Reactivity of [Fe2(CO)6(μ-CO)(μ-dppm)] towards unsaturated sulfur-containing compounds, SO2, CS2 and ArNCS: Facile carbon-sulfur bond cleavage at the diiron centre

Article abstract of DOI:10.1016/S0022-328X(99)00599-9

Photolysis of [Fe₂(CO)₆(μ-CO)(μ-dppm)] (1) with SO₂, CS₂ and ArNCS leads to the formation of [Fe₂(CO)₆(μ-SO₂)(μ-dppm)] (2), [Fe₄(CO)₁₀(μ₃-S)(μ-CS)(μ-dppm) ₂] (3), [Fe₂(CO)₃(CNAr){μ-SC(NAr)C(O)S}(μ-dppm)] (4-5) and [Fe₂(CO)₄{μ-SC(N-p-tolyl)C(O)S}(μ-dppm)] (6), respectively. Complex 2 is a simple CO substitution product, while in 3 carbon-sulfur cleavage and coupling of diiron units has occurred. Dithiolate-bridged 4-6 also result from carbon-sulfur bond cleavage of one isothiocyanate and coupling of the sulfur with CO and a second isothiocyanate. Two isomers of complexes 3-6 are found and in thiolate-bridged 4-6 these interconvert as a result of inversion at the imine nitrogen, which has been monitored by VT NMR.

Full text of DOI:10.1016/S0022-328X(99)00599-9

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 595 (2000) 134–139
Reactivity of [Fe2(CO)6(m-CO)(m-dppm)] towards unsaturated
sulfur-containing compounds, SO2, CS2 and ArNCS: facile
carbon–sulfur bond cleavage at the diiron centre
Graeme Hogarth *, Mark H. Lavender, Khalid Shukri
Department of Chemistry, Uni6ersity College London, 20 Gordon Street, London, WC1H 0AJ, UK
Received 9 September 1999; received in revised form 24 September 1999
Abstract
Photolysis of [Fe2(CO)6(m-CO)(m-dppm)] (1) with SO2, CS2 and ArNCS leads to the formation of [Fe2(CO)6(m-SO2)(m-dppm)] (2),
[Fe4(CO)10(m3-S)(m-CS)(m-dppm)2] (3), [Fe2(CO)3(CNAr){m-SC(NAr)C(O)S}(m-dppm)] (4–5) and [Fe2(CO)4{m-SC(N-p-
tolyl)C(O)S}(m-dppm)] (6), respectively. Complex 2 is a simple CO substitution product, while in 3 carbon–sulfur cleavage and
coupling of diiron units has occurred. Dithiolate-bridged 4–6 also result from carbon–sulfur bond cleavage of one isothiocyanate
and coupling of the sulfur with CO and a second isothiocyanate. Two isomers of complexes 3–6 are found and in thiolate-bridged
4–6 these interconvert as a result of inversion at the imine nitrogen, which has been monitored by VT NMR. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Iron; Sulfur dioxide; Carbon disulfide; Photolysis; Dimeric carbonyl
1. Introduction
2. Results and discussion
While diiron nonacarbonyl displays a very rich and
varied chemistry, it is characterised by the ease of
cleavage of the diiron bond [1]. In order to study the
chemistry of the diiron centre, then, we have utilised the
diphosphine, bis(diphenylphosphino)methane (dppm),
as a bridging ligand that holds the two iron atoms in
close proximity, thus retaining the integrity of the di-
iron unit. Reactions of [Fe2(CO)6(m-CO)(m-dppm)] (1)
[2] with alkynes [3], allene [4], diazoalkanes [5], alkynyl
phosphines [6], phospha-alkynes [7], acids [8], sec-
ondary phosphines [9] and diphosphines [10] have been
carried out and in all cases the diiron core is retained.
Given the high reactivity of Fe2(CO)9 towards sulfur-
containing compounds we decided to investigate the
reactivity of 1 towards small unsaturated sulfur-con-
taining ligands and herein we describe the photochemi-
cal reactions of 1 with SO2, CS2 and ArNCS (Ar=Ph,
p-tolyl) (Scheme 1).
