The transition metal carbonyl complexes of 1,3-bis(di-R-stibino)propanes (R = Me or Ph)

Article abstract of DOI:10.1016/j.jorganchem.2004.12.020

The synthesis and characterisation of complexes of two distibinopropanes R₂Sb(CH₂)₃SbR₂ (R = Me or Ph) with a variety of metal carbonyls is described. These include cis-[M(CO) ₄{R₂Sb(CH₂)₃SbR₂}] (M = Cr, Mo or W), [{Fe(CO)₄}₂{μ-R₂Sb(CH ₂)₃SbR₂}], [{Ni(CO)₃} ₂{μ-R₂Sb(CH₂)₃SbR₂}], [Co₂(CO)₆{Ph₂Sb(CH₂) ₃SbPh₂}], [Co₂(CO)₄{Me ₂Sb(CH₂)₃SbMe₂}₃][Co(CO) ₄]₂ and [Mn₂(CO)₈{Ph ₂Sb(CH₂)₃SbPh₂}]. The complexes have been characterised by analysis, mass spectrometry, IR and multinuclear NMR spectroscopy as appropriate. Comparison of the spectroscopic data on these complexes with those of other stibine complexes and with complexes of Group 16 ligands has been used to establish the relative electronic properties of the distibines.

Full text of DOI:10.1016/j.jorganchem.2004.12.020

Journal of Organometallic Chemistry 690 (2005) 1540–1548
www.elsevier.com/locate/jorganchem
The transition metal carbonyl complexes of
1,3-bis(di-R-stibino)propanes (R = Me or Ph)
Michael D. Brown, William Levason*, Joanna M. Manning, Gillian Reid
School of Chemistry, University of Southampton, Southampton SO17 1BJ, UK
Received 14 October 2004; accepted 10 December 2004
Abstract
The synthesis and characterisation of complexes of two distibinopropanes R2Sb(CH2)3SbR2 (R = Me or Ph) with a variety of metal
carbonyls is described. These include cis-[M(CO)4{R2Sb(CH2)3SbR2}] (M = Cr, Mo or W), [{Fe(CO)4}2{l-R2Sb(CH2)3SbR2}],
[{Ni(CO)3}2{l-R2Sb(CH2)3SbR2}], [Co2(CO)6{Ph2Sb(CH2)3SbPh2}], [Co2(CO)4{Me2Sb(CH2)3SbMe2}3][Co(CO)4]2 and [Mn2(CO)8-
{Ph2Sb(CH2)3SbPh2}]. The complexes have been characterised by analysis, mass spectrometry, IR and multinuclear NMR spectros-
copy as appropriate. Comparison of the spectroscopic data on these complexes with those of other stibine complexes and with
complexes of Group 16 ligands has been used to establish the relative electronic properties of the distibines.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Chromium; Molybdenum; Tungsten; Iron; Manganese; Nickel; Carbonyls; Stibines
1. Introduction
(CO)6(Ph2Sb- CH2SbPh2)] [5–7]. The Me2SbCH2SbMe2
is generally similar, although few g1-coordinated exam-
ples are known, probably due to the air sensitivity of the
‘‘free’’ Me2Sb-group [5,6]. Notably, neither ligand ap-
peared to chelate with metal carbonyl centres, although
rare examples of chelation (4-membered chelate rings)
were produced in ruthenium and rhodium halides [8].
The 1,3- and 1,4-bis(dimethylstibanylmethyl)benzene
behave as either monodentate or bridging bidentate li-
gands towards tungsten, nickel or iron carbonyl moieties
[9]. The 1,2-bis(dimethylstibanylmethyl)benzene gave
the chelated dicarbonyl species [Ni(CO)2{o-C6H4-
(CH2SbMe2)2}] and [M(CO)4{o-C6H4(CH2SbMe2)2}]
(M = Mo or W), whilst bridging bidentate behaviour
was found in [{Fe(CO)4}2{o-C6H4(CH2SbMe2)2}] [9].
A few Group 6 metal carbonyl complexes of
o-C6H4(SbMe2)2 [10] and Ph2Sb(CH2)3SbPh2 [11] were
reported in the early 1970s, but with little data. We have
now carried out systematic studies of the complexes of
the two distibinopropanes R2Sb(CH2)3SbR2 (R =
Me or Ph) with chromium, molybdenum, tungsten,
Although the first examples of ligands containing two
antimony donors were reported over 30 years ago [1–4]
studies of their coordination chemistry remain few, a
remarkable fact given the many hundreds of papers
dealing with bi- and polydentate phosphorus and ar-
senic ligands. We have recently carried out detailed stud-
ies of the metal carbonyl chemistry of two types of
distibine: the distibinomethanes (R2SbCH2SbR2,
R = Me or Ph) and three xylyl-backboned ligands 1,2-,
1,3-, and 1,4-bis(dimethylstibanylmethyl)benzene (1,2-,
1,3- or 1,4-C6H4(CH2SbMe2)2). The Ph2SbCH2SbPh2
ligand exhibits a variety of coordination modes with
substituted metal carbonyls – monodentate as in
[Fe(CO)4(Ph2SbCH2SbPh2)], bridging bidentate in
[(CO)5W(Ph2SbCH2SbPh2)W(CO)5] or [(CO)4W(Ph2-
SbCH2SbPh2)2W(CO)4], and bridging across M–M
bonds as in [Mn2(CO)6(Ph2SbCH2SbPh2)2] or [Co2-
*
Corresponding author.
