Lithium oligophosphanediides in the Li/PhPCl2 system

Article abstract of DOI:10.1002/ejic.200600571

Optimized conditions for the selective synthesis of [Li₂(P _nPh_n)(tmeda)_x] (n = 2, 3, 4) have been developed. X-ray diffraction with single crystals show [Li₂(P ₂Ph₂)(tmeda)₂

Full text of DOI:10.1002/ejic.200600571

FULL PAPER
DOI: 10.1002/ejic.200600571
Lithium Oligophosphanediides in the Li/PhPCl2 System
Daniel Stein,[a] Alk Dransfeld,[b] Michaela Flock,[b] Heinz Rüegger,[a] and
Hansjörg Grützmacher*[a]
Keywords: Alkali metals / Dianions / Ion pairs / NMR spectroscopy / Phosphorus / Reduction
Optimized conditions for the selective synthesis of
[Li2(PnPhn)(tmeda)x] (n = 2, 3, 4) have been developed. X-ray
diffraction with single crystals show [Li2(P2Ph2)(tmeda)2] and
[Li2(P4Ph4)(tmeda)2] to be ion triples, while for n = 3 the ion
pair [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– is observed. NMR ex-
periments support the assumption that these structures are
retained in solution. Structural differences between the lith-
ium and the corresponding sodium compounds, [Na2(PnPhn)-
(tmeda)x], can be partially rationalized using the electrostatic
stabilization parameters, ESP = Σ(1/rM+,M+) + Σ(1/rP–,P–) – Σ(1/
rM+,P–); M = Li, Na.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
tem in organic solvents.[4] Figure 1 summarizes these re-
sults.
Introduction
Compound I consists of a [Na(dme)3]+ cation and the
cluster anion [Na5(P2Ph2)3(dme)3]– (see Figure 1a for a
schematic representation and Figure 1b for a space-filling
model). The structure of II is shown in Figure 1 (c and d),
parts e and f show the structure of IIIa as a representative
of all [M2(P4Ph4)(solv)n] compounds. A solvent molecule
acts as bridging ligand L (L = dme, tmu, or thf) between
the two Na+ ions in IIIb–d. In the schematic pictures of the
structures of I, II, and III, a plus sign is placed at the posi-
tion of the sodium cations and a minus sign at the terminal
phosphorus centers of the dianionic (PnPhn)2– chains. Com-
pounds II and III are classical ion triples (two cations, one
dianion). The cluster anion in I may be viewed as a cyclic
trimer of a corner-sharing ion triple that is additionally
capped by two sodium cations on the top and bottom of
the central hexagonal P6 prism. With the structural param-
eters of these ionic aggregates, the electrostatic stabilization
parameter (ESP) given by Equation (1) was calculated. The
resulting data are listed in Table 1.
Dichlorophenylphosphane (PhPCl2; also known as phen-
ylphosphonous acid dichloride) is a versatile starting mate-
rial in organophosphorus chemistry that is produced on a
large scale from PCl3 and benzene.[1] Its reductive dehaloge-
nation reaction with alkali metals (M) to give cyclic oligo-
(phenyl)phosphanes, (PhP)n (n = 3–6) has been investigat-
ed.[2a–2j] Further reaction of (PhP)n with strongly reducing
metals (M = Li, Na, or K) leads to reductive bond cleavage
(RBC) and formation of alkali metal catena-oligo-
phosphane-α,ω-diides, [M2(PnPhn)(solv)x].[2a,2b,3] In their
pioneering work, Caulton[3a] and Baudler[3b,3c] were able to
obtain some structural information about the dimetal 1,2,3-
triphenyltriphosphane-1,3-diides [M2(P3Ph3)(solv)x] and
the
1,2,3,4-tetraphenyltetraphosphane-1,4-diides
[M2-
(P4Ph4)(solv)x] from 31P NMR spectroscopy in solution.
Recently, Hey-Hawkins et al.[4] and ourselves[5a–5c] have suc-
ceeded in the crystallization of various sodium catena-oligo-
phosphane-α,ω-diides, namely 1,2-diphenyldiphosphane-
1,2-diide [Na6(P2Ph2)3(dme)3] (I),[5a] 1,2,3-triphenyltriphos-
phane-1,3-diide [Na2(P3Ph3)(tmeda)3] (II),[5a] and the
1,2,3,4-tetraphenyltetraphosphane-1,4-diides [Na2(P4Ph4)-
(tmeda)2]
(IIIa),[5a]
[Na2(P4Ph4)(dme)3]
(IIIb),[5a]
[Na2(P4Ph4)(thf)4(tmu)] (IIIc),[5b] and [Na2(P4Ph4)(thf)5]
(IIId) (tmeda = tetramethylethylenediamine, tmu = tetra-
methylurea), which can be isolated from the PhPCl2/Na sys-
(1)
[a] Department of Chemistry and Applied Biosciences, HCI, ETH
Hönggerberg,
8093 Zürich, Switzerland,
Fax: +41-1-632-1032
E-mail: gruetzmacher@inorg.chem.ethz.ch
[b] Institut für Anorganische Chemie der TU Graz,
8010 Graz, Austria
The ESP was introduced by Streitwieser Jr. to account
for the amazingly high stability of ion triples in carbanion
chemistry[6] and is simply the sum of the repulsive inter-
actions between like charges, expressed by (1/r+,+) and
E-mail: alk.dransfeld@tugraz.at
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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Figure 1. Schematic representations and space-filling plots of [Na5(P2Ph2)3]– (a, b), [Na2(P3Ph3)] (c, d), and [Na2(P4Ph4)(L)] (e, f).
Table 1. Repulsive interactions r(Na+Na+) and r(P–P–) [Å] and attractive interactions r(Na+P–) [Å] and the resulting ESPs [Å–1] for I, II,
and IIIa–c. L indicates a bridging dme or tmu ligand between the Na+ ions.
[Na5(P2Ph2)3]–
I
[Na2(P3Ph3)]
II
[Na2(P4Ph4)]
IIIa
[Na2(P4Ph4)L]
IIIb
[Na2(P4Ph4)L]
IIIc
r(Na+Na+)
r(P–P–)
3.669(7)×6
3.96(1)×1
5.35(1)×3
2.20(1)×3
4.66(1)×6
5.10(1)×6
3.063(6)×6
3.158(7)×6
2.831(5)×6
4.092(7)×6
–1.17
4.781(1)
4.587(5)
3.519(6)
3.491(4)
3.146(1)
3.406(3)
3.947(4)
3.475(2)
r(Na+P–)
2.968(1)
2.966(1)
3.106(1)
3.097(1)
–0.79
2.848(4)
2.885(4)
2.829(4)
2.972(5)
–0.87
2.916(6)
2.933(6)
2.960(6)
2.849(6)
–0.84
2.974(2)×2
2.918(2)×2
ESP
–0.77
(1/r–,–), minus the sum of attractive interactions, expressed
The motivation for this work was i) to find reliable condi-
by (1/r+,–). Despite the fact that the ESP treats the ions tions for the synthesis and isolation of the dilithium(catena-
simply as point charges and completely neglects steric inter- oligophosphane-α,ω-diides) [Li2(PnPhn)(solv)x] (here and
actions and solvation energies, it can be used to interpret further on x stands for an unspecified number of solvent
the stability of ion pairs qualitatively. For example, the high molecules), ii) to determine their solid-state structures, and
negative ESP value for I explains why the structure of this iii) to make, whenever possible, proposals for their behavior
cluster is also maintained in solution.[5a] The ESP also indi- in solution. We focused on the isolation of compounds with
cates that ion pairs with the (P3Ph3)2– dianion like II may tmeda as co-ligand for Li+ in order to obtain a set of com-
be labile because of the rather short P1···P3 distance (ca. parable compounds.
