Cubane and step-form structures of dilithium bis(aryloxy)phosphines

Article abstract of DOI:10.1039/b710506a

The lithium complexes RP(3,5-^tBu₂C₆H ₂OLi)₂(THF)₄, where R = Ph or ⁱPr, (^R[OPO]Li₂)₂(THF)₄, synthesized by reaction of the 2-bromo-4,6-di-tert-butylphenol with BuLi and the appropriate dichlorophosphine, possess solid state structures composed of lithium oxide tetragons arranged in a step-form or face sharing half-cubane arrangements. Incorporation of excess lithium aryloxide results in the formation of complexes that display an extended step-form structure, [^Ph[OPO]Li ₂(ArOLi)]₂, or a distorted cubane arrangement of tetragons, [^iPr[OPO]Li₃Cl(ArOLi)](THF)₃. The Royal Society of Chemistry.

Full text of DOI:10.1039/b710506a

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www.rsc.org/dalton | Dalton Transactions
Cubane and step-form structures of dilithium bis(aryloxy)phosphines†‡
Christopher D. Carmichael and Michael D. Fryzuk*
Received 10th July 2007, Accepted 6th November 2007
First published as an Advance Article on the web 29th November 2007
DOI: 10.1039/b710506a
The lithium complexes RP(3,5-tBu2C6H2OLi)2(THF)4, where R = Ph or iPr, (R[OPO]Li2)2(THF)4,
synthesized by reaction of the 2-bromo-4,6-di-tert-butylphenol with BuLi and the appropriate
dichlorophosphine, possess solid state structures composed of lithium oxide tetragons arranged in a
step-form or face sharing half-cubane arrangements. Incorporation of excess lithium aryloxide results
in the formation of complexes that display an extended step-form structure, [Ph[OPO]Li2(ArOLi)]2, or a
distorted cubane arrangement of tetragons, [iPr[OPO]Li3Cl(ArOLi)](THF)3.
THF to a hexanes slurry of the crude product affords the dilithio
Introduction
THF adducts (Ph[OPO]Li2)2(THF)4 (1) and (iPr[OPO]Li2)2(THF)4
Lithium aryloxide complexes are known to form a variety of
(2) as colourless solids, in 70% and 51% yield, respectively
aggregate structures,1–5 the majority of which are based on
(Scheme 1).
dimeric Li2O2 rings or tetrameric Li4O4 cubanes.6,7 A measure
of control over the aggregation can be conferred through the
choice of aryloxide (monodentate vs. bridging), the substitution
pattern around the aromatic ring (sterics and electron-donating
ability), and the reaction solvent (Lewis basicity). In substituted
lithium phenoxide complexes, particularly those substituted at the
para position, structures composed of Li2O2 rings and cubanes
predominate, whereas bulky substituents at the ortho position lead
to steric crowding at the aryloxide oxygen often result in smaller
aggregates.8 Ligands containing linked aryloxide units, such as
binaphthol, can also give rise to complex structures, including
chiral chains and clusters.9 The bidentate aryloxide 2,2ꢀ-ethylidene-
bis(4,6-di-tert-butylphenol) (EDBP) possesses a flexible methyl
methyne bridge, and structures of lithium EDBP complexes con-
tain multiple Li2O2 cores that are joined in hexagonal, step-form
ladder and distorted sheet skeletons.1 Alteration of the bridging
moiety in linked aryloxides can be used to generate potentially
tridentate ligands. The phosphorus substituted ligand bis(3,5-tert-
butyl-2-phenoxy)phenylphosphine [OPO], is known,10 and simple
lithium complexes supported by the coordinating solvent 1,2-
dimethoxyethane (DME) have recently been reported.11 Herein
Scheme 1
we report the synthesis of [OPO] lithium complexes in THF and
their structural characterization.
