (R ) iPr (5) and Cy (6)). According to the X-ray diffraction study, complex
6 takes a square-pyramidal geometry, in which the xantsil ligand is bound to the Ru(II) center in κ3(Si,Si,O)
fashion and one of the silyl groups occupies the apical position. The coordinatively unsaturated Ru(II)
center is slightly stabilized by the agostic interaction by the C-H bonds in PCy3 [Ru · · · H: 2.89 and 3.06
Å]. The highly coordinatively unsaturated nature in 6 was indicated by the reaction with carbon monoxide
molecules to give [Ru(xantsil)(CO)3(PCy3)] (7) at room temperature. The typical octahedral geometry
with the κ2(Si,Si)-xantsil ligand was established by the X-ray diffraction study.
Scheme 1
Introduction
Highly coordinatively unsaturated transition-metal complexes
possessing 14 valence electrons are recognized as key inter-
mediates in the homogeneous catalytic or stoichiometric reac-
tions. In most of the reactions, the intermediates derived from
oxidative addition or binding of substrates should leave adequate
coordination vacancies, allowing further transformation reac-
tions.1 The η6-arene-coordinated complex could be a promising
candidate for such a species through the dissociation of the arene
ligand. Thus, the exchange of arene molecules between free
and bound states has been an important class of reactions in
organometallic and surface chemistry. The arene exchange has
been mechanistically investigated for late-transition-metal com-
plexes.2 Several possible mechanisms have been reported so
far. One mechanism involves an associative process as shown
in Scheme 1. An initial rearrangement of the arene from η6- to
η4-coordination occurs to give B. The incoming arene coordi-
nates with B in η2-fashion to give C. Intramolecular rearrange-
ment between two arene molecules, dissociation of the η2-arene
molecule, and rearrangement of the resultant arene ligand from
η4 to η6 give F. Taking into account the strong σ-donor and
the trans-influencing ability of the silyl ligands,3 they are
expected to exhibit an exceptionally strong trans effect.
Therefore, silyl ancillary ligands would accelerate the dissocia-
tion of the η6-arene ligand to generate highly coordinatively
unsaturated intermediates. Chelate formation often stabilizes the
complex, and a series of (phosphinoalkyl)silyl ligands were
demonstrated to work as supporting ligands and enabled
reactivity studies on their complexes.4 Recently, we have
developed a new type of bis(silyl) chelating ligand, (9,9-
* Corresponding author. E-mail: tobita@mail.tains.tohoku.ac.jp.
† International Research Centre for Elements Science, Institute for
Chemical Research, Kyoto University, Uji Kyoto, 611-0011, Japan.
‡ Institute of Chemistry, University of the Philippines, Diliman, Quezon
City 1101, Philippines.
(3) (a) Chatt, J.; Eaborn, C.; Ibekwe, S. Chem. Commun. 1966, 700. (b)
Chatt, J.; Eaborn, C.; Ibekwe, S. D.; Kapoor, P. N. J. Chem. Soc. A 1970,
1343. (c) Bentham, J. E.; Cradock, S.; Ebsworth, E. A. V. J. Chem. Soc. A
1971, 587. (d) McWeeny, R.; Mason, R.; Towl, A. D. C. Discuss. Faraday
Soc. 1969, 47, 20. (e) Mason, R.; Towl, A. D. C. J. Chem. Soc. A 1970,
1601. (f) Hartley, F. R. Chem. Soc. ReV. 1973, 2, 163. (g) Haszeldine, R. N.;
Parish, R. V.; Setchfield, J. H. J. Organomet. Chem. 1973, 57, 279. (h)
Yamashita, H.; Hayashi, T.; Kobayashi, T.; Tanaka, M.; Goto, M. J. Am.
Chem. Soc. 1988, 110, 4417. (i) Lichtenberger, D. L.; Rai-Chaudhuri, A.
J. Am. Chem. Soc. 1991, 113, 2923. (j) Levy, C. J.; Puddephatt, R. J.; Vittal,
J. J. Organometallics 1994, 13, 1559.
§ The Open University of Japan, Chiba, 261-8586, Japan.
(1) Crabtree, R. H. In ActiVation and Functionalization of Methane;
Davies, J. A. Ed.; VCH: New York, 1990; p 69.
(2) (a) Muetterties, E. L.; Bleeke, J. R.; Sievert, A. C. J. Organomet.
Chem. 1979, 178, 197. (b) Traylor, T. G.; Stewart, K. J.; Goldberg, M. J.
J. Am. Chem.Soc. 1984, 106, 4445. (c) White, C.; Thompson, S. J.; Maitlis,
P. M. J. Chem. Soc., Dalton Trans. 1977, 1654. (d) Green, M. L. H.; Joyner,
D. S.; Wallis, J. M. J. Chem. Soc., Dalton Trans. 1987, 2823.
10.1021/om701194e CCC: $40.75
2008 American Chemical Society
Publication on Web 02/15/2008

[Ru(xantsil)(CO)(η6-toluene)]
Organometallics, Vol. 27, No. 5, 2008 919
Scheme 2
dimethylxanthene-4,5-diyl)bis(dimethylsilyl), or “xantsil”.5 In
the last few decades, van Leeuwen et al. explored several
diphosphine ligands having a xanthene or xanthene-like back-
bone and demonstrated their excellent effect on metal-catalyzed
reactions based on their unique rigidity and large bite angle.6
We applied this rigid backbone, aiming at stabilizing the
bis(silyl) chelate complexes, which are easily subjected to
reductive elimination, nucleophilic substitution, insertion, and
so on. Another characteristic feature of xantsil is the existence
of the oxygen atom, capable of coordinating to the transition
metal. In the substitution reactions of the η6-arene ligand with
a two-electron donor, the intramolecular coordination of the
xanthene oxygen atom would lower the activation barrier and
stabilize the intermediate (Scheme 2). We report here the
extremely accelerated η6-arene substitution reactions on the
[Ru(xantsil)(CO)] fragment. Structures and properties of
the resulting ruthenium(II) complexes, [Ru(xantsil)(CO)Ln] [Ln
) η6-benzene, (CH3CN)3, (tBuNC)3, (PMe3)3, PiPr3, PCy3,
(CO)2(PCy3)], will also be discussed. Some of the results
reported here have appeared elsewhere in a preliminary form.5a,d
benzene is characteristic of the η6-arene ligands coordinated to
transition metals. When the 1H NMR spectrum of 1b was
measured in benzene-d6, the signal of the coordinated benzene
diminished, showing fast exchange between the η6-benzene
ligand and the benzene-d6 solvent. The arene exchange that
occurs at room temperature is sill limited and has been reported
for the nickel,7 iridium,8 and titanium9 systems. A series of
nickel-arene complexes, [(C6F5)2Ni(η6-arene)], has been syn-
thesized by a metal vapor synthetic method, in which the C6F5
group is essential for their isolation. The nickel-arene complexes
reacted with electron-rich arenes, PEt3, 1,5-cycloocatadiene, and
tetrahydrofuran to afford the substitution products at room
temperature. Treatment of the dimer [Ir(µ-OMe)(cod)]2 with
[HPiPr3](BF4) in acetone/benzene solution yielded the cationic
arene complex [(η6-benzene)Ir(H)2(PiPr3)](BF4), of which the
η6-benzene ligand was readily substituted with arenes in acetone
through
the
transient
formation
of
[(acetone)3-
Ir(H)2(PiPr3)](BF4). The reduction of TiCl4 in the presence of
AlCl3 in benzene gave [(η6-C6H6)Ti(µ-Cl)4Al2Cl4], showing
facile exchange with electron-rich arenes. Although π-arene
complexes of group 8 transition metals have been of consider-
able interest over the last few decades, due to their high
stoichiometric and catalytic activity,10 little is known about them
possessing labile π-arene ligands. Complex 1 represents the first
example of a ruthenium complex that undergoes arene exchange
at room temperature.
