Synthesis and characterization of ruthenium p-cymene complexes bearing bidentate P-N and E-N ligands (E = S, Se) based on 2-aminopyridine

Article abstract of DOI:10.1016/j.poly.2010.08.014

The syntheses and characterization of a series of cationic of Ru(II) halfsandwich complexes of the types [Ru(η⁶-p-cymene) (κ²(P,N)-PN)Cl]⁺ (PN = N-diphenylphosphino-2- aminopyridine, N-di-iso-propylphosphino-2-aminopyridine, 2-[(2-pyridyl)amino] dibenzo[d,f][1,2,3]dioxaphosphepine, N-(diisopropylphosphino)-2,6- diaminopyridine) and [Ru(η⁶-p-cymene)(κ²(E,N)- EN)Cl]⁺ (EN = N-(2-pyridinyl)amino-diphenylphosphine sulfide, N-(2-pyridinyl)amino-diisopropylphosphine sulfide, N-(2-pyridinyl)amino- diphenylphosphine selenide, N-(2-pyridinyl)amino-diisopropylphosphine selenide) is described. Some of these complexes were tested as precatalysts for the transfer hydrogenation of acetophenone to give 1-phenyl ethanol.

Full text of DOI:10.1016/j.poly.2010.08.014

Polyhedron 29 (2010) 3097–3102
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and characterization of ruthenium p-cymene complexes bearing
bidentate P–N and E–N ligands (E = S, Se) based on 2-aminopyridine
Wolfgang Lackner-Warton a, Shinji Tanaka a, Christina M. Standfest-Hauser a, Özgür Öztopcu a,
Jen-Chieh Hsieh a, Kurt Mereiter b, Karl Kirchner a,
⇑
a Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
b Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
The syntheses and characterization of a series of cationic of Ru(II) halfsandwich complexes of the types
[Ru(
phino-2-aminopyridine, 2-[(2-pyridyl)amino]dibenzo[d,f][1,2,3]dioxaphosphepine, N-(diisopropylphos-
phino)-2,6-diaminopyridine) and [Ru(
6-p-cymene)( 2(E,N)-EN)Cl]+ (EN = N-(2-pyridinyl)amino-
g j
6-p-cymene)( 2(P,N)-PN)Cl]+ (PN = N-diphenylphosphino-2-aminopyridine, N-di-iso-propylphos-
Received 12 July 2010
Accepted 12 August 2010
Available online 20 August 2010
g
j
diphenylphosphine sulfide, N-(2-pyridinyl)amino-diisopropylphosphine sulfide, N-(2-pyridinyl)amino-
diphenylphosphine selenide, N-(2-pyridinyl)amino-diisopropylphosphine selenide) is described. Some
of these complexes were tested as precatalysts for the transfer hydrogenation of acetophenone to give
1-phenyl ethanol.
Keywords:
Ruthenium
Half sandwich complexes
Aminophosphines
Hemilabile ligands
Transfer hydrogenation
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
(PN-Ph) is the most prominent member of these ligand family. An-
other interesting aspect of PN ligands is the fact that they can be fur-
Heterodifunctional ligands are intensively studied and applied
in coordination and organometallic chemistry owing to the often
unique properties of their metal complexes and their ability to gen-
erate so called hemilabile systems which often display enhanced
reactivity [1]. According to this concept introduced by Jeffrey and
Rauchfuss, such ligands provide different electronegativities at
their coordination sites [2]. In particular soft/hard, e.g., P/N and P/
O assemblies, are able to coordinate reversibly to a metal center
providing or protecting temporarily a vacant coordination site a
feature very desirable for catalysts.
In this context, we have become interested in heterodifunctional
PN ligands based on 2-aminopyridine in which the donor atoms are
separated by an amino group [3,4]. These types of ligands are easily
constructed by reacting 2-aminopyridine with R2PCl in the presence
of base (Scheme 1). R2PCl may contain both bulky and/or electron-
rich dialkyl phosphines as well as P–O and P–N bond containing
achiral and chiral phosphite units derived from diols, aminoalco-
hols, and diamines [5]. Due to the comparative ease of phospho-
rus–nitrogen bond forming reactions in comparison with those in
which phosphorus–carbon bonds are formed it is not surprising that
several examples of transition metal complexes featuring this type
of PN ligands have emerged over the last decades [6–15]. With a few
exceptions [16], however, N-diphenylphosphino-2-aminopyridine
ther functionalized by oxidation with H2O2, sulfur, and grey
selenium, respectively, to give the chalcogen O, S, and Se derivatives
according to Scheme 1 (EN ligands). Although these heterodifunc-
tional ligands have been known for some time [12], transition metal
complexes thereof are relatively scarce [8,11,17,18].
In the present contribution we report on the reactions of
[Ru(g l-Cl)Cl]2 with the PN and EN ligands shown
6-p-cymene)(
in Scheme 2 resulting, with the exception of the ON ligands, in
the formation of a series of cationic p-cymene Ru(II) complexes
of the types [Ru(g g
6-p-cymene)(PN)Cl]+ and [Ru( 6-p-cyme-
ne)(EN)Cl]+. The X-ray structures of two representative complexes
are presented. In addition, some of these complexes were tested as
precatalysts for the transfer hydrogenation of acetophenone to give
1-phenyl ethanol.
2. Results and discussion
Similarly to the known ligands PN-Ph (1a) [19], PN-iPr (1b), and
2-[(2-pyridyl)amino]dibenzo[d,f][1,2,3]dioxaphosphepine (PN-BI-
POL) (1c) [3], the new ligand PNNH2-iPr (1d) was prepared in 45%
yield by treatment of 2,6-diaminopyridine with 1 equiv. of PiPr2Cl
in the presence of a base NEt3. This compound had to be purified by
chromatography due to the formation of the doubly phosphory-
lated PNP-iPr ligand (Scheme 3) [20]. The EN ligands 2 were pre-
pared according to the literature by the addition of a small
⇑
Corresponding author. Tel.: +43 1 58801 15340; fax: +43 1 58801 16399.
E-mail address: kkirch@mail.zserv.tuwien.ac.at (K. Kirchner).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.08.014

3098
W. Lackner-Warton et al. / Polyhedron 29 (2010) 3097–3102
H2O2, S, Se
R2PCl (1equiv)
base
N
N
NH
NH
N
NH
N
NH2
N
NH
PR2
PR2
PR2
PR2
S
O
Se
PN Ligands
EN Ligands
Scheme 1.