X-Ray quality crystals of 1 containing three molecules of co-
crystallized solvent were grown by slow evaporation of a saturated
benzene solution. The solid-state molecular structure of 1 contains
two independent but structurally similar molecular fragments in
the asymmetric unit. One of these is presented in Fig. 1, along
with its crystallographically related fragment; crystallographic
data are given in Table 5, and selected bond distances and angles
are collected in Table 1. The structure is dimeric with the two
Ph[OPO]Li2 fragments bound via Li–O bonds forming a ladder
like structure composed of three Li2O2 rings. The geometry about
Li(1) is best described as a highly distorted tetrahedron where
the lithium is bound by three [OPO] oxygens and P(1), whereas
Li(2) is in a much less distorted tetrahedral geometry with the
lithium bound by two [OPO] oxygens and two THF molecules. The
structure of 1 stands in stark contrast to the simple monomeric
structure of the DME adduct, Ph[OPO]Li2(DME)2,11 with the only
chemical difference being the choice of coordinating solvent; the
Results and discussion
Synthesis of the R[OPO]Li2(THF)2 derivatives is achieved through
a modification of the published procedure;10 instead of a hydrolytic
workup, the dilithio salts can be isolated directly. Thus, reaction of
two equivalents of a 2-bromo-4,6-di-tert-butylphenol with RPCl2
(R = Ph, iPr) in the presence of four equivalents of n-BuLi yields
the crude product as a cream coloured solid. Addition of excess
Department of Chemistry, University of British Columbia, 2036 Main
Mall, Vancouver, British Columbia, Canada, V6T 1Z1. E-mail: fryzuk@
chem.ubc.ca
† The HTML version of this article has been enhanced with colour images.
‡ CCDC reference numbers 653592–653595. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b710506a
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Table 1 Selected bond distances (A), bond angles ( ), and dihedral angles
Table 2 Selected bond distances (A), bond angles ( ), and dihedral angles
(◦) for (Ph[OPO]Li2)2(THF)4, 1
(◦) for [iPr[OP(=O)O]Li2(H2O)]2, 2-O
Li(1)–P(1)
Li(1)–O(1)
Li(1)–O(2)
Li(1)–O(2*)
2.499(3)
1.948(3)
2.016(3)
1.890(3)
Li(2)–O(1)
Li(2)–O(2)
Li(2)–O(3)
Li(2)–O(4)
1.936(3)
2.148(3)
1.981(3)
1.994(3)
Li(1)–O(1)
Li(1)–O(2)
Li(1)–O(3)
Li(1)–O(3*)
P(1)–O(3)
1.854(4)
1.870(4)
1.975(4)
1.991(4)
1.5209(17)
Li(2)–O(1)
Li(2)–O(2*)
Li(2)–O(3*)
Li(2)–O(4)
1.916(4)
1.901(4)
2.026(5)
2.033(13)
P(1)–Li(1)–O(1)
P(1)–Li(1)–O(2)
P(1)–Li(1)–O(2*)
O(1)–Li(1)–O(2)
O(1)–Li(1)–O(2*)
O(2)–Li(1)–O(2*)
Li(1)–O(2)–Li(1*)
Li(1)–O(1)–Li(2)
79.76(10) O(1)–Li(2)–O(2)
93.91(13)
81.40(10) O(1)–Li(2)–O(4) 113.89(15)
136.55(15) O(1)–Li(2)–O(3) 105.51(15)
97.81(13) O(2)–Li(2)–O(3) 111.82(15)
142.18(16) O(2)–Li(2)–O(4) 123.16(15)
98.16(12) O(3)–Li(2)–O(4) 106.98(15)
81.84(12) Li(1)–O(2)–Li(2)
83.23(13)
P(1)–O(3)–Li(1)
P(1)–O(3)–Li(1*)
P(1)–O(3)–Li(2*)
O(3)– P(1)– C(13)
Li(1)–O(3)–Li(1*)
O(3)–Li(1*)–O(3*)
Li(1*)–O(3*)–Li(1)
O(3*)–Li(1)–O(3)
O(1)–Li(1)–O(2)
119.04(15) Li(1)–O(1)–Li(2)
85.3(2)
117.66(15) O(1)–Li(2)–O(3*) 93.3(2)
154.24(17) Li(2)–O(3*)–Li(1) 79.00(17)
105.51(11) O(3*)–Li(1)–O(1) 96.37(19)
85.79(18) Li(1)–O(2)–Li(2*) 85.56(19)
94.21(18) O(2)–Li(2*)–O(3) 93.4(2)
85.79(18) Li(2*)–O(3)–Li(1) 79.60(17)
76.48(12)
94.21(18) O(3)–Li(1)–O(2)
160.2(3)
96.05(19)
Li(1)–O(2)–Li(1*)–O(2*)
O(1)–Li(1)–O(2)–Li(2)
0.0
−21.45(12)
Li(1)–O(3)–Li(1*)–O(3*)
O(1)–Li(1)–O(3*)–Li(2)
O(2)–Li(1)–O(3)–Li(2*)
0.0
18.4(2)
17.3(2)
Symmetry operator *: −x, −y, 1 − z.