Results and Discussion
Facile Arene Exchange in [Ru(xantsil)(CO)(η6-C6H5CH3)]
(1a). Extremely facile arene exchange was observed at room
temperature in [Ru(xantsil)(CO)(η6-C6H5CH3)] (1a) when crys-
tals of 1a were dissolved in benzene to give [Ru(xantsil)(CO)(η6-
C6H6)] (1b) quantitatively (eq 1). NMR data of 1b closely
resemble those of 1a except for the data of the η6-benzene
ligand. The 1H and 13C NMR signals of the η6-benzene ligand
in cyclohexane-d12 were observed at δ 4.98 and 97.2, respec-
tively. The high-field shift of the signals compared to free
(4) (a) Stobart, S. R.; Zhou, X.; Cea-Olivares, R.; Toscano, A.
Organometallics 2001, 20, 4766. (b) Brost, R. D.; Bruce, G. C.; Joslin,
F. L.; Stobart, S. R. Organometallics 1997, 16, 5669, and references therein.
(c) Okazaki, M.; Tobita, H.; Ogino, H. Organometallics 1996, 15, 2790.
(d) Okazaki, M.; Tobita, H.; Ogino, H. Chem. Lett. 1997, 437. (e) Okazaki,
M.; Tobita, H.; Ogino, H. J. Chem. Soc., Dalton Trans. 1997, 3531. (f)
Okazaki, M.; Tobita, H.; Kawano, Y.; Inomata, S.; Ogino, H. J. Organomet.
Chem. 1998, 553, 1. (g) Okazaki, M.; Ohshitanai, S.; Iwata, M.; Tobita,
H.; Ogino, H. Coord. Chem. ReV. 2002, 226, 167.
(1)
Substitution Reactions in [Ru(xantsil)(CO)(η6-C6H5CH3)]
(1a) with Nitrile and Isonitrile. Crystals of 1a were dissolved
in acetonitrile-d3, and the reaction was monitored by 1H NMR
spectroscopy. Within 30 min at room temperature, the signals
assignable to 1a diminished. Instead, the signals assignable to
[Ru(xantsil)(CO)(CD3CN)3] (2-d9) and free toluene were ob-
served in the appropriate region. A large-scale experiment using
acetonitrile as a solvent allowed the isolation of [Ru-
(xantsil)(CO)(CH3CN)3] (2) as colorless crystals in 98% yield
(5) (a) Tobita, H.; Hasegawa, K.; Minglana, J. J. G.; Luh, L.-S.; Okazaki,
M.; Ogino, H. Organometallics 1999, 18, 2058. (b) Minglana, J. J. G.;
Okazaki, M.; Tobita, H.; Ogino, H. Chem. Lett. 2002, 406. (c) Okazaki,
M.; Minglana, J. J. G.; Yamahira, N.; Tobita, H.; Ogino, H. Can. J. Chem.
2003, 81, 1350. (d) Okazaki, M.; Yamahira, N.; Minglana, J. J. G.; Tobita,
H. Organometallics 2004, 23, 4531. (e) Minglana; J. J. G.; Okazaki, M.;
Hasegawa, K.; Luh, L.-S.; Yamahira, N.; Komuro, T.; Ogino, H.; Tobita,
H. Organometallics 2007, 26, 5859.
(6) (a) Kranenburg, M.; van der Burgt, Y. E. M.; Kamer, P. C. J.; van
Leeuwen, P. W. N. M. Organometallics 1995, 14, 3081. (b) Kranenburg,
M.; Delis, J. G. P.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Vrieze, K.;
Veldman, N.; Spek, A. L.; Goubitz, K.; Fraanje, J. J. Chem. Soc., Dalton
Trans. 1997, 1839. (c) Buhling, A.; Kamer, C. J.; van Leeuwen, P. W. N. M.;
Elgersma, J. W.; Goubitz, K.; Fraanje, J. Organometallics 1997, 16, 3027.
(d) Kranenburg, M.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Eur.
J. Inorg. Chem. 1998, 155. (e) Goedheijt, M. S.; Reek, J. N. H.; Kamer,
P. C. J.; van Leeuwen, P. W. N. M. Chem. Commun. 1998, 2431. (f) Goertz,
W.; Keim, W.; Vogt, D.; Englert, U.; Boele, M. D. K.; van der Veen, L. A.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M. J. Chem. Soc., Dalton Trans.
1998, 2981. (g) van der Veen, L. A.; Boele, M. D. K.; Bregman, F. R.;
Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J.; Schenk,
H.; Bo, C. J. Am. Chem. Soc. 1998, 120, 11616.
(7) (a) Klabunde, K. J.; Anderson, B. B.; Bader, M.; Radonovich, L. J.
J. Am. Chem. Soc. 1978, 100, 1313. (b) Gastinger, R. G.; Anderson, B. B.;
Klabunde, K. J. J. Am. Chem. Soc. 1989, 102, 4959.
(8) (a) Torres, F.; Sola, E.; Martín, M.; López, J. A.; Lahoz, F. J.; Oro,
L. A. J. Am. Chem. Soc. 1999, 121, 10632. (b) Torres, F.; Sola, E.; Martín,
M.; Ochs, C.; Picazo, G.; López, J. A.; Lahoz, F. J.; Oro, L. A.
Organometallics 2001, 20, 2716.
(9) Pasynkiewicz, S.; Ciezyn´ski, R.; Dzierzgowski, S. J. Organomet.
Chem. 1973, 54, 203.
(10) (a) Bennett, M. A. In ComprehensiVe Organometallic Chemistry
II; Abel, E. W., Stone, F. G., Wilkinson, G., Eds.; Pergamon: New York,
1995; Vol. 7, p 549. (b) Gimeno, J.; Cadierno, V.; Crochet, P. In
ComprehensiVe Organometallic Chemistry III; Crabtree, R. H., Mingos,
D. M. P., Eds.; Pergamon: New York, 2007; Vol. 6, p 531.

920 Organometallics, Vol. 27, No. 5, 2008
Okazaki et al.
Scheme 3. Synthesis of [Ru(xantsil)(CO)L3] (L ) CH3CN (2),
silylruthenium(II) complexes. In general, both silyl and carbonyl
ligands exhibit high trans influence, and the former is estimated
to be higher than the latter. Accordingly, the bond distances of
Ru-N1 and Ru-N1* (2.2010(16) Å) are significantly longer
than that of Ru-N2 (2.119(2) Å), and both are considerably
longer than the average Ru-N bond distances in acetonitrile-
coordinated ruthenium complexes [2.05 Å]. The xanthene core
is bent, and the dihedral angle between the least-squares planes
of the two aromatic rings is 31.03(6)°.
tBuNC (3))a
The toluene ligand in 1a was easily substituted by three
tBuNC molecules in cyclohexane at room temperature to give
[Ru(xantsil)(CO)(CNtBu)3] (3) in 82% yield [Scheme 3].
t
t
a
(i) L ) CH3CN: acetonitrile, RT, 30 min; L ) BuNC: + BuNC,
cyclohexane, RT, immediately.
