Reduction of bis(phosphonio)isophosphindolides to phosphane- functionalized benzo[c]phospholides

Article abstract of DOI:10.1002/(sici)1099-0682(199907)1999:7<1169::aid-ejic1169>3.0.co;2-q

Bis(phosphonio)benzo[c]phospholides (isophosphindolides) 1a,b have been found to react with magnesium or alkali metal naphthalenides MC₁₀H₈ (M = Li, Na, K) with reduction of one or both of the phosphonio groups. The main products are the mono- or bis(phosphanyl)-substituted heterocycles 2, 3, 6, 7, which have been characterized by in situ NMR studies and in some cases isolated. Subsequent reaction of 2 with excess [Ni(CO)₄] gave the complex 4, which has been characterized by X-ray diffractometry. Reactions of la with alkali metals followed a more complicated course and gave a mixture of 2, 3, and the substitution product 8, which was further reduced to the phosphanido- substituted benzo[c]phospholide 9. The latter could be formed selectively by first converting la into 8 by treatment with PhNa and then treating this with lithium. NMR data of the phosphane-substituted benzo[c]phospholides and the structural features of 4 are discussed.

Full text of DOI:10.1002/(sici)1099-0682(199907)1999:7<1169::aid-ejic1169>3.0.co;2-q

FULL PAPER
Reduction of Bis(phosphonio)isophosphindolides to Phosphane-Functionalized
Benzo[c]phospholides
Dietrich Gudat,*[a] Volker Bajorat,[a] Stefan Häp,[a] Martin Nieger,[a] and Gisela Schröder[a]
Dedicated to Professor Dr. Edgar Niecke on the occasion of his 60th birthday
Keywords: Phosphorus heterocycles / Phospholides / Nickel complexes / Reductions / NMR spectroscopy
Bis(phosphonio)benzo[c]phospholides (isophosphindolides)
1a,b have been found to react with magnesium or alkali
metal naphthalenides MC10H8 (M = Li, Na, K) with reduction
of one or both of the phosphonio groups. The main products
alkali metals followed a more complicated course and gave
a mixture of 2, 3, and the substitution product 8, which was
further reduced to the phosphanido-substituted benzo-
[c]phospholide 9. The latter could be formed selectively by
are the mono- or bis(phosphanyl)-substituted heterocycles 2, first converting 1a into 8 by treatment with PhNa and then
3, 6, 7, which have been characterized by in situ NMR studies treating this with lithium. NMR data of the phosphane-
and in some cases isolated. Subsequent reaction of 2 with substituted benzo[c]phospholides and the structural features
excess [Ni(CO)4] gave the complex 4, which has been
characterized by X-ray diffractometry. Reactions of 1a with
of 4 are discussed.
proceed with selective cleavage of one PϪC bond in each
exocyclic phosphonium moiety, thereby affording a mixture
of the phosphane-substituted benzophospholide anions 2
and 3. The by-products produced included the cleavage
products C6H5Li or C5H4NLi along with triphenylphos-
phane or diphenylpyridylphosphane, respectively, as well as
some LiPPh2 arising from further reduction of the latter
(Scheme 1).
Introduction
Phospholides[1] are hetero analogues of cyclopentadien-
ide anions and are distinguished by both high aromatic
character[2] and versatile ligand properties. The phospho-
lide moiety is not only capable of acting as a 6e π-donor
ligand similar to an η5-coordinated cyclopentadienide, but
may also coordinate as a terminal 2e donor through the
phosphorus lone pair, or, through a combination of σ and
π coordination, as a bridging 4e or 8e ligand.[1] Whereas
recent developments in the field of cyclopentadienides have
been focused on derivatives bearing additional ligand
groups attached either directly to the ring or on pendant
side chains,[3] reports on analogous phospholide derivatives
are scarce.[4][5] In view of the fact that a general route to
tertiary phosphanes involves reductive cleavage of phos-
phonium salts,[6] we have examined the potential of re-
duction of bis(phosphonio)-substituted isophosphindolides
incorporating a fused benzo[c]phospholide ring system.[7]
We found that this reaction gives access to previously un-
known[8] neutral and anionic benzo[c]phospholides bearing
exocyclic phosphane functionalities.
Results
Scheme 1. X ϭ Cl, Br, BPh4; M ϭ Li, Na; R ϭ Ph (1a), 2-pyri-
dyl (1b)
Reactions
The anions 2, 3 were generated in a ratio of approxi-
mately 3:1 almost irrespective of the reaction temperature.
Mixtures of similar composition were also obtained in
other solvents (DME, liq. NH3) or when sodium naph-
thalenide was used as the reducing agent. No further inter-
mediates could be detected; only mixtures of 2, 3 and unre-
acted starting material were produced when the reactions
were performed with less than four equivalents of the me-
tal naphthalenide.
Reactions of the bis(triphenylphosphonio)isophosphin-
dolide salts 1a[Cl][9] and 1b[Br] (R ϭ 2-pyridyl)[10] with four
equivalents of lithium naphthalenide in THF were found to
[a]
Anorganisch Chemisches Institut der Universität Bonn,
Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
Fax: (internat.) ϩ 49(0)228/73-5327
E-mail: dgudat@uni-bonn.de
Eur. J. Inorg. Chem. 1999, 1169Ϫ1174
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
1434Ϫ1948/99/0707Ϫ1169 $ 17.50ϩ.50/0
1169

D. Gudat, V. Bajorat, S. Häp, M. Nieger, G. Schröder
FULL PAPER
All reaction products were identified in situ by multi- creased during the course of the reaction as a new species
nuclear 1D- and 2D-NMR studies (see Experimental Sec- appeared, which was later identified as the phosphanide-
tion). A salt 2[Li(THF)x] was isolated in crude form (ap- substituted benzophospholide 9[M2] (M ϭ Li, Na). In total,
1
proximately 95% pure on the basis of 31P- and H-NMR 2, 3, and 9 constituted approximately 90% of all the phos-
data) after quenching the remaining lithiated species with a phorus-containing species; a higher percentage was pre-
stoichiometric amount of FeCl2, filtering, and precipitation vented by unspecified side reactions and slow cleavage to
of the product with diethyl ether/hexane. Attempted purifi- give MPPh2. Prolonged reaction times or elevated tempera-
cation of the product by recrystallization was unsuccessful, tures led to the decomposition of all other species, leaving
but a crystalline derivative could be obtained after reaction the phosphanides MPPh2 as the only well-defined phos-
of either crude 2[Li], or the reaction mixture containing phorus-containing reaction products.
both anions 2 and 3, with excess Ni(CO)4, followed by re-
peated recrystallization of the formed complex 4[Li(THF)4]
from THF/diethyl ether. Likewise, reaction of crude 2[Li]
with excess MeI afforded the quaternization product 5[I],
which could be isolated in pure form after recrystallization
from CH2Cl2/THF (Scheme 2).
