Cp*(iPr3P)Ru(Cl)(η2-HSiClMe 2): The first complex with simultaneous Si-H and RuCl...SiCl inter-ligand inter actions

Article abstract of DOI:10.1039/b500679a

The addition of HSiMe₂Cl to the unsaturated compound Cp*(ⁱPr₃P)RuCl gives an unstable adduct which, according to NMR (J_H-Si = 33.5 Hz), X-ray crystal structure and DFT evidence, is a silane σ-complex Cp*(ⁱPr ₃P)Ru(Cl)(η²-HSiMe₂Cl) supported by an unprecedented, simultaneous inter-ligand RuCl...SiCl hypervalent interaction between the chloride ligand on ruthenium and the SiMe₂Cl group. The Royal Society of Chemistry 2005.

Full text of DOI:10.1039/b500679a

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Cp*(iPr3P)Ru(Cl)(g2-HSiClMe2): the first complex with simultaneous
…
Si–H and RuCl SiCl inter-ligand interactions{
Alexander L. Osipov,a Sergei F. Vyboishchikov,*b Konstantin Y. Dorogov,a Lyudmila G. Kuzmina,c
Judith A. K. Howard,d Dmitrii A. Lemenovskiia and Georgii I. Nikonov*a
Received (in Cambridge, UK) 17th January 2005, Accepted 10th May 2005
First published as an Advance Article on the web 27th May 2005
DOI: 10.1039/b500679a
electron-donating R-groups at Si in 5. The formulation of 3–5 as
s-complexes is not surprising, if it is taken into account that: (i) in
Cp*(R3P)Ru(Cl)(SiR3)(H) the Ru atom is in the high
formal oxidation state IV,1 (ii) an electron-withdrawing
chloride ligand is present1 and (iii) that s-complexes occur for
the isolable compounds [Cp*(Me3P)2Ru(g2-HSiCl3)]+ and
Cp*(PhiPr2P)Ru(Cl)(g2-H2).10,11
The addition of HSiMe2Cl to the unsaturated compound
Cp*(iPr3P)RuCl gives an unstable adduct which, according to
NMR (JH–Si 5 33.5 Hz), X-ray crystal structure and DFT
evidence, is a silane s-complex Cp*(iPr3P)Ru(Cl)(g2-HSiMe2Cl)
supported by an unprecedented, simultaneous inter-ligand
…
RuCl SiCl hypervalent interaction between the chloride ligand
on ruthenium and the SiMe2Cl group.
Non-classical inter-ligand interactions are formed by electron-
deficient agostic and s-complexes1 and electron-rich hypervalent
interactions (IHI).2 Both of these types have been found for silyl
groups,3,4 and we have recently shown how both IHIs and silane
s-complexes can be stabilised in the same Cp2/PMe3 ligand
environment in titanocenes, depending on the substituents of the
SiR3 group.5 Complexes with several s-bond ligands (H2 and
HSiR3) are long known,1,6 but no examples with simultaneous
interactions of both different types at the same metal centre have
been documented so far. Here we report the synthesis and X-ray
crystal structure of the complex Cp*(iPr3P)Ru(Cl)(g2-HSiMe2Cl)
which contains a stretched silane ligand, hypervalently interacting
with the chloride ligand on ruthenium.
Complexes of type Cp*(iPr3P)Ru(Cl)(SiR3)(H) (R3 5 Cl2Me 1,
Cl3 2, PhH2 3, Ph(SiPhH2)H), prepared by the reaction of
Cp*(iPr3P)RuCl with silanes, have previously been reported as
classical on the basis of their stability at room temperature and
small Si–H coupling constants (,20 Hz3a).7,8 In contrast,
secondary silanes do not give stable adducts.9 We have found
that complexes Cp*(R3P)Ru(Cl)(HSiR3) (R3 5 PhH2 3, SiClMe2
4, SiPhMe2 5) have very different stabilities. While the reaction of
Cp*(iPr3P)RuCl with excess H3SiPh readily affords 3 along with
some Cp*(iPr3P)Ru(SiH2Ph)(H)2, in the case of HSiClMe2 and
HSiPhMe2 at room temperature the equilibrium is shifted towards
Cp*(iPr3P)RuCl and free silane. However, the adduct 4 forms at
210 uC (eqn. (1)), whereas 5 is observed only at 290 uC. The 1H
NMR spectrum of 4 at 240 uC revealed a hydride signal at
29.65 ppm, flanked by 29Si satellites with a coupling constant
JH–Si 5 33.5 Hz, suggesting the presence of a Si–H s-interaction.