(j
2(Se,N)-SeN-Ph)Cl]+ (8a), and [Ru(
iPr)Cl]+ (8b) were prepared in similar fashion by reacting [Ru(g6
p-cymene)( -Cl)Cl]2 with 2 equiv. of the ligands 3 and 4 in the
g j
6-p-cymene)( 2(Se,N)-SeN-
-
R'
N
NH
N
N
NH
PR2
NH
N
NH
l
presence of 2 equiv. of AgSbF6 in 78–86% isolated yields (Scheme
5). It has to be noted that in the absence of a silver salt no clean
reaction took place. Moreover, in the case of the ON ligands ON-
Ph (2a) and ON-iPr (2b) we were unable to obtain complexes of
PR2
PR2
PR2
S
O
Se
1a PN-Ph; R' = H
1b PN-iPr; R' = H
2a ON-Ph
2b ON-iPr
3a SN-Ph
3b SN-iPr
4a SeN-Ph
4b SeN-iPr
1c PN-BIPOL; R' = H
1d PNNH2-iPr; R' = NH2
the type [Ru(g j
6-p-cymene)( 2(O,N)-ON)Cl]+ and only intractable
materials were obtained. It has to be also noted that several at-
tempts to deprotonate complexes 7 and 8 with KOtBu failed and
intractable materials were obtained only.
Scheme 2.
All complexes are air-stable orange compounds which were
characterized by 1H, 13C{1H}, and 31P{1H} NMR spectroscopy as
well as elemental analysis. The 1H NMR spectra contain in most
cases a set of four well-resolved high-field-shifted doublets charac-
PiPr2Cl
1 equiv
+
HN
PiPr2
PNP-iPr
H2N
N
NH
N
NH
H2N
N
NH2
PiPr2
PiPr2
teristic of an
g
6-p-cymene ring attached to a metal center coordi-
1d PNNH2-iPr (45%)
nated to three different donor atoms. The methyl groups of the iPr
moiety are diastereotopic exhibiting typically two distinct dou-
blets centered at about 1.1 and 0.9 ppm. The 13C{1H} NMR spec-
trum does not bear any unusual features and is not discussed
here. In the 31P{1H} NMR spectra, 5a–d exhibit singlets which show
Scheme 3.
excess of aqueous H2O2 (30%) to a THF solution of the respective PN
ligands 1 [12a]. The EN ligands 3 and 4 were also prepared follow-
ing the literature method [8,12a] by refluxing the PN ligands 1 with
a stoichiometric quantity of sulfur and grey selenium, respectively,
in toluene.
the expected low-field shifts of the
relative to the free uncoordinated ligands [5a: 97.5 ppm
j
2(P,N)-coordinated PN ligands
(
D
d = 70.0 ppm), 5b: 123.6 ppm (
D
d = 73.7 ppm), 5c: 165.7 ppm
d = 69.8 ppm)]. This trend is re-
2(S,N)- and
2(Se,N)-coordinated EN ligands give rise to signals at 52.6, 83.6,
(D
d = 25.7 ppm), 5d: 117.3 ppm (
D
Treatment of [Ru(g l-Cl)Cl]2 with 2 equiv. of the
6-p-cymene)(
versed in the case of complexes 7a, 7b, 8a, and 8b. The
j
j
respective ligands 1a–d in the presence of 2 equiv. of Ag+ salts
ðSbF6 or CF3SO3ꢀ) in CH2Cl2 at room temperature afforded the
ꢀ
44.5, and 77.3 ppm, whereas the uncoordinated ligands are shifted
to lower fields exhibiting singlets at 63.5, 103.4, 54.4, and
102.0 ppm, respectively. In the case of the SeN complexes 8a and
8b, the phosphorus signals exhibit a pair of Se satellites with
31P–77Se coupling constants of 663 and 640 Hz, respectively. The
deprotonated complex 6 also displays a sharp single 31P{1H}
NMR resonance at 132.7 ppm which is shifted slightly to higher
field than the starting material 5b (cf. 134.1 ppm). The 1H spec-
trum of 6 is also very similar to that of 5b except that the NH res-
onance is now absent.
cationic complexes [Ru(g j
6-p-cymene)( 2(P,N)-PN-Ph)Cl]+ (5a),
[Ru(
g
6-p-cymene)(
j
2(P,N)-PN-iPr)Cl]+ (5b), [Ru(
g
6-p-cymene)-
2(P,N)-
(j
2(P,N)-PN-BIPOL)Cl]+ (5c), and [Ru(
g
6-p-cymene)(
j
PNNH2-iPr)Cl]+ (5d) in 59–88% isolated yields (Scheme 4). In the
absence of a silver salt the same reaction took place yielding the
respective complexes with chloride as counterion. There was no
evidence for the formation of intermediates of the type [Ru(
g
6-p-
cymene)(
j
1(P)-PN)Cl2] bearing a 1(P)-coordinated PN ligand.
j
Deprotonation of the PN-iPr ligand was achieved by reacting 5b
The molecular structures of 5a0 (with chloride as counter ion)
with 2 equiv. of KOtBu in THF for 3 h affording the neutral complex
ꢀ
[Ru(
(Scheme 4).
The complexes [Ru(
[Ru(
6-p-cymene)( 2(S,N)-SN-iPr)Cl]+ (7b), [Ru(
g j
6-p-cymene)( 2(P,N)-PNdep-iPr)Cl] (6) in 37% isolated yield
and 7b (with SbF6 as counter ion) were determined by X-ray crys-
tallography. ORTEP diagrams of the two Ru-complexes are de-
picted in Figs. 1 and 2 with selected bond distances and angles
reported in the captions. Both complexes adopt the typical three
g
6-p-cymene)( 2(S,N)-PN-Ph)Cl]+ (7a),
j
g
j
g
6-p-cymene)-
N
NH
R'
+
R2P
1a-d
KOtBu
Ru
PR2
Ru
N
R'
[Ru(η6-p-cymene)(μ-Cl)Cl]2
R'
Cl
Cl
PR2
with or without Ag+
THF, 3h
N
N
N
H
5a-d
6 R = i Pr, R' = H
Scheme 4.

W. Lackner-Warton et al. / Polyhedron 29 (2010) 3097–3102
3099
N
NH
+
3a,b
4a,b
PR2
E
[Ru(η6-p-cymene)(μ-Cl)Cl]2
Ru
Cl
Ag+
N
E
7a,b
HN
PR
8a,b
2
Scheme 5.
