Synthesis, crystal structure and catalytic properties of (p-cymene)ruthenium(II) azophenol complexes: Azophenyl to azophenol conversion by oxygen insertion to a ruthenium-carbon bond

Article abstract of DOI:10.1016/S0022-328X(01)01055-5

Azophenol complexes of formulation [(η⁶-p-cymene)RuCl(Lⁿ)] (1-6, n=1-6) were prepared by two synthetic methods involving either an oxygen insertion to the Ru-C bond in cycloruthenated precursors forming complexes 1 and 2 or from the reaction of [{(η⁶-p-cymene)RuCl}₂(μ-Cl)₂] with azophenol ligands (HL³-HL⁶) in the presence of sodium carbonate in CH₂Cl₂. The molecular structure of the 1-(phenylazo)-2-naphthol complex has been determined by X-ray crystallography. The complex has a η⁶-p-cymene group, a chloride and a bidentate N,O-donor azophenol ligand. The complexes have been characterized from NMR spectral data. The catalytic activity of the complexes has been studied for the conversion of acetophenone to the corresponding alcohol in the presence of KOH and isopropanol. Complexes 4 and 6 having a methoxy group attached to the ortho-position of the phenylazo moiety and 2 with a methyl group in the meta-position of the phenolic moiety show high percentage conversion (>84%).

Full text of DOI:10.1016/S0022-328X(01)01055-5

Journal of Organometallic Chemistry 633 (2001) 79–84
www.elsevier.com/locate/jorganchem
Synthesis, crystal structure and catalytic properties of
(p-cymene)ruthenium(II) azophenol complexes: azophenyl to
azophenol conversion by oxygen insertion to a rutheniumꢀcarbon
bond
Rakesh K. Rath, Munirathinam Nethaji, Akhil R. Chakravarty *
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
Received 2 April 2001; accepted 30 May 2001
Abstract
Azophenol complexes of formulation [(h6-p-cymene)RuCl(Ln)] (1–6, n=1–6) were prepared by two synthetic methods
involving either an oxygen insertion to the RuꢀC bond in cycloruthenated precursors forming complexes 1 and 2 or from the
reaction of [{(h6-p-cymene)RuCl}2(m-Cl)2] with azophenol ligands (HL3–HL6) in the presence of sodium carbonate in CH2Cl2.
The molecular structure of the 1-(phenylazo)-2-naphthol complex has been determined by X-ray crystallography. The complex has
a h6-p-cymene group, a chloride and a bidentate N,O-donor azophenol ligand. The complexes have been characterized from
NMR spectral data. The catalytic activity of the complexes has been studied for the conversion of acetophenone to the
corresponding alcohol in the presence of KOH and isopropanol. Complexes 4 and 6 having a methoxy group attached to the
ortho-position of the phenylazo moiety and 2 with a methyl group in the meta-position of the phenolic moiety show high
percentage conversion (\84%). © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Arene ruthenium; Crystal structure; Oxygen insertion; Azophenol ligands; Transfer hydrogenation; Catalysis
1. Introduction
N,O-donor ancillary ligands play an important role in
the catalytic reactions. The present work stems from
our interest in studying the reactivity of (p-cymene)-
ruthenium(II) azophenol complexes as new hydrogena-
tion catalysts.
Current interest in the chemistry of half-sandwich
(h6-arene)ruthenium(II) complexes lies in the develop-
ment of new catalytic systems for a variety of organic
transformation reactions and in the enantioselective
asymmetric induction studies [1–5]. Ruthenium-based
catalytic systems are found to be effective in the hydro-
genation of ketones for the synthesis of chiral alcohols
[6–10]. Studies by Noyori and coworkers have shown
that the transfer hydrogenation of prochiral ketones
can be achieved by high enantiomeric excess by tailor-
ing the chiral ruthenium catalysts [1b,6]. The N,N- and
We have recently reported two cycloruthenated com-
plexes [(h6-p-cymene)Ru(L%)Cl], where L% is a chelating
C,N-donor (phenylazo)phenyl (pap) and (4,4%-dimethyl-
phenylazo)phenyl (dmpap) ligands [11]. Herein, we re-
port the two azophenol complexes (1 and 2) obtained
from a regiospecific oxygenation of the ruthenium–car-
bon bond of the azophenyl moiety to form the corre-
sponding azophenol ligand (HL1, HL2). We have also
prepared a series of analogous complexes (3–6) by
reacting [{(h6-p-cymene)RuCl}2(m-Cl)2] with the
azophenol ligands, HL3–HL6. The synthesis, structure
and properties of [(h6-p-cymene)RuCl(Ln)] (1–6) (n=
1–6) are presented here (Scheme 1). Complex 5 has
been characterized by X-ray crystallography.
