2-Aminophenolate ligands for phosphorus(v): a lithium salt featuring the chiral [P(OC6H4NR)3]? anion

Article abstract of DOI:10.1039/c8dt02522c

Phosphoranes P(OC₆H₄NR)₂(OC₆H₄NHR) [R = Me (2a), Ph (2b), C₆F₅ (2c)] were synthesized by treating PCl₅ with the respective 2-aminophenol derivative (1a-c, 3.1 equiv.).

Full text of DOI:10.1039/c8dt02522c

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2-Aminophenolate ligands for phosphorus(V): a
lithium salt featuring the chiral [P(OC6H4NR)3]−
anion†
Cite this: DOI: 10.1039/c8dt02522c
Chuantian Zhan,
Zeyu Han, Brian O. Patrick and Derek P. Gates
*
Phosphoranes P(OC6H4NR)2(OC6H4NHR) [R = Me (2a), Ph (2b), C6F5 (2c)] were synthesized by treating
PCl5 with the respective 2-aminophenol derivative (1a–c, 3.1 equiv.). In one instance, an intermediate
species, P(OC6H4NR)2Cl [R = Me (3a)], was isolated and structurally characterized. Deprotonation of the
amine moieties (–NH̲R) in phosphoranes 2a and 2b with a strong alkali–metal base (e.g. n-BuLi) in the
presence of a strong-donor solvent (e.g. THF) afforded salts composed of the hexacoordinate P(V)-anions
[P(OC6H4NR)3]− (R = Me, [4a]−; Ph, [4b]−). Employing precursor 2a, the salt Li(THF)3fac-[4a]− was isolated.
The X-ray crystal of each enantiomer of [4a]− was determined and, to our knowledge, represents the
first structurally characterized example of a salt containing a hexacoordinate P(V)N3O3 anion featuring
P(V)–N bonds.
Received 21st June 2018,
Accepted 19th July 2018
DOI: 10.1039/c8dt02522c
rsc.li/dalton
phosphate [BH]−, tris(tetrachlorobenzenediolato)phosphate
(TRISPHAT) [BCl]− and related compounds are of considerable
Introduction
Hypervalent phosphorus(V) chemistry, involving the develop- interest.7,8
ment of novel six-coordinate compounds, is an area of wide-
Our group has been interested in the development of novel
spread fundamental interest.1 Despite the fact that both cat- hexacoordinate anions of phosphorus(V) that can serve as
ionic2 and neutral derivatives3 are possible for such species, by weakly coordinating anions,9,10 particularly in the area of cat-
far the most prevalent are the anionic derivatives of the form ionic polymerization.11–13 In this context, we have embarked
[PX6]− (anion [A]− in Chart 1) typified by hexafluorophosphate, upon an investigation of P(V)-anions of type [E]−, containing
[PF6]−. Historically, [PF6]− was widely touted as a “non-coordi- an N-containing ligand. Although bidentate C,O- and C,C-
nating” anion and has been primarily used within the scope of donor ligands for P(V) (e.g. [C]− and [D]−, respectively) are
this concept.4 Over the past two decades, [PF6]−, has formally known, anionic phosphates featuring nitrogen donors have
evolved to larger and more stable organic derivatives (see remained largely unexplored. Although a few examples of
Chart 1).1c,e,5,6 In particular, the family of anionic phosphates neutral hexacoordinate phosphorus(V) compounds are
bearing dioxo catechol-scaffolds such as tris(benzenediolato) known,3c,i–k the recently reported anion [F]− (see Chart 2), fea-
turing a chiral tridentate N,N,O-ligand, represents the only
structurally characterized P(V)-anion bearing N-substituents.14
We hypothesized that simple amido-donors, such as those
derived from 2-aminophenol, may provide access to P(V)-based
anions of type [E]−. Notably, the 2-aminophenol ligand
has been employed as a ligand-scaffold for P(V) to access
neutral transition-metalled phosphoranes (e.g. G, G′ and G″)15
and organophosphoranes (e.g. H,
I
and I′).16 However,
these routes employed unconventional precursors such as
hexachlorocyclotriphosphazene and phosphine oxides or
sulphides.
Chart 1 Selected examples of hexacoordinate P(V)-anions.
Herein, we report a convenient synthetic methodology start-
ing with PCl5 to access neutral phosphoranes and hexacoordi-
nate P(V)-anions featuring 2-aminophenol ligands. To our
knowledge, this is the first fully characterized salt featuring a
type [E]− anion.
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, British Columbia, Canada, V6T 1Z1. E-mail: dgates@chem.ubc.ca
†Electronic supplementary information (ESI) available. CCDC 1563689–1563692,
1849283 and 1847159. For ESI and crystallographic data in CIF or other elec-
tronic format see DOI: 10.1039/c8dt02522c
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Scheme 1 Synthesis of five-coordinate P(V)N2O3 phosphoranes from
the reaction of PCl5 with 2-aminophenol ligands.
Chart 2 Example of
a hexacoordinate P(V)-anion containing an
N-donor ligand (above line). Selected examples of known phosphoranes
featuring the 2-aminophenol ligand (below line).
Fig. 1 31P{1H} NMR spectra (121.5 MHz, toluene, 298 K) of the crude
reaction mixtures of PCl5 with: (a) 1a; (b) 1b; (b) 1c before (crude) and
after the optimization (optimized). Note: The scale corresponds to the
crude spectra in each case with the optimized spectra being offset
slightly for clarity.
Results and discussion
Five-coordinate P(V)N2O3 phosphoranes
Due to their ease of synthesis and purification, three known
amino-substituted 2-aminophenol derivatives (1a–c)17–20 were
selected as ligands for this study. In particular, methyl (N–Me,
1a), phenyl (N–Ph, 1b) and perfluorophenyl (N–C6F5, 1c) sub-
stituents were employed in an effort to shed light on the steric
and electronic factors influencing the stability of the resultant
hypervalent phosphorus(V) derivatives.
It has been shown that catechol reacts directly with PCl5 to
quantitatively afford penta-substituted O,O-containing phos-
phoranes.11,12,21,22 Following a similar protocol, we treated
PCl5 with the appropriate 2-aminophenol derivative (1a–c,
3 equiv.) in toluene solution to afford the desired phosphoranes
(2a–c, Scheme 1). In each case, the evolution of a gas, presum-
ably HCl, was observed immediately upon mixing. This was
accompanied by a gradual color change of the solution from
colorless to pale yellow. Analysis of each reaction mixture by
31P NMR spectroscopy revealed that the signal assigned to
PCl5 was not present (δ = −80.1). In its place were two new
upfield shifted resonances (see Fig. 1). For each pair of signals,
the higher-field resonance was assigned to the pentacoordi-
nated compound [δ = −48.4 ppm (2a), −53.9 ppm (2b),
−55.1 ppm (2c)] by comparison to known phosphorane I
(δ = −46.3 1.0).16a Interestingly, each of the lower-field reso-
nances showed an almost identical difference to the corres-
ponding phosphorane signal (2a–c, Δδ = 14.0). In one case, the
slow evaporation of the reaction solution derived from 1a
(2 equiv.) and PCl5 permitted the isolation of a crystalline solid
which was analyzed by X-ray diffraction. The molecular struc-
ture of intermediate chlorophosphorane 3a is shown in Fig. 2.
Fig. 2 Molecular structure of intermediate 3a (thermal ellipsoids are
displayed at 50% probability level). Hydrogen atoms are omitted for
clarity. Note: this structure has a contribution from a minor component
(ca. 7%) where the C3 has a chlorine-rather than hydrogen-substituent.
We note that the molecular structure reveals a minor com-
ponent with a chlorine-substituent at C3. Presumably, this
arises from electrophilic aromatic substitution of the arylene
ligand (before or after binding to P) with Cl2 which may be
formed from PCl5 or a related chlorinated phosphorus(V)
species. The 31P NMR spectrum of a toluene solution of the
crystals of 3a showed a predominant singlet resonance at
−34.2 ppm although smaller resonances were also observed
(see Fig. S2†). By extension, the signals at −39.9 ppm and
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Fig. 3 Molecular structures of phosphoranes 2a (a), 2b (b) and 2c (c) (thermal ellipsoids are displayed at 50% probability level). Hydrogen atoms and
the solvent of recrystallization (CH2Cl2) are omitted for clarity.
