Reactions of thioarsines with metal carbonyls: Synthesis and structural characterisation of [Fe2(CO)6(μ-AsMe2)(μ-SPh)], [Fe2Cp2(CO)2(μ-AsPh2)(μ-SPh)], [Mn2(CO)8(μ-AsPh2)(μ-SPh)]

Article abstract of DOI:10.1016/S0022-328X(99)00206-5

The thioarsine, AsMe₂(SPh), reacts thermally with [Fe(CO)₅] to give the new bimetallic butterfly complex, [Fe₂(CO)₆(μ-AsMe₂)(μ-SPh)] (1). Similarly, thermolysis of the thioarsine AsPh₂(SPh) with [Fe₂Cp₂(CO)₄] and [Mn₂(CO)₁₀] affords, respectively [Fe₂Cp₂(CO)₂(μ-AsPh₂)(μ-SPh)] (2) and [Mn₂(CO)₈(μ-AsPh₂)(μ-SPh)] (3). At room temperature, AsPh₂(SPh) reacts rapidly with [Co₂(CO)₈] to yield the trimetallic product, [Co₃(μ₃-S)(μ-AsPh₂)(CO) ₆AsPh₃] (4). The crystal structures of these four products have been determined by X-ray crystallography. Arsenic-sulfur bond cleavage is a feature of all these reactions; concomitant arsenic-carbon bond formation is observed in the production of complex 4.

Full text of DOI:10.1016/S0022-328X(99)00206-5

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 585 (1999) 141–149
Reactions of thioarsines with metal carbonyls: synthesis and
structural characterisation of [Fe2(CO)6(m-AsMe2)(m-SPh)],
[Fe2Cp2(CO)2(m-AsPh2)(m-SPh)], [Mn2(CO)8(m-AsPh2)(m-SPh)] and
[Co3(m3-S)(m-AsPh2)(CO)6AsPh3]
Gra´inne Conole a, John E. Davies b, Jason D. King b, Martin J. Mays b,*,
Mary McPartlin a, Harold R. Powell b, Paul R. Raithby b
a School of Applied Chemistry, Uni6ersity of North London, Holloway Rd., London N7 8DB, UK
b Department of Chemistry, Lensfield Rd., Cambridge CB2 1EW, UK
Received 24 February 1999; received in revised form 8 April 1999
Abstract
The thioarsine, AsMe2(SPh), reacts thermally with [Fe(CO)5] to give the new bimetallic butterfly complex, [Fe2(CO)6(m-
AsMe2)(m-SPh)] (1). Similarly, thermolysis of the thioarsine AsPh2(SPh) with [Fe2Cp2(CO)4] and [Mn2(CO)10] affords, respectively
[Fe2Cp2(CO)2(m-AsPh2)(m-SPh)] (2) and [Mn2(CO)8(m-AsPh2)(m-SPh)] (3). At room temperature, AsPh2(SPh) reacts rapidly with
[Co2(CO)8] to yield the trimetallic product, [Co3(m3-S)(m-AsPh2)(CO)6AsPh3] (4). The crystal structures of these four products have
been determined by X-ray crystallography. Arsenic–sulfur bond cleavage is a feature of all these reactions; concomitant
arsenic–carbon bond formation is observed in the production of complex 4. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Bimetallic complexes; Cobalt; Crystal structure; Iron; Manganese; Thioarsines
Co–Co edges [3]. Tetrahedrane products are also pro-
duced in the reactions of the related thiophosphine,
PPh2(StBu), with [Fe(CO)5] or with a mixture of
[Fe(CO)5] and [Co2(CO)8]; heterotrimetallic complexes
are generated in the latter reaction [4].
1. Introduction
A substantial amount of work has been carried out
on the scission of P–S bonds within the coordination
sphere of metal carbonyl complexes. Thus, thermolytic
reaction of the thiophosphine, PPh2(SPh) with
[Fe(CO)5] affords the di-iron complex, [Fe2(CO)6(m-
PPh2)(m-SPh)] [1,2] and, more recently, it has been
shown that [Mn2(CO)10] reacts with the same ligand at
150°C to yield a similar bimetallic product, [Mn2(m-
PPh2)(m-SPh)(CO)8] [3].
Rupture of the P–S bond is also a feature of the
reactions of a number of thiophosphines, PPh2(SR)
t
n
[R=Ph, Bu, Bu], with alkyne-bridged dicobalt hex-
acarbonyl complexes, and these reactions lead to a
variety of metallacyclic products containing sulfur or
phosphorus within the ring [4,5].
Although the metal-mediated breaking of As–S
bonds in inorganic molecules such as As4S4 has received
considerable attention [6], the cleavage of As–S bonds
in thioarsines remains relatively unexplored. In this
paper we report, for comparison with the work on P–S
bond cleavage in thiophosphines, the results of our
investigations into the reactions of the thioarsines
AsPh2(SPh) and AsMe2(SPh) with a variety of metal
carbonyl complexes.
The reaction of this thiophosphine with [Co2(CO)8]
does not lead to mixed-bridged dicobalt species but
instead a complex with a Co3S tetrahedrane core is
formed in which a PPh2 group bridges one of the
* Corresponding author. Fax: +44-1223-336362.
