Ammonium and Potassium Salts of a Hexacoordinate Phosphorus(V) Anion Featuring P-O and P-C Bonds

Article abstract of DOI:10.1021/acs.inorgchem.8b02174

Ammonium and potassium salts featuring the chiral mer-[P(C₆H₄CO₂)₃]^-, mer-[1]^-, have been isolated. Specifically, treating phosphorane P(C₆H₄CO₂)₂(C₆H₄CO₂H), 2, with N-containing bases [N_base = PhNMe₂, PhNH₂, pyridine (py), isoquinoline, (-)-brucine, N(n-C₈H₁₇)₃] afforded ammonium salts [N_baseH]⁺-mer-[1]^-. Each compound was fully characterized spectroscopically, and four were subjected to X-ray crystallographic analysis. Salts were isolated with the racemic mixture of the mer-[1]^- anion except in the case of [(-)-brucineH]-λ-mer-[1], for which the crystal analyzed was enantiomerically pure. The potassium salt, K-mer-[1], was synthesized by treating 2 with KH. The solid-state structure of K-mer-[1] is a coordination polymer consisting of seven- and eight-coordinate K⁺ ions that are weakly bound by oxygen of either the racemic anion or the methanol solvent. Preliminary NMR and MS data for the formation of the Br?nsted acid, H(DMF)_n[1], has also been obtained. An estimate of the basicity of anion mer-[1]^- was obtained from IR measurements of the N-H stretching frequency for [(n-C₈H₁₇)₃NH]-mer-[1]. On the basis of these measurements, anion mer-[1]^- was ranked similar to the classical weakly coordinating anion, [ClO₄]^-, in terms of its coordinating ability.

Full text of DOI:10.1021/acs.inorgchem.8b02174

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Ammonium and Potassium Salts of a Hexacoordinate
Phosphorus(V) Anion Featuring P−O and P−C Bonds
Khatera Hazin, Brian O. Patrick, and Derek P. Gates*
Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
S
* Supporting Information
ABSTRACT: Ammonium and potassium salts featuring the chiral
mer-[P(C6H4CO2)3]−, mer-[1]−, have been isolated. Specifically,
treating phosphorane P(C6H4CO2)2(C6H4CO2H), 2, with N-
containing bases [Nbase = PhNMe2, PhNH2, pyridine (py),
isoquinoline, (−)-brucine, N(n-C8H17)3] afforded ammonium salts
[NbaseH]+-mer-[1]−. Each compound was fully characterized
spectroscopically, and four were subjected to X-ray crystallographic
analysis. Salts were isolated with the racemic mixture of the mer-[1]−
anion except in the case of [(−)-brucineH]-Λ-mer-[1], for which
the crystal analyzed was enantiomerically pure. The potassium salt,
K-mer-[1], was synthesized by treating 2 with KH. The solid-state
structure of K-mer-[1] is a coordination polymer consisting of seven-
and eight-coordinate K+ ions that are weakly bound by oxygen of
either the racemic anion or the methanol solvent. Preliminary NMR and MS data for the formation of the Brønsted acid,
H(DMF)n[1], has also been obtained. An estimate of the basicity of anion mer-[1]− was obtained from IR measurements of the
N−H stretching frequency for [(n-C8H17)3NH]-mer-[1]. On the basis of these measurements, anion mer-[1]− was ranked
similar to the classical weakly coordinating anion, [ClO4]−, in terms of its coordinating ability.
initiators are particularly attractive due to their convenient
one-pot synthesis from PCl5 and C6Cl4(OH)2 in the presence
of a donor solvent L. In addition, these initiators are active for
olefin polymerization at temperatures well above the industrial
polymerization temperature of −100 °C used in butyl rubber
production. The degree of ion-pairing during propagation plays
a major role in the relative rates of propagation and chain
transfer/termination. Therefore, optimizing the coordinating
properties of the anion by varying the substituents within a
hexacoordinate phosphorus(V) anion may permit polymer-
ization activity at even higher temperatures. In this regard, we
were drawn to the phosphorus(V) anion, mer-[1]−,8 which
features both P−O and P−C moieties (Figure 2).
INTRODUCTION
■
Phosphorus displays a tremendous diversity of coordination
numbers in its compounds with the two extremes of one-
coordinate (e.g., phosphaalkyne, phosphinidene) and six-
coordinate (e.g., phosphate) systems being the rarest. Despite
the fact that the simple anions [PF6]− and [PCl6]− are
ubiquitous in inorganic chemistry, six-coordinate phosphorus-
(V) anions featuring organic substituents are rare (Figure 1).
[Et3NH][P(1,2-(O2C6H4)3] was isolated in 1963 and
represents the first salt featuring a hexacoordinate organo-
phosphate anion (i.e., [A]−).1 This catecholate system has
evolved to the widely used chiral charge delocalized tris-
(tetrachlorobenzenediolato)phosphate, [B]− (R = Cl), and the
related binol-derivative, [C]−.2 The tris(oxalato)phosphate
anion, [D]−, has attracted attention as its lithium salt for
potential application in lithium ion batteries.3 The tris-
(pentafluoroethyl)trifluorophosphate anion, [E]−, has been
widely used in ionic liquids.4 Remarkably, the only known
phosphorus(V) anion featuring P−C bonds, [F]−, was the first
P(V) anion to be resolved into its optical isomers.5
Our group has been interested in the development of
Brønsted acids featuring hexacoordinate phosphorus(V)
anions as potential initiators for the cationic polymerization
of olefins. For instance, we have reported a series of protic
acids, HL2[B] (L = Et2O, THF, CH3CN, DMF; R = Cl), and
have shown that they are effective initiators for the
polymerization of n-butyl vinyl ether, styrene, α-methylstyrene,
p-methoxystyrene, and isoprene.6,7 These weighable, solid
Herein, we report the syntheses and crystallographic
characterization of a series of ammonium [NbaseH]+ salts
featuring anion mer-[1]−. The general synthetic methodology
developed involves treating phosphorane P-
(C6H4CO2)2(C6H4COOH) (2) with various amines [Nbase
=
PhNMe2, PhNH2, pyridine (py), isoquinoline, (−)-brucine,
N(n-C8H17)3]. In addition, the potassium salt, K-mer-[1], was
prepared by treating 2 with KH, and its solid state polymeric
structure is examined to provide insight into the weakly
coordinating nature of the PO3C3 anion.
Received: August 1, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b02174
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Inorganic Chemistry
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Figure 1. Examples of known hexacoordinate phosphorus(V) weakly coordinating anions.
detailed characterization to confirm its formulation. Colorless
crystals suitable for X-ray crystallographic analysis were
obtained for [PhNMe2H]-rac-mer-[1], [pyH]-rac-mer-[1],
[isoquinolineH]-rac-mer-[1], and [(−)-brucineH]-Λ-mer-[1].
The molecular structures of these ammonium salts are shown
in Figure 4, and the metrical parameters will be discussed in
detail below. Interestingly, the crystal that was selected for
[(−)-brucineH]-rac-mer-[1] was revealed to be enantiomeri-
cally pure [(−)-brucineH]-Λ-mer-[1]. Spectroscopic analyses
of the isolated complexes were performed in either acetone-d6
or DMSO-d6 due to their low solubility in other solvents. The
31P{1H} NMR spectra revealed dominant singlet resonances
assigned to the desired anion mer-[1]− (range: −104.7 to
−135.2 ppm, see Table 1) and are comparable to those
previously reported for [Et2NH2][1] and [Et3NH][1] (δ =
−135.5 and −135.7 in DMF-d7, respectively).8
Figure 2. Hexacoordinate phosphorus(V) anion, [P(C6H4CO2)3]−,
mer-[1]−.
RESULTS AND DISCUSSION
■
Ammonium Salts of mer-[1]−. Inspired by the single
report of [Et2NH2]+ and [Et3NH]+ salts of anion mer-[1]−,8
we prepared a series of ammonium salts as a starting point to
explore the weakly coordinating anion (WCA) potential of
mer-[1]−. Initially, an acetone solution of acid P-
(C6H4CO2)2(C6H4COOH) (2) was treated with dimethylani-
line (PhNMe2) to afford [PhNMe2H]-mer-[1] (Scheme 1).
