Isomerisation and fragmentation of sulfur-containing organometallacycles on dicobalt centres induced by phosphorus donor ligands

Article abstract of DOI:10.1039/b007322i

Treatment of the dibridged dicobalt complex [Co₂(μ-PPh₂){μ-η¹(S): η¹(C):η²(C)-SPhC(O)CR′CR}(CO)₄ ] (R′ = R = H 1a) with L, at ambient temperature, affords an inseparable mixture of two mono-substituted isomeric complexes of general formula [Co₂(μ-PPh₂){μ-η¹(S):η ¹(C):η²(C)-SPhC(O)CHCH}(CO)₃(L)] [L = P(OMe)₃ 2a/3a, PPhMe₂ 2b/3b], differing only in the metal centre at which L is coordinated. When the reaction is performed with [Co₂(μ-PPh₂){μ-η¹(S):η ¹(C):η²(C)-SPhC(O)CR′CR}(CO)₄] [R′ = Me, R = H 1b], in which R′ and R are inequivalent, a similar mixture of inseparable isomers is isolated, [Co₂(μ-PPh₂){μ-η¹(S):η ¹(C):η²(C)-SPhC(O)-CMeCH}(CO)₃(L)] [L = P(OMe)₃ 4a/5a, PPhMe₂ 4b/5b] and, in addition, a third separable isomer, [Co₂(μ-PPh₂)-{μ-η¹(S):η ¹(C):η²(C)-SPhC(O)CHCMe}(CO)₃(L)] [L = P(OMe)₃, 6a, PPhMe₂ 6b], in which R′ and R have interchanged. Addition of a further equivalent of L at elevated temperature to mixtures of 2/3 results in both carbonyl substitution and a rearrangement of the bridging ligand assembly to give [Co₂(μ-SPh){μ-η¹(P):η¹(C) : η²(C)-PPh₂CRCR′C(O)}(CO)₂(L) ₂] [R′ = R = H; L = P(OMe)₃ 7a, PPhMe₂ 7b] in high yield. A similar transformation is achieved on interaction of 4/5 and 6 with L leading to [Co₂(μ-SPh){μ-η¹(P):η¹(C) :η²(C)-PPh₂CRCR′C(O)}-(CO)₂ (L)₂] [R′ = Me, R = H; L = P(OMe)₃ 8a, PPhMe₂ 8b] and, in addition, [Co₂(μ-SPh){μ-η¹(P):η¹(C) :η²(C)-PPh₂-CR′CRC(O)}(CO)₂(L )₂] [R′ = Me, R = H; L = P(OMe)₃ 9a, PPhMe₂, 9b], in which the positions of R′ and R are reversed. Reaction of 2a/3a with triphenylphosphine, gives the mixed phosphite-phosphine rearranged species [Co₂(μ-SPh){μ-η¹(P):η¹(C) :η²(C)-PPh₂CHCHC(O)}(CO)₂{P(OMe) ₃}(PPh₃)] 10 as the sole product. The facility of the bridging ligands in 1 to undergo a range of bond-breaking (C-S and C-C) and bond-forming (C-S, C-P and C-C) reactions induced by phosphorus donor ligand addition is discussed and pathways postulated. The single crystal X-ray structures of 2b, 7a and 10 are described. The Royal Society of Chemistry 2001.

Full text of DOI:10.1039/b007322i

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Isomerisation and fragmentation of sulfur-containing organo-
metallacycles on dicobalt centres induced by phosphorus donor
ligands
Jason D. King,a Martin J. Mays,*a Giles E. Pateman,a Paul R. Raithby,a Gregory A. Solan,b
Gráinne Conolec and Mary McPartlinc
a Department of Chemistry, Lensfield Road, Cambridge, UK CB2 1EW.
E-mail: mjm14@cus.cam.ac.uk
b Department of Chemistry, University of Leicester, University Road, Leicester, UK LE1 7RH
c School of Applied Chemistry, University of North London, Holloway Road, London,
UK N7 8DB
Received 11th September 2000, Accepted 23rd November 2000
First published as an Advance Article on the web 2nd January 2001
Treatment of the dibridged dicobalt complex [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CRЈCR}(CO)4]
(RЈ = R = H 1a) with L, at ambient temperature, affords an inseparable mixture of two mono-substituted
isomeric complexes of general formula [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CHCH}(CO)3(L)] [L = P(OMe)3
2a/3a, PPhMe2 2b/3b], differing only in the metal centre at which L is coordinated. When the reaction is performed
with [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CRЈCR}(CO)4] [RЈ = Me, R = H 1b], in which RЈ and R are
inequivalent, a similar mixture of inseparable isomers is isolated, [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)-
CMeCH}(CO)3(L)] [L = P(OMe)3 4a/5a, PPhMe2 4b/5b] and, in addition, a third separable isomer, [Co2(µ-PPh2)-
{µ-η1(S):η1(C):η2(C)-SPhC(O)CHCMe}(CO)3(L)] [L = P(OMe)3, 6a, PPhMe2 6b], in which RЈ and R have
interchanged. Addition of a further equivalent of L at elevated temperature to mixtures of 2/3 results in both
carbonyl substitution and a rearrangement of the bridging ligand assembly to give [Co2(µ-SPh){µ-η1(P):η1(C):
η2(C)-PPh2CRCRЈC(O)}(CO)2(L)2] [RЈ = R = H; L = P(OMe)3 7a, PPhMe2 7b] in high yield. A similar transform-
ation is achieved on interaction of 4/5 and 6 with L leading to [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CRCRЈC(O)}-
(CO)2(L)2] [RЈ = Me, R = H; L = P(OMe)3 8a, PPhMe2 8b] and, in addition, [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2-
CRЈCRC(O)}(CO)2(L)2] [RЈ = Me, R = H; L = P(OMe)3 9a, PPhMe2, 9b], in which the positions of RЈ and R are
reversed. Reaction of 2a/3a with triphenylphosphine, gives the mixed phosphite–phosphine rearranged species
[Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CHCHC(O)}(CO)2{P(OMe)3}(PPh3)] 10 as the sole product. The facility
of the bridging ligands in 1 to undergo a range of bond-breaking (C–S and C–C) and bond-forming (C–S, C–P and
C–C) reactions induced by phosphorus donor ligand addition is discussed and pathways postulated. The single
crystal X-ray structures of 2b, 7a and 10 are described.
1 Introduction
The cleavage of carbon–sulfur bonds mediated by transition
metals occurs in a range of catalytic reactions,1–4 but has found
prominence in the hydrodesulfurisation (HDS) process, in
which it represents a key step during the removal of sulfur from
organic compounds in petroleum feedstocks.5,6 A wide variety
of transition metal complexes have been employed to model the
supported HDS system (Co-/Mo-S species on Al2O3) and often
sulfur-containing organometallacyclic ring species have been
isolated and postulated as intermediates in the process.7–17
While many of these metallacyclic species are found in mono-
nuclear complexes,7–13 a number are generated on two adjacent
metal centres,14–17 a situation that has been suggested to model
an edge of a MoS2 crystallite in the commercial catalyst.18
As part of an on-going study of the chemistry of organo-
ditransition metal complexes we have developed routes to
species that contain heteroatoms incorporated into four-,
Fig. 1 Reversible fragmentation of 1a.23 [Co] = Co(CO)2.
five- or nine-membered organometallacycles.19–26 Recently we
reported the synthesis of a family of dicobalt complexes of the
type [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SRC(O)CRCR}(CO)4]
1 and have shown that the almost planar five-membered Co–S–
bond-breaking and bond-forming reactions has been postu-
lated (Fig. 1).
