Synthesis, structure, and characterization of some ruthenium arene complexes of N-(arylmethylene)-2-(methylthio)anilines and 2-(methylthio)aniline

Article abstract of DOI:10.1016/j.ica.2005.06.017

A series of cationic, half-sandwich ruthenium complexes with the general formula [(η⁶-p-cymene)RuCl(MeSC₆H₄2-NCHAr)] [PF₆] (3a-h), have been prepared from the reaction of [(η⁶-p-cymene)RuCl₂]₂ with various N,S-donor Schiff base ligands derived from 2-(methylthio)aniline and several substituted benzaldehydes. The related aniline complex [(η⁶-p- cymene)RuCl(MeS-C₆H₄-2-NH₂)][PF₆] (4) was synthesized from 2-(methylthio)aniline. All of the ruthenium complexes were characterized by IR, ¹H NMR, and UV/Vis spectroscopies. The molecular structure of complex 4 was determined by X-ray crystallography.

Full text of DOI:10.1016/j.ica.2005.06.017

Inorganica Chimica Acta 359 (2006) 846–852
www.elsevier.com/locate/ica
Synthesis, structure, and characterization of some ruthenium
arene complexes of N-(arylmethylene)-2-(methylthio)anilines
and 2-(methylthio)aniline
*
Christopher G. Hamaker , Dominic P. Halbach
Department of Chemistry, Illinois State University, Campus Box 4160, Normal, IL 61790, USA
Received 31 March 2005; accepted 10 June 2005
Available online 26 July 2005
Ruthenium and Osmium Chemistry Topical Issue
Abstract
A series of cationic, half-sandwich ruthenium complexes with the general formula [(g6-p-cymene)RuCl(MeSAC6H4A2-
N@CHAr)][PF6] (3a–h), have been prepared from the reaction of [(g6-p-cymene)RuCl2]2 with various N,S-donor Schiff base ligands
derived from 2-(methylthio)aniline and several substituted benzaldehydes. The related aniline complex [(g6-p-cymene)RuCl(MeS–
C6H4–2-NH2)][PF6] (4) was synthesized from 2-(methylthio)aniline. All of the ruthenium complexes were characterized by IR,
1H NMR, and UV/Vis spectroscopies. The molecular structure of complex 4 was determined by X-ray crystallography.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ruthenium complexes; Half-sandwich complexes; Schiff base; N,S ligands; Crystal structure
1. Introduction
a variety of catalytic reactions [7–10]. Recently, several
cationic, half-sandwich ruthenium(II) arene complexes
have been shown to exhibit anti-cancer activity [11–14].
Schiff bases are very popular ligands in coordination
chemistry due to their ease of synthesis and their ability
to be readily modified both sterically and electronically.
Schiff base ligands have also been used extensively in
catalysis [15,16]. However, there have been very few re-
ports of sulfur-containing Schiff base ligands until re-
cently [17–19]. Chakravarty and co-workers [20,21]
have utilized tridentate O,N,S-Schiff base ligands as
models for copper-containing enzymes. Recently, several
groups have investigated the activation of CAH bonds in
sulfur-containing Schiff bases by platinum [22] and palla-
dium complexes [23]. There has been much interest in
hard/soft mixed donor ligands for use in catalysis [24–
26] due to the potential hemilability of the donor atom
that is mismatched with the metal center.
Ruthenium(II) arene complexes of the general formula
[Ru(g6-arene)2]2+ were discovered in 1957 [1]. There has
been much interest [2] in the chemistry of half-sandwich
ruthenium(II) arene complexes since the development
of useful synthetic precursors with the general formula
[RuCl2(g6-arene)]n [3,4]. These complexes and related
half-sandwich compounds with the general formulas
[RuCl2(g6-arene)L] and [RuCl(g6-arene)L2]+ have been
shown to be excellent catalysts for a variety of organic
reactions, including the addition of carboxylic acids to
alkynes [5,6], transfer hydrogenation of ketones [7], poly-
merization of olefins [8], and double bond isomerization
[9]. Several new arene ruthenium(II) complexes with
Schiff base ligands have been synthesized and utilized in
*
Corresponding author. Tel.: +1 309 438 7659; fax: +1 309 438
The present work developed from our groupÕs interest
in the synthesis and utilization of new mixed-donor
5538.
E-mail address: chamaker@ilstu.edu (C.G. Hamaker).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.06.017

C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
847
Schiff base ligands. Herein, we report the synthesis and
characterization of new cationic half-sandwich ruthe-
nium(II) complexes with chelating N,S-Schiff base and
amine ligands, including the X-ray structure of the com-
plex [RuCl(g6-p-cymene)(MeS–C6H4–2-NH2)][PF6].