−40.7 ppm were assigned to chlorophosphoranes 3b and 3c, nitrogen atmosphere (1a: PCl5 mole ratio = 3.1 : 1). For 2b, a
respectively.
higher stoichiometric ratio of 1b to PCl5 (4 : 1) afforded the
The reaction conditions were varied in an effort to optimize optimal isolated yield (67%). For 2c, the optimized conditions
the procedure towards 2a–c and minimize the formation of involved refluxing a toluene solution of 1c and PCl5 (4 : 1 ratio)
3a–c. Specifically, the solvent (toluene, CH2Cl2, EtOAc and followed by the addition of Et3N (13.6 equiv.) to give the
MeCN), temperature (25 °C to 110 °C), and stoichiometric ratio product in 51% isolated yield. Phosphoranes 2a–c were isolated
(i.e. the molar ratio of 2-aminophenol derivatives 1a–c to PCl5 after passing the reaction mixtures through a silica plug under
from 1 : 1 to 4 : 1) were varied. The order of addition was also a nitrogen atmosphere. Subsequently, colorless crystals suitable
varied (i.e. dropwise addition of solutions of 1a–c into a solu- for X-ray diffraction analysis were isolated in each case by slow
tion of PCl5 and vice versa). The success of each reaction was diffusion of dry n-pentane into a concentrated CH2Cl2 solution.
assessed by 31P NMR spectroscopic analysis of each reaction
Phosphoranes 2a–c and intermediate 3a were characterized
mixture. Although there were always unassigned signals using multinuclear NMR spectroscopy (1H, 13C, 19F and 31P),
present, these optimization experiments resulted in the elim- mass spectrometry, elemental micro-analysis and X-ray crystal-
ination of the signal assigned to 3a–c in favour of signals lography. The molecular structures of 2a–c and 3a are shown
assigned to the desired phosphoranes 2a–c (see Fig. 3). The in Fig. 2 and 3. The selected metrical parameters and related
optimized conditions involved refluxing a toluene solution of X-ray crystallographic data are given in Tables 1 and 2,
2-aminophenol derivatives 1a–c with PCl5 for ca. 12 h under a respectively.
Table 1 Selected metrical parameters for phosphoranes 2a–c, 3a and Li(THF)3fac-[4a]
2a
2b
2c·CH2Cl2
3a
Li(THF)3 Λ-fac-[4a]
Li(THF)3 Δ-fac-[4a]
Bond lengths (Å)
P–O(1)
P–O(2)
P–O(3)
P–N(1)
P–N(2)
P–N(3)
1.6897(12)
1.6161(12)
1.6899(12)
1.6863(14)
1.6947(11)
1.6164(11)
1.7022(11)
1.6895(13)
1.6821(17)
1.6176(18)
1.6856(17)
1.693(2)
1.6893(12)
1.6842(11)
1.7713(15)
1.7595(15)
1.7631(16)
1.7709(19)
1.7695(18)
1.7710(19)
1.766(2)
1.762(2)
1.762(2)
1.772(2)
1.767(2)
1.770(3)
1.6805(13)
1.6803(14)
1.6851(13)
1.6845(13)
1.7009(19)
Bond angles (°)
∠O(1)–P–N(1)
∠O(2)–P–N(2)
∠O(3)–P–N(3)
89.67(6)
88.81(6)
89.51(9)
89.65(6)
90.60(6)
87.49(8)
87.95(8)
87.54(8)
87.44(10)
87.79(11)
87.50(11)
89.41(6)
89.13(6)
89.19(9)
a
∠Oap–P–Oap
179.60(6)
125.75(7)
117.09(6)
359.93(19)
176.61(6)
129.10(7)
115.43(6)
359.95(19)
177.44(10)
127.50(11)
116.22(10)
359.94(31)
178.63(6)
131.19(7)
114.41(5)
360.00(17)
b
∠Neq–P–Neq
c
∠Neq–P–Oeq or ∠Neq–P–Cleq
∑(∠X–P–Y)eq
a ap = apical. b eq = equatorial. c Average angles.
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In the solid state, phosphoranes 2a–c and intermediate 3a
displayed a similar trigonal bipyramidal geometry (Fig. 2
and 3). In each case, an identical apicophilicity was observed
with the oxygen atoms occupying the axial positions and all
endocyclic ∠O–P–N angles being nearly 90°. Notably, the bond
angle between the two axial P–O bonds (∠Oap–P–Oap) showed
only minor deviation from linearity [0.60(6)° (2a), 3.39(6)° (2b),
2.56(10)° (2c), 1.37(6)° (3a)]. The central phosphorus atom and
the three equatorial substituents are effectively co-planar in all
cases and the sum of the angles about phosphorus is close to
360° [∑(∠X–P–Y) = 359.93(19)° (2a), 359.95(19)° (2b), 359.94
(31)° (2c), 360.00(17)° (3a)]. Within the equatorial plane, the
∠N–P–N bond angles were measured to be 125.75(7)° (2a),
129.10(7)° (2b), 127.50(11)° (2c) and 131.19(7)° (3a), while the
∠N–P–O and ∠N–P–Cl bond angles are more acute [range:
112.71(6)° to 118.64(6)°]. These observations are in accord
with Bent’s rule23 which would predict a higher degree of
p-character for the more electronegative P–OR or P–Cl bond
compared to the P–NR2 bond (therefore, the average bond
angle ∠N–P–Cl < ∠N–P–OR < ∠N–P–NR2, see Table 1).
The bond lengths within the aforementioned molecules are
unremarkable and will not be discussed further.
The 1H NMR spectra of 2a–c and 3a in CDCl3 are consistent
with the structures determined in the solid state. Of particular
interest is the chemical shift of the amine proton (–NH̲R), as it
offers a rough indication of the acidity of 2a–c in solution and
the possibility of deprotonation to afford hexacoordinate
anionic phosphates. In particular, the amine –NH̲R signal in
phosphoranes 2b (δ = 5.99) and 2c (δ = 5.59), bearing aromatic
substituents, were substantially deshielded when compared to
that of 2a (δ = 3.79). The 31P{1H} NMR spectra of 2a–c and 3a
in CDCl3 revealed similarly that the aryl substituted phosphor-
anes 2b (δ = −53.8) and 2c (δ = −55.5) have similar chemical
environments whilst the methyl-substituted 2a (δ = −48.4) and
3a (δ = −34.2) are significantly different. We note that these
N2O3-substituted phosphoranes display significantly higher-
field shifts than their O5-substituted counterparts (J, δ =
−27.3;12 K, δ = −29;21 L, δ = −9;21 see Chart 3). It is plausible
that these higher-field 31P shifts are a consequence of the
more strongly donating N-donor ligands thereby reducing the
electrophilicity at phosphorus. Further support for this
hypothesis may be gleaned from the molecular structure of 3a
which has a longer P–Cl bond [2.1103(6) Å] in comparison to
the one found in its catechol analogue L (2.031 Å) (Chart 3).24
1
Examination of the H NMR spectra of 2a and 3a in CDCl3,
along with the 1H{31P} NMR spectra, permitted the determi-
Chart 3 Catechol-based analogues of 2a–c and 3a that have been
reported in the literature.
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nation of the 1H–31P coupling constant between the phos-
phorus and the six adjacent methyl protons (P̲–NCH3̲
; 3JHP = 10
Hz for 2a and 3a). There are 10 theoretical isomers for a phos-
phorane bearing asymmetric bidentate ligands. Therefore,
variable temperature NMR experiments on solutions of 2a and
2c in either C7D8 or CD2Cl2 were performed over a range of
temperatures from −66 to 89 °C (actual temperatures) in an
effort to identify any fluxional processes such as pseudorota-
tion. No significant change in either the 31P, 31P{1H}, H or H
{31P} NMR spectra was observed suggesting that isomerization
was not prevalent under these conditions. A similar obser-
vation was made for phosphorane I (Chart 2) where a single
isomer was also observed.16b
1
1
Fig. 4 31P{1H} NMR spectra (121.5 MHz, 298 K): (a) the reaction mixture
from treating phosphorane 2a in toluene with n-BuLi (1 equiv.) in
n-hexane in the presence of THF; (b) the reaction mixture from treating
phosphorane 2a in toluene with KH (2.5 equiv.) in MeCN.
Six-coordinate P(V)N3O3 anions
The O5-substituted phosphoranes J and K can be readily depro-
tonated to afford anions [BCl]− and [BH]−.8f,g,r,11–13,21,22
Therefore, we postulated that the deprotonation of the neutral
phosphoranes 2a–c would afford the corresponding hexacoor-
dinate N3O3-ligated phosphorus(V) anion. In initial efforts, we
observed that treating 2a–c with either a basic donor solvent
(Et2O, DMSO, DMF) or a mild base (NEt3) resulted in
unchanged 31P or 1H NMR spectra.
absence or presence of typical ligands for Li+ ions (e.g.
12-crown-4, Et3N and TMEDA). The treatment of an aceto-
nitrile solution of 2b with KH (ca. 2.5 equiv.) afforded the best
results. In this case, the 31P{1H} NMR spectrum of an aliquot
removed from the reaction mixture showed signals at −105.4
and −107.3 ppm [see Fig. 5(a)]. For comparison, the reaction
of 2a with KH under similar conditions also showed two
signals in its 31P{1H} NMR spectrum [δ = −97.6, −103.3, see
Fig. 4(b)]. Alternatively, treatment of a toluene solution of 2b
with a solution of LiNH2 (2.5 equiv.) in DMSO-d6 resulted in a
single product as suggested by the presence of a single reso-
nance in the 31P{1H} NMR spectrum [δ = −111.6, see Fig. 5(b)].