3.15 Å) and the significantly longer Na–P distances. These
are caused by repulsive steric interactions between the
Results and Discussion
phenyl groups, especially the one at the central phosphorus
atom, and the solvent molecules coordinated to Na+. In
structures with the (P4Ph4)2– dianion, the steric encum-
brance is less pronounced and the Na+–P– distances are
shorter, which leads to more negative ESPs.
Syntheses
The syntheses that worked best in our hands and gave
good yields of pure isolated and crystalline material are
Only in IIIc, which contains a bridging tmu molecule and outlined in Scheme 1. In a reductive bond cleavage (RBC)
a strongly folded Na2P2 ring, is the Na+–Na+ distance more reaction, pentaphenylcyclopentaphosphane (1)[2i] was
than 1 Å shorter than in IIIa (no bridging L); as a result treated with an excess of lithium powder in THF. The re-
the electrostatic stabilization is slightly less than that of II. sulting orange-red solution showed only one signal at δ =
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Lithium Oligophosphanediides in the Li/PhPCl2 System
FULL PAPER
–102.9 ppm in the 31P NMR spectrum, thus indicating the Structures
2–
formation of the P2 dianion. The primary product,
The structures of the dilithium catena-oligophosphane-
α,ω-diides [Li2(PnPhn)] (n = 2–4) were investigated by X-ray
diffraction studies. All compounds contain tmeda mole-
cules as co-ligands bonded to the lithium ions. The Li+Li+,
P–P–, and Li+P– distances in 2, 3, and 4 are listed in Table 2.
The centrosymmetric structure of 2 (Figure 2) can be
viewed as the archetypical structure of an ion triple with
two formal negative charges in the α-position of the di-
anion. The P–P distance [2.244(3) Å] is slightly longer than
the comparable one in the sodium compound [2.20(1) Å].
The main structural difference resides in the orientation of
the phenyl rings, which are in a trans arrangement in 2 while
they take a gauche conformation in the cluster anion
[Na5(P2Ph2)3]– of I (the C–P–P–C torsion angle is about
–72°[5a]). The Ph–P–P–Ph moiety in 2 is planar. As a result
of the short attractive Li+–P– interactions, the ESP for 2
(–0.94 Å–1) is considerably more negative than the ESP
(–0.72 Å–1) for a hypothetical [Na2(P2Ph2)] ion triple with
a structure analogous to that of 2 (an Na–P distance of
2.98 Å, which is the average of the data listed in Table 1, is
assumed).
[Li2(P2Ph2)(thf)x] (2Ј) was obtained as red powder after
evaporation of the solvent. Subsequent recrystallization of
2Ј from hot toluene/tmeda (2:1 by vol.) gave red crystals of
[Li2(P2Ph2)(tmeda)2] (2).
Scheme 1. Syntheses of isolable dilithium(catena-oligophosphane-
α,ω-diides), [Li2(PnPhn)(tmeda)m] 2 (n = 2, m = 2), 3 (n = 3, m =
3), and 4 (n = 4, m = 2).
The best synthesis for dilithium 1,2,3-triphenyltriphos-
phane-1,3-diide (3) was found to be the reaction of (PhP)5
with a stoichiometric amount of lithium in dme as reaction
medium. In this solvent, the product [Li2(P3Ph3)(dme)x] (3Ј)
precipitates directly from the reaction mixture as a bright-
orange powder in good yield (about 70%). The content of
dme (x = 2–3) was estimated by NMR spectroscopy. Sub-
sequently, 3Ј was dissolved in a 5:1 mixture of toluene and
tmeda and this solution was concentrated to dryness under
high vacuum to remove all volatiles, especially dme; the re-
sulting yellow powder was recrystallized at 7 °C from tolu-
ene to give yellow crystals of the composition [Li2(P3Ph3)-
(tmeda)3] (3).
Figure 2. Structure of 2. Selected distances [Å] and angles [°]: P1–
P1 2.244(3), Li–P1 2.483(1), P1–C1 1.820(1), Li–N1 2.077(1); C1–
P1–P1 98.66(2), C1–P1–Li 93.90(1), Li–P1–Li 126.28(3); torsion
angles: Li–P1–LiA–P1A 0.0, P1A–P1–C1–C2 0.0, C1–P1–P1A–
C1A 180.0.
The best method for the synthesis of pure dilithium
1,2,3,4-tetraphenyltetraphosphane-1,4-diide (4) turned out
to be the stoichiometric reaction of 3Ј with (PhP)5 (1) in
diethyl ether. After removal of all volatiles under vacuum,
the resulting orange powder (4Ј) of composition
In the solid state, 3 forms an ion pair composed of a
[Li2(P4Ph4)(solv)x] (solv = Et2O, dme) was dissolved in a [Li(tmeda)2]+ cation and an anionic ion double, namely
10:3 mixture of toluene and tmeda, again concentrated to [Li(P3Ph3)(tmeda)]–. Only one lithium ion coordinates to
dryness under vacuum, and then recrystallized from methyl the terminal phosphorus atoms P1 and P3 and, as expected
tert-butyl ether (mtbe) to give slightly yellow crystals of the for steric reasons, the coordination occurs from the oppo-
composition [Li2(P4Ph4)(tmeda)2] (4). Attempts to synthe- site site to the central phenyl group at P2. The distance
size 4Ј or 4 by a direct RBC reaction of 1 with the corre- between the two terminal phosphorus atoms P1 and P3 in
sponding amount of lithium gave a lower yield (Ͻ50%).
2 is about 0.2 Å longer (the P–P–P angle is about 8° larger)
Table 2. Selected distances [Å] and the resulting ESPs for 2–4.
[Li2(P2Ph2)(tmeda)2]
[Li(tmeda)2]+[Li(P3Ph3)(tmeda)]–
[Li2(P4Ph4)(tmeda)2]
r(Li+Li+)
r(P–P–)
r(Li+P–)
ESP
4.430(2)
2.244(3)
2.483(1)×4
–0.94
–
3.967(2)
3.229(2)
2.618(4)×2, 2.653(4)×2
–0.96
3.347(1)
2.499(7), 2.525(7)
–0.50
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FULL PAPER
than in the neutral ion triple [Na2(P3Ph3)(tmeda)3] (II), phenyl rings. Both features are also observed in the sodium
where two sodium ions coordinate to P1 and P3. The only compound. However, due to the short Li+–P– distances, the
other known triphosphanediide is found in the highly un- ESP for this ion triple is rather high (–0.96 Å–1).
stable ion pair [Na(NH3)5]+[Na(P3H3)(NH3)3]–, which con-
tains the anionic ion double [Na(P3H3)(NH3)3]–.[7] An even
longer P––P– distance (3.67 Å) and larger P–P–P angle
(113.4°) is observed in this compound. An increase of the
P––P– distance will help to diminish the repulsive interac-
tions in the ion doubles which, evidently, have less negative
ESPs than the ion triples because of the long and hence
less stabilizing Na–P distances {–0.79 Å–1 for [Na2-
(P3Ph3)(tmeda)3] II, –0.50 for [Li(P3Ph3)(tmeda)]–, and
only –0.37 for [Na(P3H3)]–}. This loss of stabilizing electro-
static energy in the anionic ion doubles is compensated for
by the solvation energy of the counter cations. Because
these are much higher for lithium than for sodium,[8,9] the
formation of an ion pair in the case of 3 and the formation
of an ion triple for the sodium compound II is easily under-
stood (Figure 3). Note that in the other ion pair, [Na-
(NH3)5]+[Na(P3H3)(NH3)3]–, the smaller size of the ammo-
nia ligand compared to tmeda allows a higher coordination
number at the sodium cations and a better solvation.
