Polyphospha[m]cyclo[n]carbons (m+n = 15, 20, 25, 30, 40)

Article abstract of DOI:10.1002/1521-3765(20001016)6:20<3806::AID-CHEM3806>3.0.CO;2-J

The Eglinton reaction of diethynyl(2,4,6-tri-tert-butylphenyl)phosphane (7a), that is, the oxidative coupling of 3, 4, 5, or 6 of these phosphane units, affords a mixture of the 15-, 20-, 25-, and 30-membered macrocycles 8, 9, 10, and 11. Pure triphosphacyclopentadecahexayne 8 and pentaphosphacyclopentacosadecayne 10 were isolated by HPLC, while the mixture of 9 and 11 could not be separated. Multistep syntheses of open-chain polyphosphapolyynes are described, whose intra- or intermolecular coupling yields the phosphamacrocycles 8, 9, and 11. Eglinton coupling of bis(ethynylphosphanyl)butadiyne (17) gave a mixture of the 20-membered tetraphosphacycloicosaoctayne 9, the 30-membered hexaphosphacyclotriacontadodecayne 11, and the 40-membered octaphosphacyclotetracontahexadecayne 23 as result of a di-, tri-, and tetramerization, respectively. Intramolecular coupling of bis[(ethynylphosphanyl)butadiynyl]phosphane 25a gave 8, while intermolecular coupling gave 11; these two compounds were isolated by chromatography to give yields of 70 and 5%, respectively. The open-chain tetraphosphaeikosaoctayne 28 couples intramolecularly to give 9 and intermolecularly to give the 40-membered octaphosphacyclotetracontahexadecayne 23, which was isolated in the pure form. Octaphosphatetracontahexadecayne 32 cyclized to give 23, exclusively. The temperature-dependent ¹H and ³¹p NMR spectra of the open-chain and cyclic ethynylphosphanes indicated a lowering of the inversion barrier of the tertiary phosphanes from the usual 130-140 kJmo1^-1 to 65-75 kJmo1^-1. Ab initio calculations proved that the dramatic reduction of the inversion barriers results from the interaction of the lone pair on phosphorus with the π orbitals of the triple bonds in the planar transition state during inversion. The situation is comparable with the dramatic reduction of the P inversion barrier in phospholes, because of the planar, aromatic transition state. The polyphospha[m]cyclo[n]carbons may be considered as precursors to cyclic P(m)C(n) systems.

Full text of DOI:10.1002/1521-3765(20001016)6:20<3806::AID-CHEM3806>3.0.CO;2-J

FULL PAPER
Polyphospha[m]cyclo[n]carbons (m‡n ˆ 15, 20, 25, 30, 40)
Gottfried Märkl,* Thomas Zollitsch, Peter Kreitmeier, Michael Prinzhorn,
Sabine Reithinger, and Ernst Eibler[a]
Abstract: The Eglinton reaction of di-
ethynyl(2,4,6-tri-tert-butylphenyl)phos-
phane (7a), that is, the oxidative cou-
pling of 3, 4, 5, or 6 of these phosphane
units, affords a mixture of the 15-, 20-,
25-, and 30-membered macrocycles 8, 9,
10, and 11. Pure triphosphacyclopenta-
decahexayne 8 and pentaphosphacyclo-
pentacosadecayne 10 were isolated by
HPLC, while the mixture of 9 and 11
could not be separated. Multistep syn-
theses of open-chain polyphosphapo-
lyynes are described, whose intra- or
intermolecular coupling yields the phos-
phamacrocycles 8, 9, and 11. Eglinton
coupling of bis(ethynylphosphanyl)bu-
tadiyne (17) gave a mixture of the 20-
membered tetraphosphacycloicosaoc-
tayne 9, the 30-membered hexaphospha-
cyclotriacontadodecayne 11, and the 40-
membered octaphosphacyclotetraconta-
hexadecayne 23 as result of a di-, tri-,
and tetramerization, respectively. Intra-
molecular coupling of bis[(ethynylphos-
phanyl)butadiynyl]phosphane 25a gave
8, while intermolecular coupling gave
11; these two compounds were isolated
by chromatography to give yields of 70
and 5%, respectively. The open-chain
tetraphosphaeikosaoctayne 28 couples
intramolecularly to give 9 and intermo-
lecularly to give the 40-membered octa-
phosphacyclotetracontahexadecayne 23,
which was isolated in the pure form.
Octaphosphatetracontahexadecayne 32
cyclized to give 23, exclusively. The
temperature-dependent 1H and 31P
NMR spectra of the open-chain and
cyclic ethynylphosphanes indicated
a
lowering of the inversion barrier of the
tertiary phosphanes fromthe usual 130 ±
140 kJmolÀ1 to 65± 75 kJmolÀ1. Ab initio
calculations proved that the dramatic
reduction of the inversion barriers results
fromthe interaction of the lone pair on
phosphorus with the p orbitals of the
triple bonds in the planar transition state
during inversion. The situation is com-
parable with the dramatic reduction of
the P inversion barrier in phospholes,
because of the planar, aromatic transition
state. The polyphospha[m]cyclo[n]car-
bons may be considered as precursors
to cyclic PmCn systems.
Keywords: coupling reactions ´ in-
version barriers
´ macrocycles ´
NMR spectroscopy ´ phosphacyclo-
polyynes ´ phosphanes
F. Sondheimer et al.[4, 5] had already achieved the synthesis
of [18]annulene by the Eglinton coupling of 1,5-hexadiyne
Introduction
The most important synthetic approach to macrocyclic poly-
ynes with diacetylenic links 2 is the oxidative coupling of
terminal bisacetylenes 1 by the various methods of Glaser,[1]
Eglinton,[2] and Hay[3] (Scheme 1).
(1a; X X ˆ CH2CH2 ). Dehydrobenzannulenes 2b[6] are
obtained by the oxidative coupling of 1,2-diethynylbenzene
(1b).
À À À
À
À
de Meijere et al. described the formation of cyclic polyynes
2c[7] (n-rotanes) with spirocyclopropane-links between 1,3-
diyne units by the coupling of 1,1-diethynylcyclopropanes 1c
À À À
( X X ˆ 1,1-cyclopropane).
Expanded radialenes 2d have been synthesized by stepwise
oxidative coupling of the diynes 1d by Diederich et al.[8]
The macrocyclic polyynes became even more fascinating,
when Diederich, McElvany et al. observed, by laser-desorp-
tion Fourier transform mass spectrometric experiments, that
[4n‡2]- and [4n]dehydroannulenes 2e, n ˆ 1 ± 3 (n ˆ 3,
C30(CO)10)[9] and dehydroannulenes 2 f, n ˆ 1 ± 3 (n ˆ 3,
C30(C14H10)5),[10] the annelation products of cyclobutene-1,2-
dione and the anthracene, respectively, formcyclo[ n]carbon
Scheme 1. Formation of macrocyclic polyynes 2 with butadiyne-1,3-diyl
bridges by oxidative coupling of 1.
[a] Prof. Dr. G. Märkl, Dr. T. Zollitsch, Dr. P. Kreitmeier,
Dipl.-Chem. M. Prinzhorn, Dr. S. Reithinger, Dr. E. Eibler
Institut für Organische Chemie der Universität Regensburg
93040 Regensburg (Germany)
‡
À
ions Cn (n ˆ 18, 24, 30) and Cn (n ˆ 18, 24, 30), which
coalesce to give fullerenes, through the elimination of CO and
anthracene, respectively.[12] Evidently, the size of the full-
Fax : (‡49)941-943-4505
E-mail: gottfried.maerkl@chemie.uni-regensburg.de
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Chem. Eur. J. 2000, 6, No. 20

3806±3820
À
Table 1. Macrocyclic polyynes 2 with different X X bridges.
erenes can be determined by the size of the cyclo[n]carbon
precursors.
À À À
1, 2
X X
n
Ref.
Macrocyclic polyynes with diacetylene units and isopropyl
links (2g) are also accessible by Cadiot ± Chodkiewicz cou-
pling reactions.[11] Table 1 presents the coupling products 2
fromvarious substrates 1.
1a, 2a
1b, 2b
1, 2, 3, 4
0, 1,2
[4, 5]
[6]
1c, 2c
1d, 2d
3, 4, 6
2, 3, 4
[7]
[8]
In a similar reaction to their synthesis of the [n]pericy-
clines,[13] Scott et al.[14] achieved the first synthesis of the
phosphacyclopolyynes tri-tert-butyl-1,4,7-triphospha[3]peri-
cycline (3) and tetra-tert-butyl-1,4,7,10-tetraphospha[4]pericy-
cline (4) by coupling of the bis-Grignard derivatives of 5a and
5b with tert-butyldichlorophosphane (Scheme 2). The expect-
ed stereoisomers of 3 and 4 could be isolated because of the
configurational stability of the pyramidal phosphines. The
structures of the cis,cis,trans-1,4,7-tri-tert-butyl-1,4,7-triphos-
pha[3]pericycline and the cis,trans,cis,trans-1,4,7,10-tetra-tert-
butyl-1,4,7,10-tetraphospha[4]pericycline were obtained by
X-ray analysis. Scott discussed the tetraphospha[4]pericycline
4 as a possible precursor of phosphacarbons PmCn.
