31P NMR studies demonstrating the assembly of catena-phosphorus frameworks from chlorophosphinochlorophosphonium cations

Article abstract of DOI:10.1021/ic102150s

New examples of chlorophosphinochlorophosphonium (4) and chlorophosphinodichlorophosphonium (5) cations have been prepared and spectroscopically characterized. These bifunctional phosphinophosphonium cations offer a new approach to the development of phosphinophosphonium frameworks using reductive coupling reactions and have been exploited as synthons to assemble larger catena-phosphorus cations. The reactions of 4 and 5 with stibine reducing agents have been studied using ³¹PP NMR spectroscopy and have been shown to produce a variety of new and known frameworks in a facile manner, depending on the reducing agent selection and the stoichiometry of the reaction. New derivatives of frameworks containing three, four, and five phosphorus atoms have been identified by ³¹PPNMRspectroscopy. Crystals of the [GaCl₄]^- salt of the five-membered dication 11(ⁱPr) have been isolated from the reaction of [4( ⁱPr)][GaCl₄] with SbBu₃, and the solid state structural features and solution state dynamics are comprehensively described in the context of ³¹P{¹H} NMR spectroscopic observations.

Full text of DOI:10.1021/ic102150s

ARTICLE
pubs.acs.org/IC
31P NMR Studies Demonstrating the Assembly of catena-Phosphorus
Frameworks from Chlorophosphinochlorophosphonium Cations
Yuen-ying Carpenter,† Neil Burford,*,† Michael, D. Lumsden,‡ and Robert McDonald§
†Department of Chemistry, Dalhousie University, Halifax, NS, B3H 4J3, Canada
‡Nuclear Magnetic Resonance Research Resource (NMR-3), Dalhousie University, Halifax, NS, B3H 4J3, Canada
§X-ray Crystallography Laboratory, Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
S Supporting Information
b
ABSTRACT: New examples of chlorophosphinochloropho-
sphonium (4) and chlorophosphinodichlorophosphonium (5)
cations have been prepared and spectroscopically characterized.
These bifunctional phosphinophosphonium cations offer a new
approach to the development of phosphinophosphonium fra-
meworks using reductive coupling reactions and have been
exploited as synthons to assemble larger catena-phosphorus
cations. The reactions of 4 and 5 with stibine reducing agents
have been studied using 31P NMR spectroscopy and have been
shown to produce a variety of new and known frameworks in a facile manner, depending on the reducing agent selection and the
stoichiometry of the reaction. New derivatives of frameworks containing three, four, and five phosphorus atoms have been identified
by 31P NMR spectroscopy. Crystals of the [GaCl4]ꢀ salt of the five-membered dication 11(iPr) have been isolated from the reaction
of [4(iPr)][GaCl4] with SbBu3, and the solid state structural features and solution state dynamics are comprehensively described in
the context of 31P{1H} NMR spectroscopic observations.
’ INTRODUCTION
Chart 1. Known Poly-Halide Functionalized catena-
Phosphorus Cations
A variety of synthetic approaches to catena-phosphinophospho-
nium cations have been developed that give access to a series of
frameworks demonstrating the potential for systematic extension
and diversification of catena-phosphorus chemistry.1 The reactions
are often high yielding due to the presence of the molecular positive
charge, which presumably provides for a distinct low energy
reaction pathway. The prototypical phosphinophosphonium (1)
framework is readily derivatized with chlorine substituents at
either the phosphine (2)2,3 or phosphonium center (3).4,5 In this
context, the well-known reduction of chlorophosphines to give
diphosphines and cyclopolyphosphines6 can be applied to chlor-
ophosphinophosphonium cations 2 to give 2,3-diphosphino-1,4-
diphosphonium cations 7,2,3 as illustrated in eq 1.
The application of reductive coupling to generate new poly-
phosphorus cations requires small halogenated cationic building
blocks, few examples of which have been reported (Chart 1).7ꢀ14
To exploit this methodology, we have prepared a series of new
derivatives of chlorophosphinochlorophosphonium (4) and
chlorophosphinodichlorophosphonium cations (5) as tetra-
chlorogallate salts and have used 31P NMR spectroscopy to
study reactions with SbPh3 or SbBu3, which effect reductive
coupling and the assembly of larger catena-phosphorus frame-
works (Chart 2). Here, we report the spectroscopic identification
of a series of catena-phosphinophosphonium frameworks as
well as the isolation and structural characterization of a cyclo-
triphosphinodiphosphonium salt.
’ RESULTS AND DISCUSSION
Reaction mixtures of a chlorophosphine (R2PCl) with a halide
abstracting agent (Abs = AlCl3, GaCl3 for any R = aryl, alkyl;
Me3SiOTf also for R = Me) quantitatively form phosphinochloro-
phosphonium cations 3, as shown in eq 2. The process can be
envisaged to involve the formation of a Lewis acidic phosphe-
nium cation [PR2]þ and subsequent coordination of the chloro-
phosphine ligand. This procedure has here been extended to the
Received: October 25, 2010
Published: March 25, 2011
r
2011 American Chemical Society
3342
dx.doi.org/10.1021/ic102150s Inorg. Chem. 2011, 50, 3342–3353
|

Inorganic Chemistry
ARTICLE
Chart 2. Representative Phosphinophosphonium Cation Frameworks
reaction of dichlorophosphines (eqs 3 and 4), where 31P{1H}
NMR spectra of reaction mixtures show the quantitative forma-
tion of 4[GaCl4] and 5[GaCl4], respectively. Chemical shifts and
coupling constants for all derivatives are summarized in Table 1.
31P{1H} NMR spectra for derivatives of 4 are sufficiently
PPh3 or trialkylphosphines via ligand exchange to produce the
prototypical phosphinophosphonium cations (1), illustrated in
eq 5.4,5 Interestingly, reactions of derivatives of 3[GaCl4] with
the less nucleophilic reductant SbPh3 yield tetrachlorogallate
salts of 1,3-diphosphino-2-phosphonium cations (6), as illu-
strated in eq 6. We envisage this reaction to proceed via formal
chloronium abstraction from 3 by SbPh3 to give a diphosphine
and a chlorostibonium cation. The diphosphine competes with
R2PCl as a ligand, effecting ligand exchange on 3 to give 6, as
proposed in Scheme 1. 31P{1H} NMR spectra of reaction
mixtures indicate that 3 is not completely consumed in the
reaction with SbPh3, whereas reduction with SbBu3 effects
quantitative formation of the extended framework 6. Reaction
with 1 equivalent of SbBu3 effects not only reduction of 3 to 6,
but also reduction of the in situ generated R2PCl to the dipho-
sphine, resulting in exchange-broadened 31P NMR spectra. The
addition of GaCl3 to the reaction mixture with either reductant
instead regenerates 3 from the eliminated chlorophosphine, as
in eq 2.