* Corresponding author. Tel.: +91-80-3092533; fax: +91-80-
3600683.
E-mail address: arc@ipc.iisc.ernet.in (A.R. Chakravarty).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)01055-5

80
R.K. Rath et al. / Journal of Organometallic Chemistry 633 (2001) 79–84
2. Results and discussion
2.1. Synthetic aspects
methane in the presence of sodium carbonate. All the
complexes were found to be air stable in the solid state
and moderately stable in the liquid state.
Complexes 1 and 2 were prepared by the insertion of
oxygen into the ruthenium–carbon bond of the precur-
sor complexes of formulation [(h6-p-cymene)Ru(L%)Cl],
(1)
where L% is
a
bidentate, chelating, C,N-donor
azophenyl ligand, using m-chloroperbenzoic acid in a
chloroform–methanol solvent (Eq. (1)). The product
yield from such a reaction is low (ꢀ20%), possibly
because of the instability of the precursor complex
under high thermal reaction conditions. While the in-
sertion of oxygen to a palladium–carbon bond is quite
common, a similar regiospecific oxygenation of a ruthe-
nium–carbon bond is relatively rare [12]. Incidentally,
it is difficult to prepare the ligand systems HL1 and
HL2, obtained from the oxygenation reaction using the
conventional methods employed in the synthesis of
HL3–HL6. Complexes 3–6 were synthesized in ꢀ90%
yield from a reaction of [{(h6-p-cymene)RuCl}2(m-Cl)2]
with the azophenol ligand (HL3–HL6) in dichloro-
2.2. Spectral studies
The visible and near-UV electronic spectra of the
complexes 1–6 in MeCN show three intense charge
transfer bands in the following ranges: 525–562, 397–
431 and 315–322 nm. Complex 5 exhibits an additional
band at 360 nm. The azophenol complexes display
lower energy bands in the visible region compared with
the azonaphthol analogues. The complexes were char-
1
acterized by H-NMR and 13C-{1H}-NMR data.
The NMR spectral data suggest a 1:1 molar ratio of
the p-cymene and azophenol ligands in 1–6. The
methyl (singlet) and the isopropyl protons (two dou-
blets) of the p-cymene ligand appear in the ranges of
2.1–2.3 and 0.7–1.2 ppm, respectively. The isopropyl
CH proton appears as a septet in the range of 2.2–2.7
ppm. The p-cymene ring protons are observed in the
range of 3.7–5.7 ppm as either four doublets (4H) or
two doublets (2H) and a singlet (2H). In 13C–{1H}-
NMR, the p-cymene resonances are observed in four
distinctive ranges of 22.2–21.8, 79.8–110.8, 30.5–31.3
and 18.7–21.9 ppm. The methyl and methoxy protons
of the N,O-donor ligands appear in the range of 2.1–
2.5 and at ꢀ4.0 ppm, respectively. The other spectral
features are as expected. The formation of the oxy-
genated product 1 and 2 is evidenced from the 13C–
{1H}-NMR studies. The disappearance of the carbon
peak at ꢀ188 ppm for the RuꢀC s bond of the
precursors and the appearance of a new peak at ꢀ170
ppm suggest the formation of a RuꢀOꢀC moiety. Com-
plexes 3–6 show a similar peak in the range of 160–178
ppm assignable to the phenolato–naphtholato carbon.
Scheme 1.
2.3. Crystal structure
The azonaphthol complex [(h6-p-cymene)Ru(L5)Cl]·
(5·MeCN) has been structurally characterized by X-ray
crystallography. An ORTEP [13] view is shown in Fig. 1.
Selected bond lengths and bond angles are given in
Table 1. The complex has an essentially octahedral
coordination geometry comprising the h6-p-cymene
ring carbons occupying one face of the octahedron
leaving the other three sites to be coordinated by a
Fig. 1. ORTEP drawing of the complex showing 50% probability
thermal ellipsoids and the atom numbering scheme for [(h6-p-
cymene)RuCl(L5)]·MeCN (5·MeCN).

