Alkyne-phosphinoalkyne coupling reactions on mixed-metal tungsten-cobalt centres; P-C(alkyne) bond cleavage versus P-C(alkyne) bond preservation

Article abstract of DOI:10.1039/b009396n

Reactions of the alkyne-bridged tungsten-cobalt complexes [(η⁵-C₅H₅)(OC)₂W(μ- R¹CCR²)Co(CO)₃](R¹ = R² = CO₂Me 1a; R¹ = H, R² = Bu^t 1b) with Ph₂PC≡CPh in refluxing toluene result in two different reaction pathways. On reaction with 1a three products are isolated namely, [(η⁵-C₅H₅)(OC)₂W{μ- C₂(CO₂Me)₂}Co(CO)₃- (PPh₂C≡CPh)] 2, the result of substitution of a cobalt carbonyl ligand by a phosphorus-bound molecule of Ph₂PC≡CPh, [(η⁵-C₅H₅)(OC)₂W{μ- PhCCC(CO₂Me)=C(CO₂Me)PPh₂} Co(CO)₂] 3 and [(η⁵-C₅H₅)(OC)W- {μ-C(CO₂Me)=C(C=CPh)C(OMe)O}(μ-PPh₂) Co(CO)₂] 4, in which phosphorus-carbon(alkyne) bond cleavage of the phosphinoalkyne has ocurred along with phosphorus-carbon bond formation (3) and/or carbon-carbon bond formation (3 and 4). In contrast, reaction of 1b (with Ph₂PC≡CPh affords two products, [(η⁵-C₅H₅)(OC)W-{μ-CBu^t CHCPhC(PPh₂)}Co(CO)₂] 5 and [(η⁵-C₅H₅)(OC)₂W{μ- CBu^tCHC(PPh₂)CPh}Co(CO)₂] 6, in which the bridging alkyne has coupled with an intact molecule of the phosphinoalkyne Ph₂PCα≡C_βPh at either its β- or α-carbon atoms, respectively. However, on reaction of 1b with the tert-butyl-substituted phosphinoalkyne, Ph₂PC≡CBu^t, regiospecific coupling and oxidation of the phosphino moiety occur to give [(η⁵-C₅H₅)(OC)W-{μ-CBu^t= CHCBu^t=C(PPh₂O)}Co(CO)₂] 8, as the sole product. The reactivity of 6 towards diiron nonacarbonyl has been explored and found to afford the trimetallic complex [(η⁵-C₅H₅)(OC)₂W{μ- CBu^tCHC(PPh₂Fe(CO)₄)-CPh}Co(CO)₂] 7 in good yield. Single crystal X-ray diffraction studies have been performed on 4, 6, 7 and 8 and possible reaction pathways for the formation of the new complexes are proposed and discussed.

Full text of DOI:10.1039/b009396n

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Alkyne–phosphinoalkyne coupling reactions on mixed-metal
tungsten–cobalt centres; P–C(alkyne) bond cleavage versus
P–C(alkyne) bond preservation
John E. Davies,a Martin J. Mays,*a Paul R. Raithby,a Koshala Sarveswarana and
Gregory A. Solanb
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
Received 23rd November 2000, Accepted 1st March 2001
First published as an Advance Article on the web 23rd March 2001
Reactions of the alkyne-bridged tungsten–cobalt complexes [(η5-C5H5)(OC)2W(µ-R1CCR2)Co(CO)3]
1
2
1
2
t
᎐
(R = R = CO Me 1a; R = H, R = Bu 1b) with Ph PC᎐CPh in refluxing toluene result in two different reaction
᎐
2
2
pathways. On reaction with 1a three products are isolated namely, [(η5-C5H5)(OC)2W{µ-C2(CO2Me)2}Co(CO)3-
(PPh C᎐CPh)] 2, the result of substitution of a cobalt carbonyl ligand by a phosphorus-bound molecule of
᎐
᎐
2
5
5
᎐
Ph PC᎐CPh, [(η -C H )(OC) W{µ-PhCCC(CO Me)᎐C(CO Me)PPh }Co(CO) ] 3 and [(η -C H )(OC)W-
᎐
᎐
2
5
5
2
2
2
2
2
5
5
᎐
{µ-C(CO Me)᎐C(C᎐CPh)C(OMe)O}(µ-PPh )Co(CO) ] 4, in which phosphorus–carbon(alkyne) bond cleavage
᎐
᎐
2
2
2
of the phosphinoalkyne has ocurred along with phosphorus–carbon bond formation (3) and/or carbon–carbon
5
᎐
bond formation (3 and 4). In contrast, reaction of 1b with Ph PC᎐CPh affords two products, [(η -C H )(OC)W-
᎐
2
5
5
{µ-CButCHCPhC(PPh2)}Co(CO)2] 5 and [(η5-C5H5)(OC)2W{µ-CButCHC(PPh2)CPh}Co(CO)2] 6, in which the
bridging alkyne has coupled with an intact molecule of the phosphinoalkyne Ph PC ᎐C Ph at either its β- or
᎐
᎐
2
α
β
α-carbon atoms, respectively. However, on reaction of 1b with the tert-butyl-substituted phosphinoalkyne,
t
5
᎐
Ph PC᎐CBu , regiospecific coupling and oxidation of the phosphino moiety occur to give [(η -C H )(OC)W-
᎐
2
5
5
{µ-CBut᎐CHCBut᎐C(PPh O)}Co(CO) ] 8, as the sole product. The reactivity of 6 towards diiron nonacarbonyl
᎐
᎐
2
2
has been explored and found to afford the trimetallic complex [(η5-C5H5)(OC)2W{µ-CButCHC(PPh2Fe(CO)4)-
CPh}Co(CO)2] 7 in good yield. Single crystal X-ray diffraction studies have been performed on 4, 6, 7 and 8 and
possible reaction pathways for the formation of the new complexes are proposed and discussed.
the pathway followed is largely determined by the nature
1 Introduction
of both the substituent R on the phosphinoalkyne and the
substituents, R1 and R2, on the bridging alkyne. In an extension
of this work, we examine here the effect of changing the Group
6 metal centre from molybdenum to tungsten. Preliminary
results revealed a preference for a pathway of type (a) to pre-
vail when [(η5-C5H5)(OC)2W{µ-C2(CO2Me)2}Co(CO)3] 1a and
᎐
The facility for phosphinoalkynes (RЈ PC᎐CR) to act as sources
᎐
2
᎐
of acetylide (–C᎐CR) and phosphide (PRЈ ) fragments on tran-
᎐
2
sition metal centres has been well documented.1–3 In some cases
oneorbothofthesefragmentscanfurtherreactwithsmallorganic
molecules or coordinated organic ligands to give a range of
new complexes, in which the phosphide and/or the acetylide has
coupled with the organic species.2–4 Conversely, the related coup-
ling chemistry of an intact phosphinoalkyne is uncommon.5
As part of our continuing studies into the chemistry of
mixed-metal alkyne-bridged Group 6–group 9 complexes4–9 we
have recently observed contrasting reaction pathways for the
molybdenum–cobalt family on their treatment with phosphino-
alkynes (Fig. 1). These pathways are either (a) phosphorus–
carbon(alkyne) bond cleavage and coupling of the resultant
phosphide and acetylide with the bridging alkyne4 or (b)
conservation of the phosphorus–carbon(alkyne) bond and
regiospecific coupling of the intact phosphinoalkyne with the
bridging alkyne.5 In these earlier studies it would appear that
t
4
᎐
Ph PC᎐CBu are employed. In this paper we report a more
᎐
2
thorough study of the reaction chemistry of tungsten–cobalt
alkyne-bridged complexes 1 with phosphinoalkynes with par-
ticular regard to deviations from the chemistry observed for
the molybdenum–cobalt family.