Hence, the loss of ESP on going from the ion triple to the
ion double can be compensated.
Figure 4. Structure of 4. Selected distances [Å] and angles [°]: Li–
P1 2.618(4), Li–P1A 2.652(4), Li–N1 2.144(4), Li–N2 2.095(5), P1–
P2 2.167(1), P1–C1 1.832(2), P2–P2A 2.190(1), P2–C7 1.851(2);
P1–Li–P1A 75.6(1), C1–P1–P2 102.26(9), P1–P2–P2A 103.37(2),
P1–P2–C7 105.55(9), P2–P2A–C7A 99.70(8); torsion angles: P1–
P2–P2A–P1A –13.3(1), C1–P1–P2–P2A –160.33(8), C1–P1–P2–C7
95.4(1), Li1–P1–P2–P2A –39.2(1), Li1A–P1A–P2A–P2 58.8(1).
The P–P distances for the (P2Ph2)2–, (P3Ph3)2–, and
(P4Ph4)2– dianions are very similar in the lithium and so-
dium compounds. In the dianions of 2 and I, the P–P dis-
tance is greater than 2.2 Å, whereas in the dianions in 3 and
II it is below 2.2 Å. The terminal P–P bonds in the
(P4Ph4)2– dianions in 4 and IIIa–d are very slightly shorter
(ca. 2.17 Å) than the central P–P bond (ca. 2.20 Å). The
bonds between the formally negatively charged terminal
phosphorus centers and the ipso-carbon atoms of the
phenyl rings are a little shorter (by ca. 0.04 Å) in all com-
pounds than the P–Cipso bonds at the central phosphorus
atoms. This observation may be taken as an indication of
some delocalization of the negative charges into the phenyl
groups, although this effect is small compared to amides.[10]
NMR Spectra
The compound [Li2(P2Ph2)(tmeda)2] (2) is sparingly solu-
Figure 3. Structure of 3. Selected distances [Å] and angles [°]: P1–
P2 2.179(1), P2–P3 2.177(1), P1–C1 1.814(3), P2–C7 1.847(3), P3–
C13 1.819(4), P1–Li1 2.493(7), P3–Li1 2.525(6), P1–P3 3.347(1),
P1–P2–P3 100.02(5), P1–Li1–P3 83.37(2), C1–P1–P2 103.7(1), C7–
P2–P3 105.8(1), C7–P2–P1 104.0(1), C13–P3–P2 102.8(1); torsion
angles: C1–P1–P2–C7 106.7(2), C1–P1–P2–P3 40.9(2), C7–P2–P3–
C13 112.9(2), C13–P3–P2–P1 139.3(1), Li1–P1–P2–C7 150.1(2),
Li1–P3–P2–C7 148.2(2).
ble in hydrocarbons but sufficiently soluble in [D8]thf to
1
7
obtain H, 13C, 31P, and Li NMR spectra. All data corre-
spond quite closely with those observed for the sodium
cluster anion [Na5(P2Ph2)3(dme)3]– in I. The ipso-13C car-
bon resonances of the phenyl groups are observed at δ =
162.2 ppm (δ = 160.7 ppm in I) and the 31P NMR shifts
also vary little (δ = –102.9 ppm in 2, δ = –106.4 ppm in I).
Unfortunately, the 31P-7Li couplings could not be resolved
7
Finally, the structure of 4 was investigated. This com- in the Li NMR spectrum (broad signal at δ = 0.6 ppm).
pound has a composition very close to the corresponding However, in view of the large loss of electrostatic stabiliza-
sodium compound IIIa (both contain two tmeda molecules) tion energy upon dissociation of the ion triple into the ion
and the solid-state structures are also very similar (Fig- pair [Li(solv)x][Li(P2Ph2)(solv)y], we believe that the struc-
ure 4). Compounds 4 and IIIa are obtained as racemic mix- ture of 2 is retained in solution.
tures and form ion triples in which the P4 chain has either
A
[D8]toluene solution of the salt [Li(tmeda)2]+-
an (R,R)- or an (S,S)-configuration. Note the highly dis- [Li(P3Ph3)(tmeda)]– (3) shows an AM2 spin system with two
torted coordination spheres around the lithium atoms and multiplets centered at δA(31P) = –52.3 ppm and δM(31P) =
their contacts to the ipso-carbon atoms of the central –71.5 ppm. From a simulation of the spectrum, the coup-
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Lithium Oligophosphanediides in the Li/PhPCl2 System
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ling constant 1JA,M Ϸ 224 Hz was obtained. These data are the Li-coordinated solvent molecules. On the contrary, the
very different from those for the sodium compound very different 31P NMR chemical shifts for the sodium
[Na2(P3Ph3)(tmeda)3] (II), which shows an eight-line AB2 compound indicate that this forms an intact ion triple in
spin system with δA = –54.0 and δB = –56.7 ppm (1JA,B
242 Hz). This finding indicates that different species con-
=
solution.
The tetraphosphanediide [Li2(P4Ph4)(tmeda)2] (4) is suf-
taining the P3Ph3 unit are present in solution. The 7Li ficiently soluble in [D8]toluene to allow NMR measure-
NMR spectrum in [D8]toluene at low temperature confirms ments. At room temperature, ill-resolved multiplets at δ =
this assumption: two signals are observed, one broad singlet –35 to –39 ppm and very broad signals at about δ Ϸ –76
at δ = 10.5 ppm for the [Li(tmeda)2]+ cation and one broad and δ Ϸ –95 ppm are observed. At low temperature
multiplet at δ = 11.4 ppm for the [Li(P3Ph3)(tmeda)]– anion, (248 K), two species (4 and 4ЈЈ) are observed in a 100:80
that is, 3 exists as an ion pair in solution, as observed in the ratio in the 31P NMR spectrum (see Figure 5, a). The major
solid state. That we could not resolve the 31P-7Li coupling is compound 4 shows two multiplets of an AAЈBBЈX2 spin
probably due to dynamic processes involving exchange of system in the 31P NMR spectrum with chemical shifts at
Figure 5. a) Experimental and simulated 31P NMR spectra of [Li2(P4Ph4)(tmeda)2] (4) and 4ЈЈ (marked with asterisks) in toluene solution
at T = 248 K. Chemical shifts and coupling constants are given in Table 3. b) 31P CMAS spectrum of [Li2(P4Ph4)(tmeda)2] (4). Top:
experimental spectrum at 6000 Hz rotation frequency. Bottom: simulated spectrum with: P2,3: δiso = –38.0, δ11 = 33, δ22 = 13, δ33
–159 ppm; P1,4: δiso = –86.3, δ11 = 20, δ22 = –62, δ33 = –217 ppm.
=
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δ = –38.0 for P2,3 and δ = –95.1 ppm for P1,4. The X part cases the compound exists as the ion triple − we assume a
is observed in the 7Li NMR spectrum, where a slightly slightly different conformation in solution, which might be
broadened triplet at δ = 10.9 ppm is observed (1JLi,P
37 Hz).
=
due to loss of the Li–Cipso interaction present in the solid
phase.
