Substitution reactions of [{Co(η5-C5H5)}2 {Fe(CO)2(PPh3)}(μ3-S) (μ3-CS)]

Article abstract of DOI:10.1016/S0022-328X(02)01228-7

On heating, the cluster [{Co(η⁵-C₅H₅)}₂{Fe(CO)₂(PPh₃)}(μ₃-S) (μ₃ -CS)], 1a, reacts with PR₃ ligands (R = (b) MeO, (c) PhO and (d) Buⁿ) by replacement of PPh₃ to give [{Co(η⁵-C₅H₅)}2{Fe(CO)₂(PR₃)} (υ₃-S)(μ₃-CS)], 1b-d, and with CNR (R = (e) Me, (f) 2,4,6-Me₃C₆H₂ and (g) 2,6-Cl₂C₆H₃) by replacement of PPh₃ and then CO to give [{Co(η⁵-C₅H₅)}₂{Fe(CO)₂(CNR)}(μ₃-S)(μ₃-CS)], 1e-g, and [{Co(η⁵-C₅H₅)}₂{Fe(CO)(CNR)₂}(μ₃-S)(μ₃-CS)], 2e-g. These reactions are successful only under a very limited range of conditions, i.e. with a large excess of the incoming ligand and very short reaction times and/or moderate temperatures. The CO ligands in [{Co(η⁵-C₅H₅)}₂{Fe(CO)₂(CNR)}(μ₃-S)(μ₃-CS)] are labile and may be replaced by more CNR in a reversible reaction or by PPh₃ to give, respectively, [{Co(η⁵-C₅H₅)}₂{Fe(CO)(CNR)₂}(μ₃-S)(μ₃-CS)], 2e-g, and [{Co(η⁵-C₅H₅)}₂{Fe(CO)(CNR)(PPh₃)}(μ₃-S)(μ₃-CS)], 2h (R = 2,6-Cl₂C₆H₃). The IR spectra of the clusters have been studied and for the first time the absorption band in each due to the ν(CS) vibration of the μ₃-CS ligand has been identified unambiguously. Its frequency depends on the FeL₃ ligand set in a predictable way and lies in the range 1022-1041 cm^-1. In the ¹³C-NMR spectra the μ₃-C atom gives rise to resonances between δ 354 and 359. The clusters do not undergo bridge terminal ligand site exchange. In particular, there is no evidence for the formation of isomers, which contain terminal CS and μ₃-CNR ligands.

Full text of DOI:10.1016/S0022-328X(02)01228-7

Journal of Organometallic Chemistry 651 (2002) 60Á65
/
www.elsevier.com/locate/jorganchem
Substitution reactions of
[{Co(h5-C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)]
Anthony R. Manning *, Anthony J. Palmer
Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
Received 4 October 2001; received in revised form 16 January 2002; accepted 16 January 2002
Abstract
On heating, the cluster [{Co(h5-C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)], 1a, reacts with PR3 ligands (Rꢀ
(d) Bun) by replacement of PPh3 to give [{Co(h5-C5H5)}2{Fe(CO)2(PR3)}(m3-S)(m3-CS)], 1bÁ
d, and with CNR (Rꢀ
Me3C6H2 and (g) 2,6-Cl2C6H3) by replacement of PPh3 and then CO to give [{Co(h5-C5H5)}2{Fe(CO)2(CNR)}(m3-S)(m3-CS)], 1eÁ
and [{Co(h5-C5H5)}2{Fe(CO)(CNR)2}(m3-S)(m3-CS)], 2eÁ
g. These reactions are successful only under a very limited range
/
(b) MeO, (c) PhO and
(e) Me, (f) 2,4,6-
g,
/
/
/
/
of conditions, i.e. with a large excess of the incoming ligand and very short reaction times and/or moderate temperatures. The
CO ligands in [{Co(h5-C5H5)}2{Fe(CO)2(CNR)}(m3-S)(m3-CS)] are labile and may be replaced by more CNR in a reversible reac-
tion or by PPh3 to give, respectively, [{Co(h5-C5H5)}2{Fe(CO)(CNR)2}(m3-S)(m3-CS)], 2eÁg, and [{Co(h5-C5H5)}2-
/
{Fe(CO)(CNR)(PPh3)}(m3-S)(m3-CS)], 2h (Rꢀ
time the absorption band in each due to the n(CS) vibration of the m3-CS ligand has been identified unambiguously. Its frequency
depends on the FeL3 ligand set in a predictable way and lies in the range 1022Á
1041 cmꢁ1. In the 13C-NMR spectra the m3-C atom
gives rise to resonances between d 354 and 359. The clusters do not undergo bridgeÁterminal ligand site exchange. In particular,
/2,6-Cl2C6H3). The IR spectra of the clusters have been studied and for the first
/
/
there is no evidence for the formation of isomers, which contain terminal CS and m3-CNR ligands. # 2002 Elsevier Science B.V. All
rights reserved.
