Synthesis and reactions of a hybrid tristibine ligand

Article abstract of DOI:10.1021/om400205d

The tripodal tristibine N(CH₂-2-C₆H ₄SbMe₂)₃ (L) has been prepared in high yield and characterized by ¹H and ¹³C{¹H} NMR spectroscopy and elemental analysis. A range o

Full text of DOI:10.1021/om400205d

Article
pubs.acs.org/Organometallics
Synthesis and Reactions of a Hybrid Tristibine Ligand
Sophie L. Benjamin, William Levason, and Gillian Reid*
School of Chemistry, University of Southampton, Southampton, U.K. SO17 1BJ
S
* Supporting Information
ABSTRACT: The tripodal tristibine N(CH2-2-C6H4SbMe2)3 (L)
1
has been prepared in high yield and characterized by H and
13C{1H} NMR spectroscopy and elemental analysis. A range of
reactions with transition-metal acceptors were carried out to probe
the coordinative properties of L. The 3/1 M/L complex
[{FeCp(CO)2}3(L)-κSb:κSb′:κSb″][BF4]3 involves tridentate bridg-
ing coordination of L to three CpFe(CO)2 fragments. In
[Mn(CO)3(L)][CF3SO3] the ligand adopts a tridentate chelating
mode via a Sb3 donor set; treatment of this complex with Me3NO in
MeCN solution gave crystals of [Mn(CO)2(L)(MeCN)][CF3SO3],
which lost MeCN in vacuo, probably resulting in coordination of
CF3SO3 coordination of the [CF3SO3]− anion. [M(L)][BF4] (M = Ag, Cu) were also prepared. The reaction of L with CuBr
leads to isolation of [Cu4Br4(L)2] in the solid state, which contains a Cu2Br4 core with a short central Cu···Cu distance, capped
with Cu(L) units at each end. The transition-metal complexes of L were characterized by elemental analysis, ESI+ mass
−
1
spectrometry, IR spectroscopy, and H, 13C{1H}, and (where appropriate) 55Mn or 63Cu NMR spectroscopy. Solid-state X-ray
structures were determined for [Mn(CO)3(L)][CF3SO3], [Mn(CO)2(L)(MeCN)][CF3SO3], [Cu4Br4(L)2], and [Cu3Br2(L)2]-
[BF4]. In each of these structures the chelating ligand adopts a twisted, propeller-like conformation. NMR spectroscopic analysis
suggests that the ligand also adopts this rigid conformation in solution.
group 6 tricarbonyl fragments, as evidenced by the crystal
structure of [Mo(CO)3{MeC(CH2SbPh2)3}].6 In early work,
the synthesis of the flexible N(CH2CH2CH2SbR2)3 (R = Me,
Ph) was also described, but no complexes were reported.7
We have previously reported the synthesis of several hybrid
distibine ligands and their complexation to a range of
transition-metal centers.8−11 Here we report the synthesis and
some coordination studies of the hybrid tristibine N(CH2-2-
C6H4SbMe2)3, a potentially tetradentate ligand and a very rare
example of a triorganostibine.
INTRODUCTION
■
Hybrid stibine ligands, which contain stibine moieties as well as
other donor atoms are increasingly of interest. They allow the
exploitation of the unusual behaviors which can be accessed
using stibine donors within a more stable or strongly binding
polydentate framework, and can be adapted for diverse
̈
purposes. Very recent examples from Gabbaı and co-workers
demonstrate that complexes of the hybrid ligand Sb{2-
C6H4PPh2}3 can undergo reaction at the Sb center without
decomplexation. Oxidation at Sb by dihalogens leads to the
observation of rare “umpolung” type Sb−Au bonds,1 and a Pd
complex of this ligand has been employed for F− anion sensing
by means of reversible acceptance of fluoride ions by the Sb
center, which causes measurable changes in the ligand’s
coordination environment.2
RESULTS AND DISCUSSION
■
Hybrid tristibine synthesis. The hybrid tristibine ligand
N(CH2-2-C6H4SbMe2)3 (1) was synthesized as shown in
Scheme 1. The precursor N(CH2-2-C6H4Br)3 was made via a
literature preparation,12 and the three stibine moieties were
introduced in the final step, to minimize the potential for
cleavage of the fragile C−Sb bonds. The reaction conditions of
this step were critical to the isolation of a pure product. Slow
addition of the trilithiate to the flask containing the halostibine
and the maintenance of low temperatures throughout allowed
the tristibine to be obtained in extremely high yield (82%).
The ligand is an oxygen-sensitive viscous oil; it was stored
and used as a stock solution in CH2Cl2. 1H NMR spectroscopy
shows two sharp singlets in a 3:1 ratio corresponding to the
Me2Sb and CH2N groups, respectively, as well as four clearly
The study of intramolecular hypervalent interactions
between stibines or bismuthines and lighter heteroatoms has
also emerged as a major area of interest in recent years.3 This
phenomenon is not observed in compounds of the lighter
group 15 elements such as phosphines; in fact, there is now
substantial evidence that heavier group 15 donors support
chemistry which is in many cases distinct from that of their
lighter counterparts.4,5 Though this understanding has led to
increased research into the synthesis and coordination of
organostibines in recent decades, this has been limited almost
entirely to monodentate and a smaller number of bidentate
examples. Only one tritertiary stibine ligand has been
coordinated to transition-metal centers, the tripodal MeC-
(CH2SbPh2)3, which behaves as a tridentate donor toward
Received: March 12, 2013
Published: April 15, 2013
© 2013 American Chemical Society
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Scheme 1. Synthesis of N(CH2-2-C6H4SbMe2)3
resolved multiplets in the aromatic region. The 13C{1H} NMR
spectrum has a single MeSb resonance to low frequency of 0
ppm, as is characteristic of alkylstibines, as well as resonances
corresponding to CH2N and six aromatic carbons.