No 29Si satellites could be seen for 3 at room temperature but a
clear JH–Si coupling constant of 30 Hz was measured at 210 uC.
For 5, JH–Si 5 32 Hz at 290 uC. Surprisingly, both values
are slightly lower than in 4, in spite of the presence of more
ð1Þ
The variation of nRu–H in the IR spectra of compounds 1–4 with
the nature of SiR3 group provides further support for the non-
classical nature of 4. Namely, the Ru–H stretch shifts to shorter
wave numbers along the series 2: 2120 cm21 . 1: 2096 cm21 . 3:
2000–2050 cm21 . 4: 1916 cm21. Although IR spectroscopy has
been less popular than NMR spectroscopy as a means for
characterising silane s-complexes, a red shift of the M–H stretch
indicates the formation of such a complex.3d For comparison, in
the classical compound Cp*(pyr3P)RuH2(SiPhMe2)12 the Ru–H
stretches are observed at much larger wave numbers (2085 and
2055 cm21 vs. 1916 cm21 in 4).
In accord with the spectroscopic evidence of a s-complex, the
X-ray structure{ of 4 (Fig. 1) revealed an elongated Ru–Si bond of
2.3982(7) s compared to the 2.2950(5)–2.364 s range found in
related chlorosilyl complexes of ruthenium7 and marginally shorter
than in classical Cp*(pyr3P)RuH2(SiPhMe2) (2.4213(7) s)12 which
…
has only donor groups at Si. In addition to the short Si
H
contact of 2.05 s, which is probably subject to the uncertainty of
…
the hydride’s location from the X-ray study, there is a short Si Cl
contact of 3.014 s between the silyl and chloride ligands (the sum
of the van der Waals radii is 3.81s).13 The Cl–Ru–Si–Cl torsion
angle of 179.5u is close to 180u and the Cl–Si–Cl angle is 165.61u,
signifying the relative trans disposition of the two Cl groups. There
appears to be a donation from the Ru-bound chloride lone pair to
the s*Si–Cl antibonding orbital of the silane, leading to a
hypervalent silicon centre and the elongation of the Si–Cl(2) bond
to 2.155(1) s, a value beyond the range 2.094–2.149 s typical of
classical chlorosilyl complexes.7,14 However, the IHI of the type
{ Electronic Supplementary Information (ESI) available: Details of the
preparation of 4 and DFT calculations of 7–10. See http://www.rsc.org/
suppdata/cc/b5/b500679a/
*vybo@stark.udg.es (Sergei F. Vyboishchikov)
nikonov@org.chem.msu.ru (Georgii I. Nikonov)
…
Ru–H Si–Cl is missing in 4 since the Si-bound chlorine and
hydride are not in a trans disposition.3d,4,5 In comparison, shorter
Si–Cl (2.144 s) and Si–Ru (2.364 s) bonds are found in the
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Chem. Commun., 2005, 3349–3351 | 3349

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Table 1 DFT-calculated bond lengths (s), bond angles (u) and JH–Si
(Hz) for model complexes 7–10
7
8a
89
9
10b
Ru–H
Ru–Cl(1)
Ru–P
1.613
2.455
2.301
2.474
1.991
1.604
[1.53]
2.451
[2.413]
2.308
[2.381]
2.427
[2.398]
2.072
[2.054]
2.168
[2.155]
—
1.602 1.603
2.444 2.444
2.314 2.315
2.426 2.388
2.076 2.104
1.598
[1.485]
2.433
[2.416]
2.325
[2.323]
2.361
[2.311]
2.156
[2.092]
2.129
[2.094]
2.104/2.107
3.110
Ru–Si
…
Si
H
Si–Cl(2)c
—
—
2.148
Si–Cl
…
Si Cl(1)
—
3.183
2.149 2.128
3.219 3.047
3.040
[3.014]
161.4
[165.6]
[3.102]
…
Cl(1) Si–Cl(2)
—
97.8
162.4
162.0
[166.4]
20.4
Jcalcd Si–H
223.0 219.5
217.3
24.7
[19]d
b
[32]d
for
[33.5]d
in
[,6]d
Fig. 1 Molecular structure of complex 4. Selected bond lengths (s) and
angles (u): Ru(1)–Si(1) 2.3982(7), Ru(1)–P(2) 2.3813(6), Ru(1)–Cl(1)
2.4129(6), Si(1)–Cl(2) 2.155(1), Si(1)–C(20) 1.872(3), Si(1)–C(21) 1.885(3),
Si(1)–Cl(1) 3.014(1), Ru(1)–H(1) 1.53(3), Si(1)–H(1) 2.05(3); Si(1)–Ru(1)–
P(1) 103.36(2), Si(1)–Ru(1)–Cl(1) 77.59(2), Cl(1)–Si(1)–C(20) 88.85(1),
Cl(1)–Si(1)–C(21) 87.62(1), Cl(1)–Si(1)–Ru(1) 51.42(1), Cl(1)–Si(1)–H(1)
85.3(10), Cl(2)–Si(1)–H(1) 81.2(10), Cl(2)–Si(1)–Ru(1) 114.20(3), Cl(2)–
Si(1)–C(20) 101.04(12), Cl(2)–Si(1)–C(21) 100.08(10), Ru(1)–Si(1)–C(20)
119.84(10), Ru(1)–Si(1)–C(21) 115.37(10), Cl(2)–Si(1)–Cl(1) 165.61(3).