(s, 3H, SCH3). IR (cmÀ1, KBr): 1627 (C@N), m.p. 60–
62 ꢁC.
2.2.3. Ar = 4-C6H4Cl (1c) [30]
2.401 g (17.25 mmol) of 2-(methylthio)aniline and
2.210 g (15.72 mmol) of 4-chlorobenzaldehyde were al-
lowed to reflux in 30 mL of absolute ethanol for 2 h to
1
yield 3.14 g of yellow solid in 76% yield. H NMR (d,
2. Experimental
ppm, CDCl3) 8.38 (s, 1H, CH@N), 7.89 (dt, 2H, HAr),
7.45 (dt, 2H, HAr), 7.23 (m, 2H, HAr), 7.14–7.18 (m,
1H, HAr), 6.99 (dd, 1H, HAr), and 2.47 (s, 3H, SCH3).
IR (cmÀ1, KBr): 1620 (C@N), m.p. 92–94 ꢁC.
2.1. General considerations
All reagents were of commercial grade and used with-
out further purification. The complex [RuCl2(g6-p-cym-
ene)]2 was synthesized using the literature procedure
[27]. The ligands were prepared by a modification of a
literature procedure [28] and are described in detail be-
low. NMR spectra were collected on a Varian Gemini
400 MHz NMR spectrometer and recorded in ppm rel-
ative to residual CHCl3 in CDCl3 at 7.26 ppm or resid-
ual CD3C(O)CD2H in CD3C(O)CD3 at 2.05 ppm. IR
spectra were collected as KBr pellets on a Nicolet 5sx
infrared spectrometer. Electronic spectra were collected
in solution on a Cary 5E UV–VIS–NIR spectrometer.
Melting points are uncorrected. Elemental analyses were
obtained from the School of Chemical Sciences Micro-
analysis Laboratory at the University of Illinois.
2.2.4. Ar = 4-C6H4NO2 (1d) [29]
1.805 g (12.97 mmol) of 2-(methylthio)aniline and
1.951 g (12.91 mmol) of 4-nitrobenzaldehyde were re-
fluxed for 2–4 h in 30 mL of absolute ethanol. The reac-
tion yielded 3.07 g of bright orange solid in 87% yield.
1H NMR (d, ppm, CDCl3) 8.52 (s, 1H, CH@N), 8.33
(d, 2H, HAr), 8.12 (d, 2H, HAr), 7.23–7.28 (m, 2H,
H
Ar), 7.18 (dt, 1H, HAr), 7.03 (d, 1H, HAr), and d 2.48
(s, 3H, SCH3). IR (cmÀ1, KBr): 1595 (C@N), 1512
(N@O, asym), and 1339 (N@O, sym), m.p. 139–140 ꢁC.
2.2.5. Ar = C6H5 (1e) [28]
2.024 g (14.54 mmol) of 2-(methylthio)aniline and
1.548 g (14.59 mmol) of benzaldehyde were refluxed in
30 mL of absolute ethanol for 5 h to yield 2.71 g of yel-
1
2.2. Synthesis of Schiff base ligands
MeSAC6H4A2-N@CHAr (1a–h)
low solid in 82% yield. H NMR (d, ppm, CDCl3) 8.42
(s, 1H, CH@N), 7.96 (dd, 2H, HAr), 7.48 (dd, 3H,
H
Ar), 7.22 (d, 2H, HAr), 7.15–7.19 (m, 1H, HAr), 6.99
(d, 1H, HAr), and 2.47 (s, 3H, SCH3). IR (cmÀ1, KBr):
1623 (C@N), m.p. 46–47 ꢁC.
2.2.1. Ar = 4-C6H4CH3 (1a) [29]
A similar procedure was used to synthesize all of the
ligands. An example is provided below for the synthesis
of the 4-CH3 ligand (1a). A 250 mL round bottom flask
equipped with a reflux condenser was charged with
30 mL of absolute ethanol, 2-(methylthio)aniline
(1.614 g, 11.54 mmol), and p-tolualdehyde (1.394 g,
11.61 mmol). The mixture was refluxed for 2–4 h, al-
lowed to cool to room temperature, and placed in a free-
zer at À50 ꢁC overnight. The yellow solid that formed
was filtered, washed with cold ethanol, and dried in va-
cuo to yield 2.20 g of yellow precipitate in 79% yield. 1H
NMR (d, ppm, CDCl3) 8.38 (s, 1H, CH@N), 7.85 (dd,
2H, HAr), 7.29 (d, 2H, HAr), 7.22 (d, 2H, HAr), 7.14–
7.18 (m, 1H, HAr), 6.98 (d, 1H, HAr), 2.46 (s, 3H,
SCH3), and 2.42 (s, 3H, PhCH3). IR (cmÀ1, KBr):
1617 (C@N), m.p. 77–78 ꢁC.