In this paper we describe the reactions of a number of
monodentate phosphorus donor ligands (viz. organo-
phosphites and -phosphines) with [Co2(µ-PPh2){µ-η1(S):
η1(C):η2(C)-SPhC(O)CRЈCR}(CO)4] (RЈ = R = H 1a; RЈ =
C–C᎐C metallacycle can undergo reversible fragmentation
᎐
at room temperature on treatment with 13CO gas.27 Although
the mechanism for this transformation is uncertain, a series
of equilibria involving carbon–sulfur and carbon–carbon
202
J. Chem. Soc., Dalton Trans., 2001, 202–210
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b007322i

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Scheme 1 Products from the reaction of 1 with L: Reagents and conditions: (i) L, 293 K, C7H8, 4 h; (ii) LЈ, 383 K, C7H8, 1 h; (iii) L, 383 K, C7H8, 1 h.
Me, R = H 1b) which lead under mild conditions not only
to carbonyl substitution, but also to reactions involving
carbon–carbon and carbon–sulfur bond cleavage along with
carbon–carbon, carbon–sulfur and carbon–phosphorus bond
formation (see Scheme 1). A portion of this work has been the
subject of a communication.28
2 Results and discussion
2.1 Reaction of 1a and 1b with L at 293 K
The reactions of [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)-
CRЈCR}(CO)4] (RЈ = R = H 1a, RЈ = Me, R = H 1b) with a
slight excess of L [L = P(OMe)3, PPhMe2] at 293 K in toluene
for 4 h give the inseparable (by chromatography) isomeric
purple complexes [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)-
CRЈCR}(CO)3(L)] [RЈ = R = H; L = P(OMe)3 2a/3a, PPhMe2
2b/3b], [RЈ = Me, R = H; L = P(OMe)3 4a/5a, PPhMe2 4b/5b] in
ratios of between 3:2 and 2:1, respectively, as determined by an
inspection of the relative intensities of the NMR signals from
each isomer. When RЈ = Me, R = H, a third separable red
complex [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CRCRЈ}-
(CO)3(L)] [RЈ = Me, R = H; L = P(OMe)3 6a, PPhMe2 6b] is
also obtained. In general, all the reactions (Scheme 1) proceed
with high combined yields. All the complexes have been charac-
terised by 1H, 13C, 31P NMR and IR spectroscopy and by mass
spectrometry and microanalysis (see Table 1 and Experimental
section). In addition, complex 2b has been the subject of a
single crystal X-ray diffraction study.
Although 2b forms part of an inseparable (by chromato-
graphy) isomeric mixture of complexes (2b/3b), crystallisation
by slow evaporation of a CH2Cl2–hexane solution at room
temperature gave crystals of 2b suitable for a single X-ray dif-
fraction study. The molecular structure of complex 2b including
the atom numbering scheme is illustrated in Fig. 2. Selected
bond distances and angles are displayed in Table 2.
The structure of 2b consists of a singly-bonded dicobalt
skeleton [Co(1)–Co(2) 2.483(2) Å] bridged by PPh2 and
SPhC(O)CHCH ligands and bound terminally by three
carbonyl and one PPhMe2 ligands. The SPhC(O)CHCH ligand
is σ-coordinated to Co(1) via S and C(1) to form an almost
planar [max. deviation from plane by C(1) = 0.134 Å] five-
Fig. 2 Molecular structure of 2b including the atom numbering
scheme. All hydrogen atoms apart from H1 and H2 have been omitted
for clarity.
which the carbon–carbon double bond is asymmetrically
π-coordinated to Co(2) via C(1) and C(2) [Co(2)–C(1) 1.98(1),
Co(2)–C(2) 2.12(1) Å]. The PPh2 ligand is asymmetric-
ally bonded to Co(1) and Co(2) [Co(1)–P(2) 2.182(4),
Co(2)–P(2) 2.135(4) Å] and its phosphorus atom lies pseudo-
trans to both the S and C(2) atoms of the metallacycle
[P(2)–Co(1)–S 132.3(1), P(2)–Co(2)–C(2) 122.8(4)Њ]. The ter-
minal PPhMe2 ligand is bound to Co(1) and occupies a site
trans to C(1) of the five-membered metallacycle [C(1)–
Co(1)–P(1) 173.8(4)Њ]. The distorted octahedral coordination
environment at each metal is completed at Co(1) by one
terminal carbonyl ligand and at Co(2) by two carbonyl
groups.
The structure of 2b can be compared with the structurally
characterised unsubstituted complexes 1a28 and [Co2(µ-PPh2)-
{µ-η1(S):η1(C):η2(C)-SBunC(O)CHCH}(CO)4]27 with no
appreciable structural variation introduced on substitution
of a carbonyl group by a phosphine.
1
The 31P and H NMR spectra for the mixture of 2b/3b both
display two sets of signals in an approximately 2:1 ratio. In the
31P NMR spectrum four broad signals are observed, two down-
field (δ 179.9 2b, 140.8 3b) corresponding to the bridging
phosphido groups16–25,29 and two upfield (δ 32.8 2b, 36.8 3b) to
the terminal PPhMe2 ligands.
membered metallacyclic ring [Co(1)–S–C(3)-C(2)᎐C(1)] in
᎐
J. Chem. Soc., Dalton Trans., 2001, 202–210
203

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Table 1 Infrared, 1H NMR and 31P NMR data for complexes 2–10
Complex
ν(CO)a/cmϪ1
1H NMR (δ)b
31P NMR (δ)c
2ad
2000s, 1965s,
7.7–7.2 [m, 15H, Ph], 6.02 [ddd, 3J(PH) 16.2, 3J(PЈH) 7.8,