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.12.020

M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
1541
CO
R2
Sb
OC
OC
M = Cr, Mo, W
M
Sb
R2
CO
Sb
Ni
SbR2
Ni
R2
i
CO
OC CO OC
CO
ii
CO
vi
Sb
CO
Mn
CO
R2
CO
Sb
R2
SbR2
SbR2
CO
iii
OC Mn
OC
CO
OC
Sb
SbR2
R2
OC
OC
OC
Fe CO
CO
Fe CO
CO
iv
v
OC
2+
CO
CO
R2
Sb
R2
Sb
Sb
R2
Sb Co
R2
Co Sb
R2
Sb
R2
R2Sb
Co
SbR2
Co
[Co(CO)4]2
CO
OC
CO
OC
CO OC
Sb
R2
Sb
R2
CO
CO
R = Me
R = Ph
Reagents: i. [M(CO)4(nbd)] in EtOH, M = Cr, Mo or [W(CO)4(piperidine)2] in EtOH; ii. Ni(CO)4 in CH2Cl2;
iii. Fe2(CO)9 in thf; iv. and v. Co2(CO)8 in toluene; vi. Mn2(CO)10 in toluene with [CpFe(CO)2]2
Scheme 1. Syntheses of the distibinopropane complexes.
manganese, iron, cobalt and nickel carbonyls, and
report our results below (see Scheme 1).
of carbon monoxide in the M(CO)6 by the distibine,
catalysed by NaBH4 was a less satisfactory route,
although one example ([Cr(CO)4{Ph2Sb(CH2)3SbPh2}])
made in this way is described in the Experimental Sec-
tion. The solid tetracarbonyl complexes are air-stable,
but the solutions in chlorocarbons are more sensitive,
and should be manipulated under dinitrogen. The com-
plexes of Me2Sb(CH2)3SbMe2 were poorly soluble in
CH2Cl2 although they dissolve easily in dimethylsulfox-
ide, and the latter was used as a solvent for 13C{1H}
NMR studies. The formulation of the complexes as
cis-[M(CO)4(distibine)] follows from their IR spectra
which show three or four carbonyl stretches (theory
2A1 + B1 + B2). The 13C{1H} NMR spectra show two
d(CO) resonances of equal intensity in each complex
and, in the case of tungsten, weak satellites due to
1J(183W–13C) couplings, the magnitude of the coupling
trans to Sb (165 Hz) placing the stibines low in the trans
influence series [13], reflecting the weak r-donation by
the antimony.
2. Results and discussion
The Ph2Sb(CH2)3SbPh2 was obtained by the litera-
ture route [3] from NaSbPh2 and Br(CH2)3Br in liquid
ammonia. The methyl analogue was made similarly
from NaSbMe2 [4,12], although this was generated in
situ by a modified procedure in liquid NH3 from the
air stable Me3SbBr2 and 4 equivalents of Na, rather
than from very reactive Me2SbBr. Ph2Sb(CH2)3SbPh2
is an air-stable white solid, whereas the methyl analogue
is a very air-sensitive colourless oil. The ligands were
1
identified by comparison of their H NMR spectra with
literature data [3,4]. The 13C{1H} NMR spectra are also
characteristic, exhibiting the usual [5] low frequency res-
onances for C–Sb units.
2.1. Group 6 complexes
2.2. Iron complexes
The displacement of the olefin or amine from
[M(CO)4(norbornadiene)] (M = Cr or Mo) or
[W(CO)4(piperidine)2] by the appropriate distibine gave
[M(CO)4(distibine)] in modest yield. Direct substitution
Both ligands react with 2 equivalents of Fe2(CO)9 in
thf solution to give, after removal of the solvent and the
Fe(CO)5 by-product, red oils identified spectroscopically

1542
M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
as [(CO)4Fe(l-distibine)Fe(CO)4], containing axially
substituted trigonal bipyramidal iron centres [5,9,14].
The 13C{1H} NMR spectra show single (CO) resonances
attributable to fluxionality of the carbonyl groups as is
usually seen [9]. For an axially substituted tbp geometry
three IR active CO stretches are expected (2A1 + E)
and three were observed for [{Fe(CO)4}2{Ph2Sb-
(CH2)3SbPh2}] both in a Nujol mull and CH2Cl2 solu-
tion. However, for [{Fe(CO)4}2{Me2Sb(CH2)3SbMe2}]
whilst three bands were seen in CH2Cl2, in the mull spec-
trum a distinct shoulder was present on the lowest band,
indicating some lowering of symmetry. Similar effects
have been reported in some iron carbonyl diphosphine
complexes [14]. The reaction of Fe2(CO)9 in thf with
Ph2Sb(CH2)3SbPh2 in a 1:1 mol ratio also gave a
red oil in which the major species was identified as
[{Fe(CO)4}{g1–Ph2Sb(CH2)3SbPh2}]. The IR vibrations
and 13C{1H} NMR of the carbonyl groups in this com-
plex are not significantly different from those in the 2:1
complex, as expected since the trimethylene chain elec-
tronically isolates the two antimony centres. However,
the formulation as [{Fe(CO)4}{g1-Ph2Sb(CH2)3-
SbPh2}] follows from the three major CH2 resonances
in the NMR spectra. Weak features in the same region
are attributable to some [{Fe(CO)4}2{Ph2Sb(CH2)3-
SbPh2}] by comparison with the spectra of the complex
discussed above. Displacement of a second carbonyl group
from iron to give [Fe(CO)3(distibine)] is not expected
under such mild conditions [14] and was not observed.