In keeping with previous studies [2–7,9,10], in the
absence of UV irradiation [Fe2(CO)6(m-CO)(m-dppm)]
(1) was unreactive towards a wide-range of organosul-
fur compounds; however, upon photolysis slow reac-
tions took place. Photolysis of an SO2-saturated THF
solution of 1 for 16 h afforded the bridging SO2 com-
plex [Fe2(CO)6(m-SO2)(m-dppm)] (2) in 90% yield. While
SO2 is known to bind to transition metals in a number
of different ways, at the binuclear centre it invariably
acts as a two-electron carbene-type bridging ligand [11].
This binding mode is formulated for 2 and is found in
the parent carbonyl complex [Fe2(CO)8(m-SO2)] [12],
while the analogous carbene complexes [Fe2(CO)6(m-
CR2)(m-dppm)] are also known [5,13]. Carbonyl bands
of 2 in the IR spectrum are shifted by approximately 20
cm−1 to higher energies as compared to 1, a result of
the more electronegative nature of SO2 versus CO, and
suggesting that the diiron centre is less electron-rich in
2 versus 1. Further bands at 1160 and 1027 cm−1 are
assigned to wa(SO2) and ws(SO2), respectively. In the
1H-NMR spectrum, the methylene protons are inequiv-
alent, indicating that m-SO2 lies at right angles to the
diphosphine, a geometric disposition also adopted by
* Corresponding author. Fax: +44-171-3807463.
E-mail address: g.hogarth@ucl.ac.uk (G. Hogarth)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00599-9

G. Hogarth et al. / Journal of Organometallic Chemistry 595 (2000) 134–139
135
Scheme 1. (i) SO2, hw, 16 h, (ii) CS2, hw, 40 h, (iii) ArNCS, hw, 16 h.
m-CO and the diphosphine in 1, and rendering the two
oxygen atoms inequivalent. In the 13C-NMR spectrum,
two signals for the ipso carbons confirm the relative
disposition of SO2 and diphosphine ligands, while in
the low-field region of the spectrum, a single broad
resonance centred at 208 ppm shows that the carbonyls
undergo trigonal rotation on the NMR timescale. This
process is probably the origin of the broadening of the
1H-NMR spectrum, however, while the methylene pro-
tons broaden upon warming to 50°C, the chemical shift
difference between them remains essentially unchanged,
showing that the fluxional process does not involve
movement of the bridging SO2 group. This is in con-
trast to the fluxional behaviour of 1, in which the five
carbonyls (four terminal and one bridging) in the plane
perpendicular to the diphosphine, undergo rapid scram-
bling which cannot be frozen out even at low tempera-
ture, and confirms the strong preference of SO2 to
adopt a bridging position.
of the oxygens of the SO2 group. This is supported by
1H-NMR studies, upon protonation by CF3CO2H in
CDCl3 no hydride signal was observed. Unfortunately
we have not been able to unambiguously confirm this
hypothesis as upon removal of excess acid 2 is regener-
ated. NMR studies show that inequivalent methylene
sites are retained although signals are broadened at
room temperature as a result of the trigonal rotation of
carbonyls. At this temperature no signal could be ob-
served for the added proton; however, warming to 50°C
resulted in a significant sharpening of both phenyl and
methylene signals together with the growth of a new
broad signal at l 8.79, which integrated to about 0.3H.
We tentatively attribute these observations to the
formation of [Fe2(CO)6(m-SO2H)(m-dppm)][CF3CO2].
Mononuclear SO2H complexes have previously been
prepared by Kubas et al. via insertion of SO2 into
a
metal–hydrogen bond and one, namely [Cp-
Mo(CO)3(h1-S(O)OH)] (Cp=h5-C5H5), has been crys-
tallographically characterised [14]. These complexes are,
however, quite unstable and readily lose SO2, while the
unique proton resonance (when observed) appears as a
broad signal between l 4.9–3.9. Since the SO2 oxygens
in 2 are inequivalent two sites of protonation are
available and we favour addition to the more sterically
accessible (as shown).
