Perpendicular to parallel reorientation of a terminal alkyne on a mixed-metal triangle; synthesis and structural characterisation

Article abstract of DOI:10.1039/b110874n

Reaction of [Fe₂(CO)₆(μ-η²-CCPh)(μ-PPh ₂)]1 with [W₂(CO)₄(η⁵-C₅H₅) ₂] affords the coordinatively unsaturated 46-electron trinuclear Fe₂W cluster [Fe₂W(CO)₅(η⁵-C₅H ₅){μ₃-η²-(⊥)-HCCPh}(μ-CO) (μ-PPh₂)]2, in which an Fe-W edge is perpendicularly-bridged by a terminal alkyne molecule. Treatment of 1 with [Mo₂(CO)₄(η⁵-C₅H ₅)₂] also gives a 46-electron cluster, [Fe₂Mo(CO)₅(η⁵-C₅H ₅){μ₃-η²-(⊥)-HCCPh}(μ-CO) (μ-PPh₂)]3, the molybdenum analogue of 2 and, in addition, the saturated 48-electron FeMo₂ trinuclear cluster [FeMo₂(CO)₅(η⁵-C₅H ₅)₂{μ₃-η²-(⊥)-CCPh}- (μ-PPh₂)]4, in which an acetylide ligand perpendicularly bridges an Fe-Mo bond. The trimetallic FeWCo acetylide-bridged species, [FeWCo(CO)₆(η⁵-C₅H₅){μ ₃-η²-(⊥)-CCPh}(μ-PPh₂)]5, is the unique product when 1 is treated with the WCo heterobimetallic complex [CoW(η⁵-C₅H₅)(CO)₇], while the corresponding reaction of 1 with [CoMo(η⁵-C₅H₅)(CO)₇], leads to 3 and the molybdenum analogue of 5, [FeMoCo(CO)₆(η⁵-C₅H₅){μ ₃-η²-(⊥)-CCPh}(μ-PPh₂)]6. Carbonylation of 3 at elevated pressure (80 atm CO) results in a ⊥-∥ alkyne reorientation to give the 48-electron cluster, [Fe₂Mo(CO)₆(η⁵-C₅H ₅){μ₃-η²-(∥)-HCCPh}(μ-CO) (μ-PPh₂)]7, as the sole product. Conversion of 7 back to 3 has been shown to occur in solution at room temperature. Single crystal X-ray diffraction studies have been performed on 2, 3, 4, 6 and 7.

Full text of DOI:10.1039/b110874n

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Perpendicular to parallel reorientation of a terminal alkyne on
a mixed-metal triangle; synthesis and structural characterisation
Martin J. Mays,*a Paul R. Raithby,a Koshala Sarveswarana and Gregory A. Solan*b
a Department of Chemistry, Lensfield Road, Cambridge, UK CB2 1EW.
E-mail: mjm14@cam.ac.uk
b Department of Chemistry, University of Leicester, University Road, Leicester, UK LE1 7RH.
E-mail: gas8@le.ac.uk
Received 27th November 2001, Accepted 30th January 2002
First published as an Advance Article on the web 22nd March 2002
Reaction of [Fe2(CO)6(µ-η2-CCPh)(µ-PPh2)] 1 with [W2(CO)4(η5-C5H5)2] affords the coordinatively unsaturated
46-electron trinuclear Fe2W cluster [Fe2W(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)] 2, in which an Fe–W
edge is perpendicularly-bridged by a terminal alkyne molecule. Treatment of 1 with [Mo2(CO)4(η5-C5H5)2] also gives
a 46-electron cluster, [Fe2Mo(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)] 3, the molybdenum analogue of
2 and, in addition, the saturated 48-electron FeMo2 trinuclear cluster [FeMo2(CO)5(η5-C5H5)2{µ3-η2-(⊥)-CCPh}-
(µ-PPh2)] 4, in which an acetylide ligand perpendicularly bridges an Fe–Mo bond. The trimetallic FeWCo acetylide-
bridged species, [FeWCo(CO)6(η5-C5H5){µ3-η2-(⊥)-CCPh}(µ-PPh2)] 5, is the unique product when 1 is treated with
the WCo heterobimetallic complex [CoW(η5-C5H5)(CO)7], while the corresponding reaction of 1 with [CoMo(η5-
C5H5)(CO)7], leads to 3 and the molybdenum analogue of 5, [FeMoCo(CO)6(η5-C5H5){µ3-η2-(⊥)-CCPh}(µ-PPh2)]
6. Carbonylation of 3 at elevated pressure (80 atm CO) results in a ⊥–|| alkyne reorientation to give the 48-electron
cluster, [Fe2Mo(CO)6(η5-C5H5){µ3-η2-(||)-HCCPh}(µ-CO)(µ-PPh2)] 7, as the sole product. Conversion of 7 back
to 3 has been shown to occur in solution at room temperature. Single crystal X-ray diffraction studies have been
performed on 2, 3, 4, 6 and 7.
1
Introduction
᎐
᎐
᎐
The facility of internal alkynes (RC᎐CR or RЈC᎐CR, R = RЈ =
᎐
hydrocarbyl) to bind to trinuclear transition metal centres has
been well documented and indeed two different bonding modes
predominate namely, µ3-η2-(⊥) and µ3-η2-(||) modes,1,2 the latter
of which is considerably more common. In the main, the
perpendicular bonding mode is exhibited for unsaturated
46-electron counts2,3 and the parallel mode for saturated
48-electron counts.1,4 One important exception to this pattern is
the 46-electron cluster [Rh3(η5-C5H5)(acac)(CO)(CF3C2CF3)]
(acac = acetylacetonate), in which the alkyne adopts an
µ3-η2-(||) coordination mode.5
Fig. 1 Thermolysis of 1 to give [Fe4(CO)8(µ-PPh2)2(µ4-PhCCCCPh)].9,10
2
Results and discussion
2.1 Reaction of 1 with [M2(CO)4(ꢀ5-C5H5)2] (M ؍ W, Mo)
Conversely, the synthesis of trimetallic complexes containing
6
᎐
coordinated terminal alkynes (RC᎐CH) are rare, due in part
Treatment of 1 with the triply bonded ditungsten complex
[W2(CO)4(η5-C5H5)2] (generated in situ) in xylene at 363 K gave
᎐
to the ready transfer of the H-substituent of the alkyne to
the metal framework.1,2,7 Moreover, to the knowledge of the
authors, only one example of a trimetallic cluster containing
a perpendicularly-bridged terminal alkyne has been reported,
namely [Fe3(CO)9{µ3-η2-(⊥)-HCCOC(O)Me}], this species
being isolable only below Ϫ70 ЊC.8
[Fe2W(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)]
2
as the sole product in 23% yield. Similar treatment of [Fe2(CO)6-
(µ-η2-CCPh)(µ-PPh2)] with [Mo2(CO)4(η5-C5H5)2] in toluene
at 353 K afforded [Fe2Mo(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}-
(µ-CO)(µ-PPh2)]
3
and [FeMo2(CO)5(η5-C5H5)2{µ3-η2-(⊥)-
Recently, Carty and our group independently reported that
the thermolysis of [Fe2(CO)6(µ-η2-CCPh)(µ-PPh2)] 1 leads to
regioselective dimerisation and carbonyl loss to give the tetra-
iron cluster [Fe4(CO)8(µ4-PhCCCCPh)(µ-PPh2)2], in which
the two phenylacetylide fragments have coupled through the
centre of the Fe4 plane (Fig. 1).9,10 In this paper we investigate
the thermolytic reactivity of 1 in the presence of bimetallic
carbonyl species including the homobimetallic group 6 com-
plexes [M2(CO)4(η5-C5H5)2] (M = W, Mo) and the hetero-
bimetallic group 6–group 9 complexes [CoM(η5-C5H5)(CO)7]
(M = W, Mo).