Symmetry operator *: 1 − x, −y, 1 − z.
attempts to crystallize 2 have thus far failed to yield X-ray quality
crystals. However, when a d6-benzene solution of 2 is allowed
to evaporate slowly in the presence of atmospheric oxygen and
water, X-ray quality crystals of a related phosphine oxide complex,
iPr
=
[ [OP( O)O]Li2(H2O)]2 (2-O), containing four equivalents of
co-crystallized benzene, are formed. The solid-state molecular
structure of 2-O is presented in Fig. 2; crystallographic data are
presented in Table 5, and selected bond distances and angles in
Table 2. Structurally, 2-O is a dimer, like 1, with a core composed
of Li2O2 rings, arranged not as a ladder but as corners of two
half-cubanes that share a face, a structural motif that is rare
in the literature.3,12 Severe disorder in the water molecule O(4)
prohibited the location of the attached hydrogens in the difference
map; however, the Li(2)–O(4) bond distance is in agreement with
other lithium water complexes.13,14 Each lithium is four-coordinate;
with Li(1) bound in a disphenoidal geometry to both phosphine
oxides and one oxygen of each [OPO], while Li(2) is bound in a
distorted tetrahedral geometry to the oxygens of one [OPO] ligand,
the phosphine oxide of the other [OPO] ligand, and the water
molecule. Li–O bond distance agree well with those of complex
1, and the phosphorus oxygen double bond is reflected in the
Fig. 1 Molecular structure (ORTEP) of (Ph[OPO]Li2)2(THF)4, 1. Ellip-
soids are drawn at 50% probability.
structure of this DME adduct is shown below. Metrical parameters
of the Ph[OPO] fragments in 1 agree well with the DME adduct.
The monomeric nature of the DME adduct may be rationalized
through the chelating nature of the coordinating solvent, which is
more strongly donating than the bridging aryloxide unit present
in the THF adduct 1.
Mass spectral analysis confirmed the dimeric nature of 1 with
the observation of a mass peak corresponding to the dimer with
loss of the THF donors. In solution 1 displays Cs symmetry, with
resonances for the t-butyl groups appearing as two distinct singlets
in the 1H NMR spectrum.
Fig. 2 Molecular structure (ORTEP) of [iPr[OP( O)O]Li2(H2O)]2, 2-O.
Ellipsoids are drawn at 50% probability.
The isopropyl derivative 2 shows similar symmetry in solution,
and a mass spectrum confirms a similar dimeric structure. All
=
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structural motif for lithium aryloxide complexes;18 the majority
of such complexes composed of greater than three Li2O2 rings
form cubanes or hexagonal structures.19 The complex contains
three distinct lithium coordination environments. Li(1) is four-
coordinate, bound in a distorted tetrahedral geometry by two
Ph[OPO] oxygens O(1) and O(1*), the substituted phenoxide O(3),
and a phosphorus P(1*). Li(3) is three-coordinate, bound in a
distorted pyramidal geometry to two Ph[OPO] oxygens O(1) and
O(2*), and the substituted phenoxide O(3*). In contrast, Li(2)
is essentially two-coordinate, bound in a bent configuration to
O(2) and O(3), with an O(2)–Li(2)–O(3) angle of 98.4◦. The low
formal coordination number at lithium is not unusual, however
the bent configuration is not often observed.20–23 The coordination
sphere is augmented by close contacts between Li(2) and one of the
aromatic rings of the ligand, and a methyl group of the nearest t-
butyl moiety. The closest interaction involves the carbon bound to
P–O bond distance of 1.52 A, which is toward the long end of the
literature values.15,16 The phosphine oxide of 1 has been utilized as
an ancillary ligand in early transition metal chemistry;10,17 however,
the solid-state structure of the lithium salt had not been previously
reported.
