Diphenylphosphinopyridine (PPh2Py) versus 2-(2- diphenylphosphinomethyl)pyridine (PPh2CH2Py) in the coordination to ruthenium centres: Study of the reaction of PPh2Py containing formato-bridged dinuclear Ru(I) c

Article abstract of DOI:10.1016/j.ica.2004.12.061

Dinuclear carboxylato-bridged Ru(I) complexes [Ru₂(μ-RCOO) ₂(CO)₄L₂] (L = RCOOH; R = H, Me) were reacted with diphenylphosphinopyridine (PPh₂Py) and 2-(2- diphenylphosphinomethyl)pyridine (PPh₂

Full text of DOI:10.1016/j.ica.2004.12.061

Inorganica Chimica Acta 359 (2006) 745–752
www.elsevier.com/locate/ica
Diphenylphosphinopyridine (PPh2Py) versus
2-(2-diphenylphosphinomethyl)pyridine (PPh2CH2Py) in the
coordination to ruthenium centres: Study of the reaction of PPh2Py
containing formato-bridged dinuclear Ru(I) complexes and
PPh2CH2Py containing mononuclear formato Ru(II)
complexes with dithioles
*
´
´
˜
Esther de la Encarnacion, Josefina Pons, Ramon Yanez, Josep Ros
` `
Departament de Quı´mica, Facultat de Ciencies, Universitat Autonoma de Barcelona, E-08193 Bellaterra-Cerdanyola del Valles, Barcelona, Spain
Received 3 December 2004; accepted 20 December 2004
Available online 2 August 2005
Ruthenium and Osmium Chemistry Topical Issue
Abstract
Dinuclear carboxylato-bridged Ru(I) complexes [Ru2(l-RCOO)2(CO)4L2] (L = RCOOH; R = H, Me) were reacted with diph-
enylphosphinopyridine (PPh2Py) and 2-(2-diphenylphosphinomethyl)pyridine (PPh2CH2Py) ligands. In agreement with previously
reported results, the reaction with PPh2Py preserves the dinuclear structure of Ru(I) complexes [Ru2(l-RCOO)2(CO)4(PPh2Py)2]
(R = H (1) and Me (2)). On the other hand, the reaction with PPh2CH2Py leads to the formation of mononuclear ionic Ru(II) com-
plexes of the type [Ru(RCOO)(PPh2CH2Py)(CO)2][RCOO] (R = H (3) and Me (4)). The reaction of 1 with HS(CH2)nSH (n = 2, 3)
gives dinuclear dithiolato-bridged Ru(I) complexes [Ru2(l-S(CH)nS)(CO)4(PPh2Py)2] (n = 2 (5), 3 (6)). The equivalent reaction of
HSCH2CH2SH with 3 forms the mononuclear neutral complex [Ru(S(CH2)2S)(CO)2(PPh2CH2Py)] (7). These complexes were char-
acterised by elemental analyses, IR, 1H, 13C and 31P NMR spectroscopies. Additional liquid mass (with electrospray) spectrometry
was used for complexes 3 and 4.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Phosphino-pyridine ligands; Dinuclear ruthenium (I) complexes; Ruthenium (II) complexes
1. Introduction
received much interest on account of their unusual
edge-sharing bioctahedral structures which stretch to
other bridging anionic groups like pyrazolato or thio-
lato ligands [5–8].
Over the course of recent years our research group has
been studying the synthesis and reactivity of carboxylate
and thiolate-bridged dinuclear ruthenium (I) complexes
of the type ½Ru2ðl-LÞ2ðCOÞ4L02ꢀ (L = RCOO, RS or 1/2
S(CH2)nS; L0 = RCOOH or monodentate ligand) [9].
Dinuclear Ru(I) compounds are very interesting from
both structural and reactivity points of view because it
Special attention was paid to ruthenium (I) and (II)
complexes containing carbonyl and carboxylato ligands
since they have shown very promising catalytic activities
in hydrogenation and carbonylation of organic sub-
strates [1–4]. Dinuclear ruthenium (I) complexes have
*
Corresponding author. Tel.: +34 93 581 1889; fax: +34 93 581
3101.