CCPh}(µ-PPh2)] 4, in a combined yield of 42% (Scheme 1).
Complexes 2, 3 and 4 have been characterised by 1H, 31P-{1H},
13C-{1H} NMR and IR spectroscopy and by mass spectrometry
and microanalysis (Table 1 and Experimental Section). In
addition, all these complexes have been the subjects of single
crystal X-ray diffraction studies.
The molecular structure of 2 is depicted in Fig. 2 while
selected bond distances and angles are, for both 2 and the
isostructural 3, listed in Table 2. The core of 2 consists of one
tungsten atom, two iron atoms and two carbon atoms in a
closo-trigonal bipyramidal arrangement. The alkyne carbon
DOI: 10.1039/b110874n
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This journal is © The Royal Society of Chemistry 2002
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Table 1 Infrared, 1H and 31P NMR data for the new complexes 2–7
Compound ν(CO)a/cmϪ1 1H NMR (δ)b
31P NMR (δ)c
2
3
4
5
6
7
2024vs, 1990vs, 1959s, 1784w
2027vs, 1992vs, 1962s, 1790w
2028vs, 1989s, 1961m
2054vs, 2010s, 1995s, 1952sh
2037m, 2010vs, 1978s, 1989sh
2046s, 2011s, 1983s, 1949m, 1893w 7.7–7.1 [m, 15H, Ph], 4.80 [s, 5H, Cp]
7.5–7.1 [m, 15H, Ph], 5.30 [s, 5H, Cp], 1.30 [d, 3J(PH) 5, 1H, CH] 160.7 [s, J(PW) 134, µ-PPh2]
7.5–7.2 [m, 15H, Ph], 5.28 [s, 5H, Cp], 1.27 [d, 3J(PH) 6, 1H, CH] 194.7 [s, µ-PPh2]
7.8–6.6 [m, 15H, Ph], 5.26 [s, 10H, Cp]
7.7–6.8 [m, 15H, Ph], 5.30 [s, 5H, Cp]
7.7–6.8 [m, 15H, Ph], 5.40 [s, 5H, Cp]
173.3 [s, µ-PPh2]
145.8 [s, µ-PPh2]
220.1 [s, µ-PPh2]
218.9 [s, µ-PPh2]
a Recorded in n-hexane solution. b 1H chemical shifts (δ) in ppm relative to SiMe4 (0.0 ppm), coupling constants in Hz in CDCl3 at 293 K. c 31P
chemical shifts (δ) in ppm relative to 85% external H3PO4 (0.0 ppm) (upfield shifts negative). Spectra were {1H}-gated decoupled and measured in
CDCl3 at 293 K.
Table 2 Selected bond distances (Å) and angles (Њ) for 2 and 3
2 (M = W)
3 (M = Mo)
M(1)–Fe(1)
M(1)–Fe(2)
M(1)–Cp(centroid)
M(1)–C(5)
M(1)–C(24)
M(1)–C(25)
M(1)–P(1)
Fe(1)–Fe(2)
Fe(2)–C(5)
Fe(2)–P(1)
Fe(2)–C(24)
Fe(1)–C(24)
Fe(1)–C(25)
C(24)–C(25)
C(25)–C(26)
Mean Fe–C(carbonyl)
2.786(1)
2.627(1)
2.025(9)
1.972(8)
2.307(8)
2.058(7)
2.417(2)
2.567(2)
2.413(8)
2.178(2)
2.053(7)
2.008(7)
1.981(7)
1.410(10)
1.501(10)
1.786
2.777(1)
2.625(1)
2.027(6)
1.960(6)
2.294(6)
2.087(5)
2.426(1)
2.568(1)
2.394(6)
2.179(2)
2.045(5)
2.025(6)
1.978(5)
1.414(7)
1.476(7)
1.784
Fe(1)–Fe(2)–M(1)
Fe(2)–Fe(1)–M(1)
Fe(1)–M(1)–Fe(2)
Fe(2)–P(1)–M(1)
Fe(2)–C(5)–M(1)
C(25)–C(24)–Fe(2)
C(25)–C(24)–Fe(1)
C(24)–M(1)–Fe(2)
C(25)–M(1)–Fe(1)
C(25)–Fe(1)–M(1)
C(24)–Fe(1)–M(1)
64.85(4)
58.62(4)
56.53(4)
69.52(7)
72.8(3)
127.6(6)
68.3(4)
48.7(2)
45.3(2)
47.5(2)
54.7(2)
64.65(3)
58.65(3)
56.69(3)
69.25(4)
73.4(2)
128.8(4)
67.6(3)
48.6(1)
45.3(1)
48.6(2)
54.4(2)
Scheme1 Reagentsandconditions:(i)[W2(CO)4(η5-C5H5)2],C6H4(CH3)2,
363 K; (ii) [Mo2(CO)4(η5-C5H5)2], C6H5CH3, 363 K; (iii) [MoCo(CO)7-
(η5-C5H5)], C6H5CH3, 373 K; (iv) [WCo(CO)7(η5-C5H5)], C6H5CH3,
373 K.
Fig.
2
Molecular structure of [Fe2W(CO)5(η5-C5H5){µ3-η2-(⊥)-
atom C(24) occupies a five-connected equatorial vertex of the
trigonal bipyramid while the other alkyne carbon atom C(25)
occupies a four-connected apical position. The W(1)–Fe(2)
edge of the polyhedron is bridged unsymmetrically by a
diphenylphosphido group [W(1)–P(1) 2.417(2), Fe(2)–P(1)
2.178(2) Å] and by a semi-bridging carbonyl group [W(1)–C(5)
1.972(8), Fe(2)–C(5) 2.413(8) Å]. The Fe(2)–W(1) bond
distance of 2.627(1) Å is significantly shorter than the Fe(1)–
W(1) bond distance 2.786(1) Å, this presumably being the
consequence of the constraints imposed by the two bridging
ligands. The orientation of the alkyne carbon–carbon bond
with respect to the Fe2W triangle is perpendicular to the Fe(1)–
HCCPh}(µ-CO)(µ-PPh2)] 2 including the atom numbering scheme.
