Bis(methimazolyl)silyl complexes of ruthenium

Article abstract of DOI:10.1021/om901067t

The new bis(methimazolyl)silane PhSiH(mt)₂ (mt = methimazolyl), obtained from methimazole (Hmt) and phenyldichlorosilane, reacts with [Ru(η⁴-C₈H₁₂)(η⁶-C ₈H₁₀)] in refiuxing tetra

Full text of DOI:10.1021/om901067t

1026 Organometallics 2010, 29, 1026–1031
DOI: 10.1021/om901067t
Bis(methimazolyl)silyl Complexes of Ruthenium
,†
Anthony F. Hill,* Horst Neumann, and Jorg Wagler*
†
,†,‡
€
†Research School of Chemistry, Institute of Advanced Studies, The Australian National University,
Canberra, ACT 0200, Australia, and ‡Institut fu€r Anorganische Chemie, Technische Universita€t
Bergakademie Freiberg, D-09596 Freiberg, Germany
Received December 12, 2009
The new bis(methimazolyl)silane PhSiH(mt)2 (mt = methimazolyl), obtained from methimazole
(Hmt) and phenyldichlorosilane, reacts with [Ru(η4-C8H12)(η6-C8H10)] in refluxing tetrahydrofuran
to provide the cis and trans isomers of [Ru{κ3Si,S,S0-SiPh(mt)2}]. The structurally characterized
trans isomer crystallizes directly from THF but on dissolution in CH2Cl2 converts exclusively to the
cis isomer.
The dihydrobis(methimazolyl)borate ligand, [H2B(mt)2]-,
coordinates to a diverse variety of metal centers and in doing
so displays a geometrically derived proclivity toward triden-
tate coordination through two sulfur donors and one three-
center, two-electron B-H-metal interaction (Chart 1; A,
κ3H,S,S0).1,2 This behavior is of particular relevance to the
mechanism by which such complexes of the platinum group
metals may evolve, via B-H activation, into dibuttres-
sed metallaboratranes which feature a dative MfB bond
(B, κ3B,S,S0).3,4 It has also been noted that rhodium com-
plexes of the bis(methimazolyl)methane ligand adopt geome-
tries that bring one C-H bond of the bridgehead methylene
into close (“pregostic”) proximity with the rhodium center,1a
while bis(imidazolyl)triselenane, when coordinated to ruthe-
nium, does so via one bridgehead selenoether and two nitro-
gen donors.5 In addition to facilitating the formation of MfB
interactions, methimazolyl bridges have also been found to
support bimetallic assemblies,1b including recent examples
of dative PdfSn, PdfSi, and PtfSi bonds in the com-
plexes [PdSn(μ-mt)4Cl2](PdfSn) and [MSi(μ-mt)4Cl2](MfSi)
(M = Pd, Pt).6 It has even been observed that in some cases the
tris(methimazolyl)borate ligand adopts the κ3H,S,S0 coordina-
tion mode in preference to the more common κ3S,S0,S00
*To whom correspondence should be addressed. E-mail: a.hill@
anu.edu.au (A.F.H.); joerg.wagler@chemie.tu-freiberg.de (J.W.).
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A. F.; Smith, M. K. Organometallics 2007, 26, 3900. (e) Hill, A. F.; Smith,
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r
pubs.acs.org/Organometallics
Published on Web 01/28/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 4, 2010 1027
Chart 1. Coordination Modes for (A) Bis(methimazolyl)borate,
(B) Bis(methimazolyl)borane, (C) Bis(methimazolyl)silane, and
(D) Bis(methimazolyl)silyl Ligands
Figure 1. Molecular structure of HSiPh(mt)2 (1) in the crystal
form (200 K, 50% displacement ellipsoids, C-bound hydrogen
atoms omitted for clarity, carbon atoms in gray). Selected bond
˚
lengths (A) and angles (deg): Si1-N3 = 1.759(1), Si1-N1 =
1.776(1), Si1-C9 = 1.8514(12), Si1-H1 = 1.372(16), S1-C1 =
1.6734(13), S2-C5 = 1.6864(12); N3-Si1-N1 = 105.31(5), N3-
Si1-C9 = 109.68(5), N1-Si1-C9 = 105.98(5), N3-Si1-H1 =
114.1(7), N1-Si1-H1 = 105.7(7), C9-Si1-H1 = 115.2(7).
Scheme 2. Reaction of 2 with Ph2PC6H4CH2SiMe2H (3; COD =
η4-1,4-Cyclooctadiene, COT = η6-1,3,5-Cyclooctatriene)10
Scheme 1. Synthesis of HSiPh(mt)2 (1)
scorpionate type of coordination.7 Thus, it would appear that
the methimazolyl moiety is well-disposed geometrically to
orchestrate or sustain unusual bonding situations.
