Two types of tetrasubstitution in [H4Ru4(CO)12]: Spectroscopic characterization and crystal structure determination of [H4Ru4(CO)8(PMe2Ph)4] and [H2Ru4(CO)9(PMe2Ph)4]

Article abstract of DOI:10.1016/S1387-7003(03)00069-8

Two tetrasubstituted tetranuclear ruthenium clusters containing dimethylphenylphosphine [H₄Ru₄(CO)₈(PMe₂Ph)₄] and [H₂Ru₄ (CO)₉(PMe₂Ph)₄] were prepared and characterized spectroscopically as well as by X-ray crystallography. Both compounds show a structure based on the usual 60-electron tetrahedral framework with each ruthenium atom being bonded to one phosphine ligand. In the case of the nonacarbonyl derivative, one of the ruthenium atoms has one terminal carbonyl group and is also bonded to two semibridging carbonyl groups; two other metal-metal bonds are bridged by the hydride groups. In the case of the octacarbonyl compound all the ruthenium atoms are bonded to two terminal carbonyls and to two bridging hydrides. NMR spectroscopical information of [H₄Ru₄(CO)₈(PMe₂Ph)₄] suggests the presence of two isomers in solution which we propose to have D_2d and Cs, symmetries. The observation of the NMR properties gives some observations about conditions that favour coupling between substituents in different ruthenium atoms.

Full text of DOI:10.1016/S1387-7003(03)00069-8

Inorganic Chemistry Communications 6 (2003) 675–679
www.elsevier.com/locate/inoche
Two types of tetrasubstitution in [H4Ru4ðCOÞ ]:
12
spectroscopic characterization and crystal structure determination
of [H4Ru4ðCOÞ ðPMe2PhÞ ] and [H2Ru4ðCOÞ ðPMe2PhÞ ]
b
8
4
9
4
a
M. Gabriela Ballinas-Lopez , Marıa J. Rosales-Hoz , Efren V. Garcıa-Baez
a,
*
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
a
Departamento de Quꢀımica, Centro de Investigacioꢀn y de Estudios Avanzados del, I.P.N. Apdo. Postal 14-740, Meꢀxico, D.F. 07000, Mexico
b
ꢀ
ꢀ
ꢀ
Departamento de Quımica, Unidad Profesional Interdisciplinaria de Biotecnologıa del I.P.N. Av. Acueducto s/n, Barrio La Laguna Ticoman,
Meꢀxico, D.F. 07340, Mexico
Received 18January 2003; accepted 11 February 2003
Abstract
Two tetrasubstituted tetranuclear ruthenium clusters containing dimethylphenylphosphine [H4Ru4ðCOÞ8ðPMe2PhÞ4] and [H2Ru4
ðCOÞ9ðPMe2PhÞ4] were prepared and characterized spectroscopically as well as by X-ray crystallography. Both compounds show a
structure based on the usual 60-electron tetrahedral framework with each ruthenium atom being bonded to one phosphine ligand. In
the case of the nonacarbonyl derivative, one of the ruthenium atoms has one terminal carbonyl group and is also bonded to two
semibridging carbonyl groups; two other metal–metal bonds are bridged by the hydride groups. In the case of the octacarbonyl
compound all the ruthenium atoms are bonded to two terminal carbonyls and to two bridging hydrides. NMR spectroscopical
information of [H4Ru4ðCOÞ8ðPMe2PhÞ4] suggests the presence of two isomers in solution which we propose to have D2d and
Cs symmetries. The observation of the NMR properties gives some observations about conditions that favour coupling between
substituents in different ruthenium atoms.
Ó 2003 Elsevier Science B.V. All rights reserved.