All hydrogen atoms except for H24 have been omitted for clarity.
W(1) vector [i.e., µ3-η2-(⊥)], a bonding mode that has been
observed for several other crystallographically characterised
46-electron alkyne-bridged trimetallic clusters.3 The carbon–
carbon bond distance [C(24)–C(25) 1.410(10) Å] of the
coordinated alkyne falls in the mid-range for other reported
alkyne-bridged trimetallic complexes.11
The coordination spheres are completed at Fe(1) by three
terminal carbonyl groups, Fe(2) by two terminal groups and
W(1) by an η5-cyclopentadienyl group. The molecular structure
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of 3 is essentially the same as 2 with a molybdenum atom
occupying the tungsten site in 2. For both 2 and 3 the alkynic
hydrogen atoms (H24) were located in the final difference maps
and refined successfully.
The structure of 4 consists of a Mo2Fe triangle in which a
phenylacetylide unit σ-bonds to Mo(1) and perpendicularly
bridges the Mo(1)–Fe(2) metal–metal bond via its π-orbitals
to form a closo-trigonal-bipyramidal arrangement. The Mo(1)–
Mo(2) vector [2.987(2) Å] is, in addition, unsymmetrically
bridged by a diphenylphosphido group [Mo(1)–P(1) 2.400(4) Å,
Mo(2)–P(1) 2.450(3) Å], with each molybdenum centre bound
by a η5-cyclopentadienyl ligand and by a terminal carbonyl
ligand. At iron three terminal carbonyl ligands complete
the coordination sphere. The acetylide C–C bond distance is
1.33(2) Å and falls in the range observed for a number of other
acetylide-bridged heterotrimetallic complexes.12 A formal elec-
tron count shows that the –CCPh unit functions as a five-
electron donor to furnish a saturated 48-electron cluster giving
rise to a closo-trigonal bipyramidal, six skeletal electron pair
structure.
The spectroscopic and analytical data for 4 are consistent
with the above formulation. In the IR spectrum, carbonyl
absorptions are observed for terminal carbonyl groups only.
The 1H NMR spectrum shows a multiplet for the phenyl
protons and one broad signal for the cyclopentadienyl ligands
integrating to ten protons despite the inequivalent chemical
environments. In the 31P-{1H} NMR spectrum a sharp singlet at
δ 173.3 is seen for the bridging phosphido group. The 13C-{1H}
NMR spectrum shows, in addition to phenyl and cyclopenta-
dienyl resonances, peaks due to the terminal carbonyl groups
and acetylide carbon atoms. The acetylide signals are seen as
singlets at δ 161.5 and 146.4, the more downfield signal being
assigned to the α-carbon and the more upfield signal to the
β-carbon atom (CPh). A similar assignment for the acetylide
α- and β-carbon atoms was made previously for [Mo3(CO)5-
(η5-C5H5)3{µ3-η2-(⊥)-CCPh}].13
The spectroscopic properties of 2 and 3 are in accord with
their solid state structures being maintained in solution. The IR
spectra of 2 and 3 show, in addition to three bands in the
terminal carbonyl region, single bands at 1784 cmϪ1 (2) and
1790 cmϪ1 (3) due to the stretching vibration of the semi-
1
bridging carbonyl groups. In the room temperature H NMR
spectra, signals for the cyclopentadienyl protons [δ 5.30 (2) and
5.28 (3)] and phenyl groups are seen as singlets and multiplets
respectively, while the alkynic hydrogen atoms can be seen
upfield as doublets at δ 1.30 [3J(PH) 5 Hz] for 2 and δ 1.27
[3J(PH) 6 Hz] for 3. A similar chemical shift for the alkynic
hydrogen atom has been observed at low temperature for
[Fe3(CO)9{µ3-η2-(⊥)-HCCOC(O)Me}], in which a singlet is seen
at δ 1.55.8
The 13C-{1H} NMR spectra at room temperature for 2 and 3
exhibit, in addition to phenyl and cyclopentadienyl peaks, two
signals for the α- and β-carbon atoms of the phenylacetylene
molecule. The downfield signals [δ 152.0 (2), 151.8 (3)] take the
form of singlets and are attributed to the β-carbon atoms (CPh)
while the upfield signals [δ 60.1 (2) and 61.8 (3)] are seen as
doublets [3J(PC) 14 Hz (2 and 3)] and are assigned to the α-
carbon atoms (CH). In [Fe3(CO)9{µ3-η2-(⊥)-HCCOC(O)Me}],8
a similar upfield chemical shift for the α-carbon is seen at δ 70.2.
Furthermore, the 13C DEPT90 NMR spectrum for 3 is consist-
ent with this assignment, with a proton being located on the
α-carbon atom. In 2, four peaks in the typical region for
iron bound carbonyl groups are observed along with a single
resonance at δ 195.0, for the bridging carbonyl group. The
31P-{1H} NMR spectra exhibit singlet resonances at δ 160.7 (2)
and 194.7 (3), the former of which is flanked by 183W satellites
[J(WP) 134 Hz].
2.2 Reaction of 1 with [CoM(CO)7(ꢀ5-C5H5)] (M ؍ W, Mo)
Reaction of 1 with [CoW(CO)7(η5-C5H5)] in toluene at 363–373
K for 24 h affords the heterotrimetallic acetylide cluster
[FeWCo(CO)6(η5-C5H5){µ3-η2-(⊥)-CCPh}(µ-PPh2)] 5 as the
sole product in moderate yield. Similar treatment of 1 with
[CoMo(CO)7(η5-C5H5)] gives [FeMoCo(CO)6(η5-C5H5){µ3-η2-
(⊥)-CCPh}(µ-PPh2)] 6, along with [Fe2Mo(CO)5(η5-C5H5)-
{µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)] 3, in good overall yield
(Scheme 1). Complexes 5 and 6 have been characterised by 1H,
31P-{1H}, 13C-{1H} NMR and IR spectroscopy along with mass
spectrometry and microanalysis (Table 1 and Experimental
section). In addition, 6 has been the subject of a single crystal
X-ray diffraction study.