E-mail address: Josep.Ros@uab.es (J. Ros).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.12.061

746
E. de la Encarnacio´n et al. / Inorganica Chimica Acta 359 (2006) 745–752
`
has been revealed that different associations are possible
in solution and in the solid state depending on the nature
of the bridge and on the ancillary ligands [10–12].
Whereas terminal L0 ligands form ½Ru2ðl-LÞ2ðCOÞ4L02ꢀ
complexes with L0 coordinated trans to metal, bidentate
L0–L0 amines or phosphines can form [Ru2(l-L)2(CO)4-
(L0–L0)2] or cationic [Ru2(l-L)(l-L0–L0)2(CO)4]+ and
[Ru2(l-L)(l-CO)2(CO)2(L0–L0)2]+ compounds. The
resulting structure is mainly due to the stability of the bite
angle of the L0–L0 ligand. The reaction of the [Ru2(l-
RCOO)2(CO)4]n polymer with PPh2Py was reported in
1997 by Haines, who described the formation of neutral
[Ru2(l-RCOO)2(CO)4(PPh2Py)2] and cationic [Ru2(l-
RCOO)2(CO)4(l-PPh2Py)2]+ complexes [13]. Related
arene ruthenium (II) complexes with PPh2Py and
PPh2CH2Py bidentate ligands were previously synthes-
ised by our group and used as catalyst precursors in the
hydrogenation of alkenes and alkynes [14].
sitat Autonoma de Barcelona on a Carlo Erba CHNS
EA-1108 instrument. Infrared spectra were run on a
Perkin–Elmer FT spectrophotometer series 2000 as
KBr pellets in the range 4000–100 cmꢁ1 under a nitrogen
atmosphere. The 1H NMR, 13C{1H} NMR, {1H}31P
NMR, COSY, HMQC, and NOESY spectra were run
on Bruker AC-250, Bruker Advance-250 and Bruker
AM-400 spectrometers. Numbering scheme of ligands
is given in Fig. 1. Chemical shifts (d) are given in ppm.
Electrospray-EM spectra (FIA-ESI-MS) were per-
formed by the staff of the Scientific-Technique Service
of the Universitat de Barcelona on a Platform II instru-
ment (Micromass, Manchester, UK) by using a Phoenix
20 syringe pump (C. E. Instruments, Milan, Italy) as an
infusion pump. The carrier was acetonitrile.
2.2. Synthesis
In order to complete these previously reported
results, this research paper presents the study of the
reactivity of 2-(2-diphenylphosphinomethyl)pyridine
(PPh2CH2Py) with dinuclear Ru(I) complexes [Ru2(l-
RCOO)2(CO)4(RCOOH)2] (R = H (1) and Me(2)). Sur-
prisingly, whereas the reaction with PPh2Py led to the
formation of dinuclear carboxylato bridged Ru(I) com-
plexes [Ru2(l-RCOO)2(CO)4(PPh2Py)2] or [Ru2(l-
RCOO)2(CO)4(l-PPh2Py)2]+ in the presence of CO
and NH4PF6 [7], the same reaction with PPh2CH2Py
produces mononuclear cationic Ru(II) complexes of
the type [Ru(RCOO)(CO)2(PPh2CH2Py)][RCOO] (R = H
(3), Me (4)) which contain CO, RCOO and PPh2CH2Py
2.2.1. [Ru2(l-HCOO)2(CO)4(PPh2Py)2] (1)
0.30 g of Ru3(CO)12 (0.47 mmol) were refluxed in 15
mL of formic acid for 2 h. The solution was cooled at
room temperature and 0.36 g (1.35 mmol) of PPh2Py
were added by stirring. The reaction mixture was re-
fluxed for 1/2 h and the solvent was removed in vacuo.
The residue was dissolved in dichloromethane and the
product was precipitated by adding hexane. The product
was filtered off, washed with hexane and dried in vacuo.
Yield: 72%.
Anal. Calc. for Ru2C40H30N2O8P2 Æ CH2Cl2: C, 48.5;
1
H, 3.2; N, 2.8. Found: C, 49.0; H, 3.1; N, 2.4%. H
NMR (CDCl3) d: 7.46 (m, 26H, Ph, Py), 8.13 (s, 2H,
HCOO), 8.81 (d, J(H,H) = 4.4 Hz, 2H, L-Py) ppm.
