Establishing the coordination chemistry of antimony(v) Cations: Systematic assessment of Ph4Sb(OTf) and Ph3Sb(OTf)2 as Lewis acceptors

Article abstract of DOI:10.1002/chem.201406469

The coordination chemistry of the stiboranes Ph₄Sb(OTf) (1 a, OTf = OSO₂CF₃) and Ph₃Sb(OTf)₂ (3) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4-methylpyridine-N-oxide (OPyrMe) and OPMe₃ enabled the characterization of [Ph₄Sb(OPyrMe)][OTf] (2 a) and [Ph₄Sb(OPMe₃)][OTf] (2 b), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph₃Sb(donor)₂][OTf]₂ [donor=OPMe₃ (6 a), OPCy₃ (6 b, Cy=cyclohexyl), OPPh₃ (6 c), OPyrMe (6 d)], [Ph₃Sb(dmap)₂(OTf)][OTf] (6 e, dmap=4-(dimethylamino)pyridine) and [Ph₃Sb(donor)(OTf)][OTf] [donor=1,10-phenanthroline (7 a) or 2,2′-bipy (7 b, bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid-state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh₃ and products of phosphine oxidation.

Full text of DOI:10.1002/chem.201406469

DOI: 10.1002/chem.201406469
Full Paper
&
Antimony(V) Cations
Establishing the Coordination Chemistry of Antimony(V) Cations:
Systematic Assessment of Ph4Sb(OTf) and Ph3Sb(OTf)2 as Lewis
Acceptors
Alasdair P. M. Robertson,[a] Saurabh S. Chitnis,[a] Hilary A. Jenkins,[b] Robert McDonald,[c]
Michael J. Ferguson,[c] and Neil Burford*[a]
Abstract: The coordination chemistry of the stiboranes
Ph4Sb(OTf) (1a, OTf = OSO2CF3) and Ph3Sb(OTf)2 (3) with
Lewis bases has been investigated. The significant steric en-
cumbrance of the Sb center in 1a precludes interaction with
most ligands, but the relatively low steric demands of
4-methylpyridine-N-oxide (OPyrMe) and OPMe3 enabled
the characterization of [Ph4Sb(OPyrMe)][OTf] (2a) and
[Ph4Sb(OPMe3)][OTf] (2b), rare examples of structurally char-
acterized complexes of stibonium acceptors. In contrast, 3
was found to engage a variety of Lewis bases, forming
stable isolable complexes of the form [Ph3Sb(donor)2][OTf]2
[donor=OPMe3 (6a), OPCy3 (6b, Cy=cyclohexyl), OPPh3
(6c), OPyrMe (6d)], [Ph3Sb(dmap)2(OTf)][OTf] (6e, dmap=4-
(dimethylamino)pyridine)
and
[Ph3Sb(donor)(OTf)][OTf]
[donor=1,10-phenanthroline (7a) or 2,2’-bipy (7b, bipy=bi-
pyridine)]. These compounds exhibit significant structural di-
versity in the solid-state, and undergo ligand exchange reac-
tions in line with their assignment as coordination com-
plexes. Compound 3 did not form stable complexes with
phosphine donors, with reactions instead leading to redox
processes yielding SbPh3 and products of phosphine oxida-
tion.
also been reported[2] along with one example of a cationic SbI
acceptor.[7] Structurally characterized complexes featuring cat-
ionic SbV acceptors, however, are rare,[8,9] although spectro-
scopic characterization has been presented in some cases.[10–15]
Furthermore, structurally characterized complexes involving
prototypical pnictonium cations, that is, [R4Pn]+ (Pn=N, P, As,
Sb, or Bi), as acceptors are rare,[8,14,16,17] likely a consequence of
steric encumbrance at the pnictogen acceptor, an effect illus-
trated by the solid-state structures of [Ph4P][X] (X=Cl or Br)
(Scheme 1a).[18,19] Both compounds present ionic formulations,
in which the phosphorus center is tetrahedral in geometry,
and the shortest phosphorus–halide contact is greater than
the sum of the P–X van der Waals radii (SvdW). The only struc-
turally characterized complex of a prototypical [R4P]+ acceptor,
[SIMesPF2Ph2][B(C6F5)4] (SIMes = 1,3-dimesitylimidazolidin-2-yli-
Introduction
Coordination chemistry of transition-metal and Group 13 ac-
ceptors has been extensively developed and describes impor-
tant features of structure, bonding, and reactivity in com-
pounds of these elements. Lewis acceptor behavior is also ob-
served for many of the other p-block elements,[1] but examples
are generally limited by the comparatively small covalent radii
and/or the limited availability of energetically appropriate ac-
ceptor orbitals. The replacement of substituents on an accept-
or center by weakly coordinating anions (e.g., OSO2CF3 (OTf),
AlX4, B(C6F5)4, PF6) can, however, enhance the Lewis acidity of
a p-block center and creates one or more vacant coordination
sites, facilitating coordination chemistry.[2–4]
Antimony(III) and antimony(V) acceptors have been shown
to engage a broad array of ligands,[5,6] and a number of struc-
turally characterized complexes of cationic SbIII acceptors have
[a] Dr. A. P. M. Robertson, S. S. Chitnis, Prof. N. Burford
Department of Chemistry, University of Victoria
P.O. Box 3065, Stn CSC, Victoria, BC V8W 3V6 (Canada)
E-mail: nburford@uvic.ca
[b] Dr. H. A. Jenkins
Department of Chemistry, McMaster University
1280 Main St. W., Hamilton, ON L8S 4M1 (Canada)
[c] Dr. R. McDonald, Dr. M. J. Ferguson
Department of Chemistry, University of Alberta
11227 Saskatchewan Drive NW, Edmonton, AB T6G 2G2 (Canada)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201406469.
Scheme 1. Solid-state structures observed for a) [Ph4P][Cl],[18] b) [SI-
MesPF2Ph2][B(C6F5)4],[16] c) Ph4SbCl,[20] and d) [Ph4Sb(dmso)][PdCl3(dmso)].[8]
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dene) (Scheme 1b),[16] contains two fluoride substituents,
which impart a significant Lewis acidity at the phosphorus
atom with minimal steric imposition.
The Lewis acceptor potential of 1a was subsequently ex-
plored by spectroscopic screening of the reactivity with an
equimolar quantity of a range of Lewis bases (Scheme 2b).
There was no evidence of reaction with PMe3, OPPh3, NEt3,
2,2’-bipy or 4,4’-bipy in CH2Cl2 over 2 h; and although reaction
mixtures of 1a with dmap indicated a shift in the resonances
The greater atomic radii of the heavier pnictogen centers fa-
cilitates increasingly high coordination numbers, such that
derivatives of Ph4SbX (X=halide) are molecular in the solid
state and contain penta-coordinate, trigonal-bipyramidal Sb
centers (Scheme 1c).[20–22] Nevertheless, only one complex
[Ph4Sb(dmso)][PdCl3(dmso)] (Scheme 1d),[8] containing a proto-
typical stibonium acceptor has been structurally characterized,
along with the recent spectroscopic characterization of
[(C6F5)4Sb(OPEt3)][B(C6F5)4].[14] We now report, therefore, the
preparation and characterization of Ph4Sb(OTf) (1a) and
Ph3Sb(OTf)2 (3), and the systematic exploration of their interac-
tion with classical ligands, evolving our preliminary results for
compound 3,[3] and establishing a potentially diverse and ex-
tensive coordination chemistry for cationic SbV centers with
implications for other heavy elements of the p block.
1
associated with the ligand in the H NMR spectrum, only 1a
was isolated upon recrystallization of the reaction products. In
contrast, treatment of 1a with a stoichiometric quantity of 4-
methylpyridine-N-oxide (OPyrMe) or OPMe3 yielded colorless
solids, which were spectroscopically characterized as the 1:1
complexes [Ph4Sb(donor)][OTf] [donor=OPyrMe (2a), OPMe3
(2b)]. In both cases the 1H NMR resonances associated with
the ligand are deshielded relative to those for the correspond-
ing free species, and for compound 2b the 31P{1H} NMR spec-
trum illustrates the expected downfield shifted singlet (dP =
42.6 ppm) (see also Table SI-1 in the Supporting Information),
consistent with coordination of the ligand to the Lewis acidic
Sb center of 1a. The possibility of a dissociative equilibrium in
solution for compounds 2a and 2b was also, however, probed
in the 31P NMR spectra of 2b in CD2Cl2 at various concentra-
tions. At concentrations below approximately 0.15m, the
chemical shift observed for solutions containing compound 2b
approaches that of free OPMe3 (dP =36.3 ppm) (see also Fig-
ure SI-6 in the Supporting Information), suggesting that associ-
ation of 1a and OPMe3 may be reversible in solution, with the
kinetics of re-association increasingly unfavorable at lower con-
centrations.
Results and Discussion
Preparation and coordination chemistry of compound 1a
Treatment of a CH2Cl2 solution of Ph4SbBr with AgOTf yields
a colorless solid, which was spectroscopically characterized as
Ph4Sb(OTf) (1a) (Scheme 2a), as previously reported through
Recrystallization from CH2Cl2/Et2O or MeCN/Et2O for 2a and
2b, respectively, furnished the complexes in analytical purity,
and crystals appropriate for analysis by single-crystal X-ray dif-
fraction. Compound 2a crystallized in the space group P21/c,
with a single formula unit in the asymmetric unit, exhibiting
a trigonal-bipyramidal geometry at the Sb center (Figure 1a).
