One-step entry to olefin-tethered N,S-heterocyclic carbene complexes of ruthenium with mixed ligands

Article abstract of DOI:10.1039/c2dt12354a

A series of Ru(ii) mixed-ligand complexes RuBr₂(PPh ₃)₂(N-AyBzTh) (Ay = prop-2-enyl; BzTh = benzothiazol-2-ylidene) (4), RuBr(OAc)(PPh₃)(N-MeAyBzTh) (5), RuBr(OAc)(PPh₃)(N-MeBnBzTh)₂ (MeBn

Full text of DOI:10.1039/c2dt12354a

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PAPER
One-step entry to olefin-tethered N,S-heterocyclic carbene complexes of
ruthenium with mixed ligands†
a
a
a,b
Nini Ding, Wenhua Zhang and T. S. Andy Hor*
Received 6th December 2011, Accepted 16th March 2012
DOI: 10.1039/c2dt12354a
A series of Ru(II) mixed-ligand complexes RuBr (PPh ) (N-AyBzTh) (Ay = prop-2-enyl; BzTh =
2
3 2
benzothiazol-2-ylidene) (4), RuBr(OAc)(PPh )(N-MeAyBzTh) (5), RuBr(OAc)(PPh )(N-MeBnBzTh)
2
3
3
(
MeBn = 3-methylbut-2-enyl) (6) and RuCl(OAc)(PPh )(N-MeBnBzTh) (7) have been synthesized from
3
Ru(OAc) (PPh ) in one-pot condensation and ligand exchange reactions. X-ray single-crystal diffraction
2
3 2
analysis revealed that they are neutral octahedral Ru(II) complexes with one or two N,S-heterocyclic
carbene (NSHC) ligands and a coordinated (4, 5 and 7) or dangling (6) olefin arm. The system displays a
range of self-selecting structural variations. Entry of the hybrid olefin–NSHC and halide ligands ejects
either one (5, 6 and 7) phosphine ligand or keeps both phosphines (4) by replacing the acetate. It is also
possible to accommodate two NSHC ligands by keeping the olefin pendant (6). Complexes 5 and 7 are
isostructural with all different ligands on the coordination sphere. Complexes 4–6 are active towards
transfer hydrosilylation showing good β(Z) selectivity, with the Ru(II) bearing acetate giving higher
yields.
crystallography. The complexes have also been examined for
their applications in selective hydrosilylation of terminal
alkynes.
Introduction
Olefin coordination and dissociation is a key feature in many cat-
1
,2
alytic systems. When these two steps are in dynamic equili-
brium, or when they operate in tandem in a catalytic cycle, the
3,4
Results and discussion
hemilability effect
may be harnessed to improve catalytic
efficacy, even though the lifetime of some coordinated olefins
may be too short for the system to be detected or isolated.
One-pot reactions between Ru(OAc) (PPh ) and a series of
2
3 2
5
olefin-bearing benzothiazolium bromides 1–3 in dry THF yield
three chemically distinctive benzothiazol-2-ylidene (BzTh)
Ru(II)–NSHC complexes, viz. RuBr (PPh ) (N-AyBzTh) (Ay =
Accordingly, we have been interested in extending the concept
of hybrid ligands to functional olefins whereby the distal end o6f
the ligand can anchor onto a metal to provide a proximity effect
to assist olefin coordination and to retain the olefin upon its
departure. This is effectively demonstrated in the use of NNHC–
olefin ligands (NNHC = N,N-heterocyclic carbene) in many
2
3 2
prop-2-enyl) (4), RuBr(OAc)(PPh )(N-MeAyBzTh) (MeAy =
3
2
-methylprop-2-enyl) (5) and RuBr(OAc)(PPh )(N-MeBnBzTh)2
3
(MeBn = 3-methylbut-2-enyl) (6). The reaction with 3 also
gives a minor product RuCl(OAc)(PPh )(N-MeBnBzTh) (7)
3
7
metal systems such as Pd(II), Ru(II), Ir(I)) and NSHC–olefin
(Scheme 1). These compounds are formed as a result of conco-
(
NSHC = N,S-heterocyclic carbene) Pd(II), Cu(I), Au(III), Rh(I),
mitant condensation and ligand exchanges, made possible by the
benzothiazolium bromides serving as sources for carbene, olefin
and halide ligands as well as protons for condensation. For-
mation of these complexes is ensured by the elimination of at
least one acetate ligand (in the form of HOAc), thus providing
the vacant sites for carbene and olefin entry. The ligand make-up
of the resultant coordination sphere is determined by the inter-
play of olefin coordination, degree of phosphine replacement,
acetate and halide coordination and entry of a second carbene
ligand.