Addition of MeI to a solution of the ligand in MeCN resulted
in the precipitation of a white solid. The ESI+ mass spectrum
shows both the doubly and singly methylated products,
although no peak was observable for a triply methylated
tricationic species.
that seen in uncharged cyclic azastibocines such as MeN(CH2-
2-C6H4)2SbCCPh (Sb···N = 2.538(3) Å).13
In addition to the presence of four donor atoms, the
backbone of the ligand 1 has some degree of flexibility. This
combination could give rise to a number of different potential
coordination modes (Figure 2). These include the very rare Sb3
A number of other routes were investigated for the synthesis
of this ligand; the order of addition was found to be a key
factor. Addition of the halostibine to the organolithiate, rather
than vice versa, resulted in observation of several products,
including evidence of the formation of cyclic species. In one
case methylation of the product mixture using MeI resulted in
isolation of a few crystals of the cyclized stibonium salt
[(Me2Sb-2-C6H4CH2)N(CH2-2-C6H4)2SbMe2][I], which were
identified by a single-crystal X-ray structure determination. The
structure of the cation (Figure 1) shows a hypervalent
interaction between the Sb and N atoms contained in the
cyclic moiety (Sb···N = 2.565(4) Å), which is comparable to
Figure 2. Examples of possible coordination modes of the ligand
N(CH2-2-C6H4SbMe2)3: (a) κSb:κSb′:κSb″; (b) Sb3 tridentate
chelating; (c) Sb3N tetradentate chelating.
chelating mode and the unknown Sb3N tetradentate chelating
mode. The coordination chemistry of this ligand with transition
metals was investigated with this versatility in mind, the specific
choice of metal centers being designed to probe the possible
coordination modes and geometries of the ligand (Scheme 2).
Transition-Metal Complexes of N(CH2-2-C6H4SbMe2)3.
[{FeCp(CO)2}3{N(CH2-2-C6H4SbMe2)3-κSb:κSb′:κSb″}][BF4]3 (2).
The precursor [FeCp(CO)2(thf)][BF4] was prepared in situ
and provides one easily accessible coordination site via
displacement of the labile thf ligand.14 Reaction of this
precursor with N(CH2-2-C6H4SbMe2)3 resulted in formation
1
of the 3/1 complex as an orange solid. The H and 13C{1H}
NMR spectra were collected in CD3CN, as the compound was
only sparingly soluble in chlorinated solvents, and show one
environment for each of the MeSb, CH2N, and Cp organic
moieties. In the 13C{1H} NMR spectrum there is a resonance at
210.4 ppm which corresponds to a single metal carbonyl
environment. This is supported by both the solution and solid-
state IR spectra, which show two strong peaks in the CO region
(a1 + b1), with frequencies almost identical with those of the
model complex [FeCp(CO)2(SbMe2Ph)][BF4] (2046, 2002 vs
2046, 2001 cm−1). These observations are consistent with a
single environment for the three CpFe(CO)2 fragments, each
of which is coordinated to one of the three stibine moieties of
the ligand. In related complexes of hybrid stibines and
bismuthines hypervalent interactions have been observed,
which can cause observable splitting in the solid-state IR
spectra due to the resulting inequivalence of the metal
centers.10 There is no evidence for this behavior in the IR
spectra of [{FeCp(CO)2}3{N(CH2-2-C6H4SbMe2)3}][BF4]3.
Figure 1. View of the structure of [(Me2Sb-2-C6H4CH2)N(CH2-2-
C6H4)2SbMe2]+ with the atom-numbering scheme. Ellipsoids are
drawn at the 50% probability level, and H atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Sb1−C5 =
2.109(5), Sb1−C12 = 2.108(5), Sb1−C1 = 2.116(5), Sb1−C2 =
2.134(5), Sb2−C3 = 2.154(6), Sb2−C4 = 2.172(6), Sb2−C19 =
2.188(6), Sb1···N1 = 2.565(4); C5−Sb1−C12 = 115.18(18), C5−
Sb1−C1 = 117.6(2), C1−Sb1−C2 = 102.4(2), C1−Sb1···N1 =
87.12(18), C2−Sb1···N1 = 170.41(19), C3−Sb2−C4 = 94.8(3).
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Scheme 2. Reactions of N(CH2-2-C6H4SbMe2)3 (L) with Transition-Metal Acceptors
Crystals of the material were grown by several methods, but
in each case X-ray crystallographic studies revealed severe
disorder within the structure. Though the positions of the
heavy atoms could be sufficiently determined to support the
assignment of a single ligand bridging three FeCp(CO)2
fragments (κSb:κSb′:κSb″), the disorder of the lighter atoms
could not be modeled satisfactorily.
Mn(I) Carbonyl Complexes of N(CH2-2-C6H4SbMe2)3.
Manganese(I) carbonyl fragments are soft Lewis acids which
are well suited to coordination with stibine ligands, several
complexes with distibines being known.15 They allow the
number of vacant sites to be varied in a controllable way, by
careful choice of precursor and decarbonylation or halide
abstraction from existing complexes.16 They also provide
several spectroscopic probes, making them good candidates
for the exploration of the coordination modes of N(CH2-2-
C6H4SbMe2)3. Coordination of soft Sb donors to the Mn(I)
Figure 3. View of the structure of [Mn(CO)3{N(CH2-2-
C6H4SbMe2)3}]+ showing the atom-labeling scheme. Ellipsoids are
drawn at the 50% probability level, and H atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Sb3−Mn1 =
2.584(2), Sb1−Mn1 = 2.599(2), Sb2−Mn1 = 2.586(2), Mn1−C29 =
1.798(12), Mn1−C28 = 1.800(11), Mn1−C30 = 1.800(12); Sb2−
Mn1−Sb1 = 94.84(5), Sb3−Mn1−Sb2 = 95.42(5), Sb3−Mn1−Sb1 =
94.44(5), C29−Mn1−Sb1 = 88.2(3), C28−Mn1−Sb1 = 178.4(3),
C30−Mn1−Sb1 = 84.6(3).
center is preferred over coordination of amine N donors,
though both are observed in [Mn(CO)3{MeN(CH2-2-
C6H4SbMe2)2}][CF3SO3], a complex of the corresponding
hybrid distibine ligand.11
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3] (3). Stirring of
[Mn(CO)3(OCMe2)3][CF3SO3] with N(CH2-2-C6H4SbMe2)3
in acetone solution resulted in the formation of fac-[Mn-
(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3], isolated after
workup as a bright orange powder. The structure was
determined by X-ray diffraction and shows the three Sb donors
of the ligand facially coordinated to the Mn center, each trans
to a CO group, with the ligand backbone arranged in a
propeller-like conformation (Figure 3). The central tertiary
amine is uncoordinated (N···Mn = 4.1637(9) Å) and roughly
equidistant from each Sb atom (N···Sb = 3.521(8), 3.601(7),
and 3.573(7) Å). These distances are similar to the sum of the
van der Waals radii of Sb and N (3.55 Å),17 meaning no
hypervalent interactions are present between the amine and any
of the Sb atoms. It is likely that, within the rigid conformation
of the ligand arising from tridentate coordination, close
approach of N to one or more Sb atoms would be disfavored,
as it would introduce too much strain into the ligand backbone.
One solvent CHCl3 molecule and one toluene molecule are
present in the asymmetric unit, and long contacts (∼3.2 Å) are
present between two of the CO groups and Cl atoms on the
CHCl3 solvate.