Scheme 2. a) Synthesis of Ph4Sb(OTf) (1a) and b) reactions of 1a with Lewis
bases. OPyrMe=4-methylpyridine-N-oxide, dmap=4-(dimethylamino)pyri-
dine, bipy=bipyridine.
an alternative synthetic methodology.[23] We postulate that 1a
adopts a trigonal-bipyramidal geometry in the solid-state as re-
ported for Ph4SbX (X=halide[21,22] or OSO2Ph[23]
)
and
(C6F5)4Sb(OTf),[14] but note that in solution the complex may be
ionic, that is, [Ph4Sb][OTf], as reported for Ph4SbI in CD3CN.[21]
Consistently the 121Sb NMR spectrum of 1a in CD3CN displays
a broad singlet at d=673 ppm (compare d=685 ppm for
Ph4SbI),[21] the observation of which is in-line with a highly
symmetric, tetrahedral Sb center. Interestingly the 121Sb NMR
spectrum of 1a in CD2Cl2 displays no such peak at ambient
temperature suggesting that in this solvent the OTf anion may
remain bound to the Sb center imposing a less symmetric
trigonal-bipyramidal geometry at the Sb, leading to rapid
quadrupolar relaxation of the Sb center.
Figure 1. Solid-state structure of the cations in a) 2a and b) 2b. All hydro-
gen atoms are omitted for clarity.
The OPyrMe ligand adopts an axial position, with a relatively
long SbÀO bond (2.449(1) Š; compare the sum of the covalent
radii (SCR)=2.03 Š),[24] which lies within the range defined by
other examples of SbVÀO coordinate bonds (1.94–2.57 Š).[8,25–27]
The three equatorial phenyl substituents adopt a propeller
conformation and are distorted towards the OPyrMe ligand
with the angles between their ipso carbon atoms and that of
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the axial Ph substituent in the range 97.2–100.68. The shortest
SbÀO inter-ion contact (5.185(2) Š) is significantly greater than
the sum of the SbÀO van der Waals radii (SvdW =3.58 Š),[28] and
as such we assign an ionic formulation for 2a, wherein the
OPyrMe ligand has nucleophilically displaced the OTf anion
from 1a. The solid-state structure of compound 2b is similar,
again illustrating a trigonal-bipyramidal geometry at the Sb
center, with the phosphine oxide ligand in an axial position
(Figure 1b). The SbÀO bond (2.406(2) Š) is shorter than that in
2a, but is significantly longer than those in examples of neu-
tral SbVÀOPR3 adducts (range: 1.94–2.15 Š).[25–27] The PÀO bond
(1.499(2) Š) is slightly longer than that reported for OPMe3
(1.488(5) Š),[29] which is consistent with coordination to the
Lewis acidic Ph4Sb+ center. As for 2a, the three ipso carbon
atoms of the equatorial Ph substituents are bent out of the
equatorial plane towards the OPMe3 ligand, presumably allevi-
ating the steric pressure imposed by interaction with the axial
Ph substituent. The shortest SbÀOTf contact is an SbÀF interac-
tion (4.312(7) Š; SvdW =3.53 Š),[28] the magnitude of which is
consistent with an ionic formulation as for 2a (Table 1).
revealed a penta-coordinate trigonal-bipyramidal Sb center, as
for the As[32] and Bi[3] analogues, with two axially bound triflate
substituents (O-Sb-O=173.21(5)8), and three equatorial phenyl
substituents in which the ipso carbon atoms are coplanar with
the Sb center (Figure 2). The two SbÀO bonds (average
2.172(2) Š; SCR =2.03 Š),[24] are consistent in length with other
examples of short SbÀOTf interactions,[33,34] and are representa-
tive of “fully coordinated” triflate substituents at Sb.
Figure 2. Solid-state structure of 3. All hydrogen atoms are omitted for
clarity.
Table 1. Selected solid-state metrical parameters for complexes 2a and
2b.
Reaction of 3 with two equivalents of the prototypical phos-
phine PMe3 in CH2Cl2 did not lead to the anticipated bis-phos-
phine complex [Ph3Sb(PMe3)2][OTf]2, but instead resulted in the
immediate precipitation of a colorless solid, spectroscopically
identified as the diphosphonium salt [Me3PÀPMe3][OTf]2 (4a)
(Scheme 3).[7,35] The concomitant formation of SbPh3 was con-
SbÀligand (SbÀO)
Shortest SbÀOTf
O-Sb-Pn
angle [8]
bond length [Š]
contact [Š]
2a
2b
2.449(1)
2.406(2)
5.185(2) (SbÀO)
4.312(7) (SbÀF)
113.73(9)
164.8(1)
As cationic complexes of stibonium acceptors are rare,[8,30]
compounds 2a and 2b represent important new examples.
The cations in both are structurally similar to that in the closely
related [Ph4Sb(dmso)][PdCl3(dmso)],[8] which contains a trigo-
nal-bipyramidal Sb center in which the ligand occupies an axial
position, and exhibits a long Sb–ligand interaction (2.567(2) Š;
SCR =2.03 Š). Steric congestion at the Sb center of 1a pre-
cludes coordination of the prototypical Lewis bases PMe3 and
dmap, but the lower steric demands of the comparatively
weak bases OPyrMe and OPMe3, resulting from an “oxygen
spacer” between the Sb center and the sterically demanding
component of the ligand, permits formation of 2a/2b, albeit
with particularly long SbÀligand bonds. The steric constraints
illustrated in 1a are apparently greater in its phosphonium an-
alogue [Ph4P][OTf] (1b), for which no evidence of reaction with
PMe3, dmap, OPyrMe, or OPMe3 was detected after stirring
over 2 h at ambient temperature in CH2Cl2.
Scheme 3. Reaction of 3 with PR3 (R=Me or nPr) to yield 4 and SbPh3.
1
firmed by the H and 13C NMR spectra of the CH2Cl2-soluble re-
action products, indicating a two-electron reduction of the Sb
center and an oxidation of each P center. The products of the
reaction are independent of stoichiometry, and attempts to
observe the perceived intermediate bis-phosphine complex
[Ph3Sb(PMe3)2][OTf]2 by low-temperature NMR spectroscopy
were unsuccessful (see the Supporting Information).
Analogous redox reactions were observed upon treatment
of 3 with two equivalents of PnPr3, yielding the previously un-
reported [nPr3PÀPnPr3][OTf]2 (4b) and SbPh3. Compound 4b
represents a new derivative in the small library of known acy-
clic diphosphonium salts,[35] and was isolated in analytic purity
following recrystallization from MeCN/Et2O. The compound ex-
hibits a singlet at d=31.2 ppm in the 31P{1H} NMR spectrum in
Preparation and coordination chemistry of compound 3
Compound 3 was prepared analogously to compound 1a,
through treatment of Ph3SbCl2 with two equivalents of AgOTf
in CH2Cl2, and was isolated as a colorless crystalline solid with
spectroscopic parameters in-line with a previous synthesis
through an alternate synthetic method.[31]
1
CD3CN (compare d=28 ppm for 4a), and the H and 13C NMR
spectra were consistent with mutually equivalent nPr groups.
Study of single crystals of 4b by X-ray diffraction confirmed
the expected atomic connectivity, with the compound crystal-
Study of crystals of 3 (space group P21/n), attained by recrys-
tallization from CH2Cl2/pentane at À308C, by X-ray diffraction
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lizing from MeCN/Et2O at À308C in
the space group P21/n with
a single formula unit in the asym-
metric unit (Figure 3). The PÀP
bond (2.2390(9) Š; SCR =2.22 Š) in
4b is slightly longer than that re-
ported in 4a (2.198(2) Š), which is
in line with the greater steric en-
cumbrance of the substituents.
The two phosphorus centers are
tetrahedral in geometry (average
X-P-X=109.58), with minimal dis-
tortion through triflate interaction,
consistent with inter-ion PÀO con-
tacts (3.624(2) and 3.827(2) Š;
Scheme 4. Reaction of 3 with two equivalents of PtBu3.
ture reveals resonances consistent with isobutylene (dH =4.66
and 1.67 ppm)[37,38] (Scheme 4). The assignment of the reso-
nance at d=219 ppm in the 31P NMR spectrum to tBu2P(OTf)
was also supported by treatment of the Et2O-soluble reaction
products (5 is insoluble in Et2O) with one equivalent of PMe3.
This reaction led to the appearance of two mutually coupled
doublet resonances at d=42.6 and 10.8 ppm (1J(P,P)=384 Hz)
in the 31P{1H} NMR spectrum, which were assigned to the previ-
ously reported phosphino-phosphonium salt [Me3PÀPtBu2]
[OTf], with the remainder of the spectroscopic data in-line
with this assignment.[35]
Figure 3. Solid-state structure
of the dication in [nPr3PÀ
PnPr3][OTf]2 (4b). All hydro-
gen atoms are omitted for
clarity.
SvdW =3.32 Š) which are greater than the SvdW for the two ele-
ments. The cation exhibits a pseudo-staggered conformation
down the PÀP bond, with narrow C-P-P-C torsions in the range
31.9(1)–34.8(1)8. In comparison, 4a has previously been shown
to crystallize in a fully staggered conformation (average torsion
angle: 60.18),[35] but also to co-crystallize with [Sb(PMe3)3][OTf]3
in an eclipsed conformation (torsion angles: 0.4(2)–0.7(2)8)[7] in-
ferring minor thermodynamic preference for the staggered
conformation. As such, we assign the counterintuitive narrow
torsions observed in 4b simply to packing effects in the solid
state.
Reaction of 3 with one or two equivalents of PPh3 gave in-
tractable mixtures with more than four products apparent by
31P{1H} NMR spectroscopy (dP =40 to 70 ppm), and complete
consumption of PPh3 in both cases. A redox reaction was,
nonetheless, again illustrated by the formation of SbPh3, which
was isolated as the only Et2O-soluble reaction product.
Although it has not been possible to isolate phosphine com-
plexes of compound 3, the unexpected redox processes lead-
ing to P–P coupling may have synthetic utility, as illustrated by
the recent report of the synthesis of [P7(AsPh3)3][OTf]3 through
reaction of PCl3 with Ph3As(OTf)2, the As analogue of com-
pound 3.[32] Furthermore, mild methods of oxidizing phospho-
rus centers while at the same time installing weakly coordinat-
ing anions are also synthetically significant in the ongoing ex-
ploration of the cationic coordination chemistry of this ele-
ment, with the ready solubility of SbPh3 in most common or-
ganic solvents facilitating removal from the primary reaction
products, and enhancing its reagent potential.