We have previously shown that 1 is readily protonated
by HBF4·Et2O to give [Fe2(CO)6(m-H)(m-CO)(m-dppm)]-
[BF4] [8]. Addition of HBF4·Et2O to a dichloro-
methane solution of 2 results in a colour change from
orange to pale yellow and a shift in the IR spectrum of
the carbonyl bands to higher wavenumbers by about 20
cm−1. This contrasts with the average shift of approxi-
mately 70 cm−1 in the terminal carbonyl bands of 1
upon protonation [8] and suggests that H+ addition
may occur not at the binuclear centre but rather at one
Unlike the clean reaction of 1 with SO2, irradiation
with CS2 afforded a mixture of products which were
separated by chromatography. The major component
eluted as a blue–black band and is tentatively formu-
lated as [Fe4(CO)10(m3-S)(m-CS)(m-dppm)2] 3a (17%). A
minor orange band followed closely afterwards afford-
ing 3b (6%) and on the basis of the very similar
spectroscopic data for 3a–b we propose that they are
isomers. Elemental analysis and mass spectrometry

136
G. Hogarth et al. / Journal of Organometallic Chemistry 595 (2000) 134–139
readily established the molecular formula. In each, all
four phosphorus atoms are inequivalent and consist of
two coupled pairs, the absence of coupling between
pairs suggesting that no iron carries more than one
phosphorus atom. The major spectroscopic difference
between 3a–b is found in their 31P-NMR spectra. While
3a is characterised by phosphorus–phosphorus cou-
pling constants of 66.9 and 77.6 Hz, values of 74.5 and
92.3 Hz are seen in 3b. Further, although chemical
shifts of three of the resonances in both spectra match
up well, the signal at 63.8 (J 77.6 Hz) ppm in 3a is
replaced by one at 74.2 (J 92.3 Hz) ppm in 3b. We thus
assume the isomers differ in the relative positions of
dppm ligands, but cannot rule out other possibilities. In
the carbonyl region of the IR spectrum the highest
frequency band at 2043–2044 cm−1, is characteristic of
an ‘Fe2(CO)5’ unit, while an absorption at 1093–1095
cm−1 is attributed to a thiocarbonyl [15] and provides
strong evidence for carbon–sulfur bond scission. Un-
fortunately due to their poor solubility, we have been
unable to confirm the presence of a thiocarbonyl ligand
by 13C-NMR.
Thiocarbonyls can bind to polynuclear metal centres
in a variety of different ways, contributing between two
and six electrons [15]. The increasing donor capacity
leads to a decrease in the frequency of the CꢀS vibra-
tion. The 1093–1095 cm−1 band is in the region ex-
pected for a doubly bridging CS ligand, although we
cannot completely rule out the possibility that it binds
in a m3-CS fashion. We can, however, rule out binding
modes in which sulfur is also metal bound as these are
generally seen at wavenumbers of \1000 cm−1 [15].
Based on the assumption that the thiocarbonyl acts as
a two-electron and the sulfido a four-electron donor,
then the original CS2 contributes a total of six electrons
to the cluster. As ‘Fe4(CO)10(dppm)2’ is a 60-electron
fragment, we conclude that 3 is a 66-electron cluster
and if electron-precise is characterised by three metal–
metal interactions.
Based on the above, the structure shown is suggested,
although it should be emphasised that this is quite
speculative and repeated attempts to grow X-ray qual-
ity crystals of either 3a or 3b have been unsuccessful.
Thus, we have little precise information concerning the
position of either the thiocarbonyl or the sulfido moi-
eties, or the relative disposition of the diphosphines.
