Reactions of σ-π alkenyl complexes [Fe2(CO)6(μ-alkenyl)(μ-PPh2)] with bis(diphenylphosphino)methane (dppm); Carbonyl substitution, migratory carbonyl insertion, phosphorus-carbon bond formation and cleavage, proton shift and alkenyl isomerisation reactions

Article abstract of DOI:10.1016/s0020-1693(99)00100-0

Products of the thermal reactions of μ-alkenyl complexes [Fe₂(CO)₆(μ-R¹C=CHR ²)(μ-PPh₂)] (1) (a, R¹=R²=H; b, R¹=EtO, R²=H; c, R¹=H, R²=Ph; d, R¹=Ph, R²=H; e, R¹=R²=Ph; f, R¹=CMe=CH₂, R²=H), with bis(diphenylphosphino)methane (dppm) are substituent dependent. Complexes 1a-c afford simple substitution products trans-[Fe₂(CO)₄(μ-alkenyl)(μ-PPh ₂)(μ-dppm)] (2a-c); while with 1d,e, α,β-unsaturated acyl complexes trans-[Fe₂(CO)₄(μ-O=C-C(Ph)=CH(R ²))(μ-PPh₂)(μ-dppm)] (3d,e) are the major products formed via a migratory-insertion reaction. A minor product of the reaction with 1d is [Fe₂(CO)₅(μ-Ph₂PC(Ph)=CH ₂)(μ-dppm)] (4), the result of phosphorus-carbon bond formation. Reaction of 1f also leads to phosphorus-carbon bond formation together with a 1,4-proton shift giving the μ-alkylidene complex [Fe₂(CO)₄(μ-HC-C(Me)=C(Me)PPh₂)(μ-dppm)] (5). Dppm addition to 1c has been followed in detail, allowing a complete reaction scheme to be developed. Initial carbonyl substitution affords the η¹-dppm complex [Fe₂(CO)₅(η ¹-dppm)(μ-HC=CHPh)(μ-PPh₂)] (6). This subsequently isomerises to trans-[Fe₂(CO)₄(μ-O=C-CH=CHPh)(μ-PPh ₂)(μ-dppm)] (3c) which then readily loses CO to give the μ-alkenyl 2c. Loss of CO from isomeric 3d occurs only upon prolonged thermolysis and also affords 2c, a result of α,β-alkenyl isomerisation. Further, heating 4 also yields 2c after CO loss, phosphorus-carbon bond cleavage, and alkenyl isomerisation. While the β-substituted phenylethenyl complex 2c is stable to prolonged reflux in toluene, heating isomeric cis-[Fe₂(CO)₄(μ-PhC=CH₂)(μ-PPh ₂)(μ-dppm)] (7) results in formation of the 5-electron μ-acyl complex [Fe₂(CO)₃(μ-O=C-C(Ph)=CH ₂)(μ-dppm)(μ-PPh₂)] ) (8); also prepared upon heating 4. Crystal structures have been carried out on 3e and 5.

Full text of DOI:10.1016/s0020-1693(99)00100-0

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 291 (1999) 178–189
Reactions of s-p alkenyl complexes [Fe2(CO)6(m-alkenyl)(m-PPh2)]
with bis(diphenylphosphino)methane (dppm); carbonyl
substitution, migratory carbonyl insertion, phosphorus–carbon
bond formation and cleavage, proton shift and alkenyl
isomerisation reactions
Graeme Hogarth a,*, Khalid Shukri a, Simon Doherty b, Arthur J. Carty c,
Gary D. Enright c
a Department of Chemistry, Uni6ersity College London, 20 Gordon Street, London WC1H 0AJ, UK
b Department of Chemistry, Uni6ersity of Newcastle, Bedson Building, Newcastle-upon-Tyne NE1 7RU, UK
c The Steacie Institute for Molecular Sciences, National Research Council of Canada, 100 Sussex Dri6e, Ottawa, Ont. K1A OR6, Canada
Received 15 October 1998
Abstract
Products of the thermal reactions of m-alkenyl complexes [Fe2(CO)6(m-R1CꢀCHR2)(m-PPh2)] (1) (a, R1=R2=H; b, R1=EtO,
R2=H; c, R1=H, R2=Ph; d, R1=Ph, R2=H; e, R1=R2=Ph; f, R1=CMeꢀCH2, R2=H), with bis(diphenylphos-
phino)methane (dppm) are substituent dependent. Complexes 1a–c afford simple substitution products trans-[Fe2(CO)4(m-
alkenyl)(m-PPh2)(m-dppm)] (2a–c); while with 1d,e, a,b-unsaturated acyl complexes trans-[Fe2(CO)4{m-OꢀC–C(Ph)ꢀ
CH(R2)}(m-PPh2)(m-dppm)] (3d,e) are the major products formed via a migratory–insertion reaction. A minor product of the
reaction with 1d is [Fe2(CO)5{m-Ph2PC(Ph)ꢀCH2}(m-dppm)] (4), the result of phosphorus–carbon bond formation. Reaction of 1f
also leads to phosphorus–carbon bond formation together with a 1,4-proton shift giving the m-alkylidene complex [Fe2(CO)4{m-
HC–C(Me)ꢀC(Me)PPh2}(m-dppm)] (5). Dppm addition to 1c has been followed in detail, allowing a complete reaction scheme to
be developed. Initial carbonyl substitution affords the h1-dppm complex [Fe2(CO)5(h1-dppm)(m-HCꢀCHPh)(m-PPh2)] (6). This
subsequently isomerises to trans-[Fe2(CO)4(m-OꢀC–CHꢀCHPh)(m-PPh2)(m-dppm)] (3c) which then readily loses CO to give the
m-alkenyl 2c. Loss of CO from isomeric 3d occurs only upon prolonged thermolysis and also affords 2c, a result of a,b-alkenyl
isomerisation. Further, heating 4 also yields 2c after CO loss, phosphorus–carbon bond cleavage, and alkenyl isomerisation.
While the b-substituted phenylethenyl complex 2c is stable to prolonged reflux in toluene, heating isomeric cis-[Fe2(CO)4(m-
PhCꢀCH2)(m-PPh2)(m-dppm)] (7) results in formation of the 5-electron m-acyl complex [Fe2(CO)3{m-OꢀC–C(Ph)ꢀCH2}(m-
dppm)(m-PPh2)] ) (8); also prepared upon heating 4. Crystal structures have been carried out on 3e and 5. © 1999 Elsevier Science
S.A. All rights reserved.
Keywords: Crystal structures; Iron complexes; Carbonyl complexes; Alkenyl complexes; Dinuclear complexes
formally a metalated alkene, and over the past 30 years
a large number of alkenyl complexes have been pre-
1. Introduction
pared and studied. More recent interest in this class of
The chemistry of small metal-bound hydrocarbyl lig-
compound stems from their proposed role as key inter-
ands continues to be an area of intense research activ-
mediates in the Fischer–Tropsch process [1]. Conse-
ity. The alkenyl moiety is one such species, being
quently, the reactivity of the ligand, which had
previously received little attention, has become an ac-
tive area of research and Maitlis and co-workers [2],
Ros and Mathieu [3], and Knox [4] have shown that
* Corresponding author. Tel.: +44-171-387 7050; fax: +44-171-
380 7463.
E-mail address: g.hogarth@ucl.ac.uk (G. Hogarth)
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00100-0