6b,8
Ir(I).
The combinative use of a robust (carbene) and fragile
(olefin) M–C bond is expected to enable the metal to be more
adaptable to coordinative changes. We are interested in the use
of hybrid NSHC–olefin in Ru(II) because of its emerging cataly-
9
tic applications, especially in metathesis. We herein report a
facile one-step route to a range of products that show a mix of
coordination spheres as elucidated by X-ray single-crystal
a
The coordinative flexibility of ligands and their different per-
mutations have led to the formation of different complexes under
similar conditions. Complex 4 is the only product that keeps
both phosphines, yet having room to accommodate the olefin-
tethered carbene ligand at the expense of acetate. Its formation
suggests that phosphine dissociation is not a necessary
Department of Chemistry, National University of Singapore, 3 Science
Drive 3, 117543, Singapore. E-mail: andyhor@nus.edu.sg
b
Institute of Materials Research and Engineering, Agency for Science,
Technology and Research, 3 Research Link, 117602, Singapore
†
Electronic supplementary information (ESI) available. CCDC
42690–842693. For crystallographic data in CIF and electronic sup-
8
plementary information (ESI) see DOI: 10.1039/c2dt12354a
5988 | Dalton Trans., 2012, 41, 5988–5994
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Scheme 1 One-step synthesis of Ru(II) benzothiazol-2-ylidene complexes 4–7.
2
prerequisite for carbene entry. It is also the only dihalo and
acetate-free complex, thus illustrating the halide–acetate
exchange ability. Complex 5 is the expected stoichiometric
product, giving all-different ligands (carbene and coordinated
olefin, phosphine, acetate and bromide) in a Ru(II) core. Replace-
ment of a phosphine and bromide by acetate (as in 4 to 5) also
eases the steric congestion and avoids two trans-labilising phos-
phines. Complex 6 highlights a potential access to di-carbene
whose formation makes olefin coordination unnecessary. The
pendant olefins also demonstrate the hemilability of these
carbene–olefin hybrid ligands in this series of products.
Complex 7 is related to 5 except with a different N-substituent
and bromide replacement by chloride; the latter of which is prob-
ably introduced during the recrystallization process upon contact
with CH Cl . Although it is sterically more demanding to
NSHC–olefin ligand with the anticipated η coordinated olefin
for 4, 5 and 7. In 4, the NSHC carbene, two bromides and
2
η
olefin occupy the four equatorial sites (mean deviation
0.0350 Å) while keeping the two trans-phosphine ligands at the
axial position. As expected, the carbene ligand (Ru(1)–C(1)
1.984(5) Å) is trans to bromide, thus avoiding a strong trans
ligand such as phosphine. The olefin attachment is slightly asym-
metrical, with the external Ru–C bond (Ru(1)–C(10) 2.230(8)
Å) being longer than the internal one (Ru(1)–C(9) 2.220(7) Å)
(Table 1). This is in contrast with the olefin-functionalized
complex RuL(CO) (PPh ) (L = 1-mesityl-3-(η -but-3-en-1-yl)
imidazol-2-ylidene) in which the internal Ru–C
longer (2.2076(14) Å). The olefinic C–C (C(9)–C(10) 1.317(7)
Å) is longer than an unperturbed CvC bond (1.299 Å), which
lends further support to Ru–olefin interaction.
2
2
3
bond is
olefin
7
c
11
2
2
accommodate two NSHC carbenes (in 6) compared to one (in
), this is compensated by a lower torsional strain in a pendant
Complex 5 retains one of the acetates, which is chelating and
7
trans to the olefin and phosphine. Removal of a PPh ligand has
3
olefin, as evident in a staggered conformation of the methylene
γ-H and its neighboring olefinic H, compared to the eclipsed
H ↔ H interaction in 7 (ESI†). These complexes are readily
soluble in CHCl , CH Cl and THF but less soluble in toluene.