13C{1H} NMR (CDCl3) d: 123.2–135.6 (Ph, Py), 150.1
(t, J = 6.9 Hz, L), 176.4 (t, J = 6.9 Hz, HCOO), 204.2
(CO) ppm. 31P{1H} NMR (CDCl3) d: 15.4 (s) ppm.
coordinated ligands and
a RCOO counteranion.
Moreover, cationic carboxylato containing ruthenium
(II) complexes were obtained with the related
PPh2CH2CH2Py ligand [15]. Following the previously
synthetic method developed in our group, we were able
to replace carboxylate RCOO anions by a dithiolato
S(CH2)nS (n = 2, 3) ligand, [9d]. Consequently, this reac-
tion yielded dinuclear Ru(I) and mononuclear Ru(II)
dithiolato complexes [Ru2(l-S(CH)nS)(CO)4(PPh2Py)2]
(n = 2 (5), 3 (6)) and [Ru(S(CH2)2S)(CO)2(PPh2CH2Py)]
(7), respectively.
IR (KBr): m(CO): 2030 (s), 1986 (m), 1958 (s) cmꢁ1
,
m(OCO): 1592 (m) cmꢁ1
.
J
J
I
K
K
L
I
2. Experimental
L
Q
G
N
N
2.1. General details
Ph2P
PPh2
H2
C
a
All reactions were carried out with the use of vacuum
line and Schlenk techniques. Ru3(CO)12 and other re-
agents were used as received. All solvents were dried
and distilled prior to use, according to standard proce-
dures. PPh2Py [16] and PPh2CH2Py [17] were prepared
by published methods.
a
a
H2
C
H2C
S
CH2
b
C
H2
S
S
S
a
The elemental analyses (C, N, H) were carried out by
the staff of the Chemical Analyses Service of the Univer-
Fig. 1. Numbering scheme of ligands.

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747
2.2.2. [Ru2(l-MeCOO)2(CO)4(PPh2Py)2] (2)
This compound was prepared in the same manner as
1 using 0.10 g of Ru3(CO)12 (0.16 mmol) and 15 mL of
acetic acid. Yield: 65%.
COO), 194.8 (d, J = 12.9 Hz, CO), 195.5 (d, J = 12.5
Hz, CO) ppm. 31P{1H} NMR (CDCl3): d = 58.7 (s)
ppm. IR (KBr): m(CO): 2064 (s), 2000 (s) cmꢁ1
,
m(OCO): 1569 (s) cmꢁ1
.
Anal. Calc. for Ru2C42H34N2O8P2: C, 52.6; H, 3.6; N,
2.9. Found: C, 51.6; H, 3.6; N, 2.7%. 1H NMR (CDCl3)
d: 1.65 (s, 6H, MeCOO), 7.42 (m, 26H, Ph, Py), 8.77 (d,
J(H,H) = 4.4 Hz, 2H, L-Py) ppm. 13C{1H} NMR
(CDCl3) d: 23.3 (MeCOO), 123.0–135.2 (Ph, Py), 150.0
(t, J = 6.5 Hz, L), 185.7 (t, J = 7.4 Hz, MeCOO),
204.9 (t, J = 3.7 Hz, CO) ppm. 31P{1H} NMR (CDCl3)
d:17.0 (s) ppm. IR (KBr): m(CO): 2026 (s), 1982 (m),
2.2.5. [Ru2(l-SCH2CH2S)(CO)4(PPh2Py)2] (5)
A solution of 0.10 g (0.11 mmol) of 1 and 0.0074
mL (0.88 mmol) of 1,2-ethanedithiol in 20 mL of tolu-
ene was refluxed for 2 h, after which time the solvent
was removed in vacuo and dichloromethane was
added. The product was precipitated with diethyl ether,
filtered off, washed with hexane and dried in vacuo.
Yield: 78%.
1953 (s) cmꢁ1, m(OCO): 1571 (s) cmꢁ1
.
