Imidovanadium(v) complexes as reaction partners for kinetically stabilized phosphaalkynes: Synthesis of 1,2,4-azaphosphavanada(v)-cyclobutenes, 1,3,5-triphosphabenzenes, and 1H-1,2,4-azadiphospholes

Article abstract of DOI:10.1002/1521-3765(20001215)6:24<4558::AID-CHEM4558>3.0.CO;2-6

Cycloaddition reactions of the kinetically stabilized phosphaalkynes 1 with the imidovanadium(v) trihalides 9 furnish the 1,2,4-azaphosphavanada(v)cyclobutenes 10. The stability of these novel metallacyclic compounds depends solely on the substitutents of the imido unit. Thus, the imidovanadium(v) species 9 with tertiary alkyl groups on the N atom form stable addition products with 1 while in the cases of compounds 9 with a lower degree of substitution at N (primary and secondary alkyl groups) the primarily formed adducts 10 undergo irreversible decomposition to afford the 1H-1,2,4-azadiphospholes 13. Reactions of an excess of the phosphaaalkyne 1 with the vanadium complexes 9 furnish the corresponding triphosphabenzenes 8 in good yields (36-68%). A catalytic reaction course has been demonstrated for the all-tert-butyl system 1a/9a in which the metallacyclic species 10a serves as the catalytically active species. Poisoning of the catalyst leads to a second reaction pathway, which results in formation of the azatetraphosphaquadricyclanes 16. By means of the stepwise use of different phosphaalkynes 1a,b this methodology provides the first access to the differently substituted triphosphabenzenes through cyclotrimerization.

Full text of DOI:10.1002/1521-3765(20001215)6:24<4558::AID-CHEM4558>3.0.CO;2-6

FULL PAPER
Organophosphorus Compounds, Part 148[=]
Imidovanadiumꢀv) Complexes as Reaction Partners for Kinetically Stabilized
Phosphaalkynes: Synthesis of 1,2,4-Azaphosphavanadaꢀv)-cyclobutenes, 1,3,5-
Triphosphabenzenes, and 1H-1,2,4-Azadiphospholes
Frank Tabellion, Christoph Peters, Uwe Fischbeck, Manfred Regitz,* and Fritz Preuss*[a]
Dedicated to Professor A. Schmidpeter on the occasion of his 70th birthday
Abstract: Cycloaddition reactions of
the kinetically stabilized phosphaal-
secondary alkyl groups) the primarily
formed adducts 10 undergo irreversible
decomposition to afford the 1H-1,2,4-
azadiphospholes 13. Reactions of an
excess of the phosphaaalkyne 1 with
the vanadium complexes 9 furnish the
corresponding triphosphabenzenes 8 in
good yields "36 ± 68%). A catalytic re-
action course has been demonstrated for
the all-tert-butyl system 1a/9a in which
the metallacyclic species 10a serves as
the catalytically active species. Poison-
ing of the catalyst leads to a second
reaction pathway, which results in for-
mation of the azatetraphosphaquadricy-
clanes 16. By means of the stepwise use
of different phosphaalkynes 1a,b this
methodology provides the first access to
the differently substituted triphospha-
benzenes through cyclotrimerization.
kynes
1 with the imidovanadium"v)
trihalides 9 furnish the 1,2,4-azaphos-
phavanada"v)cyclobutenes 10. The sta-
bility of these novel metallacyclic com-
pounds depends solely on the substitu-
tents of the imido unit. Thus, the
imidovanadium"v) species 9 with terti-
ary alkyl groups on the N atom form
stable addition products with 1 while in
the cases of compounds 9 with a lower
degree of substitution at N "primary and
Keywords: cycloadditions
´ cyclo-
oligomerizations ´ imidovanadium"v)
complexes ´ phosphaalkynes ´ phos-
phorus heterocycles
Thus, dimers, trimers, and tetramers of the phosphaalkynes
have been constructed in the coordination spheres of tran-
sition metals.[5, 6, 7] In general, phosphaalkynes preferentially
undergo cyclization to afford 1,3-diphosphacyclobutadienes in
the presence of electron-rich transition metal fragments, while
in the presence of the in situ generated 14 valence electron
species Cp2Zr they react to furnish the tricyclic complexes
3.[5a,b] The cyclotrimerization of tert-butylphosphaalkyne 1a
on unsaturated ["Cot)Hf] transition metal templates repre-
sented a major breakthrough in this research. The reaction of
"h4-butadiene)Hf"Cot) 6 with 1a at lowtemperature furnish-
ed the complex 7 "Scheme 1).[6a] When the same reaction was
performed at 258C it proceeded through smooth tetrameriza-
tion of 1a with formation of hafnium-tetraphosphabarrelene
complex.[7] A common feature of all currently known,
transition metal induced cyclooligomerization reactions of
phosphaalkynes, however, is the incorporation of the metal
complex fragment in the reaction product. The first successful
liberation of a metal-bound phosphaalkyne oligomer was
realized with an early transition metal complex through
oxidation of the metal fragment by hexachloroethane; both
stable and unstable cyclooligomers were released in this way.
Introduction
Cyclooligomerization reactions of phosphaalkynes, especially
those of the kinetically stabilized type 1, are important
processes in the current research on low-coordinated phos-
phorus compounds.[1, 2, 3] Purely thermal reactions are always
unspecific and generally lead to tetramerization products.[4]
Specific cyclooligomerization reactions have only been real-
ized in the presence of organometallic auxiliary compounds
and proceed with incorporation of the metal complex frag-
ment.
[a] Prof. Dr. M. Regitz, Prof. Dr. F. Preuss, Dr. F. Tabellion,
Dr. C. Peters, Dipl.-Chem. U. Fischbeck
Fachbereich Chemie, Universität Kaiserslautern
Erwin-Schrödinger-Strasse, 67663 Kaiserslautern "Germany)
Fax : "‡49)631-205-3921
E-mail: regitz@rhrk.uni-kl.de
fpreuss@rhrk.uni-kl.de
=
Â
[ ] Part 147: M. A. Hofmann, U. Bergsträsser, G. J. Reiû, L. Nyulazi,
M. Regitz, Angew. Chem. 2000, 112, 1318 ± 1320; Angew. Chem. Int. Ed.
2000, 39, 1261 ± 1263.
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4558±4566
Scheme 1. Cyclooligomerization of phosphaalkynes 1.
This mild oxidation agent also effected the elimination of the
zirconium fragment from 3 to liberate the highly reactive 1,3-
diphosphacyclobutadiene 4, which after further cyclodimeri-
zation could be isolated in high yield as the well known
tetraphosphacuban.[8] The triphosphabenzene 8a, which can-
not be obtained by thermally induced cyclotrimerization, was
first prepared by a comparable cleavage reaction from the h8-
cyclooctatetraene complex 7. This synthetic strategy was also
applied with success to prepare the Dewar-triphosphabenzene
valence isomer of 8a and the corresponding tetraphospha-
barrelene.[6b]
Scheme 2. Synthesis of complexes 10.
ly apparent from their spectroscopic data. The NMR spectra
of compounds 10 contain several structurally specific features
"Figure 1) which are discussed below for the example of
product 10a. The 51V NMR spectrum provides the first
indication for the formation of the four-membered ring
system: The chemical shift of d ˆ 310 for 10a is in the range
We recently described the first cyclotrimerization of
phosphaalkynes in the coordination sphere of tert-butylimi-
dovanadium"v) trichloride 9a which furnished the free 1,3,5-
triphosphabenzenes 8 directly.[9] In this context we now report
on the reactions between kinetically stabilized phosphaal-
kynes 1 and imidovanadium"v) complexes of the type 9.
Results and Discussion
Figure 1. Characteristic NMR data of the metallacycle 10a.
1,2,4-Azaphosphavanadaꢀv)cyclobutene: Reactions of equi-
molar amounts of a phosphaalkyne 1 a ± e with imidovana-
dium"v) trichloride 9a proceed through [2 ‡ 2] cycloaddition
typical for a vanadium"v) compound with a metal ± carbon
bond.[10] The 1H NMR spectrum of 10ashows the two signals
at d ˆ 1.39 and 1.41 expected for the two tert-butyl groups
"intensity ratio 1:1) with the signal at higher field being split
ꢀ
of the P C triple bond to the metal-nitrogen multiple bond to
furnish the 1,2,4-azaphosphavanada"v)cyclobutenes 1 0a ± e
which are stable at room temperature "Scheme 2). Perform-
ance of the reactions at lowtemperatures and exact observa-
tion of the stoichiometry are essential for the successful
preparation of the metallacylic products 10.