3J(HH) 4.8, 1H, C(O)CHCH], 4.48 [dd, 3J(PH) 6.3, 1H,
C(O)CHCH], 3.25 [d, 3J(PH) 11.0, 9H, P(OMe)3]
7.8–6.8 [m, 20H, Ph], 6.00 [ddd, 3J(PH) 15.9, 3J(PЈH) 7.6,
3J(HH) 4.5, 1H, C(O)CHCH], 4.46 [dd, 3J(PH) 6.1, 1H,
C(O)CHCH], 1.32 [d, 2J(PH) 8.3, 3H, PPhMe], 1.26 [d,
2J(PЈH) 8.1, 3H, PPhMe]
185.3 and 156.2 [s, br, µ-PPh2, P(OMe)3]
179.9 [s, br, µ-PPh2], 32.8 [s, br, PMe2Ph]
1948w, 1691me
2bd
1998s, 1969s,
1947w, 1641m
3ad
3bd
As for 2a
As for 2b
7.7–7.2 [m, 15H, Ph], 5.76 [ddd, J(PH) 20.1, J(PЈH) 17.7,
3J(HH) 4.8, 1H, C(O)CHCH], 4.38 [ddd, 3J(PH) 6.1, 3J(PЈH)
2.5, 1H, C(O)CHCH], 3.54 [d, 3J(PH) 11.4, 9H, P(OMe)3]
154.1 and 147.1 [s, br, µ-PPh2, P(OMe)3]
140.8 [s, br, µ-PPh2], 36.8 [s, br, PMe2Ph]
3
3
3
3
7.8–6.8 [m, 20H, Ph], 5.78 [ddd, J(PH) 19.9, J(PЈH) 17.9,
3J(HH) 4.5, 1H, C(O)CHCH], 4.19 [ddd, 3J(PH) 6.0, 3J(PЈH)
3.0, 1H, C(O)CHCH], 1.48 [d, 2J(PH) 8.5, 3H, PPhMe], 1.41
[d, 2J(PЈH) 8.3, PPhMe]
4ad
4bd
5ad
5bd
6a
2005m, 1990s,
1950s, 1683m
7.8–7.2 [m, 15H, Ph], 5.99 [dd, 3J(PH) 16.1, 3J(PЈH) 8.0, 1H,
194.8 and 156.3 [s, br, µ-PPh2, P(OMe)3]
180.2 [s, br, µ-PPh2], 11.9 [s, br, PMe2Ph]
185.3 and 152.7 [s, br, µ-PPh2, P(OMe)3]
137.8 [s, br, µ-PPh2], 31.8 [s, br, PMe2Ph]
3
C(O)CMeCH], 3.24 [d, J(PH) 11.0, 9H, P(OMe)3], 1.78 [d,
4J(PH) 4.0, 3H, C(O)CMeCH]
2004s, 1973s,
7.8–6.8 [m, 20H, Ph], 5.80 [dd, 3J(PH) 16.3, 3J(PЈH) 4.0, 1H,
1946w, 1640me
C(O)CMeCH], 1.78 [d, J(PH) 2.7, 3H, C(O)CMeCH], 1.31
4
[d, 2J(PH) 8.3, 3H, PPhMe], 1.25 [d, 2J(PЈH) 8.3, 3H, PPhMe]
7.8–7.2 [m, 15H, Ph], 5.83 [dd, 3J(PH) 21.5, 3J(PЈH) 17.9, 1H,
As for 4a
As for 4b
3
C(O)CMeCH], 3.50 [d, J(PH) 11.2, 9H, P(OMe)3], 1.86 [d,
4J(PH) 4.0, 3H, C(O)CMeCH]
7.8–6.8 [m, 20H, Ph], 5.56 [dd, 3J(PH) 18.5, 3J(PЈH) 15.2, 1H,
4
C(O)CMeCH], 1.95 [d, J(PH) 2.7, 3H, C(O)CMeCH], 1.48
[d, 2J(PH) 8.5, 3H, PPhMe], 1.36 [d, 2J(PЈH) 8.4, 3H, PPhMe]
3
3
2005m, 1990s,
1950s, 1683m
7.8–7.2 [m, 15H, Ph], 4.07 [dd, J(PH) 6.0, J(PЈH) 4.0, 1H,
C(O)CHCMe], 3.23 [d, 3J(PH) 9H, P(OMe)3], 1.95 [d, 4J(PH)
3.8, 3H, C(O)CHCMe]
176.3 [s, br, µ-PPh2], 138.8 [s, br,
P(OMe)3]
6b
7a
2004s, 1973s,
1946w, 1640m
2004s, 1956m,
1580we
Not recorded
183.1 [s, br, µ-PPh2], 15.4 [s, br, PMe2Ph]
3
3
8.0–7.0 [m, 15H, Ph], 4.09 [ddd, J(PH) 37.4, J(PЈH) 10.0,
165.7 [s, P(OMe)3], 147.6 [s, P(OMe)3],
33.9 [s, PPh2CHCHC(O)]
3J(HH) 4.3, 1H, CHCHC(O)], 3.92 [ddd, 3J(PH) 4.3, 2J(PЈH)
3
4.3, 1H, CHCHC(O)], 3.60 [d, J(PH) 11.4, 9H, P(OMe)3],
3.47 [d, 3J(PH) 10.9, 9H, P(OMe)3]
7b
8a
2009s, 1960s,
1579m
2015s, 1967s,
1588m
Not recorded
35.9 [s, PPh2CHCHC(O)], 18.2 [s, br,
PMe2Ph], 7.4 [s, br, PMe2Ph]
168.1 [s, P(OMe)3], 147.2 [s, P(OMe)3],
30.8 [s, PPh2CHCMeC(O)]
2
3
8.0–7.0 [m, 15H, Ph], 3.95 [dd, J(PH) 8.2, J(PH) 5.8, 1H,
3
CHCMeC(O)], 3.63 [d, J(PH) 11.5, 9H, P(OMe)3], 3.51 [d,
3J(PH) 10.8, 9H, P(OMe)3], 1.41 [s, 3H, CHCMeC(O)]
2
3
8b
2010s, 1960s,
1579me
8.0–6.9 [m, 10H, Ph], 3.67 [dd, J(PH) 6.4, J(PЈH) 6.3, 1H,
CHCMeC(O)], 1.63 [d, 3J(PH) 7.9, 3H, PPhMe], 1.45 [d,
3J(PH) 8.3, 3H, PPhMe], 1.42 [d, 3H, 4J(PH) 1.7,
CMeCHC(O)], 1.41 [d, 3J(PH) 8.0, 3H, PPhMe], 1.06 [d,
3J(PЈH) 8.3, 3H, PPhMe]
37.2 [s, PPh2CHCMeC(O)], 11.5 [s, br,
PMe2Ph], 3.3 [s, PMe2Ph]
9a
2020s, 1971s,
1575m
8.0–7.0 [m, 15H, Ph], 4.16 [dd, 3J(PH) 37.2, 3J(PЈH) 9.3, 1H,
167.0 [s, br, P(OMe)3], 143.2 [s, br,
P(OMe)3], Ϫ29.6 [s, PPh2CMeCHC(O)]
3
CMeCHC(O)], 3.52 [d, J(PH) 11.4, 9H, P(OMe)3], 3.36 [d,
3J(PH) 11.4, 9H, P(OMe)3], 1.41 [d, 3J(PH) 8.9, 3H,
CMeCHC(O)]
9b
10
2014s, 1970s,
1576m
1995s, 1942s,
1580m
7.8–6.9 [m, 25H, Ph], 3.97 [m, 1H, CMeCHC(O)], 1.42 [s, br,
CMeCHC(O)], 1.33 [s, br, 12H, PPhMe]
38.3 [s, PPh2CMeCHC(O)], 16.0 [s, br,
PMe2Ph], 0.8 [s, br, PMe2Ph]
146.2 [s, br, P(OMe)3], 55.4 [s, br, PPh3],
35.6 [s, PPh2CHCHC(O)]
7.8–7.0 [m, 30H, Ph], 3.82 [ddd, 3J(PH) 37.4, 3J(PH) 8.8,
3J(HH) 4.0, 1H, CHCHC(O)], 3.65 [m, 1H, CHCHC(O)],
3.40 [d, 3J(PH) 11.2, 9H, P(OMe)3]
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 external 85% H3PO4 (0.0 ppm), {1H}-gated decoupled, measured in CDCl3 at 293 K. Deduct 140.2 from
tabulated values in order to reference relative to external P(OMe)3; d Complex pairs (2a,3a), (2b,3b), (4a,5a) and (4b,5b) are inseparable mixtures of
mono-substituted species. e Recorded in CH2Cl2.
1
In the H NMR spectrum of 2b/3b two pairs of signals for
the olefinic protons are observed; the more downfield signals
(ca. δ 5.9) are assigned to the µ-SPhC(O)CHCH proton and
the more upfield (ca. δ 4.4) to the µ-SPhC(O)CHCH proton.27
For both the downfield resonances three-bond couplings to
the other vinyl proton, the phosphido-phosphorus atom and
the terminal phosphorus bound ligand lead to the resonances
taking the form of doublets of doublets of doublets (ddd). In
contrast, the more upfield resonances take the form of doublets
of doublets (dd) (2b) and doublets of doublets of doublets (3b).