Keywords: Iron; Cobalt; Thiocarbonyl; Cluster; Ligand substitution
1. Introduction
isolated and decided to reinvestigate its substitution
reactions.
We also report a very convenient synthesis for [Co(h5-
C5H5)(PPh3)2].
It has been reported from these laboratories that the
mixed-metal cluster [{Co(h5-C5H5)}2{Fe(CO)2(PPh3)}-
(m3-S)(m3-CS)], 1a, undergoes replacement of PPh3 by
other P(III) ligands [1]. The reactions were brought
about photochemically as thermal reactions resulted in
decomposition. They were limited to Lꢀ
P(OPh)3 and failed with Lꢀtrialkylphosphines and
organoisocyanides.
/
P(OMe)3 and
2. Experimental
/
Literature methods were used to prepare [Co(h5-
C5H5)(PPh3)I2] [4] and [Fe(PPh3)2(CO)2(h2-CS2)] [5].
Other chemicals were purchased.
Unless it is stated otherwise, all reactions were carried
out under an atmosphere of nitrogen in dried and
deoxygenated solvents at room temperature (r.t.).
Where necessary, reactions were monitored by infrared
spectroscopy.
Subsequently we found that 1a reacts with CS2 to give
[{Co(h5-C5H5)}2{Fe(CO)(PR3)}(m3-S)(m3-CSCS2)] [2].
Whilst studying the reactions of this adduct with Lꢀ
/
PR3 and CNR [3], we found that organoisocyanide
complexes derived from 1a were sufficiently stable to be
IR spectra were recorded on a PerkinÁElmer Paragon
2000 FT IR spectrometer. NMR spectra were run on a
JEOL JNM-GX-270 MHz spectrometer. Elemental
/
* Corresponding author. Tel.: ꢂ
2127.
E-mail address: anthony.manning@ucd.ie (A.R. Manning).
/
353-1-706-2311; fax: ꢂ353-1-706-
/
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 2 2 8 - 7

A.R. Manning, A.J. Palmer / Journal of Organometallic Chemistry 651 (2002) 60Á
/65
61
analyses were carried out in the Microanalytical La-
boratory of University College Dublin.
hexane mixtures. The first of the green bands was
identified as [{Co(h5-C5H5)}2{Fe(CO)2(CNR)}(m3-
S)(m3-CS)], 1eÁ
Rꢀ2,4,6-C6H2Me3, yieldꢀ
C6H3Cl2, yield 0.36 g, 60%), and the second as [{Co(h5-
C5H5)}2{Fe(CO)(CNR)2}(m3-S)(m3-CS)], 2eÁg (2e, Rꢀ
Me, yieldꢀ0.2 g, 40%; 2f, Rꢀ2,4,6-C6H2Me3, yieldꢀ
0.17 g, 25%; 2g, Rꢀ2,6-C6H3Cl2, yield 5%). Longer
reaction times resulted in a decrease in the yields of 1eÁ
/
g (1e, Rꢀ
/
Me, yieldꢀ/0.28 g, 55%; 1f,
2.1. Preparation of [Co(h5-C5H5)(PPh3)2]
/
/
0.40 g, 70%; 1g, Rꢀ
/2,6-
A solution of [Co(h5-C5H5)(PPh3)I2] (10 g, 15 mmol)
and PPh3 (4 g, 15 mmol) in tetrahydrofuran (250 cm3)
was shaken with an amalgam of sodium (2 g) in mercury
(60 cm3) for 15 min. The color of the mixture changed
from green to red. The mixture was allowed to stand for
20 min, the amalgam run off and the tetrahydrofuran
solution filtered. [Co(h5-C5H5)(PPh3)2] could be isolated
in 85% yield, but was normally used directly in Section
2.2 below.