In contrast to reactions with PR3 (R=Me or nPr), the reaction
of 3 with two equivalents of the highly sterically encumbered
phosphine PtBu3 (cone angle 1828, compare PMe3 =1188 and
PnPr3 =1328)[36] led to two major products, evident in the
31P NMR spectrum as singlet resonances at d=219 and
52 ppm. The latter resonance appears as a doublet (1J(P,H)=
460 Hz) of multiplets in the corresponding proton-coupled
spectrum, which is in-line with the presence of a PÀH bond.
Following removal of all volatiles under vacuum, the resulting
1
oily solid products were analyzed by H NMR spectroscopy in
CD2Cl2 indicating complete reduction of 3 to SbPh3. Crystalliza-
tion of the products from CH2Cl2/Et2O at À308C furnished well-
formed colorless crystals, which were identified by X-ray dif-
fraction and multinuclear NMR spectroscopy as [tBu3PH][OTf]
(5) (see Figure SI-1 in the Supporting Information), correlating
with the resonance at d=52 ppm in the 31P NMR spectrum of
the reaction mixture. We postulate that the formation of 5
occurs through an initial redox process between 3 and one
equivalent of PtBu3 to yield SbPh3 and [tBu3P(OTf)][OTf], with
the ligation of the latter by a second equivalent of PtBu3 to
form [tBu3PÀPtBu3][OTf]2 precluded by the steric encumbrance
of the phosphine. Instead, PtBu3 deprotonates a tBu group of
[tBu3P(OTf)]+ furnishing 5, and a zwitterionic salt, which elimi-
nates isobutylene to produce tBu2P(OTf) (Scheme 4), assigned
to the highly deshielded 31P NMR resonance at d=219 ppm of
the crude reaction mixture. Consistently, the reaction of 3 with
one equivalent of PtBu3 leads to an essentially identical
31P NMR spectrum, and only approximately 50% reduction of 3
to SbPh3 is apparent in the 1H NMR spectrum. Furthermore,
upon repeating the reaction in CD2Cl2, analysis of the reaction
The redox reactivity observed between 3 and phosphines is,
however, precluded in reactions of 3 with two equivalents of
OPR3 (R=Me, cyclohexyl (Cy), or Ph) in CH2Cl2 at ambient tem-
perature, which quantitatively yield complexes of the generic
formula [Ph3Sb(OPR3)2][OTf]2 (R=Me (6a), Cy (6b), and Ph (6c))
(Scheme 5). The respective 31P{1H} NMR spectra for the three
Scheme 5. Reaction of 3 with phosphine oxides to yield 6a–6c.
compounds show an upfield-shifted singlet (dP =73 (6a), 79
(6b), and 48 ppm (6c)) relative to the values for the corre-
sponding free ligands, and the 1H and 13C NMR spectra are
consistent with a single ligand environment and the proposed
formulations (see Table SI-2 in the Supporting Information),
with analytic purity also confirmed by elemental microanalysis.
1
mixture by H NMR spectroscopy after 4 h at ambient tempera-
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The significant chemical shifts relative to those of the starting
materials observed in all cases are consistent with the com-
plexes remaining intact in solution. Consistently, for the repre-
sentative example of complex 6c, which contains the most
weakly basic ligands, no change was observed in the 31P NMR
chemical shift over a range of concentrations, in contrast to
derivatives of 2. Nevertheless, the presence of a small dissocia-
tive equilibrium cannot be discounted. The 31P NMR shift of 6a
(73.2 ppm) is significantly more downfield than that observed
for 2b (42.6 ppm), which reflects the anticipated increased
Lewis acidity of the Ph3Sb2+ acceptor relative to Ph4Sb+.
Table 2. Selected solid-state parameters for complexes 6a and 6c.
SbÀOPR3 bond
Shortest SbÀOTf
O-Sb-O
angle [8]
PÀO bond
lengths [Š]
contact [Š]
lengths [Š]
2.104(3)
2.074(3)
2.103(2)
2.100(2)
1.526(3)
1.530(3)
1.529(2)
1.524(2)
6a
6c
4.68(3) (SbÀO)
4.998(3) (SbÀO)
179.9(1)
178.44(8)
consistent with the greater steric bulk of the OPPh3 ligands.
Despite the different angles of binding of the two OPPh3 moi-
eties in 6c, the two SbÀOPPh3 bond lengths are statistically
identical (2.100(2) Š).
The atomic connectivity of 6a and 6c has also been con-
firmed by X-ray diffraction studies of crystals obtained from
CH2Cl2/Et2O at À308C. Complex 6a crystallized in the space
¯
group P1 with a single formula unit and a CH2Cl2 molecule in
Reactions of 3 with two equivalents of the oxidation resist-
ant ligands OPyrMe or dmap also produce stable complexes of
analogous formulae Ph3Sb(donor)2(OTf)2 [donor=OPyrMe (6d)
or dmap (6e)] (Scheme 6). Following recrystallization from
the asymmetric unit. The Sb center adopts a slightly distorted
trigonal-bipyramidal geometry, in which the oxygen atoms of
the two OPMe3 ligands occupy axial positions (O-Sb-O=
179.9(1)8), and the three propeller-configured phenyl rings
occupy equatorial positions (Cipso-Sb-Cipso =117–1248) (Fig-
ure 4a). The SbÀO bonds average 2.089(3) Š (SCR =2.03 Š),[24]
Scheme 6. Reactions of 3 with OPyrMe or dmap to yield 6d and 6e.
CH2Cl2/Et2O at À308C, spectroscopic and elemental microanal-
ysis data for 6d and 6e were consistent with the assigned for-
mulae, with the solution stability of the adducts inferred by
significant shifts in the NMR resonances of the respective com-
ponents, particularly the ligands, relative to the starting materi-
als (see Table SI-3 in the Supporting Information).
Figure 4. Solid-state structures of the cations in a) 6a and b) 6c. All hydro-
gen atoms and solvent molecules are omitted for clarity.
In both cases the solid-state structures were also confirmed
by single-crystal X-ray diffraction. Compound 6d crystallized in
the space group P21/n with a single formula unit in the asym-
metric unit, and the Sb center adopts a trigonal-bipyramidal
geometry similar to those in 6a and 6c, with two oxygen-
bound OPyrMe ligands in axial positions (O-Sb-O=176.44(6)8),
and three equatorial phenyl groups (Cispo-Sb-Cipso =118–1218)
(Figure 5a). The two very similar SbÀOPyrMe (SbÀO) bonds
(average 2.139(1) Š; SCR =2.03 Š)[24] are slightly longer than
those observed in 6a and 6c, perhaps as a consequence of
a lower basicity of OPyrMe. The SbÀOPyrMe interactions are,
however, significantly shorter than that observed in the related
2a (2.449(1) Š), reflecting the lesser steric constraints and
greater Lewis acidity of the Sb site in 3 relative to that in 1a.
and the PÀO bonds (1.528(3) Š) are longer than the corre-
sponding PÀO bonds in the free ligand (1.488(5) Š),[29] which is
consistent with the coordination of OPMe3 to a highly Lewis
acidic center. The SbÀO bonds are also markedly shorter than
those in 2b (2.406(2) Š), which is in-line with the lesser steric
encumbrance of the Sb center in 3 relative to that of 1a, and
the enhanced Lewis acidity implied by respective 31P NMR
chemical shifts. The shortest SbÀOTf inter-ion interaction
(4.68(3) Š; SvdW =3.58 Š) is significantly greater than the sum of
the van der Waals radii of Sb and O, illustrating the displace-
ment of the triflate anions by the OPMe3 donors (compare SbÀ The two OPyrMe ligands in 6d bind in a bent fashion (average
OTf in compound 3: 2.172(2) Š). As such 6a represents an
ionic formulation, and is interpreted as a bis-trimethylphos-
phine oxide complex of a Ph3Sb2+ acceptor. The solid-state
structure of 6c (Figure 4b) is similar to that of 6a, again illus-
trating a trigonal-bipyramidal geometry at Sb, and key metrical
parameters are detailed in Table 2. The Sb-O-P angles, however,
which for 6a are similar (150.0(2) and 148.8(2)8), are larger for
6c and have a wider range (151.6(1) and 161.1(1)8), which is
Sb-O-N angle=117.5(1)8) to a much greater extent than ob-
served in the corresponding phosphine oxide complexes 6a
and 6c (Sb-O-P>1508), presumably facilitated by the planarity
of the OPyrMe ligand. The shortest inter-ion SbÀOTf interac-
tions in 6d (4.656(2) and 4.820(2) Š; SvdW =3.58 Š) are well
beyond the SvdW for Sb and O, which is consistent with an
ionic formulation, and the nucleophilic displacement of the tri-
flate anions in 3 by two OPyrMe ligands.
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Figure 6. Solid-state structure of one of the two cations in the asymmetric
unit of 7a. All hydrogen atoms and solvent molecules are omitted for clarity.
Figure 5. Solid-state structures of the cations in a) 6d and b) 6e. All hydro-
gen atoms and solvent molecules are omitted for clarity.