2.2.6. Ar = 3,5-C6H3(OCH3)2 (1f)
1.515 g (10.85 mmol) of 2-(methylthio)aniline and
1.807 g (10.87 mmol) of 3,5-anisaldehyde were refluxed
in 25 mL of absolute ethanol for 24 h. The reaction
yielded 2.33 g of light yellow crystals in 75% yield. Anal.
Calc. for C16H17NO2S: C, 66.87; H, 5.96; N, 4.87.
Found: C, 66.74; H, 5.93; N, 4.89%. 1H NMR (d,
ppm, CDCl3) 8.32 (s, 1H, CH@N), 7.22 (d, 2H, HAr),
7.14–7.19 (m, 1H, HAr), 7.12 (d, 2H, HAr), 6.98 (d,
1H, HAr), 6.60 (t, 1H, HAr), 3.83 (s, 6H, OCH3), and
2.47 (s, 3H, SCH3). IR (cmÀ1, KBr): 1595 (C@N),
m.p. 79–80 ꢁC.
2.2.7. Ar = 2,6-C6H3Cl2 (1g) [28]
1.477 g (10.61 mmol) of 2-(methylthio)aniline and
1.863 g (10.65 mmol) of 2,6-dichlorobenzaldehyde were
refluxed in 50 mL of absolute ethanol for 4 h to yield
2.83 g of yellow solid in 91% yield. H NMR (d, ppm,
CDCl3) 8.70 (s, 1H, CH@N), 7.40 (d, 2H, HAr), 7.21–
2.2.2. Ar = 4-C6H4OCH3 (1b) [30]
1.677 g (12.05 mmol) of 2-(methylthio)aniline and
1.645 g (14.54 mmol) of anisaldehyde were refluxed for
24 h to produce 2.21 g of yellow precipitate in 72% yield.
1H NMR (d, ppm, CDCl3) 8.34 (s, 1H, CH@N), 7.91 (d,
2H, HAr), 7.20 (d, 2H, HAr), 7.13–7.17 (m, 1H, HAr),
6.97–7.00 (m, 3H, HAr), 3.87 (s, 3H, OCH3), and 2.46
1
7.29 (m, 2H, HAr), 7.19 (t, 2H, HAr), 7.05 (d, 1H,
H
Ar), and 2.48 (s, 3H, SCH3). IR (cmÀ1, KBr): 1627
(C@N), m.p. 130–131 ꢁC.

848
C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
2.2.8. Ar = 2-C6H4Cl (1h) [28]
KBr): 1591 (C@N), 842 (P–F). UV/Vis (CH2Cl2)
max(e): 334 nm (12 700 L molÀ1 cmÀ1).
1.8228 g (13.09 mmol) of 2-(methylthio)aniline and
1.8474 g of 2-chlorobenzaldehyde were refluxed in
30 mL of absolute ethanol for 6 h to yield 1.93 g of yel-
k
2.3.3. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H4A4-Cl)][PF6] (3c)
1
low solid in 56% yield. H NMR (d, ppm, CDCl3) 8.89
(s, 1H, CH@N), 8.36 (dd, 1H, HAr), 7.42–7.36 (m, 3H,
0.0970 g of [RuCl2(g6-p-cymene)]2 (0.159 mmol) was
mixed with 0.0831 g (0.318 mmol) of 1c in 20 mL of
methanol to yield an orange solid in 38% yield after
the addition of excess NH4PF6 (0.0581 g, 0.356 mmol).
Anal. Calc. for C24H26Cl2F6NPRuS: C, 42.55; H, 3.87;
N, 2.07. Found: C, 42.29; H, 3.84; N, 2.16%. 1H
NMR (d, ppm, CDCl3) 9.07 (s, 1H, CH@N), 7.70 (d,
1H, HAr), 7.37 (d, 1H, HAr), 7.2–7.3 (m, 6H, HAr),
5.93 (d, 1H, Hcymene), 5.84 (d, 1H, Hcymene), 5.74 (d,
1H, Hcymene), 5.63 (d, 1H, Hcymene), 2.71 (sept, 1H,
CHMe2), 2.41 (s, 3H, SCH3), 2.03 (s, 3H, CH3-cymene),
1.19 (d, 3H, CH(CH3)2), 0.99 (d, 3H, CH(CH3)2). IR
(cmÀ1, KBr): 1592 (C@N), 845 (P–F). UV/Vis (CH2Cl2)
H
Ar), 7.27–7.15 (m, 3H, HAr), 7.04 (d, 1H, HAr), and
2.48 (s, 3H, SCH3). IR (cmÀ1, KBr): 1617 (C@N),
m.p. 69–70 ꢁC.