E-mail address: mjm14@cam.ac.uk (M.J. Mays)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00206-5

142
G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
Table 1b
2. Results and discussion
,
Selected bond lengths (A) and angles (°) for Fe2(CO)6(m-AsMe2)(m-
SPh) (1) molecule 2
2.1. Reaction of AsMe2(SPh) with [Fe(CO)5]
Fe(21)–Fe(22)
As(2)–Fe(21)
As(2)–Fe(22)
Fe(21)–S(2)
Fe(22)–S(2)
As(2)–C(21)
As(2)–C(22)
S(2)–C(29)
Fe(21)–C(23)
Fe(21)–C(24)
Fe(21)–C(25)
Fe(22)–C(26)
Fe(22)–C(27)
Fe(22)–C(28)
O(23)–C(23)
O(24)–C(24)
O(25)–C(25)
O(26)–C(26)
O(27)–C(27)
O(28)–C(28)
2.613(2)
As(2)–Fe(21)–Fe(22) 55.94(4)
2.3127(14)
2.3253(14)
2.259(2)
As(2)–Fe(22)–Fe(21)
S(2)–Fe(21)–Fe(22)
S(2)–Fe(22)–As(2)
S(2)–Fe(21)–As(2)
S(2)–Fe(22)–Fe(21)
Fe(21)–S(2)–Fe(22)
Fe(21)–As(2)–Fe(22)
C(29)–S(2)–Fe(21)
C(29)–S(2)–Fe(22)
C(21)–As(2)–C(22)
C(21)–As(2)–Fe(21)
C(22)–As(2)–Fe(21)
C(21)–As(2)–Fe(22)
C(22)–As(2)–Fe(22)
C(23)–Fe(21)–Fe(22)
55.49(4)
54.89(7)
76.56(7)
76.97(7)
54.59(7)
70.52(7)
68.57(5)
115.4(3)
116.5(3)
102.8(5)
119.8(4)
122.5(3)
120.6(3)
121.2(3)
97.4(3)
Reaction of AsMe2SPh with [Fe(CO)5] in refluxing
toluene gave orange crystalline [Fe2(CO)6(m-AsMe2)2]
(28%) and yellow crystalline [Fe2(CO)6(m-AsMe2)(m-
SPh)] (1) (36%). Complex 1 has been characterised by
IR, 1H- and 13C-NMR spectroscopy, mass spectrometry
and microanalysis. In addition, the complex has been
the subject of a single-crystal X-ray diffraction study.
[Fe2(CO)6(m-AsMe2)2] was identified by reference to
published data for this known compound [7].
2.267(3)
1.935(10)
1.936(10)
1.773(9)
1.799(9)
1.765(9)
1.791(10)
1.793(10)
1.772(11)
1.784(11)
1.121(10)
1.134(10)
1.136(10)
1.137(11)
1.149(12)
1.135(12)
The molecular structure of 1 is shown in Fig. 1.
Selected bond lengths and angles are presented in
C(24)–Fe(21)–Fe(22) 106.2(3)
C(25)–Fe(21)–Fe(22) 149.2(3)
C(26)–Fe(22)–Fe(21) 102.4(3)
C(27)–Fe(22)–Fe(21) 102.4(3)
C(28)–Fe(22)–Fe(21) 147.0(4)
Table 1c
,
Selected bond lengths (A) and angles (°) for Fe2(CO)6(m-AsMe2)(m-
SPh) (1) molecule 3
Fe(31)–Fe(32)
As(3)–Fe(31)
As(3)–Fe(32)
Fe(31)–S(3)
Fe(32)–S(3)
As(3)–C(31)
As(3)–C(32)
S(3)–C(39)
Fe(31)–C(33)
Fe(31)–C(34)
Fe(31)–C(35)
Fe(32)–C(36)
Fe(32)–C(37)
Fe(32)–C(38)
O(33)–C(33)
O(34)–C(34)
O(35)–C(35)
O(36)–C(36)
O(37)–C(37)
O(38)–C(38)
2.577(2)
2.330(2)
2.325(2)
2.257(2)
As(3)–Fe(31)–Fe(32) 56.29(4)
As(3)–Fe(32)–Fe(31)
S(3)–Fe(31)–Fe(32)
S(3)–Fe(32)–Fe(31)
S(3)–Fe(31)–As(3)
S(3)–Fe(32)–As(3)
Fe(31)–S(3)–Fe(32)
Fe(32)–As(3)–Fe(31)
C(39)–S(3)–Fe(31)
C(39)–S(3)–Fe(32)
C(32)–As(3)–C(31)
C(31)–As(3)–Fe(31)
C(32)–As(3)–Fe(31)
C(31)–As(3)–Fe(32)
C(32)–As(3)–Fe(32)
C(33)–Fe(31)–Fe(32)
56.48(4)
55.23(7)
55.17(6)
77.06(7)
77.14(7)
69.60(7)
67.23(5)
116.2(3)
115.7(3)
102.5(5)
121.3(4)
122.8(4)
118.9(4)
122.7(3)
97.9(3)
2.258(2)
1.938(10)
1.935(10)
1.780(8)
1.790(10)
1.758(11)
1.782(10)
1.807(10)
1.766(12)
1.781(12)
1.139(11)
1.152(12)
1.146(11)
1.130(11)
1.145(13)
1.139(13)
Fig. 1. Molecular structure of [Fe2(CO)6(m-AsMe2)(m-SPh)] (1) includ-
ing atom numbering scheme.