The 1H NMR spectrum shows two peaks of equal integration
corresponding to the MeSb protons, and two doublets are
observed for the protons of the CH2N moieties. The 13C{1H}
NMR spectrum shows two peaks in the MeSb region but only
one corresponding to CH2N. It can be concluded that reversal
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of the twist in the ligand backbone conformation either is
prevented or is slow on the NMR time scale. This results in
distinct environments for the two Me groups on each Sb and
for the two protons on each benzyl group, the latter then
geminally coupling to give rise to the observed doublets.
In the CO region of the 13C{1H} NMR spectrum, a broad
peak is observed that when closely examined appears to be split
into six evenly spaced, overlapping peaks of roughly equal
intensity. The intensity of these peaks is modest in comparison
to baseline noise, but the observation is reproducible, leading us
to postulate that they are the result of 55Mn−13C coupling, with
55
a coupling constant of ∼154 Hz. Mn−13C coupling, though
not frequently observed, was also reported in the 13C{1H}
NMR spectrum of fac-[Mn(CO)3([9]aneS3)]+ with a com-
parable coupling constant of 160 Hz.18 The 55Mn NMR (I =
5/2, 100%, Ξ = 24.8 MHz, Q = 0.40 × 10−28 m2)19 spectrum of
this complex contains a very sharp singlet at −1765 ppm, the
small line width (w1/2 ≈ 85 Hz) being consistent with a very
low electric field gradient at Mn. The shift is comparable with
that of fac-[Mn(CO)3{MeN(CH2-2-C6H4SbMe2)2}][CF3SO3]
(−1745 ppm),11 the replacement of a stibine donor with a
coordinated amine seemingly having only a small effect on the
electronic environment of the Mn center; the considerably
smaller line width is consistent with the lower electric field
gradient in the more symmetrical tristibine complex.
Figure 4. View of the structure of [Mn(CO)2{N(CH2-2-
C6H4SbMe2)3}(MeCN)]+ showing the atom-labeling scheme. Ellip-
soids are drawn at the 50% probability level, and H atoms are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Sb1−Mn1 =
2.5472(10), Sb2−Mn1 = 2.5981(11), Sb3−Mn1 = 2.6042(11), Mn1−
C28 = 1.786(7), Mn1−C29 = 1.792(7), Mn1−N2 = 1.983(6), N2−
C30 = 1.132(9); N2−Mn1−Sb1 = 178.04(18), C28−Mn1−N2 =
93.1(3), N2−Mn1−Sb2 = 83.55(18), Sb1−Mn1−Sb2 = 96.59(3),
C28−Mn1−Sb1 = 85.0(2).
The solution IR spectrum of this complex displays two sharp
bands in the carbonyl region (a1 + e). In the solid state splitting
of the e mode into two very close bands is observed, a result of
asymmetry arising from either the locking of the ligand
backbone or interactions of some CO groups with lattice
solvent molecules, as is observed in the crystal structure. The
ESI+ mass spectrum shows the molecular ion [Mn(CO)3{N-
(CH2-2-C6H4SbMe2)3}]+ and [Mn(CO)2{N(CH2-2-
C6H4SbMe2)3}]+, the result of the loss of one CO group.
[Mn(CO)2{N(CH2-2-C6H4SbMe2)3}(MeCN)][CF3SO3] (4).
Treatment of the tricarbonyl complex [Mn(CO)3{N(CH2-2-
C6H4SbMe2)3}][CF3SO3] with excess Me3NO in acetonitrile
resulted in the isolation of an orange oil. IR spectroscopy
showed two bands in the carbonyl region, to low frequency of
those in the tricarbonyl starting material. Recrystallization from
CH2Cl2 and Et2O gave orange, needle-shaped crystals which
were used in single-crystal diffraction studies. The structure
(Figure 4) shows a dicarbonyl species, with the ligand
coordinated via the three Sb donors and the final coordination
site filled by a MeCN molecule. The N atom in the ligand
backbone remains uncoordinated, and the conformation of the
ligand is very similar to that observed in the structure of the
tricarbonyl species discussed above. The Sb−Mn bond
distances trans to the CO groups (2.5981(11) and
2.6042(11) Å) are almost identical with those in the
tricarbonyl, whereas the Sb−Mn distance trans to the MeCN
ligand is slightly shorter (Sb1−Mn1 = 2.5472(10) Å).
triflate counterion, both behaviors having been observed in the
Mn(I) tricarbonyl system of the hybrid amine/stibine ligand
MeN(CH2-2-C6H4SbMe2)2.11 Given that rearrangement of the
ligand conformation in the solid state is unlikely, coordination
of [CF3SO3]− seems the more plausible of the two.
1
The H and 13C{1H} NMR spectra of this species are both
very complex, with a separate environment being observed for
each C atom in the molecule. Considering the symmetry of a
dicarbonyl complex with one other donor, two of the three
ligand arms (those trans to the CO groups) would appear to be
in the same environment. However, if we consider the ligand
backbone to be locked into a twisted position to avoid steric
repulsion of the aryl rings, as seen in the crystal structure of the
MeCN adduct, the two SbtransCO atoms are then disposed
differently from one another relative to MeCN, due to the
chirality introduced by the twist in the ligand backbone. This
accounts for the three separate environments observed for the
three ligand arms. Two very closely spaced peaks are seen in
the CO region of the 13C{1H} NMR spectrum, indicating that
due to the locked ligand conformation the two chemically
equivalent carbonyl groups are also in slightly different
magnetic environments.
[Ag{N(CH2-2-C6H4SbMe2)3}][BF4] (5). The reaction of AgBF4
with N(CH2-2-C6H4SbMe2)3 in EtOH followed by washing
with Et2O gave [Ag{N(CH2-2-C6H4SbMe2)3}][BF4] as a white,
mildly light-sensitive powder. The molecular ion, [Ag{N(CH2-
2-C6H4SbMe2)3}]+, is the only species observed in the ESI+
mass spectrum. The 13C{1H} NMR spectrum reveals two
resonances corresponding to MeSb, one corresponding to
CH2N, and six aromatic C atoms. At room temperature the 1H
NMR spectrum is very broad in the methyl and benzyl regions,
displaying two broad peaks in each, but upon cooling to −60
°C these resolve into a pair of MeSb singlets and two CH2N
The crystals were isolated by filtration and dried in vacuo for
further analysis. The solid and solution-state IR spectra
displayed two bands at frequencies almost identical with
those observed for the crude product, but no bands
corresponding to MeCN were observed. Neither was there
1
any evidence of MeCN in the H or 13C{1H} NMR spectra or
the elemental analysis, leading to the conclusion that the
coordinated MeCN molecule had been lost when the crystals
were subjected to vacuum. This requires the sixth coordination
site to be filled by a different donorwe propose that this is
either the amine from the ligand backbone or the oxygen of the
1
doublets, similar to those seen in the H NMR spectrum of
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3]. This temper-
ature-dependent behavior suggests that at room temperature
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either the coordination or conformation of the ligand is
dynamic on the 1H NMR time scale, whereas at low
temperatures the ligand backbone is locked into position with
the two MeSb groups and two benzyl protons being
inequivalent for each arm of the ligand. Given this information,
the ligand could be either tridentate (via the three Sb donors)
or tetradentate (with the N atom also coordinated); either
would lead to a rigid ligand conformation. Several recrystalliza-
tions failed to produce single crystals of quality suitable for X-
ray studies.