1
The H NMR spectrum of 3 shows two kinds of singlets for
the CNtBu ligands at δ 0.44 (9H) and 1.02 (9H × 2). The
former, located at the trans position of CO, appears at higher
field probably due to the ring current of the xanthene arene rings.
The signals for SiMe2 and 9,9-CMe2 are observed at δ 1.05
and 1.28 and δ 1.54 and 1.67, respectively. The 13C{1H} NMR
signals can also be assigned in a similar way. The 29Si{1H}
NMR spectrum shows a signal at δ -4.6, characteristic of the
silyl-ruthenium(II) complexes. In the IR spectrum, in addition
to the νCO band at 1927 cm-1, three strong-intensity bands of
νCN are observed at 2127, 2137, and 2170 cm-1. The wave-
number is indicative of their linear coordination mode.12
Complex 3 is very stable in air even in solution, reflecting the
rigid coordination of three isonitrile ligands to the Ru(II) center.
A tentative X-ray structure analysis of 3 revealed the structure,
in which three isonitirle ligands take a fac-geometry and one
of them faces the xanthene core (see the Supporting Informa-
tion).
Substitution Reactions in [Ru(xantsil)(CO)(η6-C6H5CH3)]
(1a) with Tertiary Phosphines. We examined the reactions of
1a with some tertiary phosphines. The η6-toluene ligand was
substituted by three PMe3 molecules in dichloromethane at room
temperature to give [Ru(xantsil)(PMe3)3(CO)] (4) in 84% yield
(eq 2). The molecular structure of 4 was unequivocally
determined by an X-ray diffraction study (Figure 2).5d Complex
4 takes a slightly distorted octahedral geometry, in which three
incoming PMe3 ligands occupy the fac-positions. In contrast to
2 and 3, the carbonyl ligand faces the xanthene core to avoid
the steric repulsion between the bulkier PMe3 and the xanthene
moiety. The ruthenium-silicon bonds [Ru-Si1 (2.5276(8) Å)
and Ru-Si2 (2.5234(8) Å)] are unusually long, which can be
explained by the steric requirement of the xantsil ligand, which
is enhanced by three bulky PMe3 ligands: That is, the rigid
xanthene core forces two methyl groups (C3 and C4) to be
within an extremely short interatomic distance (3.224(6) Å)
compared to the sum of the effective van der Waals radii of
two methyl groups (4.0 Å). The steric repulsion causes the other
methyl groups (C2 and C5) on the silicon atoms to move closer
to the methyl groups on the P2 and P3 phosphines (C2 · · · C25
3.250(5) Å, C5 · · · C28 3.298(5) Å), leading to considerable
stretching of the ruthenium-silicon bonds.
Figure 1. ORTEP drawing of 2. Thermal ellipsoids are drawn at
the 50% probability level, and hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-Si
2.3960(5), Ru-N1 2.2010(16), Ru-N2 2.119(2), Ru-C1 1.813(3),
Si-Ru-Si*96.17(2),C1-Ru-N1101.28(7),C1-Ru-N2170.73(9),
N1-Ru-N2 85.50(5), N1-Ru-N1* 84.96(8), C1-Ru-Si 82.87(5),
N2-Ru-Si 90.97(4), N1-Ru-Si 89.34(4), N1-Ru-Si* 173.51(4).
Asterisks indicate atoms generated by the symmetry operation (x,
-y + 1/2, z).
(Scheme 3). Elemental analysis established the formula of 2.
The infrared (IR) spectrum shows three bands at 2362, 2336,
and 1916 cm-1. The first two are assignable to the CN stretching
vibration mode of three acetonitrile ligands. The last one is
assignable to the CO stretching vibration mode, and the
wavenumber is very close to that in 1a (1913 cm-1). The
29Si{1H} NMR spectrum shows a singlet signal at δ 13.2, and
the chemical shift lies in the typical range expected for
silylruthenium(II) complexes.11
The molecular structure of 2 was determined by X-ray
analysis (Figure 1). The molecule exhibits a mirror plane
including Ru, O1, and C14 atoms. Complex 2 takes a slightly
distorted octahedral geometry in which three incoming aceto-
nitrile ligands occupy the fac-geometry, as suggested by the IR
data. The interatomic distance of Ru-O1 is 3.563(2) Å,
indicating no direct interaction between them. The Ru-Si bond
distance [2.3960(5) Å] is within the range of those in related
The high trans effect of the xantsil ligand and steric repulsion
between the xantsil and PMe3 ligands mentioned above are
reflected in the extremely high lability of the PMe3 ligands (eq
3). Even in a poorly coordinating solvent such as dichlo-
romethane, an equilibrium is achieved instantaneously between
4 and 4′ through the dissociation of one of the PMe3 ligands.
This is supported by the observation that when colorless crystals
of 4 were dissolved in CD2Cl2, the solution turned yellow and
1
(11) (a) Eisen, M. S. In The Chemistry of Organic Silicon Compounds;
Rappoport, Z., Apeloig, Y., Eds.; Wiley: New York, 1998; Vol. 2, Chapter
35, pp 2037–2128. (b) Tilley, T. D. In The Silicon-Heteroatom Bond; Patai,
S., Rappoport, Z., Eds.; Wiley: New York, 1991; Chapters 9, 10, pp 245–
308, pp 309–364.
the H NMR spectrum exhibited several signals assignable to
(12) Cotton, E. A.; Wilkinson, G. In AdVanced Inorganic Chemistry,
5th ed.; Wiley: New York, 1988; p 256.

[Ru(xantsil)(CO)(η6-toluene)]
Organometallics, Vol. 27, No. 5, 2008 921
on the potential energy surface. Dissociation of a PMe3 ligand
located at the trans position of the silyl groups would be
accelerated by their strong trans effect, giving 4a. Thus, 4a takes
a square-pyramidal geometry with the silyl group (Si1) in the
apical position. Isomerization between the pentacoordinated
4a and 4b seems facile. Subsequent intramolecular coordination
of the xanthene oxygen atom gives 4c with 18 valence electrons.
The interatomic distance of Ru-O1 (2.300 Å) in 4c is
significantly shorter than those in 4a (3.671 Å) and 4b (3.351
Å) and lies in the range expected for the Ru-O dative bonds.
Complex 4c is lowest in energy among three optimized forms.
The geometry with two chemically inequivalent PMe3 ligands
is consistent with the 31P{1H} NMR spectroscopic data. In the
dissociation of the PMe3 ligand, coordination of the intramo-
lecular oxygen atom in xantsil would be crucial to lower the
activation barrier and stabilize the intermediate.
The reaction of 1a with 5 equiv of PiPr3 in dichloromethane-
d2 was monitored by NMR spectroscopy (eq 4). After 10 min
at room temperature, an equilibrium was attained between 1a,
[Ru(xantsil)(CO)(PiPr3)] (5), toluene, and PiPr3 through the
dissociation of the η6-toluene ligand, followed by the intramo-
lecular coordination of the xanthene oxygen atom (vide infra).