/
/
/
/
/
/
/g
and a small increase in the yields of 2e and 2f but not of
2g, as this is unstable.
2.4. Reaction of [{Co(h5-C5H5)}2{Fe(CO)-
(CNC6H2Me3-2,4,6)2}(m3-S)(m3-CS)], 2f, with CO
2.2. Preparation of [{Co(h5-
C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)], 1a
When a solution of 2f in dichloromethane (15 cm3)
under an atmosphere of CO is refluxed for ca. 5 min, it
undergoes
a
ca. 30% conversion to [{Co(h5-
[Fe(PPh3)2(CO)2(h2-CS2)] (5 g, 7.0 mmol) was added
to the solution of [Co(h5-C5H5)(PPh3)2] prepared above.
The color of the mixture changed from red to dark
green. After 15 min, the reaction mixture was filtered
and evaporated to dryness at reduced pressure. The
residue was chromatographed on alumina and eluted
C5H5)}2{Fe(CO)2(CNC6H2Me3-2,4,6)}(m3-S)(m3-CS)],
1f. If anhydrous CoCl2 (0.1 g) is added to the reaction
mixture, the reaction proceeds to completion within 2 h
at r.t. Isolation and purification as above gave 1f in 50%
yield.
with CH2Cl2Á
/
hexaneÁ/tetrahydrofuran (45:45:10). The
2.5. Reaction of [{Co(h5-C5H5)}2{Fe(CO)-
(CNC6H3Cl2-2,6)2}(m3-S)(m3-CS)], 2g, with PPh3
product was recrystallized from tetrahydrofuranÁ
/
hex-
ane mixtures to give green crystals of [{Co(h5-
C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)] (yield 3.4 g,
70%).
A solution of [{Co(h5-C5H5)}2{Fe(CO)(CNC6H3Cl2-
2,6)2}(m3-S)(m3-CS)], 2g, (0.082 g, 0.13 mmol) and PPh3
(0.3 g, 1.14 mmol) in benzene (5 cm3) was refluxed for 5
min. Isolation and purification as above gave dark green
2.3. Substitution reactions of [{Co(h5-
C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)], 1a
crystals
of
[{Co(h5-C5H5)}2{Fe(CO)(CNC6H3Cl2-
2,6)(PPh3)}(m3-S)(m3-CS)], 2h (yield 0.13 g, 95%).
The compounds prepared in the course of this work
are listed in Table 1 together with their analytical data
Solutions of 1a (0.7 g, 1.0 mmol) and a large excess of
PR3 (2Á
/
3 cm3; Rꢀ(b) OMe, (c) OPh, or (d) Bun) in
/
benzene (30 cm3) were refluxed for not longer than 1
min, and then allowed to cool. The solvents were
removed at reduced pressure. The residues were chro-
matographed on alumina and the green products eluted
as for 1a above. They were recrystallized from tetra-
and IR spectra in the n(CN/n(CO) region (1900Á
cmꢁ1). Table 2 contains the frequencies of the IR
absorption bands of 1 found in the 1000Á
1100 cmꢁ1
/
2200
/
region together with their n(CO) frequencies. In Table 3
1
are listed H and 13C-NMR spectra.
hydrofuranÁ
hexane (Rꢀ
/
hexane (Rꢀ
/
OMe and OPh) or tolueneÁ
/
/
Bun) to give green crystals of [{Co(h5-
C5H5)}2{Fe(CO)2(P(OMe)3)}(m3-S)(m3-CS)], 1b (yield
0.50 g, 90%), [{Co(h5-C5H5)}2{Fe(CO)2(P(OPh)3)}(m3-
S)(m3-CS)], 1c (yield 0.62 g, 90%), and [{Co(h5-
C5H5)}2{Fe(CO)2(PBu3n)}(m3-S)(m3-CS)], 1d (yield 0.49
g, 80%).