Keywords: Tetraruthenium clusters; Dimethylphenylphosphine; NMR characterization; Crystal structures
1. Introduction
entry into the study of the properties of both deriva-
tives. However, to our knowledge, there is only one
preliminary report of a monosubstituted derivative
of the dihydride compound [10] and this was not
fully characterized. This is not the case with tetra-
substituted derivatives of formula [H4Ru4ðCOÞ8L4]
where the crystal structure of the trimethyl phosphite
compound has been described and shows a D2d sym-
metry [11]. As part of a study on the chemistry of
substituted metal clusters we now report the synthesis,
spectroscopic characterization and structural determi-
nation of [H4Ru4ðCOÞ8ðPMe2PhÞ4] (compound 1) and
[H2Ru4ðCOÞ9ðPMe2PhÞ4] (compound 2) which enables
us to make a comparison between both types of struc-
tures having the same substituent. In addition, the
analysis of NMR data allows the observation of how
hydride or carbonyl bridges affect coupling between
substituents in different ruthenium atoms. Results are
described herein.
The chemistry of [H4Ru4ðCOÞ12] has been studied
in some detail [1] and several phosphine-substituted
products have been prepared and characterized spec-
troscopically and structurally [2–4]. Substitution of car-
bonyl groups in cluster compounds with phosphorous
ligands allows the introduction of some modifications in
the electron density distribution in the cluster depending
on the donor–acceptor abilities of the ligand [5]. The
importance of tuning electronic properties of metal
clusters has been discussed in the context of the role they
could play in materials chemistry [6,7]. On the other
hand, an additional tetranuclear hydrido ruthenium
cluster [H2Ru4ðCOÞ13] has been isolated and character-
ized [8,9] and thus these two compounds provide an
* Corresponding author. Tel.: +52-5-747-3800; fax: +52-5-747-7113.
E-mail address: mrosales@mail.cinvestav.mx (M.J. Rosales-Hoz).
1387-7003/03/$ - see front matter Ó 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S1387-7003(03)00069-8

676
M.G. Ballinas-Lꢀopez et al. / Inorganic Chemistry Communications 6 (2003) 675–679
2. Results and discussion
temperature and pressure conditions or to prepare it
through substitution reactions of [H2Ru4ðCOÞ13] were
not successful. However, we managed to obtain spec-
troscopic information of both compounds.
The reaction of [H4Ru4ðCOÞ12] with an excess of
PMe2Ph in the presence of one equivalent of Me3NO
yields the products which result from substitution of
three [13] or four carbonyl groups by the phosphine,
compound 1, and a small amount of [H2Ru4ðCOÞ9
ðPMe2PhÞ4] (compound 2), which could be considered a
product from the carbonyl substitution of ½H2Ru4
ðCOÞ13Š. 1 Attempts to increase the yield of 2 by changing
Both spectroscopic [14] and structural [11] studies of
[H4Ru4ðCOÞ8fPðOMeÞ3g4] show this compound to have
the usual tetrahedral 60-electron cluster structure with
one phosphite bonded to each ruthenium atom. We thus
expected to have the same structure in the case of
compound 1. The NMR spectra were obtained from
solutions prepared with crystals of the compound ob-
tained both at room temperature and at low tempera-
ture. The symmetry present in this structure would
predict the presence of one signal in both the 31P NMR
spectrum and in the hydride zone of the 1H NMR
spectrum. However, the 31P NMR spectum of the
crystals obtained at room temperature showed two
singlets, one more intense than the other and when the
coupled spectrum was obtained, one of the signals be-
came wider while the other (the smaller one) split into a
septuplet.
1
Synthesis of [H4Ru34ðCOÞ ðPMe2PhÞ ] (1) and [H2Ru4ðCOÞ
8
4
9
ðPMe2PhÞ ] (2). [H4Ru4ðCOÞ12] [12] (0.131 g, 0.1759 mmol) was
4
dissolved in 45 ml of dichloromethane and the flask was placed in an
ultrasound bath, PMe2Ph (126 ll, 0.8802 mmol) was then added.