They are relatively stable as solids but slowly decompose in sol-
ution as indicated by a gradual color change from yellow to dark
brown or green.
eased the steric congestion of the coordination sphere, which
probably explains the slight shortening of both metal–carbene
(1.960(4) Å) and metal–olefin (Ru(1)–C(9), 2.183(4) Å and
Ru(1)–C(10), 2.202(4) Å) bonds as compared to 4.
3
2
2
12
After the earlier failures, we have successfully prepared the
first example of a Ru(II) complex with two NSHC ligands, which
is evident in the structural elucidation of 6; similar di-NNHC
1
g
Chelation coordination of the hybrid ligands in 4 and 5 is
complexes have been reported. With phosphine, chelating
acetate and bromide as additional ligands, there is no further
room for olefin coordination. Its isolation suggests that these
carbene–olefin hybrids are stable in their unidentate mode, i.e.
even when the olefin is pendant. This is an important consider-
ation in the design of coordinatively flexible catalysts supported
by this type of hybrid ligand. The crystallographic data revealed
that, as expected, the carbenes avoid a mutually trans position or
being trans to phosphine. The poor quality of the data however
precludes further discussion of the bond data.
1
evident from the solution spectroscopic data. The H NMR spec-
trum of 4 shows the γ-H (w.r.t. Ru) (CH –CHvCH ) at δ 3.92,
2
2
1
3
3
.13 ppm whereas the C NMR resonance of the neighboring
olefin carbon CH –CHvCH occurs at δ 67.8 ppm. Both
2
2
are significantly upfield shifted compared to their precursor
(δ 5.81 ppm for γ-H and δ 130.4 ppm for olefin carbon),
1
presumably due to significant π-back-bonding from the metal
to olefinic π*-orbital with a concomitant weakening of the
10
CvC bond. Similar observations are apparent in 5, which
shows γ-H resonances of δ 4.22/2.15 ppm and olefin carbon
Similar to 5, complex 7 contains five different donor ligands,
including a coordinated olefin, on the Ru(II) sphere. It also fea-
tures the shortest Ru–Ccarbene bond (1.938(5) Å) in this series,
which is consistent with the least congested coordination sphere.
The Ru–Colefin contacts (Ru(1)–C(9), 2.215(5) Å and Ru(1)–
C(10), 2.235(6) Å) are also correspondingly longer than those in
(
CH –CHvCH ) at δ 86.9 ppm, respectively.
2 2
X-ray single-crystal structure analysis was carried out on
all new products, but the data for 6 are not of sufficient quality
to justify detailed discussion (Fig. 1). They invariably
show a common octahedral Ru(II) structure with the hybrid
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Fig. 1 Ortep diagrams of the structures of 4–7 with 50% probability ellipsoids. All hydrogen atoms and solvent molecules are omitted for clarity.
Table 1 Selected bond lengths (Å) and angles (°) for 4–5 and 7
Hydrosilylation of terminal alkynes
4
5
7
Complexes 4–6 were examined for their catalytic activities in
13–15
transfer hydrosilylation of alkynes
(Table 2). The reaction
Ru(1)–C(1)
Ru(1)–P(1)
Ru(1)–P(2)
Ru(1)–C(9)
Ru(1)–C(10)
Ru(1)–Br(1)
Ru(1)–Br(2)
Ru(1)–O(1)
Ru(1)–O(2)
C(9)–C(10)
C(8)–C(9)
1.984(5)
2.453(2)
2.431(2)
2.220(7)
2.230(8)
2.5438(7)
2.6429(8)
—
1.960(4)
2.287 (1)
—
2.183(4)
2.202(4)
2.6214(6)
—
2.153(3)
2.214(3)
1.398(6)
1.528(6)
1.938(5)
2.303(1)
—
2.215(5)
2.235(6)
—
between phenylacetylene and triethylsilane catalyzed by 1 mol%
of catalyst at 100 °C gives predominantly the Z-isomer of alke-
nylsilane, with 5 and 6 (60–65% yields) being more productive
than 4 (40% yield) (Table 2, Runs 1–3). The hydrosilylation of
alkynes normally generates three regioisomers: the α, β(E), and
—
16
2.145(4)
2.198(4)
1.381(8)
1.537(7)
β(Z) isomers. In particular, the choice of transition metal cata-
lyst significantly influences the outcome of the reaction.