The molar ratio of 1a and 5 was estimated to be 1.0:1.6 based
1
on the intensity of the H NMR signals. Addition of 20 equiv
of PiPr3 shifted the equilibrium to the right side (1a:5 )
1.0:9.1), although isolation of 5 was not achieved due to
instability. Complex 5 was uniquely characterized by compari-
son of the NMR data with 6 (vide infra).
Figure 2. ORTEP drawing of 4. Thermal ellipsoids are drawn at
the 50% probability level, and hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-P1
2.4004(8), Ru-P2 2.4003(8), Ru-P3 2.3930(8), Ru-Si1 2.5276(8),
Ru-Si2 2.5234(8), Ru-C1 1.864(3), P1-Ru-P2 93.80(3),
P2-Ru-P3 97.14(3), P3-Ru-P1 93.37(3), P1-Ru-Si1 92.31(3),
P1-Ru–Si2 91.51(3), P2-Ru-Si1 85.09(3), P2-Ru-Si2 173.54(3),
P3-Ru-Si1 173.74(3), P3-Ru-Si2 86.22(3), Si1-Ru-Si2
91.02(3), C1-Ru-P1 174.88(9), C1-Ru-P2 90.12(9), C1-Ru-P3
89.41(9), C1-Ru-Si1 84.73(8), C1-Ru-Si2 84.38(9).
(4)
Treatment of 1a with a bulkier PCy3 (5 equiv) gave
[Ru(xantsil)(CO)(PCy3)] (6) in 76% yield (eq 5). The molecular
structure was fully characterized by an X-ray diffraction study
and consistent with the prediction by the DFT calculations
(Figure 4).5d A characteristic feature of 6 is the intramolecular
coordination of the oxygen atom in xantsil. The Ru-O1 distance
of 2.268(4) Å is within the range expected for the ruthenium(II)-
oxygen dative bonds and close to that in [Ru{κ2(Si,Si)-
SiMe2O(Me)SiMe2}(H){κ3(Si,Si,O)-xantsil)}(CO)] [2.289(8)
Å].5c Thus, complex 6 takes a distorted square-pyramidal
geometry with the strongly electron-releasing silyl group of
xantsil (Si1) in the apical position. The coordinatively unsatur-
ated ruthenium center is stabilized by a weak agostic interaction
of the C-H bonds in the cyclohexyl group [Ru-H15 ) 2.89
Å, Ru-H22 ) 3.06 Å] (Figure 5).
(2)
resonances of 4′ and a broad signal of free PMe3 in addition to
the signals of 4. No signal was observed in the high-field region
characteristic of the Ru-H moiety. In the 31P{1H} NMR
spectrum, three new broad signals were observed at δ -59.4,
-6.5, and 27.4. The first signal was assigned to the dissociated
PMe3, while the last two were assigned to 4′. Furthermore,
addition of excess PMe3 to the yellow solution shifted the
equilibrium in eq 3 to the left to form 4 predominantly, causing
the yellow color to disappear. These results are consistent with
the formula of 4′ as [Ru(xantsil)(CO)(PMe3)2].
(3)
(5)
To clarify the geometry of 4′, the geometry of [Ru(xantsil)-
(CO)(PMe3)2] was optimized by DFT calculations (Figure 3,
Table 2). Three intermediates were identified as stationary points
In the 1H NMR spectrum, four signals due to methyl groups
appear at δ 0.20 (6H, SiMe), 0.51 (6H, SiMe), 1.51 (3H,

922 Organometallics, Vol. 27, No. 5, 2008
Okazaki et al.
Figure 3. Optimized structures of [Ru(xantsil)(PMe3)2(CO)] by the DFT calculation (B3LYP) with the use of a basis set, i.e., SDD for Ru,
6-31G(d) for Si and P, and 6-31G for the rest.
Table 1. Crystallographic Data of 2 · CH3CN, 4, 6, 8 · CH2Cl2, and 9
2 · CH3CN
4
6
8 · CH2Cl2
9
formula
cryst size (mm)
fw
C22H30N4ORuSi2
0.40 × 0.40 × 0.10
617.86
C29H51O2P3RuSi2
0.25 × 0.20 × 0.20
681.86
C38H57O2PRuSi2
0.10 × 0.10 × 0.05
734.06
C41H59Cl2O4PRuSi2
0.25 × 0.20 × 0.10
875.00
C40H48O4Ru2Si4
0.30 × 0.10 × 0.10
907.28
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
orthorhombic
Pnma
22.3683(7)
14.0012(3)
9.5533(2)
90
orthorhombic
Pbca
17.0553(4)
20.1437(6)
19.2039(6)
90
90
90
6597.6(3)
8
triclinic
P1
monoclinic
P21/c
15.9513(5)
10.5822(3)
25.8317(10)
90
101.3523(10)
90
4275.1(2)
4
triclinic
P1
j
j
10.1305(17)
10.3795(12)
19.2411(18)
98.116(4)
92.896(6)
112.966(8)
1831.7(4)
2
10.3381(4)
10.4244(6)
10.4263(5)
93.4825(14)
115.9243(10)
109.649(3)
922.65(8)
1
90
90
2991.93(13)
4
Z
F000
1280
0.635
21 810
3355 (0.0301)
0.94 and 0.79
numerical
3353/0/194
0.0273, 0.0653
0.0287, 0.0660
1.195
2864
0.718
47 454
7552 (0.0525)
0.93 and 0.84
numerical
7552/0/349
0.0415, 0.1011
0.0525, 0.1280
1.226
776
0.569
16 127
8050 (0.0551)
0.95 and 0.95
empirical
8050/0/403
0.0594, 0.1702
0.0830, 0.2028
1.165
1832
0.624
31 960
9549 (0.0369)
0.94 and 0.86
numerical
9549/0/466
0.0420, 0.1350
0.0520, 0.1698
1.174
464
0.991
8263
4155 (0.0609)
0.91 and 0.76
numerical
4155/0/232
0.0420, 0.1175
0.0491, 0.1265
1.155
µ(Mo KR) (mm-1
)
no. of reflns collected
no. of indep reflns (Rint
max. and min. transmn
absorp corr
no. of data/restrains/params
R1, wR2 [I > 2σ(I)]
R1, wR2 [all data]
)
GOF
largest diff peak and hole (e Å-3
)
0.439 and -0.549
0.625 and -1.1015
0.888 and -1.831
1.618 and -2.425
0.813 and -0.807
9-CMe), and 1.80 (3H, 9-CMe). No signals were observed in
the high-field region typical for the metal-hydrido moiety. The
29Si{1H} NMR spectrum exhibits only a doublet signal at δ
48.6 coupled with one 31P nuclei (JSiP ) 39.0 Hz). These
spectroscopic features can be explained by assuming facile
flipping of the PCy3 ligand as illustrated in Scheme 4. Kira et
al. observed the related dynamic behavior of [(Cy3P)Pd-
{(R3Si)2SidSi(SiR3)2}] and estimated the symmetrical (Y-type)
transition state for the flipping.13 The 31P{1H} NMR spectrum
shows a signal at δ 25.0. The IR spectrum includes a strong
bond at 1876 cm-1 assigined to the νCO band.
atmosphere. Workup of the reaction mixture gave a white solid
of [Ru(xantsil)(CO)3(PCy3)] (8) in 84% yield. Recrystallization
from CH2Cl2/hexane gave colorless crystals of 8 suitable for
X-ray diffraction study (Figure 6).5d Complex 8 adopts a slightly
distorted octahedral geometry in which three carbonyl ligands
are located in a mer-relationship. Accordingly, the interatomic
distance of Ru-O1 [3.581(2) Å] indicates no interaction
between them.