On the basis of these encouraging results, other bases were also
explored [i.e., PhNH2, pyridine (py), isoquinoline, (−)-brucine
and tri(n-octyl)amine]. In some cases, excess base was needed
to ensure quantitative conversion to the desired salt.
In the case of [PhNH3]-mer-[1], the 31P{1H} NMR
spectrum in DMSO-d6 was accompanied by a second signal
at −55.7 ppm (ca. 5%). This downfield signal was assigned to
2, which may be formed by the protonation of mer-[1]− with
anilinium. This is not surprising since anilinium is the most
acidic conjugate acid of the Nbases used in the present study. In
contrast, regular monitoring of the 31P{1H} NMR spectra of
solutions of all other salts in acetone-d6 or DMSO-d6 solutions
showed only the signal attributed to mer-[1]−, even after
several weeks at ambient temperature. While the 31P{1H}
Each crude product purified by recrystallization (details
given in the Experimental Section) and was subjected to
Scheme 1. General Synthetic Route to [NbaseH]-mer-[1] with Nbase = PhNMe2, PhNH2, py, Isoquinoline, (−)-Brucine, and N(n-
C8H17)3
B
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Table 1. 31P{1H} and 1H NMR Chemical Shifts of [NbaseH]-
rac-mer-[1]
displayed a wide range of chemical shifts. For instance, the
signal assigned to the [NbaseH]+ proton of CD2Cl2 solutions of
the isoquinolinium and pyridinium salts was 16.34 and 16.37
ppm, respectively. For comparison, the same proton of the
pyridinium salt, [pyH][As(N3)6], resonates slightly upfield [δ
= 13.6 (in CD2Cl2)].10 The chemical shifts of the acidic
protons in the tertiary ammonium salts were similar to each
other and at higher field to those described for the more acidic
isoquinolinium and pyridinium salts {[PhNMe2H]-rac-mer-
[1]: δ = 9.31 in acetone-d6; [(n-C8H17)3NH]-rac-mer-[1]: δ =
9.76 in acetone-d6, 10.40 in CD2Cl2; [(−)-brucineH]-rac-mer-
[1]: δ = 10.60 in DMSO-d6; [(−)-brucineH]-Λ-mer-[1]: δ =
12.63 in CD2Cl2}. For comparison, the dimethylanilinium salt
featuring a weakly coordinating fluoroarylborate anion,
[PhNMe2H][HB(C6F5)3], resonates at 8.88 ppm in
CD2Cl2.11 In contrast, the signal for the anilinium salt,
[PhNH3]-rac-mer-[1], appears at a much higher field [δ =
6.56 in DMSO-d6] than the aforementioned salts and
[PhNH3][BF4] [δ = 8.20 in CD3CN].12
[NbaseH]+-mer-[1]−
1
compound
δ
31P
δ Hacidic
a
a
[PhNMe2H]-rac-mer-[1]
[PhNH3]-rac-mer-[1]
[pyH]-rac-mer-[1]
[isoquinolineH]-rac-mer-[1]
[(−)-brucineH]-rac-mer-[1]
[(−)-brucineH]-mer-[1]
[(n-C8H17)3NH]-rac-mer-[1]
[NEt2H2][P(C6H4CO2)3]
−107.7
−133.6
−126.8
−104.7
−135.2
9.31
6.56
b
a
a
b
b
c
16.37
16.34
10.60
12.63
c
b
c
c
−114.3, −114.6
a
c
−128.9
10.40
d
−135.5
NA
NA
d
[NEt3H][P(C6H4CO2)3]
−135.7
In acetone-d6. In DMSO-d6. In dichloromethane-d2. In DMF-d7.8
a
b
c
d
NMR spectrum of [(−)-brucineH]-mer-[1] recorded in
DMSO-d6 showed only a singlet resonance (δ = −135.2),
that recorded in CD2Cl2 displays two resonances (δ = −114.3
and −114.6), see Figure 3. Importantly, these signals cannot be
Additional insight into the solution behavior of the new salts
was gained from their 13C{1H} NMR spectra. Although the
spectra displayed signals consistent with the assigned
formulations, the signals assigned to the carboxylate ligands
within mer-[1]− for all salts were inequivalent and suggests a
lowering of the predicted C2 symmetry, perhaps due to weak
ion pairing. Specifically, three distinct signals were observed
that were assigned to the CO moieties (range: δ = 163.9−
170.7) and 18 resolved signals were observed that were
assigned to the aromatic carbons. In the case of [(−)-bruci-
neH]-rac-mer-[1], the 13C{1H} NMR spectrum revealed that
most signals assigned to the anion were broadened or split
when compared to those of enantiomerically pure [(−)-bru-
cineH]-Λ-mer-[1]. This is most likely attributable to
diastereotopism resulting from weak cation−anion interactions
that differentiates [(−)-brucineH]-Δ-mer-[1] and [(−)-bruci-
neH]-Λ-mer-[1]. A similar phenomenon was postulated above
to account for the observed 31P NMR spectrum of this
compound. In conclusion, the 13C{1H} NMR spectroscopic
data suggest a lowering of the expected symmetry of anion
mer-[1]− in solution that has not previously been observed
with salts featuring the TRISPHAT anion, [P-
(O2C6Cl4)3]−.13,14 This asymmetry of mer-[1]− will be
discussed further in the next section, which describes the
solid-state structures.
X-ray Crystallographic Characterization. Several of the
new salts featuring [1]− afforded single-crystals suitable for X-
ray crystallographic analysis. Interestingly, each complex
crystallizes as the mer-[1]− isomer, and each has solvent
molecules of crystallization. The molecular structures of
[PhNMe2H]-rac-mer-[1]·Me2CO, [pyH]-rac-mer-[1]·0.5
Me2CO, [isoquinolineH]-rac-mer-[1]·isoquinoline, and
enantiomerically pure [(−)-brucineH]-Λ-mer-[1]·2 CH2Cl2
are displayed in Figure 4. The assignment of the Λ-
configuration of mer-[1]− in the latter structure is supported
by the Flack parameter of 0.05(8).
Figure 3. 31P{1H} NMR (162 MHz, 25 °C) spectra of (a)
[(−)-brucineH]-rac-mer-[1] recorded in (CD3)2SO and (b)
[(−)-brucineH]-rac-mer-[1] recorded in CD2Cl2 solvent.
assigned to the protonated form of mer-[1]− (i.e., 2).
Therefore, we speculate that these observations indicate ion-
pairing in the solvent of lower polarity (i.e., CD2Cl2) to afford
the distinct diastereomers [(−)-brucineH]-Δ-mer-[1] and
[(−)-brucineH]-Λ-mer-[1], which have slightly different
chemical shifts than that of free mer-[1]− ion. Although we
cannot rule out the possibility of isomerization to fac-[1]−
form, it is highly unlikely given that the two signals are in a 1:1
ratio immediately upon dissolution. Such a rapid isomerization
would be inconsistent with the slow rate we have previously
observed for mer- to fac-isomerization of the related anion,
[P(OC6H4NMe)3]−.9
1
The new ammonium salts were also characterized by H
In each salt, the closest cation−anion contact was a
hydrogen-bonding interaction between the acidic N−H proton
and the oxygen of a CO moiety in [1]−. Specifically, these
O···H distances were much shorter for [PhNMe2H]-rac-mer-
[1] [O(2)···H(1) = 1.67(3) Å] than [pyH]-rac-mer-[1]
[O(2)···H(1) = 1.92(4) Å] and [(−)-brucineH]-Λ-mer-[1]
[O(2)···H(1) = 1.88(1) Å]. In each case, these contacts are
well within the sum of the van der Waals radii for oxygen and
NMR spectroscopy and the spectra were consistent with the
assigned formulation [NbaseH]-rac-mer-[1]. In each case,
signals assigned to the acidic protons of [NbaseH]-rac-mer-[1]
were detected. Their chemical shifts will be discussed below
and compared to those of related salts. It must be noted that in
1
addition to anion−cation interactions, the H chemical shifts
of the [NbaseH]+ depend on the amount of base present, the
solvent, the concentration, and the temperature. These signals
C
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Figure 4. Molecular structures of: (a) [PhNMe2H]-rac-mer-[1]·Me2CO (Λ isomer is shown); (b) [pyH]-rac-mer-[1]·0.5 Me2CO (Δ isomer
is shown); (c) [isoquinolineH]-rac-mer-[1]·(C9H7N) (Δ isomer is shown); (d) [(−)-brucineH]-Λ-mer-[1]·2.02 CH2Cl2. Ellipsoids are drawn at
the 50% probability level. Solvents of crystallization and hydrogen atoms are omitted for clarity, except for H(1). Only one enantiomer is shown in
(a−c), whereas (d) is enantiomerically pure.