originate from a very small amount of LiBr remaining as an
impurity from the ligand preparation. There was no evidence
for formation of either of these species in samples of
[Cu{N(CH2-2-C6H4SbMe2)3}][BF4] prepared from a fresh
batch of ligand. To allow full characterization, [Cu4Br4{N(CH2-
2-C6H4SbMe2)3}2] (7) was remade via a direct route as
described below.
The structure of [Cu3Br2{N(CH2-2-C6H4SbMe2)3}2]-
[BF4]·CH2Cl2 contains a disordered [BF4]− anion which was
modeled over two positions. The cation is well resolved and
contains a centrosymmetric Cu3Br2 core, with a center of
inversion at Cu2 (Figure 5). The terminal Cu1 is coordinated
Cu(I) Complexes of N(CH2-2-C6H4SbMe2)3. Reaction of
[Cu(MeCN)4][BF4] and N(CH2-2-C6H4SbMe2)3 in CH2Cl2
leads to isolation of [Cu{N(CH2-2-C6H4SbMe2)3}][BF4] (6)
as a white powder. Solid-state IR spectroscopy confirms the
presence of the [BF4]− counterion and the absence of any
MeCN remaining from the precursor. ESI+ mass spectrometry
displays the molecular ion [Cu{N(CH2-2-C6H4SbMe2)3}]+ as
the dominant species.
1
Broad ligand resonances in the H NMR spectrum suggest
dynamic behavior of the ligand in solution similar to that seen
in the silver analogue discussed above. Two environments are
observed for each of the MeSb and CH2N, signifying a locked
conformation of the ligand. Broadening could also be due to
fast relaxation caused by the proximity of the quadrupolar 63Cu
3
or 65Cu nuclei (63Cu, I = /2, 69.09%, Ξ = 26.5 MHz, Q =
3
−0.21 × 10−28 m2; 65Cu: I = /2, 30.91%, Ξ = 28.4 MHz, Q =
−0.20 × 10−28 m2),20 to which we can attribute the broadening
in the 13C{1H} NMR spectrum of the resonances correspond-
ing to C atoms which are directly bonded to Sb; the ipso C
atoms are not observed. 63Cu NMR spectroscopy reveals a
single, fairly broad resonance at −142 ppm (w1/2 = 3200 Hz).
63Cu NMR resonances are normally only observed when the
metal center is in a high-symmetry environment (giving rise to
a small electric field gradient), and for many complexes of
Cu(I) with group 15 ligands no such signal is seen.21 It can be
concluded that there is a relatively small electric field gradient
around the Cu(I) center in [Cu{N(CH2-2-C6H4SbMe2)3}]-
[BF4], suggesting a tetrahedral geometry which is often favored
by Cu(I) species. Previously structurally characterized com-
plexes of stibine ligands with Cu(I) all feature tetrahedral Cu
centers with four Sb donors.22,23 A tetrahedral geometry would
involve tetradentate Sb3N coordination, though this may be
sterically disfavored due to the semirigid nature of the ligand
backbone. Other ligands with this backbone architecture, albeit
with different donor groups, have been seen to coordinate
transition metals in a tetradentate manner, in both distorted-
tetrahedral and trigonal-bipyramidal metal geometries, confirm-
ing that the backbone does have the required flexibility.24,25
Despite these considerations, tridentate (Sb3) coordination
cannot be completely ruled out in this case.
Single-crystal X-ray studies would be critical in determining
the solid-state structure of this compound. Despite repeated
recrystallization attempts, no crystals of suitable quality for X-
ray studies could be grown, the compound always being
precipitated as a fine powder. One crystallization attempt,
involving storage of the reaction mixture at 5 °C over a period
of weeks, resulted in the isolation of a few colorless crystals,
among which were visible two separate morphologies. X-ray
structure determination proved needlelike crystals to be
[Cu3Br2{N(CH2-2-C6H4SbMe2)3}2][BF4]·1.5CH2Cl2, whereas
block-shaped crystals were [Cu4 Br4 {N(CH2 -2-
C6H4SbMe2)3}2]·4CH2Cl2. Both of these Cu(I) species were
formed as very minor products, with the Br atoms thought to
Figure 5. View of the structure of [Cu3Br2{N(CH2-2-
C6H4SbMe2)3}2]+ with atom-numbering scheme. Ellipsoids are
drawn at the 50% probability level, and H atoms are omitted for
clarity. Symmetry operation: (a) 1 − x, 1 − y, 1 − z. Selected bond
lengths (Å) and angles (deg): Sb1−Cu1 = 2.5440(14), Sb2−Cu1 =
2.5388(14), Sb3−Cu1 = 2.5378(16), Br1−Cu2 = 2.2665(13), Br1−
Cu1 = 2.5373(16), Cu1···Cu2 = 2.6900(17); Cu2−Br1−Cu1 =
67.84(5), Br1−Cu1−Sb3 = 102.73(6), Br1−Cu1−Sb2 = 118.70(5),
Br1−Cu1−Sb1 = 113.06(5), Sb2−Cu1−Sb1 = 107.67(6), Br1−
Cu1···Cu2 = 51.29(3), Sb1−Cu1···Cu2 = 90.06(3), Br1−Cu2···Cu1 =
60.87(4).
by one ligand via the three Sb groups, with the Br bridge
completing the pseudo-tetrahedral coordination geometry. The
propeller type conformation of the ligand is similar to that seen
in fac-[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3], though
the difference in coordination geometry between the pseudo-
tetrahedral Cu and the pseudo-octahedral Mn means the bite
angles of the ligands are different (mean ∠Sb−Cu−Sb =
107.2°, ∠Sb−Mn−Sb = 94.9°).