1e, 2e
1 f, 2 f
1, 2, 3
[9]
1
[10]
2g
1, 2, 3, 4
[11]
Abstract in German: Die Eglinton-Reaktion von Diethi-
nyl(2,4,6-tri-tert-butylphenyl)phosphan (7)liefert durch oxi-
dative Kupplung von 3, 4, 5 und 6 Phosphan-Bausteinen ein
Gemisch aus den 15-, 20-, 25- und 30-gliedrigen Makrocyclen
8, 9, 10 und 11. Mittels HPLC gelingt die Abtrennung von
Triphosphacyclopentadecahexain 8 und Pentaphosphacyclo-
pentacosadecain 10 in reiner Form; 9 und 11 können nicht
getrennt werden. Es werden vielstufige Synthesen offenkettiger
Polyphosphapolyine beschrieben, deren inter- bzw. intramole-
kulare Kupplung gezielt die Phosphamakrocyclen 8, 9 und 11
liefert. Bei der Eglington-Kupplung von Bis(ethinylphospha-
nyl)-butadiin 17 wird durch Di-, Tri- und Tetramerisierung ein
Gemisch aus dem 20-gliedrigen Tetraphosphacycloeikosaoc-
tain 9, dem 30-gliedrigen Hexphosphacyclotriacontadodecain
11 und dem 40-gliedrigen Octaphosphacyclotetracontahexa-
decain 23 gebildet. Bis[(ethinylphosphanyl)butadiinyl]phos-
phan 25a liefert durch intramolekulare Kupplung 8 und durch
intermolekulare Kupplung 11, die chromatagraphisch in 70-
bzw. 5-proz. Ausb. rein erhalten werden. Das offenkettige
Tetraphosphaeikosaoctain 28 wird intramolekular zu 9 und
intermolekular zum 40-gliedrigem Octaphosphacyclotetracon-
tahexadecain 23 gekuppelt, die chromatographisch getrennt
werden. Das Octaphosphatetracontahexadecain 32 cyclisiert
ausschlieûlich zu 23. Die temperaturabhängigen 1H-NMR-
und 31P-NMR-Spektren der offenkettigen wie der cyclischen
Ethinylphosphane zeigen, dass die Inversionsbarrieren der
tertiären Phosphane, die im Normalfall bei 130 ± 140 kJmolÀ1
liegen, auf 65 ± 75 kJmolÀ1 abgesenkt werden. Ab initio-Rech-
nungen bestätigen, dass diese dramatische Reduktion der
Inversionsbarrieren durch die Wechselwirkung des Phosphin-
lonepairs mit den p-Orbitalen der Dreifachbindungen im
planaren Übergangszustand der Inversion zustandekommt.
Diese Situation ist vergleichbar mit der ebenfalls dramatischen
Verringerung der P-Inversionsbarriere in Phospholen durch
den planaren, aromatischen Übergangszustand. Die Polyphos-
pha[m]cyclo[n]carbone können als Vorstufen cyclischer PmCn-
Systeme aufgefasst werden.
Scheme 2. Synthesis of 1,4,7-triphospha[3]pericycline (3) and 1,4,7,10-
tetraphospha[4]pericycline (4).
In this paper we describe the synthesis of macrocyclic
polyphosphapolyynes 8 ± 11 with diacetylenic links by a one-
pot oxidative coupling reaction of diethynyl(2,4,6-tri-tert-
butylphenyl)phosphane (7a) or by subsequent coupling steps
via open-chained polyphosphapolyynes (Scheme 3).
The triphosphacyclopentadecahexayne 8, n ˆ 1, and the
pentaphosphacyclopentacosadecayne 10, n ˆ 3, can be de-
scribed as formally 18p and 30p systems, respectively.
The question of aromaticity of these systems is similar to
that of the phospholes 13, which are not aromatic because of
the pyramidal structure of the tervalent phosphorus.[15] How-
ever, Mislow[16] demonstrated a dramatic lowering of the
inversion barrier in phospholes (ꢀ16 kcalmolÀ1 vs. ꢀ30 kcal
molÀ1 in tert-phosphanes) as result of the aromaticity of the
planar transition state. If the inversion of the pyramidal
phosphines in the polyphosphacyclopolyynes occurs more or
less simultaneously, the transition states of 8 and 10, which are
similar to that of 13, could be aromatic and the phosphane
inversion energy barriers should be reduced.
Chem. Eur. J. 2000, 6, No. 20
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3807

G. Märkl et al.
FULL PAPER
of acetylene itself in THF at roomtemperature to give
colorless crystals of phosphane 7a in 46 ± 52% yield.
Eglinton coupling of diethynylphosphane 7a: A solution of 7a
(10 mmol) in a mixture of pyridine (60 mL) and methanol
(30 mL) was added to a solution of [Cu(OAc)2] (60 mmol) in
pyridine (250 mL) over a period of 15 min. The stirred
solution was heated to 608C for 3 h. The solvent was
evaporated and the residue extracted with benzene to give a
dark yellow product (1.30 g from3.26 g 7a), which is soluble
in nonpolar solvents (e.g., benzene, toluene, CHCl3, CCl4),
and relatively insoluble in polar solvents (e.g., methanol,
CH3CN, CH3NO2). According to the FD-MS (toluene) and
the 31P NMR data, a mixture of coupling products had been
formed that was partially separated by HPLC (Scheme 3).
It was possible to isolate the 1,6,11-triphosphacylopenta-
deca-2,4,7,9,12,14-hexayne (8, n ˆ 1) and the 1,6,11,16,21-
pentaphosphacyclopentacosa-2,4,7,9,12,14,17,19,22,24-deca-
yne (10, n ˆ 3, ªpentamerº), in pure form; however, the
mixture of the tetramer 9 (n ˆ 2) and hexamer 11 (n ˆ 4) could
not be separated (Scheme 3).
The HPLC separation of the coupling mixture 8 ± 11 is time
consuming and only a few milligrams of the pure products
were obtained. For this reason, we decided to synthesize the
corresponding open-chained polyphosphapolyynes and to
study their cyclizing intra- and intermolecular Eglinton
coupling reactions. The analytical and spectroscopic data of
the phosphacyclopolyynes 8, 9, and 11 prepared this way will
be presented for this reaction. Only the pentaphosphacyclo-
pentacosaoctayne 10, not obtained by the stepwise oxidative
coupling reactions, is described in the Experimental Section
under the Eglinton coupling of 7a.
Scheme 3. Eglinton coupling of 7a to give polyphosphacyclopolyynes
8 ± 11, polyphosphacyclopolyyne polyanions 12, and comparison with
phospholes 13 and phospholyl anions 14.
In a similar manner to the phospholyl anions 14,[17] the
phosphides 12 (n ˆ 1, 3) could be expected to be aromatic 18p
and 30p systems per se.
Since the thermal cleavage of P ± aryl bonds has been dem-
onstrated (the P ± aryl bond in 1-aryl-1,2(1,4)-dihydrophos-
phinines can be cleaved thermally to give l3-phosphinines),[18]
the phosphacyclopolyynes are possible candidates for the
access of polyphosphacarbons (C12P3, C16P4, C20P5, C24P6).
Oxidative coupling of bis(ethynylphosphanyl)butadiyne (17)
Synthesis of 17 by the Eglinton coupling of diethynylphos-
phane 15b: One strategy for the synthesis of 17 is the
oxidative coupling of the monosilyl-protected diethynylphos-
phanes 15a and 15b to give 16a and 16b followed by a
twofold desilylation (Scheme 4).
Results and Discussion
Eglinton coupling of diethynylphosphane (7a)
Synthesis of 7a: The stability of tervalent phosphorus under
the reaction conditions is important for the oxidative coupling
of ethynylphosphanes. This re-
quirement is fulfilled by the
2,4,6-tri-tert-butylphenyl-substi-
tuted phosphanes[18] (Scheme 3).
(2,4,6-Tri-tert-butylphenyl)-
bis[(trimethylsilyl)ethynyl]-
phosphane (7b) was obtained
in 50 ± 60% yield by the reac-
tion of two equivalents of
lithiumtriemthylsilylacetylide
(R ˆ SiMe3) with 2,4,6-tri-tert-
butylphenyldichlorophosphane
(6) in THF at À788C
(Scheme 4). Desilylation of 7b
either with NaOH/MeOH[20] or
with TBAF/THF[21] yielded the
phosphane 7a (70%). The syn-
thesis of 7a is more straightfor-
ward by substitution of 6 with
the mono-Grignard compound
Scheme 4. Synthesis of bis[ethynyl(2,4,6-tri-tert-butylphenyl)phosphanyl]butadiyne (17) fromdiethynyl(2,4,6-
tri-tert-butylphenyl)phosphane (7a).
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Polyphosphacarbons
3806±3820
The monosilylation of diethynylphosphane 7a was rather
difficult. Metallation of 7a either with one equivalent EtMgBr
or nBuLi at À788C followed by reaction with trimethylchlo-
rosilane yielded a yellow, crystalline reaction product that was
a mixture of the bis-trimethylsilyl-substituted derivative 7b,
the desired monosilylated phosphane 15a, and the starting
material 7a (ratio 0.7:2.0:1.2) according to the EI-MS, and 1H
and 31P NMR data. This mixture could not be separated
(Scheme 4).