hydrogen [rvdw = 2.72 Å] and suggest significant ion-pairing.15
In contrast, the analogous O···H distance in [isoquinolineH]-
rac-mer-[1] is 3.13(9) Å [O(6)···H(1)] suggesting little to no
significant cation−anion interaction. This may be a con-
sequence of the presence of a second hydrogen bonding
interaction involving the isoquinoline solvent molecule
[N(2)···H(1) = 1.76(8) Å, cf. rvdw = 2.75 Å].15 Similar H-
bonding interactions have been reported for [isoquinoline-
H]4[isoquinoline]2[Mo8O26] [N(3)···H(1A) = 1.84(1) Å].16
No such interactions between the acidic N−H proton and
solvent are present in the other salts.
Furthermore, there is a short cation−anion interaction in
each salt involving the acidic nitrogen and the oxygen of a C
O moiety of [1]−. These O···N distances were within the sum
of the van der Waals radii for oxygen and nitrogen [rvdw = 3.07
Å]16 and suggest some degree of ion-pairing {O(2)···N(1) =
2.713(3) Å, [PhNMe2H]-rac-mer-[1]; O(2)···N(1) = 2.771(2)
Å, [pyH]-rac-mer-[1]; O(2)···N(1) = 2.741(10) Å, [(−)-bru-
cineH]-Λ-mer-[1]; and O(6)···N(1) = 2.936(6) Å, [isoquino-
lineH]-rac-mer-[1]}.
[N(1)−H(1)], which is at the long end of the typical range
[range: 0.84(5)−1.083(2) Å].17 The pyridinium salt features a
slightly shorter N−H distance of 0.85(4) Å [N(1)−H(1)] that
is within the range found in related salts featuring [pyH]+
[range: 0.77(6)−0.88(2) Å].18 The analogous distance within
[isoquinolineH]-rac-mer-[1] is 0.94(7) Å [N(1)−H(1)],
which fits in the middle of the normal range [range:
0.848(8)−1.13(3) Å].16,19 Likewise, the N−H distance in
[(−)-brucineH]-Λ-mer-[1] [N(2)−H(1) = 0.88(9) Å] is also
in the typical range [range: 0.80(3)−0.96(5) Å].20
As mentioned earlier, the solution NMR spectroscopic
studies suggested that there was asymmetry within the
phosphorus(V) anion [1]−. In the solid state, this is
immediately apparent on examination of the P−O bond
lengths. In each case, the P−O bond to the carboxylate moiety
that is H-bonded to the ammonium cation is significantly
longer than the uncoordinated P−O bonds. For instance, the
H-bonded P(1)−O(1) bond length in [PhNMe2H]-rac-mer-
[1] [1.92(1) Å] is significantly elongated relative to non-H-
bonded P(1)−O(3) and P(1)−O(5) [1.778(1) and 1.774(1)
Å], respectively. For comparison, these P(V)−O bond lengths
are longer than those found in related hexacoordinate P(V)
anions {e.g., 1.72 Å in [P(1,2-O2C6H4)3]−, 1.71 Å in [P(1,2-
The ammonium salts show N−H distances within the cation
that are typical of those found in related salts. For instance, the
dimethylanilinium salt has an N−H distance of 1.04(3) Å
D
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O2C6Cl4)3]−, 1.69 Å in [P(C2O4)3]−}.3,13,21,22 Virtually
identical metrical parameters to those described above are
observed in the molecular structures of [pyH]-rac-mer-[1] and
[(−)-brucineH]-Λ-mer-[1]. Likewise, analogous observations
were made with the previously characterized [NEt2H2][1] and
[Et3NH][1] avgP(V)−O: 1.853(3) and 1.856(8) Å, respectively,
which displays considerable asymmetry within mer-[1]−
[rangeP(V)−O: 1.746(1)−1.91(1) Å].8
Scheme 2. Synthetic Route to K-mer-[1]
Placement of [1]− on IR Scale for WCAs. On the basis of
the above results which suggest significant coordinating
properties for mer-[1]−, we analyzed mer-[1]− in the context
of the simple infrared scale proposed by Reed and co-workers
to assess WCA properties.23 Since there is no absolute scale to
compare the WCA properties of specific anions,24 this analysis
provides a rough idea of the donor properties of mer-[1]−.
Specifically, we compared the N−H stretching frequencies of
tri(n-octyl)ammonium salts of various anions, including mer-
[1]−, in the solid state and in solution. Solution spectra were
recorded in carbon tetrachloride, where (n-C8H17)3N+−H···A−
contact ion pairs are typically formed to varying extents
dependent upon the anion. The results for mer-[1]− and for
common anions are presented in Table 2. The stretching
copy reveals one signal at −94.0 ppm, tentatively assigned to
[1]−. No change in the spectrum was observed after a few
1
hours. Additional characterization by H and 13C{1H} NMR
spectroscopy as well as mass spectrometry {ESI (negative
mode): m/z = 391.0, mer-[1]−} supported the formulation of
the product as K-rac-mer-[1].
Confirmation of this tentative assignment was obtained by
X-ray crystallographic analysis of crystals obtained from the
methanol-d4 solution. The molecular structure is shown in
Figure 5 and reveals that K-rac-mer-[1] is a coordination
polymer with K+ ions bridging the anion centers. There are
two crystallographically unique mer-[1]− anions and three
unique K+ cations. Interestingly, K(2) is bound by two short
and two long contacts to four different mer-[1]− anions
[K(2)···O(6) = 2.660(2) Å, K(2)···O(8) = 2.668(2) Å, K(2)···
O(12) = 2.926(2) Å, K(2)···O(2) = 3.019(2) Å] and by three
methanol molecules [K···Oavg = 2.762(5) Å]. In contrast, K(1)
and K(3) both sit on special positions and are bound by eight
oxygen atoms. In each case, there are two short and two long
K···O = C contacts [avg. = 2.727(3) and 3.038(3) Å], two K···
O−P contacts [avg. 3.028(3) Å] and two K···OMe contacts
[avg. = 2.787(5) Å]. The longer contacts involve binding of K+
by two chelating CO2 moieties of anion mer-[1]− (i.e., four K···
O interactions), which are related by inversion symmetry
around K+. For comparison, a survey of the Cambridge
Crystallographic Database revealed K···O = C contacts
[between 2.678(2) and 3.135(3) Å]26 and K···O−Me contacts
of methanol [2.750(2)−3.369(3) Å]27 Thus, the two short K···
OC contacts to anion mer-[1]− and the K···O−Me contacts
are at the short end of this range. The two long K···OC
contacts are at the long end of this range. The K···O−P
cation−anion contacts in K-rac-mer-[1] [avg. 3.028(3) Å] are
slightly shorter than those found in related compounds {e.g.,
Δ,Δ-K2(DMSO)6[P(1,2-O2C6H4)3]·C7H8 [avg. 2.855(3)
Å],28 {K(CH3CN)2[P(1,2-O2C6H4)3]}6 [avg. 2.883(2) Å],28
K[P(C14H20O2)3]·1.5 C6H6·2.5 CH3CN [avg. 2.783(5) Å],29
and K[P(H2O4)C6H4NO2]·CH3OH [avg. 2.798(3) Å]}.30
Analogous to the aforementioned ammonium salts, the
phosphorus(V) anion, mer-[1]−, displays significant asymme-
try. For instance, the P(1)−O(1) bond length [1.906(2) Å] is
significantly longer than the P(1)−O(3) and P(1)−O(5)
bonds [1.765(2) and 1.786(2) Å]. The situation is identical for
P(2) with one long bond [P(2)−O(11) = 1.902(3) Å] and
two short bonds [P(2)−O(7) = 1.785(2) Å, P(2)−O(9) =
1.767(2) Å]. It is peculiar that the elongated P−O bond in
mer-[1]− is not involved in binding to K+ in K-rac-mer-[1]. In
contrast, the elongated P−O moiety within the anions of
[PhNMe2H]-rac-mer-[1], [pyH]-rac-mer-[1] and [(−)-bruci-
neH]-Λ-mer-[1] is the atom involved in hydrogen bonding to
the cation. In all salts we have crystallographically charac-
terized, the P−C bond lengths in mer-[1]− do not show
significant differences.