a
X-ray
data
4
brackets.
X-ray
data
for
Cp*(iPr2MeP)Ru(Cl)(SiCl3)(H) in brackets. The atom Cl(2) on Si is
c
d
trans to the chloride ligand Cl(1). Jobs
brackets.
for 5, 4, 1 and 2 in
Si–H
from the metal to the s*(Si–H) antibonding orbital.1
…
Noteworthily, the RuCl Si contact distance decreases from 7 to
8 and then increases again from 8 to 10 as the Ru–Si bond
shortens, whereas the rotation of the silyl in 8 to give 89 results in
an abrupt elongation of this contact and a decrease in the Si–Cl(2)
bond length from 2.168 s to 2.149 s. Overall, the rotamer 89 is
2.5 kcal mol21 less stable than 8. The rotation of the SiMe2Cl
group alone leads only to a negligible change in steric hindrance,
since the second methyl group in both forms is directed towards
the Cp ring. Furthermore, in accordance with the presence of the
classical complex Cp*(Ph3P)RuH2(SiClMe2).14 It is also informa-
tive to compare the X-ray structure of 4 to that of closely related
compound Cp*(MeiPr2P)Ru(Cl)(SiCl3)(H) 6.7 The latter of these
complexes is at a more advanced stage in the oxidative addition of
the Si–H bond to the ruthenium, and has a shorter Ru–Si bond of
2.3152 (8) s due to the presence of three electron-withdrawing
chlorine groups on the silicon. In spite of this, the observed
…
hypervalent interaction RuCl Si–Cl, in complexes 7 and 9, the
…
RuCl Si distance of 3.111(1) s in 6 is 0.097 s longer than in 4.
Si–Cl bond trans to the chloride on Ru is longer than the Si–Cl
bond trans to the Cp ring.
This difference stems from a more acute Cl(1)–Ru–Si bond angle
in 4 (4: 77.59(2)u vs. 6: 82.26(3)u), clearly demonstrating the
attraction in 4 between the chloride and silyl groups. Before this
work, such an interaction between a chloride ligand and a main-
group element was reported only for stannyl complexes in the form
The progressive weakening of the Si–H interaction from 7 to 10
is mirrored by the decrease in absolute value of the calculated JH–Si
(Table 1). The smaller absolute values of calculated JH–Si possibly
reflect a greater degree of oxidative addition in model complexes 9
and 10. Importantly, the sign of the coupling constant has been
calculated{ to be negative. The sign rather than the absolute value
of JH–Si has been recently suggested to be a more rigorous criterion
for the presence of a direct Si–H intercation.5
15
…
of MCl SnCl inter-ligand bonding.
To shed more light on the bonding arrangements in 1–6, we
used DFT§ to calculate
a series of model complexes
Cp(Me3P)Ru(Cl)(SiClnMe32n)(H) (n 5 0: 7, 1: 8, 2: 9, 3: 10) and
a rotamer of 8, the complex 89, with a methyl group trans to the
chloride ligand (Scheme 1). It can be seen from Table 1 that
progressive substitution of the Me groups at Si in 7 for chlorine
atoms leads to a shortening of the Ru–H and Ru–Si bonds and an
increase in the Si–H separation due to increased back-donation
The large values of the Mayer bond orders15 (MBO, Table 2)
and the overlap-weighted natural bond orders{ unambiguously
…
…
establish the presence of Si H and Si Cl interactions. The
…
MBOs confirm the decrease in the Si H interaction concurrent
with the strengthening of the Ru–Si and Ru–H bonds from 7 to
10. The rotation of the SiMe2Cl ligand in 8 to give 89 results in a
somewhat more advanced Si–H addition and the loss of the
…
…
hypervalent interaction Si Cl(1) (the MBO for the Si Cl(1)
interaction decreases from 0.131 to 0.074, whereas the Si–Cl(2)
bond strengthens from 0.876 to 0.915). Altogether, these data
…
suggest the presence of simultaneous s Si H and hypervalent
…
RuCl Si–Cl interactions. The latter interaction is the strongest in
complex 8, the model of real compound 4. In complex 10, the
model of real compound 2, both interactions are weak.