1H and 31P NMR spectra of the alkynylphosphanes 7, 15, 16,
17, and 20: The 31P NMR data of the bis-alkynylphosphanes 7
and 15 and the 1,6-diphosphanes 20, 16, and 17 are given in
Table 2.
Table 2. 31P{1H} NMR-data of 7, 15, 16, 17, and 20 (162 MHz, CDCl3).
Compound
d (31P NMR)
When triisopropylchlorosilane was used in the same
procedure, a mixture of 7c, 15b, and 7a was obtained in
about the same ratio (1.0:2.0:1.1). We were able to separate
this mixture by column chromatography on silica gel.
The Eglinton coupling of 15b with [Cu(OAc)2] in pyridine
at room temperature after hydrolysis and chromatography on
silica gel (CH2Cl2/hexane, 1:6) produced 16b in 84% yield.
A modification of the Eglinton coupling by de Meijere[22]
with four equivalent [Cu(OAc)2] and three equivalents CuCl
in pyridine gave 16b in ꢁ95% yield. By desilylation of 16b
with TBAF/THF at À788C, 17 was obtained in 90% yield.
7a
7b
7c
15a
15b
R ˆ R' ˆ H
À 71.61 (s)
À 70.38 (s)
À 68.85 (s)
À 71.11 (s)
À 70.37 (s)
R ˆ R' ˆ Si(CH3)3
R ˆ R' ˆ Si(iPr)3
R ˆ Si(CH3)3, R' ˆ H
R ˆ Si(iPr)3, R' ˆ H
1
20
X ˆ H
À 97.37 (d, J(P,H) ˆ 251.2 Hz)
Total synthesis of 17 from 1,3-butadiyne (18): Since 1,3-
butadiyne (18) is relatively easy to obtain by dehydrochlori-
nation of 1,4-dichloro-2-butyne,[23] we attempted the synthesis
of 17 from 18.
The bis-Grignard compound of 18 (reaction of 18 with two
equivalents of EtMgBr) was treated with two equivalents of
(tri-tert-butylphenyl)monochlorophosphane 19b[24] at À788C
to give bis[(2,4,6-tri-tert-butylphenyl)phosphanyl]butadiyne
(20) as colorless crystals in 33% yield (Scheme 5).
16a
16b
17
R ˆ Si(CH3)3
R ˆ Si(iPr)3
R ˆ H
À 67.33 (s)
À 66.53; À66.29
À 67.88
While the 31P{1H} NMR data of all bis-alkinylphosphanes
are singlets in the range of d ˆ À66.29 to À71.61, the
appearance of two signals for 16b with an integration ratio
of 1:1.3 has to be interpreted. The 31P NMR spectrumof 16b
1
was temperature dependent. Figure 1a and 1b depict the H
Scheme 5. Synthesis of 17 from1,3-butadiyne ( 18).
With a twofold excess of phosgene, the secondary phos-
phine 20 gave the butadiynediylbis[(2,4,6-tri-tert-phenylphos-
phanecarbonylchloride] (21, yield 51%), which can be
decarbonylated by heating to 160 ± 1708C to give the buta-
diynediylbis[(2,4,6-tri-tert-butylphenyl)phosphinouschloride]
(22). The treatment of chlorophosphine 22 with trimethylsi-
lylethynyl-MgBr at 08C afforded the bis-trimethylsilyl deriv-
ative 16a. Desilylation with 2n NaOH/MeOH gave 17 in 55%
yield [FD MS(CH2Cl2), m/z 650; 31P{1H} NMR, d ˆ À67.88].
Figure 1. 1H NMR spectra (400 MHz, [D8]THF) (left) and 31P{1H} NMR
spectra (162 MHz, THF) (right) of 16b at various temperatures.
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G. Märkl et al.
FULL PAPER
and 31P NMR spectra of 16b from ‡ 21 to À808C and from
midal and the planar geometries with DFT. All calculations
were carried out with Beckeꢁs hybrid functional B3LYP and a
6-31G** basis set.[30]
The energy barriers (in Hartree) for the ground state (GS)
and the transition state (TS) of the phosphane inversions are
given in Table 3. These values at least qualitatively confirm
‡40 to À408C, respectively.
1
À
In the H NMR spectrum, the signals of iPr H (d ˆ 1.07 (s))
and p-tBu (d ˆ 1.30 (s)) split at À408C to become doublets.
4
À
The doublet of the m-aryl H (d ˆ 7.48, d, J(P,H) ˆ 3.2 Hz) at
À808C changes to two broad signals at d ˆ 7.45 and 7.60.
The 31P NMR spectra at dif-
ferent temperatures were more
ꢂ
ꢂ
Table 3. Calculated energy barriers for the inversion of PH3, H2P(C CH), and HP(C CH)2.
informative: the two signals at
218C (d ˆ À66.53 and À66.29)
become sharper at 08C (d ˆ
À67.26 and À66.73) and are
baseline separated at À408C
(d ˆ À67.26 and À66.73). These
values do not change signifi-
cantly at À808C (d ˆ À67.74
ꢂ
ꢂ
PH3
H2P(C CH)
HP(C CH)2
GS [Hartree]
TS [Hartree]
DE [Hartree]
À 343.146208988 (C3v)
À 343.093123849 (D3h)
0.05308514
À 419.291730569 (Cs)
À 419.241986342 (C2v)
0.04974423
À 495.436500384 (Cs)
À 495.391053894 (C2v)
0.04544649
DE [kJmolÀ1
]
139.5
130.7
119.4
and À66.75). As the temperature is increased the two signals
coalesce at ‡35.18C and appear as a broad singlet at ‡408C.
The explanation of this phenomena is a dramatic reduction
of the inversion barrier of the pyramidal phosphine phospho-
rus in the bis-alkynylphosphine 16b.
The two 31P NMR signals of 16b at 218C belong to the
diastereomeric meso and racemic forms.
the decrease of the DG= values of the inversion barriers as the
number of triple bonds increases.
The stabilization of the planar transition state can be
understood by an overlap of the p orbitals of the triple bonds
with the P lone pair. The situation is comparable with that of
the phospholes 13. As already mentioned, Mislow[31] found
that the inversion barriers of 13 are lowered considerably by
the formation of a planar aromatic transition state.
The overlapping of p orbitals is also the result of the
reduction of the inversion barrier by aryl groups (C6H5P-
(CH3)C3H7, DG=ˆ 134 kJmolÀ1; c-C6H11P(CH3)C3H7, DG=ˆ
149 kJmolÀ1)[32] and by carbonyl groups (H3CP(CHO)2,
DG=ˆ 79 kJmolÀ1).[33]
At 35.18C the signals coalesce, which means that the
phosphane inversion is now so fast that the signals are no
longer separated. We observe one broad signal at 408C
because the high rate of inversion produces only an averaged
value. We calculated the inversion barrier according to the
method of Friebolin and Mannschreck.[25, 26]
Consequently, the singlet in the 31P NMR spectrumof 17 at
room temperature must be interpreted by the configuration of
the tervalent pyramidal phosphorus in 16 being even less
stable; therefore, the two diastereomers can not be detected
at 218C. Indeed, the coalescence temperature Tc for the bis-
terminal acetylene 17 was 2.9 Æ 28C. Already at À208C, the
With Tc ˆ 35.1 Æ 28C, the following DG= values for the
reversible inversions were obtained.
DG=A!B ˆ 65.81 Æ 0.4 kJmolÀ1
DG=B!A ˆ 65.14 Æ 0.4 kJmolÀ1
31P NMR spectrum([D ]THF) splits into two singlets (d ˆ
8
Usually the DG= values of the inversion barriers of
alkylphosphanes, arylphosphanes, and alkylarylphosphanes
are ꢀ130 ± 140 kJmolÀ1.[27] Electronegative substituents at the
phosphorus atomincrease the inversion barriers, while
electropositive substituents diminish them (for dimethylfluo-
rophosphane DG=ꢀ 226 kJmolÀ1,[28] and for trimethylsilyliso-
propylphenylphosphane DG=ꢀ 80 kJmolÀ1).[29]
À68.38 and À68.41) fromthe diastereomers of 17, and at
À608C the two signals are baseline separated (d ˆ À68.93 and
À69.01).
Oxidative Eglinton coupling of bis(ethynylphosphanyl)buta-
diyne 17 to give tetraphosphacycloicosaoctayne 9 and hexa-
phosphacyclotriacontadodecayne 11: The Eglinton coupling
of 17 in the de Meijere modification yielded a solid yellow
product after column chromatography. According to the MS
and the 31P NMR spectroscopic data, the reaction product was
a mixture of the 20-membered tetraphosphacycloicosaoc-
tayne 9 (86 ± 87%), the 30-membered hexaphosphatriaconta-
dodecayne 11 (11.1%), and the 40-membered octaphospha-
cyclotetracontahexadecayne 23 (2.4%) as result of oxidative
dimerization, trimerization, and tetramerization, respectively
To our knowledge, the value of DG=ꢀ 65 kJmolÀ1 for 16b is
one of the lowest known for phosphane inversions.
