Structural dynamics and ligand mobility in carboxylate and dithiocarbamate complexes of Ru(II) containing 1,1′-bis (diphenylphosphino)ferrocene (dppf)

Article abstract of DOI:10.1016/j.jorganchem.2003.08.037

Ruthenium(II) carboxylate and dithiocarbamate complexes containing 1,1′-bis(diphenylphosphino)ferrocene (dppf) were synthesized by displacement of triphenylphosphine in Ru(RCOO)₂ (PPh₃)₂ (R=Me, Et, Ph) and Ru(SC(S)NEt₂) ₂(PPh₃)₂ with dppf. The complexes Ru(RCOO)₂(dppf) (1a: R=Me, 1b: R=Et, 1c: R=Ph) and Ru(SC(S) NEt₂)₂(dppf) (3) were obtained in yields of 78-93%. The crystal structures of these complexes show coordination of the phosphorus atoms of dppf and four oxygen/sulphur atoms of carboxylate/ dithiocarbamate ligands to a Ru(II) centre with axial-bond-distorted octahedral geometry. Two pseudo-polymorphic forms of 1c were isolated and crystallographically characterized. VT-¹H- and ³¹P {¹H}-NMR spectral studies of 1a-c and 3 demonstrate mono- and bidentate exchange behaviour of the carboxylate or dithiocarbamate ligands, together with concerted twisting of the Cp rings of the dppf ligand. Complex 1c in CH₃CN at room temperature gives Ru(PhCOO)₂(dppf)(CH₃CN)(H₂O) (2), the crystal structure of which reveals two monodentate benzoate ligands around octahedral ruthenium and intramolecular inter-ligand H-bonding interaction between the coordinated H₂O and the pendant carboxylate oxygen atoms. The interrelationship of crystallographic properties, structural dynamics, ligand mobility and chemical instability of these complexes will be described.

Full text of DOI:10.1016/j.jorganchem.2003.08.037

Journal of Organometallic Chemistry 688 (2003) 100ꢁ111
/
www.elsevier.com/locate/jorganchem
Structural dynamics and ligand mobility in carboxylate and
dithiocarbamate complexes of Ru(II) containing 1,1?-
bis(diphenylphosphino)ferrocene (dppf)
Xiu Lian Lu, Sin Yee Ng, Jagadese J. Vittal, Geok Kheng Tan, Lai Yoong Goh *,
T.S. Andy Hor *
Department of Chemistry, National University of Singapore, Kent Ridge, Singapore 119260, Singapore
Received 11 June 2003; received in revised form 29 August 2003; accepted 29 August 2003
Abstract
Ruthenium(II) carboxylate and dithiocarbamate complexes containing 1,1?-bis(diphenylphosphino)ferrocene (dppf) were
synthesized by displacement of triphenylphosphine in Ru(RCOO)2(PPh3)2 (Rꢀ
dppf. The complexes Ru(RCOO)2(dppf) (1a: RꢀMe, 1b: RꢀEt, 1c: RꢀPh) and Ru(SC(S)NEt2)2(dppf) (3) were obtained in yields
of 78ꢁ93%. The crystal structures of these complexes show coordination of the phosphorus atoms of dppf and four oxygen/sulphur
atoms of carboxylate/dithiocarbamate ligands to a Ru(II) centre with axial-bond-distorted octahedral geometry. Two pseudo-
polymorphic forms of 1c were isolated and crystallographically characterized. VT-1H- and 31P{1H}-NMR spectral studies of 1aꢁ
/
Me, Et, Ph) and Ru(SC(S)NEt2)2(PPh3)2 with
/
/
/
/
/
c
and 3 demonstrate mono- and bidentate exchange behaviour of the carboxylate or dithiocarbamate ligands, together with concerted
twisting of the Cp rings of the dppf ligand. Complex 1c in CH3CN at room temperature gives Ru(PhCOO)2(dppf)(CH3CN)(H2O)
(2), the crystal structure of which reveals two monodentate benzoate ligands around octahedral ruthenium and intramolecular inter-
ligand H-bonding interaction between the coordinated H2O and the pendant carboxylate oxygen atoms. The interrelationship of
crystallographic properties, structural dynamics, ligand mobility and chemical instability of these complexes will be described.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Ruthenium; Carboxylate; Dithiocarbamate; 1,1?-Bis(diphenylphosphino)ferrocene (dppf); Structural dynamics
1. Introduction
awareness that dppf enhances the catalytic activity of
metal complexes [7ꢁ19], this will be of interest and in
/
Ruthenium carboxylate phosphine complexes have
attracted much attention because of their structural
this paper, we describe the structures and dynamic
behaviour of some of these dppf ruthenium complexes
with carboxylate or dithiocarbamate as coligand.
diversity [1ꢁ
applications [9ꢁ
carboxylate complexes containing diphosphines are
efficient catalysts [12ꢁ16]. Such carboxylate dipho-
/
6], extensive chemistry [4ꢁ
/
8] and catalytic
/15]. In particular, many ruthenium
/
2. Experimental
sphine complexes are easily synthesized by substitution
of PPh3 in Ru(RCO2)2(PPh3)2. However, the reaction of
Ru(RCO2)2(PPh3)2 with metallocene-based diphosphine
ligands, such as 1,1?-bis(diphenylphosphino)ferrocene
(dppf) has not been studied. In view of the growing
All reactions were performed under dry nitrogen
using Schlenk techniques. Solvents were freshly distilled
1
from standard drying agents. H- and 31P{1H}-NMR
spectra were recorded on a Bruker ACF300 FT NMR
spectrometer, with chemical shifts referenced to residual
non-deuterio solvent and external H3PO4, respectively.
The VT-1H-NMR spectra of complex 3 was recorded on
a Bruker ACF500 FT NMR spectrometer. IR spectra
* Corresponding authors. Tel.: ꢂ
1691.
E-mail
andyhor@nus.edu.sg (T.S.A. Hor).
/
65-6874-2677; fax: ꢂ
/
65-6779-
addresses:
chmgohly@nus.edu.sg (L.Y.
Goh),
were measured in KBr pellet on a PerkinꢁElmer 1600
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.08.037