The absence of a third coupling for 2b suggests that the site of
the terminal phosphine ligand is such that there are more than
three bonds between it and the vinyl proton. On this basis 2b is
assigned the molecular structure described above in which there
are four bonds between the µ-SPhC(O)CHCH proton and the
terminal phosphine ligand. The presence of a third coupling for
3b for the corresponding proton, however, suggests the struc-
ture illustrated in Scheme 1 in which the phosphine is posi-
tioned on the cobalt atom in closer proximity to this proton
(i.e. through three bonds). A similar location of a phosphine
ligand to that in 3b has been reported for the structurally
related complex [Co2(µ-PPh2){µ-η1(P):η1(C):η2(C)-PPh2C(O)-
3
CHCH}(CO)3(PPh3)] and indeed a similar J(PH) coupling is
observed for the corresponding proton.19
Microanalysis of the mixture of 2b and 3b is consistent with
the two complexes having the same composition while the FAB
204
J. Chem. Soc., Dalton Trans., 2001, 202–210

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Table 2 Selected bond distances (Å) and angles (Њ) for 2b
Co(1)–Co(2)
Co(1)–P(1)
Co(1)–C(1)
Co(2)–P(2)
Co(2)–C(2)
C(2)–C(3)
2.483(2)
2.234(4)
1.97(1)
2.135(4)
2.12(1)
1.41(2)
1.14(1)–1.16(2)
Co(1)–S
2.266(4)
2.182(4)
1.98(1)
1.92(1)
1.42(2)
1.20(2)
1.73(2)–1.76(2)
Co(1)–P(2)
Co(2)–C(1)
S–C(3)
C(1)–C(2)
C(3)–O(3)
Co–C (carbonyl)
C–O (carbonyl)
S–Co(1)–Co(2)
P(1)–Co(1)–S
P(2)–Co(1)–S
83.0(1)
89.3(1)
132.3(1)
51.1(4)
173.8(4)
140.6(5)
55.8(1)
51.1(4)
78.4(3)
40.4(5)
99.1(5)
70.2(1)
117.7(9)
64.4(7)
123(1)
P(1)–Co(1)–Co(2)
P(2)–Co(1)–Co(2)
P(2)–Co(1)–P(1)
C(1)–Co(1)–S
C(1)–Co(1)–P(2)
C(11)–Co(1)–S
C(1)–Co(2)–P(2)
C(2)–Co(2)–P(2)
C(21)–Co(2)–Co(1)
C(12)–P(1)–Co(1)
C(13)–P(1)–Co(1)
Co(2)–C(1)–Co(1)
C(2)–C(1)–Co(2)
C(3)–C(2)–Co(2)
C(2)–C(3)–S
123.7(1)
54.0(1)
97.8(1)
86.8(4)
81.4(4)
114.7(5)
82.6(4)
122.8(4)
144.9(5)
115.5(5)
119.8(5)
77.8(4)
75.2(7)
101.1(9)
110(1)
C(1)–Co(1)–Co(2)
C(1)–Co(1)–P(1)
C(11)–Co(1)–Co(2)
P(2)–Co(2)–Co(1)
C(1)–Co(2)–Co(1)
C(2)–Co(2)–Co(1)
C(2)–Co(2)–C(1)
C(3)–S–Co(1)
Co(2)–P(2)–Co(1)
C(2)–C(1)–Co(1)
C(1)–C(2)–Co(2)
C(3)–C(2)–C(1)
mass spectrum reveals a single molecular ion peak along with
fragmentation peaks corresponding to the loss of up to three
carbonyl ligands.
On the basis of the close similarity of the spectroscopic data,
structures similar to 2b are postulated for 2a, 4a and 4b (with
L bound to the metallacyclic Co) while complexes 3a, 5a, 5b, 6a
and 6b are ascribed structures similar to 3b (with L bound to
the Co atom not in the metallacycle). For 5 and 6, which are
structurally identical apart from the disposition of the inequiv-
alent RЈ and R groups, the orientation of the vinyl group is
1
assigned on the basis of a comparison of the H NMR data
with that for 3. In a similar way, the disposition of the R groups
in 4 is determined by comparison with the corresponding data
for 2. While complexes 4/5 are inseparable, complexes 6 can be
isolated cleanly and do not isomerise to 4/5 even on prolonged
standing (2–3 days) in solution.
A general feature of the inseparable complexes 2/3 and 4/5
is the presence of up to six resonances in the terminal carbonyl
regions of their 13C-{1H} NMR spectra at 293 K corresponding
to three signals per isomer. This would suggest that at this tem-
perature the carbonyl groups are inequivalent. Indeed, this is a
feature that has also been observed in the 13C NMR spectra of
the precursor complexes 1a and 1b in each of which four
distinct resonances are displayed.27 Due to the broadness of
these signals for 2/3 and 4/5, however, no coupling to geminal
phosphorus centres could be detected.
Fig. 3 Molecular structure of 7a including the atom numbering
scheme. Hydrogen atoms have been omitted for clarity.
addition, complexes 7a and 10 have been the subjects of single
X-ray diffraction studies.
The molecular structure of complex 7a is illustrated in Fig. 3;
selected bond distances and angles for both are listed in Table 3.
In complex 7a the Co–Co single bond [2.466(2)] is bridged
by SPh and PPh2CHCHC(O) ligands such that one Co atom
2.2 Reaction of 2/3, 4/5 or 6 with L at 383 K
The reactions of [Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)-
CRЈCR}(CO)3(L)] [RЈ = R = H; L = P(OMe)3 2a/3a, PPhMe2
2b/3b], [RЈ = Me, R = H; L = P(OMe)3 4a/5a, PPhMe2 4b/5b]
[Co(2)] is incorporated into a five-membered Co–P–C᎐C–C
᎐
metallacycle whose unsaturated C–C bond is π-coordinated to
the second Co atom [Co(1)]. The P–C᎐C–C system is folded so
᎐
and
[Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CRCRЈ}-
as to make the Co–Co and the C᎐C axes almost perpendicular.
᎐
(CO)3(L)] [RЈ = Me, R = H; L = P(OMe)3 6a, PPhMe2 6b] with
excess (up to 5 equivalents) L, at 383 K in toluene for 1 h gives
the green complexes [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2-
CRCRЈC(O)}(CO)2(L)2] [RЈ = R = H; L = P(OMe)3 7a, PPh-
Me2 7b], [RЈ = Me, R = H; L = P(OMe)3 8a, PPhMe2 8b] and
[Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CRЈCRC(O)}(CO)2-
(L)2] [RЈ = Me, R = H; L = P(OMe)3 9a, PPhMe2 9b] in com-
bined high yield (Scheme 1). Reaction of 2a/3a with triphenyl-
phosphine gives the mixed phosphine–phosphite species
[Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CHCHC(O)}(CO)2-
{P(OMe)3}(PPh3)] 10 in 78% yield.
The thiolato group bridges the two metal centres symmetrically
[Co(1)–S(1) 2.238(2) and Co(2)–S(1) 2.251(2)]. Both Co(1) and
Co(2) atoms are bound by P(OMe)3 ligands occupying sites
trans to the metal–metal bond [P(2)–Co(2)–Co(1) 163.3(8),
P(3)–Co(1)–Co(2) 162.4(1)Њ]. The relative configuration of the
phosphorus donor ligands can be regarded as pseudo-cis with a
torsion angle of 7Њ. A single carbonyl ligand completes the
distorted octahedral coordination environment at each metal
centre.
A partial determination of the molecular structure of
complex 10 was made;30 this is depicted in Fig. 4. The X-ray
analysis is consistent with the proposed structure but the poor
quality of the data precludes discussion of the structural
details.
1
All the complexes have been characterised by H, 13C, 31P
NMR and IR spectroscopy and by mass spectrometry and
microanalysis (see Table 1 and Experimental section) and, in
J. Chem. Soc., Dalton Trans., 2001, 202–210
205

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Table 3 Selected bond distances (Å) and angles (Њ) for 7a
region (δ 203.1, 207.1) and a slightly sharper singlet carbonyl
resonance at lower field (δ 224.2) is assigned to the CO of
the metallacycle.