Rhodium catalysts have been used for the selective generation of
—
1.317(7)
1.511(8)
17
both E- and Z-vinylsilanes. The Z-isomer has also been suc-
13,15,18
P(1)–Ru(1)–P(2)
C(9)–Ru(1)–C(10)
172.92(6)
34.4(2)
—
37.2(2)
—
36.1(2)
cessfully generated from iridium and ruthenium catalysts.
In addition, ruthenium as well as platinum catalysts have been
14,19
employed for the selective formation of the α-isomers.
The
more ready labilisation of acetate (in 5 and 6) could pave a direct
5
. The Ru–olefin interactions in this series are generally weak
and facile entry to an unsaturated metal, especially under thermal
due to the absence of electron-withdrawing substituents on the
olefin.
conditions. Saturation of the metal with two PPh ligands (in 4)
could also explain its lower effectiveness. Oro et al. reported
3
2
i
5990 | Dalton Trans., 2012, 41, 5988–5994
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Table 2 Hydrosilylation of terminal alkynes with silanes catalyzed by complexes 4–6
Run
Cat.
Conv. (%) R′CuCH
α (%)
β(E) (%)
β(Z) (%)
A
a
1
2
3
4
4
5
6
5
5
49
80
83
41
87
1
2
1
1
3
3
3
4
2
2
40
63
64
33
1
4
a
11
11
5
a
b
c
5
76
a
b
c
Reaction conditions: 100 °C, 24 h. R′ = Ph, R = Et. R′ = Ph, R
3
= Me(OSiMe
3
)
2
.
3
R′ = Me Si, R = Et.
similar problems in RuH(OAc)(CO)(PPh ) with two phosphines
of alternatives (viz. mono- or di-carbene, mono- or bis-phos-
phine, carbene or phosphine, coordinated or pendant olefin,
acetate or halide, acetate or phosphine, etc.) provides the metal
ample choices of a ligand environment. This is an important par-
ameter that could determine the value of this system towards not
only hydrosilylation but other catalytic reactions. The present
study has also highlighted a simple entry to asymmetric Ru(II)
NHC complexes with all-different ligands.
3
2
in giving lower yield and selectivity towards PhCuCH and
15b
HSiEt3.
Since 5 also gives a slightly better selectivity of
∼
1 : 20 for β(E) : β(Z), its effect on different silanes and alkynes
has been further examined (runs 4 to 5). With the more bulky
bis(trimethylsiloxy)methylsilane, the Z-isomer is still the favored
product, albeit in a lower yield of ∼33%. Use of a bulkier alkyne
(R = Me Si) gives the dehydrogenative silylation product as the
3
main product (76%) instead of the hydrosilylation product. The
formation of the dehydrogenative product, which has also been
observed in other Ir- and Rh-catalyzed reactions, indicates the
Experimental section
17
limit of using sterically demanding alkynes in hydrosilylation.
All manipulations were carried out under nitrogen atmosphere
using standard Schlenk techniques. Ru(OAc) (PPh ) was pre-
pared according to the literature method. Other commercially
available reagents were purchased from Sigma-Aldrich. All sol-
Ru-NHC-catalyzed hydrosilylation is generally rare in the lit-
erature. Among the few examples are those catalyzed by
2
3 2
20
1
4
Grubbs’ second generation catalysts.
For example,
1
4a
RuCl (IMes)(PCy )(vCHPh)
favors the formation of the Z
1
13
2
3
vents were freshly distilled from standard drying agents. H,
C
isomer (β(Z) : β(E) : α = 14.5 : 0 : 1) with ∼50% yield in a reac-
tion between phenylacetylene and triethylsilane with 1 mol% of
catalyst at 65 °C for 16 h. This is comparable to our system.