Scheme 3
The formation of 8 by substitution of the cation 1a by
C6H5M (which was generated in the initial reduction of 1a
to give 2 and 3) was proven by its independent synthesis
from 1a[Cl] and one equivalent of C6H5Na. Since a control
experiment revealed that lithium reduction of an isolated
sample of 2 under similar conditions did not yield any de-
tectable amount of 9[M2], formation of this product can be
assumed to occur exclusively through the intermediate 8.
This was confirmed by an investigation of the reaction of
pure 8 with lithium under ultrasound sonification, which
gave 9[M2] together with a small amount (10Ϫ15%) of
LiPPh2 as the only reaction products detectable by 31P-
Scheme 2
NMR spectroscopy. Even though all attempts to isolate
Only one phosphonium moiety was reduced in reactions
9[M2] from any of the reaction mixtures have hitherto been
of 1a[X] (X ϭ Cl, BPh4) with magnesium. As in the case of
unsuccessful, it could be characterized in situ by multi-
the naphthalenide reduction, two main products were
nuclear NMR spectroscopy (see below).
formed, which were identified by 31P-NMR spectroscopy as
the neutral species 6 and 7 (Scheme 1; the generation of 7
was accompanied by the formation of Ph3P). The exact re-
action conditions and the product ratio varied with the
NMR-Spectroscopic Investigations
specific physical state of the employed metal: The use of
The identities of the neutral and anionic benzophosphol-
magnesium turnings required activation by treatment with ides 2Ϫ4, 6, 7, and 9, the benzophosphole 8, and the cation
1
I2 or CCl4 and produced some 25Ϫ50% of the cleavage 5 were unequivocally established from their H-, 13C-, and
product 7; in contrast, application of a suspension of mag- 31P-NMR data. Substitution patterns at the fused ring sys-
nesium powder, freshly prepared by thermal decomposition tem were easily assigned from the habit of the 31P{1H}-
of magnesiumϪanthracene,[11] resulted in shorter overall re- NMR spectra, which featured characteristic A2X (2, 4, 5),
action times and a higher selectivity, giving up to 80% of A2B (8), AMX (6, 9), or AX patterns (3, 7). Consequently,
the phosphane-substituted heterocycle 6. Isolation and the 1H-NMR spectra displayed ABCD (3, 6, 7, 9) or
further spectroscopic characterization of this product was AAЈBBЈ patterns (2, 4, 5, 8) for the four protons of the
feasible after solvent extraction of the reaction mixture and benzenoid fragment of the fused ring system. In addition,
recrystallization from toluene. The by-product 7 decom- the spectra of 3 and 7 also featured a resonance for the 2-
posed during the workup procedure and could not be H proton, showing characteristic splitting due to coupling
further characterized.
with the two phosphorus atoms. Discrimination between
A different and more complicated reaction pathway was phosphonio (Ph3PϪ), phosphane (Ph2PϪ), and phos-
observed when alkali metals were used instead of their phanido [Ph(M)PϪ] substituents was feasible on the basis
naphthalenides as reducing agents. NMR-spectroscopic of characteristic 31P chemical shift differences (Table 1).
monitoring of the early stages of the reactions of 1a[Cl] Signals for the first two types of substituents appear in
with Li or Na revealed, besides the presence of the anions common spectral regions, while the resonance of the phos-
2, 3 [and concomitant formation of the cleavage products phanide group in 9 appears at much higher field than in
C6H5Li(Na) and Ph3P], the formation of the substitution simple diarylphosphanides [δ31P
product 8 (Scheme 3). The concentration of the latter de- Ph2P(Na, Li)[12]]. The resonances of the Ph(M)P and Ph2P
ϭ Ϫ22.5, Ϫ36 for
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Eur. J. Inorg. Chem. 1999, 1169Ϫ1174

Bis(phosphonio)isophosphindolides to Phosphane-Functionalized Benzo[c]phospholides
Table 1. 31P- and selected 13C-NMR data of 2؊9
FULL PAPER
δ31P
JP,P [Hz]
δ13C
JP,C [Hz]
2[Li]
3[Li]
4[Li]
5[I]
Ϫ20.0 (PAPh2)
216.4 (ϪPXϪ)
Ϫ21.9 (PAPh2)
174.0 (ϪPXϪ)
10.3 (PAPh2)
130
124.4 (PXϪCϪPA)
51 (JP(X),C), 13 (JP(A),C), 10 (JP(AЈ),C)
219
Ϫ[a]
Ϫ[a]
Ϫ[a]
164
Ϫ[a]
237.3 (ϪPXϪ)
12.5 (PAPh3)
92
109.4 (PXϪCϪPA)
54 (JP(X),C), 96 (JP(A),C), 14 (JP(AЈ),C)
229.0 (ϪPXϪ)
6
Ϫ21.4 (PAPh2)
76 (JP(A),P(X)
82 (JP(M),P(X)
)
92.8 (PXϪCϪPM)
143.2 (PXϪCϪPA)
99 (JP(M),C), 60 (JP(X),C), 10 (JP(A),C
)
ϩ
14.7 (PMPh3
)
)
53 (JP(M),C), 14 (JP(A),C), 12 (JP(X),C)
218.4 (ϪPXϪ)
7
15.1 (PAPh3)
88
Ϫ[a]
Ϫ[a]
190.2 (ϪPXϪ)
ϩ
8
8.0 (PAPh3
14.0 (PBPh)
)
122
33.3 (PAϪCϪPB)
119.2 (JP(A),C), 11.4 (JP(B),C),
Ϫ9.3 (JP(A)Ј,C)[b]
9[Li2]
Ϫ87.1 (PAPhLi)
Ϫ20.8 (PMPh2)
194.2 (ϪPXϪ)
Ϫ86.2 (PAPhNa)
Ϫ20.8 (PMPh2)
193.2 (ϪPXϪ)
108 (JP(A),P(X)
61 (JP(M),P(X)
)
)
116.0 (PXϪCϪPA)
139.2 (PXϪCϪPM)
52 (JP(X),C), 8 (JP(A),C), 5 (JP(M),C)
)
46 (JP(X),C), 30 (JP(M),C), 6 (JP(A),C)
9[Na2]
106 (JP(A),P(X)
66 (JP(M),P(X)
Ϫ[a]
Ϫ[a]
)
[a]
[b]
4
Not determined. Ϫ Spectral analysis as [A]2BX system gave JP(B),C/JP(BЈ),C < 0 and JP(B),P(BЈ) ϭ 5.5 Hz.