significantly decomposing in a few hours at ambient
temperatures with deposition of black solids. Despite
this instability the spectroscopic data required to corre-
late the electronic properties of these ligands with other
stibines are readily extracted (Table 1). The reaction of
excess Ni(CO)4 with Me2Sb(CH2)3SbMe2 in CH2Cl2
proceeded rapidly at room temperature with visible evo-
lution of CO to form [(CO)3Ni{l-Me2Sb(CH2)3SbMe2}-
Ni(CO)3] as the only product, which was isolated as a
colourless wax on removal of the excess tetracarbonyl-
nickel and the solvent in vacuo. The formulation as a tri-
carbonyl dimer follows from the characteristic 13C{1H}
NMR d(CO) value and two IR active carbonyl stretches
(theory A1 + E). The presence of one d(Me) and two
d(CH2) resonances in the 1H and 13C{1H} NMR spectra
confirm bidentate coordination of the distibine. If
the reaction is repeated using a deficit of Ni(CO)4, the
product is a mixture of a tricarbonyl and a dicarbonyl
complex (see Section 3). However, none of the frequen-
cies of the three Me and five CH2 resonances observed in
the NMR spectra of the mixture match with those of
[(CO)3Ni{Me2Sb(CH2)3SbMe2}Ni(CO)3] or with free
Me2Sb(CH2)3SbMe2. Hence we formulate the tricar-
bonyl as [(CO)3Ni{g1-Me2Sb(CH2)3SbMe2}], and the
dicarbonyl as [Ni(CO)2{Me2Sb(CH2)3SbMe2}], the lat-
ter containing chelating distibine. Several attempts to
convert the products completely to the dicarbonyl either
by prolonged stirring or heating of the reaction mixture
failed, only decomposition occurred. In the case of
Ph2Sb(CH2)3SbPh2 the reaction with excess Ni(CO)4 in
CH2Cl2 solution was much slower, and after several
hours in situ IR studies showed a mixture of a tricar-
bonyl, a dicarbonyl and unchanged tetracarbonylnickel
present. The solution darkened over time indicating
2.3. Nickel complexes
Like other nickel carbonyl distibines [5,9], the com-
plexes formed by the distibinopropanes were unstable,
Table 1
Spectroscopic data for [Ni(CO)3(ligand)] or [(CO)3Ni(ligand)Ni(CO)3]
Ligand
m(CO) (cmÀ1 a
)
13C CO (ppm)a
References
b
Ph2Sb(CH2)3SbPh2
Me2Sb(CH2)3SbMe2
m-C6H4(CH2SbMe2)2
p-C6H4(CH2SbMe2)2
m-C6H4(SbMe2)2
Me2SbCH2SbMe2
Ph2SbCH2SbPh2
SbEt3
2071, 1996
2067, 1989
2068, 1993
2068, 1993
2070, 1995
2067, 1994
2072, 2004
2067, 1996
196.8
197.1
197.0
197.1
196.9
197.1
196.3
197.9
197.5
196.5
197.0
196.5
b
[9]
[9]
[9]
[5]
[5]
[20,25]
[20]
[20]
[20]
[20]
SbMe3
SbPh3
2074, 2004
SbMe2Ph
SbMePh2
Spectroscopic data for [Ni(CO)2(ligand)]
Ph2Sb(CH2)3SbPh2
b
b
2005, 1947
1992, 1933
2002, 1939
2000, 1941
2004, 1949
201.8
201.5
201.0
201.0
Me2Sb(CH2)3SbMe2
o-C6H4(CH2SbMe2)2
m-C6H4(SbMe2)2
[9]
[9]
2SbEt3
[25]
a
Chlorocarbon solvents (CH2Cl2 or CDCl3).
This work.
b

M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
1543
the onset of decomposition. The presence of four major
CH2 resonances in the 13C{1H} NMR spectrum of the
mixture suggest that [{Ni(CO)3}2{l-Ph2Sb(CH2)3-
SbPh2}] and [Ni(CO)2{Ph2Sb(CH2)3SbPh2}] are the
major complexes present.
material showed most of the carbonyl groups had been
lost. Due to this instability we have been unable to ob-
tain satisfactory analytical data, but comparison of the
spectroscopic data (reproducible from different samples)
obtained immediately after isolation allowed its identifi-
cation as [Co2(CO)4(Me2Sb(CH2)3SbMe2)3][Co(CO)4]2.
In particular the IR spectrum of the solid is very simple,
consisting of two strong broad absorptions at 1968 and
1876 cmÀ1. These are very similar to those reported for
several diarsine complexes [15] and consistent with the
formulation proposed. The band at 1878 cmÀ1 corre-
sponds to the familiar tetracarbonylcobaltate(-1) anion,
whilst the broad band in the cation is consistent with
two five coordinate cobalt(I) centres ‘‘Co(CO)2-
(Me2Sb(CH2)3SbMe2)+’’ bridged by the third distibine
ligand [15]. The ESÀ mass spectrum showed [Co(CO)4]À
as the only significant feature, and the ES+ mass spec-
trum a weak feature corresponding to [Co(CO)2-
(Me2Sb(CH2)3SbMe2)2]+ and further ions due to
sequential loss of the carbonyl groups. The 59Co
NMR spectrum (CH2Cl2 solution) (59Co, I = 7/2,
100%) showed a very sharp resonance at d À2999 as-
signed to the Td [Co(CO)4]À which compares with the
literature value of d À3100 obtained [17] from Na[Co-
(CO)4] in water, the difference attributable to solvent ef-
fects, given the very large chemical shift range observed
for the cobalt nucleus. We were unable to observe a 59Co
NMR resonance from the cation, no doubt due to extre-
mely large line width resulting from fast quadrupolar
2.4. Cobalt complexes
The substitution chemistry of dicobalt octacarbonyl
with bidentate Group 15 donor ligands is complicated
with a variety of stoichiometries being observed with
different ligands, often with several isomers identified
[5,15]. For many ligands ionic [Co(CO)3(L–L)]-
[Co(CO)4] form first and these transform to neutral di-
mers [Co2(CO)6(L–L)] on warming in solution. In other
cases the [Co2(CO)4(L–L)3][Co(CO)4]2 complexes are
obtained [15]. The two distibinopropane ligands gave
different complexes on reaction with dicobalt octacar-
bonyl in toluene solution, both rather unstable, signifi-
cantly decomposing in solution at room temperature
in a few hours and more slowly (1–2 days) in the solid
state. The complexes also contrast with the [Co2(CO)6-
(R2SbCH2SbR2)] obtained the distibinomethanes which
contain two bridging carbonyls and a bridging distibine
in addition to a Co–Co bond [5]. The reaction of
[Co2(CO)8] in toluene solution with Ph2Sb(CH2)3SbPh2
at room temperature gave a dark red-brown solution
from which a brown powder separated on standing at
À18 ꢁC overnight. The solid isolated had a composition
corresponding to [Co2(CO)6{Ph2Sb(CH2)3SbPh2}] and
was very poorly soluble in chlorocarbon or hydrocarbon
solvents, which hindered spectroscopic studies and pre-
vented 13C{1H} or 59Co NMR spectra being obtained.