Table 1a
,
Selected bond lengths (A) and angles (°) for Fe2(CO)6(m-AsMe2)(m-
SPh) (1) molecule 1
Fe(11)–Fe(12)
As(1)–Fe(11)
As(1)–Fe(12)
Fe(11)–S(1)
Fe(12)–S(1)
As(1)–C(11)
As(1)–C(12)
S(1)–C(19)
Fe(11)–C(13)
Fe(11)–C(14)
Fe(11)–C(15)
Fe(12)–C(16)
Fe(12)–C(17)
Fe(12)–C(18)
O(13)–C(13)
O(14)–C(14)
O(15)–C(15)
O(16)–C(16)
O(17)–C(17)
O(18)–C(18)
2.599(2)
2.3065(14)
2.327(2)
2.266(2)
2.269(2)
1.932(10)
1.935(10)
1.784(9)
1.785(10)
1.757(10)
1.785(11)
1.793(10)
1.772(10)
1.780(10)
1.132(11)
1.134(12)
1.142(11)
1.129(11)
1.133(11)
1.143(11)
As(1)–Fe(11)–Fe(12) 56.26(4)
C(34)–Fe(31)–Fe(32) 102.7(4)
C(35)–Fe(31)–Fe(32) 149.6(3)
As(1)–Fe(12)–Fe(11)
S(1)–Fe(11)–Fe(12)
S(1)–Fe(12)–Fe(11)
S(1)–Fe(11)–As(1)
S(1)–Fe(12)–As(1)
Fe(11)–S(1)–Fe(12)
Fe(11)–As(1)–Fe(12)
C(19)–S(1)–Fe(11)
C(19)–S(1)–Fe(12)
C(11)–As(1)–C(12)
C(11)–As(1)–Fe(11)
C(12)–As(1)–Fe(11)
C(11)–As(1)–Fe(12)
C(12)–As(1)–Fe(12)
C(13)–Fe(11)–Fe(12)
55.51(4)
55.10(7)
54.97(6)
77.50(7)
77.01(7)
69.93(7)
68.23(5)
115.0(3)
116.1(3)
102.7(6)
122.7(4)
122.0(4)
117.9(4)
121.8(4)
94.6(3)
C(36)–Fe(32)–Fe(31)
99.8(3)
C(37)–Fe(32)–Fe(31) 100.4(4)
C(38)–Fe(32)–Fe(31) 147.4(4)
Tables 1a–c. The complex crystallizes with three
molecules in the asymmetric unit. No major differences
are noted in the overall geometries of these three
molecules. Bond lengths and angles for molecule 1 are
used in the following discussion.
The localized environment about each iron atom,
neglecting any metal–metal bonding, may be pictured
as a distorted tetragonal pyramid with a carbonyl lig-
and in the apical position and the square base com-
posed of the remaining two CO ligands and the
C(14)–Fe(11)–Fe(12) 108.6(4)
C(15)–Fe(11)–Fe(12) 147.4(3)
C(16)–Fe(12)–Fe(11) 105.1(3)
C(17)–Fe(12)–Fe(11)
99.4(3)

G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
143
Table 2
bridging arsenic and sulfur atoms. The iron atoms are
,
Selected bond lengths (A) and angles (°) for Fe2Cp2(CO)4(m-
AsPh2)(m-SPh) (2)
,
situated a mean distance of 0.37 A out of this basal
plane towards the apical carbonyl ligand.
The 18-electron rule requires the presence of a
metal–metal bond and inclusion of this interaction
produces a distorted octahedral arrangement about
each metal atom. Fig. 1 thus displays the molecule as
a ‘butterfly’ structure with the AsMe2 and SPh groups
at the wing-tips with an angle of 98.5° between the
Fe–Fe–As and Fe–Fe–S planes.
Fe(1)–As(1)
Fe(2)–As(1)
Fe(1)–S(1)
Fe(2)–S(1)
Fe(1)–Ccarbonyl 1.748(4)
Fe(2)–Ccarbonyl 1.754(4)
C(105)–O(105) 1.154(5)
C(205)–O(205) 1.149(5)
Fe(1)–CCp
As(1)–C(1)
As(1)–C(7)
S(1)–C(13)
2.3504(7)
2.3460(7)
2.2965(11)
2.2920(10)
S(1)–Fe(1)–As(1)
S(1)–Fe(2)–As(1)
Fe(2)–As(1)–Fe(1)
Fe(2)–S(1)–Fe(1)
C(105)–Fe(1)–S(1)
78.13(3)
78.32(3)
98.72(2)
101.91(4)
96.05(13)
C(105)–Fe(1)–As(1) 89.51(14)
C(205)–Fe(2)–S(1) 94.25(14)
C(205)–Fe(2)–As(1) 91.53(14)
2.080(4)–2.110(4) C(7)–As(1)–Fe(1) 116.59(12)
1.968(4)
1.959(4)
1.796(4)
,
The Fe–Fe distance of 2.599(2)A in 1 is shorter
C(7)–As(1)–Fe(2)
C(1)–As(1)–Fe(1)
C(1)–As(1)–Fe(2)
C(7)–As(1)–C(1)
C(13)–S(1)–Fe(2)
C(13)–S(1)–Fe(1)
115.02(12)
112.64(11)
114.62(11)
100.1(2)
111.52(12)
111.64(13)
than in [Fe2(CO)6(m-AsMe2)2] [8] (2.733(4) and
,
2.726(4) A) but longer than that in [Fe2(CO)6(m-SEt)2]
,
[9] (2.507(5) A) and very close to those found in the
i
,
complexes [Fe2(CO)6(m-AsPh2)(m-S Pr)] [10] (2.626 A)
and [Fe2(CO)6(m-StBu)(AsMe)]2 [11] (2.586(1) and
,
2.596(1) A), which are the only other reported species
containing an Fe2AsS butterfly core. The Fe–As
,
bond lengths (2.3065(14) and 2.327(2) A) are com-
1
The H-NMR spectrum of 1 at room temperature
exhibits, in addition to the phenyl resonances of the
SPh group, a sharp singlet at l 1.90, integrating to
three protons and a further singlet at l 1.52 of the
same intensity which may be assigned to the two
methyl groups attached to arsenic. The fact that they
are inequivalent on the NMR timescale at room tem-
perature implies that the butterfly structure for the
complex found in the crystal structure, in which the
Fe–S–Fe and Fe–As–Fe wings are non-coplanar, is
maintained in solution. The ‘wing-flapping’ fluxional
process identified by Vahrenkamp [8] for the symmet-
rically bridged complex, [Fe2(CO)6(m-AsMe2)2] at tem-
peratures greater than 70°C, which renders the two
methyl groups in this molecule equivalent, is not op-
erative for 1 at room temperature.