Scheme 1 Model complexes 7–10 drawn as Newman projections down
the Si–Ru bond, so that the Ru atom is eclipsed and hence not visible.
3350 | Chem. Commun., 2005, 3349–3351
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{31111/411/311}). On other atoms, the standard 6–31G** basis set was
employed. Full geometry optimization for all the molecular structures was
Table 2 Mayer bond orders for 7–10, calculated from the DFT
density matrix
1
performed. The H–29Si spin–spin coupling constants for complexes 7–10
were calculated at B3LYP level using an extended basis set within the
Gauge-Including Atomic Orbitals (GIAO) approach22 using the Gaussian-
03 program.17 Natural bond orbital analysis was performed using the NBO
3.1 program,23 incorporated in the Gaussian-03 package. The Kohn–Sham
orbitals resulting from the DFT calculations were employed.
7
8
89
9
10
Ru–H
0.684
0.701
0.691
0.805
0.653
0.157
0.876
0.711 0.708 0.722
0.734 0.718 0.757
0.796 0.791 0.781
0.690 0.694 0.730
0.149 0.143 0.125
0.915 0.919 0.962
Ru–Cl(1)a 0.707
Ru–P
Ru–Si
…
0.806
0.619
0.172
—
—
Si
Si–Cl(2)
H
1 G. J. Kubas, Metal Dihydrogen and s-Bond Complexes, Kluwer
Academic/Plenum, New York, 2001.
Si–Cl9
…
—
0.131
—
0.983 1.013/1.028
2 G. I. Nikonov, J. Organomet. Chem., 2001, 635, 24.
3 (a) U. Schubert, Adv. Organomet. Chem., 1990, 30, 151; (b) J. Y. Corey
and J. Braddock-Wilking, Chem. Rev., 1999, 99, 175; (c) Z. Lin, Chem.
Soc. Rev., 2002, 31, 239; (d) G. I. Nikonov, Adv. Organomet. Chem., in
press.
Si Cl(1) 0.095
0.074 0.122 0.101
a
Chloride ligand Cl(1) is in a trans position with respect to the atom
Cl(2).
4 (a) S. R. Dubberley, S. K. Ignatov, N. H. Rees, A. G. Razuvaev,
P. Mountford and G. I. Nikonov, J. Am. Chem. Soc., 2003, 125, 644; (b)
G. I. Nikonov, L. G. Kuzmina, S. F. Vyboishchikov, D. A. Lemenovskii
and J. A. K. Howard, Chem.–Eur. J., 1999, 5, 2497.
5 S. K. Ignatov, R. B. Tyrrel, S. R. Dubberley, N. H. Rees,
A. G. Razuvaev, P. Mountford and G. I. Nikonov, Chem.–Eur. J.,
2004, 10, 4991.
6 K. Hussein, C. J. Marsden, J.-C. Barthelat, V. Rodriguez, S. Conejero,
S. Sabo-Etienne, B. Donnadieu and B. Chaudret, Chem. Commun.,
1999, 1315.
s-Complexes with secondary Si–H interactions6 related to the
cis-effect1 have previously been reported and can alternatively be
viewed as containing the distorted (R3SiH2)2 moiety.2 In 4, two
different types of inter-ligand interactions occur simultaneously at
the same metal centre—the residual s-Si–H interaction and the
…
unprecedented Cl Si–Cl hypervalent interaction. The relative
…
stabilities of 3, 4 and 5 show that the presence of the RuCl Si–Cl
7 A. L. Osipov, S. M. Gerdov, L. G. Kuzmina, J. A. K. Howard and
G. I. Nikonov, Organometallics, 2005, 24, 587.
8 (a) B. K. Campion, R. H. Heyn and T. D. Tilley, Chem. Commun.,
1988, 278; (b) B. K. Campion, R. H. Heyn and T. D. Tilley, Chem.
Commun., 1992, 1201.
interaction can stabilise the adduct, even for a tertiary silane.
Interestingly, the values of JH–Si in 3–5 are very similar, in spite of
the very different nature of their SiR3 groups. Electron-with-
drawing groups tend to decrease JH–Si in s-complexes because of
9 P. B. Glazer and T. D. Tilley, Organometallics, 2004, 23, 5799.
10 S. T. N. Freeman, F. R. Lemke and L. Brammer, Organometallics,
2002, 21, 2030.
the increased back-donation from the metal onto the antibonding
1,3
orbital s*Si–H
.