R.K. Rath et al. / Journal of Organometallic Chemistry 633 (2001) 79–84
81
Table 1
tones (Table 2) [8b,c,17]. While the MPV reduction
involves a direct transfer of a hydride through the
formation of a non-hydridic intermediate (I), the half-
sandwich ruthenium(II) complexes mediates through
the formation of a hydride species (II) generated by
KOH from the chloro precursor [6a,10b]. The present
work is of significance towards developing the chem-
istry of chiral azophenol complexes as promoters in
transfer hydrogenation reactions.
,
Bond lengths (A) and bond angles (°) for 5·MeCN with estimated
SDs in parentheses
Bond lengths
Ru(1)ꢀO(1)
Ru(1)ꢀN(1)
Ru(1)ꢀCl(1)
Ru(1)ꢀC(2)
Ru(1)ꢀC(3)
2.049(3)
2.080(3)
2.426(2)
2.216(4)
2.207(4)
Ru(1)ꢀC(4)
Ru(1)ꢀC(5)
Ru(1)ꢀC(6)
Ru(1)ꢀC(7)
Ru(1)ꢀC0
2.194(4)
2.205(4)
2.168(4)
2.206(4)
1.694(4)
Bond angles
O(1)ꢀRu(1)ꢀCl(1) 84.47(10)
O(1)ꢀRu(1)ꢀN(1) 86.30(13)
N(1)ꢀRu(1)ꢀCl(1) 85.57(10)
C0ꢀRu(1)ꢀCl(1)
C0ꢀRu(1)ꢀO(1)
C0ꢀRu(1)ꢀN(1)
127.89(15)
125.53(18)
131.65(17)
C0, the centroid of the h6-arene ring.
chloride and the bidentate chelating N,O-donor azon-
aphthol ligand. The RuꢀC(arene) distances vary consid-
,
erably from 2.168 to 2.215 A [14,15]. The structural
features correspond well with the reported Schiff-base
3. Conclusions
(p-cymene)–ruthenium(II) complexes [14–16].
We have prepared a series of (arene)ruthenium(II)
azophenol complexes that are catalytically active in the
hydrogenation of acetophenone to 1-phenylethanol.
The complexes 2, 4 and 6 having meta-methyl and
ortho-methoxy group are found to be moderately active
in the catalytic reaction showing a percentage conver-
sion of \84%. Two complexes have been prepared by
a novel oxygen-insertion reaction to the RuꢀC bond of
the azophenyl precursors.
2.4. Catalytic acti6ity
The catalytic hydrogenation of acetophenone in the
presence of 1–6 has been studied in an isopropanol–
KOH medium using a mole ratio of 1:2.5:100 for the
catalyst, KOH and ketone in 5 ml isopropanol (Eq.
(2)). The percentage conversions obtained using the
complexes as promoters are given in Table 2. Com-
plexes 2, 4 and 6 gave conversions in the range of
84–96%. The higher activity in complexes 4 and 6
could be related to the presence of the ortho-methoxy
group of the phenylazo moiety.
4. Experimental
All reactions were carried out under a dry dinitrogen
atmosphere following conventional Schlenk techniques.
The solvents were distilled from the appropriate drying
agents and deoxygenated prior to use. Acetophenone
was distilled under vacuum. m-Chloroperbenzoic acid
was purified before each use. Cycloruthenated precur-
sors [11], [(h6-p-cymene)RuCl2]2 [18] and the ligands
HL3–HL6 [19] were prepared by procedures outlined
earlier. All other chemicals were of reagent grade and
(2)
The activity of the present complexes is compared
with those of other achiral catalysts including alu-
minum isopropoxide which is known as a promoter in
Meerwein–Ponndorf–Verley (MPV) reduction of ke-
Table 2
A comparison of the activity of achiral promoters in transfer hydrogenation of acetophenone in refluxing isopropanol
Entry
Catalyst
Base
t (H)
Conversion (%)
Reference
1
2
3
4
5
6
7
8
9
Al(OiPr)3
–
12
6
6
1
6
6
6
6
6
93
94
94
54
75
ꢀ46
87
59
84
96
[17a]
[8c]
[8c]
[8b]
[(h6-p-Cymene)Ru(C16H15NOP)Cl]
[(h6-p-Cymene)Ru(C16H16NOP)Cl]Cl
[(h6-Benzene)Ru(C14H17N2O2P)Cl](O3SCF3)
RuCl2(PPh3)3
NaOiPr
NaiOPr
NaOiPr
NaOiPr
KOH
KOH
KOH
KOH
KOH
[17b]
Complexes 1, 5
Complex 2
Complex 3
Complex 4
This work
This work
This work
This work
This work
10
Complex 6
6

82
R.K. Rath et al. / Journal of Organometallic Chemistry 633 (2001) 79–84
used as such. Elemental analysis was performed on a
140.93, 142.28 (C3–6,8–12), 156.09, 162.91 (C2,7), 170.74
(C1) (L2 ligand).