The variable-temperature NMR study on the CD2Cl2 solution
of 8 clearly indicated the existence of fluxional behavior. At
230 K, the Si-Me groups on xantsil shows four signals, which
Complex 6 can be a good synthon for the facile generation
of a coordinatively unsaturated ruthenium(II) complex bearing
14 valence electrons through dissociation of the xanthene oxygen
atom.14 The coordinative unsaturation of 6 was indicated by
the reaction with CO (Scheme 5). A dichloromethane solution
of 6 was stirred at room temperature for 1 h under a CO
(14) (a) Ogasawara, M.; Huang, D.; Streib, W. E.; Huffman, J. C.;
Gallego-Planas, N.; Maseras, F.; Eisenstein, O.; Caulton, K. G. J. Am. Chem.
Soc. 1997, 119, 8642. (b) Huang, D.; Streib, W. E.; Bollinger, J. C.; Caulton,
K. G.; Winter, R. F.; Scheiring, T. J. Am. Chem. Soc. 1999, 121, 8087. (c)
Baratta, W.; Herdtweck, E.; Rigo, P. Angew. Chem., Int. Ed. 1999, 38, 1629.
(d) Carmona, D.; Vega, C.; Lahoz, F. J.; Atencio, R.; Oro, L. A.; Lamata,
M. P.; Viguri, F.; SanJose, E. Organometallics 2000, 19, 2281. (e) Sanford,
M. S.; Henling, L. M.; Day, M. W.; Grubbs, R. H. Angew. Chem., Int. Ed.
2000, 39, 3451. (f) Watson, L. A.; Ozerov, O. V.; Pink, M.; Caulton, K. G.
J. Am. Chem. Soc. 2003, 125, 8426.
(13) Kira, M.; Sekiguchi, Y.; Iwamoto, T.; Kabuto, C. J. Am. Chem.
Soc. 2004, 126, 12778.

[Ru(xantsil)(CO)(η6-toluene)]
Organometallics, Vol. 27, No. 5, 2008 923
Figure 4. ORTEP drawing of 6. Thermal ellipsoids are drawn at
the 50% probability level, and hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-C1
1.803(6), Ru-O1 2.268(4), Ru-Si1 2.2870(16), Ru-Si2 2.3584(16),
Ru-P 2.4522(15), C1-Ru-O1 158.9(2), C1-Ru-Si1 87.8(2),
O1-Ru-Si182.05(11),C1-Ru-Si283.0(2),O1-Ru-Si281.31(11),
Si1-Ru-Si2 102.97(6), C1-Ru-P 103.7(2), O1-Ru-P 96.62(11),
Si1-Ru-P 102.08(6), Si2-Ru-P 154.30(6).
Figure 5. Agostic interactions between the Ru(II) center and
cyclohexyl groups on PCy3.
Scheme 4. Flipping of PCy3 on the Ru(xantsil)(CO) Fragment
is consistent with the X-ray crystal structure. On warming, the
signals at δ 0.64 and 0.72 coalesce at 270 K [∆ν (at 230 K) )
26.6 Hz], and those at δ 0.46 and 0.66 at 286 K [∆ν (230 K)
) 61.1 Hz]. Finally, they become two singlet signals at room
temperature. From the data, the barriers for two exchange
process of Si-Me groups were calculated by the coalescence
point method to be ∆Gq270 ) 57.7 kJ mol-1 and ∆Gq286 ) 56.2
kJ mol-1, respectively. A likely process is the inversion of the
puckered chelate ring (Scheme 6). Such a fluxional behavior
Scheme 5
was also observed in 1, and the activation barrier of ∆Gq
)
240
47 kJ mol-1 was almost the same as that in 8. The 31P{1H}
NMR spectrum shows a singlet signal at δ 39.3. The 29Si{1H}
NMR spectrum at 230 K exhibits two doublet signals at δ -6.2
(JPSi ) 45.1 Hz) and -2.2 (JPSi ) 8.8 Hz), where the former is
assigned to the silicon atom trans to PCy3 and the latter to that
trans to CO based on the coupling constants of JPSi. The IR
spectrum in CD2Cl2 contains three strong-intensity bands at
2040, 1992, and 1946 cm-1, characteristic of the mer-relation-
ship of three carbonyl ligands.
The reaction of 6 with CO was monitored spectroscopically
(Scheme 5). Introduction of CO gas into an NMR tube
containing the CD2Cl2 solution of 6 at room temperature caused
the solution to turn from orange to dark green and then finally
colorless. Accordingly, the 31P{1H} NMR spectrum indicated
the existence of the intermediate 7 (δ 37.6), which was
subsequently converted to the single product 8 (δ 39.3). The
trans geometry of two carbonyl ligands in 7 is clearly supported
by the IR spectrum: The intensity of the symmetric vibration
at 2036 cm-1 is quite weak, while that of the asymmetric
vibration at 1927 cm-1 is strong. In the 29Si{1H} NMR
spectrum, except the signals for 6 and 8, a new doublet signal
was observed at δ 21.8 coupled with the 31P nuclei (2JPSi
)
23.2 Hz) that was attributable to 7. On the basis of these
spectroscopic data, complex 7 is likely to take a square-
pyramidal geometry with the silyl group in the axial position,
which exhibits dynamic behavior including flipping of the PCy3
ligand as in 6.
Thermolysis of [Ru(xantsil)(CO)(η6-C6H5CH3)] (1a) in
the Absence of Donor Molecules. When 1a was heated in
n-decane at 140 °C for 1 day in the absence of donor molecules,
the dimer [Ru(xantsil)(CO)]2 (9) was obtained as yellow crystals
in 73% yield. No NMR spectroscopic data were obtained for 9
due to its poor solubility in organic solvents. A strong band at
1917 cm-1 in the IR spectrum confirms the presence of CO,

924 Organometallics, Vol. 27, No. 5, 2008
Okazaki et al.
Figure 7. ORTEP drawing of 9. Thermal ellipsoids are drawn at
the 50% probability level, and hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-C1
1.818(4), Ru-C12 2.392(3), Ru-C13 2.288(4), Ru-C14 2.272(4),
Ru-C15 2.251(3), Ru-C16* 2.415(3), Ru-C17 2.458(3), Ru-Si1
2.4392(10), Ru-Si2 2.4321(10), C6-C7 1.399(5), C7-C8 1.394(6),
C8-C9 1.391(6), C9-C10 1.392(5), C10-C11 1.384(5), C11-C6
1.393(5), C12-C13 1.417(5), C13-C14 1.422(5), C14-C15
1.407(5), C15-C16* 1.428(5), C16*-C17 1.403(5), C17-C12
1.416(5), C1-Ru-Si1 81.40(12), Si1-Ru-Si2 95.26(3),
C1-Ru-Si2 79.49(12). Asterisks indicate atoms generated by the
symmetry operation (-x, -y, -z).