parable to those measured in a wide range of com-
plexes containing an arsenido-bridged Fe–Fe bond
,
(2.31–2.40 A) [8]. The Fe–S bond lengths of 2.266(2)
and 2.269(2) A are almost exactly that found in the
,
only other complex of this type with one arsenido
and one thiolato group, [Fe2(CO)6(m-AsPh2)(m-SiPr)]
,
[10] (2.264 A).
Fig. 2. Molecular structure of [Fe2Cp2(CO)2(m-AsPh2)(m-SPh)] (2)
including atom numbering scheme. Hydrogen atoms have been omit-
ted for clarity.
Fig. 3. Molecular structure of [Mn2(CO)8(m-AsPh2)(m-SPh)] (3) in-
cluding atom numbering scheme.

144
G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
The two different methyl groups are also apparent in
the 13C-NMR spectrum at room temperature, in which
signals at l 11.0 and 4.0 are observed. Phenyl resonances
due to the SPh group are also present, as is a single
carbonyl resonance at l 210.6. If an approximately
octahedral environment is assumed for the iron atom,
some fluxional process must occur to render the carbonyl
groups equivalent. This may be a dissociative site-ex-
change process or a non-dissociative reorientation of the
Fe(CO)3 groups.
Table 3
˚
Selected bond lengths (A) and angles (°) for Mn2(CO)8(m-AsPh2)(m-
SPh) (3)
Mn(1)–As(1)
Mn(2)–As(1)
Mn(1)–S(1)
Mn(2)–S(1)
As(1)–C
2.4642(8) S(1)–Mn(1)–As(1)
2.4674(7) S(1)–Mn(2)–As(1)
2.4132(10) Mn(2)–As(1)–Mn(1)
2.4164(10) Mn(2)–S(1)–Mn(1)
1.969(3), C(11A)–As(1)–Mn(1) 115.64(10)
1.970(3)
78.90(3)
78.77(3)
99.27(3)
102.16(4)
S(1)–C(11)
Mn–Caxial
1.791(3)
C(11A)–As(1)–Mn(2) 115.06(10)
1.854(4)–1.871(4) C(11B)–As(1)–Mn(1) 116.40(9)
Mn–Cequatorial 1.808(4)–1.843(4) C(11B)–As(1)–Mn(2) 113.87(10)
C(11A)–As(1)–C(11B) 97.62(13)
Fig. 6. Molecular structure of [Co3(m3-S)(m-AsPh2)(CO)6(AsPh3)] (4)
including atom numbering scheme. Hydrogen atoms have been omit-
ted for clarity.
C(11)–S(1)–Mn(1)
C(11)–S(1)–Mn(2)
117.52(13)
111.09(11)
Table 4
˚
Selected bond lengths (A) and angles (°) for Co3(m3-S)(m-
AsPh2)(CO)6(AsPh3) (4)
Co(1)–Co(2)
Co(1)–Co(3)
Co(2)–Co(3)
Co(1)–S(1)
Co(2)–S(1)
Co(3)–S(1)
Co(1)–As(1)
Co(2)–As(1)
Co(3)–As(2)
As–Cphenyl
2.526(2)
2.533(2)
2.585(2)
2.182(3)
2.176(3)
2.160(3)
2.296(2)
2.310(2)
2.333(2)
Co(1)–Co(2)–Co(3) 59.41(5)
Co(1)–Co(3)–Co(2) 59.13(5)
Co(2)–Co(1)–Co(3) 61.47(5)
S(1)–Co(1)–Co(2)
S(1)–Co(1)–Co(3)
S(1)–Co(2)–Co(1)
S(1)–Co(2)–Co(3)
S(1)–Co(3)–Co(1)
S(1)–Co(3)–Co(2)
Co(2)–S(1)–Co(1)
54.47(8)
53.91(8)
54.69(8)
53.11(8)
54.71(8)
53.68(8)
70.84(9)
73.20(9)
71.38(9)
1.933(9)–1.957(9)
Co–Ccarbonyl 1.751(12)–1.784(12) Co(3)–S(1)–Co(2)
C–Ocarbonyl 1.129(12)–1.172(12) Co(3)–S(1)–Co(1)
Fig. 4. Possible reaction mechanism for formation of complex 1.
As(1)–Co(1)–Co(2) 57.01(5)
As(1)–Co(2)–Co(1) 56.47(5)
Co(1)–As(1)–Co(2) 66.52(6)
S(1)–Co(1)–As(1)
S(1)–Co(2)–As(1)
S(1)–Co(3)–As(2)
93.52(9)
93.29(9)
99.98(9)
2.2. Reaction of AsPh2(SPh) with [FeCp(CO)2]2
Co-thermolysis of equimolar amounts of AsPh2SPh
and [FeCp(CO)2]2 in refluxing toluene for 4 h produced,
in addition to two faint orange bands which were not
collected, the green product, [Fe2Cp2(CO)2(m-AsPh2)(m-
SPh)] (2) in 27% yield. Complex 2 has been characterised
Fig. 5. Possible reaction mechanism for formation of complexes 2
[MLn=FeCp(CO)] and 3 [MLn=Mn(CO)4].