The formation of these novel complexes 10 from one
equivalent each of phosphaalkyne 1 and vanadium halide 9a
is confirmed by their analytical and mass spectral data. The
constitutions of the cycloaddition products are unambiguous-
4
into a doublet with a J"H,P) coupling constant of 1.2 Hz. At
highest field the 13C{1H} NMR spectrum reveals doublets at
d ˆ 31.8 and 32.9 with 3J"C,P) coupling constants of 6.4 Hz for
the methyl carbon atoms of the two tert-butyl groups. On
account of the identical coupling constants it can safely be
assumed that the phosphorus atom lies between the C and N
atoms bearing the tert-butyl groups. The signal for the ring
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M. Regitz, F. Preuss et al.
FULL PAPER
carbon atom is strongly shifted to lowfield " d ˆ 310.2) and can
only be observed at a high accumulation rate or at lower
temperature "170 K); it is very broad and has a plateau-like
appearance. Splittings attributable to the directly adjacent P
and V atoms cannot be detected. Both the shape of the signal
and the conditions required for its detection are typical
phenomena always observed for vanadium-carbon com-
pounds are due to quadrupole relaxations of the coupling
51V nucleus "I ˆ 7/2). The relaxation of the vanadium nucleus
is only accelerated to such an extent by reducing the
temperature that the resonances of the carbon atom become
visible. This effect must also be held responsible for the
absence of splitting and widening of the signals of the
quaternary carbon atoms "d ˆ 55.9 and 73.8) of the two tert-
butyl groups. In the case of the tert-butyl group at the nitrogen
atom the quadrupole effects of the 51V and 14N nuclei are
complementary. The 31P NMR spectrum of 10a contains a
signal at d ˆ À73.0 for the ring phosphorus atom. This
relatively strong shielding and the resultant high field shift
has previously only been observed for phosphaalkynes with
inverse electron densities.[11, 12] The deshielding of the neigh-
boring ring carbon atom must also be viewed in this context
and considered as being characteristic for systems of this type
as well as emphasizing the electron situation "10B).
Scheme 3. Synthesis of complex 12.
The signals in the 13C{1H} NMR spectrum of 12 are of
particular interest. As expected the ring carbon atom gives
rise to a doublet signal at very lowfield " d ˆ 301.3) with a
1J"C,P) coupling constant of 108.6 Hz. Analogously, the
quaternary carbon atoms of the two tert-butyl groups also
couple with the ring phosphorus atom. The signal at d ˆ 65.9 is
assigned to the quaternary carbon atom of the tert-butyl group
on nitrogen on account of its stronger shift to lower field and
smaller 2J"C,P) coupling while the doublet at d ˆ 49.9 is
assigned to that of the tert-butyl group on the carbon atom.
The methyl carbon atoms give rise to signals at almost
identical chemical shifts of d ˆ 34.1 and 33.1 with comparable
3J"C,P) coupling constants "8.6 and 7.3 Hz). The exocyclic tert-
butylimido ligand gives rise to singlet signals at d ˆ 81.1 and
31.4. The good agreement of the 31P and 13C NMR data for
10a and 12 as well as the characteristic coupling constants of
12 support the proposed four-membered ring structure.
Changes in the alkyl group R1 of the phosphaalkyne have
no effect on the stability of the complexes 10 whereas changes
in the alkyl group R2 of the imido units of 9 do have a
pronounced effect: Reactions of the trichlorides 9a ± d with
1a furnish the stable and isolable [2 ‡ 2] cycloaddition
products 10a, f, g, and h "Scheme 4), the metallacyclic species
10i ± l with secondary or primary alkyl groups on the ring
nitrogen atom are merely detected as intermediates in the
reaction mixture by spectroscopy "Table 1).
In analogy to 13C NMR spectroscopy the quadrupole effect
of the 51V nucleus is also apparent from the characteristic
signal shape and slight broadening of the signal.[10] However,
this is markedly less pronounced than in complexes in which
the vanadium atom is directly adjacent to the phosphorus
2
atom.[13] The J"P,V) coupling constant was determined by
spectral simulation.[14] With a magnitude of 30.3 Hz it is
markedly less than the range of known 1J"P,V) coupling
constants "160 ± 480 Hz) and may thus be assigned to the
2
previously unknown J"P,V) coupling.[15, 16] Molecular weight
measurement and analysis of the 51V, 13C, and 31P NMR
spectra unequivocally confirms that compounds 10 contain
the previously unknown azaphosphametallacyclobutene ring
system.
We have also examined the question of whether this
cyclization reaction can be applied to the easily accessible
bis"tert-butylimido)chromium"vi)dichloride 11, in particular
for the purpose of eliminating the disturbing quadrupole
effect of the vanadium atom "pronounced line broadening),
thus obtaining additional spectroscopic data in support of the
four-membered ring structure. Indeed, reaction of the phos-
phaalkyne 1a with an equimolar amount of 11 resulted in the
quantitative formation of the metallacyclic product 12.
In contrast to the reactions with the imidovanadium"v)
complexes 9 neither the reaction temperature nor the stoichi-
ometry has a significant effect on the course of the reaction.
The possible second addition to the remaining metal-nitrogen
multiple bond in 12 was not observed even in the presence of a
large excess of the starting phosphaalkyne 1a.
The 31P NMR spectrum of 12 contains a singlet at d ˆ
À76.2. This chemical shift is almost identical with those seen
for the vanadium-containing cycloaddition products 10 and
can thus be considered to be typical for these four-membered
ring systems with an inverse electron density of the phos-
phaalkene unit "12A$ 12B) "Scheme 3).
These unstable metallacyclic species 10i ± l undergo quan-
titative conversion to the 1H-1,2,4-azadiphospholes[17] 1 3a ± d
within 24 h "Table 2).
NMR spectroscopic monitoring of the reaction does not
provide information about possible intermediates which lead
to products 13. It can only be shown that after completion of
the reaction the free imidovanadium component 9 is no longer
present in the reaction mixture. Thus, although a simple
transfer reaction of a phosphaalkyne unit between two
molecules of the metallacyclic species 10 with liberation of
one equivalent of 9 and subsequent reductive elimination of
VCl3 can be excluded, the mechanism of formation of 13
remains unknown.
Elemental analyses and mass spectral data clearly confirm
that the heterodiphospholes are made up from two equiv-
alents of phosphaalkyne 1a with incorporation of the imido
ligands from the vanadium compounds 9e ± h.
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Phosphaalkynes
4558±4566
diphospholes "d ˆ 247.3 and 148.1).[18] This splitting pattern
and the resultant coupling constant of 34.9 Hz is only
compatible with a 2,4-arrangement of the two P atoms. The
13C NMR data for the ring carbon atoms C-3 and C-5
unequivocally confirm the constitution. Because of its cou-
pling with the two directly adjacent atoms P-2 and P-4 the
signal for the carbon atom C-3 "d ˆ 202.2) is split into a double
1
doublet with two almost identical J"C,P) coupling constants
of 62.3 and 52.5 Hz. A double doublet signal is also observed
for C-5 "d ˆ 193.8) but with a small coupling to P-2 [2J"C,P) ˆ
1
3.7 Hz] and a J"C,P) coupling of 59.8 Hz to P-4.
Although changes in the alkyl rest bonded to the imido
nitrogen atom had clear effects on the stability of the
cycloaddition products 10, exchange of the halogen atoms
"Cl ! Br) did not result in any changes in this reaction. Thus,
cyclization of 1a with 14 also proceeded smoothly to furnish
the stable bromo analogue 15 "Scheme 5).
Scheme 4. Stable and unstable complexes 10, synthesis of 1H-1,2,4-
azadiphospholes 13.
Table 1. Characteristic 51V and 31P NMR data of metallacycles 10 and 15.
Compound
51V NMR signal[a]
31P NMR signal[a]
Scheme 5. Synthesis of complex 15.
