High versatility of 3,4-dimethyl-1-phenyl-phosphole and 3-methyl-1-phenyl-phosphole as ligands in the reaction with [Re 2(CO)8(CH3CN)2] and [Ru3(CO)12]: X-ray structures of [Re2(CO)7(1:2:2-PhPC 4H2Me2)], [Re2(CO)7(1:2:2-PhPC4H3Me)] and [Ru2(CO)4(PhPC 4H3Me)2]

Article abstract of DOI:10.1016/j.ica.2013.04.002

The reaction of [Re₂(CO)₈(CH₃CN) ₂] with 3,4-dimethyl-1-phenylphosphole affords three chromatographically inseparable isomers of [Re₂(CO) ₈(PhPC₄H₂Me₂)₂] (1) identified by means of spectroscopic methods, in which the phosphole ligand acts as a tertiary phosphine bonded through the phosphorus atom, and the σ-π complex [Re₂(CO)₇(¹: ²:²-PhPC₄H₂Me ₂)] (2) obtained in low yields. Thermolysis of the mixture of isomers gives (2) in good yields, while photolysis in dichloromethane at room temperature causes metal-metal bond cleavage to give [Re(CO) ₄(PhPC₄H₂Me₂)Cl] (3) and [Re(CO)₅Cl] (4). The reaction with 3-methyl-1-phenyl-phosphole gives only the σ-π complex [Re₂(CO)₇(¹: ²:²-PhPC₄H₃Me)] (5). Furthermore, the main product of the reaction of [Ru₃(CO) ₁₂] with 3-methyl-1-phenyl-phosphole was [Ru₂(CO) ₄(PhPC₄H₃Me)₂] (6) a sandwich type complex without metal-metal bond.

Full text of DOI:10.1016/j.ica.2013.04.002

Inorganica Chimica Acta 404 (2013) 77–81
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
High versatility of 3,4-dimethyl-1-phenyl-phosphole and 3-methyl-1-
phenyl-phosphole as ligands in the reaction with [Re2(CO)8(CH3CN)2]
and [Ru3(CO)12]: X-ray structures of [Re2(CO)7(g1 g2 2-PhPC4H2Me2)],
: :g
[Re2(CO)7(g1 g2 2-PhPC4H3Me)] and [Ru2(CO)4(PhPC4H3Me)2]
: :g
a
a
a
a
Yomaira Otero a, , Alejandro Arce , Ysaura De Sanctis , Rubén Machado , María C. Goite ,
⇑
Teresa Gonzalez b, Alexander Briceño b
a Laboratorio de Química de Metales de Transición, Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Química, Apartado 21827, Caracas 1020-A, Venezuela
b Laboratorio de Caracterización de Nuevos Materiales, Instituto Venezolano de Investigaciones Científicas (IVIC), Centro de Química, Apartado 21827, Caracas 1020-A, Venezuela
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of [Re2(CO)8(CH3CN)2] with 3,4-dimethyl-1-phenylphosphole affords three chromatograph-
ically inseparable isomers of [Re2(CO)8(PhPC4H2Me2)2] (1) identified by means of spectroscopic methods,
in which the phosphole ligand acts as a tertiary phosphine bonded through the phosphorus atom, and the
Received 18 December 2012
Received in revised form 22 March 2013
Accepted 5 April 2013
r–p : :g
complex [Re2(CO)7(g1 g2 2-PhPC4H2Me2)] (2) obtained in low yields. Thermolysis of the mixture
Available online 18 April 2013
of isomers gives (2) in good yields, while photolysis in dichloromethane at room temperature causes
metal–metal bond cleavage to give [Re(CO)4(PhPC4H2Me2)Cl] (3) and [Re(CO)5Cl] (4). The reaction with
3-methyl-1-phenyl-phosphole gives only the
Furthermore, the main product of the reaction of [Ru3(CO)12] with 3-methyl-1-phenyl-phosphole was
[Ru2(CO)4(PhPC4H3Me)2] (6) a sandwich type complex without metal–metal bond.
Ó 2013 Elsevier B.V. All rights reserved.
Keywords:
Phospholes
Dinuclear rhenium
Triruthenium cluster
r–p Complex
r–p : :g
complex [Re2(CO)7(g1 g2 2-PhPC4H3Me)] (5).