G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
145
by IR, 1H- and 13C-NMR spectroscopy, mass spec-
trometry and microanalysis. In addition, the complex
has been the subject of a single crystal X-ray diffraction
study.
Fe-carbonyl vectors are approximately perpendicular to
the metal–metal axis.
2.3. Reaction of AsPh2(SPh) with [Mn2(CO)10]
The molecular structure of 2 is shown in Fig. 2.
Selected bond lengths and angles are presented in Table
2. The complex crystallizes with one molecule of
dichloromethane in the lattice per two molecules of 2.
This solvent molecule is disordered over two possible
sites as displayed in the Figure.
Co-thermolysis of [Mn2(CO)10] and one equivalent of
AsPh2(SPh) in toluene, heated with stirring in an auto-
clave at 140°C for 12 h gave a small amount of
unreacted [Mn2(CO)10] and yellow [Mn2(CO)8(m-
AsPh2)(m-SPh)] (3) in 44% yield. Complex 3 has been
1
The two iron atoms in 2 are bridged by a AsPh2
ligand and by a SPh ligand. In addition, each iron is
ligated by one carbonyl group and a cyclopentadienyl
ligand. Since the bridging ligands, the cyclopentadienyl
rings and the carbonyl act as three-, five- and two-elec-
tron donors, respectively, each iron atom has 18 elec-
trons and so a metal–metal bond would not be
characterised by IR, H- and 13C-NMR spectroscopy,
mass spectrometry and microanalysis and by a single
crystal X-ray diffraction study.
The molecular structure of 3 is shown in Fig. 3.
Selected bond lengths and angles are presented in Table
3. The two manganese atoms in this complex are
bridged by one AsPh2 group and one SPh ligand. In
addition, each metal centre is ligated by four carbonyl
groups, two located axially and two equatorially. This
completes an approximately octahedral arrangement
about each manganese atom. No metal–metal bond is
predicted by application of the eighteen-electron rule
˚
expected. The Fe···Fe distance of 3.564 A suggests that
this is the case and that the two metal centres are held
together by virtue of the bridging ligands only.
The central Fe2AsS unit adopts a ‘butterfly’ structure
with the As and S atoms in the wing-tip positions.
However, the angle between the Fe–As–Fe and Fe–S–
Fe planes at 163.4° means that there is a maximum
˚
and the long Mn···Mn separation of 3.758 A is incon-
sistent with a bonding interaction between the two
metal centres.
˚
deviation from planarity of only 0.13 A. The arsenido
and thiolato groups are displaced onto the same side of
the molecule as the cyclopentadienyl rings and the
While the As–Mn–S angles of 78.90(3) and 78.77(3)°
are marginally smaller than the P–Mn–S angles found
Fig. 7. Possible reaction mechanism for formation of complex 4: (i) +AsPh2(SPh), −2CO; (ii) +Co2(CO)8, −PhCo(CO)4; (iii)−3CO; (iv)
AsPh3.

146
G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
Table 5
X-ray crystallographic and data processing parameters for complexes 1, 2, 3 and 4
Complex
1
2
3
4
Instrument
u (A)
Rigaku Raxis-IIc
0.71069
Rigaku AFC5R
0.71069
Siemens P4
0.71073
Rigaku AFC5R
0.71069
˚
Formula
M
C
493.91
14H11AsFe2O6S
C30H25AsFe2O2S·0.5 CH2Cl2
678.64
C26H15AsMn2O8S
762.24
C36H25As2Co3O6S
912.25
Colour and habit of crystal
Crystal size (mm)
Crystal system
Space group
Orange prism
0.36×0.22×0.20
Monoclinic
P21/c
Dark green prism
0.42×0.25×0.25
Triclinic
Yellow prism
0.48×0.36×0.32
Triclinic
Red–brown prism
0.30×0.15×0.10
Triclinic
(
(
(
P1
P1
P1
Unit cell dimensions
˚
a (A)
13.856(2)
22.189(2)
18.261(3)
10.214(2)
11.125(2)
14.632(2)
96.840(10)
100.360(10)
116.340(10)
1427.9(4)
9.7748(18)
11.460(2)
11.640(2)
18.370(3)
9.426(2)
101.13(2)
110.03(2)
72.710(10)
1798.7(6)
2
˚
b (A)
˚
c (A)
13.6233(18)
92.562(14)
98.148(14)
114.834(13)
1361.7(4)
h (°)
i (°)
k (°)
94.98(2)
3
˚
V (A )
5593.2(13)
12
3.453
1.45–25.28
−16516, −26526,
−21521
Z
2
2
v(Mo–Ka) (mm−1
q-range (°)
)
2.359
2.256
3.294
2.10–25.00
−12510, 0513,
−17517
1.26–22.00
−1518, −1519,
−20519
2.52–22.50
0512, −18519,
−1059
Limiting hkl indices
Reflections collected
Independent reflections
Data/restraints/parameters
S on F2
27335
9584
9584/0/649
1.489
R1=0.0831,
wR2=0.1484
R1=0.0942,
wR2=0.1586
0.0324 and 16.5869
0.394 and −0.487
5311
5030
5007/43/371
1.071
R1=0.0370,
wR2=0.0914
R1=0.0664,
wR2=0.1660
0.0474 and 0.6058
0.468 and −0.661
8960
7420
7420/102/541
0.980
R1=0.0341,
wR2=0.0879
R1=0.0472,
wR2=0.0934
0.0574 and 0.1902
0.534 and −0.419
4969
4692
4676/0/433
1.046
R1=0.0478,
wR2=0.0991
R1=0.1557,
wR2=0.2182
0.0334 and 0.5534
0.525 and −0.513
Final R indices a [I\2|(I)]
R indices (all data)
a
Weights a, b
Largest difference peak and hole
−3
˚
(eA
)
a S=[ꢀ w(F2o−Fc2)2/(n−p)]V where n is number of reflections and p is the total number of parameters, R1=ꢀ ꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀ ꢁFoꢁ, wR2=
ꢀ [w(F2o−F2c)2]/ꢀ [w(F2o)2]V, w−1=[|2(Fo)2+(aP)2+bP], P=[max(Fo2, 0)+2(F2c)]/3.