ꢀ
Fig. 2. Molecular structure of 7b (50% displacement ellipsoids, SbF6 anion and
most H atoms omitted for clarity). Selected bond lengths (Å) and angles (°): <Ru1–
Ccymene> = 2.189(2), Ru1–N1 = 2.138(1), Ru1–S1 = 2.4394(6), Ru1–Cl1 = 2.4043(6),
N1–Ru1–S1 = 92.56(5), N1–Ru1–Cl1 = 84.71(5), S1–Ru1–Cl1 = 85.80(2); N2ꢁ ꢁ ꢁCl1 =
3.183(2) (not shown).
Table 1
Catalytic transfer hydrogenation of acetophenone.a
Fig. 1. Molecular structure of 5a0 (50% displacement ellipsoids, most H atoms
omitted for clarity). Selected bond lengths (Å) and angles (°): <Ru1–Ccymene> =
2.237(2), Ru1–N1 = 2.099(2), Ru1–P1 = 2.283(1), Ru1–Cl1 = 2.394(1), N1–Ru1–
P1 = 79.84(4), N1–Ru1–Cl1 = 83.23(4), P1–Ru1–Cl1 = 91.56(2), N2ꢁ ꢁ ꢁCl2 = 3.032(2).
Entry
C
S:C:B
T (°C)
Time (h)
Conv. (%)
1
2
3
4
5
6
7
8
9
5b
5b
5b
5b
5b
5b
6
7b
7b
8b
8b
200:1:20
200:1:20
2000:1:20
200:1:20
200:1:20
20:1:20
200:1:20
200:1:20
200:1:20
200:1:20
200:1:20
75
75
75
25
25
25
75
75
25
75
25
22
2.2
22
44
22
22
22
22
22
22
22
99
25
75
99
20
75
99
99
–
legged piano stool configuration with Cl and the N and P atoms and
the N and S atoms of the bidentate PN-Ph and SN-iPr ligands,
respectively, as the legs. The p-cymene ring is essentially planar
with C–C bond distances in the range 1.392(3)–1.435(3) Å, giving
a mean value of 1.417(3) Å. The Ru–C distances range from
2.173(2) to 2.201(2) Å (mean 2.189(2) Å) in 5a0 and from
2.192(2) to 2.261(2) Å (mean 2.237(2) Å) in 7b. In the case of 5a0
the NH group of the complex forms a characteristic hydrogen bond
to the free chloride ion Cl2 with a comparatively short distance
N2ꢁ ꢁ ꢁCl2 = 3.032(2) Å. Further coherence of the solid state struc-
ture is provided by four C–Hꢁ ꢁ ꢁCl interactions to Cl2 (not Cl1) with
Cꢁ ꢁ ꢁCl distances from 3.321(2) to 3.726(2) Å. In the case of 7b the
NH group forms a N–Hꢁ ꢁ ꢁCl hydrogen bond to the chloride of a
neighbouring Ru complex, N2ꢁ ꢁ ꢁCl1 = 3.183(2) Å, thus giving rise
to infinite chains parallel to [1 0 1] of H-bonded Ru-complexes.
The SbF6 counter ions are located between these chains and are an-
chored via a five different C–Hꢁ ꢁ ꢁF interactions with Cꢁ ꢁ ꢁF distances
between 3.120(2) and 3.464(2) Å.
Transfer hydrogenation of acetophenone to give 1-phenyl etha-
nol in refluxing 2-propanol was carried out to test the catalytic
activity of complexes 5b, 7b, and 8b using typically 0.1 M aceto-
phenone solution, 0.5 mol% of the complex as catalyst, and
10 mol% of KOtBu as the base. Under these conditions all four com-
plexes acted as efficient catalyst reaching 99% conversion within
22 h (Table 1, entries 1, 8, and 10). Under the same conditions,
but with 0.1 mol% of 5b the conversion dropped to 75% (entry 3).
Performing the reaction at room temperature with 0.5 mol% of
10
11
99
–
a
S = acetophenone, C = catalyst, B = KOtBu.
the precatalysts 5b, 7b, and 8b, and 10 mol% of KOtBu resulted in
either very poor (entry 5) or no conversion (entries 9 and 11). With
5 mol% of 5b the yield of 1-phenyl ethanol was 75% (entry 3). Per-
forming the catalysis with the deprotonated complex 6 gave the
same results as with 5b (entry 7). The catalytic effect of the ruthe-
nium complexes was confirmed by running the reaction without
catalyst. No product was formed and only starting materials were
isolated from the reaction mixture.
The nature of the catalytically active species is not clear at the
moment. On the one hand p-cymene ligand displacement may
not be dismissed, on the other hand the PN and SN ligands may
be hemilabile under the reaction conditions forming reactive
16eꢀ intermediates with
j j
1(P)-bonded or 1(N)-bonded ligands.
However, both 1H and 31P{1H} NMR spectra of 5b, 6, 7b, and 8b
in CD3NO2 at 100 °C did not significantly change as compared to
the room temperature spectra and there was no indication of any
dynamic processes. Moreover, it has to be noted that the addition
of AgSbF6 (stoichiometric with respect to the catalyst) as chloride

3100
W. Lackner-Warton et al. / Polyhedron 29 (2010) 3097–3102
scavenger had no effect on both reaction rates and conversions and
it thus seems that the chloride ligand is not removed from the me-
tal center during the catalysis.