31
and P NMR spectra were recorded on a Bruker AMX 500
spectrometer. The chemical shifts (δ) are referenced to TMS for
1
13
1
31
1
H and C{ H} and H PO (85%) for P{ H}. Elemental ana-
i
3
4
However, other non-carbene systems such as RuHCl(CO)(P Pr ) ,
3
2
lyses were performed on a Perkin-Elmer PE 2400 elemental ana-
lyzer. The yields of hydrogenation products were determined by
using a Hewlett Packard Series 6890 GC (Santa Clara, CA,
USA) coupled to a Hewlett Packard 5973 MS detector.
i
RuH(OAc)(CO)(P Pr ) , [RuCl (p-cymene)] and RuCl(CO)
SiMe Ph)(P Pr ) have been reported to give better yields
2 3 2
>80%) with selectivity β(Z) : β(E) > 95 : 5 in the reaction
between phenylacetylene and triethylsilane. These systems
could be carried out at lower temperature and completed within a
short duration. For example, high selectivity (β(Z) : β(E) = 97 : 2)
and yield (97%) of the Z isomer could be obtained with 1 mol%
of RuH(OAc)(CO)(P Pr ) in 1,2-dichloroethane at r.t. in
.5 h. Our results suggested that NHC carbene may be used
3
2
2
2
i
(
(
1
5
General procedures for the preparation of ligand (1–3)
i
A mixture of benzothiazole (2.71 g, 20.0 mmol) and allyl or
butenyl bromide (22.0 mmol) was stirred at 80 °C overnight to
yield a yellow crude solid of 1–3. It was washed with Et O and
3
2
15a
1
as an alternative to classical phosphines towards hydrosilylation,
but more optimization study is needed on the ligand composition
in order to match the efficiency of the phosphine system. It is
our goal to develop greener phosphine-free Ru(II) hydrosilylation
catalysts.
2
a small amount of CH Cl to afford light yellow powder which
2
2
was collected and dried in vacuum.
N-Prop-2-enylbenzothiazolium bromide (1). Yield: 4.87 g
1
(
19.0 mmol, 95%). H NMR (500.1 MHz, CD Cl ): δ 12.28 (s,
2
2
3
1
H, NCHS), 8.27 (d, 1H, J = 8.0 Hz, Ar–H), 8.05 (d, 1H,
HH
3
JHH = 8.4 Hz, Ar–H), 7.87 (m, 1H, Ar–H), 7.81 (m, 1H, Ar–H),
Summary
3
6
.17 (m, 1H, CHvCH ), 5.81 (d, 2H, J
= 6.0 Hz, CH ),
2
HH 2
3
3
Isolation of these complexes under self-assembly conditions
suggested that Ru(OAc) (PPh ) is a suitable precursor for this
5.57 (d, 1H, J = 17.1 Hz, CHvCHH
), 5.53 (d, 1H, J
trans HH
HH
13
= 10.4 Hz, CHvCHHcis). C NMR (125.8 MHz, CD Cl ):
2
3 2
2
2
type of mixed-ligand carbene–olefin complex and that a variety
δ 166.0 (NCS), 140.6 (Ar–C), 130.4 (CHvCH ) 129.4, 129.1,
2
of ligand combinations can be tolerated by Ru(II). The multitude
125.1, 123.0 (Ar–C), 117.2 (CHvCH ) 55.5 (CH ).
2
2
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N-(2-Methyl)prop-2-enylbenzothiazolium bromide (2). Yield:
(202.4 MHz, CD Cl ): 55.7 (s). Anal. Calc for C H BrNO
2-
PRuS: C, 53.84; H, 4.23; N, 2.02. Found: C, 53.53; H, 4.11; N,
1.67.