fragments in 9 are further distinguished by different multi- mation) in solution. Of diagnostic relevance in the 13C-
plicities in 1H non-decoupled 31P spectra, showing coupling NMR spectra are the signals of the ring carbon atoms ad-
to two or four ortho protons, respectively. The chemical jacent to the two-coordinate phosphorus atoms: Carbon
shifts of the phospholide P atoms in 2, 4, 6, and 9 are seen atoms bearing exocyclic phosphonio groups display similar
1
to be somewhat more shielded as in 1a (δ31P ϭ 241.8[9]), but chemical shifts and exocyclic J(P,C) couplings as seen in
significantly less shielded than in monocyclic phospholides 1a, whereas those bearing phosphanyl groups exhibit lower
(δ31P ϭ 55Ϫ142[1b]). This trend could be confirmed by a 1J(P,C) values and chemical shifts appear further downfield
comparison with calculated[13] δ31P values of model com- resembling those due to the α-carbon atoms in phospho-
pounds (Table 2). This revealed that the deshielding of the lides.[1]
resonance of 1a (as well as of 2 and 4) compared to those
of the monocyclic phospholides can be attributed to similar
contributions from both the benzanellation and the influ-
Crystal Structure of Compound 4
ence of the phosphonio (phosphane) substituents. Inspec-
tion of the results of calculations suggests that the deshield-
ing shows a correlation with both a continuously decreasing
energy gap between the phosphorus lone pair and the low-
est π* orbital, and an increasing shift of π electron density
from the two-coordinate phosphorus atom to the adjacent
carbon atoms, which tends to impose some “ylidic” charac-
ter on the PϪC bond.
The results of an X-ray crystal structure analysis of
4[Li(THF)4] revealed a salt-like composition with two inde-
pendent, only slightly different pairs of [Li(THF)4]ϩ cations
and benzophospholide anions per asymmetric unit (Figure
1). The bonding parameters in the fused ring systems of the
anions do not differ significantly from those in the phos-
phonio-substituted cation 1a.[14] On the other hand, the ex-
˚
ocyclic PϪC distances (1.774Ϫ1.789 A) are longer than the
Comparison of δ31P values for the corresponding nuclei
in the lithium and sodium salts of the anions 2, 3, and 9
indicates some influence of the counterion, which is less
pronounced for the monoanions 2, 3 than for 9 and sug-
gests some degree of ionic association (contact ion pair for-
corresponding bonds in 1a (1.747Ϫ1.749 A[14]) but shorter
˚
than the peripheral PϪC(phenyl) distances (1.825Ϫ1.847
˚
A). The PϪNi distances in 4 are comparable with typical
[15]
˚
values in PPh3ϪNi complexes (2.225 ± 0.070 A).
The
remaining bond parameters display no peculiarities. On the
whole, these findings suggest that electronic perturbation of
Table 2. Calculated [GIAO-B3LYP/6Ϫ311ϩg(2d,d,p)//B3LYP/ the 10π system in 4 by hyperconjugation with the substitu-
6Ϫ31ϩg(d,p)] 31P chemical shifts of phospholides and of the pa-
ents[7] is lower than that in 1a. In view of the rather low
rent and 1,3-disubstituted benzo[c]phospholides[12]
degree of electronic interaction between the five- and six-
membered rings in a structurally characterized benzo-
[b]phospholide,[8] the anion 4 would seem to represent the
first example of a benzophospholide with a unique 10π elec-
tron system having an electronic structure comparable to
that found in heteronaphthalenic benzodithiaphospholium
cations.[16]
δ31P
[C4H4P]Ϫ
139.4
200.5
306.0
311.5
[C8H6P]Ϫ (benzo[c]phospholide)
[1,3-(H2P)2-C8H4P]Ϫ
[1,3-(H3P)2-C8H4P]ϩ
Eur. J. Inorg. Chem. 1999, 1169Ϫ1174
1171

D. Gudat, V. Bajorat, S. Häp, M. Nieger, G. Schröder
FULL PAPER
of reductive PϪC cleavage in phosphonium salts generally
parallels the ability of the leaving group to stabilize a nega-
tive charge,[6] the observed product ratio in the reduction
of 1a suggests a slightly higher charge-stabilizing capacity
of a triphenylphosphoniobenzophospholide as compared to
a phenyl moiety, whereas selective cleavage of pyridyl in-
stead of phenyl groups in the reduction of 1b suggests that
the pyridyl group is superior to both.
