Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine: Di- and tri-substituted triruthenium and phosphido-bridged diruthenium complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.11.042

Reaction of [Ru₃(CO)₁₂] with tri(2-furyl)phosphine, P(C₄H₃O)₃, at 40 °C in the presence of a catalytic amount of Na[Ph₂CO] furnishes two triruthenium complexes [Ru₃(CO)₁₀{P(C₄H₃O)₃}₂] (1) and [Ru₃(CO)₉{P(C₄H₃O)₃}₃] (2) with the ligand coordinated through the phosphorus atom. Treatment of 1 and 2 with Me₃NO at 40 °C affords the dinuclear phosphido-bridged complexes [Ru₂(CO)₆(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}] (3) and [Ru₂(CO)₅(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}{P(C₄H₃O)₃}] (4), respectively, that are formed via phosphorus-carbon bond cleavage of a coordinated phosphine followed by coordination of the dissociated furyl moiety to the diruthenium center in a σ,π-alkenyl mode. Reaction of [Ru₃(CO)₁₂] with tri(2-furyl)phosphine in refluxing benzene gives, in addition to 3 and 4, low yields of the cyclometallated complex [Ru₃(CO)₉{μ-η¹,η¹-P(C₄H₃O)₂(C₄H₂O)}₂] (5). Treatment of 3 with EPh₃ (E = P, As, Sb) at room temperature yields the monosubstituted derivatives [Ru₂(CO)₅(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}(EPh₃)] (E = P, 8; E = As, 9; E = Sb, 10). Similar reactions of 3 with P(C₄H₃O)₃, P(OMe)₃ and Bu^tNC yield 4, [Ru₂(CO)₅(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}{P(OMe)₃}] (11) and [Ru₂(CO)₅(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}(NCBu^t)] (12), respectively. The molecular structures of complexes 3, 4 and 8 have been elucidated by single crystal X-ray diffraction studies. Each complex contains a bridging σ,π-alkenyl group and while in 4 the phosphine is bound to the σ-coordinated metal atom, in 8 it is at the π-bound atom. Protonation of 3 and 4 gives the hydride complexes [(μ-H)Ru₂(CO)₆(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}]⁺ (6) and [(μ-H)Ru₂(CO)₅(μ-η¹,η²-C₄H₃O){μ-P(C₄H₃O)₂}{P(C₄H₃O)₃}]⁺ (7), respectively, while heating 3 with dimethylacetylenedicarboxylate (DMAD) in refluxing toluene gives the cyclotrimerization product, C₆(CO₂Me)₆.

Full text of DOI:10.1016/j.jorganchem.2007.11.042

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1645–1655
www.elsevier.com/locate/jorganchem
Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine: Di- and
tri-substituted triruthenium and phosphido-bridged
diruthenium complexes
Noorjahan Begum a, Mohammad A. Rahman b, Mohammad R. Hassan a, Derek A. Tocher c,
a,
c,
b,
*
*
*
Ebbe Nordlander , Graeme Hogarth , Shariff E. Kabir
a Inorganic Chemistry Research Group, Chemical Physics, Center for Chemistry and Chemical Engineering,
Lund University, Box 124, SE-221 00 Lund, Sweden
b Department of Chemistry, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh
c Department of Chemistry, University College London, 20 Gordon Street, London WC1H OAJ, UK
Received 10 November 2007; received in revised form 22 November 2007; accepted 22 November 2007
Available online 21 February 2008
Abstract
Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine, P(C4H3O)3, at 40 °C in the presence of a catalytic amount of Na[Ph2CO] fur-
nishes two triruthenium complexes [Ru3(CO)10{P(C4H3O)3}2] (1) and [Ru3(CO)9{P(C4H3O)3}3] (2) with the ligand coordinated through
the phosphorus atom. Treatment of 1 and 2 with Me3NO at 40 °C affords the dinuclear phosphido-bridged complexes [Ru2(CO)6(l-
g1,g2-C4H3O){l-P(C4H3O)2}] (3) and [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}] (4), respectively, that are formed via
phosphorus–carbon bond cleavage of a coordinated phosphine followed by coordination of the dissociated furyl moiety to the diruthe-
nium center in a r,p-alkenyl mode. Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine in refluxing benzene gives, in addition to 3 and 4,
low yields of the cyclometallated complex [Ru3(CO)9{l-g1,g1-P(C4H3O)2(C4H2O)}2] (5). Treatment of 3 with EPh3 (E = P, As, Sb) at
room temperature yields the monosubstituted derivatives [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}(EPh3)] (E = P, 8; E = As, 9;
E = Sb, 10). Similar reactions of 3 with P(C4H3O)3, P(OMe)3 and ButNC yield 4, [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}{P(OMe)3}]
(11) and [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}(NCBut)] (12), respectively. The molecular structures of complexes 3, 4 and 8 have
been elucidated by single crystal X-ray diffraction studies. Each complex contains a bridging r,p-alkenyl group and while in 4 the
phosphine is bound to the r-coordinated metal atom, in 8 it is at the p-bound atom. Protonation of 3 and 4 gives the hydride complexes
[(l-H)Ru2(CO)6(l-g1,g2-C4H3O){l-P(C4H3O)2}]+ (6) and [(l-H)Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}]+ (7), respec-
tively, while heating 3 with dimethylacetylenedicarboxylate (DMAD) in refluxing toluene gives the cyclotrimerization product,
C6(CO2Me)6.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Ruthenium carbonyl; Tri(2-furyl)phosphine; Substitution; Phosphido-bridge; Cyclotrimerization; P–C cleavage
1. Introduction
phorus ligands being accessible. More recently, the reactivity
of group 8 metal carbonyls with functionalized phosphines
such as diphenyl(2-thienyl)phosphine [8–11], di(2-thie-
nyl)phenylphosphine [12], diphenyl(benzothienyl)phos-
phine [12], tri(2-thienyl)phosphine [13–15], diphenyl(2-
pyridyl)phosphine [16–21] and 2-indolyl phosphine [22] have
attracted considerable attention since the presence of a sec-
ond coordinating atom provides a diversity of coordination
modes. It is well-documented that heterodifunctional
The chemistry of [Ru3(CO)12] with simple alkyl-, aryl- and
alkoxy-substituted tertiary phosphines is well-established
[1–7] with derivatives containing one, two and three phos-
*
Corresponding authors. Tel.: +880 1713041114; fax: +880 27791052.
E-mail addresses: Ebbe.Nordlander@chemphys.lu.se (E. Nordlander),
g.hogarth@ucl.ac.uk (G. Hogarth), skabir_ju@yahoo.com (S.E. Kabir).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.042

1646
N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
ligands exhibit very interesting properties, such as selective
binding to metal ions of different types, dynamic behavior
via reversible dissociation of the weaker metal–ligand bond
and stereoelectronic control of the coordination sphere of
the metal [23]. Deeming and co-workers have reported that
the reaction of [Ru3(CO)12] with diphenyl(2-thienyl)phos-
phine gives, in addition to the phosphine derivatives of the
trinuclear cluster, the carbon–hydrogen activated products
[Ru3(CO)9(l3-Ph2PC4H2S)(l-H)] and [Ru3(CO)8 (Ph2
PC4H3S)(l3-Ph2PC4H2S)(l-H)], the former reacting further
with [Ru3(CO)12] to yield the thiophyne cluster
[Ru4(CO)11(l3-Ph2PC4H2S)(l4-PPh)(l4-C4H2S)(l-H)]
resulting from phosphorus–carbon bond cleavage [8]. The
CO substitution reaction of [Ru3(CO)12] by tertiary phos-
phines occurs favorably via electron-transfer catalysis condi-
tions using sodium diphenylketyl [22,24]. Recently, we have
investigated the reaction of [Ru3(CO)12] with tri(2-thie-
nyl)phosphine via electron-transfer catalysis conditions
and have obtained the mono-, di- and tri-substituted phos-
phine derivatives together with carbon–hydrogen and phos-
phorus–carbon bond cleavage products [25].
procedures and were freshly distilled prior to use. Ruthe-
nium carbonyl and ButNC were purchased from Strem
and tri(2-furyl)phosphine, PPh3, Ph3Sb, Ph3As and
DMAD from Acros and used as received. Infrared spectra
were recorded on Nicolet Avatar and Shimadzu FTIR 8101
spectrometers. 1H and 31P{1H} NMR spectra were
recorded on Varian Unity Plus 500 and Bruker DPX 400
instruments. All chemical shifts are reported in d units with
reference to the residual protons of the deuterated solvents
for proton and to external 85% H3PO4 for 31P chemical
shifts. Elemental analyses were performed by the Microan-
alytical Laboratories, University College London. Fast
atom bombardment mass spectra were obtained on a JEOL
SX-102 spectrometer using 3-nitrobenzyl alcohol as matrix
and CsI as calibrant. Preparative thin layer chromatogra-
phy (TLC) was performed on commercial plates
(20 Â 20 cm), precoated with 0.5 mm silica gel, or with
plates prepared at Jahangirnagar University.