1
Perkin–Elmer 2400 CHN analyzer. The H- and 13C–
{1H}-NMR spectra were recorded on Bruker 200 MHz
and Bruker AMX 400 (carbon channel 100.6 MHz)
spectrometers using Me4Si as the standard. Visible elec-
tronic spectra were obtained from a Hitachi U-3400
spectrophotometer.
4.2. Synthesis of [(p6-p-cymene)Ru(Ln)Cl] (3–6)
(n=3–6)
Complexes 3–6 were synthesized by a general proce-
dure in which a 0.33 mmol (200 mg) of [(h6-p-
cymene)RuCl2]2 was treated with 0.70 mmol of the
ligand HLn in the presence of 0.83 mmol (90 mg) of
Na2CO3 under continuous stirring for 4 h in 15 ml
CH2Cl2 at 25 °C. The solid product thus obtained was
thoroughly washed with n-hexane and dried under vac-
uum (yield: ꢀ90%). Dark-red crystals of 5·MeCN were
obtained on cooling a solution of the complex in a
mixture of Me2CO, petroleum ether and MeCN at
−10 °C.
4.1. Synthesis of [(p6-p-cymene)Ru(Ln)Cl] (n=1, 2)
from oxygen-insertion reactions (1, 2)
The complexes 1 and 2 were prepared by reacting
0.21 mmol of [(h6-p-cymene)Ru(L%)Cl], where L% is
monoanionic, C,N-donor (phenylazo)-phenyl or 4,4%-
dimethyl(phenylazo)phenyl, with 0.31 mmol (54 mg) of
m-chloroperbenzoic acid under refluxing condition in a
10 ml solution of CHCl3 and MeOH (1:1, v/v) for 6 h.
After cooling the reaction mixture to an ambient tem-
perature, it was filtered through celite, reduced to a
volume of ꢀ3 ml and subjected to column chromatog-
raphy using neutral alumina, deactivated with MeOH
prior to use. Elution with a mixture of MeOH and
CHCl3 (1:20, v/v) gave the product as a reddish band,
which was separated and dried under vacuum (yield:
ꢀ20%).
Anal. Found: C, 57.20; H, 4.85; N, 6.21. Calc. for
C22H23N2OClRu (1): C, 56.46; H, 4.90; N, 5.99%. Visi-
ble spectral data: umax (nm) (m, l mol−1 cm−1) (MeCN):
330 (23 990), 456 (12 760), 551 (6040). 1H-NMR
(CDCl3, 200 MHz, l ppm): 0.68, 0.86 (2d, 2×3H,
[3JHH=8 Hz], CHMe2), 2.18 (s, 3H, Me), 2.21 (sp,
[3JHH=7 Hz], CHMe2), 5.09, 5.38, 5.69, 5.77 (4d,
4×1H, [3JHH=6 Hz], four ring H) (p-cymene), 7.3 (m,
H4,5), 7.53 (m, H9–11), 8.12 (m, H8,12), 8.30 (m, H3), 8.50
(m, H6) (L1 ligand) (Hn, the hydrogen atom number
corresponding to the Cn given in Scheme 1, s, singlet; d,
doublet; m, multiplet; sp, septet). 13C-NMR (CH2Cl2,
200 MHz, l ppm): 18.87 (CHMe2), 21.12, 22.21
(CHMe2), 30.84 (Me), 85.9, 87.03, 92.59, 96.58, 102.2,
108.0 (ring C6H4) (p-cymene), 122.96, 124.60, 128.47,
129.92, 130.30, 130.50, 130.96, 133.58, 140.17 (C3–6,8–12),
157.0, 163.50 (C2,7), 168.85 (C1) (L1 ligand).