X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ
/111
101
spectrometer. FAB mass spectra were obtained on a
Finnigan MAT95XL-T spectrometer. All elemental
analyses were carried out in-house. RuCl2(PPh3)3 [20],
(d, CDCl3, 300 K): 4.27 (s, 4H, b-H’s on C5H4), 4.41 (s,
/
4H, a-H’s on C5H4), 7.16 and 7.31 (each triplet, Jꢀ
8
Hz, 6H, C6H5COO) sitting on two overlapping broad
peaks centred at d 7.17 and 7.25 (n1/2 32 and 24 Hz,
Ru(RCOO)2(PPh3)2 (RꢀMe, Et, Ph) [9,21], and
/
Ru[SC(S)N(CH3CH2)2]2(PPh3)2 [22] were synthesized
according to published procedures. Other reagents
used were of AR grade obtained from commercial
sources.
respectively, 8H, C6H5P), 7.57 (d, Jꢀ8 Hz, 4H,
/
C6H5COO) sitting on a broad peak centred at d 7.61
(n1/2 30 Hz, 12H, C6H5P). 31P-NMR (d, CDCl3): 62.6 (s,
dppf). FABꢂ-MS: m/z 777 [Mꢃ
/
PhCOOꢂ
/
H]ꢂ, 655
[Mꢃ
/
2PhCOOꢂ
/
H]ꢂ. IR (KBr, cmꢃ1), n(OCO (biden-
2.1. Synthesis
tate)): 1499(m), 1422(s).
Because it appeared that more yellow crystals were
obtained during a longer recrystallization time at low
temperature, the above reaction was repeated both in
refluxing toluene and in CH2Cl2 at 5 8C; these condi-
tions gave mainly red and yellow crystals, respectively.
X-ray diffraction quality red crystals of 1c were
obtained from the high-temperature reaction by recrys-
2.1.1. Ru(RCOO)2(dppf) (1a: Rꢀ
/
Me; 1b: RꢀEt; 1c,
/
RꢀPh)
/
A yellow solution of Ru(MeCOO)2(PPh3)2 (50 mg,
0.067 mmol) and dppf (37 mg, 0.069 mmol) in CH2Cl2 (5
ml) was stirred for ca. 1 h at room temperature (r.t.).
The yellow product solution was concentrated to ca. 1
ml and hexane (ca. 3 ml) was added. Yellow crystals of
Ru(MeCOO)2(dppf) (1a) were obtained after cooling at
tallization of the product in 1:3 CH2Cl2ꢁhexane (layer-
/
ing) at r.t. after overnight standing. From the yellow
microcrystalline product of the low-temperature reac-
tion were obtained diffraction-quality reddish yellow
ꢃ5 8C for ca. 4 h (42 mg, 0.054 mmol, 80% yield). Anal.
/
Calc. for RuFeC38H34O4P2: C, 59.0; H, 4.4; P, 8.0; Fe,
1
7.2. Found: C, 58.8; H, 4.5; P, 7.8; Fe, 6.8%. H-NMR
crystals of 1c×
/
1.25H2O from 1:2 CH2Cl2ꢁ
/
hexane (layer-
(d, CDCl3, 300 K): 1.38 (s, 6H, CH3), 4.25 (s, 8H,
C5H4), 7.34 and 7.37 (br., overlapping singlets, 12H,
ing) after 8 h at ꢃ
/
5 8C.
C6H5) together with 7.58 (s, n1/2
31P-NMR (d, CDCl3): 62.3 (s, dppf). FABꢂ-MS: m/z
774 [Mꢂ CH3COOꢂ
H]ꢂ, 714 [Mꢃ H]ꢂ, 655 [Mꢃ
2(CH3COO)ꢂ
H]ꢂ. IR (KBr, cmꢃ1), n(OCO(biden-
ꢀ
/
29 Hz, 8H, C6H5).
2.1.2. Ru(PhCOO)2(dppf)(CH3CN)(H2O) (2)
CH3CN (8 ml) was added to Ru(PhCOO)2(dppf) (1c)
(100mg, 0.11 mmol), and the suspension was stirred for
3 h at r.t. The clear yellow solution was concentrated to
ca. 2 ml and ether (ca. 8 ml) was added. Yellow crystals
of Ru(PhCOO)2(dppf)(CH3CN)(H2O) (2) were obtained
after cooling at 0 8C for 4 h followed by standing at r.t.
for 12 h (83 mg, 0.087 mmol, 77% yield). Anal. Calc. for
RuFeC50H43NO5P2: C, 62.7; H, 4.5; N, 1.5. Found: C,
62.7; H, 4.7; N, 1.4%. 1H-NMR (d, CDCl3, 300 K)
shows two species, possibly isomers, which vary with
concentration. Major isomer: 1.81 (s, 3H, CH3CN), 4.23
(s, 3H, C5H5), 4.30 (s, 3H, C5H5), 4.62 (broad s, 2H,
/
/
/
/
/
bidentate)): 1459(s), 1434(m, sh).
A similar reaction of Ru(EtCOO)2(PPh3)2 (50 mg,
0.065 mmol) with dppf (36 mg, 0.065 mmol) gave
Ru(EtCOO)2(dppf) (1b) as red crystals (41 mg, 0.051
mmol, 78% yield). Anal. Calc. for RuFeC38H38O4P2: C,
59.9; H, 4.7; P, 7.7. Found: C, 59.8; H, 4.7; P, 8.1%. 1H-
NMR (d, CDCl3, 300 K): 0.67 (t, Jꢀ
1.70 (q, Jꢀ8 Hz, 4H, CH2), 4.24 (s, 4H, C5H4), 4.30 (s,
broad, 4H, C5H4), 7.32ꢁ7.38 (pseudo-quartet with main
peaks centred at d 7.35 and 7.32, 12H, C6H5P), 7.57 (s,
n1/2
21 Hz, 8H, C6H5P). 31P-NMR (d, CDCl3): 62.5 (s,
dppf). FABꢂ-MS: m/z 802 [MꢂH]ꢂ, 729 [Mꢃ
H]ꢂ.
/8 Hz, 6H, CH3),
/
/
C5H5), 7.05ꢁ7.75 (m, 30H, C6H5COO and C6H5P);
/
ꢀ
/
Minor isomer: 1.87 (s, 3H, CH3CN), 3.47 (s, 1H, C5H5),
3.85 (s, 1H, C5H5), 4.07 (s, 2H, C5H5), 4.53 (s, 3H,
/
/
CH3CH2COOꢂ
/
H]ꢂ, 655 [Mꢃ
/
2CH3CH2COOꢂ
/
C5H5), 5.46 (s, 1H, C5H5), 7.05ꢁ
C6H5COO and C6H5P); 31P-NMR (d, CDCl3): 54.7
(d, Jꢀ34 Hz), 60.3 (d, Jꢀ
34 Hz). FABꢂ-MS: m/z 898
[MꢃCH3CNꢃH2Oꢂ 818 [MꢃPhCOOꢃ
H]ꢂ,
H2Oꢂ PhCOOꢃCH3CNꢃH2Oꢂ
H]ꢂ, 777 [Mꢃ
H]ꢂ. IR
/8.43 (m, 30H,
IR (KBr, cmꢃ1), n(OCO(bidentate)): 1504(m),
1471(s),1439(vs); n(CH): 3057(w).
/
/
A yellow solution of Ru(PhCOO)2(PPh3)2 (50 mg,
0.056 mmol) with dppf (32 mg, 0.057 mmol) in CH2Cl2
(5 ml) was stirred for ca. 1 h at r.t. The yellow product
solution was concentrated to ca. 1 ml and hexane (ca. 3
ml) was added. After cooling at 0 8C for ca. 4 h, red
crystals of Ru(PhCOO)2(dppf) (1c) (ca. 45 mg, 0.050
/
/
/
/
/
/
/
/
/
/
H]ꢂ, 655 [Mꢃ
/
2PhCOOꢃ
/
CH3CNꢃ
/
H2Oꢂ
/
(KBr, cmꢃ1), n(CH3CN): 2277(s). n(OCO (monoden-
tate)): 1624(m), 1380(s).
mmol, 88% yield) and yellow crystals of 1c×
/
nH2O (ca. 3
2.1.3. Ru[SCSNEt2]2(dppf) (3)
mg, 0.003 mmol, 5% yield) were found to have formed
on different parts of the walls of the flask. Both types
were yellow when pulverized, and possessed indistin-
guishable IR, NMR and MS-FAB spectra. Anal. Calc.
for RuFeC48H38O4P2: C, 64.2; H, 4.2; P, 6.9; Fe, 6.2.
Found for 1c: C, 63.9; H, 4.2; P, 5.9; Fe, 5.9%. 1H-NMR
A yellow solution of Ru(SC(S)NEt2)2(PPh3)2 (50 mg,
0.054 mmol) and dppf (30 mg, 0.054 mmol) in toluene (5
ml) was refluxed for ca. 2 h. The solution was
concentrated to ca. 0.2 ml and CH2Cl2 (ca. 1 ml) was
added to redissolve some precipitated solids. Hexane
(ca. 3 ml) was added and orangeꢁyellow crystals of
/