Based on the high-field chemical shifts observed, we specu-
lated that the potassium and lithium salts of [4b]− were
formed successfully. Despite multiple efforts to obtain crystals
suitable for X-ray diffraction, the products, M[4b] (M = Li, K),
could only be isolated as powders.
Our strategy then shifted towards employing stronger bases
that might deprotonate the unbound Ar–NH̲R moiety
(Scheme 2). Treating phosphorane 2a with n-BuLi (1 equiv.) in
a mixture of toluene and THF (ca. 4 : 1 vol./vol.) resulted in an
immediate color change from colorless to pale yellow. After ca.
12 h, 31P{1H} NMR spectroscopic analysis of an aliquot
removed from the reaction mixture revealed that the signal
assigned to phosphorane 2a (δ = −48.4) had been consumed
and replaced by a new resonance at −97.6 ppm [see Fig. 4(a)].
The observation of such a high field chemical shift is charac-
teristic of a hexacoordinate phosphorus(V) center (cf. Li[BH],
δP = −81.7; Li[P(1,2-O2C6F4)3], δP = −71.3; etc.).8g,k,o,r,25 After
removing the volatiles in vacuo, the crude reaction product was
dissolved in a minimum of THF. The slow evaporation of the
solvent afforded colorless crystals of Li(THF)3fac-[4a] that were
analyzed by X-ray diffraction (see Fig. 6).
The analogous reaction of the phenyl-derivative, 2b, with
n-BuLi (1 equiv.) afforded several products as suggested by 31P
{1H} NMR spectroscopy (range: −20 to −60 ppm). Thus, reac-
tions with different bases (e.g. KH, LiNH2) were attempted in a
variety of solvents (e.g. Et2O, THF, DMSO and MeCN) in the
Fig. 5 31P{1H} NMR spectra (121.5 MHz, 298 K): (a) the isolated precipi-
tate in THF from the reaction of 2b with KH (2.5 equiv.); (b) the crude
reaction mixture of 2b in toluene first treated with DMSO-d6 and then
LiNH2 (2.5 equiv.).
Scheme 2 Synthesis of six-coordinate P(V)N3O3 anions from five-coor-
dinate P(V)N2O3 phosphoranes.
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As mentioned previously, single crystals suitable for X-ray
Of particular interest are the P(V)–N bonds in the fac-[4a]−
crystallographic analysis were obtained for Li(THF)3fac-[4a]. The anion [avg. 1.7701(21) Å]. These bonds are considerably longer
molecular structure is shown in Fig. 6 and reveals the presence than the P(V)–N single bonds found in tetracoordinate phos-
of the desired hexacoordinate phosphorus(V) anionic centre that phorus(V) compounds of the type X2P(vX)–NR2 (1.662 Å).26
is countered by
a
hexacoordinate lithium cation (Li+). The P(V)–N bonds of only structurally characterized hexacoordi-
Intriguingly, this compound crystallizes in the chiral space nate phosphorus(V) anion, [F]−, has recently been reported
group P212121 and the assignment of the Λ-isomer was sup- and displays quite similar bond lengths {[HNEt3][F], avg.
ported by a Flack parameter of 0.06(4). Analysis of three 1.787(3) Å} to those of fac-[4a]−.14
additional crystals finally afforded the structure of the Δ-isomer,
Despite being six-coordinate, the lithium cation of
whose assignment was supported by the Flack parameter of Li(THF)3fac-[4a] is highly distorted from octahedral and may
0.07(4). Selected metrical parameters and related X-ray crystallo- be alternatively be envisaged as a distorted tetrahedral geo-
graphic data are tabulated in Tables 1 and 2, respectively.
metry with the vertices being comprised of the three THF
Of note, anions of both Λ- and Δ-fac-[4a]− bind to Li+ molecules and the average O-position of the anion [4a]−. The
through the octahedral face containing the three phenoxy Li–O distances involving donor solvent molecules (THF)
oxygens (P–O̲
–Ar). Anion fac-[4a]− shows significant deviations [avg. 2.015(5) Å] are shorter than those involving fac-[4a]−
from regular octahedral symmetry with angles at phosphorus [avg. 2.233(5) Å] in Li(THF)3fac-[4a]. A survey of The Cambridge
ranging from 83.38(7)° to 95.45(11)°. In addition, the P–O Structural Database (CSD) revealed that the typical coordi-
bond lengths [avg. 1.7640(18) Å] are significantly longer than a nation number for Li+ and O-donors is four such as in
typical P(V)–O single bond (range: 1.571 Å to 1.689 Å)26 and to [Li(THF)4]+. The Li–O bond lengths generally fall in the range
those in 2a–c. For comparison, the P–O bonds in fac-[4a]− are from 1.890 Å to 1.950 Å. With an increasing coordination
also longer than those found in salts of anion [B]−, number, an elongation of the Li–O bond is expected due to the
namely Et3NH[BH] [avg. 1.716(6) Å],8c,d H(DMSO)2[BH] [avg. reduced electrophilicity at the cationic lithium centre. The
1.716(1) Å],11 H(DMF)2[BH] [avg. 1.711(1) Å],11 K(DMSO)3[BH] Li–O bond lengths in the limited examples of complexes con-
[avg. 1.715(1) Å],22 K(MeCN)2[BH] [avg. 1.7123(9) Å],22 cinchoni- taining six-coordinate lithium cations are substantially longer
dinium-[BCl] [avg. 1.714(6) Å],8f H(OEt2)2[BCl] [avg. 1.715(1) than in the four coordinate complexes. Examples include
Å],12 H(OEt2)(MeCN)[BCl] [avg. 1.717(1) Å],12 H(THF)2[BCl] Li[Monensin]·MeCN [Li–Oavg = 2.245(5) Å],27 [Li(THF)6]+ (Li–
[avg. 1.716(4) Å],13 H(THF)(MeCN)[BCl] [avg. 1.713(2) Å]13 and Oavg = 2.169 Å),28,29 [Li(THF)3S3]+ (Li–Oavg = 2.105 Å),30 [Li(O–
H(DMF)2[BCl] [avg. 1.715(5) Å].13
O–O)2]+ [O–O–O = trispirotetrahydrofuran, Li–Oavg = 2.0785(18)
Fig. 6 Molecular structures of: (a) Li(THF)3 Δ-fac-[4a] and (b) Li(THF)3 Λ-fac-[4a] (thermal ellipsoids are displayed at 50% probability level).
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and angles (°): Li(THF)3 Δ-fac-[4a]: Li(1)–O(1) = 2.164(5), Li(1)–O(2) = 2.232(6),
Li(1)–O(3) = 2.297(5), Li(1)–O(4) = 1.990(6), Li(1)–O(5) = 2.015(6), Li(1)–O(6) = 2.036(5), P(1)–Li(1)–O(4) = 119.8(2), P(1)–Li(1)–O(5) = 118.9(2), P(1)–Li
(1)–O(6) = 122.1(2), O(4)–Li(1)–O(5) = 98.6(2), O(4)–Li(1)–O(6) = 95.8(2), O(5)–Li(1)–O(6) = 96.1(2), O(1)–P(1)–N(2) = 171.07(11), O(1)–P(1)–O(2) =
83.39(9), O(1)–P(1)–O(3) = 83.97(10), O(1)–P(1)–N(3) = 93.09(10), O(2)–P(1)–N(3) = 171.40(11), O(2)–P(1)–O(3) = 84.33(10), O(2)–P(1)–N(1) = 94.43
(10), O(3)–P(1)–N(1) = 171.31(11), O(3)–P(1)–N(2) = 93.79(11), N(1)–P(1)–N(2) = 94.51(11), N(3)–P(1)–N(2) = 95.45(11), N(3)–P(1)–N(1) = 94.25(11);
Li(THF)3 Λ-fac-[4a]: Li(1)–O(1) = 2.167(4), Li(1)–O(2) = 2.237(4), Li(1)–O(3) = 2.298(4), Li(1)–O(4) = 1.989(4), Li(1)–O(5) = 2.017(5), Li(1)–O(6) = 2.042(4),
P(1)–Li(1)–O(4) = 119.06(18), P(1)–Li(1)–O(5) = 122.04(18), P(1)–Li(1)–O(6) = 119.74(17), O(4)–Li(1)–O(5) = 96.08(17), O(4)–Li(1)–O(6) = 98.71(19),
O(5)–Li(1)–O(6) = 95.69(18), O(1)–P(1)–N(2) = 171.24(8), O(1)–P(1)–O(2) = 83.38(7), O(1)–P(1)–O(3) = 84.01(7), O(1)–P(1)–N(3) = 93.11(8), O(2)–P(1)–
N(3) = 171.41(9), O(2)–P(1)–N(1) = 93.42(8), O(2)–P(1)–O(3) = 84.31(8), O(3)–P(1)–N(1) = 171.40(9), O(3)–P(1)–N(2) = 93.90(9), N(1)–P(1)–N(2) =
94.31(9), N(1)–P(1)–N(3) = 94.26(9), N(2)–P(1)–N(3) = 95.30(8).