Afterwards a solution of Me3NO (0.0132 g, 0.1757 mmol) in 53 ml of
CH3CN was added dropwise. The reaction mixture was kept under the
action of utrasound for 3 h after which the solvent was removed under
vacuum. The reaction mixture is purified by column chromatography
(1.5:1; hexane:dichloromethane) to yield [H4Ru4ðCOÞ ðPMe2PhÞ ]
9
3
(52.4% yield), [H4Ru4ðCOÞ ðPMe2PhÞ ] (9.6% yield) and [H2Ru4
8
4
ðCOÞ ðPMe2PhÞ ] (4.5% yield). The yield of compound 1 can be
9
4
increased to over 30% yield if the reaction, carried out as described
above, is stopped after 90 min, the solvent volume reduced and an-
other 2.5 equivalents of phosphine and another equivalent of Me3NO
are added and the reaction mixture is maintained for another 2 h in the
ultrasound bath. Spectroscopic data for 1: IR mCO (cmꢀ1, in hexane):
2057(w), 2044(w), 2020(w), 2004(w), 1977(vs), 1969(vs) and 1946(m).
The presence of two types of phosphine is confirmed
when an analysis of the methyl zone of the spectrum is
carried out. Once again there are two signals, one is a
1
doublet (2Jð H–31PÞ ¼ 9 Hz) while the other one shows a
virtual triplet, similar to the one described for the tri-
methyl phosphite derivative [14] as can be appreciated in
Fig. 1. This coupling pattern would thus be the result of
the coupling of the methyl protons with two phosphorus
atoms; one is the one to which the methyl group is directly
bonded and the other is the one found in a pseudotrans
1H NMR (in CDCl3): )16.69(tt, Jð H–31PÞ ¼ 7:2 Hz), dHðPhÞ ¼ 7:45
1
ðmÞ, dHðMe; CsÞ ¼ 1:86 (d, 2J1H–31P ¼ 9 Hz), dHðMe; D2dÞ ¼ 1:72
(virtual triplet, jð J1H–31PÞ þ ð J1H–31PÞj ¼ 7:4 Hz), 31P NMR (in
2
5
CDCl3): 2.03(s, D2d), 1.17(s, Cs), 31Pð HÞ ¼ 1:99ðsÞ, )1.22(sept), 13C
1
NMR (in CDCl3): d (CO, D2d) ¼ 200.75 (virtual triplet, jJð13Ci–
31PÞ þ Jð13Ci–31PÞj ¼ 7:32 Hz), aromatics: dðCi; CsÞ ¼ 140:78(d,
1Jð31P–13CiÞ ¼ 43:32 Hz), dðCp; CsÞ ¼ 129:17 (d, 2Jð13C–31PÞ ¼
2:17 Hz), dðCi; D2dÞ ¼ 143:14 (complex, jðJ13Ci–31P þ J13Ci–31PÞj ¼
37:3 Hz), dðCpÞ ¼ 128:63(s, br), dðCo; D2dÞ ¼ 128:8(complex,
jJð13Co–31PÞ þ Jð13Co–31PÞj ¼ 10:18Hz), dðCm; D2dÞ ¼ 128:52 (com-
plex, jJð13Cm–31PÞ þ Jð13Cm–31PÞj ¼ 8:68Hz), methyl: dðMe; CsÞ ¼
20:87 (d, 1Jð31P–13CÞ ¼ 29:1 Hz), dðMe; D2dÞ ¼ 22:47 (complex,
jJð13C–31PÞ þ Jð13C–31PÞj ¼ 25:5 Hz). FAB: 1185 uma. Microanalysis:
C: 40.92(40.54)%, H: 4.12(4.08)%. Spectroscopic data for compound 2.