Anal. Found: C, 58.25; H, 5.40; N, 5.83. Calc for
C24H27N2ORuCl (2): C, 58.11; H, 5.45; N, 5.65%. Visi-
ble spectral data: umax (nm) (m, l mol−1 cm−1) (MeCN):
349 (21 570), 443 (13 010), 547 (6620). 1H-NMR
(CDCl3, 400 MHz, l ppm): 0.73, 0.88 (2d, 2×3H,
[3JHH=7 Hz], CHMe2), 2.10 (s, 3H, Me), 2.24 (sp,
[3JHH=7 Hz], CHMe2), 5.06, 5.14, 5.54, 5.64 (4d,
4×1H, [3JHH=6 Hz], four ring H) (p-cymene), 2.46 (s,
6H, C5ꢀMe, C10ꢀMe), 6.97 (d, [3JHH=7 Hz], H4), 7.27
(d, [3JHH=8 Hz], H8,12), 8.05 (m, H3,6,9,11) (L2 ligand).
13C-NMR (CDCl3, 400 MHz, l ppm): 19.70 (CHMe2),
21.12, 22.65 (CHMe2), 31.31 (Me), 85.76, 87.77, 92.36,
96.73, 103.42, 107.52 (ring C6H4) (p-cymene), 22.97,
24.49 (C5ꢀMe, C10ꢀMe), 123.35, 126.76, 129.47, 131.90,
Anal. Found: C, 57.51; H, 4.94; N, 5.89. Calc. for
C23H25N2OClRu (3): C, 57.32; H, 5.19; N, 5.82%. Visi-
ble spectral data: umax (nm) (m, l mol−1 cm−1) (MeCN):
316 (19 700), 398 (11 320), 562 (7980). 1H-NMR
(CDCl3, 400 MHz, l, ppm): 1.07, 1.14 (2d, 2×3H,
[3JHH=7 Hz], CHMe2), 2.19 (s, 3H, Me), 2.55 (sp,
[3JHH=7 Hz], CHMe2), 4.47, 4.93 (2d, 2×1H, [3JHH
=
6 Hz], ring H), 5.35 (s, 2H, ring H) (p-cymene), 2.21 (s,
3H, Me), 6.95, 7.09 (2d, 2×1H, [3JHH=9 Hz], H5,6),
7.37–7.48 (m, H5,9–11), 7.88 (m, H8,12) (L3 ligand).
13C-NMR (CDCl3, 400 MHz; l ppm): 19.21 (CHMe2),
20.34, 22.53 (CHMe2), 31.51 (Me), 81.34, 83.21, 86.14,
95.57, 99.97 (ring C6H4) (p-cymene), 30.95 (Me),
117.63, 121.53, 123.51, 124.34, 127.29, 128.27, 129.36,
136.32, 151.69 (C3–6,8–12), 156.73 (C2,7), 161.98 (C1) (L3
ligand).
Anal. Found: C, 56.80; H, 5.31; N, 5.49. Calc. for
C24H27N2O2ClRu (4): C, 56.30; H, 5.28; N, 5.47%.
Visible spectral data: umax (nm) (m, l mol−1 cm−1
)
(MeCN): 317 (17 310), 431 (13 440), 557 (6490). 1H-
NMR (CDCl3, 200 MHz, l ppm): 1.05, 1.11 (2d,
2×3H, [3JHH=8 Hz], CHMe2), 2.10 (s, 3H, Me), 2.63
(sp, [3JHH=7 Hz], CHMe2), 3.76, 4.91, 5.13, 5.53 (4d,
4×1H, [3JHH=6 Hz], four ring H) (p-cymene), 2.17 (s,
3H, Me), 4.03 (s, 3H, OMe), 6.86–7.17 (m, H5,9–11),
7.36–7.61 (m, H3,6,12) (L4 ligand). 13C-NMR (CDCl3,
400 MHz; l ppm): 18.92 (CHMe2), 20.19, 21.81
(CHMe2), 30.75 (Me), 80.77, 81.35, 82.50, 101.43,
103.07, 110.78 (ring C6H4) (p-cymene), 22.67 (Me),
56.02 (OMe), 117.72, 120.11, 121.09, 122.67, 125.64,
128.79, 136.03, 145.54 (C3–6,8–12), 147.54, 152.23 (C2,7),
172.23 (C1) (L4 ligand).
Anal. Found: C, 59.65; H, 4.91; N, 5.37. Calc. for
C26H25N2OClRu (5): C, 60.29; H, 4.83; N, 5.41%. Visi-
ble spectral data: umax (nm) (m, l mol−1 cm−1) (MeCN):
322 (15 400), 360 (15 010), 397 (11 820), 529 (10 200).