2.1. Reaction of [Ru3(CO)12] with tri(2-furyl)phosphine in
the presence of Na[Ph2CO]
In contrast to the extensive chemistry of the pyridyl- and
thienylphosphines, there are a few examples of the reactions
of tri(2-furyl)phosphine with metal carbonyl clusters [26]
although it has become an important ligand in transition
metal catalysis [27]. Recently, Wong et al. reported the for-
mation of dinuclear [Ru2(CO)6(l-g1,g2-C4H3O){l-
P(C4H3O)2}] from the reaction of [Ru3(CO)12] with
P(C4H3O)3 at 67 °C. This results from phosphorus–carbon
bond cleavage and coordination of the dissociated heteroar-
omatic group to the bimetallic framework in a r,p-alkenyl
fashion, and they went on to investigate reactions with
alkynes [26a] and diphosphines [26b]. Wong and Ting also
investigated the reaction of tri(2-furyl)phosphine with
[Ru4(l-H)4(CO)12] obtaining a series of tetraruthenium
compounds containing furyl, furyne, phosphido- and phos-
phinidene ligands [26c]. We were interested in preparing a
new family of triruthenium compounds containing furyl
phosphines from the Na[Ph2CO] catalyzed reaction between
[Ru3(CO)12] with tri(2-furyl)phosphine in order to study the
carbon–hydrogen and phosphorus–carbon bond cleavage of
these compounds under mild conditions and in a controlled,
stepwise manner. Here we describe the isolation of the di-
and tri-substituted clusters, [Ru3(CO)10{P(C4H3O)3}2] (1)
and [Ru3(CO)9{P(C4H3O)3}3] (2), and their subsequent
transformation under mild conditions to the dinuclear com-
plexes [Ru2(CO)6(l-g1,g2-C4H3O){l-P(C4H3O)2}] (3) and
[Ru2(CO)5(l-g1,g2-C4H3O) {l-P(C4H3O)2}{P(C4H3O)3}]
(4), respectively. We have also investigated the reactivity of
3 towards a series of two-electron donor ligands as well as
the activated alkyne, dimethylacetylenedicarboxylate
(DMAD), the latter leading to cyclotrimerization.
A dry nitrogen flushed 100 mL three necked flask was
charged with [Ru3(CO)12] (200 mg, 0.312 mmol), tri(2-
furyl)phosphine (146 mg, 0.628 mmol) and 40 mL of freshly
distilled THF and the mixture was warmed to 40 °C to dis-
solve the [Ru3(CO)12]. Na[Ph2CO] in THF (five drops) was
then added via a syringe. Carbon monoxide was evolved,
the solution readily darkened and consumption of
[Ru3(CO)12] was confirmed by TLC. The solvent was then
removed in vacuo, and the resultant residue was subjected
to TLC on silica gel. Elution with hexane/CH2Cl2 (7:3, v/
v) developed two bands. The faster moving band afforded
the previously reported [25a] disubstituted compound
[Ru3(CO)10{P(C4H3O)3}2] (1) (160 mg, 48%) as red crystals
after recrystallization from hexane/CH2Cl2 at À4 °C. The
slower moving band gave [Ru3(CO)9{P(C4H3O)3}3] (2)
(40 mg, 10%) as red crystals after recrystallization from hex-
ane/CH2Cl2 at +4 °C. Anal. Calc. for C45H27O18P3Ru3: C,
43.18; H, 2.17. Found: C, 43.35; H, 2.30%; IR (m(CO), CH2Cl2):
2062 m, 2002 vs, 1989 vs, 1962 m cmÀ1; 1H NMR (CDCl3): d
7.64 (m, 9H), 6.61 (m, 9H), 6.42 (m, 9H); 31P{1H} NMR
(CDCl3): d À16.1 (s); MS (FAB): m/z 1253 [M]+.
2.2. Thermolysis of 1 in the presence of Me3NO
To a CH2Cl2 solution (30 mL) of 1 (50 mg, 0.048 mmol)
was added Me3NO (4.3 mg, 0.057 mmol) and heated to
reflux for 2 h during which time the color changed from
red to yellow. Work-up and chromatographic separation
as above afforded the known compound [Ru2(CO)6(l-
g1,g2-C4H3O){l-P(C4H3O)2}] (3) (20 mg, 69%) [26a].
2. Experimental
2.3. Thermolysis of 2 in the presence of Me3NO
All reactions were performed under a nitrogen atmo-
sphere. Reagent grade solvents were dried using standard
Thermolysis of a CH2Cl2 solution (30 mL) of 2 (70 mg,
0.056 mmol) and Me3NO (4.9 mg, 0.065 mmol) for 12 h

N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
1647
followed by chromatographic separation afforded
2.6. Reactions of 3 with Ph3E (E = P, As, Sb)
[Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}] (4)
(40 mg, 88%) as pale yellow crystals after recrystallization
from hexane/CH2Cl2 at +4 °C. Anal. Calc. for
C29H18O11P2Ru2: C, 43.19; H, 2.25. Found: C, 43.28; H,
2.39%. IR (m(CO), CH2Cl2): 2064 vs, 2018 vs, 2000 vs,
A CH2Cl2 solution (20 mL) of 3 (30 mg, 0.049 mmol)
and one equivalent of Ph3E (E = P, As, Sb) was stirred
at room temperature (E = P, 2 h; E = As, 6 h; E = Sb,
12 h). The color changed from pale yellow to dark yel-
low. The solvent was removed by rotary evaporation
and the resultant residue was subjected to TLC on silica
gel. Elution with hexane/CH2Cl2 (7:3, v/v) developed
only one band which afforded [Ru2(CO)5(l-g1,g2-
C4H3O) {l-P(C4H3O)2}(Ph3E)] (8, E = P, 33 mg, 79%;
9, E = As, 34 mg, 77%; 10, E = Sb, 36 mg, 78%) as yel-
low crystals after recrystallization from CH2Cl2/hexane
at +4 °C. Spectroscopic data for 8: IR (m(CO), CH2Cl2):