The modest yields for these lithium salt syntheses suggest that
other reaction pathways are available in these reactions. For
example, during the synthesis of 1, a different lithium complex
can be isolated in low yields from the concentrated toluene
solution after the removal of LiCl but before the addition of
THF. The isolated material has been structurally characterized
as [Ph[OPO]Li2]2(ArOLi)2 (3), where ArOLi is lithium 2,4-di-tert-
butylphenoxide. The solid-state structure is presented in Fig. 3;
crystallographic data are given in Table 5 and selected bond
distances and angles in Table 3. Complex 3 is dimeric in the
sense that it contains two molecules of Ph[OPO]Li2, but also
present are two molecules of ArOLi, and three molecules of co-
crystallized toluene are also present in the unit cell. The core
of Li2O2 rings is arranged in an open ‘S’ shape, a very rare
˚
phosphorus Li(2) · · · C(1) (2.46 A) with other interactions greater
˚
˚
than 2.7 A, while the methyl interaction Li(2) · · · C(44) (2.57 A)
is intermediate. The interactions are all longer than the sum of
the van der Waals radii for lithium and carbon.21 Close contacts
between lithium and saturated and unsaturated carbon fragments
are a common characteristic of coordination complexes where the
lithium is formally two coordinate and there is no Lewis base.22–24
Li–O and Li–P distances agree well with complex 1 and with other
literature values.25–29
In solution 3 is the only lithium complex of [OPO] to display
1
phosphorus lithium coupling, the 31P{ H} NMR spectrum is a
1
1 : 1 : 1 : 1 quartet with a JPLi coupling of 107.1 Hz. This value
is on the large end of the 35–122 Hz range observed for similar
lithium phosphide complexes,30–32 and significantly larger than the
value of 33 Hz observed for Ph[OPO]Li2(DME)2.11
Synthesis of the isopropyl derivative also yields additional
lithium aryloxide complexes, one of which can be obtained in low
yield from the hexanes filtrate following the isolation of 2. Concen-
tration of the hexanes filtrate yields colourless crystals that have
been structurally characterized as [iPr[OPO]Li3Cl(ArOLi)](THF)3
(4). The solid-state structure is shown in Fig. 4, crystallographic
data are given in Table 5, and selected bond distances and angles
are collected in Table 4. The structure contains one molecule
of iPr[OPO]Li2, one molecule of ArOLi, and an equivalent of
lithium chloride arranged in a distorted cubane of Li2O2 rings.
Fig. 3 Molecular structure (ORTEP) of [Ph[OPO]Li2]2(ArOLi)2, 3. Ellip-
soids are drawn at 50% probability.
◦
˚
Table 3 Selected bond distances (A), bond angles ( ), and dihedral angles
(◦) for [Ph[OPO]Li2]2(ArOLi)2, 3
Li(1)–P(1*)
Li(1)–O(1)
Li(1)–O(1*)
Li(1)–O(3)
Li(2)–O(2)
2.467(4)
1.960(4)
2.085(5)
1.883(5)
1.849(5)
Li(3)–O(1)
Li(3)–O(2*)
Li(3)–O(3*)
Li(2)–O(3)
1.897(5)
1.826(5)
2.051(5)
1.869(5)
P(1*)–Li(1)–O(1)
P(1*)–Li(1)–O(1*)
P(1*)–Li(1)–O(3)
Li(1)–P(1*)–C(1)
O(1)–Li(1)–O(1*)
Li(1)–O(1*)–Li(1*)
O(1*)–Li(1*)–O(1)
Li(1*)–O(1)–Li(1)
116.6(2)
Li(1)–O(1*)–Li(3*) 79.46(19)
81.06(14) O(1*)–Li(3*)–O(3) 98.7(2)
125.1(2)
96.44(13) O(3)–Li(1)–O(1*)
96.46(18) Li(2)–O(3)–Li(3*)
83.61(19) O(3)–Li(3*)–O(2)
96.38(14) Li(3*)–O(2)–Li(2)
83.62(19) O(2)–Li(2)–O(3)
Li(3*)–O(3)–Li(1)
80.65(19)
98.0(2)
79.7(2)
93.0(2)
86.4(2)
98.4(2)
Li(1)–O(1)–Li(1*)–O(1*)
O(3)–Li(1)–O(1*)–Li(3*)
Li(2)–O(3)–Li(3*)–O(2)
0.0
14.0(2)
−11.7(2)