1
observation of a Si-H resonance at 6.38 ppm in the H
Given the diagonal relationship between boron and
silicon, we therefore considered whether ligands based on
poly(methimazolyl)silanes might show novel features that
parallel those already demonstrated for the poly(methimazolyl)-
borates: i.e., agostic Si-H-metal coordination (C) leading
to Si-H bond activation (D). Herein we report the synthesis
of bis(methimazolyl)phenylsilane and its reactions with the
complexes [Ru(η4-C8H12)(η6-C8H10)] and [Ru(CO)2(PPh3)3],
which do indeed proceed via Si-H activation.
NMR spectrum and indirectly by the coupling displayed
(1JSiH = 290 Hz) by the doublet resonance observed at -
33.8 ppm in the 29Si NMR spectrum. Although the com-
pound is very prone to hydrolysis, satisfactory mass spectra
(low and high resolution) were obtained which confirmed the
gross composition, as do elemental microanalytical data.
Despite the remarkable versatility of the zerovalent ruthe-
nium complex [Ru(η4-C8H12)(η6-C8H10)] (2)8 and the early
report that 2 catalyzes the hydrosilylation of alkenes,9 it is
only recently that stoichiometric reactions between 2 and
silanes have been explored by Sabo-Etienne and co-workers
as part of a wider study of σ-complex formation.10 Specifi-
Results and Discussion
The reaction of phenyldichlorosilane with methimazole
(Hmt, 1-methyl-2-mercaptoimidazole) in the presence of
triethylamine results in the formation of bis(methimazolyl)-
phenylsilane, HSiPh(mt)2 (1), in high yield (Scheme 1).
Although 1 is the first example of a hydride-substituted
methimazolyl silane, it is but one of a diverse range of
methimazolylsilanes which we have now prepared via similar
protocols and on which we will report in detail subsequently.
The formulation of 1 rests on both spectroscopic and crystal-
lographic data (Figure 1). The spectroscopic data call
for little comment, other than to note that the retention of
the Si-H functional group is indicated directly by the
cally, the reaction of
2 with the γ-phosphinosilane
Ph2PC6H4CH2SiMe2H (3) results in the formation of a bis-
chelate complex derived from benzylic C-H (cf. Si-H)
activation and featuring two agostic Si-H-Ru interactions
(4; Scheme 2). Agostic Si-H-Ru interactions are also
present in the products of the reactions of 2 with chelating
€
(8) (a) Fischer, E. O.; Muller, J. Chem. Ber. 1963, 96, 3217. (b) Pertici,
P.; Vitulli, G.; Porri, L. J. Chem. Soc., Chem. Commun. 1975, 846.
(c) Pertici, P.; Vitulli, G.; Paci, M.; Porri, L. J. Chem. Soc., Dalton Trans.
1980, 1961. (d) Itoh, K.; Nagashima, H.; Ohshima, T.; Ohshima, N.;
Nishiyama, J. J. Organomet. Chem. 1984, 272, 179. (e) Frosin, K.-M.;
Dahlenburg, L. Inorg. Chim. Acta 1990, 167.
(9) Hori, Y.; Mitsudo, T.; Watanabe, Y. Bull. Chem. Soc. Jpn. 1988,
61, 3011.
(10) Montiel-Palma, V.; Munoz-Hernandez, M. A.; Ayed, T.;
Barthelat, J.-C.; Grellier, M.; Vendier, L.; Sabo-Etienne, S. Chem.
Commun. 2007, 3963.
(7) (a) Abernethy, R. J.; Hill, A. F.; Tshabang, N.; Willis, A. C.;
Young, R. D. Organometallics 2009, 28, 488. (b) Foreman, M. R. St.-J.;
Hill, A. F.; Owen, G. R.; White, A. J. P.; Williams, D. J. Organometallics
2003, 22, 4446.
~
ꢀ

1028 Organometallics, Vol. 29, No. 4, 2010
Scheme 3. Reaction of 2 with HSiPh(mt)2 (1)
Hill et al.
Figure 2. Molecular structure of trans-5 in a crystal of 5 THF
3
(200 K, 50% displacement ellipsoids, solvent and hydrogen
atoms omitted for clarity, atoms in gray generated by the
crystallographic inversion center at Ru1 = 1/2, 1/2, 0). Selected
˚
bond lengths (A) and angles (deg): Ru1-Si1 = 2.349(1),
Ru1-S1 = 2.3895(9), Ru1-S2 = 2.3990(9), Si1-N1 = 1.820(3),
Si1-N3 = 1.837(3), Si1-C9 = 1.888(4), S1-C5 = 1.703(4),
S2-C1 = 1.711(4); Si1-Ru1-S1* = 94.81(3), Si1-Ru1-S1 =
85.19(3), Si1-Ru1-S2* = 95.01(3), Si1-Ru1-S2 = 84.99(3),
S1-Ru1-S2* = 92.71(3), S1-Ru1-S2 = 87.29(3), N1-Si1-
N3 = 99.43(15), N1-Si1-C9 = 102.49(16), N3-Si1-C9 =
100.57(16), N1-Si1-Ru1 = 106.5(1), N3-Si1-Ru1 = 105.24(10),
C9-Si1-Ru1 = 136.91(13), C5-S1-Ru1 = 105.19(13), C1-
S2-Ru1 = 105.04(13) (asterisks denote symmetry-generated
atoms).
disilanes in the presence of additional phosphines (PR3)
under hydrogen pressure, though perhaps under such con-
ditions intermediates of the form [RuH2(H2)2(PR3)2] quite
possibly play a role.11 We therefore envisaged that 2 would
serve as a suitable substrate for investigating the possibility
of 1 entering into agostic Si-H-Ru interactions.
