The photochemical generation of heterobimetallic complexes containing carbon disulfide

Article abstract of DOI:10.1039/a704141a

Photochemistry has been used to generate a number of heterobimetallic complexes containing π + σ CS₂ bridging groups. Broad-band UV photolysis of tetrahydrofuran (thf) solutions of [M(CO)₆] (M = Cr, Mo or W) with [Fe(CO)₂(PR₃)₂(η²-CS ₂)] (R = Et or Ph) leads to the formation of the bimetallic complexes [(PR₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)M(CO)₅]. Photolysis of acetonitrile solutions of [Os₃(CO)₁₂] with [Fe(CO)₂(PR₃)₂(η²-CS ₂)] leads to [(PR₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)Os₃(CO)₁₁]. Photolysis of a thf solution of (PEt₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)M(CO)₅] with PEt₃ results in the formation of the phosphine-substituted complex [(PPh₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)M(CO)₄(PEt ₃)]. Single-crystal X-ray diffraction has been used to determine the molecular structures of [(PPh₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)W(CO)₅], [(PEt₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)Os₃(CO)₁₁] and [(PPh₃)₂(CO)₂Fe(μ-η ²:η¹-CS₂)Cr(CO)₄(PEt ₃)].

Full text of DOI:10.1039/a704141a

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The photochemical generation of heterobimetallic complexes
containing carbon disulfide
Peter V. Broadhurst, Nicholas E. Leadbeater,* Jack Lewis and Paul R. Raithby
Department of Chemistry, Lensfield Road, Cambridge, UK CB2 1EW
Photochemistry has been used to generate a number of heterobimetallic complexes containing π ϩ σ CS2 bridging
groups. Broad-band UV photolysis of tetrahydrofuran (thf) solutions of [M(CO)6] (M = Cr, Mo or W) with
[Fe(CO)2(PR3)2(η2-CS2)] (R = Et or Ph) leads to the formation of the bimetallic complexes [(PR3)2(CO)2Fe-
(µ-η2 : η1-CS2)M(CO)5]. Photolysis of acetonitrile solutions of [Os3(CO)12] with [Fe(CO)2(PR3)2(η2-CS2)] leads to
[(PR3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11]. Photolysis of a thf solution of (PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5]
with PEt3 results in the formation of the phosphine-substituted complex [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)4-
(PEt3)]. Single-crystal X-ray diffraction has been used to determine the molecular structures of [(PPh3)2(CO)2Fe-
(µ-η2 : η1-CS2)W(CO)5], [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11] and [(PPh3)2(CO)2Fe(µ-η2 : η1-
CS2)Cr(CO)4(PEt3)].
The interaction of heteroallene molecules such as carbonyl
sulfide (COS), carbon disulfide (CS2) and carbon dioxide
(CO2) with transition metals has become an area of increased
research interest.1,2 Firstly, petrochemical feedstocks have
sulfur-containing compounds as impurities which poison many
hetero- or homo-geneous catalysts used in processing.3 If the
behaviour of these impurities with transition-metal centres is
established, an insight into the mechanism for poisoning
could be gained and attempts made to prevent it. In addition,
phosphines, η2-co-ordinating ligands can be stabilised. This is
as a result of a strong increase in binding energy which is con-
sistent with increased π-back donation in the phosphine-
substituted complex. Indeed, ab initio calculations7 have shown
that replacement of carbonyl groups by phosphines in iron(0)
carbon disulfide complexes results in an increased overlap
between the interacting orbitals on Fe and CS2, this being con-
comitant with deformation of the CS2 geometry which itself
enhances the effect.
heteroallenes show interesting chemistry undergoing
a
Irradiation of a tetrahydrofuran (thf) solution of [Fe(CO)3-
(PR3)2] (R = Et 2a or Ph 2b) with CS2 leads to the η2-CS2 co-
ordinated complex [Fe(CO)2(PR3)2(η2-CS2)] (R = Et 3a or Ph
3b) [equation (1)] as characterised by comparison of the
number of transformations such as insertion, dimerisation and
disproportionation.1a
Work in our research group has focused on the photo-
chemical generation of carbon disulfide-containing complexes
of the Group 8 transition metals and their subsequent reaction
chemistry. To date, many of the Group 8 transition-metal–CS2
complexes reported have been prepared by thermolysis or
pyrolysis routes. Although illustrating interesting chemistry, in
many cases the CS2 moiety does not remain intact, often form-
ing, for example, carbide, sulfide, CS, C2S2, CS3 and C2S4 groups
in various co-ordination modes.4 Photochemistry offers a
simple, and often highly selective, route to organometallic com-
pounds, overcoming large enthalpy barriers.5,6 As a consequence,
it is often possible to prepare complexes that are otherwise
inaccessible by conventional thermochemical routes. We have
studied the photochemical behaviour of [Fe(CO)5] 1 and
[Fe(CO)3(PR3)2] (R = Et 2a or Ph 2b) with CS2 and the reaction
chemistry of the photolysis products has been investigated.
hν
[Fe(CO)3(PR3)2]
[Fe(CO)2(PR3)2(η2-CS2)]
(1)
CS2
spectral data with those reported previously for 3b.8 The trans
1
stereochemistry of 3a and 3b was evident from the H NMR
parameters (see below). The disulfide products are formed in
high yields, this being a marked improvement on the con-
ventional synthetic routes of either refluxing [Fe2(CO)9] and
tertiary phosphine in CS2 as the solvent8,9 or ligand exchange
reactions.10 The bonding of the CS2 group is considered to be
analogous to the Dewar–Chatt model proposed for alkenes.