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
179
coupling of alkenyl and C1 fragments can occur readily
at the binuclear metal centre.
somewhat slower, occurring over 3 h in refluxing
toluene to afford trans-[Fe2(CO)4(m-EtOCꢀCH2)(m-
PPh2)(m-dppm)] (2b) in 90% yield. The trans structure
was readily ascertained from the phosphorus–phospho-
rus coupling constants to the phosphido-bridge (77.4
and 77.1 Hz), and is unusual as to date all such
a-substituted complexes have adopted a cis conforma-
tion [7,9,10]. Isolation of the trans isomer here may
reflect the site selectivity of the substitution process or
result from the initial formation of the cis isomer which
rearranges to the more stable trans form under the
reaction conditions.
At the binuclear metal centre, the preferred ligand
binding is that in which it bridges the two metal centres
acting as both a s- and p-donor ligand. In 1975,
Shapley et al. [5] first reported that such ligands can
display stereochemical non-rigidity via ‘windshield
wiper’ fluxionality. Here, while the a-carbon remains
bound to both metal centres, the b-carbon oscillates
between them and since it generally occurs with reten-
tion of stereochemistry [6], the proposed transition state
is one in which the two carbons are symmetrically
bound to both metal centres.
We became interested in this fluxional process as a
result of preparing isomeric m-alkenyl complexes,
[Fe2(CO)4(m-alkenyl)(m-PR2)(m-dppm)], which displayed
quite different free energies of activation for the process
[7–9]. In an effort to investigate this further, we sought
access to a wider range of such complexes, to date
prepared via the room temperature (r.t.) hydrodimeta-
lation of alkynes to cis-[Fe2(CO)4(m-H)(m-CO)(m-PPh2)-
(m-dppm)] [7,9]. While this works well for primary
alkynes and the activated alkyne dimethylacetylene di-
carboxylate [10], less reactive disubstituted alkynes re-
quire elevated temperatures at which benzene
Characterisation of 2b was straightforward, being
based on a comparison of spectroscopic data with that
of 1b. Noteworthy is the extremely low-field resonance
for the a-carbon at 219.60 (d, J 25.9 Hz) ppm, while in
the 1H NMR spectrum the alkenyl protons are ob-
served at l 2.51 (dt, J 17.4, 6.4) and 2.29 (ddd, J 13.7,
10.6, 6.4 Hz). The static nature of the alkenyl ligand at
r.t. on the NMR timescale is clearly shown by the
inequivalence of the two ends of the diphosphine, rep-
resented by signals at 76.2 (dd, J 121.8, 77.4) and 72.3
(dd, J 121.8, 77.1 Hz) ppm in the 31P NMR spectrum
and the appearance of four separate carbonyl reso-
nances in the 13C NMR spectrum. Consequently, a
variable temperature 31P NMR study was carried out in
d8-toluene; raising the temperature to 87°C resulted in
the coalescence of the two diphosphine signals allowing
a free energy of activation to be calculated at 67.192
kJ mol−1. This is essentially the same as that found for
unsubstituted 2a (67.592) [13], and methyl substituted
trans-[Fe2(CO)4(m-MeCꢀCH2)(m-PCy2)(m-dppm)] (]68
92 kJ mol−1) [8], suggesting that substitution at the
a-position has little effect on the rate of alkenyl fluxion-
ality. In contrast, we have previously shown that substi-
tution at the b-carbon leads to a considerable reduction
in the free energy of activation for this process [7,9].
elimination
yielding
[Fe2(CO)5(m-PhPCH2PPh2)(m-
PPh2)] is rapid and dominant [11]. In contrast, r.t.
hydrodimetalation of [Fe2(CO)7(m-H)(m-PPh2)] occurs
with both mono- and di-substituted alkynes [12]. We
thus sought to prepare further dppm-bridged alkenyl
complexes via the carbonyl substitution of hexacar-
bonyl complexes [Fe2(CO)6(m-R1CꢀCHR2)(m-PPh2)] (1).
While in a number of cases simple carbonyl substitution
did occur to give the dppm-bridged alkenyl complexes,
in many reactions the alkenyl group was non-innocent
and took part in the reaction; migratory carbonyl inser-
tion, alkenyl isomerisation, phosphorus–carbon bond
formation and 1,4-proton shift reactions all being ob-
served. Herein, we report full details of this work.
2. Results and discussion
2.1. Carbonyl substitution reactions
Heating
a
toluene solution of [Fe2(CO)6(m-
HCꢀCH2)(m-PPh2)] (1a) and dppm for 10 min resulted
in the formation of trans-[Fe2(CO)4(m-HCꢀCH2)(m-
PPh2)(m-dppm)] (2a) in 75% yield, while the b-phenyl-
alkenyl complex [Fe2(CO)6(m-HCꢀCHPh)(m-PPh2)] (1c)
reacts in a similar fashion to afford trans-[Fe2(CO)4(m-
HCꢀCHPh)(m-PPh2)(m-dppm)] (2c) in 60% yield after 1
h. Both have been previously prepared [7] via hy-
drodimetalation of respective alkynes by cis-
[Fe2(CO)4(m-H)(m-CO)(m-PPh2)(m-dppm)]. Reaction of
[Fe2(CO)6(m-EtOCꢀCH2)(m-PPh2)] (1b) and dppm was
2.2. Bridging acyl complexes 6ia migratory carbonyl
insertion
The thermal reaction of [Fe2(CO)6(m-PhCꢀCH2)(m-
PPh2)] (1d) and dppm appears to follow a quite differ-
ent course to that found for isomeric 1c. Heating a
toluene solution of 1d and dppm to 100°C resulted in a
considerable and immediate darkening of the solution
and formation of the a,b-unsaturated bridging acyl

180
G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
complex trans - [Fe2(CO)4{m - O ꢀ C – C(Ph) ꢀ CH2}(m -
PP-h2)(m-dppm)] (3d) in 81% yield as the major reac-
tionproduct. In an analogous manner, reaction of
[Fe2(CO)6(m-PhCꢀCHPh)(m-PPh2)] (1e) gave trans-
[Fe2(CO)4{m-OꢀC – C(Ph)ꢀCHPh}(m-PPh2)(m-dppm)]
(3e) in 72% yield as the only isolable product. Char-
acterisation as bridging acyl complexes was based on
spectroscopic and analytical data. Significantly, both
showed a low field resonance in the 13C NMR spec-
trum attributed to the acyl carbon, appearing at 300.1
(t, J 20.5) and 297.9 (t, J 30.5 Hz) ppm for 3d and
3e, respectively, while the trans arrangement of phos-
phorus-containing ligands was again clear from 31P
NMR spectroscopy.
Fig. 1. Molecular structure of 3e.
In order to unambiguously establish the migratory
carbonyl insertion reaction, an X-ray crystallographic
study was carried out on 3e the results of which are
summarised in Table 1 and Fig. 1. The diiron vector
,
ond [Fe(2)–C(5) 1.992(4) A]. The carbon–oxygen
,
bond length of 1.291(4) A is typical of values found
for related acyl complexes [9,14–16] as is the planar
nature of the Fe2–C(5)–O(5) arrangement (the
biggest deviation from this plane being 0.03 A). The
carbon–carbon bonds within the acyl ligand [C(5)–
C(6) 1.516(5), C(6)–C(7) 1.351(5) A] are consistent
with a localised single and double bond formulation,
while the two phenyl groups have maintained their cis
arrangement.
,
[Fe(1)–Fe(2) 2.6637(10) A] is bridged symmetrically
,
by the phosphido [Fe(1)–P(3) 2.2250(12), Fe(2)–P(3)
,
2.2263(13) A] and diphosphine [Fe(1)–P(1) 2.2830(13),
,
,
Fe(2)–P(2) 2.2653(13) A] ligands which adopt a rela-
tive trans arrangement. The bridging acyl ligand lies
cis to both, being bound through oxygen to one
,
metal [Fe(1)–O(5) 2.005(3) A] and carbon to the sec-
Migratory carbonyl insertion into a metal–alkenyl
moiety has previously been noted [17], while a num-
ber of related diiron a,b-unsaturated acyl complexes
have also been reported [9,14,15]. We have crystallo-
graphically characterised the dicyclohexylphosphido
analogue of 3d, being isolated as a minor product of
the reaction of trans-[Fe2(CO)4(m-H)(m-CO)(m-PCy2)(m-
dppm)] and PhCꢁCH [9], while Seyferth and co-work-
ers have prepared related thiolate- [14] and
phosphido-bridged [15] diiron hexacarbonyl com-
plexes. For example, the hexacarbonyl analogue of
3c, namely [Fe2(CO)6(m-OꢀC–CHꢀCHPh)(m-PPh2), re-
sults from addition of the acid chloride to
Na[Fe2(CO)6(m-PPh2)] [15]. A noteworthy feature of
the thiolate-bridged hexacarbonyl complexes is the
generally ready loss of CO and formation of the
alkenyl complex upon dissolution in THF [14]. Both
3d and 3e are indefinitely stable under these condi-
tions, however, at higher temperatures CO is lost
from 3d as discussed below.
Table 1
,
Selected bond lengths (A) and bond angles (°) for 3e
,
Bond lengths (A)
Fe(1)–Fe(2)
Fe(1)–C(2)
Fe(2)–C(4)
Fe(1)–O(5)
Fe(2)–P(2)
Fe(2)–P(3)
C(5)–C(6)
2.6637(10)
1.761(4)
1.819(4)
Fe(1)–C(1)
Fe(2)–C(3)
Fe(2)–C(5)
Fe(1)–P(1)
Fe(1)–P(3)
O(5)–C(5)
C(6)–C(7)
1.794(4)
1.789(4)
1.992(4)
2.2830(13)
2.2250(12)
1.291(4)
1.351(5)
2.005(3)
2.2653(13)
2.2263(13)
1.516(5)
Bond angles (°)
Fe(1)–Fe(2)–C(3)
Fe(1)–Fe(2)–C(5)
Fe(2)–Fe(1)–C(2)
Fe(1)–Fe(2)–C(5)
C(3)–Fe(2)–C(4)
P(2)–Fe(2)–P(3)
Fe(2)–C(5)–O(5)
O(5)–C(5)–C(6)
155.1(2)
68.64(11)
95.34(13)
68.64(11)
90.3(2)
144.54(5)
113.1(3)
112.7(3)
Fe(1)–Fe(2)–C(4)
Fe(2)–Fe(1)–C(1)
Fe(2)–Fe(1)–O(5)
C(1)–Fe(1)–C(2)
P(1)–Fe(1)–P(3)
Fe(1)–P(3)–Fe(2)
C(5)–C(6)–C(7)
101.80(14)
159.7(2)
71.08(7)
93.9(2)
151.71(4)
73.51(4)
120.5(4)