The hapticity of sulfur is also unknown and we favour
m3-coordination as it is common in cluster chemistry
and seen in related clusters formed from the reaction of
Fe3(CO)12 with CS2 [16,17]. Thus, Fe3(CO)12 reacts with
CS2 at 80°C and under 10 atm CO/Ar to afford both
tetranuclear [Fe4(CO)12(m3-S)(m4-CS)] [16] and pentanu-
clear [Fe5(CO)13(m3-S)2(m4-CS)] [17] clusters containing
m4-CS and m3-S ligands. While the m4-CS ligands are
bound somewhat differently in each of these clusters,
an IR band is seen below 1000 cm−1 in both [Fe4-h3-C-
h1-S 963 cm−1 [16]; Fe5-h2-C-h2-S 921 cm−1 [17]],
whereas in 3 there are no absorptions in this region of
the spectrum. On this basis we have ruled out the
possibility that 3 is a derivative of [Fe4(CO)12(m3-S)(m4-
CS)] although the proposed structure has many similar
characteristics. Reaction of other metal carbonyls with
CS2 has also lead to carbon–sulfur bond scission and
the generation of thiocarbonyl and sulfido ligands [18].
Conditions used are often quite harsh; however these
may be required to remove tightly bound carbonyl
ligands rather than reflecting the strength of the car-
bon–sulfur bond.
The mode of formation of 3a–b is unclear. Reaction of
Fe2(CO)9 with CS2 is known to produce the side-bound
CS2 complex [Fe(CO)4(h2-SꢀCꢁS)] [19], a phosphine
derivative of which has been crystallographically char-
acterised [20]. The latter react readily with 16-electron
metal fragments to produce binuclear complexes in
which the CS2 bridges metal centres via an h2-CS, h1-S
coordination mode and donates a total of four elec-
trons to each metal centre [21]. Under photolysis,
[Fe2(CO)6(m-CO)(m-dppm)] (1) readily loses between 1
and 3 mol of CO [2–9] and it is possible that CS2
bridges between binuclear centres in a related fashion.
Further loss of CO requires that the donor capacity of
the CS2 unit increase and complexes are known in
which CS2 donates up to six electrons, with both car-
bon–sulfur bonds remaining intact [22]. However, this
may place unfavourable geometric constraints which
carbon–sulfur bond scission could help relieve.
Carbon–sulfur bond cleavage also occurs upon reac-
tion of 1 with aryl isothiocyanates (ArNCS; ArꢁPh,
p-tolyl). Photolysis of toluene solutions with a slight
excess of the isothiocyanate resulted in a slow reaction
which afforded a mixture of products from which the
major constituents were isolated and characterised as
dithiolate-bridged products [Fe2(CO)3(CNAr){m-SC-
(NAr)C(O)S}(m-dppm)] (4–5) and [Fe2(CO)4{m-SC(N-
p-tolyl)C(O)S}(m-dppm)] (6). Formulation as tricar-
bonyl–isocyanide and tetracarbonyl complexes, re-
spectively was made on the basis of the IR spectra, the
isocyanide coming at characteristically low frequency
(4, 2087; 5, 2092 cm−1). Further, for all complexes low
frequency CꢁO (1605–1593 cm−1) and CꢁN (1504–
1484 cm−1) bands were also observed suggesting of the
presence of ketonic carbonyl and imine functionalities
respectively. On this basis and supported by analytical
and mass spectral results the above formulations are
made.

G. Hogarth et al. / Journal of Organometallic Chemistry 595 (2000) 134–139
137
binds to iron. Clearly, it is not possible to predict the
order of events leading to the generation of dithiolate-
bridged complexes. Isothiocyanates have previously
been shown to add to low-valent metal centres via
carbon–sulfur bond scission [23,24]. Thus, addition of
RNCS to [CpCo(CO)(PPh3)] affords [Cp3Co3(m3-S)(m3-
CNR)] [23], while thermolysis of PhNCS and [Cp2Ru2-
(CO)2{m-C(O)C(Ph)ꢁC(Ph)}] yields [Cp2Ru2(CO)2(m-
CO){m-C(O)C(Ph)ꢁC(Ph)C(ꢁNPh)}] [24]. It is notewor-
thy that in both of these examples and in the formation
of 4–6 it is always the sulfur–carbon bond that is
cleaved. Formation of thiolate-bridged complexes is not
unexpected as a large number of related diiron species
have previously been prepared and are very stable.