1H-NMR (CDCl3, 200 MHz, l ppm): 1.05, 1.12 (2d,
2×3H, [3JHH=7 Hz], CHMe2), 2.25 (s, 3H, Me), 2.51
(sp, [3JHH=7 Hz], CHMe2), 4.58, 4.96 (2d, 2×1H,

R.K. Rath et al. / Journal of Organometallic Chemistry 633 (2001) 79–84
83
[3JHH=6 Hz], ring H), 5.40 (s, 2H, ring H) (p-cymene),
7.14–7.56 (m, H3,4,12–16), 7.67 (d, [3JHH=9 Hz], H5),
7.98 (d, [3JHH=7 Hz], H6,7), 8.28 (d, [3JHH=8 Hz], H8)
(L5 ligand). 13C-NMR (CDCl3, 400 MHz, l ppm):
18.79 (CHMe2), 21.89, 22.72 (CHMe2), 30.50 (Me),
83.41, 83.72, 85.83, 88.08, 101.14, 101.80 (ring C6H4)
(p-cymene), 121.95, 123.44, 124.50, 124.82, 127.19,
127.71, 128.27, 130.13, 134.91, 137.23, 153.18 (C1,3–16),
162.29 (C2) (L5 ligand).
the structure solution and refinement. Data were cor-
rected for Lorentz, polarization and absorption effects.
Crystal data: C28H28N3OClRu, Mr=558.6, monoclinic,
,
P21/a, a=7.759(4), b=17.135(3), c=18.594(3) A, i=
3
92.61(2)°, V=2469.5(13) A , Dcalc=1.496 g cm−3
,
,
Z=4, F(000)=1132, v(Mo–Ka)=7.69 cm−1, T=
293(2) K.
The structure was solved by Patterson’s heavy atom
method using the program SHELXS-86 [20], which re-
vealed the position of the ruthenium atom in the crys-
tallographic asymmetric unit. The positions of the
remaining atoms were determined by successive DF
synthesis using the program SHELXL-97 [21]. All non-
hydrogen atoms except the nitrogen of the solvent
molecule were refined anisotropically. The hydrogen
atom positions were generated and isotropic thermal
parameters were assigned, riding to the atoms they were
bonded with. After the assignment of the core struc-
Anal. Found: C, 59.31; H, 5.11; N, 4.98. Calc. for
C28H27N2O2ClRu (6): C, 59.18; H, 4.93; N, 5.11%.
Visible spectral data: umax (nm) (m, l mol−1 cm−1
)
1
(MeCN): 315 (24 500), 418 (22 870), 525 (13 600). H-
NMR (CDCl3, 200 MHz, l ppm): 1.03, 1.11 (2d,
2×3H, [3JHH=7 Hz], CHMe2), 2.12 (s, 3H, Me), 2.58
(sp, CHMe2), 3.63, 5.13, 5.18, 5.59 (4d, 4×1H,
[3JHH=6 Hz], four ring H) (p-cymene), 4.06 (s, 3H,
OMe), 7.06–7.64 (m, H4,5–8,13–16), 9.38 (d, [3JHH=9
Hz], H3) (L6 ligand). 13C-NMR (CDCl3, 400 MHz, l
ppm): 18.90 (CHMe2), 21.74, 22.63 (CHMe2), 30.69
(Me), 79.80, 81.25, 82.10, 89.55, 100.34, 103.44 (ring
C6H4) (p-cymene), 56.12 (OMe), 110.71, 121.11, 122.58,
123.39, 123.69, 123.87, 127.85, 127.94, 128.08, 128.44,
130.03, 135.95, 147.91, 152.05 (C1,3–16), 177.90 (C2) (L6
ligand).
ture, four peaks with an electron density of ꢀ2.3
−3
,
e A
were observed in the DF map. The peaks were
assigned for a disordered acetonitrile molecule. While
two peaks having the site occupancy factor (SOF) of
1.0 are assigned to carbon atoms, the remaining two
terminal peaks were assigned for the two nitrogen
atoms with a SOF value of 0.5. The model is based on
the fact that the peaks are arranged in an essentially
linear fashion and the distance between the peaks fits
well for a disordered MeCN lattice molecule. An empir-
ical absorption correction [22] was made to the data
after obtaining the complete structural model. The
transmission coefficients were in the range of 0.67–0.87.