Anal. Calc. for Ru2C40H32N2O4P2S2: C, 51.5; H, 3.5;
N, 3.0. Found: C, 52.5; H, 3.7; N, 2.6%. 1H NMR
(CDCl3) d: 0.93 (s, 2H, CH2), 7.38 (m, 26H, Ph, Py),
8.68 (d, 2H, J(H,H) = 4.19 Hz, L-Py) ppm. 13C{1H}
NMR (CDCl3) d: 32.2 (s, Ca) 123.0–136.3 (Ph, Py),
149.8 (t, J = 6.7 Hz, L), 203.4 (s, CO) ppm. 31P{1H}
NMR (CDCl3) d: 39.56 (s) ppm. IR (KBr): m(CO):
2.2.3. [Ru(HCOO)(CO)2(PPh2CH2Py)][HCOO] (3)
A mixture of 0.30 g of Ru3(CO)12 (0.47 mmol) and 15
mL of formic acid was refluxed for 2 h and cooled at
room temperature. 0.49 g of PPh2CH2Py (1.76 mmol)
were added and the mixture was refluxed for 1/2 h.
The solvent was evaporated in vacuo to dryness and
the residue was dissolved in dichloromethane. The prod-
uct was precipitated with diethyl ether. Yield: 63%.
Anal. Calc. for RuC22H18NO6P: C, 50.4; H, 3.5; N,
2.7. Found: C, 49.2; H, 3.4; N, 2.2%. ES (+) MS (m/
z): 479 (100%) [Ru(HCOO)(CO)2(PPh2CH2Py)]+
2013 (s), 1977 (m), 1948 (s) cmꢁ1
.
2.2.6. [Ru2(l-S(CH2)3S)(CO)4(PPh2Py)2] (6)
This compound was prepared in the same manner as
5 using 0.10 g (0.11 mmol) of 1 and 0.088 mL (0.88
mmol) of 1,3-propanedithiol. Yield: 75%.
1
(C21H17NO4PRu). H NMR(CDCl3) d: 4.05 (dd, 1H,
J(H,H) = 16.7, J(H,P) = 12.4, CH2), 4.38 (dd, 1H,
J(H,H) = 16.7 Hz, J(H,P) = 12.2 Hz, CH2), 7.63 (m,
13H, Ph, Py), 7.85 (s, 1H, HCOO anion), 8.47 (d, 1H,
Anal. Calc. for Ru2C41H34N2O4P2S2: C, 52.0; H, 3.6;
N, 3.0. Found: C, 51.5; H, 4.3; N, 2.5%. 1H NMR
(CDCl3) d: 0.93 (broad, 6H, CH2), 7.49 (m, 26H, Ph,
Py), 8.71 (d, J(H,H) = 4.12 Hz, 2H, L-Py) ppm.
13C{1H} NMR (CDCl3) d: 19.7 (s, Ca), 34.5 (s, Cb),
123.1–135.7 (Ph, Py), 149.9 (t, J = 8.0 Hz, L), 201.9 (t,
J = 7.6 Hz, CO) ppm. 31P{1H} NMR (CDCl3) d:
41.77 (s) ppm. IR (KBr): m(CO): 2014 (s), 1978 (m),
J(H,P) = 10.93
Hz,
HCOO),
8.98
(d,
1H,
J(H,H) = 5.37 Hz, L-Py). 13C{1H} NMR (CDCl3) d:
41.1 (d, J = 31.2 Hz, G), 123.6–139.9 (Ph, Py), 151.8
(s, L), 159.7 (d, J = 3.8 Hz, Q), 167.1 (HCOO anion),
167.9 (d, J = 3.4 Hz, HCOO), 194.5 (d, J = 12.5 Hz,
CO), 195.8 (d = 12.9 Hz, CO) ppm. 31P{1H} NMR
(CDCl3) d: 58.3 (s) ppm. IR (KBr): m(CO): 2069 (s),
1948 (s) cmꢁ1
.
2006 (s) cmꢁ1, m(OCO): 1624 (s) cmꢁ1
.
2.2.7. [Ru(SCH2CH2S)(CO)2(PPh2CH2Py)] (7)
0.10 g (0.21 mmol) of 3 and 0.074 mL (0.88 mmol) of
1,2-ethanedithiol were refluxed in 20 mL of toluene for 2
h. The evaporation of solvent in vacuo and the addition
of hexane gave the desired product. Yield 80%.