2
2
31 29
1
4
.50 g (16.6 mmol, 83%). H NMR (500.1 MHz, CD Cl ):
2
2
3
δ 12.07 (s, 1H, NCHS), 8.41 (d, 1H, J = 8.2 Hz, Ar–H), 8.08
d, 1H, J = 8.2 Hz, Ar–H), 7.82 (m, 1H, Ar–H), 7.78 (m,
HH
3
(
HH
1
1
H, Ar–H), 5.80 (s, 2H, CH ), 5.13 (s, 1H, CHvCH ), 4.95 (s,
2 2
1
3
Procedures for the preparation of complexes 6 and 7
H, CH ), 1.78 (s, 3H, CH ). C NMR (125.8 MHz, CD Cl ):
2
3
2
2
δ 165.8 (NCS), 140.5, 137.2 (Ar–C), 131.4 (CHvCH ), 130.0,
2
A mixture of Ru(OAc) (PPh ) (0.25 mmol, 0.186 g), NaOAc
2
3 2
1
29.0, 129.1, 125.1, 117.1 (Ar–C), 116.4 (CHvCH ), 58.5
2
(0.042 g, 0.5 mmol) and 3 (0.50 mmol) was stirred under
(
CH ), 19.6 (CH ). Anal. Calc for C H BrNS: C, 48.89; H,
2 3 11 12
vacuum at 50 °C for 1 h. THF (15 mL) was then added and the
suspension refluxed overnight. After cooling, the solvent was
removed under vacuum, leaving a yellow residue, which was
washed with hexane and re-dissolved in toluene (15 mL). The
filtrate was diffused with hexane to yield a mixed yellow and
orange crystalline solid in 1–2 weeks. The solid was re-dissolved
in hot toluene (10 mL) and filtered. The filtrate was diffused
with hexane to yield crystals (6) in a week. The residual powder
was recrystallized from CH Cl (5 mL) and hexane (10 mL) to
4
.48; N, 5.18. Found: C, 48.68; H, 4.11; N, 5.05.
N-(3-Methyl)but-2-enylbenzothiazolium bromide (3). Yield:
1
4
1
(
.55 g (16.0 mmol, 80%). H NMR (500.1 MHz, CD Cl ): δ
2
2
3
2.05 (s, 1H, NCHS), 8.30 (d, 1H, J = 8.2 Hz, Ar–H), 7.99
d, 1H, J = 8.8 Hz, Ar–H), 7.85 (m, 1H, Ar–H), 7.79 (m,
HH
3
HH
3
1
H, Ar–H), 5.64 (d, 2H, J
= 7.6 Hz, CH ), 5.50 (m, 1H,
HH 2
1
3
CHvC), 1.97 (s, 3H, CH ), 1.83 (s, 3H, CH ). C NMR
3
3
2
2
(
125.8 MHz, CD Cl ): δ 165.2 (NCS), 143.6, 140.4 (Ar–C),
2 2
yield 7.
1
31.7 (CHvC), 129.9, 129.0, 124.8, 116.8 (Ar–C), 114.6
(
CHvC), 51.7 (CH ), 25.5 (CH ), 18.7(CH ). Anal. Calc for
2 3 3
RuBr(MeCOO)(PPh
0.11 mmol, 45%). H NMR (500.1 MHz, CD Cl ): δ 7.34–7.18
m, Ar–H), 7.15–7.11 (m, Ar–H), 6.69 (m, CH ), 5.85 (m, CH ),
3
)(N-MeBnBzTh)
2
(6). Yield: 0.10
g
C H BrNS: C, 50.71; H, 4.96; N, 4.93. Found: C, 50.70; H,
4
1
1
2 14
(
(
2
2
.75; N, 4.65.
2 2
5
4
1
.52 (m, CH ), 5.32 (m, CH), 5.31 (m, CH ), 5.17 (m, CH ),
2 2 2
.92 (m, CH), 4.83 (m, CH ), 3,43 (m, CH ), 1.98 (s, CH ),
General procedures for the preparation of complexes (4–5)
2
2
3
.86 (s, CH ), 1.75–1.60 (CH and CH COO), 1.16 (s, CH ).
3
3
3
3
3
1
A mixture of Ru(OAc) (PPh ) (0.25 mmol, 0.186 g), NaOAc
P NMR (202.4 MHz, CD Cl ): 59.9, 57.9 and 57.4 (s). Anal.
2 2
2
3 2
(0.042 g, 0.5 mmol) and 1 or 2 (0.50 mmol) was stirred under
Calc for C H BrN O PRuS : C, 58.14; H, 4.88; N, 3.08.
44 44 2 2 2
vacuum at 50 °C for 1 h. An aliquot of THF (15 mL) was then
added and the suspension refluxed overnight. After cooling, the
solvent was removed under vacuum, leaving a yellow residue,
Found: C, 57.90; H, 4.10; N, 2.96.