Table 2. νN−H Frequencies for [(n-C8H17)3NH]+[anion]−
Salts in CCl4 and Solid State
νN−H [cm−1] in CCl4 νN−H [cm−1] solid
[anion]−
solution
or wax
ref
[B(C6F5)4]−
[PF6]−
3233
3241
3219
3156
23
23
23
25
23
3191
3133
3129
3086
3069
[BF4]−
[P(1,2-O2C6H4)3]−
[N(SO2CF3)2]−
[1]−
3064
this
work
[ClO4]−
[CF3SO3]−
[NO3]−
[Cl]−
3050
3031, 2801
2451
3098
3056, 2815
2571
23
23
23
23
2330
2452
frequency for [(n-C8H17)3 NH]-rac-mer-[1] in CCl4 (νN−H
=
3069 cm−1, 0.01 M) was close to those of classical WCAs such
as [ClO4]− (νN−H = 3050, 2801 cm−1) and [N(SO2CF3)2]−
(νN−H = 3086 cm−1). For comparison, very weakly donating
[B(C6F5)4]− and [CMeB11F11]− rank much higher (νN−H
=
3233 and 3219 cm−1, respectively), whereas the strongly
donating Cl− ranks much lower (νN−H = 2330 cm−1). The
results in the solid state also suggest that the WCA properties
of mer-[1]− are comparable to perchlorate and triflamide
according to this simple scale and are entirely consistent with
the moderate cation−anion interactions described for mer-[1]−
in solution and in the solid-state.
K+ and H+ Salts of [1]−. With several ammonium salts in
hand and a preliminary ranking of mer-[1]− on the WCA scale,
we explored the potential synthesis of alkali metal based salts
and stronger Brønsted acids featuring mer-[1]−. Treating a
THF solution of [NEt3H][1] with KH (1.5 equiv) resulted in
the immediate evolution of a gaseous species (presumably H2)
(Scheme 2). Over 2 h, a colorless precipitate was observed that
was separated and dried. The solid was dissolved in methanol-
d4, and the solution was analyzed by 31P{1H} NMR
spectroscopy. A singlet resonance was observed at −127.6
ppm, consistent with the preservation of the anion mer-[1]−.
K-mer-[1] dissolves in H2O. Analysis by 31P NMR spectros-
E
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Article
Figure 5. Extended structure showing the coordination polymer formed by K-rac-mer-[1]·3 CH3OH (K-Δ,Δ-mer-[1] is shown). Ellipsoids are
drawn at the 50% probability level. Hydrogen atoms are omitted for clarity. O(13), O(14), and O(15) are methanol solvate oxygen atoms. Oxygen
atoms O(2), O(5), O(6), O(7), O(8), and O(12) are associated with anion mer-[1]− related by inversion symmetry and translation around K+
with O(13)*, O(13), O(7)*, O(8)*, O(2)*, O(5)*, O(6)*, O(14)*, O(12)*, O(14), O(6), O(5), O(12)*, and O(2)*.
Finally, the potential synthesis of strong Brønsted acids of
mer-[1]− was explored by dissolving phosphorane 2 in weakly
basic solvents such as DMF. Heating the reaction mixture to
120 °C and monitoring the reaction progress by 31P{1H} NMR
spectroscopy suggested the quantitative formation of mer-[1]−
after 1 month. Namely, the signal assigned to phosphorane 2
(δ = −55.9) was replaced by two sharp singlet resonances at
−134.6 and −138.9 ppm (ca. 9:1 ratio) (see Figure 6). The
preliminary data, efforts are underway to isolate this postulated
Brønsted acid of mer-[1]− (Scheme 3).
Scheme 3. Proposed Route to H(DMF)n-mer-[1] (n ≥ 1)
SUMMARY
■
The synthesis, isolation, and characterization of a series of salts
incorporating the hexacoordinate phosphorus(V) anion mer-
[1]− has been reported. These compounds were conveniently
obtained by treating phosphorane P(C6H4CO2)2-
(C6H4COOH) with an N-containing base or KH. Significantly,
the crystal structures of [pyH]-rac-mer-[1], [isoquinolineH]-
rac-mer-[1], [(−)-brucineH]−Λ-mer-[1], [PhNMe2H]-rac-
mer-[1], and K-rac-mer-[1] were obtained. In the case of
enantiomerically pure (−)-brucine, the solution data suggests
two diastereomers in solution whereas the solid state structure
determined was for enantiomerically pure [(−)-brucineH]-Λ-
mer-[1]. The solid-state structure of K-rac-mer-[1] reveals a
coordination polymer with K+ ions bridging the anion centers.
A preliminary assessment of the basicity of the mer-[1]− was
conducted and revealed that the tri(n-octylammonium) salt
has a νN−H frequency similar to those of the salts of [ClO4]−
and [CF3SO3]−. Finally, preliminary evidence for the potential
synthesis of the Brønsted acid, H(DMF)n-mer-[1], has been
obtained. Future work will explore the potential isolation of
these novel protic species and the possible applications of the
mer-[1]− ion as a novel WCA for application in catalysis and
polymerization.
Figure 6. 31P{1H} NMR (162 MHz, 25 °C) spectra of (a) reaction
mixture of H(DMF)n-mer-[1] recorded after 2 days and (b) reaction
mixture of H(DMF)n-mer-[1] recorded after ca. 4 weeks. 2 is
phosphorane P(C6H4CO2)2(C6H4COOH).
chemical shift of the signals assigned to these anions is
consistent with that previously observed for anion mer-[1]−
(Table 1). The presence of two signals may suggest that both
mer-and fac-isomers are present or, similar to that postulated
for [(−)-brucineH]-mer-[1], strong ion-pairing is observed.
Although attempts to isolate or crystallize this product were
not successful, the major signal in the electrospray mass
spectrum (ESI−MS, negative mode) was consistent with the
formulation of [1]− (m/z = 390.9; calcd mass of mer-[1]− =
391.0). Moreover, the positive mode ESI-MS showed a signal
that may be consistent with the cation [H(DMF)]+ (m/z =
74.4; calcd for C3H8N1O1: m/z = 74.1). On the basis of these
EXPERIMENTAL SECTION
■
All experiments were performed using standard Schlenk or glovebox
techniques under nitrogen atmosphere. CH2Cl2 (Sigma-Aldrich) was
deoxygenated with nitrogen and dried by passing through a column
containing activated, basic alumina. Subsequently, the CH2Cl2 was
F
DOI: 10.1021/acs.inorgchem.8b02174
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Article
dried over CaH2, freshly distilled, and freeze−pump−thaw (×3)
degassed. Acetonitrile (Sigma-Aldrich) and DMF (Fisher Scientific)
were dried over calcium hydride, freshly distilled, and freeze−pump−
thaw (×3) degassed. Acetone (Fisher Scientific) was dried over
calcium sulfate and freshly distilled. For extended periods of storage
(1 day to 2 weeks), anhydrous solvents were stored over 3 Å
molecular sieves. THF (Fisher Scientific) was freshly distilled from
sodium/benzophenone ketyl immediately prior to use. Potassium
hydride (30 wt % dispersion in mineral oil) was purchased from
Sigma-Aldrich, washed with hexanes, and dried in vacuo prior to use.
