Versatile coordination of 2-pyridinetetramethyldisilazane at ruthenium: Ru(II) vs Ru(IV) as evidenced by NMR, X-ray, neutron, and DFT studies

Article abstract of DOI:10.1021/ja901140v

The novel disilazane compound 2-pyridinetetramethyldisilazane (1) has been synthesized. The competition between N-pyridine coordination and Si-H bond activation was studied through its reactivity with two ruthenium complexes. The reaction between 1 and Ru

Full text of DOI:10.1021/ja901140v

Published on Web 05/12/2009
Versatile Coordination of 2-Pyridinetetramethyldisilazane at
Ruthenium: Ru(II) vs Ru(IV) As Evidenced by NMR, X-ray,
Neutron, and DFT Studies
Mary Grellier,*,† Tahra Ayed,‡ Jean-Claude Barthelat,‡ Alberto Albinati,§
Sax Mason,⊥ Laure Vendier,† Yannick Coppel,† and Sylviane Sabo-Etienne*,†
CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne,
F-31077 Toulouse, France, UniVersite´ de Toulouse, UPS, INPT, F-31077 Toulouse, France,
Laboratoire de Physique Quantique, IRSAMC (UMR 5626), UniVersite´ Paul Sabatier,
118 route de Narbonne, 31062 Toulouse Cedex 4, France, Department of Structural Chemistry
(DCSSI), UniVersity of Milan, 21, Via G. Venezian, 20133 Milan, Italy, and Institut
Laue-LangeVin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9, France
Received February 13, 2009; E-mail: grellier@lcc-toulouse.fr; sylviane.sabo@lcc-toulouse.fr
ࠗ
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This paper contains enhanced objects available on the Internet at http://pubs.acs.org/jacs.
Abstract: The novel disilazane compound 2-pyridinetetramethyldisilazane (1) has been synthesized. The
competition between N-pyridine coordination and Si-H bond activation was studied through its reactivity
with two ruthenium complexes. The reaction between 1 and RuH2(H2)2(PCy3)2 led to the isolation of the
new complex RuH2{(η2-HSiMe2)N(κN-C5H4N)(SiMe2H)}(PCy3)2 (2) resulting from the loss of two dihydrogen
ligands and coordination of 1 to the ruthenium center via a κ2N,(η2-Si-H) mode. Complex 2 has been
characterized by multinuclear NMR experiments (1H, 31P, 13C, 29Si), X-ray diffraction and DFT studies. In
particular, the HMBC 29Si-1H spectrum supports the presence of two different silicon environments: one
Si-H bond is dangling, whereas the other one is η2-coordinated to the ruthenium with a JSiH value of 50
Hz. DFT calculations (B3PW91) were also carried out to evaluate the stability of the agostic species versus
a formulation corresponding to a bis(σ-Si-H) isomer and confirmed that N-coordination overcomes any
stabilization that could be gained by the establishment of SISHA interactions. There is no exchange between
the two Si-H bonds present in 2, as demonstrated by deuterium-labeling experiments. Heating 2 at 70 °C
under vacuum for 24 h, leads to the formal loss of one equivalent of H2 from 2 and formation of the 16-
electron complex RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}(PCy3)2 (3) formulated as a hydrido(silyl) species on
the basis of multinuclear NMR experiments. The dehydrogenation reaction is fully reversible under
dihydrogen atmosphere. Reaction of Ru(COD)(COT) with 3 equiv of 1 under a H2 pressure led to the
isolation of the new complex RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}3 (4) characterized as a hydridotrisilyl
complex by multinuclear NMR techniques, X-ray and neutron diffractions, as well as DFT calculations.
The 29Si HMBC experiments confirm the presence of two different silicon atoms in 4, with a signal at -14.64
ppm for three dangling Si-Me2H fragments and a signal at 64.94 ppm (correlating with the hydride signal)
assigned to three Si-Me2N groups bound to Ru. Comparison of DFT and neutron parameters involving the
hydride clearly indicates an excellent correlation. The Si-H distance of ∼2.15 Å is much shorter than the
sum of the van der Waals radii and typically in the range of a significant interaction between a silicon and
a hydrogen atom (SISHA interactions). In 4, three dangling Si-H groups remain accessible for further
functionalization.
Introduction
bonds. For example, it has been shown that they are good
precursors for refractory materials,1 surface functionalization,2,3
Silazane (R3Si)nN(R′)3-n (n ) 1-3) compounds display a
wide area of applications, from materials to organic chemistry.
The 1,1,3,3-tetramethyldisilazane (Me2HSi)2NR′ family has
received particular attention in recent years, due to additional
reactivity that can be gained from the presence of the Si-H
silylated macromolecules,4 or silylated organic heterocycles.5,6
(1) Wrobel, A. M.; Blaszczyk, I.; Walkiewicz-Pietrzykowska, A.; Tracz,
A.; Klemberg-Sapieha, J. E.; Aoki, T.; Hatanaka, Y. J. Mater. Chem.
2003, 13, 731–737.
(2) Zapilko, C.; Widenmeyer, M.; Nagl, I.; Estler, F.; Anwander, R.;
Raudaschl-Sieber, G.; Groeger, O.; Engelhardt, G. J. Am. Chem. Soc.
2006, 128, 16266–16276.
† CNRS, LCC (Laboratoire de Chimie de Coordination), Universite´ de
Toulouse.
(3) Giraud, L.; Jenny, T. Organometallics 1998, 17, 4267–4274.
(4) Rasul, T.; Son, D. Y. J. Organomet. Chem. 2002, 655, 115–119.
(5) Trost, B. M.; Ball, Z. T. J. Am. Chem. Soc. 2003, 125, 30–31.
(6) Tamao, K.; Nakagawa, Y.; Arai, H.; Higuchi, N.; Ito, Y. J. Am. Chem.
Soc. 1988, 110, 3712–3714.
‡ Laboratoire de Physique Quantique, IRSAMC (UMR 5626), Universite´
Paul Sabatier.
§ Department of Structural Chemistry (DCSSI), University of Milan.
⊥ Institut Laue-Langevin.
9
10.1021/ja901140v CCC: $40.75  2009 American Chemical Society
J. AM. CHEM. SOC. 2009, 131, 7633–7640 7633

A R T I C L E S
Grellier et al.