Cu2 is also in the Cu(I) oxidation state but is in a linear
coordination environment between the two symmetry-related
Br1 atoms. The angle ∠Cu1−Br−Cu2 is very acute
(67.84(5)°), meaning Cu1−Cu2 is short (2.690(2) Å), a
common phenomenon in polynuclear Cu(I) species. This
should not be viewed as a Cu−Cu bond, as Cu(I) has a closed-
shell electronic configuration, but could be the result of a type
of attractive dispersion interaction which has been termed
“cuprophilicity”.26
The second serendipitously isolated species, [Cu4Br4{N-
(CH2-2-C6H4SbMe2)3}2], was subsequently prepared directly
by stirring of CuBr and N(CH2-2-C6H4SbMe2)3 in a 2/1 ratio
in CH2Cl2 solution. Crystals of this material with a different
unit cell were also analyzed by X-ray diffraction and proved to
be the same molecule but without the solvated CH2Cl2
molecules (Figure 6). The bond lengths and angles within
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the complex are very similar between the two structures; the
data for the solvated complex are presented in the Supporting
Information.
and CH2N, suggesting that the ligand retains coordination in
solution but either the coordination or the conformation of the
ligand is dynamic on the 1H NMR time scale. Peaks are
observed in the 13C{1H} NMR spectrum for the CH2N moiety
and the six aromatic C atoms, though none could be discerned
for MeSb. No signal was observed in the 63Cu NMR spectrum,
unsurprisingly considering the likelihood of dissociation in
solution leading to more than one low-symmetry 63Cu
environment. The main peak in the high-resolution ESI+
spectrum is [CuL]+ (L = N(CH2-2-C6H4SbMe2)3), but lower
intensity peaks can also be observed for aggregates
[CunBrn−1L2]+ (n = 2−5).
CONCLUSIONS
■
A high-yielding synthesis of a very rare tristibine has been
reported. Complexes of N(CH2-2-C6H4SbMe2)3 with a variety
of transition-metal fragments represent the first coordination
complexes of a tetradentate ligand containing Sb donors.
Through careful selection of transition-metal acceptors it has
been shown that this ligand is capable of coordinating in several
different modes, though a marked preference for tridentate
chelating Sb3 donation was observed in the complexes
obtained. This could be due to either a thermodynamic
preference for tridentate coordination or simply an increased
tendency for crystallization of these rigid structures. Examples
of this mode have been observed in both octahedral and
tetrahedral metal geometries, demonstrating the flexible bite
angle of the ligand; in each case the ligand backbone adopts a
propeller-like conformation which leads to magnetic inequiva-
lence of chemically equivalent organic moieties. The
κSb:κSb′:κSb″ mode was also observed, and there is some
evidence to support tetradentate coordination of the ligand in
[Cu{N(CH2-2-C6H4SbMe2)3}][BF4], though this could not be
structurally confirmed. The bulky nature of the ligand gives rise
to the isolation of unusual copper(I) bromide oligomers in the
solid state, which contain short Cu···Cu distances.
Figure 6. View of the structure of [Cu4Br4{N(CH2-2-C6H4SbMe2)3}2]
with atom-numbering scheme. Ellipsoids are drawn at the 50%
probability level, and H atoms are omitted for clarity. Symmetry
1
3
operation: (a) /2 − x, /2 − y, 1 − z. Selected bond lengths (Å) and
angles (deg): Sb1−Cu1 = 2.5190(8), Sb2−Cu1 = 2.5134(9), Sb3−
Cu1 = 2.5300(7), Br1−Cu2 = 2.3419(9), Br1−Cu1 = 2.4253(8),
Br2−Cu2 = 2.4027(9), Br2−Cu2a = 2.4297(9), Cu2···Cu2a =
2.5763(12); Cu2−Br1−Cu1 = 99.31(3), Cu2−Br2−Cu2a =
64.43(3), Br1−Cu1−Sb2 = 117.10(3), Br1−Cu1−Sb1 = 110.38(3),
Sb2−Cu1−Sb1 = 106.86(3), Br1−Cu1−Sb3 = 105.36(3), Sb2−Cu1−
Sb3 = 110.08(3), Sb1−Cu1−Sb3 = 106.64(3), Br1−Cu2−Br2 =
124.06(3), Br1−Cu2−Br2a = 120.33(3), Br2−Cu2−Br2a =
115.57(3), Br1−Cu2···Cu2a = 176.93(4).
The molecule comprises a central Cu2Br4 unit with trigonal-
planar Cu(I) centers which is structurally comparable with the
well-known [Cu2Br4]2−‑ anion, though in this case each outer
Br atom bridges to a pseudo-tetrahedral [Cu{N(CH2-2-
C6H4SbMe2)3}]+ unit, which has a geometry comparable to
that of the equivalent moiety in [Cu3Br2{N(CH2-2-
C6H4SbMe2)3}2][BF4]·CH2Cl2. The central Cu(I)···Cu(I)
distance of 2.5763(12) Å is shorter than that in any
[Cu2Br4]2− unit previously reported in the Cambridge
Structural Database.27
Similar halocuprate oligomers in which the terminal Cu
atoms are coordinated by neutral ligands have been reported.