Anal. Calc. for RuC22H20NO2PS2: C, 50.2; H, 3.8; N,
2.7. Found: C, 49.2; H, 3.8; N, 2.2%. 1H NMR (CDCl3) d:
2.31 (dddd, 1H, 2J(Ha,Hc) = 11.80 Hz, 3J(Ha,Hb) = 7.87
2.2.4. [Ru(MeCOO)(CO)2(PPh2CH2Py)][MeCOO]
(4)
This compound was prepared in the same manner as
3 using 0.30 g of Ru3(CO)12 (0.47 mmol), 15 mL of ace-
tic acid and 0.37 g of PPh2CH2Py (1.35 mmol). Yield:
52%.
Anal. Calc. for RuC24H22NO6P Æ CH2Cl2: C, 47.1; H,
3.8; N, 2.2. Found: C, 48.1; H, 4.4; N, 2.0%. ES (+) MS
(m/z): 493 (100%) [Ru(MeCOO)(CO)2(PPh2CH2Py)]+
(C22H19NO4PRu). 1H NMR (CDCl3) d: 1.53 (s, 3H,
CH3COO), 2.20 (s, 3H, CH3COO anion), 3.99 (dd,
1H, J(H,H) = 16.4 Hz, J(H,P) = 11.6 Hz, CH2), 4.34
(dd, 1H, J(H,H) = 16.4 Hz, J(H,P) = 12.2 Hz, CH2),
7.68 (m, 13H, Ph, Py), 8.98 (d, 1H, J(H,H) = 5.69 Hz,
L-Py) ppm. 13C{1H} NMR (CDCl3) d: 22.8 (s,
CH3COO anion), 23.3 (d, J = 4.3 Hz, CH3COO), 41.5
(d, J = 31.2 Hz, G), 123.2–139.5 (Ph, Py), 152.0 (s, L),
159.8 (s, Q), 176.1 (s, MeCOO anion), 177.1 (d, Me-
3
4
Hz, J(Ha,Hd) = 3.32 Hz, Ha), J(Ha,P) = 1.23 Hz, 2.47
(dddd, 1H, 2J(Hb,Hd) = 11.25 Hz, 3J(Ha,Hb) = 7.87
3
4
Hz, J(Hb,Hc) = 3.33 Hz, J(Hb,P) = 2.10 Hz, Hb), 2.59
2
3
(dddd, 1H, J(Ha,Hc) = 11.80 Hz, J(Hb,Hc) = 3.33 Hz,
3J(Hc,Hd) = 7.53 Hz, 4J(Hc,P) = 1.00 Hz, Hc), 2.79
(dddd, 1H, 2J(Hb,Hd) = 11.25 Hz, 3J(Ha,Hd) = 3.32
3
4
Hz, J(Hc,Hd) = 7.53 Hz, J(Hd,P) = 2.27 Hz, Hd), 4.12
(dd, 1H, J(H,H) = 16.8 Hz, J(H,P) = 13.3 Hz, CH2Py),
4.42 (dd, 1H, J(H,H) = 16.8 Hz, J(H,P) = 10.0 Hz,
CH2Py), 7.51 (m, 13H, Ph, Py), 9.78 (d, 1H,
J(H,H) = 5.5 Hz, L-Py) ppm. 13C{1H} NMR (CDCl3)
d: 36.7(s, SCH2CH2S), 36.9 (s, SCH2CH2S), 42.8 (d,

748
E. de la Encarnacio´n et al. / Inorganica Chimica Acta 359 (2006) 745–752
J = 28.8 Hz, G), 123.5–138.9 (Ph, Py), 152.2 (s, L), 160.7
(d, J = 5.20 Hz, Q), 192.3 (d, J = 8.64 Hz, CO), 199.2 (d,
J = 9.12 Hz, CO) ppm .31P{1H} NMR (CDCl3) d: 47.6
respectively), which indicate a cis geometry of carbonyl
ligands. A third very broad and intense band corre-
sponding to the carboxylate group is observed at 1624
1
(s) ppm. IR (KBr): m(CO): 2039 (s), 1979 (s) cmꢁ1
.
and 1569 cmꢁ1, respectively. H and 13C NMR spectra
measured in CDCl3 display the signals corresponding to
coordinated PPh2CH2Py and RCOO ligands and the
RCOO counteranion. Methylene protons are diastereo-
topic thus leading to two doublets of doublets with ex-
pected 2J(H,H) and 2J(H,P) values. The {1H}31P spectra
3. Results and discussion
Complexes [Ru2(l-RCOO)2(CO)4(PPh2Py)2] (R = H
(1), Me (2)) previously described by J. S. Field and
col. [13] were obtained by reacting prepared in situ
[Ru2(l-RCOO)2(CO)4(RCOOH)2] complexes with 2
molar equivalents of PPh2Py under reflux (Scheme 1).