The pathway by which the formation of the phenylacetylene
ligands in 2 and 3, from the reaction of 1 with [M2(CO)4(η5-
C5H5)2] (M = W, Mo), takes place is uncertain. By analogy
with the low temperature reaction of the anionic triiron cluster
[Fe3(CO)9{µ3-η2-(⊥)-CCOC(O)Me}]Ϫ with protonic acids,
which affords [Fe3(CO)9{µ3-η2-(⊥)-HCCOC(O)Me}],8 it would
seem likely that the anionic species [Fe2M(CO)5(η5-C5H5){µ3-η2-
(⊥)-CCPh}(µ-CO)(µ-PPh2)]Ϫ (M = W, Mo) are generated
initially followed by protonation to give 2 or 3. This protonation
may occur, for example, during the chromatographic work-up.
The molecular structure of 4 is depicted in Fig. 3 while
A view of 6 is shown in Fig. 4 and selected bond distances and
angles are collected in Table 4. The molecule consists of core
atoms Mo(1), Fe(1), Co(1), C(8) and C(7) which adopt a closo-
Fig.
3
Molecular structure of [FeMo2(CO)5(η5-C5H5)2{µ3-η2-(⊥)-
CCPh}(µ-PPh2)] 4 including the atom numbering scheme. All hydrogen
atoms have been omitted for clarity.
selected bond distances and angles are listed in Table 3. Crystals
suitable for the X-ray structure determination were obtained by
slow evaporation from a dichloromethane–hexane solution at
273 K.
Fig. 4 Molecular structure of [FeMoCo(CO)6(η5-C5H5){µ3-η2-(⊥)-
CCPh}(µ-PPh2)] 6 including the atom numbering scheme. All hydrogen
atoms have been omitted for clarity.
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Table 3 Selected bond distances (Å) and angles (Њ) for 4
Fe(1)–Mo(1)
Fe(1)–Mo(2)
Mo(2)–C(5)
Mo(2)–C(6)
Mo(1)–P(1)
Mo(1)–C(1)
Mo(1)–C(6)
Fe(1)–C(7)
C(7)–C(8)
2.845(2)
2.738(2)
1.947(15)
2.266(13)
2.400(4)
1.98(2)
1.992(12)
2.089(11)
1.47(2)
Mo(1)–Mo(2)
Mo(2)–Cp(centroid)
Mo(2)–P(1)
Mo(2)–C(7)
Mo(1)–Cp(centroid)
Fe(1)–C(6)
2.987(2)
1.993(7)
2.450(3)
2.248(12)
2.018(8)
2.065(12)
1.33(2)
C(6)–C(7)
Mean Fe–C(carbonyl)
1.79
Mo(1)–Mo(2)–Fe(1)
Mo(1)–Fe(1)–Mo(2)
Mo(1)–C(6)–C(7)
C(6)–Fe(1)–C(7)
59.42(5)
64.64(5)
155.5(10)
37.2(5)
Fe(1)–Mo(1)–Mo(2)
Mo(1)–P(1)–Mo(2)
C(6)–Mo(2)–C(7)
Mo(1)–C(6)–Mo(2)
C(6)–C(7)–C(8)
55.94(5)
76.02(10)
34.2(4)
88.8(5)
140.9(12)
Fe(1)–C(7)–Mo(2)
78.2(4)
Table 4 Selected bond distances (Å) and angles (Њ) for 6
Mo(1)–Fe(1)
2.819(1)
2.749(1)
2.010(8)
1.997(6)
2.375(2)
1.980(8)
2.501(1)
1.785
Fe(1)–C(7)
Fe(1)–C(8)
Co(1)–C(7)
Co(1)–C(8)
Co(1)–P(1)
C(7)–C(8)
Mean Fe–C(carbonyl)
2.032(6)
2.086(7)
2.065(6)
2.056(7)
2.207(2)
1.314(9)
1.790
Mo(1)–Co(1)
Mo(1)–Cp(centroid)
Mo(1)–C(7)
Mo(1)–P(1)
Mo(1)–C(1)
Fe(1)–Co(1)
Mean Co–C(carbonyl)
Fe(1)–Co(1)–Mo(1)
Fe(1)–Mo(1)–Co(1)
Mo(1)–Fe(1)–Co(1)
Co(1)–P(1)–Mo(1)
Mo(1)–C(7)–C(8)
64.75(3)
53.36(3)
61.90(3)
73.64(6)
153.2(5)
Fe(1)–C(7)–Co(1)
Fe(1)–C(8)–Co(1)
Co(1)–C(7)–Mo(1)
Fe(1)–C(7)–Mo(1)
C(7)–C(8)–C(9)
75.2(2)
74.3(2)
85.2(2)
88.8(3)
144.0(6)
trigonal bipyramidal arrangement with C(7) sitting in an
equatorial site and C(8) an axial site. The acetylide ligand is
σ-bonded to the molybdenum atom and at the same time
forms a transverse bridge across the Co(1)–Fe(1) bond. The
molybdenum–cobalt bond is bridged unsymmetrically by the
diphenylphosphido group [Co(1)–P(1) 2.207(2) Å, Mo(1)–P(1)
2.375(2) Å]. The acetylide moiety is coordinated to the
FeCoMo triangular face with its α-carbon bound to all three
metal atoms with bond distances Mo(1)–C(7) 1.997(6) Å,
Fe(1)–C(7) 2.032(6) Å and Co(1)–C(7) 2.065(6) Å. The
β-carbon atom is linked to the Fe(1) and Co(1) atoms with
bond distances Fe(1)–C(8) 2.086(7) Å and Co(1)–C(8) 2.056(7)
Å. The acetylide carbon–carbon bond distance of 1.314(9) Å
compares well with 4 [1.33(2) Å] and is within the range
reported for other known acetylide-bridged trimetallic com-
plexes.12 The majority of known crystallographically character-
ised heterotrimetallic acetylide clusters contain either one or
two different kinds of metal atoms, whereas examples contain-
ing three unique metal atoms are, to the knowledge of the
authors, unknown.14
Scheme 2 Reagents and conditions: (i) CO (80 atm.), C6H5CH3, 293 K;
(ii) CDCl3, 293 K.
complex
[Fe2Mo(CO)6(η5-C5H5){µ3-η2-(||)-HCCPh}(µ-CO)-
(µ-PPh2)] 7 is isolated as the sole product (Scheme 2). Complex
1
7 has been characterised by H, 31P-{1H}, 13C-{1H} NMR and
IR spectroscopy and by mass spectrometry (Table 1 and
Experimental section). Furthermore, 7 has been the subject of
a single crystal X-ray diffraction study.