2 Results and discussion
2.1 Reaction of [(ꢀ5-C5H5)(OC)2W{ꢁ-C2(CO2Me)2}Co(CO)3]
᎐
1a with Ph PC᎐CPh
᎐
2
Reaction of [(η5-C5H5)(OC)2W{µ-C2(CO2Me)2}Co(CO)3] 1a
5
᎐
with Ph PC᎐CPh in toluene at 383 K affords [(η -C H )-
᎐
2
5
5
Fig. 1 Reactivity of phosphinoalkynes towards alkyne-bridged molybdenum–cobalt complexes.4,5
DOI: 10.1039/b009396n
J. Chem. Soc., Dalton Trans., 2001, 1269–1277
This journal is © The Royal Society of Chemistry 2001
1269

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Table 1 Infrared, 1H and 31P NMR data for the new complexes 2–8
Compound ν(CO)a/cmϪ1
1H NMR (δ)b
31P NMR (δ)c
᎐
᎐
17.8 [s, PPh2C᎐CPh]
᎐
2
2178w (C᎐C), 2026m, 1993s, 7.7–7.2 [m, 15H, Ph], 5.30 [s, 5H, Cp], 3.30
᎐
1962s
[s, 6H, CO2Me]
2178w (C᎐C), 2026m, 1993s,
᎐
᎐
3
4
2010m, 1971vs, 1944s, 1705w 7.8–6.5 [m, 15H, Ph], 5.34 [s, 5H, Cp], 3.80
[s, 3H, CO2Me], 3.40 [s, 3H, CO2Me]
2010m, 1967vs, 1924sh,
1682w, 1546w
61.3 [s, µ-PhCCC(CO2Me)᎐C(CO2Me)PPh2]
᎐
7.6–6.7 [m, 15H, Ph], 5.50 [d, 3J(PH) 1.3,
5H, Cp], 3.60 [s, 3H, CO2Me], 3.10
[s, 3H, CO2Me]
118.4 [s, J(PW) 124.0, µ-PPh2]
5
6
7
8
2002vs, 1950vs, 1828br
2016vs, 1961s, 1907m
7.7–6.5 [m, 15H, Ph], 5.10 [s, 1H, CH], 5.00
Ϫ56.9 [s, J(PW) 53.6, µ-CBut=CHCPh᎐C(PPh2)]
᎐
[s, 5H, Cp], 1.28 [s, 9H, But]
7.8–6.5 [m, 15H, Ph], 5.10 [d, 3J(PH) 2.0, 1H,
CH], 4.90 [s, 5H, Cp], 1.06 [s, 9H, But]
7.4–6.6 [m, 15H, Ph], 6.10 [s, 1H, CH], 5.07
[s, 5H, Cp], 1.28 [s, 9H, But]
Ϫ17.1 [s, µ-CBut=CHC(PPh2)CPh]
60.2 [s, µ-CBut=CHC(PPh2Fe(CO)4)CPh]
71.5 [s, µ-CBut=CHCBut=C(PPh2O)]
2046s, 2024vs, 1968s, 1933s
1982vs, 1930vs, 1116 (P–O)
7.8–7.1 [m, 10H, Ph], 6.20 [s, 1H, CH], 5.0
[s, 5H, Cp], 1.30 [s, 9H, But], 1.07 [s, 9H, But]
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.
t
᎐
᎐
Scheme 1 Reagents and conditions: (i) Ph2PC᎐CPh, 383 K, C6H5Me; (ii) Ph2PC᎐CBu , 383 K, C6H5Me; (iii) Fe2(CO)9, 333 K, THF.
᎐
᎐
5
᎐
(OC) W{µ-C (CO Me) }Co(CO) (PPh C᎐CPh)] 2, [(η -C H )-
NMR spectrum reveals a broad singlet resonance at δ 61.3
which can be assigned to the PPh2 fragment incorporated into a
five-membered metallacycle.4 The broadness of the resonance
can be attributed to the proximity of the quadrupolar 59Co
centre and is further evidence that the phosphorus atom is
bound to cobalt.
᎐
2
2
2
2
2
2
5
5
(OC) W{µ-PhCCC(CO Me)᎐C(CO Me)PPh }Co(CO) ]
3
᎐
2
2
2
2
2
5
᎐
and [(η -C H )(OC)W{µ-C(CO Me)᎐C(C᎐CPh)C(OMe)O}-
᎐
᎐
5
5
2
(µ-PPh2)Co(CO)2] 4 in yields between 19 and 35% (Scheme 1).
All the complexes have been characterised spectroscopically
(see Table 1 and Experimental section) and, in addition, the
molecular structure of 4 has been determined by single crystal
X-ray diffraction.
The molecular structure of 4 is shown in Fig. 2 while
Table 2 lists selected bond distances and angles. Crystals of 4
were grown by slow evaporation of a CH2Cl2–hexane solution
at 273 K. The structure of 4 consists of two independent
molecules (A and B) within the unit cell with the only
appreciable difference between them being the orientation of
the phenylacetylide and methyl carboxylate groups. The bond
parameters for A and B are essentially the same but only A will
be discussed throughout the following; bond lengths and angles
are listed separately for the two molecules A and B in Table 2.
The structure reveals a (η5-C5H5)(OC)W–Co(CO)2 skeleton
bridged by a diphenylphosphido group and by a vinyl group
which σ-bonds to tungsten [W(1)–C(10) 2.142(7) Å] and π-
bonds to cobalt [C(10)–Co(1) 1.968(7), C(9)–Co(1) 2.102(6)
Å]. The β-carbon of the vinyl group has two substituents
namely phenylacetylide and methyl carboxylate, the latter of
The spectroscopic properties of 2 show it has a structure
analogous to that of [(η5-C5H5)(OC)2W{µ-C2(CO2Me)2}Co-
t
4
᎐
᎐
2
(CO) (PPh C᎐CBu )]. Thus in the IR spectrum three v(CO)
2
bands assigned to the terminal carbonyls are observed in the
region 2030–1950 cmϪ1 and a weak absorption at 2178 cmϪ1
᎐
which is assigned to the C᎐C stretch of the non-coordinated
᎐
alkyne. In the 31P-{1H} NMR spectrum there is a single peak at
δ 17.8, in the normal range for coordinated phosphines.
The structure of 3 is assigned on the basis of the close
similarity in spectroscopic properties with [(η5-C5H5)-
(OC) W{µ-ButCCC(CO Me)᎐C(CO Me)PPh }Co(CO) ].4 In
᎐
2
2
2
2
2
the IR spectrum three terminal carbonyl absorptions are
observed along with a band at 1705 cmϪ1 which is ascribed to
the non-coordinated methyl carboxylate groups. The 31P-{1H}
1270
J. Chem. Soc., Dalton Trans., 2001, 1269–1277

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and [(η5-C H )(OC)W{µ-C(CO Me)᎐CHC(OMe)O}(µ-SPh)-
Table 2 Selected bond distances (Å) and angles (Њ) for 4
Molecule A
᎐
5
5
2
8
᎐
Co(CO){PPh (SPh)}]. The uncoordinated alkyne C᎐C bond
᎐
2
Molecule B
distance of 1.199(9) Å lies in the normal range for free alkynes.
The metal–metal bond is asymmetrically bridged by the
phosphido group [W(1)–P(1) 2.400(3), Co(1)–P(1) 2.197(2) Å]
in keeping with the larger atomic radius of tungsten as com-
pared to cobalt. The observed W–Co bond distance [2.651(2)
Å] is similar to that found in other structurally characterised
W–Co complexes.16
W(1)–Co(1)
W(1)–O(4)
W(1)–C(10)
W(1)–(C5H5)centroid
W(1)–P(1)
Co(1)–C(10)
Co(1)–C(9)
Co(1)–P(1)
C(4)–C(7)
C(7)–C(8)
C(8)–C(9)
C(9)–C(13)
C(13)–O(4)
C(9)–C(10)
2.651(2)
2.210(4)
2.142(7)
1.991(7)
2.400(3)
1.968(7)
2.102(6)
2.197(2)
1.444(9)
1.199(9)
1.441(9)
1.437(8)
1.352(7)
1.457(8)
2.653(2)
2.203(4)
2.167(6)
1.988(7)
2.394(2)
1.962(7)
2.089(6)
2.186(2)
1.431(9)
1.188(8)
1.450(8)
1.450(8)
1.318(7)
1.470(8)
The IR spectrum of complex 4, recorded in hexane, shows in
addition to terminal carbonyl absorptions, two absorptions due
to the carbonyl bands of the ester group at 1682 and 1546 cmϪ1
.