3. Results and discussion
The work reported herein describes the thermal
substitution of Ph3P in [{Co(h5-C5H5)}2{Fe(CO)2-
(PPh3)}(m3-S)(m3-CS)], 1a, by other R3P ligands, and of
Ph3P and then CO by organoisocyanides. With both
types of ligands we were able to prepare successfully
compounds that were not accessible photochemically
[1]. The reactions carried out in the course of this work
are illustrated in Scheme 1. 1 and 2 are neutral [{Co(h5-
C5H5)}2{Fe(ligand)3}(m3-S)(m3-CS)] derivatives contain-
ing the Fe(CO)2L and Fe(CO)L2 moieties, respectively.
Analytical and spectroscopic data for all of the
clusters described herein are consistent with the struc-
Solutions of 1a (0.5 g, 0.71 mmol) and CNR (1.5 cm3)
(Rꢀ(e) Me, (f) 2,4,6-C6H2Me3 and (g) 2,6-C6H3Cl2) in
/
dichloromethane (30 cm3) were refluxed for 80 min. The
reaction mixtures were cooled, their volume reduced to
ca. 3 cm3 and this residue chromatographed on alumina.
Elution with dichloromethaneÁhexane mixtures gave
/
two green bands. The compounds were isolated from the
latter by removal of eluent at reduced pressure and
recrystallization of the residues from tetrahydrofuranÁ
/

62
A.R. Manning, A.J. Palmer / Journal of Organometallic Chemistry 651 (2002) 60Á65
/
Table 1
Analyses and IR spectra (1900Á
/
2200 cmꢁ1 region) of the compounds described in the text
a
b
Compound
Analyses
IR spectra
L
Number
%C
%H
%P/N/others
n(CN)/n(CO)
[{Co(h5-C5H5)}2{Fe(CO)2(L)}(m3-S)(m3-CS)] (1)
c
Ph3P
1a
1b
1c
1d
1e
1f
53.7 (53.4)
3.7 (3.5)
Sꢀ
/
8.7 (9.1)
1982 (10)
1993 (10)
1995 (10)
1978 (10)
2180 (6)
1927 (7)
1944 (5)
1947 (8)
1924 (8)
2000 (10)
2000 (10)
2000 (10)
c
(MeO)3P
(PhO)3P
Bun3 P
c
46.9 (47.0)
37.9 (37.8)
47.5 (47.5)
36.9 (36.8)
5.9 (5.8)
2.7 (2.7)
3.6 (3.6)
2.2 (2.3)
5.1 (4.9)
2.8 (2.9)
2.4 (2.4)
2.1 (2.3)
MeNC
MesNC
1954 (5)
1958 (6)
1966 (7)
d
2123 (10)
2103 (10)
d
DcNC
1g
[{Co(h5-C5H5)}2{Fe(CO)(L)2}(m3-S)(m3-CS)] (2)
MeNC
MesNC
2e
2f
38.7 (39.1)
55.1 (55.0)
2.9 (3.3)
4.8 (4.6)
5.6 (5.7)
3.8 (4.0)
2173 (10)
2119 (10)
2119 (10)
2075 (8)
2153 (6)
2083 (7)
2078 (5)
2041 (10)
1948 (6)
1959 (4)
1964 (3)
1944 (7)
e
DcNC
(DcNC)(PPh3)
2g
2h
52.9 (53.2)
3.5 (3.4)
1.6 (1.6)
a
Found (calculated).
b
Peak positions (cmꢁ1) with relative peak heights in parentheses. Spectra run in CH2Cl2 solution unless it is stated otherwise. n(CN)ꢀ
1920Á
2000 cmꢁ1
Taken from ref. [1] for comparison. IR spectra run in KBr discs.
MesNCꢀ2,4,6-Me3C6H2NC. DcNCꢀ2,6-Cl2C6H3NC.