2.3. Synthesis of [RuCl(g6-p-cymene)
(MeSAC6H4A2-N@CHAr)][PF6] complexes 3a–h
2.3.1. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H4A4-CH3)][PF6] (3a)
A similar procedure was used to synthesize all of the
complexes. A detailed example is given for the synthesis
of [(g6-p-cymene)RuCl(MeSAC6H4A2-N@CHAC6H4A
4-CH3)][PF6] using ligand 1a. 0.1568 g of [RuCl2(p-cym-
ene)]2 (0.256 mmol) was added to 0.1239 g of 1a
(0.513 mmol) in a 30 mL flask containing 20 mL of
methanol. The reaction was stirred at room temperature
for 4 h, filtered, cooled to 0 ꢁC, and an excess of
NH4PF6 (0.0968 g, 0.594 mmol) was added to the red
solution. An orange solid precipitated and was collected
by vacuum filtration, washed once with cold methanol,
and dried in vacuo. Yield: 31%. Anal. Calc. for
C25H29ClF6NPRuS: C, 45.70; H, 4.45; N, 2.13. Found:
k
max(e): 330 nm (12100 L molÀ1 cmÀ1).
2.3.4. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H4A4-NO2)][PF6] (3d)
0.0987 g of [RuCl2(g6-p-cymene)]2 (0.163 mmol) was
mixed with 0.0886 g (0.325 mmol) of 1d in 15 mL of
methanol to yield an orange solid in 70% yield after
the addition of 0.0581 g (0.356 mmol) NH4PF6. Anal.
Calc. for C24H26ClF6N2O2PRuS: C, 41.90; H, 3.81; N,
1
C, 45.62; H, 4.47; N, 2.21%. H NMR (d, ppm, CDCl3)
9.03 (s, 1H, CH@N), 7.72 (dd, 1H, HAr), 7.37 (dd, 1H,
H
1
4.07. Found: C, 41.63; H, 3.74; N, 4.09%. H NMR
(d, ppm, CDCl3) 9.24 (s, 1H, CH@N), 8.16 (d, 2H,
Ar), 7.23 (dt, 1H, HAr), 7.18–7.20 (m, 3H, HAr), 7.09
H
Ar), 7.73 (dd, 1H, HAr), 7.50 (d, 2H, HAr), 7.33–7.27
(d, 2H, HAr), 5.89 (d, 1H, Hcymene), 5.77 (d, 1H,
Hcymene), 5.72 (d, 1H, Hcymene), 5.63 (d, 1H, Hcymene),
2.71 (sept, 1H, CHMe2), 2.39 (s, 3H, SCH3), 2.33 (s,
3H, 4-CH3-SN), 2.01 (s, 3H, CH3-cymene), 1.18 (d, 3H,
CH(CH3)2), 1.02 (d, 3H, CH(CH3)2). IR (cmÀ1, KBr):
1595 (C@N), 854 (P–F). UV/Vis (CH2Cl2) kmax(e):
335 nm (12500 L molÀ1 cmÀ1).
(m, 2H, HAr), 7.21 (d, 1H, HAr), 5.97 (d, 1H, Hcymene),
5.89 (d, 1H, Hcymene), 5.79 (d, 1H, Hcymene), 5.66 (d,
1H, Hcymene), 2.73 (sept, 1H, CHMe2), 2.47 (s, 3H,
SCH3), 2.06 (s, 3H, CH3-cymene), 1.21 (d, 3H,
CH(CH3)2), 0.97 (d, 3H, CH(CH3)2). IR (cmÀ1, KBr):
1594 (C@N), 857 (P–F), 1525 (N@O, asym), 1350
(N@O, sym). UV/Vis (CH2Cl2)
kmax(e): 315 nm
(9980 L molÀ1 cmÀ1).