explained in terms of the trans influence of the bridging
in the analogous ‘butterfly’ complex, [Mn2(CO)8(m-
PPh2)(m-SPh)] [3] (79.0(1) and 79.0(1)°), the Mn–S–Mn
angle is slightly larger for 3 than for the analogue
(102.16(4)° 3 vs. 100.2(1)°).
ligands.
1
The H-NMR spectrum of 3, as expected, contains
resonances corresponding to phenyl protons only and
phenyl carbon resonances are also observed in the 13C
spectrum. In the case of complex 3 there are clearly two
sets of four-line signals, one with the ipso-carbon at l
140.1 and the other with the ipso-carbon at l 137.7.
The ratio of intensities is approximately 1:2.
The first of these signals is assigned to the phenyl
ring attached to sulfur and the second to the two rings
bound to arsenic. Since the two rings attached to
arsenic appear to be in the same chemical environment,
the RS group must be fluxional. In addition, the
Mn2AsS framework must be planar or if, in solution,
the molecule retains the solid-state butterfly structure
where the Mn–As–Mn and Mn–S–Mn ‘wings’ are
non-coplanar, a fluxional, ‘wing-flapping’ process must
be operative in solution, which would also render the
two phenyl groups on arsenic equivalent.
There are slight changes in the other geometric
parameters of the core which must be attributable to
the substitution of phosphorus for arsenic. To accom-
modate the larger arsenic atom, the manganese atoms
˚
move further apart (Mn···Mn: 3.678 A in [Mn2(CO)8(m-
˚
PPh2)(m-SPh)], 3.758 A in 3) but since the Mn–As
bonds are significantly longer than the Mn–P bonds
˚
˚
(2.4642(8) and 2.4674(7) A vs. 2.401(2) and 2.393(2) A)
the Mn–As–Mn angle becomes 99.27(3)°, which is
slightly smaller than the Mn–P–Mn angle in
[Mn2(CO)8(m-PPh2)(m-SPh)] (100.4(1)°).
The Mn–C bonds to the carbonyls cis to the bridging
groups are significantly longer than those to the trans
˚
carbonyls [M–Cax: 1.854(4)–1.871(4) A; M–Ceq:
˚
1.808(4)–1.843(4) A], an observation most reasonably

G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
147
˚
Similar conclusions can be reached by an analysis of
the carbonyl region of the 13C-NMR spectrum. A signal
at l 217.6 is assigned to the four carbonyls cis to the
bridging ligands. Two further signals at l 214.9 and
211.4 are of equal intensity and each of approximately
half the intensity of the first signal. These two signals
are ascribed to the four carbonyls trans to the bridging
ligands. Two of these carbonyl groups project onto the
same side of the molecule as the AsPh2 group while the
other two carbonyls are directed towards the SPh
moiety.
The Co(1)–Co(2) bond at 2.526(1) A is the shortest
of the three Co–Co bonds, presumably due to the
constraints of the arsenido bridge, although it is longer
than the corresponding bond in the phosphorus ana-
˚
logue (2.496(2) A) since arsenic has a larger covalent
radius. The triphenylarsine molecule is ligated equatori-
ally, which places it on the same side of the complex as
Co(2) and thus renders Co(1) and Co(2) inequivalent.
This provides some explanation for the disparity in the
lengths of the remaining metal–metal bonds [Co(1)–
˚
˚
Co(3) 2.533(2) A and Co(2)–Co(3) 2.585(2) A] and also
for the inequality of the Co–As(1) bond lengths
˚
2.4. Mechanism of bimetallic product formation
(2.296(2) and 2.310(2) A).
In the 13C-NMR spectrum of 4, two equal intensity
phenyl signals are observed with ipso-carbons located
at l 143.8 and 142.8. A more intense phenyl signal with
an ipso-carbon resonance at l 136.2 is assigned to the
three equivalent phenyl rings of the AsPh3 ligand. The
other two signals are due to the phenyl groups of the
bridging m-AsPh2 unit. Since one ring projects onto the
same side of the cluster as the apical sulfur, and the
other is located on the opposite side of the molecule,
the two rings occupy dissimilar environments which
accounts for the two distinct groups of signals.
The reaction of AsPh2(SPh) with [Co2(CO)8] parallels
that of the thiophosphine, PPh2(SPh) with [Co2(CO)8].