In conclusion, this work has extended the already
rich photochemical reactivity of [Fe2(CO)6(m-CO)(m-
dppm)] (1) to yield some otherwise inaccessible new
organoiron complexes. All the organosulfur compounds
used were heterocumulene type species, and the positive
outcome suggests that other members of this class of
compound may also be worthy of study. We have tried
to extend the reactivity of 1 to saturated sulfur-contain-
ing species with limited success. Thus, H2S reacts read-
ily but does not produce any tractable products while
no significant reaction was noted with disulfides
RSCH2SR (RꢁPh, Me).
It was clear from the NMR data that all three products
were a mixture of two isomers a–b between a 3:1 and
6:1 ratio, and VT NMR studies have shown that these
interconvert. As it gives the simplest spectra, discussion
will focus around tetracarbonyl 6. In the 31P-NMR
spectrum, at low temperature (253 K) two distinct
resonances are observed in a 5.3:1 ratio (6a:6b). Each
isomer is represented by only a single phosphorus reso-
nance suggesting a plane of symmetry bisecting the two
phosphorus and iron atoms. Upon warming to 323 K,
the peaks broaden to a single resonance at 57.2 ppm
showing that the two isomers are in fast exchange at
this temperature. These changes are mirrored in the
1H-NMR spectra, the methylene and methyl regions
being most informative. At 253 K, four virtual quartets
are clearly observed between l 4.36–3.68 showing that
for each isomer the methylene protons are inequivalent,
while two methyl resonances are also observed. In
contrast, but in keeping with the isomers being in
exchange at higher temperatures, at 323 K a single
methyl resonance is seen while the four methylene
protons collapse into two broad peaks. A number of
possible processes could be envisaged to account for
these observations, however, as a similar process oper-
ates for all three complexes, isocyanide fluxionality can
be discounted. This leaves inversion at the imine moiety
as the most likely reason and indeed such a process is
known to have a substantial energy barrier. Thus we
believe that the isomers seen for complexes 4–6 relate
to the different aryl positions on the imine and given
the large steric nature of the diphosphine, it seems
reasonable to suggest that the major isomer is that in
which the aryl group points away from this.
3. Experimental
3.1. General procedures
General experimental methods have been described
previously [9]. Complex 1 was prepared by the litera-
ture method [10]. All reactions were carried out in dry
degassed solvents under a nitrogen atmosphere but
work-up was carried out in air unless otherwise stated.
UV photolysis was carried out using a Hanovia
medium-pressure mercury lamp.
3.2. Reaction with SO2
A THF solution (200 cm3) of 1 (0.50 g, 0.72 mmol)
was purged with SO2 for 10 min in order to form a
saturated solution. This was then irradiated for 16 h
resulting in the formation of a dark-brown solution.
Volatiles were removed under reduced pressure to give
a brown solid. This was washed with 40–60 light-
petroleum and crystallised upon addition of hexanes to
a dichloromethane solution to give brown [Fe2(CO)6(m-
SO2)(m-dppm)] (2) (0.47 g, 90%). IR (CH2Cl2) w(CO)
2068s, 2026s, 2007m, 1981m, 1960sh cm−1; (KBr)
2064m, 2023m, 1998s, 1973s, 1160s (SO2), 1123m,
Formation of 4–5 involves loss of three carbonyls
from 1 and addition of two equivalents of aryl isothio-
cyanate. One of the isothiocyanates remains intact and
couples with a carbonyl via formation of a new car-
bon–carbon bond. The second undergoes sulfur–car-
bon bond cleavage with the resulting sulfur also
coupling to a carbonyl, while the generated isocyanide
1095m, 1073w, 1027s (SO2), 998m cm−1
.