RuCl(MeCOO)(PPh )(N-MeBnBzTh) (7). Yield: 0.007
3
g
1
(
(
0.01 mmol, 4%). H NMR (500.1 MHz, CD Cl ): δ 7.62–6.80
2 2
m, 19H, Ar–H), 6.57 (s, CH CHvC(CH ) ), 3.98 (m,
which was washed with hexane and re-dissolved in CH Cl2
2
(15 mL). The filtrate was collected, upon which hexane was care-
2
3 2
CH CHvC(CH ) ), 3.53 (d, CH CHvC(CH ) ), 3.10 (d,
fully added as a layer. Slow diffusion within 1–2 weeks gave
yellow crystals of crystallographic quality.
2
3 2
2
3 2
CH CHvC(CH ) ), 2.66 (m, CH CHvC(CH ) ), 1.98 (s,
2
3 2
2
3 2
CH ), 1.23, 1.21 (CH , CH COO), 0.71, 0.69 (s, CH ,
3
3
3
3
3
1
RuBr (PPh ) (N-AyBzTh) (4). Yield: 0.17 g (0.18 mmol,
CH COO), 0.57 (CH ). P NMR (202.4 MHz, CD Cl ): 53.6,
3 3 2 2
2
3 2
1
7
2%). H NMR (500.1 MHz, CD Cl ): δ 7.80–7.77 (m, 8H, Ar–
39.6 (s). Anal. Calc for C H ClNO PRuS: C, 58.13; H, 4.73;
32 31 2
2
2
H), 7.34 (m, 6H, Ar–H), 7.17–7.02 (m, 21H, Ar–H), 6.81 (d,
N, 2.12. Found: C, 58.48; H, 5.04; N, 2.49.
1
3
H, Ar–H), 4.90 (m, 1H, CHvCH ), 4.06 (d, 1H, CHvCH ),
2 2
2
3
.92 (q, 1H, J = 12.0 Hz, J = 6.3 Hz, CH ), 3.63 (m, 1H,
HH
HH
2
2
3
General procedure for the transfer hydrosilylation reaction
CHvCH ), 3.13 (q, 1H, J = 12.0 Hz, J = 5.6 Hz, CH2).
2
HH
HH
1
3
C NMR (125.8 MHz, CD Cl ): δ 141.4, 136.8, 134.6, 134.2,
2
2
The transfer hydrosilylation experiments were carried out using
standard Schlenk techniques. A mixture of appropriate amount
of ruthenium complexes 4–6 (1 mol%), alkyne (1.2 mmol) and
silane (1 mmol) was dissolved in toluene (15 mL). The solution
was heated to 100 °C for about 24 h. The reaction mixture was
then directly passed through a pad of silica gel with CH Cl .
1
1
33.8, 133.6, 129.2, 129.0, 128.6, 128.2, 127.2, 125.0, 122.8,
20.9, 111.3 (Ar–C), 67.8 (CHvCH ), 66.3 (CH ), 51.9
2
2
31
(
CHvCH2). P NMR (202.4 MHz, CD Cl ): 21.6, 18.6 (q,
JPP = 325 Hz). Anal. Calc for C H Br NP RuS·(CH Cl ) :
2 0.8
2 2
2
46
39
2
2
2
C, 54.64; H, 3.98; N, 1.36. Found: C, 54.75; H, 3.68; N, 1.30.
2
2
The crude product was collected for GC-mass chromatography
analysis.
RuBr(MeCOO)(PPh )(N-MeAyBzTh) (5). A few drops of
3
toluene were added to assist crystallisation. Yield: 0.14 g
1
(
0.20 mmol, 80%). H NMR (500.1 MHz, CD Cl ): δ 7.37 (d,
2 2
1
H, Ar–H), 7.31–7.26 (m, 10H, Ar–H), 7.21–7.11 (m, 7H, Ar–
X-ray diffraction studies
2
H), 7.05 (d, 1H, Ar–H), 4.22 (d, 1H, J = 12.0 Hz, CH ), 4.01
HH
2
(
2
(
1
1
1
5
s, 1H, CvCHHtrans), 3.05 (d, 1H, JHH = 11.4 Hz, CvCHHcis),
Suitable crystals mounted on quartz fibers and X-ray data were
collected on a Bruker AXS APEX diffractometer equipped with
a CCD detector, using graphite-monochromated Mo Kα radi-
ation (λ = 0.71073 Å). The data were corrected for Lorentz and
polarization effects with the SMART program suite and for
absorption effects with SADABS. The crystal structures were
solved by direct methods and refined by full-matrix least squares
2
.15 (d, 1H, J = 12.0 Hz, CH ), 1.89 (s, 3H, CH COO), 1.64
HH 2 3
13
2
s, 3H, CH3). C NMR (125.8 MHz, CD Cl ): δ 231.3 ( J
=
2
2
CP
5 Hz, NCS), 188.0 (CH COO), 142.8, 138.3, 134.2, 134.1,
3
32.9, 132.5, 130.2, 129.2, 128.4, 128.1, 128.0, 126.8, 125.5,
24.1, 122.3, 112.6 (Ar–C), 86.9 (CvCH ), 59.7 (CvCH ),
2
2
3
1
8.9 (CH2), 25.3 (CH COO), 25.1 (CH3).