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
181
Table 2
2.3. Phosphorus–carbon bond formation and clea6age
,
Selected bond lengths (A) and bond angles (°) for 5
A minor product from the reaction of 1d and dppm
was characterised as the vinylphosphine com-
plex [Fe2(CO)5{m-Ph2PC(Ph)ꢀCH2}(m-dppm)] (4) (12%
yield). The IR spectrum is characteristic of a diiron
pentacarbonyl fragment, a formulation confirmed by
mass spectrometry. The formation of a new carbon–
phosphorus bond was clearly shown by the absence of
a low-field phosphido-bridge resonance in the 31P
NMR spectrum, which consists of doublets of dou-
blets at 77.7 (J 113.6, 21.4), 75.7 (J 113.6, 98.2) and
58.2 (J 98.2, 21.4 Hz) ppm. Formation of 4 from 1d is
a result of carbonyl loss, diphosphine coordination
and coupling of the alkenyl and phosphido moieties.
Mays and co-workers [18] have described the synthesis
of vinylphosphine dimolybdenum complexes via an
analogous phosphorus–carbon bond forming process.
Further, we have previously prepared the related
,
Bond lengths (A)
Fe(1)–Fe(2)
Fe(1)–C(2)
Fe(2)–C(4)
Fe(2)–C(6)
Fe(2)–C(8)
Fe(1)–P(3)
P(3)–C(8)
2.6325(4)
1.7519(21)
1.7554(24)
2.0488(18)
2.1252(22)
2.2139(6)
1.7809(22)
1.439(3)
Fe(1)–C(1)
Fe(2)–C(3)
Fe(1)–C(6)
Fe(2)–C(7)
Fe(1)–P(1)
Fe(2)–P(2)
C(6)–C(7)
C(7)–C(9)
1.7770(22)
1.7393(22)
1.9827(21)
2.0826(21)
2.2358(6)
2.1794(6)
1.411(3)
C(7)–C(8)
C(8)–C(10)
1.509(3)
1.513(3)
Bond angles (°)
Fe(1)–Fe(2)–C(3)
Fe(1)–Fe(2)–C(6)
Fe(1)–Fe(2)–C(8)
Fe(2)–Fe(1)–C(2)
Fe(1)–Fe(2)–P(2)
Fe(2)–Fe(1)–P(3)
C(3)–Fe(2)–C(4)
P(3)–Fe(1)–C(6)
Fe(2)–C(7)–C(6)
Fe(2)–C(7)–C(9)
C(6)–C(7)–C(9)
C(7)–C(8)–C(10)
164.30(8)
48.15(6)
80.02(6)
153.07(8)
99.094(18) Fe(2)–Fe(1)–P(1)
72.437(18) C(1)–Fe(1)–C(2)
96.66(11)
81.62(6)
68.74(11)
127.95(15)
123.09(20)
121.26(20)
Fe(1)–Fe(2)–C(4)
Fe(1)–Fe(2)–C(7)
Fe(2)–Fe(1)–C(1)
Fe(2)–Fe(1)–C(6)
76.03(7)
77.40(6)
111.73(6)
50.33(5)
93.060(13)
93.91(10)
165.491(24)
71.32(11)
71.61(12)
P(1)–Fe(1)–P(3)
Fe(2)–C(6)–C(7)
Fe(2)–C(7)–C(8)
C(6)–C(7)–C(8)
C(8)–C(7)–C(9)
ethenylphosphine
complex
[Fe2(CO)5(m-Ph2PCHꢀ
114.31(19)
122.59(19)
CH2)(m-dppm)] [13] via irradiation of diphenylvinyl-
phosphine and [Fe2(CO)6(m-CO)(m-dppm)], and spec-
troscopic data for this and 4 are similar.
,
1.9827(21), Fe(2)–C(6) 2.0488(18) A]. This carbon car-
ries an unsaturated substituent, the carbon–carbon
,
double bond of which [C(7)–C(8) 1.439(3) A] is p-
bonded to Fe(2) [Fe(2)–C(7) 2.0826(21), Fe(2)–C(8)
,
2.1252(22) A]. The other end of the olefinic group is
bound to what was the phosphido-bridge [P(3)–C(8)
,
1.7809(22) A] and is now linked to only a single metal
The reaction between [Fe2(CO)6{m-C(CMeꢀCH2)ꢀ
CH2}(m-PPh2)] (1f) and dppm followed a quite differ-
ent course to those described above. Overnight reflux
was required and resulted in a colour change from
yellow to orange with the isolation of the
m-alkylidene complex [Fe2(CO)4{m-HC–C(Me)ꢀC-
(Me)PPh2}(m-dppm)] (5) in 51% yield. The appearance
of four carbonyl bands in the IR spectrum initially
appeared to suggest that it was a simple diphosphine
derivative of 1f, however, the absence of a low-field
phosphido-bridge resonance in the 31P NMR spectrum
was again indicative of phosphorus–carbon bond for-
mation. Likewise, the appearance of two methyl reso-
nances in the 1H NMR spectrum suggested that a
significant rearrangement of the alkenyl ligand had
occurred. In order to elucidate the precise nature of 5
an X-ray crystallographic study was carried out, the
results of which are summarised in Table 2 and Fig. 2.
The molecule consists of two iron atoms [Fe(1)–
,
centre [Fe(1)–P(3) 2.2358(6) A]. This phosphorus
atom lies approximately trans to one end of the
,
Fe(2) 2.6325(4) A] bridged by the dppm ligand with
each carrying two carbonyls. The diiron centre is also
bridged somewhat asymmetrically by what can be con-
sidered as a substituted alkylidene ligand [Fe(1)–C(6)
Fig. 2. Molecular structure of 5.

182
G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
tre appearing at l −19.0 (J 60.8 Hz) ppm in the 31P
NMR spectrum. Further heating of a toluene solution
of 6 gave a yellow solution after 40 min, which after
chromatography afforded an inseparable mixture of
m-acyl trans-[Fe2(CO)4(m-OꢀC–CHꢀCHPh)(m-PPh2)(m-
dppm)] (3c) and m-alkenyl trans-[Fe2(CO)4(m-
HCꢀCHPh)(m-PPh2)(m-dppm)] (2c) in an approximate
2:3 ratio. Complex 3c could not be isolated free of 2c
but unambiguous characterisation was based on a
comparison of spectroscopic data with isomeric 3d.
Pertinently, the two acyl protons appear as AB dou-
blets at l 6.22 and 6.00 in the 1H NMR spectrum
with a coupling constant of 15.9 Hz indicating their
trans disposition. Further heating of this mixture for
90 min resulted in quantitative conversion to the m-
alkenyl complex 2c.
Scheme 1.
diphosphine [P(1)–Fe(1)–P(3) 165.491(24)°], account-
ing for the coupling constant of 163.8 Hz between
them.
The overall transformation of 1f to 5 involves: (i)
substitution of two carbonyls for dppm, (ii) phospho-
rus–carbon bond formation between the phosphido-
bridge and the a-carbon of the alkenyl ligand, (iii) a
1,4-proton shift from the olefinic carbon to the b-car-
bon of the alkenyl ligand, and (iv) coordination of
the deprotonated olefinic carbon. The precise order of
these steps is not known, however, the close proxim-
ity of the phosphido-bridge to the a-carbon of the
alkenyl ligand may facilitate the carbon–phosphorus
bond formation process. A possible route is shown
(Scheme 1). If metal coordination of the diphosphine
promotes attack of the phosphido-bridge at the a-car-
bon of the alkenyl group then this will facilitate a
1,4-proton transfer to the b-carbon. One might expect
this process to be facile since 1f can be viewed as a
metalated 1,4-diene. Finally, coordination of the car-
bene carbon and the olefinic bond give rise to 5 as
shown.
2.5. Thermal stability of h,i-unsaturated acyl
complexes and alkenyl isomerisation
As previously alluded to, many of the thiolate-
bridged a,b-unsaturated acyl complexes reported by
Seyferth undergo ready CO loss to afford the corre-
sponding alkenyl complexes [14], a process shown to
follow first-order kinetics [19]. Exceptions to this
ready CO loss are complexes with alkyl groups on
the a-carbon, which lose CO only very slowly upon
prolonged thermolysis, under which conditions dithio-
late-bridged [Fe2(CO)6(m-SEt)2] is a major product
[14]. This enhanced stability of the acyl-bridge has
been attributed to electronic factors, as electron-do-
nating groups are known to stabilise acyl binding. A
further point of note is that when Na[Fe2(CO)6(m-
PPh2)] reacts with H2CꢀCH–C(O)Cl, the alkenyl
complex 1a was the sole product, suggesting that here
CO loss from the acyl may be facile [15].
2.4. Mechanistic insights: a closer look at the reaction
of 1c and dppm
As noted earlier, thermolysis of 1c and dppm for 1
h afforded the m-alkenyl complex 2c in 60% yield.
When this reaction was followed spectroscopically,
two intermediates were characterised enabling a clear
reaction scheme to be established. In the presence of
a slight excess of dppm, warming 1c to reflux resulted
in the rapid formation of a bright orange solution
from which the h1-dppm complex [Fe2(CO)5(h1-
dppm)(m-HCꢀCHPh)(m-PPh2)] (6) was isolated in 45%
yield after chromatography. Characterisation was
straight-forward, the uncoordinated phosphorus cen-
In an attempt, then, to assess the stability of m-acyl
complexes 3d and 3e, prolonged toluene thermolysis
of both was carried out. Complex 3e was found to be
indefinitely stable under these conditions, however,