Unstable; consistent analyses could not be obtained.
/
2041Á
/
2180 cmꢁ1; n(CO)ꢀ
/
/
.
c
d
e
/
/
tures shown in the Scheme. They are similar to that
found in the solid state for [{Co(h5-C5H5)}2{Fe(CO)2-
(PPh3)}(m3-S)(m3-CS)] [1] with a m3-CS group capping
one face of a Co2Fe triangle and a m3-S ligand the other.
characterized fully, but 2g is unstable and was identified
by its IR spectrum only.
3.1. Ligand substitution
There is no evidence for isomers of 1eÁ
/
g and 2eÁh which
/
contain a m3-CNR ligand. The CS ligand strongly
prefers the m3 position and inhibits any m3-terminal
ligand exchange processes. This contrasts with the
situation in [{Co(h5-C5H5)}2{Fe(CO)(CNR)(PPh3)}-
(m3-S)(m3-CO)] where CO and CNR exchange between
terminal and bridging positions is usually facile [6].
Contrary to our previous report [1], 1a undergoes a
thermal reaction with the three P(III) ligands investi-
gated, Lꢀ
replacement of Ph3P and retention of the cluster frame-
work to give, respectively, 1bÁd in good yields. How-
/
(b) (MeO)3P, (c) (PhO)3P, and (d) Bun3P, with
/
ever, the reactions must be carried out under very
specific conditions. It is necessary to use a three to
fourfold excess of the free ligand and a 1 min reflux in
benzene solution. At lower temperatures or lower
concentrations of the free ligand, the reaction is too
The compounds described herein, 1aÁ
/
g and 2eÁh, are
/
dark green or green-brown solids soluble in the normal
organic solvents. Most are reasonably stable both in the
solid state and in solution. They may be isolated, and
Table 2
The frequencies of the absorption bands due to the n(CO) and n(CS) modes of [{Co(h5-C5H5)}2{Fe(CO)2(L)}(m3-S)(m3-CS)] (1) and [{Co(h5-
C5H5)}2{Fe(CO)(CNMe)2}(m3-S)(m3-CS)] (2e)
b
c
d
L
n(CO)
n(CO)
n(CO)mean
Absorption bands in the 1000Á1000 region
/
Bun3 P
Ph3P
1d 1978 (10)
1a 1982 (10)
1b 1993 (10)
1e 2000 (10)
1f 2000 (10)
1g 2000 (10)
2e
1924 (8)
1927 (7)
1944 (5)
1954 (5)
1958 (6)
1966 (7)
1948 (10)
1951
1955
1969
1977
1979
1983
1948
1061 (2.7)
1062 (1.9)
1062 (2.8)
1062 (2.8)
1063 (2.8)
1064 (2.4)
1060 (2.0)
1026 (3.3)
1022 (3.2, sh)
1030 (3.3)
1018 (3.2)
1034 (3.2, sh)
1036 (3.3)
1037 (3.3)
1038 (3.3)
1041 (3.3)
1022 (5.0)
(MeO)3P
MeNC
MesNC
DcNC
e
CNMe
Spectra measured in CH2Cl2 solution. Peak positions in cmꢁ1 with relative peak heights in parentheses.
b
Due to the symmetric vibration of the Fe(CO)2 moiety of 1.
Due to the antisymmetric vibration of the Fe(CO)2 moiety of 1.
c
d
n(CO)mean
ꢀ
/12[n(CO)sym
ꢂ
/
n(CO)antisym] for 1.
e
[{Co(h5-C5H5)}2{Fe(CO)(CNMe)2}(m3-S)(m3-CS)].