Heating a solution of 1 (2 equiv) and 2 in tetrahydrofuran
under reflux for 1 h results in the formation of an orange
precipitate and a dark brown supernatant. The orange
63.17 which is tentatively assigned to trans-5, with the caveat
that in this solvent during the requisite data acquisition
period, significant conversion to cis-6 had clearly occurred.
Although the RuS4Si2 donor set is without precedent,
there nevertheless exist copious structural data for silyl
complexes of divalent ruthenium,12 against which to assess
the metrical parameters displayed by trans-5. Selected repre-
sentative examples are collated in Table 1, which presents
Ru-Si bond lengths for mononuclear octahedral (or pseu-
do-octahedral) ruthenium bound to nonchelated four-coor-
dinate silicon LnRu-SiR3, in addition to the sum of the
angles between the substituents “R” (Σ).
precipitate is the single compound 5 THF, and 5 is also
3
present in the supernatant in addition to a second com-
pound, 6. Over a period of 5 h in CD2Cl2 solution at room
temperature, preisolated 5 was found to slowly but comple-
tely convert to yellow 6 and both 5 and 6 were found to have
the same composition by mass spectrometry. These two
compounds are therefore formulated as the isomers
trans-[Ru{κ3-SiPh(mt)2}2] (5; Scheme 3), which precipitates
as a monosolvate from THF, and the more soluble cis-[Ru-
{κ3-SiPh(mt)2}2] (6; Scheme 3), which is the preferred geo-
metry in the more polar solvent CH2Cl2. The isomer cis-6 is
also unstable for prolonged periods in CD2Cl2, eventually
decomposing completely over 24 h to unidentified products
possibly arising from chloromethylation of the electron-rich
From Table 1 it appears that replacing hydrocarbon
silicon substituents with halides generally results in a con-
˚
traction of the Ru-Si bond lengths, which span almost 0.2 A.
The values of Ru-Si and Σ for trans-5 are, however, very
close to the mean values for this series, and so it might be
concluded that the constraints of chelation are not mani-
fested in any untoward distortion of the SiCN2 geometry.
Interligand angles are all close to 90°, although notably those
between donors of the same chelate are acute while those
between donors on adjacent chelates are obtuse. The Ru-S
thione group(s). Crystals of trans-5 THF were obtained
3
from THF, allowing the formulation to be confirmed by a
crystallographic study (vide infra, Figure 2).
The yellow isomer cis-6, having C2 symmetry, gives rise to
two methyl and four NCHCHN resonances in the 1H NMR
spectrum. Similarly, two distinct methimazolyl environ-
ments are observed in the 13C{1H} NMR spectra, while a
single silicon environment is indicated by the 29Si{1H} NMR
spectrum (δSi 58.80, cf. δ -34.70 for 1). By way of contrast,
the isomer trans-5 displays only one methimazolyl environ-
ment in each spectrum. Due to the poor solubility of trans-5
in most solvents, the 29Si resonance was not identified with
confidence. A weak signal was observed in CD2Cl2 at δSi
˚
separations of 2.3895(9) and 2.3990(9) A are somewhat
shorter than those for poly(methimazolyl)borate and -borane
complexes of ruthenium, e.g., [RuH(CO)(PPh3){HB(mt)3}]
7b
(2.4448(11), 2.470(2) A) and [Ru(CO)(PPh3){B(mt)3}]
˚
(2.4857(11), 2.4066(14), 2.4112(14) A),3h presumably reflect-
˚
ing the more compact nature of the cage due to the formal
Ru-Si covalent bonds. The one geometric parameter that is
anomalous is the Ru1-Si1-C9 angle, which at 136.91(13)°
clearly indicates a departure from ideal tetrahedral silicon
(11) (a) 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. (b) Lachaize, S.; Sabo-Etienne, S. Eur. J. Inorg. Chem. 2006,
2105.
(12) Conquest; Cambridge Crystallographic Data Centre, Cambridge,
U.K., February 2009 release.