(−)-Brucine (Sigma-Aldrich) was dried under vacuum at 40 °C prior
to use. Aniline (Sigma-Aldrich) and N,N′-dimethylaniline (Sigma-
Aldrich) were dried over CaH2 and freshly distilled under partial
vacuum at 40 °C. Pyridine (Fisher Scientific), trimethylamine (Fisher
Scientific), isoquinoline (Sigma-Aldrich), and N,N′-dimethylaniline
(Acros Organics) were distilled under partial vacuum at 30−50 °C.
Tri(n-octyl)amine, [N(n-C8H17)3] (Sigma-Aldrich), was degassed
with N2 gas prior to use. (C6H4CO2)2P(C6H4CO2H), 2,31 and
[HNEt3][P(C6H4CO2)3]8 were prepared following literature proce-
dure. Elemental analyses, mass spectrometry, and NMR spectra were
performed in the University of British Columbia Facilities. Low
resolution electrospray ionization mass spectra, ESI-LRMS, were
recorded on Bruker Esquire LC mass spectrometer. High-resolution
electrospray ionization mass spectra, ESI-HRMS, were recorded on
Micromass LCT time-of-flight (TOF) mass spectrometer. 1H,
13C{1H} and 31P{1H} NMR spectra were recorded on Bruker Avance
400 MHz spectrometers at ambient temperature unless noted. H3PO4
(85%) was used as external standard for 31P NMR spectra with δ =
0.0. 1H NMR and 13C{1H} NMR spectra were referenced to
deuterated solvents. Infrared spectra were recorded either in powder
form or in CCl4 solution {0.01 M for [(n-C8H17)3NH][1]} on a
PerkinElmer FT-IR Frontier spectrometer.
anhydrous aniline (2.00 mL, 2.05 g, 22.0 mmol), a colorless solution
was obtained, which was concentrated in vacuo to give a colorless oil.
The oily residue was washed with anhydrous dimethylformamide.
Yield = 0.28 g (includes N,N-dimethylformamide). A ∼5 mg sample
was prepared for elemental analysis by drying in vacuo for ca. 1 day at
40 °C.
31P{1H} NMR (162 MHz, (CD3)2SO, 25 °C): δ −133.6. 1H NMR
(400 MHz, (CD3)2SO, 25 °C): δ 7.84−7.22 (m, 11H, Ar−H), 7.17−
6.78 (m, 5H, PhNH3−Ar−H), 6.56 (br s, 3H, PhNH3), 6.10 (dd, JHH
= 7.4 Hz, 1H, Ar−H). 13C{1H} NMR (101 MHz, (CD3)2SO, 25 °C):
δ 168.6 (s, CO), 167.2 (s, CO), 167.1 (s, CO), 156.9 (s, Ar−
C), 154.0 (s, Ar−C), 145.0 (s, PhNH3, Ar−C), 142.3 (s, Ar−C),
133.6 (s, Ar−C), 133.4 (s, Ar−C), 132.7 (s, Ar−C), 132.4 (s, Ar−C),
131.6 (s, Ar−C), 131.4 (s, Ar−C), 129.9 (s, Ar−C), 129.5 (s, PhNH3,
Ar−C), 129.4 (d, JCP = 6.1 Hz, Ar−C), 129.1 (d, JCP = 3.3 Hz, Ar−C),
126.7 (s, Ar−C), 126.3 (d, JCP = 14.4 Hz, Ar−C), 125.0 (s, Ar−C),
124.8 (s, Ar−C), 121.2 (s, Ar−C), 119.7 (s, Ar−C), 119.2 (s, PhNH3,
Ar−C), 116.6 (s, PhNH3, Ar−C). IR (neat) ν: 3354 (vw), 3081 (vw),
3021 (vw), 2935 (vw), 2864 (vw), 1721 (m), 1754 (s), 1653 (s),
1594 (m), 1498 (w), 1483 (w), 1458 (s), 1397 (w), 1338 (m), 1292,
(s), 1276 (s), 1253 (m), 1242 (s), 1123 (s), 1108 (s), 1063 (s), 1023
(w), 967 (w), 855 (s), 816 (m), 745 (s), 729 (m), 698 (s), 687 (s)
cm−1. Elem. anal. calcd for C27H20N1O6P1·0.15 C3H7N1O1: C, 66.42;
H, 4.27; N, 3.27. Found: C, 66.57; H, 4.07; N, 3.51.
Synthesis of [pyH]-mer-[1]. To
a solution of P-
(C6H4CO2)2(C6H4COOH) (0.36 g, 0.92 mmol) in anhydrous
acetone (7 mL) was added pyridine (0.10 mL, 0.10 g, 1.26 mmol),
and the colorless reaction mixture was stirred for 2 h at ambient
temperature to afford a colorless precipitate. The precipitate was
filtered, washed with cold acetone (1.2 mL), and dried in vacuo. Yield
= 0.26 g, 60%. Single crystals suitable for X-ray crystallography were
isolated by cooling a saturated solution of the crude product in
CH2Cl2/hexane (1:1) to −30 °C.
Synthesis of [PhNMe2H]-mer-[1]. P(C6H4CO2)2(C6H4COOH)
(0.11 g, 0.28 mmol) was dissolved in anhydrous acetone (3 mL). To
the colorless solution was added anhydrous N,N′-dimethylaniline
(0.16 mL, 0.15 g, 1.23 mmol). The solution was stirred overnight and
concentrated in vacuo to afford a colorless precipitate. The crude
product was washed with a minimal amount of acetone and dried in
vacuo. Single crystals suitable for X-ray diffraction analysis were
obtained by cooling a concentrated solution of the crude product in
anhydrous acetone (−30 °C, ca. 2 weeks). Yield = 0.23 g (includes
acetone of crystallization).
31P{1H} NMR (162 MHz, (CD3)2CO, 25 °C): δ −126.8. 31P{1H}
1
NMR (162 MHz, CD2Cl2, 25 °C): δ −118.1. H NMR (400 MHz,
CD2Cl2, 25 °C): δ 16.37 (s, 1H, C5H5NH), 8.45 (d, JHH = 7.3 Hz,
2H, Ar−H), 8.11−8.02 (m, 5H, Ar−H), 7.73−7.69 (m, 4H, Ar−H),
7.54−7.48 (m, 3H, C5H5NH), 7.46−7.41(m, 1H, C5H5NH), 7.11 (d,
JHH = 6.4 Hz, 1H, C5H5NH), 7.06 (d, JHH = 7.3 Hz, 1H, Ar−H). 1H
NMR (400 MHz, (CD3)2CO, 25 °C): δ 15.18 (br s, 1H, N−H).