The outcome of the reduction of 1a with alkali metals in
the absence of naphthalene is consistently explained in
terms of two competing reaction channels, viz. reduction of
the cation 1a and its substitution by the formed metal phe-
nyl to give 8. The successful competition of the two differ-
ent pathways under these conditions is again attributable to
kinetic factors: the reduction proceeds at a much lower rate
when solid metals are used rather than soluble metal naph-
thalenides, so that the slower substitution of the formed
phenylmetal compound with still present starting material
to give 8 may take place. Further conversion of 8 to the
dimetallated species 9[M2] requires the reductive cleavage of
phenyl groups from both the two exocyclic ylide moieties
and the endocyclic phosphorus atom. Both types of reac-
tions are known in principle. Reductive cleavage of tri-
phenylphosphonium ylides has been reported, and even
Figure 1. Representation of one of the two crystallographically in-
dependent anions in crystalline 4[Li(THF)4] (50% thermal ellip-
˚
soids); selected bond lengths [A] and angles [°] (data of the second
anion in brackets): P(1)ϪC(2) 1.732(4) [1.747(4)], P(1)ϪC(9)
1.736(4) [1.744(4)], C(2)ϪC(3) 1.441(5) [1.423(5)], C(2)ϪP(2)
1.789(4) [1.777(4)], C(3)ϪC(4) 1.416(5) [1.416(5)], C(3)ϪC(8)
1.432(5) [1.440(5)], C(4)ϪC(5) 1.367(5) [1.371(5)], C(5)ϪC(6)
1.399(6) [1.401(5)], C(6)ϪC(7) 1.372(5) [1.380(5)], C(7)ϪC(8)
1.413(5) [1.400(5)], C(8)ϪC(9) 1.440(5) [1.431(5)], C(9)ϪP(3)
1.780(4) [1.774(4)], P(2)ϪNi(2) 2.241(1) [2.238(1)], P(3)ϪNi(3)
2.241(1) [2.240(1)]; C(2)ϪP(1)ϪC(9) 93.0(2) [92.6(2)]
Discussion
The reported reactions of the bis(phosphonio)isophos- though this process is not fully understood, it is considered
phindolide cations 1a, b conform to the general scheme of to follow a different mechanism than the reduction of phos-
the reduction of phosphonium salts through cleavage of phonium salts,[17] thus accounting for the different nature
PϪC bonds to give phosphanes and carbanions. The latter of the obtained product. Reductive cleavage of PϪPh bonds
may be protonated to give the corresponding hydrocarbons in phospholes has been extensively studied, in particular by
during workup.[6] For the bis(phosphonium) cations studied Mathey and co-workers.[1] Since no further intermediates
here, the extent of the reduction appears to be controlled were identified, the exact mechanism of the reaction from
by the reductive power of the metal: The reaction with mag- 8 to 9 cannot be further elucidated. Nonetheless, it appears
nesium stops after reduction of the first phosphonium func- reasonable to assume reduction of one of the phosphonium
tionality, while the stronger reducing agent alkali metal/ moieties as the first step.
naphthalene attacks both substituents. The failure to ob-
serve the neutral species 6, 7 as intermediates under these
conditions, which would be expected if a stepwise reaction
is assumed, may be attributed to kinetic factors: The second
Conclusion
Our investigations have shown that bis(phosphonio)iso-
phosphindolides can be reduced with preservation of the
fused aromatic ring system to give phosphane-substituted
benzo[c]phospholides. Despite the formation of mixtures of
products, which arise from the presence of different PϪC
bonds in the starting materials that may possibly be cleaved,
the novel phosphane-substituted benzophospholide 6 and
the anionic nickel complex 4 could be isolated. Further in-
vestigations into the syntheses and reactivities of other
phosphane-substituted (poly)phospholide derivatives, in
particular with respect to a side-on π coordination to tran-
sition metal ions, are currently in progress.
reaction step may be faster, presumably due to the low solu-
bility of the starting material in the solvents employed.
The formation of product mixtures in the observed reac-
tions reflects the presence of different types of PϪC single
bonds: Starting from the cation 1a, cleavage of a peripheral
phenyl group affords the phosphane-substituted phosphol-
ide 6 and the corresponding phenylmetal compound, both
of which were observed in the reaction mixtures, while fis-
sion of a PϪC(ring) bond should liberate Ph3P and an α-
deprotonated benzophospholide anion. The latter was not
directly detected and is most likely quenched by abstraction
of a proton (presumably from a solvent molecule) to afford
the neutral compound 7, which could be isolated in the co-
urse of the reaction with magnesium. Further reduction of
6 and 7 with alkali metals can be expected to afford a mix-
ture of 2 and 3, together with Ph3P and the parent benzo-
phospholide anion. The latter was not observed, suggesting
that the second reduction step occurs either with selective
PϪC(phenyl) bond fission, or that this product decomposes
Experimental Section
General Remarks: NMR spectra were recorded at 30°C with a
Bruker AMX 300 spectrometer (300.13, 121.50, and 75.46 MHz for
1H, 31P, and 13C). Chemical shifts are referenced to external TMS
(1H, 13C) or 85% H3PO4. 13C,31P{1H}INEPT spectra were recorded
under the reaction conditions. If one considers that the ease with a 5-mm triple-resonance probe head equipped with an inner
1172 Eur. J. Inorg. Chem. 1999, 1169Ϫ1174

Bis(phosphonio)isophosphindolides to Phosphane-Functionalized Benzo[c]phospholides
FULL PAPER
tunable coil adjusted to 13C and a second coil double-tuned to H
and 31P. The spectra of 3 and 6 were recorded directly from the
reaction mixtures with suppression of the solvent signals by pre-
saturation. Signal assignments were made with the aid of (semi)se-
lective 1D 13C,31P{1H}-INEPT and 2D 1H,1H-COSY/TOCSY,
1H,13C-HMQC, and 1H,31P-HMQC-TOCSY spectra. The atoms
of the benzophospholide moiety are denoted by C-1 to C-7a and
1-H to 7-H, the carbon atoms of the phenyl groups by Cpara, Cmeta
etc., and the designation of the phosphorus nuclei is as given in
Table 1. Resonances in the 13C spectra forming part of [A]2MY or
[A]2Y spin systems (A, M ϭ 31P) were in some cases analyzed using
the program WINDAISY; in the remaining cases the given values
of ΣJ and JM denote the sum of the couplings to the isochronous
31P nuclei of the [A]2 fragments and the coupling to the endocyclic
phosphorus atom, respectively. Ϫ IR spectra: Nicolet Magna 550
FT-IR spectrometer.