The resonances of the protons in the para-position of the
The other species (4ЈЈ) observed in [D8]toluene solution
phenyl rings are sharp, whereas those of the ortho- and at 248 K also shows an AAЈBBЈX spin system (marked with
meta-protons are broadened at low temperature. This is asterisks in Figure 5a) with chemical shifts at δ
=
probably due to hindered rotation of the phenyl groups in –39.7 ppm for P2,3 and a broad resonance at δ = –74.4 ppm
4. This species corresponds to the ion triple with a structure for P1,4 in the 31P NMR spectrum. For this species, no sig-
7
close to that observed in the solid state.
nal could be found in the Li NMR spectrum.
This is further bolstered by the solid-state 31P CPMAS
spectrum of 4 (Figure 5, b). Only one species is present in
the isolated crystalline material. The observation of only
two isotropic chemical shifts (δiso = –38.0 and –86.3 ppm
for the central and terminal P spins, respectively) is in agree-
ment with the crystallographic C2 symmetry of the ion
triple 4 (see Figure 4). The principal elements of the chemi-
cal shift tensor, δ11 = 33, δ22 = 13, δ33 = –159 and δ11 = 20,
δ22 = –62, δ33 = –217 ppm were obtained by a Herzfeld–
Berger[11] analysis of the intensities of the spinning
side-bands and refined by spectral simulation using the
SIMPSON package.[12] It should be noted that the fine
structure observed in the resonances shown in Figure 5 (b)
is a consequence of orientation-dependent cross-terms in-
volving the scalar and dipolar coupling and the chemical
shift interactions and depends significantly on the fre-
quency of magic angle spinning.[13] For the purpose of spec-
tral simulation, phosphorus–phosphorus scalar coupling
constants were taken into account as their isotropic solu-
tion values (Table 3) but were not refined, and coupling to
the lithium isotopes was accounted for by processing with
an appropriate Gaussian line-shape function.
Computations
Recently, Kaupp et al. have calculated the dependence of
the JP,P coupling constants for the conformations A and B
of the P4 chain based on the experimentally known
M2(P4R4) structures (Figure 6).[14] The coupling constants
given in Table 3 depend on the alignment of nonbonding
electron pairs at the phosphorus centers. In A, which has a
small P–P–P–P torsion angle φ, the couplings follow the
order J1,4 (Ͼ300 Hz) ϾϾ J1,3/J2,4 (11–35 Hz), whereas in B,
Figure 6. Conformations of the P4 chains in tetraphosphanediides
of type A {found in all [M2(P4Ph4)(solv)x] with M = Li, Na, and
[Na2(P4tBu4)(thf)4]} and B {observed in [M2(P4Mes4)(thf)x] M =
Na, x = 4; M = K, x = 6}. The ipso carbons of the aryl groups are
indicated as Ci and the nonbonding electron pairs at the phospho-
It is interesting to note that while the isotropic chemical
shifts of the central phosphorus atoms (δiso = –38.0 ppm)
are equal, those of the terminal ones differ (δiso = –86.3
and –95.1 ppm in the solid state and solution, respectively).
As there is no doubt about the constitution of 4 − in both rus centers are shown as magenta-colored arrows.
Table 3. Experimentally derived 31P–31P coupling constants [Hz] of the P1–P2–P3–P4 chain in IIIa,[5a] [Na2(P4tBu4)(thf)4],[4] [Na2-
[b]
[b]
(P4Mes4)(thf)4],[4] 4, and 4ЈЈ. The computed,[a] geometric, and magnetic properties for Li2(P4H4)opt
,
Na2(P4H4)opt
,
Li2(P4Ph4)-
[c]
[c]
(tmeda)2,cry,trunc
,
and the Li2(tmeda)1(P4Ph4)opt,trunc isomers A and B are also given.
1
1
Entry
Experimental
Type
P1–P2/P3–P4 [d] J1,2/1J3,4
P2–P3 J2,3
φ
J1,3/J2,4 P1···P4 J1,4
1
2
3
4
5
[Na2(P4Ph4)(tmeda)2] (IIIa)
[Na2(P4tBu4)(thf)4]
[Na2(P4Mes4)(thf)4]
[Li2(P4Ph4)(tmeda)2] (4)
4ЈЈ
A
A
B
2.160
2.169
2.165
2.166
–322
–341
–310
–271
–266
2.185 –306
2.222 –306
2.261 –118
2.190 –268
–15
20.3 –11
8.8 –13
72.7 120
13.3 –35
67
3.406 310
3.615 201
4.247
3
A
3.229 310
280
Calculated
[b]
6
7
8
9
10
11
[Na2(P4H4)]opt
A
A
A
A
2.251
2.166
2.248
2.166
2.215/2.231
2.213
–200
–304
–190
–267
2.248 –229
2.207 –323
2.252 –204
2.190 –321
25.7 –26
32.1 –21
24.3 –22
13.3 –29
23.6 –27/–20 3.364 417
38.3 –25 3.451 323
3.644 292
3.486 432
3.414 320
3.229 529
[14]
[a]
[Na2(P4Ph4)(thf)2.5 cry,trunc
]
[b]
[Li2(P4H4)]opt
[Li2(P4Ph4)(tmeda)2]cry,trunc
[c]
Li2(tmeda)1(P4Ph4)opt,trunc; Isomer A
–270/–259 2.254 –323
–305 2.262 –317
Li2(tmeda)1(P4Ph4)opt,trunc; Isomer B[c]
[a] Coupling constants in Hz calculated at GIAO/B3LYP/6-311+G**//B3LYP/6-31G*.[15] [b] opt = properties of B3LYP/6-31G*-optimized
structure. [c] trunc = truncated geometry; the NMR properties are calculated for the molecule where phenyl groups have been replaced
by H atoms at a standard P–H distance of 1.427 Å and solvent molecules (tmeda) are omitted. [d] P1–P2 = P3–P4 if only one distance
1
1
and J1,2 = J3,4 and J1,3 = J2,4 if only one coupling is given.
4162
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Eur. J. Inorg. Chem. 2006, 4157–4167

Lithium Oligophosphanediides in the Li/PhPCl2 System
FULL PAPER
which has a large angle (Ͼ70°), a poor 1,4 alignment of the difference ∆δ = δ(P1,P4) – δ(P2,P3) between the calculated
lone pairs causes the inverse ordering J1,4 (Ͻ5 Hz) ϽϽ J1,3
J2,4 (Ͼ100 Hz).
/
chemical shifts of the terminal and internal 31P nuclei is
strongly dependent on the alkali cation and significantly
larger for Na [Na2(P4H4): ∆δ = –176 ppm, with δ(P1,P4) =
We performed the following computations:[15] i) 31
P
chemical shifts were calculated at the GIAO/B3LYP/6-31G* –232 and δ(P2,P3) = –56 ppm; Li2(P4H4): ∆δ = –137 ppm,
level for a number of structural isomers of molecules of the with δ(P1,P4) = –241 and δ(P2,P3) = –104 ppm]. It is note-
general formula [Li2(P4Ph4)(tmeda)n] (n = 0, 1, 2). The val- worthy that the shifts of the atoms directly attached to the
ues obtained for [Li2(P4Ph4)(tmeda)2] (4) with the structure different cations are less affected than the remote phospho-
observed in the crystal and with the optimized structure rus centers. Although much less pronounced, this is re-
(B3LYP/6-31G*), denoted as 4cry and 4opt, respectively, are flected by the experimental data {[Na2(P4Ph4)(tmeda)2]
δ = –108 (4cry, terminal), –52 (4cry, inner), –70 (4opt, ter- (IIIa): ∆δ = –64.2 ppm with δ(P1,P4) = –89.1 and δ(P2,P3)
minal), and –17 ppm (4opt, inner), respectively. The chemi- = –24.9 ppm; [Li2(P4Ph4)(tmeda)2] (4): ∆δ = –57.1 ppm,
cal shift difference, ∆δ, between the terminal and the inner with δ(P1,P4) = –95.1 and δ(P2,P3) = –38.0 ppm}.