washed with diethyl ether and dried under vacuum. Yield:
0.514 g (78%). Anal. Calc. for C28H29ClF3N2O3PRuS: C, 48.17; H,
4.19; N, 4.01. Found: C, 48.24; H, 4.11; N, 4.09%. 1H NMR (d, CD2Cl2,
20 °C): 9.28 (d, JHH = 2.92 Hz, 1H, NH), 8.70 (d, JHH = 5.48 Hz, 1H,
py6), 7.90–7.20 (m, 11H, Ph, py4), 7.12 (s, 1H, py5), 6.84 (t,
JHH = 6.28 Hz, 1H, py3), 6.02 (d, JHH = 6.17 Hz, 1H, cym), 5.74 (d,
JHH = 6.62 Hz, 1H, cym), 5.62 (d, JHH = 5.71 Hz, 1H, cym), 4.82 (d,
JHH = 3.65 Hz, 1H, cym), 2.88 (m, JHH = 7.08 Hz, 1H, CH(CH3)2),
2.09 (s, 3H, CH3), 1.06 (d, JHH = 6.85 Hz, 3H, CH(CH3)2), 0.87 (d,
JHH = 6.85 Hz, 3H, CH(CH3)2). 13C{1H} NMR (d, CD2Cl2, 20 °C):
In sum we have shown that the dimeric complex [Ru(
cymene)( -Cl)Cl]2 reacts readily with PN and EN ligands to give
cationic p-cymene Ru(II) complexes of the types [Ru(
6-p-cyme-
g
6-p-
l
g
ne)(PN)Cl]+ and [Ru( 6-p-cymene)(EN)Cl]+. In the case of [Ru(g6
g -
p-cymene)(PN)Cl]+ with PN = PN-iPr we have also demonstrated
that deportonation of the acidic NH proton of the PN ligand is pos-
sible yielding the neutral complex [Ru(g j
6-p-cymene)( 2(P,N)-
PNdep-iPr)Cl]. Some of these complexes act as moderately active
precatalysts for the transfer hydrogenation of acetophenone to give
1-phenyl ethanol.
161.5 (d, JCP = 12.07 Hz, py2), 154.7 (s, py6), 140.1 (s, py4),
2
3
136.3–128.2 (Ph), 117.5 (s, py5), 112.3 (d, JCP = 9.20 Hz, py3),
2
108.8 (s, cym), 101.5 (s, cym), 98.4 (d, JCP = 7.47 Hz, cym), 93.1
2
2
(d, JCP = 5.75 Hz, cym), 88.7 (d, JCP = 2.30 Hz, cym), 86.8 (d,
2JCP = 1.46 Hz, cym), 30.6 (s, CH(CH3)2), 22.4 (s, CH(CH3)2), 21.3 (s,
CH(CH3)2), 18.1 (s, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C): 97.5.
3. Experimental section
3.1. General procedure
3.2.3. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.500 g, 0.817 mmol) and PN-Ph (0.344 g,
2.64 mmol) as starting materials but in the absence of a silver salt.
Yield: 0.420 g (88%). Anal. Calc. for C27H29Cl2N2PRu: C, 55.48; H,
5.00; N, 4.79. Found: C, 55.24; H, 5.10; N, 4.88%. The NMR spectra
of this complex are virtually the same as those of 5aꢁCF3SO3 except
that the NH proton is shifted from 9.28 to 9.43 ppm.
g
6-p-cymene)(j2(P,N)-PN-Ph)Cl]Cl (5a0)
-
All manipulations were performed under an inert atmosphere
of argon by using Schlenk techniques. The solvents were purified
l
according to standard procedures [21]. [Ru(
-Cl)Cl]2 [22], N-diphenylphosphino-2-aminopyridine (PN-Ph)
g
6-p-cymene)-
(l
(1a), N-diisopropylphosphino-2-aminopyridine (PN-iPr) (1b),
2-[(2-pyridyl)amino]dibenzo[d,f][1,2,3]-dioxaphosphepine (PN-BI-
POL) (1c) [4], N-(2-pyridinyl)amino-diphenylphosphine oxide
(ON-Ph) (2a), N-(2-pyridinyl)amino-diisopropylphosphine oxide
(ON-iPr) (2b), N-(2-pyridinyl)amino-diphenylphosphine sulfide
(SN-Ph) (3a), N-(2-pyridinyl)amino-diisopropylphosphine sulfide
(SN-iPr) (3b), N-(2-pyridinyl)amino-diphenylphosphine selenide
(SeN-Ph) (4a), and N-(2-pyridinyl)amino-diisopropylphosphine
selenide (SN-iPr) (4b) were prepared according to the literature
[9d]. The deuterated solvents were purchased from Aldrich and
dried over 4 Å molecular sieves. 1H, 13C{1H}, and 31P{1H} NMR
spectra were recorded on a Bruker AVANCE-250 spectrometer
and were referenced to SiMe4 and H3PO4 (85%), respectively.
3.2.4. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.808 g, 1.32 mmol), PN-iPr (0.555 g,
g j
6-p-cymene)( 2(P,N)-PN-iPr)Cl]SbF6. (5b)
-
l
2.64 mmol), and AgSbF6 (0.907 g, 2.64 mmol) as starting materials.
Yield: 1.61 g (85%) Anal. Calc. for C21H33ClF6N2PRuSb: C, 35.19; H,
4.64; N, 3.91. Found: C, 35.00; H, 4.51; N, 4.04%. 1H NMR (d, CD2Cl2,
20 °C): 8.63 (d, JHH = 5.4 Hz, 1H, py6), 7.59 (t, JHH = 6.7 Hz, 1H, py4),
7.03 (d, JHH = 8.0 Hz, 1H, py3), 6.83 (t, JHH = 5.0 Hz, 1H, py5), 6.76 (s,
1H, NH), 6.15 (d, JHH = 4.97 Hz, 1H, cym), 5.96 (d, JHH = 4.97 Hz, 2H,
cym), 5.80 (d, JHH = 1.91 Hz, 1H, cym), 2.89 (m, JHH = 6.31 Hz, 2H,
CH(CH3)2), 2.56 (m, JHH = 5.55 Hz, 1H, CH(CH3)2), 2.11 (s, 3H,
CH3), 1.50–1.00 (m, 18H, CH(CH3)2). 13C{1H} NMR (d, CD2Cl2,
3.2. Synthesis
2
20 °C): 161.3 (d, JCP = 9.20 Hz, py2), 154.7 (s, py6), 140.1 (s, py4),
3.2.1. N-(Diisopropylphosphino)-2,6-diaminopyridine (PNNH2-iPr) (1d)
PiPr2Cl (3.35 g, 22 mmol) was added dropwise to a solution of
2,6-diaminopyridine (2.18 g, 20 mmol) and triethylamine (2.2 g,
22 mmol) in THF (30 mL) at 0 °C. The mixture was stirred for
20 h at room temperature. After that ethyl acetate was added
and the solution was filtered over neutral Al2O3. The solvent was
removed under reduced pressure and the crude product was chro-
matographed with an ethyl acetate/hexane mixture (1:1) as eluent
in order to remove the doubly phosphorylated PNP-iPr ligand [20].