7.56 [m, 8 H, Hmeta(PPh2)], 7.20Ϫ7.05 [m, 12 H, Hortho/para(PPh2)],
6.96 (m, 2 H, 4-H/7-H), 6.28 (m, 2 H, 5-H/6-H). Ϫ IR (THF): ν˜
1
(CO) ϭ 2056 (s), 1982 (vs), 1972 (vs) cmϪ1
.
Bis(methyldiphenylphosphonio)isophosphindolide Iodide (5[I]):
A
solution of 0.50 g (3.5 mmol) of methyl iodide in 5 mL of THF
was added dropwise to a solution of 1.00 g (1.25 mmol) of crude
2[Li(THF)x] in 10 mL of THF. The mixture was refluxed for
10 min, allowed to cool to room temperature, and then concen-
trated to dryness. The residue was extracted with 10 mL of CH2Cl2,
the extract was filtered, and the filtrate was concentrated to a vol-
ume of 5 mL. Addition of 15 mL of THF led to the deposition of
620 mg (63%) of an off-white precipitate of 5[I], m.p. 185°C, which
was collected by filtration and dried in vacuo. Ϫ 1H NMR
(CDCl3): δ ϭ 7.75Ϫ7.53 (m, 20 H, C6H5), 7.08 (m, 2 H) and 6.93
2
4
(m, 2 H, C6H4), 2.77 (dd, 6 H, JH,P ϭ 12.8 Hz, JH,P ϭ 1.4 Hz,
CH3). Ϫ 13C{1H}NMR (CH2Cl2): δ ϭ 143.5 (m, ΣJ ϭ 25.4 Hz,
JM ϭ 2.2 Hz, C-3a/C-7a), 133.7 (s, Cpara), 132.4 (m, ΣJ ϭ 10.7 Hz,
Reduction of 1a[Cl] with Lithium Naphthalenide: A freshly prepared
solution of lithium napththalenide [obtained from 180 mg Cortho), 129.4 (m, ΣJ ϭ 13.1 Hz, Cmeta), 122.8 (dd, JP(A),C
ϭ
(30 mmol) of Li and 3.84 g (30 mmol) of C10H8] in 150 mL of THF
was slowly added to a stirred suspension of 1a[Cl] (5.45 g,
7.5 mmol) in 50 mL of THF at 0°C. Stirring was continued for 1 h.
Anions 2, 3, Ph3P, and PhLi were identified in situ in the dark-red
mixture by multinuclear NMR analyses. A stoichiometric amount
of FeCl2 was then added to quench the PhLi, and the resulting
mixture was stirred for a further 2 h. After addition of 10 mL of
Et2O, stirring was continued for another 30 min, then the mixture
was filtered. The filtrate was concentrated in vacuo to a volume of
15 mL and 100 mL of a Et2O/hexane (2:1) mixture was added. The
resulting precipitate was collected by filtration, redissolved in a
little THF, and reprecipitated with Et2O/hexane. 31P- and 1H-NMR
analysis revealed that the product consisted of approximately 95%
2[Li(THF)x]; yield 3.00 g (50%). The same protocol was used for
the reduction of 1a[Cl] with C10H8Li and for that of 1a,b[Cl] with
C10H8Na. Ϫ 2[Li]: 1H NMR (THF): δ ϭ 7.53 (m, 8 H, Hortho),
7.45 (m, 2 H, 4-H/7-H), 7.08 (m, 8 H, Hmeta), 7.04 (m, 4 H, Hpara),
6.49 (m, 2 H, 5-H/6-H). Ϫ 13C{1H}NMR (THF): δ ϭ 145.2 (m,
89.0 Hz, JP(X),C ϭ 2.9 Hz, Cipso), 120.8 (s) and 119.8 (m) (C-4/C-7
and C-5/C-6), 109.4 (ddd, JP,C ϭ 95.5, 54.3 and 14.3 Hz, C-1/C-3),
12.6 (dd, JP(A),C ϭ 61.2 Hz, JP(X),C ϭ 7.9 Hz, CH3). Ϫ C34H30I2P3
(785.34): calcd. C 52.00, H 3.85; found C 51.5, H 3.8.