10a
10b
10c
10d
10e
1 0 f
10g
10h
310.0
320.5
312.3
320.4
317.2
316.0
380.3
363.3
315.5
324.5
344.8
320.4
472.1
À 73.0
À 72.5
À 71.9
À 71.4
À 71.8
À 73.5
À 64.8
À 69.1
À 69.4
À 66.3
À 62.2
À 68.8
À 62.4
As expected, the formal exchange of three chlorine atoms
for three bromine atoms at the metal center resulted in a low
field shift of the 51V NMR signal of 15 "d ˆ 472) with all other
NMR data remaining in harmony with those of the chlorine
derivative 10a; thus no detailed discussion is necessary.
[b]
10i
[b]
10j
[b]
10k
1,3,5-Triphosphabenzenes: On reaction with an excess of the
cycloaddition partners 1 a ± e "4 equiv) under otherwise com-
parable conditions, compound 9a afforded the substituted
triphosphabenzenes 8a ± e, which were obtained as yellow
solids after column chromatographic work-up with the
exception of 8c "yellowoil).
[b]
10l
15
[a] Singlet. [b] Unstable intermediate.
Table 2. Characteristic 31P NMR data of 1H-1,2,4-azadiphospholes 13.
The easy accessibility of the cyclotrimerization starting
product 9a, the generally satisfactory yields "36 ± 68%), and
the one-pot procedure represent major advantages over the
previously reported syntheses of 8a and 8b,[6b,c] the only
previously known examples of the 1,3,5-triphosphabenzenes;
thus the reaction opens a novel and simple approach to this
class of compounds.
Compound
31P NMR[a]
2J"P,P)
13a
13b
13c
13d
148.1, 247.3
154.1, 259.3
148.6, 258.8
127.1, 250.0
34.9
29.7
26.2
27.1
[a] Doublet.
Elemental analyses and mass spectral data demonstrate the
composition of compounds 8 from three phosphaalkyne
building blocks. The constitutions of the newtriphosphaben-
zenes 8c ± e is unequivocally supported by their spectroscopic
data and comparison with the previously known compounds
8a,b "Table 3).[6b,c]
The constitutions were elucidated on the basis of NMR
spectroscopic studies as described belowfor the example of
compound 13a. The 1H NMR spectrum with two signals each
for the tert-butyl groups "d ˆ 1.63 and 1.39) and the isopropyl
groups "d ˆ 4.69 and 1.38) demonstrates the unsymmetrical
nature of the 1H-azadiphospholes although the splitting
patterns of the couplings with the ring phosphorus atoms do
not allowany firm conclusions on the arrangement of the two
P atoms in the ring "2,4 or 2,3 positions). The 31P NMR
spectrum exhibits a characteristic AX spin system for the two
phosphorus atoms in the lowfield region typical for hetero-
Table 3. Characteristic 31P and 13C NMR data of triphosphabenzenes 8.
Compound
8a
8b
8c
8d
8e
31P NMR[a]
13C NMR[b]
232.6
211.8
238.1
212.2
238.8
208.8
234.2
211.8
242.8
212.1
[a] Singlet. [b] X part of A2BX spin system.
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As to be expected from the C3 symmetry of the molecules,
the 31P NMR spectra each showa singlet signal in the region
characteristic for phosphinines "d ˆ 234.2 ± 242.8).[19] Besides
the less important signals for the individual substituents "see
Experimental Section), the 13C NMR spectra of 8c ± e contain
the structurally relevant signals for the ring carbon atoms
between d ˆ 208.8 ± 212.2. Their coupling patterns correspond
to the X part of an A2BX spin system.
In the case of the reaction of 9a with 1a the process is
product specific for 8a "16a cannot be detected), whereas on
the other hand lowlevels of formation of the azatetraphos-
phaquadricylanes 16b ± e can be observed in the cyclotrime-
rizations of the phosphaalkynes 1 b ± e "Scheme 6). The
hypothesis, compound 9a was allowed to react with eight
equivalents of tert-butylphosphaalkyne 1a.
Column chromatographic work-up analogous to that used
for the 1:4 reaction furnished 8a in a comparable yield of 68%
referred to the employed phosphaalkyne. The magnitude of
this yield unambiguously supports the catalytic nature of the
reaction. The renewed formation of the catalyst, as a typical
feature of catalytic reactions, is confirmed by 31P/51V NMR
spectroscopy. Besides 10a, 31P NMR spectroscopic monitoring
of the reaction solution reveals the presence of traces of the
tetraphosphabarrelene 17[6] "Scheme 7) and the azatetraphos-
Scheme 7. Catalytic cyclotrimerization of 1a.
phaquadricyclane 16a.[9, 20] Although the formation of the
barrelene 17 can be considered as a known subsequent
reaction of 1a with 8a,[21] the formation of the azatetraphos-
phaquadricyclane is most certainly an alternative reaction
pathway proceeding with destruction of the catalyst.
The proposed reaction mechanism for the cyclotrimeriza-
tion process is as follows "Scheme 8): The first step involves a
Scheme 6. Synthesis of 1,3,5-triphosphabenzenes 8.
heterocyclic compounds 16 can also be obtained selectively by
the reaction between the DME adduct of 9a with the
corresponding phosphaalkyne.[9, 20] The trimethylsilylimido-
vanadium"v) trichloride 9d or tribromide 14 may also be used
for the preparation of 8a; these species exhibit an identical
reaction behavior to 9a in the presence of an excess of the
phosphaalkyne 1a "4 equiv), but are not synthetically advan-
tageous on account of their more difficult syntheses.
The participation of the metallacylic species 10 in the
cyclotrimerization process is clearly apparent: Compound 10
can always be detected by spectroscopy at the end of the
reaction and is thus involved in the cyclotrimerization. When
10ais allowed to react with two or three equivalents of 1a the
formation of the triphosphabenzene 8a in the expected yield
is observed. Other intermediates to 8a cannot be identified.
The reaction of 9a with two or three equivalents of 1a also
furnishes the cyclotrimerization product 8a directly. In all
reactions of 9a with more than one equivalent of 1a it is clear
that one equivalent of the cycloaddition partner is always
required for the formation of the metallacyclic species 10a
which is also present in the solution after completion of the
trimerization reaction.
Scheme 8. Proposed reaction mechanism for the cyclotrimerization of 1.
[2 ‡ 2]-cycloaddition reaction between 9 and 1 with formation
of the metallacyclic species 10. Insertion of a further molecule
of 1 into the metal ± carbon bond affords the intermediate 19.
This six-membered ring species can undergo both ring
expansion with a third equivalent of 1 to give the metal-
lacyclooctatriene 18 and a [4 ‡ 2] Diels ± Alder reaction to
form the metallabarrelene derivative 20. The reaction step
with a fourth equivalent of 1 completing the cycle results in
Consideration of these facts allows only one conclusion,
namely that the formation of the 1,3,5-triphosphabenzenes 8
is a catalytic process and that the metallacyclic compound 10
is the catalytically active species. In order to confirm this
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Phosphaalkynes
4558±4566
liberation of the 1,3,5-triphosphabenzene 8 with renewed
formation of the catalyst 10. The catalytic sequence is
interrupted when the insertion of a molecule of 1 does not
occur in the metal ± carbon but rather in the metal ± nitrogen
bond of 10. As already reported, this leads to formation of the
azatetraphosphaquadricyclane 16 with irreversible destruc-
tion of the catalyst.[9, 20] Further support of the catalytic
trimerization process is provided by the reactions of the
metallacylic species 10a,b with the phophaalkynes 1b,a.
Besides the known uniformly substituted heteroaromatic
products 8 these reactions represent the first accesses to the
differently substituted derivatives 21 and 22. The different
products obtained conclusively confirms that 10a, 10b
participate both in the formation of the unsymmetrically
substituted triphosphabenzenes 21, 22 as well as, after their
renewed formation as 10b, 10a in the catalytic process. The
symmetrically substituted 1,3,5-triphosphabenzenes 8a,b are
then formed in a further reaction sequence "Scheme 9).
substituted azatetraphosphaquadricyclane as a by-product.[20]
Subsequent reactions of the triphenylmethyl-substituted met-
allacyclic species 10g with 1a were completely suppressed.