IR mCO (cmꢀ1, in hexane): 2058(w), 2044(w), 2020(m), 2004(s), 1988(m),
1980(m), 1962(m), 1950(m), 1942(m, sh). 1H NMR (in CDCl3):
Hydrides: )18.49(tt, 2Jð31P–1HÞ ¼ 6:34 Hz), dðMeBÞ ¼ 1:94(s, br),
dðMe2AÞ ¼ 1:74(s, br), dðMeCÞ ¼ 1:61(s, br), dðPhÞ ¼ 7:39ðmÞ, 1H
NMR (in CDCl3 at )30 °C) dðHydridesÞ ¼ ꢀ18:69(tt, 2Jð31P–1HÞ ¼
5:86 Hz), dðMeBÞ ¼ 1:97 (d, 2Jð31P–1HÞ ¼ 9:77 Hz), dðMeAÞ ¼ 1:89
(d, 2Jð31P–1HÞ ¼ 8:79 Hz), dðMeAÞ ¼ 1:69 (d, 2Jð31P–1HÞ ¼ 7:81 Hz),
dðMeCÞ ¼ 1:59 (d, 2Jð31P–1HÞ ¼ 8:79 Hz), dðPhÞ ¼ 7:4(m). 31P NMR
(in CDCl3): dðPBÞ ¼ 14:55ðsÞ, dð2PAÞ ¼ 12:58ðsÞ, dðPCÞ ¼ ꢀ0:95ðsÞ;
31P NMR (at )30 °C, in CDCl3): dðPBÞ ¼ 15:44ðtÞ, dð2PAÞ ¼ 12:58(d,
3Jð31P–31PÞ ¼ 11:89 Hz), dðPBÞ ¼ ꢀ0:33(s); 13C NMR (in CDCl3):
carbonyls: 202.61(s, br); aromatics: d129.59(m), 128.7(m); methyls:
dðMeCÞ ¼ 21:97 (d, 1Jð31P–13CÞ ¼ 26:22 Hz), dðMeAþBÞ ¼ 20:14 (d,
1Jð31P–13CÞ ¼ 26:74 Hz); 13C NMR (at )30 °C, in CDCl3): carbonyls:
2
1
5
1
position to this, j Jð H–31PÞ þ Jð H–31PÞj ¼ 7:4 Hz.
The relative intensities of the two signals are 10:24.
dð4AÞ ¼ 202:55(d, 1Jð31P–13CÞ ¼ 5:5 Hz); dð3BÞ ¼ 203:95(s, br),
d
(2CObridge) ¼ 197.96(s, br); aromatics: dðCp; Co; CmÞ ¼ 128:7ðmÞ,
d ðCiÞ ¼ 142:27 (d, 1Jð31P–13CÞ ¼ 40:9 Hz), d ðCiÞ ¼ 141:52(d,
1Jð31P–13CÞ ¼ 34:66 Hz), dðCiÞ ¼ 140:21(d, 1Jð31P–13CÞ ¼ 43 Hz);
methyls: dðMeCÞ ¼ 21:68(d,
1Jð31P–13CÞ ¼ 24:6 Hz), d ðMeBÞ ¼
Fig. 1. Methyl zone of the 1H NMR spectrum of the mixture of
isomers present in the crystals of compound 1 obtained at room
temperature.
17:83 (d, 1Jð31P–13CÞ ¼ 28:1 Hz), dðMe2AÞ ¼ 17:73 (d, 1Jð31P–13CÞ ¼
30:57 Hz). FAB: 1211 uma. Microanalysis: C ¼ 46.58(46.15)%,
H ¼ 5.29(5.12)%.

M.G. Ballinas-Lꢀopez et al. / Inorganic Chemistry Communications 6 (2003) 675–679
677
Scheme 1.
Heteronuclear (31P–1H) irradiation experiments showed
D2d isomer and the weaker signals are thus assigned to
the Cs isomer. Virtual coupling is proposed to take place
through one of the metal–metal bonds not bridged by a
hydride. That coupling is not observed in the Cs isomer,
where we propose the corresponding bond would be
hydride-bridged. This behaviour could be explained by
the fact that in the crystal structure results, P–Ru–Ru–P
torsion angles in the hydride bridged metal–metal bonds
fall in a range of 80.6–89.9° while those that involve a
non-bridged metal–metal bond have torsion angle val-
ues of 31.17° and 40.2°. An analysis of the crystals ob-
tained at room temperature shows the presence of two
types of sample, with different unit cell dimensions.