1
1978 vs cmÀ1; H NMR (CDCl3): d 7.64 (s, 1H), 7.55 (m,
3H), 7.45 (s, 2H), 6.60 (m, 3H), 6.41 (m, 3H), 6.38 (m,
1H), 6.34 (s, 1H), 6.26 (s, 1H), 6.22 (s, 1H), 5.50 (m, 1H),
4.09 (m, 1H); 31P{1H} NMR (CDCl3): d 53.7 (d, J
20.2 Hz), À11.0 (d, J 20.2 Hz); MS (FAB): m/z 808 [M]+.
2.4. Protonation of 3 and 4
To
a
CD2Cl2 solution (0.75 mL) of
3
(10 mg,
2061 vs, 2009 vs, 1978 s, 1960 s cmÀ1 1H NMR
;
0.016 mmol) in an NMR tube was added CF3COOH
(CDCl3): d 7.51 (s, 1H), 7.42–7.27 (m, 17H), 6.40 (s,
1H), 6.28 (s, 1H), 6.12 (s, 1H), 5.82 (s, 1H), 5.44 (s,
1H), 3.58 (s, 1H); 1H NMR (CD2Cl2, 273 K): d 7.72
(dt, J 2.0, 1.0 Hz, 1H), 7.46 (quintet, J 0.7 Hz, 1H),
7.45 (dd, J 2.0, 0.9 Hz, 1H), 7.41–7.28 (m, 15H), 6.45
(ddd, J 3.4, 1.8, 0.5 Hz, 1H), 6.27 (ddd, J 3.3, 1.5,
0.7 Hz, 1H), 6.15 (ddd, J 3.3, 1.8, 1.0 Hz, 1H), 5.77
(dd, J 2.6, 1.7 Hz, 1 H), 5.42 (dd, J 2.5, 2.4 Hz, 1H),
3.75 (ddd, J 6.3, 3.7, 2.8 Hz, 1H); 31P{1H} NMR
(CDCl3): d 48.3 (d, J 15.3 Hz), 45.7 (d, J 15.3 Hz);
MS (FAB): m/z 838 [M]+. Anal. Calc. for
C35H24O8P2Ru2: C, 50.25; H, 2.89. Found: C, 50.39;
H, 3.07%. Spectroscopic data for 9: IR (m(CO),
1
(one drop from a Pasteur pipette). The H and 31P NMR
spectra indicated formation of the cation [(l-
H)Ru2(CO)6(l-g1,g2-C4H3O){l-P(C4H3O)2}]+ (6). IR
(m(CO), CH2Cl2): 2137 s, 2122 vs, 2085 vs, 2065 vs cmÀ1
;
1H NMR (CDCl3): d 8.27 (m, 1H), 8.01 (s, 1H), 7.82 (m,
1H), 7.38 (m, 1H), 6.83 (m, 1H), 6.61 (m, 1H), 6.58 (m,
1H), 6.52 (m, 1H), 6.24 (m, 1H), À12.25 (d, J = 24.8 Hz);
31P{1H} NMR (CDCl3): d 58.6 (s). A similar protonation
to that above of
4
gave [(l-H)Ru2(CO)5(l-g1,g2-
C4H3O){l-P(C4H3O)2}{P(C4H3O)3}]+ (7). IR (m(CO),
1
CH2Cl2): 2121 vs, 2088 s, 2071 s, 2051 s cmÀ1; H NMR
(CDCl3): d 7.77 (s, 2H), 7.66 (s, 1H), 7.60 (s, 3H), 6.64
(m, 3H), 6.55 (m, 6H), 6.50 (m, 1H), 5.49 (m, 2H),
À11.91 (dd, J 23.6, 24.0 Hz); 31P{1H} NMR (CDCl3): d
48.4 (d, J 22.4 Hz), À5.81 (d, J 22.4 Hz). Attempts to iso-
late 6–7 as PF6 salts upon addition of an aqueous solution
of [NH4][PF6] resulted only in complete deprotonation to
give 3–4, respectively.
CH2Cl2): 2064 vs, 2007 vs, 1978 s, 1956 m cmÀ1 1H
;
NMR (CDCl3): d 7.68 (s, 1H), 7.43 (s, 1H), 7.36 (m,
10H), 7.29 (m, 6H), 6.40 (s, 1H), 6.24 (s, 1H), 6.19
(s, 1H), 6.16 (s, 1H), 5.23 (m, 1H), 3.84 (m, 1H);
31P{1H} NMR (CDCl3): d 50.1 (s); MS (FAB): m/z
882 [M]+. Anal. Calc. for C35H24O8PAsRu2: C, 47.74;
H, 2.75. Found: C, 47.95; H, 2.90%. Spectroscopic data
for 10: IR (m(CO), CH2Cl2): 2065 vs, 2008 vs, 1978 s,
2.5. Thermal reaction of [Ru3(CO)12] with
tri(2-furyl)phosphine
1958 s cmÀ1 1H NMR (CDCl3): d 7.66 (s, 1H), 7.39
;
(m, 10H), 7.32 (m, 6H), 7.18 (s, 1H), 6.45 (s, 1H),
6.40 (s, 1H), 6.26 (s, 1H), 6.18 (m, 1H), 5.48 (m, 1H),
3.87 (m, 1H); 31P{1H} NMR (CDCl3): d 53.6 (s); MS
(FAB): m/z 92 [M]+. Anal. Calc. for C35H24O8PSbRu2:
C, 45.33; H, 2.61. Found: C, 45.55; H, 2.75%.
A benzene solution (40 mL) of [Ru3(CO)12] (200 mg,
0.313 mmol) and P(C4H3O)3 (146 mg, 0.628 mmol) was
refluxed for 15 min during which time the color changed
from orange to pale yellow. The solvent was removed
under reduced pressure and the resultant residue was sub-
jected to TLC on silica gel. Elution with hexane/CH2Cl2
(9:1, v/v) gave three bands. The first band gave 3
(140 mg, 74%) as yellow crystals after recrystallization
from hexane/CH2Cl2 at +4 °C. The second moving band
afforded [Ru3(CO)9{P(C4H3O)2(C4H2O)}2] (5) (20 mg,
6%). Anal. Calc. for C33H16O15P2Ru3: C, 38.95; H, 1.58.
Found: C, 39.15; H, 1.78%. IR (m(CO), CH2Cl2): 2087 w,
2.7. Reaction of 3 with P(OMe)3
Using the same procedure as above, P(OMe)3 (10 mg,
0.09 mmol) was reacted with 3 (50 mg, 0.083 mmol) to
yield [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}{P(OMe)3}]
(11) (40 mg, 69%) as yellow crystals after recrystallization
from hexane/CH2Cl2 at +4 °C. Anal. Calc. for
C20H18O11P2Ru2: C, 34.39; H, 2.60; Found: C, 34.52;
H, 2.78%. IR (m(CO), CH2Cl2): 2063 vs, 2019 vs, 1996
1
2077 m, 2057 w, 2032 vs, 2015 s, 1968 s cmÀ1; H NMR
(CDCl3): d 7.61 (s, 2H), 7.56 (s, 2H), 6.99 (s, 2H), 6.95
(d, J 3.2 Hz, 2H), 6.55 (d, J 3.2 Hz, 2H), 6.39 (m, 2H),
6.10 (m, 2H), 5.92 (s, 2H); 31P{1H} NMR (CDCl3): d
90.0 (s); MS (FAB): m/z 1019 [M]+. The slowest moving
band gave 4 (25 mg, 10%) as yellow crystals after recrystal-
lization from hexane/CH2Cl2 at +4 °C.
vs, 1980 vs cmÀ1 1H NMR (CDCl3): d 7.64 (s, 1H),
;
7.59 (s, 1H), 7.50 (s, 1H), 6.64 (s, 1H), 6.35 (m, 3H),
6.03 (s, 1H), 3.96 (s, 1H), 3.53 (d, J 12.46 Hz, 9H);
31P{1H} NMR (CDCl3): d 157.9 (d, J 18.2 Hz), 49.1
(d, J 18.2 Hz); MS (FAB): m/z 700 [M]+.

1648
N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
2.8. Reaction of 3 with tri(2-furyl)phosphine
similar reaction to that above of
6.04 (s, 1H), 4.13 (m, 1H), 1.40 (s, 9H); 31P{1H} NMR
(CDCl3): d 55.4 (s); MS (FAB): m/z 659 [M]+.
A
3 (30 mg,
0.049 mmol) and P(C4H3O)3 (26 mg, 0.11 mmol) for 24 h
at 25 °C followed by similar chromatographic separation
gave 4 (35 mg, 87%).
2.10. Reaction of 3 with dimethylacetylenedicarboxylate
(DMAD)
A toluene solution (20 mL) of 3 (40 mg, 0.066 mmol)
and DMAD (200 mg, 1.41 mmol) was refluxed for 6 h.
The solvent was removed under reduced pressure and the
residue chromatographed by TLC on silica gel. Elution
with hexane/CH2Cl2 (1:1, v/v) developed two bands. The
faster moving band afforded unreacted 3 (10 mg) and the
slower moving band afforded C6(CO2CH3)6 (13) (50 mg,
25%) as colorless crystals after recrystallization from hex-
ane/CH2Cl2 at +4 °C. Anal. Calc. for C18H18O12: C,
50.71; H, 4.26; Found: C, 50.92; H, 4.40%; 1H NMR
(CDCl3): d 3.87 (s); 13C{1H} NMR (CDCl3): d 165.2 (s),
133.9 (s), 53.5(s).