Fig. 4 Molecular structure (ORTEP) of [iPr[OPO]Li3Cl-(ArOLi)](THF)3,
4. Ellipsoids are drawn at 50% probability.
Symmetry operator *: −x, −y, 1 − z.
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does provide further evidence for the range of complex structures
available for lithium aryloxide derivatives.
Table 4 Selected bond distances (A), bond angles ( ), and dihedral angles
(◦) for [iPr[OPO]Li3Cl(ArOLi)](THF)3, 4
Li(1)–O(1)
Li(1)–O(4)
Li(1)–Cl(1)
Li(3)–O(1)
Li(3)–O(2)
2.027(4)
1.933(5)
2.445(5)
1.999(3)
1.810(5)
Li(2)–O(1)
Li(2)–O(2)
Li(2)–O(3)
Li(2)–Cl(1)
Li(3)–P(1)
2.000(4)
1.999(4)
1.929(4)
2.445(4)
2.340(5)
Experimental
General procedures
Unless otherwise stated, all manipulations were performed under
an atmosphere of dry oxygen-free dinitrogen or argon by means of
standard Schlenk or glovebox techniques (Vacuum Atmospheres
HE-553-2 glovebox equipped with a MO-40-2H purification
system and a −40 ◦C freezer). Anhydrous hexanes and toluene
were purchased from Aldrich, sparged with dinitrogen, and
further dried by passage through a tower of silica followed by
passage through a tower of Ridox (or Q-5) catalyst prior to
use.39 Anhydrous pentane, benzene, tetrahydrofuran and diethyl
ether were purchased from Aldrich, sparged with dinitrogen,
and passed through an Innovative Technologies SPS-PureSolv-
400-4 apparatus. All organic solvents were tested with addition
of sodium benzophenone prior to use to ensure absence of
oxygen and water. Nitrogen gas was dried and deoxygenated by
passage through a column containing activated molecular sieves
and MnO.
O(1)–Li(2)–O(2)
Li(2)–O(2)–Li(3)
O(2)–Li(3)–O(1)
Li(3)–O(1)–Li(2)
Li(1)–O(1)–Li(2)
O(1)–Li(2)–Cl(1)
Li(2)–Cl(1)–Li(1)
Cl(1)–Li(1)–O(1)
O(3)–Li(2)–O(1)
O(3)–Li(2)–O(2)
96.11(16) Cl(1)–Li(2)–O(2)
82.83(16) Li(2)–O(2)–Li(2*)
102.61(18) Li(1)–O(1)–Li(3)
78.28(18) O(1)–Li(3)–O(1*)
88.50(19) P(1)–Li(3)–O(1)
100.15(15) P(1)–Li(3)–O(2)
70.16(12) O(4)–Li(1)–O(1)
99.39(17) O(4)–Li(1)–Cl(1)
95.80(16)
92.5(2)
82.99(15)
96.8(2)
86.40(15)
166.2(3)
120.79(17)
116.7(2)
114.07(17)
132.7(2)
O(3)–Li(2)–Cl(1)
111.01(19)
Li(1)–O(1)–Li(3)–O(1*)
Li(3)–O(2)–Li(2*)–O(1*)
Cl(1)–Li(2)–O(2)–Li(2*)
11.3(2)
3.2(2)
15.2(2)
Symmetry operator *: x, 1/2 − y, z.