For example, the mixed-valence [CuII(4,4′-Me2-2,2′-bipy)2(μ-
Br)CuI(μ-Br)2CuIBr] contains a central Cu2Br4 unit geometri-
cally comparable to the core of [Cu4Br4{N(CH2-2-
C6H4SbMe2)3}2], though in this case it is only capped at one
end.28 Another mixed-valence species with a very similar
geometry is [CuIIBr(C33H43N3)]2[CuI2Br4], which, like
[Cu4Br4{N(CH2-2-C6H4SbMe2)3}2], is capped at both ends
by coordinated Cu moieties, except that the CuII−Br distance
of 2.689(2) Å is long enough for this to be considered as an
associated ion pair.29
EXPERIMENTAL SECTION
■
Infrared spectra were recorded as Nujol mulls between NaCl plates
using a Perkin-Elmer Spectrum 100 spectrometer over the range
4000−500 cm−1, and solution spectra used NaCl solution cells over
the range 2200−1800 cm−1. 1H and 13C{1H} NMR spectra were
recorded using a Bruker AV300 or Bruker DPX400 spectrometer at
ambient temperature (25 °C) unless otherwise stated and are
referenced to the residual solvent signal. Microanalyses on new
complexes were outsourced to Medac Ltd. or London Metropolitan
University. Positive ion electrospray (ESI+) mass spectra were run in
MeCN solution using a VG Biotech platform. Preparations were
undertaken using standard Schlenk and glovebox techniques under a
N2 atmosphere. Solvents were dried by distillation from CaH2
(CH2Cl2, MeCN), Na/benzophenone ketyl (thf, diethyl ether), Na
wire (toluene, hexane), or Mg/I2 (EtOH). Starting materials were
purchased from Sigma Aldrich and used as received. SbMe2Ph was
made as described previously.32
The isolation of finite chains or clusters of halide-bridged
Cu(I) atoms within more complex systems is common, and it
has been observed that the nature of the cation affects the
formation of these anions in the solid state.30 However, studies
have shown that these conformations are not generally retained
in solution, extensive dissociation to simple anions generally
being observed.31 It seems probable that the bulky nature of the
[Cu{N(CH2-2-C6H4SbMe2)3}]+ moiety is what causes the
crystallization of species containing discrete polynuclear Cu(I)
bromide cores, but it is likely that these structures are
N(CH2-2-C6H4SbMe2)3 (1). A solution of SbMe2Ph (3.73 g, 16.3
mmol) in toluene (300 mL) was flushed with HBr gas for 15 min. The
resulting SbMe2Br solution was stirred under a sealed atmosphere for
30 min, followed by purging with a stream of N2 gas for 20 h, and then
cooled to 0 °C. A thf (250 mL) solution of N(CH2-2-C6H4Br)3 (2.67
g, 5.1 mmol) was cooled to −78 °C and nBuLi (1.6 M in hexane, 9.56
mL, 15.3 mmol) added dropwise. The resulting pink solution was
stirred for 10 min and then added slowly to the cooled, stirred solution
of SbMe2Br. The reaction mixture was stirred for 18 h and then
degassed and deionized water (100 mL) was added slowly. The
organic layer was separated, the aqueous layer was washed with Et2O
1
dissociated in solution. The peaks in the H NMR spectrum
of [Cu4Br4{N(CH2-2-C6H4SbMe2)3}2] are extremely broad,
with two pairs of resonances which can be assigned to MeSb
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(40 mL), the combined organics were dried over MgSO4 and filtered,
and the volatiles were removed in vacuo to give a sticky, opaque white
oil. This crude product was redissolved in CH2Cl2, the solution was
filtered through Celite to remove a small amount of insoluble white
powder, and the volatiles were removed in vacuo, yielding a sticky
clear oil. Yield: 3.11 g, 82%. Anal. Calcd for C27H36N1Sb3 (739.5): C,
43.8; H, 4.9; N, 1.9. Found: C, 44.0; H, 4.8; N, 2.0. 1H NMR
(CDCl3): δ 0.89 (s, [18H], MeSb), 3.80 (s, [6H], CH2N), 7.21 (dt,
[3H]), 7.30 (dt, [3H]), 7.48 (dd, [3H]) and 7.62 (dd, [3H])
(aromatic CH). 13C{1H} NMR (CDCl3): δ −1.6 (MeSb), 60.5
(CH2N), 127.2, 128.2, 129.3, 133.4, 138.5, and 144.4 (Caromatic).
A small portion of the product was dissolved in MeCN and treated
with an excess of MeI, and the mixture was stirred for 5 h. The
volatiles were then removed in vacuo, leaving a white solid residue. MS
(ESI+): m/z 754 [N(CH2-2-C6H4SbMe2)2(CH2-2-C6H4SbMe3)]+, 604
[N(CH2C6H5)(CH2-2-C6H4SbMe2)(CH2-2-C6H4SbMe3)]+, 588
[(Me2Sb-2-C6H4CH2)N(CH2-2-C6H4)2SbMe2]+, 452 [N-
(CH2C6H5)2(CH2-2-C6H4SbMe3)]+, 436 [(C6H5CH2)N(CH2-2-
C6H4)2SbMe2]+, 420 [N(CH2-2-C6H4)3SbMe]+, 384.5 [N(CH2-2-
C6H4SbMe2)(CH2-2-C6H4SbMe3)2]2+, 309.5 [N(CH2C6H5)(CH2-2-
mL) was added, the solution was filtered to remove a small amount of
pale solid, and the filtrate was stored at 5 °C over 24 h, yielding orange
needlelike crystals and some pale orange solid. The crystals were
isolated by decanting the supernatant and their structure was
determined by X-ray methods. They were then dried in vacuo for 2
h, after which NMR, IR and elemental analysis was undertaken. Yield:
0.05 g, 25%. Anal. Calcd for C30H36F3MnNO5SSb3 (999.4): C, 36.0;
H, 3.6; N, 1.4. Found: C, 35.9; H, 3.5; N, 1.6. IR (Nujol/cm−1): 1943
s, 1887 s (CO), 1261 s, br (CF3SO3). IR (CH2Cl2/cm−1): 1949 s,
1
1890 s. H NMR (CDCl3): δ 0.26 (s, [3H]), 0.52 (s, [3H]), 0.56 (s,
[3H]), 1.22 (s, [3H]), 1.45 (s, [3H]), 1.47 (s, [3H]) (MeSb), 2.82−
2
2.89 (3 overlaid doublets, [3H]), 3.76 (d, JHH = 12 Hz, [1H]), 3.83
(d, 2JHH = 12 Hz, [1H]), 3.95 (d, 2JHH = 12 Hz, [1H]) (CH2N), 7.32−
7.45 (m, [8H]), 7.60−7.66 (m, [3H]), 7.82−7.85 (m, [1H]) (aromatic
CH). 13C{1H} NMR (CDCl3): δ −2.5, −1.5, −1.0, −0.9, −0.3, and 1.6
(MeSb), 63.07, 63.11, and 63.4 (CH2N), 129.0, 129.2, 130.4, 130.5,
130.6, 132.75, 132.81, 133.0, 133.4, 134.0, 134.1, 134.55, 134.57,
136.2, 136.4, 141.5, 142.6, and 142.8 (Caromatic), 223.5 and 223.7 (CO).
19F NMR (CDCl3): δ −78.1. 55Mn NMR (CH2Cl2/CDCl3): not
observed. (ESI+): m/z 850 [Mn(CO)2{N(CH2-2-C6H4SbMe2)3}]+.
[Ag{N(CH2-2-C6H4SbMe2)3}][BF4] (5). AgBF4 (0.053 g, 0.27
mmol) was dissolved in EtOH (20 mL), and a solution of N(CH2-
2-C6H4SbMe2)3 (0.20 g, 0.27 mmol) in CH2Cl2 (5 mL) was added.