Sandwich complexes
1. Introduction
phosphole. In general, its mode of bonding is restricted to the
two-electron type typical of a tertiary phosphine [7].
The chemistry of phospholes is governed by their low aromatic-
ity and the strong overlap between the P–R exocyclic bond
As part of our work on the reactivity of phospholes ligands with
transition metal carbonyls, we have investigated the reaction of
3,4-dimethyl-1-phenyl-phosphole toward triosmium and triruthe-
nium clusters [8–9] and we have found simple substitution com-
plexes, derivatives containing ring-opened ligands and the
insertion of a phospholide unit into a metal–metal bond. Herein
we report the coordination behavior of 3,4-dimethyl-1-phenyl-
phosphole and 3-methyl-1-phenyl-phosphole ligands toward
[Re2(CO)8(CH3CN)2], giving rise not only to mono- and binuclear
r–p
and the dienic system. Hence, phospholes may formally be consid-
ered as two-electron donors, when only the lone-pair electrons of
the phosphorus atom takes part in coordination. They also behave
as four-electron donors when the dienic system is coordinated, but
if both functions operate simultaneously a six-electron donor li-
gand is obtained [1]. The area of coordination chemistry is favored
with the development of these rings, and phosphole-complexes
now known have been used in many catalytic transformations of
synthetic relevance, such as hydroformylation, hydrosilylation or
asymmetric allylic substitution [2–5]. They have also been investi-
derivates but also to
r–p complexes. We also report a bimetallic
sandwich Ru-complex obtained from the reaction of 3-methyl-1-
phenyl-phosphole with [Ru3(CO)12].
´
´
gated in fields as diverse as OLEDs, WOLEDs and non linear optics
[6].
The compound 3,4-dimethyl-1-phenylphosphole is frequently
used as a ligand in complexes prepared as potential catalysts,
and there is a vast literature on the formation, characterization,
and practical applications of mononuclear complexes with this
2. Experimental
2.1. General remarks
[Re2(CO)10(CH3CN)2], 3,4-dimethyl-1-phenyl-phosphole and
3-methyl-1-phenyl-phosphole were synthesized as previously de-
scribed [10,11]. All solvents were purified by standard tech-
niques.[12] 1H, 13C and 31P NMR spectra were recorded using
⇑
Corresponding author. Tel.: +58 2125041637.
E-mail addresses: yomaira@gmail.com, yotero@ivic.gob.ve (Y. Otero).
0020-1693/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2013.04.002

78
Y. Otero et al. / Inorganica Chimica Acta 404 (2013) 77–81
Bruker Avance AM300 and AM500 spectrometers, and assignment
of carbon chemical shifts was based on HMBC and HMQC experi-
characterized as [Re2(CO)7(g1 g2 2-PhPC4H3Me)] (5) (56% yield)
: :g
obtained as yellow crystals by slow evaporation of a cyclohexane
ments. IR spectra were recorded on a Nicolet 5DXC. [Ru3(CO)12
]
solution.
was used as supplied by Aldrich Chemical Company.
2.7. Reaction of [Ru3(CO)12] with 3-methyl-1-phenyl-phosphole
2.2. Crystal structure determination
A solution of [Ru3(CO)12] (100 mg, 0.156 mmol) and 3-methyl-
1-phenyl-phosphole (27 lL, 0.156 mmol) in dried cyclohexane
(50 mL) was taken to reflux under nitrogen for 1.5 h. After evapo-
ration of the solvent, TLC (SiO2) of the red residue (eluant hex-
ane:dichloromethane, 9:1 v:v) gave one main band characterized
as [Ru2(CO)4(PhPC4H3Me)2] (6) (56% yield) obtained as red crystals
by slow evaporation of a cyclohexane solution.