Among the trimerization reagents 9 the imido trichlorides
9e ± h bearing secondary or primary alkyl groups again
occupy a special position. Although their reactions with four
equivalents of tert-butylphosphaalkyne 1a also resulted in the
formation of the 1,3,5-triphosphabenzene 8a, the tetraphos-
phacubane 5[8] and the corresponding 1H-azadiphosphole 13
were also formed in comparable amounts "Scheme 10).
Scheme 10. Reaction of complexes 9e ± h bearing secondary or primary
alkyl groups with four equivalents 1a.
While the formation of 13 had already been observed as a
result of decomposition reactions during the preparation of
the unstable metallacyclic compounds 1 0i ± l, the formation of
the tetraphosphacubane 5 is rather a surprising result in this
case. 31P NMR spectroscopic monitoring of the reaction
clearly reveals the primary formation of the triphosphaben-
zene 8a. This process, however, comes to a halt with
increasing reaction time with a parallel increase in the
formation of the 1H-azadiphosphole 13. The increasing
concentration of the 1H-azadiphosphole is accompanied by
a pronounced formation of the cubane 5 "Scheme 10) which
finally becomes the dominating reaction. In the final stages
only an increase in the concentration of the cubane can be
observed while the contents of 8a and 13 in the solution
remain constant.
Scheme 9. Synthesis of 1,3,5-triphosphabenzenes 21 and 22.
The separation of the two compounds was not possible,
even by column chromatography. However, the identities of
the novel heteroaromatic compounds 21 and 22 were un-
equivocally demonstrated by analysis of the 31P NMR
spectrum of the reaction mixture and by mass spectroscopy.
In both cases the molecular ion peaks for 21, 22, respectively,
were observed together with those for the known 1,3,5-
triphosphabenzenes 8a,b. The 31P NMR spectrum of the
mixture 21, 22 contains signals with the characteristic AB2
spin systems for the substitution pattern with 2J"P,P) coupling
constants of 6.2 and 7.9 Hz. With 31P NMR chemical shifts of
d ˆ 235.4/235.2 and 237.2/237.0, respectively, compounds 21, 22
fit into the series between the uniform tert-butyl and the
uniform 1-adamantyl derivatives 8a,b. The close relationship
of products 21, 22 with the corresponding symmetrical
derivatives 8b,a is also documented by their chemical shifts;
thus, for example, the signals of 22 are markedly closer to
those of 8a than to those of 8b on account of its higher
content of tert-butyl groups.
The ready availability of the 1,3,5-triphosphabenzenes 8
and the 1H-1,2,4-azadiphospholes 13 have enabled us to study
the reactivity of these two phosphorus-containing heterocyclic
systems. In accord with our current research interests
emphasis will be placed on the addition and cycloaddition
behavior of these species.
As expected in analogy to the 1:1 reactions, variation of the
alkyl group on the imido ligand in 9 does result in a change in
the reaction behavior. Although the trimethylsilyl derivative
9d also reacts with an excess of 1a "4 equiv) to furnish the
trimer 8a exclusively; reaction of the 1-adamantyl derivative
9b under comparable conditions affords the N-adamantyl-
Experimental Section
General: All experiments were carried out under argon "purity >99.998%)
in previously evacuated and oven-dried Schlenk vessels. The solvents are
anhydrous and stored under argon prior to use. NMR spectra were
Chem. Eur. J. 2000, 6, No. 24
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0624-4563 $ 17.50+.50/0
4563

M. Regitz, F. Preuss et al.
FULL PAPER
recorded on Bruker WP 200 and AM 400 instruments. Chemical shifts for
the 1H and 13C NMR nuclei are reported in parts per million "d) relative to
tetramethylsilane as the internal standard; chemical shifts for 31P are
relative to external 85% orthophosphoric acid and 51V are relative to
external VOCl3. Elemental analyses were performed on Perkin ± Elmer
Analyser EA 240 and 2400 CHN. Bulb-to-bulb distillations were carried
out in a Büchi GKR 50 apparatus "temperatures given refer to the heating
mantle). Mass spectra were recorded on a Finnigan MAT 90 spectrometer.
Starting compounds 1a,[22a,b] 1b,[22c] 1c,[22d] 1d,e,[22e] 9a,[23a,b] 9b ± h,[23d] 11,[24]
and 14[23c] were prepared by published methods.
2.3 Hz, cyclohexyl-CH2], 33.1 [d, 3J"C,P) ˆ 5.9 Hz, NC"CH3)3], 41.5 [d,
3J"C,P) ˆ 7.0 Hz, cyclohexyl-CH2], 41.8 [d, 3J"C,P) ˆ 8.2 Hz, cyclohexyl-
CH2], 62.4 [m, CC"CH2)2CH3], 73.9 [m, NC"CH3)3], [CC"CH3)3] not found;
31P NMR "C6D6, 81.0 MHz, 258C): d ˆ À71.8 "s); 51V NMR "C6D6,
52.6 MHz, 258C): d ˆ 317.2 [s, n1/2 ˆ 214 Hz]; MS "70 eV, EI): m/z "%):
‡
‡
‡
367 "7) [M] , 311 "36) [M À C4H8] , 275 "22) [M À C4H9Cl] , 57 "100)
‡
[C4H9] ; C12H22Cl3NPV "368.59).
1-ꢀ1-Adamantyl)-3-tert-butyl-4,4,4-trichloro-1-aza-2-phospha-4-vanadaꢀv)-
cyclobut-2-ene ꢀ10 f): Compound 9b "130 mg, 0.41 mmol) in toluene "5 mL)
and 1a "40 mg, 0.41 mmol) furnished 1 0 f "170 mg, 100%) as a brown
powder. 1H NMR "C6D6, 200 MHz, 258C): dˆ1.41 ± 2.20 [m, 15H, Ad-H], 1.52
[s, 9H, C"CH3)3]; 13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 30.8 [s, Ad-CH2],
31.9 [d, 3J"C,P) ˆ 6.6 Hz, C"CH3)3], 35.7 [s, Ad-CH], 47.0 [d, 3J"C,P) ˆ
4.0 Hz, Ad-CH2], 55.9 [s, CC"CH3)3], 75.9 [s, Ad-C], [CC"CH3)3] not
found; 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ À73.5 "s); 51V NMR "C6D6,
52.6 MHz, 258C): d ˆ 316.0 [s, n1/2 ˆ 193 Hz]; MS "70 eV, EI): m/z "%): 135
General procedure for the preparation of the metallacycles 10a ± h, 12, and
15: An equimolar amount of phosphaalkyne 1 was added at À788C to a
solution of the imido compound 9, 11, or 14 in toluene. The mixture was
allowed to warm up and the solvent was removed at 208C at 10À2 mbar. The
metallacyclic products were obtained as dark residues in quantitative yield.
1,3-Di-tert-butyl-4,4,4-trichloro-1-aza-2-phospha-4-vanadaꢀv)cyclobut-2-
ene ꢀ10a): Compound 9a "260 mg, 1.15 mmol) in toluene "5 mL) and 1a
"120 mg, 1.15 mmol) afforded 10a "380 mg, 100%) as a brown powder.
1H NMR "C6D6, 200 MHz, 258C): d ˆ 1.39 [s, 9H, C"CH)3], 1.41 [d,
4J"H,P) ˆ 1.2 Hz, 9H, C"CH)3]; 13C NMR "C6D6, 50.3 Hz, 170 K): d ˆ 31.8
‡
‡
‡
"80) [C10H15] , 92 "100) [C7H8] , 57 "8) [C4H9] ; C15H24Cl3NPV "406.63).