The IR spectra both in the solid and in CH2Cl2 solution
showed a very broad asymmetric band with shoulders to
both high and low frequency due to terminal CO
stretches and significantly no bridging carbonyls present
(cf. [Co2(CO)6(R2SbCH2SbR2)] [5]). Comparison of the
pattern in the carbonyl region of the IR spectrum with
the extensive data reported by Thornhill and Manning
[15] for cobalt carbonyl diphosphine and diarsine com-
plexes, leads to a tentative structural formulation as an
oligo- (or poly-)meric[{Co(CO)3(Ph2Sb(CH2)3SbPh2)-
Co(CO)3}n] with unbridged Co2(CO)6 units linked by
bridging distibine into oligomers. Stirring or heating this
complex in toluene with more Ph2Sb(CH2)3SbPh2 re-
sulted in decomposition with complete loss of the car-
bonyl groups and no other complex seemed to form.
The product from the reaction of [Co2(CO)8] in toluene
solution with Me2Sb(CH2)3SbMe2 at room temperature
was also a dark brown solid, poorly soluble in most or-
ganic solvents, and even less stable. Initially the solid
was poorly soluble in chlorocarbon solvents which al-
lowed some spectroscopic studies, but after a few days
the solid had darkened in colour and was completely
insoluble in all solvents, and the IR spectrum of this
1
relaxation in the low symmetry environment. The H
NMR spectrum of the freshly prepared complex showed
two d (Me) resonances in approximately 1:2 ratio assign-
able to the bridging and chelating stibines.
2.5. Manganese complexes
Manganese carbonyl and Ph2Sb(CH2)3SbPh2
refluxed together in toluene in the presence of [{CpFe-
(CO)2}2] gave a single major product, which after recrys-
tallisation from CH2Cl2 was identified by analysis as
[Mn2(CO)8{Ph2Sb(CH2)3SbPh2}]. Photolysis (254 nm)
of Mn2(CO)10 and Ph2Sb(CH2)3SbPh2 in toluene gave
mainly the same product, but the photolysis route also
produced some minor by-products and significant
decomposition, and since purification proved difficult,
the chemical route is preferred. The IR spectra in the
carbonyl region in both Nujol mull and CH2Cl2 solution
were similar, and contained six terminal CO stretches.
Of the possible isomers [17,18], this rules out the diaxial
(1 strong band), but is similar to the eq,eq pattern re-
ported in [Mn2(CO)8(distibinomethane)], although the
longer backbone in Ph2Sb(CH2)3SbPh2 will probably re-
sult in further significant twisting of the Mn units away
from the eclipsed geometry (I) than is observed with the
smaller ring ligand [7] or in [Mn2(CO)8(Cy2PCH2PCy2)]
[18]. The 13C{1H} NMR spectrum appears to show

1544
M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
shows the r donor properties follow from the nature of
the R-group, and in this series steric effects are unimpor-
tant/absent. The 13C NMR d(CO) chemical shifts pro-
vide the same ordering, the higher the frequency the
more donating the stibine [20]. The second part of Table
1 shows some data on the less common [Ni(CO)2(disti-
bine)] complexes where the trends are less clear, and
we attribute this to the presence of a steric component
due to the different ligand architectures or chelate ring
sizes.
Fig. 1.
The relative bonding properties of corresponding
PR3, AsR3 and SbR3 have been discussed in detail else-
where [19,20] and clearly our distibine data are broadly
in line with the accepted trends. However, we also
sought to compare the distibine ligand properties with
those of group 16 donor analogues (dithioether, disele-
noether and ditelluroether). Since nickel carbonyl com-
plexes of these ligands appear to be unknown, the
comparison following the data in Table 1 is impossible.
However, an essentially complete set of data exist for the
Group 6 metal carbonyl species cis-[M(CO)4(ligand)]
and these are summarised in Table 2. Since in chelate
complexes the ring size is known to have a significant
effect on the spectroscopic properties [21], we compare
only 6-membered ring complexes. The data also
reflect both r-donor and p-acceptor properties of the
neutral ligands, although the current view [22] is that
p-acceptance by Group 16 donors is unimportant in
low valent species and that both r-donor and p-acceptor
power decreases down Group 15 [20]. Two minor cave-
ats need to be added: (i) that for a number of the com-
plexes only three of the expected four bands in the IR
carbonyl spectra are resolved, and (ii) for the Group
16 donor ligand complexes meso and DL invertomers
three d(CO) resonances although these partially overlap
and are broadened by the 55Mn quadrupole making the
number of resonances uncertain, although the data are
consistent with (I) (Fig. 1).