Given the temperature at which the reaction occurs and
the ease with which [Co2(CO)8] fragments to give
Co(CO)4, it is reasonable to suggest a mechanism in-
volving radicals. One possibility, shown in Fig. 7, is
based on that proposed by Solan for the thiophosphine
reaction [3]. The initial formation of a mixed-bridged
dicobalt complex is reasonable, since analogous com-
plexes can be synthesized from other dimeric metal
carbonyls and AsPh2(SPh) (see 2 and 3). This is fol-
lowed by loss of the phenyl group from sulfur and
concomitant S–Co bond formation. Cleavage of an
S–C bond also takes place, for example, in the genera-
tion of the related species, [Co3(m3-S)(CO)9] from
[Co2(CO)8] and PhSH [13]. Metal–metal bond forma-
tion could then occur with loss of carbon monoxide to
give [Co3(m3-S)(m-AsPh2)(CO)7]. The phosphido ana-
logue of this complex was isolated in the reaction of
PPh2(SPh) and [Co2(CO)8] but with AsPh2(SPh), the
reaction proceeds further to give the AsPh3 derivative
only.
Reaction of the thioarsines, AsR2(SPh) [R=Me, Ph]
with the metal carbonyl complexes [Fe(CO)5], [FeCp-
(CO)2]2 and [Mn2(CO)10] most likely proceeds via a
dinuclear intermediate with a four-electron donor
bridging AsR2–SR ligand (Figs. 4 and 5), obtained by
substitution of a carbonyl ligand from each metal cen-
tre. In the reaction of [Co2(m-RCCR)(CO)6] with P2Ph4
similar dinuclear species have been isolated as stable
products [12]. Subsequent cleavage of the As–S bond
would generate one thiolato and one arsenido ligand. If
these groups adopt bridging modes, they both act as
three electron donors. The extra two electrons donated
to the metals require rupture of the M–M bond in
order to maintain adherence to the effective atomic
number rule; thus complexes 2 and 3 are generated. In
the case of complex 1, however, there is no Fe–Fe
bond to break. To maintain an electron count of eigh-
teen at both iron centres, an Fe–Fe bond forms with
concomitant loss of one carbonyl group from each
metal atom.
2.5. Reaction of [Co2(CO)8] with AsPh2(SPh)
Stirring [Co2(CO)8] with one equivalent of AsPh2
(SPh) in dichloromethane at room temperature for 20
h. gave red–brown [Co3(m3-S)(CO)6(m-AsPh2)(AsPh3)] 4
in 49% yield. Complex 4 has been characterised by IR,
1H- and 13C-NMR spectroscopy, mass spectrometry
and microanalysis and by a single crystal X-ray diffrac-
tion study.
The molecular structure of 4 is shown in Fig. 6. Sel-
ected bond lengths and angles are collected in Table 4.
The molecule is constructed around a distorted tetrahe-
dral core, containing three cobalt atoms and an apical
sulfur. A diphenylarsenido group bridges Co(1) and
Co(2), coordinating these atoms pseudo-equatorially.
Each cobalt is further ligated by two carbonyl ligands,
one located equatorially and the other at the axial site.
The remaining equatorial position on Co(3) is occupied
by a triphenylarsine molecule. The structure adopted
resembles that of the phosphorus-containing analogue
of complex 4, [Co3(m3-S)(m-PPh2)(CO)6(PPh3)] [3].
3. Conclusions
On reaction with the metal carbonyl complex
[Fe(CO)5], the As–S bond of the thioarsine
AsMe2(SPh) is readily cleaved with both fragments of
the cleaved ligand being retained as bridging groups
within the di-iron product. The same process occ-
urs when the thioarsine AsPh2(SPh) reacts with

148
G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
[FeCp(CO)2]2, [Mn2(CO)10] or [Co2(CO)8], although in
the last case, S–C bond cleavage also occurs and a
trimetallic product result. From these studies it ap-
pears that the reactivity of the thioarsines parallels
that of the more extensively studied thiophosphine
analogues.
AsMe2)(SPh)] (1) (109 mg, 36%). Crystals of 1 suit-
able for X-ray diffraction were grown by slow
evaporation of an n-hexane solution of the complex
at −18°C. Complex 1 (found: C, 34.05%; H, 2.20%.
C14H11AsFe2O6S. Requires: C, 34.05%; H, 2.24%).
Mass spectrum m/e 494 (M+): M+ −n(CO) (n=1–
6). IR (wmax cm−1 hexane): 2061m, 2039w, 2023vs,
1993s, 1978s. 1H-NMR (CDCl3): l 7.4–7.1 (m, 5H,
Ph), l 1.90 (s, 3H, Me), l 1.52 (s, 3H, Me). 13C-
NMR: l 210.6 (CO), l 139.9–127.5 (Ph), l 11.0 (s,
Me), l 4.0 (s, Me).
4. Experimental
All reactions were carried out under an atmosphere
of dry, oxygen-free nitrogen, using solvents which
were freshly distilled from the appropriate drying
agent.
4.2. Reaction of AsPh2(SPh) with [FeCp(CO)2]2
Infrared spectra were recorded in n-hexane or
CH2Cl2 solution in 0.5 mm NaCl cells, using a
Perkin–Elmer Paragon 1000 Fourier-Transform spec-
trometer or a Perkin–Elmer 1600 series spectrometer.
Fast atom bombardment mass spectra were obtained
on a Kratos MS890 instrument. Fast ion bombard-
ment mass spectra were obtained on a Kratos MS50
instrument. Nitrobenzyl alcohol was used as a matrix.
1H- and 13C-NMR spectra were recorded on
Bruker AM400 or WM250 spectrometers using the
solvent resonance as an internal standard. Micro-
analyses were performed by the Microanalytical De-
partment of the University of Cambridge.
Preparative thin-layer chromatography was carried
out on 1 mm plates prepared at the University Chem-
ical Laboratory, Cambridge. Column chromatography
was performed on Kieselgel 60 (70–230 mesh). The
products are given in order of decreasing Rf values.