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Å;31 O–O–O
[Li(THF)3RuH3
1.989(4) Å],34 [Li(THF)3BH3
1.963 Å;37,38 1.956 Å;39 1.942(10) Å],40 [Li(THF)3C3]+ (Li–Oavg
=
trispiro ether, Li–Oavg
]+ (Li–Oavg = 2.032 Å),33 [Li(THF)3FCl2]+ [Li–Oavg
]+ [Li–Oavg = 2.051 Å,35 1.979(6) Å;36
=
2.079(2) Å],32
̲
=
̲
=
1.978 Å).41 Therefore, the Li–O bonds in Li(THF)3fac-[4a] are at
the long end of the range for other six-coordinate Li+ ions sug-
gestive of the weakly coordinating nature of the fac-[4a]− anion.
The new salt, Li(THF)3fac-[4a] was also characterized by 31P,
1H and 13C{1H} NMR spectroscopy in DMSO-d6 solution. The
1
assignments were made with the aid of H–13C HSQC, HMBC,
31P{1H} and 1H{31P} NMR experiments. The 31P NMR spectrum
3
shows a decet resonance (δ = −99.6, JPH = 11 Hz), resulting
from coupling to three N–CH3 moieties. Consistent with this
observation, the 1H NMR spectrum shows one doublet reso-
nance assigned to the N–CH3 moieties (δ = 2.65, JHP = 11 Hz,
3
Fig. 7 31P{1H} NMR spectra (121.5 MHz, 298 K) of Li(THF)3fac-[4a] in: (a)
Et2O; (b) THF; (c) DMSO-d6 after 10 min; (d) DMSO-d6 after six months;
(e) CDCl3; (f) C7D8.
9 H). The equivalence of the N–CH3 moieties is consistent with
the retention of the fac-configuration for [4a]− in DMSO-d6
solution. Consistent with this hypothesis, the 13C{1H} NMR
spectrum shows a doublet resonance assigned to the equi-
2
valent N–CH3 moieties of fac-[4a]− (δ = 32.3, JCP = 2 Hz). In
the integration and the fact that there are three distinct
H-environments, we conclude that this new species is the
mer-[4a]− isomer (ca. 78%). Efforts to selectively crystallize
Li(mer-[4a]) or to separate it in pure form have not yet been
successful. The isomerization process can be accelerated by
heating a solution of Li(THF)3fac-[4a] in DMSO to 120 °C for
15 h (ca. 75% conversion).
addition, six resonances with the appropriate 13C–31P coup-
lings were assigned to the aromatic carbon atoms of the equi-
valent 2-(methylamino)phenoxy ligands of fac-[4a]−. Signals
were also observed in the 1H and 13C{1H} NMR spectra solu-
tion that were assigned to the THF moieties in the DMSO-d6
solution of Li(THF)3fac-[4a] (δH = 3.62 and 1.78; δC = 67.5 and
25.6). These signals integrate to two THF molecules per
lithium and are similar to those of free THF in DMSO-d6 (δH
=
3.58 and 1.72; δC = 67.21 and 25.31).42 A THF spiking experi-
ment suggests that these THF moieties are not bound to Li+ in
solution. Although the NMR data were fully consistent with
Experimental section
Materials and methods
the proposed structure, we were unable to obtain satisfactory All manipulations were performed under a nitrogen atmo-
elemental analysis for Li(THF)3 fac-[4a]. The C and H analysis sphere using standard Schlenk or glovebox techniques.
were consistently low, perhaps resulting from incomplete com- n-Hexane was deoxygenated with dry nitrogen and dried over a
bustion of the salt, variability in the THF content, and impuri- column containing activated alumina. Acetonitrile (MeCN), di-
ties (e.g. LiOH) in the n-BuLi reagent used.
chloromethane (CH2Cl2), diethyl ether (Et2O), ethyl acetate
To evaluate the stability of the new P(V)N3O3 anion, [4a]−, (EtOAc), n-pentane, toluene, and triethylamine (Et3N) were dis-
crystals of Li(THF)3fac-[4a] were dissolved in several organic tilled over calcium hydride (CaH2) and stored over molecular
solvents under a nitrogen atmosphere (THF, Et2O, DMSO-d6, sieves (3 Å). Dimethyl sulfoxide (DMSO) and dimethyl-
CDCl3, C7D8) and their 31P NMR spectra were recorded. The formamide (DMF) were dried over molecular sieves (3 Å) and
spectra are shown in Fig. 7 and reveal that the fac-[4a] anion distilled prior to use. THF was dried over sodium/benzophe-
was most stable in DMSO-d6 [Fig. 7(c)] with traces of phosphor- none ketyl and distilled prior to use. Methanol (MeOH)
ane 2a (δ = −47.2) being present in Et2O and THF [Fig. 7(a) was purchased from Sigma-Aldrich and used as received.
and (b)]. The spectra in poorly donating solvents (CDCl3, C7D8) CDCl3 was purchased from Cambridge Isotope Laboratories
are indicative of considerable degradation of the P-based Inc. and used as received. Other deuterated solvents (CD2Cl2,
anion [Fig. 7(e) and (f)]. In DMSO, no degradation was CD3CN, DMSO-d6 and C7D8) were purchased from Sigma-
observed with one dominant signal being observed in the 31P Aldrich and used as received. Phosphorus(V) pentachloride
NMR spectrum (δ = −99.6, dectet, 3JPH = 11 Hz) assigned to fac- (PCl5) was purchased from Sigma-Aldrich and sublimed twice
[4a]. Presumably, the Li+ ion is bound by DMSO and/or THF. prior to use. Potassium hydride (KH) (30 wt% dispersion in
Remarkably, a second signal at −105.4 ppm [Fig. 7(d)], barely mineral oil) was purchased from Sigma-Aldrich, washed with
visible in the initial spectrum, becomes dominant after six hot n-hexane and dried prior to use. 2-Anisidine (≥99.0%),
months (78% based on integration of the 31P NMR spectrum). boron tribromide (BBr3, Reagent-Plus®, ≥99.0%), n-BuLi
The 1H NMR of this new species shows three doublet (1.6 M in n-hexane), 12-crown-4 ether (98.0%), hexafluoroben-
resonances (δ = 2.78, 2.74 and 2.69; 3H, 3H and 3H, respect- zene (C6F6, 99.0%), lithium amide (LiNH2, 95.0%) and potass-
ively) in addition to the doublet resonance previously assigned ium bis(trimethylsilyl)amide (KHMDS, 95.0%) were purchased
to the N–CH3 moieties of fac-[4a]− (δ = 2.65, ∼2.6H). Based on from Sigma-Aldrich and used as received. 2-(Methylamino)
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phenol (1a)20 and 2-(phenylamino)phenol (1b)18,19 were syn- the aqueous layer was adjusted to 6 by adding 5% aqueous
thesized following literature procedures. Compound 1a was NaOH solution. The organic layer was separated, and the
further purified by recrystallization from Et2O or sublimation aqueous layer was extracted with EtOAc (3 × 50 mL). The com-
in vacuo prior to use. Similarly, compound 1b was sublimed in bined organic layers were dried over Na2SO4, filtered, and the
vacuo prior to use.
solvent was removed in vacuo. The isolated beige solid was
Unless specified, 1H, 13C{1H}, 19F{1H} and 31P{1H} NMR recrystallized from n-hexane to give 1c as a white solid (0.72 g,
spectra were recorded at room temperature (ca. 24 °C) on 75%). δH (300 MHz, CDCl3) 7.03–6.76 (4H, m, Ar–H), 5.42 (1H,
Bruker Avance 300 or 400 MHz spectrometers. 1H NMR spectra br s, –NH), 5.30 (1H, s, –OH); δF (282 MHz, CDCl3) −152.8 (2F,
were referenced to the residual protonated solvent signal and d, JFF = 19 Hz, Ar–F), −164.1 (2F, t, JFF = 22 Hz, Ar–F), −165.4
13C{1H} NMR spectra were referenced to the deuterated solvent (1F, t, JFF = 22 Hz, Ar–F).
signal. Phosphoric acid (H3PO4, 85%) and trichlorofluoro-
Phosphorane 2a. A mixture of 2-(methylamino)phenol (1a)
methane (CFCl3) were used as external standards (δ = 0.0) for (0.38 g, 3.1 mmol) and PCl5 (0.21 g, 1.0 mmol) was dissolved
31P and 19F, respectively. Elemental micro-analyses were per- in toluene (10 mL). Evolution of gas was observed immedi-
formed in the University of British Columbia Chemistry Micro- ately. The resultant reaction mixture was stirred and refluxed
analysis Facility. Mass spectra were acquired on a Waters for 12 h, during which time the solution changed from color-
Micromass ZQ™ Mass Spectrometer in ESI mode (LRMS), less to pale yellow. The 31P{1H} NMR spectrum of an aliquot
Kratos MS 50 instrument in EI mode (70 eV, HRMS) or Waters removed from the solution suggested the almost quantitative
Micromass LCT Premier TOF Mass Spectrometer in ESI mode conversion of PCl5 (δ = −80.1) to 2a (δ = −47.6). The reaction
(HRMS).
mixture was then cooled to room temperature and passed
through a silica plug (230–400 mesh) under a nitrogen atmo-
sphere. Removal of the solvent afforded 2a as a white solid
(0.29 g, 73%). Colorless crystals of 2a suitable for X-ray diffrac-
Syntheses
2-[(Perfluorophenyl)amino]phenol (1c). Compound 1c has tion were obtained from slow diffusion of n-pentane into a
been reported previously17 but was prepared here in two steps concentrated CH2Cl2 solution of 2a at −30 °C over several days.
from 2-anisidine following a different procedure.