That at lower frequency is indicative of oxygen coordination
and suggests that the solid state structure of 4 is maintained
in solution. The 31P-{1H} NMR spectrum displays a singlet at
δ 118.4 with 183W satellites [J(PW) 124 Hz], the chemical shift
of which is consistent with the phosphido group bridging a
tungsten–cobalt single bond.8,9
C(10)–W(1)–O(4)
O(4)–W(1)–P(1)
76.2(2)
129.6(1)
78.8(1)
51.3(1)
82.5(2)
52.8(2)
58.5(1)
176.2(6)
169.1(7)
121.2(5)
117.4(6)
80.2(2)
166.4(2)
70.3(1)
75.4(2)
131.8(1)
81.2(1)
51.0(1)
84.6(2)
53.5(2)
58.4(1)
172.2(7)
176.9(6)
124.4(5)
115.9(5)
79.8(2)
165.5(2)
70.6(1)
In the 13C-{1H} NMR spectrum, in addition to phenyl and
cyclopentadienyl resonances, there are signals corresponding to
metal-bound carbonyl ligands, at δ 237.0, typical of a tungsten-
bound terminal carbonyl and broad singlets at δ 210.0 and
207.0, typical of cobalt-bound terminal carbonyl groups. All
three carbonyl ligands give rise to distinct resonances showing
that there is no carbonyl fluxionality at this temperature
(293 K).
O(4)–W(1)–Co(1)
P(1)–W(1)–Co(1)
C(10)–Co(1)–P(1)
C(10)–Co(1)–W(1)
P(1)–Co(1)–W(1)
C(8)–C(7)–C(4)
C(7)–C(8)–C(9)
C(8)–C(9)–C(10)
C(9)–C(10)–C(11)
Co(1)–C(10)–W(1)
Co(1)–W(1)–(C5H5)centroid
W(1)–P(1)–Co(1)
A plausible pathway for the formation of 3 and 4 is shown in
Scheme 2. Initial displacement of a cobalt-bound carbonyl
group in 1a by the phosphinoalkyne (coordinated through
phosphorus) gives 2 which is followed by oxidative addition of
Fig.
2
Molecular structure of [(η5-C5H5)(OC)W{µ-C(CO2Me)᎐
᎐
᎐
C(C᎐CPh)C(OMe)O}(µ-PPh2)Co(CO)2]
4
including the atom
᎐
numbering scheme. All hydrogen atoms have been omitted for clarity.
which adopts a trans position with respect to the other CO2Me
group and wraps around to coordinate via the ketonic group to
tungsten [W(1)–O(4) 2.210(4) Å] so as to form a five-membered
W–C᎐C–C–O metallacycle. Related metallacyclic rings have
᎐
5
t
᎐
been reported for [(η -C H )(OC)W{µ-C(CO Me)᎐C(C᎐CBu )-
᎐
᎐
5
5
2
C(OMe)O}(µ-PPh2)Co(CO)2]4 and for a range of other homo-
and hetero-bimetallic complexes [Fe2,10 Mo2,11 Ru2,12 Mn2,13
Co2,14 FeCo,15 MoCo,6 WCo 8]. The carbon–carbon bond
[C(8)–C(9)] formed by the linking of the acetylide to the β-
carbon of the vinyl group of the metallacyclic ring has a dis-
tance of 1.441(9) Å indicating some conjugation between the
acetylide group and the ring. The Cα–Cβ bond distance in the
vinyl group is 1.457(8) Å [C(9)–C(10)] identical within experi-
mental error to the corresponding distances in [(η5-C5H5)(OC)-
Scheme 2 Possible reaction pathways for the formation of complexes
3 and 4.
t
4
᎐
W{µ-C(CO Me)᎐C(C᎐CBu )C(OMe)O}(µ-PPh )Co(CO) ]
᎐
᎐
2
2
2
J. Chem. Soc., Dalton Trans., 2001, 1269–1277
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Table 3 Selected bond distances (Å) and angles (Њ) for 6
the phosphinoalkyne at the cobalt centre to yield A. Migration
of the acetylide ligand in A to the bridging alkyne gives the
vinyl-bridged species B which can then form 4 by displacement
of a tungsten carbonyl group by coordination through oxygen
of one of the CO2Me groups in B. Related P–C bond cleavage
in organophosphines and migration of the resultant organic
group to a bridging alkyne ligand has been previously observed
in dimolybdenum systems,11 while acetylide–alkyne coupling
and C–C bond formation at the α-carbon atom of the acetylide
has been reported for related diiron17 and dicobalt18 systems.
Conversely, P–C bond formation at the tungsten centre in B and
displacement of the coordinated alkene by the alkyne moiety
gives 3. Scheme 2 also shows an alternative pathway for the
formation of 3 involving P–C bond formation at the cobalt
centre in A to give C, followed by acetylide–alkene coupling to
afford 3.
W(1)–Co(1)
W(1)–C(5)
Co(1)–C(5)
Co(1)–C(7)
P(1)–C(7)
2.689(1)
2.224(7)
2.096(8)
2.078(8)
1.847(8)
1.415(11)
W(1)–C(8)
W(1)–(C5H5)centroid 1.980(8)
Co(1)–C(6)
Co(1)–C(8)
C(5)–C(6)
C(7)–C(8)
2.154(8)
2.117(7)
2.056(8)
1.411(11)
1.424(1)
C(6)–C(7)
C(8)–W(1)–C(5)
C(5)–W(1)–Co(1)
C(7)–Co(1)–W(1)
C(7)–C(6)–C(5)
C(6)–C(7)–P(1)
74.5(3)
49.4(2)
79.4(2)
116.8(7)
122.2(6)
C(8)–W(1)–Co(1)
C(8)–Co(1)–W(1)
C(5)–Co(1)–W(1)
C(6)–C(7)–C(8)
C(8)–C(7)–P(1)
Co(1)–C(8)–W(1)
48.7(2)
51.9(2)
53.7(2)
114.7(7)
123.0(6)
79.4(3)
Co(1)–W(1)–(C5H5)centroid 158.0(5)
2.2 Reaction of [(ꢀ5-C5H5)(OC)2W(ꢁ-HCCBut)Co(CO)3] 1b
᎐
with Ph PC᎐CPh
᎐
2
Reaction of [(η5-C5H5)(OC)2W(µ-HCCBut)Co(CO)3] 1b with
᎐
Ph PC᎐CPh in toluene at 383 K affords the complexes
᎐
2
[(η5-C5H5)(OC)W{µ-CButCHCPhC(PPh2)}Co(CO)2]
5
and
in
[(η5-C5H5)(OC)2W{µ-CButCHC(PPh2)CPh}Co(CO)2]
6
moderate yield (Scheme 1). The complexes have been charac-
terised by 1H, 31P, 13C NMR, IR spectroscopy and mass
spectrometry and, in addition, 6 has been the subject of a single
crystal X-ray diffraction study.
The assignment of the structure of 5 has been made on the
basis of the close similarity of its spectroscopic properties
to those of [(η5-C5H5)(OC)Mo{µ-CButCHCPhC(PPh2)}-
Co(CO)2].5 Thus three terminal carbonyl bands are seen in
the IR spectrum between 2002 and 1828 cmϪ1. The 31P-{1H}
NMR spectrum shows a peak at δ –56.9 with satellites due
to coupling to 183W [J(PW) 54 Hz] and consistent with the
phosphorus atom being bound to tungsten rather than
1
to cobalt. In the H NMR a singlet is observed for the CH
proton of the bridging butadiene ligand at δ 5.1 in addition to
resonances for the phenyl, tert-butyl and cyclopentadienyl
groups.
The molecular structure of 6 is shown in Fig. 3; Table 3 lists
selected bond distances and angles. The molecule consists of a
tungsten and cobalt atom singly bonded to each other [W(1)–
Co(1) 2.689(1) Å]16 and bridged by a µ-C4 ligand derived from
Fig.