1H-NMR
(CDCl3) l 7.62–7.10 (m, 20H, Ph), 3.89 (q, J 13.2, 1H,

138
G. Hogarth et al. / Journal of Organometallic Chemistry 595 (2000) 134–139
CH2), 2.89 (q, J 13.0, 1H, CH2). 13C-NMR (CDCl3)
208.7 (br, CO), 133.6 (t, J 29.4, Ci), 132.8 (t, J 23.9, Ci).
132.3 (m, Cm), 131.2 (d, J 18.4, Co), 128.8 (t, J 4.2, Cp),
128.6 (t, J 4.9, Cp), 31.2 (t, J 20.3, CH2) ppm. 31P-NMR
(CDCl3) 64.1 (s) ppm; mass spectrum (FAB+) m/z 728
[M+]. Anal. Calc. for Fe2C31H22O8P2S1: C, 51.10; H,
3.02; S, 4.40. Found: C, 49.78; H, 2.91; S, 4.39%.
J 77.6) ppm; mass spectrum (FAB+) m/z 1348 [M+],
1124 [M+−8CO], 1096 [M+−9CO], 1068 [M+−
10CO]. Anal. Calc. for Fe4C61H44O10P4S2CH2Cl2: C,
51.92; H, 3.21; P, 8.65; S, 4.47. Found: C, 52.49; H,
3.45; P, 8.54; S, 4.37%. Elution with 60%
dichloromethane gave an orange band 3b (30 mg, 6%):
IR (CH2Cl2) 2044s, 2008s, 1980s, 1962s, 1942s, 1911m,
1
1889w, 1095m cm−1. H-NMR (CDCl3) l 7.84–6.90
3.3. Protonation of 2
(m, 40H, Ph), 4.07 (brq, 1H, CH2), 3.53 (brq, 1H,
CH2), 3.29 (brq, 1H, CH2), 2.93 (brq, 1H, CH2). 31P-
NMR (CDCl3) 78.4 (d, J 74.5), 74.2 (d, J 92.3), 64.1 (d,
J 74.5), 59.9 (d, J 92.3) ppm. Mass spectrum (FAB+)
m/z 1348 [M+], 1305 [M+−CS], 1081 [M+−CS−
8CO].
Addition of
a
drop of HBF4·Et2O to
a
dichloromethane solution (10 cm3) of 2 (30 mg) resulted
in an immediate colour change from orange to yellow
and the development of new bands in the IR spectrum;
w(CO) (CH2Cl2) 2088s, 2050s, 2033m, 2010m cm−1
.
Upon removal of the solvent, washing with diethyl
ether resulted in the removal of excess acid concomitant
with regeneration of 2 (as shown by IR). Addition of a
drop of CF3CO2H to 2 (20 mg) in CDCl3 led to the
3.5. Reaction with PhNCS
A toluene solution (250 cm3) of 1 (0.50 g, 0.72 mmol)
and PhNCS (0.3 cm3) was irradiated for 16 h resulting
in the formation of a dark solution. Removal of
volatiles under reduced pressure gave a dark solid,
which was absorbed onto alumina. Column chromatog-
raphy on alumina with light-petroleum gave a number
of bands. Eluting with 70% dichloromethane gave an
orange band which afforded [Fe2(CO)3(CNPh) {m-SC-
(NPh)C(O)S) (m-dppm)] (4) (70 mg, 11%) as a mixture
1
generation of a yellow solution. H-NMR (CDCl3) (303
K) l 7.61–7.29 (br, 20H, Ph), 3.89 (br, 1H, CH2), 3.16
(br, 1H, CH2); (333 K) l 8.79 (br, 0.3H, SO2H), 7.61–
7.29 (m, Ph, 20H), 3.97 (q, J 12.2, 1H, CH2), 3.10 (q, J
11.5, 1H, CH2).