2.6. Some comparisons
These studies have provided a range of spectroscopic
data on carbonyl complexes of two distibinopropanes,
which when they chelate form 6-membered rings. Thus,
they allow some comparisons with previous work on
distibinomethanes which have so far yielded no fully
characterised chelate complexes with metal carbonyl
residues [1,5,6], with the isomeric o-, m- and p-xylyl
distibines [9], and with the more restricted range of com-
plexes reported for o- [10], m- and p-phenylene distibines
[9], both latter types providing a range of ligand archi-
tectures. Table 1 summarises the m(CO) frequencies
and 13C NMR d(CO) resonances of a series of
Ni(CO)3(stibine) units for these ligands and some re-
lated monodentates. Following Tolmanꢀs [19] classifica-
tion of phosphine ligands which utilises the higher
frequency (A1) mode to rank the electronic properties
of the donor group, a similar examination of the IR data
Table 2
Comparative spectroscopic data for some cis-tetracarbonyl complexes of Group 6 metals
Ligand
[Cr(CO)4(L–L)]
m(CO) (cmÀ1 a
[Mo(CO)4(L–L)]
m(CO) (cmÀ1
[W(CO)4(L–L)]
m(CO) (cmÀ1
References
)
13C (ppm)a
222.8, 228.9
)
13C (ppm)
)
13C (ppm)
b
b
Ph2Sb(CH2)3SbPh2
Me2Sb(CH2)3SbMe2
o-C6H4(CH2SbMe2)2
MeS(CH2)3SMe
2004, 1911, 1895
2021, 1927, 1912,
1892
2014, 1903, 1880
211.0, 215.6
2015, 1916, 1902,
1882
2011, 1896, 1870
201.4, 205.1
1995, 1900, 1885,
1875
223.7, 229.9
213.0, 218.4
210.9, 215.5
207.1, 217.0
208.3, 216.8
203.5, 208.2
201.7, 206.1
202.7, 207.6
203, 206c
2017, 1935, 1901,
1867
2012, 1935, 1901,
1873
[9]
2015, 1900, 1890,
1854
2009, 1984, 1852
217.0, 225.8
219.0, 227.0
2023, 1910, 1895,
1856
2018, 1897, 1890,
1852
[23]
[23]
MeSe(CH2)3SeMe
2020, 1908, 1895,
1855
222.9, 228.0c 2015, 1908, 1862
222.3, 227.5c 2018, 1907, 1875
2015, 1896, 1885,
1850
210.6, 215.7c 2010, 1894, 1859
210.2, 215.6c 2013, 1895, 1869
MeTe(CH2)3TeMe
PhTe(CH2)3TePh
2000, 1887, 1858
2003, 1903, 1891,
1870
203.5, 206.2c [23]
203.9, 205.4c [23]
a
CH2Cl2 solutions except c.
This work.
b
c
Due to slow pyramidal inversion at Te in these complexes, separate resonances are observed for the DL and meso invertomers (in unequal
abundance). These chemical shifts quoted are (unweighted) averages values for the two invertomers and as such are subject to some error.

M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
1545
exist [23]. The two invertomers are not distinguishable in
the carbonyl IR spectra, but are potentially so in the
13C{1H} NMR data. Fast pyramidal inversion in the
dithioether and diselenoether complexes at ambient tem-
peratures for the chromium and molybdenum com-
plexes mean the resonances of the individual
invertomers are not observed, however the higher inver-
sion barriers at Te result in separate resonances for each
isomer in the telluro-ether complexes [23]. In Table 2,
the ditelluroether chemical shifts have been averaged
and these values (unweighted for the isomer abundance
since this is not accurately known) introduce some small
error. However, a comparison of the data in Table 2
shows that, in addition to the usual effects of the R-
groups, the electronic properties of the distibines suggest
they place more electron density on the Group 6 metal
than dithioether or diselenoether analogues, and that
they are closest to the ditelluroethers in properties. Pre-
vious detailed analysis of metal carbonyl complexes with
Group 16 ligands [22–24] has shown that to low valent,
electron rich metal centres r-donation w.r.t. to donor
centre is S < Se ꢀ Te, whereas in Group 15 it is ac-
cepted to be P > As > Sb [20]. As found with telluroe-
thers [22], it is probable that stibines would be
relatively less good ligands for higher and possibly med-
ium oxidation state centres than selenium or sulfur do-
nors as the metal orbitals contract and the metal
centre becomes harder, but insufficient spectroscopic
data are available at present to explore this further.
with degassed H2O (100 cm3) and the organic layer sep-
arated. The aqueous layer was extracted with diethyl
ether (2 · 100 cm3), and then the combined organics
were dried over anhydrous MgSO4 for 3 h. Following
filtration the solvents were distilled off and the resulting
yellow oil was fractionated in vacuo. 65 ꢁC/0.5 mm
1
(5.2 g, 50%) H NMR (CDCl3) 1.70 (q) [2H], 1.40 (t)
[4H], 0.65 (s) [12H]. 13C{1H} NMR (CDCl3): 24.45
CH2CH2, 19.60 CH2Sb, À5.00 CH3.
3.2. [Cr(CO)4{Ph2Sb(CH2)3SbPh2}]
Method 1. [Cr(CO)6] (0.48 g, 0.22 mmol) and
Ph2Sb(CH2)3SbPh2 (0.125 g, 0.22 mmol) were dissolved
in ethanol (50 cm3), NaBH4 (0.1 g) added and the mix-
ture refluxed for 2 h. during which it became yellow.
The solvent was removed in vacuo, and the residue sha-
ken up with water (20 cm3) and CH2Cl2 (20 cm3). The
organic layer was separated, dried (MgSO4), and evapo-
rated to small volume to produce a yellow powder.
Spectroscopic data identical to those below.
Method 2. [Cr(CO)4(C7H8)] (0.13 g, 0.5 mmol) and
Ph2Sb(CH2)3SbPh2 (0.297 g, 0.5 mmol) were dissolved
in methylcyclohexane (50 cm3) and stirred overnight.
The reaction was heated to reflux for 2 h, cooled and re-
duced in volume by 50%. A pale greenish precipitate was
formed, and the mixture was refrigerated overnight. The
resulting pale yellow-green solid was filtered off and
dried in vacuo. Yield: 0.094 g, 84%. Anal. Found: C,
48.7; H, 3.4. Calc. for C31H26CrO4Sb2: C, 49.1; H,
3.5%. 1H NMR (CDCl3) 2.0–2.2(m) [6H], 7.1–7.6(m)
[20H]. 13C{1H} NMR (CH2Cl2/CDCl3) 20.8 CH2Sb,
23.5 CH2CH2, 129.5, 130.2, 133.1, 134.8 aryl-C, 222.8,
228.9 CO. MS (APCI) m/z 645 [Cr{Ph2Sb(CH2)3-
3. Experimental
Metal carbonyls were obtained commercially (Al-
drich or Strem) and used as received. All reactions were
performed under dinitrogen in dried solvents. Physical
measurements were made as described elsewhere [5,9].