2.3.2. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H4A4-OCH3)][PF6] (3b)
0.1564 g of [RuCl2(g6-p-cymene)]2 (0.255 mmol) was
mixed with 0.1320 g (0.513 mmol) of 1b in 20 mL of
methanol. After stirring for 4 h at room temperature,
addition of an excess of NH4PF6 (0.0946 g,
0.580 mmol) yielded 0.0806 g of orange solid in 25%
yield. Anal. Calc. for C25H29ClF6NOPRuS: C, 44.61;
H, 4.34; N, 2.08. Found: C, 44.31; H, 4.31; N,
2.18%. 1H NMR (d, ppm, CDCl3) 8.93 (s, 1H,
CH@N), 7.71 (dd, 1H, HAr), 7.45 (dd, 1H, HAr), 7.29
(d, 2H, HAr), 7.25–7.19 (m, 2H, HAr), 6.77 (d, 2H,
2.3.5. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H5)][PF6] (3e)
0.1318 g of [RuCl2(g6-p-cymene)]2 (0.215 mmol) was
allowed to react with 0.0980 g (0.431 mmol) of 1e in
15 mL of methanol which yielded 0.187 g of orange solid
in 67% yield after the addition of 0.0775 g (0.475 mmol)
NH4PF6. Anal. Calc. for C24H27ClF6NPRuS: C, 44.83;
H, 4.23; N, 2.18. Found: C, 44.79; H, 4.23; N, 2.21%.
1H NMR (d, ppm, CDCl3) 9.12 (s, 1H, CH@N), 7.72
(dd, 1H, HAr), 7.36–7.44 (m, 1H, HAr), 7.20–7.34 (m,
6H, HAr), 7.16 (t, 1H, HAr), 5.92 (d, 1H, Hcymene), 5.81
(d, 1H, Hcymene), 5.74 (d, 1H, Hcymene), 5.64 (d, 1H,
H
Ar), 5.87 (d, 1H, Hcymene), 5.75 (d, 1H, Hcymene),
5.71 (d, 1H, Hcymene), 5.63 (d, 1H, Hcymene), 3.82 (s,
3H, OCH3), 2.69 (sept, 1H, CHMe2), 2.37 (s, 3H,
SCH3), 2.00 (s, 3H, CH3-cymene), 1.17 (d, 3H,
H
cymene), 2.72 (sept, 1H, CHMe2), 2.41 (s, 3H, SCH3),
2.02 (s, 3H, CH3-cymene), 1.19 (d, 3H, CH(CH3)2), 1.02
(d, 3H, CH(CH3)2). IR (cmÀ1, KBr): 1600 (C@N), 843
CH(CH3)2), 1.03 (d, 3H, CH(CH3)2). IR (cmÀ1
,

C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
849
(P–F).
UV/Vis
(CH2Cl2)
k
max(e):
314 nm
CH(CH3)2). IR (cmÀ1, KBr): 1603 (C@N), 852 (P–F).
UV/Vis (CH2Cl2) kmax(e): 311 nm (3050 L molÀ1 cmÀ1).
(10 900 L molÀ1 cmÀ1).
2.3.9. [RuCl(g6-p-cymene)(MeS–C6H4–2-NH2)][PF6]
(4)
2.3.6. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H3A3,5-(OCH3)2)][PF6] (3f)
This complex was prepared in a manner similar to
that of compounds 3a–h. A 30 mL flask was charged
with 0.133 g (0.218 mmol) of [RuCl2(g6-p-cymene)]2,
0.0607 g (0.436 mmol) of 2-(methylthio)aniline, and
15 mL of methanol. The mixture was stirred for 4 h
at room temperature and filtered to remove impurities.
Excess (0.0801 g, 0.491 mmol) NH4PF6 was added and
the resulting mixture was placed in a À50 ꢁC freezer.
The resulting precipitate was collected by vacuum fil-
tration, washed with cold methanol, and dried in va-
cuo to yield 0.1676 g (70%) of 4 as an orange solid.
Anal. Calc. for C17H23ClF6NPRuS: C, 36.79; H,
4.18; N, 2.52. Found: C, 36.60; H, 4.21; N, 2.55%.
1H NMR (d, ppm, CD3C(O)CD3) 8.09 (d, 1H, HAr),
7.85 (t, 1H, HAr), 7.56 (t, 1H, HAr), 7.44 (d, 1H,
0.1012 g of [RuCl2(g6-p-cymene)]2 (0.165 mmol) was
reacted with 0.0936 g (0.326 mmol) of 1f in 15 mL of
methanol to yield 0.129 g of orange solid in 56% yield
after the addition of 0.590 g (0.362 mmol) NH4PF6.