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
183
slow carbonyl loss from 3d was noted over 2d afford-
ing, not the anticipated a-substituted product, but
rather the b-substituted alkenyl complex 2c in 83%
yield. This transformation represents not only a loss of
CO but also a,b-isomerisation of the alkenyl ligand. A
further isomerisation of the a- to b-phenyl ethenyl
ligand was observed upon heating the vinylphosphine
complex 4 in toluene for 1 h which afforded 2c (52%).
Closely related to the latter is our earlier observation
that the ethenylphosphine complex [Fe2(CO)5(m-
Ph2PCHꢀCH2)(m-dppm)] converts cleanly into 2a after
CO loss and phosphorus–carbon bond cleavage [13]. A
second complex isolated from the thermal degradation
of 4 was the dppm cleavage product [Fe2(CO)6(m-
CH2PPh2)(m-PPh2)] (22%) [20], which presumably forms
upon loss of the vinylphosphine and CO scavenging.
In the preceding section, two examples were given in
which the a-phenyl ethenyl ligand was transformed into
its b-isomer. In light of this, and the absence of isola-
tion of 7 from the reaction of 1c with dppm, we decided
to test the thermal stability of 7, specifically to see if it
would convert to a trans a-substituted complex or
isomeric 2c.
Heating a toluene solution of 7 for 30 min resulted in
the isolation of three products after chromatography.
The b-substituted isomer 2c was formed in 22% yield,
together with the carbon–phosphorus bond formation
product [Fe2(CO)5{m-Ph2PC(Ph)ꢀCH2}(m-dppm)] (4)
(7%). Since we have already noted that under thermoly-
sis 4 transforms into 2c, alkenyl isomerisation here
presumably proceeds via 4. A third product was iden-
tified as the novel 5-electron donor a,b-unsaturated acyl
complex [Fe2(CO)3{m-OꢀC–C(Ph)ꢀCH2}(m-dppm)(m-
PPh2)] (8) isolated as an orange crystalline solid in 14%
yield. Characterisation was made on the basis of analyt-
ical and spectroscopic data, and a comparison of the
latter with the related bis(diphenylphosphino)ethane
(dppe) complex [Fe2(CO)3{m-OꢀC–C(Ph)ꢀCH2}(h2-
dppe)(m-PPh2)] which we have recently prepared and
crystallographically characterised [22]. In the IR spec-
trum, two intense absorptions at 1968 and 1917 cm−1
are characteristic of an Fe2(CO)3 fragment, a formula-
tion supported by the carbonyl region of the 13C NMR
In a recent communication we reported that the
a-phenylethenyl ligand can isomerise to its b-isomer at
the diiron centre. For example, 1d transforms into 1c
over 1 h in refluxing toluene [21], and we proposed that
this may occur via a hydrido–alkyne complex, the
latter acting as a 2-electron ligand lying parallel to the
metal–metal vector. We were never able to detect such
a species spectroscopically nor did we see any evidence
of reversible CO insertion into the alkenyl ligand.
Clearly, further experiments are required in order to
fully elucidate the nature of this novel a-b alkenyl
isomerisation reaction.
1
spectrum. In the H NMR spectrum, the two alkenyl
protons appear at l 3.43 (d, J 7.9) and 2.05 (t, J 9.3
Hz), both showing couplings to phosphorus but not to
each other, and in the 13C NMR spectrum the acyl
carbon appears at 303.1 (t, J 19.6 Hz) ppm, being
shifted some 3 ppm down-field of the same resonance in
the isomeric 3-electron acyl complex 3d. Complexation
of the carbon–carbon double bond results in a signifi-
cant shift of these carbon atoms from 155.4 and 78.6 in
3d to 161.3 and 114.3 for the a- and b-carbons,
respectively.
2.6. Thermal instability of cis-[Fe2(CO)4(v-PhCꢀCH2)-
(v-PPh2)(v-dppm)] (7): synthesis of a y-bound
5-electron donor h,i-unsaturated acyl complex
Isomerisation of 7 to 8 results from migratory CO
insertion into the alkenyl fragment and subsequent
metal coordination of the olefinic double bond such
that the steric and electronic saturation of the diiron
centre is preserved, while it should also be noted that
there is a cis–trans rearrangement of phosphorus-con-
taining ligands. Trace amounts of 8 were also isolated
from the direct reaction of [Fe2(CO)6(m-PhCꢀCH2)(m-
PPh2)] (1d) and dppm and thus, it appears that here a
In earlier work we showed that hydrodimetalation of
phenylethyne by [Fe2(CO)4(m-H)(m-CO)(m-PPh2)(m-
dppm)] afforded isomeric trans-[Fe2(CO)4(m-HCꢀ
CHPh)(m-PPh2)(m-dppm)] (2c) and cis-[Fe2(CO)4(m-
PhCꢀCH2)(m-PPh2)(m-dppm)] (7) in an approximate
1:10 ratio [7]. The cis-disposition of phosphorus-con-
taining ligands in 7 is noteworthy and is believed to be
a consequence of the relatively bulky a-phenyl group.

184
G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
Scheme 2.
small amount of 7 is generated but cannot be isolated
due to later thermal rearrangements to 4 and 8. The
5-electron acyl complex 8 is also formally related to 3d
via CO loss and olefin coordination, yet it is not formed
upon thermolysis of the latter, suggesting that here,
thermal carbonyl extrusion from the acyl bridge is more
facile than metal–carbonyl loss. In contrast, the related
5-electron acyl dppe complex [Fe2(CO)3{m-OꢀC–
C(Ph)ꢀCH2}(h2-dppe)(m-PPh2)] is generated slowly
(\4 h) upon thermolysis of the analogous 3-electron
migratory carbonyl insertion reaction, with all such
complexes adopting a relative trans disposition of phos-
phorus-containing ligands. The rate of carbonyl extru-
sion from 3 is strongly dependent upon the alkenyl
substituents, allowing their isolation in a number of
instances. For 1a,b, the rate determining step is pre-
sumably the initial carbonyl substitution with subse-
quent steps being rapid, thus precluding the
observation of any intermediates. We cannot rule out
the possibility that here the second CO substitution
reaction occurs much more rapidly than carbonyl inser-
tion, and thus that 1a and 1b are formed directly from
an h1-dppm complex. With 1c, the rates of the three
separate steps are similar, the use of a slight excess of
diphosphine serving to accelerate the initial carbonyl
substitution reaction and thus allowing the isolation of
6. With 1d,e, carbonyl loss from the m-acyl complexes
3d,e is slow and these are the major products.
acyl
complex
[Fe2(CO)4{m-OꢀC–C(Ph)ꢀCH2}(h2-
dppe)(m-PPh2)] [22]. However, since it formed from the
thermal reaction of dppe with 1d at 90°C for 10 min,
this must be a minor pathway to it.
3. Conclusions
The reaction of 1d and dppm also affords some
minor yield products, namely 2c (6%), 4 (12%) and 8
(trace), the relative amounts of which depend upon
reaction time and scale. The expected dppm-bridged
complex cis-[Fe2(CO)4(m-PhCꢀCH2)(m-PPh2)(m-dppm)]
(7) is not isolated, but separate experiments reveal that
at toluene reflux this converts rapidly to a mixture of 2c
(22%), 4 (7%) and 8 (14%), while heating 4 itself affords
2c (52%) and 8 (26%). These experiments suggest that
the putative h1-dppm adduct [Fe2(CO)5(m-PhCꢀCH2)(m-
PPh2)(h1-dppm)] initially formed upon addition of
dppm to 1d preferentially isomerises to give m-acyl 3d,
We have shown in this paper that the potentially
simple substitution reaction of two carbonyls by dppm
in m-alkenyl complexes [Fe2(CO)6(m-alkenyl)(m-PPh2)]
(1), leads to a number of different products and reac-
tion pathways as summarised (Scheme 2). In all cases it
seems that initial carbonyl substitution occurs to yield
an h1-dppm complex, a reaction which is site-selective,
probably occurring at the s-bound iron centre and
trans to the phosphido-bridge as this pattern of substi-
tution has been noted with monodentate phosphines
[21,23]. This then isomerises to afford the m-acyl com-
plex as a result of an intramolecular phosphine assisted