102
X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ111
/
Ru(SCSNEt2)2(dppf) (3) were obtained after cooling
overnight at ꢃ5 8C (41 mg, 0.043 mmol, 80% yield).
Anal. Calc. for RuFeC44H48N2P2S2: C, 55.5; H, 5.1; N,
recrystallized as red single crystals of 1c from CH2Cl2ꢁ
hexane at room temperature, whereas the yellow form
was the major product from a low-temperature reaction
/
/
2.9. Found: C, 55.7; H, 5.4; N, 2.6%. 1H-NMR (d,
and recrystallized as reddish yellow single crystals of 1c×
/
CDCl3, 300 K): 0.98 (s, br., 12H, CH3), 3.24 (s, n1/2
Hz, 2H, CH2), 3.53 (s, n1/2 33 Hz, 6H, CH2), 4.20 (s,
2H, C5H4), 4.36 (s, 2H, C5H4), 4.44 (s, 4H, C5H4), 7.17
and 7.24 (overlapping triplets, Jꢀ8 Hz, 12 H, C6H5P),
7.68 (s, n1/2
26 Hz, 8H, C6H5P). 31P-NMR (d, CDCl3):
48.9 (s, dppf). FABꢂ-MS: m/z 952 [MꢂH]ꢂ, 804 [Mꢃ
SC(S)NEt2ꢂ
H]ꢂ. IR (KBr, cmꢃ1): n(SC(S)): 1485(m),
ꢀ
/
42
1.25H2O after 8 h at ꢃ5 8C in CH2Cl2ꢁhexane. The
/
/
ꢀ
/
difference between them shows up in their structures
which reveal 2.5 disordered water molecules in the
asymmetric unit of the hydrate.
/
ꢀ
/
Complexes 1aꢁc are stable in the solid state; in
/
/
/
CH2Cl2, all are very stable, but in CDCl3, 1b is very
unstable, followed by 1a and 1c.
/
1428(m), 1271(s).
The ruthenium dithiocarbamate dppf complex 3 was
prepared via an analogous reaction of Ru(SC(S)NEt2)2-
(PPh3)2 with dppf for 2 h in refluxing toluene (Scheme
2.2. X-ray diffraction analysis
2). Unlike complexes 1aꢁ
be very stable in both CDCl3 and CH2Cl2. Ru(Ph-
nH2O) in CH3CN gives Ru(Ph-
COO)2(CH3CN)(H2O)(dppf) (2) in high yield after
stirring for 3 h at ambient temperature.
/
c, this compound was found to
Diffraction-quality single crystals of 1c and 1c×
/
1.25H2O were obtained as described above; those of
COO)2(dppf) (1c/1c×
/
1aꢁ
CH2Cl2 layered with hexane, after 4ꢁ
while single crystals of 2×CH3CN×0.5H2O were obtained
/
b and 3×
/
2CH2Cl2×
/
2H2O were also obtained from
/
8 h at ꢃ5 8C,
/
/
/
from CH3CN layered with ether after 4 h at 0 8C
followed by 12 h at r.t. The crystals were mounted on
quartz fibres. X-ray data were collected on a Bruker
3.2. Structures
It is of interest to examine the structure of these tris-
chelate complexes, since the chelating behaviour of a
large-bite ligand such as dppf and a small-bite ligand
such as carboxylate and dithiocarbamate is expected to
be significantly different. We also wish to seek an
understanding of the unexpected high instability of 1
in solution and a structural explanation for the easy
conversion of 1c to 2 in CH3CN.
AXS SMART CCD diffractometer, using Moꢁ
/
Ka
0.71073 A) at 223 K except for 1a at
˚
radiation (lꢀ
/
296 K.
The program SMART [23] was used for collecting the
intensity data, and for the determination of lattice
parameters, SAINT [23] was used for integration of the
intensity of reflections and scaling, SADABS [24] was used
for absorption correction and SHELXTL [25] for space
group and structure determination, least-squares refine-
ments on F2. The structure was solved by direct methods
to locate the heavy atoms, followed by difference maps
for the light, non-hydrogen atoms. The Cp and Ph
hydrogens were placed in calculated positions. There are
2.5 disordered water molecules in nine places in the
yellow crystal of 1c, and two H2O and two CH2Cl2
solvents per formula unit in 3. Crystal data and
refinement parameters are given in Table 1.
A detailed crystallographic analysis of the key com-
plexes showed that crystals of 1a, 1b, 1c×
CH3CN×0.5H2O are triclinic, possessing P1 space
group, while those of 1c and 3×2CH2Cl2×2H2O are
monoclinic with space groups Cc and C2/c, respectively.
Complexes 1aꢁc and 3 are isostructural (Figs. 1ꢁ4),
/
1.25H2O and 2×
/
¯
/
/
/
/
/
with three chelates (dppf and two bidentate carboxylate
or dithiocarbamate ligands) at 18e-Ru centres. Since the
bite angle of the diphosphine (Pꢀ
100.64(9)8) is significantly larger than the chelate angle
of the dithiocarbamate (SꢀRuꢀS: 71.94(6)8) or the
carboxylate (OꢀRuꢀO: 59.3(3)ꢁ61.76(12)8), a regular
/
Ruꢀ
/
P: 95.48(4)ꢁ
/
/
/
/
/
/
3. Results and discussion
octahedral structure cannot be achieved, giving rise to
distortion in the axial bonds. The structures of 1c and
3.1. Reactions
1c×
independent molecules in the asymmetric unit in 1c and
1c×1.25H2O.
/
1.25H2O are pseudo-polymorphic. There are two
The ruthenium carboxylate dppf complexes were
synthesized in high yields by substitution of PPh3 in
Ru(RCOO)2(PPh3) (1a: Rꢀ
at ambient temperature as shown in Scheme 1. For Rꢀ
Ph, the reaction produced a mixture of red crystals of 1c,
as major product and a small amount of yellow crystals
/
The structure of 2 (Fig. 5) shows two monodentate
benzoate ligands at an 18e-Ru centre. This is the only
structure among the complexes here that can be suitably
described as (near)octahedral, made possible by remov-
ing the geometric demands of the small bite angles of
chelating carboxylate ligands. The two monodentate
carboxylates are trans to different ligands (phosphine
and CH3CN), and the two phosphine donors are trans
to different donors (aqua and carboxylate). There exists
/
Me, 1b: Rꢀ
/
Et, 1c: RꢀPh)
/
/
of solvate, 1c×
/
nH2O; both forms were yellow when
pulverized and were indistinguishable in their IR, NMR
and MS spectra. It was observed that the red form was
the main product from a high-temperature reaction, and