Anal. Calc. for C26H31ClF6NO2PRuS: C, 44.42; H,
1
4.44; N, 1.99. Found: C, 44.21; H, 4.42; N, 2.05%. H
NMR (d, ppm, CDCl3) 9.09 (s, 1H, CH@N), 7.69 (d,
1H, HAr), 7.34 (d, 1H, HAr), 7.24–7.17 (m, 2H, HAr),
6.45 (dd, 3H, HAr), 5.90 (d, 1H, Hcymene), 5.81 (d, 1H,
H
cymene), 5.75 (d, 1H, Hcymene), 5.65 (d, 1H, Hcymene),
3.71 (s, 6H, OCH3), 2.69 (sept, 1H, CHMe2), 2.40 (s,
3H, SCH3), 2.02 (s, 3H, CH3-cymene), 1.16 (d, 3H,
CH(CH3)2), 0.99 (d, 3H, CH(CH3)2). IR (cmÀ1, KBr):
1589 (C@N), 838 (P–F). UV/Vis (CH2Cl2) kmax(e):
331 nm (12 200 L molÀ1 cmÀ1).
H
Ar), 6.24 (d, 1H, Hcymene), 6.08 (d, 1H, Hcymene),
5.94 (d, 1H, Hcymene), 5.78 (d, 1H, Hcymene), 2.99 (sept,
1H, CHMe2), 2.81 (s, 3H, SCH3), 2.29 (s, 3H,
CH3-cymene), 1.32 (d, 3H, CH(CH3)2), 1.22 (d, 3H,
2.3.7. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H3A2,6-Cl2)][PF6] (3g)
CH(CH3)2). IR (cmÀ1
,
KBr): 3454 (NAH),
0.0915 g of [RuCl2(g6-p-cymene)]2 (0.149 mmol) was
reacted with 0.0886 g (0.299 mmol) of 1g in 15 mL of
methanol to yield 0.125 g of orange solid in 59% yield
after the addition of 0.0574 g (0.353 mmol) NH4PF6.
Anal. Calc. for C24H25Cl3F6NPRuS: C, 40.49; H, 3.54;
N, 1.97. Found: C, 40.10; H, 3.48; N, 2.07%. 1H
NMR (d, ppm, CDCl3) 8.95 (s, 1H, CH@N), 7.81 (d,
2H, HAr), 7.49–7.61 (m, 5H, HAr), 5.76 (d, 1H, Hcymene),
5.55 (d, 1H, Hcymene), 5.50 (d, 1H, Hcymene), 5.31 (d, 1H,
3276 (NH), 775–900 (br, N–H + P–F). UV/Vis
(CH2Cl2) kmax(e): 317 (11860 L molÀ1 cmÀ1), 368 nm
(585 L molÀ1 cmÀ1).
2.4. Crystallography
Orange crystals of [RuCl(g6-p-cymene)(MeS–C6H4–
2-NH2)][PF6] (4) were isolated by slow evaporation of
a concentrated methanol solution. Data were collected
on a Bruker P4/RA/SMART 1000 CCD diffractometer
using Mo Ka radiation at À80 ꢁC. Unit cell parameters
were obtained from a least-squares refinement of 4139
centered reflections from the data collection. The sys-
tematic absences indicated the space group to be P21
(No. 4) [31], and the compound crystallized as a racemic
mixture. The data were corrected for absorption
through use of the SADABS procedure. See Table 1 for a
summary of crystal data and X-ray collection
information.
H
cymene), 2.67 (sept, 1H, CHMe2), 2.51 (s, 3H, SCH3),
1.80 (s, 3H, CH3-cymene), 1.02 (d, 3H, CH(CH3)2), 0.99
(d, 3H, CH(CH3)2). IR (cmÀ1, KBr): 1610 (C@N), 839
(P–F). UV/Vis (CH2Cl2) kmax(e): Shoulder at 298 nm
(6400 L molÀ1 cmÀ1
(1220 L molÀ1 cmÀ1).