backbone 31P nuclei is rather constant (–53 ppm relaxed
With respect to a possible structure for the second species
and –56 ppm crystal geometry). The calculated data repro- 4ЈЈ in solutions of 4, the data in Table 3 give some hints:
duce the experimental ones satisfactorily, which means that the slightly smaller J1,4 and the positive J1,3 = J2,4 indicate
the chosen theoretical level is sufficient; ii) for comparison, that the conformation of the P4 chain in 4ЈЈ has a P–P–P–
the structures of the simple molecules [Li2(P4H4)] and P torsion angle φ that is significantly larger than in 4 (ϾϾ
[Na(P4H4)] were optimized at the B3LYP/6-31G* level; 20°). The very small 1J2,3 indicates that the P2–P3 bond may
iii) the 31P–31P coupling constants were calculated for also be elongated. The fact that broadened 31P NMR sig-
model compounds in which the structure of the M2P4 core nals for the terminal phosphorus nuclei P1, P4 are observed
7
of the complete [Li2(P4Ph4)(tmeda)n] was maintained but and no Li signal could be recorded even at low tempera-
the phenyl groups were replaced by hydrogen atoms and the tures point to fast exchange processes. For the sodium com-
tmeda molecules omitted. These truncated geometries are pound, we have suggested previously the equilibrium
denoted as [Li2(P4Ph4)(tmeda)n]trunc
Table 3 lists the P–P coupling constants for the sodium δ1 = –73.3, δ2 = –30.8, δ3 = –16.8, and δ4 = –70.4 ppm and
.
[Na2(P4Ph4)(thf)x] p [Na(thf)y]+ + [Na(P4Ph4)(thf)z]–, (with
1
1
tetraphosphanediides
[Na2(P4Ph4)(tmeda)2]
(IIIa),[5a] 1J1,2 = 340, J2,3 = 340, J3,4 = 274, and J2,4 = 148 Hz for
[Na2(P4Ph4)(thf)5] (IIId),[5] [Na2(P4tBu4)(thf)4],[4] and the the [Na(P4Ph4)(thf)z]– anion).[5] A computational search of
lithium tetraphosphanediides 4 and 4Ј as obtained by simu- possible structures for a [Li(P4Ph4)(thf)z]– anion only gave
lating the experimental spectra. The calculated data for species with an almost co-planar P4 chain and at least one
Li2(P4H4)opt
,
Na2(P4H4)opt
,
[Li2(P4Ph4)(tmeda)2]cry,trunc
,
significantly high-frequency-shifted resonance for an in-
and the isomers A and B of Li2(tmeda)(P4Ph4)opt,trunc are ternal phosphorus nucleus (Ͼ39 ppm). This finding is not
given for comparison. We have also included the data of compatible with the experimental results, which show that
[Na2(P4Ph4)(thf)2.5 cry,trunc
]
reported by Kaupp et al.[14]
the chemical shifts of the external 31P nuclei in 4 and 4ЈЈ
The experimental data listed for compounds of structure are quite different. In view of the rather high ESP, it seems
1
1
type A show that the one-bond P–P couplings J1,2 = J3,4 likely that 4ЈЈ also has the structure of an ion triple with a
are somewhat smaller for M = Li (entries 4, 5) than for M strongly distorted P4 chain. We therefore inspected various
= Na (entries 1–3) and this trend is reproduced with the possible structures for 4ЈЈ that contain only one tmeda
calculated model structures (entries 6–9). The P1,2–P3,4 molecule as co-ligand to lithium (Scheme 2).
bonds in the optimized models [M2(P4H4)]opt (M = Li, Na)
Two isomers were found: isomer A, with a chelating
are longer than in the truncated structures [M2(P4H4)]trunc tmeda molecule binding to only one Li ion in a κ2-fashion,
1
and consequently the 1J couplings are smaller. The J2,3 and isomer B, where the tmeda molecule bridges the two
coupling is influenced by both the P2–P3 distance and also lithium ions in a µ2-κ1,κ1-fashion. Isomer A is about
by the dihedral angle φ. In compounds with structure B 3 kcalmol–1 more stable than isomer B. The calculated (gas-
(entry 3), where φ is large, the 1J2,3 coupling is rather small. phase) energies, ∆Hr, for the dissociation of one tmeda from
As expected, the couplings J1,3 = J2,4 in the dilithium tetra- 4 are in a reasonable range (21–24 kcalmol–1; Scheme 2) to
phosphanediide [Li2(P4Ph4)(tmeda)2] (4) are in the range of allow this process in solution. This idea is supported by
the disodium compounds with the same structure type A measuring the diffusion coefficients of the (P4Ph4)2–-con-
and are smaller (entry 4) than for compounds with struc- taining species (0.26746×10–9 m2 s–1) and the tmeda mole-
ture type B (entry 3). The J1,4 coupling shows a dependency cules (0.29214×10–9 m2 s–1) by pulsed field gradient NMR
on the P1···P4 distance and on the dihedral angle φ. At techniques.[16] The significantly larger diffusion coefficient
longer distances (Ͼ3.6 Å), J1,4 decreases (compare entries 2 (ca. 10%) for the tmeda molecules is compatible with the
with entries 1 and 4). To some extent, this is also reflected dissociation process, [Li2(P4Ph4)(tmeda)2] p [Li2(P4Ph4)-
by the calculations (compare entries 6 with 7 and 8 with 9). (tmeda)] + tmeda, where, on average, three tmeda molecule
Especially small values for J1,4 are observed for large tor- are coordinated and one tmeda molecule is free.
sion angles φ (entry 3). In agreement with the experiment,
Indeed, the P–P–P–P torsion angle φ in A (23.6°) and
the calculated coupling constants for [Na2(P4H4)]opt and especially B (38.3°) is somewhat larger than that observed
[Li2(P4H4)]opt show only little differences. Nevertheless, the in crystals (13.3°) and calculated (12°) for 4. For isomer A,
Eur. J. Inorg. Chem. 2006, 4157–4167
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4163

D. Stein, A. Dransfeld, M. Flock, H. Rüegger, H. Grützmacher
FULL PAPER
Scheme 2. Computed reaction enthalpies for the dissociation [Li2(P4Ph4)(tmeda)2] Ǟ [Li2(P4Ph4)(tmeda)] + tmeda.
the predicted 31P chemical shifts are: P1: δ = –74.03 ppm; a larger aggregate. Also, the fact that [Na2(P3Ph3)(solv)x]
P2: δ = 6.87 ppm; P3: δ = –28.52 ppm; P4: δ = –30.06 ppm; forms an intact ion triple but the lithium analogue readily
and for the more symmetric isomer B: P1,P4: δ = –55 ppm; dissociates into an ion pair is expected. Specifically, the
P2,P3: δ = 7 ppm. Considering that the equilibrium shown large drop of the ESP when going from the ion triple
in Scheme 2 is likely to be fast on the NMR timescale, the [Na2(P3Ph3)] (–0.79) to a hypothetical ion pair [Na]+-
chemical shift difference (∆δ = –42 ppm) between the [Na(P3Ph3)]– (ESP = –0.35; calculated with Na–P = 2.98 Å,
averages of the chemical shifts for the external and internal P–P = 3.14 Å) cannot be overcompensated by the solvation
31P nuclei, ½(P1 + P4) = –53 ppm and ½(P2 + P3) = of the dissociated Na+ cation in an organic solvent. Further
–11 ppm, in isomer A fits better the experimental data for studies will concentrate on the question of whether these
4ЈЈ (∆δ = –34.7 ppm) than isomer B (∆δ = –62 ppm). How- different aggregates also have different reactivity.
ever, the agreement between the calculated and experimen-
tal 31P–31P couplings is very poor (see Table 3) and at this
point we cannot draw any definitive conclusion about the
exact nature of 4ЈЈ.