3.4. Reaction with CS2
1
of isomers 4a:4b (3:1 by H-NMR). IR (CH2Cl2) w(CO)
Carbon disulfide (1 cm3) was added to a toluene
solution (250 cm3) of 1 (0.50 g, 0.72 mmol) via a
degassed syringe. The reaction mixture was irradiated
for 40 h. Volatiles were removed under reduced pres-
sure and the resulting solid was absorbed onto alumina.
Column chromatography on alumina with 40–60 light-
petroleum resulted in the separation of a number of
bands. Elution with 10% dichloromethane gave a minor
brown band (ca. 10 mg): IR (CH2Cl2) w(CO) 1999m,
1982s, 1951m cm−1. Elution with 25% dichloromethane
afforded a minor brown band (ca. 10 mg): IR (CH2Cl2)
w(CO) 2009s, 1996s, 1974m, 1962m, 1932w cm−1. Elu-
tion with 45% dichloromethane gave a minor brown
band (ca. 10 mg): IR (CH2Cl2) w(CO) 2005m, 1982m,
1950m cm−1. Elution with 55% dichloromethane gave
a blue–black band which afforded [Fe4(CO)10(m4-
h2,h2,h3-CS2)(m-dppm)2] (3a) (82 mg, 17%) as a dark
solid. Dark blue–black crystals were obtained upon
2087m (CꢂN), 1971s, 1928s, 1915sh, 1605m (CꢁO),
1586m (CꢁN) cm−1 1H-NMR (CDCl3) l 7.70–6.50
.
(m, 30H, Ph), 4.46 (q, J 11.2, 1H, CH2, 4a), 4.26 (q, J
12.8, IH, CH2, 4b), 3.76 (q, J 11.3, 1H, CH2, 4a), 3.66
(q, J 12.8, 1H, CH2, 4b). 13C-NMR (CDCl3) 220.14 (d,
J 26.7, CO), 213.0 (d, J 3.8, CO), 210.2 (s, CO), 178.70
(d, J 28.8, CNPh), 162.63 (s, CꢁO), 146.06 (s, CꢁNPh),
140–120 (m, Ph), 49.14 (t, J 22.5, CH2), 48.83 (t, J 21.8,
CH2, 4b) ppm. 31P-NMR (CDCl3) 65.8 (d, J 57.1, 4a),
65.3 (s, 4b), 63.8 (d, J 57.1, 4a) ppm. Anal. Calc. for
Fe2C43H32O4P2S2N2: C, 58.76; H, 3.64; N, 3.19; S, 7.29.
Found: C, 58.46; H, 3.66; N, 3.09; S, 7.20%. Further
elusion with 35% dichloromethane gave a yellow band
(ca. 15 mg): IR (CH2Cl2) w(CO) 2111w (CꢂN), 2033s,
1989m, 1712w cm−1
.
3.6. Reaction with p-tolylNCS
slow
diffusion
of
light-petroleum
into
a
A THF solution (150 cm3) of 1 (0.50 g, 0.72 mmol)
and p-tolylNCS (0.5 cm3) was irradiated for 16 h,
resulting in the formation of a deep-red–black solution.
Removal of volatiles under reduced pressure gave a
dark solid, which was absorbed onto alumina. Column
chromatography on alumina with light-petroleum gave
a number of bands. Eluting with 40% dichloromethane
gave a blue band (ca. 10 mg): IR (CH2Cl2) w(CO)
dichloromethane solution. IR (CH2Cl2) w(CO) 2043s,
2005s, 1978vs, 1958s, 1945s, 1909m, 1889w, 1605w
cm−1; IR (methylcyclohexane) 2048s, 2012s, 1990vs,
1980s, 1965m, 1950s, 1937w, 1918s, 1897w; IR (KBr)
2037s, 2003s, 1978vs, 1956s, 1942s, 1911s, 1889m,
1885m, 1460m, 1435m, 1093m cm−1
.