)
and shoulder at 393 nm
2.3.8. [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHA
C6H4A2-Cl)][PF6] (3h)
0.1511 g (0.247 mmol) of [RuCl2(g6-p-cymene)]2 was
allowed to react with 0.1365 g (0.521 mmol) of 1h in
10 mL of methanol. The resulting product was dried
and weighed to yield 0.0757 g of 3h after the addition
of 0.1006 g (0.617 mmol) NH4PF6. Anal. Calc. for
C24H26Cl2F6NPRuS: C, 42.55; H, 3.87; N, 2.07. Found:
The structure of 4 was solved using the direct meth-
ods program SIR-92 [32] and refinement was completed
using the program SHELXL-93 [33]. Hydrogen atoms at-
tached to carbon were assigned positions based on the
geometries of their attached carbons. The hydrogens at-
tached to nitrogen were assigned positions based on the
Fourier difference map. The final model for 4 refined to
values of R1(F2) = 0.0183 (for 4197 data with
F2 > 2r(F2)) and wR2(F2) = 0.0474 (for all 4249 inde-
pendent data). The largest peak in the final difference
1
C, 42.51; H, 3.79; N, 2.18%. H NMR (d, ppm, CDCl3)
9.22 (s, 1H, CH@N), 7.76 (d, 1H, HAr), 7.40 (d, 1H,
HAr), 7.35–7.25 (m, 4H, HAr), 7.15 (t, 1H, HAr), 7.03
(d, 1H, HAr), 5.91 (d, 1H, Hcymene), 5.78 (d, 1H,
H
cymene), 5.76 (d, 1H, Hcymene), 5.64 (d, 1H, Hcymene),
Fourier map has a density of 0.473 e AÀ3, and is without
˚
chemical significance.
2.82 (sept, 1H, CHMe2), 2.44 (s, 3H, SCH3), 2.12 (s,
3H, CH3-cymene), 1.26 (d, 3H, CH(CH3)2), 1.10 (d, 3H,

850
C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
Table 1
Summary of structure determination of compound 4, [RuCl(p-
cymene)(MeSAC6H4A2-NH2)][PF6]
Formula
C17H23ClF6NPRuS
Formula weight
Crystal dimensions (mm)
Crystal system
Space group
Unit cell parameters
554.91
0.36 · 0.21 · 0.17
monoclinic
P21 (No. 4)
˚
a (A)
10.5857(7)
8.5114(6)
12.4692(9)
110.9980(10)
1048.86(13)
2
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
qcalc (g cmÀ1
)
1.757
1.106
l (mmÀ1
Radiation
)
˚
Mo Ka (k = 0.71069 A)
4249/263/1
R1 = 0.0183, wR2 = 0.0472
R1 = 0.0186, wR2 = 0.0474
1.058
Reflections/parameters/restraints
R indices (F2 > 2r(F2))
R indices (all data)
Goodness-of-fit
3. Results and discussion
3.1. Ligand syntheses
The ligands were prepared by condensing aromatic
aldehydes with 2-(methylthio)aniline in refluxing etha-
nol (Scheme 1). All of the Schiff bases precipitated upon
cooling to À50 ꢁC and were isolated by filtration. All of
the Schiff bases were characterized by IR, 1H NMR, and
melting point, and the new compound 1f was satisfacto-
rily characterized by elemental analysis.
Scheme 1.
groups show up as two inequivalent doublets and all
four aromatic protons are inequivalent. Additionally,
the C@N stretch in the infrared spectra of the com-
plexes is shifted to lower frequency compared to the
free ligand upon coordination to the cationic ruthe-
nium center.
3.2. Synthesis and characterization of ruthenium
complexes
Treatment of [RuCl2(g6-p-cymene)]2 with N,S-Schiff
bases at room temperature in methanol followed by
addition of NH4PF6 led to formation of air-stable, cat-
ionic complexes with the general formula [RuCl(g6-p-
cymene)(N–S)][PF6], 3a–h (Scheme 1). Complex 4,
The complexes 3a–f and 4 have intense absorbance
bands in their electronic spectra between 314 and
335 nm with molar absorptivities between 10 000 and
13 000 MÀ1 cmÀ1 which are attributed to MLCT bands
[34]. The two complexes with ortho-chloro groups, 3g
and 3h, showed smaller molar absorptivities of 6400
and 3050 MÀ1 cmÀ1, respectively. The absorptions for
the complexes 3a–f and 4 occur at higher energy than
for the related complex [RuCl(g6-p-cymene)(C5H4N-2-
CH@NAC6H11)][PF6] [34].
[RuCl(g6-p-cymene)(MeS–C6H4–2-NH2)][PF6],
was
synthesized similarly. The complexes were easily isolated
by suction filtration due to their low solubilities in meth-
anol. All complexes gave satisfactory elemental
analyses.
Coordination of the Schiff base ligands to the cat-
ionic ruthenium center is readily observed by changes
in the H NMR. The imine N = CH peak shifts down-
field between 0.59 and 0.86 ppm for all of the ligands
upon coordination except for the 2,6-dichlorophenyl
derivative (ligand 1g, complex 3g) where it shifts
Once complexed to the cationic ruthenium center, the
Schiff base ligands are rather susceptible to hydrolysis as
evidenced by the low yields for some of the complexes
3a–h. To confirm ligand hydrolysis upon complexation,
the filtrate liquid was examined after isolation of the
complexes. Analysis revealed the presence of aldehyde
from ligand hydrolysis and the 2-(methylthio)aniline
complex 4. We have recently developed a new set of
N,S-donor Schiff base ligands that are much more stable
with respect to hydrolysis [35].