Complexes 1 and 2 were obtained in 72% and 65% yield,
respectively, and their elemental analyses together with
IR and NMR (1H, 13C, 31P) spectra validate their for-
mation and purity. Synthetic method, analytical and
spectroscopic data for 1 and 2 are displayed in Section
2. In like manner, the reaction of prepared in situ
[Ru2(l-RCOO)2(CO)4(RCOOH)2] (R = H, Me) com-
plexes with 2 molar equivalents of PPh2CH2Py in a re-
flux of 1/2 h gave in moderate yields, air-unstable
yellow products which were soluble in alcohols but
insoluble in low polar solvents like ether, THF or
CH2Cl2. These compounds were characterised as
[Ru(RCOO)(CO)2(PPh2CH2Py)][RCOO] (R = H (3),
Me (4)) (Scheme 2). The ionic compounds 3 and 4 exhi-
bit two intense bands in the CO stretching region of
2
of complexes 3 and 4 allowed us to assign the J(H,H)
values for each proton (between 12.4 and 11.6 Hz)
and to distinguish between signals of coordinated and
uncoordinated HCOO formate anions for complex 3.
13C NMR spectra of complexes 3 and 4 display signals
of carboxylato, carbonyl and phosphine ligands to-
gether with those of uncoordinated carboxylate anions.
NMR heteronuclear HMQC and homonuclear COSY
1
spectra were used to assign signals of H and 13C spec-
tra to most H and C atoms of these complexes. Com-
plete NMR data are presented in Section 2. The
{1H}31P NMR spectra of these complexes exhibit well-
resolved singlets at 58.3 ppm for 3 and 58.7 ppm for
4, respectively, which are consistent with the chelated
bicoordination of the PPh2CH2Py ligand [16]. The posi-
tive ionisation spectra of complexes 3 and 4 gave peaks
with m/z values of 479 and 493, respectively, thus cor-
roborating thus the ionic nature of the products. Even
though we were unable to obtain complexes 3 or 4
in a crystalline form to undertake a crystal structure
their IR spectra (2069, 2066 and 2064, 2000 cmꢁ1
,
Scheme 1.
R
O
Ru
OC
OC
O
3
Ru3(CO)12 + 6 RCOOH + 3 PPh2CH2Py
+ 3 [RCOO]
+ 6 CO
+ 3/2 H2
N
Ph2P
R = H (3)
R = Me (4)
Scheme 2.

E. de la Encarnacio´n et al. / Inorganica Chimica Acta 359 (2006) 745–752
749
determination, analytical and spectroscopic data have
allowed us to assign to cationic complexes the structure
shown in Scheme 2. That structure is in agreement with
spectroscopic data that suggest that CO ligands are in a
cis disposition and that both RCOO and PPh2CH2Py li-
gands act as bidentate ligands. In addition, the observed
2J(P,C) coupling constants of ca. 12.5 Hz clearly con-
firm the cis disposition of CO and P ligands. Cation
complexes 3 and 4 should exist in two enantiomeric
forms.
Following the synthetic method previously developed
in our laboratory, we attempted the substitution of the
HCOO bridge by thiolato or dithiolato ligands in the
dinuclear system [Ru2(l-HCOO)2(CO)4(PPh2Py)2] (1).
The reaction of 1 with an excess of RSH thiols gave
the total substitution of the formato ligand and the for-
mation of a mixture of products which could not be sep-
arated by column chromatography. However, the
reaction with HS(CH2)nSH led to the formation of
[Ru2(l-(CH)nS2)(CO)4(PPh2Py)2] (n = 2 (5), 3 (6)) in
H
H
(CH2)n
O
O
S
S
O
O
HS(CH2)nSH
- 2 HCOOH
Ru
Ru
PPh2Py
PyPh2P
OC
PyPh2P
OC
Ru
Ru
PPh2Py
CO
CO
CO
OC
OC
CO
Scheme 3. n = 2 (5); n = 3 (6).