δP (121.5 MHz, CDCl3) −48.4; δP (162 MHz, CD2Cl2) −47.5;
Step (a). This method was adopted from a general method δH (300 MHz, CDCl3) 6.97–6.37 (12H, m, Ar–H), 3.79 (1H, s,
used to convert Ar–NH2 to Ar–NH(C6F5).43 To a stirred solution –NH), 3.36 (6H, d, 3JHP = 10 Hz, N–CH3), 2.66 (3H, s, NH–CH3);
of 2-anisidine (2.46 g, 20.0 mmol) in THF (7.5 mL) at −78 °C δH (400 MHz, CD2Cl2) 7.15–6.54 (12H, m, Ar–H), 4.02 (1H, s,
3
was added dropwise KHMDS (6.70 g, 40.0 mmol) in THF –NH), 3.49 (6H, d, JHP = 10 Hz, N–CH3), 2.79 (3H, br s,
(20.5 mL). The reaction mixture slowly turned to deep red after NH–CH3); δC (100.5 MHz, CD2Cl2) 144.9 (d, JCP = 2 Hz, Ar–C),
10 min. Subsequently, C6F6 (1.80 g, 10.0 mmol) was rapidly 141.8 (d, JCP = 5 Hz, Ar–C), 140.6 (d, JCP = 11 Hz, Ar–C), 134.8
added and the reaction mixture was slowly warmed up to (d, JCP = 25 Hz, Ar–C), 129.1 (s, Ar–C), 128.3 (s, Ar–C), 124.9 (d,
ambient temperature with vigorous stirring. After 3 d, H2O JCP = 3 Hz, Ar–C), 120.5 (s, Ar–C), 119.9 (d, JCP = 2 Hz, Ar–C),
(50 mL) was added, and this aqueous–organic mixture was 116.0 (d, JCP = 3 Hz, Ar–C), 110.5 (d, JCP = 2 Hz, Ar–C), 108.9 (d,
2
extracted with Et2O (3 × 25 mL). The combined organic layers JCP = 14 Hz, Ar–C), 108.5 (d, JCP = 10 Hz, Ar–C), 33.3 (d, JCP
=
were dried with Na2SO4, filtered and the solvent was removed
2
Hz, N–CH3), 30.3 (s, NH–CH3). HRMS (ESI+): m/z
in vacuo. The isolated yellow-brown solid was further purified 396.1477 (calcd for C21H23N3O3P: 396.1477). Anal. calcd for
by column chromatography on silica gel (230–400 mesh) with C21H22N3O3P: C, 63.79; H, 5.61; N, 10.63. Found: C, 63.04; H,
n-hexane to afford 2,3,4,5,6-pentafluoro-N-(2-methoxyphenyl) 5.71; N, 10.15.
aniline (1c′) as a colorless solid (2.89 g, 70%). δH (300 MHz,
Phosphorane 2b. A mixture of 2-(phenylamino)phenol (1b)
CDCl3) 7.0–6.9 (3H, m, Ar–H), 6.7–6.6 (1H, m, Ar–H), 5.9 (1H, (0.74 g, 4.0 mmol) and PCl5 (0.21 g, 1.0 mmol) was dissolved
br s, –NH), 4.0 (3H, s, –CH3); δF (282 MHz, CDCl3) −149.1 (2F, in toluene (10 mL). The resultant solution was stirred under
dd, 1JFF = 19 Hz, 2JFF = 4 Hz, Ar–F), −163.6 (3F, m, Ar–F). HRMS reflux for 12 h, during which time the solution turned from
(EI, 70 eV): m/z 289.0526 (calcd for C13H8F5NO: 289.0526). colorless to pale yellow. Analysis of an aliquot removed from
Anal. calcd for C13H8F5NO: C, 53.99; H, 2.79; N, 4.84. Found: the solution by 31P NMR spectroscopy suggested the complete
C, 54.30; H, 3.19; N, 4.72.
consumption of PCl5 (δ = −80.1) to afford 2b (δ = −53.9). The
Step (b). This method was adopted from a general method reaction mixture was then cooled to room temperature and
for the demethylation of Ar–OMe.44 To a stirred solution of passed through a silica plug (230–400 mesh) under a nitrogen
2,3,4,5,6-pentafluoro-N-(2-methoxyphenyl)aniline (1c′, 1.01 g, atmosphere. Removal of the solvent afforded 2b as a white
3.5 mmol) in CH2Cl2 (20 mL) at −78 °C was added dropwise solid (0.39 g, 67%). Colorless crystals of 2b were obtained from
BBr3 (6.6 mL, 70 mmol) in CH2Cl2 (70 mL). The reaction slow diffusion of n-pentane into a concentrated CH2Cl2 solu-
mixture was then slowly warmed to ambient temperature (ca. tion at −30 °C over several days. δP (121.5 MHz, CDCl3) −53.8;
1 h) with vigorous stirring. After 60 h, MeOH was added δH (300 MHz, CDCl3) 7.44–6.18 (27H, m, Ar–H), 6.00 (1H, s,
(50 mL) to the reaction mixture at 0 °C followed by the –NH). LRMS (ESI−): m/z (%) 580.5, 581.5 (100, 28, M − H+).
addition of H2O (50 mL). The mixture was further stirred for
Phosphorane 2c. A mixture of 2-[(perfluorophenyl)amino]
another 2 h at ambient temperature. Subsequently, the pH of phenol (1c) (1.11 g, 4.0 mmol) and PCl5 (0.21 g, 1.0 mmol) was
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dissolved in toluene (10 mL). Evolution of gas was observed nitrogen atmosphere. The 31P{1H} NMR spectrum was
immediately. The reaction mixture was stirred and heated to recorded occassionaly. After six months at room temperature
reflux for 12 h, during which time the solution turned from (ca. 24 °C), the spectrum revealed that the resonance assigned
colorless to pale yellow. An aliquot was removed, and analyzed to fac-[4a] (δ = −99.6) was no longer dominant and a second
by 31P NMR spectroscopy. The signal assigned to PCl5 (δ = singlet resonance at −105.4 ppm was dominant. The new
−80.1) was not present and a new dominant high-field reso- higher-field signal was assigned to Li(THF)3mer-[4a]. Attempts
nance was observed (δ = −40.7). Subsequently, the solution to separate Li(THF)3mer-[4a] were unsuccessful. δP (162 MHz,
was cooled to room temperature and Et3N (1 mL) was added. DMSO-d6) −105.4; δH (400 MHz, DMSO-d6) 6.60–6.00 (12H, m,
3
Analysis of the resultant solution by 31P{1H} NMR spectroscopy Ar–H), 3.62 (m, THF, OCH2CH2), 2.78 (3H, d, JHP = 11 Hz,
3
3
showed that the aforementioned signal (δ = −40.7) was no –CH3), 2.74 (3H, d, JHP = 9 Hz, –CH3), 2.69 (3H, d, JHP
=
longer present and two new higher-field resonances were 12 Hz, –CH3), 1.78 (m, THF, OCH2CH2); δC (100.5 MHz, DMSO-
observed (δ = −54.6 and −56.5). The reaction mixture was then d6) 147.1 (s, Ar–C), 146.8 (s, Ar–C), 146.4 (s, Ar–C), 141.2 (d,
2
passed through a silica plug (230–400 mesh) under a nitrogen 2JCP = 19 Hz, Ar–C), 140.0 (d, JCP = 10 Hz, Ar–C), 139.9 (d,
atmosphere. Removal of the solvent afforded 2c as a white 2JCP = 12 Hz, Ar–C), 119.2 (s, Ar–C), 119.1 (s, Ar–C), 118.3 (s,
solid (0.43 g, 51%). Colorless crystals of 2c suitable for X-ray Ar–C), 113.9 (s, Ar–C), 113.1 (s, Ar–C), 112.9 (s, Ar–C), 107.1 (d,
diffraction were obtained from slow diffusion of n-pentane 3JCP = 12 Hz, Ar–C), 106.8 (d, 3JCP = 2 Hz, Ar–C), 106.7 (d, 3JCP
=
=
3
3
into a concentrated CH2Cl2 solution at −30 °C over several 4 Hz, Ar–C), 104.0 (d, JCP = 12 Hz, Ar–C), 103.4 (d, JCP
3
days. δP (121.5 MHz, CDCl3) −55.5; δH (300 MHz, CDCl3) 12 Hz, Ar–C), 103.0 (d, JCP = 14 Hz, Ar–C), 67.5 (s, THF,
2
2
7.06–6.27 (12H, m, Ar–H), 5.59 (1H, s, –NH); δF (282 MHz, OCH2CH2), 33.5 (d, JCP = 1 Hz, –CH3), 33.0 (d, JCP = 2 Hz,
CDCl3) −145.5 (4F, d, JFF = 17 Hz, Ar–F), −149.5 (2F, d, JFF
=
–CH3), 32.9 (d, 2JCP = 3 Hz, –CH3), 25.6 (s, THF, OCH2CH2).