1
downfield by only 0.25 ppm. Fig.
1 shows the
1
400 MHz H NMR spectra for ligand 1a (i) and com-
plex 3a (ii). Also of note is the loss of the 2-fold sym-
metry of the g6-p-cymene ligand. The isopropyl methyl

C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
851
Fig. 1. 400 MHz NMR spectra of (i) MeSAC6H4A2-N@CHA4-C6H4CH3, 1a; and (ii) [RuCl(g6-p-cymene)(MeSAC6H4A2-N@CHAC6H4A4-
CH3)][PF6], 3a. Solvent peaks are indicated by an x.
3.3. Crystal structure of complex 4
An ORTEP [36] view of complex 4 is shown in Fig. 2
and selected bond length and angle data are listed in
Table 2. The ruthenium atom is coordinated to the
nitrogen and sulfur of the 2-(methylthio)aniline ligand.
The complex has an essentially octahedral coordination
geometry with the g6-p-cymene ligand occupying one
face of the octahedron. The other three coordination
sites are occupied by the chloride and the chelating
2-(methylthio)aniline ligand. The average Ru–Ccymene
and Ru–Cl distances are in agreement with other struc-
turally characterized cationic g6-p-cymene ruthenium
˚
complexes. The Ru–N distance of 2.1257(18) A is simi-
lar to other structurally characterized g6-arene ruthe-
nium(II) complexes with primary amines and the Ru–S
6
˚
distance of 2.3750(5) A is also in line with other g -arene
ruthenium(II) thioether complexes [37]. All of the bond
angles through ruthenium involving the Cl, N, and S
atoms are in the range of about 81–83ꢁ, indicating a dis-
tortion from the 90ꢁ bond angles in an idealized
octahedron.
Fig. 2. ORTEP plot of the cation [RuCl(g6-p-cymene)(MeSA
C6H4A2-NH2)]+ in complex 4. Drawn with 50% ellipsoids and
hydrogen atoms omitted for clarity.

852
C.G. Hamaker, D.P. Halbach / Inorganica Chimica Acta 359 (2006) 846–852
Table 2
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˚
Selected bond lengths (A) and angles (ꢁ) for complex 4
233.
Ru–N1
Ru–Cl1
Ru–S
Ru–Cavg
S–C7
2.1257(18)
2.4069(6)
2.3750(5)
2.196
1.818(2)
1.778(2)
1.453(3)
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S–C2
N1–C1
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(2003) 393.
N1–Ru–Cl1
S–Ru–Cl1
N1–Ru–S
C11–N–Ru
C2–S–Ru
C7–S–Ru
C2–S–C7
82.88(5)
83.06(2)
81.63(5)
117.42(15)
100.37(8)
111.69(9)
99.78(11)
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The reaction of [RuCl2(g6-p-cymene)]2 with 2-(meth-
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derived from substituted benzaldehydes and 2-(methyl-
thio)aniline yielded cationic, half-sandwich ruthenium
complexes. The Schiff base ligands are susceptible to-
wards hydrolysis upon coordination to the cationic
ruthenium(II) center. The molecular structure of com-
plex 4 was determined by single-crystal X-ray crystallog-
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complexes as catalysts for several reactions.
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´
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5. Supplementary material
Crystallographic data for compound 4 have been
deposited with the Cambridge Crystallographic Data
Centre (CCDC), CCDC No. 267413. These data can
be obtained free of charge via www.ccdc.cam.ac.uk/da-
ta_request/cif, or by emailing data_request@ccdc.
cam.ac.uk, or by contacting The Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336033.
[24] D.D. McGuinness, P. Wasserscheid, D.H. Morgan, J.T. Dixon,
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[33] G.M. Sheldrick, SHELXL-93: Program for the Refinement of
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Acknowledgements
CGH thank Illinois State University for financial
support (URG-NFIG and URG-PFIG grants). The
authors thank Robert McDonald of the University of
Alberta X-ray Crystallography Laboratory for collec-
tion of low-temperature, CCD X-ray data.
[35] C.G. Hamaker, D.P. Halbach, in preparation.
[36] ORTEP3 for Windows L.J. Farrugia, J. Appl. Crystallogr. 30
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