The net structural effect of σ donation from the π molecular
orbitals (MO) on CS2 to the iron and back donation from iron
to a π* MO on the disulfide is a distortion of the CS2 moiety
towards the geometry observed in the first excited state.10 Con-
comitant with this is a lengthening of the CS bonds as shown by
the decrease in CS stretching frequency from 1535 cmϪ1 in free
carbon disulfide (ν2)11 to 1116 in 3a. From comparison of this
value with those for analogous η2-CS2 complexes reported in
the literature,8–10 a correlation between νCS and the electronic
properties of the phosphorus ligand is found, phosphite ligands
having higher νCS values than analogous phosphines. Although
informative, data for the C᎐S stretching frequency must be con-
sidered carefully since coupling with other ligand modes is
often severe in the νCS region of the infrared spectrum12 with
the result that significance cannot be placed on absolute values
of frequencies reported here or in other CS2-containing
molecules.10 The analogous complex [Fe(CO)2(PMe3)(PPh3)-
(η2-CS2)] 3c has been characterised crystallographically and
shows definitively both the lengthening of the CS bonds and
also significant deformation of the CS2 moiety, the S᎐C᎐S angle
being 139Њ.10
Results and Discussion
Photolysis of [Fe(CO)5] 1 and [Fe(CO)3(PR3)2] (R ؍ Et 2a or Ph
2b) with CS2
Broad-band UV photolysis of a hexane solution of [Fe(CO)5] 1
containing CS2 leads rapidly to the formation of a brown pre-
cipitate, which is insoluble in organic solvents. Due to this
insolubility, characterisation of the reaction product has not
been possible. The aim of this experiment was to prepare the η2-
CS2 co-ordinated complex [Fe(CO)4(η2-CS2)], analogous to the
olefin complex [Fe(CO)4(η2-C2H4)]. Since carbon disulfide is
not as good a π-acceptor ligand as ethene, the formation of the
η2-CS2 complex is not possible using the present experimental
methods due to the inherent instability of the complex.
Attention was turned to phosphine-substituted mononuclear
iron carbonyl complexes since, by replacing carbonyl groups by
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586
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Fig. 1 The molecular structure of [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5] 7b
The η2-CS2 co-ordinated complexes 3a and 3b are stable in
solution for extended periods. In addition, the complexes are
stable to displacement of CS2 by phosphines, this being in con-
trast to that of [Fe(CO)4(η2-C2H4)]5 in which the alkene moiety
is substituted readily. If a solution of 3a or 3b is heated under
an atmosphere of carbon monoxide, the CS2 group is replaced
by CO to yield 2a or 2b.
The reaction chemistry of [Fe(CO)2(PEt3)2(ç2-CS2)] and
[Fe(CO)2(PPh3)2(ç2-CS2)] with mononuclear and cluster carbonyl
fragments
The reaction chemistry of [Fe(CO)2(PEt3)2(η2-CS2)] 3a and
[Fe(CO)2(PPh3)2(η2-CS2)] 3b with [M(CO)6] (M = Cr, Mo or W)
and [Os3(CO)12] has been investigated. The unco-ordinated sul-
fur in transition-metal η2-co-ordinated CS2 complexes is highly
nucleophilic and is therefore susceptible to attack by electro-
philes.13 This is demonstrated clearly by reaction with methyl
iodide yielding, in the case of 3a, [Fe(CO)2(PEt3)2(η2-CS2Me)]ϩ
4a.
Broad-band UV photolysis of a thf solution of complex 3a
with [M(CO)6] (M = Cr, Mo or W) leads to the formation of the
CS2-bridged complex [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5]
(M = Cr 5a, Mo 6a or W 7a) [equation (2)] as characterised
Fig. 2 The molecular structure of [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)-
W(CO)5] 7b showing the crystallographic disorder of the CS2 and one
CO ligand (phenyl rings removed for clarity)
chemically. The IR spectrum of the products shows five bands
in the CO stretching region this being in agreement with local
C4v symmetry at the M centre (three νCO bands) and retention
of the local C2v symmetry of the [Fe(CO)2(PR3)2(η2-CS2)] frag-
ment. Slight splitting of one of the bands due to the M centre is
observed, this being attributed to the slight deviation from a
regular octahedral geometry. This assignment has been con-
firmed by the determination of the molecular structure of
[(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5] 7b by a single-crystal
X-ray diffraction study (Figs. 1 and 2). Selected bond lengths