Yield: 2.02 g (45%). Anal. Calc. for C11H20N3P: C, 58.65; H, 8.95; N,
18.65. Found: C, 58.74; H, 8.70; N, 18.79%. 1H NMR (d, CDCl3,
20 °C): 7.18 (t, J = 7.75 Hz, 1H, py4), 6.40 (dd, J = 6.25 Hz,
J = 1.75 Hz, 1H, py3), 5.83 (d, J = 7.75 Hz, 1H, py5), 4.47 (d,
J = 11.0 Hz, 1H, NH), 4.32 (b, 2H, NH2) 1.70 (m, J = 5.25 Hz, 2H,
CH(CH3)2), 1.06–0.96 (m, 12H, CH(CH3)2). 13C{1H} NMR (d, CDCl3,
20 °C): 169.8 (d, J = 20.8 Hz, py2), 157.3 (py6), 139.5 (d, J = 1.9 Hz,
py4), 98.0 (py3), 97.7 (py5), 26.3 (d, J = 11.3 Hz, CH(CH3)2), 18.6
(d, J = 19.5 Hz, CH(CH3)2), 17.0 (d, J = 7.5 Hz, CH(CH3)2). 31P{1H}
NMR (d, CDCl3, 20 °C): 47.5.
3
117.1 (s, py5), 111.2 (d, JCP = 6.90 Hz, py3), 107.4 (s, cym), 99.0
2
2
(s, cym), 96.4 (d, JCP = 5.75 Hz, cym), 92.5 (d, JCP = 5.75 Hz, cym),
2
2
88.3 (d, JCP = 2.87 Hz, cym), 87.1 (d, JCP = 2.87 Hz, cym), 31.6 (d,
1JCP = 28.16 Hz, CH(CH3)2), 31.3 (s, CH(CH3)2), 28.4 (d, JCP
=
1
2
28.74 Hz, CH(CH3)2), 22.1 (d, JCP = 20.12 Hz, CH(CH3)2), 18.1 (s,
CH(CH3)2), 17.9 (d, 2JCP = 14.94 Hz, CH(CH3)2), 16.8 (d, JCP = 2.87 Hz,
CH3). 31P{1H} NMR (d, acetone-d6, 20 °C): 134.1.
3.2.5. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.223 g, 0.364 mmol) und PN-iPr (0.153 g,
g
6-p-cymene)(j2(P,N)-PN-iPr)(Cl)]Cl (5b0)
-
l
0.728 mmol) as starting materials but in the absence of a silver salt.
Yield: 0.317 g (84%). Anal. Calc. for C21H33Cl2N2PRu: C, 48.84; H,
6.44; N, 5.42. Found: C, 48.69; H, 6.54; N, 5.38%. The NMR spectra
of this complex are virtually the same as those of 5a except that the
NH proton is shifted from 6.76 to 10.61 ppm.
3.2.6. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.199 g, 0.324 mmol), PN-BIPOL (0.200 g,
g j
6-p-cymene)( 2(P,N)-PN-BIPOL)Cl]CF3SO3. (5c)
-
l
3.2.2. [Ru(
g
6-p-cymene)(
j
2(P,N)-PN-Ph)Cl]CF3SO3. (5a)
6-p-cymene)(
-Cl)Cl]2 (0.290 g, 0.474
0.649 mmol), and AgCF3SO3 (0.167 g, 0.649 mmol) as starting
materials. Yield: 0.280 g (59%). Anal. Calc. for C28H27ClF3N2O5PRuS:
C, 46.19; H, 3.74; N, 3.85. Found: C, 46.14; H, 3.80; N, 3.99%. 1H
NMR (d, CD2Cl2, 20 °C): 9.49 (d, JHH = 7.54 Hz, 1H, py6), 8.74 (d,
JHH = 5.71 Hz, 1H, py4), 7.80–7.10 (m, 9H, Ph, py5), 7.12 (s, 1H,
NH), 6.95 (t, JHH = 6.62 Hz, 1H, py3), 6.16 (d, JHH = 5.03 Hz, 2H,
cym), 5.63 (d, JHH = 5.03 Hz, 1H, cym), 5.13 (d, JHH = 5.94 Hz, 1H,
To a solution of [Ru(
g
l
mmol) in CH2Cl2 (10 mL) PN-Ph (0.263 g, 0.947 mmol) and AgCF3-
SO3 (0.243 g, 0.947 mmol) were added and the mixture was stirred
at room temperature for 3 h. After that insoluble materials (AgCl)
were removed by filtration through Celite, and the solvent was re-
moved under reduced pressure. The resulting orange solid was

W. Lackner-Warton et al. / Polyhedron 29 (2010) 3097–3102
3101
cym), 2.51 (m, JHH = 6.80 Hz, 1H, CH(CH3)2), 2.05 (s, 3H, CH3), 1.07
(d, JHH = 6.85 Hz, 3H, CH(CH3)2), 0.97 (d, JHH = 6.85 Hz, 3H,
CH(CH3)2). 13C{1H} NMR (d, CD2Cl2, 20 °C): 161.5 (d, 2JCP = 20.69 Hz,
0.326 mmol), and AgSbF6 (0.112 g, 0.330 mmol) as starting materi-
als. Yield: 0.195 g (80%). Anal. Calc. for C21H33ClF6N2PRuSSb: C,
33.68; H, 4.44; N, 3.74. Found: C, 33.59; H, 4.51; N, 3.71%. 1H
NMR (d, CD2Cl2, 20 °C): 9.24 (br, 1H, NH), 9.08 (d, JHH = 6.00 Hz,
1H, py6), 7.99 (t, JHH = 7.42 Hz, 1H, py4), 7.70 (d, JHH = 7.90 Hz, 1H,
py3), 7.31 (t, JHH = 6.48 Hz, 1H, py5), 6.01 (d, JHH = 6.00 Hz, 1H,
cym), 5.97 (d, JHH = 5.69 Hz, 1H, cym), 5.55 (d, JHH = 5.69 Hz, 1H,
cym), 5.53 (d, JHH = 5.37 Hz, 1H, cym), 3.01 (m, JHH = 7.27 Hz, 1H,
CH(CH3)2), 2.95 (m, JHH = 6.63 Hz, 1H, CH(CH3)2), 2.32 (m,
JHH = 7.06 Hz, 1H, CH(CH3)2), 1.66 (s, 3H, CH3), 1.64–1.33 (m, 12H
2
py2), 155.2 (s, py6), 149.2 (d, JCP = 15.52 Hz, Ph), 147.6 (d,
2JCP = 6.32 Hz, Ph), 140.6 (s, py4), 134.3–121.4 (Ph), 119.8 (s, py5),
3
112.4 (d, JCP = 10.92 Hz, py3), 109.8 (s, cym), 109.0 (s, cym), 99.5
2
2
(d, JCP = 10.92 Hz, cym), 97.5 (d, JCP = 5.75 Hz, cym), 89.3 (d,
2JCP = 2.30 Hz, cym), 85.7 (s, cym), 30.8 (s, CH(CH3)2), 22.5 (s,
CH(CH3)2), 21.0 (s, CH(CH3)2), 18.6 (s, CH3). 31P{1H} NMR (d, CD2Cl2,
20 °C): 165.7.