Intensity data were recorded at room temperature on a Rigaku
AFC-7S diffractometer equipped with a with a Mercury CCD detec-
tor using monochromated Mo (Ka) radiation (k = 0.71070 Å). An
empirical absorption correction (multi-scan) was applied using
the package CrystalClear. The structures were solved by Direct
Methods and refined by full-matrix least-squares on F2 using the
SHELXTL-PLUS package. Hydrogen atoms on C atoms were placed at
fixed positions using the HFIX instruction. All the H atoms were re-
fined with isotropic displacement parameters set to 1.2 Â Ueq of
the attached atom. In the crystal structure of [Ru2(CO)4(PhPC4H3-
Me)2] (6) either the methyl group bound at C5 atom or a cyclohex-
ane molecule were found disordered. The occupational parameters
for methyl group was fixed to be 50:50. In relation to cyclohexane
molecule, different attempts were made to model this disorder or
3. Results and discussion
Heating [Re2(CO)8(CH3CN)2] and 3,4-dimethyl-1-phenyl-phosp-
hole in refluxing cyclohexane affords in good yields three isomers
of formula [Re2(CO)8(PhPC4H2Me2)2] (1), which are chromato-
graphically inseparable, and another compound in less than 5%
split it into two positions, but were unsuccessful. PLATON
/SQUEZZE rou-
yield [Re2(CO)7(g1 g2 2-PhPC4H2Me2)] (2). Thermal treatment
: :g
tine was used to correct the data for the presence of disordered sol-
vent. A potential solvent volume of 475.8 Å3 was found. The
stoichiometry of the solvent was calculated to be approximately
0.5 molecule of cyclohexane per formula unit, which results in a to-
tal of 111 electrons per unit cell. This molecule was used to calcu-
late expected molecular weight, DXcalc and F(000).
of the mixture of isomers gives in good yields [Re2(CO)7(g1 g2 g2
: : -
PhPC4H2Me2)] (2), while on irradiation with white light at room
temperature [Re(CO)4(PhPC4H2Me2)Cl] (3) and [Re(CO)5Cl] (4) are
obtained (Scheme 1).
The bonding modes for the mixture of isomers (1) is readily
solved from the spectroscopic data; the IR spectrum in the car-
bonyl region is very similar to those found for octacarbonyl disub-
tituted Re-compounds [13–15]. The 31P{1H} NMR spectrum shows
three singlets at d = 4.57, À6.84 and À7.29 ppm (Table 1) suggest-
ing the presence of isomers mixture (1a, 1b, 1c), while the simplic-
ity of the 1H NMR spectrum favors symmetric structures for the
ligand coordination as ax,eq and ax,ax bonding geometries, sug-
gesting the presence of an isomers mixture of 1a, 1b and 1c. All
spectroscopic data (IR and NMR) and previously reported results
[16–18] indicate that the structures shown for 1a, 1b and 1c in
Scheme 1 are the most likely.
Photolysis of the isomers mixture in dichloromethane leads to
compounds 3 and 4. The characterization of the mononuclear
[Re(CO)5Cl)] 4 was straightforwardly made by comparison with
spectroscopic data [16]. For 3, its IR spectra in the carbonyl region
indicates the presence of a mononuclear compound similar to
[Mn(CO)4(PPh3)Cl] obtained from the photolysis of [Mn2(CO)8(-
PPh3)2] in CCl4 [16] or by replacement of a CO ligand in [Mn(CO)5-
Cl] by PPh3 [17]. The 1H NMR spectrum of 3 indicates P-bonding of
the phosphole, because the proton signals show very small differ-
ences in comparison to those of the free ligand. Photolysis of the
isomers (UV light) gives metal–metal bond homolysis to produce
the 17-electron radical species ÁRe(CO)4L (L = phosphole) and
Re(CO)5, which undergoes atom and electron transfer with organic
halides to give the mononuclear [Re(CO)4(phosphole)Cl] similar to
[Re(CO)4(PPh3)Cl] [18].
2.3. Reaction of [Re2(CO)8(CH3CN)2] with 3,4-dimethyl-1-phenyl-
phosphole
A solution of [Re2(CO)8(CH3CN)2] (100 mg, 0.147 mmol) and
3,4-dimethyl-1-phenyl-phosphole (30 lL, 0.147 mmol) in dried
cyclohexane (50 mL) was taken to reflux under nitrogen for 2 h.
After evaporation of the solvent, TLC (SiO2) of the yellow residue
(eluant hexane:dichloromethane, 8:2 v:v) gave three inseparable
isomers of formula [Re2(CO)8(
g
1-PhPC4H2Me2)2] (1) (39% yield)
and [Re2(CO)7(g1 2-PhPC4H2Me2)] (2) (5% yield).