13C{1H} NMR (101 MHz CD2Cl2, 25 °C): δ 170.2 (s, CO), 170.1
(s, CO), 166.0 (s, CO), 146.2 (s, C5H5NH), 141.2 (s, Ar−C),
140.1 (s, Ar−C), 139.8 (s, C5H5NH), 138.1 (s, Ar−C), 134.9 (s, Ar−
C), 134.7 (s, Ar−C), 134.1 (s, Ar−C), 133.9 (s, Ar−C), 133.2 (d, JCP
= 2.9 Hz, Ar−C), 132.4 (d, JCP = 2.9 Hz, Ar−C), 132.1 (s, Ar−C),
31P{1H} NMR (162 MHz, (CD3)2CO, 25 °C): δ −107.7. 1H NMR
(400 MHz, (CD3)2CO, 25 °C): δ 9.31 (br s, 1H, N(CH3)2C6H5H),
8.14−8.04 (m, 5H, Ar−H), 7.89−7.81 (m, 4H, Ar−H), 7.63−7.55
(m, 2H, Ar−H), 7.34−7.29 (m, 1H, Ar−H), 7.28−7.24 (m, 2H,
N(CH3)2C6H5H), 6.95−6.91 (m, 2H, N(CH3)2C6H5H), 6.84−6.80
(tt, JHH = 7.3 Hz, 1H, N(CH3)2C6H5H), 2.97(s, 6H, N-
(CH3)2C6H5H). 13C{1H} NMR (101 MHz, (CD3)2CO, 25 °C): δ
168.2 (s, CO), 168.1 (s, CO), 165.2 (s, CO), 149.4 (s,
N(CH3)2C6H5H), 141.2 (s, Ar−C), 140.8 (s, Ar−C), 139.7 (s, Ar−
C), 138.8 (s, Ar−C), 135.1 (s, Ar−C), 134.9 (s, Ar−C), 134.3 (s, Ar−
C), 134.1 (s, Ar−C), 133.6 (d, JCP = 3.7 Hz, Ar−C), 132.5 (s, Ar−C),
132.3 (d, JCP = 5.1 Hz, Ar−C), 132.2 (s, Ar−C), 130.4 (s, Ar−C),
130.3 (s, Ar−C), 130.1 (d, JCP = 5.1 Hz, Ar−C), 129.3 (s, Ar−C),
129.1 (s, N(CH3)2C6H5H), 129.0 (s, Ar−C), 128.9 (s, Ar−C), 126.7
(s, N(CH3)2C6H5H), 126.5 (s, N(CH3)2C6H5H), 118.1 (s, N-
(CH3)2C6H5H), 114.0 (s, N(CH3)2C6H5H), 40.9 (s, N-
(CH3)2C6H5H). IR (neat) ν: 3405 (vw), 3055 (vw), 3035 (vw),
2966 (vw), 2670 (vw), 1700 (s), 1644 (m), 1633 (sh, m), 1592 (m),
1574 (m), 1511 (m), 1495 (m), 1452 (m), 1353 (m), 1299 (vw),
1277 (s), 1241 (s), 1195 (w), 1159 (w), 1125 (s), 1110 (s), 1061(s),
1024 (w), 994 (w), 904 (m), 852 (s), 769 (m), 748 (s), 728 (sm),
700 (s), 684 (s) cm−1. LRMS (ESI, positive mode) m/z = 122.3
[M]+. HRMS (ESI/TOF, negative mode) m/z = [M]− calcd for
C21H12O6P1 391.0372, found 391.0373.
131.9 (s, Ar−C), 131.2 (s, Ar−C), 131.1 (s, Ar−C), 130.1 (d, JCP
=
3.7 Hz, Ar−C), 129.3 (s, Ar−C), 129.2 (s, Ar−C), 129.0 (s, Ar−C),
128.9 (s, Ar−C), 126.8 (s, C5H5NH), 126.7 (s, C5H5NH), 125.0 (s,
C5H5NH). IR (neat) ν: 3187 (vw), 3132 (vw), 3101 (w), 3068 (vw),
2141 (vw), 1721 (m), 1699 (s), 1638 (m), 1613 (sh, m), 1593 (sh,
m), 1574 (w), 1548 (m), 1482 (m), 1455 (m), 1399 (vw), 1352 (m),
1309 (w), 1274 (s), 1239 (s), 1159 (m), 1127 (m), 1112 (s), 1065
(m), 1059 (m), 1025 (w), 1001 (w), 881 (vw), 854 (s), 819 (w), 759
(s), 730 (m), 669 (s), 661 (s) cm−1. Elem. anal. calcd for
C26H18NO6P1·0.2 CH2Cl2: C, 64.87; H, 3.81; N, 2.89. Found: C,
64.96; H, 4.06; N, 2.80.
Synthesis of [IsoquinolineH]-mer-[1]. To a stirred solution of
P(C6H4CO2)2(C6H4COOH) (0.21 g, 0.54 mmol) in anhydrous
acetone (9 mL) was added isoquinoline (0.11 mL, 0.12 g, 0.93 mmol)
via syringe. The reaction mixture was stirred for 2 days at ambient
temperature and the solvent was removed in vacuo. The residue was
dissolved in CH2Cl2/hexane (4 mL, 3 mL) and stored at −30 °C to
afford a colorless precipitate. The precipitate was filtered, washed with
CH2Cl2 (ca. 1 mL), and dried in vacuo. Yield = 0.19 g, 68%. The
aforementioned filtrate was cooled (−30 °C) to afford single crystals
suitable for X-ray crystallography.
Synthesis of [PhNH3]-mer-[1]. P(C6H4CO2)2(C6H4COOH)
(0.15 g, 0.38 mmol) was dissolved in anhydrous N,N-dimethylforma-
mide (4 mL). The white suspension was stirred at ambient
temperature for 40 min until fully dissolved. Upon addition of
31P{1H} NMR (162 MHz, (CD3)2CO, 25 °C): δ −104.7. 1H NMR
(400 MHz, CD2Cl2, 25 °C): δ 16.34 (s, 1H, NH), 9.19 (s, 1H,
isoquinoline−Ar−H), 8.29 (d, 1H, isoquinoline−Ar−H), 8.09−8.04
(m, 5H, isoquinoline−Ar−H), 8.02−7.41 (m, 11H, Ar−H), 6.99 (dd,
G
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JHH = 7.8 Hz, 1H, Ar−H). 13C{1H} NMR (101 MHz, CD2Cl2, 25
°C): δ 170.7 (s, CO), 170.6 (s, CO), 166.8 (s, CO), 148.9 (s,
isoquinolineH, Ar−C), 145.0 (s, Ar−C), 144.12 (s, Ar−C), 143.44 (s,
Ar−C), 142.1 (s, Ar−C), 137.4 (s, isoquinolineH, Ar−C), 136.1 (s,
isoquinolineH, Ar−C), 134.0 (s, Ar−C), 133.9 (d, JCP = 2.2 Hz, Ar−
C), 133.7 (s, Ar−C), 132.2 (d, JCP = 2.9 Hz, Ar−C), 132.0 (s, Ar−C),
(s), 1088 (w),1071 (m), 1065 (w), 1027 (m), 1012 (w), 986 (m),
964 (w), 938 (vw), 885 (vw), 849 (s), 817 (sh, w), 790 (w), 762 (sh,
w), 728 (s), 719 (m), 701 (s), 684 (m) cm−1. Elem. anal. calcd for
C45H41N2O10P·0.7 CH2Cl2·0.9 C3H6O: C, 63.71; H, 5.30; N, 3.06.
Found: C, 63.81;H, 5.40; N, 3.10.
Synthesis of [(n-C8H17)3NH]-mer-[1]. To a suspension of
P(C6H4CO2)2(C6H4COOH) (0.23 g, 0.58 mmol) in anhydrous
acetone (6 mL) was added degassed tri(n-octyl)amine, N(n-C8H17)3,
(0.50 mL, 0.40 g, 1.13 mmol). Within seconds, the reaction mixture
dissolved and was stirred overnight. Subsequently, the solvent was
removed in vacuo to afford pale yellow oil. The oily residue was
washed with n-hexane, filtered, and heated in vacuo at 140 °C for 4 h
to remove residual solvent. Yield = 0.31 g, 73%.
131.0 (s, Ar−C), 130.9 (s, Ar−C), 130.8 (s, Ar−C), 129.7 (d, JCP
=
3.7 Hz, Ar−C), 129.3 (s, isoquinolineH, Ar−C), 129.1 (s,
isoquinolineH, Ar−C), 128.3 (s, Ar−C), 128.1 (s, Ar−C), 127.9 (s,
Ar−C), 127.8 (s, Ar−C), 127.6 (s, Ar−C), 126.9 (s, isoquinolineH,
Ar−C), 126.8 (s, isoquinolineH, Ar−C), 126.6 (s, isoquinolineH, Ar−
C), 123.1 (s, isoquinolineH, Ar−C). IR (neat) ν: 3417 (vw), 3132
(vw), 3067 (w), 3009 (vw), 2998 (vw), 2930 (vw), 2764, 2112 (vw),
1975 (vw), 1709 (s), 1651 (s), 1616 (m), 1593 (w), 1575 (w), 1494
(w), 1452 (m), 1397 (w), 1341 (m), 1278 (s), 1242 (s), 1154 (m),
1128 (s), 1114 (s), 1065 (s), 1029 (vw), 976 (w), 951 (w), 853 (s),
824 (m), 802 (m), 746 (s), 731 (s), 717 (m), 700 (s), 696 (s), 685
(s) cm−1. HRMS (ESI/TOF, positive mode) m/z = [M]+ calcd for
C9H8N1 130.0657, found 130.0658. HRMS (ESI/TOF, negative
mode) m/z = [M]− calcd for C21H12O6P1 391.0372; found 391.0376.