1
resolved at room temperature to distinguish JPP, but spectra
for derivatives of 5 contain broad peaks, perhaps indicating
dynamic dissociation of the coordinate PꢀP bond due to the
comparatively weak donation from the dichlorophosphine. At-
tempts to prepare dichlorophosphinophosphonium cations
using these methods showed no evidence of reaction or yielded
salts of triphosphenium cations [R3PꢀPꢀPR3]þ.15
Reaction mixtures of chlorophosphinochlorophosphonium
cations (4) with either SbPh3 or SbBu3 show a number of
products in the 31P{1H} NMR spectra depending on the reaction
stoichiometry. The addition of 1 equivalent of SbPh3 to [4(Ph)]-
[GaCl4] in CH2Cl2 results in a mixture of [10(Ph)][GaCl4],17
[12(Ph)][GaCl4]2,18 and [3(Ph)][GaCl4] as the major products
after 12 h (summarized in Table 2a). The addition of 2
equivalents of SbPh3 to [4(Ph)][GaCl4] gives a similar product
distribution, with [6(Ph)][GaCl4] as a minor product. In con-
trast, the addition of 2 equivalents of the stronger reductant
SbBu3 to [4(Ph)][GaCl4] gives the more reduced (less charged)
species, [10(Ph)][GaCl4] and Ph2P-PPh2. The addition of 1.5
equivalents of SbBu3 to [4(Ph)][GaCl4] yields [10(Ph)]-
[GaCl4] with Ph2P-PPh2 and [6(Ph)][GaCl4]. The addition of
less than 1 equivalent of either reducing agent results in incom-
plete consumption of 4.
The addition of 2 equivalents of SbPh3 and 1 equivalent of
GaCl3 to 4(Ph) results in nearly quantitative conversion to the
dication 12(Ph). The previously observed decomposition18 of
[12(Ph)][GaCl4]2 to the five-membered monocation [10(Ph)]-
[GaCl4] (t1/2 = 24 h) in solution is negligible in this mixture. This
preference for the more charged species is effected by the
In contrast to reactions of 1-chloro-1-phosphino-2-phospho-
nium cations (2) with PPh3 according to eq 1,2,3 the isomeric
1-phosphino-2-chloro-2-phosphonium cations (3) react with
3343
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Table 1. 31P{1H} NMR Parameters for Selected Phosphinophosphonium Gallate Saltsa
cation
donor
acceptor
spin system
δBorX [ppm] (phosphonium)
δA [ppm] (phosphine)
1JPP [Hz] (T)b
3(Ph)16
4(Ph)c
5(Ph)c
3(Me)16
4(Me)
5(Me)
3(Et)d
4(Et)c
5(Et)c
4(iPr)
Ph2(Cl)P
PPh2
AX
AB
73
0
ꢀ393
PPh(Cl)
PPh(Cl)
PMe2
72
57
ꢀ395
Ph(Cl)2P
Me2(Cl)P
131
99
81ꢀ85
ꢀ33
74
broad (213 K)
ꢀ340
AX
AB
AX
AX
AB
AX
AB
AB
AB
PMe(Cl)
PMe(Cl)
PEt2
93
ꢀ365
154
109
107
137
110
101
76
97
ꢀ400 (213 K)
ꢀ378
Et2(Cl)P
ꢀ19
79
PEt(Cl)
PEt(Cl)
PiPr(Cl)
PCy(Cl)
PMe(Cl)
ꢀ391
Et(Cl)2P
iPr2(Cl)P
Cy2(Cl)P
Ph2(Cl)P
92
ꢀ446 (193 K)
ꢀ431
93
4(Cy)
88
ꢀ437
ꢀ378
4(Ph2/Me)
72
a Substituents are indicated in parentheses in cation labels 3(R), 4(R), and 5(R). Data are reported for spectra obtained in CH2Cl2 at 101.3 MHz.
b Spectra recorded at 298 K unless otherwise indicated. c 31P NMR spectra are consistent with previously reported [AlxCly]ꢀ derivatives. d Correction to
previously reported 31P NMR data for this compound.16
Scheme 1. Proposed Mechanism for a Reductive Coupling
Chain Extension of 3, As Observed in eq 6
dicationic ring 11(Ph2/Me). While all other known derivatives
of 11 adopt a trans orientation of substituents at the adjacent
phosphine sites, 11(Ph2/Me) was consistently produced as a 2:1
mixture of the trans and cis isomers (Figure 2). The higher (Cs)
symmetry of the cis isomer readily distinguishes it as an ABB0XX0
spin system in 31P{1H} NMR spectra. The magnitude of the one-
bond coupling constant between the phosphine sites (P4/P5)
was observed to be substantially larger in the cis isomer (1JPP(cis)
=
1
ꢀ323 Hz; JPP(trans) = ꢀ260 Hz). This is in agreement with
previous experimental20ꢀ22 and theoretical23,24 studies indicat-
ing the substantial stereochemical dependence of 31Pꢀ P
31
coupling constants—specifically, that coupled phosphorus nu-
clei with cis-oriented lone pairs exhibit one-bond coupling
constants that are substantially greater than their trans-oriented
analogues, i.e., |1JPP(cis)| > |1JPP(trans)|.6,22,24 In addition, the 31
P
NMR chemical shifts of all three phosphine sites in the cis isomer
are considerably upfield shifted relative to the trans isomer (Δδ =
25ꢀ35 Hz). Although rare among cisꢀtrans isomers of neutral
cyclopolyphosphines, such a large magnitude difference in
chemical shift has been previously observed in the case of
cyclo-(tBuP)2PiPr.6 [11(Ph2/Me)][GaCl4]2 represents, how-
ever, the first observation of adjacent cis substituents in a cationic
catena-phosphorus ring system.
comparatively weak reducing agent (SbPh3 vs SbBu3) as well as
the in situ formation of the [Ga2Cl7]ꢀ anion from [GaCl4]ꢀ. The
addition of excess GaCl3 suppresses the equilibrium dissociation
of [GaCl4]ꢀ to yield chloride, which is proposed to undergo
nucleophilic attack on the dication 12.