Such an unusual trend in complexes 3–5 can be
accounted for by steric factors. Namely, the increased repulsion of
the larger tertiary silanes from the bulky Cp* ligand impedes the
oxidative addition of the Si–H bond.
11 T. J. Johnson, P. S. Coan and K. Caulton, Inorg. Chem., 1993, 32, 4594.
12 V. Rodriguez, B. Donnadieu, S. Sabo-Etienne and B. Chaudret,
Organometallics, 1998, 17, 3809.
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14 S. B. Duckett, L. G. Kuzmina and G. I. Nikonov, Inorg. Chem.
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15 (a) M. Elder, W. A. G. Graham, D. Hall and R. Kummer, J. Am.
Chem. Soc., 1968, 90, 2189; (b) T. Szymanska-Buzar, in Ring Opening
Metathesis Polymerisation and Related Chemistry, ed. E. Khosravi and
GIN is grateful to RFBR for research grant (no. 00-03-32850).
JAKH and LGK thank the Royal Society (London) for financial
support.
Alexander L. Osipov,a Sergei F. Vyboishchikov,*b
´
T. Szymanska-Buzar, Kluwer Academic, Dordrecht, 2002, pp. 349; (c)
Konstantin Y. Dorogov,a Lyudmila G. Kuzmina,c Judith A. K. Howard,d
Dmitrii A. Lemenovskiia and Georgii I. Nikonov*a
V. K. Bel’sky, A. N. Protsky, B. M. Bulychev and G. L. Soloveichik,
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aChemistry Department, Moscow State University, Vorob’evy Gory,
119992, Moscow, Russia. E-mail: nikonov@org.chem.msu.ru;
Fax: +7 (095) 9328846; Tel: +7 (095) 9391976
16 I. Mayer, Chem. Phys. Lett., 1985, 97, 117, addendum.
17 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb,
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A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox,
T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara,
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bInstitut de Qu´ımica Computacional, Campus de Montilivi, Universitat
de Girona, 17071, Girona, Catalonia, Spain. E-mail: vybo@stark.udg.es;
Fax: +34 97241 8356; Tel: +34 97241 8362
cInstitute of General and Inorganic Chemistry RAS, Leninskii Prosp. 31,
119991, Moscow, Russia. E-mail: kuzmina@igic.ras.ru;
Fax: +7 (095) 9541279; Tel: +7 (095) 9521803
dChemistry Department, University of Durham, South Road, Durham,
UK DH1 3LE. E-mail: j.a.k.howard@durham.ac.uk;
Fax: +44 (0)191 384 4737; Tel: +44 (0)191 374 4647
Notes and references
{ Selected X-ray data for 4: C27H50ClMoN2P2Si, Mr 5 526.58, monoclinic,
space group P21/c, a 5 10.9544(3), b 5 15.0911(4), c 5 15.4986(4) s,
b 5 99.898(1)u, V 5 2524.00(12) s3, Z 5 4, T 5 123.0(2) K, m 5
0.948 mm21, rcalcd 5 1.386 g cm23, R 5 0.0339, Rw 5 0.0797 for 6694
unique reflections with 239 variables. CCDC 261259. See http://
www.rsc.org/suppdata/cc/b5/b500679a/ for crystallographic data in CIF
or other electronic format.
§ DFT calculations: All calculations were carried out using the Gaussian-03
package16 applying Becke’s exchange functional18 in combination with
Perdew’s correlation functional (B-P86)19 and the Perdew–Burke–
Ernzerhof exchange and correlation functionals (PBE-PBE).20 The
calculations were performed using the ‘‘Stuttgart’’ 28 electron effective
core potential21 on the ruthenium atom, with a corresponding triple-f
valence basis set augmented by one diffuse p function (contraction scheme
18 A. D. Becke, Phys. Rev. A, 1988, 38, 3098.
19 B. P. Perdew, Phys. Rev. B: Condens. Matter, 1986, 33, 8822.
20 (a) J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett., 1996, 77,
3865; (b) J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett.,
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21 D. Andrae, U. Ha¨ussermann, M. Dolg, H. Stoll and H. Preuss, Theor.
Chim. Acta, 1990, 77, 123.
22 R. Ditchfield, J. Chem. Phys., 1976, 65, 3123.
23 E. D. Glendening, A. E. Reed, J. E. Carpenter and F. Weinhold, NBO
Version 3.1.
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Chem. Commun., 2005, 3349–3351 | 3351