K[4a]. To a MeCN (ca. 0.5 mL) solution of phosphorane 2a
(50 mg, 0.13 mmol) in an NMR tube at room temperature was
19 Hz, Ar–F), −153.9 (2F, t, JFF = 21 Hz, Ar–F), −161.3 (2F, s,
Ar–F), −162.2 (2F, t, JFF = 21 Hz, Ar–F), −163.5 (3F, m, Ar–F).
Phosphorane 3a. A mixture of 2-(methylamino)phenol (1a) added KH (ca. 40 mg, 1.0 mmol). Evolution of gas was
(0.26 g, 2.1 mmol) and PCl5 (0.21 g, 1.0 mmol) was dissolved observed immediately. 31P NMR spectroscopic analysis indi-
in toluene (10 mL). Evolution of gas was observed immedi- cated the complete consumption of 2a (δ = −47.6) and the for-
ately. The resultant solution was stirred at room temperature mation of two new higher-field resonances ([4a]−, δ = −97.6
for 12 h, during which time the solution slowly turned from and −103.3) upon standing for 12 h. The solution was filtered,
colorless to deep green and then settled with a pale-yellow and the solvent was removed in vacuo to afford K[4a] as a white
color. Analysis of an aliquot removed from the solution by 31P solid. Yield not determined. δP (121.5 MHz, CD3CN) −97.6
NMR spectroscopy showed the almost quantitative conversion (20%), −103.3 (80%).
of the starting material (PCl5, δ = −80.1) to chlorophosphorane
3a (δ = −34.2). Slow evaporation of the solvent afforded 3a as 4.0 mmol) in toluene (40 mL) at ambient temperature was
colorless crystals over week (0.26 g, 85%). δP NMR added DMSO-d6 (ca. 8 mL) followed by the addition of LiNH2
(121.5 MHz, toluene) −34.2; δH (300 MHz, CDCl3) 7.08–6.72 (0.23 g, 10.0 mmol). The solution slowly turned from orange to
(8H, m, Ar–H), 3.40 (6H, d, 3JHP = 10 Hz, –CH3).
deep brown along with the formation of an orange precipitate.
Li[4b]. To a stirred solution of phosphorane 2b (2.32 g,
a
Li(THF)3fac-[4a]. To a stirred solution of phosphorane 2a Over a period of 3 h, the 31P{1H} spectrum of the reaction
(1.58 g, 4.0 mmol) in toluene (40 mL) at ambient temperature mixture revealed quantitative conversion of the starting
was added THF (ca. 10 mL) followed by the addition of n-BuLi material (2b, δ = −53.8) by a new resonance ([4b]−, δ = −111.6).
in n-hexane (4.2 mmol, 1.6 M, 2.6 mL). The solution immedi- The solvent was removed in vacuo to yield Li[4b] as an orange
ately turned pale yellow. After 10 h, the 31P{1H} spectrum of an powder. Yield not determined. δP (121.5 MHz, DMSO-d6)
aliquot removed from the reaction solution revealed the quan- −111.6.
titative conversion of the starting material (2a, δ = −47.6) to
K[4b]. To a stirred solution of phosphorane 2b (2.32 g,
the product ( fac-[4a]−, δ = −97.6). The solvent was removed 4.0 mmol) in toluene (40 mL) at ambient temperature was
in vacuo, and the resultant yellow residue was re-dissolved in added DMSO-d6 (ca. 8 mL) followed by the addition of LiNH2
minimum amount of THF. Recrystallization over several days (0.23 g, 10.0 mmol). The solution slowly turned from orange to
afforded colorless crystals of Li(THF)3fac-[4a] suitable for X-ray deep brown along with the formation of an orange precipitate
analysis (2.24 g, 91%). δP (162 MHz, DMSO-d6) −99.6; over a period of 12 h. Analysis of an aliquot removed from the
δH (400 MHz, DMSO-d6) 6.50–6.07 (12H, m, Ar–H), 3.62 (10H, reaction solution by 31P NMR spectroscopy revealed the quanti-
3
m, THF, OCH2CH2), 2.65 (9H, d, JHP = 11 Hz, –CH3), tative conversion of the starting material (2b, δ = −53.8) to a
1.78 (10H, m, THF, OCH2CH2); δC (100.5 MHz, DMSO-d6) new higher-field resonance ([4b]−, δ = −111.6). Removed of the
2
147.6 (s, Ar–C), 139.2 (d, JCP = 21 Hz, Ar–C), 118.1 (s, Ar–C), solvent in vacuo afforded Li[4b] as an orange powder. Yield not
3
114.2 (s, Ar–C), 118.1 (s, Ar–C), 106.3 (d, JCP = 13 Hz, Ar–C), determined. δP (121.5 MHz, THF) −105.4 (85%), −107.3 (15%).
3
103.8 (d, JCP = 13 Hz, Ar–C), 67.5 (s, THF, OCH2CH2), 32.3
X-ray crystallography
(d, 2JCP = 2 Hz, –CH3), 25.6 (s, THF, OCH2CH2).
Li(THF)3mer-[4a]. Crystals of Li(THF)3fac-[4a] (50 mg) were Selected metrical parameters are given in Table 1. Crystal data
dissolved in DMSO-d6 (ca. 0.5 mL) in an NMR tube under a and refinement parameters are listed in Table 2. All single
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crystals were immersed in oil and mounted on a glass fibre.
All measurements were made on a Bruker X8 APEX II diffract-
Acknowledgements
ometer with a TRIUMPH curved-crystal monochromator with We thank the Natural Sciences and Engineering Research
MoKα radiation. Data were collected and integrated using the Council (NSERC) of Canada for supporting this work.
Bruker SAINT45 software package and corrected for absorption
effects using the multi-scan technique (SADABS).46 All struc-
tures were solved by direct methods47 and subsequent Fourier
difference techniques. Unless noted, all nonhydrogen atoms
Notes and references
were refined anisotropically, whereas all hydrogen atoms were
included in calculated positions but not refined. All data sets
were corrected for Lorentz and polarisation effects. All refine-
ments were performed using SHELXL-201448 via the OLEX2
interface.49 In the case of 3a, after complete anisotropic refine-
ment and addition of hydrogen atoms in calculated positions,
a large residual electron density remained at a position (∼1.70
from C3). This was modelled and refined with partial occu-
pancy of this position with a chlorine atom (0.07) and is
shown in Fig. S1.† All crystallographic data has been deposited
with the Cambridge Structural Database (CCDC 1563689 (2a),
1563691 (2b), 1563692 (2c·2CH2Cl2), 1849283 (3a), 1563690
(Li(THF)3 Λ-fac-[4a]), 1847159 (Li(THF)3 Δ-fac-[4a])†).
1 For selected reviews on six-coordinate derivatives of phos-
phorus(V), see: (a) C. Y. Wong, D. K. Kennepohl and
R. G. Cavell, Chem. Rev., 1996, 96, 1917–1951; (b) R. Herbst-
Irmer and M. Pulm, Curr. Sci., 2000, 78, 473–478;
(c) S. Constant and J. Lacour, Top. Curr. Chem., 2005, 250,
1–41; (d) J. Lacour and D. Linder, Chem. Rec., 2007, 7, 275–
285; (e) K. C. K. Swamy, S. Kumaraswamy, M. A. Said,
R. S. K. Kishore and J. Lacour, C. R. Chim., 2010, 13, 985–
997; (f) L. V. Bezgubenko, S. E. Pipko and A. D. Sinitsa,
Russ. J. Gen. Chem., 2011, 81, 1596–1614.