1
CH(CH3)2), 1.14 (dd, J = 19.27 Hz, JHH = 6.63 Hz, 3H, CH(CH3)2),
3.2.7. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)(
-Cl)Cl]2 (0.200 g, 0.327 mmol), PNNH2-iPr (0.147 g,
g
6-p-cymene)(
j
2(P,N)-PNNH2-iPr)Cl]CF3SO3. (5d)
0.70 (dd, J = 18.64 Hz, JHH = 6.95 Hz, 3H, CH(CH3)2). 13C{1H} NMR
2
-
(d, CD2Cl2, 20 °C): 157.8 (d, JCP = 5.98 Hz, py2), 156.2 (s, py6),
3
l
140.9 (s, py4), 120.2 (s, py5), 119.7 (d, JCP = 3.99 Hz, py3), 102.0
0.653 mmol), and AgCF3SO3 (0.168 g, 0.654 mmol) as starting
materials. Yield: 0.374 g (87%). Anal. Calc. for C22H34ClF3N3O3PRuS:
C, 40.96; H, 5.31; N, 6.51. Found: C, 40.87; H, 5.54; N, 6.49%. 1H
NMR (d, CD2Cl2, 20 °C): 7.55 (d, JHH = 5.00 Hz, 1H, py5), 7.30 (t,
JHH = 6.50 Hz, 1H, py4), 6.51 (d, JHH = 5.00 Hz, 1H, py3), 6.23 (m,
2H, cym), 6.11 (b, 1H, NH), 5.97 (m, 2H, cym), 5.82 (d,
JHH = 13.38 Hz, 2H, NH), 3.08 (m, 1H, CH(CH3)2), 2.63 (m, 1H,
CH(CH3)2), 2.55 (m, 1H, CH(CH3)2), 1.92 (s, 3H, CH3), 1.65–1.00
(m, 18H, CH(CH3)2). 13C{1H} NMR (d, CD2Cl2, 20 °C): 162.3 (s,
(s, cym), 101.5 (s, cym), 90.2 (s, cym), 86.1 (s, cym), 83.6 (s,
cym), 82.4 (s, cym), 32.3 (d, JCP = 49.37 Hz, CH(CH3)2), 30.8 (s,
CH(CH3)2), 25.9 (d, JCP = 54.35 Hz, CH(CH3)2), 22.2–15.7 (CH(CH3)2),
14.6 (s, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C): 83.6.
3.2.11. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.100 g, 0.163 mmol), SN-Ph (0.114 g,
g j
6-p-cymene)( 2(Se,N)-SeN-Ph)Cl]SbF6. (8a)
-
l
0.319 mmol), and AgSbF6 (0.115 g, 0.335 mmol) as starting materi-
als. Yield: 0.238 g (86%). Anal. Calc. for C27H29ClF6N2PRuSbSe: C,
37.55; H, 3.38; N, 3.24. Found: C, 37.54; H, 3.41; N, 3.19%. 1H
NMR (d, CD2Cl2, 20 °C): 9.47 (br, 1H, NH), 9.18 (d, JHH = 6.00 Hz,
1H, py6), 8.48 (d, JHH = 7.90 Hz, 1H, py4), 8.42 (d, JHH = 7.90 Hz,
1H, py3), 8.10–7.10 (m, 11H, Ph, py5), 5.82 (d, JHH = 6.63 Hz, 1H,
cym), 5.68 (d, JHH = 5.37 Hz, 1H, cym), 5.35 (d, JHH = 6.00 Hz, 1H,
cym), 5.20 (d, JHH = 5.37 Hz, 1H, cym), 2.77 (m, JHH = 6.87 Hz, 1H,
CH(CH3)2), 1.75 (s, 3H, CH3), 1.24 (d, JHH = 6.95 Hz, 3H, CH(CH3)2),
1.21 (d, JHH = 6.95 Hz, 3H, CH(CH3)2). 13C{1H} NMR (d, CD2Cl2,
2
py6), 160.2 (d, JCP = 7.98 Hz, py2), 145.9 (s, cym), 141.0 (s, py4),
3
135.1 (s, cym), 102.0 (s, py5), 99.5 (d, JCP = 6.98 Hz, py3), 128.8
(s, cym), 126.2 (s, cym), 31.0 (s, CH(CH3)2), 30.4–29.7 (m,
CH(CH3)2), 23.8–16.8 (m, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C):
117.3.
3.2.8. [Ru(g j
6-p-cymene)( 2(P,N)-PNdep-iPr)Cl] (6)
A solution of 5b (200 mg, 0.28 mmol) in THF (15 mL) was trea-
ted with KOtBu (38 mg, 0.33 mmol) for 2 h at room temperature.
After removal of the solvent under reduced pressure the residue
was dissolved in benzene (20 mL). Insoluble materials were re-
moved by filtration and the solvent was again removed under re-
duced pressure affording an orange solid which was dried under
vacuum. Yield: 50 mg (37%). Anal. Calc. for C21H32ClN2PRu: C,
52.55; H, 6.72; N, 5.89. Found: C, 51.90; H, 6.84; N, 5.79%. 1H
NMR (d, acetone-d6, 20 °C): 8.49 (d, J = 6.6 Hz, 1H, py6), 7.00 (t,
J = 7.5 Hz, 1H, py4), 6.48 (d, J = 8.3 Hz, 1H, py3), 6.21 (d, J = 6.6 Hz,
1H, cym), 6.02 (d, J = 6.6 Hz, 1H, cym), 5.95 (t, J = 6.6 Hz, 1H, py5),
5.70 (d, J = 6.6 Hz, 1H, cym), 5.59 (d, J = 6.6 Hz, 1H, cym), 2.66–
2.50 (m, 3H, CH(CH3)2), 2.01 (s, 3H, CH3), 1.42–1.00 (m, 18H,
CH(CH3)2). 31P{1H} NMR (d, acetone-d6, 20 °C): 132.7.