Each lithium is four-coordinate, bound in a distorted tetrahedral
geometry, and Li–O, Li–P and Li–Cl bond distances are in
agreement with previously discussed complexes and literature
values. Incorporation of a chloride in place of an oxygen in lithium
aryloxide cubane structures is very rare, only three examples are
known.33,34 However, lithium chloride adducts, or ‘ate’ complexes,
are very common in early transition metal and lanthanide
aryloxide chemistry,35 where the retention of lithium chloride is at
least partially driven by the electron deficient nature of the metal
center,36,37 and the oxophilic nature of lithium.34,38 Thus, their rarity
in lithium aryloxide chemistry could be attributed to the ease of
deprotonation reactions for their synthesis and a relative lack of
salt metathesis pathways.
Formation of complexes 3 and 4 is capricious in nature and
isolated yields can vary from reaction to reaction. However, the
low yields of both 3 and 4 suggest that the lithium 2,4-di-tert-
butylphenoxide impurity is also small, of the order of 1–2%. The
most likely source of the phenoxide is from trace amounts of non-
brominated phenol in the reaction mixture, although a reaction
of adventitious water with a lithium intermediate cannot be ruled
out.
Deuterated benzene was dried by refluxing with molten
sodium/potassium alloy in a sealed vessel under partial pres-
sure, then trap-to-trap distilled, and freeze–pump–thaw-degassed
31
1
1
three times. 1H, 31P, 1H{ P}, 31P{ H}, 7Li{ H} NMR spectra
were recorded on either a Bruker AMX-500 instrument operating
at 500.13 MHz for 1H spectra, a Bruker AVA-400 instrument
1
operating at 400.13 MHz for H spectra, or a Bruker AVA-300
1
1
instrument operating at 300.13 MHz for H spectra. H NMR
spectra were referenced to residual protons in deuterated solvent
as follows: CDCl3 (d 7.24) and C6D5H (d 7.15) with respect to
tetramethylsilane at d 0.0. 31P NMR spectra were referenced to
either external or internal P(OMe)3 (d 141.0 with respect to 85%
1
H3PO4 at d 0.0). 7Li{ H} NMR spectra were referenced to external
LiCl (0.3 M solution in MeOH at d 0.0). Elemental analyses
were performed by Mr P. Borda and Mr M. Lakha and mass
spectrometry (EI/MS on a Kratos MS 50 unless otherwise stated)
by Mr M. Lapawa, all at the University of British Columbia,
Department of Chemistry.
Materials
The compounds 2,4-di-tert-butylphenol and n-bromosuccinimide
were purchased from Aldrich and used as received. Dichloro-
phenylphosphine (PhPCl2) and dichloroispropylphosphine
(iPrPCl2) were purchased from Strem Chemicals and used
without further purification.
Conclusions
This work illustrates the complexity of lithium–aryloxide struc-
tures that can be obtained from very similar materials. Isolation of
the dilithium salt of the Ph[OPO] ligand from 1,2-dimethoxyethane
results in a completely different structural motif as compared to
isolation of the same material from tetrahydrofuran: the former
is a monomeric dilithio species, whereas the latter is a bridged
dimer that has a step-form structure linking the four lithium
cations. Oxidation of the iPr[OPO] ligand results in a new structural
form that now shows a cubane geometry in the solid state. The
presence of small impurities can also lead to the isolation of new
structure types as indicated by the [iPr[OPO]Li3Cl(ArOLi)](THF)3
derivative. While this species and the oxidized iPr[OPO] system
are not available on synthetic scales, their adventitious isolation
Synthesis of 2-bromo-4,6-di-tert-butylphenol10
n-Bromosuccinimide (18.21 g, 102.3 mmol) was added in portions
to a solution of 2,4-di-tert-butylphenol (20.10 g, 97.4 mmol) in
CH3CN (300 mL) at 0 ◦C with stirring. The bright yellow solution
was then warmed slowly to ambient temperature and the resulting
orange solution stirred for 12 h. The reaction was quenched with
a saturated solution of sodium bisulfite (10 mL), and the resultant
mixture was extracted into petroleum ether (4 × 50 mL) and
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−37.56 (s). Li{ H} NMR (194.3 MHz, C6D6, 25 ◦C): d −1.06
(br s). MS (EI) m/z, (%): 1060, (100) [M − (THF)4]+. Anal. calcd
for C84H122Li4O8P2·2C6H6: C, 76.57; H, 8.97. Found: C, 76.33; H,
9.05%.