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
185
but a small amount loses CO to yield dppm-bridged 7,
2b: IR (CH2Cl2): 1978s, 1947vs, 1914s, 1900sh cm−1
;
which is unstable under the reaction conditions and
rearranges to afford a mixture of 2c, 4 and 8. We
cannot, however, rule out the possibility that the h1-
dppm complex also isomerises to 4 directly, a result of
carbon–phosphorus bond formation which competes
with the migratory insertion reaction and results in the
coupling of the alkenyl and phosphido-bridges. Cer-
tainly with 1f, carbon–phosphorus bond formation is
more facile than the migratory insertion reaction and
1H NMR (CDCl3): l 8.72–7.0 (m, Ph, 30H), 4.03 (dt, J
18.5, 15.2, 1H, PCH2P), 3.22 (dt, J 14.6, 11.6, 1H,
PCH2P), 2.93 (t, J 11.9, 1H, CꢀCH2), 2.51 (dt, J 17.4,
6.4, 1H, OCH2), 2.29 (ddd, J 13.7, 10.6, 6.4, 1H,
OCH2), 2.02 (t, J 8.9, 1H, CꢀCH2), 0.12 (t, J 6.4, 3H,
CH3); 13C NMR (CDCl3): 221.8 (s, CO), 219.9 (d, J 9.5,
CO), 219.6 (d, J 25.9, Ca), 216.5 (t, J 21.7, CO), 213.6
(t, J 20.7, CO), 142–126 (m, Ph), 67.8 (s, OCH2), 59.4
(d, J 9.8, Cb), 34.5 (t, J 26.8, PCH2P), 13.5 (s, CH3)
ppm; 31P NMR (CDCl3): 193.5 (t, J 77.3, m-PPh2), 76.2
(dd, J 121.8, 77.4, dppm), 72.3 (dd, J 121.8, 77.1,
dppm) ppm; mass spectrum (FAB+): m/z 864 (M+),
837 (M−CO), 808 (M−2CO), 780 (M−3CO), 753
(M−4CO); Anal. Calc. for Fe2C45H39O5P3·0.25CH2Cl2:
C, 61.33; H, 4.46. Found: C, 61.01; H, 4.41%.
the subsequent 1,4-proton shift produces
a new
organophosphorus ligand which does not undergo car-
bon–phosphorus bond cleavage, thus accounting for
the isolation of 5.
These experiments have shown that seemingly simple
carbonyl substitution reactions at the m-alkenyl sup-
ported diiron centre are more complex than initially
might have been envisaged, this being primarily due to
the high reactivity of the alkenyl ligand itself. Thus, it
participates in a number of reactions including coupling
to a carbonyl ligand to give a m-acyl ligand, coupling to
the phosphido-bridge (which may occur with internal
proton transfer) to give alkenyl phosphines and a-b
isomerisation.
4.4. [Fe2(CO)6(v-HCꢀCHPh)(v-PPh2)] (1c)
Heating a toluene solution (25 cm3) of 1c (50 mg,
0.088 mmol) and dppm (37 mg, 0.097 mmol) for 1 h
resulted in a slight darkening of the solution. After
removal of the solvent, chromatography eluting with
ether:light-petroleum (1:4) gave a yellow band which
afforded
dppm)] (2c) (47 mg, 60%).
trans-[Fe2(CO)4(m-HCꢀCHPh)(m-PPh2)(m-
Heating a toluene solution (25 cm3) of 1c (70 mg,
0.12 mmol) and dppm (60 mg, 0.16 mmol) for 10 min
resulted in a colour change from yellow to orange.
After removal of the solvent, chromatography afforded:
a yellow band eluting with light-petroleum which gave
unreacted 1c (8 mg); an orange band eluting with
4. Experimental
4.1. General procedures
General experimental methods have been described
previously. Alkenyl complexes 1a–f [12] and 8 [7], were
prepared by literature methods. All reactions were car-
ried out in dry toluene under a nitrogen atmosphere but
work-up was carried out in air unless otherwise stated.
ether:light-petroleum
which
gave
[Fe2(CO)5(h1-
dppm)(m-HCꢀCHPh)(m-PPh2)] (6) (45 mg, 45%); a yel-
low band eluting with ether:light-petroleum (1:4) which
gave 50 mg of an inseparable mixture of 2c and trans-
[Fe2(CO)4(m-OꢀC–CHꢀCHPh)(m-PPh2)(m-dppm)] (3c)
1
4.2. [Fe2(CO)6(v-HCꢀCH2)(v-PPh2)] (1a)
in a 1:2 ratio (by H NMR spectroscopy).
Heating a toluene solution (25 cm3) of 6 (40 mg,
0.043 mmol) for 40 min resulted in the formation of a
yellow solution. Proton NMR spectroscopy revealed
this to be a mixture of 2c and 3c (3:2) with the complete
absence of 6.
Heating a toluene solution (25 cm3) of 1a (120 mg,
0.24 mmol) and dppm (109 mg, 0.28 mmol) resulted in
a colour change from yellow to orange over 10 min.
After removal of the solvent, chromatography eluting
with ether:light-petroleum (1:9) gave a yellow band
which afforded trans-[Fe2(CO)4(m-HCꢀCH2)(m-PPh2)(m-
dppm)] (2a) (150 mg, 75%).
Heating a toluene solution (25 cm3) of a 1:2 mixture
of 2c and 3c (85 mg) for 90 min resulted in the isolation
of pure 2c (80 mg, ca. 100%) after column
chromatography.
4.3. [Fe2(CO)6(v-EtOCꢀCH2)(v-PPh2)] (1b)
6: IR (CH2Cl2): 2031s, 1978vs, 1950s, 1916m cm−1
;
1H NMR (CDCl3): l 8.22 (ddd, J 27.3, 13.0, 6.4, 1H,
Ha), 7.85–6.95 (m, Ph, 33H), 6.54 (d, J 7.3, 2H, Ph),
3.98 (dd, J 13.0, 5.3, 1H, Hb), 3.43 (m, 2H, CH2); 13C
NMR (CDCl3): 218.8 (t, J 12.0, CO), 213.8 (br, 3CO),
213.2 (t, J 19.3, CO), 153.8 (t, J 26.1, Ca), 141.5–124.5
(m, Ph), 89.8 (d, J 17.1, Cb), 32.1 (dd, J 34.5, 21.7,
CH2) ppm; 31P NMR (CDCl3): 178.6 (d, J 93.4, m-
PPh2), 64.3 (dd, J 93.4, 60.8, Fe–PPh2), −19.0 (d, J
Heating a toluene solution (20 cm3) of 1b (55 mg,
0.103 mmol) and dppm (45 mg, 0.117 mmol) for 3 h
resulted in a colour change from yellow to orange.
After removal of the solvent, chromatography eluting
with ether:light-petroleum (2:3) afforded trans-
[Fe2(CO)4(m-EtOCꢀCH2)(m-PPh2)(m-dppm)] (2b) (80
mg, 90%).