¯
The dmap derivative 6e crystallized in the space group P1
with a single formula unit and three molecules CH2Cl2 in the
asymmetric unit. In contrast to the structures of 6a and 6c/
6d, the Sb center of 6e adopts a pseudooctahedral geometry
by virtue of a short contact with a triflate anion, along with
bonds to two dmap ligands and three phenyl substituents,
and is best represented as [Ph3Sb(dmap)2(OTf)][OTf] (Fig-
ure 5b). The two dmap ligands are trans configured (N-Sb-N=
170.69(7)8) as for the ligands in 6a and 6c/6d, with the ipso
carbon atoms of the phenyl substituents and an oxygen atom
of a triflate anion occupying the remaining four coordination
sites all of which are essentially coplanar. The two similar SbÀN
bonds (average 2.222(2) Š; SCR =2.11 Š)[24] are relatively short,
but consistent with other examples of coordinate NÀSb bonds
(range=2.27–2.81 Š).[2] Although a short SbÀOTf inter-ion con-
tact clearly prevails in 6e (SbÀO=2.714(2) Š), the SbÀO dis-
tance is significantly longer than those observed in 3 (average
2.172(2) Š; SvdW 3.58 Š), which is consistent with the coordina-
tion of two donor atoms at Sb. The second triflate anion, for
which SbÀOTf=5.248(2) Š, is considered non-interacting, and
ray diffraction. The solid-state structure of 7a (Figure 6), which
crystallized in the space group Cc, with two formula units and
three molecules of MeCN in the asymmetric unit, reveals
a pseudooctahedral geometry at the Sb in the two closely re-
lated cations, analogous to that observed in 6e, with the cis ni-
trogen atoms of the phen ligand trans to the phenyl substitu-
ents. The ipso carbon centers of these phenyl rings are above
the plane defined by the phen ligand and the Sb center, and
the phenyl rings are twisted from this plane by 51–658. The
other coordination sites are occupied by the third phenyl sub-
stituent and a triflate anion, which are trans configured with
respect to each other. The SbÀOTf bond (average 2.25(1) Š) is
significantly shorter than that in 6e (2.714(2) Š), and is similar
to those observed in 3 (2.172(2) Š). The proximity of the
oxygen atom of the triflate anion to the Sb center in com-
pound 7a is likely facilitated by the planarity of the phen
ligand, which contrasts the observed separate planes occupied
by the two dmap rings in 6e. The SbÀN bonds average
2.262(7) Š, and are similar in magnitude to those in 6e. At-
tempts to elucidate the solid-state structure of the correspond-
as such 6e is ionic, but contains a monocation. The short SbÀ ing 2,2’-bipy complex 7b were repeatedly hampered by desol-
OTf contact in 6e contrasts the observations for the otherwise
closely related cations in 6a and 6c/6d, and is likely a conse-
quence of the end-on binding and planarity of dmap, which
minimize the steric pressure at the Sb center.
vation of single crystals following recrystallization from various
solvent mixtures. A rough structure, appropriate for determina-
tion of atomic connectivity only, nonetheless revealed a struc-
ture analogous to that of 7a (see Figure SI-2 in the Supporting
Information).
Reactions of 3 with one equivalent of the chelating nitrogen
donors 1,10-phenanthroline (phen) or 2,2’-bipyridine (2,2’-bipy)
in CH2Cl2 furnished compounds of the form [Ph3Sb(L-L)(OTf)]
[OTf] (L-L=phen (7a), 2,2’-bipy (7b)) (Scheme 7). The colorless
solid products were recrystallized from MeCN/Et2O (7a) or
Although the extent of interaction between the Sb center
and the triflate anions varies for compounds 6a–6e and 7a/
7b, all seven can be considered to be derived from Ph3Sb2+
acceptors, and represent the first such structurally character-
ized complexes. The bis-ligand complexes 6a–6e (Scheme 8,
structures A and B) contrast the previous reports of mono-
ligand complexes of R3Pn2+ for Pn=P or As (Scheme 8, struc-
tures D and E).[35,39] Attempts to obtain analogous 1:1 com-
plexes of compound 3 with OPMe3 and dmap from equimolar
mixtures gave NMR spectra that are interpreted as mixtures of
the previously described 2:1 adducts 6a or 6e and new spe-
cies tentatively assigned as Ph3Sb(OPMe3)(OTf)2 (8a) or
Ph3Sb(dmap)(OTf)2 (8b), respectively, with the latter proving
impossible to isolate through recrystallization. Furthermore,
complexes of R3Pn2+ (Pn=P or As) with chelating ligands have
1
CH2Cl2/Et2O (7b) at À308C, and were characterized by H, 13C,
and 19F NMR spectroscopies (see also Table SI-3 in the Support-
ing Information), elemental microanalysis, and single-crystal X-
Scheme 7. Reaction of 3 with chelating nitrogen donors to yield 7a/b.
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ties of these ligands compared to those discussed above. The
reactivity of 3 with p-block Lewis bases is summarized in
Scheme 9.
The Sb–ligand bonding in complexes of 3 was also probed
through representative ligand exchange reactions of each class
of complex. Treatment of solutions of 6a, 6d, 6e, or 7b in
CH2Cl2 with two equivalents of OPMe3, OPyrMe, dmap, or 2,2’-
bipy were studied by NMR spectroscopy after stirring over
18 h at ambient temperature. In all cases evidence of exchange
was apparent, which is consistent with the description of the
reported derivatives of 6 and 7 as coordination complexes. In-
complete ligand exchange is observed in most reactions, with
the two ligand classes presumably competitively binding the
Sb center and reaching equilibrium. Notably, however, the ad-
dition of two equivalents of dmap, OPyrMe, or OPMe3 to 7b
led to quantitative displacement of the bipy ligand, and clean
formation of complexes 6a, 6d, and 6e, respectively, based on
Scheme 8. Observed solid-state structural motifs for cationic complexes de-
rived from R3Pn(OTf)2 [Pn=P or Sb (3)]. A–C represent structures observed
in this study, and D and E represent previously reported structures for phos-
phorus[35,39] and arsenic,[32] respectively.
1
analysis by H NMR spectroscopy. The representative reaction
of 6e with two equivalents of PMe3 was also explored and led
to the quantitative formation of 4a and liberation of dmap
and SbPh3, although this reaction cannot be directly compared
to the other equilibrium processes as the formation and pre-
cipitation of 4a are presumably irreversible.
yet to be reported, and as such complexes 7a/7b (Scheme 8,
structure C) represent a unique class of complexes of PnV
Lewis acceptors. The differing coordination preferences of
R3Pn2+ (Pn=P or As) and R3Sb2+ acceptors is attributed to the
radii of the respective pnictogen elements, with the smaller
phosphorus center unable to accommodate a second donor
atom, that is, adopt a penta-coordinate geometry, consistent
with the previously described ionic nature of [Ph4P][Cl] and
molecular nature of Ph4SbCl. We note that attempts to prepare
the phosphorus analogue of 3, Ph3P(OTf)2, for comparative pur-
poses through reactions of Ph3PX2 (X=Cl or I) with AgOTf or
Me3SiOTf, or reactions of OPPh3 with triflic anhydride were un-
successful.
Conclusion
The stiboranes Ph4Sb(OTf) (1a) and Ph3Sb(OTf)2 (3) have been
prepared and characterized as synthons for the coordination
chemistry of cationic antimony(V). Complexes with classical ni-
trogen, oxygen, phosphorus, sulfur, arsenic, and antimony
donors have been investigated, and two series of derivatives
have been isolated and comprehensively characterized. Com-
pound 3 was also shown to undergo redox reactions with
phosphines to give phosphonium and diphosphonium cations.
The significant steric encumbrance of the Sb center in 1a
limits its coordination chemistry, and no reaction is observed
between 1a and prototypical phosphine or amine
donors. Nevertheless, compounds with the generic formula
Mixtures of 3 with PnPh3 (Pn=As or Sb), ChPPh3 (Ch=S or
Se), NEt3, or SMe2 show no evidence of reaction at ambient
temperature in CH2Cl2, and unreacted 3 was recovered in all
cases. These observations reflect the relatively low Lewis basici-
[Ph4Sb(donor)][OTf]
[donor=
OPyrMe (2a) and OPMe3 (2b)]
are feasible due to the “oxygen
spacer” between the donor and
the sterically restricted core of
the acceptor. The steric pres-
sures impose comparatively long
bonds between the Sb center
and the ligand in the solid-state
structures of derivatives of 2.
These compounds expand the
small library of structurally char-
acterized complexes of stiboni-
um acceptors, and adopt a trigo-
nal-bipyramidal geometry at the
Sb center with the ligands occu-
pying axial positions. Corre-
sponding mixtures of the analo-
gous phosphonium salt, [Ph4P]
Scheme 9. Overview of the reactivity of 3 with p-block donor ligands. Blue = phosphorus donors, red = oxygen
donors, green = nitrogen donors, pink = no reaction.
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mounted in paratone oil on a MiTeGen loop, then placed in the
cold stream of the diffractometer (173 K). Data were collected by
using 0.5 degree w and f scans on a Bruker Apex2 diffractometer
by using MoKa radiation. Unit cell parameters were determined
from three consecutive scans at different orientations. The data
were integrated by using SAINT[40] and then corrected for absorp-
[OTf] (1b) with the ligand library employed for compound 1a
show no evidence of reaction.
Compound 3 forms complexes of the generic formulae
[Ph3Sb(donor)2][OTf]2 [donor=OPMe3 (6a), OPCy3 (6b), OPPh3
(6c), OPyrMe (6d)], [Ph3Sb(donor)2(OTf)][OTf] [donor=dmap
(6e)], and [Ph3Sb(donor)(OTf)][OTf] [donor=1,10-phen (7a) or
2,2’-bipy (7b)]. The solid-state structures of the compounds
containing oxygen donors (6a–6d) involve a trigonal-bipyrami-
dal Sb center around which the ligands occupy both axial posi-
tions, and represent dicationic complexes of the Ph3Sb2+ ac-
ceptor. The corresponding compounds containing nitrogen
donors (6e and 7a/7b) adopt octahedral geometries at the Sb
center by virtue of a short contact to a triflate anion, an inter-
action presumably facilitated by the lower steric pressures of
the planar nitrogen donors relative to the conical OPR3, and
side-on binding OPyrMe. In 6e, the dmap ligands are trans
configured, analogous to the ligand configurations in 6a–6d,
with the chelating donors present in 7a/7b enforcing a cis
configuration of the donors. Compound 3 does not form
stable adducts with the weaker Lewis bases SPPh3, SePPh3,
AsPh3, SbPh3, SMe2, or NEt3 under ambient conditions.
tion with SADABS,[41] solved with SHELXT[42] and refined against Fo
2
data with SHELXL-97.[42] Software: Bruker APEX2 v2014.9–0: Bruker
AXS Inc., Madison, WI. In the case of samples analyzed at the Uni-
versity of Alberta, crystallographic analysis was carried at 173 K, on
a Bruker D8/APEX II CCD by using graphite-monochromated MoKa
radiation. Structures were solved by using SHELXT and refined
against all Fo2 data with using SHELXL-97. For full crystallographic
details, see the Supporting Information. Molecular structures pre-
sented in the manuscript were plotted by using ORTEP-3V2.02,
with thermal ellipsoids at the 50% probability level. CCDC 975311
(6c), 975313 (6e), 975315 (3), 1037803 (4b), 1037804 (6a),
1037805 (7a), 1037806 (2b), 1037807 (2a), 1037808 (6d) and
1037809 (5) contain the supplementary 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.