Article
Organometallics, Vol. 29, No. 4, 2010 1029
Table 1. Selected Structural Data for Silyl Complexes of
Ruthenium(II)12-20
forms slowly in contrast to the rapid reaction of 7 with CO
liberated by the formation of 8 to provide [Ru(CO)3(PPh3)2]
(9) (δP 57.423b) and triphenylphosphine (δP -4.0). The
identification of complex 9 included a crystallographic study
of a previously unknown but otherwise unremarkable trigo-
nal modification (Experimental Section). The second side
product (ca. 15%) was identified as the dihydrido complex
P
a
˚
complex LnRu-SiR3
Ru-Si (A)
(deg)
[Cp*(Me3P)2Ru(SiMe2CH2Ph3)]þ
2.381
2.339
2.282
2.294
2.302
2.446
2.362
2.436
2.325
2.409
2.463
2.37
30413
30614
29415
29615
29815
31416
30817
30318
29918
30119
29820
302
(η6-C6H4 Bu2)(CO)2Ru(SiCl3)2
t
Cp(PMe2Ph)2Ru(SiCl3)
Cp(PMe3)2Ru(SiCl2Me)
Cp(PMe3)2Ru(SiCl2Ph)
(CO)3(PPh3)HRu(SiPh3)
[Cl3(CO)2Ru(SiClPh2)]2-
(η-C6H6)(PPh3)Ru(SiMe3)2
(η-C6H6)(PPh3)Ru(SiCl3)2
Cl(CO)(S2CNMe2)(PPh3)2Ru(SiClPh2)
(PMe3)4HRu(SiMe3)
mean
2
cct-RuH2(CO)2(PPh3)2] (δH -12.5, t, JPH = 19.4 Hz),
which has previously been noted as the sole product of the
reaction of 7 with more conventional silanes.24 Nevertheless,
sufficient salient spectroscopic data could be extracted from
spectra of the three-component product mixture to confi-
dently arrive at the formulation of 8. The 29Si NMR spec-
trum comprises a doublet (δSi 48.0) showing coupling to
phosphorus (2JPSi = 139 Hz), the magnitude of which is
consistent with the mutually trans disposition of phosphorus
and silicon. Once again, this falls outside the typical chemical
shift range for nonchelated ruthenium silyls and may emerge
trans-5
2.349
303
a Mean distances for complexes with two silyl ligands.
geometry. This perhaps reflects a mutual destabilization of
the trans-Si-Ru-Si assembly based on the potent trans-
directing silyl groups surrounded by a collar of π-dative
sulfur donors. Most likely, however, this deformation also
represents a response to the cage ring strain. Similar, though
less pronounced, openings of the Ru-Si-Ph angles of a
range of monotethered silyl complexes have been noted.19
This would account for the downfield 29Si chemical shifts of
both 5 and 6 relative to those for more conventional non-
chelated ruthenium silyl complexes (ca. -10 to þ20 ppm).11b
While the silyl substituents will contribute to the chemical
shift, we note that the tripyrrolylsilyl complex [Ru{Si(pyr)3}-
H3(PPh3)3] (pyr = 1-pyrrolyl)21 with N-heterocyclic Si sub-
stituents has δSi 8.6 while the dichloromethylsilyl analogue
[Ru(SiMeCl2}H3(PPh3)3]22 has δSi 36.4. It should however
also be noted that both these complexes involve three
1
as a recurrent feature of this ligand cage. The H NMR
spectrum includes a doublet resonance (δH -5.90), showing
coupling (2JPH = 12 Hz) consistent with the hydride ligand
coordinating cis to the phosphine in addition to revealing
two methimazolyl environments. These data taken together
point to the geometry depicted in Scheme 4. The complex is thus
somewhat reminiscent of the previously reported borate com-
plexes [RuH(CO)(PPh3){κ3H,S,S0-HxB(mt)4-x] (x = 1, 2).7b
Interestingly, and in contrast to 7, the osmium analogue
[Os(CO)2(PPh3)3] does react with simple silanes via Si-H
oxidative addition,24 while 7 has been shown to react with
tripyrrolylsilane to provide [RuH{Si(pyr)3}(CO)2(PPh3)2]
(pyr = 1-pyrrolyl).25 Thus, although our working hypothesis,
on the basis of boron chemistry, is that the initial chelation
through sulfur geometrically predisposes the Si-H bond for
oxidative addition, we should not discount the possibility that
the first step actually involves coordination through silicon
followed by cage closure as a phosphine and carbonyl ligand
depart.
Concluding Remarks. Initial results indicate that, at least
in terms of geometrical factors and diagonal relationships,
the parallels indicated in Chart 1 between boron and silicon
derivatives of methimazole can be demonstrated. Thus, the
coordination and organometallic chemistry of poly-
(methimazolyl)silanes would appear to be a viable and
potentially fertile area of study. However, there is a subtle
difference that may have significant ramifications. The
boron-based chemistry begins with the salts Na[HxB-
(mt)4-x] (x = 1, 2), which with the exception of group 6
binary carbonyls have been exclusively combined with
metal substrates where the metal is in a positive oxidation
state, proceeding via salt elimination. Neutral poly-
(methimazolyl)silanes in combination with low-valent
metal substrates in principle offer an alternative react-
ion pathway via initial Si-H activation followed by cage
closure.
secondary RuIV-H Si interactions, thereby compromis-
3 3 3
ing direct comparison.