The molecular structure of 7 is shown in Fig. 5 and selected
bond distances and angles are given in Table 5. The core of the
molecule consists of a triangle of two iron atoms and one
The spectroscopic properties of 5 and 6 are entirely in accord
with expectation and correlate with those observed for the
acetylide analogue 4. The IR spectra display three absorption
bands in the terminal carbonyl region. The 31P-{1H} NMR
spectra shows for each complex a singlet [δ 145.8 (5), 220.1 (6)]
with the chemical shifts varying on replacement of tungsten by
molybdenum. In the 13C-{1H} NMR spectra at room temper-
ature, peaks are seen for the α-carbon atoms [δ 188.9 (5), 174.6
(6)] and the β-carbon atoms [δ 147.5 (5), 155.0 (6)] of the acetyl-
ide ligand in addition to resonances for the carbonyl, phenyl
and cyclopentadienyl groups.
2.3 Carbonylation of [Fe2Mo(CO)5(ꢀ5-C5H5){ꢁ3-ꢀ2-(⊥)-
HCCPh}(ꢁ-CO)(ꢁ-PPh2)] 3
To further support the coordinative unsaturation in the 46-
electron complexes 2 and 3, complex 3 has been reduced by
addition of a molecule of carbon monoxide. On treatment of 3
at room temperature in toluene under a pressure of 80 atm.,
Fig.
5
Molecular structure of [Fe2Mo(CO)6(η5-C5H5){µ3-η2-(||)-
HCCPh}(µ-CO)(µ-PPh2)] 7 including the atom numbering scheme.
All hydrogen atoms except for H8 have been omitted for clarity.
1674
J. Chem. Soc., Dalton Trans., 2002, 1671–1677

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Table 5 Selected bond distances (Å) and angles (Њ) for 7
Mo(1)–Fe(1)
Fe(1)–Fe(2)
Mo(1)–P(1)
2.714(2)
2.680(3)
2.351(4)
2.448(15)
2.233(15)
2.286(14)
2.006(13)
Mo(1)–Fe(2)
Fe(1)–P(1)
Fe(1)–C(4)
Fe(1)–C(8)
Fe(2)–C(9)
C(8)–C(9)
Mean Fe–C(carbonyl)
2.715(2)
2.248(4)
1.789(16)
1.991(13)
1.971(13)
1.352(19)
1.785
Fe(2)–C(4)
Mo(1)–C(8)
Mo(1)–C(9)
Mo(1)–Cp(centroid)
Mo(1)–Fe(2)–Fe(1)
Fe(1)–Mo(1)–Fe(2)
Fe(1)–C(4)–Fe(2)
C(8)–C(9)–Fe(2)
C(9)–C(8)–Mo(1)
60.36(6)
59.17(6)
76.7(6)
108.0(9)
74.7(9)
Fe(2)–Fe(1)–Mo(1)
Fe(1)–P(1)–Mo(1)
Fe(1)–C(8)–C(9)
C(8)–C(9)–Mo(1)
C(8)–Mo(1)–C(9)
60.44(6)
72.3(1)
111.1(1)
70.5(9)
34.8(5)
molybdenum atom with a molecule of phenylacetylene adopt-
ing a parallel bonding mode and lying parallel to the Fe(1)–
Fe(2) edge of the Fe2Mo triangle. This observed geometry is
consistent with σ-bonding to Fe(1) and Fe(2) [Fe(1)–C(8)
1.991(13) Å, Fe(2)–C(9) 1.971(13) Å] and π-bonding to the
molybdenum atom [Mo(1)–C(9) 2.286(14) Å, Mo(1)–C(8)
2.233(15) Å]. The C(8)–C(9) bond distance of the alkyne is
1.352(19) Å and is similar to those found in other trimetallic
48-electron parallel-bonded alkyne-bridged clusters.15 The
iron–molybdenum bond lengths are almost symmetrical despite
the Fe(2)–Mo(1) bond being spanned by a diphenylphosphido
group [Fe(2)–Mo(1) 2.715(2) Å, Fe(1)–Mo(1) 2.714(2) Å]. The
Fe(1)–Fe(2) bond [2.680(3) Å] is slightly longer than that in 3
[2.568(1) Å] and is additionally linked by a semibridging
carbonyl group [Fe(1)–C(4) 1.789(16), Fe(2)–C(4) 2.448(15) Å].
Three terminal groups complete the coordination sphere at
Fe(2), two at Fe(1) and one carbonyl and cyclopentadienyl
group at Mo(1).
It is noteworthy that the ⊥–|| alkyne reorientation during
conversion of 3 to give 7 is in accord with polyhedral skeletal
electron pair theory. Complex 3 is a six skeletal electron pair
system and should therefore assume a closo-trigonal bipyr-
amidal geometry. On the other hand the electron precise
complex 7 has seven skeletal electron pairs and is thus consist-
ent with the nido-octahedral structure observed. Similar ⊥–||
reorientation of internal alkynes has been reported previously
for a number of homotrimetallic group 8 clusters.2,4c,16 To the
knowledge of the authors this is the first report of the reorient-
ation of an alkyne occurring on heterotrimetallic centres and,
moreover, with a terminal alkyne molecule.
The infrared spectrum of 7 in the carbonyl region confirms
that reduction has taken place in its formation from 3. New
bands appear in the carbonyl stretching region due to terminal
carbonyl groups and an additional weak band at 1893 cmϪ1
suggests the presence of a semibridging carbonyl group. The 1H
NMR spectrum shows, in addition to phenyl resonances, a sing-
let at δ 4.8 which is assigned to the cyclopentadienyl ring. The
peak due to the alkynic hydrogen atom could not be seen; it
presumably overlaps with the phenyl group multiplets and is
obscured by them. Notably, the alkynic hydrogen atom of the
48-electron cluster [Fe3(CO)9(µ-CO){µ3-η2-(||)-HCC(C6H10-
OH)}]5a is observed as a downfield singlet at δ 6.93. The reson-
ance for the phosphido bridge is seen as a singlet in the 31P-{1H}
NMR spectrum at δ 218.9.
clusters containing the phenylacetylide ligands (4–6) adopt
perpendicular bonding modes, possess 48-electron configur-
ations, and are σ-bonded to the group 6 metal centre. The
unsaturated 46-electron clusters (2 and 3) contain phenylacetyl-
eneligandsperpendicularlybondingacrossaniron–group6metal
edge. Conversion of 3 to the saturated 48-electron cluster 7
with concomitant carbonylation and ⊥–|| reorientation of the
terminal alkyne has been demonstrated as has the reconversion
back to 3.
3
Experimental
3.1 General techniques
All reactions were carried out under an atmosphere of dry,
oxygen-free nitrogen, using standard Schlenk techniques.
Solvents were distilled under nitrogen from appropriate drying
agents and degassed prior to use.17 Infrared spectra were
recorded in hexane solution in 0.5 mm NaCl cells, using a
Perkin-Elmer 1710 Fourier-transform spectrometer. Fast atom
bombardment (FAB) mass spectra were recorded on a Kratos
MS 890 instrument using 3-nitrobenzyl alcohol as a matrix.