Scheme 1
Scheme 2
The multicenter reactivity of such ligands is well illustrated
in amido lanthanidocene systems. The amidodisilazane fragment
coordinates to the metal center with two or one agostic ꢀ-Si-H
interactions (see Scheme 1, species a and b).7-10 Recently, we
have reported an unprecedented coordination mode of 1,1,3,3-
tetramethyldisilane to ruthenium: a disilazane complex with two
σ-Si-H bonds and without nitrogen coordination was isolated
(Scheme 1, species c).11 The stability of this coordination mode
c could be explained by the presence of secondary interactions
(SISHA) between the hydrides and the silicon atoms.12,13 These
secondary interactions are present in a wide series of silane,
disilane, and disiloxane ruthenium complexes.14 The specific
coordination mode on ruthenium allowed us to achieve, in very
mild conditions, catalytic selective deuteration of NH(SiHMe2)2
into NH(SiDMe2)2 under D2 atmosphere.11
A good understanding of silazane coordination to a metal
center is crucial to control some key steps involved in catalytic
hydrosilylation processes.15,16 There are several parameters that
can be used to monitor the degree of activation of a Si-H bond
between the initial step and the final one resulting in oxidative
addition. In such a process and of course in the microscopic
reverse reductive elimination, σ-silane complexes are often
considered as intermediates.13,17,18 Alternatively, substrate func-
tionalization can be achieved without any change in the metal
oxidation state by successive formation of σ-isomeric com-
plexes, as recently illustrated by the concept of the σ-CAM
mechanism (σ-complex assisted metathesis mechanism at late
transition metals).19 NMR is a useful technique to discriminate
a σ-formulation from the corresponding product of oxidative
addition. In the specific case of silane activation, H and 29Si
NMR data (chemical shifts and coupling constants) can give
some key information, but overlaps exist for the different classes
of compounds, and the silicon substituents play also a major
role. It is thus important to support the assignments by structural
studies. The M-Si and Si-H bond distances are good indicators
to define the activation degree of the Si-H bond. Typically,
the upper limit for a σ-Si-H (or agostic) bond distance is set
up at ∼1.90 Å, whereas SISHA interactions take place in the
range of 2.00-2.40 Å. In the absence of neutron data, hydrogen
location by X-ray diffraction is always subject to debate. In
hydride and σ-complex chemistry it is thus particularly useful
to perform DFT calculations as a complementary tool to support
hydrogen location.20
In this paper, we report the synthesis of 2-pyridinetetram-
ethyldisilazane (1), a compound bearing different functionalities,
and its coordination to the two ruthenium complexes, RuH2-
(H2)2(PCy3)2 and its precursor Ru(COD)(COT). 1 is a good
model to evaluate several possible chelating modes as illustrated
in Scheme 2: κN,(η2-Si-H) (A), bis(σ-Si-H) (B), and κN,N′
(C). A combination of multinuclear NMR, structural and DFT
studies, including a neutron determination in the case of a
ruthenium (IV) hydridotrisilyl complex, allows us to discuss
the activation mode of the Si-H bonds and in particular to
highlight the differences between agostic η2-Si-H bonds,
SISHA interactions, and products of oxidative addition.
1
(7) Klimpel, M. G.; Gorlitzer, H. W.; Tafipolsky, M.; Spiegler, M.;
Scherer, W.; Anwander, R. J. Organomet. Chem. 2002, 647, 236–
244.
(8) Eppinger, J.; Spiegler, M.; Hieringer, W.; Herrmann, W. A.; Anwander,
R. J. Am. Chem. Soc. 2000, 122, 3080–3096.
(9) Herrmann, W. A.; Eppinger, J.; Spiegler, M.; Runte, O.; Anwander,
R. Organometallics 1997, 16, 1813–1815.
Results and Discussion
(10) Otero, A.; Fernandez-Baeza, J.; Lara-Sanchez, A.; Alonso-Moreno,
C.; Marquez-Segovia, I.; Sanchez-Barba, L. F.; Rodriguez, A. M.
Angew. Chem., Int. Ed. 2009, 121, 2210-2213.
The synthesis of the silylated aminopyridine 1 was performed
by using a standard method.21 2-Aminopyridine was deproto-
nated by one equivalent of n-butyllithium followed by addition
of one equivalent of chlorodimethylsilane. The procedure was
conducted twice to introduce a second SiMe2H fragment, but
without isolating the monosilylated compound. After workup,
1 was obtained as an oily product in 86% yield. Typical NMR
patterns for RNSiMe2H fragments were obtained for 1: a high-
field 29Si resonance at -11.21 ppm and in the 1H NMR spectrum
a septet at 4.97 ppm (3JHH ) 3.3 Hz and 1JSiH ) 191.6 Hz) for
the Si-H groups and four pyridinic-proton signals at 8.10, 7.06,
6.71, and 6.39 ppm.
(11) Ayed, T.; Barthelat, J.-C.; Tangour, B.; Prade`re, C.; Donnadieu, B.;
Grellier, M.; Sabo-Etienne, S. Organometallics 2005, 24, 3824–3826.
(12) Atheaux, I.; Delpech, F.; Donnadieu, B.; Sabo-Etienne, S.; Chaudret,
B.; Hussein, K.; Barthelat, J. C.; Braun, T.; Duckett, S. B.; Perutz,
R. N. Organometallics 2002, 21, 5347–5357.
(13) Lachaize, S.; Sabo-Etienne, S. Eur. J. Inorg. Chem. 2006, 2115–2127.
(14) Delpech, F.; Sabo-Etienne, S.; Daran, J. C.; Chaudret, B.; Hussein,
K.; Marsden, C. J.; Barthelat, J. C. J. Am. Chem. Soc. 1999, 121,
6668–6682.
(15) Marciniec, B. Coord. Chem. ReV. 2005, 249, 2374–2390.
(16) Marciniec, B. In Applied Homogeneous Catalysis with Organometallic
Compounds, 2nd ed.; Cornils, B., Herrmann, W. A., Eds.; Wiley-VCH:
Weinheim, 2002; p 491.
(17) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175–292.
(18) Kubas, G. J. Metal Dihydrogen and σ-Bond Complexes; Kluwer
Academic/Plenum Publishers: New York, 2001.
(19) Perutz, R. N.; Sabo-Etienne, S. Angew. Chem., Int. Ed. 2007, 46, 2578–
2592.
(20) Alcaraz, G.; Sabo-Etienne, S. Coord. Chem. ReV. 2008, 252, 2395–
2409.
(21) Wiseman, G. H.; Wheeler, D. R.; Seyferth, D. Organometallics 1986,
5, 146–152.