3
Molecular structure of [(η5-C5H5)(OC)2W{µ-CButCHC-
(PPh2)CPh}Co(CO)2] 6, including the atom numbering scheme. All
hydrogen atoms except for H6 have been omitted for clarity.
coupling of the bridging alkyne in 1b with the α-carbon of
᎐
Ph PC ᎐C Ph. The C fragment is incorporated into a tungsta-
solid-state structure being maintained in solution. The IR
spectrum shows absorptions in the terminal carbonyl region
and this evidence is supported by the 13C-{1H} NMR spectrum
which identifies four separate terminal carbonyl resonances at
δ 224.3, 222.6, 203.8 and 202.8, the broadness and chemical
shift of the last two signals being consistent with cobalt-bound
carbonyls. In the 1H NMR spectrum of 6 the proton on the C4
unit is seen, as in 5, at δ 5.1 but in the case of 6 the resonance
᎐
2
α
β
4
cyclopentadienyl ring with C(5) and C(8) unsymmetrically
σ-bonded to the tungsten atom [W(1)–C(5) 2.224(7), W(1)–C(8)
2.154(8) Å] while the carbon–carbon double bonds are both
π-bonded to the cobalt atom [Co(1)–C(5) 2.096(8), Co(1)–C(6)
2.117(7), Co(1)–C(7) 2.078(8), Co(1)–C(8) 2.056(8) Å]. Each
substituent on the C4 unit is different, with the terminal carbon
atoms bearing But and Ph groups while the internal carbon
atoms possess H and Ph2P substituents. The similar carbon–
carbon bond distances within the tungstacyclopentadienyl
ring [C(5)–C(6) 1.411(11), C(6)–C(7) 1.415(11), C(7)–C(8)
1.424(1) Å] coupled with coplanarity of the four carbon atoms
implies some delocalisation in the ring. The coordination
sphere of the tungsten atom is completed by a η5-cyclo-
pentadienyl and two carbonyl ligands while on cobalt it is com-
pleted by two carbonyl groups. Three other crystallographically
characterised W–Co complexes bridged by butadiene ligands
have been reported namely [(η5-C5H5)(OC)2W{µ-C(CF3)C-
(CF3)C(CF3)C(CF3)}Co(CO)2],16c [(η5-C5H5)(OC)2W{µ-C(C6-
H4Me-4)CEtCEtC(C6H4Me-4)}Co(CO)2]19 and [(Ph3P)(OC)2-
Co{µ-CPhCMeCMeC(OH)}W(CO)4][BF4],20 the last of which
is unique in that it differs from all other examples in that the
butadiene ligand is η4-coordinated to tungsten rather than
cobalt.
3
takes the form of a doublet with J(PH) 2 Hz. The 31P-{1H}
NMR spectrum of 6 shows a singlet for the uncoordinated
diphenylphosphino group at δ Ϫ17.1.
The anticipated reactivity of the pendant diphenylphosphino
group in 6 was realised during its reaction with [Fe2(CO)9]
(Scheme 1) in THF at 333 K. The complex [(η5-C5H5)(OC)2-
W{µ-CButCHC(PPh2Fe(CO)4)CPh}Co(CO)2] 7 was isolated
in 41% yield and has been characterised spectroscopically
(see Table 1 and Experimental section) and in addition, the
molecular structure has been determined by single crystal X-ray
diffraction.
The molecular structure of 7 is depicted in Fig. 4; bond
lengths and angles are collected in Table 4. The structure is
essentially the same as that of 6 with the C4 unit bridging a
W–Co vector but having the diphenylphosphino substituent
coordinated to an axial site of an Fe(CO)4 unit. The presence
of the coordinated Fe(CO)4 fragment has little effect on the
The spectroscopic properties of 6 are consistent with the
1272
J. Chem. Soc., Dalton Trans., 2001, 1269–1277

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carbonyl region. The 31P-{1H} NMR spectrum shows a peak at
Table 4 Selected bond distances (Å) and angles (Њ) for 7
δ 60.2 which is assigned to the coordinated diphenylphosphino
group in the complex, being shifted downfield by ca. 77 ppm
compared to that of 6. In the 13C-{1H} NMR spectrum of 7 in
addition to phenyl, cyclopentadienyl and tert-butyl signals, four
upfield resonances are seen in the terminal carbonyl region and
four downfield resonances are observed for the inequivalent
carbon atoms of the bridging C4 unit [δ 179.2, 168.4, 150.4,
119.0]. The upfield carbonyl resonances at δ 221.9 and 220.4
are attributed to inequivalent tungsten-bound carbonyls, the
W(1)–Co(1)
Co(1)–C(9)
Co(1)–C(10)
Fe(1)–P(1)
C(10)–C(11)
W(1)–(C5H5)centroid
P(1)–C(10)
2.682(2)
2.070(6)
2.106(6)
2.263(2)
1.408(9)
1.987(6)
1.842(6)
W(1)–C(9)
2.181(6)
2.108(6)
1.437(9)
2.201(7)
2.103(7)
1.414(9)
Co(1)–C(12)
C(9)–C(10)
W(1)–C(12)
Co(1)–C(11)
C(11)–C(12)
C(9)–W(1)–Co(1)
C(9)–W(1)–C(12)
C(11)–Co(1)–C(12)
C(12)–Co(1)–W(1)
C(9)–C(10)–Co(1)
49.1(2)
74.6(2)
39.2(2)
53.1(2)
68.5(3)
C(9)–Co(1)–C(11)
C(12)–W(1)–Co(1)
C(9)–Co(1)–W(1)
C(11)–C(10)–C(9)
C(9)–C(10)–P(1)
69.6(3)
50.0(2)
52.7(2)
113.8(6)
130.2(5)
2
doublet at δ 213.8 with J(PC) 17 Hz to the equivalent iron-
bound carbonyls and the broad resonances at δ 202.3 to the
cobalt-bound carbonyls. It is noteworthy that the cobalt-bound
carbonyls in 6 are inequivalent in the 13C-{1H} NMR spectrum
[δ 203.8 and 202.8] whereas in 7 they lie at the same chemical
shift. Given the similarity in the structure of 6 and 7 it is
unlikely that a fluxional process is operative for 7 and not 6
at this temperature (293 K) and more likely that the cobalt
carbonyl resonances coincide.
Co(1)–W(1)–(C5H5)centroid 159.1(4)
C(12)–C(11)–C(10) 118.1(6)
C(10)–C(11)–Co(1)
C(11)–C(12)–W(1)
C(9)–Co(1)–C(12)
C(12)–Co(1)–C(10)
C(10)–Co(1)–W(1)
C(10)–C(9)–Co(1)
Co(1)–C(9)–W(1)
70.6(4)
114.8(4)
78.9(2)
70.1(2)
79.9(2)
71.2(4)
78.2(2)
C(11)–C(12)–Co(1)
Co(1)–C(12)–W(1)
C(9)–Co(1)–C(10)
C(11)–Co(1)–W(1)
C(10)–P(1)–Fe(1)
C(10)–C(9)–W(1)
70.2(4)
76.9(2)
40.2(2)
78.9(2)
113.8(2)
116.9(4)
The mechanism for the formation of 5 and 6 is uncertain but
a possible pathway is shown in Scheme 3. It is proposed that
Fig. 4 Molecular structure of [(η5-C5H5)(OC)2W{µ-CButCHC(PPh2-
Fe(CO)4)CPh}Co(CO)2] 7. Details as in Fig. 3.
Scheme 3 Possible reaction pathways for the formation of complexes
5 and 6.
bond parameters within the tungstacyclopentadiene ring when
compared with 6, the only slight variation being the W–C bond
distances which in 7 are closer in length [W(1)–C(9) 2.181(6),
W(1)–C(12) 2.201(7) Å] than the corresponding distances in 6
[W(1)–C(5) 2.224(7) Å, W(1)–C(8) 2.154(8) Å]. W(1) is also
linked to Co(1) via a metal–metal bond of 2.682(2) Å, which is
similar to the W(1)–Co(1) distance of 2.689(1) Å in 6, and to
the distances reported for other W–Co complexes.16 The
magnitude of the Co(1) ؒ ؒ ؒ Fe(1) [4.687 Å] and W(1) ؒ ؒ ؒ Fe(1)
[6.410 Å] distances in 7 precludes any metal–metal bonding
interactions. The Fe(1)–P(1) bond distance of 2.263(2) Å
indicates a dative bond to the iron atom. The P–C bond dis-
tance of 1.842(6) Å is almost the same as in 6 [1.847(8) Å] and
consistent with a single bond.
displacement of carbonyl group on cobalt in 1b by the phos-
phinoalkyne, coordinating as a two electron donor via one
π bond of the alkyne moiety to the cobalt centre, gives E.