Ab initio calculations possibly give an explanation of this
phenomena. According to these results, the pyramidal inver-
sion of ethynylphosphanes is supported by the interaction of
the phosphorus lone pair with the p-orbitals of the triple
bonds in the planar transition state. The geometries of PH3,
ꢂ
ꢂ
H2P(C CH), and HP(C CH)2 were calculated for the pyra-
3810
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Chem. Eur. J. 2000, 6, No. 20

Polyphosphacarbons
3806±3820
Scheme 6. Formation of the 20-, 30-, and 40-membered polyphosphacyclopolyynes 9, 11, and 23 by Eglinton coupling of 17.
[31P NMR (162 MHz, C2D2Cl4) at 1208C: d(9) ˆ À65.24,
d(11) ˆ À63.53, d(23) ˆ À63.03] (Scheme 6).
butylphenyl)[(triisopropylsilyl)ethynyl]phosphanyl}butadiyne
26 (1%), which is the monocoupling product of 24 with 7a.
Since the yield of 25b could not be improved by several
variations of this method, we studied the Pd/Cu-catalyzed
coupling according to Elbaumet al. [36] However, this method
(catalytic amounts of CuI and [Pd(CH3CN)2] in isopropyl-
amine) produced a similar composition of reaction products,
and the yield of 25b did not increase.
The best approach to 25b started fromthe isolated bis-Cu-
salt 7d that can be prepared according to Scott and Cooney[35]
by treatment of 7a with nBuLi (2.1 mol) in THF at À788C
and then with CuCl (2.1 mol) at 08C. After replacement of the
THF by pyridine, the bromoacetylene 24 was added slowly to
the Cu salt 7d.
Since 9, 11, and 23 can be obtained in a pure formby
different approaches (as described in the following sections),
the separation of the reaction mixture was not investigated.
Oxidative coupling of phosphane 25a to give triphosphacy-
clopentadecahexayne 8 and hexaphosphacyclotriacontado-
decayne 11
Synthesis of 25a: The strategy for the synthesis of 25a is the
Cadiot ± Chodkiewicz coupling of (bromethynyl)(2,4,6-tri-
tert-butylphenyl)[(triisopropylsilyl)ethynyl]phosphane (24)
with the copper salt 7d of diethynyl(2,4,6-tri-tert-butylphen-
yl)phosphane (7a) followed by desilylation (Scheme 7).
The hexayne 25b was isolated by column chromatography
in 27% yield. The byproducts were formed in smaller
quantities (16b in 10%, 24 in 4% yield, while 15b could not
be detected at all). The phos-
A solution of 15b in THF was treated with an aqueous
solution of NaOBr.[34] Chromatographic purification afforded
phane 25a was obtained by desi-
lylation of 25b with TBAF/THF
at À788C in 63% yield as yellow
crystals.
Oxidative Eglinton coupling of
25a: The oxidative coupling of
25a according to the modified
Eglinton method (as discussed
above) can be expected to be
either intramolecular to give the
15-membered ring 8 or intermo-
lecular by formation of the 30-
Scheme 7. Synthesis of 25a, 25b by Cadiot ± Chodkiewicz coupling.
membered ring 11 (Scheme 8).
24 as a colorless viscous oil in 44% yield. The preferred
method was the reaction of the lithium acetylide of 15b
(treatment of 15b with nBuLi at À788C) with p-toluenesul-
fonylbromide[35] (yield 75%). The spectroscopic data of 24
confirmed the structure (see the Experimental Section).
Several different procedures for the Cadiot ± Chodkiewicz
coupling have been described in the literature. The reaction of
diacetylene 7a with CuCl and NH2OH ´ HCl in THF/isopro-
pylamine (v/v ˆ 1:1) and addition of 24 in THF at room
temperature gave the desired hexayne 25b in only 11% yield.
Byproducts were 15b (6%), the tetrayne 16b (18%), which is
an autocoupling product of 24, and the hitherto unknown
[ethynyl(2,4,6-tri-tert-butylphenyl)phosphanyl]{2,4,6-tri-tert-
The crude, brown, solid reaction product yielded after
chromatography (silica gel, CH2Cl2/hexane 1:6) an orange-
yellow powder. Repeated chromatography (silica gel,
CH3CN/n-hexane 1:200) gave orange-yellow crystals of 8
(m.p. 78 ± 848C) and yellow crystals of 11 [m.p. ꢀ 1758C
(decomp)].
Triphosphacyclopentadecahexayne 8: According to the spec-
troscopic data, the product with the low melting point was the
intramolecular coupling product 8 (70%) and that with the
high melting point was the intermolecular coupling product 11
(5%). The latter had been observed already as a byproduct in
the oxidative trimerization of 17.
Chem. Eur. J. 2000, 6, No. 20
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3811

G. Märkl et al.
FULL PAPER
Gibbs DG= values have been
calculated according to the
method of Friebolin and Mann-
schreck[26]
:
DG=A!B ˆ 74.7 Æ 0.4 kJmolÀ1
DG=B!A ˆ 74.0 Æ 0.4 kJmolÀ1
The decrease in the phos-
phane inversion barrier can be
interpreted again by an inter-
action of the p orbitals of the
triple bonds with the orbitals of
the P lone pair in the transition
state. The singlet at 1008C can
be rationalized in the sense of a
more or less synchronous inver-
sion of all three pyramidal
phosphine units. In this case
we must take an aromatic 18p
transition state into account.
This assumption is in accord-
Scheme 8. Formation of the 15- and 30-membered polyphosphacyclopolyynes 8 and 11 by Eglinton coupling of
25a.
The 31P{1H} NMR spectrumof 8 (Figure 2a) has three
signals at d ˆ À68.14 (s), À68.62 (s), and À69.41 (s) with an
integration ratio of 1:2:0.8. This confirms the formation of
both possible isomers, the all-cis-compound 8a (d ˆ À69.41
and the cis,cis,trans-compound 8b [d ˆ À68.14 (1P) and
ance with the planar aromatic transition state of the phos-
pholes 13 during inversion.[33]
The 1H{31P} NMR spectra (400 MHz, C2D2Cl4) confirmthe
conclusion drawn fromthe 31P NMR data. The three singlets
of the o-tBu-H at d ˆ 1.632, 1.647, and 1.660 and the three
superimposing doublets of the m-aryl-H (d ˆ 7.370 ± 7.410) at
808C collapse to two broad singlets (Figure 2b).
Hexaphosphacyclotriacontadodecayne 11: The intermolecular
oxidative coupling of 29 produced the 30-membered hexamer
11 only as a byproduct in 5% yield. Nevertheless, it was
isolated as pure yellow crystals by column chromatography.
The 31P NMR spectrum(400 MHz, CDCl 3) of 11 at 218C is
a broad singlet (d ˆ À63.95), which sharpens at 508C.
In the 1H NMR spectrum(162 MHz, CDCl ) at roomtem-
3
perature, all o-tBu-H appear as one singlet (dˆ 1.64, 108H) and
the m-aryl-H as one doublet (dˆ À7.45, 4J(P,H)ˆ 3.5 Hz, 12H).
Since in the triphosphacyclopentadecahexayne 8 this phe-
nomena can be observed in both the 31P NMR and the
1H NMR signals only at elevated temperatures [31P NMR
(1008C), d ˆ À68.03 (s); 1H NMR (808C), d ˆ 1.647 (s), o-tBu,
d ˆ 7.39 (brs), m-aryl-H)], this result can be rationalized by a
further reduction of the inversion barrier of the pyramidal
phosphorus in 11.
The discussion, however, also has to take account of the
conformational mobility of the whole ring system as a result of
the chair± boat ± chair conformations. As in hexaphenylcy-
Figure 2. Temperature-dependant NMR spectra of 8. a) 31P{1H} NMR
spectra (162 MHz, C2D2Cl4) from21 8C to 1008C; b) 1H NMR spectra
(400 MHz, C2D2Cl4) from21 8C to 808C. (The d scales are related to the
spectra at 218C. Because of the temperature drift of the signals at higher
temperatures the scales no longer correlate with the values of the signals).
[37]
clohexaphosphane (P-C6H5)6
or hexaspirocyclopropylcy-
clotriacontadodecayne ([6]-rotane),[22] compound 11 should
exist in the chair conformation in the solid state.
Oxidative coupling of tetraphosphaicosaoctayne 28 to give 9
and octaphosphacyclotetracontahexadecayne 23 by intra- and
intermolecular Eglinton coupling, respectively
À68.62 (2P)]. The 31P{1H} NMR spectrumof 8 was temper-
ature dependant. As the temperature was increased, the sharp
signals at 218C broadened and coalesced at 83.88C. At 1008C
an averaged, broad singlet at d ˆ À68.03 was observed.
This result can be rationalizedÐas in the open-chain
diphosphanes 16b and 17Ðby a distinct reduction of the
inversion barriers of the pyramidal tertiary phosphanes. The
Synthesis of 28 by the Cadiot ± Chodkiewicz coupling of 17
with 24: The strategy for the synthesis of 28 is the Cadiot ±
Chodkiewicz coupling of the bis-copper salt of 17 with 24,
followed by desilylation of the coupling product 27
(Scheme 9).