Co(1)–Co(2)
Co(1)–S(1)
Co(2)–P(1)
Co(2)–C(1)
C(2)–C(3)
Co(1)–C(3)
Co(1)–P(3)
Co–C(carbonyl)
2.466(2)
2.238(2)
2.194(2)
2.002(8)
1.424(9)
2.023(2)
2.149(2)
1.768(8)–1.803(8)
Co(2)–S(1)
C(1)–C(2)
P(1)–C(3)
C(1)–O(1)
Co(1)–C(2)
Co(2)–P(2)
Co(2)–C(2)
2.251(2)
1.47(1)
1.796(7)
1.231(7)
2.058(2)
2.171(2)
1.803(8)
On the basis of a comparison with the spectroscopic data for
7a and 10 the structures of the bis-substituted complexes 7b, 8a,
8b, 9a and 9b are assigned related structures with a singly bond-
ed dicobalt unit bridged by SPh and PPh2CRЈCRC(O) ligands
and bound terminally by two phosphorus-bound ligands. The
proposed orientation of the RЈ and R substituents in 8 and 9,
1
1
is based on the H NMR data. For example, the H NMR
C(12)–Co(1)–P(3)
C(12)–Co(1)–S(1) 105.2(3)
P(3)–Co(1)–S(1) 110.2(1)
C(12)–Co(1)–Co(2) 96.8(2)
P(3)–Co(1)–Co(2) 162.4(1)
S(1)–Co(1)–Co(2)
C(1)–Co(2)–P(2)
C(13)–Co(2)–P(1)
C(1)–Co(2)–P(1)
P(2)–Co(2)–P(1)
C(1)–Co(2)–S(1)
P(2)–Co(2)–S(1)
98.5(1)
P(1)–Co(2)–S(1)
C(13)–Co(2)–Co(1) 101.5(2)
C(1)–Co(2)–Co(1)
P(1)–Co(2)–Co(1)
P(2)–Co(2)–Co(1) 163.3(8)
S(1)–Co(2)–Co(1)
C(3)–P(1)–Co(2)
Co(1)–S(1)–Co(2)
C(2)–C(1)–Co(2)
C(1)–C(2)–C(3)
C(2)–C(3)–P(1)
130.5(1)
spectra of 8a and 9a both show doublet of doublet resonances
for the vinyl protons [µ-PPh CH᎐CMeC(O) or µ-PPh2-
᎐
2
68.7(2)
74.5(8)
CMe᎐CHC(O)] at δ 3.95 (8a) and at δ 4.16 (9a). The presence,
᎐
however, of a coupling constant of 37.2 Hz for 9a indicates that
the vinyl proton is located trans to the phosphido group [PPh2-
CMeCHtransC(O)]. A comparison of the corresponding data for
the µ-PPh2CHCHC(O) ligand in 7a supports both assignments.
It is noteworthy that complexes 1a and 1b can be converted
directly into 7a, 7b, 8a, 9a and 9b by reaction with excess of
L [P(OMe)3 or PPhMe2] at 363 K in toluene in high yield.
57.0(1)
97.3(2)
98.5(3)
80.6(3)
113.3(1)
76.7(2)
112.8(1)
56.4(1)
94.9(3)
66.2(1)
108.9(4)
116.9(7)
109.2(6)
2.3 Mechanistic implications
The isolation of 6 from the room-temperature reaction of 1b
with one equivalent of L demonstrates that fragmentation of
the µ-SPhC(O)CMe᎐CH ligand must occur during the reaction
᎐
in order to account for the reversal in the disposition of the
vinyl group substituents (in 6). These results can be compared
to the reversible fragmentation of the µ-SPhC(O)CHCH ligand
observed, even at room temperature, on treatment of 1a
with 13CO gas. This gives [Co2(µ-PPh2){µ-SPh13C(O)CHCH}-
(13CO)2(CO)2] 1aЈ, in which a pathway involving bond-breaking
and bond-making of carbon–sulfur and carbon–carbon bonds
has been invoked (see Fig. 1).23 A similar set of bond-breaking
and bond-forming transformations is capable of accounting for
the formation of 6 and it seems likely that reversible fragmen-
tation of the µ-SPhC(O)CRЈCR ligand occurs during the
formation of 2–5. Indeed, the fact that complexes 2/3 or 4/5
are inseparable, irrespective of the phosphorus-donor ligand L
or the nature of the vinyl substituents, suggests that in solution
an equilibrium exists between them involving reversible
fragmentation of the µ-SPhC(O)CRЈCR ligand.
While addition of one equivalent of L causes isomerisation
and probably reversible fragmentation of the µ-SPhC(O)-
CRЈCR ligand in 1, addition of a second equivalent at elevated
temperature causes permanent sulfur–carbon bond rupture
and phosphorus–carbon bond formation to give the PPh2-
CRCRC(O)/SPh–bridged dicobalt complexes 7–10. Several
points are worth highlighting about these reactions. Firstly,
only on thermolysis of 2–6 with a second equivalent of L does
this rearrangement occur; heating these complexes alone does
not initiate the rearrangement. Secondly, the yield ratio of the
isomeric products 8:9, in which RЈ ≠ R, is independent of which
mono-substituted isomeric starting material is used (4/5 or 6)
suggesting a common intermediate(s). Thirdly, the reaction of
2a/3a with PPh3 affords only one product (10) implying that
both 2a and 3a form a common intermediate.
Scheme 2 illustrates a plausible pathway to account for the
formation of the mono-substituted phosphite/phosphine com-
plexes 2–6. Initial substitution of a terminal carbonyl group in
1 by L may occur preferentially at one metal centre [Co1] to give
2 or 4 (the major isomers of the inseparable pairs) initiating
a reversible ‘ring-flip’ of the SPhC(O)CRЈCR ligand to Co2
to give respectively 3 or 5. This ‘ring-flip’ mechanism occurs
through extrusion of SPh and CO groups from the metallacycle
(in 2 or 4) and the formation of an intermediate complex A
containing a perpendicularly η2 :η2-bridged alkyne group and a
pendant thiolate group (see Fig. 1 for additional related pos-
sible intermediates). The pendant SPh group in A can then shift
to Co(2) to give B in a manner similar to that identified for
Fig. 4 Partially determined molecular structure of 10 including the
atom numbering scheme. All hydrogen atoms apart from H4 and H5
have been omitted for clarity.
Examples of similar, structurally characterised dicobalt
complexes that incorporate the µ-PPh2CRCRC(O) ligand in-
clude the phosphido-bridged complexes [Co2(µ-PPh2){µ-η1(P):
η1(C):η2(C)-PPh2CHCPhC(O)}(CO)4]19 and [Co2(µ-PPh2)-
{µ-η1(P):η1(C):η2(C)-PPh2CHCHC(O)}(CO)2(PPhMe2)2]23
and, indeed, the conformations of the µ-PPh2CRCRC(O)
ligands in these complexes are very similar to those in 7a
and 10. The coupling of a CO and an alkyne to a bridging
phosphido group has been reported in a number of other
dinuclear transition metal complexes leading to µ-PPh2C(O)-
CRCR species in which the CO is positioned between the
phosphide and vinyl groups.19,31
The spectroscopic properties of 7a and 10 are in accordance
with their solid-state structures being maintained in solution
with weak IR bands (ca. 1580 cmϪ1) being assigned to ν(CO) of
the PPh2CHCHC(O) ketonic group. In the 31P-{1H} NMR
spectra of 7a and 10 three broad resonances are observed in
each case. By comparison with previously reported dicobalt
complexes19,20,23 the resonances at δ 33.9 (7a) and 35.6 (10) are
assigned to the PPh2CHCHC(O) phosphorus atom while
P(OMe)3 resonances are seen in the region δ 146.2–165.7 and
the PPh3 signal at δ 55.4. In the 13C-{1H} NMR spectrum of
7a two broad signals are observed in the terminal carbonyl
206
J. Chem. Soc., Dalton Trans., 2001, 202–210

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phosphido group can then take place to give E, followed by
coupling of the alkyne, CO and a phosphide groups to give
7–10. Since the phosphide group may couple with the alkyne
by insertion into either of two Co(1)–C bonds, two regio-
chemistries of the resulting vinyl group are possible and,
indeed, observed in 8 and 9. In Scheme 3 we propose initial
phosphide rather than CO insertion, as we have previously
isolated µ-PPh2CRCR-bridged dicobalt complexes from
alkyne-bridged precursor complexes and moreover, have
observed the related carbonylation reaction of these com-
plexes.19 The subsequent insertion of CO in Scheme 3 must be
irreversible, as treatment of 7a with 13CO at 383 K does not
result in labelling of the ketonic carbonyl group. The reason for
the absence of an isomer of 10 in which the phosphorus donor
ligands have exchanged positions is unclear, but the reduced
steric demands of a P(OMe)3 group over a PPh3 group at the
crowded metallacyclic Co atom may be significant.