2.9. Reaction of 3 with ButNC
A CH2Cl2 solution (5 mL) of ButNC (4 mg, 0.048 mmol)
was added dropwise to a CH2Cl2 solution (20 mL) of 3
(30 mg, 0.049 mmol) at 0 °C and stirred for 6 h. The color
of the solution turned from pale yellow to yellow. Work-up
and chromatographic separation as above developed two
bands. The minor band gave unreacted 3 (7 mg) and the
major
band
gave
[Ru2(CO)5(l-g1,g2-C4H3O){l-
P(C4H3O)2}(ButNC)] (12) (18 mg, 55%) as pale yellow
crystals after recrystallization from hexane/CH2Cl2 at
+4 °C. Anal. Calc. for C22H18O8P1N1Ru2: C, 40.19; H,
2.76; Found: C, 40.22; H, 2.80%. IR (m(CO), CH2Cl2):
2058 vs, 2013 vs, 1994 vs, 1978 vs cmÀ1; IR (m(NC),
2.11. X-ray structure determination of compounds 3, 4 and 8
CH2Cl2): 2174 vs cmÀ1
;
1H NMR (CDCl3): d 7.64 (s,
Single crystals of 3, 4, and 8 suitable for X-ray diffrac-
1H), 7.59 (s, 1H), 7.50 (s, 1H), 6.65 (s, 1H), 6.36 (m, 3H),
tion were grown by slow diffusion of hexane into a
Table 1
Crystallographic data and structure refinementa for 3, 4 and 8
3
4
8
Empirical formula
Formula weight
Crystal system
Space group
C
602.36
18H9O9PRu2
C29H18O11P2Ru2
806.51
Monoclinic
P21/c
21.3397(14)
16.4859(11)
18.4174(12)
90
110.0880(10)
90
6085.2(7)
8
1.761
1.157
3184
C35H24O8P2Ru2
836.62
Triclinic
Monoclinic
P21/n
9.2384(12)
12.4863(17)
17.673(2)
90
97.521(2)
90
2021.1(5)
4
ꢀ
P1
˚
a (A)
11.2573(6)
11.8204(7)
13.1742(7)
86.1070(10)
69.6650(10)
85.0590(10)
1636.32(16)
2
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
Volume (A )
Z
Dcalc (Mg/m3)
l (Mo Ka) (mmÀ1
F(000)
1.980
1.622
1168
1.698
1.073
832
)
Crystal size (mm3)
h Range (°)
0.25 Â 0.24 Â 0.10
0.21 Â 0.18 Â 0.05
0.35 Â 0.16 Â 0.16
2.00–28.31°
1.60–28.28
1.65–28.27
Index ranges
À12 6 h 6 12
À16 6 k 6 16
À23 6 l 6 23
À27 6 h 6 28
À21 6 k 6 21
À24 6 l 6 24
À14 6 h 6 14
À15 6 k 6 15
À17 6 l 6 17
Reflections collected
17331
52663
14416
Independent reflections
4822 [Rint = 0.0198]
4504
0.6873 and 0.8546
0.0315, 1.8788
4822/0/272
14503 [Rint = 0.0286]
12147
0.7931 and 0.9444
0.0283, 2.0349
14503/0/818
1.021
7507 [Rint = 0.0135]
6920
0.7052 and 0.8471
0.0241, 0.6295
7507/0/436
1.028
Reflections with F2 > 2r
Maximum and minimum transmission
Weighting parameters a, b
Data/restraints/parameters
Goodness-of-fit on F2
0.976
Final R indices [I > 2r(I)]
R1 = 0.0212
wR2 = 0.0555
R1 = 0.0234
wR2 = 0.0566
0.815 and À0.449
R1 = 0.0268
wR2 = 0.0603
R1 = 0.0352
wR2 = 0.0635
0.600 and À0.413
R1 = 0.0203
wR2 = 0.0486
R1 = 0.0228
wR2 = 0.0496
0.446 and À0.477
2
R indices (all data)
À3
˚
Largest difference in peak and hole, e A
a
˚
Details in common: X-radiation, Mo Ka (k = 0.71073 A), temperature (K) 150(2), refinement method: full-matrix least-squares on F .

N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
1649
dichloromethane solution at À4 °C. All geometric and
crystallographic data of 3, 4, and 8 were collected at
150 K on a Bruker SMART APEX CCD diffractometer
10% yields, respectively, by addition of a catalytic amount
of Na[Ph2CO] into a 1:2 solution of Ru3(CO)12 and tri(2-
furyl)phosphine in THF at 40 °C. Compound 1 has been
previously reported as a minor product (10% yield) from
the thermal reaction of [Ru3(CO)12]with tri(2-furyl)phos-
phine [26a]. Cluster 1 was characterised by comparison
with the previously reported spectroscopic data [26a].
Tri-substituted 2 has been characterized by a combination
˚
using Mo Ka radiation (k = 0.71073 A). Data reduction
and integration was carried out with SAINT+ and absorp-
tion corrections were applied using the program SADABS
[28]. Structures were solved by direct methods and devel-
oped using alternating cycles of least-squares refinement
and difference-Fourier synthesis. All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were
placed in the calculated positions and their thermal
parameters linked to those of the atoms to which they
were attached (riding model). The SHELXTL PLUS V6.10
program package was used for structure solution and
refinement [29]. Final difference maps did not show any
residual electron density of stereochemical significance.
The details of the data collection and structure refine-
ment are given in Table 1.
1
of IR, H NMR and 31P{1H} NMR spectroscopy, mass
spectrometry, elemental analysis and single crystal X-ray
diffraction studies [30]. The pattern of the IR spectrum in
the carbonyl region is similar to that of other previously
reported tertiary phosphine substituted derivatives of the
type [Ru3(CO)9(PR3)3] [7], indicating that they are isostruc-
tural. As expected, the 1H NMR spectrum shows three
multiplets at d 7.64, 6.61 and 6.42, each integrating for
nine hydrogens and the absence of any metal-hydride res-
onance confirmed that no carbon–hydrogen activation had
occurred. The 31P{1H} NMR spectrum contains a singlet
at d À16.1 assigned to three equivalent terminally coordi-
nated phosphine ligands, the coordination of the tri(2-
furyl)phosphine to the ruthenium center resulting in a
downfield shift from d À76.8 in the free ligand [27] to d
À16.1 for the cluster. The FAB mass spectrum exhibits
the molecular ion peak at m/z 854 and fragmentation
peaks due to the sequential loss of nine carbonyl groups
are also observed.
3. Results and discussion
3.1. Synthesis of [Ru3(CO)10{P(C4H3O)3}2] (1) and
[Ru3(CO)9{P(C4H3O)3}3] (2)
The electron precise and air stable di-and tri-substituted
clusters [Ru3(CO)10{P(C4H3O)3}2] (1) and [Ru3(CO)9-
{P(C4H3O)3}3] (2) (Scheme 1) are obtained in 48% and
Fu
Fu
+
Fu
Fu
H
P
P
CD2Cl2
40 oC
Me3NO
Ru
O
Ru
Ru
Ru
CF3CO2H
O
L
3
6
Ru
Ru
Ru
L
1
O
THF, RT
+
+
P
Ru3(CO)12
O
Na[Ph2CO]
L
O
Ru
L
L = PFu3
Ru
Ru
L
2
Fu
P
Fu
Ru
+
Fu
Fu
L
40 oC
Me3NO
H
L
P
CD2Cl2
CF3CO2H
Ru
Ru
Ru
O
O
4
7
Scheme 1.

1650
N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
3.2. Formation of binuclear phosphido-bridged complexes via
phosphorus–carbon bond cleavage
Thermolysis of 1 in the presence of Me3NO at 40 °C
gives the known dinuclear complex [Ru2(CO)6{l-
P(C4H3O)2}(l-g1,g2-C4H3O)] (3) (Scheme 1) in 69% yield.
Isolation of 3 in this reaction indicates that its previous for-
mation from the reaction of [Ru3(CO)12] with tri(2-
furyl)phosphine at 68 °C proceeded via the intermediate
formation of 1. Heating 2 at 40 °C in the presence of
Me3NO leads to the formation of dinuclear [Ru2(CO)5(l-
g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}] (4) in 57%
yield (Scheme 1). Both 3 and 4 have been characterized
by spectroscopic data and single crystal X-ray diffraction
analysis. The X-ray structure of compound 3 is known
[26a] but we redetermined this at low temperature
[150(2) K]. A determination of the unit cell parameters
indicated that the molecule had packed in a different unit
cell than that reported by Wong et al. [26a]. The molecular
structure of 3 is shown in Fig. 1 and selected bond dis-
tances and angles are listed in the caption.