The reductive coupling of [4(Me)][GaCl4] (summarized in
Table 2b) demonstrates a thermodynamic preference for the
five-membered dicationic ring [11(Me)][GaCl4]219 over the six-
membered alternative. Likewise, the reaction of [4(Et)][GaCl4]
with 1 equivalent of SbBu3 yields a mixture of [3(Et)][GaCl4]
with 10(Et) and [11(Et)][GaCl4]2 (summarized in Table 2c). In
contrast, the 31P NMR spectrum of the reaction mixture of SbPh3
with GaCl3 and [4(Et)][GaCl4] indicates nearly quantitative
Crystals of [11(iPr)][GaCl4]2 have been isolated from the
reaction of [4(iPr)][GaCl4] with SbBu3. Views of the cation
are shown in Figure 3. Using the PLATON software
package,25 the solid state structure of [11(iPr)][GaCl4]2 was
determined to approximate an 4E envelope conformation with
a CremerꢀPople26 phase angle (j) of 286.80(5)° and puck-
ering amplitude (Q) of 0.9040(7) Å. Bond lengths and angles
within the ring are generally comparable to those observed for
the two previously reported19 cyclo-triphosphino-1,3-dipho-
sphonium cations (Table 3), although the angle about one
phosphonium center (P3) is significantly smaller in 11(iPr),
presumably as a result of substituent steric strain. The closest
cationꢀanion contact is a ClꢀH interaction at 2.68 Å
(Σrvdw 2.84 Å) between a tetrachlorogallate anion and a
methyl proton of one isopropyl group in the adjacent
asymmetric unit.
formation
of
[Et2(Cl)PꢀPEtꢀPEtꢀP(Cl)Et2][GaCl4]2,
[70(Et)][GaCl4]2, identified by the characteristic AA0XX0 spin
system shown in Figure 1. Attempted crystallization of
[70(Et)][GaCl4]2 by slow evaporation over a period of weeks
resulted in the precipitation of a yellow solid identified as
[11(Et)][GaCl4]2 (31P{1H} NMR parameters: Table 4), sug-
gesting that 70 is a kinetically stabilized intermediate en route to
11 (Scheme 2). In the analogous reduction reaction of
[Ph2(Cl)P-PMeCl][GaCl4], 4(Ph2/Me), the kinetic product
70(Ph2/Me) was observed in the reaction solution according to
31P{1H} NMR spectroscopy for less than 22 h prior to its
complete conversion to the thermodynamically favored
Simulation of the AGHMX spin system apparent in 31P-
{1H} NMR spectra of solutions of 11(iPr) at 188 K (Figure 4,
3344
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Table 2. Products Observed for Reductive Coupling Reactionsa of [R2(Cl)P-PR0Cl][GaCl4] Including (a) 4(Ph), (b) 4(Me), and
(c) 4(Et)b
a All reactions conducted in CH2Cl2 unless otherwise noted. b Relative conversion (based on the area of the 31P{1H} NMR signals) to each of the
products vs. the most predominant species (assigned as 100) is indicated by shading according to the ranges shown in the key at the top. c Also contains a
moderate amount of PhPCl2. d [11(Me)][GaCl4]2 was isolated as a precipitate from CH2Cl2 reactions and redissolved in MeCN to confirm its identity
by 31P{1H} NMR spectroscopy. Relative abundance could not be assessed by NMR, so shading indicates only the presence or absence of this product in
these reactions. e 31P{1H} NMR parameters could not be simulated due to overlap with other products (approximate chemical shifts: δ = 91 ( 1, 12 ( 3,
and ꢀ3 ( 4 ppm). f 31P{1H} NMR parameters, A2BX system: δA = ꢀ62.3, δA = ꢀ54.4, δX = 12.5 ppm; 1JAB = ꢀ225, 1JBX = ꢀ112, 2JAX = 21. g Also
contains Et2P-PEt2 (δ31P = ꢀ25 ppm, broad singlet) as a major product.
3345
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Table 4) yields chemical shift and coupling constant
parameters that are comparable to those of known
substituted, the magnitude of nJPP is expected to depend more
specifically on the relative lone pair orientation (jLP) of the
phosphorus atoms in question.24 jLP may be formally defined
by the dihedral angle between the bisectors of the RꢀPꢀR
angle at each phosphorus atom and is therefore inversely
proportional to the dihedral angle between the substituents.
Among the three crystallographically characterized derivatives
of 11, there is substantial variation in the CꢀP4ꢀP5ꢀC
dihedral angle between the trans-oriented substituents in the
solid state (Table 3). The observed CꢀP4ꢀP5ꢀC dihedral
angle in 11(iPr) (93°) implies a large jLP angle and a
1
derivatives19 of 11. However, JPP between the backbone
phosphorus atoms P4ꢀP5 was observed to be significantly
smaller in magnitude (ꢀ149 Hz) for 11(iPr) relative to other
derivatives of 11 with trans-oriented substituents (ꢀ260 to
ꢀ315 Hz). Although all derivatives in Table 4 are trans-
1
correspondingly small magnitude JP4P5 relative to 1100
(CꢀP4ꢀP5ꢀC 143°).
31P{1H} NMR analysis of EtCN solutions of crystalline
[11(iPr)][GaCl4]2 at a variety of temperatures revealed sub-
stantial peak broadening near room temperature (Figure 5),
indicative of dynamic behavior in solution. It is particularly note-
worthy that the resonance attributed to P2 (ꢀ44 ppm [291 K] to
ꢀ53 ppm [188 K]) appeared sharp, with a line shape that was
relatively invariant as a function of the temperature, implying that
the solution exchange process(es) occur remotely from the
position of this atom. Further, low temperature 31P NMR data
for 11(iPr) suggests a molecule with C1 symmetry, whereas, at
high temperatures, the observed AMM0XX0 spin system suggests
effectively time-averaged C2 or Cs symmetry. A survey of existing
five-membered ring systems (I,22,27,28 II,29 III,30 IV,31 and 1017)
with a predominantly catena-phosphorus frame indicate a
preference for low symmetry (C1) solid state structures, with
varied symmetry in solution (C1 symmetry (ABCDX) for two
derivatives of 10,17 [(PhP)4PPhMe][OTf] and [(PhP)4PPht-
Bu][GaCl4], and higher symmetry for I22 (AA0BB0C), II29
(ABB0CC0), III32 (AA0BB0), and IV31 (ABCD at ꢀ100 °C;
AA0BB0 at 60 °C) and other derivatives of 10 (AA0BB0X),17
[10(Me)][OTf], [10(Me2/Cy)][OTf], [10(Ph)][OTf], and
[10(Me2/Ph)][OTf]). These observations have been previously
rationalized by invoking inversion at phosphorus, static solution
C2 or Cs conformations, or pseudorotation (ring-puckering)
processes. To understand the fluxional process occurring in
Figure 1. Experimental (upright) and simulated (inverted) expansions
of the P{1H} NMR spectra of [70(Et)][GaCl4]2 in the reaction
31
mixture of [4(Et)][GaCl4] with 2SbPh3 and GaCl3. Minor impurities
in the reaction mixture are marked with asterisks.
Scheme 2. Conversion of [70(Et)][GaCl4]2 to
[11(Et)][GaCl4]2
Figure 2. Experimental (upright) and simulated (inverted) expansions of the 31P{1H} NMR spectrum at 202.6 MHz of the 2:1 mixture of trans (blue)
and cis (red) isomers of 11(Ph2/Me), with characteristic AGHMX and ABB0XX0 spin systems, respectively. Broad peaks at 0.5 and 72 ppm (not
simulated) correspond to the phosphinophosphonium cation 3(Ph).