7
1
quickly filtered through a small plug of silica gel. Evaporation
of the solvent gave the product as a colourless solid. Yield 23.12 g
(83%). 1H NMR (300 MHz, CDCl3, 25 ◦C): d 7.22 (s, 1H, Ph), 7.18
(S, 1H, Ph), 5.58 (s, 1H, OH), 1.31 (s, 9H, o-PhC(CH3)3), 1.21 (s,
9H, p-PhC(CH3)3.
Synthesis of (iPr[OPO]Li2)2(THF)4 (2)
Synthesis of (Ph[OPO]Li2)2(THF)4 (1)
With the same procedure described above for 1, the bromophenol
(7.87 g, 27.59 mmol) was reacted with iPrPCl2 (2.00 g, 13.80 mmol).
Yield: 8.84 g (51%).◦ Calc. MW: 1281.54 g mol−1. 1H NMR
(300 MHz, C6D6, 25 C): d 7.72–7.46 (m, 8H, Ph), 3.06 (s, 16H,
THF-OCH2CH2), 2.92 (m, 2H, P–CH(CH3)2), 1.64 (s, 36H, o-
To a solution of the bromophenol (20.24 g, 70.96 mmol) in
Et2O (150 mL) was added a 1.6 M solution of BuLi in hexanes
(95.0 mL, 152.0 mmol) dropwise at −78 ◦C. The solution was
warmed to ambient temperature. After stirring for 1 h the solution
was cooled to −78 ◦C and PhPCl2 (4.8 mL, 35.4 mmol) was
added dropwise by syringe. The solution was allowed to warm
to ambient temperature slowly, stirred for 8 h, and then the
solvent was removed under vacuum. The residue was extracted
with toluene (100 mL), the solution filtered through Celite and
evaporated to dryness. The pale yellow residue was slurried in
hexanes (50 mL), THF was added (10.30 g, 142 mmol) and the
solution cooled to −40 ◦C. The resulting colourless microcrystals
were collected, washed with minimal pentane and dried under
vacuum. Yield: 16.73 g (70%). Calc. MW: 1349.58 g mol−1. X-Ray
quality crystals of 1 containing three molecules of co-crystallized
solvent were grown by slow evaporation of a saturated benzene
3
PhC(CH3)3), 1.36 (s, 36H, p-PhC(CH3)3), 1.39 (d, J = 12.5 Hz,
1
12H, P–CH(CH3)2), 1.24 (s, 16H, THF-OCH2CH2). 31P{ H}
◦
7
1
NMR (121.4 MHz, C6D6, 25 C): d −29.56 (s). Li{ H} NMR
◦
(194.3 MHz, C6D6, 25 C): d −0.72 (s, 2Li), −1.22 (s, 2Li). MS
(EI) m/z, (%): 969, (100) [M − (THF)4]+. Elemental analysis was
not obtained.