The mechanism by which 5 and 6 form could proceed in
one of two ways. The first is simple substitution of the cyclic
polyolefins by two 1 ligands, followed by Si-H activation
and elimination of hydrogen. Alternatively, under the con-
ditions employed (THF reflux), rearrangement to the sym-
metric [Ru(η5-C8H11)2] could occur8 followed by sequential
transfer of hydrogen from 1 to generate cyclooctadiene. We
have no evidence in support of either possibility but have,
with only modest success, investigated the reaction of 1 with
[Ru(CO)2(PPh3)3] (7, δP 51.1),23 a zerovalent ruthenium
substrate that is devoid of ligands which could act as hydro-
gen acceptors. Although a reaction ensued, with complete
consumption of 7, attempts to isolate a pure complex met
with failure, due to the formation of two inseparable side
products (vide infra). The major product was the desired
complex [RuH(CO)(PPh3){κ3-SiPh(mt)2}] (8); however, this
(13) Grumbine, S. K.; Mitchell, G. P.; Straus, D. A.; Tilley, T. D.;
Rheingold, A. L. Organometallics 1998, 17, 5607.
(14) Einstein, F. W. B.; Jones, T. Inorg. Chem. 1982, 21, 987.
(15) Freeman, S. T. N.; Petersen, J. L.; Lemke, F. R. Organometallics
2004, 23, 1153.
Experimental Section
(16) Brinkley, C. G.; Dewan, J. C.; Wrighton, M. S. Inorg. Chim. Acta
1986, 121, 119.
(17) Berenbaum, A.; Lough, A. J.; Manners, I. Acta Crystallogr.,
Sect. E: Struct. Rep. Online 2002, 58, m679.
(18) Burgio, J.; Yardy, N. M.; Petersen, J. L.; Lemke, F. R. Organo-
General Considerations. All manipulations were carried out
under a dry and oxygen-free nitrogen atmosphere using stan-
dard Schlenk, vacuum line, and inert atmosphere (argon) dry-
box techniques, with dried and degassed solvents which were
distilled from either calcium hydride (CH2Cl2) or sodium-
potassium alloy and benzophenone (ethers and paraffins).
NMR spectra were obtained at 25 °C on Varian Gemini
300BB (1H at 299.9 MHz and 13C at 75.43 MHz, referenced to
metallics 2003, 22, 4928.
(19) Kwok, W.-H.; Lu, G.-L.; Rickard, C. E. F.; Roper, W. R.;
Wright, L. J. J. Organomet. Chem. 2004, 689, 2979.
(20) Dioumaev, V. K.; Procopio, L. J.; Carroll, P. J.; Berry, D. H.
J. Am. Chem. Soc. 2003, 125, 8043.

1030 Organometallics, Vol. 29, No. 4, 2010
Hill et al.
Scheme 4. Reaction of 1 with [Ru(CO)2(PPh3)3] (7)
reflections and 194 parameters, with residual electron density
between -0.54 and þ 0.58 e A -3. CCDC 705043.
˚
Synthesis of [Ru(η4-COD)(η6-COT)](2). Various modifica-
tions8d,e of the Vitulli procedure8b,c,26 for preparing this com-
plex have been described, including the observation that
complex mixtures are often obtained.8d Our attempts to scale
up this method from the original 1.3 mmol procedure resulted
in a reduction in yield relative to the 50% originally claimed,
though this may be related in part to the variable composition
of “RuCl3 xH2O” and the activity of the zinc dust used.
3
Commercial cyclooctadiene was passed through a column of
neutral alumina under an atmosphere of argon to remove
peroxides (unidentified yellow orange material remained
bound to the alumina). Zinc dust was degassed in vacuo
overnight. To a solution of “RuCl3 xH2O” (1.02 g ≈ 3.9
3
mmol) in degassed ethanol (20 mL) was added peroxide-free
1,5-cyclooctadiene (30.0 mL, 24.3 mmol) followed by de-
gassed zinc dust (9.00 g, 138 mmol, excess). The brown mixture
was heated to 80 °C for 3 h, resulting in a black-green
suspension. Upon cooling, the mixture was filtered through
a plug of degassed diatomaceous earth which was rinsed
through with benzene (3 ꢀ 20 mL). The combined filtrates
were freed of volatiles in vacuo at 30 °C. The residue was
extracted with pentane, and the combined extracts were
filtered through a column (5 cm3) of alumina (degassed,
activity III) and concentrated to ca. 20 mL. Cooling to -20 °C
overnight afforded a small amount of black deposit that was
removed by filtration though diatomaceous earth. The filtrate
was concentrated to ca. 5 mL and cooled (-20 °C) to afford
yellow crystals that were isolated by decantation, washed with
cold pentane, and dried in vacuo. Yield: 0.390 g (30%). The
residual protio solvent peaks; 31P at 121.4 MHz, referenced to
external 85% D3PO4; 29Si at 59.59 MHz) or Bruker Avance 600
(1H at 600.0 MHz and 13C at 150.9 MHz) spectrometers.