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Polyphosphacarbons
3806±3820
The EI MS (70 eV) and the fragmentation pattern confirm
the structure of 26. In the 1H NMR spectrum, the acetylenic H
3
appears at d ˆ 3.24 (d, J(P,H) ˆ 0.4 Hz).
The 31P{1H} NMR spectrum(CDCl 3) of 26 at 218C contains
three signals at d ˆ À66.12, À66.28, and À67.87, which can be
interpreted by the presence of two diastereomers (erythro-26,
and threo-26 Scheme 9). By comparison with the 31P NMR
spectra of 15b and 17, the signals at d ˆ À66.12 and À66.28
can be assigned to P2 and P2', and the signal at d ˆ À67.87 to
P1 and P1'. The temperature-dependant 31P NMR spectra
(from À20 to ‡508C) allows the rationalization of the
stereochemistry of 26 (Figure 3). At À208C two signals are
Scheme 9. Formation of 3,8,13,18-tetraphosphaicosaoctaynes 27 and 28 by
Cadiot ± Chodkiewicz coupling.
As described for the synthesis of 25b, the isolated bis-
copper salt of 17 in pyridine was treated with 24 at room
temperature. Four fractions were isolated from the reaction
mixture by column chromatography: these fractions yielded
yellow crystals of 16b (2%, reductive coupling of 24 with
itself; m.p. 111 ± 1138C), yellow crystals of the desired twofold
coupling product 27 (16%, m.p. 80 ± 1118C), 15b (2%), and
the monocoupling product 29 (6%, as viscous yellow oil).
3,8,13,18-Tetraphosphaicosa-1,4,6,9,11,14,16,19-octayne
(28) can be isolated in 54% yield by desilylation with TBAF in
THF at À788C and column chromatography. The doublet at
d ˆ 3.25 (3J(P,H) ˆ 0.4 Hz) in the 1H NMR spectrumindicates
the terminal acetylenic hydrogens. The 31P{1H} NMR spec-
trumshows two singlets at d ˆ À63.85 and À67.81. The first
one belongs to the two inner P atoms and the second one to
the two outer P atoms.
Figure 3. Temperature-dependent 31P{1H} NMR spectrum(162 MHz,
[D8]THF) of 26.
observed for each diastereomer. One isomer shows a P ± P
coupling 6J(P,P) ˆ 2.3 Hz. The coalescence temperature for
P2/P2' is 35.4 Æ 28C. The free activation energy DG= for the
inversion energy of P2/P2' was determined by the method of
Friebolin and Mannschreck.[25]
DG=A!B (P2/P2') ˆ 66.75 Æ 0.4 kJmolÀ1
DG=B!A (P2/P2') ˆ 66.48 Æ 0.4 kJmolÀ1
The coalescence temperature of P1/P1' is between 0 and
218C. The lineshape does not allow the determination of an
exact value.
Synthesis of 28 by Eglinton coupling of butadiyne 26:
The temperature-dependant NMR spectra of 26 confirm
that the dramatic reduction of the inversion barriers in
tervalent phosphines by adjacent triple bonds is a general
phenomenon.
The Eglinton coupling of 26 was carried out by stirring it
with [Cu(OAc)2] (4 equiv) and CuCl (3 equiv) in pyridine for
15 h at room temperature. Chromatography of the crude oil at
Al2O3 gave 27 as yellow crystals in a nearly quantitative yield,
m.p. 76 ± 1118C.
In the 31P{1H} NMR spectrum, two singlets at d ˆ À63.87
and À66.17 (ratio 1:1) are observed. By comparison with the
31P{1H} signals of 25a, the signal at d ˆ À63.87 can be assigned
Synthesis of 26: The alternative synthetic approach to 28 is the
monodesilylation of 16b to give 26 followed by an Eglinton
coupling to give 27 and formation of 28 by desilylation
(Scheme 9). Treatment of 16b with TBAF (0.13 mol) in THF
at À788C (1 h) and column chromatography [Al2O3, petro-
leumether (40 ± 60)] of the reaction mixture gave the starting
material 16b (30%). The desired monodesilylated 26 (39%)
was isolated with CH2Cl2/petroleumether (v/v ˆ 1:20). The
third fraction, eluted with CH2Cl2/hexane (v/v ˆ 1:6), is the
bis-desilylated 17 (pale yellow crystals, 15%).
Chem. Eur. J. 2000, 6, No. 20
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3813

G. Märkl et al.
FULL PAPER
to the two inner phosphorus atoms, and the signal at d ˆ
À66.17 to the two outer P atoms.
The large melting interval of more than 308C for 27 is
probably caused by the presence of a mixture of stereo-
isomers. Theoretically, compound 27 has four chiral phospho-
rus atoms in the symmetric system and could form ten
stereoisomers. Since in 27 the inversion barriers of the
pyramidal tervalent phosphanes are expected to be reduced
considerably, the stereochemical situation certainly is rather
complex.
The desilylation of 27 to give 28 is achieved with TBAF in
THF as described above.
Oxidative coupling of 28 to give the polyphosphacyclo-
polyynes 9 and 23: The modified Eglinton coupling of 28
yields, after column chromatography, two yellow, crystalline
compounds. These are the tetraphosphacycloicosaoctayne 9
(65%) and the octaphosphacyclotetracontahexadecayne 23
(2%, Scheme 10).
Figure 4. Temperature-dependent 31P NMR spectrumof 9 (162 MHz,
CDCl3): 218C, À208C; (C2D2Cl4): 1408C.
In the 1H NMR spectrumof 9 at 218C, the singlet observed
at d ˆ 1.29 corresponds to the p-tBu-H and the signal at d ˆ
1.64 to the o-tBu-H, while the doublet at d ˆ 7.43 (d, 4J(P,H) ˆ
3.1 Hz) corresponds to the m-aryl-H. At À208C these signals
are split because of the slower inversion of the tervalent
phosphane phosphorus atoms.
The physical and spectroscopic data of the 40-membered
octaphosphacyclotessaracontahexadecayne 23 is discussed in
the following section.
Oxidative coupling of hexadecayne 32 to give 23:
Synthesis of octayne 30: The synthetic strategy is the mono-
desilylation of 27 to give 30 followed by a modified Eglinton
coupling to give the bis(triisopropylsilyl) derivative 31
(Scheme 11).
Scheme 10. Formation of the 20- and 40-membered polyphosphacyclo-
polyynes 9 and 23 by an intra- and intermolecular Eglinton coupling of 28.
The 31P{1H} NMR spectrum(Figure 4) at 21 8C shows
several broad signals from d ˆ À64.7 to À66.2. On heating the
sample to 1408C, only one sharp signal at d ˆ À64.9 remains.
The broad signals of 9 at roomtemperature sharpen at
À208C. The temperature dependence of the 31P spectrumof 9
is clearly the result of the temperature dependence of the
inversion of the pyramidal phosphorus. At À208C the
inversion is frozen, and so we observe the signals for all four
possible isomers 9a ± 9d.
Since the all-cis-configured 9a is the less favored one for
steric reasons, we believe it to be formed in the lowest yield
(d ˆ À68.13, 5%). The main isomer 9d (46.3%) has the
lowest symmetry and therefore gives rise to three signals at
Scheme 11. Synthesis of octaphosphatetracontahexadecayne 32.
The monodesilylation of 27 was carried out by treatment
with TBAF (0.3 equiv) in THF at À788C for 2 h. One obtains
a mixture of the substrate 27 and the mono- and bis-
desilylated tetraphosphaicosaoctynes 30 and 28 as a yellow
oil; this mixture can be separated by column chromatography
on Al2O3.
In accordance with the unsymmetrical structure of 30, in the
31P{1H} NMR spectrum(162 MHz, CDCl 3) four different
signals with equal intensity are observed. These can be
assigned by comparison with the values of 27 and 28: d ˆ
6
6
d ˆ À65.56 (t, J(Pc,Pb) ˆ 1.1 Hz, Pc), À66.18 (t, J(Pa,Pb) ˆ
8.4 Hz, Pa) and À66.80 (dd, 6J(Pa,Pb) ˆ 8.4 Hz, 6J(Pb,Pc) ˆ
1.1 Hz, 2 Pb). The signal at d ˆ À65.56 (27%) is assigned to
9c and that at d ˆ À66.26 (22%) to 9b.
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Chem. Eur. J. 2000, 6, No. 20

Polyphosphacarbons
3806±3820
À67.78 (s, Pa), À63.82 (s, Pb), À63.88 (s, Pc) and À66.16 (s, Pd).
Comparison of the pyramidal inversion barriers of the 15-, 20-,
25-, 30-, and 40-membered tri-, tetra-, penta-, hexa-, and
octaphospha ring systems 8, 9, 10, 11, and 23: In the 31P NMR
of the 15-membered triphosphacyclopentadecahexayne 8 the
three signals of the two isomers at room temperature are
sharp lines. However, the inversion barrier of the pyramidal
phosphorus atoms is dramatically lowered (74.8 kJmolÀ1).