The final refinement was converged to R1=0.0401 and
4.3. General procedure for the catalytic hydrogenation
of acetophenone
In a typical reaction, a mixture containing 0.05 mmol
of the catalyst (1–6), 0.125 mmol (7 mg) of KOH and
5 mmol (0.6 ml) of acetophenone was heated to reflux
in 5 ml of isopropanol for 6 h. The reaction mixture
was cooled to room temperature (r.t.). The catalyst was
removed by the addition of 15 ml of petroleum ether
(b.p., 40–60 °C) followed by filtration and subsequent
neutralization with dilute HCl. The petroleum ether
layer was extracted and dried over anhydrous Na2SO4.
The solvent was distilled off to obtain a crude mixture
containing acetophenone and its hydrogenated product,
1-phenylethanol. Percentage conversion was calculated
by comparing the methyl proton signals of acetophe-
none (s, l=2.62 ppm) and 1-phenylethanol (d, l=
wR2={Sw[(F2o−Fc2)2/Sw(F2o)2]}1/2=0.1010 with
a
weighting
scheme:
w=1/[|2(F2o)+(0.0613P)2+
2.6228P], where P=(Fo2 +2F2c)/3 [R indices (all data):
R=0.0596, wR=0.1131] using 306 parameters for
4335 reflections. Final DF map showed the largest peak
and hole as 0.79 and −0.38 e A−3. The goodness-of-fit
,
on F2 was 1.035.
5. Supplementary material
3
1
1.50 ppm, JHH=6.8 Hz) in the H-NMR spectra of
Crystallographic data for structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 160046. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
the crude mixture.
4.4. X-ray structure determination of 5·MeCN
A crystal of approximate dimensions 0.2×0.18×
0.56 mm3 was mounted on a glass fiber with epoxy
cement. Unit cell dimensions were obtained using 24
reflections on an Enraf–Nonius CAD-4 diffractometer,
equipped with graphite monochromated Mo–Ka radia-
Acknowledgements
,
tion (u=0.71073 A). The intensity data were collected
(05h59; 05k520; −225l522) within the 2°5
2q550° range using a ꢀ-scan mode. Out of 4335
unique reflections, 3355 with Fo]4|(Fo) were used for
This work was supported by the Council of Scientific
and Industrial Research, New Delhi. We thank the

84
R.K. Rath et al. / Journal of Organometallic Chemistry 633 (2001) 79–84
(b) P. Braunstein, M.D. Fryzuk, F. Naud, S.J. Rettig, J. Chem.
Soc. Dalton Trans. 0 (1999) 589;
(c) P. Braunstein, F. Naud, S.J. Rettig, New J. Chem. 25 (2001)
32.
Sophisticated Instrumentation Center, IISc, for the
NMR data.
[9] (a) Y. Shvo, I. Goldberg, D. Czeerkie, D. Reshef, Z. Stein,
Organometallics 16 (1997) 133;
References
(b) M. Bernard, F. Delbecq, P. Sautet, F. Fache, M. Lemaire,
Organometallics 19 (2000) 5715.
[1] (a) R. Noyori, Asymmetric Catalysis in Organic Synthesis, Wi-
ley, New York, 1994;
[10] (a) A. Katho, D. Carmona, F. Viguri, C.D. Remacha, J. Kovacs,
F. Joo, L.A. Oro, J. Organomet. Chem. 593/594 (2000) 299;
(b) Y.R.S. Laxmi, J.E. Backvall, Chem. Commun. (2000) 611.
[11] R.K. Rath, S.G. Valavi, K. Geetha, A.R. Chakravarty, J.
Organomet. Chem. 596 (2000) 232.
(b) T. Ohkuma, R. Noyori, Compr. Asymmetric Catal. 1 (1999)
199.
[2] (a) H. Brunner, Adv. Organomet. Chem. 18 (1980) 151;
(b) H. Brunner, Angew. Chem. Int. Ed. Engl. 38 (1999) 1194;
(c) H. Brunner, M. Prommesberger, Tetrahedron: Asymmetry 9
(1998) 3231.
[12] P. Wadhawani, D. Bandopadhyay, Organometallics 19 (2000)
4435.
[3] (a) G. Consiglio, F. Morandini, Chem. Rev. 87 (1987) 151;
(b) S.G. Davies, J.P. Mcnally, A.J. Smallridge, Adv. Organomet.
Chem. 30 (1991) 1.
[4] (a) D.L. Davis, J. Fawcett, S.A. Garratt, D.R. Russell, Chem.
Commun. (1997) 1351;
[13] C.K. Johnson, ORTEP-II, A Program for Thermal Ellipsoid
Plotting, Oak Ridge National Laboratory, Oak Ridge, Tennes-
see, 1978.