The mixture was stirred in the absence of light for 1 1/2 h, resulting in
a slightly cloudy colorless solution, which was filtered, and the volatile
components of the filtrate were removed in vacuo. The resultant tacky
white solid was washed with Et2O (20 mL), leaving a fine white
powder, which was dried in vacuo for 2 h. Despite drying, both the
NMR spectra and the elemental analysis suggested the presence of a
less than stoichiometric amount of Et2O remaining. The NMR
resonances correspond exactly to free Et2O, making it unlikely that this
solvent is coordinated to the metal center. Yield: 0.16 g, 61%. Anal.
Calcd for C27H36AgBF4NSb3·0.5C4H10O (971.4): C, 35.8; H, 4.3; N,
1.4. Found: C, 36.8; H, 4.1; N, 1.7. IR (Nujol/cm−1): 1051 vbr (BF4).
1H NMR (CDCl3, 25 °C): δ 0.42 (vbr, [9H], MeSb), 1.35 (vbr, [9H],
MeSb), 3.09 (vbr, [3H], CH2N), 3.90 (vbr, [3H], CH2N), 7.35−7.38
C6H4SbMe3)2]2+
, 301.5 [(Me3Sb-2-C6H4CH2)N(CH2-2-
C6H4)2SbMe2]2+.
[{FeCp(CO)2}3{N(CH2-2-C6H4SbMe2)3}][BF4]3 (2). [FeCp(CO)2I]
(0.25 g, 0.81 mmol) and Ag[BF4] (0.16 g, 0.81 mmol) were dissolved
in CH2Cl2 (20 mL), and thf (0.1 mL) was added. The mixture was
stirred in the absence of light for 2 h and then filtered to remove the
resultant pale precipitate. The red filtrate was added to a solution of
N(CH2-2-C6H4SbMe2)3 (0.20 g, 0.27 mmol) in CH2Cl2 (5 mL), and
the reaction mixture was stirred for 18 h, resulting in an orange
solution. The volatiles were removed in vacuo, yielding an orange
solid, which was washed with Et2O (10 mL) and dried in vacuo. Yield:
0.22 g, 53%. Anal. Calcd for C48H51B3F12Fe3NO6Sb3 (1532.2): C,
37.7; H, 3.4; N, 0.9. Found: C, 37.2; H, 2.8; N, 1.0. IR (Nujol/cm−1):
2038 s, br, 1987 s, br (CO), 1049 s, vbr (BF4). IR (CH2Cl2/cm−1):
2046 s, 2001 s. 1H NMR (CD3CN): δ 1.76 (s, [18H], MeSb), 3.93 (s,
[6H], CH2N), 5.26 (s, [15H], Cp), 7.41 (m, [3H]), 7.47 (m, [3H]),
7.57 (t, [3H]), 8.05 (d, [3H]), (aromatic CH). 13C{1H} NMR
(CD3CN): δ 2.6 (MeSb), 59.0 (CH2N), 86.7 (Cp), 128.5, 128.8,
129.3, 132.9, 144.5 (Caromatic), 210.4 (CO). (ESI+): m/z 547
1
(m, [9H], aromatic CH), 7.49−7.52 (m, [3H], aromatic CH). H
NMR (CDCl3, −60 °C): δ 0.32 (s, [9H], MeSb), 1.21 (t, [1.5H],
Et2O) 1.36 (s, [9H], MeSb), 3.08 (d, [3H], CH2N), 3.47 (q, [1H],
Et2O), 3.87 (d, [3H], CH2N), 7.35−7.38 (m, [9H], aromatic CH),
7.43−7.46 (m, [3H], aromatic CH). 13C{1H} NMR (CDCl3, 25 °C):
δ −2.9 (MeSb), 63.2 (CH2N), 128.8, 129.2, 133.3, 134.0, 135.9, and
141.1 (Caromatic). (ESI+): m/z 848 [Ag{N(CH2-2-C6H4SbMe2)3}]+.
[Cu{N(CH2-2-C6H4SbMe2)3}][BF4] (6). [Cu(MeCN)4][BF4]
(0.063 g, 0.20 mmol) was dissolved in CH2Cl2 (20 mL), and a
solution of N(CH2-2-C6H4SbMe2)3 (0.15 g, 0.20 mmol) in CH2Cl2
(10 mL) was added. The reaction mixture was stirred for 18 h,
resulting in a cloudy, colorless solution, which was filtered and then
reduced in vacuo to ∼5 mL. Et2O (15 mL) was added, precipitating a
white solid, which was isolated by filtration and washed with Et2O (5
mL). Yield: 0.09 g, 50%. Anal. Calcd for C27H36BCuF4NSb3 (890.1):
C, 36.4; H, 4.1; N, 1.6. Found: C, 37.4; H, 4.3; N, 1.5%. IR (Nujol/
[{FeCp(CO)2}2{N(CH2-2-C6H4SbMe2)3}]2+
, 678 [{FeCp-
(CO)2}3{N(CH2-2-C6H4SbMe2)3}{BF4}]2+, 860 [Fe(CO)2{N(CH2-
2-C6H4SbMe2)3}]+.
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3] (3). A mixture of
[Mn(CO)5Br] (0.074 g, 0.27 mmol) and Ag[CF3SO3] (0.069 g, 0.27
1
mmol) was refluxed for 1 /2 h in acetone solution (30 mL). The
resultant yellow solution was filtered to remove the off-white
precipitate, and a solution of N(CH2-2-C6H4SbMe2)3 (0.20 g, 0.27
mmol) in CH2Cl2 (5 mL) was added. The reaction mixture was stirred
for 18 h, resulting in a clear orange solution. The volatile components
were removed in vacuo, resulting in a bright orange oil. Trituration
with Et2O (15 mL) gave a bright orange solid, which was isolated by
filtration. Yield: 0.135 g, 49%. Recrystallization from toluene/CHCl3
(18 °C, 72 h) gave orange-yellow crystals which were used for the X-
ray data collection. Anal. Calcd for C31H36F3MnNO6SSb3 (1027.9): C,
36.2; H, 3.5; N, 1.4. Found: C, 36.4; H, 4.3; N, 1.5. IR (Nujol/cm−1):
2006 s, 1934 sh, 1926 s (CO), 1262 s, br (CF3SO3). IR (CH2Cl2/
1
cm−1): 1057 vbr (BF4). H NMR (CDCl3): δ 0.47 (br, [9H], MeSb),
1.34 (br, [9H], MeSb), 3.34 (vbr, [3H], CH2N), 3.86 (vbr, [3H],
CH2N), 7.35−7.52 (m, [12H], CH aromatics). 13C{1H} NMR
(CDCl3): δ −3.0 (MeSb), 64.6 (CH2N), 129.1, 129.5, 133.1, 133.9,
134.1, and 140.8 (Caromatic). 63Cu NMR (CDCl3): δ −142 (w1/2 = 3200
Hz). MS (ESI+): m/z 804 [Cu{N(CH2-2-C6H4SbMe2)3}]+.