186
G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
60.8, PPh2) ppm; mass spectrum (FAB+): m/z 925
(M+), 896 (M−CO), 868 (M−2CO), 813 (M−4CO),
784 (M−5CO); Anal. Calc. for Fe2C50H39O5P3: C,
64.94; H, 4.22. Found: C, 65.45; H, 4.49%.
Cb), 27.7 (t, J 16.4, CH2) ppm; 31P NMR (CDCl3): 77.7
(dd, J 113.6, 21.4), 75.7 (dd, J 113.6, 98.2), 58.2 (dd, J
98.2, 21.4) ppm; mass spectrum (FAB+): m/z 925 (M),
868 (M−2CO), 812 (M−4CO), 784 (M−5CO); Anal.
Calc. for Fe2C50H39O5P3: C, 64.93; H, 4.22; P, 10.06.
Found: C, 64.58; H, 3.94; P, 10.29%.
3c: IR (CH2Cl2): 1982s, 1949vs, 1917s, 1900 sh (KBr)
1479w, 1433m, 1415w cm−1 1H NMR (CDCl3): l
;
8.00−6.85 (m, Ph), 6.47 (t, J 7.7, 1H, Ph), 6.27 (d, J
7.4, 1H, Ph), 6.22 (d, J 15.9, 1H, CꢀCH), 6.00 (d, J
15.9, 1H, CꢀCH), 3.59 (dt, J 13.2, 10.1, 1H, CH2), 2.79
(dt, J 14.4, 10.4, 1H, CH2); 13C NMR (CDCl3): 297.6
(t, J 18.6, CꢀO), 233.1 (d, J 31.9, CO), 219.7 (t, J 22.5,
CO), 218.1 (t, J 16.4, CO), 216.9 (s, CO), 213.1 (s, CO),
144.1 (s, Ca), 143–122 (m, Ph), 68.1 (s, Cb), 37.3 (dd, J
25.4, 13.5, CH2) ppm; 31P NMR (CDCl3): 218.8 (dd, J
111.0, 54.5, m-PPh2), 59.6 (dd, J 63.6, 54.5, dppm), 49.7
(dd, J 111.0, 63.6, dppm) ppm.
4.6. [Fe2(CO)6(v-PhCꢀCHPh)(v-PPh2)] (1e)
Heating a toluene solution (45 cm3) of 1e (230 mg,
0.36 mmol) and dppm (165 mg, 0.43 mmol) for 5 min
resulted in a considerable darkening of the solution.
After removal of the solvent, chromatography recov-
ered 30 mg of 1e while eluting with ether:light-
petroleum (1:4) gave an orange band which afforded
trans - [Fe2(CO)4{m - O ꢀ C – C(Ph) ꢀ CHPh}(m - PPh2)(m -
dppm)] (3e) (200 mg, 65%). Large red crystals suitable
for X-ray crystallography were grown upon slow diffu-
sion of methanol into a saturated dichloromethane
solution.
4.5. [Fe2(CO)6(v-PhCꢀCH2)(v-PPh2)] (1d)
Heating a toluene solution (60 cm3) of 1d (160 mg,
0.31 mmol) and dppm (150 mg, 0.39 mmol) for 10 min
resulted in a considerable darkening of the solution.
After removal of the solvent, chromatography gave: an
orange band eluting with ether:light-petroleum (1:5)
which afforded trans-[Fe2(CO)4{m-OꢀC–C(Ph)ꢀCH2}-
(m-PPh2)(m-dppm)] (3d) (130 mg, 81%); a yellow band
eluting with ether:light petroleum (1:4) which gave 2c
(10 mg, 6%); a red band eluting with ether:light-
petroleum (1:1) which afforded [Fe2(CO)5{m-Ph2PC-
(Ph)ꢀCH2}(m-dppm)] (4) (20 mg, 12%). This was air-
sensitive in chlorinated solvents and was handled ac-
cordingly. When the experiment was carried out on a
larger scale a small amount of 8 was isolated which
proved difficult to separate from 3d by chromatography
(see later).
3e: IR (CH2Cl2): 1981s, 1950vs, 1911s, 1985sh (KBr)
1481w, 1433m, 1405m cm−1 1H NMR (CDCl3): l
;
8.1–6.8 (m, Ph, 38H, Ph), 6.26 (d, J 7.6, 2H, Ph), 5.72
(br, 1H, Hb), 3.61 (q, J 12.9, 1H, CH2), 2.62 (dt, J 13.6,
10.0, 1H, CH2); 13C NMR (CDCl3): 297.9 (t, J 30.5,
CꢀO), 219.8 (t, J 21.1, CO), 218.3 (t, J 18.3, CO), 218.0
(s, CO), 212.9 (s, CO), 146.3 (s, Ca), 146–126 (m, Ph),
77.2 (d, J 12.0, Cb), 37.6 (dd, J 25.1, 12.2, CH2) ppm;
31P NMR (CDCl3): 217.8 (dd, J 111.0, 56.9, m-PPh2),
58.8 (t, J 59.3, dppm), 48.2 (dd, J 111.0, 61.2, dppm)
ppm; mass spectrum (FAB+): m/z 1002 (M), 972 (M−
CO), 944 (M−2CO), 860 (M−5CO); Anal. Calc. for
Fe2C56H43O5P3: C, 67.20; H, 4.30. Found: C, 66.47; H,
4.09%.
3d: IR (CH2Cl2): 1981s, 1949vs, 1917s, 1902sh (KBr)
1479w, 1433m, 1404m cm−1
;
1H NMR (CDCl3): l
4.7. [Fe2(CO)6{v-C(CMeꢀCH2)ꢀCH2}(v-PPh2)] (1f)
8.2–6.85 (m, 33H, Ph), 5.88 (d, J 7.1, 2H, Ph), 5.42 (s,
1H, CꢀCH2), 5.30 (s, 1H, CꢀCH2), 3.55 (m, 1H, CH2),
2.50 (ddd, J 10.3, 8.3, 1.9, 1H, CH2); 13C NMR
(CDCl3): 300.1 (t, J 20.5, CꢀO), 219.7 (t, J 22.0, CO),
218.2 (t, J 17.1, CO), 217.8 (s, CO), 212.7 (s, CO), 155.4
(s, Ca), 142–124 (m, Ph), 78.6 (s, Cb), 37.8 (dd, J 23.8,
13.1, CH2) ppm; 31P NMR (CDCl3): 218.7 (dd, J 109.1,
56.4, m-PPh2), 58.9 (t, J 60, dppm), 48.1 (dd, J 109.1,
62.6, dppm) ppm; mass spectrum (FAB+): m/z 896
(M−CO), 868 (M−2CO), 841 (M−3CO), 812 (M−
4CO), 784 (M−5CO); Anal. Calc. for Fe2C50H39O5P3:
C, 64.94; H, 4.22. Found: C, 64.77; H, 3.97%.
Thermolysis of a toluene solution (20 cm3) of 1f (55
mg, 0.103 mmol) and dppm (45 mg, 0.113 mmol) for 24
h resulted in the formation of a bright orange solution.
After removal of the solvent, chromatography afforded:
an orange band eluting with dichloromethane:
light-petroleum (1:3) which gave 15 mg of an uniden-
tified product. IR (CH2Cl2): 1993s, 1957vs, 1924vs,
1901sh cm−1
;
31P NMR (CDCl3): 158.6 (d, br, J 59),
59) ppm; eluting with
54.0 (br), −27.7 (d,
J
dichloromethane:light-petroleum (1:2) gave an orange
band which afforded [Fe2(CO)4{m-HC–C(Me)ꢀC
(Me)PPh2}(m-dppm)] (5) (45 mg, 51%). Orange crystals
suitable for X-ray crystallography were grown upon
4: IR (CH2Cl2): 2012m, 1981vs, 1954s, 1925s, 1521w
1
cm−1; H NMR (CDCl3): l 7.9–7.0 (m, 36H, Ph+
CꢀCH2), 5.16 (d, J 27.0, 1H, CꢀCH2), 5.16 (q, J 12.1,
1H, CH2), 3.10 (q, J 12.4, 1H, CH2); 13C NMR
(CDCl3): 237.0 (br, CO), 217.3 (s, CO), 212.7 (d, J 25.6,
CO), 212.3 (t, J 13.7, CO), 209.0 (t, J 14.9, CO),
142–125 (m, Ph), 66.9 (d, J 25.9, Ca), 53.9 (d, J 6.4,
slow diffusion of methanol into
dichloromethane solution.
a
saturated
5: IR (CH2Cl2): 1975s, 1929vs, 1908s, 1882m cm−1
;
1H NMR (CDCl3): l 8.2–6.9 (m, 21H, Ph+m-CH),
3.67 (q, J 13.8, 1H, CH2), 2.42 (dt, J 14.3, 10.3, 1H,

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
187
CH2), 1.71 (s, 3H, CH3), 1.57 (s, 3H, CH3) ppm; 13C
Table 3
Crystallographic data
NMR (CDCl3): 227.8 (t, J 8.0, CO), 217.2 (t, J 18.9,
CO), 216.4 (t, 12.9, CO), 216.3 (d, J 13.6, CO), 150.8 (t,
J 17.7, m-C), 140–127 (m, Ph), 112.8 (dd, J 36.6, 6.7,
CMe), 46.8 (dd, J 33.6, 9.2, CMe), 43.1 (t, J 12.2, CH2),
22.2 (d, J 4.3, Me), 16.3 (s, Me) ppm; 31P NMR
(CDCl3): 81.2 (d, J 94.7, dppm), 78.7 (d, J 163.8, Ph2),
72.2 (dd, J 163.8, 94.7, dppm) ppm; mass spectrum
(FAB+): m/z 860 (M), 804 (M−2CO), 748 (M−
4CO); Anal. Calc. for Fe2C46H39O4P3 · 0.5CH2Cl2: C,
61.82; H, 4.43. Found: C, 61.93; H, 4.30%.
3e
5 · 0.45CHCl3
Empirical formula
Colour
Space group
Fe2C55H43O5P3 Fe2C46.45H39.45O4P3Cl1.35
red
P21/n
orange
P1
Unit cell dimensions
,
a (A)
12.839(3)
19.583(4)
19.980(4)
90
90.08(3)
90
5024
4
1.286
7.17
8809
10.2324(10)
11.96720(11)
19.54540(20)
102.768(5)
95.870(5)
110.711(5)
2140
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
4.8. Thermolysis of cis-[Fe2(CO)4(v-PhCꢀCH2)-
(v-PPh2)(v-dppm)] (7)
3
,
V (A )
Z
2
Dcalc (g cm−3
)
1.392
8.90
8708
6934
v(Mo Ka) (cm−1
)
A toluene solution (35 cm3) of 7 (410 mg, 0.46 mmol)
was heated at reflux for 30 min resulting in a consider-
able darkening of the solution. After removal of the
solvent, chromatography afforded: an orange band
eluting with ether:light-petroleum (1:5) which gave
[Fe2(CO)3{m-OꢀC–C(Ph)ꢀCH2}(m-PPh2)(m-dppm)] (8)
(60 mg, 14%); a yellow band eluting with ether:light-
petroleum (1:4) gave 2c (90 mg, 22%); an orange band
eluting with ether:light-petroleum (3:2) gave 4 (30 mg,
7%).
No. data measured
No. unique data used 8807
for sln
No. parameters
R (all data)
595
653
0.053(0.079)
0.128(0.152)
0.802
0.033(0.047)
0.032(0.033)
0.430
Rw (all data)
Largest peak (e A
Largest hole (e A
−3
,
)
)
−3
,
−0.494
−0.400
;
8: IR (CH2Cl2): 1968s, 1917s cm−1 1H NMR
and intensity data were taken using an automated
four-circle diffractometer (Nicolet R3mV) equipped
with Mo Ka radiation (u=0.71073A) at 1991°C. The
(CDCl3): l 8.1–6.4 (m, Ph, 35H), 3.59 (q, J 11.5, 1H,
CH2), 3.43 (d, J 7.9, 1H, CꢀCH2), 2.67 (dt, J 12.3, 9.4,
1H, CH2), 2.05 (t, J 9.3, 1H, CH2); 13C NMR (CDCl3):
303.1 (t, J 19.6, CꢀO), 220.1 (dd, J 23.6, 13.2, CO),
218.3 (t, J 22.0, CO), 214.1 (s, CO), 161.3 (s, Ca), 114.3
(s, Cb), 37.7 (dd, J 24.7, 9.7, CH2) ppm; 31P NMR
(CDCl3): 218.9 (dd, J 98.6, 42.4, m-PPh2), 61.1 (dd, J
62.1, 42.4, dppm), 43.1 (dd, J 98.6, 62.1, dppm) ppm;
mass spectrum (FAB+): m/z 896 (M), 868 (M−CO),
840 (M−2CO), 812 (M−3CO), 784 (M−4CO); Anal.
Calc. for Fe2C49H39O4P3 · 0.25CH2Cl2: C, 64.43; H,
4.31. Found: C, 64.37; H, 4.70%.
,
lattice vectors were identified by application of the
automatic indexing routine of the diffractometer to the
positions of a number of reflections taken from a
rotation photograph and centred by the diffractometer.
The v–2q technique was used to measure reflections in
the range 5°52q550°. Three standard reflections (re-
measured every 97 scans) showed no significant loss in
intensity during data collection. The data were cor-
rected for Lorentz and polarisation effects and empiri-
cally for absorption. The unique data with I]2.0|(I)
were used to solve and refine the structure. The struc-
ture was solved by direct methods and developed using
alternating cycles of least-squares refinement and differ-
ence-Fourier synthesis. All non-hydrogen atoms were
refined anisotropically. All hydrogens except H(7) were
placed in idealised positions (C–H, 0.96 A) which was
found in a difference map. All were assigned a common
isotropic thermal parameter (U=0.08 A ). Structure
solution was made using the SHELXTL PLUS programme
package [24] on a PC. Crystallographic data for 3e and
5 are presented in Table 3. Positional parameters are
listed in Table 4.
4.9. Thermolysis of [Fe2(CO)5{v-Ph2PC(Ph)ꢀCH2}-
(v-dppm)] (4)
A toluene solution (30 cm3) of 4 (20 mg, 0.022 mmol)
was refluxed for 1 h. After removal of the solvent,
chromatography afforded: a yellow band eluting with
ether:light-petroleum (1:9) which gave [Fe2(CO)6(m-
PPh2CH2)(m-PPh2)] (3 mg, 22%); an orange band elut-
ing with ether:light-petroleum (1:4) which gave 8 (5 mg,
26%); a yellow band eluting with ether:light-petroleum
(1:3) which gave 2c (10 mg, 52%).
,
2
,
For 5 · 0.45CHCl3; all geometric and intensity data
were taken using a Siemens SMART CCD diffractome-
4.10. Crystallographic structure determinations
,
ter equipped with Mo Ka radiation (u=0.71073 A) at
1991°C. The lattice vectors were identified by centring
6502 reflections with I\5|(I). The v technique was
Crystals of 3e and 5 were grown from slow diffusion
of methanol into dichloromethane solutions. Crystals
were mounted on a glass fibre. For 3e; all geometric