[14] (a) P. Lahuerta, J. Lattore, M. Sanau, F.A. Cotton, W.
Schwotzer, Polyhedron 7 (1988) 1311;
(b) A.J. Davenport, D.L. Davis, J. Fawcett, S.A. Garratt, D.R.
Russell, J. Chem. Soc. Dalton Trans. (2000) 4432.
[5] (a) J.W. Faller, J. Parr, Organometallics 19 (2000) 1829;
(b) D. Carmona, C. Cartiviela, S. Elipe, F.J. Lahoz, M.P.
Lamata, M. Pilar, L. deViu, L.A. Oro, C. Vega, F. Viguri,
Chem. Commun. (1997) 2351;
(b) H. Brunner, R. Oeschey, B. Nuber, Inorg. Chem. 34 (1995)
3349.
[15] (a) S.K. Mandal, A.R. Chakravarty, J. Organomet. Chem. 417
(1991) C59;
(b) S.K. Mandal, A.R. Chakravarty, Polyhedron 11 (1992) 823;
(c) S.K. Mandal, A.R. Chakravarty, J. Chem. Soc. Dalton
Trans. (1992) 1627;
(d) S.K. Mandal, A.R. Chakravarty, Inorg. Chem. 32 (1993)
3851.
(c) H.C.L. Abbenhuis, M. Pfeffer, J.P. Sutter, A. deCian, J.
Fischer, H.L. Ji, J.H. Nelson, Organometallics 12 (1993) 4464;
(d) C. Bruneau, P.H. Dixneuf, Chem. Commun. (1997) 507;
(e) V. Ritleng, J.P. Sutter, M. Pfeffer, C. Sirlin, Chem. Commun.
(2000) 129;
[16] (a) S. Roy, C. Sudha, A.R. Chakravarty, Indian J. Chem. 37A
(1998) 1045;
(f) W. Ferstl, I.K. Sakodinskaya, N.B. Sutter, G.L. Borgne, M.
Pfeffer, A.D. Ryabov, Organometallics 16 (1997) 411.
[6] (a) M. Yamakawa, H. Ito, R. Noyori, J. Am. Chem. Soc. 122
(2000) 1466;
(b) S. Roy, R.K. Rath, C. Sudha, A.R. Chakravarty, Indian J.
Chem. 39A (2000) 838.
[17] (a) A.L. Wilds, Org. React. 2 (1944) 178;
(b) R.L. Chowdhury, J.E. Backvall, J. Chem. Soc. Chem. Com-
mun. (1991) 1063.
[18] M.A. Bennet, T.N. Huang, T.W. Matheson, A.K. Smith, Inorg.
Synth. 21 (1985) 75.
[19] A.I. Vogel, A Textbook of Practical Organic Chemistry, Long-
man, London, 1984, p. 714.
(b) K. Mikami, T. Korenaga, M. Terada, T. Ohkuma, T. Pham,
R. Noyori, Angew. Chem. Int. Ed. Engl. 38 (1999) 495;
(c) M. Kitamura, M. Yoshimura, N. Kanda, R. Noyori, Tetra-
hedron 55 (1999) 8769;
(d) K.J. Haack, S. Hashiguchi, A. Fujii, T. Ikariya, R. Noyori,
Angew. Chem. Int. Ed. Engl. 36 (1997) 285.
[20] G.M. Sheldrick, SHELXS-86: Program for the Solution of Crystal
Structures, University of Go¨ttingen, Go¨ttingen, Germany, 1986.
[21] G.M. Sheldrick, SHELXL-97: A Program for Crystal Structure
Refinement, Release 97-2, University of Go¨ttingen, Go¨ttingen,
Germany, 1997.
[7] (a) D.G.I. Petra, P.C.J. Kamer, P.W.N.M.V. Leeuwen, K. Goul-
bitz, A.M.V. Loon, J.G.D. Vries, H.E. Schoemaker, Eur. J.
Inorg. Chem. (1999) 2335;
(b) K. Everaere, J.F. Carpentier, A. Mortreux, M. Bulliard,
Tetrahedron: Asymmetry 10 (1999) 4663.
[22] A.C.T. North, D.C. Phillips, F.S. Mathews, Acta Crystallogr.
Sect. A 24 (1968) 351.
[8] (a) B.D.B. Holscher, J. Heinen, J. Organomet. Chem. 570 (1998)
141;
.