Experimental procedures
Synthesis of Ph4SbOTf (1a): To
a solution of Ph4SbBr (0.5 g,
Derivatives of 2, 6, and 7 highlight a potentially diverse and
extensive coordination chemistry for cationic SbV, which
evolves from the coordination chemistry of transition metals,
but offers the unusual feature of reductive elimination of phos-
phine ligands. Together with the demonstrated ligand ex-
change reactivity, this new avenue of coordination chemistry
has interesting possibilities for catalysis.
0.98 mmol) was added solid AgOTf (0.25 g, 0.98 mmol) leading to
the precipitation of a yellow solid over 2 h at ambient temperature
in the dark. The mixture was then filtered and all volatiles were re-
moved under high vacuum to furnish the product as a colorless
1
solid. Yield: 0.52 g, 92%; H NMR (300 MHz, CD2Cl2): dH =7.82–7.71
(m, 4H; Ph), 7.71 ppm (apparent doublet, J(H,H)=5 Hz, 16H; Ph);
13C{1H} NMR (76 MHz, CD2Cl2): dC =136.0 (s, Ph), 134.6 (s, Ph), 131.9
(s, Ph), 122.5 ppm (s, Ph); 19F NMR (283 MHz, CD2Cl2): dF =
À78.9 ppm (s, CF3); 121Sb NMR (86 MHz, CD3CN): dSb =673 ppm
(brs, [Ph4Sb]).
Experimental Section
Synthesis of complexes of Ph4Sb(OTf) (1a): The syntheses of both
complexes of 1a were carried out by analogous method, with the
synthesis of [Ph4Sb(OPyrMe)][OTf] (2a) described in full as a repre-
sentative example.
All reactions and manipulations were performed under an atmos-
phere of nitrogen by using either standard Schlenk techniques, or
within an MBraun or Innovative Technology glovebox. All non-deu-
terated solvents were initially dried using a Grubbs-type solvent
purification system, and subsequently distilled from CaH2. Deuter-
ated solvents were purchased from Sigma Aldrich Ltd. and dried
over 3 Š (CD3CN) or 4 Š (CD2Cl2) molecular sieves. Unless otherwise
stated, all chemicals were purchased from Sigma Aldrich Ltd. and
purified according to the following regimes. Ph4SbBr, OPPh3,
OPCy3, OPMe3, 4-methylpyridine-N-oxide (OPyrMe), SPPh3, SePPh3,
and PPh3 were dried under high vacuum overnight. NEt3 was dis-
tilled from CaH2. 4-(Dimethylamino)pyridine (dmap) and 1,10-phe-
nanthroline (phen) were sublimed under reduced pressure. 2,2’-Bi-
pyridine (2,2’-bipy) was recrystallized from CH2Cl2. PMe3 and AgOTf
were purchased from Strem Chemicals, and the former was dis-
tilled prior to use.
[Ph4Sb(OPyrMe)][OTf] (2a): To a solution of 1a (100 mg, 0.17 mmol)
in CH2Cl2 (3 mL) at ambient temperature was added solid OPyrMe
(18.8 mg, 0.17 mmol), and the resulting clear, colorless solution
was stirred for 2 h. All volatiles were then removed under high
vacuum to quantitatively furnish the product as a colorless solid.
Yield: 100 mg, 84%; m.p. 115–1178C; 1H NMR (300 MHz, CD2Cl2):
dH =7.74–7.56 (m, 20H; SbPh4), 7.25 (dm, J(H,H)=7 Hz, 2H; Ar-H
[OPyrMe]), 6.91 (dm, J(H,H)=7 Hz, 2H; Ar-H [OPyrMe]), 2.26 ppm
(s, 3H; CH3); 13C{1H} NMR (76 MHz, CD2Cl2): dC =142.7 (s), 138.8 (s),
135.7 (s), 133.3 (s), 131.2 (s), 127.5 (s), 127.4 (s), 20.6 ppm (s, Me);
19F NMR (276 MHz, CD2Cl2): dF =À78.7 ppm (s, CF3); FTIR (Nujol
mull, ranked intensities): n˜ =1264 (1), 1225 (6), 1179 (7), 1158 (4),
1031 (2), 1068 (10), 995 (9), 736 (5), 693 (8), 637 cmÀ1 (3); elemental
analysis calcd (%): C 54.09, H 3.95, N 2.03; found: C 54.23, H 3.83,
N 2.04.
NMR spectra were recorded using either Bruker Avance 500, 360,
or 300 MHz spectrometers. Chemical shifts are reported relative to
residual protonated solvent peaks (1H, 13C), or to external H3PO4
(31P), CFCl3 (19F), and Me2Se (77Se). IR spectra were recorded on
a Perkin–Elmer Spectrum 1000 FTIR spectrometer as Nujol mulls on
KBr plates, and elemental analyses were performed by Canadian
Microanalytical Service Ltd, Delta British Columbia, Canada. Melting
point data was collected on a Gallenkamp melting point apparatus
in sealed capillaries.
[Ph4Sb(OPMe3)][OTf] (2b): Colorless solid; yield: 98 mg, 85%; m.p.
141–1438C; 1H NMR (300 MHz, CD2Cl2): dH =7.74–7.58 (m, 20H;
SbPh4), 1.09 ppm (d, J(H,P)=13 Hz, 9H; OP(CH3)3); 31P{1H} NMR
(122 MHz, CD2Cl2): dP =42.6 ppm (s); 13C{1H} NMR (76 MHz, CD2Cl2):
dC =135.7 (s, Ph), 133.4 (s, Ph), 131.2 (s, Ph), 128.5 (s, Ph), 17.2 ppm
(d, J(C,P)=70 Hz, P(CH3)3); 19F NMR (276 MHz, CD2Cl2): dF =
À78.8 ppm (s, CF3); FTIR (Nujol mull, ranked intensities): n˜ =1300
(3), 1264 (1), 1224 (6), 1133 (4), 1071 (10), 1030 (2), 949 (8), 737 (7),
693 (9), 637 cmÀ1 (5); elemental analysis calcd (%): C 55.10, H 4.35;
found: C 55.32, H 4.29.
X-ray crystallographic data were collected at the MAX Diffraction
Facility at McMaster University or at the University of Alberta X-Ray
Facility. In the former case, suitable crystals were selected and
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Mixtures of 1a with PMe3 or NEt3: To a solution of 1a (50 mg,
0.086 mmol) in CH2Cl2 (2.5 mL) was added neat PMe3 or NEt3
(0.17 mmol) at ambient temperature, and the resulting mixture
was stirred for 2 h before removing all volatiles under high
vacuum to furnish a colorless solid. Analysis by H NMR spectrosco-
py in CD2Cl2 showed only unreacted 1a, with unreacted PMe3/NEt3
1H NMR (300 MHz, CD2Cl2): dH =8.08–8.02 (m, 6H; Ph), 7.85–
7.73 ppm (m, 9H; Ph); 13C{1H} NMR (76 MHz, CD2Cl2): dC =135.0 (s),
134.7 (s), 131.6 (s), 131.5 ppm (s); 19F NMR (283 MHz, CD2Cl2): dF =
À78.0 ppm (s, CF3).
1
Reactions of 3 with phosphines
Reaction of 3 with two equivalents of PMe3: To a solution of
Ph3SbCl2 (100 mg, 0.24 mmol) in CH2Cl2 (3 mL) was added solid
AgOTf (121 mg, 0.47 mmol) at ambient temperature and the mix-
ture was stirred in the dark for 2 h before filtering through glass
fibre paper. To the resulting clear, colorless solution was then
added neat PMe3 (48.8 mL, 0.47 mmol), leading to the immediate
precipitation of a colorless solid, and the mixture was then stirred
for a further 1 h. All volatiles were then removed under high
vacuum to yield a colorless solid, which was dissolved in CD3CN for
analysis by multinuclear NMR spectroscopy, indicating the forma-
tion of [Me3PÀPMe3][OTf]2 (4a) and Ph3Sb. The products were sepa-
rated by removing all volatiles under high vacuum and washing
the resulting solids with CH2Cl2. The residue was then re-dissolved
in CD3CN and analyzed by NMR spectroscopy, confirming this com-
ponent as compound 4a. 1H NMR (300 MHz, CD3CN): dH =2.45–
2.28 ppm (m, 18H); 31P{1H} NMR (122 MHz, CD3CN): dP =28.4 ppm
(s, [Me3P-PMe3]); 13C{1H} NMR (76 MHz, CD3CN): dC =8.83–7.99 ppm
(m, CH3); 19F NMR (283 MHz, CD3CN): dF =À79.4 ppm (s, CF3). The
CH2Cl2 washings were combined and the solvent removed under
high vacuum before re-solvating in CD2Cl2 for multinuclear NMR
presumably removed under vacuum.
Mixtures of 1a with 2,2’-bipy or 4,4’-bipy: To a solution of 1a
(50.0 mg, 0.086 mmol) in CH2Cl2 (2.5 mL) was added solid 2,2’-bipy
(13.5 mg, 0.086 mmol) or 4,4’-bipy (6.7 mg, 0.043 mmol) at ambient
temperature, and the resulting mixture was stirred for 2 h before
removing all volatiles under high vacuum to furnish a colorless
1
solid in both cases. Analysis of the solids by H NMR spectroscopy
in CD2Cl2 showed only unreacted compound 1a and bipy, with re-
crystallization of the solid from CH2Cl2/Et2O at À308C in the latter
1
case yielding crystals identified as pure 1a by H NMR spectrosco-
py.