Elemental microanalysis was performed by the microanalytical
service of the Australian National University. Electrospray
(ESI) and EI mass spectrometry was performed by the Research
School of Chemistry mass spectrometry service. Data for X-ray
crystallography were collected with a Nonius Kappa CCD
diffractometer. The compounds [Ru(η4-C8H12)(η6-C8H10)] (2)8
and [Ru(CO)2(PPh3)3] (7)23b were prepared according to the
indicated published procedures. Other reagents were used as
received from commercial suppliers.
same procedure using RuCl3 xH2O (1.30 g), EtOH (25 mL),
COD (40 mL), and Zn (9.0 g) afforded a comparable yield of
0.430 g (27%).
3
Synthesis of HSiPh(mt)2 (1). A solution of methimazole
(1.20 g, 10.5 mmol) and triethylamine (1.4 g, 13.9 mmol) in
THF (30 mL) was added dropwise to a cooled (-5 °C) solution
of phenyldichlorosilane (0.94 g, 5.3 mmol) in THF (10 mL).
Immediately a precipitate of triethylammonium chloride
formed. The mixture was stored at 4 °C for 2 h and then
filtered. The residue was washed with THF (15 mL) and the
solvent removed under reduced pressure from the combined
filtrate and washings to provide a colorless foam, which was
recrystallized from toluene (15 mL) to yield colorless crystals
of 1. The supernatant was decanted and the crystals dried
under vacuum. Yield: 1.51 g (4.54 mmol, 86%). N.B.: expo-
sure to air results in complete hydrolysis to provide Hmt.
Anal. Found: C, 50.41; H, 5.12; N, 16.65. Calcd. for
C14H16N4S2Si: C, 50.57; H, 4.85; N, 16.85. 1H NMR
(CDCl3, 600.0 MHz): δH 3.56 (s, 6 H, CH3), 6.38 (s, 1 H,
Synthesis of trans-[Ru{K3Si,S,S0-SiPh(mt)2}2](THF) (5 THF).
3
A mixture of [Ru(COD)(COT)] (2; 0.090 g, 0.29 mmol) and
PhSiH(mt)2 (1; 0.190 g, 0.57 mmol) in THF (16 mL) was heated
under reflux for 1 h, during which time a bright orange
precipitate formed. The suspension was cooled slowly to room
temperature without stirring and then cooled further in an ice
bath. The supernatant was removed by cannula and the residue
washed with THF (2 ꢀ 1 mL) and then dried in vacuo. Yield
of 5 THF: 0.100 g (0.131 mmol, 45%). The volatiles were
3
removed from the supernatant, and this was then dissolved in
CD2Cl2 and the 1H NMR spectrum measured immediately to
reveal an approximate 1:1 mixture of 5 and 6. N.B.: both 5 and
6 are immediately decomposed upon exposure of their solu-
tions to air. Data for 5 are as follows. IR (KBr, cm-1): 1455 s,
1379 vs, 1295 m, 1280 m, 1170s, 1131 m, 1098 m, 1065 m, 912 w,
957 w. No peaks were observed in regions typical of Ru-H,
Si-H, or Si-H-Ru modes (1600-2500 cm-1). Anal. Found:
C, 45.82; H, 4.54; N, 13.11. Calcd for C32H38N8RuS4Si2O
3
3
Si-H), 6.52 (d, 2 H, JHH 2.5 Hz, C3N2H2), 6.73 (d, 2, JHH
2.5 Hz, C3N2H2), 7.47 [m, 3 H, H3-5(C6H5)), 7.71 (d, 2 H,
3JHH 8.0 Hz). 1H NMR (CD2Cl2, 299.9 MHz): δH 3.52 (s, 6 H,
CH3), 6.35 (s, 1 H, Si-H), 6.41 (d, 2 H, 3JHH 2.1 Hz, C3N2H2),
3
6.78 (d, 2, JHH 2.4 Hz, C3N2H2), 7.45-7.55 (m, 3 H, H3-5
-
(5 THF): C, 45.96; H, 4.58; N, 13.40. ESI-MS (positive ion,
CH2Cl2/MeOH): m/z (%) 882.9 (28) [M þ Na þ 3MeOH]þ,
3
(C6H5)), 7.77 (dd, 2 H, 3JHH 8.0 Hz, 4JHH 1.5 Hz, H2,6(C6H5)).