3346
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Figure 3. ORTEP views of the cation in [11(iPr)][GaCl4]2 CH2Cl2. Thermal ellipsoids are shown at the 50% probability level. Carbon atoms are
3
unlabeled, and hydrogen atoms are omitted for clarity. The right view shows only the phosphorus framework and associated R carbons, indicating an 4E
conformation.
Table 3. Selected Homoatomic Distances (Å) and Bond
Angles (deg)a in the Solid State Structure of
phosphonium center and effective C1 symmetry in asymmetri-
cally substituted derivatives. Pseudorotation is, however, insuffi-
cient to explain the symmetry observed in high temperature
NMR spectra of 11(iPr), as even a time-averaged planar structure
presents only C1 symmetry. Inversion at phosphorus may be
additionally invoked to rationalize the observed AMM0XX0 spin
system at high temperatures.
[11(iPr)][GaCl4] CH2Cl2 and Comparative Values for 110
3
19,b
and 1100
The significant steric strain imposed by the multiple isopropyl
substituents in 11(iPr) may promote comparatively rapid inver-
sion at P2 or P4/P5, as shown in Scheme 3. Assuming a first-
order mechanism, the activation parameters for this process,
which effectively exchanges the resonances of P1/P3 and P4/P5,
were calculated by line-shape analysis of 31P{1H} NMR spectra
between 246 and 292 K (Figure 6). In EtCN at 298 K, the free
energy of activation ΔG‡ was determined to be 52 ( 1.5
kJ molꢀ1 (95% C.I. by weighted linear regression). This is in
3
good agreement with a barrier of 50 kJ molꢀ1 estimated33 using
3
an approximate coalescence temperature (Tc) of 277 K. This is
significantly lower than the previously determined barrier for the
inversion of substituted diphosphines34 (94ꢀ100 kJ molꢀ1) or
3
phosphorus cages (77ꢀ126 kJ molꢀ1).6
3
However, the mechanism of this inversion process is not
a Angles indicated in bold center on the phosphonium centers (P1, P3).
b Also indicated are the calculated CremerꢀPople25,26 puckering angle
(j, deg), puckering parameter (Q, Å), and conformation.
i
unambiguous. In addition to the steric requirements of the Pr
substituents, the lower inversion barrier in 11(iPr) could alter-
natively be rationalized by invoking partial double bond character
along P1ꢀP2ꢀP3. Furthermore, in light of the solution ring-
opening reactions of this species (vide infra), an intermolecular
reaction of 11(iPr) with free chloride ions may also be proposed
as a low-energy pathway for net inversion. Previous experimental
and computational work from Humbel and co-workers has
indicated that an HCl-induced inversion pathway might reduce
solution for 11(iPr), it is instructive to compare it directly with
the analogous monocation 10.
the inversion barrier for chlorophosphines to ∼40 kJ mol
.
ꢀ1 35 It
3
is possible that a similar interaction occurs between P2 in 11(iPr)
and a tetrachlorogallate anion. Heated solutions of [11(iPr)]-
[GaCl4]2 in EtCN give a single product that is tentatively
1
assigned as [8(iPr)][GaCl4] on the basis of the 31P and H
NMR parameters (Scheme 4).
As the reductive coupling reactions for derivatives of 4[GaCl4]
result in the assembly of alkyl and aryl cyclophosphinopho-
sphonium cations, analogous reactions of the chlorophosphino-
dichlorophosphonium [5(Ph)][GaCl4] yield a new chloro-
substituted cyclophosphinophosphonium [100(Ph)][GaCl4]
(Scheme 5), which is identified using 31P NMR spectroscopy
(Figure 7; Table 5).
For monocations 10, pseudorotation provides sufficient ra-
tionale for the observation (31P{1H} NMR) of effective C2
symmetry in derivatives with symmetric substituents at the
3347
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Figure 4. Experimental (upright) and simulated (inverted) expansions of the 31P{1H} NMR spectrum of [11(iPr)][GaCl4]2 in EtCN at 101.3 MHz and
188 K. Parameters for the AGHMX spin system are collected in Table 4.
Table 4. 31P{1H} NMR Parametersa for [11(Et)][GaCl4]2, [11(iPr)][GaCl4]2, and [11(Ph2/Me)][GaCl4]2 in Comparison with
Previously Reported Heteroleptic Derivatives of 11[OTf]b
a Bold values indicate parameters involving the phosphonium center(s). All parameters were derived by iterative fitting of experimental data at
101.3 MHz. b Substituents at P4 and P5 are trans-oriented in all cases. c Chemical shift assignments for P1 and P3 were not specified in the original
reference. The assignments here are assumed and based on similarities of the magnitude of the chemical shifts but should not be taken as definitive.
d Line-broadening remains significant at 188 K, so |2JPP| values < 10 Hz could only be approximated. e Designation of this spin system according to
convention would erroneously imply a first order relationship between P4 and P5. For clarity, an ABGMX designation, as labeled, is used instead.
31P{1H} NMR spectra of reaction mixtures of 5(Ph) with
SbPh3 initially show the formation of PhPCl2 and 100(Ph),
followed by the gradual formation of 10(Ph) (Figure 8), suggest-
ing conversion between 100(Ph) and 10(Ph) by slow Ph/Cl
substituent exchange (t1/2 = 6ꢀ7 days) between phosphorus
and antimony. Substituent exchange behavior, although uncom-
mon for phosphorus, is well-known for antimony36,37 and
appears to be facilitated by GaCl3, as substantiated by the
immediate observation (31P NMR) of a 1:1 mixture of
[100(Ph)][GaCl4] and [10(Ph)][GaCl4] when PhPCl2 was
3348
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Scheme 5. Reductive Coupling of [5(Ph)][GaCl4] to Yield
[100(Ph)][GaCl4]
’ CONCLUSION
New derivatives of chlorophosphinochlorophosphonium (4)
and chlorophosphinodichlorophosphonium (5) cations have
been used as synthons for the assembly of larger cationic
polyphosphorus frameworks via reductive coupling. 31P NMR
studies of reactions with stibine reducing agents show the
dependence of product distribution on stoichiometry and the
reductants used. These reactions were shown to readily produce
a variety of new and known acyclic and cyclic frameworks,
including three new chloro-functionalized cations, highlighted
in Chart 3. The first cis-substituted derivative of the cyclo-
triphosphino-1,3-diphosphonium framework [11(Ph2/Me)]-
[GaCl4]2 has been observed by 31P NMR spectroscopy, and
the solution dynamics have been analyzed in the context of the
variable temperature solution spectra and the solid state crystal-
lographic data for [11(iPr)][GaCl4]2.
Figure 5. Variable-temperature 31P{1H} NMR spectra of
[11(iPr)][GaCl4]2 in EtCN at 101.3 MHz.