1-tert-Butyl-4,4,4-trichloro-3-ꢀtriphenylmethyl)-1,2,4-azaphosphavana-
daꢀv)cyclobut-2-ene ꢀ10g): Compound 9c "271 mg, 0.65 mmol) in toluene
"5 mL) and 1a "65 mg, 0.65 mmol) furnished 10g "336 mg, 100%) as a
brown powder. 1H NMR "C6D6, 200 MHz, 258C): d ˆ 1.43 [d, 4J"H,P) ˆ
7.3 Hz, 9H, C"CH)3], 6.90 ± 7.50 [m, 15H, Ph]; 13C NMR "C6D6, 50.3 Hz,
3
3
[d, J"C,P) ˆ 6.4 Hz, C"CH3)3], 32.9 [d, J"C,P) ˆ 6.4 Hz, C"CH3)3], 55.9 [s,
CC"CH3)3], 73.8 [s, NC"CH3)3], 314.2 [s, CC"CH3)3]; 31P NMR "C6D6,
81.0 MHz, 258C): d ˆ À73.0 "s); 51V NMR "C6D6, 52.6 MHz, 258C): d ˆ
3
258C): d ˆ 31.9 [d, J"C,P) ˆ 7.5 Hz, C"CH3)3], 55.9 [s, CC"CH3)3], 95.7 [s,
‡
C"C6H5)3], 141.6 [s, C"C6H5)3], 143.8 [s, C"C6H5)3], 145.8 [s, C"C6H5)3],
149.0 [s, C"C6H5)3], 314.6 [s, CC"CH3)3]; 31P NMR "C6D6, 81.0 MHz, 258C):
310.0 [s, n1/2 ˆ 209 Hz]; MS "70 eV, EI): m/z "%): 327 "2) [M] , 270 "7) [M À
‡
‡
‡
C4H9] , 235 "6) [M À C4H9Cl] , 57 "100) [C4H9] ; molecular weight "cryosc,
C6H6): calcd 328.52, found 345; elemental analysis calcd for C9H18Cl3NPV
"328.52): C 32.90, H 5.52, N 4.26; found C 32.7, H 5.5, N 4.1.
d ˆ À64.8 "s); 51V NMR "C6D6, 52.6 MHz, 258C): d ˆ 380.3 [s, n1/2
ˆ
‡
‡
230 Hz]; MS "70 eV, EI): m/z "%): 257 "3) [NCPh3] , 243 "7) [CPh3] , 77
‡
"100) [Ph] ; C23H24Cl3NPV "502.73): calcd C 56.00, H 4.70, N 2.72; found C
3-ꢀ1-Adamantyl)-1-tert-butyl-4,4,4-trichloro-1-aza-2-phospha-4-vana-
daꢀv)cyclobut-2-ene ꢀ10b): Compound 9a "130 mg, 0.41 mmol) in toluene
"5 mL) and 1b "40 mg, 0.41 mmol) furnished 10b "170 mg, 100%) as a
brown powder. 1H NMR "C6D6, 200 MHz, 258C): d ˆ 1.50 ± 2.40 [m, 15H,
Ad-H], 1.61 [s, 9H, C"CH)3]; 13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 29.2 [d,
4J"C,P) ˆ 1.1 Hz, Ad-CH], 32.8 [d, 3J"C,P) ˆ 5.5 Hz, NC"CH3)3], 36.0 [s,
Ad-CH2], 44.4 [d, 3J"C,P) ˆ 7.6 Hz, Ad-CH2], 60.0 [m, Ad-C], 73.5 [m,
NC"CH3)3], [ring-C)] not found; 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ
À72.5 "s); 51V NMR "C6D6, 52.6 MHz, 258C): d ˆ 320.5 [s, n1/2 ˆ 193 Hz];
55.1, H 4.6, N 2.4.
1-tert-Butyl-4,4,4-trichloro-3-ꢀtrimethylsily)-1,2,4-azaphosphavanadaꢀv)-
cyclobut-2-ene ꢀ10h): Compound 9d "177 mg, 0.73 mmol) in toluene
"5 mL) and 1a "73 mg, 0.73 mmol) furnishes 10h "250 mg, 100%) as a
black-brown oil. 1H NMR "C6D6, 200 MHz, 258C): d ˆ 0.12 [s, 9H, SiMe3],
4
1.45 [d, J"H,P) ˆ 0.8 Hz, 9H, C"CH)3]; 13C NMR "C6D6, 50.3 Hz, 170 K):
d ˆ 2.1 [s, Si"CH3)3], 30.9 [d, 3J"C,P) ˆ 6.4 Hz, C"CH3)3], 55.9 [s, CC"CH3)3],
316.4 [s, CC"CH3)3]; 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ À69.1 "s); 51
V
‡
‡
NMR "C6D6, 52.6 MHz, 258C): d ˆ 363.3 [s, n1/2 ˆ 240 Hz]; C8H18Cl3NPSiV
MS "70 eV, EI): m/z "%): 405 "7) [M] , 178 "76) [PC"1 À Ad)] , 57 "100)
‡
"344.60).
[C4H9] ; C15H24Cl3NPV "406.63).
1,3-Di-tert-butyl-4,4,-dichloro-4-tert-butylimido-1-aza-4-chromaꢀVI)-2-
phosphacyclobut-2-ene ꢀ12): Compound 11 "180 mg, 0.66 mmol) in toluene
"5 mL) and 1a "70 mg, 0.70 mmol) furnished 12 "246 mg, 100%) as a green
1-tert-Butyl-4,4,4-trichloro-3-ꢀ1,1-dimethylpropyl)-1,2,4-azaphosphavana-
daꢀv)cyclobut-2-ene ꢀ10c): Compound 9a "228 mg, 1.00 mmol) in toluene
"5 mL) and 1c "114 mg, 1.00 mmol) furnished 10c "342 mg, 100%) as a
black-brown oil. 1H NMR "C6D6, 200 MHz, 258C): d ˆ 0.96 [t, 3J"H,H) ˆ
7.1 Hz, 3H, CH2CH3], 1.33 [s, 6H, C"CH3)2C2H5], 1.43 [s, 9H, NC"CH3)3],
1.81 [q, 3J"H,H) ˆ 7.1 Hz, 2H, CH2CH3] ; 13C NMR "C6D6, 50.3 Hz, 258C):
d ˆ 10.5 [d, 4J"C,P) ˆ 1.2 Hz, CH2CH3], 29.7 [d, 3J"C,P) ˆ 7.0 Hz,
C"CH3)"CH3)C2H5], 29.9 [d, 3J"C,P) ˆ 8.2 Hz, C"CH3)"CH3)C2H5], 33.5
[d, 3J"C,P) ˆ 4.7 Hz, NC"CH3)3], 38.5 [d, 3J"C,P) ˆ 4.7 Hz, CH2CH3], 60.6
[m, CC"CH3)2C2H5], 74.2 [m, NC"CH3)3], 317.7 [m, CC"CH3)3]; 31P NMR
"C6D6, 81.0 MHz, 258C): d ˆ À71.9 "s); 51V NMR "C6D6, 52.6 MHz, 258C):
1
powder. H NMR "C6D6, 200 MHz, 258C): d ˆ 1.24 [s, 9H, C"CH3)3], 1.32
[s, 9H, C"CH3)3], 1.44 [d, 4J"H,P) ˆ 1.1 Hz, 9H, C"CH3)3]; 13C NMR "C6D6,
3
50.3 Hz, 170 K): d ˆ 31.4 [s, C"CH3)3], 33.1 [d, J"C,P) ˆ 7.3 Hz, C"CH3)3],
3
2
34.1 [d, J"C,P) ˆ 8.6 Hz, C"CH3)3], 49.9 [d, J"C,P) ˆ 19.5 Hz, CC"CH3)3],
65.9 [d, 2J"C,P) ˆ 12.2 Hz, NC"CH3)3], 81.1 [s, NC"CH3)3], 301.3 [d,
1J"C,P) ˆ 108.6 Hz, CC"CH3)3]; 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ
‡
‡
À76.2 "s); MS "70 eV, EI): m/z "%): 364 "16) [M] , 349 "17) [M À CH3] ,
‡
‡
293 "67) [M À C4H9N] , 57 "100) [C4H9] ; C13H27Cl2CrN2P "365.3).
‡
d ˆ 312.3 [s, n1/2 ˆ 205 Hz]; MS "70 eV, EI): m/z "%): 341 "1) [M] , 306 "1)
4,4,4-Tribromo-1,3-di-tert-butyl-1-aza-2-phospha-4-vanadaꢀv)cyclobut-2-
ene ꢀ15): Compound 14 "160 mg, 0.45 mmol) in toluene "5 mL) and 1a
"45 mg, 0.45 mmol) furnished 15 "205 mg, 100%) as a red-brown powder.
1H NMR "C6D6, 200 MHz, 258C): d ˆ 1.48 [s, 9H, C"CH3)3], 1.50 [s, 9H,
C"CH3)3]; 13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 32.0 [d, 3J"C,P) ˆ 6.6 Hz,
‡
‡
‡
[M À Cl] , 285 "4) [M À C4H8] , 57 "100) [C4H9] ; C10H20Cl3NPV "342.44).