Two crystallographically independent molecules are
seen in the asymmetric unit of 4. The respective bond
lengths and angles in the two molecules show only minor
variations. The structure of one of these molecules is shown
in Fig. 2 and selected bond distances are listed in the cap-
tion. Binuclear 4 can be derived from 3 by substitution of
one carbonyl group by a P(C4H3O)3 ligand. Both consist
of a (OC)3Ru–Ru(CO)2L [3, L = CO; 4, L = P(C4H3O)3]
skeleton spanned by a difurylphosphido group and a furyl
moiety derived by phosphorus–carbon bond cleavage of
the coordinated P(C4H3O)3 ligand. The l-C4H3O moiety
Fig. 2. Molecular structure of one of the two crystallographically
independent molecules of [Ru2(CO)5{l-P(C4H3O)2}(l-g2-C4H3O){P-
(C4H3O)3}] (4) showing 50% probability thermal ellipsoids. Selected bond
˚
distances (A) and angles (°): Ru(1)–Ru(2) = 2.7711(3), Ru(1)–
P(1) = 2.3595(5),
Ru(2)–P(1) = 2.3304(5),
Ru(1)–P(2) = 2.3068(6),
Ru(1)–C(6) = 2.3081(19), Ru(1)–C(7) = 2.378(2), Ru(2)–C(6) = 2.078(2),
P(2)–Ru(1)–P(1) = 104.821(19), C(6)–Ru(1)–Ru(2) = 47.22(5), C(6)–
Ru(2)–Ru(1) = 54.61(5), C(7)–Ru(1)–Ru(2) = 77.11(5), P(2)–Ru(1)–
Ru(2) = 154.980(15),
P(1)–Ru(1)–Ru(2) = 53.298(13),
P(1)–Ru(2)–
Ru(1) = 54.267(13), Ru(2)–P(1)–Ru(1) = 72.435(16).
is bonded through a r bond between C(1) and Ru(2) in 3
˚
[Ru(2)–C(1) = 2.071(2) A] and C(6) and Ru(2) in 4
2
˚
[Ru(2)–C(6) = 2.078(2) A] and through an g -interaction
between C(1), C(2) and Ru(1) for
3
[Ru(1)–
C(1) = 2.367(2), Ru(1)–C(2) = 2.413(2) A] and C(6), C(7)
and Ru(1) for [Ru(1)–C(6) = 2.3081(19), Ru(1)–
˚
4
˚
C(7) = 2.378(2) A], thus forming a r,p-alkenyl bridge
between the metal atoms. The Ru–C bond distances involv-
ing the p-interaction are shorter and more asymmetric in 4
than those of the corresponding distances in 3. The Ru–Ru
˚
bond distance of 2.7711(3) A in 4 is comparable to that of
˚
2.7695(3) A in 3.
The coordination sphere of the molecules is completed
by six terminal carbonyls in 3 and five carbonyls and the
tri(2-furyl)phosphine ligand for 4. The Ru–P distances
involving the phosphido moiety are more symmetric in 3
˚
[Ru(1)–P(1) = 2.3418(6), Ru(2)–P(1) = 2.3228(6) A] than
˚
in 4 [Ru(1)–P(2) = 2.3595(5), Ru(1)–P(2) = 2.3068(6) A]
and comparable to those found in related diruthenium
complexes. The Ru–P–Ru angle in 4 [72.43(2)°] is very sim-
ilar to the corresponding angle in 3 [72.80(2)°]. In 4, the ter-
minal phosphine is axially coordinated to the ruthenium
atom to which the furyl moiety is p-bonded [P(2)–Ru(1)–
Ru(2) = 154.98(2)°]. Both the l-g1,g2-furyl and l-
P(C4H3O)2 ligands donate three-electrons and thus both
3 and 4 have a 34-valence electron count.
Fig. 1. Molecular structure of [Ru2(CO)6{l-P(C4H3O)2}(l-g2-C4H3O)]
(3) showing 50% probability thermal ellipsoids. Hydrogen atoms have
been omitted for clarity. Selected bond distances (A) and angles (°):
Ru(1)–Ru(2) = 2.7695(3), Ru(1)–P(1) = 2.3418(6), Ru(1)–C(1) = 2.367(2),
Ru(1)–C(2) = 2.413(2), Ru(2)–P(1) = 2.3228(6), Ru(2)–C(1) = 2.071(2),
P(1)–Ru(1)–Ru(2) = 53.264(13), C(1)–Ru(2)–Ru(1) = 56.36(6), P(1)–
Ru(2)–Ru(1) = 53.897(15), Ru(2)–P(1)–Ru(1) = 72.840(17).
˚
Spectroscopic data for 4 indicate that it retains its solid-
state structure in solution. The IR spectrum shows only ter-
minal carbonyl groups and the pattern is consistent with an

N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
1651
Ru2(CO)5 moiety. In the 1H NMR spectrum, in addition to
three multiplets at d 7.55, 6.60 and 6.41, each integrating
for three hydrogens, that are assigned to the ring protons
of the tri(2-furyl)phosphine ligand, the spectrum contains
nine well-separated signals between d 7.64–4.09, each inte-
grating for one hydrogen, assigned to the l-P(C4H3O)2 and
l-C4H3O ligands. The 31P{1H} NMR spectrum consists of
two equal intensity doublets at d À11.0 and 53.7 (JPÀP
20.2 Hz) assigned to the phosphido and phosphine ligands
respectively, while the FAB mass spectrum contains a
molecular ion peak at m/z 808 and fragmentation peaks
due to the sequential loss of five carbonyls.
Upon addition of excess CF3CO2H to a CD2Cl2 solu-
tion of 3, the color rapidly changed from pale yellow to yel-
low, and consistent with the formation of cationic species,
the m(CO) absorption bands were strongly shifted to higher
wave numbers. The cation generated is formulated as [(l-
H)Ru2(CO)6(l-g1,g2-C4H3O){l-P(C4H3O)2}]+ (6) and
protonation across the Ru–Ru vector is indicated by the
appearance of a high-field doublet at d À12.25 (JPÀH
24.8 Hz). In an analogous manner, addition of CF3CO2H
to 4 results in formation of cation [(l-H)Ru2(CO)5(l-
g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}]+ (7). In sup-
port of this, the hydride region of the 1H NMR of 7 exhib-
its a doublet of doublets at d À11.91 (JPÀH 23.6, 24.0 Hz),
while the 31P {1H} NMR spectrum shows two doublets at d
48.40 and À5.81 (JPÀP 25.3 Hz).
NMR spectrum, which displays eight well-separated sig-
nals in the region d 7.61–5.92 (each integrating for two pro-
tons), assigned to the protons of the furyl rings. The
31P{1H} NMR spectrum of 5 contains only a singlet at d
90.0 showing that the two phosphorus-containing ligands
are equivalent. Based on the spectroscopic data, we postu-
late that 5 is a 48-electron cluster with two bridging ortho-
metallated trifurylphosphine ligands {i.e. l-g1,g1-
P(C4H3O)2(C4H2O)} and nine carbonyl groups. The pre-
cise relative orientation of the phosphine ligands is
unknown. Complex 5 probably forms via the intermediate
generation of 1 followed by carbon–hydrogen activation of
one of the furyl rings of the coordinated ligand and subse-
quent H2 elimination. This transformation is accompanied
by dissociation of carbonyl in order to keep the closed triru-
thenium framework. We have recently reported a similar
bonding mode of the l-g1,g1-P(C4H3S)2(C4H2S) ligand in
the triosmium cluster [Os3(CO)9{P(C4H3S)3{l-P(C4H3S)2-
(C4H2S)}(l-H)] obtained from the reaction of Os3(CO)12
with tri(2-thienyl)phosphine at 110 °C [13]. To the best of
our knowledge, this type of furyl cyclometallation at a
trimetallic framework is unprecedented in the literature.
3.4. Facile CO substitution in Ru2(CO)6{l-P(C4H3O)2}
(l-g1,g2-C4H3O)] (3)
Previous studies have shown that 3 reacts with a series of
diphosphines including Ph2PXPPh2 (X = CH2, NH, NMe)
and Ph2P(CH2)nPPh2 (n = 2–3) at elevated temperatures
(110 °C), the products depending critically upon the nature
of the backbone. Thus Ph2PXPPh2 produce the substitution
3.3. Thermolytic reaction of [Ru3(CO)12] and
tri(2-furyl)phosphine
Heating [Ru3(CO)12] and tri(2-furyl)phosphine in ben-
zene affords, together with the dinuclear complexes 3 and
4 in 74% and 10% yields respectively, a third minor (6%
yield) product characterized as trinuclear [Ru3(CO)9{l-
g1,g2-P(C4H3O)2(C4H3O)}2] (5) (Scheme 2). We were
unable to obtain X-ray quality crystals of 5 and therefore
characterization is based on elemental analysis, IR, 1H
NMR, 31P-{1H} NMR and mass spectral data.