P
NMR
3
5992 | Dalton Trans., 2012, 41, 5988–5994
This journal is © The Royal Society of Chemistry 2012

View Article Online
Table 3 Summary of crystallographic parameters and refinement results for complexes 4–5 and 7
4
5
7
Formula
Fw
Cryst. syst.
Space group
a (Å)
b (Å)
c (Å)
C
46
H
39Br
2
2
NP RuS
C
35
H
34BrClNO
2
PRuS
C
39 2
H39ClNO PRuS
960.67
780.09
Monoclinic
P2(1)/n
10.207(1)
14.900(2)
20.374(3)
90
98.004(3)
90
3068.5(6)
4
753.26
Triclinic
P1ˉ
Monoclinic
P2(1)/n
14.5506(9)
22.4113(14)
24.7481(15)
90
96.027(2)
90
8025.7(9)
8
10.208(1)
12.203(2)
14.881(2)
87.596(3)
71.425(3)
80.448(3)
1732.6(4)
2
α (°)
β (°)
γ (°)
V (Å )
3
Z
−3
D calcd (g cm
)
1.590
2.548
3856
1.689
2.056
1576
1.444
0.672
776
−
1
μ (mm
F(000)
)
No. of reflns collected
No. of unique reflns
57 253
18 387
0.0952
9159
21 534
7041
0.0419
5825
22 698
7948
0.0824
R
int
No. of observed reflns
Parameters
975
417
90(2)
0.0575
0.1336
1.068
1.039
−1.335
419
T (K)
293(2)
0.1387
0.1244
0.906
0.721
−0.617
100(2)
0.0995
0.1694
1.143
1.668
−1.311
a
R
1
(all data)
b
wR c(all data)
2
GOF
−
3
Δρmax (e Å
)
3
−
Δρmin (e Å
)
a
b
2
2
1/2
c
2
1/2
R
1
= Σ||F
o
| − |F
c
||/Σ|F
o
|. wR
2
= {wΣ(|F
o
| − |F
c
|) /Σw|F
o
| }}
.
GOF = {Σw(|F
o
| − |F
c
|) /(n − p)} , where n is the number of reflections and p is
the total number of parameters refined.
2
21
on F using the SHELXTL program package. In 4, each allyl
group in the two asymmetric units is disordered into two pos-
itions with occupancy factors for C8,C9,C10/C8A,C9A,C10A
and C18,C19,C20/C18A,C19A,C20A being 0.76/0.24 and 0.53/
M. Trost, F. D. Toste and A. B. Pinkerton, Chem. Rev., 2001, 101, 2067;
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Handbook of Transition Metal Polymerization Catalysts, ed. R. Hoff and
(
(
0
.47, respectively. In complex 5, the solvated toluene is disor-
dered with dichloromethane, with each occupancy factor being
.50. All non-hydrogen atoms were refined anisotropically.
Hydrogen atoms were calculated in ideal geometries and refined
isotropically. Selected crystal data for complexes 4–5 and 7 are
summarized in Table 3.
R. T. Mathers, John Wiley
&
Sons Inc., 2010, 459;
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0
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4
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We thank the National University of Singapore (NUS),
Ministry of Education and Agency for Science, Technology
and Research for financial support (Grant R-143-000-361-112)
as well as the staff at the CMMAC of NUS for technical
assistance.
(
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5994 | Dalton Trans., 2012, 41, 5988–5994
This journal is © The Royal Society of Chemistry 2012