Figure 6. ORTEP drawing of 8. Thermal ellipsoids are drawn at
the 50% probability level, and hydrogen atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-C1
1.934(4), Ru-C2 1.913(4), Ru-C3 1.928(4), Ru-P 2.4935(8),
Ru-Si1 2.5366(9), Ru-Si2 2.5730(9), C1-Ru-C2 159.89(14),
C1-Ru-C3 95.72(15), C2-Ru-C3 99.33(15), C1-Ru-P
96.25(10),C2-Ru-P197.90(10),C3-Ru-P86.53(10),C1-Ru-Si1
85.88(10), C2-Ru-Si1 83.27(10), C3-Ru-Si1 81.43(10), C1-
Ru-Si2 83.99(10), C2-Ru-Si2 80.05(10), C3-Ru-Si2 175.93(11),
P-Ru-Si1 167.93(3), P-Ru-Si2 97.54(3), Si1-Ru-Si2 94.50(3).
Conclusion
The η6-toluene ligand in [Ru(xantsil)(η6-toluene)(CO)] (1a)
can be readily replaced with an arene or some two-electron
donor ligands under mild conditions. The substitution products
also exhibit high lability through dissociation of the incoming
ligands. The exceptionally high lability in the xantsil-ruthe-
nium(II) system is attributable to (i) strong trans effect of two
silyl groups, (ii) steric requirement of the xantsil leading to the
severe repulsion between the SiMe2 parts of xantsil and
the outgoing ligands, and (iii) intramolecular coordination of
the xantsil oxygen atom leading to stabilization of the transition
state and/or intermediate. Considering the high lability of the
η6-toluene ligand, complex 1a could become a synthetic
equivalent of the Ru(II) species with 12 or 14 valence electrons
depending on the coordination of the xanthene oxygen atom.
Such a highly coordinatively unsaturated species is expected
to show higher catalytic activity than the corresponding 16-
electron species due to the presence of two or three easily
accessible, low-lying empty orbitals that can be used in the
reactions involving successive binding of substrates, oxidative
addition, σ-bond metathesis, migration, etc.
Scheme 6. Inversion of the Puckered Xanthene Chelate Ring
in 8
and the value is comparable to that in 1a (1913 cm-1). A weak
peak of M+ was observed at m/z 908 in the mass spectrum (EI).
The structure of 9 was unequivocally determined by an X-ray
diffraction study (Figure 7). Complex 9 is proven to be a dimer
in which one of the arene rings of xantsil is coordinated to the
ruthenium atom in a η6-fashion. The structure is essentially
the same as 1a except that a Ru(xantsil)(CO) moiety replaces
the η6-toluene as the η6-coordinated ligand. The ruthenium atom
is bound equivalently to the six carbon atoms of the xanthene
arene rings. The aryl C-C bond lengths of the η6-coordinated
xantsil moiety range from 1.403(5) to 1.428(5) Å, while the
aryl C-C bond lengths in the noncoordinated moiety range from
1.384(5) to 1.399(5) Å. The Si1-Ru-Si2 angle of 95.26(3)° is
almost the same as that in 1a [94.81(6) Å]. There is no direct
interaction between the two ruthenium atoms (Ru-Ru* 4.794
Å).
Experimental Section
General Procedures. All manipulations were carried out under
a dry nitrogen atmosphere. Hexane and benzene were distilled from
sodium-benzophenone ketyl and dichloromethane and acetonitrile
from calcium hydride immediately prior to use. Benzene-d6 and
cyclohexane-d12 were dried over a potassium mirror and dichlo-
romethane-d2 and acetonitrile-d3 over molecular sieves 3 and 4 Å,

[Ru(xantsil)(CO)(η6-toluene)]
Organometallics, Vol. 27, No. 5, 2008 925
respectively. They were transferred into an NMR tube under
vacuum. [Ru(xantsil)(CO)(η6-toluene)] (1a) was prepared according
to the literature method.5a,e Other chemicals were purchased and
used as received.
mmol), PMe3 (22.0 mg, 0.289 mmol), and CH2Cl2 (0.5 mL) and
connected to a vacuum line. The reaction mixture immediately
turned yellow accompanied by the formation of colorless crystals
of [Ru(xantsil)(CO)(PMe3)3] (4). The tube was flame-sealed and
opened in a glovebox. The mother liquor was decanted and stored
at -35 °C to give more crystals of 4. The crystals were washed
Physical Measurements. NMR spectra were obtained at room
temperature unless otherwise indicated on a Bruker ARX-300 or
1
AV-300 spectrometer. H, 13C{1H}, and 29Si{1H} NMR spectra
1
with hexane and dried under vacuum. Yield: 21.0 mg (84%). H
and 31P NMR data were collected in the presence of free PMe3.
13C and 29Si NMR spectral data could not be obtained due to the
low solubility of 4 in organic solvents. Anal. Calcd for
C29H51O2P3RuSi2: C, 51.08; H, 7.54. Found: C, 50.53; H, 7.40.
MS (EI, 70 eV): m/z 530 (M+ - 2PMe3, 8), 502 (M+ - 2PMe3 -
CO, 17), 325 (100). 1H NMR (300 MHz, CD2Cl2): δ 0.53, 0.62 (s,
6H × 2, SiMe2), 1.31, 1.71 (s, 3H × 2, 9,9′-CMe2), 1.34 (br., 18H,
2PMe3 cis to CO), 1.47 (d, 9H, 2JPH ) 6.7 Hz, PMe3 trans to CO),
6.96–7.21 (m, 6H, xanthene). 31P{1H} NMR (121.5 MHz, CD2Cl2):
were recorded at 300, 75.5, and 59.6 MHz, respectively, and
referenced to SiMe4. 31P{1H} NMR spectra were recorded at 121.5
MHz and referenced to 85% aqueous H3PO4. 29Si{1H} NMR
spectra were obtained by a DEPT pulse sequence. IR spectra were
recorded on a Horiba FT-730 spectrometer. Mass spectra were
measured using a JEOL JMS-HX110 or Hitachi M2500S spectro-
meter.
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with Benzene.
Colorless crystals of 1a (10.0 mg, 0.0183 mmol) were dissolved
in benzene (5 mL). After stirring for 3 h at room temperature, the
solution was evaporated to dryness to give an analytically pure
sample of [Ru(xantsil)(CO)(η6-C6H6)] (1b) as a white powder.
Yield: 9.7 mg (100%). Anal. Calcd for C26H30O2Si2Ru: C, 58.73;
H, 5.69. Found: 58.56; H, 5.89. MS (FAB, m-nitrobenzyl alcohol):
m/z 532 (M+, 22), 454 (M+ - benzene, 100). 1H NMR (300 MHz,
C6D12): δ 0.57, 0.64 (s, 6H × 2, SiMe2), 1.39, 1.78 (s, 3H × 2,
9,9′-CMe2), 4.98 (s, 6H, η6-C6H6), 7.00–7.26 (m, 6H, xanthene).
13C{1H} NMR (75.5 MHz, C6D12): δ 4.6, 9.8 (SiMe2), 22.8, 31.0
(9,9′-CMe2), 36.5 (9,9′-CMe2), 97.2 (η6-C6H6), 122.9, 124.1, 129.6,
134.1, 138.3, 159.0 (xanthene), 201.2 (CO). 29Si{1H} NMR (59.6
MHz, C6D12): δ 13.3. IR (KBr, cm-1): 1911vs (νCO).