The FAB mass spectrum of 5 shows a molecular ion
peak at m/z 1019 and fragmentation peaks due to the
sequential loss of nine carbonyl groups suggesting an
Ru3(CO)9 core while the IR spectrum indicates that all car-
bonyl groups are terminal. Most informative is the 1H
products
[Ru2(CO)4(l-g1,g2-C4H3O){l-P(C4H3O)2}(l-
Ph2PXPPh2)] in which the diphosphine and the furyl ligands
simultaneously bridge the ruthenium–ruthenium vector,
whereas Ph2P(CH2)nPPh2 give the cyclometallated products
[Ru2(CO)5{l-g1-C6H4PPh(CH2)nPPh2}{l-P(C4H3O)2}] by
elimination of the coordinated furyl moiety [26b]. Following
these observations we set out to investigate the reactivity of 3
with a series of two-electron donor ligands to see the effect of
the steric bulk of the ligand on the structures of the products.
Complex 3 reacts rapidly and smoothly with an equimolar
amount of EPh3 (E = P, As, Sb) at room temperature to give
the substitution products [Ru2(CO)5(l-g1,g2-C4H3O){l-
P(C4H3O)2}(EPh3)] (E = P, 8; E = As, 9; E = Sb, 10) in
good yields. Compounds 8–10 have been characterized by
a combination of elemental analysis, IR, NMR and mass
spectral data together with single crystal X-ray diffraction
analysis for 8.
The molecular structure of 8 is depicted in Fig. 3 and
selected bond distances and angles are collected in the cap-
tion. The salient features of 8 in the solid-state remain
essentially the same as those of 4 except that the phosphine
ligand is coordinated to the ruthenium atom [Ru(1)] that is
r-bonded by the bridging r–p alkenyl moiety. The distri-
bution of carbonyl ligands around the diruthenium center
is the same as that found in 4 and satisfies the requirement
for an electron precise 34 valence electron complex. The
Fu
O
Fu
P
Ru
Ru
PFu3
Ru
Ru
3
+
Ru
P
Ru
4
+
80 oC
Fu
Fu
Fu = C4H3O
O
5
Scheme 2.

1652
N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
2 and 3). The ‘‘windshield–wiper” fluxionality [31] of r–p
alkenyl ligands is well-documented. In related diiron com-
plexes, it has been established that free energies of activa-
tion for this process vary significantly between a- and
b-substituted alkenyl ligands [32–35], the barriers for
b-substituted complexes being significantly lower than
those for isomeric a-alkenyl complexes. Further, disubsti-
tuted complexes behave essentially like their b-substituted
analogues. For example, the free energies of activation
for the isomeric pair [Fe2(CO)4(l-PhC@CH2)(l-PPh2)(l-
dppm)] and [Fe2(CO)4(l-HC@CHPh)(l-PPh2)(l-dppm)]
are 63 1 and 45 1 kJ molÀ1, respectively [35]. Since
all the r–p alkenyl complexes studied here are disubsti-
tuted we would expect them to have low free energies of
activation for the windshield–wiper fluxionality. The situa-
tion in unsymmetrically substituted binuclear centers, such
as the (CO)3Ru–Ru(CO)2L framework here, is complicated
by the inequivalence of the metal atoms in the high temper-
ature regime. Nevertheless, given that both r- and p-bound
phosphine derivatives are accessible (as shown by the solid-
state structures of 8 and 4, respectively) we would not
expect a major energy difference between the two. We
attempted to probe the fluxionality of 8 by variable temper-
ature NMR. At room temperature, the 31P{1H} NMR
spectrum of 8 in CD2Cl2 consists of two doublets at d
48.5 and 46.4 (JPÀP 16.4 Hz). Upon cooling to 233 K only
small changes are noted, including a slight increase in the
separation of the two signals from ca. 2–4 ppm, however,
below this temperature the spectrum changes significantly.
Thus, at 196 K it consists of a series of very broad reso-
nances spanning nearly 20 ppm. We have not been able
to go to lower temperatures but this data clearly shows that
the observed room temperature data is a high temperature-
limiting spectrum. The extreme broadening observed at 196
K cannot simply be attributed to the r–p alkenyl fluxional-
ity and probably results from a combination of this and
fluxionality of the Ru(CO)2(PPh3) unit via the well known
trigonal-twist process. If both of these processes are frozen
out then a total of six isomeric structures are possible and it
may be that at room temperature a number of these are
populated. In further support of the facile r–p alkenyl
fluxionality in 8 (and presumably other complexes of this
type) we note that for the related diphosphine-bridged
complexes [Ru2(CO)4(l-g1,g2-C4H3O){l-P(C4H3O)2}(l-
Ph2PXPPh2)] (X = CH2, NH), Wong and co-workers
report that the phosphorus nuclei of the diphosphine
ligands are equivalent at room temperature [25 b]. They
conclude that this is coincidental but we suggest that it is
rather due to the facile r–p alkenyl fluxionality of the furyl
ligand. They further report that the methylene protons of
the dppm ligand in [Ru2(CO)4(l-g1,g2-C4H3O){l-
P(C4H3O)2}(l-dppm)] are also equivalent at room temper-
ature – a situation that is only possible if both r–p alkenyl
fluxionality and diphosphine fluxionality are facile. We
have recently detailed an example of the latter in the
somewhat related complex [Fe2(CO)4{l-S(CH2)3S}(l-
dppm)] [36] and we suggest that a similar concerted dou-
Fig. 3. Molecular structure of [Ru2(CO)5{l-P(C4H3O)2}(l-g2-
C4H3O)(PPh3)] (8) showing 50% probability thermal ellipsoids. Selected
˚
bond distances (A) and angles (°): Ru(1)–Ru(2) = 2.78306(19), Ru(1)–
P(1) = 2.3322(4), Ru(1)–P(2) = 2.3198(4), Ru(2)–P(1) = 2.3508(4), Ru(1)–
C(6) = 2.0693(16), Ru(2)–C(6) = 2.3467(15), Ru(2)–C(7) = 2.3950(16),
C(6)–Ru(2)–Ru(1) = 77.85(5), C(6)–Ru(1)–Ru(2) = 55.52(4), C(6)–Ru(2)–
C(7) = 34.65(5),
C(7)–Ru(2)–Ru(1) = 76.66(4),
P(2)–Ru(1)–Ru(2) =
150.819(12), P(1)–Ru(1)–Ru(2) = 53.846(11), P(1)–Ru(2)–Ru(1) = 53.231
(11), C(6)–Ru(1)–P(2) = 103.41(4), P(2)–Ru(1)–P(1) = 108.669(15), Ru(1)–
P(1)–Ru(2) = 77.85(5).
furyl moiety is r-bonded to Ru(1) [Ru(1)–
˚
C(6) = 2.069(3) A] and p-bound to Ru(2) [Ru(2)–
˚
C(6) = 2.3467(15), Ru(2)–C(7) = 2.3950(16) A]. These
Ru–C distances are comparable to those observed in 3
and 4. The l-P(C4H3O)2 ligand asymmetrically spans the
Ru–Ru edge and the Ru–P distances [Ru(2)–
˚
P(1) = 2.3304(5), Ru(1)–P(1) = 2.3595(5) A] are compara-
ble to those observed for 3 and 4. The Ru(1)–P(1)–Ru(2)
angle of 108.67(2)° is significantly larger compared to the
corresponding angles in 3 and 4. Although bound to a dif-
ferent ruthenium center than that found in 4, the phosphine
still occupies an axial position lying trans to the ruthe-
nium–ruthenium bond [P(2)–Ru(1)–Ru(2) = 150.82(2)°].
Spectroscopic data for 8–10 are broadly consistent with
the solid state structure found in 8. Their IR spectra in
the carbonyl region are virtually indistinguishable, suggest-
ing structural similarity. The room temperature 31P{1H}
NMR spectrum of 8 consists of two doublets at d 45.7
and 48.3 (JPÀP = 15.3 Hz) while 9 and 10 exhibit only sing-
lets at d 50.1 and 53.6, respectively. In addition to the usual
1
phenyl proton resonances, the H NMR spectra of 8–10
display well-separated signals for the bridging C4H3O
and P(C4H3O)2 ligands and FAB mass spectra all show
molecular ions at m/z 838, 882 and 928, respectively.
3.5. Stereochemical nonrigidity of the substituted furyl-
bridged diruthenium complexes
We were intrigued as to why the phosphine coordination
in 4 and 8 differed, as shown by the X-ray structures (Figs.