All reagents were obtained from commercial suppliers
and used without further purification.
AsPh2(SPh) (477 mg, 1.41 mmol) and [FeCp(CO)2]2
(500 mg, 1.41 mmol) were refluxed in 50 ml toluene
for 4 h. After removal of the reaction solvent, the
residue was redissolved in the minimum amount of
dichloromethane and applied to the base of silica
TLC plates. Elution with hexane/ethyl acetate (9:1)
gave two faint orange bands which were not collected
and
green–brown
crystalline
[Fe2Cp2(CO)2(m-
AsPh2)(m-SPh)] (2) (240 mg, 27%). Crystals suitable
for diffraction were grown by slow evaporation from
a solution of CH2Cl2/n-hexane at 0°C. Complex 2
(Found: C, 56.32%; H, 3.83%. C30H25AsFe2O2S. Re-
quires: C, 56.64%; H, 3.96%). Mass spectrum m/e 636
(M+):
M
+ −n(CO) (n=1–2). IR (wmax cm−1
CH2Cl2): 1954s. 1H-NMR (CDCl3): l 7.7–7.0 (m,
15H, Ph), l 4.34 (s, 10H, Cp). 13C-NMR: l 223.6 (s,
CO), l 140.0–124.5 (Ph), d78.8 (s, Cp).
4.3. Reaction of AsPh2(SPh) with [Mn2(CO)10]
The reaction of AsR2Cl with NaSPh was employed
to prepare AsR2(SPh) (R=Me, Ph). The procedure
was based on the literature preparation of
AsPh2[S(C5H11)] [14] but the sodium mercaptide was
generated using sodium hydride rather than sodium
metal. AsMe2Cl [15,16] was prepared by reduction of
cacodylic acid. The oxide, (AsPh2)2O [17,18], was syn-
thesised by reaction of PhMgBr and As2O3. Treat-
ment of this oxide with HCl generated AsPh2Cl
[18,19].
AsPh2(SPh) (426 mg, 1.26 mmol) and [Mn2(CO)10]
(500 mg, 1.26 mmol) were dissolved in 50 ml toluene
and heated with stirring in an autoclave at 140°C for
12 h. After removal of reaction solvents under vac-
uum, the residue was dissolved in a minimum quan-
tity of dichloromethane and adsorbed onto silica. The
silica was pumped dry and transferred to the top of a
silica chromatography column. Elution with 6:4 hex-
ane–CH2Cl2 gave
a small amount of unreacted
[Mn2(CO)10] and yellow [Mn2(CO)8(m-AsPh2)(m-SPh)]
(3) (373 mg, 44%). Crystals of 3 suitable for X-ray
diffraction were grown by slow evaporation at 0°C of
an n-hexane–CH2Cl2 solution of the complex. Com-
4.1. Reaction of AsMe2SPh with [Fe(CO)5]
AsMe2SPh (263 mg, 1.23 mmol) and [Fe(CO)5] (241
mg, 1.23 mmol) were refluxed in 50 ml toluene. After
removal of reaction solvents under vacuum, the
residue was dissolved in a minimum quantity of
CH2Cl2 and adsorbed onto silica. The silica was
pumped dry and transferred to the top of a silica
chromatography column. Elution with 19:1 hexane–
acetone gave orange crystalline [Fe2(CO)6(m-AsMe2)2]
(84 mg, 28%) and yellow crystalline [Fe2(CO)6(m-
plex
3
(Found:
C,
46.34%;
H,
2.19%.
C26H15AsMn2O8S. Requires: C, 46.45%; H, 2.25%).
Mass spectrum m/e 672 (M+): M+ −n(CO) (n=1–
4,8). IR (nmax cm−1 CH2Cl2): 2063m, 2006s, 1958m.
1H-NMR (CDCl3): l 7.7–7.2 (m, 15H, Ph). 13C-
NMR: l 217.6 (s, 4CO), l 214.9 (s, 2CO), l 211.4 (s,
2CO), l 140.1–126.8 (Ph).

G. Conole et al. / Journal of Organometallic Chemistry 585 (1999) 141–149
149
Acknowledgements
4.4. Reaction of AsPh2(SPh) with [Co2(CO)8]
We thank the Defence Research Agency (Fort Hal-
stead) for financial support to J.D.K and the EPSRC and
the Cambridge Crystallographic Data Centre for support
to J.E.D.
[Co2(CO)8] (500 mg, 1.46 mmol) and AsPh2(SPh) (493
mg, 1.46 mmol) were dissolved in 100 ml
dichloromethane and stirred for 20 h. After removal of
reaction solvents under vacuum, the residue was dis-
solved in a minimum quantity of CH2Cl2 and adsorbed
onto silica. The silica was pumped dry and transferred
to the top of a silica chromatography column. Elution
with 7:3 hexane–CH2Cl2 gave green [Co3(m3-S)(CO)6(m-
AsPh2)(AsPh3)] (4) (435 mg, 49%). Crystals suitable for
X-ray diffraction were grown by slow evaporation at 0°C
of a CH2Cl2–n-hexane solution of 4. Complex 4 (Found:
C, 47.06%; H, 2.63%. C36H25As2Co3O6S. Requires: C,
47.40%; H, 2.76%). Mass spectrum m/e 912 (M+):
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4.5. X-ray crystal structure determinations
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5. Supplementary material
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be obtained free of charge from The Director, CCDC,
12 Union Road, Cambridge CB2 1EZ (Fax: +44-1223-
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.