:
g2
:g
2.4. Thermal treatment of the mixture of [Re2(CO)8(
isomers
g
1-PC12H13)2]
A solution of 1 (50 mg) in 20 mL of n-octane was heated to re-
flux under nitrogen for 6 h gave two yellow bands (eluant hex-
ane:dichloromethane, 8:2 v:v). The first one gave unreacted 1
(15% yield), and the other gave compound 2 (84% yield) isolated
as yellow crystals from cyclohexane.
2.5. Photolysis of the [Re2(CO)8(g
1-PC12H13)2] isomers mixture
A solution of 1 (50 mg) in 15 mL of dried dichloromethane was
irradiated with white light, the solution color changed from yellow
to colorless over 6 h. The solvent was removed and TLC work-up on
SiO2 (eluant hexane:dichloromethane, 7:3 v:v) gave two colorless
Thermolysis of the mixture of isomers [Re2(CO)8(PhPC4H2-
Me2)2] (1) affords in high yield the dinuclear derivative [Re2(CO)7(-
bands. The first one was identified as [Re(CO)4(
g
1-PhPC4H2Me2)Cl]
g1 g2 2-PhPC4H2Me2)] (2). Its IR spectroscopic data (Table 1) is
: :g
(3) (90% yield) and the lower band gave [Re(CO)5Cl] (4) (9% yield).
analogous to the parent complex [Mn2(CO)7L] [19,20]. The 1H
NMR spectrum shows the signals for the dienic system shifted to
a higher field, indicating coordination to two rhenium atoms. The
X-ray crystal structure of 2 is shown in Fig. 1. The structure shows
a dinuclear rhenium with one phosphole ring coordinated as a
bridging ligand behaving as a six-electron donor, so each rhenium
atom has the optimal 18-valence electron configuration. The axial
carbonyl groups are not parallel to the metal–metal bond
[C12A–Re1–Re2 163.0(3)° and C23A–Re2–Re1 168.0(3)°], theses
angles being somewhat larger than the reported for the analogous
2.6. Reaction of [Re2(CO)8(CH3CN)2] with 3-methyl-1-phenyl-
phosphole
A solution of [Re2(CO)8(CH3CN)2] (100 mg, 0.147 mmol) and
3-methyl-1-phenyl-phosphole (26 lL, 0.147 mmol) in dried
cyclohexane (50 mL) was taken to reflux under nitrogen for 4.5 h.
After evaporation of the solvent, TLC (SiO2) of the yellow residue
(eluant hexane:dichloromethane, 8:2 v:v) gave one main band

Y. Otero et al. / Inorganica Chimica Acta 404 (2013) 77–81
79
Scheme 1.
Table 1
Spectroscopic data for compounds 1–6.
Compound
m
(CO)a
(cmÀ1
NMRb (d, ppm)
J (Hz)
)
31P
13C {1H}
1H
[Re2(CO)8(h1-PC12H13)2]
1
2068 m
2013 s
1969 s
1936 w
1916 m
4.57 s
7.53 m, o
P–H 34.6 (a)
P–H 34.7 (b)
P–H 35.3 (c)
À1.75 s
7.36 m, m, p
6.55 d, H (a)
6.54 d, H (c)
6.52 d, H (b)
2.44 s, CH3 (b)
2.19 s, CH3 (a)
2.05 s, CH3 (c)
7.46 m, m, p
7.19 m, o
À6.8 s
[Re2(CO)7(h1:h2:h2-PC12H13)]
2
2075 s
2010 s
1990 m
1981 s
1955 w
1939 s
195.6 s, CO
193.7 d, CO
190.7 d, CO
188.9 d, CO
138.6 d, C4
132.0 s, Cp
128.6 d, Cm
127.4 d, Co
96.6 d, C3
P–H 28.4
P–C2 49.4
P–C4 25.4
P–C3 3.9
P–Co 6.9
P–Cm 9.0