N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
1653
ble trigonal-twist of the diphosphine may be occurring in
the above-mentioned dppm-bridged diruthenium com-
plex. If indeed a diphosphine is able to change coordina-
tion sites readily, then this suggests that movement of
monodentate ligands in a similar system is likely to be
very facile. We are currently investigating the fluxionality
of [Ru2(CO)4(l-g1,g2-C4H3O){l-P(C4H3O)2}(l-Ph2PCH2-
PPh2)] in order to confirm this. Thus we believe that
the room temperature NMR data for 8 (and presumably
9–10 and related complexes discussed below) represent
the high temperature-limiting spectra and therefore r–p
alkenyl fluxionality and the trigonal-twist of the
Ru(CO)2L moieties are both rapid on the NMR time-
scale at this temperature. The differences in the observed
solid-state structures of 4 and 8 then represent only dif-
ferences brought about by packing effects and other
solid-state interactions. It is clear that positioning of
the phosphine trans to the ruthenium–ruthenium vector
is preferred (since the structures of both 4 and 8 show
this) but other conformations must be accessible to per-
mit the suggested fluxional scheme (see Scheme 3).
For comparison, we have also studied the reactions of 3
with P(C4H3O)3 and P(OMe)3. Treatment of 3 with an
equimolar amounts of P(C4H3O)3 and P(OMe)3 yields 4
and [Ru2(CO)5(l-g2-C4H3O){l-P(C4H3O)2}{P(OMe)3}]
(11) in 87% and 69% yields, respectively. Their IR spectra
are very similar, indicating that they are isostructural.
The presence of a P(OMe)3 ligand in 11 is shown in the
31P{1H} NMR spectrum, which consists of equal intensity
doublets at d 157.9 and 49.1 (JPÀP 18.2 Hz), the former
being assigned to P(OMe)3 and latter to P(C4H3O)2. The
1H NMR spectrum of 11 contains six singlets at d 7.64,
7.59, 7.50, 6.64, 6.03 and 3.96 (each integrating for 1H),
a multiplet at d 6.35 (integrating for 3H), assignable to
the protons of the bridging C4H3O and P(C4H3O)2 ligands
and a doublet at d 3.53 (integrating for 9H) assigned to the
P(OMe)3 ligand.
Isocyanide is isoelectronic with CO and undergoes inser-
tion into M–C bonds, which represents reactions of funda-
mental importance for stoichiometric organic synthesis and
industrial catalysis [37–40]. As part of our investigations
into the chemistry of 3, we set out to investigate its reaction
with ButNC to see whether it inserts into Ru–C(furyl) bond
or displaces CO like the other two-electron donors
described above. Reaction of 3 with an equimolar amount
of ButNC at room temperature gives intractable materials.
However, dropwise addition of a CH2Cl2 solution of
ButNC to a solution of 3 (3/ButNC molar ratio = 1:1) in
the same solvent at 0 °C, followed by chromatographic sep-
aration, gives [Ru2(CO)5(l-g1,g2-C4H3O){l-P(C4H3O)2}
(NCBut)] (12) in 55% yield, instead of the expected inser-
tion product. The IR spectrum of 12 closely resembles that
of other monosubstituted derivatives, but 12 is only slightly
more electron rich as shown by the shift to lower wave
1
numbers (ca. 2–6 cmÀ1). The H NMR spectrum contains
six singlets at d 7.64, 7.59, 7.50, 6.65, 6.04, 4.13 (each inte-
grating for 1H) and a multiplet at d 6.36 (integrating for
3H) assigned to the protons of the bridging C4H3O and
P(C4H3O)2 ligands, with a further singlet at d 1.40 (9H),
assigned to the ButNC ligand. As expected, the 31P{1H}
NMR spectrum shows only a singlet (d 55.4) and the
FAB mass spectrum gives a molecular ion peak at m/z 659.
3.6. Cyclotrimerization of dimethylacetylenedicarboxylate
(DMAD)
The synthesis and reactivity of organometallic com-
plexes have attracted considerable attention because of
their application to effective organic transformation [41–
44]. The reactivity of 3 with a variety of terminal alkynes
to give a head-to-tail coupling of a 1-alkyne with the l-
g1,g2-C4H3O moiety of 3 to form a furyl based four-car-
bon chain with l-g1,g1,g2,g3-coordination mode to the
ruthenium centers has been demonstrated by Wong et al.
Fu
Fu
Fu
Fu
P
Fu
Fu
Ph3E
P
P
L
EPh3
L
Ru
O
Ru
Ru
O
Ru
Ru
O
Ru
3
E = P, 8
PFu3
L = P(OMe)3, 11
L = ButNC, 12
RC CR
E = As, 9
E = Sb, 10
R
R
R
R
Fu
Fu
R = CO2Me
P
R
Ru
Ru PFu3
R
O
13
4
Scheme 3.

1654
N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
[26a]. The cyclotrimerization of alkynes to form highly
substituted benzenes is an intriguing reaction that has con-
tinued to be of interest. Reaction of 3 with excess DMAD
in refluxing toluene for 4 h gives a pale yellow solution
that, upon separation by TLC, affords C6(CO2Me)6 in
addition to some unconsumed 3. The cyclotrimerization
product has been characterized by 1H, 13C NMR spectros-
copy and elemental analysis, the former corresponding to
data reported by Thomas and Darkwa [45].
University for sabbatical leave. M.A.R. gratefully
acknowledges the Dutch-Bangla Bank Foundation for a
Scholarship. This research has been sponsored by the
Swedish International Development Agency (SIDA) via
and the Swedish Research Links programme and the Swed-
ish Research Council (VR). We thank Prof. A.J. Deeming
for valuable discussions.
References
4. Conclusions
[1] M.I. Bruce, G. Shaw, F.G.A. Stone, J. Chem. Soc., Dalton Trans.
(1972) 2094.
[2] M.I. Bruce, T.W. Hambely, B.K. Nicholson, M.R. Snow, J. Orga-
nomet. Chem. 235 (1982) 83.
[3] M.I. Bruce, J.G. Matisons, B.K. Nicholson, J. Organomet. Chem.
247 (1983) 321.
[4] M.I. Bruce, M.J. Liddell, C.A. Hughes, B.W. Skelton, A.H. White, J.
Organomet. Chem. 347 (1988) 157.
[5] M.I. Bruce, M.J. Liddell, C.A. Hughes, I.M. Patrick, B.W. Skelton,
A.H. White, J. Organomet. Chem. 347 (1988) 181.
[6] N.E. Leadbeater, P.R. Raithby, J. Coord. Chem. 54 (2001) 101.
[7] M.I. Bruce, M.J. Liddell, O. bin Shawkataly, C.A. Hughes, B.W.
Skelton, A.H. White, J. Organomet. Chem. 347 (1988) 207.
[8] A.J. Deeming, S.N. Jayasuriya, A.J. Arce, Y. De Sanctis, Organo-
metallics 15 (1996) 786.
[9] A.J. Deeming, M.K. Shinhmar, A.J. Arce, Y.De. Sanctis, J. Chem.
Soc., Dalton Trans. (1999) 1153.
[10] N.K. Kiriakidou Kazemifar, M.J. Stchedroff, M.A. Mottalib, S.
Selva, M. Monari, E. Nordlander, Eur. J. Inorg. Chem. (2006)
2058.
[11] S.P. Tunik, I.G. Koshevoy, A.J. Poe¨, D.H. Farrar, E. Nordlander,
M. Haukka, P.A. Pakkanen, Dalton Trans. (2003) 2457.
[12] N.K. Kiriakidou Kazemifar, M.J. Stchedroff, M.H. Johansson, M.A.
Mottalib, M. Monari, E. Nordlander, Unpublished results.
[13] M.A. Mottalib, S.E. Kabir, D.A. Tocher, A.J. Deeming, E. Nord-
lander, J. Organomet. Chem. 692 (2007) 5007.
[14] J.D. King, M. Monari, E. Nordlander, J. Organomet. Chem. 573
(1999) 272.
[15] U. Bodensieck, H. Vahrenkamp, G. Rheinwald, H. Stoeckli-Evans,
J. Organomet. Chem. 488 (1995) 85.
The present work has demonstrated the variable coordi-
nation modes of the tri(2-furyl)phosphine ligand. It can
serve as monodentate two-electron phosphorus donor in
the substitution of [Ru3(CO)12] with tri(2-furyl)phosphine
under mild conditions to afford the di- and tri-substituted
complexes [Ru3(CO)10{P(C4H3O)3}2] (1) and [Ru3(CO)9-
{P(C4H3O)3}3] (2), respectively. Unlike the triruthenium
complexes of related P, S-donor ligands, gentle heating of
these clusters in the presence of Me3NO affords the phos-
phido-bridged dinuclear compounds [Ru2(CO)6(l-l-
g1,g2-C4H3O){(l-P(C4H3O)2)}] (3) and [Ru2(CO)5(l-
g1,g2-C4H3O){l-P(C4H3O)2}{P(C4H3O)3}] (4), respec-
tively, upon extrusion of a ruthenium atom and concomi-
tant phosphorus–carbon bond cleavage of the
coordinated tri(2-furyl)phosphine ligand with the dissoci-
ated furyl moiety binding to the diruthenium unit in a
r,p-alkenyl fashion. We have established that the previous
formation of 3 from the direct reaction of [Ru3(CO)12] pro-
ceeds via the intermediate formation of 2. Two-electron
donor ligands such as EPh3 (E = P, As, Sb), P(OMe)3,
ButNC and P(C4H3O)3 react smoothly with 3 at room tem-
perature to give substitution products 8–12 and 4, respec-
tively. In 8, the substitution takes place at the r-bonded
ruthenium atom, whereas in 4 it is bound to the p-bonded
ruthenium atom. We believe that all monosubstituted
derivatives are highly fluxional at room temperature; thus,
the structures determined by X-ray crystallography are
likely to be determined by solid-state interactions (e.g.
packing effects) and are not necessarily representative of
the (preferred) solution structure(s).