188
G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
Table 4
Table 5
2
3
Positional parameters (×104) and Ueq (A ×10 ) for 3e
Positional parameters and Biso for 5
,
x
y
z
Ueq
35(1)
x
y
z
Biso
Fe(1)
Fe(2)
P(1)
P(2)
P(3)
O(1)
O(2)
O(3)
O(4)
O(5)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
515(1)
2199(1)
1102(1)
2961(1)
761(1)
2769(1)
2304(1)
2683(1)
2019(1)
2721(1)
3529(2)
1473(2)
2233(2)
883(2)
6127(1)
6759(1)
5052(1)
5776(1)
7228(1)
5848(2)
6156(2)
7868(2)
7115(2)
6188(1)
5962(2)
6142(2)
7413(2)
6960(2)
6465(2)
6479(2)
6754(2)
5061(2)
4519(2)
4078(2)
3672(3)
3693(3)
4123(3)
4534(2)
4509(2)
3843(2)
3457(2)
3719(3)
4377(3)
4771(2)
5409(2)
5011(3)
4709(3)
4785(3)
5174(3)
5488(2)
5760(2)
6266(2)
6269(3)
5771(4)
5273(4)
5261(3)
7786(2)
8315(2)
8751(2)
8670(3)
8154(3)
7708(3)
7697(2)
7964(3)
8312(4)
8381(4)
8062(4)
7726(3)
6120(2)
6349(3)
5974(4)
5388(4)
5156(3)
5517(3)
6878(2)
7099(3)
7282(3)
7202(3)
6974(4)
6825(3)
Fe1
Fe2
P1
P2
P3
O1
O2
O3
O4
C1
C2
C3
C5
C4
C6
C7
C8
0.12639(3) 0.84113(3)
0.28769(3) 1.07668(3)
0.03851(5) 0.88187(5)
0.20468(5) 1.15995(5)
0.24228(6) 0.85246(5)
0.27689(16) 0.70627(15)
0.225853(16) 2.021(13)
0.287904(16) 2.303(13)
36(1)
37(1)
38(1)
39(1)
87(1)
64(1)
91(1)
77(1)
39(1)
48(1)
43(1)
53(1)
49(1)
39(1)
41(1)
48(1)
42(1)
45(1)
62(1)
79(2)
83(2)
77(2)
58(1)
41(1)
53(1)
67(1)
65(1)
68(1)
58(1)
44(1)
68(1)
89(2)
83(2)
66(1)
52(1)
46(1)
58(1)
77(2)
88(2)
87(2)
67(1)
45(1)
56(1)
69(1)
74(2)
72(2)
63(1)
45(1)
81(2)
109(2)
99(2)
120(3)
99(2)
48(1)
69(1)
99(2)
107(3)
96(2)
68(1)
54(1)
61(1)
77(2)
100(2)
114(3)
94(2)
0.12901(3)
0.21457(3)
0.33085(3)
0.14560(9)
0.20598(11)
0.37210(11)
0.19534(10)
0.17741(11)
0.21518(12)
0.33849(13)
0.12710(11)
0.23188(13)
0.28632(11)
0.35814(11)
0.37910(11)
0.40864(13)
0.45381(13)
0.04484(11)
0.01411(14)
2.130(24)
2.360(25)
2.57(3)
−1420(3)
−625(3)
3708(3)
1586(3)
1568(2)
−634(3)
−160(3)
3152(4)
1814(3)
2390(3)
3296(3)
4216(3)
2549(3)
544(3)
4.22(9)
−0.11725(18) 0.61123(16)
0.52175(21) 1.30300(18)
0.46791(17) 1.00631(16)
0.22118(20) 0.76268(19)
−0.02310(22) 0.70461(20)
0.42442(24) 1.21477(22)
0.11569(21) 1.04542(19)
0.39052(22) 1.02520(20)
0.07916(20) 0.97239(18)
0.14990(22) 1.03306(19)
0.27269(22) 1.00708(19)
5.66(11)
7.13(12)
4.90(10)
2.67(10)
3.20(12)
3.94(12)
2.67(10)
3.23(12)
2.40(10)
2.80(10)
2.95(11)
4.19(13)
4.52(14)
2.70(10)
4.53(14)
6.23(19)
5.62(17)
4.95(14)
3.78(12)
2.39(9)
2.92(11)
3.97(13)
4.38(14)
4.36(14)
3.55(12)
2.77(10)
3.91(12)
4.93(15)
5.44(17)
5.26(17)
3.86(13)
2.87(10)
4.01(13)
4.86(16)
5.06(15)
4.91(15)
3.97(13)
3.73(13)
5.46(17)
8.5(3)
3523(1)
3264(2)
1987(2)
2285(2)
1434(2)
3268(2)
3763(2)
3579(2)
2573(2)
2006(2)
1600(3)
1121(3)
1061(3)
1467(3)
1939(3)
3448(2)
3391(2)
3980(3)
4622(3)
4685(2)
4102(2)
1153(2)
840(3)
C(8)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(40)
C(41)
C(42)
C(43)
C(44)
C(45)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(60)
C(61)
C(62)
C(63)
C(64)
C(65)
C(70)
C(71)
C(72)
C(73)
C(74)
C(75)
C(80)
C(81)
C(82)
C(83)
C(84)
C(85)
C9
0.1027(3)
0.3628(3)
1.11952(23)
1.06663(24)
0.06601(21) 0.79761(20)
1115(4)
601(5)
C10
C11
C12
C13
C14
C15
C16
C21
C22
C23
C24
C25
C26
C31
C32
C33
C34
C35
C36
C41
C42
C43
C44
C45
C96
C51
C52
C53
C54
C55
C56
C61
C62
C63
C64
C65
C66
H42
H43
H44
H45
H46
−463(6)
−1045(5)
−542(4)
908(3)
0.1819(3)
0.2025(3)
0.1086(3)
0.84592(24)
0.7747(3)
0.6554(3)
−0.04722(17)
−0.07802(15)
−0.0038(3)
0.60485(24) −0.04754(14)
573(3)
417(4)
599(4)
929(4)
−0.02561(25) 0.67515(22)
−0.15324(19) 0.84665(18)
−0.24001(21) 0.82153(20)
−0.38333(23) 0.80112(24)
−0.44042(23) 0.8045(3)
−0.35630(24) 0.8278(3)
−0.21275(22) 0.85001(23)
0.07735(21) 1.22806(19)
0.12813(25) 1.34219(22)
0.0369(3)
−0.1091(3)
−0.1608(3)
−0.06912(23) 1.16803(22)
0.33098(21) 1.28410(19)
0.28611(24) 1.35696(23)
0.01323(13)
0.10729(11)
0.15669(12)
0.13986(14)
0.07417(14)
0.02424(14)
0.04117(12)
0.24187(12)
0.29343(14)
0.31940(15)
0.29479(17)
0.24526(17)
0.21761(14)
0.18533(12)
0.15028(14)
0.12540(16)
0.13516(16)
0.16944(16)
0.19451(15)
0.33284(12)
0.34900(15)
0.34689(18)
1082(4)
2764(3)
3541(4)
3346(5)
2402(5)
1626(4)
1812(4)
4404(3)
4958(3)
6049(4)
6597(4)
6072(4)
4975(4)
−81(3)
339(4)
206(3)
−115(3)
185(2)
814(2)
1.39499(24)
1.3332(3)
1.2205(3)
2077(2)
1735(2)
1717(3)
2049(3)
2403(3)
2411(3)
2209(2)
1823(2)
1458(3)
1486(3)
1854(3)
2216(3)
3539(2)
3817(3)
4447(4)
4793(3)
4567(4)
3942(3)
4435(2)
4940(2)
5548(3)
5649(4)
5148(4)
4547(3)
4031(3)
4708(2)
5111(3)
4851(4)
4203(5)
3774(4)
0.3811(3)
0.5229(3)
1.44583(24)
1.46347(24)
0.56898(25) 1.39235(24)
0.47463(23) 1.30294(22)
0.41012(23) 0.83038(24)
−309(5)
−1383(5)
−1813(4)
−1163(4)
774(3)
0.5415(3)
0.6648(3)
0.6578(4)
0.5282(4)
0.4039(3)
0.9284(3)
0.9025(4)
0.7845(5)
0.6874(4)
0.7091(3)
1667(5)
1629(6)
752(6)
0.32922(20) 10.2(4)
0.31200(19) 8.5(3)
0.31367(16) 5.50(19)
0.38952(12) 3.02(11)
0.38500(14) 4.30(14)
0.43479(16) 5.50(17)
0.48973(16) 5.59(18)
0.49552(15) 5.32(17)
0.44552(14) 4.26(14)
−112(7)
−105(5)
3143(3)
2461(4)
2338(5)
2876(6)
3544(5)
3683(4)
5139(3)
5030(4)
5893(5)
6856(5)
7017(4)
6146(4)
0.15573(23) 0.76019(20)
0.0102(3)
−0.0563(3)
0.0214(3)
0.7242(3)
0.6703(3)
0.6536(3)
0.6888(3)
0.74168(23)
0.1657(3)
0.2329(3)
0.1858(22) 1.3434(20)
0.3414(24) 1.4906(22)
0.5882(23) 1.5245(21)
0.6674(24) 1.4048(22)
0.5099(21) 1.2577(20)
0.1432(12)
0.1007(13)
0.1164(13)
0.1796(13)
0.2183(12)
4.8(6)
6.0(6)
5.4(6)
5.6(6)
4.5(5)
(Continued)