Unfortunately the quality of one of the types of crystals
(presumably the Cs isomer) did not permit us to obtain
the corresponding crystal structure.
that the more intense 31P signal is related to the more
1
intense signals in the H NMR spectrum and the same
happens with the weaker signals in both spectra. The 13
C
spectrum also shows two signals due to methyl groups,
one doublet and a virtual triplet. The sample prepared
with the crystals obtained at )10 °C only showed the
more intense signals.
We believe this behaviour to be due to the existence
of two isomers: a D2d isomer mixed with a Cs isomer,
the two isomeric types of structures already observed in
monosubstituted [H4Ru4ðCOÞ11L] derivatives [15] and
which are shown in Scheme 1. Comparison of the
spectra of 1 with those of [H4Ru4ðCOÞ8fPðOMeÞ3g4]
indicates that the more intense signals correspond to the
The infrared spectrum of compound 2 shows it to
have bridging carbonyl groups, similar to what is ob-
served in [H2Ru4ðCOÞ13] [8]. The NMR data of com-
1
pound 2 can be easily explained considering three
types of phosphine ligands in the molecule where the
three phosphorus signals in the 31P NMR spectrum
obtained at room temperature do not show coupling
between them. However, if the spectrum is obtained at
)30 °C, the signal observed at higher frequency splits
into a triplet while the central signal becomes a doublet
and the third signal remains a singlet. This coupling
pattern indicates that two of the phosphines are equiv-
alent (PA) while the two other ones are different (PB and
PC) as shown in Scheme 2. The hydride signal appears as
a triplet of triplets indicating coupling to all the phos-
1
phorus ligands. The methylic zone of the H spectrum
also supports the presence of three different phosphine
groups although it has to be pointed out that if the
spectrum is obtained at )30 °C, four doublets are
Scheme 2.

678
M.G. Ballinas-Lꢀopez et al. / Inorganic Chemistry Communications 6 (2003) 675–679
observed. Heteronuclear irradiation experiments suggest
that the two signals assigned as bonded to PA look as
two doublets as a consequence of virtual coupling be-
tween the methyl groups of PA with PC. An analysis
from the crystal structure results indicates that P–Ru–
Ru–P torsion angles for the metal–metal bonds bridged
by the carbonyl group have values of 9.92° and 9.95°
while those bridged by the hydride groups have values of
64.03° and )67.97°. We believe that the phosphine
groups involved in the virtual coupling are bonded to
ruthenium atoms which have a semibridging carbonyl
group between them (PA and PC).
3. Crystal structure results
2
Molecular plots for compounds 1 and 2 are shown
in Figs. 2 and 3, respectively, and some selected bond
lengths and angles are also reported there. Both com-
pounds show the expected closo-tetrahedral 60-electron
structure, but while in compound 1 we find the usual
arrangement of four long, hydride bridged, and two
short metal–metal bonds, in 2 the presence of the two
semibridging carbonyl groups changes the distribution
to two long (hydride-bridged), two short (CO bridged)
and two intermediate (unbridged) metal–metal bonds.
The phosphine groups are bonded one to each ruthe-
nium atom. In the case of compound 1, the coordina-
tion sphere around each ruthenium atom is that of a
ꢁ
Fig. 2. Molecular structure of compound 1. Selected bond lengths (A)
are Ru(1)–Ru(2) 2.9978(9), Ru(1)–Ru(3) 2.8009(6), Ru(1)–Ru(4)
3.0058(8), Ru(2)–Ru(3) 3.0126(6), Ru(2)–Ru(4) 2.7960(7), Ru(3)–
Ru(4) 2.9775(6), Ru(1)–P(1) 2.3323(10), Ru(2)–P(2) 2.3339(11), Ru(3)–
P(3) 2.3509(11) and Ru(4)–P(4) 2.3426(11).