The coalescence temperature is 838C and at 1008C only one
sharp signal (d ˆ À68.3) is observed. In the 31P NMR
spectrum of the 20-membered tetraphosphacycloeikosaoc-
tyne 9 at À208C, sharp signals for all four possible isomers are
observed. However, at roomtemperature the signal broad-
ening indicates that there is a high rate of pyramidal inversion
of the phosphorus atoms in all isomers. At 1408C, the
inversion is so fast that only one 31P NMR signal (d ˆ
À64.91) is observed. In the 25-membered pentaphosphacy-
clopentaicosadecayne 10 and the 30-membered hexaphos-
phacyclotriacontadodecayne 11 the reduction of the barrier of
the P inversion is no longer restricted by ring strains and,
therefore, at roomtemperature only broad 31P signals (10: d ˆ
À65.51; 11: d ˆ À63.95) are observed. In the 31P NMR
spectrum of the 40-membered octaphosphacyclotetraconta-
hexadecayne 23 at roomtemperature these effects already
lead to one sharp signal for all eight pyramidal phosphorus
atoms (d ˆ À65.52).
The FD MS (CH2Cl2), m/z 1455 also supports the formula of
30.
Eglinton coupling of 30 to give hexadecayne 31: The oxidative
coupling of 30 was carried out according to the modified
Eglinton method. The disappearance of 30 was monitored by
TLC. After column chromatography, 31 was isolated as a pale
yellow microcrystalline solid (yield 87%).
1
In the H NMR (400 MHz, CDCl3) of 31 the signal of the
acetylenic hydrogen (d ˆ 3.25, s) disappeared. The integration
proves the presence of two triisopropylsilyl groups (d ˆ 1.04, s,
À1
ꢂ
42H). In the IR spectrumthe CH signal at n ˆ 3300 cm
also disappears.
In agreement with the symmetric structure of 31, the 31P{1H}
NMR (162 MHz, CDCl3) shows three broad singlets with an
integration ratio of 2:1:1. The assignment is possible by
comparison with the 31P NMR spectrumof 27 [d ˆ À66.17 (s,
2Pa); À63.87 (s, 2Pb), À63.70 (s, 2Pc, 2Pd)]. In the FD-MS
(CH2Cl2) the expected peak of 31 (m/z 2908) cannot be
detected, probably because the molecule is no longer
desorbed from the RhC emitter or it decomposes below the
desorption temperature.
The desilylation of 31 occurs smoothly by means of the
standard method (TBAF in THFat À788C) and 32 is obtained
ꢂ
as a pale yellow precipitate. The IR spectrum[ n( CH) ˆ
À1
3300 cmÀ1 (w); n(C C) ˆ 2160 (w), 2060 cm (m)] confirms
ꢂ
the formation of 32. As a result of the insolubility in all the
usual solvents, no satisfactory H and 13C NMR and no FD-
Experimental Section
1
General methods: 1H NMR spectra were recorded on a VarianT60
(60 MHz), Bruker AW80 (80 MHz), and Bruker ARX400 (400.13 MHz)
spectrometers. 13C NMR spectra on a Bruker ARX400 (100.61 MHz), 31P
NMR spectra on Bruker ARX400 (196.98 MHz) instruments. The UV/Vis
spectra were recorded on a HitachiU-2000. The mass spectra are obtained
with a Finnigan MAT311A and 112S (EI) and a Finnigan MAT95 (FAB,
FD). The ESI-mass spectra were studied with a Finnigan MATSSQ7000.
MS spectra could be obtained.
Intramolecular Eglinton coupling of 32 to give hexadecayne
23: The oxidative coupling of 32 was achieved again by means
of the modified Eglinton method ([Cu(OAc)2] (4 equiv),
CuCl2, (3 equiv), and pyridine). Because of the insolubility of
32, the coupling was carried out by adding small portions of
the solid 32 to the reaction mixture over a period of four hours
at 658C. Heating was continued for a further two hours and
the mixture was then stirred for 24 hours at room temper-
ature. After hydrolysis, column chromatography of the crude
brown solid yielded the yellow, microcrystalline compound of
the 40-membered octaphospha ring system 23 in 9% yield.
This result confirms that both the intermolecular coupling
of the tetraphosphine 28 and the intramolecular coupling of
32 form the same 40-membered ring system 23.
2,4,6-Tri-tert-butyldichlorophosphane (6): The dichlorophosphane 6 was
synthesized according to the procedure of Yoshifuji et al.,[19] improved by
Kreitmeier[38] and Reithinger[39] from1-broom-2,4,6-tri-
tert-butylben-
zene.[40] Colorless needles, m.p. 70 ± 718C (fromacetonitrile), 70%;
1H NMR (60 MHz, CDCl3): d ˆ 1.33 (s, 9H, p-tBu), 1.62 (s, 18H, o-tBu),
4
7.39 (d, J(P,H) ˆ 4.2 Hz, 2H, m-aryl).
Diethynyl(2,4,6-tri-tert-butylphenyl)phosphane (7a):[41]. A saturated sol-
ution of acetylene in THF was prepared by bubbling acetylene into THF
(200 mL) at 08C for 30 min. EtMgBr (10.0 mL, 10m in THF, 100 mmol) was
then added dropwise at 08C, while the addition of acetylene was continued
(30 min). The reaction mixture was allowed to warm to room temperature
and a solution of 6 (13.9 g, 40.0 mmol) in THF (200 mL) was added. After
stirring for 12 h, the mixture was hydrolyzed with NH4Cl solution (10%,
200 mL). The organic layer was separated and the aqueous solution
extracted with diethyl ether (3 Â 40 mL). After drying and evaporation, the
crude solid product was purified by column chromatography (SiO2; CHCl3/
hexane 1:2). Recrystallization fromethanol (99%, 15 mL) afforded 7a in
52% yield as colorless crystals. M.p. 91 ± 928C; 1H NMR (60 MHz, CDCl3):
ꢂ
In the IR spectrum(KBr) of 23 the n( CH) band at
3300 cmÀ1 disappears; the following signals are observed:
n(C C) ˆ 2200 (w), 2165 (w), 2100 cmÀ1 (m).
ꢂ
Amazingly, the 1H NMR spectrum(400 MHz, CDCl
,
3
218C) of 23 is extremely simple. The 72H of the p-tBu groups
forma singlet at d ˆ 1.30, the 144H of the o-tBu groups forma
singlet at d ˆ 1.63, and the 16m-aryl-H groups forma doublet
at d ˆ 7.45, 4J(H,H) ˆ 3.5 Hz. The 31P{1H} NMR spectrum
(162 MHz, CDCl3) shows one broad singlet for all eight
phosphine phosphorus atoms in the expected region (d ˆ
À63.52). Neither the FD MS (CH2Cl2) nor the ESI MS
(CHCl3/MeOH/H2O 10:10:1) confirmthe molecular weight of
23 (m/z ˆ 2596); however, this does not place doubt on the
structure of the ring system.
ꢂ
d ˆ 1.33 (s, 9H, p-tBu), 1.72 (s, 18H, o-tBu), 3.23 (s, 2H, CH), 7.43 (d,
4J(P,H) ˆ 3.6 Hz, 2H, m-aryl); IR (KBr): nÄ ˆ 3300, 3260 (s, CH),
ꢂ
2030 cmÀ1 (m, C C); elemental analysis calcd (%) for C22H31P (326.46):
ꢂ
C 80.94, H 9.57; found C 80.55, H 9.70.
(2,4,6-Tri-tert-butylphenyl)bis[(trimethylsilyl)ethynyl]phosphane (7b): A
solution of trimethylsilylacetylene (1.96 g, 20 mmol) in diethyl ether
(20 mL) was metallated with nBuLi (12.5 mL, 20.0 mmol) at À508C over
a period of 30 min. This solution was then added slowly to a solution of 6
(3.58 g, 10.0 mmol) in diethyl ether (30 mL) at À788C. The mixture was
allowed to warmto roomtemperature and the LiCl was filtered off in a
sintered glass tube. All operations were carried out with the exclusion of
Chem. Eur. J. 2000, 6, No. 20
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0620-3815 $ 17.50+.50/0
3815

G. Märkl et al.
FULL PAPER
‡
‡
‡
moisture. After removal of the solvent, the yellow, crystalline crude 7b was
purified by column chromatography (SiO2/hexanes). The byproduct 1,3,5-
tri-tert-butylbenzene was removed by sublimation at 708C/10À2 mmHg.
Recrystallization frommethanol gave 7b as colorless crystals (72%). M.p.
105.5 ± 106.58C; 1H NMR (60 MHz, CDCl3/CD2Cl2): d ˆ 0.25 (s, 18H,
Si(CH3)3), 1.36 (s, 9H, p-tBu), 1.71 (s, 18H, o-tBu), 7.51 (d, 4J(P,H) ꢀ 4 Hz,
2H, m-aryl); 13C NMR (22.64 MHz, CDCl3): d ˆ 0.36 (s, C11), 31.23 (s, C8),
34.20 (d, 4J(P,C) ˆ 7.30 Hz, C6), 34.98 (s, C7), 39.95 (d, 3J(P,C) ˆ 4.64 Hz,
(2) [M À CH3] , 595 (5) [M À C3H7] , 481 (3) [M À C9H21Si] , 231 (9)
‡
‡
[C17H27] , 57 (38) [C4H9] ; elemental analysis calcd (%) for C40H71PSi2
(639.2): C 75.17, H 11.20; found C 75.10, H 10.92.