9
7634 J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009

Complex with General Formula RuH(SiR3)3L3 Synthesized
A R T I C L E S
Scheme 3
-10.70, -13.55 ppm are well-resolved and assigned to Hc, Ha
Reaction of 2-Pyridinetetramethyldisilazane (1) with RuH2-
(H2)2(PCy3)2. We have previously demonstrated that the bis-
(dihydrogen) complex RuH2(H2)2(PCy3)2 is the precursor of
choice to prepare a series of bis(silane) complexes of general
formula RuH2{(η2-HSiMe2)Z}2(PCy3)2. When the spacer linking
the two silicons is larger than one atom (Z ) C6H4, (CH2)n,
OSiMe2O) a similar structure was observed with two (η2-Si-H)
in a trans configuration,14,22 whereas in the case of a short spacer
(Z ) O, NH) the two (η2-Si-H) are in a cis configuration due
to a steric constraint.11,12 The reaction between 1 and RuH2(H2)2-
(PCy3)2 leads to the isolation of a new complex RuH2{(η2-
HSiMe2)N(κN-C5H4N)(SiMe2H)}(PCy3)2 (2) resulting from the
loss of two dihydrogen ligands and coordination of 1 to the
ruthenium center via a κ2N,(η2-Si-H) A mode (see Schemes 2
and 3). Complex 2 has been characterized by multinuclear NMR
experiments and X-ray diffraction. At room temperature, the
1H NMR spectrum in C6D6 exhibits four signals at 9.31, 6.60,
6.48, 5.90 ppm, characteristic of a pyridine group coordinated to
a ruthenium center (the ortho proton of the pyridine fragment is
deshielded by 1.20 ppm compared to the free ligand 1). The HMBC
29Si-1H spectrum supports the presence of two different silicon
environments. The dangling Si-Hb group is characterized by a
29Si NMR high field signal at -14.5 ppm and by a septet in the
1H NMR spectrum integrating for one hydrogen at 5.33 ppm
(1JHSi ) 207 Hz) as well as a doublet integrating for six
hydrogen atoms at 0.40 ppm. The singlet integrating for six
hydrogens at 1.10 ppm correlates with a silicon resonance at
56.9 ppm and is characteristic of a Si coordinated to a ruthenium
and Hd, respectively, on the basis of the following experiments:
1
(i) by recording a H{31P} NMR spectrum the triplet at -3.79
turns into a singlet, the multiplet at -10.70 leads to a doublet
2
with a JHH ) 10 Hz and the doublet of triplet at -13.55
simplifies into a doublet with also a 2JHH ) 10 Hz. (ii) 1D NOE
1H NMR experiments with a mixing time of 300 ms show that
only the hydride at -3.79 ppm is close to the ortho pyridinic
hydrogen. (iii) The HMBC 29Si-1H experiment reveals a
correlation between the silicon at 56.9 ppm and the hydride at
-10.70 ppm, whereas a homodecoupled 1H{31P} NMR on the
signal at -13.55 ppm turns the signal at -10.70 ppm into a
singlet and allows the measurement of the silicon satellites.
The JSiH value of 50 Hz is in the range characteristic of
σ-silane complexes and thus indicates a significant activation
of the Si-H bond.23 Finally, at higher temperatures, exchange
of the three hydrides is observed with an estimated ∆Gq of
51 kJ · mol-1 at 313 K leading at 333 K to a very broad signal
1
at -10 ppm. On the basis of these H, 29Si and 31P NMR
studies at various temperatures, we can propose a structure
consistent with the ruthenium surrounded by two equivalent
phosphine ligands, a N pyridinic atom, two hydrides and one
η2-Si-H on the ruthenium as described in Scheme 3. Such a
formulation is confirmed by an X-ray diffraction analysis (see
Table 1). The X-ray structure is depicted in Figure 2, and the
most relevant geometrical parameters are reported in Table 2.
The crystal structure of 2 is characterized by a symmetry
plane through the pyridinic ring, the disilazane fragment and
the ruthenium-hydrides core. The two tricyclohexylphosphines
are in a trans configuration with a P-Ru-P angle bent toward
the hydrides (155.71 (3)°). The three hydrides could be located,
and DFT calculations support their location (see below). The
Si1-H1a bond is η2-coordinated to the ruthenium center as
illustrated by the bond distances of Ru-Si1 2.415(1) Å, Ru-H1a
1.66 (4) Å and Si1-H1a 1.63(4) Å. The Si1-H1a bond distance
is longer than that in the dangling Me2SiH group (Si2-H1b of
1.44(5) Å). The η2-Si-H distance is in the lower limit of the
range reported for a series of σ-Si-H ruthenium complexes,17,18,24
and close to the values found in a bis(cyclometalated) ruthenium
complex displaying two ꢀ-agostic Si-H bonds (1.76(4) Å and
1.65(3) Å).25 Because of the problems associated with the
hydride location by X-ray diffraction, we carried out a DFT
optimization of 2 without any simplification and using B3PW91
as a functional. A good correlation was found between the X-ray
data for 2 and the calculated geometrical parameters for 2a as
can be seen from Table 2. The Ru-Si distance in particular is
1
center. At 298 K, the upfield region in the H NMR spectrum
is almost featureless as a result of a fast exchange between the
different hydrogen atoms coordinated to ruthenium (Figure 1).
At 223 K, three upfield signals of equal intensity at -3.79,
(22) Delpech, F.; Sabo-Etienne, S.; Chaudret, B.; Daran, J.-C. J. Am. Chem.
Soc. 1997, 119, 3167–3168.
(23) Alcaraz, G.; Helmstedt, U.; Clot, E.; Vendier, L.; Sabo-Etienne, S.
J. Am. Chem. Soc. 2008, 130, 12878–12879.
(24) Schubert, U. AdV. Organomet. Chem. 1990, 30, 151–187.
(25) Montiel-Palma, V.; Munoz-Hernandez, M. A.; Ayed, T.; Barthelat,
J.-C.; Grellier, M.; Vendier, L.; Sabo-Etienne, S. Chem. Commun.
2007, 3963–3965.
Figure 1. Variable-temperature 1H NMR (400 MHz) spectra of 2 in C7D8
in the hydride region (* indicates impurities).
9
J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009 7635

A R T I C L E S
Grellier et al.
Table 1. Crystal Data and Details of the Structure Refinement for
2 and 4 (X-ray and Neutron Diffraction)
Table 2. Comparison between Selected Geometrical Parameters
(distances in Å, angles in deg) for the Experimental X-ray 2 and
Calculated 2a-c (DFT/B3PW91) Structures
2 (X-ray)
4 (X-ray)
4 (neutron)
2 (X-ray)
2a (DFT)
2b (DFT)
2c (DFT)
formula
C45H86N2P2RuSi2 C27H52N6RuSi6
C27H52N6RuSi6
730.33
20(1)
ILL D19
neutron
Ru-H1a
1.66(4)
1.632
1.608
1.700
1.648
1.605
2.422
2.434
1.963
1.819
2.403
2.156
2.405
2.301
1.655
1.715
1.602
1.620
2.492
2.878
1.751
1.600
3.527
4.059
3.776
3.443
molecular weight
temperature, K
diffractometer
radiation
874.35
730.33
Ru-H1b
Ru-H1c
160(2)
110(2)
XCALIBUR
Mo KR
XCALIBUR
Mo KR
1.62(4)
1.54(4)
2.4150(14)
1.634
1.603
2.418
Ru-H1d
Ru-Si1
(λ ) 0.71073 Å) (λ ) 0.71073 Å) (λ ) 1.1695(1) Å)
crystal system
space group (no.)