Coordination of the second π bond of the alkyne to tungsten
with displacement of a carbonyl group gives the bis(alkyne)–
bridged species F or FЈ depending on the relative disposition
of the substituents on the two perpendicularly bridged alkynes.
cis Coupling of the less bulky CH terminus of the coordinated
t-butylacetylene with the β-carbon atom of the coordinated
᎐
Ph PC ᎐C Ph ligand in F, with concomitant coordination
᎐
2
α
β
of the phosphino group, gives 5. Conversely, cis coupling
of the CH terminus with the α-carbon atom of the coordi-
᎐
nated Ph PC ᎐C Ph ligand in FЈ affords, on carbonylation, 6.
᎐
2
α
β
Similar coupling of bis(alkyne)-bridged Group 6–Group 9
complexes has been reported by Davidson et al. in which the
presence of CO has been shown to promote the coupling
reaction.16c
The spectroscopic properties of 7 in solution are in accord-
ance with the solid-state structure. In the IR spectrum
four strong carbonyl bands are observed in the terminal
J. Chem. Soc., Dalton Trans., 2001, 1269–1277
1273

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Table 5 Selected bond distances (Å) and angles (Њ) for 8
of bringing the phosphorus atom closer to the tungsten and
allows some W–P bonding interactions [W(1)–P(1) 2.867(2) Å].
Similar structural parameters have been observed for the
molybdenum analogue of 8, [(η5-C5H5)(OC)Mo{µ-CButCH-
CButC(PPh2O)}Co(CO)2]5 although the M–O–P angle is
marginally larger in 8 [96.3(1) (8) vs. 95.7(1)Њ].
W(1)–Co(1)
W(1)–C(25)
Co(1)–C(26)
C(26)–C(27)
W(1)–O(4)
Co(1)–C(28)
P(1)–O(4)
2.685(1)
2.172(6)
2.086(5)
1.455(7)
2.250(4)
2.070(5)
1.546(4)
2.110(5)
W(1)–P(1)
P(1)–C(28)
W(1)–C(28)
W(1)–(C5H5)centroid
Co(1)–C(27)
C(25)–C(26)
C(27)–C(28)
2.867(2)
1.745(5)
2.151(5)
2.005(5)
2.107(5)
1.418(7)
1.405(7)
The IR spectrum of 8 shows two terminal carbonyl bands
(1982, 1930 cmϪ1) and an intense band at 1116 cmϪ1 which is
assigned to the P–O stretching frequency. The 31P-{1H} NMR
Co(1)–C(25)
1
spectrum shows a downfield signal at δ 71.5. In the H NMR
C(28)–W(1)–C(25)
C(25)–W(1)–Co(1)
O(4)–W(1)–Co(1)
C(25)–W(1)–O(4)
75.7(2)
50.1(1)
86.9(1)
136.4(2)
C(28)–W(1)–O(4)
C(28)–W(1)–P(1)
Co(1)–W(1)–P(1)
C(28)–W(1)–Co(1) 49.2(2)
O(4)–W(1)–Co(1) 86.9(1)
C(28)–Co(1)–W(1) 51.8(2)
P(1)–O(4)–W(1) 96.3(2)
68.9(1)
37.4(1)
71.0(1)
spectrum resonances for the phenyl, cyclopentadienyl and tert-
butyl resonances are observed along with a singlet at δ 6.2
integrating as one proton and corresponding to the butadiene
CH proton. The 13C-{1H} NMR spectrum shows, in addition to
phenyl, cyclopentadienyl and tert-butyl resonances, a singlet at
δ 236.7 assigned to a tungsten-bound carbonyl, and a broad
singlet at δ 208.5 due to the cobalt-bound carbonyl groups.
Only three of the inequivalent carbon atoms of the bridging
C4 unit can clearly be seen in the 13C-{1H} NMR spectrum
(the fourth presumably masked by the phenyl resonances) at
δ 175.3, 171.2 and 108.7. Notably, the first of these signals is
assigned to the α-carbon of the µ-CButCHCButC(PPh2O)
ligand since the signal takes the form of a doublet with 3J(PC)
3 Hz and is flanked by 183W satellites with J(WC) 41 Hz.
Co(1)–W(1)–(C5H5)centroid 157.7(2)
C(25)–W(1)–P(1)
O(4)–P(1)–W(1)
O(4)–P(1)–C(28)
111.7(2)
51.3(1)
98.1(2)
As with the analogous molybdenum–cobalt complex
[(η5-C5H5)(OC)Mo{µ-CButCHCButC(PPh2O)}Co(CO)2]5 the
source of the oxygen atom in 8 is uncertain but could either be
a carbonyl group, molecular oxygen or water. Insertion of an
oxygen atom into a phosphorus–iron bond in the complex
5
᎐
[Fe(η -C H )(CO) (PPh C᎐CR)][BF ] (R = C H Me-4 or Ph)
᎐
5
5
2
2
4
6
4
during the reaction with Me3NOؒ2H2O has recently been
reported.23 Notably, oxidation occurs only when there are two
tertiary butyl groups on the metallacyclopentadiene ring
regardless of the Group 6 metal centre. The high electron
density on the metallacyclopentadiene ring as a consequence of
the electron donating capability of the tert-butyl substituents
may result in increased oxophilicity of the phosphorus centre.
Fig.
5
Molecular structure of [(η5-C5H5)(OC)W{µ-CBut᎐CH-
᎐
CBut᎐C(PPh2O)}Co(CO)2] 8, including the atom numbering scheme.
᎐
᎐
2.4 Comparisons of the reactivity of 1 towards Ph PC᎐CR with
᎐
2
All hydrogen atoms except for H28 have been omitted for clarity.
the reactivity of Mo–Co analogues
As was the case in the reactions of [(η5-C5H5)(OC)2Mo-
(µ-alkyne)Co(CO)3] with phosphinoalkynes,4,5 two reaction
pathways can also operate for the tungsten analogues (1a
and 1b) namely one involving scission of the P–C(alkyne) bond
of the phosphinoalkyne to give 3 and 4 (Scheme 2) or one
involving coupling of the intact phosphinoalkyne with the
bridging alkyne in 1 to give 5 and 6 (Scheme 3). In our earlier
2.3 Reaction of [(ꢀ5-C5H5)(OC)2W(ꢁ-HCCBut)Co(CO)3] 1b
t
᎐
with Ph PC᎐CBu
᎐
2
The reaction of [(η5-C5H5)(OC)2W(µ-HCCBut)Co(CO)3] 1b
t
᎐
with Ph PC᎐CBu in toluene at 383 K affords the complex
᎐
2
[(η5-C5H5)(OC)W{µ-CButCHCButC(PPh2O)}Co(CO)2]
8 in
good yield (Scheme 1). The complex has been characterised
1
by H, 31P, 13C NMR, IR spectroscopy and mass spectrometry
studies on the reactivity of [(η5-C5H5)(OC)2Mo(µ-R1CCR2)-
᎐
and in addition has been the subject of a single crystal X-ray
diffraction study.
Co(CO) ] towards Ph PC᎐CR the nature of the substituent
᎐
3
2
R on the phosphinoalkyne and the substituents R1 and R2 on
the bridging alkyne have been shown to affect the course of
the reaction. In this work a similar trend is observed; how-
ever, the effect of having tungsten in place of molybdenum
introduces a number of significant differences in reactivity.