Synthesis of [(−)-BrucineH]-mer-[1]. To a solution of P-
(C6H4CO2)2(C6H4COOH) (0.19 g, 0.48 mmol) in anhydrous
acetone (6.5 mL) was slowly added a solution of (−)-brucine (0.22
g, 0.56 mmol) in anhydrous acetone (4 mL). The reaction mixture
was stirred for 1 h to afford a colorless precipitate. The precipitate was
filtered, washed with anhydrous acetone, and dried in vacuo. Yield =
0.30 g, 79%. Cooling a concentrated solution of the crude product (80
mg) in CH2Cl2 (5 mL) afforded colorless crystals (−30 °C, ca. 5
days). Yield = 38 mg, 48%. A crystal was selected for X-ray
crystallographic analysis without drying. In addition, a concentrated
solution of the crude product was dissolved in DMSO-d6 solvent.
Single crystals suitable for X-ray diffraction analysis were obtained
upon standing for 20 min at ambient temperature.
31P{1H} NMR (162 MHz, (CD3)2CO, 25 °C): δ −128.9; δ
1
(CD2Cl2) − 125.6; H NMR (400 MHz, (CD3)2CO, 25 °C): δ 9.76
(br s, 1H, (CH3(CH2)5CH2CH2)3NH), 8.50−7.20 (m, 11H, Ar−H),
3
6.29 (dd, JHH = 7.3 Hz, 1H, Ar−H), 3.04 (t, JHH = 8.3 Hz, 6H,
( C H 3 ( C H 2 ) 5 C H 2 C H 2 ) 3 N H ) , 1 . 6 9 ( m , 6 H ,
( C H 3 ( C H 2 ) 5 C H 2 C H 2 ) 3 N H ) , 1 . 3 1 ( b r s , 3 0 H ,
1
(CH3(CH2)5CH2CH2)3NH), 0.89 (t, JHH = 6.9 Hz, 9H,
(CH3(CH2)5CH2CH2)3NH). 1H NMR (400 MHz, CD2Cl2, 25
°C): δ 10.40 (s, 1H, (CH3(CH2)5CH2CH2)3NH). 13C{1H} NMR
(101 MHz, CD3OD, 25 °C): δ 169.4 (s, CO), 169.3 (s, CO),
163.9 (s, CO), 156.5 (s, Ar−C), 154.3 (s, Ar−C), 135.8 (s, Ar−C),
135.7 (s, Ar−C), 134.9 (s, Ar−C), 134.8 (s, Ar−C), 132.3 (s, Ar−C),
132.1 (s, Ar−C), 131.7 (s, Ar−C), 131.5 (s, Ar−C), 130.7 (d, JCP
=
3.7 Hz, Ar−C), 130.6 (s, Ar−C), 130.4 (s, Ar−C), 128.5 (d, JCP = 4.4
Hz, Ar−C), 127.2 (s, Ar−C), 127.0 (s, Ar−C), 124.8 (d, JCP = 2.2 Hz,
Ar−C), 124.7 (s, Ar−C), 52.5 (s, (CH3(CH2)5CH2CH2)3NH), 31.6
( s , ( C H 3 ( C H 2 ) 5 C H 2 C H 2 ) 3 N H ) , 2 9 . 0 ( s ,
(CH3(CH2)5CH2CH2)3NH), 28.9 (s, (CH3(CH2)5CH2CH2)3NH),
2 6 . 4 ( s , ( C H 3 ( C H 2 ) 5 C H 2 C H 2 ) 3 N H ) , 2 3 . 3 ( s ,
(CH3(CH2)5CH2CH2)3NH), 22.4 (s, (CH3(CH2)5CH2CH2)3NH),
13.5 (s, (CH3(CH2)5CH2CH2)3NH). IR (CCl4) ν: 3069 (vw), 2955
(m), 2927 (m), 2879 (w), 2857 (m), 1709 (s), 1653 (m), 1596 (m),
1579 (w), 1454 (m), 1378 (vw), 1280 (s), 1242 (s), 1127 (s),
1112(m), 1071 (m), 1061(s), 1023 (w), 984 (m), 856 (s), 809 (w),
784 (s), 757 (s), 731 (sh, m), 700(m), 686 (w). IR (neat) ν: 3064
(vw), 3021 (vw), 2954 (m), 2925 (m), 2870 (w), 2856 (m), 1707
(s), 1653 (m), 1595 (m), 1579 (w), 1453 (m), 1378 (vw), 1277 (s),
1240 (s), 1125 (s), 1113 (s), 1071 (m), 1061(s), 1022 (w), 984 (m),
855 (s), 809 (w), 784 (s), 757 (s), 731 (sh, m), 699 (s), 686 (m)
cm−1.
Synthesis of K-mer-[1]. To a colorless solution of [NEt3H][P-
(C6H4CO2)3] (0.17 g, 0.34 mmol) in anhydrous THF (12 mL) was
slowly added a suspension of potassium hydride (0.02g, 0.52 mmol)
in anhydrous THF (6 mL) at ambient temperature. The immediate
evolution of gas (i.e., H2) was observed and the reaction mixture was
stirred for 2 h at ambient temperature to afford a colorless precipitate.
The precipitate was filtered and washed with minimal amount of
anhydrous THF and dried in vacuo. Yield = 0.12 g, 82%. Single
crystals suitable for X-ray diffraction were obtained by cooling a
concentrated solution of the crude product (44 mg) in MeOH-d4 (1.5
mL) (−30 °C, ca. 9 days).