a, Å
b, Å
monoclinic
P21/m (10)
9.831(2)
21.651(4)
11.917(2)
90
trigonal
R3 (148)
18.645(2)
18.645(2)
19.061(2)
90
trigonal
Ru-Si2
j
j
R3 (148)
Si1-H1a
Si2-H1b
Si1-H1c
Si1-H1d
Si2-H1a
Si2-H1d
Ru-N1
1.63(4)
1.44(5)
1.840
1.488
18.5880(3)
18.5880(3)
18.8361(3)
90
90
120
5636.2(2)
6
1.290
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
109.44(3)
90
90
120
2.191(3)
155.71(3)
42.2(13)
2.215
155.36
49.52
2391.9(9)
2
5739(1)
6
P-Ru-P
H1a-Ru-Si1
H1b-Ru-Si2
N-Ru-Si
114.55
53.81
48.32
150.23
44.50
28.61
F
calcd, g cm-3
1.214
0.476
3.41-26.37
1.268
0.623
3.31-25.68
7095
µ, mm-1
0.201
θ range (deg)
2.74-61.69
13183
4285
78.79(9)
79.00
no. reflns collected 34507
no. independ. reflns 4805
2409
lowest in energy, whereas complexes 2b and 2c are 48 kJ ·mol-1
and 51 kJ ·mol-1 less stable than 2a, respectively. Isomer 2b
displays a B coordination mode (Scheme 2) with a geometry
very similar to the X-ray structure reported for the disilazane
complex RuH2{(η2-HSiMe2)2NH}(PCy3)2. The two phosphines
are in a cis position to allow the formation of two σ-Si-H bonds
(Si1-H1a ) 1.963 and Si2-H1b ) 1.819 Å) and four SISHA
interactions (Si· · ·H distances ∼2.3 Å). In 2c, the phosphines
are in a trans position, thus preventing any stabilization by
SISHA interactions (Si · · ·H distances > 3.4 Å), and the
activation degree of the two Si-H bonds is quite different as
demonstrated by the different values obtained for the Ru-Si
and Si-H distances (Table 2).
observed reflns
Rint
4391
1598
3216
0.097
0.0698
0.1306
1.119
a
0.046
0.0403
0.0912
1.101
0.051
0.0361
0.0566
0.894
R(Fo) [I > 2σ(I)]
b
2
Rw (Fo ) [I > 2σ(I)]
GOF
a
b
Rint ) Σ|Fo -〈Fo〉|/ΣFo ; R(Fo) ) Σ||Fo| - |Fc||/Σ|Fo|. Rw(Fo2) )
2
2
[Σ[w(Fo2 - Fc2)2 ]/Σ[ w(Fo2)2]]1/2; GOF ) [Σ [w(Fo2 - Fc2)2]/(N - P)]1/2
where N, P are the number of observations and parameters, respectively.
,
It is noteworthy that nitrogen coordination of a N sp2 involved
in an aromatic ring such as pyridine or quinoline is highly
favored.26,27 In the present system, N-coordination overcomes
any stabilization that could be gained by the establishment of
SISHA interactions. Our calculations allow us to estimate the
energy difference between an agostic Si-H bond and a bis
σ-Si-H formulation. They are also useful to support IR
assignment for the Ru-H and Ru-H-Si stretching modes.14
Indeed, the IR spectrum (Nujol) of 2 displays three medium
bands in the range 2200-1890 cm-1. The two bands at 2191
cm-1 and 1987 cm-1 are assigned to the H-Si stretch of the
dangling SiMe2H group and the Ru-H stretches, respectively,
whereas the broadband at 1897 cm-1 corresponds to a mixing
of Ru-H and Ru-H-Si stretches.
Figure 2. X-ray structure of compound 2. Thermal ellipsoids are shown
at the 50% probability level. All the hydrogen atoms are omitted for clarity
except those bound to the ruthenium.
Even though 2 is very stable in the solid state, we noticed
some decomposition upon storage, over a long period, at room
well reproduced as well as the P-Ru-P angle. The η2-Si-H
coordination is confirmed by DFT with a significant lengthening
of the Si-H bond: 1.840 Å. This value, longer than the
measured X-ray distance, indicates a substantial activation of
the Si-H bond in agreement with the JSiH value of 50 Hz.
Moreover, theoretical calculations were carried out to evaluate
the stability of the agostic species 2a versus a formulation
corresponding to a bis(σ-Si-H) isomer. As mentioned in the
introduction, we have already demonstrated that such a structure
with two σ-Si-H bonds in a cis position (RuH2{(η2-
HSiMe2)2NH}(PCy3)2) could be obtained.11 Here, we did not
use any simplified model, and the calculations were carried out
at the B3PW91 level. As depicted in Figure 3, two other isomers
were optimized to a local minimum: complex 2a (A coordination
mode, Scheme 2) corresponding to the X-ray structure is the
Figure 3. Three B3PW91-optimized isomeric structures of 2. Carbons are
in gray, silicons in pink, nitrogens in green, phosphorus atoms in orange,
ruthenium atoms in blue and hydrogen atoms in black. For clarity, only the
C attached to P of the tricyclohexylphosphines have been represented.
9
7636 J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009

Complex with General Formula RuH(SiR3)3L3 Synthesized
A R T I C L E S
Scheme 4
Scheme 5
temperature under an argon atmosphere (33% decomposition
in 2 years!). A new complex was detected by NMR that could
be isolated as an orange solid on a preparative scale by heating
2 at 70 °C under vacuum for 24 h. The thermal decomposition
is quantitative and corresponds to the formal loss of one
equivalent of H2 from 2. The new complex RuH{(SiMe2)N(κN-
C5H4N)(SiMe2H)}(PCy3)2 (3) is formulated as a hydrido(silyl)
species on the basis of multinuclear NMR experiments (see
Scheme 3). The 31P{1H} NMR spectrum exhibits one singlet at
52.7 ppm consistent with two equivalent phosphines. In the 1H
NMR spectrum, the hydrogen in the ortho position of the
pyridinic fragment is shielded at 8.74 ppm. The three other
hydrogen atoms of the aromatic ring are deshielded by ∼0.35
ppm compared to compound 2. The HMQC 29Si-1H experiment
shows two silicon resonances at -16.6 ppm for the dangling
SiH and 64.1 ppm for the silyl group (Ru-SiMe2). In the
hydride region, only one triplet is observed at -12.70 ppm (2JHP
) 25 Hz). The 1H{31P} NMR experiment allows the detection
Table 3. Comparison between Selected Geometrical Parameters
for Compound 4 Obtained from X-ray and Neutron Diffraction As
Well As DFT Calculations (distances in Å, angles in deg).
4
X-ray
neutron
DFT
Ru-H10
1.41(5)
2.3291(9)
2.120(9)
1.45(3)
2.231(2)
80.32(6)
63.59(3)
124.76(6)
1.559(7)
2.326(3)
2.154(8)
1.481(5)
2.226(2)
80.12(6)
63.81(8)
124.86(6)
1.557
2.346
2.162
1.491
2.246
79.98
63.56
124.98
Ru-Si1
Si1-H10
Si2-H11
Ru-N1
N1-Ru-Si1
H10-Ru-Si1
H10-Ru-N1
apparent coupling constant JHSiapp of 7.5 Hz. All the integration
ratios are in agreement with the presence of three pyridinic,
three SiMe2H and three SiMe2 fragments for only one hydride.