2
Crystal data and details of refinement. Compound 1: C40H48O8
P4Ru4, fw ¼ 1184.94; cryst. size ¼ 0:2 ꢁ 0:12 ꢁ 0:1 mm; cryst. system:
ꢁ
ꢁ3
ꢁ
monoclinic; space group: P21/c; a ¼ 15:252ð3Þ A, b ¼ 14:757ð3Þ A,
ꢁ
c ¼ 20:576ð4Þ A, b ¼ 99:10ð3Þ°, V ¼ 4572:8ð16Þ A ; Z ¼ 4; qcalcd:
¼
1:721 M g=m3; l ¼ 1:483 mmꢀ1; radiation: Mo-Ka, k ¼ 0:71073 A;
F ð000Þ ¼ 2352; index range: ꢀ19 > h > 19, ꢀ19 > k > 19, ꢀ26 > l >
26; 2H range: 6.82–55°; temp: 253(2) K; collected refl. ¼ 132386;
unique refl. ¼ 10471; observed refl. ðF > 4rðF ÞÞ ¼ 8070; Rint ¼ 0:1203;
ꢁ
no. of variables ¼ 529; GoF ¼ 1.051;
R
ð4rÞ
¼ 0:0349; final wR2
ꢁ3
(all data) ¼ 0.0789; large res. peak ¼ 0.867 e/A . Compound 2:
C
47H58O9P4Ru4, fw ¼ 1295.09; cryst. size ¼ 0:35 ꢁ 0:21 ꢁ 0:12 mm;
ꢁ
cryst. system: triclinic; space group: P-1; a ¼ 10:3078ð6Þ A, b ¼
ꢁ
ꢁ
15:7447ð10Þ A, c ¼ 17:4434ð11Þ A, a ¼ 75:500ð2Þ°, b ¼ 99:10ð3Þ°, c ¼
ꢁ3
80:110ð2Þ°; V ¼ 2647:2ð3Þ A ; Z ¼ 2; qcalcd: ¼ 1:625 M g=m3; l ¼ 1:290
mmꢀ1
;
radiation: Mo-Ka, k ¼ 0:71073 A; F ð000Þ ¼ 1296; index
ꢁ
range: ꢀ12 > h > 12, ꢀ19 > k > 19, ꢀ20 > l > 21; 2H range: 2.46–
51.98°; temp: 293(2) K; collected refl. ¼ 17568; unique refl. ¼ 10368;
observed refl. ðF > 4rðF ÞÞ ¼ 5420; Rint ¼ 0:070; no. of variables ¼ 585;
GoF ¼ 0.864; R
¼ 0:0551; final wR2 (all data) ¼ 0.1362; large res.
ð4rÞ
ꢁ3
peak ¼ 1.167 e/A . A molecule of cyclohexane is present in the
asymmetric unit. In both compounds, hydrogen atoms from phenyl
and methyl groups were fixed in idealized positions and their positions
refined. Hydrogen atoms of the hydrides were localized in Fourier
maps and their coordinates refined. Crystallographic data for com-
pounds 1 and 2 have been deposited with the Cambridge Crystallo-
graphic Data Centre with the deposition numbers CCDC 198845 and
198846, respectively. Copies if this information may be obtained free of
charge from: The Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1223-336-033; e-mail: deposit@ccdc.ac.uk, or
http://www.ccdc.ac.uk).
Fig. 3. Molecular structure of compound 2. Selected bond lengths
ꢁ
(A) and angles (°) are Ru(1)–Ru(2) 2.9689(10), Ru(1)–Ru(3) 2.7504
(9), Ru(1)–Ru(4) 2.9082(8), Ru(2)–Ru(3) 2.8271(10), Ru(2)–Ru(4)
2.9723(10), Ru(3)–Ru(4) 2.7537(9), Ru(1)–P(1) 2.350(2), Ru(2)–P(2)
2.330(2), Ru(3)–P(3) 2.338(2), Ru(4)–P(4) 2.346(2), Ru(1)–C(13)
2.384(9), Ru(3)–C(13) 1.953(10), Ru(3)–C(34) 1.970(9), Ru(4)–C(34)
2.326(8); O(13)–C(13)–Ru(1) 128.7(7), O(13)–C(13)–Ru(3) 153.3(7),
O(34)–C(34)–Ru(3) 149.9(7) and O(34)–C(34)–Ru(4) 130.8(7).