H
O
Ru
S
OC
OC
O
N
OC
OC
S
N
HSCH2CH2SH
Ru
[HCOO]
- 2HCOOH
Ph2P
Ph2P
(7)
Scheme 4.
2.80
2.76
2.72
2.68
2.64
2.60
2.56
(ppm)
2.52
2.48
2.44
2.40
2.36
2.32
2.28
1
Fig. 2. 31P coupled (up) and decoupled (down) H NMR 500 Mz spectrum of 7 in the SCH2CH2S region with Gaussian treatment.

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E. de la Encarnacio´n et al. / Inorganica Chimica Acta 359 (2006) 745–752
good yields (Scheme 3). These yellow compounds are
soluble in MeOH, THF and CH2Cl2 but insoluble in
hexane. Analytical and spectroscopic data of 5 and 6
agree with the formation of dinuclear dithiolato-bridged
Ru(I) complexes analogous to those peviously described
in the literature [8,9d,18]. IR spectra of complexes 5 and
6 exhibit three bands in the stretching CO region with
the common pattern of [Ru2(l-X)(CO)4L2] complexes
improve the resolution of peaks and thus calculate the
J(H,H) and J(H,P) coupling constants (Fig. 2). This
method showed that each proton is coupled with the
corresponding geminal one, with each proton of the
neighbouring CH2 and with the P atom, giving rise to
a double ddd system. The decoupled {31P}1H NMR
spectrum shows how these signals turn into dd systems,
which allowed us to determine the geminal 2J(H,H) and
1
4
[19]. H and 13C NMR spectra of complexes show sig-
the J(H,P) constants. The COSY (Fig. 3) and NOESY
nals of coordinated ligands compatible with in a C2v
(Fig. 4) experiments were performed to assign signals to
protons Ha, Hb, Hc and Hd of SCH2CH2S fragment.
1
symmetry setting. H and 13C NMR signals were as-
signed by means of cross-peak system in the HMQC
spectra of complexes. {1H}31P NMR spectra of these
compounds show well-resolved singlets at ca. 40 ppm,
supporting the P-coordination of PPh2Py ligand.
The reaction of mononuclear Ru(II) complex [Ru(H-
COO)(CO)2(PPh2CH2Py)][HCOO] (3) with an excess of
HS(CH2)2SH at reflux of toluene gave the neutral com-
plex [Ru(SCH2CH2S)(CO)2(PPh2CH2Py)] (7) in 80%
yield (Scheme 4). This yellow compound 7 is soluble in
MeOH, THF and CH2Cl2 but insoluble in hexane.
Two intense bands in the stretching CO region of the
IR spectrum are consistent with a cis geometry of car-
1
bonyl ligands. The H NMR spectrum displays a com-
plicated whole of signals corresponding to coordinated
SCH2CH2S and PPh2CH2Py ligands. Thus, dithiolate
protons are observed as four multiplet signals between
2.31 and 2.79 ppm and CH2 protons of PPh2CH2Py li-
gand appear at 4.12 and 4.42 ppm as two doublets of
doublets (2J(H,H) = 16.80 Hz and J(H,P) = 13.30 and
2
Fig. 4. Detail of NOESY spectrum of 7 in the SCH2CH2S region.
9.98 Hz). Signals of phenyl and pyridine are observed
at 7.20–7.82 ppm except proton L which is observed at
9.78 ppm. Since the proton spectrum determined at
250 MHz apparatus shows a complicated spin system
of CH2CH2 group of the dithiolate ligand, we measured
the spectrum with a 500 MHz apparatus using a Gauss-
ian treatment of the Fourier transformation in order to
Table 1
1H NMR results: chemical shifts (ppm, CDCl3); 1H, 1H and 1H, 31P
coupling constants (Hz) for SCH2CH2S fragment of 7
c Hb
H
Hd
Ha
C
C
S
S
d Ha
d Hb
d Hc
d Hd
2.31
2.47
2.59
2.79
2J(Ha,Hc) = 11.80
2J(Hb,Hd) = 11.25
3J(Ha,Hb) = 7.87
3J(Ha,Hd) = 3.32
3J(Hb,Hc) = 3.33
3J(Hc,Hd) = 7.53
4J(Ha,P) = 1.23
4J(Hc,P) = 1.00
4J(Hb,P) = 2.10
4J(Hd,P) = 2.27
Ha
Hb
S
S
Hc
Hd
Ru
Fig. 5. Eclipsed disposition of hydrogens of the SCH2CH2S ligand
Fig. 3. Detail of COSY spectrum of 7 in the CH2 region.
in 7.