Ph2Sb(CH2)3SbPh2 The ligand was made as a white
air-stable powder by reaction of Ph3Sb, Na and
Br(CH2)3Br in liquid ammonia, and recrystallised from
ethanol. Yield 44% [3]. 1H NMR (300 MHz CDCl3)
1.8–2.0(m) [6H], 7.0–7.5(m) [20H]. 13C{1H} NMR
(100.6 MHz, CDCl3) 25.1 CH2Sb, 26.5 CH2CH2,
128.7, 128.9, 136.0, 137.9 (aryl C).
SbPh2}]+ IR spectrum (cmÀ1
)
CH2Cl2: 2004(s),
1911(sh), 1895(vs,br); Nujol: 2000(s), 1916(m), 1897(s),
1865(s).
3.3. [Mo(CO)4{Ph2Sb(CH2)3SbPh2}]
[Mo(CO)4(norbornadiene)] (0.15 g, 0.5 mmol) and
Ph2Sb(CH2)3SbPh2 (0.3 g, 0.5 mmol) were dissolved in
methylcyclohexane (50 cm3) and the mixture stirred
overnight. The solution was filtered, and the filtrate
evaporated in vacuum to produce a pale yellow solid
which was dried in vacuo. Yield 0.33 g, 81%. Anal.
Found: C, 47.0; H, 3.1. Calc. for C31H26MoO4Sb2: C,
3.1. Me2Sb(CH2)3SbMe2
Liquid ammonia (500 cm3) was condensed using an
acetone/CO2 slush, and then sodium (5.63 g, 0.24 mol)
was added slowly and the solution was left to stir for
30 m. Me3SbBr2 (20 g, 0.06 mol) was added in portions,
and then the reaction was left to stir for 90 m. NH4Cl
(3.2 g, 0.06 mol) was added to destroy the MeNa and
then 1,3-dibromopropane (6.06 g, 0.03 mol) was added
dropwise. The reaction was stirred overnight to evapo-
rate the liquid ammonia. The reaction was hydrolysed
46.4; H, 3.3%. H NMR (CDCl3) 2.0–2.2(m) [6H], 7.1–
1
7.7(m). 13C{1H} NMR (CH2Cl2/CDCl3) 20.9 CH2Sb,
23.6 CH2CH2, 129.4, 130.1, 133.1, 134.8 aryl-C, 211.0,
215.6 CO. 95Mo NMR (CH2Cl2/CDCl3) À1849. MS
(APCI) m/z 746 [Mo(CO)2{Ph2Sb(CH2)3SbPh2}]+, 718
[Mo(CO){Ph2Sb(CH2)3SbPh2}]+,
690
[Mo{Ph2Sb-
(CH2)3SbPh2}]+. IR spectrum (cmÀ1) CH2Cl2: 2021(s),
1927(sh), 1912(vs), 1892(s); Nujol: 2015(s), 1928(m),
1906(vs), 1872(s).

1546
M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
3.4. [W(CO)4{Ph2Sb(CH2)3SbPh2}]
tion of [Co2(CO)8]. The reaction mixture was stirred
for 1 h. and then filtered. The dark brown filtrate was
refridgerated overnight, and the red-brown solid which
deposited filtered off and dried in vacuo. Yield 0.13 g,
42%. The product is unstable and was stored in the free-
zer. It is poorly soluble in non-polar solvents. Anal.
Found: C, 43.6; H, 3.4. Calc. for C33H26Co2O6Sb2: C,
45.0; H, 3.0%. 1H NMR (CDCl3) 1.5–2.0(m), 7.1–
[W(CO)4(piperidine)2] (0.23 g, 0.5 mmol) and
Ph2Sb(CH2)3SbPh2 (0.3 g, 0.5 mmol) were refluxed
gently in ethanol (30 cm3), then the mixture was cooled
and filtered. The solvent was removed in vacuo, the res-
idue extracted with CH2Cl2 , the solution filtered, and
the filtrate concentrated to 10 cm3. Addition of diethyl
ether (10 cm3) produced a yellow solid, which was sepa-
rated and dried in vacuo. Yield 0.11 g, 24%. Anal.
Found: C, 39.1; H, 3.0. Calc. for C31H26O4-
7.6(m). IR spectrum (cmÀ1
)
CH2Cl2: 1995(m),
1969(s,br), 1934(sh); Nujol: 2004(sh), 1980(s,br),
1953(sh).
1
Sb2W Æ CH2Cl2: C, 39.4; H, 3.5%. H NMR (CDCl3)
2.2(m) [6H], 5.4(s) CH2Cl2, 7.3–7.6(m). 13C{1H} NMR
(CH2Cl2/CDCl3) 20.0 CH2Sb, 23.8 CH2CH2, 129.4,
130.3, 132.1, 134.7 aryl-C, 201.4 (1JWC = 116 Hz)
205.1(1JWC = 165 Hz) CO. MS (APCI) m/z 891
3.8. [Mn2(CO)8{Ph2Sb(CH2)3SbPh2}]
[Mn2(CO)10] (0.45 g, 1.15 mmol), Ph2Sb(CH2)3SbPh2
(0.683 g, 1.15 mmol) and [{(Cp)Fe(CO)2}2] (0.08 g,
0.23 mmol) were dissolved in toluene (50 cm3) and re-
fluxed for 24 h. The dark brown solution was then
cooled, reduced in volume to 50% and then hexane
(10 cm3) was added. A waxy brown solid was collected
by filtration, dissolved in the minimum volume of
CH2Cl2, the solution filtered, and reduced to dryness
to afford a brown solid, which was dried in vacuo. Yield
0.32 g, 41%. Anal. Found: C, 44.6; H, 2.9. Calc. for
[W{Ph2Sb(CH2)3SbPh2}(CO)4]+. IR spectrum (cmÀ1
CH2Cl2: 2015(s), 1916(sh), 1902(vs), 1882(sh); Nujol:
2012(s), 1920(sh), 1900(vs), 1869(s).