2 For salts containing cationic six-coordinate phosphorus(V),
see: (a) K. Y. Akiba, R. Nadano, W. Satoh, Y. Yamamoto,
S. Nagase, Z. P. Ou, X. Y. Tan and K. M. Kadish, Inorg.
Chem., 2001, 40, 5553–5567; (b) J. Lacour, L. Vial and
G. Bernardinelli, Org. Lett., 2002, 4, 2309–2312;
(c) K. Y. Akiba, Heteroat. Chem., 2011, 22, 207–274;
(d) P. A. Gray and N. Burford, Coord. Chem. Rev., 2016, 324,
1–16.
3 For compounds containing neutral six-coordinate phos-
phorus(V), see: (a) C. Y. Wong, R. McDonald and
R. G. Cavell, Inorg. Chem., 1996, 35, 325–334; (b) F. Carre,
C. Chuit, R. J. P. Corriu, A. Mehdi and C. Reye, Inorg. Chim.
Acta, 1996, 250, 21–28; (c) R. R. Holmes, Chem. Rev., 1996,
96, 927–950; (d) A. Chandrasekaran, R. O. Day and
R. R. Holmes, J. Am. Chem. Soc., 1997, 119, 11434–11441;
(e) N. V. Timosheva, A. Chandrasekaran, R. O. Day and
R. R. Holmes, Inorg. Chem., 1998, 37, 4945–4952;
(f) R. R. Holmes, Acc. Chem. Res., 1998, 31, 535–542;
(g) K. Toyota, Y. Yamamoto and K. Y. Akiba, J. Organomet.
Chem., 1999, 586, 171–175; (h) R. R. Holmes, Phosphorus,
Sulfur Silicon Relat. Elem., 1999, 144, 1–4; (i) C. Peters,
F. Tabellion, M. Schroder, U. Bergstrasser, F. Preuss and
M. Regitz, Synthesis, 2000, 417–428; ( j) K. M. Kadish,
Z. P. Ou, V. A. Adamian, R. Guilard, C. P. Gros, C. Erben,
S. Will and E. Vogel, Inorg. Chem., 2000, 39, 5675–5682;
(k) L. Simkhovich, A. Mahammed, I. Goldberg and
Summary
A new methodology has been developed to synthesize neutral
phosphoranes and anionic phosphates featuring penta- and
hexacoordinate phosphorus(V) moieties with 2-aminophenol
ligands. In particular, substitution reactions of PCl5 with
ligands 1a–c (3.1 equiv.) have enabled the facile synthesis and
structural characterization of a novel class of phosphoranes
(2a–c and 3a). Subsequent activation of the last potential
binding site (–N̲RH) in phosphorane 2a using n-BuLi (1 equiv.)
afforded the isolable lithium salt, Li(THF)3fac-[4a], which con-
tains the chiral P(V)-anion, fac-[4a]−. This compound was
characterized spectroscopically and structurally. Of note, X-ray
diffraction analysis of Li(THF)3[4a] revealed a fac-configuration
for anion [4a]− and the structures of both the Λ- and Δ-enan-
tiomers were determined by random selection of single crys-
tals. Additionally, lithium cation (Li+) adopts a six-coordinate
geometry being bound by the three phenoxy oxygens of anion
fac-[4a]− and by three THF molecules. Examination of the
long-term stability of solutions of Li(THF)3fac-[4a] in various
organic solvents has led to the observation of the spontaneous
yet slow isomerization of fac-[4a]− into mer-[4a]−. To our
knowledge, this is a rare anionic example that contains a σ6,λ6
phosphorus(V) centre with P(V)–N bonds. Future work is under-
way to further investigate the chemical characteristics of
Li(THF)3[4a] and its potential use as a weakly coordinating
chiral anion.
Z. Gross, Chem.
–
Eur. J., 2001, 7, 1041–1055;
(l) N. V. Timosheva, A. Chandrasekaran, R. O. Day and
R. R. Holmes, J. Am. Chem. Soc., 2002, 124, 7035–7040;
(m) K. Kumar, N. S. Kumar and K. C. K. Swamy, New
J. Chem., 2006, 30, 717–728; (n) K. Kumar, M. P. Pavan and
K. C. K. Swamy, Inorg. Chem. Commun., 2009, 12, 544–547;
(o) A. Ghosh and M. Ravikanth, Chem. – Eur. J., 2012, 18,
6386–6396; (p) T. Chatterjee, W. Z. Lee and M. Ravikanth,
Dalton Trans., 2016, 45, 7815–7822.
4 H. G. Mayfield and W. E. Bull, J. Chem. Soc. A, 1971, 14,
2279–2281.
Conflicts of interest
There are no conflicts to declare.
5 D. Hellwinkel, Angew. Chem., Int. Ed. Engl., 1965, 4, 356–365.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2018

View Article Online
Dalton Transactions
Paper
6 A. Chandrasekaran, R. O. Day and R. R. Holmes, Inorg. 12 P. W. Siu, K. Hazin and D. P. Gates, Chem. – Eur. J., 2013,
Chem., 2002, 41, 1645–1651. 19, 9005–9014.
7 For selected reviews on chiral-anion mediated applications 13 K. Hazin, S. C. Serin, B. O. Patrick, M. B. Ezhova and
using tetrachlorocatechol-based P(V)-anions, see: D. P. Gates, Dalton Trans., 2017, 46, 5901–5910.
(a) J. Lacour and V. Hebbe-Viton, Chem. Soc. Rev., 2003, 32, 14 D. Uraguchi, H. Sasaki, Y. Kimura, T. Ito and T. Ooi, J. Am.
373–382; (b) J. Lacour and D. Moraleda, Chem. Commun.,
2009, 46, 7073–7089.
Chem. Soc., 2018, 140, 2765–2768.
15 For selected examples of transition-metalled phosphoranes
featuring 2-aminophenol ligands, see: (a) B. N. Anand,
R. Bains, K. Aggarwal and K. Usha, Indian J. Chem., Sect. A:
Inorg., Bio-inorg., Phys., Theor. Anal. Chem., 1995, 34, 27–30;
(b) K. Kubo, H. Nakazawa, K. Kawamura, T. Mizuta and
K. Miyoshi, J. Am. Chem. Soc., 1998, 120, 6715–6721;
(c) H. Nakazawa, K. Kawamura, K. Kubo and K. Miyoshi,
Organometallics, 1999, 18, 2961–2969; (d) H. Nakazawa,
K. Kubo and K. Miyoshi, Bull. Chem. Soc. Jpn., 2001, 74,
2255–2267.
8 For six-coordinate P(V)-anions featuring catechol and tetra-
chlorocatechol ligands, see: (a) H. R. Allcock, J. Am. Chem.
Soc., 1963, 85, 4050–4051; (b) H. R. Allcock, J. Am. Chem.
Soc., 1964, 86, 2591–2595; (c) H. R. Allcock and E. C. Bissell,
J. Chem. Soc., Chem. Commun., 1972, 11, 676–677;
(d) H. R. Allcock and E. C. Bissell, J. Am. Chem. Soc., 1973,
95, 3154–3157; (e) M. Koenig, A. Klaebe, A. Munoz and
R. Wolf, J. Chem. Soc., Perkin Trans. 2, 1976, 8, 955–958;
(f) J. Lacour, C. Ginglinger, C. Grivet and G. Bernardinelli,
Angew. Chem., Int. Ed. Engl., 1997, 36, 608–610; 16 For selected examples of organophosphoranes featuring
(g) M. Handa, M. Suzuki, J. Suzuki, H. Kanematsu and
Y. Sasaki, Electrochem. Solid-State Lett., 1999, 2, 60–62;
(h) A. Skowronska, J. Kowara, R. Kaminski, G. Bujacz and
M. W. Wieczorek, J. Org. Chem., 2000, 65, 304–315;
(i) J. Lacour, A. Londez, C. Goujon-Ginglinger, V. Buss and
G. Bernardinelli, Org. Lett., 2000, 2, 4185–4188; (j) J. Lacour,
D. Monchaud, G. Bernardinelli and F. Favarger, Org. Lett.,
2001, 3, 1407–1410; (k) N. Nanbu, T. Shibazaki and
Y. Sasaki, Chem. Lett., 2001, 9, 862–863; (l) J. Lacour and
A. Londez, J. Organomet. Chem., 2002, 643, 392–403;
(m) J. Lacour, A. Londez, D. H. Tran, V. Desvergnes-Breuil,
S. Constant and G. Bernardinelli, Helv. Chim. Acta, 2002, 85,
1364–1381; (n) J. Lacour, S. Constant and V. Hebbe,
Eur. J. Org. Chem., 2002, 3580–3588; (o) N. Nanbu,
K. Tsuchiya, T. Shibazaki and Y. Sasaki, Electrochem. Solid-
State Lett., 2002, 5, A202–A205; (p) C. Perollier, S. Constant,
J. J. Jodry, G. Bernardinelli and J. Lacour, Chem. Commun.,
2003, 16, 2014–2015; (q) J. Lacour and V. Hebbe-Viton,
Chem. Soc. Rev., 2003, 32, 373–382; (r) M. Eberwein,
2-aminophenol ligands, see: (a) H. R. Allcock and R. L. Kugel,
Chem. Commun., 1968, 24, 1606–1607; (b) H. R. Allcock and
R. L. Kugel, J. Am. Chem. Soc., 1969, 91, 5452–5456;
(c) T. Koizumi, Y. Watanabe, Y. Yoshida and E. Yoshii,
Tetrahedron Lett., 1974, 12, 1075–1078; (d) C. Malavaud and
J. Barrans, Tetrahedron Lett., 1975, 35, 3077–3080;
(e) H. R. Allcock, R. L. Kugel and G. Y. Moore, Inorg. Chem.,
1975, 14, 2831–2837; (f) C. D. Reddy, S. S. Reddy and
M. S. R. Naidu, Synthesis, 1980, 1004–1005; (g) L. Z. Liu,
B. Z. Cai and R. Y. Chen, Acta Chim. Sin., 1987, 45, 1096–
1100; (h) J. Hernandez-Diaz, R. Contreras and B. Wrackmeyer,
Heteroat. Chem., 2000, 11, 11–15; (i) S. A. Terent’eva,
I. L. Nikolaeva, A. R. Burilov, D. I. Kharitonov, E. V. Popova,
M. A. Pudovik, I. A. Litvinov, A. T. Gubaidullin and
A. I. Konovalov, Russ. J. Gen. Chem., 2001, 71, 389–395;
(j) S. A. Terent’eva, M. A. Pudovik, A. T. Gubaidullin,
I. A. Litvinov and A. N. Pudovik, Russ. J. Gen. Chem., 2001, 71,
330–336; (k) D. Krasowska, J. Chrzanowski, P. Kielbasinski
and J. Drabowicz, Molecules, 2016, 21, 1–44.