2
20 °C): 155.9 (d, JCP = 4.72 Hz, py2), 155.5 (s, py6), 141.2 (s, py4),
3
134.6–128.4 (Ph), 120.9 (s, py5), 120.2 (d, JCP = 4.04 Hz, py3),
102.1 (s, cym), 101.6 (s, cym), 88.7 (s, cym), 84.1 (s, cym), 83.3
(s, cym), 79.2 (s, cym), 31.0 (s, CH(CH3)2), 22.1 (s, CH(CH3)2), 21.3
(s, CH(CH3)2), 17.3 (s, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C): 44.5
(with satellites JP-Se = 663 Hz).
3.2.12. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.100 g, 0.163 mmol), SeN-iPr (0.096 g,
g j
6-p-cymene)( 2(Se,N)-SeN-iPr)Cl]SbF6. (8b)
-
l
0.332 mmol), and AgSbF6 (0.124 g, 0.361 mmol) as starting materi-
als. Yield: 0.202 g (78%). Anal. Calc. for C21H33ClF6N2PRuSbSe: C,
31.70; H, 4.18; N, 3.52. Found: C, 31.68; H, 4.08; N, 3.55%. 1H
NMR (d, CD2Cl2, 20 °C): 9.20 (d, JHH = 4.87 Hz, 1H, py6), 8.45 (br,
1H, NH), 8.03 (t, JHH = 7.61 Hz, 1H, py4), 7.58 (d, JHH = 7.77 Hz, 1H,
py3), 7.37 (t, JHH = 5.48 Hz, 1H, py5), 6.08 (d, JHH = 4.72 Hz, 1H,
cym), 5.97 (d, JHH = 5.18 Hz, 1H, cym), 5.62 (d, JHH = 4.87 Hz, 1H,
cym), 5.46 (d, JHH = 4.72 Hz, 1H, cym), 2.95 (m, 2H, CH(CH3)2),
2.45 (m, 1H, CH(CH3)2), 1.60 (s, 3H, CH3), 1.54–1.08 (m, 15H
CH(CH3)2), 0.79 (dd, J = 19.26 Hz, JHH = 6.93 Hz, 3H, CH(CH3)2).
3.2.9. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.100 g, 0.163 mmol), SN-Ph (0.106 g,
g j
6-p-cymene)( 2(S,N)-SN-Ph)Cl]SbF6. (7a)
-
l
0.332 mmol), and AgSbF6 (0.114 g, 0.342 mmol) as starting materi-
als. Yield: 0.223 g (84%). Anal. Calc. for C27H29ClF6N2PRuSSb: C,
39.70; H, 3.58; N, 3.43. Found: C, 39.74; H, 3.64; N, 3.59%. 1H
NMR (d, CD2Cl2, 20 °C): 9.50 (br, 1H, NH), 9.08 (d, JHH = 5.03 Hz,
1H, py6), 8.50–7.30 (m, 13H, Ph, py), 5.90 (d, JHH = 5.48 Hz, 1H,
cym), 5.65 (d, JHH = 5.63 Hz, 1H, cym), 5.35 (d, JHH = 5.18 Hz, 1H,
cym), 5.25 (d, JHH = 5.33 Hz, 1H, cym), 2.77 (m, JHH = 6.66 Hz, 1H,
CH(CH3)2), 1.75 (s, 3H, CH3), 1.25 (d, JHH = 7.01 Hz, 3H, CH(CH3)2),
1.23 (d, JHH = 6.85 Hz, 3H, CH(CH3)2). 13C{1H} NMR (d, CD2Cl2,
2
13C{1H} NMR (d, CD2Cl2, 20 °C): 157.8 (d, JCP = 5.39 Hz, py2),
3
156.2 (s, py6), 141.1 (s, py4), 120.7 (s, py5), 120.4 (d, JCP = 4.04 Hz,
py3), 101.9 (s, cym), 101.5 (s, cym), 90.3 (s, cym), 85.5 (s, cym), 83.8
(s, cym), 81.3 (s, cym), 32.6 (d, JCP = 39.07 Hz, CH(CH3)2), 30.9 (s,
CH(CH3)2), 26.2 (d, JCP = 47.16 Hz, CH(CH3)2), 22.0–15.7 (CH(CH3)2),
14.9 (s, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C): 77.3 (with satellites JP-
Se = 640 Hz).
2
20 °C): 155.6 (s, py6), 155.3 (d, JCP = 5.39 Hz, py2), 141.2 (s, py4),
3
134.6–129.2 (Ph), 120.7 (s, py5), 119.5 (d, JCP = 4.72 Hz, py3),
102.1 (s, cym), 101.8 (s, cym), 89.7 (s, cym), 84.1 (s, cym), 83.7
(s, cym), 81.4 (s, cym), 30.8 (s, CH(CH3)2), 21.7 (s, CH(CH3)2), 21.5
(s, CH(CH3)2), 17.3 (s, CH3). 31P{1H} NMR (d, CD2Cl2, 20 °C): 52.6.
3.3. X-ray structure determination of 5a0 and 7b
X-ray data of 5a0 and 7b were collected on a Bruker Smart APEX
3.2.10. [Ru(
This complex has been prepared analogously to 5a with [Ru(g6
p-cymene)( -Cl)Cl]2 (0.100 g, 0.163 mmol), SN-iPr (0.080 g,
g
6-p-cymene)(
j
2(S,N)-SN-iPr)Cl]SbF6. (7b)
CCD diffractometer using graphite-monochromated Mo
radiation (k = 0.71073 Å) and 0.3° -scan frames. Corrections for
absorption and k/2 effects were applied [23]. After structure
Ka
-
x
l

3102
W. Lackner-Warton et al. / Polyhedron 29 (2010) 3097–3102
solution with program SHELXS97 refinement on F2 was carried out
with the program SHELXL97 [24]. Non-hydrogen atoms were refined
anisotropically. H atoms were placed in calculated positions and
thereafter treated as riding. Important crystallographic data are:
5a0: C27H29Cl2N2PRu, Mr = 584.46, orange block from CD2Cl2, 0.59 ꢂ
0.38 ꢂ 0.30 mm, monoclinic, space group P21/n (no. 14), a =
9.2754(5) Å, b = 18.7332(10) Å, c = 15.1296(8) Å, b = 106.380(1)°,
References
[1] (a) A. Bader, E. Lindner, Coord. Chem. Rev. 108 (1991) 27. and references cited
therein;
(b) M. Bassetti, Eur. J. Inorg. Chem. (2006) 4473;
(c) G. Helmchen, A. Pfaltz, Acc. Chem. Res. 33 (2000) 336;
(d) H.A. McManus, P. Guiry, Chem. Rev. 104 (2004) 4151;
(e) P. Braunstein, Chem. Rev. 106 (2006) 134;
(f) V.V. Grushin, Chem. Rev. 104 (2004) 1629;
V = 2522.2(2) Å3,
Z = 4,
l
= 0.916 mmꢀ1
,
dx = 1.539 g cmꢀ3
,
(g) T.Q. Ly, J.D. Woollins, Coord. Chem. Rev. 176 (1998) 451.