and angles are shown in Table 1. The molecular structure shows
disorder in the CS2 group and one of the carbonyl groups at
hν
[Fe(CO)2(PR3)2(η2-CS2)]
[M(CO)6]
[(PR3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5] (2)
1
initially by IR and H NMR spectroscopy. Analogous com-
plexes 5b, 6b or 7b are formed with 3b.
The complexes are formed presumably by attack of 3a on
[M(CO)5(thf)], the latter intermediate being formed photo-
4580
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586

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Table 1 Selected bond lengths and angles for complex 7b
Table 2 Selected bond lengths and angles for complex 8a
W᎐S(2)
W᎐C(12)
W᎐C(14)
Fe᎐P(1)
Fe᎐S(1)
Fe᎐C(1)
Fe᎐C(21)
Fe᎐C(22Ј)
C(1)᎐S(2)
C(1Ј)᎐S(2)
C(12)᎐O(12)
C(14)᎐O(14)
C(21)᎐O(21)
C(22Ј)᎐O(22Ј)
2.531(4)
2.017(17)
2.039(16)
2.293(4)
2.299(1)
1.850(1)
1.790(15)
1.800(1)
1.760(1)
1.760(1)
1.134(16)
1.138(16)
1.151(16)
1.150(1)
W᎐C(11)
W᎐C(13)
W᎐C(15)
Fe᎐P(2)
Fe᎐S(1Ј)
Fe᎐C(1Ј)
Fe᎐C(22)
S(1)᎐C(1)
C(1Ј)᎐S(1Ј)
C(11)᎐O(11)
C(13)᎐O(13)
C(15)᎐O(15)
C(22)᎐O(22)
2.02(2)
Os(1)᎐Os(2)
Os(2)᎐Os(3)
Os(1)᎐C(12)
Os(1)᎐S(1)
Os(2)᎐C(22)
Os(2)᎐C(24)
Os(3)᎐C(32)
Os(3)᎐C(34)
C(12)᎐O(12)
C(1)᎐S(1)
Fe᎐C(1)
Fe᎐C(2)
Fe᎐P(1)
C(2)᎐O(2)
2.886(2)
2.877(2)
1.91(3)
2.461(6)
1.92(3)
1.93(3)
1.86(4)
1.83(4)
1.16(3)
1.64(2)
1.95(2)
1.81(1)
2.270(9)
1.091(1)
Os(1)᎐Os(3)
Os(1)᎐C(11)
Os(1)᎐C(13)
Os(2)᎐C(21)
Os(2)᎐C(23)
Os(3)᎐C(31)
Os(3)᎐C(33)
C(11)᎐O(11)
C(13)᎐O(13)
C(1)᎐S(2)
Fe᎐S(2)
Fe᎐C(3)
Fe᎐P(2)
C(3)᎐O(3)
2.883(1)
1.861(3)
1.85(3)
1.86(3)
1.83(3)
1.92(2)
1.93(3)
1.17(4)
1.15(3)
1.65(2)
2.341(7)
1.803(19)
2.284(10)
1.13(3)
2.044(18)
1.977(16)
2.289(4)
2.300(1)
1.850(1)
1.79(2)
1.669(9)
1.576(12)
1.15(2)
1.15(2)
1.161(16)
1.17(3)
C(11)᎐W᎐S(2)
C(13)᎐W᎐S(2)
C(15)᎐W᎐S(2)
W᎐C(12)᎐O(12) 179.0(15)
W᎐C(14)᎐O(14) 175.4(13)
W᎐S(2)᎐C(1)
S(2)᎐C(1)᎐S(1)
S(2)᎐C(1)᎐Fe
C(1)᎐S(1)᎐Fe
C(1)᎐Fe᎐P(1)
C(1)᎐Fe᎐C(21)
C(1Ј)᎐S(1Ј)᎐Fe
C(1Ј)᎐Fe᎐P(2)
C(1Ј)᎐Fe᎐C(22Ј)
89.7(4)
93.8(4)
174.6(4)
C(12)᎐W᎐S(2)
C(14)᎐W᎐S(2)
W᎐C(11)᎐O(11) 175.2(15)
W᎐C(13)᎐O(13) 176.1(14)
W᎐C(15)᎐O(15) 177.9(13)
W᎐S(2)᎐C(1Ј)
S(2)᎐C(1Ј)᎐S(1Ј) 136.2(4)
S(2)᎐C(1Ј)᎐Fe
C(1)᎐Fe᎐S(1)
C(1)᎐Fe᎐P(2)
C(1)᎐Fe᎐C(22)
C(1Ј)᎐Fe᎐P(1)
C(1Ј)᎐Fe᎐C(21)
83.5(4)
95.6(4)
Os(2)᎐Os(1)᎐Os(3)
Os(1)᎐Os(3)᎐Os(2)
Os(3)᎐Os(1)᎐C(11)
Os(3)᎐Os(1)᎐C(12)
Os(3)᎐Os(1)᎐C(13)
C(11)᎐Os(1)᎐C(12)
Os(2)᎐Os(1)᎐S(1)
C(11)᎐Os(1)᎐S(1)
C(13)᎐Os(1)᎐S(1)
Os(3)᎐Os(2)᎐C(21)
Os(3)᎐Os(2)᎐C(22)
Os(1)᎐Os(2)᎐C(23)
Os(1)᎐C(11)᎐O(11)
Os(1)᎐C(13)᎐O(13)
S(1)᎐C(1)᎐S(2)
59.8(1)
60.1(1)
101.3(6)
154.5(10)
84.3(6)
103.7(11)
87.4(2)
88.7(8)
176.0(1)
103.9(8)
149.4(11)
84.9(11)
177.4(19)
178(3)
Os(1)᎐Os(2)᎐Os(3)
Os(2)᎐Os(1)᎐C(11)
Os(2)᎐Os(1)᎐C(12)
Os(2)᎐Os(1)᎐C(13)
C(11)᎐Os(1)᎐C(13)
C(12)᎐Os(1)᎐C(13)
Os(3)᎐Os(1)᎐S(1)
C(12)᎐Os(1)᎐S(1)
Os(1)᎐Os(2)᎐C(21)
Os(1)᎐Os(2)᎐C(22)
C(21)᎐Os(2)᎐C(22)
Os(3)᎐Os(2)᎐C(23)
Os(1)᎐C(12)᎐O(12)
Os(1)᎐S(1)᎐C(1)
S(1)᎐C(1)᎐Fe
60.0(1)
160.1(7)
95.8(9)
96.1(9)
87.3(12)
91.6(11)
95.9(1)
109.0(2)
138.7(3)
139.8(4)
52.7(1)
94.1(6)
153.7(5)
53.1(1)
151.0(4)
139.8(4)
45.9(3)
94.0(6)
99.1(7)
90.3(12)
167.2(5)
89.9(9)
163.4(8)
90.2(11)
106.2(14)
95.1(11)
176(3)
110.5(9)
138.8(14)
55.3(8)
92.2(12)
87.5(16)
140.5(16)
80.7(9)
S(2)᎐C(1)᎐Fe
C(1)᎐S(2)᎐Fe
iron which precludes an assessment of the bond parameters in
7b. It is, however, clear from the structure that the CS2 group
interacts in a π manner with the iron centre and in a σ manner
with the tungsten; this bridging bonding mode being denoted as
π ϩ σ. Of all the bridging modes of CS2 structurally character-
ised, the π ϩ σ motif is relatively uncommon.14 The reasons
why 7b adopts this configuration are not clear but the stability
of the π bond between iron and CS2 and the mild reaction
conditions used in the coupling reaction with [W(CO)6] may be
significant factors. Although not statistically different at the 3σ
level, the W᎐C(15) bond, at 1.977(16) Å, is apparently shorter
than the other W᎐C (O) bonds, average 2.02(4) Å. This is
indicative of the increased back donation as a result of the
replacement of a trans carbonyl by a trans σ bonding sulfur
which is not competing for the electron density available for
back donation. This effect has been reported previously for
sulfur-substituted Group 6 carbonyls.15,16 The other bond
lengths and the angles in the W(CO)5S moiety are unexcep-
tional, a very slight distortion from a regular octahedral geom-
etry being observed.