1-tert-Butyl-4,4,4-trichloro-3-ꢀ1-methylcyclopentyl)-1,2,4-azaphosphava-
nadaꢀv)cyclobut-2-ene ꢀ10 d): Compound 9a "228 mg, 1.00 mmol) in
toluene "5 mL) and 1d "126 mg, 1.00 mmol) furnished 10d"354 mg, 100%)
3
1
C"CH3)3], 33.0 [d, J"C,P) ˆ 6.6 Hz, C"CH3)3], 56.0 [s, CC"CH3)3], 74.3 [s,
as a black-brown oil. H NMR "C6D6, 200 MHz, 258C): d ˆ 0.85 ± 2.05 [m,
NC"CH3)3], 319.0 [s, CC"CH3)3]; 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ
À62.4.0 "s); 51V NMR "C6D6, 52.6 MHz, 258C): d ˆ 472.1 [s, n1/2 ˆ 191 Hz];
8H, cyclopentyl-CH2], 1.32 [s, 3H, CH3], 1.42 [s, 9H, NC"CH3)3]; 13C NMR
"C6D6, 50.3 Hz, 258C): d ˆ 24.7 [s, cyclopentyl-CH2], 28.4 [d, 3J"C,P) ˆ
7.6 Hz, CH3], 32.5 [s, NC"CH3)3], 42.7 [d, 3J"C,P) ˆ 4.2 Hz, cyclopentyl-
CH2], 43.6 [d, 3J"C,P) ˆ 7.6 Hz, cyclopentyl-CH2], 67.6 [m, CC"CH2)2CH3],
73.6 [m, NC"CH3)3], [CC"CH3)3] not found; 31P NMR "C6D6, 81.0 MHz,
‡
‡
MS "70 eV, EI): m/z "%): 349 "2) [M À C8H16] , 100 "5) [C5H9P] , 57 "100)
‡
[C4H9] ; C9H18Br3NPV "461.88).
General procedure for the preparation of the 1H-1,2,4-azadiphospholes
1 3a ± d: An equimolar amount of phosphaalkyne 1a at À788C was added
to a solution of the imidovanadium compound 9e ± h in toluene. The
mixture was allowed to warm up, stirred for 24 h at room temperature, and
then the solvent was removed at 208C at 10À2 mbar. After extraction with
n-pentane "20 mL), the solvent was distilled off under reduced pressure
"208C at 10À2 mbar), and the residue purified by bulb-to-bulb distillation.
258C): d ˆ À71.4 "s); 51V NMR "C6D6, 52.6 MHz, 258C): d ˆ 320.4 [s, n1/2
ˆ
‡
‡
208 Hz]; MS "70 eV, EI): m/z "%): 353 "1) [M] , 297 "3) [M À C4H8] , 267
‡
‡
"100) [M À C6H14] , 126 "4) [PC"C5H8)CH3] ; C11H20Cl3NPV "354.55).
1-tert-Butyl-4,4,4-trichloro-3-ꢀ1-methylcyclohexyl)-1,2,4-azaphosphavana-
daꢀv)cyclobut-2-ene ꢀ10e): Compound 9a "228 mg, 1.00 mmol) in toluene
"5 mL) and 1e "140 mg, 1.00 mmol) furnished 10e "368 mg, 100%) as a
black-brown oil. 1H NMR "C6D6, 200 MHz, 258C): d ˆ 0.90 ± 2.12 [m, 10H,
cyclohexyl-CH2], 1.22 [s, 3H, CH3], 1.44 [s, 9H, NC"CH3)3]; 13C NMR
"C6D6, 50.3 Hz, 258C): d ˆ 23.7 [d, 3J"C,P) ˆ 5.9 Hz, CH3], 25.9 [s, cyclo-
hexyl-CH2], 28.9 [d, 4J"C,P) ˆ 2.3 Hz, cyclohexyl-CH2], 29.0 [d, 4J"C,P) ˆ
3,5-Di-tert-butyl-1-isopropyl-1,2,4-azadiphosphole ꢀ13a): Compound 9e
"140 mg, 0.63 mmol) and 1a "63 mg, 0.63 mmol) furnished 13a "55 mg,
67%) as a white powder "b.p. 1308C at 10À2 mbar); 1H NMR "C6D6,
200 MHz, 258C): d ˆ 1.38 [d, 3J"H,H) ˆ 6.6 Hz, 6H, CH"CH3)2], 1.39 [d,
4564
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0947-6539/00/0624-4564 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 24

Phosphaalkynes
4558±4566
4J"H,P) ˆ 2.2 Hz, 9H, C"CH3)3], 1.63 [dd, 4J"H,P) ˆ 1.8, 0.7 Hz, 9H,
C"CH3)3], 4.69 [dsept, 3J"H,H) ˆ 6.6 Hz, 3J"H,P) ˆ 2.7 Hz, 1H, CH"CH3)2];
13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 27.6 [d, 3J"C,P) ˆ 12.1 Hz, CH"CH3)2],
32.0 [d, 3J"C,P) ˆ 13.4 Hz, C"CH3)3], 35.4 [dd, 3J"C,P) ˆ 11.0, 8.6 Hz,
C"CH3)3], 37.4 [dd, 2J"C,P) ˆ 21.8, 17.3 Hz, C"CH3)3], 38.2 [dd, 2J"C,P) ˆ
19.1, 3J"C,P) ˆ 2.5 Hz, C"CH3)3], 53.2 [dd, 2J"C,P) ˆ 17.1 Hz, 3J"C,P) ˆ
2.5 Hz, CH"CH3)2], 193.8 [dd, 1J"C,P) ˆ 59.8 Hz, 2J"C,P) ˆ 3.7 Hz,
CC"CH3)3], 202.2 [dd, 1J"C,P) ˆ 62.3, 52.5 Hz, CC"CH3)3]; 31P NMR
"C6D6, 81.0 MHz, 258C): d ˆ 148.1, 247.3 [each d, 2J"P,P) ˆ 34.9 Hz]; MS
0.7 Hz, C"CH3)3], 211.8 [X part of A2BX spin system, jJ"P,P) jˆ 8.0 Hz,
1J"C,P) ˆ 77.0 Hz, 3J"C,P) ˆ 15.2 Hz, "nA À nB) ˆ 10.2 Hz, ring C]; 31P NMR
"C6D6, 81.0 MHz, 258C): d ˆ 232.6 "s); MS "70 eV, EI): m/z "%): 300 "39)
‡
‡
‡
[M] , 169 "100) [M À C5H9P2] , 100 "32) [M À C10H18P2] ; C15H27P3 "300.30).
2,4,6-Trisꢀ1-adamantyl)-1,3,5-triphosphabenzene ꢀ8b): Compound 9a
"140 mg, 0.60 mmol) in toluene "3 mL) and 1b "428 mg, 2.4 mmol) in
toluene "3 mL) produced 8b "150 mg, 36%) as a yellowpowder. 1H NMR
"C7D8, 400 MHz, 258C): d ˆ 1.75 [m, 18H, CH2], 2.13 [m, 9H, CH], 2.48 [m,
18H, CH2]; 13C NMR "CD2Cl2, 100.6 MHz, 258C): d ˆ 30.4 [s, CH], 37.0 [s,
CH2], 38.7 [X part of A2BX spin system, jJ"P,P) jˆ 5.9 Hz, 3J"C,P) ˆ
15.5 Hz, 5J"C,P) ˆ 1.0 Hz, "nA À nB) ˆ 0.1 Hz, CH2], 46.5 [X part of A2BX
‡
‡
"70 eV, EI): m/z "%): 257 "29) [M] , 242 "6) [M À CH3] , 200 "12) [M À
‡
‡
C3H7N] , 84 "100) [C4H5P] ; elemental analysis calcd for C13H25NP2
"257.30): C 60.69, H 9.76, N 5.44; found C 59.7, H 9.8, N 5.1.