)
3.5. [{Fe(CO)4}2{Ph2Sb(CH2)3SbPh2}]
Fe2(CO)9 (0.92 g, 2.6 mmol) and Ph2Sb(CH2)3SbPh2
(0.75 g, 1.26 mmol) were dissolved in anhydrous tetra-
hydrofuran (50 cm3) and the solution stirred at room
temperature for 2d. Filtration and removal of all vola-
tiles in vacuum left a viscous dark red-brown oil. Yield
1.14 g, 97%. 1H NMR (CDCl3) 2.0(m) [4H], 2.3(m)
[2H], 7.3–7.6(m) [20H]. 13C{1H} NMR (CH2Cl2/
CDCl3) 22.9 CH2Sb, 25.9 CH2CH2, 129.4, 129.9,
131.2, 134.7 aryl C, 213.2 (CO). MS (APCI) m/z 762
[Fe(CO)4{Ph2Sb(CH2)3SbPh2}]+, 732 [Fe(CO)3{Ph2Sb-
(CH2)3SbPh2}]+, 678 [Fe(CO){Ph2Sb(CH2)3SbPh2}]+,
1
C35H26Mn2O8Sb2: C, 45.3; H, 2.8%. H NMR (CDCl3)
2.0–2.2 (br) [6H], 7.0–7.6(br) [20H]. 13C{1H} NMR
(CH2Cl2/CDCl3) 20.6 CH2Sb, 21.6 CH2CH2, 129.3,
130.0, 134.6, 136.4 aryl C, 214.5, 217.2, 217.9 (CO). IR
spectrum (cmÀ1) CH2Cl2: 2055(m), 2034(w), 1977(vbr,s),
1966(sh), 1953(s,sh), 1914(sh); Nujol: 2055(m), 2023(m),
1966(s,br), 1947(s), 1919(sh).
650 [Fe{Ph2Sb(CH2)3SbPh2}]+. IR spectrum (cmÀ1
CH2Cl2: 2044(s), 1967(m), 1934(s,br); Nujol: 2041(s),
2060(sh), 1913(vbr).
)
3.9. [{Ni(CO)3}2{Ph2Sb(CH2)3SbPh2}] and
[Ni(CO)2{Ph2Sb(CH2)3SbPh2}]
CARE: Ni(CO)4 is volatile and extremely toxic: All
reactions were conducted in a good fume cupboard and
in sealed equipment fitted with bromine water scrubbers.
Spectroscopic samples were also handled in fume cup-
board. Residues were destroyed with bromine–water.
Excess Ni(CO)4 (ca. 1 cm3) was added to a stirred
solution of the ligand (0.3 g, 0.55 mmol) in CH2Cl2
(20 cm3). The progress of the reaction was monitored
by IR spectroscopy and when reaction had ceased,
the solvent and excess tetracarbonylnickel were re-
moved in vacuo leaving a yellow oil, which darkens
in a few hours indicative of decomposition. It also
blackened slowly in chlorocarbon solutions. Spectro-
scopic studies showed an inseparable mixture of the
two complexes. 1H NMR (CDCl3) 2.0, 2.2(m), 7.3–
7.7(m). 13C{1H} NMR (CH2Cl2/CDCl3) 20.8, 22.8,
23.5, 24.0, 129.3, 129.8, 133.0, 134.9, 196.8 (Ni(CO)3),
3.6. [Fe(CO)4{Ph2Sb(CH2)3SbPh2}]
This was obtained also as a red-brown oil using a 1:1
Fe2(CO)9: Ph2Sb(CH2)3SbPh2 ratio. The NMR spectra
show some contamination with [{Fe(CO)4}2-
{Ph2Sb(CH2)3SbPh2}] (see text). 1H NMR (CDCl3)
1.8–2.0(m), 7.1–7.6(m). 13C{1H} NMR (CH2Cl2/CDCl3)
23.4, 24.2 CH2Sb, 25.6 CH2CH2, 128.9, 129.8, 131.0,
134.7, 136.0, 137.5 aryl C, 213.3 (CO). MS (APCI) m/z
763 [Fe(CO)4{Ph2Sb(CH2)3SbPh2}]+. IR spectrum
(cmÀ1) CH2Cl2: 2044(s), 1967(m), 1934(s,br); Nujol:
2041(s), 1913(vbr).
3.7. [Co2(CO)6{Ph2Sb(CH2)3SbPh2}]
[Co2(CO)8] (0.17 g, 0.5 mmol) was dissolved in dry
toluene (50 cm3) and the solution was filtered.
Ph2Sb(CH2)3SbPh2 (0.297 g, 0.5 mmol) was dissolved
in dry toluene (50 cm3), and added to the toluene solu-
201.8 (Ni(CO)2). IR spectrum (cmÀ1
)
CH2Cl2:
2071(s), 1996(vs), 1947(m); thin film: 2072(s), 2005(s),
1997(s), 1957(m).

M.D. Brown et al. / Journal of Organometallic Chemistry 690 (2005) 1540–1548
1547
3.10. [W(CO)4{Me2Sb(CH2)3SbMe2}]
duced to dryness and the dark red oil was dried in vacuo.
1
Yield 0.65 g, 95%. H NMR (CDCl3) 0.75(s) [6H], 1.4–
[W(CO)4(piperidine)2] (0.26 g, 0.55 mmol) and
Me2Sb(CH2)3SbMe2 (0.19 g, 0.55 mmol) were refluxed
gently in ethanol (30 cm3), then the mixture was cooled
and filtered. The solvent was removed in vacuo, the res-
idue extracted with CH2Cl2, the solution filtered, and
the filtrate concentrated to 10 cm3. Addition of diethyl
ether (10 cm3) produced a yellow solid, which was sepa-
1.8(m) [3H]. 13C{1H} NMR (CH2Cl2/CDCl3) À5.1
CH3, 20.8 CH2Sb, 25.6 CH2CH2, 213.6 CO. IR spec-
trum (cmÀ1) CH2Cl2: 2055(s), 1968(m), 1927(vbr,s); Nu-
jol: 2042(m), 1965(m), 1932(s,br), 1914(sh).