[Cu4Br4{N(CH2-2-C6H4SbMe2)3}2] (7). CuBr (0.058 g, 0.40 mmol)
was suspended in CH2Cl2 (20 mL), and a solution of N(CH2-2-
C6H4SbMe2)3 (0.15 g, 0.20 mmol) in CH2Cl2 (10 mL) was added.
The mixture was stirred for 18 h, and the resultant slightly cloudy,
colorless solution was filtered. The filtrate was reduced in volume to
∼5 mL, and Et2O (15 mL) was added, precipitating a flocculant white
solid which was isolated by filtration and washed with Et2O (5 mL).
Yield: 0.12 g, 58%. Colorless block-shaped crystals grew from the
filtrate over 2 days, which were used for X-ray data collection. Anal.
Calcd for C27H36Br2Cu2N1Sb3 (1026.4): C, 31.6; H, 3.5; N, 1.4.
Found: C, 31.9; H, 3.2; N, 1.7. 1H NMR (CDCl3): δ 0.33 (vbr, [9H],
SbMe), 1.17 (vbr, [9H], SbMe), 3.03 (vbr, [3H], CH2N), 3.81 (vbr,
1
cm−1): 2015 s, 1943 m (CO). H NMR (CD2Cl2): δ 0.51 (s, [9H],
MeSb), 1.56 (s, [9H], MeSb), 3.05 (d, [3H], CH2N), 3.80 (d, [3H],
CH2N), 7.4−7.8 (m, [12H], aromatic CH). 13C{1H} NMR (CDCl3):
δ 0.0 and 1.5 (SbMe), 63.1 (CH2N), 130.2, 131.8, 132.1, 134.4, 134.7,
and 143.1 (Caromatic), 218.9 (1:1:1:1:1:1 sextet, 1JMnC ≈ 154 Hz). 55Mn
NMR (CH2Cl2/CDCl3): δ −1765 (w1/2 = 85 Hz). (ESI+): m/z 878
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}]+, 850 [Mn(CO)2{N(CH2-2-
C6H4SbMe2)3}]+.
[Mn(CO)2{N(CH2-2-C6H4SbMe2)3}][CF3SO3] (4). Freshly prepared
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3] (0.21 g, 0.20 mmol)
was dissolved in MeCN (10 mL) and a solution of Me3NO (0.030 g,
0.40 mmol) in MeCN (10 mL) added. The reaction mixture was
stirred for 18 h, and then the volatiles were removed in vacuo, leaving
a bright orange oil, which was redissolved in CH2Cl2 (10 mL). Et2O (5
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[3H], CH2N), 7.28−7.36 (m, [9H], aromatic CH), 7.52−7.54 (m,
[3H], aromatic CH). 13C{1H} NMR (CD2Cl2): δ 63.4 (CH2N), 129.0,
129.5, 134.0, 134.7, 136.7, and 142.8 (Caromatic). MS (HR ESI+): m/z
2116 [Cu5Br4{N(CH2-2-C6H4SbMe2)3}2]+, 1972 [Cu4Br3{N(CH2-2-
C6H4SbMe2)3}2]+, 1829 [Cu3Br2{N(CH2-2-C6H4SbMe2)3}2]+, 1687
[Cu2Br1{N(CH2-2-C6H4SbMe2)3}2]+, 804 [Cu{N(CH2-2-
C6H4SbMe2)3}]+.
(11) Benjamin, S. L.; Levason, W.; Reid, G.; Rogers, M. C. Dalton
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X-ray Crystallography. Crystals were obtained as described
above. Details of the crystallographic data collection and refinement
parameters are given in Table S1 (Supporting Information). Data
collection was carried out using either a Rigaku AFC12 goniometer
equipped with an enhanced sensitivity (HG) Saturn724+ detector
mounted at the window of an FR-E+ SuperBright molybdenum
rotating anode generator with VHF Varimax optics (70 μm focus) or a
Rigaku R-Axis Spider including curved Fujifilm image plate and a
graphite-monochromated sealed-tube Mo generator. Structure sol-
ution and refinement were routine33,34 except where mentioned
below; hydrogen atoms on C were added to the model in calculated
postions using the default C−H distance. Disorder of the [BF4]− unit
in [Cu3Br2{N(CH2-2-C6H4SbMe2)3}2][BF4]·1.5CHCl2 was modeled
over two positions. The site occupation factor for the CH2Cl2 solvate
molecules was determined by refinement. The toluene solvate in
[Mn(CO)3{N(CH2-2-C6H4SbMe2)3}][CF3SO3]·CHCl3·C7H8 exhib-
its disorder which could not be satisfactorily modeled; however, the
other components of the structure are well resolved.
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Soc. 1995, 117, 8468.
The CCDC reference numbers 924062−924067 contain supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
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̈
(27) Allen, F. Acta Crystallogr., Sect. B 2002, 58, 380.
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(29) Le Gall, B.; Conan, F.; Cosquer, N.; Kerbaol, J.-M.; Kubicki, M.
M.; Vigier, E.; Le Mest, Y.; Sala Pala, J. Inorg. Chim. Acta 2001, 324,
300.
ASSOCIATED CONTENT
* Supporting Information
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S
(30) Jagner, S.; Helgesson, G. Adv. Inorg. Chem. 1991, 37, 1.
CIF files for the crystal structures described, together with
crystallographic data (Table S1) and the structural information
for [Cu4Br4{N(CH2-2-C6H4SbMe2)3}2]·4CH2Cl2. This materi-
al is available free of charge via the Internet at http://pubs.acs.
org.
̈
(31) Hasselgren, C.; Stenhagen, G.; Ohrstrom, L.; Jagner, S. Inorg.
Chim. Acta 1999, 292, 266.
̈
(32) Levason, W.; Matthews, M. L.; Reid, G.; Webster, M. Dalton
Trans. 2004, 51.
(33) Sheldrick, G. M. SHELXS-97, program for crystal structure
solution; University of Gottingen, Gottingen, Germany, 1997.
̈
̈
(34) Sheldrick, G. M., SHELXL-97, program for crystal structure
refinement; University of Gottingen, Gottingen, Germany, 1997.
AUTHOR INFORMATION
Corresponding Author
*E-mail for G.R.: G.Reid@soton.ac.uk.
■
̈
̈
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We thank the EPSRC for financial support and for a Doctoral
Prize (S.L.B.). We also thank Dr. M. Webster for assistance
with crystallographic analyses.
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