X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ
/111
103
Table 1
Crystal data and parameters related to the structure determination and refinement for complexes
Complexes
1a
1b
1c
1c×/1.25H2O
2×/
CH3CN×/0.5H2O
3×/
2CH2Cl2×/2H2O
Empirical
formula
Formula
weight
C38H34FeO4P2Ru
C40H38FeO4P2Ru
C48H38FeO4P2Ru
C48H40.50FeO5.25P2Ru C52H47FeN2O5.50P2Ru C46H56Cl4FeN2O2P2Ru
773.51
801.56
897.64
920.16
1006.7
1157.83
Temperature (K)
Crystal
296(2)
223(2)
223(2)
223(2)
223(2)
223(2)
Triclinic
Triclinic
Monoclinic
Triclinic
Triclinic
Monoclinic
system
¯
P1
¯
P1
¯
P1
¯
P1
Space
Cc
C 2/c
group
˚
a (A)
˚
b (A)
9.4134(5)
10.1319(6)
18.6193(11)
96.112(1)
103.675(1)
100.951(1)
1672.60(17)
4
9.2367(6)
13.5453(8)
14.5017(9)
90.269(1)
100.939(1)
93.342(1)
1778.14(19)
2
10.3305(3)
17.9596(5)
42.5516(12)
90
10.3963(4)
19.2080(8)
21.3477(9)
87.271(1)
81.658(1)
82.205(1)
4177.2(3)
4
10.6184(7)
14.1725(9)
17.3114(11)
91.105(2)
104.7390(10)
108.8170(10)
2370.1(3)
2
29.119(3)
13.3221(12)
14.6545(12)
90
˚
c (A)
a (8)
b (8)
g (8)
93.455(1)
90
112.731(2)
90
3
˚
V (A )
7880.3(4)
8
5243.3(8)
4
Z
Dcalc (g cmꢃ3
Absorption
)
1.536
1.497
1.513
1.463
1.411
1.467
0.833
0.963
0.879
0.833
0.742
1.027
coefficient (mmꢃ1
F(000)
)
1882
820
3664
1882
1034
2376
Crystal size (mm)
Theta range for
data collection (8)
Index ranges
0.24ꢄ
/
0.16ꢄ
/
0.12
0.38ꢄ
/
0.28ꢄ
/
0.04
0.24ꢄ
/
0.18ꢄ
/
0.10
0.24ꢄ
/
0.16ꢄ
/
0.12
0.38ꢄ
/
0.30ꢄ
/
0.30
0.46ꢄ
/
0.36ꢄ/0.12
1.46ꢁ25.00
/
1.43ꢁ30.08
/
0.96ꢁ25.00
/
1.46ꢁ25.00
/
1.22ꢁ25.00
/
1.52ꢁ25.00
/
ꢃ
/
125
225
255
45 416
Independent reflections 14 731
/
h 5
k 5
l 525
/
12,
ꢃ
/
105
195
205
/
h 5
k 5
l 516
/
12,
ꢃ
/
125
215
505
/
h 5
k 5
l 544
/
12,
ꢃ
/
125
225
255
/
h 5
k 5
l 525
/
12,
ꢃ
/
125
165
205
/
h 5
k 5
l 520
/
12,
ꢃ
/
345
155
175
/
h 5
k 5
l 516
/
31,
ꢃ/
/
/22,
ꢃ/
/
/
19,
ꢃ/
/
/17,
ꢃ/
/
/22,
ꢃ/
/
/14,
ꢃ/
/
/
15,
ꢃ/
/
/
ꢃ/
/
/
ꢃ/
/
/
ꢃ/
/
/
ꢃ/
/
/
ꢃ/
/
/
Reflections collected
14 398
9713
22 723
11 428
45 416
14 731
13 594
8293
14 699
4617
Max/min transmission
Data/restraints/
parameters
0.9170, 0.8017
14731/0/11045
0.9625, 0.7110
9713/0/428
0.9123, 0.6830
11428/2/481
0.9170, 0.8017
14731/0/1045
1.0000, 0.6123
8293/10/512
0.8330, 0.5223
4617/1/1264
Goodness-of-fit on F2 c 1.039
Final R indices R1ꢀ
[I ꢀ wR2ꢀ
2s(I )] a,b
R1ꢀ0.0618,
wR2ꢀ0.1116
0.958 and ꢃ
1.121
1.145
1.039
1.080
1.182
/
0.0424,
R1ꢀ
wR2ꢀ
R1ꢀ0.0532,
wR2ꢀ0.1169
0.434 1.697 and ꢃ
/
0.0463,
R1ꢀ
wR2ꢀ
R1ꢀ0.0925,
wR2ꢀ0.1826
0.802 1.265 and ꢃ
/
0.0639,
R1ꢀ
wR2ꢀ
R1ꢀ0.0618,
wR2ꢀ0.1116
0.563 0.958 and ꢃ
/
0.0424,
R1ꢀ
wR2ꢀ
R1ꢀ0.0689
wR2ꢀ0.1727
1.685 and ꢃ
/
0.0629,
R1ꢀ
wR2ꢀ
R1ꢀ0.0978,
wR2ꢀ0.2716
2.857 and ꢃ
/
0.0846,
/
/0.1066
/0.1070
/0.1317
/0.1066
/0.1659
/0.2551
R indices (all data)
/
/
/
/
/
/
/
/
/
/
/
/
Largest difference
/
/
/
/0.434
/
1.133
/0.786
ꢃ3
˚
peak and hole (e A
)
a
Rꢀ
/
(S½Fo½ꢃ
Rwꢀ[(Sv½Fo½ꢃ
GoFꢀ[(Sv½Fo½ꢃ
/
½Fc½)S½Fo½.
½Fc½)2/Sv½Fo½2]1/2
½Fc½)2/(Nobs
Nparam)].
b
c
/
/
.
/
/
ꢃ/
inter-ligand hydrogen-bonding between the aqua pro-
tons and the two pendant carboxylate oxygen atoms of
monodentate benzoates. This intramolecular interaction
stabilizes the molecule by decreasing the lability of uni-
bidentate exchange (discussed below). Indeed, it was
phosphine carboxylate complex, which possibly has a
potential in asymmetric catalysis.
Selected bond lengths and bond angles of the com-
plexes are collectively given in Table 2. The Ruꢀ
lengths gradually decrease in the order: 1aꢀ1bꢀ
agreement with the order of nucleophilicity of the
carboxylate groups (PhCOOꢀEtCOOꢀMeCOO), in-
dicating that the higher steric demands of PhCOO has
not offset electronic effects on the magnitude of the Ruꢀ
/O bond
/
/1c, in
observed that unlike 1aꢁc, 2 no longer decomposed in
/
/
/
CDCl3, indicative of the arrest of exchange behaviour.
The IR spectrum in KBr pellet shows coordinated
CH3CN at n 2277 cmꢃ1. This compares well with
values of 2270 and 2310 cmꢃ1 for reported cases of
CH3CN coordinated to Ru [26]. The IR data also
support the presence of unidentate carboxylate ligands
[27]. It is noted that the asymmetric arrangement of the
ligands in 2 resulted in an unusual chiral Ru(II)
/
O bond length. The bond distances of Ru to O, ‘‘trans’’
to phosphorus atoms, are considerably longer than that
‘‘trans’’ to oxygen atoms. This is due to the high trans
effect of the strongly s-donating phosphorus atom. The
difference in the two Ru to O bond distances is most