Mixtures of 1a with dmap: To
a solution of 1a (50.0 mg,
0.086 mmol) in CH2Cl2 (2.5 mL) was added solid dmap (10.5 mg,
0.17 mmol) at ambient temperature, and the resulting mixture was
stirred for 2 h before removing all volatiles under high vacuum to
1
furnish a colorless solid. Analysis of the solids by H NMR spectros-
copy in CD2Cl2 indicated a shift in the resonances of the dmap
ligand [dH =7.88 (2H), 6.42 (2H), 2.95 ppm (6H)] from that of the
free ligand in the same solvent, along with resonances consistent
with compound 1a. Recrystallization the crude reaction products
from CH2Cl2/Et2O at À308C, however, repeatedly yielded crystals
only of 1a.
1
analysis, which confirmed the second product to be SbPh3. H NMR
(300 MHz, CD2Cl2): dH =7.49–7.42 (m, 6H; Ph), 7.37–7.32 ppm (m,
9H; Ph); 13C{1H} NMR (76 MHz, CD2Cl2): dC =138.8 (s, Ph), 136.8 (s,
Ph), 129.5 (s, Ph), 129.3 ppm (s, Ph).
Synthesis of [Ph4P][OTf] (1b): To a solution of [Ph4P][Cl] (0.4 g,
1.07 mmol) in CH2Cl2 (7 mL) was added solid AgOTf (0.27 g,
1.07 mmol) and the mixture stirred at ambient temperature in the
dark for 2 h; before filtering, and removing all volatiles under high
vacuum to furnish 1b as a colorless solid. Yield: 0.47 g, 90%;
1H NMR (300 MHz, CD2Cl2): dH =7.95–7.88 (m, 4H; Ph), 7.80–7.72
(m, 8H; Ph), 7.67–7.58 ppm (m, 8H; Ph); 31P{1H} NMR (122 MHz,
CD2Cl2): dP =23.3 ppm (s); 13C{1H} NMR (76 MHz, CD2Cl2): dC =136.1
(d, J(C,P)=2 Hz, Ph), 134.8 (d, J(C,P)=11 Hz, Ph), 131.0 (d, J(C,P)=
13 Hz, Ph), 118.0 ppm (d, J(C,P)=90 Hz, Ph); 19F NMR (283 MHz,
CD2Cl2): dF =À78.8 ppm (s, CF3).
To investigate the intermediate presence of [Ph3Sb(PMe3)2][OTf]2,
the reaction was monitored at low temperature. Neat PMe3 was
vacuum transferred onto a frozen (À1968C) CD2Cl2 solution of
compound 3 in a J. Young NMR tube and warmed to À808C in the
NMR spectrometer. Analysis of the mixture suggested no 31P-con-
taining species in solution, similarly at À608C and at ambient tem-
perature. Consistently, upon removing the sample from the spec-
trometer a colorless solid was apparent in solution, identified as
4a by subsequent isolation and analysis by 31P NMR spectroscopy
in CD3CN. 31P{1H} NMR (122 MHz, CD3CN): dP =28.4 ppm (s, [Me3PÀ
PMe3]).
Mixtures of 1b and Me3P, dmap, OPMe3, or OPyrMe: To a solution of
1b (40 mg, 0.08 mmol) in CH2Cl2 (2 mL) was added neat Me3P or
solid dmap, OPMe3, or OPyrMe (0.08 mmol), respectively, and the
resulting clear colorless mixtures were stirred at ambient tempera-
ture for 2 h before removing all volatiles under high vacuum. Anal-
ysis of the resulting solids by NMR spectroscopy in CD2Cl2 in all
cases indicated the presence of only 1b and free ligand, with the
exception of the reaction with Me3P (b.p.=408C), which indicated
the presence of only 1b.
Reaction of 3 with one equivalent of PMe3: To a solution of Ph3SbCl2
(100 mg, 0.24 mmol) in CH2Cl2 (4 mL) at ambient temperature was
added solid AgOTf (121 mg, 0.47 mmol) and the mixture then
stirred at ambient temperature in the dark for 2 h before filtering.
To the resulting clear, colorless solution was added neat PMe3
(18.0 mg, 0.24 mmol) leading to immediate precipitation of a color-
less solid, and the mixture was stirred for 1 h before removing all
volatiles under high vacuum. The solid products were then dis-
solved in CD3CN for analysis by multinuclear NMR spectroscopy.
1H NMR (360 MHz, CD3CN): dH =8.07–8.02 (m, Ph3Sb(OTf)2), 7.85–
7.75 (m, Ph3Sb(OTf)2), 7.43–7.39 (m, SbPh3), 7.35–7.30 (m, SbPh3),
2.39–2.24 ppm (m, [Me3P-PMe3]); 31P{1H} NMR (146 MHz, CD3CN):
dP =28.6 ppm (s, [Me3PÀPMe3]).
Reaction of 3 with two equivalents of PnPr3: To a solution of
Ph3SbCl2 (200 mg, 0.47 mmol) in CH2Cl2 (6 mL) was added solid
AgOTf (242 mg, 0.94 mmol) and the mixture then stirred at ambi-
ent temperature in the dark for 2 h before filtering to furnish
a clear, colorless solution. Neat PnPr3 (188.8 mL, 0.94 mmol) was
then added dropwise leading to the immediate precipitation of
a colorless solid. The mixture was stirred subsequently for 1 h at
ambient temperature before filtering through glass fibre filter
paper. All volatiles were removed from the filtrate to furnish an
oily white solid, which was analyzed by multinuclear NMR spectros-
Synthesis of Ph3SbCl2: To a solution of Ph3Sb (5.0 g, 8.5 mmol) in
CH2Cl2 (50 mL) was added a 1m solution of SO2Cl2 in CH2Cl2
(9.3 mL, 9.4 mmol) at À788C, and the mixture was stirred for
15 min before warming to ambient temperature and stirring for
a further 1 h. All volatiles were then removed under high vacuum
to leave an off-white solid, which was recrystallized from CH2Cl2/
Et2O at À308C. Yield: 5.5 g, 91%; 1H NMR (300 MHz, CDCl3): dH =
8.33–8.25 (m, 6H; Ph), 7.63–7.54 ppm (m, 9H; Ph).
Synthesis of Ph3Sb(OTf)2 (3): To a solution of Ph3SbCl2 (0.10 g,
0.28 mmol) in CH2Cl2 (3 mL) was added solid AgOTf (0.12 g,
0.47 mmol) at ambient temperature and the mixture was stirred
for 2 h in the dark before filtering to yield a clear, colorless solu-
tion. All volatiles were then removed under high vacuum and the
resulting solid was recrystallized at À308C from CH2Cl2/pentane.
Chem. Eur. J. 2015, 21, 7902 – 7913
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Full Paper
copy in CD2Cl2 indicating the formation of Ph3Sb. 1H NMR
(300 MHz, CD2Cl2): dH =7.55–7.48 (m, 6H; SbPh3), 7.40–7.34 (m, 9H;
SbPh3), and various minor aliphatic resonances between 3 and
1 ppm. The residue of the filtration was collected by dissolution in
MeCN (4 mL), and recrystallized by layering with Et2O and storing
at À308C overnight. Large colorless crystals of the product, charac-
terized as [nPr3P-PnPr3][OTf]2 (4b), were collected and dried under
high vacuum before analyzing by multinuclear NMR spectroscopy.
1J(C,P)=31, 2J(C,P)=5 Hz, P(C(CH3)3)2), 32.2 (dd, 2J(C,P)=13,
3J(C,P)=6 Hz, P(C(CH3)3)2), 14.7 ppm (dd, 1J(C,P)=42, 2J(C,P)=Hz,
PMe3); 19F NMR (282 MHz, CD2Cl2): dF =À78.9 ppm (s, CF3).
Reaction of 3 with PPh3: To a solution of Ph3SbCl2 (50 mg,
0.12 mmol) in CH2Cl2 (2 mL) was added solid AgOTf (60.5 mg,
0.24 mmol) and the mixture was stirred at ambient temperature in
the dark for 2 h, before filtering to furnish a clear, colorless solu-
tion. Solid PPh3 (61.9 mg, 0.24 mmol) was then added initially lead-
ing to the precipitation of a colorless solid, which re-dissolved
upon stirring at ambient temperature over 2 h. All volatiles were
then removed under high vacuum to furnish a colorless solid,
which was analyzed by NMR spectroscopy in CD2Cl2 indicating the
complete consumption of PPh3 and the formation of four new un-
identified species. 31P{1H} NMR (146 MHz, CD2Cl2): dP =65.9 (s) [3%],
1
Yield: 0.15 g, 33%; m.p.>2208C (decomposed); H NMR (300 MHz,
CD2Cl2): dH =2.72–2.60 (m, 4H; PCH2), 1.82–1.65 (m, 4H; CH2CH3),
1.12 ppm (tt, J(H,H)=7, J(H,P)=1 Hz, 9H; CH3); 31P{1H} NMR
(146 MHz, CD2Cl2): dP =31.2 ppm (s); 13C{1H} NMR (91 MHz, CD2Cl2):
dC =21.3 (apparent triplet, J(C,P)=16 Hz), 17.8 (s), 15.5 ppm (appar-
ent triplet, J(C,P)=10 Hz); 19F NMR (276 MHz, CD2Cl2): dF =
À79.2 ppm (s, CF3); FTIR (Nujol mull, ranked intensities): n˜ =1418
(7), 1257 (1), 1224 (5), 1156 (4), 1072 (6), 1030 (2), 757 (1), 638 (3),
573 (9), 517 cmÀ1 (8); elemental analysis calcd (%): C 38.83, H 6.84;
found: C 38.95, H 7.18.