S(2)᎐Fe᎐C(1)
S(2)᎐Fe᎐C(3)
S(2)᎐Fe᎐P(2)
C(2)᎐Fe᎐P(1)
C(3)᎐Fe᎐P(1)
P(1)᎐Fe᎐P(2)
43.9(7)
108.9(7)
91.5(3)
88.9(9)
88.5(8)
S(2)᎐Fe᎐C(2)
S(2)᎐Fe᎐P(1)
C(2)᎐Fe᎐C(3)
C(2)᎐Fe᎐P(2)
149.7(7)
91.5(3)
101.3(10)
89.4(9)
C(3)᎐Fe᎐P(2)
89.4(9)
176.8(3)
Broad-band UV photolysis of an acetonitrile solution of
complex 3a with [Os3(CO)12] leads to the formation of
the mononuclear-cluster linked compound [(PEt3)2(CO)2Fe-
(µ-η2 : η1-CS2)Os3(CO)11] 8a [equation (3)] as characterised
hν
[Fe(CO)2(PR3)2(η2-CS2)]
[Os3(CO)12
]
[(PR3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11] (3)
Fig. 3 The molecular structure of [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Os3-
(CO)11] 8a
initially by IR and 1H NMR spectroscopy. An analogous com-
pound 8b is formed with 3b. Again, the trans stereochemistry of
the iron centre is unchanged in the reaction and the bonding of
the CS2 is π to the iron centre and σ to one of the osmium atoms
of the trinuclear cluster. It is presumed that the reaction occurs
by way of an attack of 3a or 3b on [Os3(CO)11(MeCN)], the
latter formed by photosubstitution of a carbonyl group for
acetonitrile.17
is confirmed, the bonding to the iron centre being unchanged
and the second S atom of the disulfide bonding to an osmium
atom in an axial position. The site preference of ligands
depends on a balance of steric and electronic factors.18,19 Simple
calculations on [Os3(CO)12ϪnLn] systems show that the
equatorial sites in approximately anticuboctahedral structures
are less sterically hindered than axial sites.20 It is therefore inter-
esting that in 8a, co-ordination occurs through an axial site on
the osmium atom of the cluster especially since in the only
other structurally characterised example of a triosmium cluster
The molecular structure of 8a has been determined by single-
crystal X-ray diffraction (Fig. 3) and selected bond lengths and
angles are presented in Table 2. The π ϩ σ co-ordination of CS2
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586
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containing
a σ-co-ordinated sulfur moiety, [Os3(CO)11-
{S(CH2)3}],21 the ligand occupies the expected equatorial pos-
ition. If the S was co-ordinated equatorially in 8b there would
be considerable steric repulsions between the carbonyl groups
on the osmium cluster with those on the iron centre. Electronic
arguments must also be taken into account. Both [Os3(CO)11-
(MeCN)] and [Os3(CO)10(MeCN)2] exhibit axial co-ordination
of the σ-donor ligands, this being due to the σ-donor character-
istics of these ligands. Good σ-donor ligands, such as
acetonitrile, prefer to lie trans to a carbonyl group rather than,
in the case of good π-acceptor ligands, trans to the metal–metal
bonds.22
The Os᎐Os bonds are not significantly different to those
in [Os3(CO)12]23 in contrast to the case of [Os3(CO)11-
{S(CH2)3}]21 where the equatorially situated thietane group
exerts a significant trans influence lengthening one of the
metal–metal bonds. Unlike the case of 7b, in 8a the σ-co-
ordinated sulfur atom does not seem to have any significant
effect on the trans situated carbonyl group on Os(1). This
may be explained by a delocalisation of the electron density
across all the carbonyl bonds in the cluster rather than the
localised effect seen in 7b.
Table 3 Selected bond lengths and angles for complex 9a
Fe᎐S(1)
Fe᎐P(1)
2.342(1)
2.276(1)
1.796(4)
1.674(3)
2.431(1)
1.840(6)
1.514(8)
1.536(8)
1.837(3)
1.138(5)
2.398(1)
1.850(4)
1.885(4)
1.852(3)
1.519(5)
1.539(7)
1.158(5)
1.139(5)
Fe᎐C(1)
Fe᎐P(2)
1.934(3)
2.273(1)
1.755(4)
1.639(3)
1.805(5)
1.801(4)
1.496(7)
1.839(5)
1.829(4)
1.142(5)
1.823(4)
1.884(3)
1.850(4)
1.829(5)
1.521(5)
1.160(5)
1.149(4)
Fe᎐C(14)
S(1)᎐C(1)
S(2)᎐Cr
P(1)᎐C(4)
C(2)᎐C(3)
C(6)᎐C(7)
P(2)᎐C(10)
C(14)᎐O(1)
Cr᎐P(3)
Cr᎐C(23)
Cr᎐C(25)
P(3)᎐C(18)
C(16)᎐C(17)
C(20)᎐C(21)
C(23)᎐O(4)
C(25)᎐O(6)
Fe᎐C(15)
C(1)᎐S(2)
P(1)᎐C(2)
P(1)᎐C(6)
C(4)᎐C(5)
P(2)᎐C(8)
P(2)᎐C(12)
C(15)᎐O(2)
Cr᎐C(22)
Cr᎐C(24)
P(3)᎐C(16)
P(3)᎐C(20)
C(18)᎐C(19)
C(22)᎐O(3)
C(24)᎐O(5)
S(1)᎐Fe᎐C(1)
S(1)᎐Fe᎐P(2)
44.8(1)
89.0(1)
141.9(1)
91.7(1)
96.2(2)
86.9(1)
87.9(1)
103.8(2)
80.6(1)
139.7(2)
177.2(3)
92.9(1)
88.5(1)
87.5(1)
179.1(1)
89.7(1)
89.0(2)
89.3(2)
176.3(2)
176.3(3)
175.0(3)
S(1)᎐Fe᎐P(1)
93.0(1)
115.1(1)
93.2(1)
160.0(2)
174.7(1)
90.2(1)
91.4(1)
54.6(1)
139.7(2)
120.3(1)
175.9(4)
172.2(2)
96.2(1)
93.5(1)
90.0(1)
85.9(2)
87.3(2)
90.9(2)
176.3(4)
174.8(3)
S(1)᎐Fe᎐C(14)
C(1)᎐Fe᎐P(1)
C(1)᎐Fe᎐C(14)
P(1)᎐Fe᎐P(2)
S(1)᎐Fe᎐C(15)
C(1)᎐Fe᎐P(2)
C(1)᎐Fe᎐C(15)
P(1)᎐Fe᎐C(14)
P(2)᎐Fe᎐C(14)
C(14)᎐Fe᎐C(15)
Fe᎐C(1)᎐S(1)
S(1)᎐C(1)᎐S(2)
Fe᎐C(14)᎐O(1)
S(2)᎐Cr᎐P(3)
S(2)᎐Cr᎐C(23)
S(2)᎐Cr᎐C(25)
P(3)᎐Cr᎐C(23)
P(3)᎐Cr᎐C(25)
C(22)᎐Cr᎐C(24)
C(23)᎐Cr᎐C(24)
C(24)᎐Cr᎐C(25)
Cr᎐C(23)᎐O(4)
Cr᎐C(25)᎐O(6)
The photochemical reaction of [Fe(CO)2(PR3)2(η2-CS2)] with
[Os3(CO)12] is significantly lower for R = Ph (3a) than for R = Et
(3b). In the case of the former, reaction is significantly slower
and a significant quantity of [Os3(CO)11(PPh3)] is formed as a
by-product. Since a facile phosphine exchange has been
observed for [Fe(CO)2(PR3)2(η2-CS2)]9,10 complexes and 3b is
particularly unstable in solution,8 dissociation of triphenyl-
phosphine is not unexpected. The slower reaction of 3a as
compared to 3b may be due to both the increased steric bulk24
and decreased basicity25 of PPh3 as compared to PEt3 which
both restricts access of 3b to the available co-ordination site on
the osmium cluster and results in a less nucleophilic donor
sulfur atom in the PPh3-substituted compound.