spin system, jJ"P,P) jˆ 6.0 Hz, 2J"C,P) ˆ 22.0 Hz, 4J"C,P) ˆ 1.5 Hz, "nA
À
nB) ˆ 0.8 Hz, adamantyl-C], 212.2 [X part of A2BX spin system, jJ"P,P) j
ˆ 5.9 Hz, 1J"C,P) ˆ 77.5 Hz, 3J"C,P) ˆ 15.5 Hz, "nA À nB) ˆ 10.2 Hz, ring-C];
31P NMR "C6D6, 81.0 MHz, 258C): d ˆ 238.1 "s); MS "70 eV, EI): m/z "%):
3,5-Di-tert-butyl-1-n-propyl-1,2,4-azadiphosphole ꢀ13b): Compound 9 f
"118 mg, 0.28 mmol) and 1a "28 mg, 0.28 mmol) furnished 13b "39 mg,
55%) as a colorless oil "b.p. 1408C at 10À2 mbar); 1H NMR "C6D6,
200 MHz, 258C): d ˆ 0.81 [t, 3J"H,H) ˆ 6.8 Hz, 3H, CH2CH2CH3], 1.36 [d,
4J"H,P) ˆ 1.6 Hz, 9H, C"CH3)3], 1.46 [ps, 3J"H,H) ˆ 6.8 Hz, 2H,
CH2CH2CH3], 1.62 [d, 4J"H,P) ˆ 1.8 Hz, 9H, C"CH3)3], 4.10 [m, 2H,
CH2CH2CH3]; 13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 11.35 [s, CH2CH2CH3],
19.39 [d, 3J"C,P) ˆ 2.78 Hz, CH2CH2CH3], 33.7 [d, 3J"C,P) ˆ 15.8 Hz,
C"CH3)3], 35.7 [dd, 3J"C,P) ˆ 12.1, 9.2 Hz, C"CH3)3], 37.6 [dd, 2J"C,P) ˆ
33.8, 21.6 Hz, C"CH3)3], 38.7 [dd, 2J"C,P) ˆ 21.4 Hz, 3J"C,P) ˆ 3.0 Hz,
C"CH3)3], 53.1 [dd, 2J"C,P) ˆ 15.4 Hz, 3J"C,P) ˆ 3.0 Hz, CH2CH2CH3],
198.6 [dd, 1J"C,P) ˆ 45.4 Hz, 2J"C,P) ˆ 7.3 Hz, CC"CH3)3], 203.8 [dd,
1J"C,P) ˆ 45.1, 38.7 Hz, CC"CH3)3]; 31P NMR "C6D6, 81.0 MHz, 258C):
‡
‡
534 "21) [M] , 325 "100) [M À C11H15P2] ; C33H45 P3 "534.64).
2,4,6-Trisꢀ1,1-dimethylpropyl)-1,3,5-triphosphabenzene ꢀ8c): Compound
9a "305 mg, 1.34 mmol) in toluene "3 mL) and 1c "612 mg, 5.36 mmol)
produced 8c "271 mg, 59%) as an orange-yellowoil. 1H NMR "CDCl3,
200 MHz, 258C): d ˆ 0.84 [t, 3J"H,H) ˆ 7.4 Hz, 9H, CH2CH3], 1.74 [s, 18H,
C"CH3)2C2H5], 2.14 [q, 3J"H,H) ˆ 7.4 Hz, 6H, CH2CH3]; 13C NMR "CDCl3,
50.3 MHz, 258C): d ˆ 9.2 [s, CH2CH3], 32.7 [m, C"CH3)C2H5], 40.5 [m,
CH2CH3], 46.9 [m, C"CH3)C2H5], 208.8 [m, ring C][25]
;
31P NMR "CDCl3,
‡
81.0 MHz, 258C): d ˆ 238.8 "s); MS "70 eV, EI): m/z "%): 342 "31) [M] , 197
‡
‡
"100) [M À C6H11P2] , 114 "9) [C6H11P] ; elemental analysis calcd for
2
d ˆ 154.1, 259.3 [each d, J"P,P) ˆ 29.7 Hz]; MS "70 eV, EI): m/z "%): 257
C18H33P3 "342.38): C 63.15, H 9.71; found C 63.13, H 10.1.
‡
‡
‡
"100) [M] , 242 "4) [M À CH3] , 214 "5) [M À C3H7] ; C13H25NP2 "257.30).
2,4,6-Trisꢀ1-methylcyclopentyl)-1,3,5-triphosphabenzene ꢀ8d): Compound
9a "313 mg, 1.37 mmol) in toluene "3 mL) and 1d "691 mg, 5.48 mmol)
3,5-Di-tert-butyl-1-ꢀ2,2-dimethyl)propyl-1,2,4-azadiphosphole ꢀ13c): Com-
pound 9g "157 mg, 0.65 mmol) and 1a "65 mg, 0.65 mmol) furnished 13c
"80 mg, 87%) as a white powder "b.p. 1508C at 10À2 mbar); 1H NMR
produced 8d "192 mg, 37%) as a yellowpowder.
1H NMR "CDCl3,
200 MHz, 258C): d ˆ 1.54 [s, 9H, CH3], 1.78 ± 1.94 [m, 12H, CH2], 2.24 ±
2.42 [m, 12H, CH2]; 13C NMR "CDCl3, 100.6 MHz, 258C): d ˆ 22.9 [s,
cyclopentyl-CH2], 35.4 [m, CH3], 42.3 [m, cyclopentyl-CH2], 55.6 [m,
4
"C6D6, 200 MHz, 258C): d ˆ 0.96 [s, 9H, CH2C"CH3)3], 1.45 [d, J"H,P) ˆ
1.7 Hz, 9H, C"CH3)3], 1.64 [d, 4J"H,P) ˆ 1.5 Hz, 9H, C"CH3)3], 4.13 [dd,
3J"H,P) ˆ 14.4, 4J"H,P) ˆ0.7, 2H, CH2C"CH3)3]; 13C NMR "C6D6, 50.3 Hz,
258C): d ˆ 28.8 [s, CH2C"CH3)3], 30.25 [d, 3J"C,P) ˆ 2.4 Hz, CH2C"CH3)3],
33.1 [d, 3J"C,P) ˆ 14.9 Hz, C"CH3)3], 35.4 [dd, 3J"C,P) ˆ 11.7, 8.6 Hz,
C"CH3)3], 37.1 [dd, 2J"C,P) ˆ 34.8, 21.1 Hz, C"CH3)3], 38.5 [dd, 2J"C,P) ˆ
C"CH2)2CH3], 211.8 [m, ring C][25]
;
31P NMR "CDCl3, 81.0 MHz, 258C):
‡
d ˆ 234.2 "s); MS "70 eV, EI): m/z "%): 378 "33) [M] , 221 "100) [M À
‡
‡
C7H11P2] , 126 "15) [C7H11P] ; elemental analysis calcd for C21H33 P3
"378.42): C 66.65, H 8.79; found C 66.5, H 9.0.
3
2
3
19.6 Hz, J"C,P) ˆ 3.9 Hz, C"CH3)3], 61.9 [dd, J"C,P) ˆ 16.4 Hz, J"C,P) ˆ
3.1 Hz, CH2C"CH3)3], 195.6 [dd, 1J"C,P) ˆ 55.6 Hz, 2J"C,P) ˆ 4.5 Hz,
CC"CH3)3], 202.0 [dd, 1J"C,P) ˆ 56.3, 36.0 Hz, CC"CH3)3]; 31P NMR
"C6D6, 81.0 MHz, 258C): d ˆ 148.6, 258.8 [each d, 2J"P,P) ˆ 26.2 Hz]; MS
2,4,6-Trisꢀ1-methylcyclohexyl)-1,3,5-triphosphabenzene ꢀ8e): Compound
9a "209 mg, 0.92 mmol) in toluene "2 mL) and 1e "516 mg, 3.68 mmol)
produced 8e "170 mg, 44%) as a yellowpowder. 1H NMR "C6D6, 200 MHz,
258C): d ˆ 1.36 ± 1.74 [m, 18H, CH2], 1.65 [s, 9H, CH3], 2.05 ± 2.11 [m, 6H,
CH2], 2.81 ± 2.88 [m, 6H, CH2]; 13C NMR "C6D6, 100.6 MHz, 258C): d ˆ
23.2 [s, cyclohexyl-CH2], 26.6 [s, cyclohexyl-CH2], 35.8 [m, CH3], 41.6
[pseudo t, 3J"C,P) ˆ 16.2 Hz, cyclohexyl-CH2], 47.6 [pseudo-t, 2J"C,P) ˆ
‡
‡
"70 eV, EI): m/z "%): 285 "100) [M] , 270 "20) [M À CH3] , 228 "5) [M À
‡
C5H11N] ; C15H29NP2 "285.35).