P–(C)H3 2.9
P–CO 42.3
P–CO 11.9
P–CO 8.4
À36.1 s
3.15 d, H
2.72 s, CH3
45.9 d, C2
13.5 d, CH3
185.1 d, CO
184.2 s, CO
183.5 d, CO
153.1 d, C3
131.4 d, Co
131.0 d, Cp
129.1 d, C4
129.0 d, Cm
125.1 d, C2
17.6 d, CH3
[Re(CO)4(h1-PC12H13)Cl]
3
2106 w
2010 m
1943 s
7.67 m, o
P–H 33.6
P–(C)H3 12.4
P–CO 9.17
P–CO 37.5
3.21 s
7.41 m, m, p
6.79 dd, H
2.19 s, CH3
H–C(H)3 0.7
P–C2 50.7
P–C4 47.8
P–Co 10.0
P–Cm 10.5
P–Cp 2.2
[Re(CO)5Cl]
2050 m
1980 m
2076 s
2013 s
1989 s
1982 s
1959 m
1941 s
4
[Re2(CO)7(h1:h2:h2-PhPC4H3Me)]
194. 7 s, CO
193.5 s, CO
193.2 s, CO
190.5 d, CO
190.1 d, CO
188.8 d, CO
138.2 d, C6
132.1 s, Cp
128.7 d, Cm
127.6 d, Co
98.6 d, C4
7.47 m, m, p
7.23 m, Ho
5.17 dd, H4
3.17 dd, H2
2.98 ddd, H5
2.74 s, CH3
H2–H5 1.9
H4–H5 4.1
P–H2 29.6
P–H4 14.8
P–H5 28.5
P–C2 49.4
P–C3 3.0
P–C4 4.4
P–C5 48.7
P–C6 23.6
P–Co 17.0
P–Cm 9.3
P–CO 41.1
P–CO 16.8
P–CO 8.2
À25.9 s
5
47.4 d, C2
42.0 d, C5
18.1 d, CH3
15.2 d, C3
[Ru2(CO)4(h1:h2:h2-PC11H11)2]
2007 s
1956 s
7.34 m, o, m, p
5.80d, H4
H2–H5 12.8
H4–H5 13.0
P–H2 29.4
P–H5 27.4
57.44 s
6
3.08 dd, H2
2.70 dd, H5
2.38 s, CH3
a
C6H12
CDCl3.
.
b
manganese derivative [Mn2(CO)7(g1
phosphorus atom lies out of the mean plane of the four carbon
atoms of the diene moiety [0.371(1) Å] describing a ring with an
opened envelope-type conformation. The three carbon–carbon
:
g2
:g
2-PC10H17
]
[19]. The
bond lengths of the diene system are statistically similar [C7–
C8 = 1.429(11) Å, C8–C9 = 1.429(12) Å, C9–C10 = 1.404(11) Å] and
comparable to those of [Mn2(CO)7(g1 g2 2-PC10H17] [19]. The
: :g
apparent shortening of the P–C(diene) bonds [1.791(8) Å,

80
Y. Otero et al. / Inorganica Chimica Acta 404 (2013) 77–81
Fig. 1. Molecular structure of 2.
Fig. 2. Molecular structure of 5.
Table 2
Selected bond lengths (Å) and angles (°) for compounds 2 and 5.
[Re2(CO)7(g1
:
g2
:
g
2-PC12H13)] (2)
[Re2(CO)7(g1
:
g2
:
g
2-PhPC4H3Me)] (5)
Re1–Re2
P1–Re2
C7–Re1
C8–Re1
C9–Re1
C10–Re1
C7–C8
C8–C9
C9–C10
P1–C7
P1–C10
Re1–Re2–C12A
Re2–Re1–C23A
C22A–Re2–C24A
C11A–Re1–C13A
3.046 (14)
2.403 (3)
2.294 (8)
2.295 (8)
2.286 (9)
2.303 (8)
1.425 (11)
1.429 (12)
1.403 (12)
1.792 (8)
1.797 (8)
163.2 (3)
168.0 (3)
177.4 (4)
92.7 (4)
Re1–Re2
P5–Re2
Re1–C1
Re1–C2
Re1–C3
Re1–C4
C1–C2
C2–C3
C3–C4
P5–C1
P5–C4
3.064 (14)
2.394 (3)
2.328 (9)
2.315 (11)
2.286 (11)
2.309 (10)
1.422 (15)
1.445 (15)
1.435 (16)
1.774 (10)
1.802 (10)
163.3 (5)
166.2 (3)
178.0 (5)
92.8 (5)
Scheme 2.
1.795(8) Å] and of the C–C(diene) bond lengths cannot be taken as
a proof of delocalization of the electron pair of the phosphorus
atom but could be interpreted as the donation of electron density
from the rhenium atom to the phosphole ring as has been sug-
gested for [Mn2(CO)7(g1 g2 2-PC10H17] [19].