P(1)᎐Fe᎐C(15)
P(2)᎐Fe᎐C(15)
Fe᎐S(1)᎐C(1)
Fe᎐C(1)᎐S(2)
C(1)᎐S(2)᎐Cr
Fe᎐C(15)᎐O(2)
S(2)᎐Cr᎐C(22)
S(2)᎐Cr᎐C(24)
P(3)᎐Cr᎐C(22)
P(3)᎐Cr᎐C(24)
C(22)᎐Cr᎐C(23)
C(22)᎐Cr᎐C(25)
C(23)᎐Cr᎐C(25)
Cr᎐C(22)᎐O(3)
Cr᎐C(24)᎐O(5)
The reaction chemistry of [(PEt3)2(CO)2Fe(ì-ç2 : ç1-CS2)-
M(CO)5] (M ؍ Cr, Mo or W)
hν
PEt3
[Fe(CO)2(PEt3)2(η2-CS2)M(CO)5]
[(PEt3)(CO)2Fe(µ-η2 : η1-CS2)M(CO)4(PEt3)] (4)
There are few CS2-containing compounds for which reactivity
studies have been reported. These include [{Pt(Ph2PCH2-
PPh2)Cl}2(µ-CS2)]26 and [Pt2(PBu2Ph)2(µ-CS2)2]27,28 which con-
tain a dithiocarboxylate-type disulfide unit. In an attempt to
compare the chemistry of the dithiocarboxylate and σ ϩ π
bonding modes of carbon disulfide, some reaction chemistry of
[(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5] (M = Cr 5a, Mo 6a or W
7a) has been investigated. Since one approach to building
organometallic clusters involves the interaction of a metal
fragment with the CS2 moiety of a co-ordinated disulfide com-
plex inducing fragmentation of CS2 to yield S and CS ligands,
attempts at cluster synthesis have been made here. There are
only a few examples of clusters reported in the literature as a
result of this type of fragmentation of CS2; these include
[(CoCp)3(µ3-CS)(µ-S)] (Cp = η5-C5H5)29 and [Fe4(CO)12(µ3-CS)-
(µ-S)].30
1
IR and H NMR spectroscopy. Vibrational analysis of the IR
spectra points towards a cis disposition of the phosphine and
CS2 ligands at the Group 6 metal centre. It is presumed that
the reaction occurs by way of a simple attack of PEt3 on
[(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)4(thf)], the latter formed
by photosubstitution of a carbonyl group by thf. Definitive
characterisation of [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)4-
(PEt3)] 9a was made by a single-crystal X-ray diffraction study
(Fig. 4). Selected bond lengths and angles are given in Table 3.
The bonding around the iron centre in 9a is unaffected by the
phosphine substitution at chromium. As in 7b and 8a, the
disulfide unit forms a π bond to iron and a σ bond to the Group
6 metal. The C(1)᎐S(1) and C(1)᎐S(2) bond lengths are not
significantly different at the 3σ level. By extending the currently
accepted theory for bonding of CS2 to transition metals,8 a
possible explanation for the similarity in C(1)᎐S(1) and
C(1)᎐S(2) bond lengths may be forwarded. The good π-
accepting properties of the π-co-ordinating CS2 ligand are
explained in terms of three modes of interaction. Initially the
π* orbitals on the π-co-ordinated C᎐S bond accept electron
density from the metal centre. This is augmented by π accept-
ance by the d orbitals of the co-ordinated sulfur from the metal
in a dπ–dπ interaction and by π* orbitals of the unco-ordinated
C᎐S bond which lies perpendicular to the xy plane and is able to
accept electron density from the filled dxz and dyz orbitals on the
metal. These three interactions result in lengthening of both the
C᎐S co-ordinated and C᎐S unco-ordinated bonds as is seen in
No reaction was observed between [(PEt3)2(CO)2Fe(µ-η2 : η1-
CS2)M(CO)5] (5a–7a) and [N(PPh3)2][BF4] or NEt3 using either
1 equivalent or a significant excess of the reagents. There was
also no observed reaction between 5a, 6a or 7a and ammonia at
either room temperature or at elevated temperatures. This sug-
gests that these complexes are not susceptible to nucleophilic
attack either at the CS2 moiety or at the Group 6 metal
centre. This parallels the reaction chemistry of [Pt2(PBu2Ph)2-
(µ-CS2)2].30 This is in agreement with the proposal14 that the
CS2 ligand must bridge a metal–metal bond before fragment-
ation can occur.
Broad-band UV photolysis of a thf solution of 5a, 6a or 7a
with PEt3 leads to substitution of the Group 6 metal centre
yielding [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)4(PEt3)] (M = Cr
9a, Mo 10a, W 11a) [equation (4)] as characterised initially by
4582
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586

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choice for substitution since yields are higher and reaction
times shorter. This gives credence to our assertion that photo-
chemistry not only offers a route to novel complexes but also to
known products both faster and in higher yields than the
analogous thermolytic pathways.
Conclusion
Photochemistry has been used to generate a number of hetero-
bimetallic complexes containing π ϩ σ CS2 bridging groups.
Unlike thermolysis reactions in which often the CS2 moiety is
broken, in the case of photolysis the CS2 unit remains intact.