Proton (reference to SiMe4), 31P NMR and 13C NMR spectra
were recorded on either a Bruker WM250 or AM400 spec-
trometer, 31P NMR chemical shifts are referenced to 85%
H3PO4. Preparative thin-layer chromatography (TLC) was
carried out on commercial Merck plates with a 0.25 mm layer
of silica, or on 1 mm silica plates prepared at the Department
of Chemistry, Cambridge. Column chromatography was
performed on Kieselgel 60 (70–230 or 230–400 mesh). Products
are given in order of decreasing Rf values. Elemental analyses
were performed at the Department of Chemistry, Cambridge.
Unless otherwise stated all reagents were obtained from
commercial suppliers and used without further purification.
The syntheses of 1,18 [M2(η5-C5H5)2(CO)6] (M = W, Mo),19 and
[CoM(η5-C5H5)(CO)7] (M = W, Mo)20 have been reported
previously.
3.2 Synthesis of 2
[W2(CO)6(η5-C5H5)2] (0.90 g, 1.35 mmol) in xylene (60 cm3) was
refluxed vigorously at 433 K for 48 h whilst purging gently with
nitrogen to remove evolved CO. After cooling to 363 K, 1 (0.76
g, 1.34 mmol) was added and the solution maintained at 363 K
for 24 h. After the removal of solvent under reduced pressure
the mixture was absorbed onto a minimum quantity of silica,
added to the top of a chromatography column and eluted with
hexane–dichloromethane (1 : 1). This gave in addition to a
small amount of starting materials, the brown crystalline
complex [Fe2W(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-
PPh2)] 2 (0.32 g, 23%). Complex 2: FAB mass spectrum, m/z 813
(Mϩ) and Mϩ Ϫ nCO (n = 1–5). NMR (CDCl3, 293 K): 13C (1H
composite pulse decoupled), δ 229.5 [s, W–CO], 215.8 [s,
Fe–CO], 211.7 [d, 2J(PC) 14, Fe–CO], 210.8 [d, 2J(PC) 7,
Fe–CO], 195.0 [s, µ-CO], 152.0 [s, Cβ], 142–127 [m, Ph], 94.9 [s,
C5H5], 60.1 [d, 2J(PC) 14, Cα].
Interestingly complex 7, on standing in solution at ambient
temperature, converts, in the absence of CO, slowly back to 2 by
the loss of a molecule of CO. A similar decarbonylation reac-
tion has been observed for the triiron cluster [Fe3(CO)9{µ3-η2-
(||)-MeOCH2CCCH2OMe}].4c
Conclusions
A series of phosphido-bridged triangular heterotrimetallic
clusters (2–7) has been prepared incorporating phenylacetylene
or phenylacetylide as the organic bridging ligand. All the
J. Chem. Soc., Dalton Trans., 2002, 1671–1677
1675

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Table 6 Crystallographic and data processing parameters for complexes 2, 3, 4, 6 and 7
Complex
Formula
2
3
4
6
7
C31H21Fe2O6PW
C31H21Fe2MoO6P
C35H25FeMo2O5P
C31H20CoFeMoO6P
C32H21Fe2MoO7Pؒ
CH2Cl2
M
816.00
0.20 × 0.15 × 0.15
293(2)
728.09
0.20 × 0.20 × 0.10
293(2)
804.25
0.30 × 0.25 × 0.10
293(2)
730.16
0.50 × 0.30 × 0.20
293(2)
841.02
0.38 × 0.31 × 0.14
180(2)
Crystal size/mm
Temperature/K
Crystal system
Space group
Triclinic
P1
Triclinic
P1
Triclinic
P1
Monoclinic
P21/n
Triclinic
P1
¯
¯
¯
¯
Lattice parameters
a/Å
b/Å
c/Å
α/Њ
β/Њ
11.122(3)
13.160(4)
10.756(2)
100.34(3)
111.19(2)
75.27(3)
1413(1)
2
11.108(2)
13.177(3)
10.810(2)
100.85(2)
111.25(1)
74.77(2)
1415(1)
2
10.505(4)
19.905(5)
9.282(2)
97.65(2)
112.72(2)
85.76(3)
1774(1)
2
10.577(4)
20.399(4)
13.625(2)
90
93.51(2)
90
2929(1)
4
1.656
9.403(1)
12.500(4)
14.208(2)
93.07(1)
98.32(1)
104.59(2)
1592(1)
2
γ/Њ
U/Å3
Z
Dc/Mg mϪ3
1.916
1.709
1.506
1.754
F(000)
2552
5.174
5681
5348
0.0371
371/0
R1 = 0.0431,
wR2 = 0.1100
R1 = 0.0718,
wR2 = 0.1404
1.034
728
1.548
5255
4973
0.0294
373/0
R1 = 0.0375,
wR2 = 0.0857
R1 = 0.0796
wR2 = 0.1617
1.040
800
1.506
6794
4617
0.0881
409/0
R1 = 0.0592,
wR2 = 0.1704
R1 = 0.1159
wR2 = 0.3883
1.070
1456
1.567
5453
5152
0.0459
370/0
R1 = 0.0466,
wR2 = 0.1075
R1 = 0.1227
wR2 = 0.2186
1.048
840
1.554
6691
5571
0.1529
381/0
R1 = 0.0938,
wR2 = 0.2173
R1 = 0.1760
wR2 = 0.2607
1.030
µ(Mo-Kα)/mmϪ1
Reflections collected
Independent reflections
Rint
Parameters/restraints
Final R indices [I > 2σ(I )]
Final R indices (all data)
Goodness of fit on F 2 (all data)
2
2
Data in common: graphite-monochromated Mo-Kα radiation, λ = 0.71073 Å; R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|, wR2 = [Σw(Fo Ϫ Fc2)2/Σw(Fo )2]1/2, wϪ1
=
[σ2(Fo)2 ϩ (aP)2], P = [max(Fo ,0) ϩ 2(Fc2)]/3, where a is a constant adjusted by the program; goodness of fit = [Σ(Fo2 Ϫ Fc2)2/(n Ϫ p)]1/2 where n is the
number of reflections and p the number of parameters.
2
3.3 Synthesis of 3 and 4
δ 216.5 [s, Fe–CO], 216.0 [d, 2J(PC) 16, W–CO], 215.0 [s,
Fe–CO], 209.8 [s, Co–CO], 205.3 [s, Co–CO], 188.9 [s, Cα], 147.5
[s, Cβ], 145–128 [m, Ph], 89.7 [s, C5H5].