When the substituents on the bridging alkyne are electron
withdrawing (1a) products are isolated in which P–C(alkyne)
bond cleavage invariably occurs (5 and 6) irrespective of
whether the R group on the phosphinoalkyne is Ph or But (see
Scheme 1 and ref. 4). In contrast, for the reactions of the
molybdenum analogue of 1a the nature of the R substituent on
the phosphinoalkyne controls the pathway. That is P–C(alkyne)
bond scission occurs when R = But but coupling of the intact
phosphinoalkyne with the bridging alkyne takes place when
R = Ph.4,5
The molecular structure of 8 is shown in Fig. 5 while selected
bond distances and angles are given in Table 5. The molecule
consists of (η5-C5H5)(OC)W and Co(CO)2 units linked by a
single metal–metal bond [W(1)–Co(1) 2.685(1) Å]16 and
bridged by a butadiene ligand which σ-bonds to tungsten via
C(25) [W(1)–C(25) 2.172(6) Å] and C(28) [W(1)–C(28) 2.151(5)
Å] and π-bonds to cobalt via the butadiene C–C double bonds
[Co(1)–C(25) 2.110(5), Co(1)–C(26) 2.086(5), Co(1)–C(27)
2.107(5), Co(1)–C(28) 2.070(5) Å]. The substituents on the
terminal carbon atoms C(25) and C(28) of the butadiene ligand
are t-Bu and Ph2PO the latter of which wraps around and
coordinates to tungsten through O(4) so as to form a four-
membered metallacyclic ring W(1)–C(28)–P(1)–O(4). The
W(1)–O(4) and O(4)–P(1) bond distances within the four-
membered ring of 2.250(4) and 1.546(4) Å are slightly longer than
those in related tungsten structures [range (W–O): 2.038–2.200,
range (P–O), 1.488–1.537 Å]21,22 and, due to the constraints of
the four-membered ring, the W–O–P angle is unusually small
[96.3(2) vs. 121.2–168.5Њ].21,22 The smaller W–O–P has the result
Having an electron donating (1b) substituent on the bridging
alkyne results in products (5, 6, 8) which are exclusively the
result of coupling of the intact phosphinoalkyne with the
t
᎐
᎐
bridging alkyne for both Ph PC᎐CPh and Ph PC᎐CBu ,
᎐
᎐
2
2
a reactivity pattern that is mirrored in the corresponding
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J. Chem. Soc., Dalton Trans., 2001, 1269–1277

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molybdenum–cobalt chemistry.5 However, the coupling reac-
NMR (CDCl3, 293 K): δ 235.0 [s, W–CO], 210.0 [s, Co–CO],
᎐
tion does not exhibit regiospecificity in the case of Ph PC᎐CPh,
174.2 [s, CO2Me], 135–128 [m, Ph], 88.0 [s, C5H5] and 60.5
[s, CO2Me]. Complex 3: FAB mass spectrum, m/z 848 (Mϩ)
and Mϩ Ϫ nCO(n = 1–4); 13C (1H composite pulse decoupled)
NMR (CDCl3, 293 K): δ 206.0 [s, Co–CO], 136–127 [m, Ph],
87.0 [s, C5H5], 53.4 [s, CO2Me] and 52.7 [s, CO2Me]. Complex
4 (Found: C, 50.1; H, 4.0. C34H26CoO7PW requires C, 49.5;
H, 3.8%). FAB mass spectrum, m/z 820 (Mϩ) and Mϩ Ϫ
nCO(n = 1–3); 13C (1H composite pulse decoupled) NMR
(CDCl3, 293 K): δ 237.0 [s, W–CO], 210.0 [s, Co–CO], 207.0 [s,
Co–CO], 187.4 [s, CO2Me], 178.8 [s, CO2Me], 143.0 [d, 2J(PC)
᎐
2
with the carbon–carbon coupling occurring at both the α- (6)
and β-carbon (5) atoms of the phosphinoalkyne in a ratio
of respectively 4 : 1. In contrast, for the molybdenum analogue
the coupling takes place uniquely with the β-carbon. With
t
᎐
Ph PC᎐CBu regiospecific coupling (8) with the β-carbon
᎐
2
occurs in the tungsten case as well along with oxidation of the
phosphino moiety as also observed for the molybdenum–cobalt
analogue. Notably, in this study, 8 is the only product isolated
and there is no evidence for the non-oxidised species although
this is obtained as a product in the reaction of [(η5-C5H5)-
᎐
38.2 Hz, µ-C(CO Me)C(C᎐CPh)C(OMe)], 133–127 [m, Ph],
᎐
2
t
t 5
᎐
᎐
(OC) Mo(µ-Bu CCH)Co(CO) ] with Ph PC᎐CBu .
90.5 [s, µ-C(CO Me)C(C᎐CPh)C(OMe)], 90.0 [s, C H ], 85.3
[s, µ-C(CO Me)C(C᎐CPh)C(OMe)], 52.8 [s, CO Me] and 51.1
᎐
᎐
2
3
2
2
5
5
᎐
The explanation as to the different reactivity patterns is
unclear but may stem from the initial mode of coordination
of the phosphinoalkyne to the tungsten–cobalt framework
which is dictated by the electronic demands of the particular
bimetallic system. When the alkyne bridge has electron with-
drawing substituents (1a) the bimetallic framework is electron
deficient so the phosphinoalkyne binds to the cobalt centre
through the phosphorus (good σ-donor) atom (see 2 in Scheme
2). Conversely, when the alkyne bridge has electron donating
substituents (1b) the metal framework is electron rich causing
the phosphinoalkyne to bind to the cobalt centre through the
alkyne moiety (good π acceptor) of the phosphinoalkyne
(see E in Scheme 3).
᎐
2
2
[s, CO2Me].
5 and 6. To a solution of [(η5-C5H5)(OC)2W(µ-HCCBut)-
Co(CO)3] 1b (1.20 g, 2.3 mmol) in toluene (50 cm3) was added
᎐
Ph PC᎐CPh (0.70 g, 2.4 mmol). The solution was stirred at
᎐
2
383 K for 6 h and after removal of all volatiles under reduced
pressure the residue was purified by preparative TLC with
hexane–ethyl acetate (3 : 1) as eluent. This gave, in addition to
a small amount of starting material, the orange complexes
[(η5-C5H5)(OC)2W{µ-CButCHCPhC(PPh2)}Co(CO)2] 5 (0.12 g,
7%)
and
[(η5-C5H5)(OC)W{µ-CButCHC(PPh2)CPh}Co-
(CO)2] 6 (0.50 g, 28%). Complex 5: FAB mass spectrum,
m/z 760 (Mϩ) and Mϩ Ϫ nCO(n = 1–3); 13C (1H composite pulse
decoupled) NMR (CDCl3, 298 K): δ 222.0 [s, W–CO], 214.0
[s, Co–CO], 210.7 [s, Co–CO], 132–128 [m, Ph], 91.9 [s,
µ-CBut᎐CHCPh᎐C(PPh )], 87.7 [s, C H ], 37.0 [s, CMe ] and
3 Experimental section
3.1 General techniques
᎐
᎐
2
5
5
3
33.9 [s, CMe3]. Complex 6: FAB mass spectrum, m/z 788 (Mϩ)
and Mϩ Ϫ nCO(n = 1–4); 13C (1H composite pulse decoupled)
NMR (CDCl3, 293 K): δ 224.3 [s, W–CO], 222.6 [s, W–CO],
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.24 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 on a Kratos MS 890
instrument using 3-nitrobenzyl alcohol as a matrix, proton
(reference to SiMe4), 31P and 13C NMR spectra on either a
Bruker WM250 or AM400 spectrometer; 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.
203.8 [s, Co–CO], 202.8 [s, Co–CO], 171.1 [s, µ-CBut᎐CHC-
᎐
᎐
2
(PPh )᎐CPh], 168.9 [d, J(PC) 27, µ-CBut᎐CHC(PPh )᎐CPh],
1
᎐
᎐
2
152.6 [d, 2J(PC) 9, µ-CBut᎐CHC(PPh )᎐CPh], 139–123 [m, Ph],
᎐
᎐
2
111.3 [d, J(PC) 22, µ-CBut᎐CHC(PPh )᎐CPh], 88.4 [s, C H ],
2
᎐
᎐
2
5
5
43.5 [s, CMe3] and 34.5 [s, CMe3].