1H-NMR
(CDCl3) l 7.65–6.70 (m, 40H, Ph), 4.13 (brq, J 9.3, 1H,
CH2), 3.55 (brq, J 8.0, 1H, CH2), 3.33 (brq, J 9.3, 1H,
CH2), 2.86 (brq, J 8.3, 1H, CH2). 31P-NMR (CDCl3)
78.2 (d, J 66.9), 63.8 (d, J 77.6), 62.8 (d, J 66.9), 57.8 (d,
2099m (CꢂN), 2014m, 1990m, 1962s, 1945m cm−1
.
Eluting with 50% dichloromethane gave an orange
band which afforded [Fe2(CO)4{m-SC(N-p-tolyl)-

G. Hogarth et al. / Journal of Organometallic Chemistry 595 (2000) 134–139
139
References
C(O)S}(m-dppm)] (6) (60 mg, 10%) as a mixture of
isomers (6a:6b 5.3:1 by 31P-NMR). Orange crystals
were obtained upon slow diffusion of light-petroleum
into a dichloromethane solution: IR (CH2Cl2) w(CO)
1987m, 1948s, 1912s, 1605w (CꢁO), 1483w (CꢁN)
cm−1. 1H-NMR (CDCl3) (323 K) l 7.63–6.97 (m, 24H,
Ph), 4.24 (br, 1H, CH2), 3.73 (br, 1H, CH2), 2.32 (s,
3H, Me); (253 K) l 7.64–6.96 (m, 24H, Ph), 4.36 (q, J
11.3, 1H, CH2, 6a), 4.12 (q, J 10.9, 1H, CH2, 6b), 3.74
(q, J 11.3, 1H, CH2, 6a), 3.68 (q, J 11, 1H, CH2, 6b),
2.37 (s, 3H, CH3, 6b), 2.35 (s, 3H, CH3, 6a). 31P-NMR
(CDCl3) (323 K) 57.2 (s); (253 K) 57.6 (s, 6a), 57.1 (s,
6b) ppm. Mass spectrum (FAB+) m/z 790 [M+−CO],
761 [M+−2CO]. Anal. Calc. for Fe2C38H29O5P2S2N1:
C, 55.81; H, 3.55; N, 1.71. Found: C, 56.03; H, 3.82; N,
1.68%. Eluting with 65% dichloromethane gave an or-
ange band which afforded [Fe2(CO)3(CN-p-tolyl){m-
SC(N-p-tolyl)C(O)S}(m-dppm)] (5) (60 mg, 9%) as a
mixture of isomers 5a:5b (6:1 by 1H-NMR). Orange
crystals were grown by slow diffusion of light-
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a
dichloromethane solution: IR
(CH2Cl2) w(CO) 2092m (CꢂN), 1970s, 1926s, 1920sh,
1
1593m (CꢁO), 1504w (CꢁN) cm−1. H-NMR (CDCl3)
(323 K) l 7.68–6.96 (m, 26H, Ph), 6.56 (br, 2H, Ph),
4.37 (br, 1H, CH2), 3.79 (br, 1H, CH2), 2.38 (s, 3H,
CH3), 2.30 (s, 3H, CH3); (253 K) l 7.71–6.92 (m, 26H,
Ph), 6.52 (d, J 7.4, 2H, Ph, 5b), 6.43 (d, J 7.6, 2H, Ph,
5a), 4.48 (q, J 11.9, 1H, CH2, 5a), 4.29 (br, 1H, CH2,
5b), 3.75 (q, J 11.7, 1H, CH2, 5a), 3.63 (m, 1H, CH2,
5b), 2.37 (s, 3H, CH3, 5b), 2.34 (s, 3H, CH3, 5a), 2.29 (s,
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(293 K) 65.9 (d, J 57.4, 5a), 65.5 (s, 5b), 64.0 (d, J 57.4,
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100% dichloromethane gave a yellow band (ca. 10 mg):
IR (CH2Cl2) w(CO) 2117s (CꢂN), 2067w, 2032m, 1973m
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Acknowledgements
We thank University College London for the award
of a studentship to M.H.L., Dr Tony Hill (Imperial
College) for advice concerning the SO2H complex and
Joe Fletcher for the initial synthesis of 4a–b.
.