Scheme 3. Possible Inversion Pathways for 11(iPr) Which
Effect Time-Averaged C2 Symmetry
’ SYNTHETIC PROCEDURES AND CHARACTERIZA-
TION DATA
Unless otherwise specified, reactions were carried out in a
glovebox under an inert N2 atmosphere. Solvents were dried on
an MBraun solvent purification system and stored over 4 Å
molecular sieves unless otherwise specified. Anhydrous MeCN
was purchased from Aldrich, sparged with dry nitrogen or argon,
and stored over 3 Å molecular sieves before use, and Et2O was
dried by refluxing it over Na/benzophenone and distilled before
use. Deuterated solvents were purchased from Aldrich or Cam-
bridge Isotope Laboratories and stored over molecular sieves for
24 h prior to use. Me2PCl and MePCl2 were purchased from
Strem and used as received. PPh3, SbPh3, CyPCl2, Et2PCl,
i
iPrPCl2, and Pr2PCl were purchased from Aldrich and used as
received. Ph2PCl, PhPCl2, EtPCl2, and Me3SiOTf were pur-
chased from Aldrich and purified by vacuum distillation prior to
use. GaCl3 was purchased from Aldrich or Strem and sublimed
under a static vacuum prior to use. SbnBu3 was used as received
(supplier unknown). [3(Ph)][GaCl4] and [3(Me)][GaCl4]
were prepared according to literature methods.5,16
Figure 6. Eyring plot for the dynamic behavior of [11(iPr)][GaCl4]2 in
EtCN based on rate constants (k) from a line shape analysis of 31P{1H}
NMR spectra between 246 and 292 K (simulated and experimental spectra
available in the Supporting Information). Error bars are plotted on the basis
of error estimates in dNMR line shape fitting, and the 95% confidence
interval about the regression line is indicated with dashed lines.
1
Solution H, 13C, and 31P NMR spectra were collected at
room temperature on Bruker AC-250 (5.9 T) and Bruker Avance
500 (11.7 T) NMR spectrometers. Chemical shifts are reported
in parts per million relative to trace protonated solvent (1H), to
perdeuterated solvent (13C), or to an external reference standard
(31P, 85% H3PO4). NMR spectra of reaction mixtures were
obtained by transferring an aliquot of the bulk solution to a 5 mm
NMR tube, which was then capped and sealed with Parafilm.
31P{1H} NMR integrations are estimated to be accurate to
within (10% for identical coordination numbers or (20%
otherwise.38 All reported 31P{1H} NMR parameters for sec-
ond-order spin systems (except [11(iPr)][GaCl4]2) were de-
rived by iterative simulation of experimental data obtained at
both fields (31P Larmor frequencies of 101.3 and 202.6 MHz)
Scheme 4. Ring Opening of [11(iPr)][GaCl4]2 in EtCN
Observed Using 31P{1H} NMR Spectroscopy
added to a 1:1 mixture of SbPh3/GaCl3, as well as the generation
of 4(Ph) from 5(Ph) under the same conditions.
3349
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
31
Figure 7. Experimental (upright) and simulated (inverted) expansions of the P{1H} NMR spectrum of [100(Ph)][GaCl4], cyclo-[(Ph5P5)Cl]-
[GaCl4], at 280 K and 202.6 MHz, displaying an AGHMX spin system with a downfield resonance (δX = 89 ppm) characteristic of a Cl-substituted
phosphonium center.
31
Table 5. P{1H} NMR Parametersa for [100(Ph)][GaCl4] in
Comparison to Those for [10(Ph)][OTf]17 and
[90(Cy)][OTf]14
using gNMR, version 4.0 or 5.0.6.0.39,40 Typically, the higher
field experimental spectrum was used to find the spin system
parameters, and the lower field data were subsequently used to
ensure that the parameters were valid at both fields. For
[11(iPr)][GaCl4]2, only data acquired at 188 K and 101.3
MHz were used for iterative fitting and determination of 31P{1H}
NMR parameters. For [100(Ph)][GaCl4], data acquired at 298 K
and 202.6 MHz showed line broadening that prevented a viable
simulation, so the sample was cooled to 280 K. The signs of the
PꢀP coupling constants reported in Table 4 have been estab-
1
lished by assigning the JPP coupling constants as negative.24,41
Letter designations for the phosphorus spin systems have been
assigned by calculating the ratio |Δν/J|, where Δν is the
difference in 31P chemical shifts in Hertz, and using a value of
10 at the lower field as the threshold between a first and second
order letter designation. Temperatures reported above 298 K for
31P{1H} NMR spectra of [11(iPr)][GaCl4]2 were calibrated
against a neat ethylene glycol standard according to equations
reported by Ammann et al.42 Temperatures below 298 K are
reported on the basis of a linear plot of observed temperatures vs
temperatures calculated42 from 1H NMR measurements of a neat
MeOH standard over the range 188ꢀ309 K. Rate constants k for
the solution dynamics of [11(iPr)][GaCl4]2 in EtCN (ca. 0.04 M)
were calculated by line-shape analysis using dynamic NMR as
implemented in gNMR, version 5.0.6.0,40 assuming a two site
exchange between P1/P3 and P4/P5. Simulated and experimental
31P{1H} NMR spectra included in this analysis are included in the
Supporting Information. Data from temperatures above 292 K
were omitted owing to observed thermal decomposition of
11(iPr) to 8(iPr). Data from temperatures below 246 K were
omitted, as the small magnitude rate constants resulted in
a Numbers in square brackets indicate the phosphorus atoms, as labeled
above. Bold values indicate parameters involving the phosphonium
center. All parameters were derived by iterative fitting of experimental
data at 101.3 MHz.
3350
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
Figure 8. 31P{1H} NMR spectrum of the reaction mixture of [5(Ph)][GaCl4] with SbPh3 after 30 h (top) and 7 days (bottom) at 101.3 MHz,
indicating the transformation of [100(Ph)][GaCl4] to [10(Ph)][GaCl4]. t1/2 was estimated by integration of the well-separated phosphonium
resonances in [10(Ph)][GaCl4] (shaded) vs. [100(Ph)][GaCl4]. The remaining 31P resonances for [10(Ph)][GaCl4] overlap with those of
[100(Ph)][GaCl4] in the region between ꢀ25 and ꢀ45 ppm. PhPCl2 (162 ppm, not shown) is also present.
atoms were refined anisotropically, while hydrogen atoms were
assigned positions based on the sp2 or sp3 hybridization geome-
tries of their attached carbons and were given thermal parameters
20% greater than those of their parent atoms.
Chart 3. Framework Drawings of Halide-Functionalized
catena-Phosphinophosphonium Cationsa
Electrospray ionization mass spectrometric (ESI-MS) ana-
lyses were performed on a Bruker Daltonics microTOF instru-
ment in both positive and negative ion modes. Instrument
parameters were set as follows: spray voltage, 4500 V (positive) or
3300 V (negative); nebulizer gas (N2), 1 bar; dry gas (N2), 4 L/min;
dry temperature, 180 °C; exit voltage of the heated capillary, 130 V
(positive) or 90 V (negative); and sample flow rate, 2 uL/min.