: :g
Re2–Re1–C13A
Re1–Re2–C23A
C21A –Re2–C24A
C11A–Re1–C12A
The reaction of [Re2(CO)8(CH3CN)2] with 3-methyl-1-phenyl-
phosphole in refluxing cyclohexane gave one main compound
characterized as [Re2(CO)7(g1 g2 2-PhPC4H3Me)] (5) (Scheme 2);
: :g
its IR spectrum is characteristic of a heptacarbonyl dinuclear com-
pound similar to 2; its 31P{1H} NMR spectrum shows one singlet at
d = À25.96 indicating an
g
1-coordination of the phosphorus atom
Table 3
Selected bond lengths (Å) and angles (°) for compound 6.
as observed in 2, the 1H and 13C NMR signals of the phosphole ring
are at higher field compared to the free ligand, suggesting a similar
coordination of the diene as in 2. The X-ray studies confirm these
findings; its structure is shown in Fig. 2. The structure shows the
Ru1–P1
C5–C7
2.874 (3)
1.463 (12)
1.416 (17)
101.0 (4)
P1–C7
1.770 (9)
2.219 (8)
2.226 (8)
86.4 (5)
Ru1–C7
Ru1–C5
C7–P1–C7
C5–C5
phosphole ligand
g
1-coordinated through the lone-pair electrons
g2 through the dienic sys-
C11–Ru1–C7
of the phosphorus atom to Ru2 and g2
:
tem to Ru1, showing an identical coordination mode to that of 3,4-
dimethyl-1-phenylphosphole. The bond lengths and angles are
compare with those of 2 (Table 2). The phosphorus atom length
to the mean plane of the four carbon atoms of the diene
[0.367(1) Å] is similar to the one found for 2, and the P–Re distance
of 2.395(3) Å compares well with the value of 2.402(3) Å in 2 (see
Table 2).
CO
CO
H3
C
Ru
P
Δ
H
C
3
Cyclohexane
[Ru3(CO)]12
+
P
1.5 h
OC
P
Ru
OC
C
H3
The main product of the reaction of [Ru3(CO)12] with 3-methyl-
1-phenyl-phosphole was the diruthenium [Ru2(CO)4(PhPC4H3-
Me)2] (6), a sandwich type complex (Scheme 3), which was charac-
terized by IR, NMR and X-ray analysis. The infrared data are very
similar to that of [Fe2(CO)4(PhPC4H2Me2)2] [21]; the dienic coordi-
nation mode of the phosphole ring is indicated by the highfield
shifts of the 1H and 13C NMR signals. The molecular structure of
6 consists of two discrete Ru(CO)2(PhPC4H3Me) groups related by
a crystallographic center of symmetry as shown in Fig. 3, forming
6
Scheme 3.
a dimer. The bond lengths and angles are shown in Table 3. The
crystal structure of 6 shows a bimetallic compound without me-
tal–metal bond (RuÁ Á ÁRu 3.933 Å); the distance between the mean
plane of the four carbon atoms of the diene and the phosphorus

Y. Otero et al. / Inorganica Chimica Acta 404 (2013) 77–81
81
Appendix A. Supplementary material
CCDC 903536, 903537 and 915468 contains the supplementary
crystallographic data for 2, 5 and 6. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.ica.2013.04.002.
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atom [0.631(1) Å] is longer than those observed for 2 [0.371(1) Å]
and 5 [0.367(1) Å], probably due to the coordination to the two
metallic centers, which are distant.
In conclusion we have found that the donor ability of 3,4-di-
methyl-1-phenyl-phosphole is higher than that of 3-methyl-1-
phenyl-phosphole as expected, due to the donor properties of the
methyl groups in the 3,4-dimethyl-phosphole unit. From the reac-
tion with [Re2(CO)8(CH3CN)2] or [Ru3(CO)12], mono-, binuclear, and
r
–p
complexes are obtained when 3,4-dimethyl-1-phenyl-phosp-
hole is used as a ligand, while with 3-methyl-1-phenyl-phosphole
only complexes and a bimetallic sandwich type complex are
obtained.
r–p
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Acknowledgements
We thank FONACIT for project G-20050000447 and to Laborato-
rio Nacional de Difracción de Rayos-X, project LAB-97000821.