G. Hogarth et al. / Inorganica Chimica Acta 291 (1999) 178–189
189
Table 5 (continued)
References
x
y
z
Biso
4.6(5)
[1] P.M. Maitlis, H.C. Long, R. Quyoum, M.L. Turner, Z-Q. Wang,
J. Chem. Soc., Chem. Commun. (1996) 1.
[2] (a) J.M. Martinez, H. Adams, N.A. Bailey, P.M. Maitlis, J. Chem.
Soc., Chem. Commun. (1989) 286. (b) J. Martinez, J.B. Gill, H.
Adams, N.A. Bailey, I.M. Saez, G.J. Sunley, P.M. Maitlis, J.
Organomet. Chem. 394 (1990) 583.
[3] (a) R. Yanez, J. Ros, X. Solans, M. Font-Altaba, R. Mathieu,
Organometallics 9 (1990) 543. (b) R. Yanez, J. Ros, F. Dahan,
R. Mathieu, Organometallics 9 (1990) 2484. (c) J. Ros, X. Solans,
M. Font-Altaba, R. Mathieu, Organometallics 3 (1984) 1014.
[4] (a) S.A.R. Knox, J. Cluster Sci. 3 (1992) 385. (b) G.C. Bruce,
B. Gagnus, S.E. Garner, S.A.R. Knox, A.G. Orpen, A.J. Phillips,
J. Chem. Soc., Chem. Commun. (1990) 1360.
H32
H33
H34
H35
H36
H22
H23
H24
H25
H26
H52
H53
H54
H55
H56
H62
H63
H64
H65
H66
H12
H13
H14
H15
H16
H5A
H5B
H9A
H9B
H9C
H10A
H10B
H10C
H6
0.2274(22) 1.3840(20)
0.0731(23) 1.4714(21)
−0.1736(25) 1.3678(23)
0.3117(12)
0.3548(13)
0.3134(14)
0.2275(14)
0.1827(12)
0.2028(11)
0.17 54(12)
0.0636(13)
5.5(6)
6.4(7)
6.9(7)
4.6(5)
3.3(5)
4.8(6)
5.4(6)
5.5(6)
4.4(5)
5.7(6)
9.1(9)
−0.259(3)
1.1776(23)
−0.1057(22) 1.0915(20)
−0.1995(20) 0.8186(18)
−0.4398(22) 0.7848(20)
−0.5370(23) 0.7920(21)
−0.3936(23) 0.8264(21)
−0.1557(21) 0.8669(20)
0.5478(24) 1.0094(21)
−0.0214(13)
0.0062(12)
0.3626(13)
0.3594(17)
0.751(3)
0.735(4)
0.516(3)
0.312(3)
0.975(3)
0.764(3)
0.605(3)
0.642(3)
[5] J.R. Shapley, S.I. Ricter, M. Tachikawa, J.B. Keister, J.
Organomet. Chem. 94 (1975) C43.
0.3262(20) 12.2(11)
0.3005(18) 10.5(10)
[6] See for example: (a) L.J. Farrugia, Y. Chi, W.-C. Tu,
Organometallics 12 (1993) 1616. (b) C.P. Casey, S.R. Marder,
B.R. Adams, J. Am. Chem. Soc. 107 (1985) 7700. (c) A.F. Dyke,
S.A.R. Knox, M.J. Morris, P.J. Naish, J. Chem. Soc., Dalton
Trans. (1983) 1417.
[7] G. Hogarth, M.H. Lavender, J. Chem. Soc., Dalton Trans. (1992)
2759.
[8] G. Hogarth, M.H. Lavender, K. Shukri, Organometallics 14
(1995) 2325.
[9] G. Hogarth, M.H. Lavender, K. Shukri, J. Organomet. Chem.
527 (1997) 247.
[10] G. Hogarth, M.H. Lavender, J. Chem. Soc., Dalton Trans. (1994)
3389.
[11] G. Hogarth, M.H. Lavender, J. Chem. Soc., Dalton Trans. (1993)
143.
[12] S.A. McLaughlin, S. Doherty, N.J. Taylor, A.J. Carty,
Organometallics 11 (1992) 4315.
0.3007(15)
0.3472(13)
0.4271(15)
0.5256(14)
0.5329(14)
0.4488(13)
0.0363(13)
−0.0649(15)
−0.1191(14)
−0.0682(13)
0.0323(12)
0.1003(11)
0.1007(11)
0.4391(13)
0.3847(13)
0.4424(13)
0.4704(13)
0.4873(13)
0.4577(13)
0.2693(10)
8.0(8)
5.1(6)
7.2(7)
6.8(7)
6.8(7)
5.3(6)
5.4(6)
8.3(8)
6.6(7)
5.8(6)
4.9(6)
3.6(5)
3.5(5)
6.2(6)
5.4(6)
5.9(6)
5.9(6)
6.3(6)
6.1(6)
2.9(4)
−0.0432(23) 0.7335(21)
−0.159(3)
−0.026(3)
0.224(3)
0.6445(24)
0.6154(24)
0.6779(23)
0.3320(23) 0.7660(21)
0.2490(23) 0.9290(21)
0.284(3)
0.812(3)
0.1213(25) 0.6093(23)
−0.0741(23) 0.5209(21)
−0.1020(22) 0.6387(20)
0.0470(20) 1.0650(18)
0.1875(20) 1.0515(18)
0.1781(24) 1.1880(22)
0.0357(23) 1.1474(21)
0.0578(24) 1.0800(22)
0.3863(24) 1.1563(22)
0.3171(24) 1.0297(22)
0.4504(24) 1.0571(22)
−0.0028(19) 0.9950(17)
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used to measure reflections in the range 3°52q5
52.5°. No significant loss in intensity occurred during
data collection. The data were corrected for Lorentz
and polarisation effects and empirically for absorp-
tion. The unique data with I]2.5|(I) were used to
solve and refine the structure. The structure was
solved by direct methods and developed using alter-
nating cycles of least-squares refinement and differ-
ence-Fourier synthesis. All non-hydrogen atoms were
refined anisotropically except the chlorine which was
refined isotropically as were the hydrogens. Structure
solution was carried out on the NRCVAX system
[25]. Positional parameters are listed in Table 5.
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257.
[23] G. Hogarth, S. Doherty, unpublished results.
[24] G.M. Sheldrick, SHELXTL PLUS, program package for structure
solution and refinement, version 4.2, Siemens Analytical Instru-
ments Inc., Madison, WI, 1990.
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Acknowledgements
The authors thank Professor M.R. Truter for help
with the crystal structure determination of 3e and
G.H. thanks the NRC for sabbatical funding.