Methyl substituents on the silicon atoms are diastereotopic. The
29Si HMBC experiments confirm the presence of two different
silicon atoms in 4. The signal at -14.24 ppm is assigned to
three dangling SiMe2H fragments, whereas the signal at 64.94
ppm which correlates with the hydride signal is assigned to three
SiMe2N groups bound to Ru.
After having obtained crystals for X-ray diffraction, it was
also possible to grow a few crystals suitable for neutron
diffraction. Selected distances and angles are listed in Table 3,
as well as those calculated from the corresponding theoretical
model. An ORTEP view of the neutron structure is shown in
Figure 4.
2
of the silicon satellites and a JSiH value of 11 Hz can be
measured. All the data are in agreement with the formation of
a hydrido(silyl) complex. The silyl group which is the strongest
σ-donor ligand is trans to the vacant site.28
The dehydrogenation process is fully reversible. Thus,
bubbling H2 in a C6D6 solution of 3 allows total conversion to
1
2, as monitored by H and 31P NMR. We then examined the
behavior of a C7D8 solution of 2 under D2 atmosphere. After
bubbling D2 for 3.25 h, NMR monitoring showed 53% of
deuterium incorporation into the two hydrides and the η2-Si-H
bond (see Scheme 4). No deuterium incorporation was detected
in the dangling Si-H bond. This observation confirms that there
is no exchange between the two Si-H bonds present in 2. This
opens some possibilities for further functionalization of the
dangling Si-H group, for example by hydrosilylation.
As already mentioned above, hydrogen location by X-ray
diffraction is difficult and subject to systematic errors always
Reaction of 2-Pyridinetetramethyldisilazane (1) with Ru-
(COD)(COT). In view of the reversible dehydrogenation process
between 3 and 2, it was tempting to test the reactivity of 1 with
Ru(COD)(COT), the precursor for the synthesis of the bis(di-
hydrogen) complex RuH2(H2)2(PCy3)2. In that context, oxidative
addition of the Si-H bonds could compete toward N-coordina-
tion. Reaction of Ru(COD)(COT) with 3 equiv of 1 under a H2
pressure for a few minutes, led after workup to the isolation of
the new complex RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}3 (4)
(Scheme 5) characterized as a hydridotrisilyl ruthenium (IV)
complex by multinuclear NMR techniques, X-ray and neutron
diffractions, as well as DFT calculations.
In the hydride region, the 1H NMR spectrum of 4 shows one
singlet at -13.63 ppm displaying silicon satellites with an
(26) Matthes, J.; Gru¨ndemann, S.; Toner, A.; Guari, Y.; Donnadieu, B.;
Spandl, J.; Sabo-Etienne, S.; Clot, E.; Limbach, H. H.; Chaudret, B.
Organometallics 2004, 23, 1424–1433.
(27) Toner, A.; Matthes, J.; Grundemann, S.; Limbach, H. H.; Chaudret,
B.; Clot, E.; Sabo-Etienne, S. Proc. Natl. Acad. Sci. U.S.A. 2007, 104,
6945–6950.
Figure 4. Neutron structure of RuH{(SiMe2)N(κN-C5H4N)(SiMe2H)}3 (4).
Movie in GIF format of neutron structure of 4. All the hydrogen atoms are
omitted for clarity, except those on ruthenium and silicon atoms.
(28) Lachaize, S.; Caballero, A.; Vendier, L.; Sabo-Etienne, S. Organo-
metallics 2007, 26, 3713–3721.
9
J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009 7637

A R T I C L E S
Grellier et al.
leading to an underestimation of the M-H distances. However,
we and others have found that useful and reliable information
can, nonetheless, be obtained from this technique by combining
the X-ray results with those from DFT calculations.13,20,29 Here,
we had a unique opportunity to compare X-ray, neutron and
DFT values. We have thus performed a DFT/B3PW91 calcula-
tion on 4 without any simplification on the model used. Table
3 allows a direct comparison of some selected values obtained
by the three methods. The Ru-H distance of 1.41(5) Å by
X-ray, and 1.559(7) Å by neutron, can be compared to the
median value of 1.59 Å for terminal Ru-H distances obtained
by X-ray diffraction from the Cambridge Structural Data Center.
Four neutron diffraction structures of ruthenium complexes with
a terminal hydride have been previously reported: the cationic
complex [RuH(H2)(dppe)2][BF4] displays a Ru-H distance of
1.64(2) Å,30 whereas slightly shorter values have been found
in CpRuH(PMe3)2 (1.630(4) Å), [CpRuH2(PMe3)2][BF4] (1.599(8)
Å and 1.604(9) Å, respectively),31 and RuH2(H2)2(PCyp3)2
(1.628(4) Å 1.625(4) Å).32 As expected, X-ray Ru-H distances
are systematically shorter than those from neutron. The Ru-Si
distance is 2.3291(9) Å by X-ray and 2.326(3) Å by neutron.
This is a rather short distance, but in the range found for 58 Si
attached to ruthenium complexes from the CSD (in the range
2.19-2.47 Å) with a median value of 2.43 Å. Comparison of
DFT and neutron parameters involving the hydride clearly
indicates an excellent correlation. The Si-H distance of ∼2.15
Å is much shorter than the sum of the van der Waals radii and
typically in the range of a significant interaction between a
silicon and a hydrogen atom (SISHA).12,13 It is worth noting
that all the Ru-H bonds reported in the CSD refer to octahedral
complexes with a defined trans ligand to the hydride. In our
case, the Ru-H vector is pointing to the middle of the triangular
face defined by the three symmetry-related Si atoms bonded to
Ru. We are in presence of a seven-coordinated ruthenium: a
capped octahedron which is unprecedented for mononuclear
neutral Ru complexes.
pyridine group is always favored, no matter the ruthenium
oxidation state and the number of ligands around the metal. By
addition to the bis(dihydrogen) complex RuH2(H2)2(PCy3)2 we
could form either a dihydride ruthenium (II) complex 2 stabilized
by an agostic Si-H interaction or an unsaturated hydrido(silyl)
16-electron species 3. The hydrogenation/dehydrogenation
process is fully reversible under a dihydrogen atmosphere.
Interestingly, deuterium incorporation in 2 is selective with
isotopic labeling occurring only at hydrogen atoms bound to
the metal.
Access to the first hydridotrisilyl ruthenium (IV) complex 4
was possible by direct reaction of 1 with Ru(COD)(COT). The
reaction performed under dihydrogen atmosphere allows alkene
ligand hydrogenation and access to the Ru center. We have
obtained the first neutron structure of a ruthenium silyl complex
which moreover has three silyl groups in the coordination sphere
of the metal. The synthesis of such a complex with a general
formulation RuH(SiR3)3L3 is particularly interesting in view of
the controversial discussions on the analogous trihydride(silyl)
RuH3(SiR3)L3 family.13,33-40 In our system, a ruthenium (IV)
formulation is highly favored, leading to the formation of three
Ru-Si bonds. The short Ru-Si and Ru-H distances are in
agreement with such a formulation, and the Si-H bond distances
are characteristic of secondary interactions (SISHA) between
the hydride and the three silicon atoms. It is noteworthy that
the JSiH value in 4 is comparable to typical JSiH values for a
coupling between methyl protons bound to silicon atoms.