7. To
a
solution of [(η5-C5H5)(OC)2W{µ-CButCHC-
(PPh2)CPh}Co(CO)2] 6 (0.45 g, 0.57 mmol) in THF (50 cm3)
was added [Fe2(CO)9] (0.28 g, 0.76 mmol). The solution was
stirred at 333 K for 5 h and after removal of the volatiles under
reduced pressure the residue was purified by preparative
TLC using hexane–ethyl acetate (3 : 1) as eluent. This gave in
addition to a small amount of starting material, the orange
complex [(η5-C5H5)(OC)2W{µ-CButCHC(PPh2Fe(CO)4)CPh}-
Co(CO)2] 7 (0.23 g, 41%). FAB mass spectrum: m/z 956 (Mϩ)
and Mϩ Ϫ nCO(n = 1–8). 13C (1H composite pulse decoupled)
NMR (CDCl3, 293 K): δ 221.9 [s, W–CO], 220.4 [s, W–CO],
213.8 [d, 2J(PC) 17, Fe–CO], 202.3 [s, Co–CO], 179.2 [s,
µ-CBut᎐CHC(PPh Fe(CO) )᎐CPh], 168.4 [d, 1J(PC) 21, µ-
Unless otherwise stated all reagents were obtained from
commercial suppliers and used without further purification.
The syntheses of [(η5-C5H5)(OC)2W(µ-R1CCR2)Co(CO)3]
᎐
᎐
4
᎐
4
(R1 = R2 = CO2Me 1a; R1 = H, R2 = But 1b)25,26 and Ph PC᎐CR
2
᎐
᎐
2
CBut᎐CHC(PPh Fe(CO) )᎐CPh], 150.4 [d, J(PC) 9, µ-CBut᎐
2
᎐
᎐
(R = But or Ph)27 have been reported previously.
2
2
CHC(PPh Fe(CO) )᎐CPh], 137–124 [m, Ph], 119.0 [d, J(PC)
᎐
4
2
12, µ-CBut᎐CHC(PPh Fe(CO) )᎐CPh], 89.3 [s, C H ], 45.9 [s,
᎐
᎐
2
4
5
5
3.2 Syntheses
CMe3] and 34.5 [s, CMe3].
2, 3 and 4. To a solution of [(η5-C5H5)(OC)2W{µ-C2(CO2-
Me)2}Co(CO)3] 1a (0.70 g, 1.1 mmol) in toluene (70 cm3) was
8. To a solution of [(η5-C5H5)(OC)2W(µ-HCCBut)Co(CO)3]
1b (1.0 g, 1.88 mmol) in toluene (50 cm3) was added Ph2PC-
᎐
added Ph PC᎐CPh (0.35 g, 1.1 mmol). The solution was stirred
᎐
2
t
᎐
at 383 K for 8 h. After removal of the solvent under reduced
pressure, the mixture was absorbed onto the minimum quantity
of silica, added to the top of a chromatography column and
purified with hexane–ethyl acetate (4 : 1) as eluent. This gave, in
addition to a small amount of starting material, the complexes
᎐CBu (0.50 g, 1.88 mmol). The solution was stirred at 383 K
᎐
for 6 h and after removal of solvent under reduced pressure the
residue was purified by preparative TLC using hexane–ethyl
acetate (3 : 1) as eluent. This gave, in addition to starting
material, the orange complex [(η5-C5H5)(OC)W{µ-CButCH-
CButC(PPh2O)}Co(CO)2] 8 (0.64 g, 34%). FAB mass spectrum:
m/z 776 (Mϩ) and Mϩ Ϫ nCO(n = 1–3). 13C (1H composite pulse
decoupled) NMR (CDCl3, 293 K): δ 236.7 [s, W–CO], 208.5
[s, Co–CO], 175.3 [d, 3J(PC) 3, J(WC) 41, µ-CBut᎐CHCBut᎐C-
[(η5-C H )(OC) W{µ-PhCCC(CO Me)᎐C(CO Me)PPh }Co-
᎐
5
5
2
2
2
2
(CO) ] 3 (0.10 g, 19%), [(η5-C H )(OC)W{µ-C(CO Me)᎐C-
᎐
2
5
5
2
᎐
(C᎐CPh)C(OMe)O}(µ-PPh )Co(CO) ] 4 (0.16 g, 19%) and
᎐
2
2
5
᎐
᎐
2
[(η -C H )(OC) W{µ-C (CO Me) }Co(CO) (PPh C᎐CPh)]
2
᎐
᎐
5
5
2
2
2
2
2
(0.30 g, 35%). Complex 2: FAB mass spectrum, m/z 848 (Mϩ)
and Mϩ Ϫ nCO(n = 1–4); 13C (1H composite pulse decoupled),
(PPh O)], 171.2 [s, µ-CBut᎐CHCBut᎐C(PPh O)], 138–127 [m,
᎐ ᎐
2 2
Ph and µ-CBut᎐CHCBut᎐C(PPh O)], 108.7 [d, 2J(PC) 18,
᎐
᎐
2
J. Chem. Soc., Dalton Trans., 2001, 1269–1277
1275

View Article Online
Table 6 Crystallographic and data processing parameters for complexes 4, 6, 7 and 8
4
6
7
8
Empirical formula
Formula weight
Crystal system
Space group
a/Å
b/Å
c/Å
C34H26CoO7PW
820.30
Monoclinic
P21/c
15.501(16)
12.623(14)
31.390(14)
91.95(6)
C35H30CoO4PWؒCH2Cl2
873.27
Monoclinic
P21/n
9.451(5)
9.870(5)
35.91(2)
91.59(3)
3348(2)
C39H30CoFeO8PW
956.23
Monoclinic
P21/n
11.688(6)
17.919(9)
17.359(9)
103.54(2)
3535(3)
C32H34CoO4PW
756.34
Monoclinic
P21/n
10.990(5)
12.809(5)
21.080(5)
102.81(4)
2894(1)
β/Њ
U/Å3
6138(10)
Z
8
4
4
4
µ(Mo-Kα)/mmϪ1
Reflections collected
Independent reflections
Parameters/restraints
Final R indices I > 2σ(I)a
4.386
32480
10491 (Rint = 0.069)
793/0
R1 = 0.0476
wR2 = 0.1017
R1 = 0.0592
wR2 = 0.1150
4.174
5886
5875 (Rint = 0.038)
364/0
R1 = 0.0462
wR2 = 0.0974
R1 = 0.0656
wR2 = 0.1178
4.214
4644
4605 (Rint = 0.029)
463/0
R1 = 0.0308
wR2 = 0.0780
R1 = 0.0404
wR2 = 0.0864
4.636
23089
4999 (Rint = 0.063)
359/0
R1 = 0.0352
wR2 = 0.0663
R1 = 0.0583
wR2 = 0.0709
All data
Data in common: graphite-monochromated Mo-Kα radiation, λ = 0.71073 Å, 180(2) K.
µ-CBut᎐CHCBut᎐C(PPh O)], 90.2 [s, C H ], 45.7 [s, CMe ],
37.0 [s, CMe3], 34.9 [s, CMe3] and 32.1 [s, CMe3].
5 J. E. Davies, M. J. Mays, P. R. Raithby, K. Sarveswaran and
G. A. Solan, J. Chem. Soc., Dalton Trans., 2000, 3331.
6 A. Martín, M. J. Mays, P. R. Raithby and G. A. Solan, J. Chem.
Soc., Dalton Trans., 1993, 1431.
7 S. L. Ingham, M. J. Mays, P. R. Raithby, G. A. Solan,
B. V. Sundavadra, G. Conole and M. Kessler, J. Chem. Soc., Dalton
Trans., 1994, 3607.
8 J. D. King, M. J. Mays, G. E. Pateman, P. R. Raithby, M. A. Rennie,
G. A. Solan, N. Choi, G. Conole and M. McPartlin, J. Chem. Soc.,
Dalton Trans., 1999, 4447.
9 J. E. Davies, M. J. Mays, P. R. Raithby, K. Sarveswaran and
G. A. Solan, Chem. Commun., 2000, 1313.
10 D. Mantlo, J. Suades, F. Dahan and R. Mathieu, Organometallics,
1990, 9, 2933.