1
58.6 (brs) [57%], 48.4 (s) [19%], 44.2 ppm (s) [21%]. The H NMR
spectrum of the products showed a complex series of over-lapping
aryl resonances between 7.0 and 8.0 ppm. Purification of the indi-
vidual components of the mixture proved not to be possible de-
spite attempted recrystallization under various conditions. The re-
action of 3 with a single equivalent of PPh3 under the same condi-
tions again led to a mixture of four unidentified products by
31P NMR spectroscopy: 31P{1H} NMR (146 MHz, CD2Cl2): dP =74.8 (s)
[29%], 50.0 (s) [30%], 40.4 (s) [19%], 44.2 ppm (s) [22%].
Reaction of 3 with two equivalents of PtBu3: To a solution of
Ph3SbCl2 (100 mg, 0.24 mmol) in CH2Cl2 (3 mL) was added solid
AgOTf (121 mg, 0.47 mmol) and the resulting mixture then stirred
at ambient temperature in the dark for 2 h before filtering. A solu-
tion of PtBu3 (95.4 mg, 0.47 mmol) in CH2Cl2 (0.85 mL) was then
added, and the resulting clear, colorless solution was stirred for
18 h. All volatiles were then removed to furnish a colorless oily
solid, which was dissolved in CD2Cl2 for analysis by NMR spectros-
copy. 31P{1H} NMR (146 MHz, CD2Cl2): dP =219.1 (s), 123.0 (minor sin-
glet), 51.8 ppm (s); 31P NMR (146 MHz, CD2Cl2): dP =219.1 (m), 123.0
Syntheses of complexes of 3: The syntheses of all complexes of 3
from Ph3SbCl2 were carried out through a similar method. The syn-
thesis of [Ph3Sb(OPMe3)2][OTf]2 (6a) is described as a representative
example, followed by characterization data for all compounds.
[Ph3Sb(OPMe3)2][OTf]2 (6a): To
a solution of Ph3SbCl2 (0.15 g,
1
1
(m), 51.8 ppm (dm, J(H,P)=460 Hz). H NMR spectroscopy also in-
dicated complete consumption of compound 3 to yield Ph3Sb. Re-
crystallization of the crude products from CH2Cl2/Et2O at À308C af-
forded well-formed single crystals, identified spectroscopically and
0.35 mmol) in CH2Cl2 (4 mL) was added solid AgOTf (0.18 g,
0.71 mmol) and the mixture was then stirred for 2 h at ambient
temperature in the dark. The mixture was then filtered through
glass fibre filter paper leaving a clear, colorless solution. Solid
OPMe3 (65.1 mg, 0.71 mmol) was then added, and the mixture was
stirred at ambient temperature for 1 h before removing all volatiles
under high vacuum to furnish a colorless solid, which was recrys-
tallized from CH2Cl2/Et2O at À308C. Yield: 0.23 g, 78%; m.p. 185–
1878C; 1H NMR (300 MHz, CD2Cl2): dH =8.10–8.04 (m, 6H; SbPh),
7.89–7.79 (m, 9H; SbPh), 1.48 ppm (d, J(H,P)=13 Hz, 18H; PMe);
31P{1H} NMR (146 MHz, CD2Cl2): dP =73.2 ppm (s); 13C{1H} NMR
(91 MHz, CD2Cl2): dC =134.9 (s, Ar), 134.1 (s, Ar), 133.6 (s, Ar), 132.2
(s, Ar), 121.4 (q, J(C,F)=321 Hz, CF3), 15.9 ppm (d, J(C,P)=68 Hz,
Me); 19F NMR (282 MHz, CD32Cl2): dF =À78.8 ppm (s, CF3); FTIR
(Nujol mull, ranked intensities): n˜ =1306 (6), 1266 (2), 1226 (7),
1152 (5), 1043 (3), 1030 (1), 997 (8), 962 (9), 735 (10), 638 cmÀ1 (4);
elemental analysis calcd (%): C 37.38, H 3.98; found C 37.07, H
4.07.
1
crystallographically as [tBu3PH][OTf] (5): H NMR (360 MHz, CD2Cl2):
1
3
dH =6.14 (d, J(H,P)=460 Hz, 1H; [HPtBu3]+), 1.62 ppm (d, J(H,P)=
15 Hz, 27H; tBu); 31P{1H} NMR (146 MHz, CD2Cl2): dP =52.0 ppm (s,
[tBu3PH]+); 31P{1H} NMR (146 MHz, CD2Cl2): dP =52.0 ppm (dm,
1J(H,P)=460 Hz, [tBu3PH]+); 13C{1H} NMR (91 MHz, CD2Cl2): dC =
121.4 (q, 1J(C,P)=321 Hz, CF3), 37.6 (d, 1J(C,P)=29 Hz, C(CH3)3),
30.4 ppm (s, C(CH3)3); 19F NMR (283 MHz, CD2Cl2): dF =À78.9 (s,
CF3). Analysis of the reaction mixture in CD2Cl2 after 4 h, evidenced
complete conversion to the products based on 31P NMR spectros-
copy, and the 1H NMR spectrum illustrated two peaks consistent
with isobutylene at dH =4.66 and 1.67 ppm, respectively, along
with Ph3Sb and “tBuP”-containing products.
Reaction of 3 with two equivalents of PtBu3, and subsequently one
equivalent PMe3: To a solution of Ph3SbCl2 (100 mg, 0.24 mmol) in
CH2Cl2 (2 mL) was added solid AgOTf (121 mg, 0.47 mmol) and the
resulting mixture was stirred at ambient temperature in the dark
for 2 h before filtering. A solution of PtBu3 (95.4 mg, 0.47 mmol) in
CH2Cl2 (0.85 mL) was then added, and the resulting clear, colorless
solution was stirred for 18 h. The mixture was then precipitated
into Et2O (10 mL) and the solids (identified as compound 5 by
NMR spectroscopy) were removed by filtration. Neat PMe3
(17.9 mg, 0.24 mmol) was then added leading to the precipitation
of a colorless solid, and the resulting mixture was stirred at ambi-
ent temperature for 1 h. The solids were then removed by filtration
and analyzed by NMR spectroscopy in CD2Cl2, and the results were
consistent with the formation of [Me3PÀPtBu2][OTf] as the primary
product: 1H NMR (300 MHz, CD2Cl2): dH =2.15 (dd, 2J(H,P)=13,
3J(H,P)=2 Hz, 9H; PMe3), 1.45 ppm (dd, 3J(P,P)=13, 4J(P,P)=1 Hz,
18H; PtBu2); 31P{1H} NMR (146 MHz, CD2Cl2): dP =42.6 (d, 1J(P,P)=
384 Hz, PMe3), 10.8 ppm (d, 1J(P,P)=384 Hz, PtBu2); 13C{1H} NMR
(91 MHz, CD2Cl2): dC =121.4 (q, 1J(C,F)=321 Hz, CF3), 37.2 (dd,
[Ph3Sb(OPCy3)2][OTf]2 (6b): Colorless solid; yield: 0.45 g, 61%; m.p.>
3188C (decomposed with gas evolution); 1H NMR (300 MHz,
CD3CN): dH =8.12–8.03 (m, 6H; Ph), 7.97–7.87 (m, 9H; Ph), 1.87–
1.68 (m, 6H; Cy), 1.53 (brs, 18H; Cy), 1.36 (brs, 12H; Cy), 0.81–
0.24 ppm (m, 30H; Cy); 31P{1H} NMR (203 MHz, CD3CN): dP =
78.6 ppm (s); 13C{1H} NMR (126 MHz, CD3CN): dC =135.9 (s, Ph),
135.1 (s, Ph), 134.6 (s, Ph), 133.3 (s, Ph), 35.7 (d, J(C,P)=56 Hz, Cy),
27.1 (d, J(C,P)=13 Hz, Cy), 26.6 (d, J(C,P)=4 Hz, Cy), 26.3 ppm (s,
Cy); 19F NMR (282 MHz, CD3CN): dF =À79.2 ppm (s, CF3); FTIR (Nujol
mull, ranked intensities): n˜ =1265 (2), 1222 (6), 1146 (4), 1031 (1),
995 (5), 892 (10), 735 (7), 690 (9), 637 (3), 517 cmÀ1 (8); elemental
analysis calcd (%): C 54.06, H 6.56; found C 54.22, H 6.98.
[Ph3Sb(OPPh3)2][OTf]2 (6c): Colorless solid; yield: 0.51 g, 71%; m.p.
1
196–1988C; H NMR (300 MHz, CD2Cl2): dH =7.62–7.55 (m, 15H; Ph),
7.49–7.42 (m, 6H; Ph), 7.38–7.30 (m, 12H; Ph), 7.10–6.91 ppm (m,
12H; Ph); 31P{1H} NMR (122 MHz, CD2Cl2): dP =48.4 ppm (s,
Ph3Sb(OPPh3)2); 19F NMR (283 MHz, CD2Cl2): dF =À78.6 ppm (s, CF3);
Chem. Eur. J. 2015, 21, 7902 – 7913
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for details of the 13C{1H} NMR spectrum see the Supporting Infor-
mation; FTIR (Nujol mull, ranked intensities): n˜ =1262 (1), 1150 (3),
1115 (4), 1030 (2), 1009 (6), 993 (5), 687 (7), 636 (8), 534 (9), 516
(10), 456 cmÀ1 (11); elemental analysis calcd (%): C 55.69, H 3.76;
found: C 55.41, H 3.57.
bient temperature for 2 h. All volatiles were then removed, and the
resulting colorless solid was analyzed by NMR spectroscopy in
CD2Cl2. In the reaction with dmap, the H NMR spectrum indicated
conversion of dmap to two new products, consistent with com-
pound 8b and the previously assigned 1:2 adduct 6e in a 7.5:1
ratio. In the reaction with OPMe3 a similar mixture was apparent,
but in this case compound 8a and the 1:2 adduct 6a were present
in a 4:1 ratio. Separation of the 1:1 adducts from 6a and 6e, re-
spectively, by recrystallization proved to be impossible.