A. Schmid, M. Schmidt, M. Zabel, T. Burgemeister, 17 E. F. Kolchina, I. Y. Kargapolova and T. N. Gerasimova,
J. Barthel, W. Kunz and H. J. Gores, J. Electrochem. Soc., Bull. Acad. Sci. USSR Div. Chem. Sci., 1986, 35, 1685–1689.
2003, 150, A994–A999; (s) F. Favarger, C. Goujon-Ginglinger, 18 Y. M. Li, H. F. Wang, L. L. Jiang, F. F. Sun, X. M. Fu and
D. Monchaud and J. Lacour, J. Org. Chem., 2004, 69, 8521– C. Y. Duan, Eur. J. Org. Chem., 2010, 6967–6973.
8524; (t) S. Constant, R. Frantz, J. Muller, G. Bernardinelli 19 D. Maiti and S. L. Buchwald, J. Am. Chem. Soc., 2009, 131,
and J. Lacour, Organometallics, 2007, 26, 2141–2143; 17423–17429.
(u) J. Lacour and D. Moraleda, Chem. Commun., 2009, 46, 20 B. Yadagiri and J. W. Lown, Synth. Commun., 1990, 20, 175–
7073–7089; (v) G. M. Miyake, Y. T. Zhang and E. Y. X. Chen, 181.
Macromolecules, 2010, 43, 4902–4908; (w) Y. T. Zhang, 21 M. Koenig, A. Klaebe, A. Munoz and R. Wolf, J. Chem. Soc.,
L. O. Gustafson and E. Y. X. Chen, J. Am. Chem. Soc., 2011, Perkin Trans. 2, 1979, 40–44.
133, 13674–13684; (x) N. R. Khasiyatullina, V. F. Mironov 22 P. W. Siu and D. P. Gates, Can. J. Chem., 2012, 90, 574–583.
and O. I. Gnezdilov, Russ. J. Gen. Chem., 2012, 82, 939–941; 23 H. A. Bent, Chem. Rev., 1961, 61, 275–311.
(y) M. F. Rectenwald, J. R. Gaffen, A. L. Rheingold, 24 R. K. Brown and R. R. Holmes, Inorg. Chem., 1977, 16,
A. B. Morgan and J. D. Protasiewicz, Angew. Chem., Int. Ed.,
2014, 53, 4173.
9 I. Krossing and I. Raabe, Angew. Chem., Int. Ed., 2004, 43,
2066–2090.
2294–2299.
25 U. Wietelmann, W. Bonrath, T. Netscher, H. Noeth,
J.-C. Panitz and M. Wohlfahrt-Mehrens, Chem. – Eur. J.,
2004, 10, 2451–2458.
10 S. H. Strauss, Chem. Rev., 1993, 93, 927–942.
11 P. W. Siu and D. P. Gates, Organometallics, 2009, 28, 4491–
4499.
26 J. R. Rumble, CRC Handbook of Chemsitry and Physics, CRC
Press/Taylor & Francis, Boca Raton, Florida, United States,
98th edn (Internet Version 2018).
This journal is © The Royal Society of Chemistry 2018
Dalton Trans.

View Article Online
Paper
Dalton Transactions
27 A. Huczynski, M. Ratajczak-Sitarz, A. Katrusiak and 40 K. Izod, C. Wills, W. Clegg and R. W. Harrington,
B. Brzezinski, J. Mol. Struct., 2007, 871, 92–97. Organometallics, 2006, 25, 38–40.
28 C. Schenk, F. Henke, G. Santiso-Quinones, I. Krossing and 41 A. V. Zabula, A. S. Filatov, S. N. Spisak, A. Y. Rogachev and
A. Schnepf, Dalton Trans., 2008, 33, 4436–4441. M. A. Petrukhina, Science, 2011, 333, 1008–1011.
29 C. Schenk and A. Schnepf, Angew. Chem., Int. Ed., 2007, 46, 42 G. R. Fulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb,
5314–5316.
A. Nudelman, B. M. Stoltz, J. E. Bercaw and K. I. Goldberg,
Organometallics, 2010, 29, 2176–2179.
30 J. C. Friese, A. Krol, C. Puke, K. Kirschbaum and
D. M. Giolando, Inorg. Chem., 2000, 39, 1496–1500.
31 J. Tae, R. D. Rogers and L. A. Paquette, Org. Lett., 2000, 2,
139–142.
32 L. A. Paquette, J. Tae, E. R. Hickey, W. E. Trego and
R. D. Rogers, J. Org. Chem., 2000, 65, 9160–9171.
33 M. Plois, R. Wolf, W. Hujo and S. Grimme, Eur. J. Inorg.
Chem., 2013, 17, 3039–3048.
34 S. R. Dubberley, S. Evans, C. L. Boyd and P. Mountford,
Dalton Trans., 2005, 8, 1448–1458.
35 G. F. Zi, H. W. Li and Z. W. Xie, Organometallics, 2001, 20,
3836–3838.
43 N. Roy, S. Sproules, E. Bill, T. Weyhermuller and
K. Wieghardt, Inorg. Chem., 2008, 47, 10911–10920.
44 J. T. Gupton, E. J. Banner, A. B. Scharf, B. K. Norwood,
R. P. F. Kanters, R. N. Dominey, J. E. Hempel, A. Kharlamova,
I. Bluhn-Chertudi, C. R. Hickenboth, B. A. Little, M. D. Sartin,
M. B. Coppock, K. E. Krumpe, B. S. Burnham, H. Holt,
K. X. Du, K. M. Keertikar, A. Diebes, S. Ghassemi and
J. A. Sikorski, Tetrahedron, 2006, 62, 8243–8255.
45 SAINT, Version 8.34A, Bruker AXS Inc., Madison, WI,
1997–2013.
46 SADABS, Version 2014/5. L. Krause, R. Herbst-Irmer,
G. M. Sheldrick and D. Stalke, J. Appl. Crystallogr., 2015, 48,
3–10.
36 H. H. Giese, H. Noth, H. Schwenk and S. Thomas,
Eur. J. Inorg. Chem., 1998, 7, 941–949.
37 D. M. Liu, H. Shen, Y. R. Wang, Y. P. Cai and Z. W. Xie, 47 SHELXT: G. M. Sheldrick, Acta Crystallogr., Sect. C: Struct.
Chem. – Asian J., 2011, 6, 628–637. Chem., 2015, 71, 3–8.
38 S. Molitor and V. H. Gessner, Chem. – Eur. J., 2013, 19, 48 SHELXT: G. M. Sheldrick, Acta Crystallogr., Sect. A: Found.
11858–11862. Crystallogr., 2008, 64, 112–122.
39 Y. Z. Wang, Y. M. Xie, M. Y. Abraham, P. R. Wei, 49 OLEX2, Version 1.2.6: O. V. Dolomanov, L. J. Bourhis,
H. F. Schaefer, P. v. R. Schleyer and G. H. Robinson,
Organometallics, 2011, 30, 1303–1306.
R. J. Gildea, J. A. K. Howard and H. Puschmann, J. Appl.
Crystallogr., 2009, 42, 339–341.
Dalton Trans.
This journal is © The Royal Society of Chemistry 2018