3 Conclusions
The reaction of phosphorus donor ligands (L) with the asym-
metrically bridged 1 is much more complex than the simple
substitution of carbonyl groups by the L ligands. Indeed, sub-
stitution of the carbonyl ligands does occur but with the effect
of inducing two types of intramolecular rearrangement reac-
tion. Firstly, the orientation of the R groups on the vinyl unit of
the sulfur-containing Co–S–C–C᎐C metallacycle in 1b can be
᎐
reversed on mono-substitution at moderate temperatures (293
K). Secondly, the metallacycle, Co–S–C–C᎐C, in 1 can be
᎐
converted to a phosphorus-containing Co–P–C᎐C–C metal-
᎐
lacycle, in 7–10, on bis-substitution at elevated temperatures
(383 K).
4 Experimental
4.1 General techniques and reagents
Scheme
2
Proposed pathway for ‘ring-flip’ interconversion and
formation of 2–6 from 1. [Co] = Co(CO)2 or Co(CO), L = P(OMe)3 or
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.37 Infrared spectra were
recorded in dichloromethane 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. 1H, 13C and 31P spectra were recorded on either a Bruker
WM 250 spectrometer or a Bruker AM 400 spectrometer.
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 University Chemical
Laboratory, Cambridge. Column chromatography was per-
formed on Kieselgel 60 (70–230 or 230–400 mesh). Products are
given in order of decreasing Rf values.
PPhMe2.
related mixed-metal systems26 and then reform the metallacycle
via SPh, CO and alkyne coupling. The formation of the
isomers 5 and 6, in which the disposition of the R substituents
on the vinyl group is reversed, can be understood as resulting
from insertion of the CO or SPh group (see Fig. 1) into one or
other of the metal–carbon bonds between Co(2) and the
alkyne-bridge in B. On the other hand, it is not clear why
an isomer of 4 with the R substituents on the vinyl group
reversed is not formed via the same process. It is note-
worthy that a similar regiospecificity is observed in the form-
ation of 1b from the reaction of [Co2(µ-MeCCH)(CO)6] with
PPh2(SPh).27
Although we were unable to detect by solution NMR spectro-
scopy any of the postulated intermediate species in the form-
ation of 2–6, related complexes containing the proposed or
similar bridging ligands have been isolated and demonstrated to
undergo related bond-forming and bond-breaking reactions.
For example, reversible coupling of alkynes with CO on
bimetallic centres has been well documented19,27–29,31–35 while
recent reports have disclosed thiolate-alkyne coupling.25,26 In
addition, the ‘ring-flip’ mechanism proposed here can be
compared to the shift of a hydride and an oscillation of
a η1 :η2-vinyl group between two metal centres detected by
Deeming et al.36
Unless otherwise stated all reagents were obtained from
commercial suppliers and the compounds [Co2(µ-PPh2){µ-η1-
(S):η1(C):η2(C)-SPhC(O)CRЈCR}(CO)4] (RЈ = R = H 1a;
RЈ = Me, R = H 1b) were prepared by literature methods.27
4.2 Room temperature reactions of 1a with L
(i) L ؍ P(OMe)3. To a solution of [Co2(µ-PPh2){µ-η1(S):
η1(C):η2(C)-SPhC(O)CHCH}(CO)4] 1a (0.300 g, 0.52 mmol)
in toluene (50 cm3) was added P(OMe)3 (0.20 cm3, 1.70 mmol)
in toluene (50 cm3). The reaction mixture was stirred at 293 K
for 4 h and after removal of the solvent under reduced pressure,
purified by TLC using hexane–dichloromethane (2:1) as eluent.
This gave in addition to a small amount of unreacted starting
material, the inseparable isomeric purple crystalline complexes
[Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CHCH}(CO)3-
{P(OMe)3}] 2a/3a (0.315 g, 90%). Compounds 2a/3a: NMR
(CDCl3, 293 K): 13C(1H composite pulse decoupled), (2a)
Scheme 3 illustrates a plausible pathway for the formation of
7–10. Addition of LЈ to all mono-substituted structural types
2–6 is proposed to give a pair of common bis-substituted
intermediates C and D. As in Scheme 2 these intermediates
arise via fragmentation of the SPhC(O)CRCR ligand and con-
tain transverse µ-η2 :η2-alkyne and pendant thiolate groups.
For C, however, exchange of a thiolate group with a bridging
J. Chem. Soc., Dalton Trans., 2001, 202–210
207

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Scheme 3 Proposed pathway to rearranged complex 10 from 2a/3a. [Co] = Co(CO)2 or Co(CO), L = P(OMe)3, LЈ = PPh3.
δ 208.6 [s, CoCO], 205.7 [s, CoCO], 203.7 [s, CoCO], 180.8 [d,
3J(PC) 22, SPhC(O)CHCH], 142–124 [m, Ph], 124.6 [dd, 2J(PC)
50, 2J(PЈC) 35, SPhC(O)CHCH], 68.0 [s, SPhC(O)CHCH] and
52.3 [d, 2J(PC) 6 Hz, P(OMe)3]; (3a) δ 207.9 [s, CoCO], 203.4 [s,
CoCO], 202.5 [s, CoCO], 181.8 [d, 3J(PC) 22, SPhC(O)CHCH],
Calc. for C28H28Co2O7P2S: C, 55.81; H, 4.07. Found: C, 55.63;
H, 4.12%. FAB mass spectrum, m/z 688 (Mϩ) and (Mϩ Ϫ nCO)
(n = 1–3). Compound 6a: FAB mass spectrum, m/z 688 (Mϩ)
and (Mϩ Ϫ nCO) (n = 1–3).
2
2
142–124 [m, Ph], 116.3 [dd, J(PC) 46, J(PЈC) 31, SPhC(O)-
(ii) L ؍ PPhMe2. As above in (i) using PPhMe2 (0.20 cm3,
1.40 mmol). Elution with hexane–dichloromethane (10:1) gave
4b/5b (0.143 g, 40%) and 6b (0.144 g, 40%). Compounds 4b/5b:
FAB mass spectrum, m/z 702 (Mϩ) and (Mϩ Ϫ nCO) (n = 1–3).
Compound 6b: FAB mass spectrum, m/z 702 (Mϩ) and
(Mϩ Ϫ nCO) (n = 1–3).
2
CHCH], 62.1 [s, SPhC(O)CHCH] and 51.8 [d, J(PC) 4 Hz,
P(OMe)3]. Fast atom bombardment (FAB) mass spectrum, m/z
674 (Mϩ) and (Mϩ Ϫ nCO) (n = 1–3). Anal. Calc. for C27H26-
Co2O7P2S: C, 48.1; H, 3.9. Found: C, 48.3; H, 4.0%.
(ii) L ؍ PPhMe2. As above in (i) using PPhMe2 (0.20 cm3,
1.40 mmol). Eluted with hexane–dichloromethane (10:1) gave
2b/3b (0.291 g, 83%). Compounds 2b/3b: Anal. Calc. for
C32H28Co2O4P2S: C, 55.81; H, 4.07. Found: C, 55.63; H,
4.12%. FAB mass spectrum, m/z 688 (Mϩ) and (Mϩ Ϫ nCO)
(n = 1–3).
4.4 Thermolytic reactions of 2/3 with L
(i) 2a/3a with P(OMe)3 (L). To a solution of [Co2(µ-PPh2)-
{µ-η1(S):η1(C):η2(C)-SPhC(O)CHCH}(CO)3{P(OMe)3}] 2a/
3a (0.200 g, 0.29 mmol) in toluene (50 cm3) was added a solu-
tion of P(OMe)3 (0.20 cm3, 1.70 mmol) in toluene (50 cm3). The
reaction mixture was stirred at 383 K for 1 h and after removal
of the solvent under reduced pressure the mixtures were puri-
fied by TLC using hexane–ethyl acetate (10:1) as eluent. This
gave in addition to a small amount of unreacted starting
material, the green complex [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-
PPh2CHCHC(O)}(CO)2{P(OMe)3}2] 7a (0.171 g, 75%). Com-
pound 7a: NMR (CDCl3, 293 K): 13C(1H composite pulse
decoupled), δ 224.2 [s, PPh2CHCHC(O)], 207.1 [s, CoCO],
203.1 [s, CoCO], 144–125 [m, Ph], 72.0 [s, br, PPh2CHCHC(O)],
51.7 [m, br, P(OMe)3] and 31.9 [m, br, PPh2CHCHC(O)]. Anal.