3,5-Di-tert-butyl-1-cyclohexyl-1,2,4-azadiphosphole ꢀ13d): Compound 9h
"199 mg, 0.78 mmol) and 1a "78 mg, 0.78 mmol) furnished 13d "71 mg,
61%) as a colorless oil "b.p. 1808C at 10À2 mbar); 1H NMR "C6D6,
200 MHz, 258C): d ˆ 0.76 ± 2.15 [m, 28H, C"CH3), cyclohexyl-CH2], 4.33 [s,
1H, NCH]; 13C NMR "C6D6, 50.3 Hz, 258C): d ˆ 22.7 [s, CH2], 23.55 [s,
CH2], 27.30 [d, 3J"C,P) ˆ 4.5 Hz, CH2], 33.9 [d, 3J"C,P) ˆ 14.5 Hz, C"CH3)3],
35.0 [dd, 3J"C,P) ˆ 10.39, 7.5 Hz, C"CH3)3], 37.1 [dd, 2J"C,P) ˆ 30.1, 18.0 Hz,
C"CH3)3], 38.7 [dd, 2J"C,P) ˆ 20.0 Hz, 3J"C,P) ˆ 4.0 Hz, C"CH3)3], 56.9 [dd,
2J"C,P) ˆ 20.54, 3J"C,P) ˆ 5.4 Hz, NCH], 197.6 [dd, 1J"C,P) ˆ 50.0 Hz,
2J"C,P) ˆ 5.2 Hz, CC"CH3)3], 202.5 [dd, 1J"C,P) ˆ 43.2, 39.7 Hz, CC"CH3)3];
31P NMR "C6D6, 81.0 MHz, 258C): d ˆ 147.1, 250.0 [each d, 2J"P,P) ˆ
19.5 Hz, C"CH2)2CH3], 212.1 [m, ring C][25]
;
31P NMR "C6D6, 81.0 MHz,
‡
258C): d ˆ 242.8 "s); MS "70 eV, EI): m/z "%): 420 "18) [M] , 249 "100)
‡
‡
[M À C8H13P2] , 140 "7) [C8H13P] ; C24H39P3 "420.50).
2,4-Bisꢀ1-adamantyl)-6-tert-butyl-1,3,5-triphosphabenzene ꢀ21): Com-
pound 1a "59 mg, 0.59 mmol) was added at À788C to a solution of 9a
"140 mg, 0.59 mmol) in toluene "5 mL) and the mixture was then allowed to
warm to room temperature. After cooling back to À788C a solution of 1b
"320 mg, 1.77 mmol) in toluene "2 mL) was added and the mixture was
allowed to warm up. The solvent was distilled off under reduced pressure
"208C at 10À2 mbar). The residue was redissolved in n-pentane and purified
by column chromatography on silica gel "deactivated with 4% water,
column: 20 Â 2.0 cm). The yellowfraction "210 mg) was found to contain 21
contaminated by traces of 8b. 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ 237.0,
237.2 [AB2 spin system, 2J"P,P) ˆ 6.2 Hz]; MS "70 eV, EI): m/z "%): 456 "5)
‡
27.13 Hz]; MS "70 eV, EI): m/z "%): 297 "100) [M] , 214 "17) [M À
‡
‡
C6H11] , 200 "2) [M À C6H11N] ; C16H29NP2 "297.36).
General procedure for the preparation of the 1,3,5-triphosphabenzenes
8a ± e: Four equivalents 1 a ± e were added at À788C to a solution of 9a in
toluene. After the mixture was allowed to warm up, toluene was distilled
off at 208C at 10À2 mbar, the residue was redissolved in n-pentane, and
purified by column chromatography on silica gel "deactivated with 4%
water, column: 20 Â 2.0 cm). The yellowfraction afforded 8a ± e after
removal of the solvent. In the cases of 8a ± c no further purification was
necessary, 8d and 8e were recrystallized from n-pentane.
‡
‡
[M] , 325 "100) [M À C5H9P2] ; C27H39P3 "456.53).[26]
6-ꢀ1-Adamantyl)-2,4-di-tert-butyl-1,3,5-triphosphabenzene ꢀ22): A solu-
tion of 1b "120 mg, 0.66 mmol) in toluene "3 mL) was added at À788C to
a solution of 9a "150 mg, 0.66 mmol) in toluene "5 mL), and the mixture
was then allowed to warm to room temperature. After cooling back to
À788C 1a "200 mg, 2.00 mmol) was added and the mixture allowed to
warm up again. The solvent was distilled off under reduced pressure "208C
at 10À2 mbar). The residue was redissolved in n-pentane and purified by
column chromatography on silica gel "deactivated with 4% water, column:
2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene ꢀ8a): Compound 9a "100 mg,
0.47 mmol) in toluene "5 mL) and 1a "180 mg, 1.8 mmol) produced 8a
"120 mg, 68%) as a yellowpowder. 1H NMR "[D8]THF, 400 MHz, 258C):
d ˆ 1.34 [s, 27H, C"CH3)3]; 13C NMR "[D8]THF, 100.6 MHz, 258C): d ˆ
36.1 [X part of A2BX spin system, jJ"P,P) jˆ 8.0 Hz, 3J"C,P) ˆ 14.5 Hz,
5J"C,P) ˆ 1.1 Hz, "nA À nB) ˆ 0.1 Hz, C"CH3)3], 44.53 [X part of A2BX spin
system, jJ"P,P) jˆ 8.1 Hz, 2J"C,P) ˆ 24.5 Hz, 4J"C,P) ˆ 1.6 Hz, "nA À nB) ˆ
20 Â 2.0 cm). The yellowfraction "200 mg) was found to contain
22
contaminated by traces of 8a. 31P NMR "C6D6, 81.0 MHz, 258C): d ˆ 235.2,
235.4 [AB2 spin system, 2J"P,P) ˆ 7.9 Hz]; MS "70 eV, EI): m/z "%): 378 "14)
‡
‡
[M] , 169 "100) [M À C11H15P2] ; C21H33P3 "378.42).[26]
Chem. Eur. J. 2000, 6, No. 24
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0624-4565 $ 17.50+.50/0
4565

M. Regitz, F. Preuss et al.
FULL PAPER
[12] E. Fuchs, F. Krebs, H. Heydt, M. Regitz, Tetrahedron 1994, 50, 759 ±
Acknowledgement
774.
[13] F. Preuss, M. Steidel, M. Vogel, G. Overhoff, G. Hornung, W. Towae,
W. Frank, G. Reiû, S. Müller-Becker, Z. Anorg. Allg. Chem. 1997, 623,
1220 ± 1228.
We are grateful to the Fonds der Chemischen Industrie, the Deutsche
Forschungsgemeinschaft "Graduate College Phosphorus as Connecting
Link Between Various Chemical Disciplines), as well as the Landesregie-
rung von Rheinland-Pfalz for generous financial support. We also would
like to thank Dr. D. Gudat, University of Bonn for the measurement and
simulation of a 31P{1H,14N} NMR spectrum of 10a.
2
[14] The simulation of the coupling constants J"P,V) was performed with
the help of the program Q*U*A*D*C*A "D. Gudat, University of
Bonn).
[15] D. Rehder, Bull. Magn. Reson. 1982, 4, 33 ± 83.
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[25] The coupling constants of the A2BX spin systems of 8c ± e were not
determined by simulations.
[26] The experimental data "31P/MS) were determined from the unsepar-
able mixtures of 21/8b and 22/8a.
[10] F. Preuss, H. Becker, T. Wieland, Z. Naturforsch. 1990, 45b, 191 ± 198.
[11] E. Fuchs, B. Breit, H. Heydt, W. Schoeller, T. Busch, C. Krüger, P.
Betz, M. Regitz, Chem. Ber. 1991, 124, 2843 ± 2855.
Received: October 7, 1999
Revised version: August 22, 2000 [F2073]
4566
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0947-6539/00/0624-4566 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 24