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with CH3-
CN. A suspension of 1a (150 mg, 0.275 mmol) in acetonitrile (5
mL) was stirred at room temperature for 1 h. Removal of volatiles
under vacuum gave a white solid of Ru(xantsil)(CO)(CH3CN)3 (2),
which was washed by hexane and dried under vacuum. Yield: 155
mg (98%). Anal. Calcd for C26H33N3O2RuSi2 · CH3CN: C, 54.43;
H, 5.87; N, 9.07. Found: C, 54.10; H, 5.93; N, 8.65. 1H NMR (300
MHz, CD3CN, RT): δ 0.407, 0.411 (s, 6H × 2, SiMe2), 1.39, 1.78
(s, 3H × 2, 9-CMe2), 7.03–7.27 (m, 6H, xanthene). 13C{1H} NMR
(75.5 MHz, CD3CN, 260 K): δ 5.0, 5.1 (SiMe2), 22.7, 30.4 (9-
CMe2), 36.4 (9-CMe2), 123.0, 123.2, 131.2, 133.2, 138.7, 159.4
(xanthene), 206.0 (CO). 29Si{1H} NMR (59.6 MHz, CD3CN, 260
K): δ 13.2. IR (KBr, cm-1): 2362w (νCN), 2336w (νCN), 1916vs
(νCO), 1389vs, 1254m, 1227s, 1198w, 1125w, 835m, 815m, 777m,
750w. Due to the high lability of acetonitrile ligands, their 1H and
13C NMR signals were not assigned.
2
2
δ -19.5 (d, JPP ) 36.5 Hz, 2PMe3 cis to CO), -16.2 (t, JPP
)
36.5 Hz, PMe3 trans to CO). IR (KBr, cm-1): 1932vs (νCO).
Behavior of 4 in CD2Cl2. A Pyrex NMR tube was charged with
4 (15 mg, 0.022 mmol), and CD2Cl2 (0.5 mL) was introduced into
this tube under high vacuum by the trap-to-trap transfer technique.
The colorless solution immediately turned yellow. The yellow
solution displayed the 1H and 31P NMR signals of 4, [Ru(xantsil)-
(CO)(PMe3)2] (4′), and free PMe3. Equilibrium was achieved
immediately between 4, 4′, and PMe3 at room temperature. The
molar ratio of 4 to 4′ was estimated to be approximately 10:9 based
1
on the intensity ratio of the H NMR signals. The NMR tube was
opened in a glovebox. Addition of excess PMe3 into the tube
resulted in the formation of a colorless solution containing a single
1
product, 4. Data for 4′: H NMR (300 MHz, CD2Cl2): δ 0.53 (s,
3H × 4, SiMe2), 1.12 (br, 9H, PMe3), 1.23, 1.66 (s, 3H × 2,
9-CMe2), 1.44 (br, 9H, PMe3), 7.05 (m, 2H, xanthene), 7.20 (m,
2H, xanthene), 7.45 (m, 2H, xanthene). 31P{1H} NMR (121.5 MHz,
CD2Cl2): δ -6.5, 27.4 (br, PMe3).
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with PiPr3. A
Pyrex NMR tube was charged with 1a (5.0 mg, 9.2 µmol) and PiPr3
(8.8 µL, 5 equiv), and dichloromethane-d2 (0.5 mL) was transferred
into the tube under vacuum. The tube was flame-sealed. After 30
min at room temperature, the reaction attained equilibrium between
1a and [Ru(xantsil)(CO)(PiPr3)] (5) in the molar ratio of 1:1.7. Due
to the extremely high lability of PiPr3 ligands, isolation of 5 was
1
not achieved even in the presence of excess PiPr3. H NMR (300
MHz, CD2Cl2): δ 0.24, 0.52 (s, 6H × 2, SiMe2), 1.03 (dd, 3JHH
)
7.0 Hz, 3JHP ) 13.0 Hz, 18H, P(CHMe2)3), 1.44, 1.79 (s, 3H × 2,
9-CMe2), 2.18 (septet, 3JHH ) 7.0 Hz, 3H, P(CHMe2)3), 7.14–7.33
(m, 6H, xanthene). 31P{1H} NMR (121.5 MHz, CD2Cl2): δ 33.0.
t
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with BuNC.
A Pyrex NMR tube was charged with 1a (20.0 mg, 0.0366 mmol),
tBuNC (14.0 mg, 0.168 mmol), and C6D12 (0.4 mL), and the
solution was deaerated by argon for 5 min. The reaction was
2
29Si{1H} NMR (59.6 MHz, CD2Cl2): 51.8 (d, JPSi ) 41.8 Hz).
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with PCy3. A
dichloromethane solution (14 mL) of 1a (100 mg, 0.183 mmol)
and PCy3 (257 mg, 0.916 mmol) was stirred at room temperature
in a glovebox. The solution turned from yellow to orange and finally
to reddish-orange. After stirring for 30 min, volatiles were removed
under reduced pressure. The resulting reddish-orange solid of
[Ru(xantsil)(CO)(PCy3)] (6) was washed with hexane three times
to remove excess PCy3 and dried under vacuum. Yield: 102 mg
(76%). Anal. Calcd for C38H57O2PRuSi2: C, 62.17; H, 7.83. Found:
1
monitored by H NMR spectroscopy. Signals of 1a were cleanly
replaced with those of [Ru(xantsil)(CO)(CNtBu)3] (3) within 1 h.
The solution was slowly concentrated under vacuum to give
colorless crystals of 3. Yield: 21.0 mg (82%). Anal. Calcd for
C35H51O2Si2N3Ru: C, 59.79; H, 7.31; N, 5.98. Found: C, 59.80; H,
7.28; N, 5.91. MS (EI, 70 eV): m/z 703 (M+, 5), 675 (M+ - CO,
37), 620 (M+ - CNtBu, 84), 593 (M+ - CO - CNtBu, 100). 1H
NMR (300 MHz, C6D6): δ 0.44 (s, 9H, CNtBu trans to CO), 1.02
(s, 18H, CNtBu cis to CO), 1.05, 1.28 (s, 6H × 2, SiMe2), 1.54,
1.67 (s, 3H × 2, 9,9′-CMe2), 7.18–7.69 (m, 6H, xanthene). 13C{1H}
NMR (121.5 MHz, C6D6): δ 7.0, 8.8 (SiMe2), 24.5, 30.4
(CNC(CH3)3), 29.8, 30.1 (CNC(CH3)3), 36.4, 55.6 (9,9′-CMe2), 55.3
(9,9′-CMe2), 122.9, 124.4, 131.0, 133.2, 139.7, 159.5 (xanthene),
151.1 (CNC(CH3)3), 205.4 (CO). Only one 13C NMR signal
assignable to the CNtBu3 ligands was found probably due to
accidental overlap of the second signal with other signals or its
low intensity.
1
C, 61.76; H, 7.98. H NMR (300 MHz, CD2Cl2): δ 0.20, 0.51 (s,
6H × 2, SiMe2), 0.80–2.01 (m, 33H, PCy3), 1.51, 1.80 (s, 3H × 2,
9-CMe2), 7.14–7.36 (m, 6H, xanthene). 13C{1H} NMR (75.5 MHz,
CD2Cl2): δ 5.44 (d, 2JPC ) 5.2 Hz, SiMe), 8.17 (d, 2JPC ) 5.2 Hz,
SiMe), 23.6, 31.0 (9-CMe2), 26.4 (Cy), 27.8 (d, JPC ) 9.2 Hz, Cy),
30.7 (Cy), 35.6 (d, JPC ) 8.0 Hz, Cy), 37.6 (9-CMe2), 124.2, 125.7,
2
130.8, 135.7, 136.4, 161.8 (xanthene), 208.0 (d, JPC ) 3.5 Hz,
CO). 31P{1H} NMR (121.5 MHz, CD2Cl2): δ 25.0. 29Si{1H} NMR
(59.6 MHz, CD2Cl2): δ 48.6 (d, 2JPSi ) 39.0 Hz), IR (KBr, cm-1):
1876vs (νCO).