1
[Ph3Sb(OPyrMe)2][OTf]2 (6d): Colorless solid; yield: 0.37 g, 72%; m.p.
181–1838C; 1H NMR (300 MHz, CD2Cl2): dH =8.14–8.07 (m, 6H;
SbPh), 7.98 (brd, 4H; J(H,H)=6 Hz, C6H4N), 7.79–7.73 (m, 9H;
SbPh), 7.26 (brd, 4H; J(H,H)=6 Hz, C6H4N), 2.37 ppm (s, 6H; CH3);
13C{1H} NMR (76 MHz, CD2Cl2): dC =140.5 (s), 135.7 (s), 135.1 (s),
132.3 (s), 129.3 (s), 127.4 (s), 121.5 ppm (q, J(C,F)=320 Hz, CF3);
19F NMR (282 MHz, CD2Cl2): dF =À78.8 ppm (s, CF3); IR (Nujol mull,
ranked intensities): n˜ =1286 (2), 1251 (1), 1221 (5), 1200 (7), 1152
(4), 1027 (3), 835 (10), 760 (9), 741 (8), 636 cmÀ1 (6); elemental anal-
ysis calcd (%): C 44.32, H 3.36, N 3.22; found C 44.57, H 3.48, N
3.28.
Mixtures of 3 with two equivalents of NEt3 or SMe2: To a solution of
Ph3SbCl2 (100 mg, 0.24 mmol) in CH2Cl2 (2 mL) was added solid
AgOTf (121 mg, 0.47 mmol), and the mixture was stirred for 2 h at
ambient temperature in the dark before filtering. Neat NEt3
(65.6 mL, 0.47 mmol) or SMe2 (34.6 mL, 0.47 mmol) was then added,
and the mixtures were stirred for 1 h before removing all volatiles
to furnish colorless solids in both cases. Analysis of the solids by
1H NMR spectroscopy in CD2Cl2 showed only compound 3 in solu-
tion, with the unreacted volatile ligands presumably removed
under vacuum.
[Ph3Sb(dmap)2(OTf)][OTf] (6e): Colorless solid; yield: 0.38 g, 71%;
m.p. 200–2028C; 1H NMR (500 MHz, CD2Cl2): dH =7.79–7.69 (m,
15H; Ph), 7.59 (d, J(H,H)=8 Hz, 4H; Ar-H [dmap]), 6.56 (d, J(H,H)=
8 Hz, 4H; Ar-H [dmap]), 3.09 ppm (s, 12H; NMe2); 13C{1H} NMR
(126 MHz, CD2Cl2): dC =156.8 (s), 145.0 (s), 135.3 (s), 134.5 (s), 132.1
(s), 130.0 (s), 121.3 (q, J(C,F)=321 Hz, CF3), 108.7 (s), 40.2 ppm (s,
N(CH3)2); 19F NMR (283 MHz, CD2Cl2): dF =À78.8 ppm (s, CF3); FTIR
(Nujol mull, ranked intensities): 1621 (7), 1258 (1), 1228 (4), 1150
(5), 1028 (2), 1008 (6), 995 (8), 739 (10), 725 (9), 635 cmÀ1 (3); ele-
mental analysis calcd (%): C 45.60, H 3.94, N 6.26; found: C 45.32,
H 3.97, N 6.22.
Mixtures of 3 with two equivalents of ChPPh3 (Ch=S or Se): To a solu-
tion of Ph3SbCl2 (100 mg, 0.24 mmol) in CH2Cl2 (2 mL) was added
solid AgOTf (121 mg, 0.47 mmol), and the mixture was stirred for
2 h at ambient temperature in the dark before filtering. Solid
ChPPh3 (Ch=S or Se) (0.47 mmol) was then added, and the mix-
tures were stirred for 1 h before removing all volatiles to furnish
colorless solids. Analysis of the solids by 31P NMR spectroscopy in
CD2Cl2 showed signals consistent with the starting materials in
both cases (Ch=S, dP =43.1 ppm; Ch=Se, dP =34.8 ppm (s, with
77Se satellites J(P,Se)=348 Hz). Recrystallization of both solids from
CH2Cl2/Et2O furnished only crystals identified as unreacted ChPPh3
[Ph3Sb(phen)(OTf)][OTf] (7a): In this case the product was found to
precipitate from CH2Cl2 upon addition of the ligand, as a colorless
solid. The solids were collected by decantation and washed with
CH2Cl2 (3 mL) before drying under high vacuum, and subsequently
recrystallizing from MeCN/Et2O at À308C. Yield: 0.22 g, 55%;
m.p.>2628C (decomposed); 1H NMR (300 MHz, CD3CN): dH =9.18
(dm, J(H,H)=8 Hz, 2H; [phen]), 8.90 (dd, J(H,H)=6, J(H,H)=1 Hz,
2H; [phen]), 8.48 (s, 2H; [phen]), 8.26 (dd, J(H,H)=8, J(H,H)=5 Hz,
2H; [phen]), 7.85–7.79 (m, 6H; Ph), 7.68–7.55 ppm (m, 9H; Ph);
13C{1H} NMR (76 MHz, CD3CN): dC =147.1 (s), 146.2 (s), 137.7 (s),
136.0 (s), 134.1 (s), 133.6 (s), 132.0 (s), 129.8 (s), 128.9 (s), 121.4 ppm
(q, J(C,F)=320 Hz, CF3); 19F NMR (283 MHz, CD3CN): dF =À79.2 ppm
(s, CF3); FTIR (Nujol mull, ranked intensities): n˜ =1437 (2), 1261 (1),
1235 (7), 1208 (6), 1157 (5), 1029 (3), 980 (4), 739 (9), 716 (10),
638 cmÀ1 (8); elemental analysis calcd (%): C 46.23, H 2.79, N 3.37;
found: C 46.18, H 2.78, N 3.29.
1
(S or Se) by H, 13C, and 31P NMR spectroscopy.
Mixtures of 3 with two equivalents of PnPh3 (Pn=As or Sb): To a solu-
tion of Ph3SbCl2 (100 mg, 0.24 mmol) in CH2Cl2 (2 mL) was added
solid AgOTf (121 mg, 0.47 mmol), and the mixture was stirred for
2 h at ambient temperature in the dark before filtering. Solid AsPh3
or SbPh3 (0.24 mmol) was then added, and the resulting mixtures
were stirred at ambient temperature for 1 h before removing all
volatiles under high vacuum to furnish colorless solids. Analysis of
the products by 1H NMR spectroscopy indicated that no reaction
had occurred, showing signals consistent with both unreacted
compound 3 and the free ligand.
Ligand exchange reactions of compounds 6a, 6d, 6e, and 7b:
All exchange reactions were carried out according to analogous
protocols, and the reaction of compound 7b with OPMe3 is there-
fore described in full as a representative example: To a solution of
compound 7b (40 mg, 0.05 mmol) in CH2Cl2 (2 mL) was added
solid OPMe3 (9.1 mg, 0.1 mmol), and the resulting clear, colorless
mixture was stirred at ambient temperature for 18 h. All volatiles
were then removed under high vacuum, and the resulting solids
were analyzed by 1H NMR spectroscopy in CD2Cl2, illustrating the
quantitative formation of compound 6a, as previously assigned,
and the presence of free 2,2-bipy in solution.
[Ph3Sb(bipy)(OTf)][OTf] (7b): Colorless solid; yield: 0.29 g, 61%; m.p.
180–1828C; 1H NMR (500 MHz, CD2Cl2): dH =9.12 (d, J(H,H)=8 Hz,
2H; Ar-H [bipy]), 8.65 (d, J(H,H)=6 Hz, 2H; Ar-H [bipy]), 8.62 (t,
J(H,H)=8.0 Hz, 2H; Ar-H [bipy]), 7.93 (t, J(H,H)=7 Hz, 2H; Ar-H
[bipy]), 7.71 (d, J(H,H)=8 Hz, 6H; Ph), 7.66–7.61 (m, 3H; Ph), 7.61–
7.56 ppm (m, 6H; Ph); 13C{1H} NMR (126 MHz, CD2Cl2): dC =146.7
(s), 144.1 (s), 141.8 (s), 136.3 (s), 135.1 (s), 133.4 (s), 131.4 (s), 130.1
(s), 126.5 (s), 120.5 ppm (q, J(C,F)=320 Hz, CF3); 19F NMR (283 MHz,
CD2Cl2): dF =À78.6 ppm (s, CF3); FTIR (Nujol mull, ranked intensi-
ties): n˜ =1601 (11), 1261 (1), 1232 (4), 1201 (5), 1157 (2), 1030 (3),
987 (7), 734 (8), 723 (9), 691 (10), 631 (6), 517 cmÀ1 (12); elemental
analysis calcd: C 44.63, H 2.87 N 3.47; found: C 44.60, H 2.87, N
3.47.
In cases where the ligand exchange was not quantitative, the
degree of exchange was estimated through the relative integrals
of resonances corresponding to each complex.
Attempted
synthesis
of
Ph3Sb(OPMe3)(OTf)2
(8a)
and
Ph3Sb(dmap)(OTf)2 (8b): To
a
solution of Ph3SbCl2 (150 mg,
Acknowledgements
0.35 mmol) in CH2Cl2 (4 mL) was added solid AgOTf (181.8 mg,
0.71 mmol), and the mixture was stirred for 2 h at ambient temper-
ature in the dark before filtering. A solution of dmap or OPMe3
(0.35 mmol) in CH2Cl2 (1 mL) was then added dropwise over ap-
proximately 15 min, and the resulting solutions were stirred at am-
The authors thank the Natural Sciences and Engineering Re-
search Council of Canada (NSERC) and the Vanier Canada Grad-
uate Scholarship Program for funding (S.S.C.).
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Full Paper
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Published online on April 15, 2015
Chem. Eur. J. 2015, 21, 7902 – 7913
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