Broad-band UV photolysis of thf solutions of [M(CO)6]
(M = Cr, Mo or W) and acetonitrile solutions of [Os3(CO)12]
with [Fe(CO)2(PR3)2(η2-CS2)] (R = Et 3a or Ph 3b) leads to the
formation of the bimetallic complexes [(PR3)2(CO)2Fe(µ-η2 : η1-
CS2)M(CO)5] (R = Et, M = Cr 5a, Mo 6a or W 7a; R = Ph,
M = Cr 5b, Mo 6b or W 7b) and [(PR3)2(CO)2Fe(µ-η2 : η1-
CS2)Os3(CO)11] (R = Et 3a or Ph 3b) respectively. The reaction
chemistry of [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5] (5a–7a) has
been investigated and it is found that these complexes are not
susceptible to nucleophilic attack either at the CS2 moiety or at
the Group 6 metal centre. Broad-band UV photolysis of a thf
solution of [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5] (5a–7a) with
PEt3 leads to the formation of the phosphine-substituted com-
plexes [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)4(PEt3)] (M = Cr
9a or Mo 10b).
Fig. 4 The molecular structure of [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)-
Cr(CO)4(PEt3)] 9a
[Fe(CO)2(PMe3)(PPh3)(η2-CS2)],10 where the bond lengths for
co-ordinated and unco-ordinated C᎐S bonds are 1.676 and
1.615 Å, respectively (cf. C᎐S bond length of 1.56 Å in free
CS2 31). On donation from the unco-ordinated sulfur, as seen in
3a, to osmium, as seen in 8a, back-donation from the iron
centre to the π* orbitals of the C᎐S bond to osmium is
increased and that to the π* set of the C᎐S bond to iron
decreased. Overall this gives an increase in the electron density
donated to the orbitals related to the C᎐S bond to osmium and
hence a lengthening of that bond, this equating the two C᎐S
bond lengths. Alternatively, there may be some donation from
filled non-bonding orbitals on the sulfur co-ordinated to the
iron to the π* orbitals of the C᎐S bond to osmium. This would
increase the strength of the bond co-ordinated to iron and
decrease that of the other.
This confirms the postulation made for 8a that donation
from the unco-ordinated sulfur of a π CS2 ligand to a metal
centre surrounded by good π-acceptor ligands removes electron
density from the sulfur leaving it relatively δϩ. This leads to an
electron drift towards that sulfur from the carbon of the
disulfide unit. To compensate for this either back donation from
iron to π* orbitals of the C(1)᎐S(1) bond is reduced or electron
density is donated from the filled non-bonding orbitals S(1) to
C(1). This increases the carbene character of the Fe(1)᎐C(1)
bond; this being less marked in 9a [Fe(1)᎐C(1) = 1.934(3) Å] as
compared to 8a.
Of interest is the cis disposition of the CS2 and PEt3 ligands
at the Cr centre in 9a. Steric arguments would favour a trans
arrangement as is observed in all the crystallographically char-
acterised S᎐Cr(CO)4᎐P fragments published to date32 with the
exception of those with a bidentate S᎐P containing ligand
where cis geometry is forced. However, the cis disposition of the
S and P ligands about the metal centre has the advantage that
these σ-donor ligands are then both trans to π-accepting car-
bonyls. This has a co-operative effect, the strength of the M᎐S
and M᎐P bonds being increased as does that of the trans situ-
ated carbonyl groups.
Experimental
General
Unless stated otherwise, all syntheses were performed under
an inert atmosphere of dry nitrogen using standard Schlenk
techniques. All photochemical reactions were performed in a
specially designed glass reaction vessel fitted with a nitrogen
bubbler, reflux condenser and dry-ice cooling finger. A 125 W
mercury arc broad-band UV lamp was used as the irradiation
source and reflectors placed around the reaction vessel to
maximise efficiency. The reaction mixtures were maintained at
low temperature by means of a dry-ice cooling finger. Routine
separation of products was performed by thin-layer chrom-
atography (TLC), using commercially prepared glass plates,
precoated to a thickness of 0.25 mm with Merck Kieselgel 60
F254 as supplied by Merck. Alternatively laboratory prepared
glass plates, coated to a thickness of 1.0 mm with Merck
Kieselgel 60 F254, were used. All reagents were purchased from
commercial sources and used as received unless noted other-
wise. Literature methods were used to prepare [Os3(CO)12].33
Physical measurements
Infrared spectra were recorded using a Perkin-Elmer PE 1710
Fourier-transform infrared spectrometer, solution spectra in
NaCl solution cells (path length 0.5 mm) and solid-state spectra
in compressed KBr pellets. All values quoted are in wave-
1
numbers (cmϪ1). The H NMR spectra were recorded using
Bruker AM400, WM250 or WP80SY Fourier-transform NMR
spectrometers and data reported using the chemical shift scale
in units of ppm relative to the solvent resonance. Fast atom
bombardment (FAB) mass spectra were recorded using a
KRATOS MS-50 spectrometer, with either 3-nitrobenzyl alco-
hol or thioglycerol as a matrix and CsI as calibrant. Micro-
analyses were performed by the Department of Chemistry
microanalysis section. Infrared and NMR data are collected in
Table 4 and yields, mass spectral and microanalytical data in
Table 5.
The phosphine-substituted complexes [(PEt3)2(CO)2Fe-
(µ-η2 : η1-CS2)M(CO)4(PEt3)] can also be prepared thermally.
In refluxing methanol, [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5]
reacts with PEt3 to give moderate yields of [(PEt3)2(CO)2-
Fe(µ-η2 : η1-CS2)M(CO)4(PEt3)] (9a or 10b) together with
[Fe(CO)2(PEt3)2(η2-CS2)] 3a. The reaction times varied from
2¹ h for Cr to 54 h for W, this being a measure of the
¯
²
relative kinetic stability of the reactants. For thermolysis, like
photolysis, the reaction must be performed in a co-ordinating
solvent; reaction in refluxing hexane leads to decomposition.