Compound 15b: 1H NMR (400 MHz, CDCl3): d ˆ 1.05 (s, 21H, iPr), 1.30 (s,
3
ꢂ
9H, p-tBu), 1.68 (s, 18H, o-tBu), 3.18 (d, J(P,H) ˆ 1.1 Hz, 1H, CH), 7.44
(d, J(P,H) ˆ 3.1 Hz, 2H, m-aryl); 13C NMR (101 MHz, CDCl3): d ˆ 11.25
4
4
4
(d, J(P,C) ˆ 0.9 Hz, C11), 18.56 (s, C12), 31.11 (s, C8), 34.10 (d, J(P,C) ˆ
7.6 Hz, C6), 34.92 (s, C7), 39.80 (s, 3J(P,C) ˆ 4.8 Hz, C5), 82.98 (d, 3J(P,C) ˆ
8.8 Hz, C13), 96.40 (d, 2J(P,C) ˆ 13 Hz, C14), 104.63 (d, 1J(P,C) ˆ 15 Hz,
C9), 114.40 (d, 2J(P,C) ˆ 2.2 Hz, C10), 123.71 (d, 3J(P,C) ˆ 9.2 Hz, C3),
1
2
C5), 104.21 (d, J(P,C) ˆ 12.61 Hz, C9), 116.62 (d, J(P,C) ˆ 3.98 Hz, C10),
123.92 (d, 3J(P,C) ˆ 9.29 Hz, C3), 125.06 (s, C1), 151.50 (d, 4J(P,C) ˆ
1.99 Hz, C4), 157.79 (d, 2J(P,C) ˆ 17.25 Hz, C2); 31P NMR (101.27 MHz,
1
4
124.20 (d, J(P,C) ˆ 23 Hz, C1), 151.65 (d, J(P,C) ˆ 2.4 Hz, C4), 157.87 (d,
À1
ꢂ
CDCl3): d ˆ À70.20; IR (KBr): nÄ ˆ 2080 (m, C C), 1240, 840 cm (vs,
2J(P,C) ˆ 18 Hz, C2); 31P{1H} NMR (162 MHz, CDCl3): d ˆ À70.37; IR
Si(CH3)3); elemental analysis calcd (%) for C28H47PSi2 (470.83): C 71.42 H
10.06; found C 71.29 H 10.09.
À1
ꢂ
ꢂ
(film): nÄ ˆ 3310, 3280 (m, CH), 2100, 2040 cm (w, C C); UV/Vis (n-
hexane): lmax (e) ˆ 290 (3300), 237 (17600), 210 nm(44400); MS (EI,
‡
‡
‡
Bis(ethinyl)-2,4,6-tri-tert-butylphenylphosphane (7a) by desilylation of 7b:
NaOH (2n, 5 mL) was added to a solution of 7b (0.47 g, 1.00 mmol) in
methanol/diethyl ether (30 mL, 2:1). The mixture was stirred for 1 h and
then poured into HCl (2n, 50 mL) and diethyl ether (50 mL). The aqueous
phase was washed with diethyl ether (3 Â 10 mL), and the combined diethyl
ether solutions were dried with Na2SO4 and evaporated. Recrystallization
fromethanol afforded colorless crystals of 7a, (71%). M.p. 91 ± 928C.
70 eV): m/z (%): 638 (100) [M] , 623 (2) [M À CH3] , 595 (5) [M À C3H7] ,
‡
‡
‡
481 (3) [M À C9H21Si] , 231 (9) [C17H27] , 57 (38) [C4H9] ; elemental
analysis calcd (%) for C31H51PSi (482.8): C 77.12, H 10.64; found C 77.57, H
10.94.
Partial desilylation of 7c to 15b: A solution of TBAF in THF (0.50 mL,
0.50 mmol, 1m in THF) was added to a solution of 7c (3.20 g, 5.00 mmol) in
THF (100 mL) at À788C. After 3 h, the mixture was quenched with water
and dried with Na2SO4, and the solvent evaporated under reduced
pressure. The resulting yellow oil was purified by column chromatography
(Al2O3, hexane). Fraction 1: starting material 7c, colorless oil (927 mg,
29%); fraction 2: 15b, light yellow oil (941 mg, 39%); fraction 3: 7a, m.p.
90 ± 918C (261 mg, 16%).
Eglinton coupling of 7a to give a mixture of the polyphosphacyclopolyynes
8, 9, 10, and 11: A solution of 7a (500 mg, 1.50 mmol) in pyridine/methanol
(15 mL, 2:1) was added dropwise over a period of 15 min at room
temperature to a solution of [Cu(OAc)2] ´ H2O (2.00 g, 10.0 mmol) in
pyridine (50 mL). The mixture was heated to 608C for 3 h. After
evaporation in vacuo, the residue was extracted with benzene (2 Â
50 mL). The organic solution was washed with water (2 Â 20 mL), HCl
(2n, 10 mL), and again with water (3 Â 10 mL). Column chromatography
(SiO2/benzene) yielded a dark yellow powder (decomp ꢀ2508C), 402 mg
(82% related to 7a). The product was a mixture of the polyphosphacy-
clopolyynes 8, 9, 10, and 11 and was soluble in nonpolar solvents and
insoluble in polar solvents. It was possible to partially separate the mixture
by HPLC (Polygosil 60.7 cm, Machery-Nagel, Büren), n-hexane/methyl-
pentane (99.6%)/CH3CN (0.04%), 40 bar). The 15-membered ring system
8 and the 25-membered ring 10 were isolated in pure form; compounds 9
and 11 could not be separated. Since 8, 9, and 11 are obtainable in better
General procedure for the Eglinton coupling in the de Meijere modifica-
tion:[21] A solution of the terminal acetylene (1.00 mmol) in pyridine
(10 mL) was added dropwise to a stirred solution of [Cu(OAc)2] (4 mmol)
and CuCl (3 mmol) in pyridine (10 mL) at room temperature. The reaction
mixture was stirred for a further 10 h, and after evaporation in vacuo, the
residue was dissolved in CH2Cl2/water (40 mL, 1:1). The organic phase was
washed with HCl (2n, 10 mL), saturated NaHCO3 solution (7 mL), and
water (10 mL). The CH2Cl2 solution was dried over Na2SO4 and then
filtered through silica gel (CH2Cl2/hexanes, 1:6).
Eglinton coupling of 15b to give bis{(2,4,6-tri-tert-butylphenyl)[(triisopro-
pylsilyl)ethynyl]phosphanyl}butadiyne (16b): The 3-phosphapentadiyne
15b (1.54 g, 3.20 mmol) was coupled according to the general procedure.
The coupling product 16b formed as a yellow oil, which crystallized within
yields by
a consecutive, multistep synthesis, only 10, not available
otherwise, is described here.
1,6,11,16,21-Pentakis(2,4,6-tri-tert-butylphenyl)-1,6,11,16,21-pentaphos-
phacyclopentacosa-2,4,7,9,12,14,17,19,22,24-decayne (10): 1H NMR
(400 MHz, CDCl3): d ˆ 1.29 (s, 45H, p-tBu), 1.64 (s, 90H, o-tBu), 7.44 (d,
4J(P,H) ˆ 2.7 Hz, 10H, m-aryl); 13C NMR (100.61 MHz, CDCl3): d ˆ 121.4
(d, 1J(P,H) ˆ 20.5 Hz, Aryl-C1), 92.99 (d, 1J(P,C) ˆ 16.9 Hz, C9), 81.33 (s,
1
a few days (1.47 g, 95%). M.p. 111 ± 1138C; H NMR (400 MHz, CDCl3):
d ˆ 1.07 (s, 42H, iPr), 1.30 (s, 18H, p-tBu), 1.65 (s, 36H, o-tBu), 7.48 (d,
4J(P,H) ˆ 3.2 Hz, 4H, m-aryl); 13C NMR (101 MHz, CDCl3): d ˆ 11.24 (s,
4
C13), 18.56 (s, C14), 31.10 (s, C8), 34.10 (d, J(P,C) ˆ 7.5 Hz, C6), 34.95 (s,
3
C7), 39.73 (d, J(P,C) ˆ 4.8 Hz, C5), 82.82 (m, C9, 9'), 93.18 (m, C10, 10'),
C10); 31P{1H} NMR (162 MHz, CDCl3): d ˆ À65.51 (brs); IR (KBr): nÄ ˆ
103.58 (d, 1J(P,C) ˆ 12 Hz, C11), 115.19 (d, 2J(P,C) ˆ 1.6 Hz, C12), 123.52
(m, C1), 123.81 (d, 3J(P,C) ˆ 9.8 Hz, C3), 151.83 (m, C4), 157.88 (d,
2J(P,C) ˆ 18 Hz, C2); 31P{1H} NMR (162 MHz, THF): d ˆ À66.53, À66.29
‡
2070 cmÀ1 (C C); MS (PI FD, toluene): m/z (%): 1621 (90) [M À H] ,
ꢂ
‡
‡
‡
1622.1 (100) [M] , 1623.1 (60) [M‡H] , 1624.2 (30) [M‡2H] , 1625 (10)
‡
[M‡3H] ; elemental analysis calcd (%) for C110H145P5 (1622.2): C 81.45, H
(ratio 1:1.3); IR (KBr): nÄ ˆ 2090, 2060 cmÀ1 (w, C C); UV/Vis (n-hexane):
ꢂ
9.01; found C 81.78 H 9.22.
lmax (e) ˆ 329 (6700), 289 (33900), 232 (47100), 211 nm(94200); elemental
analysis calcd (%) for C62H100P2Si2 (963.6): C 77.28, H 10.46; found C 77.62,
H 10.65.