[Mo2(CO)6(η5-C5H5)2] (0.90 g, 1.83 mmol) in toluene (60 cm3)
was refluxed vigorously at 383 K for 24 h whilst purging gently
with nitrogen to remove evolved CO. After cooling to 353 K,
1 (1.0 g, 1.76 mmol) was added and the solution maintained at
353 K for 24 h. After the removal of solvent under reduced
pressure the residue was absorbed onto a minimum quantity of
silica, added to the top of a chromatography column and eluted
with hexane-dichloromethane (1 : 1). This gave in addition
to small quantity of starting material, the brown complex
3.5 Synthesis of 6
To a solution of [CoMo(η5-C5H5)(CO)7] (1.10 g, 2.64 mmol)
in toluene (60 cm3) was added 1 (1.49 g, 2.63 mmol) and the
solution heated to 363 K for 24 h. After the removal of solvent
under reduced pressure, the mixture was absorbed onto a
minimum quantity of silica, added to the top of a chrom-
atography column and eluted with hexane–dichloromethane
(3 : 1). This gave in addition to a small amount of starting
materials, the brown crystalline complexes [Fe2Mo(CO)5(η5-
C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)] 3 (0.40 g, 21%) and
[FeMoCo(CO)6(η5-C5H5){µ3-η2-(⊥)-CCPh}(µ-PPh2)] 6 (0.70 g,
36%). Complex 6: FAB mass spectrum, m/z 732 (Mϩ) and Mϩ
Ϫ nCO (n = 1–6). NMR (CDCl3, 293 K): 13C (1H composite
pulse decoupled), δ 236.8 [s, Mo–CO], 213.2 [s, Fe–CO], 174.6
[s, Cα], 155.0 [s, Cβ], 146–128 [m, Ph], 89.5 [s, C5H5].
[Fe2Mo(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-CO)(µ-PPh2)]
3
(0.31 g, 21%) and [FeMo2(CO)5(η5-C5H5)2{µ3-η2-(⊥)-CCPh}-
(µ-PPh2)] 4 (0.35 g, 21%). Complex 3: (Found: C, 50.7; H, 2.9.
C31H21Fe2MoO6P requires C, 51.1; H, 2.9%). FAB mass
spectrum, m/z 728 (Mϩ) and Mϩ Ϫ nCO (n = 1–5). NMR
(CDCl3, 293 K): 13C (1H composite pulse decoupled), δ 151.8 [s,
2
Cβ], 132–127 [m, Ph], 96.8 [s, C5H5], 61.8 [d, J(PC) 14, Cα].
Complex 4: (Found: C, 52.4; H, 3.1. C35H25FeMo2O5P requires
C, 52.3; H, 3.1%). FAB mass spectrum, m/z 728 (Mϩ) and
Mϩ Ϫ nCO (n = 1–5). NMR (CDCl3, 293 K): 13C (1H composite
pulse decoupled), δ 215.0 [s, FeCO], 211.5 [s, FeCO], 208.5 [s,
FeCO], 161.5 [s, Cα], 146.4 [s, Cβ], 144–127 [m, Ph], 98.9 [s,
C5H5], 95.2 [s, C5H5].
3.6 Carbonylation of 3 to give 7
A solution of [Fe2Mo(CO)5(η5-C5H5){µ3-η2-(⊥)-HCCPh}(µ-
CO)(µ-PPh2)] 3 (0.70 g, 0.96 mmol) in toluene (60 cm3) in a 100
cm3 Roth autoclave was pressurised with 80 atmospheres of
CO. The sealed system was stirred at room temperature for 24
h. After venting the gas, the solvent was removed under reduced
pressure and the residue dissolved in the minimum quantity of
dichloromethane. The solution was applied to base of prepar-
ative TLC plates and eluted with hexane–dichloromethane
(4 : 1). This gave, in addition to a small amount of starting
material, the brown crystalline complex [Fe2Mo(CO)6-
(η5-C5H5){µ3-η2-(||)-HCCPh}(µ-CO)(µ-PPh2)] 7 (0.57 g, 70%).
Complex 7: (Found: C, 50.0; H, 3.1. C32H21FeMo2O5P requires
C, 50.8; H, 2.8%). FAB mass spectrum, m/z 756 (Mϩ) and Mϩ Ϫ
nCO (n = 1–7). NMR (CDCl3, 293 K): 13C (1H composite pulse
decoupled), not stable in solution.
3.4 Synthesis of 5
To a solution of [CoW(η5-C5H5)(CO)7] (0.97 g, 1.92 mmol)
in toluene (60 cm3) was added 1 (1.10 g, 1.94 mmol) and the
solution heated to 373 K for 24 h. After the removal of solvent
under reduced pressure, the mixture was absorbed onto a
minimum quantity of silica, added to the top of a chrom-
atography column and eluted with hexane-dichloromethane
(3 : 1). This gave, in addition to a small amount of starting
materials, the brown crystalline complex [FeWCo(CO)6(η5-
C5H5){µ3-η2-(⊥)-CCPh}(µ-PPh2)] 5 (0.60 g, 38%). Complex 5:
FAB mass spectrum, m/z 818 (Mϩ) and Mϩ Ϫ nCO (n = 1–5).
NMR (CDCl3, 293 K): 13C (1H composite pulse decoupled),
1676
J. Chem. Soc., Dalton Trans., 2002, 1671–1677

View Article Online
6 For spectroscopically characterised examples of parallel-bonded
3.7 Crystallography
terminal alkyne trimetallic clusters, see: (a) E. Gatto, G. Gervasio,
D. Marabello and E. Sappa, J. Chem. Soc., Dalton Trans., 2001,
1485; (b) S. Aime and A. J. Deeming, J. Chem. Soc., Dalton Trans.,
1981, 828.
7 See, for example: (a) E. Sappa, O. Gambino, L. Milone and
G. Cetini, J. Organomet. Chem., 1972, 39, 169; (b) M. Catti,
G. Gervasio and S. A. Mason, J. Chem. Soc., Dalton Trans., 1977,
2266.
8 (a) J. A. Hriljac and D. F. Shriver, J. Am. Chem. Soc., 1987, 109,
6010; (b) J. A. Hriljac and D. F. Shriver, Organometallics, 1985, 4,
2225.
9 J. E. Davies, M. J. Mays, P. R. Raithby and K. Sarveswaran, Angew.
Chem., Int. Ed. Engl., 1997, 36, 2668.
X-Ray intensity data was collected using Rigaku AFC5R (2, 3,
4 and 6) and Stoe diffractometers (7). Both systems were
equipped with an Oxford Cryosystems Cryostream. Details of
data collection, refinement and crystal data are listed in Table 6.