The Si-H bond activation by coordination of 1 to a ruthenium
center can thus range from an agostic level to a full oxidative
addition process, but the formation of a “true” σ-complex is
avoided, N-coordination of the pyridine fragment being pre-
dominant. Our study combining X-ray, neutron and DFT data
gives again more credit to the location of hydrogen atoms by
X-ray. Caution should remain, however, but geometrical
parameters obtained from the combined use of low-temperature
X-ray data on high-quality crystals and DFT calculations seem
to be quite reliable. Finally, it is worth pointing out that in 4,
three dangling Si-H groups remain accessible for further
functionalization as well as for grafting the organometallic
fragment into various supports. More generally, in suitable
conditions, addition of different substrates to the ruthenium (0)
precursor Ru(COD)(COT) could lead to the access of new
species for applications in catalysis or materials science.
Conclusion
We have synthesized a new silylated aminopyridine com-
pound 1 which allows us to tune the Si-H bond activation upon
coordination to a ruthenium center. Three new ruthenium
complexes have been prepared in which N-coordination of the
(29) Maseras, F.; Lledos, A.; Clot, E.; Eisenstein, O. Chem. ReV. 2000,
100, 601–636.
Experimental Section
(30) Albinati, A.; Klooster, W. T.; Koetzle, T. F.; Fortin, J. B.; Ricci, J. S.;
Eckert, J.; Fong, T. P.; Lough, A. J.; Morris, R. H.; Golombek, A. P.
Inorg. Chim. Acta 1997, 259, 351–357.
All reactions and workup procedures were performed under an
argon atmosphere using a conventional vacuum line and Schlenk
tube techniques or in a drybox. Solvents were dried and freshly
distilled according to standard procedures and degassed prior to
use. RuH2(H2)2(PCy3)2 and Ru(COD)(COT) were prepared accord-
ing to published procedures.41,42 All NMR solvents were dried and
degassed using appropriated methods. NMR spectra were acquired
on Bruker AC 200, AV 300, Avance 400 and Avance 500
spectrometers. GC/MS analysis and microanalysis were performed
by the Laboratoire de Chimie de Coordination Microanalytical
Service. The GC/mass spectra were measured at 70 eV on a HP
5973 attached to a HP 6890 (capillary column HP-5MS, 30 m, 0.25
mm, 0,250 mm with a temperature ramp 80 °C (2 min); 10 °C/
min; 280 °C (5 min)). Infrared spectra were obtained as Nujol mulls
on a Perkin-Elmer 1725 FT-IR spectrometer.
(31) Brammer, L.; Klooster, W. T.; Lemke, F. R. Organometallics 1996,
15, 1721–1727.
(32) Grellier, M.; Vendier, L.; Chaudret, B.; Albinati, A.; Rizzato, S.;
Mason, S.; Sabo-Etienne, S. J. Am. Chem. Soc. 2005, 127, 17592–
17593.
(33) Yardy, N. M.; Lemke, F. R.; Brammer, L. Organometallics 2001, 20,
5670–5674.
(34) Dioumaev, V. K.; Yoo, B. R.; Procopio, L. J.; Carroll, P. J.; Berry,
D. H. J. Am. Chem. Soc. 2003, 125, 8936–8948.
(35) Hu¨bler, K.; Hu¨bler, U.; Roper, W. R.; Schwerdtfeger, P.; Wright, L. J.
Chem.-Eur. J. 1997, 3, 1608–1616.
(36) Mohlen, M.; Rickard, C. E. F.; Roper, W. R.; Salter, D. M.; Wright,
L. J. J. Organomet. Chem. 2000, 593-594, 458–464.
(37) Hussein, K.; Marsden, C. J.; Barthelat, J. C.; Rodriguez, V.; Conejero,
S.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret, B. Chem. Commun.
1999, 1315–1316.
(38) Nikonov, G. I. Angew. Chem., Int. Ed. 2001, 40, 3353–3355.
(39) Dioumaev, V. K.; Procopio, L. J.; Carroll, P. J.; Berry, D. H. J. Am.
Chem. Soc. 2003, 125, 8043–8058.
(41) Borowski, A. F.; Sabo-Etienne, S.; Christ, M. L.; Donnadieu, B.;
Chaudret, B. Organometallics 1996, 15, 1427–1434.
(42) Pertici, P.; Vitulli, G.; Paci, M.; Porri, L. J. Chem. Soc., Dalton Trans.
1980, 1961–1964.
(40) Lachaize, S.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret, B. Chem.
Commun. 2003, 214–215.
9
7638 J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009

Complex with General Formula RuH(SiR3)3L3 Synthesized
A R T I C L E S
Synthesis and Characterization of 2-Pyridinetetramethyld-
isilazane (1). To a solution of 2-aminopyridine (3.00 g, 31.3 mmol)
in diethyl ether (100 mL) at 0 °C in a 250 mL round flask Schlenk,
20 mL of n-BuLi (1.6 M in hexane) was added. This solution was
stirred for 2 h at 0 °C. A solution of HSiMe2Cl (3.5 mL, 31.5 mmol)
in 20 mL of diethyl ether was added slowly to the previous solution
at 0 °C leading the formation of a precipitate. This mixture was
stirred for 2 h at 0 °C. After this period, another equivalent of
n-BuLi (20 mL, 1.6 M in hexane) was added to the suspension
and maintained at 0 °C. After 2 h of stirring at this temperature,
another one equivalent of HSiMe2Cl (3.5 mL, 31.5 mmol) was
added. The suspension was allowed to return to room temperature
and was stirred for 48 h. The mixture was filtered, and the white
solid was washed with 2 × 20 mL of Et2O. The collected solutions
were combined, and the solvent was evaporated to dryness. The
resulting oil was distillated by trap-to-trap technique. The pale-
yellow oil was isolated in 86% yield (5.62 g).
Anal. Calcd. for RuC45H84N2Si2P2: C, 61.96; H, 9.71; N, 3.21.
Found: C, 62.24; H, 10.24; N, 3.07.
Synthesis and Characterization of RuH{(SiMe2)N(KN-C5H4N)-
(SiMe2H)}3 (4). To a solution of Ru(COD)(COT) (120 mg, 380
µmol) in 8 mL of pentane placed in a Fischer-Porter bottle, 3 equiv
of 1 were added (240 mg, 1.140 mmol). The solution was
pressurized under 3 bar of H2. After 10 min a solid precipitated.
After 14 h the pressure was released, the solution was removed by
cannula, and the solid was washed twice with 2 mL of pentane.
After drying under vacuum, the pale cream-yellow compound 4
was isolated in 60% yield (166 mg).