Table 3
NMR spectroscopic data for some of the compounds described in the text
a
b
Compound
L
1H
13C
C5H5
L
m3-CS
CO
CNR
C5H5
L
[{Co(h5-C5H5)}2{Fe(CO)2(L)}(m3-S)(m3-CS)] (1)
c
c
Ph3P, 1a
4.52 (10H) 7.1Á/7.8 (15H, m)
355.5
216.7 (d,
87.7
88.6
136.3 (d, Jꢀ
Jꢀ10.2)
30.4 (d, Jꢀ
/
42.6), 133.1 (d, Jꢀ
/
11.9), 130.0, 128.1 (d,
Jꢀ
216.4 (d,
Jꢀ18.7)
/17.0)
/
Bun3 P, 1d
4.65 (10H)
1.69 (6H, dd, Jꢀ
br, m), 0.94 (9H, t, Jꢀ
3.43 (3H)
6.88 (2H), 2.35 (6H), 2.28 (3H)
7.37 (2H, d, Jꢀ8.5), 7.18 (1H, t, Jꢀ
/
8.9 and 16.5), 1.35 (12H, 357.4 (d,
/
25.6), 25.8, 24.3 (d, Jꢀ
/13.7), 13.8
/
6.9) Jꢀ3.4)
/
/
MeNC, 1e
MesNC, 1f
DcNC, 1g
4.68 (10H)
4.71 (10H)
4.79 (10H)
358.0
355.7
8.5) 354.5
212.9
212.8
212.1
157.9
167.5
179.1
87.8
87.8
88.1
30.8
138.2, 134.2, 128.5, 128.4, 21.2, 18.7
131.8, 128.6, 128.3, 128.2
/
/
[{Co(h5-C5H5)}2{Fe(CO)2(L)2}(m3 -S)(m3 -CS)] (2)
d
MeNC 2e
MesNC, 2f
4.68 (10H)
4.68 (10H)
3.45 (6H)
6.47 (4H), 2.29 (12H), 1.95 (6H)
DcNC at 7.37 (2H, d, Jꢀ
Jꢀ8.5); Ph3P at 7.48 (6H, m), 7.33 (9H, Jꢀ
m)
87.0
87.6
87.8,
87.9
,
356.9
216.6
219.8 (d,
176.8
191.8 (d,
137.1, 134.2, 128.7, 127.5, 20.9, 18.73
DcNC at 132.3, 131.3, 128.4,127.4; Ph3P at 137.2 (d, Jꢀ
133.8 (d, Jꢀ10.2), 130.1, 128.2 (d, Jꢀ10.2)
(DcNC)(PPh3), 4.39 (5H)
2h 4.51 (5H)
/
8.5), 7.18 (1H, d, 359.0 (d,
/40.9),
/
/3.4)
Jꢀ
/
17.1)
Jꢀ
/
17.0)
/
/
a
Spectra measured in CDCl3 solution unless it is stated otherwise. Chemical shifts in ppm downfield from Me4Si as an internal standard. All resonances are singlets unless it is stated otherwise. In
doublet, tꢀtriplet, mꢀmultiplet) and coupling constant J in Hz.
parentheses are integration where appropriate, multiplicity (dꢀ
/
/
/
b
c
MesNCꢀ
/
2,4,6-Me3C6H2NC. DcNCꢀ2,6-Cl2C6H3NC.
/
Taken from ref. [1]. Spectrum run in C6D6 solution.
Low sample solubility prevents the observation of all resonances.
d

64
A.R. Manning, A.J. Palmer / Journal of Organometallic Chemistry 651 (2002) 60Á65
/
reversible equilibrium is demonstrated by allowing a
solution of 2f to stand under an atmosphere of CO,
when ca. 30% of it is converted to 1f. The reaction goes
to completion if CoCl2 is added to the reaction mixture
to sequester the free CNMes. It may also catalyse the
ligand substitution (cf. ref. [7]). CO does not replace the
remaining CNMes ligand in 1f under these conditions.
3.2. Spectroscopy
3.2.1. IR spectra
These show numerous absorption bands but the only
ones which can be identified with confidence are those
due to n(CN), n(CO) and, in most cases, n(CS)
vibrations of the CNR, CO and CS ligands. The
n(CN) and n(CO) bands are listed in Table 1, and the
n(CS) bands in Table 2 together with n(CO) data for
comparison.