Observed peaks with intensities g 2% relative to the base peak are
reported.
The melting point of [11(iPr)][GaCl4]2 was obtained using
an electrothermal apparatus on crushed crystalline material
flame-sealed in a glass capillary under dry nitrogen. Infrared
spectra of the crystals of [11(iPr)][GaCl4]2 were obtained as a
Nujol mull, so CꢀH stretching frequencies were obscured.
Sample Preparation for Derivatives of [R2(Cl)Pꢀ
PR0Cl][GaCl4], 4[GaCl4]. The addition of R0PCl2 (0.20 mmol)
and then R2PCl (0.20 mmol) to a stirring solution of GaCl3 (35
mg, 0.20 mmol) in CH2Cl2 (1 mL) afforded a pale yellow
solution, which showed virtually quantitative formation of
4[GaCl4] (>99% by 31P NMR) after 1 h at room temperature.
Solvent removal in vacuo or the addition of Et2O or pentane
yielded an oil.
Sample Preparation for Derivatives of [R(Cl)2Pꢀ
PRCl][GaCl4], 5[GaCl4]. RPCl2 (0.40 mmol) was added to a
stirring solution of GaCl3 (35 mg, 0.20 mmol) in CH2Cl2
(1 mL). The formation of 5[GaCl4] was quantitative (>99%
by 31P NMR) after 30ꢀ60 min at room temperature. Removal of
the solvent in vacuo or the addition of Et2O or pentane yielded
an oil.
aVertices represent phosphorus atoms. The first derivatives of frame-
works in boxes are reported here as products of the reductive coupling of
the phosphinophosphonium cations in the dotted box.
estimated errors in k on the same order of magnitude as k itself.
Weighted linear regression and error analysis of the Eyring plot
data [ln(k/T) versus 1/T]43 were performed using Octave44 and
plotted using Sigmaplot.45 Details of the regression and error
analysis for ΔH‡, ΔS‡, and ΔG‡ can be found in the Supporting
Information.
Single crystal X-ray diffraction data were collected on a Bruker
D8/APEX II CCD diffractometer at 173 K using ω scans with a
width of 0.3° and 15 s exposures. All measurements were made
with graphite monochromated Mo KR radiation (0.71073 Å).
The data were corrected for absorption through Gaussian
integration from indexing of the crystal faces. The structures
were solved by direct methods (SHELXS-9746) and refined using
full-matrix least-squares on F2 (SHELXL-9746). All non-hydrogen
Generalized Procedure for Reductive Coupling Reactions.
Phosphinophosphonium salts 3ꢀ5[GaCl4] (0.2ꢀ0.3 mmol)
were synthesized in situ and allowed to stir for 30 min to 1 h in
0.7ꢀ1 mL of CH2Cl2 (unless otherwise noted) before the
3351
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
addition of either tri-n-butylstibine or triphenylstibine. For
reactions involving 1 equivalent of SbPh3 or less, phosphinopho-
sphonium salts were initially synthesized in 0.5 mL of CH2Cl2,
and SbPh3 was dissolved in another 0.5 mL of CH2Cl2 to be
added by pipet. Otherwise, the solution of phosphinophospho-
nium gallate was transferred directly onto solid SbPh3 by pipet.
SbBu3 was added directly to the stirring solution by micropipet.
For reactions involving additional equivalent(s) of GaCl3, these
were weighed out and added to the initial solution of the
phosphinophosphonium gallate, before the addition of any reducing
agent. Solutions were allowed to stir at room temperature for 1 h and
18ꢀ24 h before NMR spectra were collected. Reactions of 4(Me)
resulted in the precipitation of CH2Cl2-insoluble solids, so reaction
mixtures were filtered through a pipet filter. The isolated solids were
washed with CH2Cl2 and dissolved in MeCN, so that both the
supernatant and precipitate could be analyzed separately by 31PNMR
spectroscopy.
was not performed owing to the observed decomposition at
1
elevated temperatures. Low temperature resolution of H/13C
NMR peaks could not be achieved. FT-IR (nujol mull, cmꢀ1
,
[intensity]): 1275 [m], 1222 [s], 1024 [s], 935 [w], 901 [m], 884
[m], 739, [w], 705 [m], 538 [m], 419 [s]. ESI-MS (10ꢀ5 M in
MeCN), positive ion mode [m/z (relative intensity, assign-
ment)]: ꢀ223.1 (4, [iPr3P3 þ H]þ), 242.3 (3, unassigned),
265.1 (100, [iPr4P3]þ), 299.1 (4, unassigned), 306.2 (6, [iPr4P3
þ MeCN]þ), 339.2 (51, [iPr5P4]þ), 413.3 (7, [iPr6P5]þ), 429.2
(6, [iPr4P3 þ 4MeCN]þ), 445.1 (3, unassigned); negative ion
mode, [GaCl4]ꢀ confirmed by isotope pattern analysis (base
peak: 210.8). Crystal data: C21H49Cl8Ga2P5 CH2Cl2, fw 964.42;
3
colorless blocks, crystal size 0.58 ꢁ 0.41 ꢁ 0.34 mm; monoclinic,
P21/n, a = 11.6226(11) Å, b = 22.014(2) Å, c = 16.9005(15) Å, β
= 98.2769(11)°, V = 4279.0(7) Å3, Z = 2, μ = 2.086 mmꢀ1; 2θmax
= 54.92°, collected (independent) reflections = 37146 (9779);
380 refined parameters, R1 (I > 2σ(I)) = 0.0399, wR2 (all data) =
0.1136, GOF = 1.025, ΔF max/min = 1.041/ꢀ0.777 eÅꢀ3
[8(iPr)][GaxCly]
.
0
0
NMR Observation of [Et2(Cl)PXꢀPAEtꢀPA EtꢀPX (Cl)Et2]-
[GaCl4]2, [70(Et)][GaCl4]2 and cyclo-[Et7P5][GaCl4]2, [11(Et)]-
[GaCl4]2. Following the generalized procedure for reductive
coupling, [4(Et)][GaCl4] was synthesized in situ (0.3 mmol)
and reacted in a ratio of 1:1:2 equivalents of 4(Et)/GaCl3/SbPh3.