Experimental Section
General Techniques: All manipulations were performed under ar-
gon. All solvents were dried and purified using standard procedures
and were freshly distilled under argon from sodium/benzophenone
(THF, toluene, tmeda, dme, mtbe) or from sodium/diglyme/benzo-
Conclusions
phenone (n-hexane) prior to use. Air sensitive compounds were
stored and weighed in a glove box (Braun MB 150 B-G system)
and reactions on small scale were performed directly in the glove
box.
Optimized conditions for the selective syntheses of di-
lithium (catena-oligophosphane-α,ω-diides) [Li2(PnPhn)-
(solv)x] have bee developed and the species with solv =
tmeda and n = 2, 3, and 4 have been isolated as crystalline
materials and structurally characterized. The compounds
[Li2(P2Ph2)(tmeda)2] and [Li2(P4Ph4)(tmeda)2] form centro-
symmetric genuine ion triples in the solid state and very
NMR Spectra were measured on Bruker AVANCE 500, 400, 300,
and 250 systems. The chemical shifts (δ) are measured according
to IUPAC[17] and expressed in ppm relative to TMS (1H, 13C), LiCl
(7Li), and H3PO4 (31P). No satisfactory elemental analysis could
probably also in solution. The lithium salt of the triphos-
be obtained due to the high air and moisture sensitivity of the
phanediide behaves differently and is an ion pair, [Li-
compounds.
(tmeda)2]+[Li(P3Ph3)(tmeda)]–, in the solid and in solution.
On average, the Li–P bonds (average of Li–P distances
listed in Table 2: 2.55 Å) are 15% shorter than the Na–P
distances (av. 2.98 Å) in comparable sodium oligophos-
Solid State NMR: 31P CP-MAS solid-state NMR spectra were ac-
quired at room temperature on a Bruker Avance instrument op-
erating at a 1H Larmor frequency of 500 MHz. Conventional cross-
polarization and magic-angle-spinning techniques were im-
phane-α,ω-diides (see Table 1). As a consequence, the elec-
trostatic stabilization parameters, ESPs, of the lithium
phosphanediides are significantly larger. Within its limits,
this very simple model, which involves placing point
charges at the positions of the cations and terminal phos-
phorus centers and neglecting all solvation energies and ste-
ric interactions, can be used to rationalize why Li2(P2Ph2)
plemented using 4-mm rotors, with which rotational frequencies of
more than 11 kHz were achieved. The 13C carboxylate resonance
of α-glycine appeared at δ = 176.0 ppm. As a consequence, refer-
encing of all isotopes could be achieved as for the solution NMR
using the unified Ξ scale.[17] Chemical shifts are expressed relative
to H3PO4.
X-ray Crystallographic Investigations and Crystal Data: Data col-
forms a simple ion triple while the sodium analogue forms lection for the X-ray structure determinations were performed on
4164 Eur. J. Inorg. Chem. 2006, 4157–4167
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Lithium Oligophosphanediides in the Li/PhPCl2 System
FULL PAPER
a Bruker SMART Apex diffractometer system with CCD area de-
tector by using graphite-monochromated Mo-Kα (0.71073 Å) radi-
ation and a low-temperature device. Crystals of [Li2(P2Ph2)-
(tmeda)2] (2) suitable for X-ray diffraction were obtained by
crystallization of a saturated toluene/tmeda solution at ambient
temperature. Those of [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– (3) were
grown from a toluene solution at 7 °C and of [Li2(P4Ph4)(tmeda)2]
(4) from a saturated mtbe solution at ambient temperature. In order
to avoid quality degradation the single crystals were mounted in
paraffin oil on top of a glass fiber and then brought into the cold
nitrogen stream of a low-temperature device so that the oil solidi-
fied. All calculations were performed with SHELXTL (ver. 6.12)
and SHELXL-97 (G.M. Sheldrick, Göttingen, 1997). The struc-
tures were solved by direct methods and successive interpretation of
the difference Fourier maps, followed by full-matrix least-squares
refinement (against F2). Moreover, an empirical absorption correc-
tion using SADABS (ver. 2.03) was applied to all structures. All
non-hydrogen atoms were refined anisotropically in the X-ray
structures of [Li2(P2Ph2)(tmeda)2] (2) and [Li2(P4Ph4)(tmeda)2] (4),
whereas the tmeda ligand in [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– (3)
was refined isotropically. The ethylene bridge of the tmeda ligand
is highly disordered on two positions and a large number (17) of
restraints had to be used to achieve a satisfactory wR2 value. The
contribution of the hydrogen atoms, in their calculated positions,
was included in the refinement using a riding model for the X-ray
structures of [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– (3) and [Li2(P4Ph4)-
(tmeda)2] (4). Some hydrogen atoms of [Li2(P2Ph2)(tmeda)2] (2)
could be located in the Fourier difference map and hence were re-
fined freely. The disordering in this molecule, which is caused by a
flip of the Li–P–P–Li plane by 48° with respect to the Li–Li vector,
was fixed using the bond lengths of the main structure, resulting in
a large number (12) of restraints. The contribution of the hydrogen
atoms of the disordered part was included by using a riding model.
Upon convergence, the final Fourier difference map of all struc-
tures showed no significant peaks. Relevant data concerning crys-
tallographic data, data collection, and refinement details are sum-
marized in Table 4.
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif
Computational Methods: Geometries were ab initio optimized[15] at
the B3LYP/6-31G* level unless otherwise stated. Chemical shifts
and nuclear spin-spin coupling constants were obtained for these
geometries and truncated moieties by the GIAO/B3LYP/6-31G*
method. The 31P chemical shift of PH3 (δ = 586 ppm) was calcu-
lated using a B3LYP/6-31G* structure at the GIAO/B3LYP/6-31G*
level and set to –240 ppm vs. H3PO4 as the reference shift for all
computed structures.
Synthesis of [Li2(P2Ph2)(tmeda)2] (2): Lithium sand (39 mg,
5.62 mmol, 6 equivalents) and (P5Ph5) (500 mg, 0.925 mmol,
1 equiv.) were stirred for 24 h in THF (10 mL). The remaining lith-
ium sand was filtered off and the solvent of the deep red filtrate
was removed under high vacuum. The orange red powder was sus-
pended in hot toluene (10 mL) and filtered off. The red powder
was recrystallized from a hot mixture of toluene (4 mL) and tmeda
(2 mL) and, on cooling to ambient temperature, the product sepa-
rated as red crystals (673 mg, 63%). Red, very air-sensitive single
crystals of [Li2(P2Ph2)(tmeda)2] were obtained by storing a satu-
rated toluene/tmeda solution at ambient temperature.
[Li2(P2Ph2)(tmeda)2] (C24H42Li2N4P2, M = 462.45 gmol–1): M.p.