11 G. R. Doel, N. D. Feasey, S. A. R. Knox, A. G. Orpen and
J. Webster, J. Chem. Soc., Chem. Commun., 1986, 542; G. Conole,
M. McPartlin, M. J. Mays and M. J. Morris, J. Chem. Soc., Dalton
Trans., 1990, 2359.
12 A. J. P. Domingos, B. F. G. Johnson, J. Lewis and G. M. Sheldrick,
J. Chem. Soc., Chem. Commun., 1973, 912.
13 F. J. Garcia Alonso, V. Riera, M. A. Ruiz, A. Tiripicchio and
M. Tiripicchio Camellini, Organometallics, 1992, 11, 370.
14 A. J. M. Caffyn, M. J. Mays, G. Conole, M. McPartlin and
H. R. Powell, J. Organomet. Chem., 1992, 436, 83.
᎐
᎐
2
5
5
3
3.3 Crystal structure determinations of complexes 4, 6, 7 and 8
X-Ray intensity data was collected using a Siemens STOE
AED four-circle diffractometer (compounds 6 and 7) and a
Rigaku RAXIS-IIC image plate system (4 and 8). Both
instruments were equipped with an Oxford Cryosystems
Cryostream. Details of data collection, refinement and crystal
data are listed in Table 6. All data were corrected for Lorentz-
polarisation factors. Semi-empirical absorption corrections
based on ψ scans28 were applied to the data for 6 and 7, a
spherical absorption correction was applied to the data for 8
and no absorption correction was applied to the data for 4.
Structures were solved and refined with the programs SHELXS
9729 and SHELXL 9730 respectively. Refinement was based on
F2. Hydrogen atoms were placed in idealised positions and
refined using either a riding model or as rigid methyl groups.
CCDC reference numbers 154853–154856.
See http://www.rsc.org/suppdata/dt/b0/b009396n/ for crystal-
lographic data in CIF or other electronic format.
15 I. Moldes, J. Ros, R. Mathieu, X. Solans and M. Font-Bardia,
J. Organomet. Chem., 1992, 423, 65.
16 Single metal–metal bond distances for organo-bridged Co–W
complexes range from 2.55 to 2.76 Å, see for example (a) T. M.
Wido, G. H. Young, A. Wojcicki, M. Calligaris and G. Nardin,
Organometallics, 1988, 7, 452; (b) J. Antonio Abad, L. W. Bateman,
J. C. Jeffery, K. A. Mead, H. Razay, F. G. A. Stone and P.
Woodward, J. Chem. Soc., Dalton Trans., 1983, 2075; (c) J. L.
Davidson, L. Manojlovic-Muir, K. W. Muir and A. N. Keith,
J. Chem. Soc., Chem. Commun., 1980, 749; (d) J. C. Jeffery,
I. Moore, H. Razay and F. G. A. Stone, J. Chem. Soc., Dalton
Trans., 1984, 1581.
17 W. F. Smith, N. J. Taylor and A. J. Carty, J. Chem. Soc., Chem.
Commun., 1976, 896.
18 J. C. Jeffery, R. M. S. Pereira, M. D. Vargas and M. J. Went, J. Chem.
Soc., Dalton Trans., 1995, 1805.
19 P. Dunn, J. C. Jeffery and P. Sherwood, J. Organomet. Chem., 1986,
311, C55.
20 I. J. Hart, J. C. Jeffery, M. J. Grosse-Ophoff and F. G. A. Stone,
J. Chem. Soc., Dalton Trans., 1988, 1867.
21 For phosphine oxides constrained into a chelate ring with tungsten,
see J. L. Davidson, G. Vasapollo, J. C. Millar and K. W. Muir,
J. Chem. Soc., Dalton Trans., 1987, 2165; S. L. Brock and
J. M. Mayer, Inorg. Chem., 1991, 30, 2138.
Acknowledgements
We thank the EPSRC for funding for the X-ray diffractometer,
the image plate system and for financial support to J. E. D.
We are also grateful to the Cambridge Commonwealth Trust
and Professor B. F. G. Johnson for funding to K. S.
References
1 A. J. Carty, Pure Appl. Chem., 1982, 54, 113; A. J. Carty, Adv.
Chem. Ser., 1982, 196, 163; A. A. Cherkas, L. H. Randall,
S. A. MacLaughlin, G. N. Mott, N. J. Taylor and A. J. Carty,
Organometallics, 1988, 7, 969; A. J. Carty, D. Nucciarone, S. A.
MacLaughlin and N. J. Taylor, Organometallics, 1988, 7, 106.
2 M. H. A. Benvenutti, M. D. Vargas, D. Braga, F. Grepioni,
E. Parisini and B. E. Mann, Organometallics, 1993, 12, 2955;
M. H. A. Benvenutti, M. D. Vargas, D. Braga, F. Grepioni,
B. E. Mann and S. Naylor, Organometallics, 1993, 12, 2947; M. D.
Vargas, R. M. S. Periera, D. Braga and F. Grepioni, J. Chem. Soc.,
Chem. Commun., 1993, 1008.
3 B. J. Bobbie, N. J. Taylor and A. J. Carty, J. Chem. Soc., Chem.
Commun., 1991, 1511; E. Sappa, A. Pasquinelli, A. Tiripicchio
and M. Tiripicchio Camellini, J. Chem. Soc., Dalton Trans., 1989,
601.
4 J. E. Davies, M. J. Mays, P. R. Raithby, K. Sarveswaran and
G. P. Shields, J. Organomet. Chem., 1999, 573, 180.
22 For terminal organophosphine oxides bound to W see, G. R. Clark,
A. J. Nielson and C. E. F. Rickard, J. Chem. Soc., Dalton Trans.,
1995, 1907; S. C. N. Hsu, W.-Y. Yeh and M. Y. Chiang,
J. Organomet. Chem., 1995, 492, 121; J. D. Lichtenhan, J. W. Ziller
and N. M. Doherty, Inorg. Chem., 1992, 31, 4210; F. A. Cotton,
P. A. Kibala and C. S. Miertschin, Inorg. Chem., 1991, 30, 548;
1276
J. Chem. Soc., Dalton Trans., 2001, 1269–1277

View Article Online
S. Z. Goldberg and K. N. Raymond, Inorg. Chem., 1973, 12, 2923;
A. J. Nielson, P. A. Hunt, C. E. F. Rickard and P. Schwerdtfeger,
J. Chem. Soc., Dalton Trans., 1997, 3311.
25 W. L. F. Armarego and D. D. Perrin, Purification of Laboratory
Chemicals, Butterworth Heinemann, 4th edn., 1996.
26 R. Mathieu, R. Yanez and N. Lugan, Organometallics, 1990, 9,
2998.
27 G. E. Pateman, PhD Thesis, University of Cambridge, 1996.
28 A. J. Carty, N. K. Hota, T. N. Ng, H. A. Patel and T. J. O’Connor,
Can. J. Chem., 1971, 49, 2706.
29 A. C. T. North, D. C. Phillips and F. S. Matthews, Acta Crystallogr.,
Sect. A, 1968, 24, 351.
30 G. M. Sheldrick, SHELXS 97, program for crystal structure
solution, University of Göttingen, 1997.
23 F. A. Cotton and S. K. Mandal, Eur. J. Solid State Inorg. Chem.,
1991, 28, 775; J. T. Lin, C. C. Chen, P. S. Huang, F.-E. Hong and
Y.-S. Wen, Organometallics, 1993, 12, 4016; J. M. Ball, P. M.
Boorman and J. F. Richardson, Inorg. Chem., 1986, 25, 3325;
J. F. de Wet, M. R. Caira and B. J. Gellatly, Acta Crystallogr.,
Sect. B, 1978, 34, 762; L. H. Hill, N. C. Howlader, F. E. Mabbs,
M. B. Hursthouse and K. M. A. Malik, J. Chem. Soc., Dalton
Trans., 1980, 1475.
24 E. Louattani, I. Moldes, J. Suades, J. F. Piniella and A. A. Larena,
Organometallics, 1998, 17, 3394.
31 G. M. Sheldrick, SHELXL 97, program for crystal structure
refinement, University of Göttingen, 1997.
J. Chem. Soc., Dalton Trans., 2001, 1269–1277
1277