E. de la Encarnacio´n et al. / Inorganica Chimica Acta 359 (2006) 745–752
751
Fig. 6. Detail of NOESY spectrum of 7 showing NOE interaction of L proton of PPh2CH2Py ligand with Hc and Hd.
Chemical shifts d and J(H,H) and J(H,P) coupling
constants for this SCH2CH2S fragment are displayed
in Table 1. Geminal 2J(H,H) values of @3 Hz and
3J(H,H) coupling constants of @8 Hz agree with a nearly
eclipsed conformation of the SH2CH2S chain as seen in
Fig. 5 [20]. The detailed analysis of cross peaks from sig-
nals of Ha, Hb, Hc and Hd protons of the NOESY spec-
trum of 7 (Fig. 4) corroborates this conformation thus,
signals of Ha/Hc and Hb/Hd interactions are intense
whereas those corresponding to Ha/Hb and Hc/Hd are
weak. In addition, no H–H NOE interaction was ob-
served for Ha/Hd and Hb/Hc pairs of protons. The pres-
ence of two doublets at 192.3 and 199.2 ppm,
4. Conclusions
The present paper has established different reactivity
of dinuclear carboxylato-bridged ruthenium (I) com-
plexes with PPh2Py and PPh2CH2Py ligands. Whereas
the reaction with PPh2Py does not alter the dinuclear
nature of complexes exchanging CO ligands trans to me-
tal–metal bond (this work) or acting as a bridge between
metals [13], the reaction with PPh2CH2Py leads to the
formation of cationic mononuclear ruthenium (II) com-
plexes. Apparently, this important difference would
arise from the P–N bite angle which preferably stabilises
five-member metallocycles. This reactivity of dinuclear
carboxylato-bridged ruthenium (I) with P–N ligands is
different to that with diphosphine ligands previously
reported by Sherlock et al. [7]. These authors showed
that the reaction with 1 equivalent of R2PCH2PR2
(L2) yields the usual polymers [Ru2(l-RCOO)2(CO)4-
(L2)]n whereas reaction with 2 equivalents of ligand L2
(L2 = R2PCH2PR2 or R2PCH2CH2PR2) yields the neu-
tral substituted dimer [Ru2(l-RCOO)2(CO)4(g1-L2)].
Two types of cationic dinuclear compounds [Ru2-
(l-RCOO)(CO)4(L2)2]+ are obtained when the reaction
is performed in alcohols. Our results point out that P–
P and P–N ligands do not lead the same type of prod-
ucts, therefore opening a new path to the synthesis of
mononuclear dicarbonyl ruthenium (II) complexes con-
taining anionic (carboxylato or dithiolato) and neutral
(PPh2CH2Py) ligands. The structures of these new com-
pounds were established by different NMR techniques.
2
respectively, with J(C,P) of 8.64 and 9.12 ppm in the
{1H}13C NMR spectrum of 7 suggests a cis disposition
of CO ligands with respect to phosphorus atom [21].
This hypothesis was confirmed as well by the NOE inter-
action between proton L (ortho in relation to N) of the
pyridine ring and Ha and Hb protons of the dithiolate li-
gand observed in the NOESY spectrum (Fig. 6), all of
which suggests that this two hydrogens point towards
the pyridine of the PPh2CH2Py ligand. A structure opti-
misation of 7 using the WebLab ViewerPro software [22]
taking into account the cis disposition of all ligands, de-
duced from spectroscopic data, is shown in Fig. 7. Like
complexes 5 and 6, this dithiolato complex should exist
in two enantiomeric forms.
Acknowledgement
This work was supported by the Ministerio de Edu-
´
cacion y Ciencia of Spain, Project BQU2003-03582.
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