151–153 °C (single crystal, uncorrected). 1H NMR (500.23 MHz,
[D8]THF, 25 °C): δ = 2.18 [s, 8 H, CH3(TMEDA)], 2.34 [s, 24 H,
CH2(TMEDA)], 6.33 (m, 2 H, p-H), 6.62 (m, 4 H, m-H), 7.26 ppm
(m, 4 H, o-H). 7Li NMR (194.4 MHz, DME/[D8]toluene, 25 °C): δ
= 0.6 ppm [s (br.)]. 13C NMR (125.8 MHz, [D8]THF, 25 °C): δ =
46.7 [s, CH3(TMEDA)], 59.4 [s, CH2(TMEDA)], 117.5 [s (br.), 4-C in
4
Ph], 126.7 [t, (3JC,P + JC,P) = 2.4 Hz, 3,5-C in Ph], 131.0 [t, (2JC,P
+
3JC,P) = 12.2 Hz, 2,6-C in Ph], 162.2 ppm [t, (1JC,P 2JC,P) =
+
34.8 Hz, 1-C in Ph]. 31P NMR (202.5 MHz, [D8]THF, 25 °C): δ =
–102.9 ppm (s).
Synthesis of [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– (3): Lithium sand
(45 mg, 6.47 mmol; 3.5 equiv.) and (P5Ph5) (1.00 g, 1.85 mmol;
1 equiv) were stirred for 24 h in dme (10 mL). The orange precipi-
tate was filtered off, washed with dme (2 mL), and dried in high
vacuum. The light orange powder was dissolved in a mixture of
toluene (5 mL) and tmeda (1 mL). The solvent was removed under
CCDC-280997 to -280999 (for 2–4, respectively) contain the sup-
plementary crystallographic data for this paper. These data can be
Table 4. Crystallographic data for compounds 2, 3, and 4.
Compound
[Li2(P2Ph2)(tmeda)2] (2)
[Li(tmeda)2]+ [Li(P3Ph3)(tmeda)]– (3) [Li2(P4Ph4)(tmeda)2] (4)
Empirical formula
M
C24H42Li2N4P2
462.44
C36H63Li2N6P3
686.71
C36H52Li2N4P4
678.58
Crystal system
Space group
a [Å]
b [Å]
c [Å]
monoclinic
C2/m (no. 12)
12.192(1)
14.059(1)
8.335(1)
101.905(2)
1398.2(1)
0. 172
monoclinic
P21/c (no. 14)
13.283(1)
17.535(1)
18.331(1)
99.828(2)
4207.2(4)
0.172
monoclinic
C2/c (no. 15)
10.299(1)
17.644(1)
21.464(1)
93.412(2)
3893.4(5)
0.223
β [°]
V [Å3]
µ [mm–1]
Dcalcd. [gcm–3]
Crystal dimensions [mm]
Z
1.098
0.52×0.45×0.34
2
1.084
0.24×0.13×0.05
4
1.158
0.14×0.13×0.10
4
T [K]
2θmax [°]
100
104.30
100
52.90
200
52.74
Reflections measured
Reflections unique
Parameters/restraints
R1 [I Ն 2σ(I)]
wR2 (all data)
Max./min. resid. e– dens. [eÅ–3]
22784
8099 (Rint = 0.0191)
184/12
0.0411
0.1260
37854
8646 (Rint = 0.0781)
377/17
0.0968
0.2233
14022
3975 (Rint = 0.0505)
212/0
0.0594
0.1391
1.035/–0.449
0.930/–0.747
0.355/–0.181
Eur. J. Inorg. Chem. 2006, 4157–4167
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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4165

D. Stein, A. Dransfeld, M. Flock, H. Rüegger, H. Grützmacher
FULL PAPER
high vacuum to give a yellow powder (1.525 g, 72%). Yellow, very
air-sensitive single crystals of [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]–
were obtained by storing a saturated toluene solution for several
days at 7 °C. [Li(tmeda)2]+[Li(P3Ph3)(tmeda)]– (C36H63Li2N6P3, M
= 686.73 gmol–1): M.p. 166 °C (single crystal, uncorrected). 1H
NMR (300.1 MHz, [D8]toluene, 25 °C): δ = 1.92 [s (br.), 12 H,
CH2(TMEDA)], 2.03 [s (br.), 36 H, CH3(TMEDA)], 6.87 (m, 1 H, p-H
Acknowledgments
This work was supported by Ciba Speciality Chemicals and the
ETH Zürich.
[1] Z.-W. Wang, Li-S. Wang, Green Chem. 2003, 5, 737.
in Ph at PA), 6.89 (m, 2 H, p-H in Ph at PM), 6.97 (m, 2 H, m-H [2] Reviews: a) K. Issleib, Z. Chem. 1962, 2, 163; b) M. Baudler,
K. Glinka, Chem. Rev. 1993, 93, 1623. The formation of cyclic
oligophosphanes is described from PhPCl2/Li in: c) P. R.
Bloomfield, K. Parvin, Chem. Ind. 1959, 541; from PhPCl2/Na:
d) F. Pass, H. Schindlbauer, Monatsh. Chem. 1959, 90, 148; e)
L. Horner, P. Beck, H. Hoffmann, Chem. Ber. 1959, 92, 2088;
f) W. Kuchen, H. Buchwald, Chem. Ber. 1958, 91, 2296; from
PhPCl2/Mg: g) W. A. Henderson, M. Epstein, F. S. Seichter, J.
Am. Chem. Soc. 1963, 85, 2462; h) A. Hinke, W. Kuchen,
Chem. Ber. 1983, 116, 3003; from PhPCl2/Zn: i) M. Scherer, D.
Stein, F. Breher, J. Geier, H. Schönberg, H. Grützmacher, Z.
Anorg. Allg. Chem. 2005, 631, 2770; j) H. Grützmacher, J. Ge-
ier, H. Schönberg, M. Scherer, D. Stein, S. Boulmaâz, WO2004/
050668.
in Ph at PA), 7.20 (m, 4 H, m-H in Ph at PM), 8.04 (m, 4 H, o-H
in Ph at PM), 8.18 ppm (m, 2 H, o-H in Ph at PA). 7Li NMR
(194.4 MHz, [D8]toluene, –73 °C): δ = 11.4 [m (br.)], 10.5 ppm [s
(br.)]. 13C NMR (75.5 MHz, [D8]toluene, 25 °C): δ = 45.9 [s,
CH3(TMEDA)], 57.2 [s, CH2(TMEDA)], 120.0 (s, 4-C in Ph at PM),
124.8 (s, 4-C in Ph at PA), 127.4 (m, 3,5-C in Ph at PA), 128.1 (m,
3,5-C in Ph at PM), 130.0 (m, 2,6-C in Ph at PM), 131.0 (m, 2,6-C
in Ph at PA), 155.8 (m, 1-C in Ph at PM), 159.1 ppm (m, 1-C in Ph
at PA). Multiplets in the 13C NMR spectra represent the X part of
an AMMЈX spin system. 31P NMR (101.3 MHz, [D8]toluene,
25 °C): δ = –52.3 [m, 1JP(M),P(A) = 223.8 Hz, A part of an AM2 spin
1
system, PA], –71.5 ppm [m, JP(M),P(A) = 223.8 Hz, M part of an
[3] [M2(PnPhn)], M = Li–Cs, n = 3, 4: a) P. R. Hoffman, K. G.
Caulton, J. Am. Chem. Soc. 1975, 97, 6370; b) M. Baudler, D.
Koch, Z. Anorg. Allg. Chem. 1976, 425, 227; [M2(P3Ph3)], M =
Na, K: c) M. Baudler, D. Koch, E. Tolls, K. M. Diedrich, B.
Kloth, Z. Anorg. Allg. Chem. 1976, 420, 146; [Na2(P2Ph2)]: d)
J. W. B. Reesor, G. F. Wright, J. Org. Chem. 1957, 22, 385;
[Li2(P2Ph2)] and [K2(P2Ph2)]: e) K. Issleib, K. Krech, Chem.