31P{1H} NMR (162 MHz, (CD3)2SO, 25 °C): δ −135.2; δ
1
(CD2Cl2) −114.3, −114.6. H NMR (300 MHz, CD2Cl2, 25 °C): δ
12.63 (s, 1H, NH), 8.01−7.94 (m, 3H, Ar−H), 7.79 (s, 1H,
(−)-brucinium, Ar−H), 7.75−7.35 (m, 8H, Ar−H), 6.77 (s, 1H,
(−)-brucinium, Ar−H), 6.45 (dd, JHH = 7.4 Hz, 1H, Ar−H), 6.18 (t,
JHH = 6.2 Hz, 1H, (−)-brucinium, CH), 4.35−4.32 (m, 1H,
(−)-brucinium, O−CH), 4.27−4.21 (m, 2H, (−)-brucinium,
OCH2), 4.10 (dd, JHH = 8.8 Hz, 1H, (−)-brucinium, CH), 3.93 (s,
1H, (−)-brucinium, −N−CH−C−), 3.91 (s, 3H, (−)-brucinium,
OCH3), 3.88 (s, 3H, (−)-brucinium, OCH3), 3.82 (d, JHH = 13.7 Hz,
1H, (−)-brucinium, −N−CH2−), 3.63−3.59 (m, 1H, brucinium,
CH2), 3.14 (s, 1H, (−)-brucinium, CH), 3.09 (t, JHH = 8.8 Hz, 1H,
(−)-brucinium, CH2), 3.02−2.94 (m, 1H, (−)-brucinium, CH), 2.87
(d, JHH = 14.7 Hz, 1H, (−)-brucinium, CH), 2.67 (dd, JHH = 3.9 Hz,
1H, (−)-brucinium, CH), 2.00−1.86 (m, 3H, (−)-brucinium, 3 ×
CH), 1.47 (d, JHH = 14.7 Hz, 1H, (−)-brucinium, CH), 1.33 (dt, JHH
= 10.8 Hz, 1H, (−)-brucinium, CH). 1H NMR (400 MHz,
(CD3)2SO, 25 °C): δ 10.60 (br s, 1H, N−H). 13C{1H} NMR (101
MHz, CD2Cl2, 25 °C): δ 172.5 (s, (−)-brucinium, CO), 172.2 (s,
CO), 168.3 (s, CO), 168.1 (s, CO), 150.5 (s, Ar−C), 148.9 (s,
Ar−C), 146.9 (s, Ar−C), 136.0 (s, Ar−C), 135.5 (s, Ar−C), 133.4 (s,
Ar−C), 133.2 (s, Ar−C), 133.0 (s, (−)-brucinium, Ar−C), 132.8 (s,
(−)-brucinium, Ar−C), 132.5 (s, Ar−C), 132.3 (s, Ar−C), 131.7 (s,
Ar−C), 131.5 (s, Ar−C), 129.9 (s, (−)-brucinium), 129.1 (s,
(−)-brucinium), 127.2 (s, (−)-brucinium), 127.0 (s, Ar−C), 126.5
(s, Ar−C), 126.3 (s, Ar−C), 125.9 (s, Ar−C), 125.7 (s, Ar−C), 125.1
(s, Ar−C), 124.9 (s, Ar−C), 118.8 (s, (−)-brucinium), 105.6 (s,
(−)-brucinium), 101.0 (s, (−)-brucinium), 77.3 (s, (−)-brucinium),
64.0 (s, (−)-brucinium), 61.2 (s, (−)-brucinium), 59.2 (s,
(−)-brucinium), 56.6 (s, (−)-brucinium), 56.1 (s, (−)-brucinium),
52.1 (s, (−)-brucinium), 52.0 (s, (−)-brucinium), 50.2 (s,
(−)-brucinium), 46.9 (s, (−)-brucinium), 42.0 (s, (−)-brucinium),
40.5 (s, (−)-brucinium), 30.4 (s, (−)-brucinium), 24.7(s, (−)-bru-
cinium). IR (neat) ν: 3494 (vw), 3061 (vw), 3056 (vw), 2997 (vw),
2959 (vw), 2872 (vw), 2829 (vw), 1708 (sh, m), 1668 (s), 1648 (sh,
s), 1594 (m), 1577 (w), 1502 (m), 1451 (m), 1414 (m), 1362 (w),
1331 (w), 1283 (s), 1245 (m), 1220 (m), 1198 (m), 1176 (w), 1111
31P{1H} NMR (162 MHz, CD3OD, 25 °C): δ −127.6, δ
((CD3)2CO) −136.4. 1H NMR (400 MHz, CD3OD, 25 °C): δ
7.94−7.28 (m, 11H, Ar−H), 6.26 (dd, JHH = 7.6 Hz, 1H, Ar−H).
13C{1H} NMR (101 MHz, CD3OD, 25 °C): δ 170.7 (s, CO),
169.9 (s, CO), 169.8 (s, CO), 155.4 (s, Ar−C), 154.3 (s, Ar−C),
153.2 (s, Ar−C), 133.3 (s, Ar−C), 133.1 (s, Ar−C), 132.3 (s, Ar−C),
132.1 (d, JCP = 2.9 Hz, Ar−C), 130.2 (s, Ar−C), 130.1 (s, Ar−C),
129.0 (d, JCP = 2.9 Hz, Ar−C), 128.9 (s, Ar−C), 128.7 (d, JCP = 3.7
Hz, Ar−C), 128.6 (s, Ar−C), 126.0 (s, Ar−C), 125.9 (s, Ar−C),
125.8 (s, Ar−C), 124.7 (s, Ar−C), 124.5 (s, Ar−C). IR (neat) ν: 2962
(vw), 1689 (s), 1632 (sh, w), 1595 (m), 1580 (w), 1453 (m), 1391
(w), 1332 (w), 1282 (s), 1244 (s), 1120 (s), 1071 (m), 1062 (m),
1025 (w), 855 (s), 813 (w), 745 (s), 729 (s), 718 (w), 697 (s), 684
(m) cm−1; LRMS (ESI, negative mode) m/z = 391.0 [M]−.
Attempted Synthesis of H(DMF)n-mer-[1]. To P-
(C6H4CO2)2(C6H4COOH) (0.20 g, 0.57 mmol) was added
H
DOI: 10.1021/acs.inorgchem.8b02174
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
anhydrous N,N-dimethylformamide (5 mL). The initially cloudy
solution cleared within a few seconds and was subsequently stirred for
ca. 16 h. Despite heating to 120 °C over ca. 4 weeks, no additional
changes were observed in the 31P{1H} NMR spectrum of the reaction
mixture. An aliquot was removed from the reaction mixture for mass
spectrometric analysis.
ORCID
Derek P. Gates: 0000-0002-0025-0486
Notes
The authors declare no competing financial interest.
31P{1H} NMR (162 MHz, N(CH3)2COH, 25 °C): δ −55.9, −
34.6, −138.9. LRMS (ESI, negative mode) m/z = 391.0 [M]−.
X-ray Crystallography. All single crystals were immersed in oil
and mounted on a glass fiber. Data were collected on a Bruker X8
APEX II diffractometer with graphite-monochromated Mo Kα
radiation, integrated using the Bruker SAINT software package,32
and corrected for absorption effect using SADABS.33 All structures
were solved by direct methods and subsequent Fourier difference
techniques. All non-hydrogen atoms were refined anisotropically. All
hydrogen atoms were placed in calculated positions and were not
refined with the exception of N−H hydrogens, which were located in
a difference map and refined isotropically. All data sets were corrected
for Lorentz and polarization effects. All refinements were performed
using the SHELXT-201534 via the Olex2 interface.35
[PhNMe2H]-rac-mer-[1] crystallizes with one molecule of solvent
acetone in the asymmetric unit. [pyH]-rac-mer-[1] was solved using
nonoverlapped data from a major twin component. Subsequent
refinements were carried out using a data set containing complete
data from component one and any overlaps from component two.
The material crystallizes with one-half-molecule of acetone in the
asymmetric unit. Additionally, one coordinated benzoic acid ligand is
disordered and is modeled in two orientations. The compound
[isoquinolineH]-rac-mer-[1] crystallizes as a twin, with a ∼9:1 ratio
between the major and minor twin components. [(−)-BrucineH]-Λ-
mer-[1] crystallizes with two molecules of solvent methylene chloride
in the asymmetric unit. One of these solvent molecules is disordered
and was modeled in three orientations, such that their combined site
occupancies summed to one. K-rac-mer-[1] crystallizes with three
MeOH molecules coordinated to the potassium cation. Additionally,
the material crystallizes with disordered free MeOH in the lattice. The
disorder could not be reasonably modeled; therefore, the PLATON/
SQUEEZE36 program was used to generate a data set free of
disordered solvent. O−H hydrogen atoms were located in difference
maps and refined isotropically. All other hydrogen atoms were placed
in calculated positions. Additional crystal data and details of data
collection are given in the Supporting Information. All crystallo-
graphic data has been deposited with the Cambridge Structural
Database: CCDC−1857626 [isoquinolineH]-rac-mer-[1], CCDC−
1857627 [PhNMe2H]-rac-mer-[1], CCDC−1857628 [pyH]-rac-mer-
[1], CCDC−1857629 K-rac-mer-[1], and CCDC−1857630
[(−)-brucineH]-rac-mer-[1].
ACKNOWLEDGMENTS
■
We are grateful to the Natural Sciences and Engineering
Counsel (NSERC) of Canada for financial support of this work
in the form of Discovery, Collaborative Research & Develop-
ment, and Research Tools grants to D.P.G.
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* Supporting Information
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NMR spectra, X-ray crystallographic data, tabulated
metrical parameters (PDF)
Accession Codes
CCDC 1857626−1857630 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: dgates@chem.ubc.ca.
■
organischer Derivate des funf-und sechsbindigen Phosphors, I. Das
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Tris-biphenylen-phosphat-Anion und Bis-biphenylen-biphenylyl-(2)-
I
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