[2] J.C. Jeffrey, T.B. Rauchfuss, Inorg. Chem. 18 (1979) 2658.
[3] D. Benito-Garagorri, K. Mereiter, K. Kirchner, Collect. Czech. Chem. Commun.
72 (2007) 527.
[4] C.M. Standfest-Hauser, G. Dazinger, J. Wiedermann, K. Mereiter, K. Kirchner,
Eur. J. Inorg. Chem. (2009) 4085.
[5] J. Ansell, M. Wills, Chem. Soc. Rec. 31 (2002) 259.
[6] W.-J. Zhao, S.-J. Zhang, Y. Deng, Z.-Z. Zhang, Y.-F. Ma, W.-P. Huang, H.-G. Wang,
Jiegou Huaxue 15 (1996) 44.
T = 100(2) K. 22820 reflections were collected up to hmax = 30.0°
and, after applying absorption corrections, merged to 7261 inde-
pendent data (Rint = 0.018); final R indices: R1 = 0.0306 (6781
reflections with I > 2r(I)), wR2 = 0.0789 (all data), 298 parameters.
7b: 21H33ClF6N2PRuSSb, Mr = 748.79, orange plates from
C
CD2Cl2, 0.34 ꢂ 0.26 ꢂ 0.22 mm, monoclinic, space group P21/n
(no. 14), a = 11.1387(2) Å, b = 20.6898(3) Å, c = 12.5233(2) Å, b =
[7] W. Seidel, H. Schöler, Z. Chem. 11 (1967) 431.
104.463(1)°, V = 2794.63(8) Å3, Z = 4,
l
= 1.788 mmꢀ1, dx = 1.780
[8] W. Ainscough, L.K. Peterson, Inorg. Chem. 9 (1970) 2699.
[9] H. Brunner, H. Weber, Chem. Ber. 118 (1985) 3380.
[10] (a) W. Schirmer, U. Flörke, H.J. Haupt, Z. Anorg. Allg. Chem. 545 (1987) 83;
(b) W. Schirmer, U. Flörke, H.J. Haupt, Z. Anorg. Allg. Chem. 574 (1989) 239.
[11] S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, Phosphorus Sulfur Silicon 124–125
(1997) 473.
[12] (a) S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, J. Chem. Soc., Dalton Trans. (2000)
2559;
(b) A.M.Z. Slawin, J. Wheatley, M.V. Wheatley, J.D. Woollins, Polyhedron 22
(2003) 1397.
[13] G. Sanchez, J. Garcia, D. Meseguer, J.L. Serrano, L. Garcia, J. Perez, G. Lopez,
Inorg. Chim. Acta 357 (2004) 4568.
g cmꢀ3
, T = 100(2) K. 41994 reflections were collected up to
hmax = 30.0° and, after applying absorption corrections, merged to
8266 independent data (Rint = 0.027); final R indices: R1 = 0.0306
(8266 reflections with I > 2r(I)), wR2 = 0.0777 (all data), 317
parameters.
3.4. Hydrogen transfer catalysis with the precatalysts 5b, 6, 7b, and 8b
[14] (a) E. Smolensky, M. Kapon, J.D. Woollins, M.S. Eisen, Organometallics 24
(2005) 3255;
(b) E. Smolensky, M. Kapon, M.S. Eisen, Organometallics 26 (2007) 4510.
[15] S.M. Nabavizadeh, E.S. Tabei, F.N. Hosseini, N. Keshavarz, S. Jamali, M. Rashidi,
New J. Chem. 34 (2010) 495.
[16] I. Macías-Arce, M.C. Puerta, P. Valerga, Eur. J. Inorg. Chem. (2010) 1767.
[17] H.-G. Henning, U. Ladhoff, Z. Chem. 13 (1973) 6.
[18] For related tridentate ENE ligands see for example: N. Biricik, Z. Fei, R.
Scopelliti, P.J. Dyson, Helv. Chim. Acta 86 (2003) 3281.
[19] (a) W.J. Knebel, R.J. Angelici, Inorg. Chim. Acta 7 (1973) 713;
(b) W.J. Knebel, R.J. Angelici, Inorg. Chem. 13 (1974) 632;
(c) E.W. Ainscough, A.M. Brodie, S.T. Wong, J. Chem. Soc., Dalton Trans. (1977)
915.
In a typical procedure, to a 0.1 M solution of acetophenone in
2-propanol the pre-catalyst (0.5 mol%) and KOtBu (10 mol%) were
added (acetophenone:precatalyst:KOtBu = 200:1:20) to a Schlenk
tube and heated at 75 °C for 22 h unless otherwise noted (see Table
1). After the reaction time the solvent was removed under pressure
and the product distribution was determined by 1H NMR
spectroscopy.
4. Supplementary material
[20] D. Benito-Garagorri, E. Becker, J. Wiedermann, W. Lackner, M. Pollak, K.
Mereiter, J. Kisala, K. Kirchner, Organometallics 25 (2006) 1900.
[21] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, third ed.,
Pergamon, New York, 1988.
[22] M.A. Bennett, A.K. Smith, J. Chem. Soc., Dalton Trans. (1974) 233.
[23] Bruker Programs: SMART, Version 5.625; SAINT, Version 6.54; SADABS, Version
2.10; SHELXTL, Version 6.1, Bruker AXS Inc., Madison, WI, 2003.
[24] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
Crystallographic data for the crystal structures of 5a0 and 7b
have been deposited with the Cambridge Crystallographic Data
Centre as supplementary publication under reference CCDC
771456 (5a0) and 782837 (7b). These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.