104
X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ111
/
Scheme 1.
˚
1.467(9) A), slightly longer than
distances (1.329(9)ꢁ
previous values (1.288(8)ꢁ
mate complexes [28] are indicative of partial double-
bond character (CꢀS, 1.81; CÄS, 1.61; CꢀN, 1.47 and
N, 1.27 A) [29]. In accordance with the HSAB
/
˚
/
1.52(9) A) for dithiocarba-
/
/
/
˚
CÄ
/
principle, the S-donor ligands of 3 bond more strongly
to Ru than do the O-donor atoms of carboxylate
ligands; this is reflected in the relative instability of
complexes 1.
In 1a, the atoms in each acetate group are coplanar
and the inter-planar angle is 106.48. The structure of 1b
shows one CH3 group pointing to the Ru centre (C11ꢀ
C12ꢀC15ꢀ114.3(3)8), whereas the other group points
away from Ru (C13ꢀC14ꢀC16ꢀ113.5(5)8). The Pꢀ
RuꢀP bond angles of 1 decrease in the order: 1a
(99.58(5)8)ꢀ1b (97.95(3)8)ꢀ1c (96.53(13), 95.48(4)8),
/
/
/
/
/
/
/
/
/
/
Fig. 1. Molecular structure of Ru(CH3COO)2(dppf) (1a).
in accordance with the increasing steric demands of the
R group in the carboxylate ligands.
3.3. NMR spectral studies
The ambient temperature proton NMR spectra show
broad signals for the Cp protons (1aꢁc) or the ethyl
/
protons (1b, 3), suggesting that they are fluxional in
solution. Fluxionality arising from uni-bidentate ex-
change processes of the carboxylate ligands would
involve the interconversions of 14el
/
16el
/
18e Ru(II),
which could have a catalytic implication. We therefore
decided to study their variable-temperature (VT) NMR
spectra in detail.
Fig. 2. ORTEP diagram of Ru(EtCOO)2(dppf) (1b). Hydrogen atoms
are omitted. Thermal ellipsoids are drawn to 50% probability level.
The VT proton resonances of the phenyl and Cp rings
of Ru(RCOO)2(dppf) (1a and 1b) in the range of 328ꢁ
/
evident in 1c and 1c×
found in 2. The Ruꢀ
significantly longer than the corresponding Ruꢀ
/
1.25H2O. Similar observations are
213 K in CDCl3 are very similar. As shown for 1a in Fig.
6(a), the Cp protons are observed as two overlapping
singlets of approximately equal intensity at d 4.29 and
˚
/
P distance (2.3174(18) A) in 3 is
/P dis-
˚
tance (2.2235(12)ꢁ
difference between Ruꢀ
bond lengths in 1aꢁc (2.108(3)ꢁ
reflective of the relative size of the sulphur and oxygen
atoms. The CꢀS bond lengths in 3 (1.718(7) and 1.715(7)
A), slightly longer than the CÄS double bond, are
comparable to previously reported values for dithiocar-
/
2.2860(13) A) in 1aꢁ
/c, whereas the
4.24 at 328ꢁ313 K; the former peak broadens rapidly
/
˚
/
S (2.4175(18) A) in 3 and Ruꢀ
/O
with lowering of temperature while the latter peak
remains sharp to 258 K (d 4.26), at which temperature
line-broadening has set in; at 213 K and below complete
resolution had occurred, giving four sharp signals at d
˚
/
/
2.267(10) A) is only
/
1
˚
/
4.41, 4.28, 4.23 and 4.11. This pattern of VT H-NMR
spectral variations is typical of the general fluxional
behaviour of dppf complexes and has been attributed to
˚
bamate ligands (1.700(7)ꢁ
/
1.79(2) A) and the Cꢀ
/
N
Scheme 2.