The variation of the n(CO) frequencies of 1 suggests
that the overall electron-withdrawing ability of the
phosphine, phosphite and isocyanide ligands L increases
along the series Lꢀ
/
PBun3 B
CNDc. It also suggests
/
PPh3B
/
P(OMe)3B
/
P(OPh)3BCNMeBCNXyB
/
/
/
that the CNDc (CNC6H3Cl2-2,6) ligand is, in many
respects, comparable to CO itself as the n(CO) fre-
quency of 2h with its Fe(CO)(CNDc)(PPh3) ligand set
(1944 cmꢁ1) is lower than the mean n(CO) frequency
for 1a with its Fe(CO)2(PPh3) set (1954 cmꢁ1).
Scheme 1. CO ligands have been omitted for clarity. R3Pꢀ
(b) (MeO)3P, (c) (PhO)3P, (d) n Bu3P; RNCꢀ
(e) MeNC, (f) 2,4,6-
Me3C6H2NC, (g) 2,6-Cl2C6H3NC.
/
(a) Ph3P,
The unambiguous identification of the absorption
band due to the n(CS) vibration of clusters containing
the m3-CS ligand has proved difficult. The IR spectra of
/
complexes containing this ligand, 1aÁ
C5H5)}3(m3-S)(m3-CS)], all have two or three absorption
bands in the appropriate region (1000Á
1100 cmꢁ1
/
c and [{Co(h5-
slow; at higher temperatures, decomposition is too fast.
There is no evidence for the substitution of CO by R3P.
Clusters containing the Fe(CO)(PR3)2 moiety are not
formed even with Ph2PCH2CH2PPh2.
/
)
where only one would be anticipated [1,8,9], and the
same is true for the new compounds reported here.
However, the [{Co(h5-C5H5)}2{Fe(CO)2(L)}(m3-S)(m3-
Similar constraints were observed in the substitution
reactions of 1a with organoisocyanides CNR {Rꢀ(e)
/
CS)] compounds 1aÁg represent the most extensive
/
Me, (f) 2,4,6-Me3C6H2 (Mes) or (g) 2,6-Cl2C6H3 (Dc)}
where very large excesses of CNR were used (10 to 40-
fold) together with low temperatures. The reactions
could be carried out at room temperature when they
series of isostructural clusters containing the m3-CS
ligand which has been reported to date. Furthermore,
we were able to obtain good quality spectra of these
compounds in the appropriate region using CH2Cl2
solutions. This removes the consequences of solid state
effects so that absorption band frequencies can be
compared. It would be expected that changes of the s-
donor/p-acceptor abilities of L should affect the n(CS)
frequencies of 1 in the same way as they affect their
n(CO) frequencies. Consequently we are able to say that
required 50Á70 h for completion, but the best results
/
were obtained on refluxing in dichloromethane solution
for 80 min. This substitution proceeds in two stages (i)
by Ph3P replacement to give 1eÁ/g and then (ii) by CO
replacement to give 2eÁg. Increasing the reaction times
/
to 110 min resulted in a marked decrease in the yields of
1e and 1f, but only a small increase in the yields of 2e
and 2f. There is no evidence for the formation of
[{Co(h5-C5H5)}2{Fe(CNR)3}(m3-S)(m3-CS)] derivatives.
the band at ca. 1061Á
1064 cmꢁ1 found in all spectra,
/
which has a frequency that is virtually independent of L,
is unlikely to be due to the n(CS) vibration. The bands
which follow the required pattern lie between 1020 and
1041 cmꢁ1 and their frequencies increase along the same
The reaction of 1eÁg with excess CNR suggests that
/
their CO ligands are labile. This is further demonstrated
by refluxing 1g with a large excess of Ph3P in benzene
solution which converts it to [{Co(h5-C5H5)}2{Fe(CO)-
(CNDc)(PPh3)}(m3-S)(m3-CS)], 2h. That stage (ii) is a
series as above, i.e. Lꢀ
P(OMe)3 (1036)BCNMe (1037)B
CNDc (1041 cmꢁ1). The appropriate band in the
/
PBun3 (1026)B
CNMes (1038)B
/
PPh3(1030)B
/
/
/
/

A.R. Manning, A.J. Palmer / Journal of Organometallic Chemistry 651 (2002) 60Á
/65
65
spectrum of 2e lies at 1022 cmꢁ1, again following the
pattern set by the n(CO) frequencies.
labile and may be replaced by another CNR ligand in
a reaction which is shown to be reversible, and by PPh3.