Calc. for C29H35Co2O9P3S: C, 45.2; H, 4.6; P, 12.1. Found: C,
45.4; H, 4.5; P 12.0%. FAB mass spectrum, m/z 770 (Mϩ) and
(Mϩ Ϫ nCO) (n = 1–3).
4.3 Room-temperature reactions of 1b with L
(i) L ؍ P(OMe)3. To a solution of [Co2(µ-PPh2){µ-η1(S):
η1(C):η2(C)-SPhC(O)CMeCH}(CO)4] 1b (0.300 g, 0.51 mmol)
in toluene (50 cm3) was added P(OMe)3 (0.20 cm3, 1.70 mmol)
in toluene (50 cm3). The reaction mixture was stirred at 293 K
for 4 h and after removal of the solvent under reduced pressure,
purified by TLC using hexane–dichloromethane (2:1) as eluent.
This gave in addition to a small amount of unreacted starting
material, the inseparable isomeric purple crystalline complexes
[Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CMeCH}(CO)3-
{P(OMe)3}] [L = 4a/5a (0.154 g, 44%)] and the red crystal-
line complex [Co2(µ-PPh2){µ-η1(S): η1(C):η2(C)-SPhC(O)-
CHCMe}(CO)3{P(OMe)3}] 6a (0.126 g, 36%). Compounds 4a/
5a: NMR (CDCl3, 293 K): 13C(1H composite pulse decoupled),
(4a) δ 209.4 [s, CoCO], 203.9 [s, CoCO], 202.3 [s, CoCO], 177.3
[d, 3J(PC) 16, SPhC(O)CMeCH], 142–127 [m, Ph and SPhC(O)-
CMeCH], 68.1 [s, SPhC(O)CMeCH], 51.7 [d, 2J(PC) 4 Hz,
P(OMe)3] and 23.7 [s, SPhC(O)CMeCH]; (5a) δ 208.0 [s,
CoCO], 204.6 [s, CoCO], 203.0 [s, CoCO], 181.5 [d, 3J(PC) 20,
SPhC(O)CMeCH], 147.2 [dd, 2J(PC) 50, 2J(PЈC) 34, SPhC(O)-
CMeCH], 142–127 [m, Ph], 66.6 [s, SPhC(O)CMeCH], 52.3 [d,
2J(PC) 6 Hz, P(OMe)3] and 23.2 [s, SPhC(O)CMeCH]. Anal.
(ii) 2b/3b with PPhMe2 (L). As above in (ii) using 2a/3b (0.200
g, 0.29 mmol) and PPhMe2 (0.20 cm3, 1.40 mmol). Elution with
hexane–dichloromethane (2:1) gave 7b (0.181 g, 78%). Com-
pound 7b: NMR (CDCl3, 293 K): 13C(1H composite pulse
decoupled), δ 226.8 [s, PPh2CHCHC(O)], 208.8 [s, CoCO],
203.9 [s, CoCO], 144–125 [m, Ph], 72.0 [s, br, PPh2CHCHC(O)],
32.3 [m, br, PPh2CHCHC(O)] and 18.2 [d, 2J(PC) 18 Hz,
PPhMe2]. FAB mass spectrum, m/z 798 (Mϩ) and (Mϩ Ϫ nCO)
(n = 1–3).
208
J. Chem. Soc., Dalton Trans., 2001, 202–210

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Table 4 X-Ray crystallographic and data processing parameters for 2b and 7aa
Complex
2b
7a
Formula
M
C32H28Co2O4P2S
687.98
C29H35Co2O9P3S
750.2
Crystal size/mm
Temperature/K
0.38 × 0.32 × 0.23
293(2)
1.0 × 1.0 × 1.0
295(2)
Crystal system
Space group
Monoclinic
P21/n
Triclinic
P1 (no. 2)
¯
a/Å
b/Å
c/Å
α/Њ
13.648(2)
16.213(3)
13.934(3)
90
9.360(4)
10.433(5)
19.106(8)
85.51(3)
β/Њ
100.46(2)
90
3032(1)
77.05(3)
67.33(3)
1678(1)
γ/Њ
V/Å3
Z
4
2
Dc/g cmϪ3
1.508
1.485
F(000)
1408
12.3
752
12.42
µ(Mo-Kα)/cmϪ1
θ range/Њ
3.00–25.00
Ϫ15 to 15, 0–18, 0–16
5782
2402 [I > 3σ(I)]
1.000 and 0.658
2402/0/352
—
2.50–22.50
Ϫ10 to 2, Ϫ11 to 10, Ϫ20 to 20
5023
4402 [Rint = 0.01]
1.000 and 0.916
5023/0/423
Limiting hkl indices
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
GOFb of fit on F2
Final R indicesc
I > 2σ(I)
1.53
R = 0.0689, RЈ = 0.0682d
—
0.743 and Ϫ0.852
R1 = 0.0501, Rw = 0.0782
R1 = 0.0625, Rw = 0.0853
1.13 and Ϫ1.01
All data
Largest diff. peak and hole/e ÅϪ3
a Data common to all compounds: Mo-Kα (λ = 0.71073 Å). b GOF = [Σw(Fo2 Ϫ Fc2)/(n Ϫ p)]1/2 where n = number of reflections and p = total number
2
2
of parameters. c R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|, wR2 = [Σw(Fo2 Ϫ Fc2)2/Σw(Fo )2]1/2, wϪ1 = [σ2(Fo)2 ϩ (aP)2 ϩ bP], P = [max(Fo ,0)ϩ2(Fc2)]/3; R = Σ(∆F)/Σ(Fo);
RЈ = [Σw(∆F )2/Σw(Fo)2]1/2; wϪ1 = σ2(F ). d I > 3σ(I).
4.5 Thermolytic reactions of 4/5 with L
stirred at 383 K for 1 h and after removal of the solvent under
reduced pressure the mixture was purified by TLC using
hexane–ethyl acetate (10:1) as eluent. This gave in addition to a
small amount of unreacted starting material, the green complex
[Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CHCMeC(O)}(CO)2-
{P(OMe)3}2] 8a (0.136 g, 60%) and [Co2(µ-SPh){µ-η1(P):
η1(C):η2(C)-PPh2CMeCHC(O)}(CO)2{P(OMe)3}2] 9a (0.027
g, 12%).
(i) 4a/5a with P(OMe)3 (L). To a solution of [Co2(µ-PPh2)-
{µ-η1(S):η1(C):η2(C)-SPhC(O)CMeCH}(CO)3{P(OMe)3}] 4a/
5a, (0.200 g, 0.29 mmol) in toluene (50 cm3) was added
P(OMe)3 (0.20 cm3, 1.70 mmol) in toluene (50 cm3). The solu-
tion was stirred at 383 K for 1 h and after removal of
the solvent under reduced pressure the mixture was purified
by TLC using hexane–ethyl acetate (10:1) as eluent. This gave
in addition to a small amount of unreacted starting material,
the green complexes [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2-
CHCMeC(O)}(CO)2{P(OMe)3}2] 8a (0.136 g, 60%) and
[Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-PPh2CMeCHC(O)}(CO)2-
{P(OMe)3}2] 9a (0.027 g, 12%). Compound 8a: NMR (CDCl3,
293 K): 13C(1H composite pulse decoupled), δ 224.3 [s, PPh2-
CHCMeC(O)], 206.5 [s, CoCO], 203.2 [s, CoCO], 144–124 [m,
Ph], 72.1 [d, 2J(PC) 26.7, PPh2CHCMeC(O)], 51.8 [m, br,
P(OMe)3], 31.6 [d, 1J(PC) 41.2 Hz, PPh2CHCMeC(O)] and 15.1
[s, PPh2CHCMeC(O)]. Anal. Calc. for C30H37Co2O9P3S: C,
45.9; H, 4.7. Found: C, 45.9; H, 4.7%. FAB mass spectrum, m/z
784 (Mϩ) and (Mϩ Ϫ nCO) (n = 1–3). Compound 9a: Anal
Calc. for C40H41Co2O3P3S: C, 59.1; H, 5.1. Found: C, 59.0; H,
5.1%. FAB mass spectrum, m/z 812 (Mϩ) and (Mϩ Ϫ nCO)
(n = 1–3).