13C{1H} NMR (CDCl3, 150.9 MHz): δC 34.4 (CH3), 119.3,
764.0 (100) [M]þ. Acc mass: m/z found 764.0093, calcd for
28H30N8102RuS4Si2 764.0091. 1H NMR: δH 1.81 (m, 4 H,
C2H4), 3.41 (s, 6 H, NCH3), 3.68 (m, 4 H, OCH2), 6.67, 6.77
120.7 (NCHCHN),127.0 (C1(C6H5)), 128.5, 134.9 (C2,3,5,6
-
C
(C6H5)), 131.7 (C4(C6H5)), 168.2 (CdS). 29Si NMR (CDCl3,
99.32 MHz): δSi -33.8 (d, 1JSiH 290 Hz). 29Si NMR (CD2Cl2,
59.59 MHz): δSi -34.70. EI-MS (positive ion, CH2Cl2): m/z
333.0 [HM]þ. Crystals of 1 suitable for diffractometry were
obtained from a cooled concentrated solution of 1 in toluene.
Crystal data: C14H16N4S2Si; Mr = 332.52; triclinic; P1 (No. 2);
(d ꢀ 2, 4 H ꢀ 2, 3JHH = 1.8 Hz, NCHCHN), 7.45, 7.76 (m ꢀ 2,
€
€
(21) Hubler, K.; Hubler, U.; Roper, W. R.; Schwerdtfeger, P.;
Wright, L J. Chem. Eur. J. 1997, 3, 1608.
(22) Yardy, N. M.; Lemke, F. R.; Brammer, L. Organometallics 2001,
20, 5670.
(23) (a) Cavit, B. E.; Grundy, K. R; Roper, W. R. Chem. Commun.
1972, 60. (b) Hill, A. F.; Tocher, D. A.; White, A. J. P.; Williams, D. J.;
Wilton-Ely, J. D. E. T. Organometallics 2005, 24, 5342.
(24) Clark, G. R.; Flower, K. R.; Rickard, C. E. F.; Roper, W. R.;
Salter, D. M.; Wright, L. J. J. Organomet. Chem. 1993, 462, 331.
˚
˚
˚
a = 7.1934(1) A; b = 8.7353(2) A; c = 13.6170(2) A; R =
105.738(1)°; β = 95.836(1)°; γ = 96.114(1)°; V = 811.23(3)
3
˚
A ; Z = 2; colorless plate, 0.64 ꢀ 0.45 ꢀ 0.22 mm; Dc = 1.361
Mg m-3; μ(Mo KR) = 0.40 mm-1; T = 200(2) K. A total of
42 980 absorption-corrected reflections provided 7124 in-
dependent reflections, 5135 of which were observed (|I| >
2σ(|I|), 2θ e 70°). F2 refinement gave R1 = 0.0437 and wR2 =
0.1172 for 5135 independent, observed, absorption-corrected
€
(25) Hubler, K.; Roper, W. R.; Wright, L. J. Organometallics 1997,
16, 2730.
(26) Pertici, P.; Vitulli, G.; Spink, W. C.; Rausch, M. D. Inorg. Synth.
1983, 22, 176.

Article
Organometallics, Vol. 29, No. 4, 2010 1031
10 H, C6H5). 13C{1H} NMR (150.88 MHz, 25 °C, CD2Cl2):
25.94 (C2H4), 34.82 (NCH3), 68.12 (OCH2), 116.4, 117.5
(NCHCHN), 127.2, 128.4, 134.6 (C6H5); CdS resonances not
unequivocally identified. 29Si{1H} NMR (59.59 MHz, 25 °C,
CD2Cl2): δSi 63.17 (tentative, see text). The complex cis-6 was
not isolated as such, due to the preferred crystallization of the
less soluble form trans-5. Solutions of cis-6 were obtained by
allowing trans-5 to stand in dichloromethane for 5 h, by
which time NMR assay indicated complete isomerization
had occurred. ESI-mass spectrometry of these solutions pro-
vided data identical with those for the isomer trans-5. Data for
PPh3. N.B.: no definitive information is available regarding
possible side products devoid of phosphorus due to poor
signal/noise in the 29Si{1H} NMR spectrum and the generally
uninformative nature of the 1H NMR spectrum. The plausible
products of silane decomposition and methimazole captured tby
7 or 8, i.e. [RuH(mt)(CO)(PPh3)2] and [Ru(mt)2(PPh3)2],5 were
conclusively absent, however (31P{1H} NMR). NMR (CDCl3/
THF, 25 °C): 29Si{1H} (59.59 MHz) δSi = 48.00 (d, 2JPSi = 139
Hz); 1H (299.9 MHz) δH -5.90 (d, 2JPH = 12.6 Hz). Attempts to
obtain pure 8 from the above 7/8/9 mixture by fractional
crystallization afforded instead crystals of 9. Crystal data for
[Ru(CO)3(PPh3)2] (9): C39H30O3P2Ru; Mr = 709.64; trigonal;
1
cis-6 are as follows. NMR (CD2Cl2, 25 °C): H (299.9 MHz)
˚
˚