In the IR spectra of these complexes, the n(CS) band of
the m3-CS ligands has been identified. Its frequency is a
3.2.2. 1H-NMR spectra
These are generally unremarkable except to confirm
the formulae. They all show the expected resonances due
to the h5-C5H5 and L ligands (Table 3). There are two
C5H5 resonances in the spectrum of 2h due to its chiral
Fe(CO)(CNDc)(PPh3) moiety which renders the two
Co(h-C5H5) inequivalent. This has been observed pre-
viously in the 1H-NMR spectrum of [{Co(h5-
C5H5)}2{Fe(CO)(CNMe)(PPh3)}(m3-S)(m3-CO)] [6].
function of L and lies in the range 1022Á
1041 cmꢁ1
/
whilst in their 13C-NMR spectra the resonance due to
these m3-C atoms has been detected for the first time at d
354Á359.
/
There is no evidence for the formation of isomers of
[{Co(h5-C5H5)}2{Fe(CO)2(CNR)}(m3-S)(m3-CS)]
and
[{Co(h5-C5H5)}2{Fe(CO)(CNR)2}(m3-S)(m3-CS)] which
contain t-CS and m3-CNR ligands. This is a reflection
of the very strong preference of the thiocarbonyl ligand
3.2.3. 13C-NMR spectra
for a bridging situation which prevents mÁ
/
t site ex-
Where obtained, these are more informative than the
1H spectra. They show resonances due to the ligating C
atoms of CO, CNR and CS ligands. Their chemical
shifts are listed in Table 3 together with those for the
C5H5 and L ligands. Resonances due to m3-CS ligands
are very weak and have not been observed previously.
change.
References
[1] A.R. Manning, L. O’Dwyer, P.A. McArdle, D. Cunningham, J.
Organomet. Chem. 551 (1998) 139.
They are strongly deshielded at ca. d355Á
/
359. They may
ca. 3 Hz).
appear as doublets due to coupling to 31P (Jꢀ
/
[2] A.R. Manning, A.J. Palmer, C.J. McAdam, B.H. Robinson, J.
Simpson, J. Chem. Soc. Chem. Commun. (1998) 1577.
[3] A.R. Manning, A.J. Palmer, C.J. McAdam, B.H. Robinson, J.
Simpson, Unpublished work.
These coupling constants are quite small when com-
pared with those to the CO or CNR groups of the
FeL2(PR3) moiety (Jꢀ17-21 Hz).
/
[4] R.B. King, Inorg. Chem. 5 (1966) 82.
[5] (a) M.C. Baird, G. Hartwell Jr., G. Wilkinson, J. Chem. Soc. (A)
(1967) 2037;
4. Conclusions
(b) P. Conway, S.M. Grant, A.R. Manning, J. Chem. Soc. Dalton
Trans. (1979) 1920.
The PPh3 ligand in the trigonal bipyramidal [{Co(h5-
C5H5)}2{Fe(CO)2(PPh3)}(m3-S)(m3-CS)] cluster may be
replaced successfully by other PR3 and by CNR ligands
in thermal reactions but only under very specific
conditions. The CO ligands in the [{Co(h5-
C5H5)}2{Fe(CO)2(CNR)}(m3-S)(m3-CS)] complexes are
[6] A.R. Manning, L. O’Dwyer, P.A. McArdle, D. Cunningham, J.
Organomet. Chem. 573 (1999) 109.
[7] M.O. Albers, N.J. Colville, T.V. Ashworth, E. Singleton, H.E.
Swanpoel, J. Organomet. Chem. 199 (1980) 55.
[8] H. Werner, K. Leonhard, O. Kolb, E. Rottinger, H. Vahrenkamp,
¨
Chem. Ber. 113 (1980) 1654.
[9] J. Fortune, A.R. Manning, Organometallics 2 (1983) 1719.