X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ
/111
105
shifting of the broad peak at d 7.59 (n1/2
multiplets at d 7.31ꢁ
found at d 7.68 (n1/2
overlapping multiples at d 7.41ꢁ
ꢀ
/
18 Hz) and
/
7.38 at 328 K to lower field, being
18 Hz) together with two sets of
7.52 and 7.27ꢁ7.35 at
ꢀ
/
/
/
213 K. Throughout this temperature range, the singlet
31P resonance remained unchanged (1a, d 62.3; 1b, d
62.5). The Me resonance of the acetate groups in 1a
remained unchanged at d 1.37, suggesting non-fluxional
behaviour. This is in contrast to uni-bidentate fluxion-
ality of acetate ligands, observed by Jia for Ru-
Cl(OAc)(Cyttp) (ttpꢀ
/
PhP(CH2CH2CH2PPh2)2) [3]
and by Wong for Ru(OAc)2PPh3(dppm) (dppmꢀ
/
Ph2P(CH2)PPh2) [5] and also for the carboxylate ligands
found in 1b. The VT behaviour of the ethyl protons of
1b is shown in Fig. 6(b). At 300 K, the Me protons are
seen as one triplet at d 0.70 and the CH2 protons as a
quartet at d 1.70. As the temperature is lowered, these
peaks broaden. At 243 K, the broad methylene peak has
begun to resolve into two broad signals which at 213 K
Fig. 3. Two independent molecules of Ru(PhCOO)2(dppf) (1c).
are seen at unresolved quartets as d 1.46 (Jꢀ
/
8 Hz) and
1.89 (Jꢀ8 Hz), while the Me resonance is still seen as
/
one (unresolved triplet-like) signal. These VT features of
the ethyl protons can be rationalized on the basis of
bidentateꢁmonodentate exchange of the carboxylate
/
ligands, as shown in Fig. 7. At ambient temperature
this process is fast, rendering equivalent the methylene
protons and likewise the methyl protons. Below 233 K,
the presence of two CH2 signals suggests two inequi-
valent ethyl groups, pertaining to a mono- and a
bidentate carboxylate ligand, respectively, as in species
B?, which is likely to achieve six-coordination involving
ligated solvent as shown in B. A similar mechanism has
been proposed for rapid intramolecular exchange of
mono- and bidentate carboxylate ligands in
Fig. 4. ORTEP diagram of Ru[SCSNEt2]2(dppf) (3). Hydrogen atoms
are omitted. Thermal ellipsoids are drawn to 50% probability level.
Ru(OAc)2(PPh3)(diphosphine) (diphosphineꢀdppm,
/
dppb, dppp) [1]. It is not immediately obvious why
these processes have so little effect on the chemical
environments of the P atoms of the dppf ligand. One
possibility is that the predominant intermediate species
is indeed the five-coordinate species B?, which being
stereochemically non-rigid, renders the P atoms non-
differentiating in the NMR time-scale.
The VT-proton and 31P{1H}-NMR spectra of Ru(Ph-
COO)2(dppf) (1c) in the range 328ꢁ
shown in Fig. 8. In the temperature range 328ꢁ
/
213 K in CDCl3 are
258 K
/
the Cp protons are observed as singlets at d 4.42 and
4.28, with the former peak rapidly increasing in line-
width as the temperature is lowered, from n1/2 of 7 Hz at
328 K to 69 Hz at 258 K. In this temperature range,
there is little change in the Ph proton resonances which
at 300 K appear as a set of multiplets consisting of a
Fig. 5. Molecular structure of Ru(PhCOO)2(CH3CN)(H2O)dppf (2).
Hydrogen atoms are omitted.
triplet at d 7.17 (Jꢀ
Hz), overlapping with another broad peak centred at d
7.25 (n1/2 24 Hz), together with a doublet at d 7.57
(Jꢀ8 Hz) on top of a broad base centred at d 7.61
(n1/2 30 Hz). In contrast to a single temperature-
/8 Hz) on a broader peak (n1/2
ꢀ32
/
mutual twisting of the Cp rings and bridge-reversal at
the metal [17]. In the temperature range studied, the
only change seen in the Ph proton resonances is a slight
ꢀ
/
/
ꢀ
/

Table 2
˚
Selected bond lengths (A) and angles (8)
1a
1b
1c
1c×
/
1.25H2O
2×
/
CH3CN×/0.5H2O
3×
/
2CH2Cl2×2H2O
/
Ru(CH3COO)2dppf
Ru(CH3CH2COO)2dppf
Ru(PhCOO)2dppf
Ru(PhCOO)2dppf
Ru(PhCOO)2(CH3CN)(H2O)dppf
Ru[S2CN(CH3CH2)2]2dppf
Bond lengths
Ru1ꢀ
Ru1ꢀ
Ru1ꢀ
Ru1ꢀ
Ru1ꢀ
Ru1ꢀ
/
P1
2.2741(14)
2.2860(13)
2.178(3)
2.129(3)
2.139(3)
2.118(3)
1.255(6)
1.259(5)
1.258(6)
1.263(6)
2.2602(8)
2.2719(8)
2.143(2)
2.184(2)
2.180(3)
2.118(2)
1.284(4)
1.265(4)
1.253(6)
1.3056(5)
2.236(3)
2.224(4)
2.110(9)
2.267(10)
2.240(9)
2.109(8)
1.272(15)
1.221(17)
1.232(15)
1.248(15)
2.2235(12)
2.2512(12)
2.127(3)
2.190(3)
2.207(3)
2.108(3)
1.273(5)
1.264(5)
1.259(5)
1.276(5)
2.2633(10)
2.3004(12)
2.3174(18)
2.3174(18)
2.4175(18)
2.4109(16)
/P2
/
X1
X2
X3
X4
Ru1ꢀ
Ru1ꢀ
Ru1ꢀ
/
O2 2.150(3)
O4 2.100(3)
O5 2.157(3)
/
/
/
/
/
O1ꢀ
O2ꢀ
O3ꢀ
O4ꢀ
O5ꢀ
O5ꢀ
Ru2ꢀ
Ru2ꢀ
Ru2ꢀ
Ru2ꢀ
Ru2ꢀ
Ru2ꢀ
/
C11
C11
C13
C13
O1
C(11)ꢀ
C(11)ꢀ
C(12)ꢀ
C(12)ꢀ
/
O(3) 1.248(6)
O(4) 1.264(6)
O(1) 1.238(5)
O(2) 1.263(5)
/
/
/
/
/
/
/
2.599(3)
/
O3
2.599(3)
/
P3
2.252(4)
2.236(4)
2.081(10)
2.241(9)
2.215(11)
2.097(9)
2.2584(12)
2.2313(12)
2.109(3)
2.199(3)
2.182(3)
2.139(3)
S1ꢀ
S2ꢀ
N1ꢀ
N1ꢀ
N1ꢀ
/
C6 1.718(7)
/
P4
/
C6 1.715(7)
/
X5
X6
X7
X8
/
C6 1.329(9)
C7 1.467(9)
C9 1.452(5)
/
/
/
/
/
Bond angles
X1ꢀ
X3ꢀ
P1ꢀRu1ꢀ
P1ꢀRu1ꢀ
P1ꢀRu1ꢀ
P1ꢀRu1ꢀ
P1ꢀRu1ꢀ
P2ꢀRu1ꢀ
P2ꢀRu1ꢀ
P2ꢀRu1ꢀ
P2ꢀRu1ꢀ
X5ꢀRu2ꢀ
X7ꢀRu2ꢀ
P3ꢀRu2ꢀ
/
Ru1ꢀ
Ru1ꢀ
/
X2
60.76(12)
61.17(12)
99.58(5)
60.67(8)
61.76(12)
97.95(3)
88.00(7)
93.05(6)
168.62(9)
108.18(8)
107.89(6)
163.95(6)
88.00(8)
91.50(7)
59.6(4)
59.3(3)
96.53(13)
97.2(2)
155.3(3)
94.8(3)
95.1(3)
96.1(3)
94.5(3)
156.5(2)
99.2(3)
60.5(4)
61.4(4)
96.48(14)
60.55(11)
60.66(10)
95.48(4)
90.58(8)
93.94(8)
161.76(8)
102.63(8)
103.91(8)
161.91(8)
93.62(8)
95.76(8)
61.13(11)
60.70(12)
96.12(4)
71.94(6)
71.94(6)
100.64(9)
89.17(6)
104.75(6)
163.41(6)
104.75(6)
163.41(6)
92.50(6)
89.17(6)
104.75(6)
/
/X4
/
/
P2
98.39(4)
/
/
X1
X2
X3
X4
X1
X2
X3
X4
89.63(9)
89.77(9)
N(1)ꢀ
O(4)ꢀ
O(2)ꢀ
O(5)ꢀ
N(1)ꢀ
O(4)ꢀ
O(2)ꢀ
O(5)ꢀ
/
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
Ru(1)ꢀ
/
P(1) 88.29(10)
P(1) 96.72(9)
P(1) 175.07(8)
P(1) 89.80(8)
P(2) 98.24(10)
P(2) 89.71(10)
P(2) 84.78(9)
P(2) 171.79(8)
/
/
/
/
/
/
165.24(10)
108.48(9)
166.19(9)
108.67(9)
90.84(9)
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
/
87.90(10)
/
/
/
/
X6
/
/
X8
/
/
P4
X1ꢀ
X3ꢀ
X5ꢀ
X7ꢀ
X1ꢀ
X2ꢀ
X3ꢀ
X4ꢀ
X5ꢀ
/
C11ꢀ
C13ꢀ
C17ꢀ
C19ꢀ
C11ꢀ
C11ꢀ
C13ꢀ
C13ꢀ
C17ꢀ
/
X2
120.2(5)
118.4(5)
118.1(3)
119.2(3)
121.9(13)
120.6(12)
118.1(14)
120.9(14)
117.1(12)
120.8(12)
123.2(12)
115.9(11)
122.5(13)
118.3(4)
118.8(4)
118.5(4)
117.9(4)
120.5(4)
121.2(4)
121.5(4)
119.7(4)
120.3(4)
O(1)ꢀ
O(3)ꢀ
/
C(12)ꢀ
C(11)ꢀ
/
O(2) 126.0(4)
O(4) 125.8(4)
111.4(4)
111.4(4)
/
/X4
/
/
/
/X6
/
/X8
/
/
C12
C12
C14
C14
C18
120.0(5)
119.9(5)
119.0(5)
122.6(5)
119.7(3)
122.2(3)
117.3(4)
123.5(5)
/
/
/
/
/
/
/
/