Reduction of 1a[Cl] with Magnesium: To a stirred suspension of
3.0 g (12.3 mmol) of Mg powder (freshly prepared by decompo-
sition of C14H10Mg[11]) in 150 mL of THF was added 6.91 g
(10 mmol) of 1a[Cl]. Once the reaction had commenced, stirring
was continued overnight. 31P-NMR-spectroscopic assay of the
dark-red mixture confirmed the formation of 6 (ca. 80%) and 7/
Ph3P (ca. 20%). The mixture was subsequently treated with 40 mL
of Et2O, filtered, and the filtrate was concentrated in vacuo. The
residue was suspended in 120 mL of DME/Et2O (5:1), stirred for
1 h, and then filtered. The volume of the filtrate was reduced to 40
mL, and the product was precipitated by addition of 100 mL of
MeOH. Recrystallization from toluene afforded 3.35 g (58%) of 6
as a yellow powder, m.p. 150°C. Ϫ 1H NMR (CDCl3): δ ϭ 7.67 (m,
1 H, 4-H), 7.60 [m, 6 H, Hortho(PPh3)], 7.48 [m, 4 H, Hortho(PPh2)],
ΣJ ϭ 18.2 Hz, JM ϭ 2.2 Hz, Cipso), 144.1 (m, ΣJ ϭ 15.1 Hz, JM
ϭ
7.35Ϫ7.45 [m,
9 H, Hmeta/para(PPh3)], 7.15Ϫ7.25 [m, 6 H,
3
5
7.6 Hz, C-3a/C-7a), 132.9 (m, JP(A),C ϭ 18.7 Hz, JP(M),C ϭ 1 Hz,
Hmeta/para(PPh2)], 6.91 (m, 1 H, 7-H), 6.85 (m, 1 H, 6-H), 6.74 (m,
4
Cmeta), 126.9 (m, spectral analysis gave JP(A),P(A)Ј ϭ 1.8 Hz,
3
1 H, 5-H). Ϫ 13C{1H}NMR (CDCl3): δ ϭ 146.3 (ddd, JP(A),C
ϭ
1
2JP(A),C ϭ 5.5 Hz, Cortho), 125.6 (s, Cpara), 124.4 (ddd, JP(M),C
ϭ
2
2
17.2 Hz, JP(M),C ϭ 15.3 Hz, JP(X),C ϭ 6.5 Hz, C-7a), 144.3 (ddd,
51.0 Hz, JP(A)/AЈ C
, ϭ 13, 10 Hz, C-1/C-3), 119.4 (m, ΣJ ϭ 10 Hz,
2JP(A),C ϭ 10.2 Hz, JP(X),C ϭ 5.4 Hz, JP(M),C ϭ 1.2 Hz, C-3a),
2
3
JM ϭ 6.8 Hz, C-4/C-7), 115.1 (s, C-5/C-6). Ϫ 3[Li]: 1H NMR
1
1
3
143.2 (ddd, JP(X),C ϭ 53.4 Hz, JP(A),C ϭ 14.1 Hz, JP(M),C
ϭ
2
4
(THF): δ ϭ 7.58 (dd, JH,P(X) ϭ 39.3 Hz, JH,P(A) ϭ 2.9 Hz, 1 H,
3-H), 7.50 (m, 4 H, Hmeta), 7.47 (m, 1 H, 4-H), 7.34 (m, 1 H, 7-H),
7.07 (m, 4 H, Hortho), 7.02 (m, 2 H, Hpara), 6.52 (m, 1 H, 6-H), 6.40
(m, 1 H, 5-H).
1
3
11.9 Hz, C-3), 140.4 [dd, JP(A),C ϭ 10.7 Hz, JP(X),C ϭ 8.8 Hz,
Cipso(PPh2)], 134.0 [dd, JP(M),C ϭ 10.3 Hz, JP(X),C ϭ 1.1 Hz,
Cortho(PPh3)], 133.3 [dd, JP(A),C ϭ 18.3 Hz, JP(X),C ϭ 1.2 Hz,
2
4
3
5
4
Cmeta(PPh2)], 132.9 [d, JP(M),C ϭ 3.1 Hz, Cpara(PPh3)], 129.1 [d,
2
Reduction of 1b[Br] with Lithium Naphthalenide: The reduction of
1b[Br] (1.94 g, 2.5 mmol) with lithium naphthalenide [obtained
3JP(M),C ϭ 12.8 Hz, Cmeta(PPh3)], 127.8 [d, JP(A),C ϭ 6.9 Hz,
1
Cortho(PPh2)], 127.4 [s, Cpara(PPh2)], 125.2 [dd, JP(M),C ϭ 89.7 Hz,
from 60 mg (10 mmol) of Li and 1.28 g (10 mmol) of C10H8] was 3JP(X),C ϭ 1.9 Hz, Cipso(PPh3)], 120.7 (dd, JP(A),C ϭ 12.1 Hz,
3
carried out under analogous conditions as described above. Anions
2, 3, (2-py)Ph2P, and (2-py)Li were identified in situ in the dark-
red solution by 31P- and 1H-NMR analyses. No further workup of
the reaction mixture was attempted.
3JP(X),C ϭ 7.5 Hz, C-4), 120.0 (d, JP,C ϭ 4.2 Hz, C-7), 119.4 (d,
1
JP,C ϭ 3.1 Hz, C-5), 118.3 (s, C-6), 92.8 (ddd, JP(X),C ϭ 98.8 Hz,
1JP(M),C ϭ 60.0 Hz, 3JP(A),C ϭ 10.1 Hz, C-1). Ϫ C38H29P3 (578.57):
calcd. C 78.89, H 5.05; found C 78.0, H 4.9.
Nickel Complex 4[Li(THF)4]: A solution of 1.00 g (1.25 mmol) of
crude 2[Li(THF)x] in 10 mL of THF was added dropwise with
stirring to a freshly prepared solution of 1.2 mL of Ni(CO)4 in
Reduction of 1a[Cl] with Lithium: To a stirred suspension of 1a[Cl]
(1.45 g, 2 mmol) in 15 mL of THF was added approximately 60 mg
(10 mmol) of freshly cut lithium wire. After 30 min, 31P-NMR-
10 mL of THF. After stirring for a further 2 h, the mixture was spectroscopic monitoring revealed, besides the presence of unre-
concentrated to a volume of 5 mL, treated with 5 mL of Et2O, and
filtered. Storage of the filtrate at 2°C for several weeks led to the
deposition of a colorless precipitate, which was recrystallized once
acted 1a, the formation of 2, 3, Ph3P, Ph2PLi (from cleavage of
Ph3P), as well as of the substitution product 8. Prolonged reaction
times led to a decay of the signals due to 8, while those due to a
from THF to give 540 mg (40%) of complex 4[Li(THF)4], m.p. new product 9 intensified. Continuation of the reaction for several
150°C (dec.), as colorless cubic crystals. Ϫ 1H NMR (CDCl3): δ ϭ days, or heating, led to the disappearance of all resonances other
Eur. J. Inorg. Chem. 1999, 1169Ϫ1174
1173

D. Gudat, V. Bajorat, S. Häp, M. Nieger, G. Schröder
FULL PAPER
than that due to Ph2PLi. Similar results were obtained when the
reduction of 1a[Cl] was performed with sodium.
atoms as a riding model, wR2(F2) ϭ 0.145, R[F, I > 2σ(I)] ϭ 0.049.