Ber. 1966, 99, 1310; PhPNa2 has been assumed to be a by-
product in the reaction of (PhP)n with sodium: f) W. Kuchen,
H. Buchwald, Chem. Ber. 1958, 91, 2296; [Na2(tBu3Si–P–P=P–
P–SitBu3)]: g) N. Wiberg, A. Wörner, K. Karaghiosoff, D. Fen-
ske, Chem. Ber./Recueil 1997, 130, 135.
AMMЈ spin system, P(M+MЈ)].
Synthesis of [Li2(P4Ph4)(tmeda)2] (4): [Li2(P3Ph3)(dme)x] (3Ј;
892 mg, 1.466 mmol, 5 equiv., x = 3) and (P5Ph5) (158 mg,
0.242 mmol, 1 equiv.) were suspended in Et2O (30 mL). The yellow
suspension was stirred for 24 h. The almost clear yellow solution
was filtered through a Teflon filter. The solvent was removed under
high vacuum and the obtained orange powder was dissolved in a
mixture of toluene (10 mL) and tmeda (3 mL). The solvent was
removed under high vacuum to give a yellow powder (865 mg,
87%). Slightly yellow, very air-sensitive single crystals of
[Li2(P4Ph4)(tmeda)2] were obtained by storing a saturated mtbe
solution for several days at ambient temperature. [Li2(P4Ph4)-
(tmeda)2] (C36H52Li2N4P4, M = 678.6 gmol–1): M.p. 174 °C (single
[4] R. Wolf, A. Schisler, P. Lönnecke, C. Jones, E. Hey-Hawkins,
Eur. J. Inorg. Chem. 2004, 3277.
[5] a) J. Geier, H. Rüegger, M. Wörle, H. Grützmacher, Angew.
Chem. 2003, 115, 4081; Angew. Chem. Int. Ed. 2003, 42, 3951;
b) J. Geier, J. Harmer, H. Grützmacher, Angew. Chem. 2004,
116, 4185–4189; Angew. Chem. Int. Ed. 2004, 43, 4093–4097c)
D. Stein, J. Geier, H. Schönberg, H. Grützmacher, Chimia
2005, 59, 119.
1
crystals, uncorrected). H NMR (500.2 MHz, [D8]toluene, 25 °C):
δ = 1.76 [s (br.), 8 H, CH2(TMEDA)], 1.95 [s (br.), 24 H,
CH3(TMEDA)], 6.86 (m, 2 H, p-H in Ph at PA), 7.02 (m, 2 H, p-H
in Ph at PB), 7.09 (m, 4 H, m-H in Ph at PA), 7.14 (m, 4 H, m-H
in Ph at PB), 7.72 (m, 4 H, o-H in Ph at PA), 8.22 ppm (m, 4 H, o-
H in Ph at PB). 7Li NMR (194.4 MHz, [D8]toluene, –25 °C): δ =
[6] A. Streitwieser Jr, Acc. Chem. Res. 1984, 17, 353.
[7] N. Korber, J. Aschenbrenner, J. Chem. Soc., Dalton Trans.
2001, 1165.
1
10.9 ppm (t, JLi,P = 37.3 Hz, 2 Li) ppm. 13C NMR (125.8 MHz,
[8] Compare, for example, the molar enthalpy of solution for LiCl
[D8]toluene, 25 °C):
δ
=
46.1 [s, CH3(TMEDA)], 56.8 [s,
(–37.03 kJmol–1) and NaCl (3.88 kJmol–1).
CH2(TMEDA)], 120.6 (s, 4-C in Ph at PA), 125.7 (s, 4-C in Ph at PB),
127.5 (s, 3,5-C in Ph at PA), 127.6 (s, 3,5-C in Ph at PB), 130.2 (m,
2,6-C in Ph at PA), 133.9 (m, 2,6-C in Ph at PB), 148.3 [m (br), 1-
C in Ph at PB], 154.3 ppm [m (br.), 1-C in Ph at PA]. Multiplets in
the 13C NMR spectra represent the X part of an AAЈBBЈX spin
system. 31P NMR (202.5 MHz, [D8]toluene, 25 °C): δ = –2.3 [m,
(PPh)5], –36.8 (br., [Li2(P4Ph4)(tmeda)2]), –53.3 (m, [Li2(P3Ph3)-
(tmeda)3]), –73.0 (m, [Li2(P3Ph3)(tmeda)3]), –76.0 (br., [Li2(P4Ph4)-
(tmeda)2]), –95.4 (br., [Li2(P4Ph4)(tmeda)2]) ppm. 31P NMR
(202.5 MHz, [D8]toluene, –25 °C): δ = –38.0 (m, B part of an
AAЈBBЈX2 spin system, PB [4]), –39.7 (m, B part of an AAЈBBЈX
spin system, PB [4ЈЈ]), –74.4 (m, A part of an AAЈBBЈX spin sys-
tem, PA [4ЈЈ]), –95.1 ppm (m, A part of an AAЈBBЈX2 spin system,
PA [4]); ratio 4/4ЈЈ = 100:81. 31P{1H} CPMAS (202.5 MHz, 25 °C):
δiso = –38, δ11 Ϸ 50, δ22 Ϸ –10, δ33 Ϸ –155 (B part); δiso = –87, δ11
[9] H. Bock, C. Nather, Z. Havlas, A. John, C. Arad, Angew.
Chem. 1994, 106, 931; Angew. Chem. Int. Ed. Engl. 1994, 33,
875.
[10] For the structure of [K(18-C-6)][NHPh] see: P. B. Hitchcock,
A. V. Khvostov, M. F. Lappert, A. V. Protchenko, J. Or-
ganomet. Chem. 2002, 647, 198 and references cited therein.
[11] J. Herzfeld, A. E. Berger, J. Chem. Phys. 1980, 73, 6021.
[12] M. Bak, J. T. Rasmussen, J. C. Nielsen, J. Magn. Reson. 2000,
147, 296.
[13] G. Wu, B. Sun, R. E. Wasylishen, R. G. Griffin, J. Magn. Re-
son. 1997, 124, 366.
[14] M. Kaupp, A. Patrakov, R. Reviakine, O. L. Malkina, Chem.
Eur. J. 2005, 11, 2773.
[15] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery Jr, T. Vreven,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tom-
asi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratch-
ian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli,
J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Sal-
vador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D.
7
Ϸ 0, δ22 Ϸ –55, δ33 Ϸ –205 ppm (A part). Li NMR (194.4 MHz,
1
[D8]toluene, –25 °C): δ = 10.9 ppm (t, JLi,P = 37.3 Hz, 2 Li).
Supporting Information (see footnote on the first page of this arti-
cle): Plots of the 13C NMR spectra of compounds 2, 3, and 4 and
details of the simulation of the 31P CP-MAS spectrum with the
SIMPSON package.
4166
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 4157–4167

Lithium Oligophosphanediides in the Li/PhPCl2 System
FULL PAPER
Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Ba-
boul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Lia-
shenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T.
Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W.
Wong, C. Gonzalez, J. A. Pople, Gaussian 03, revision C.02,
Gaussian, Inc., Wallingford CT, 2004.
[16] M. Valentini, H. Rüegger, P. S. Pregosin, Helv. Chim. Acta
2001, 84, 2833.
[17] R. K. Harris, E. D. Becker, S. M. Cabral de Menezes, R. Good-
fellow, P. Granger, Pure Appl. Chem. 2001, 73, 1795.
Received: April 26, 2006
Published Online: August 18, 2006
Eur. J. Inorg. Chem. 2006, 4157–4167
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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