Table 2 (Continued)
1a
1b
1c
1c×/1.25H2O
2×
/
CH3CN×
/
0.5H2O
3×
/
2CH2Cl2×2H2O
/
X6ꢀ
X7ꢀ
X8ꢀ
C11ꢀ
C13ꢀ
O5ꢀH5cꢀ
O5ꢀH5fꢀO3
S1ꢀC6ꢀ
S2ꢀC6ꢀ
C7ꢀ
/
C17ꢀ
C19ꢀ
C19ꢀ
/
C18
C20
C20
119.4(13)
123.7(13)
115.1(13)
121.2(4)
121.3(4)
120.8(5)
/
/
/
/
/
C12ꢀ
C14ꢀ
O1
/C15
114.3(3)
113.5(5)
/
/C16
/
/
164
164
/
/
/
/N1
122.1(6)
126.5(5)
117.5(6)
/
/N1
/
N1ꢀ
/
C9
(For compounds 1a, 1b, and 1c, Xꢀ
/
O; For compound 3, XꢀS).
/

108
X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ111
/
Fig. 6. VT 1H-NMR spectra of (a) Ru(RCOO)2dppf (Rꢀ
impurity).
/
CH3 (1a), RꢀCH3CH2 (1b)); (b) Ethyl group proton resonances of 1b. (#, from an
/
invariant P resonance in 1a and 1b, the P signal of 1c
exhibits VT-behaviour. The sharp signal at d 62.9 at 328
d 4.53 (n1/2
isomer C, the P signal (D) and the proton signals at d
ꢀ28 Hz) be assigned to the bis(bidentate)
/
K shifts to d 63.1 with broadening (n1/2
K), before resolving into several peaks which at 213 K
ꢀ131 Hz at 258
/
4.25 and 4.22 with peak(s) overlapping with d 4.33 to
the bidentateꢁmonodentate isomer D, and the P singlet
/
are seen at (C) d 62.9, (D) d 63.8 and d 65.5 (both d,
JPP
peak (E) and the two proton singlets at d 4.15 and d
4.61 to the bis(monodentate) isomer E. The presence of
a mixture of isomers is in agreement with the increased
complexity of the multiplet for the phenyl protons at
temperatures below 233 K. In view of the high reactivity
expected of the coordinatively and electronically un-
saturated 16e isomer Ru(h2-PhCOO)(h1-PhCOO)(dppf)
(D?) and the 14e isomer Ru(h1-PhCOO)2(dppf) (E?), it is
very likely they are present as the six-coordinate 18e
solvento complexes D and E. In the presence of a good
coordinating solvent, like CH3CN, such a solvento
complex (2) is indeed obtained (Scheme 3); herein the
unbound O atoms of bis(unidentate) benzoate are
hydrogen-bonded to a water ligand, which we believe
ꢀ42 Hz) and (E) d 59.8, with relative intensities
/
1.5:2:1. These observations are consistent with the
occurrence of a facile dynamic process at higher
temperatures, equilibrating all the P atoms, e.g. a rapid
monodentateꢁ
ligand, as reported previously for RuCl(OAc)(Cyttp)
(ttpꢀPhP(CH2CH2CH2PPh2)2) [3] and Ru(OAc)2PPh3-
(dppm) (dppmꢀPh2P(CH2)PPh2) [5]; slowing down of
/bidentate exchange of the carboxylate
/
/
the process with lowering of temperature, allows the
‘‘freezing out’’ of isomers containing monodentate and
bidentate benzoate ligands shown in Fig. 9. It is here
proposed that at 213 K, the P signal (C) and the
corresponding proton signals at d 4.33 (n1/2
ꢀ7 Hz) and
/
Fig. 7. Proposed isomers of 1b and 3. (1b: Eꢀ
/
O, Rꢀ
/
CH2CH3; 3: Eꢀ
/
S, RꢀN(CH2CH3)2).
/

X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ
/111
109
Fig. 8. VT NMR spectra of Ru(PhCOO)2dppf (1c) in CDCl3: (a) 1H spectra and (b) 31P{1H} spectra.
originates from water in the crystal lattice of 1c, since
the reaction was carried out in dried solvent. The non-
isolation of a monodentate carboxylate of 1a is con-
sistent with no indication of uni- and bidentate exchange
in studies of its VT-NMR spectral behaviour. However,
though this exchange is observed in the VT-NMR
spectra of 1b, a monodentate carboxylate derivative
from 1b has not been isolated. Presumably, the facile
The VT proton spectral changes of 3 in CDCl3 are
shown in Fig. 10. At 328 K, the proton spectrum of
complex 3 shows one sharp unresolved triplet at d 1.00
for the two Me groups and broad signals with relative
intensity ca. 1:3 at d 3.33 (n1/2
ꢀ/46 Hz) and 3.62 (n1/2
ꢀ
/
29 Hz) for the CH2 protons, and four equal-intensity
singlets at d 4.19, 4.32, 4.42 and 4.45 for the Cp protons
of dppf. The phenyl protons are seen as a singlet at d
bidentateꢁ/unidentate transformation in 1c is facilitated
7.70 together with a multiplet at d 7.24ꢁ7.19 (relative
/
by the electron-withdrawing effect of the phenyl ring in
weakening the M-O(carboxylate) bond.
intensity 2:3). As the temperature is lowered, the multi-
plicity of the Cp resonances changes, indicative of
alteration in equivalence of the rings. The 31P signal of
Fig. 9. Proposed isomers of [Ru(PhCOO)2dppf] (1c).