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC-101915. Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
U.K. [Fax: (internat.) ϩ 44-1223/336033; E-mail: deposit@ccdc.ca-
m.ac.uk].
Benzophosphole 8: A freshly prepared solution of phenyllithium
(26.6 mmol) in 100 mL of THF was added dropwise to a suspen-
sion of 1a[Cl] (15.7 g, 21.7 mmol) in 80 mL of THF at 0°C. The
mixture was stirred for 5 h at 0°C, then treated with 20 mL of
Et2O, and filtered. The filtrate was concentrated to dryness, the
residue was refluxed for 1 h with 250 mL of toluene, and the hot
solution was filtered. Slow cooling of the filtrate resulted in the
deposition of a crystalline precipitate, which was collected by fil-
tration and dried in vacuo to give 14.3 g (90%) of 8 as black
needles; m.p. 160°C. Ϫ 1H NMR (CDCl3): δ ϭ 7.55 [m, 12 H,
Acknowledgments
Financial support by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie is gratefully acknowledged.
Hmeta(PPh3)], 7.38 [m,
6 H, Hpara(PPh3)], 7.27 [m, 12 H,
Hortho(PPh3)], 7.21Ϫ7.15 [m, 3 H, Hortho/para(PPh)], 6.91 [m, 2 H,
Hmeta(PPh)], 6.08 (m, 2 H, 5-H/6-H), 5.94 (m, 2 H, 4-H/7-H). Ϫ
13C{1H} NMR (CDCl3):[18] δ ϭ 154.6 [m, 1JP(B),C ϭ 58.7 Hz, ΣJ ϭ
2.6 Hz, Cipso(PPh)], 148.3 (m, ΣJ ϭ 29 Hz, 2JP(B),C ϭ 0.5 Hz, C-3a/
[1] [1a]
[1b]
F. Mathey, Coord. Chem. Rev. 1994, 137, 1. Ϫ
K. B.
Dillon, F. Mathey, J. F. Nixon, Phosphorus: The Carbon Copy,
J. Wiley & Sons, Chichester, 1998, p. 227.
2
C-7a), 133.9 [m, JP(A),C ϭ 9.6 Hz, 4JP(B),C ϭ 2.0 Hz, Cortho(PPh3)],
[2] [2a]
[2b]
E. J. Padma Malar, J. Org. Chem. 1992, 57, 3694. Ϫ
D.
4
1
130.8 [m, JP(A),C ϭ 2.3 Hz, Cpara(PPh3)], 129.7 [m, JP(A),C
ϭ
B. Chesnut, L. D. Quin, J. Am. Chem. Soc. 1994, 116, 9638. Ϫ
3
3
[2c]
86.7 Hz, JP(B),C ϭ ϩ3.1 Hz, Cipso(PPh3)], 128.2 [d, JP(B),C
ϭ
B. Goldfuss, P. v. R. Schleyer, F. Hampel, Organometallics
3
6.9 Hz, Cmeta(PPh)], 127.8 [m, JP(A),C ϭ 11.1 Hz, Cmeta(PPh3)],
1996, 15, 1755.
[3]
126.4 [d, 2JP(B),C ϭ 4.6 Hz, Cortho(PPh)], 125.7 [s, Cpara(PPh)], 116.6
See, for example: P. Jutzi, T. Redeker, Eur. J. Inorg. Chem. 1998,
663, and references cited therein
1
(m, ΣJ ϭ 1.9 Hz, C-4/C-7), 116.3 (s, C-5/C-6), 33.3 (m, JP(A),C
ϭ
[4] [4a]
A. Espinosa Ferao, B. Deschamps, F. Mathey, Bull. Soc.
3
1
[4b]
119.2 Hz, JP(A)Ј C ϭ Ϫ9.3 Hz, JP(B),C ϭ 11.4 Hz, C-1/C-3). Ϫ
,
Chim. Fr. 1993, 130, 695. Ϫ
S. Holand, M. Jeanjean, F.
C50H39P3 (732.78): calcd. C 81.95, H 5.36; found C 81.0, H 5.1.
Mathey, Angew. Chem. 1997, 109, 117; Angew. Chem. Int. Ed.
Engl. 1997, 36, 98.
Reduction of Benzophosphole 8 with Lithium: To a solution of 1.00 g
(1.37 mmol) of 8 in 25 mL of THF was added an excess of lithium
powder, and the resulting mixture was allowed to react for 30 min
under sonification with ultrasound. 1H- and 31P-NMR-spectro-
scopic assays confirmed the formation of 9[Li2] (accounting for ca.
85Ϫ90% of the phosphorus-containing material), some Ph2PLi (ca.
10Ϫ15%), and phenyllithium. Characterization of the major prod-
uct 9[Li2] was achieved in situ by multinuclear (1H-, 13C-,
31P-)NMR analyses. All attempts to isolate and further purify the
product were unsuccessful, invariably resulting in partial or com-
[5]
[6]
For the generation of side-chain-functionalized phospholides in
[5a]
metal coordination spheres, see:
Organometallics 1992, 11, 1411. Ϫ
Glinsböckel, B. Ganter, Organometallics 1997, 16, 2862. Ϫ
[5c] C. Ganter, L. Brassat, B. Ganter, Chem. Ber. 1997, 130, 1771.
H. J Cristau, F. Plenat, in The Chemistry of Organophosphorus
Compounds, vol. 3 (Ed.: F. R. Hartley), J. Wiley & Sons, Chich-
ester, 1994, p. 45.
D. Gudat, V. Bajorat, M. Nieger, Bull. Soc. Chim. Fr. 1995,
132, 280.
For the synthesis and characterization of a benzo[b]phosphol-
ide, see: E. Niecke, M. Nieger, P. Wenderoth, Angew. Chem.
1994, 106, 362; Angew. Chem. Int. Ed. Engl. 1994, 33, 353.
A. Schmidpeter, M. Thiele, Angew. Chem. 1991, 103, 333; An-
gew. Chem. Int. Ed. Engl. 1991, 30, 308.