Isolation of [Ph[OPO]Li2]2(ArOLi)2 (3)
During the synthesis of 1, prior to the addition of THF, a
concentrated toluene solution was allowed to stand for 24 h during
which time a colourless solid crystallized. Several X-ray quality
crystals of 3 were removed and the remaining solid was isolated
by filtration and dried under vacuum. Yield: 0.8 g (4.5%) based on
bromophenol. 1H NMR (300 MHz, C6D6, 25 ◦C): d 7.63–7.03 (m,
24H, Ph), 1.46 (s, 18H, o-PhC(CH3)3), 1.39 (s, 36H, o-PhC(CH3)3),
solution. H NMR (500 MHz, C6D6, 25 ◦C): d 7.53 (m, 10H,
1
Ph), 7.06 (m, 8H, Ph), 3.29 (16, 8H, THF-OCH2CH2), 1.60 (s,
36H, o-PhC(CH3)3), 1.30 (s, 36H, p-PhC(CH3)3), 1.26 (s, 16H,
THF-OCH2CH2). 31P{ H} NMR (202.4 MHz, C6D6, 25 ◦C): d
1
Table 5 Crystallographic and structure refinement data for (Ph[OPO]Li2)2(THF)4 (1), [iPr[OP( O)O]Li2(H2O)]2 (2-O), [Ph[OPO]Li2]2(ArOLi)2 (3), and
=
[
iPr[OPO]Li3Cl(ArOLi)](THF)3 (4)
iPr
Ph[OPO]Li2)2(THF)4 (1)
[
[OP( O)O]Li2 (H2O)]2 (2-O)
[
Ph[OPO]Li2(ArOLi)]2 (3)
[
iPr[OPO]Li3Cl(ArOLi)] (THF)3 (4)
=
(
CCDC number
Formula
M
653592
653593
653594
653595
C57H92ClLi4O6P
968.55
C84H122Li4O8P2·3C6H6
C62H98Li4O8P2·4C6H6
C96H132Li6O6P2·3C7H8
1583.84
1369.50
1747.97
Colour, habit
Crystal size/mm
Crystal system
Space group
a/
Colourless, irregular
0.25 × 0.15 × 0.05
Triclinic
Colourless, block
0.30 × 0.20 × 0.20
Monoclinic
P21/c (no. 14)
10.2530(11)
19.8120(16)
20.8950(19)
90
Colourless, irregular
0.50 × 0.20 × 0.20
Triclinic
Colourless, rod
0.35 × 0.25 × 0.10
Orthorhombic
Pnma (no. 62)
17.7457(3)
18.2033(4)
18.3850(3)
90
¯
¯
P1 (no. 2)
P1 (no. 2)
13.4016(13)
13.8466(17)
27.718(3)
77.004(5)
80.257(4)
76.333(4)
4833.1(9)
2
12.9823(14)
15.5897(15)
16.1226(16)
103.686(2)
101.950(1)
111.550(2)
2788.4(8)
1
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
102.419(3)
90
4145.1(7)
90
90
3
˚
V/A
5938.91(19)
4
Z
2
T/◦C
−100
1.088
1716
1
−100
1.097
1480
1
−100
1.041
946
1
−100
1.082
2104
1
qcalc/g cm−3
F(000)
l(Mo-Ka)/mm−1
0.097
0.104
0.088
0.135
Transmission factors
0.8956–1.0000
56.0
0.8924–1.0000
53.4
0.8895–1.0000
55.6
0.9013–1.0000
54.1
◦
2hmax
/
Total no. of reflns
No. of unique reflns
Rmerge
72152
23119
0.0318
23709
8047
0.0421
6000
25238
11572
0.0526
8470
130426
6708
0.0462
5011
No. reflns with I ≥ 2r(I) 17228
No. of variables
R (F2, all data)
Rw (F2, all data)
R (F, I >2r(I))
Rw (F, I >2r(I))
GOF
1057
475
653
389
0.0765
0.1466
0.0533
0.1332
1.035
0.1013
0.2212
0.0765
0.1980
1.060
0.1102
0.2190
0.0806
0.1942
1.047
0.0756
0.1670
0.0526
0.1490
1.037
804 | Dalton Trans., 2008, 800–806
This journal is
The Royal Society of Chemistry 2008
©

View Article Online
1
1.34 (s, 36H, p-PhC(CH3)3), 1.25 (s, 18H, p-PhC(CH3)3). 31P{ H}
Acknowledgements
NMR (121.4 MHz, C6D6, 25 ◦C): d −31.87 (q, 1JPLi = 107.1 Hz).
◦
7Li{ H} NMR (155.5 MHz, C6D6, 25 C): d −1.13 (d, JPLi
=
1
1
Dr B. O. Patrick is gratefully thanked for crystallography assis-
tance. We thank the NSERC of Canada for generous financial
support.
107.1 Hz, O–LiP–O), −1.34 (s), −1.84 (s). MS (EI) m/z, (%):
1485, (34) [M]+. Elemental analysis was not obtained.
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806 | Dalton Trans., 2008, 800–806
This journal is
The Royal Society of Chemistry 2008
©