1H NMR (500.33 MHz, C6D6, 298 K): δ ) 7.68 (dd, 1 H, Pyr,
4
3
3
3JHH ) 6.0, JHH ) 2.1), 6.96 (ddd, 1 H, Pyr, JHH ) 8.7, JHH
)
4
3
6.9, JHH ) 2.1), 6.81 (d, 1 H, Pyr, JHH ) 8.4), 6.09 (ddd, 1 H,
Pyr, 3JHH ) 6.9, 3JHH ) 5.7,4JHH ) 1.2), 5.10 (hept, 1 H, SiH, 3JHH
1
) 3.2, JHSi ) 203.6), 1.10 and 0.30 (2 s, 6H, Ru-SiMe2), 0.48
and 0.40 (2 d, 6H, NSiHMe2, 3JHH ) 3.6); -13.63 (s, 1 H, Ru-H,
JSiHapp ) 7.5). 13C{1H} NMR (125.82 MHz, C6D6, 298 K): 166.4,
149.1, 135.9, 112.8, 112.4 (all for Pyr), 11.9(RuSiMe2), 5.64
(RuSiMe2), -2.1(NSiMe2H), -2.4 (NSiMe2H). 29Si HMBC and
HMQC NMR (99.39 MHz, C6D6, 298 K): -14.24 (SiMe2H), 64.94
(Ru-SiMe2). IR (Nujol mulls, cm-1): 2185 (s, νSi-H).
1H NMR (200.13 MHz, C6D6, 298 K): 8.10 (ddd, 1 H, Pyr, 3JHH
4
5
3
) 5.0, JHH ) 2.0, JHH ) 1.0), 7.06 (ddd, 1 H, Pyr, JHH ) 8.3,
3JHH ) 7.2, JHH ) 2), 6.71 (dt, 1 H, Pyr, JHH ) 8.3, JHH ) 1.0,
4
3
4
5JHH ) 1.0), 6.39 (ddd, 1 H, Pyr, JHH ) 7.2, JHH ) 5.0, JHH
)
3
3
4
3
1
1.0), 4.97 (sept, 2 H, SiH, JHH ) 3.3, JHSi ) 191.6), 0.48 (d, 12
H, SiMe2, 3JHH ) 3.3). 13C{1H} NMR (50.32 MHz, C6D6, 298 K):
161.0, 147.0, 136.8, 114.5, 112.3 (all for Pyr), -0.8 (4C, SiMe2H).
29Si INEPTRD NMR (99.39 MHz, C6D6, 298 K): -11.21 (s). IR
(Nujol mulls, cm-1) 2135 (s, νSi-H). EI-MS: m/z 209 (M - 1).
Synthesis and Characterization of RuH2(η2-HSiMe2)(N-
{(C5H4N)(SiMe2H)})(PCy3)2 (2). One equivalent of 1 was added
to a suspension of RuH2(H2)2(PCy3)2 (62 mg, 93 µmol) in 5 mL of
pentane. The solution became homogeneous, and after 5 min a
precipitate appeared. The solid was separated from the solution and
washed with 3 × 1.5 mL of pentane and dried under vacuum. 2
was obtained as a pale-yellow solid in 50% isolated yield.
Anal. Calcd for RuC27H52N6Si6: C, 44.40; H, 7.17; N, 11.50.
Found: C, 44.42; H, 7.10; N, 10.74.
Neutron Structure Determination of 4. A prismatic, dark-
yellow crystal, with an approximate volume of 4 mm3, was mounted
in an inert Ar atmosphere between two wads of quartz wool inside
a thin-walled quartz tube, sealed with an O-ring to a purpose-
designed Al base.43 The sample was mounted on a Displex
cryorefrigerator on the ILL thermal-beam diffractometer D19
equipped with the new horizontally curved “banana-shaped”
position-sensitive detector.44 This detector is based on a multiwire
gas counter technology (5 atm 3He and 1 atm CF4), with innovative
use of an electrostatic lens to improve vertical resolution, and
subtends 30° vertically and 120° horizontally. The read-out of 256
pixels (vert.) and 640 pixels (horiz.) gives a nominal spatial
definition of 1.56 mm (vert.) and 2.50 mm(horiz.), although the
actual resolution is about 3 mm. This detector is mounted
symmetrically around the equatorial plane, with a sample-to-detector
distance of 76 cm. This new setup assures accurate data and fast
data collection times even with “small” size crystals (e1 mm3).
The crystal was cooled slowly (2 K/min), while monitoring the
3
1H NMR (400.13 MHz, Tol-d8, 223 K): 9.31 (d, 1 H, Pyr, JHH
3
3
) 5.2), 6.60 (t, 1 H, Pyr, JHH ) 7.2), 6.48 (d, 1 H, Pyr, JHH
)
8.4), 5.90 (t, 1 H, Pyr), 0.5.33 (sept, 1 H, SiH, 3JHH ) 3.6, 1JHSi
)
207), 3.00-1.00 (m, 66H, PCy3), 1.10 (s, 6H, Ru-SiMe2); 0.40
2
(d, 6 H, HSiMe2). -3.79 (t, RuH, JHP ) 27.2), -10.70 (m, 1H,
2
2
2
RuH, JHP ) 9.5, JHH ) 9.5), -13.55 (dt, 1H, RuH, JHP ) 21.5,
2JHH ) 9.5). 13C{1H} NMR (160.62 MHz, Tol-d8, 298 K): 166.64,
1
160.32, 133.71, 111.23, 110.93 (all for Pyr), 35.49 (t, JPC ) 9.1,
3
PCH), 31.57, 29.58, 28.11, 27.08 (CH2 of PCy3), 13.99 (t, JCP
)
4.1, SiMe2Ru), -2.49 (SiMe2H). 31P{1H} NMR (161.97 MHz, Tol-
d8, 223 K): 66.6 (s, PCy3); 29Si {31P 66.6 ppm} HMQC NMR (99.39
MHz, Tol-d8, 223 K): -14.5 (SiMe2H), 56.9 (Ru-SiMe2). IR (Nujol
mulls, cm-1) 2191(m, νSi-H dangling), 1987 (m, νRu-H), 1897
(m br, νRu-H + νRu-H-Si). We are confident in the band
assignments by comparison to the values obtained from DFT
calculations.
j
diffraction pattern, to 20 K. The space group R3 was confirmed at
20 K. No significant changes in the crystal mosaic or splitting of
the peaks were observed during cooling. The chosen neutron
wavelength of 1.16954(2) Å from the Cu(331) planes of a Cu (220)-
cut monochromator in reflection (at the high resolution 90° takeoff
angle) was accurately determined by refining the 2θ values of 2272
reflections from a DKDP standard crystal. The accessible intensities,
up to 2θ e 123.38°, were measured, to preset monitor counts, in a
series of 80° ω scans, in steps of 0.07° and typical counting times
of 16 s per step; this rather long time-per-frame was considered
necessary to obtain reasonable counting statistics. A wide range of
crystal orientations (different φ and ꢁ positions) was used to cover
reciprocal space with massive redundancy as a test of both the
sample and the detector stability. Because of its large horizontal
opening, only one detector position was required. Between the long
scans, 10 strong reflections were monitored every 8 h in shorter
scans and showed no significant change. The unit cell dimensions
were calculated precisely (ILL program Rafd19) at the end of the
data collection, from the centroids in 3D of 2535 strong reflections
(5.5 e 2θ e 122.0°). We note that the total time for the reported
20 K experiment was less than 3 days, compared to a typical 7-9
days data collection time for a similar experimental setup using
the previous detectors. It is also interesting to notice that the mean
Anal. Calcd for RuC45H86N2Si2P2: C, 61.81; H, 9.91; N, 3.20.