D. Gudat, Phosphorus Sulfur Silicon 1993, 77, 238.
W. A. Herrmann, C. Zybill, in Synthetic Methods of Organome-
tallic and Inorganic Chemistry, vol. 1 (Ed.: W. A. Herrmann),
Georg Thieme Verlag, Stuttgart, 1996, p. 41.
J. C. Tebby, in Phosphorus-31 NMR Spectroscopy in Stereoch-
emical Analysis (Eds.: J. G. Verkade, L. D. Quin), VCH, Deer-
field Beach, 1987, p. 1.
B. Deschamps, F. Mathey,
C. Ganter, L. Brassat, C.
[5b]
[7]
[8]
1
plete decomposition. Ϫ 9[Li2]: H NMR (CDCl3): δ ϭ 7.60 (m, 1
[9]
H, 6-H), 7.44 [m, 4 H, Hmeta(PPh2)], 7.38 (m, 1 H, 4-H/5-H), 7.22
(m, 1 H, 5-H/4-H), 7.13 [m, 2 H, Hmeta(PPh)], 6.91 [m, 4 H,
[10]
[11]
H
ortho(PPh2)], 6.80 (m, 1 H, 7-H), 6.68 [m, 2 H, Hortho(PPh)], 6.40
[m, 2 H, Hpara(PPh2)], 6.28 [m, 1 H, Hpara(PPh)]. Ϫ 13C{1H}NMR
1
3
(CDCl3): δ ϭ 160.2 [dd, JP(A),C ϭ 45.8 Hz, JP(X),C ϭ 7.6 Hz,
Cipso(PPh)], 146.6 [dd, JP(M),C ϭ 14.3 Hz, JP(X),C ϭ 5.0 Hz,
Cipso(PPh2)], 144.8 (dd, JP(M)/A,C ϭ 15.0 Hz, JP(X),C ϭ 7.2 Hz, C-
3a/C-7a), 144.5 (dd, JP(M)/A,C ϭ 7.5, 1 Hz, JP(X),C ϭ 1 Hz, C-7a/
C-3a), 139.2 (ddd, JP(X),C ϭ 46.1 Hz, JP(M),C ϭ 30.3, JP(A),C
6.3 Hz, C-3), 133.6 [dd, JP(M),C ϭ 18.7 Hz, JP(X),C ϭ 1.5 Hz,
Cmeta(PPh2)], 128.2 [dd, JP(A),C ϭ 17.8 Hz, JP(X),C ϭ 2.0 Hz,
[12]
[13]
1
3
1
3
1
3
All calculations were performed with the Gaussian 94 package:
M. J. Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G.
Johnson, M. A. Robb, J. R. Cheeseman, T. Keith, G. A. Peters-
son, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V.
G. Zakrzewski, J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y.
Ayala, W. Chen, M. W. Wong, J. L. Andres, E. S. Replogle, R.
Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees,
J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez, J. A.
Pople, Gaussian 94, Rev. B.3, Gaussian, Inc., Pittsburgh PA,
1995.
1
1
3
ϭ
3
5
3
5
3
C
meta(PPh)], 126.9 [d, JP(M),C ϭ 5.7 Hz, Cortho(PPh2)], 126.1 [d,
3JP(M),C ϭ 5.7 Hz, Cortho(PPh)], 120.6 (dd, JP(A),C ϭ 7 Hz,
3
3JP(X),C ϭ 6 Hz, C-7), 120.4 (dd, 4JP(A)/M,C ϭ 4 Hz, 4JP(X),C ϭ 6 Hz,
4
4
C-4/C-5), 119.7 (ddd, JP(A)/M,C ϭ 5.5, 1.7 Hz, JP(X),C ϭ 12.0 Hz,
C-5/C-4), 118.6 (dd, JP(M),C ϭ 15.7 Hz, JP(X),C ϭ 4.8 Hz, C-6),
116.5 [s, Cpara (PPh2)], 116.0 [s, Cpara(PPh)], 116.0 (ddd, JP(X),C
52 Hz, JP(A),C ϭ 8 Hz, JP(M),C ϭ 5 Hz).
[14]
[15]
3
4
D. Gudat, M. Nieger, M. Schrott, Chem. Ber. 1995, 128, 259.
International Tables for Crystallography, vol. C (Ed.: A. J. C.
Wilson), Kluwer Academic Publishers, Dordrecht, 1992, p. 680.
1
ϭ
1
3
[16] [16a] N. Burford, B. W. Royan, A. Linden, T. S. Cameron, Inorg.
[16b]
Chem. 1989, 28, 144. Ϫ
N. Burford, A. I. Dipchand, B. W.
X-ray Crystal Structure Determination of 4[Li(THF)4]:
Royan, P. S. White, Inorg. Chem. 1990, 29, 4938. Ϫ [16c] N. Bur-
ford, A. I. Dipchand, B. W. Royan, P. S. White, Acta Crys-
tallogr. 1989, C45, 1485.
C38H24Ni2O6P3 · Li(THF)4 · Et2O, colorless, Mr ϭ 1156.4; mono-
˚
clinic, space group P21/c (No. 14), a ϭ 32.3511(7) A, b ϭ
[17]
[18]
˚
˚
13.8186(5) A, c ϭ 29.4593(8) A, β ϭ 116.262(2)°, V ϭ 11810.3(6)
A. W. Johnson, Ylides and Imines of Phosphorus, J. Wiley &
Sons, New York, 1993, p. 139.
A , Z ϭ 8, µ(Mo-Kα) ϭ 0.78 mmϪ1, T ϭ 123(2) K, 68443 reflec-
3
˚
Couplings in higher order multiplets were determined by spec-
tions measured (2θmax ϭ 50°), 19310 independent reflections used
for structure solution (direct methods) and refinement (on F2 aniso-
tropic with SHELXL-93), 1348 parameters, 2915 restraints, H
4
tral analysis and by using JP(B),P(BЈ) ϭ 5.5 Hz.
Received December 28, 1998
[I98453]
1174
Eur. J. Inorg. Chem. 1999, 1169Ϫ1174