31P{1H} NMR spectra (101.3 MHz, 298 K, CH2Cl2) collected
after 1 h indicated nearly quantitative conversion to a single
product with an AA0BB0 spin system, assigned as 70(Et) [δA =
Proposed synthesis of [iPr2(Cl)PꢀPiPrꢀPiPrCl][GaxCly],
1
2
111, δX = ꢀ38, 1JAA = ꢀ271 Hz, JAX = 1JA X = ꢀ374 Hz, JAX
=
0
0
0
0
JA X = 86 Hz, 3JXX = 84 Hz]. Attempted crystallization by vapor
diffusion of pentane into the reaction mixture yielded a viscous
oil, which, upon standing for 6 months, gave rise to a colorless
semicrystalline material coated in yellow oil. 31P{1H} NMR
spectra of the inseparable redissolved material showed effectively
2
0
0
A sample of [11(iPr)][GaCl4]2 (26 mg, 0.029 mmol) in EtCN
was heated in an NMR tube at 60 °C for 1 h under Ar, after
which time, complete conversion to 8(iPr) was indicated by
31P{1H} spectroscopy. Removal of the solvent in vacuo yielded
an oil. Yield: 18.4 mg (0.034 mmol, based on a GaCl4 anion).
31P{1H} NMR (EtCN, 101.3 MHz, 294 K): AMX spin system
1
complete conversion to [11(Et)][GaCl4]2. H NMR spectra
indicated that the mixture was predominantly composed of
[11(Et)][GaCl4]2 and the oxidized antimony byproduct
[Ph3SbCl][GaCl4] or Ph3SbCl2.
1
δA = ꢀ79, δM(phosphonium) = 96, δX 1= 132; JAM = ꢀ375 Hz,
2
1JAM = ꢀ224 Hz, JMX = 29 Hz. H{31P} NMR (CD2Cl2,
500.1 MHz, 298K): δ = 1.22 (broad s, 3H, ꢀPACHCH3), 1.27
(d, 3H, ꢀPXCHCH3), 1.31 (d, ꢀPACHCH03) and 1.33
(broad s, ꢀPMCH0CH003) [6H together], 1.37 (broad s,
3H, ꢀPMCHCH3), 1.42 (broad s, 3H, ꢀPMCHCH03), 1.48
(d, 3H, ꢀPXCHCH03), 1.63 (d, 3H, ꢀPMCH0CH0003), 2.45
(sept, 1H, ꢀPACH), 2.63 (sept, 1H, ꢀPMCH), 2.95 (sept,
1H, ꢀPMCH0), 3.17 ppm (sept, 2H, ꢀPXCH). Assignment of
NMR Observation of cyclo-[(MeP)3(PPh2)2][GaCl4]2,
[11(Ph2/Me)][GaCl4]2. Following the generalized procedure
for reductive coupling, [4(Ph2/Me)][GaCl4] was synthesized
in situ (0.3 mmol) and reacted with 0, 1, or 2 equivalents of GaCl3
and either 1 equivalent of SbBu3 or 1ꢀ2 equivalents of SbPh3.
31P{1H} NMR spectra collected after 18 h indicated 11(Ph2/
Me) and 3(Ph) as the major products, along with 3ꢀ20% of
13(Ph2/Me). In all cases, the ratio of the trans/cis isomers of 11
was approximately 2:1, as assessed by the relative areas of the
31P{1H} NMR resonances. 31P{1H} NMR of [11(Ph2/Me)]-
[GaCl4]2 (101.3 MHz, 298 K, CH2Cl2): trans-isomer—
AGHMX spin system, see Table 4; cis-isomer ꢀ ABB0XX0 spin
1
1
1H resonances was based on Hꢀ H COSY NMR, chemical
1
31
1
shift, and observed Hꢀ P coupling in H NMR spectra. 13C
NMR (d3-MeCN, 125.8 MHz, 298K): 17.6ꢀ18.96 (overlapping
signals in HSQC, ꢀCH3), 21.4 (m, ꢀPMCH), 23.2 (m,
ꢀPXCH), 24.0 (m, ꢀPMCH0), 31.2 (m, ꢀPACH). Assignment
1
of 1H resonances was based on 13Cꢀ H HSQC NMR spectra.
system: δA = ꢀ63.3, δB = ꢀ34.4, δX = 52.8, 1JAX = 1JAX = ꢀ314
0
ESI-MS (10ꢀ5 M in MeCN), positive ion mode [m/z (relative
intensity, assignment)]: ꢀ223.2 (4, [iPr3P3 þ H]þ), 265.1 (100,
[iPr4P3]þ), 320.2 (3, [iPr4P3 þ EtCN]þ), 339.2 (2, [iPr5P4]þ);
negative ion mode, [GaCl4]ꢀ confirmed by isotope pattern
analysis (base peak: 210.8).
Hz, 1JBX = 1JB X = ꢀ350 Hz, JBB = ꢀ323 Hz, JBX = JB X = 17
1
2
2
0
0
0
0
0
Hz, 2JAB = 10 Hz, 2JAB = 2 Hz, 2JXX = 21 Hz.
0
0
Synthesis of cyclo-[iPr7P5][GaCl4]2, [11(iPr)][GaCl4]2.
[iPr2(Cl)PꢀPiPrCl][GaCl4], [4(iPr)][GaCl4] (0.3 mmol), was
synthesized in situ in 0.7 mL of CH2Cl2 according to the
generalized procedure (vide supra) and allowed to stir for 1 h
at room temperature prior to the addition of SbBu3 (73.8 uL, 0.3
mmol). No readily identifiable products could be distinguished
from the reaction solution by 31P{1H} NMR spectroscopy after
1.5 h. Upon standing for 20ꢀ24 h in an NMR sample tube,
colorless crystals suitable for X-ray diffraction precipitated from
the reaction solution. The solution was decanted, and the crystals
were washed with 2 ꢁ 1 mL CH2Cl2 and dried. Yield: 26 mg
(0.030 mmol, 30%). D.p. 178ꢀ182 °C. An elemental analysis
’ ASSOCIATED CONTENT
S
Supporting Information. Comparisons of simulated and
b
experimental 31P{1H} NMR spectra for line shape analysis,
calculated rate constants, numerical values for the reductive
coupling product ratios in Table 2, and the crystallographic
information file (CIF) for [11(iPr)][GaCl4]2. This material is
available free of charge via the Internet at http://pubs.acs.org.
3352
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353

Inorganic Chemistry
ARTICLE
’ AUTHOR INFORMATION
(27) Spencer, C. J.; Simpson, P. G.; Lipscomb, W. N. Acta Crystal-
logr. 1962, 15, 509.
(28) Spencer, C. J.; Lipscomb, W. N. Acta Crystallogr. 1961, 14
250–256.
Corresponding Author
*E-mail: Neil.Burford@dal.ca.
(29) Schisler, A.; Lonnecke, P.; Huniar, U.; Ahlrichs, R.; Hey-
Hawkins, E. Angew. Chem., Int. Ed. 2001, 40, 4217–4219.
(30) Lex, J.; Baudler, M. Z. Anorg. Allg. Chem. 1977, 431, 49–60.
(31) Wolf, R.; Hey-Hawkins, E. Chem. Commun. 2004, 2626–2627.
(32) Hoffman, P. R.; Caulton, K. G. Inorg. Chem. 1975,
14, 1997–1999.