Found: C, 61.83; H, 9.98; N, 3.00.
Synthesis and Characterization of RuH{(SiMe2)N(KN-C5H4N)-
(SiMe2H)}(PCy3)2 (3). The complex was prepared by heating 2 (20
mg in a Schlenk tube) at 70 °C under vacuum for 24 h. The resulting
orange powder was characterized by multinuclear NMR. 3 is very
air-sensitive.
1H NMR (300.13 MHz, C6D6, 298 K): δ ) 8.74 (d, 1 H, Pyr,
3
3
4
3JHH ) 4.8), 6.99 (ddd, 1 H, Pyr, JHH ) 6.9, JHH ) 8.4, JHH
)
)
3
4
1.8), 6.76 (d, 1 H, Pyr, JHH ) 8.1), 6.28 (ddd, 1 H, Pyr,, JHH
3
1
0.9), 5.25 (hept, 1 H, SiH, JHH ) 3.6, JHSi ) 204), 2.22-1.20
(m, 66H, PCy3), 0.83 (s, 6H, Ru-SiMe2); 0.53 (d, 6 H, HSiMe2,
3JHH ) 3.6). -12.70 (t, RuH, 2JHP ) 25, 2JHSi ) 11). 13C{1H} NMR
(75.47 MHz, C6D6, 298 K): δ ) 167.08, 150.46, 132.22, 111.41,
110.67 (all for Pyr), 36.66 (t, 1JPC ) 6.4, PCH), 31.70, 30.09, 28.32,
26.88 (all for CH2 of PCy3), 12.78 (s, SiMe2Ru), -2.32 (SiMe2H).
31P{1H} NMR (121.49 MHz, C6D6, 298 K): 52.7 (s, PCy3); 29Si
HMQC NMR (59.6 MHz, C6D6, 298 K): δ ) -16.6 (SiMe2H);
64.1 (Ru-SiMe2) and 29Si HMQC NMR (79.49 MHz, Tol-d8, 233
K): δ ) -15.9 (SiMe2H); 65.0 (Ru-SiMe2).
(43) Archer, J.; Lehmann, M. S. J. Appl. Crystallogr. 1986, 19, 456.
(44) Buffet, J. C.; et al. Nucl. Instrum. Methods Phys. Res. A 2005, 554,
392–405.
9
J. AM. CHEM. SOC. VOL. 131, NO. 22, 2009 7639

A R T I C L E S
Grellier et al.
number of reflections present in any one frame (a function of both
the wavelength used and the cell volume) was about 40. Raw
intensity data were corrected for vertical and horizontal positional
distortions, and Bragg intensities were integrated in 3D using a
new version of the program Retreat,45 modified for the new detector
geometry. For the 2510 strongest reflections the mean positional
errors for the centroids were 0.03°, 0.03° and 0.04° (in the scan,
horizontal and vertical directions, respectively). In all 13183 Bragg
reflections were obtained, of which 4258 were independent. The
Bragg intensities were corrected for attenuation by the cylindrical
aluminum and vanadium Displex heat-shields (minimum and
maximum transmission coefficients 0.9066 and 0.9625). Further
crystallographic data and experimental details are given in Table 1
and in the CIF file. The starting structural model for the refinement
was based on the atomic coordinates for the heavy atoms taken
polarization valence basis set was employed for C, N, Si and P
(d-type function exponents were 0.80 for C atom and 0.45 for N,
Si and P atoms). For hydrogen, a standard primitive (4s) basis
contracted to (2s) was used. A p-type polarization function
(exponent 0.9) was added for the hydrogen atoms directly bound
to ruthenium and silicon. The geometry of the various critical points
on the potential energy surface was fully optimized with the gradient
method available in GAUSSIAN 03. Calculations of harmonic
vibrational frequencies were performed to determine the nature of
each critical point. The calculations on 4 have also been performed
at the B3PW91 level. The ruthenium and silicon atoms were
represented by the relativistic effective core potential (RECP) from
the Stuttgart group and their associated basis set,55,56 augmented
by polarization functions (Rf ) 1.235, Ru; Rd ) 0.284, Si).57,58
The remaining atoms (C, H, N) were represented by 6-31G(d,p)
basis sets.59 Full optimizations of geometry without any constraint
were performed. Calculations of harmonic vibrational frequencies
were performed to determine the nature of each extrema. Due to
the absence of symmetry, the data reported in Table 3 correspond
to an average of the different bond distances and angles.
from the X-ray structural determination. The structure was refined
2
by full matrix least-squares, minimizing the function [∑w(Fo
-
(1/k)Fc2)2] and using all the independent data. The final structure
model included coordinates and anisotropic displacement parameters
for all atoms. No extinction correction was deemed necessary. Upon
convergence the final Fourier difference map showed no significant
features. The coherent scattering amplitudes used were those
tabulated by Rauch and Waschkowski.46 Calculations were carried
out by using the PC version of the programs SHELX-97,47 WINGX
and ORTEP48,49
Acknowledgment. We thank the CNRS and the ANR (pro-
gramme blanc ANR-06-BLAN-0060-01) for support (M.G., L.V.,
S.S.E.). This work is also supported by the European network
IDECAT. A generous allocation of computer time was given by
the CINES (Montpellier, France) and CALMIP (Toulouse, France),
and A.A. acknowledges support from the MIUR, PRIN 2007
program.
Computational Details. DFT calculations were performed with
the GAUSSIAN 03 series of programs50 using the nonlocal hybrid
functional denoted as B3PW91.51,52 For compounds 2a, 2b and
2c, the core electrons of ruthenium were represented by a relativistic
small core pseudopotential using the Durand/Barthelat method.53
The 16 electrons corresponding to the 4s, 4p, 4d and 5s atomic
orbitals were described by a (7s,6p,6d) primitive set of Gaussian
functions contracted to (5s,5p,3d). Standard pseudopotentials
developed in Toulouse were used to describe the atomic cores of
all other non-hydrogen atoms (C, N, Si and P).54 A double plus
Supporting Information Available: X-ray and neutron crys-
tallographic files for 2 and 4 (CIF). Computational details and
Cartesian coordinates for the calculated structures. Complete
refs 44 and 50.This material is available free of charge via the
Internet at http://pubs.acs.org.
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