This is a situation where photolysis is the synthetic method of
Photolyses
[Fe(CO)5] 1 with CS2 in thf. A thf solution of [Fe(CO)5] 1
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586
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Table 4 Infrared and NMR data for the carbon disulfide complexes
Compound
ν(CO)a/cmϪ1
ν(CS)b/cmϪ1 δ(1H)c
3a [Fe(CO)2(PEt3)2(η2-CS2)]
3b [Fe(CO)2(PPh3)2(η2-CS2)]
4a [Fe(CO)2(PEt3)2(η2-CS2Me)]ϩ
1982s, 1921vs
1992s, 1932vs
2035s, 1973vs
1116
1143
1140
1.60 (m, CH2), 1.18 (m, CH3)
7.55 (m, Ph)
3.13 (s, SCH3), 1.64 (m,
CH2), 1.12 (m, CH3)
1.67 (m, CH2), 1.21 (m, CH3)
1.70 (m, CH2), 1.18 (m, CH3)
1.68 (m, CH2), 1.19 (m, CH3)
7.45 (m, Ph)
7.60 (m, Ph)
7.45 (m, Ph)
1.77 (m, CH2), 1.18 (m, CH3)
5a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)5]
6a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)5]
7a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5]
5b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)5]
6b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)5]
7b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5]
8a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11]
2054m, 1996s, 1982s, 1934 (sh), 1926vs, 1879m 1132
2064m, 1996s, 1981s, 1933 (sh), 1928vs, 1885m 1131
2062m, 1999s, 1983s, 1935 (sh), 1920vs, 1880m 1111
2055m, 2002m, 1982s, 1940 (sh), 1928s, 1884s
2069m, 2005m, 1984s, 1948 (sh), 1923s, 1884s
2064m, 2004m, 1986s, 1943 (sh), 1926s, 1887s
2098w, 2045s, 2027m, 2009s, 1998 (sh),
1986w, 1977m, 1964w, 1949m
2098w, 2044s, 2023m, 2008s, 2002 (sh),
1974w, 1964m, 1940m
d
d
1141
1099
8b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11]
1129
7.47 (m, Ph)
9a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)4(PEt3)] 2003 (sh), 2000w, 1990s, 1934m, 1900m, 1889s,
1.72 (m, CH2), 1.12 (m, CH3)
1.69 (m, CH2), 1.15 (m, CH3)
1.70 (m, CH2), 1.09 (m, CH3)
d
1864s
10a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)4(PEt3)] 2010 (sh), 2008w, 1991s, 1924m, 1900m, 1889s,
d
d
1865s
11a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)4(PEt3)] 2010 (sh), 2005w, 1990s, 1934s, 1897m, 1886s,
1861s
a Hexane solution. b Nujol mull. c In CDCl3. d Not unambiguously assigned.
Table 5 Yields, mass spectral and microanalytical data for the carbon disulfide complexes
Analysesa (%)
Compound
Yield (%)
m/z
C
H
P
S
3a [Fe(CO)2(PEt3)2(η2-CS2)]
80
75
95
65
60
50
60
50
424
712
—
616
622
750
b
b
b
b
b
—
—
—
—
—
—
—
—
—
—
—
—
3b [Fe(CO)2(PPh3)2(η2-CS2)]
4a [Fe(CO)2(PEt3)2(η2-CS2)]ϩ
5a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)5]
6a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)5]
7a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5]
5b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)5]
6b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)5]
7b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5]
8a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11]
8b [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11]
9a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)4(PEt3)]
10a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Mo(CO)4(PEt3)]
11a [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)4(PEt3)]
39.17 (38.97)
36.61 (36.38)
31.91 (32.11)
59.10 (58.42)
56.47 (55.71)
51.05 (50.99)
22.91 (23.97)
38.05 (37.74)
4.97 (4.91)
4.75 (4.58)
4.06 (4.04)
3.41 (3.34)
3.42 (3.19)
2.87 (2.92)
2.40 (2.32)
2.07 (1.90)
10.32 (10.05)
9.22 (9.38)
8.39 (8.28)
6.14 (6.85)
6.59 (6.53)
6.07 (5.98)
4.56 (4.75)
3.95 (3.89)
10.09 (10.40)
10.91 (9.71)
8.51 (8.57)
7.62 (7.09)
6.94 (6.76)
5.63 (6.19)
4.48 (4.92)
4.06 (4.03)
50
80
50
60c/18d
50c/21d
40c/10d
b
b
b
a Calculated values in parentheses. b Decomposes in mass spectrometer. c Photochemical. d Thermochemical.
(1 ml in 150 ml) containing excess CS2 (1 ml) was irradiated
using the broad-band UV source, the reaction mixture main-
tained at low temperature by means of the dry-ice cooling fin-
ger. A brown precipitate was formed, this being insoluble in
common organic solvents and consequently characterisation of
the photolysis products was not possible.
of [M(CO)6] (30 mg in 150 ml) containing a stoichiometric
equivalent of [Fe(CO)3(PR3)2(η2-CS2)] (3a or 3b) was irradiated
(4 h) using the broad-band UV source. From analysis of the
spectral data it was proposed that the yellow complex
[(PR3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)5] was formed. The product
was purified by TLC (diethyl ether–hexane, 15:85, as eluent).
[Fe(CO)3(PR3)2] (R ؍ Et 2a or Ph 2b) with CS2 in dichloro-
methane. In a typical reaction, a dichloromethane solution of
[Fe(CO)3(PR3)2] (R = Et 2a or Ph 2b) (30 mg in 150 ml) contain-
ing excess CS2 (1 ml) was irradiated (3 h) using the broad-band
UV source. From comparison with literature data7 it was pro-
posed that the yellow complex [Fe(CO)3(PR3)2(η2-CS2)] (R = Et
3a or Ph 3b) was formed. The product was purified by TLC
(diethyl ether–hexane, 20:80, as eluent).
[Os3(CO)12] with [Fe(CO)3(PR3)2(ç2-CS2)] (R ؍ Me 3a or Ph
3b) in acetonitrile. In a typical reaction, an acetonitrile solution
of [Os3(CO)12] (40 mg in 150 ml) containing a stoichiometric
equivalent of [Fe(CO)3(PR3)2(η2-CS2)] (3a or 3b) was irradiated
(4 h) using the broad-band UV source. From analysis of the
spectral data it was proposed that the dark red complex
[(PR3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11] (8a or 8b) was formed.
The product was purified by TLC (dichloromethane–hexane,
20:80, as eluent).
[Fe(CO)3(PEt3)2(ç2-CS2)] 3a with methyl iodide in dichloro-
methane. A dichloromethane solution of [Fe(CO)3(PEt3)2(CS2)]
(30 mg in 100 ml) was stirred with methyl iodide (1 ml) at room
temperature for 2 h. The product [Fe(CO)3(PEt3)2(η2-CS2Me)]ϩ
was obtained as an orange crystalline material on addition of
hexane.