110
X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ111
/
Scheme 3.
Fig. 10. VT 1H-NMR spectra of Ru(SC(S)NEt2)2(dppf) (3) in CDCl3.
the dithiocarbamate complex 3 remains essentially
temperature-invariant, with only a small variation in
the chemical shift and line-width of the singlet signal as
broad peaks, which at 213 K are observed at d 3.00, 3.26
and 3.58 (n1/2 ca. 23 Hz) (relative intensity 1:2:1). The
incidence of uni- and bidentate dithio ligand exchange
as suggested here is reminiscent of earlier examples, viz.
follows: 328 K, d 47.1 (n1/2
(n1/2 110 Hz); 273 K, d 48.8 (n1/2
48.5 (n1/2 259 Hz); 233 K, d 48.6 (n1/2
K, d 48.9 (n1/2 81 Hz); 213 K, d 49.1 (n1/2
ꢀ
/
86 Hz); 300 K, d 48.9
336 Hz); 243 K, d
173 Hz); 223
48 Hz),
ꢀ
/
ꢀ
/
(C5Me5)M(S2CNMe2)2 (MꢀRh, Ir), conclusively stu-
/
ꢀ
/
ꢀ
/
died via kinetic line-shape analysis [30] and
CpMo(NO)(S2COMe)2, also studied by VT-NMR spec-
tral analysis [31]. Indeed, such phenomena are quite
ꢀ
/
ꢀ
/
indicating rapid exchange processes. The variation in
line broadening is in agreement with similar variations
in the methylene resonances of the ethyl group, dis-
cussed below. With decrease of temperature, the Me
resonance becomes resolved into two triplet signals of
equal intensity, becoming fully resolved at 253 K (d 0.98
and 0.88), in agreement with inequivalent Me groups.
This suggests that at these low temperatures, the
molecule is totally in the form of species B?/B (Fig. 7),
with one monodentate dithiocarbamate ligand, since
more than two Me resonances are expected for a
mixture of isomer A and B?/B or only one resonance
for isomer A. Below 300 K, the CH2 resonances
broaden, merging at 253 K into a broad ‘‘band’’ centred
common in transition metal complexes containing (SꢁS)
/
ligands and it has been pointed out in previous reports
that simultaneous mono- and bidentate coordination of
the SꢁS groups may arise because of geometrical
/
constraints imposed by the central metal atom or
electronic factors [32,33]. There is no evidence of
monomerꢁdimer equilibrium in 3 as found for
/
[Os(S2CNEt2)3]ꢂ [34].
4. Conclusion
The bis(RCOOꢃ) and bis(S2CNEt2ꢃ) ligands of
Ru(dppf) complexes exhibit temperature-dependent
at d 3.47 (n1/2
ꢀ185 Hz), before emerging again as three
/

X.L. Lu et al. / Journal of Organometallic Chemistry 688 (2003) 100ꢁ
/111
111
[8] L. Matas, J. Muniente, J. Ros, A. Alvarez-Larena, J.F. Piniella,
Inorg. Chem. Commun. 2 (1999) 364.
uni-bidentate exchange for Rꢀ
/
Et and Ph, but not for
RꢀMe. This fluxional difference among the analogues
/
[9] R.W. Mitchell, A. Spencer, G. Wilkinson, J. Chem. Soc. Dalton
Trans. (1973) 846.
was not expected. VT-NMR spectral observations of the
acetate and propionate complexes are consistent with
fluxionality of the bidentate dppf ligand involving
concerted twisting of the Cp rings around its axis and
bridge-reversal at Ru. These ligand geometric and
coordination mobilities, together with the stereochemi-
cal non-rigidity of the metal would make these com-
plexes potentially catalytic. The catalytic role of similar
carboxylate complexes in Pd(II) in Heck-type syntheses
is well documented. Our immediate target is to examine
related behaviour of these Ru(II) complexes and their
potential as precursors to enter into mixed-metal
carboxylates.
[10] A. Begiun, H.-C.h. Bottcher, G. Suss-Fink, B. Walther, J. Chem.
Soc. Dalton Trans. (1992) 2133.
[11] A. Salvini, P. Frediani, F. Piacenti, J. Mol. Catal. A: Chem. 159
(2000) 185.
[12] R. Noyori, Chem. Soc. Rev. 18 (1989) 187 (and references
therein).
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[16] H. Doucet, P.L. Gendre, C. Bruneau, P.H. Dixneuf, J.-C. Souvie,
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[17] K.S. Gan, T.S.A. Hor, in: A. Togni, T. Hayashi (Eds.),
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5. Supplementary material
[18] T. Ishiyama, M. Mori, A. Suzuki, N. Miyaura, J. Organomet.
Chem. 525 (1996) 225.
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre; 1a: CCDC No. 202630; 1b: 202631; 1c:
[19] J. Louie, M.S. Driver, B.C. Hamann, J.F. Hartwig, J. Org. Chem.
62 (1997) 1268.
202632; 1c×
/
1.25H2O: 202633; 2×
/
CH3CN×
/
0.5H2O:
[20] B.H. Simmons, Inorg. Synth. 12 (1970) 238.
[21] J.D. Gilbert, G. Wilkinson, J. Chem. Soc. (A) (1969) 1749.
[22] M. Menon, A. Pramanik, N. Bag, A. Charkravorty, J. Chem.
Soc., Dalton Trans. 10 (1995) 1543.
202634 and 3×
/
2CH2Cl2×2H2O: 202635. Copies of this
/
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB12
1EZ, UK (Fax: ꢂ44-1223-336033; e-mail: deposit@
[23] SMART and SAINT Software Reference manuals, version 6.22,
Bruker AXS Inc., Madison, WI, 2000.
[24] G.M. Sheldrick, SADABS software for empirical absorption
/
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
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¨ ¨
[25] SHELXTL Reference Manual, version 5.1, Bruker AXS Inc.,
Madison, WI, 1998.
Acknowledgements
[26] G. Suss-Fink, G. Herrmann, P. Morys, J. Ellermann, A. Veit, J.
Organomet. Chem. 284 (1985) 263.
Support of the National University of Singapore in
the form of Grant Nos. RP14300077112 and
RP143000135112 to L.Y.G. and research scholarship
to X.L.L. is gratefully acknowledged.
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