(ii) 6b with PPhMe2. As above in (i) using 6b (0.200 g, 0.28
mmol) and PPhMe2 (0.20 cm3, 1.40 mmol). Elution with
hexane–dichloromethane (2:1) gave green 8b (0.127 g, 56%)
and 9b (0.180 g, 8%).
4.7 Thermolytic reaction of 2a/3a with PPh3
Triphenylphosphine (0.050 g, 0.19 mmol) was added to
[Co2(µ-PPh2){µ-η1(S):η1(C):η2(C)-SPhC(O)CHCH}(CO)3-
{P(OMe)3}] 2a/3a (0.100 g, 0.15 mmol) in toluene (50 cm3) and
the reaction mixture stirred for 1 h at 383 K. The solvent was
removed under reduced pressure and the mixture purified by
preparative TLC using hexane–ethyl acetate (10:1) as eluent to
yield the green complex [Co2(µ-SPh){µ-η1(P):η1(C):η2(C)-
PPh2CHCHC(O)}(CO)2{P(OMe)3}(PPh3)] 10 (0.105 g, 78%).
Compound 10: Anal. Calc. for C44H41Co2O6P3S: C, 58.15; H,
4.51. Found: C, 58.08; H, 4.53%. FAB mass spectrum, m/z 908
(Mϩ) and (Mϩ Ϫ nCO) (n = 1–3).
(ii) 4b/5b with PPhMe2 (L). As above in (i) using 4b/5b (0.200
g, 0.28 mmol) and PPhMe2 (0.20 cm3, 1.40 mmol). Elution with
hexane–dichloromethane (2:1) gave green 8b (0.127 g, 56%)
and 9b (0.180 g, 8%). Compound 8b: FAB mass spectrum, m/z
784 (Mϩ) and (Mϩ Ϫ nCO) (n = 1–3). Compound 9b: FAB mass
spectrum, m/z 812 (Mϩ) and (Mϩ Ϫ nCO) (n = 1–3).
4.8 Crystal structure analysis of complexes 2b and 7a
Suitable single crystals were mounted on glass fibres with
epoxy-resin, and transferred to an X-ray diffractometer. Details
of the data-collection procedures, structure solution and
refinements are presented in Table 4.
4.6 Thermolytic reactions of 6 with L
(i) 6a with P(OMe)3 (L). To a solution of [Co2(µ-PPh2)-
{µ-η1(S):η1(C):η2(C)-SPhC(O)CHCMe}(CO)3{P(OMe)3}] 6a
(0.200 g, 0.29 mmol) in toluene (50 cm3) was added P(OMe)3
(0.20 cm3, 1.70 mmol) in toluene (50 cm3). The solution was
X-Ray intensity data for 2b were collected on a Philips
PW1100 four-circle diffractometer. Lorentz-polarisation and
absorption corrections were applied to the data of all the
compounds. The positions of the metal atoms in 2b were
J. Chem. Soc., Dalton Trans., 2001, 202–210
209

View Article Online
15 W. D. Jones and R. M. Chin, J. Organomet. Chem., 1994, 472,
deduced from Patterson syntheses. The remaining non-
hydrogen atoms and H(1) and H(2) were revealed from sub-
sequent difference-Fourier syntheses. Refinement was based on
F.38 The phenyl rings were constrained to refine as rigid hexa-
gons. The positions of the hydrogen atoms on C(1) and C(2)
were obtained from a difference-Fourier map based on low
angle data (θ < 20Њ), and were included without refinement. The
remaining hydrogen atoms were placed in idealised positions;
all hydrogen atoms were assigned displacement parameters of
0.1 Å2. After initial refinement with isotropic displacement
parameters empirical absorption corrections39 were applied to
the data. All non-hydrogen atoms were assigned anisotropic
displacement parameters in the final cycles of full-matrix least-
squares refinement.
X-Ray intensity data for 7a were measured on a Siemens
R3m/V diffractometer. The structure was solved by direct
methods and refined by blocked full-matrix least-squares
analysis;40 phenyl hydrogens were placed in idealised positions
and allowed to ride on the relevant carbon atoms. Positional
disorder was detected for four oxygens of the trimethyl-
phosphite groups with 43 and 57% of occupancy, respectively;
only one of them was studied isotropically.
311.
16 S. Luo, A. E. Skaugset, T. B. Rauchfuss and S. R. Wilson, J. Am.
Chem. Soc., 1992, 114, 1732.
17 A. E. Ogilvy, M. Draganjac, T. B. Rauchfuss and S. R. Wilson,
Organometallics, 1988, 7, 1171.
18 W. D. Jones, D. A. Vicic, M. Chin, J. H. Roache and A. W. Myers,
Polyhedron, 1997, 16, 3115.
19 A. J. M. Caffyn, M. J. Mays, G. A. Solan, D. Braga, P. Sabatino,
G. Conole, M. McPartlin and H. R. Powell, J. Chem. Soc., Dalton
Trans., 1991, 3103.
20 A. J. M. Caffyn, M. J. Mays, G. A. Solan, D. Braga, P. Sabatino,
A. Tiripicchio and M. Tiripicchio-Camellini, Organometallics, 1993,
12, 1876.
21 A. J. Edwards, A. Martín, M. J. Mays, D. Nazar, P. R. Raithby and
G. A. Solan, J. Chem. Soc., Dalton Trans., 1993, 355.
22 A. J. M. Caffyn, M. J. Mays, G. A. Solan, G. Conole and
A. Tiripicchio, J. Chem. Soc., Dalton Trans., 1993, 2345.
23 A. J. M. Caffyn, A. Martín, M. J. Mays, P. R. Raithby and
G. A. Solan, J. Chem. Soc., Dalton Trans., 1994, 609.
24 A. Martín, M. J. Mays, P. R. Raithby and G. A. Solan, J. Chem.
Soc., Dalton Trans., 1993, 1789.
25 A. Martín, M. J. Mays, P. R. Raithby and G. A. Solan, J. Chem.
Soc., Dalton Trans., 1993, 1789; 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.
26 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.
CCDC reference number 186/2284 for 2b and code KumKei
for 7a (see ref. 28).
27 G. Conole, M. Kessler, G. E. Pateman, M. J. Mays and G. A. Solan,
Polyhedron, 1998, 17, 2993.
Acknowledgement
28 A. J. Edwards, A. Martín, M. J. Mays, P. R. Raithby and G. A.
Solan, J. Chem. Soc., Chem. Commun., 1992, 1416.
29 A. J. Carty, Adv. Chem. Ser., 1982, 196, 163; A. J. Carty, Pure Appl.
Chem., 1982, 54, 113.
We are grateful to the EPSRC (G. E. P. and G. A. S.) for
financial support.
30 Complex 10: monoclinic, space group P21/c, a = 20.316(4), b =
12.918(3), c = 18.011(4) Å; β = 116.28(3)Њ; V = 4238(2) Å3.
31 R. Regragui, P. H. Dixneuf, N. J. Taylor and A. J. Carty,
Organometallics, 1990, 9, 2234; R. Regragui, P. H. Dixneuf,
N. J. Taylor and A. J. Carty, Organometallics, 1984, 3, 814;
J. D. King, M. J. Mays, C.-Y. Mo, P. R. Raithby, M. A. Rennie,
G. A. Solan, T. Adatia and G. Conole, J. Organomet. Chem., 2000,
601, 271.
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