M.G. Ballinas-Lꢀopez et al. / Inorganic Chemistry Communications 6 (2003) 675–679
679
distorted octahedron, as it had been observed in the
trimethyl phosphite derivative [4]. In the case of com-
pound 2, Ru(3), which is bonded to the two semibrid-
ging carbonyl and only one terminal carbonyl groups,
shows angles with more different values from the ideal
90° or 180° expected in an ideal octahedron. This can be
appreciated by comparing the one large (transoid) P–
Ru–Ru angle sustained by each metal atom and which,
for Ru(1), Ru(2) and Ru(4), have values of 167° and
170° while Ru(3) has two large angles of 143.00(7)° and
149.28(8)°. This must be due to the larger steric bulk of
the bridging carbonyl groups in comparison with that of
the hydrides. The effect of the semibridging CO groups
can also be appreciated by comparing the P–Ru–Ru–P
torsion angles which have values close to 9° for the
carbonyl bridged edge, to 65° for the hydride bridged
and values of 2° and 160° for the non-bridged edges. The
corresponding values for hydride bridged edges in
compound 1 are closer to 80°, while those not bridged
metal–metal bonds show P–Ru–Ru–P torsion angles of
31° and 40°.
four ruthenium atoms are bonded to a phosphine group
therefore suggesting that steric reasons could be the
important factor affecting the relative stability of these
systems.
Acknowledgements
M.G.B.L. thanks Conacyt for the award of a grant.
ꢀ
Thanks are given to Marco Antonio Leyva and Vıctor
M. Gonzalez for their assistance with the X-ray struc-
ꢀ
tures and NMR spectra, respectively. Thanks are also
given to Dr. Susana Rojas-Lima from the Universidad
Autonoma del Estado de Hidalgo for her help in ob-
taining the X-ray data.
References
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Comprehensive Organometallic Chemistry II, vol. 7, Pergamon
Press, Oxford, 1995, pp. 845–847.
There are no significant differences in the Ru–P bond
lengths in either 1 or 2 and the values are also similar to
what had been observed in [H4Ru4ðCOÞ11ðPMe2PhÞ]
[15]. The semibridging nature of the two such CO
groups in 2 can be appreciated by the two bond lengths
[2] S. Aime, M. Botta, R. Gobetto, L. Milone, D. Osella, R. Gellert,
E. Rosenberg, Organometallics 14 (1995) 3693.
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(1978) 1271.
[4] G. Orpen, R.K. McMullen, J. Chem. Soc. Dalton Trans. (1983)
463.
ꢁ
observed for each CO (average values: 2.3545 A for the
ꢁ
longer bond and 1.961 A for the shorter one).
[5] L. Fernandez, M.R. Wilson, A. Prock, W.P. Giering, Organo-
metallics 20 (2001) 3429.
It is important to point out that no evidence of a
compound similar to 2 was obtained when PðOMeÞ3 or
PðOEtÞ3 was used. Neither did we observe the presence
of more than one isomer in the [H4Ru4ðCOÞ8L4] deriv-
atives with the phosphites as ligands. The monosubsti-
tuted derivative [H4Ru4ðCOÞ11ðPMe2PhÞ] also shows a
different structure from that derived from PðOMeÞ3 or
PðOEtÞ3. This could be an effect of the cone angle shown
by PMe2Ph (122°) intermediate between the value for
PðOEt3Þ (109°) and the corresponding values in PPh3
(145°), a phosphine also used in reactivity studies of
these systems [2]. Puga et al. [16] proposed that the
stability of the Cs isomer in the [H4Ru4ðCOÞ10(diphos-
phine)] systems they studied was due to the preference of
the hydrides to be located as close as possible to the
electron donating alkyl-substituted phosphine. This no
longer stands for the tetrasubstituted systems since all
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