δ 3.38, 3.63 (s ꢀ 2, 3 H ꢀ 2, NCH3), 6.26, 6.35, 6.55, 6.70 (d ꢀ 4, 2
H ꢀ 4, 3JHH = 1.8 Hz), 7.10, 7.22 (m ꢀ 2, 10 H, C6H5); 13C{1H}
(75.42 MHz) δC 33.89, 34.71 (NCH3), 117.4, 117.5, 122.6, 122.7
(NCHCHN), 127.1, 134.5 (4C ꢀ 2, C2,3,5,6(C6H5)), 128.5
(C4(C6H5)), 139.0 (C1(C6H5)), 171.8, 173.1 (CS); 29Si{1H}
(59.59 MHz) δSi 58.80. Acc. mass: m/z found 764.0063, calcd
P3c1; a = b = 15.6749(1) A; c = 23.0971(3) A; V = 4914.71(8)
3
˚
A ; Z = 6; yellow needle, 0.49 ꢀ 0.27 ꢀ 0.11 mm; Dc = 1.439 Mg
m-3; μ(Mo KR) = 0.613 mm-1; T = 100(2) K. A total of
107 567 absorption-corrected reflections provided 8918 inde-
pendent reflections, 6235 of which were observed (|I| > 2σ(|I|),
2θ e 76°). F2 refinement gave R1 = 0.0328, wR2 = 0.0845 for
6235 independent, observed, absorption corrected reflections and
205 parameters without restraints, with residual electron density bet-
for C28H30N8102RuS4Si2 764.0091. Crystals of trans-5 THF
3
suitable for diffractometry were obtained from a cooled con-
centrated solution of trans-5 in tetrahydrofuran. Crystal data:
C28H30N8RuS4Si2C4H8O; Mr = 836.19; monoclinic; P21/n;
ween -0.63 and þ 0.81 e A-3. CCDC 705045. The crystals struc-
˚
tures of 9 C4H8O27 and 9 CH2Cl228 have been reported previously,
while the solvate free modification presented here is isomorphous
3
3
˚
˚
˚
a = 14.4461(3) A; b = 13.1482(2) A; c = 19.7672(4) A; β =
3
92.121(1)°; V = 3752.01(12) A ; Z = 4; orange plate, 0.12 ꢀ
with the corresponding osmium analogue described by Ibers.29
˚
0.10 ꢀ 0.05 mm; Dc = 1.480 Mg m-3; μ(Mo KR) = 0.743 mm-1
;
T = 200(2) K. A total of 44 750 absorption-corrected reflec-
tions provided 7339 independent reflections, 5503 of which
were observed (|I| > 2σ(|I|), 2θ e 52°). F2 refinement gave R1 =
0.0453 and wR2 = 0.1248 for 5503 independent, observed,
absorption-corrected reflections and 466 parameters and 54
restraints, with residual electron density between -1.13 and þ
Acknowledgment. We thank the Australian Research
Council (ARC) for financial support (Grant Nos.
DP0771497 and DP0881692) and the Deutscher Akade-
mischer Austauschdienst for a postdoctoral fellowship
(to J.W.).
0.92 e A -3. CCDC 705044.
˚
Reaction of [Ru(CO)2(PPh3)3] (7) with PhSiH(mt)2 (1). A
mixture of [Ru(CO)2(PPh3)3]23b (7; 0.390 g, 0.414 mmol) and
PhSiH(mt)2 (1; 0.140 g, 0.422 mmol) in tetrahydrofuran (2 mL)
was stirred at 60 °C for 30 min and then freed of volatiles. The
crude mixture thus obtained comprised (31P NMR, CDCl3/
THF) [Ru(CO)3(PPh3)2] (9; δP 57.1, integral 108 for 2 PPh3),
[RuH{PhSi(mt)2}(CO)(PPh3)] (8; δP 39.4, integral 54 for 1
PPh3), and PPh3 (δP -4.2, integral 89) in addition to unreacted
[Ru(CO)2(PPh3)3] (7; δ 50.5, integral 46 for 3 PPh3) and traces of
[RuH2(CO)2(PPh3)2] (δP 58.6, integral 12 for 2 PPh3), corres-
ponding the overall reaction stoichiometry 1 þ 7 þ 7 f 8 þ 9 þ 2
Supporting Information Available: CIF files giving full details
of the crystal structure determinations of 1 (CCDC 705043),
trans-5 THF (CCDC 705044), and 9 (CCDC 705045). This
material is available free of charge via the Internet at http://
pubs.acs.org.
3
(27) Dahan, F.; Sabo, S.; Chaudret, B. Acta Crystallogr., Sect. C:
Cryst. Struct. Commun. 1984, 40, 786.
(28) Ng, S. Y.; Goh, L. Y.; Koh, L. L.; Leong, W. K.; Tan, G. K.; Ye,
S.; Zhu, Y. Eur. J. Inorg. Chem. 2006, 663.
(29) Stalick, J. A.; Ibers, J. A. Inorg. Chem. 1969, 8, 419.