3.14. [Co2(CO)4{Me2Sb(CH2)3SbMe2}3][Co(CO)4]2
1
rated and dried in vacuo. Yield 0.13 g, 37%. H NMR
[Co2(CO)8] (0.38 g, 1.1 mmol) was dissolved in dry
degassed toluene (50 cm3) and the solution filtered.
Me2Sb(CH2)3SbMe2 (0.39 g, 1.1 mmol) was added to
the solution and the mixture stirred for 1 h. The brown
precipitate produced was filtered off and dried in vacuo.
(CD2Cl2) 1.3 (s) [6H], 1.7(m) [2H], 2.1(m) [H].
13C{1H} NMR (dmso/d6-dmso) À1.9 CH3, 16.6 CH2Sb,
24.4 CH2CH2, 203.5 (1J = 120 Hz), 208.2 (1J = 165 Hz).
MS (APCI) m/z 569 [W(CO)2{MeSb(CH2)3SbMe2}],
557 [W(CO){Me2Sb(CH2)3SbMe2}], 543 [W(CO)-
{MeSb(CH2)3SbMe2}], 528 [W{Me2Sb(CH2)3SbMe2}].
IR spectrum (cmÀ1) CH2Cl2: 2011(m), 1896(vs,br),
1870(sh); Nujol: 2009(s), 1886(vs, br),1869(sh).
1
Yield 0.15 g, 20%. H NMR (CDCl3) 0.6(s) [2H]. 0.8(s)
[4H], 1.2–1.7(m) [3H]. 59Co NMR (CH2Cl2) À2999
w1/2 = 40 Hz. ESÀ (MS) 171 Co(CO)4, ES+ MS 803
Co(CO)2{Me2Sb(CH2)3SbMe2}2, 776 Co(CO){Me2-
Sb(CH2)3SbMe2}2, 749 Co{Me2Sb(CH2)3SbMe2}2. IR
3.11. [Mo(CO)4{Me2Sb(CH2)3SbMe2}]
spectrum (cmÀ1
)
1885(s,br); Nujol: 1968(s,br), 1878(s,br).
CH2Cl2: 1990(sh), 1972(s,br),
[Mo(CO)4(C7H8)]
(0.17 g,
0.55 mmol)
and
Me2Sb(CH2)3SbMe2 (0.19 g, 0.55 mmol) were dissolved
in degassed EtOH (25 cm3) and the yellow solution
was stirred overnight. The reaction was refluxed for
2 h, the solvent removed in vacuo and the residue dis-
solved in the minimum of CH2Cl2. Hexane (10 cm3)
was added to precipitate the pale brown solid which
was filtered and dried in vacuo. Yield 0.030 g, 11%. Anal.
Found: C, 23.8; H, 3.1. Calc. for C11H18CrO4Sb2: C,
3.15. [{Ni(CO)3}2{Me2Sb(CH2)3SbMe2}]
A large excess of Ni(CO)4 (ca. 1 cm3) was added to a
stirred solution of Me2Sb(CH2)3SbMe2 (0.19 g,
0.55 mmol) in CH2Cl2 (20 cm3). Carbon monoxide was
rapidly evolved, and progress of the reaction was mon-
itored by IR spectroscopy of aliquots of the solution
at regular intervals. When reaction had ceased, the ex-
cess tetracarbonylnickel and the solvent was removed
in vacuo to leave a yellowish oil. 1H NMR (CDCl3)
1.0(s) [6H], 1.6(m) [2H], 1.8(m) [H]. 13C{1H} NMR
(CH2Cl2/CDCl3) À3.4 CH3, 19.1 CH2Sb, 24.1 CH2CH2,
197.1 CO. IR spectrum (cmÀ1) CH2Cl2: 2067(s),
1991(vs); thin film: 2069(s), 1996(br,s).
1
23.8; H, 3.3%. H NMR (CDCl3) 1.05(s) [6H], 1.55(m)
[2H], 1.90(m) [H]. 13C{1H} NMR (dmso/d6 dmso)
À1.6 CH3, 17.8 CH2Sb, 24.5 CH2CH2, 213.0, 218.4
CO. 95Mo NMR (dmso/d6-dmso) À1843. IR spectrum
(cmÀ1) CH2Cl2: 2014(m), 1903(vs,br), 1880(sh); Nujol:
2013(m), 1946(sh), 1894(vs,br), 1866(sh).
Reaction using a deficit of tetracarbonylnickel: 1H
NMR (CDCl3) 0.68(s), 0.96(s), 0.98(s), 1.40–1.85(m).
13C{1H} NMR (CH2Cl2/CDCl3) À4.9, À3.2, À1.4 CH3,
18.3, 19.6, 20.9, 24.1, 24.9 CH2, 197.1, 201.5 CO. IR spec-
trum (cmÀ1) CH2Cl2: 2066(s), 1991(vs), 1933(m); thin
film: 2069(s), 2006(sh), 1996(br,s), 1950(m).
3.12. [Cr(CO)4{Me2Sb(CH2)3SbMe2}]
Made similarly to the molybdenum complex but
using [Cr(CO)4(C7H8)]. The pale green solid was recrys-
tallised from CH2Cl2 and Et2O, and dried in vacuo.
1
Yield 45%. H NMR (CDCl3) 1.1(s) [6H], 1.6(t) [2H],
1.9(m) [H]. 13C{1H} NMR (CH2Cl2/CDCl3) À2.1
CH3, 17.9 CH2Sb, 24.0 CH2CH2, 223.7, 229.9 CO. MS
(APCI) m/z 509 [Cr(CO)4{Me2Sb(CH2)3SbMe2}], 481
Acknowledgement
We thank EPSRC for support.
[Cr(CO)3{Me2Sb(CH2)3SbMe2}]. IR spectrum (cmÀ1
)
CH2Cl2: 1995(s), 1900(sh), 1885(s,vb), 1875(sh); Nujol:
1993(s), 1903(sh), 1888(vs,br), 1862(sh).
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