’ ACKNOWLEDGMENT
We thank the Natural Sciences and Engineering Research
Council of Canada, the Killam Foundation, the Canada Research
Chairs Program, the Canada Foundation for Innovation, the
Nova Scotia Research and Innovation Trust Fund, the Walter C.
Sumner Foundation, and the Eliza Ritchie Scholarship for
funding, as well as Prof. Peter D. Wentzell for assistance and
advice on error analysis in linear regression.
(33) G€unther, H. . In NMR Spectroscopy: Basic Principles Concepts,
and Applications in Chemistry; Wiley: Chichester, U.K., 1992; pp
335ꢀ390.
(34) Lambert, J. B.; Jackson, G. F., III; Mueller, D. C. J. Am. Chem.
Soc. 1970, 92, 3093–3097.
(35) Humbel, S.; Bertrand, C.; Darcel, C.; Bauduin, C.; Jugꢀe, S. Inorg.
Chem. 2003, 42, 420–427.
(36) Nunn, M.; Sowerby, D. B.; Wesolek, D. M. J. Organomet. Chem.
1983, 251, C45–C46.
(37) Balꢀazs, L.; Breunig, H. J. Coord. Chem. Rev. 2004, 248, 603–621.
(38) Huynh, K.; Rivard, E.; LeBlanc, W.; Blackstone, V.; Lough, A. J.;
Manners, I. Inorg. Chem. 2006, 45, 7922–7928.
(39) Budzelaar, P. H. M. gNMR for Windows, 4.0; Cherwell Scientific
Publishing Limited: Oxford, U.K., 1997.
(40) Budzelaar, P. H. M. gNMR for Windows, 5.0.6.0; Ivorysoft:
Winnipeg, MB, Canada, 2006.
(41) Finer, E. G.; Harris, R. K. Prog. Nucl. Magn. Reson. Spectrosc.
1971, 6, 61–118.
(42) Ammann, C.; Meier, P.; Merbach, A. E. J. Magn. Reson. 1982,
46, 319–321.
(43) Sandstr€om, J. Dynamic NMR Spectroscopy; Academic Press:
’ REFERENCES
(1) Dyker, C. A.; Burford, N. Chem. Asian J. 2008, 3, 28–36.
(2) Dyker, C. A.; Burford, N.; Lumsden, M. D.; Decken, A. J. Am.
Chem. Soc. 2006, 128, 9632–9633.
(3) Carpenter, Y.; Dyker, C. A.; Burford, N.; Lumsden, M. D.;
Decken, A. J. Am. Chem. Soc. 2008, 130, 15732–15741.
(4) Burford, N.; Cameron, T. S.; Ragogna, P. J.; Ocando-Mavarez,
E.; Gee, M.; McDonald, R.; Wasylishen, R. E. J. Am. Chem. Soc. 2001,
123, 7947–7948.
(5) Burford, N.; Ragogna, P. J.; McDonald, R.; Ferguson, M. J. Am.
Chem. Soc. 2003, 125, 14404–14410.
(6) Baudler, M.; Glinka, K. Chem. Rev 1993, 93, 1623–1667 and
references therein.
(7) Tarasova, R. I.; Zykova, T. V.; Shagvaleev, F. Sh.; Sitdikova, T.
Sh.; Moskva, V. V. Zh. Obshc. Khim. 1989, 60, 1775–1779.
(8) Tarasova, R. I.; Sitdikova, T. Sh.; Zykova, T. V.; Shagvaleev, F.
Sh.; Moskva, V. V.; Kormachev, V. V.; Rusanov, V. M.; Baranov, Yu. I.;
Danilov, S. D. . U.S.S.R. Patent SU 1449565, July 1, 1989; Scifinder
Scholar: 1989:497499.
(9) Shagvaleev, F. Sh.; Zykova, T. V.; Tarasova, R. I.; Sitdikova, T.
Sh.; Moskva, V. V. Zh. Obshch. Khim. 1990, 60, 1775–1779.
(10) Tarasova, R. I.; Zykova, T. V.; Shagvaleev, F. Sh.; Sitdikova, T.
Sh.; Moskva, V. V. Zh. Obshch. Khim. 1991, 61, 2529–2532.
(11) Krossing, I.; Raabe, I. Angew. Chem., Int. Ed. Engl. 2001,
40, 4406–4409.
London, 1982.
(44) Eaton, J. W. Octave, 3.2.4; University of Wisconsin: Madison,
WI, 2010.
(45) Sigmaplot for Windows, 10.0.0.54; Systat Software Inc.: Point
Richmond, CA, 2006.
(46) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112–122.
(12) Gonsior, M.; Krossing, I.; M€uller, L.; Raabe, I.; Jansen, M.; van
W€ullen, L. Chem.—Eur. J. 2002, 8, 4475–4492.
(13) Krossing, I. Dalton Trans. 2002, 500–512.
(14) Weigand, J. J.; Burford, N.; Davidson, R. J.; Cameron, T. S.;
Seelheim, P. J. Am. Chem. Soc. 2009, 131, 17943–17953.
(15) Schmidpeter, A.; Lochschmidt, S.; Sheldrick, W. S. Angew.
Chem., Int. Ed. 1985, 24, 226–227.
(16) Burford, N.; Cameron, T. S.; LeBlanc, D. J.; Losier, P.; Sereda,
S.; Wu, G. Organometallics 1997, 16, 4712–4717.
(17) Dyker, C. A.; Riegel, S. D.; Burford, N.; Lumsden, M. D.;
Decken, A. J. Am. Chem. Soc. 2007, 129, 7464–7474.
(18) Weigand, J. J.; Burford, N.; Lumsden, M. D.; Decken, A. Angew.
Chem., Int. Ed. 2006, 45, 6733–6737.
(19) Riegel, S. D.; Burford, N.; Lumsden, M. D.; Decken, A. Chem.
Commun. 2007, 4668–4670.
(20) Albrand, J. P.; Gagnaire, D.; Robert, J. B. J. Am. Chem. Soc. 1973,
95, 6498–6500.
(21) Albrand, J. P.; Gagnaire, D.; Robert, J. B. J. Am. Chem. Soc. 1974,
96, 1643.
(22) Albrand, J. P.; Robert, J. B. Chem. Commun. 1974, 644–645.
(23) Albrand, J. P.; Faucher, H.; Gagnaire, D.; Robert, J. B. Chem.
Phys. Lett. 1976, 38, 521–523.
(24) Forgeron, M. A. M.; Gee, M.; Wasylishen, R. E. J. Phys. Chem.
2004, 108, 4895–4908.
(25) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
(26) Cremer, D.; Pople, J. A. J. Am. Chem. Soc. 1975, 97, 1354–1358.
3353
dx.doi.org/10.1021/ic102150s |Inorg. Chem. 2011, 50, 3342–3353