Semiempirical absorption corrections based on φ-scan data
were applied21 to the data. The structures were solved by direct
methods [SHELXS86 (3, 6);22a SHELXS97 (2, 4, 7)22b] and
subsequent Fourier-difference syntheses and refined aniso-
tropically on all ordered non-hydrogen atoms by full-matrix
least squares on F 2 [SHELXL93 (3, 6);23a SHELXL97 (2, 4,
7)23b]. Hydrogen atoms were placed in geometrically idealised
positions and refined using a riding model. In the final cycles of
refinement a weighting scheme was introduced which produced
a flat analysis of variance.
10 A. J. Carty, G. Hogarth, G. Enright and G. Frapper, Chem.
Commun., 1997, 1833.
11 Carbon–carbon bond distances for perpendicularly-bridged alkyne
trimetallic complexes range from 1.39 to 1.44 Å., see ref. 3.
12 Carbon–carbon bond distances for perpendicularly-bridged
acetylide trimetallic complexes range from 1.27 to 1.33 Å. See, for
example: (a) A. Marinetti, E. Sappa, A. Tiripicchio and
M. Tiripicchio Camellini, J. Organomet. Chem., 1980, 197, 335; (b)
M. Green, K. Marsden, I. D. Salter, F. G. A. Stone and
P. Woodward, J. Chem. Soc., Chem. Commun., 1983, 446; (c)
A. J. Carty, N. J. Taylor, E. Sappa, A. Tiripicchio and M. Tiripicchio
Camellini, Organometallics, 1991, 10, 1907; (d ) A. J. Carty,
S. A. Maclaughlin, N. J. Taylor and E. Sappa, Inorg. Chem., 1981,
20, 4437; (e) M. I. Bruce, P. J. Low, A. Werth, B. W. Skelton and
A. H. White, J. Chem. Soc., Dalton Trans., 1996, 1551; ( f ) C. S.-W.
Lau and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1999, 607; (g)
Z. Dawoodi, M. J. Mays and K. Henrick, J. Chem. Soc., Dalton
Trans., 1984, 1769; (h) G. Gervasio, R. Gobetto, P. J. King,
D. Marabello and E. Sappa, Polyhedron, 1998, 17, 2937; (i)
D.-K. Hwang, Y. Chi, S.-M. Peng and G.-H. Lee, Organometallics,
1990, 9, 2709.
CCDC reference numbers 175751–175755.
See http://www.rsc.org/suppdata/dt/b1/b110874n/ for crystal-
lographic data in CIF or other electronic format.
Acknowledgements
We thank the EPSRC for funding for the X-ray diffractometer
and the image plate system. We are also grateful to the
Cambridge Commonwealth Trust and Professor B. F. G.
Johnson for funding to K. S. Thanks are also due to
Dr J. E. Davies (University of Cambridge) for collection of
the X-ray data and Dr G. Griffiths (University of Leicester) for
help with NMR data.
13 A. W. Al-Saadoon, M. Green, R. J. Mercer and A. G. Orpen,
J. Organomet. Chem., 1990, 384, C12.
14 Based on a CCD search (to October 2001, 233000 entries).
15 Carbon–carbon bond distances for parallel-bridged alkyne
trimetallic complexes range from 1.39 to 1.44 Å. See refs. 1 and 4.
16 S. Rivomanana, G. Lavigne, N. Lugan and J. J. Bonnet, Inorg.
Chem., 1991, 30, 4112.
17 W. L. F. Armarego and D. D. Perrin, Purification of Laboratory
Chemicals, Butterworth Heinemann, London, 4th edn., 1996.
18 A. A. Cherkas, L. H. Randall, S. A. MacLaughin, G. N. Mott,
N. J. Taylor and A. J. Carty, Organometallics, 1988, 7, 969.
19 (a) A. R. Manning, P. Hackett, R. Birdwhistell and P. Soye, Inorg.
Synth., 1991, 28, 148; (b) M. D. Curtis and M. S. Hay, Inorg. Synth.,
1991, 28, 150.
20 H. B. Abrahamson and M. S. Wrighton, Inorg. Chem., 1978, 17,
1003.
21 A. C. T. North, D. C. Phillips and F. S. Matthews, Acta Crystallogr.
Sect. A, 1968, 24, 351.
22 (a) G. M. Sheldrick, SHELXS86, University of Göttingen,
Germany, 1990; (b) G. M. Sheldrick, SHELXS97, program
for crystal structure solution, University of Göttingen, Germany,
1997.
23 (a) G. M. Sheldrick, SHELXL93, University of Göttingen,
Germany, 1993; (b) G. M. Sheldrick, SHELXL97, program for
crystal structure refinement, University of Göttingen, Germany,
1997.
References
1 (a) E. Sappa, A. Tiripicchio and P. Braunstein, Chem. Rev., 1983, 83,
203; (b) D. Osella and P. R. Raithby, in Stereochemistry of
Organometallic and Inorganic Compounds, ed. I. Bernal, Elsevier,
Amsterdam, 1988, vol. 3.
2 M. P. Brown, P. A. Dolby, M. M. Harding, A. J. Matthews,
A. K. Smith, D. Osella, M. Arbrun, R. Gobetta, P. R. Raithby and
P. Zanello, J. Chem. Soc., Dalton Trans., 1993, 827.
3 (a) J. F. Blount, L. F. Dahl, C. Hoogzand and W. Hübel, J. Am.
Chem. Soc., 1966, 88, 292; (b) V. Busetti, G. Granozzi, S. Aime,
R. Gobetto and D. Osella, Organometallics, 1984, 3, 1510; (c)
J. A. Clucas, P. A. Dolby, M. M. Harding and A. K. Smith, J. Chem.
Soc., Chem. Commun., 1987, 1829; (d ) M. E. Garcia, J. C. Jeffery,
P. Sherwood and F. G. A. Stone, J. Chem. Soc., Dalton Trans.,
1987, 1209; (e) S. Rivomanana, C. Mongin and G. Lavigne,
Organometallics, 1996, 15, 1195.
4 See for example: (a) L. Busetto, M. Green, B. Hessner, J. A. K.
Howard, J. C. Jeffery, R. M. Mills, F. G. A. Stone and P. Woodward,
J. Chem. Soc., Chem. Commun., 1981, 1101; (b) J. R. Shapely,
J. T. Parks, M. R. Churchill, C. Bueno and H. J. Wasserman, J. Am.
Chem. Soc., 1981, 103, 7385; (c) D. Lentz and M. Reuter, Chem. Ber.,
1991, 124, 773; (d ) D. Nuel, F. Dahan and R. Mathieu,
Organometallics, 1985, 4, 1436.
5 (a) R. S. Dickson and O. M. Paravegne, Organometallics, 1991, 10,
721.
J. Chem. Soc., Dalton Trans., 2002, 1671–1677
1677