Reaction of [Ru(xantsil)(CO)(η6-toluene)] (1a) with PMe3. A
Pyrex tube (10 mm o.d.) was charged with 1a (20.0 mg, 0.0366

926 Organometallics, Vol. 27, No. 5, 2008
Okazaki et al.
Table 2. Selected Interatomic Distances (Å) and Angles (deg) in
Monitoring the Reaction of [Ru(xantsil)(CO)(PCy3)] (6)
with CO. A Pyrex NMR tube was charged with 6 (7.0 mg, 9.5
µmol) and dichloromethane (0.5 mL). The solution was treated with
CO gas (350 µL, 1.6 equiv) via syringe at room temperature and
vigorously stirred. The orange solution gradually turned dark green.
According to the NMR spectroscopic data, the reaction mixture
consists of 6, [Ru(xantsil)(CO)2(PCy3)] (7), and [Ru(xantsil)-
(CO)3(PCy3)] (8) in the molar ratio of 0.3:1.3:1.0. Due to
contamination of 6 and 8, isolation of 7 was not achieved. Data
4a-c
4a
4b
4c
Ru-Si1
2.396
2.498
2.437
2.457
1.857
3.671
2.592
2.471
2.492
2.256
1.890
3.351
98.9
90.0
91.1
175.0
159.2
91.1
108.1
108.1
88.3
2.512
2.455
2.482
2.282
1.900
2.300
Ru-Si2
Ru-P1
Ru-P2
Ru-C1
Ru-O1
Si1-Ru-Si2
Si1-Ru-P1
Si1-Ru-P2
Si1-Ru-C1
Si2-Ru-P1
Si2-Ru-P2
Si2-Ru-C1
P1-Ru-P2
P1-Ru-C1
P2-Ru-C1
Si1-Ru-O1
Si2-Ru-O1
C1-Ru-O1
P2-Ru-O1
98.2
97.8
1
for 7: H NMR (300 MHz, CD2Cl2): δ 0.43 (s, SiMe2). 31P NMR
98.6
96.2
89.5
160.7
93.0
83.5
94.6
87.1
173.7
91.4
92.0
172.0
164.8
93.3
76.4
98.6
86.1
95.9
83.1
78.7
96.1
164.6
(121.5 MHz, CD2Cl2): 37.6. 29Si{1H} NMR (59.6 MHz, CD2Cl2):
2
δ 21.8 (d, JPSi ) 23.2 Hz). IR (CD2Cl2, cm-1): 1927vs, 2036vw
(νCO).
Synthesis of [Ru(xantsil)(CO)3(PCy3)] (8). A Schlenk tube was
charged with a solution of 6 (75 mg, 0.102 mmol) in CH2Cl2 (5
mL), placed in liquid N2, and evacuated. After filling the tube with
CO, the solution was allowed to warm to room temperature and
then stirred for 1 h. Volatiles were removed under reduced pressure.
The resulting white solid of 8 was washed with hexane three times
and dried under vacuum. Yield: 68 mg (84%). Anal. Calcd for
C40H57O4PRuSi2: C, 60.81; H, 7.27. Found: C, 60.45; H, 7.45. 1H
NMR (300 MHz, CD2Cl2, 230 K): δ 0.46, 0.64, 0.66, 0.72 (s, 3H
× 4, SiMe2), 0.77–2.31 (m, 33H, Cy), 1.29, 1.71 (s, 3H × 2,
9-CMe2), 6.93–7.43 (m, 6H, xanthene). 13C{1H} NMR (75.5 MHz,
CD2Cl2, 200 K): δ 4.84, 6.20, 7.81 (SiMe), 7.11 (d, JPC ) 4.2 Hz,
SiMe), 13.5, 21.5, 22.2, 35.6 (Cy), 24.8–31.2 (m, Cy and 9-CMe2),
34.9 (9-CMe2), 40.8–41.5 (Cy), 121.7, 121.8, 123.2, 123.4, 130.2,
131.1, 131.3, 132.1, 132.9, 156.5, 156.7 (xanthene), 197.6, 203.8,
98.2
meter with graphite-monochromated Mo KR radiation. Data were
collected at 150 K to a maximum 2θ value of 55.0°. Empirical or
numerical absorption correction was applied, and the data were
corrected for Lorentz and polarization effects. The structure was
solved by direct methods and refined by full matrix least-squares
techniques on all F2 data (SHELXL-97).15 The non-hydrogen atoms
were refined anisotropically, and hydrogen atoms were located on
idealized positions and refined using a restricted riding model.
Selected crystallographic data are listed in Table 1.
204.5 (br, CO). 31P{1H} NMR (121.5 MHz, CD2Cl2): δ 39.3.
2
29Si{1H} NMR (59.6 MHz, CD2Cl2, 230 K): δ -6.2 (d, JPSi
)
2
45.1 Hz, Si trans to PCy3), -2.2 (d, JPSi ) 8.8 Hz, Si trans to
CO). IR (KBr, cm-1): 2040vs, 1992vs, 1946vs (νCO).
Thermolysis of [Ru(xantsil)(CO)(η6-C6H5CH3)] (1a) in n-
Decane. Complex 1a (10.0 mg, 0.0183 mmol) and n-decane (1.0
mL) were placed in a Pyrex tube, which was flame-sealed under
high vacuum. The sample was heated at 140 °C in an oil bath for
1 day. Fine crystals precipitated and the solution became light brown
in color. The tube was opened inside the glovebox, and the mother
liquor was decanted. The yellow crystals of [Ru(xantsil)(CO)]2 (9)
were washed with hexane and dried under vacuum. Yield: 6.0 mg
(72%). Due to the poor solubility of 9 in organic solvents, no NMR
data were available. No acceptable data for elemental analysis were
obtained because 9 cannot be purified due to its poor solubility. IR
(KBr, cm-1): 1913 (νCO). Mass (EI, 70 eV): m/z 908 (M+, 29),
396 (M+/2 - SiMe2, 23), 381 (M+/2 - SiMe2 - Me, 100).
X-ray Crystal Structure Determination. Crystals of 2 · CH3CN,
4, 6, 8 · CH2Cl2, and 9 were mounted at the end of a glass fiber for
analysis using a Rigaku RAXIS-RAPID imaging plate diffracto-
Acknowledgment. This work was supported by Grants-
in-Aid for Scientific Research (Nos. 18064003 and 18350027)
from the Ministry of Education, Culture, Sports, Science and
Technology of Japan.
Supporting Information Available: A preliminary X-ray
structure analysis of 3 in PDF format. Crystallographic data in CIF
format for 2 · CH3CN, 4, 6, 8 · CH2Cl2, and 9. These materials are
available free of charge via the Internet at http://pubs.acs.org.
OM701194E
(15) (a) Sheldrick, G. M. SHELXS-97, Programs for Solving X-ray
Crystal Structures; University of Göttingen, 1997. (b) Sheldrick, G. M.
SHELXL-97, Programs for Refining X-ray Crystal Structures; University
of Göttingen, 1997.