[16] (a) A.J. Deeming, M.B. Smith, J. Chem. Soc., Chem. Commun.
(1993) 844;
(b) A.J. Deeming, M.B. Smith, J. Chem. Soc., Dalton Trans. (1993)
3383.
[17] N. Lugan, G. Lavigne, J.-J. Bonnet, Inorg. Chem. 26 (1987) 585.
[18] V.I. Ponomarenko, T.S. Pilyugina, V.D. Khripun, E.V. Grachova,
S.P. Tunik, M. Haukka, T.A. Pakkanen, J. Organomet. Chem. 691
(2006) 111.
[19] C.G. Arena, D. Drommi, F. Faraone, M. Lanfranchi, F. Nicolo, A.
Tiripicchio, Organometallics 15 (1996) 3170.
[20] R. Gobetto, C.G. Arena, D. Drommi, F. Faraone, Inorg. Chim.
Acta 248 (1996) 257.
5. Supplementary material
CCDC 655913, 655914, 655915 contain the supplemen-
tary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_re-
quest/cif.
[21] (a) K. Wajda-Hermanowicz, F. Pruchnik, M. Zuber, G. Rusek, E.
Gladecki, Inorg. Chim. Acta 232 (1995) 207;
(b) K. Wajda-Hermanowicz, M. Koralewicz, F.P. Pruchnik, Appl.
Organomet. Chem. 4 (1990) 173;
(c) E. Gladecka, K. Gladecki, K. Wajda-Hermanowicz, F.P. Pruch-
nik, J. Chem. Crystallogr. 25 (1995) 717;
(d) K. Wajda-Hermanowicz, F. Pruchnik, M. Zuber, J. Organomet.
Chem. 508 (1996) 75;
Acknowledgements
(e) F.-E. Hong, S.-C. Chen, Y.-T. Tsai, Y.-C. Chang, J. Organomet.
Chem. 655 (2002) 172;
(f) D. Belletti, C. Graiff, C. Massera, G. Predieri, A. Tiripicchio,
Inorg. Chim. Acta 350 (2003) 421.
N.B. thanks Sher-e-Bangla Agricultural University for
leave to work at Lund University. S.E.K. acknowledges
the Royal Society (London) for a fellowship to work at
University College London, and thanks Jahangirnagar
[22] E. Lam, D.H. Farrar, C.S. Browning, A.J. Lough, Dalton Trans.
(2004) 3383.

N. Begum et al. / Journal of Organometallic Chemistry 693 (2008) 1645–1655
1655
[23] K. Wajda-Hermanowicz, Z. Ciunik, A. Kochel, Inorg. Chem. 45
(2006) 3369.
[32] G. Hogarth, M.H. Lavender, J. Chem. Soc., Dalton Trans. (1992)
2759.
[24] (a) M.I. Bruce, D.C. Kehoe, J.G. Matisons, B.K. Nicholson, P.H.
Rieger, M.L. Williams, J. Chem. Soc., Chem. Commun. (1982) 442;
(b) M.I. Williams, M.I. Bruce, J.G. Matisons, B.K. Nicholson, J.
Organomet. Chem 247 (1983) 321;
[33] G. Hogarth, K. Shukri, S. Doherty, A.J. Carty, G.D. Enright, Inorg.
Chim. Acta 291 (1999) 178.
[34] M.K. Anwar, G. Hogarth, O.S. Senturk, W. Clegg, S. Doherty,
M.R.J. Elsegood, J. Chem. Soc., Dalton Trans. (2001) 341.
[35] G. Hogarth, M.H. Lavender, K. Shukri, J. Organomet. Chem. 527
(1997) 247.
(c) J.E. Cyr, P.H. Rieger, Organometallics 10 (1991) 2153;
(d) J.E. Cyr, J.A. DeGray, D.K. Gosser, E.S. Lee, S. Elizabeth, P.H.
Rieger, Organometallics 4 (1985) 950;
(e) M. Arewgoda, B.H. Robinson, J. Simpson, J. Am. Chem. Soc.
105 (1983) 1893;
(f) B.M. Peake, B.H. Robinson, J. Simpson, D.J. Watson, J. Chem.
Soc., Chem. Commun. (1974) 945;
(g) P.A. Dawson, B.M. Peake, B.H. Robinson, J. Simpson, Inorg.
Chem. 19 (1980) 465.
[36] F.I. Adam, G. Hogarth, I. Richards, J. Organomet. Chem. 692 (2007)
3957.
[37] M. Knorr, I. Jourdain, P. Braunstein, C. Strohmnn, A. Tiripicchio,
F. Ugozzoli, Dalton Trans. (2006) 5248, and references therein.
[38] (a) J. Durand, B. Milani, Coord. Chem. Rev. 250 (2006) 542;
(b) C. Bianchini, A. Meli, W. Oberhauser, Dalton Trans. (2003) 2627;
(c) S. Meeking, Coord. Chem. Rev. 203 (2000) 542;
(d) C. Bianchini, A. Meli, Coord. Chem. Rev. 225 (2002) 35;
(e) K.J. Cavell, Coord. Chem. Rev. 155 (1996) 209.
[39] (a) Y. Yamamoto, H. Yamazaki, Coord. Chem. Rev. 8 (1972) 225;
(b) P.M. Maitlis, Acc. Chem. Res. 9 (1976) 93.
[40] M. Catellani, E. Motti, I. Paterlini, J. Organomet. Chem. 593–594
(2000) 240.
[41] Y. Uozumi, M. Nakazono, Adv. Synth. Catal. 344 (2002) 274, and
references therein.
[25] S.E. Kabir, E. Nordlander, Unpublished results.
[26] (a) W.-Y. Wong, F.-L. Ting, W.-L. Lam, J. Chem. Soc., Dalton
Trans. (2001) 2981;
(b) W.-Y. Wong, F.-L. Ting, W.-L. Lam, Eur. J. Inorg. Chem. (2002)
2103;
(c) W.-Y. Wong, F.-L. Ting, Z. Lin, Organometallics 22 (2003) 5100.
[27] M. Ackermann, A. Pascarifu, T. Ho¨cher, H.-U. Siehl, S. Berger, J.
Am. Chem. Soc. 128 (2006) 8434.
[28] SMART and SAINT software for CCD diffractometers, version 6.1,
Madison, WI, 2000.
[29] G.M. Sheldrick, SHELXTL PLUS, version 6.1, Bruker AXS, Madison,
WI, 2000.
[30] S.E. Kabir, D.A. Tocher, G. Hogarth, Unpublished results.
[31] (a) J.R. Shapley, S.I. Richter, M. Tachikawa, J.B. Keister, J.
Organomet. Chem. 94 (1975) C43;
[42] (a) C.C. Yin, A.J. Deeming, J. Organomet. Chem. 144 (1978) 351;
(b) C.Y. Ren, W.C. Cheng, W.C. Chan, C.H. Yeung, P.C. Lau, J.
Mol. Catal. 59 (1990) L1;
(c) W. Baidossi, N. Goren, J. Blum, H. Schumann, H. Hemling, J.
Mol. Catal. 85 (1993) 153.
[43] N. Mori, S. Ikeda, K. Odashima, J. Chem. Soc., Chem. Commun.
(2001) 181.
(b) L.J. Farrugia, Y. Chi, W.-C. Tu, Organometallics 12 (1993) 1616,
and references therein.
[44] M. Deng, W.K. Leong, Organometallics 19 (2000) 1221.
[45] M.S. Thomas, J. Darkwa, Polyhedron 17 (1998) 1811.