[(PEt3)2(CO)2Fe(ì-ç2 : ç1-CS2)M(CO)5] (M ؍ Cr 5a, Mo 6a
or W 7a) with PEt3 in thf. A thf solution of [(PEt3)2(CO)2Fe-
(µ-η2 : η1-CS2)M(CO)5] (5a, 6a or 7a) (30 mg in 150 ml) contain-
ing excess PEt3 (1 ml) was irradiated (2 h) using the broad-band
UV source. From analysis of the spectral data it was proposed
that the orange complex [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)M(CO)4-
(PEt3)] was formed. The product was purified by TLC (diethyl
ether–hexane, 20:80, as eluent).
[M(CO)6] (M ؍ Cr, Mo or W) with [Fe(CO)3(PR3)2(ç2-CS2)]
(R = Me 3a or Ph 3b) in thf. In a typical reaction, a thf solution
4584
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Table 6 Crystal data and structure refinement parameters for [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5] 7b, [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Os3(CO)11] 8a
and [(PEt3)2(CO)2Fe(µ-η2 : η1-CS2)Cr(CO)4(PEt3)] 9aa
Compound
7b
8a
9a
Molecular formula
M
C44H30FeO7P2S2W
1036.62
C26H30FeO13Os3P2S2
1304.23
C25H45CrFeO6P3S2
704.45
Crystal habit
Crystal size/mm
a/Å
b/Å
c/Å
α/Њ
β/Њ
Yellow needles
0.38 × 0.19 × 0.11
12.024(3)
13.029(4)
16.412(5)
101.47(3)
103.46(3)
115.70(3)
2117
Dark brown needles
0.23 × 0.16 × 0.14
10.496(3)
13.532(4)
14.625(5)
89.19(3)
74.11(3)
72.55(3)
1901
Orange blocks
0.27 × 0.24 × 0.23
8.522(3)
12.320(4)
18.386(6)
102.09(3)
99.88(3)
γ/Њ
106.53(3)
1754
U/Å3
Z
2
2
2
Dc/Mg mϪ3
1.626
2.278
1.334
F(000)
1024
3.297
1212
10.590
740
0.962
µ/mmϪ1
Maximum, minimum transmission
Index ranges
0.948, 0.779
Ϫ14 р h р 14, Ϫ16 р k р 16,
0 р l р 20
4687
0.931, 0.451
Ϫ10 р h р 11, Ϫ16 р k р 17,
0 р l р 18
3354
0.577, 0.551
Ϫ8 р h р 8, Ϫ15 р k р 15,
0 р l р 23
4825
Reflections measured
Independent reflections (Rint
)
4175 (0.0167)
257, 8
0.0590
0.0589
0.001
3015 (0.0076)
299, 0
0.0512
0.0467
0.000
4138 (0.0054)
344, 0
0.0337
0.0347
0.0003
Parameters, restraints
R1b
wR1b
Pb
Observed reflections
3769 [F > 4σ(F )]
1.890, Ϫ1.836
2436 [F > 4σ(F )]
1.529, Ϫ1.151
4059 [F > 3σ(F )]
0.624, Ϫ0.337
Peak, hole in final difference map/ e ÅϪ3
a
Details in common: crystal system triclinic; space group P1 (no. 2); data collection range 3.0 < 2θ < 55.0Њ. b R1 = Σ||Fo| Ϫ Fc||/Σ|Fo|,
¯
¹
¹
wR1 = [Σw²(||Fo| Ϫ |Fc||)/Σw²Fo], w = 1/[σ2(Fo)2 ϩ PF2].
X-Ray crystallography
difference syntheses revealed two peaks of weight у 1 e ÅϪ3 at
distances of ca. 1 Å from W in 7b, these and similar peaks in the
vicinity of the Os atoms in 8a have no chemical significance and
may be ascribed to absorption effects.
Structural determinations were undertaken on single crystals
of [(PPh3)2(CO)2Fe(µ-η2 : η1-CS2)W(CO)5] 7b, [(PEt3)2(CO)2-
Fe(µ-η2 : η1-CS2)Os3(CO)11] 8a and [(PEt3)2(CO)2Fe(µ-η2 : η1-
CS2)Cr(CO)4(PEt3)] 9a using X-ray diffraction analyses. All
CCDC reference number 186/744.
measurements were made at 298
K
with graphite-
Acknowledgements
monochromated radiation (λ = 0.71073 Å) in the ω–θ scan
mode on a Stoe-Siemens AED diffractometer. Crystal data and
data acquisition details are summarised in Table 6. Cell param-
eters were obtained by least-squares refinement on diffract-
ometer angles from 25 centred reflections (20 < 2θ < 22.5Њ).
Semiempirical absorption corrections based on ψ-scan data
were applied for 7b, 8a and 9a.34
Girton College Cambridge is thanked for a Research Fellow-
ship. This work was funded in part by the EPSRC. The advice
and assistance of G. P. Shields and R. E. Hosking is greatly
appreciated.
References
The structures were solved by direct (8a and 9a) and
Patterson methods (7b) followed by Fourier-difference syn-
theses and refined by blocked-cascade (8a and 9a) or full-matrix
(7b) least-squares fits on F (SHELXL 76).35 All non-hydrogen
atoms in 9a, W, Fe, P, S, and C and O atoms of ordered CO
ligands in 7b and Os, Fe, P, S, and C and O atoms of CO ligands
on Fe and some C atoms of Et groups in 8a were treated aniso-
tropically. Some of the ethyl groups in 8a were subject to slight
thermal libration which could not be described successfully
with a two-fold disorder model. The hydrogen atoms were
placed in idealised positions and allowed to ride on the relevant
carbon atom. In the final cycles of refinement a weighting
scheme was introduced which produced a flat analysis of vari-
ance. The phenyl rings on the triphenylphosphine moieties in 7b
were refined as rigid groups. The CS2 group and one of the
carbonyl groups in 7b are disordered over two orientations
about the C(1)᎐S(1) and C(22)᎐O(22) bonds with relative occu-
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C(1)᎐S(2), C(1Ј)᎐S(2Ј), Fe᎐C(22Ј) and C(22Ј)᎐O(22Ј) distances
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bution are annotated with a prime (Ј). As a further check, alter-
native settings of the cell were checked for the presence of a
twin, but no reasonable alternatives could be found. The final
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Received 13th June 1997; Paper 7/04141A
4586
J. Chem. Soc., Dalton Trans., 1997, Pages 4579–4586