(2,4,6-Tri-tert-butylphenyl)bis[(triisopropylsilyl)ethynyl]phosphane (7c)
and
ethynyl(2,4,6-tri-tert-butylphenyl)[(triisopropylsilyl)ethynyl]phos-
phane (15b) by silylation of 7a: A solution of 7a (816 mg, 2.50 mmol) in
THF (70 mL) was metallated at À788C with nBuLi (1.56 mL, 2.50 mmol,
1.6 m in hexane). After stirring for another hour at À788C, triisopropyl-
chlorosilane (0.60 g, 2.80 mmol) was added. After further 3 h reaction time
at roomtemperature, hydrolytic workup provided a dark oil, which was
purified by column chromatography (Al2O3/hexane). The first fraction
contained 7c (200 mg, 13%), which was isolated as colorless oil, followed
by 15b (330 mg, 25%) as a yellow oil, and finally unreacted starting
material 7a (m.p. 90 ± 918C) was recovered (110 mg, 14%).
2,4,6-Tri-tert-butylphosphane (19a): The reduction of 6 with LiAlH4 was
described for the first time by Issleib et al.[24] and optimized by Kreit-
meier.[38] Yield: 63%; colorless needles (fromacetonitrile); m.p. 159 ±
1618C; 1H NMR (80 MHz, CDCl3): d ˆ 1.23 (s, 9H, p-tBu), 1.50 (s, 18H,
1
4
o-tBu), 4.15 (d, J(P,H) ˆ 211 Hz, 2H, P-H), 7.37 (d, J(P,H) ˆ 2.6 Hz, 2H,
m-Aryl); IR (KBr): nÄ ˆ 2410, 2350, 2280 cmÀ1 (m, P-H).
(2,4,6-Tri-tert-butylphenyl)monochlorophosphane (19b): The monochlo-
rophosphane was prepared from 19a by reaction with CCl4/azoisobutyr-
onitrile according to Escudie et al.[24b] The procedure was improved by
Reithinger.[39] Colorless product, m.p. 105 ± 1128C (further purification of
the crude 19b by recrystallization was not possible); 1H NMR (80 MHz,
CDCl3): d ˆ 1.28 (s, 9H, p-tBu), 1.60 (s, 18H, o-tBu), 7.24 (d, 1J(P,H) ˆ
213 Hz, 1H, P-H), 7.46 (d, 4J(P,H) ˆ 4.0 Hz, 2H, m-aryl); IR (KBr): nÄ ˆ
2405 cmÀ1, (w, P-H).
Compound 7c: 1H NMR (400 MHz, CDCl3): d ˆ 1.04 (s, 42H, iPr), 1.30 (s,
9H, p-tBu), 1.69 (s, 18H, o-tBu), 7.43 (d, 4J(P,H) ˆ 3.1 Hz, 2H, m-aryl);
13C NMR (101 MHz, CDCl3): d ˆ 11.29 (d, 4J(P,C) ˆ 1.0 Hz, C11), 18.56 (d,
5J(P,C) ˆ 0.1 Hz, C12), 31.12 (s, C8), 34.14 (d, 4J(P,C) ˆ 7.6 Hz, C6), 34.92 (s,
C7), 39.72 (d, 3J(P,C) ˆ 4.7 Hz, C5), 105.87 (d, 1J(P,C) ˆ 14 Hz, C9), 113.58
(d, 2J(P,C) ˆ 2.9 Hz, C10), 123.47 (d, 3J(P,C) ˆ 9.0 Hz, C3), 125.13 (d,
1J(P,C) ˆ 24 Hz, C1), 151.37 (d, 4J(P,C) ˆ 2.1 Hz, C4), 157.69 (d, 2J(P,C) ˆ
17 Hz, C2); 31P{1H} NMR (162 MHz, CDCl3), d ˆ À68.85; IR (Film): nÄ ˆ
1,3-Butadiyne (18):[44] This compound is accessible in good yields by
dehydrochlorination of 1,4-dichloro-2-butyne[43] with aqueous KOH (yield
about 50%). Because of its instability the 1,3-butadiyne was prepared just
before use. It can be stored only in THF solution at À788C.
2070 cmÀ1 (m, C C); UV/Vis (n-hexane): lmax (e) ˆ 286 (3200), 238
ꢂ
‡
(18600), 216 nm(31800); MS (70 eV, EI): m/z (%): 638 (100) [M] , 623
3816
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0620-3816 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 20

Polyphosphacarbons
3806±3820
Bis[ethynyl(2,4,6-tri-tert-butylphenyl)phosphanyl]butadiyne (20):[45] A sol-
ution of EtMgBr in THF (13.9 mL, 26.5 mmol, 1.9m in THF) was added to a
solution of 1,3-butadiyne (670 mg, 13.4 mmol) in THF (20 mL) at À788C.
aryl); 31P NMR (162 MHz, C2D2Cl4) at 218C: several broad signals from
d ˆ À64.33 to À69.03, at 1208C: three sharp singlets at d ˆ À63.03, À63.53,
and À65.24 with an intensity of 1 (23), 4.5 (11) and 35 (9); IR (KBr): nÄ ˆ
At
08C
(2,4,6-tri-tert-butylphenyl)monochlorophosphane
(8.29 g,
2160 (w), 2060 (w, C C), the CH signal at ꢀ3300 cmÀ1 had disappeared.
ꢂ
ꢂ
26.5 mmol) in THF (70 mL) was added dropwise to the bis-Grignard
compound of 1,3-butadiyne over a period of 35 min. After hydrolysis and
extraction with diethyl ether, the obtained crude product (2.16 g) was
recrystallized fromhexane (43%). Colorless crystals (1.85 g); m.p. 147 ±
1488C (decomp); 1H NMR (80 MHz, CDCl3): d ˆ 1.26 (s, 18H, p-tBu), 1.56
(s, 36H, o-tBu), 5.80 (d, 1J(P,H) ˆ 252 Hz, 2H, P-H), 7.42 (d, 4J(P,H) ˆ
2.4 Hz, 4H, m-aryl); IR (KBr): nÄ ˆ 2410 cmÀ1 (w, P-H).
1-(Bromoethynyl)(2,4,6-tri-tert-butylphenyl)[(triisopropylsilyl)ethynyl]-
phosphane (24): A solution of 15b (770 mg, 1.60 mmol) in THF (50 mL)
was metallated at À788C with nBuLi (1.20 mL, 1.92 mmol, 1.6m in n-
hexane). After 20 min, p-tosylbromide (450 mg, 1.90 mmol) in THF (4 mL)
was added slowly at À788C. The reaction mixture was stirred at room
temperature 2 h and then hydrolyzed (10 mL). The organic phase was
treated with H2SO4 (2n, 5 mL), saturated NaHCO3 solution (5 mL), and
water (2 Â 20 mL). Evaporation afforded a reddish brown oil, which was
purified by column chromatography (Al2O3, hexanes). The phosphane 24
was obtained as a pale yellow oil (675 mg, 75%). A small amount (108 mg,
14%) of the starting material 15b was recovered. 1H NMR (400 MHz,
CDCl3): d ˆ 1.05 (s, iPr), 1.31 (s, 9H, p-tBu) 1.66 (s, 18H, o-tBu), 7.44 (d,
4J(P,H) ˆ 3.2 Hz, 2H, m-aryl); 13C NMR (101 MHz, CDCl3): d ˆ 11.25 (d,
4J(P,C) ˆ 0.8 Hz, C11), 18.56 (s, C12), 31.11 (s, C8), 34.10 (d, 4J(P,C) ˆ
Butadiynediylbis[(2,4,6-tri-tert-butylphenyl)phosphinecarbonylchloride]
(21):[38] A solution of phosgene (3.00 mL, 12.0 mmol, 4.0m in toluene) was
added to a solution of 1,6-diphosphahexadiyne 20 (1.81 g, 3.00 mmol) in
toluene (20 mL). The mixture was stirred for 1 h at room temperature.
After removal of the excess phosgene and the solvent, the residue was
recrystallized frompetroleumether (80 ± 100 8C) to give yellow crystals of
21 (57%). M.p. 165 ± 1668C (decomp); 1H NMR (80 MHz, CDCl3): d ˆ 1.28
(s, 18H, p-tBu), 1.55 (s, 36H, o-tBu), 7.50 (d, 4J(P,H) ˆ 4.0 Hz, m-aryl); IR
3
7.6 Hz, C6), 34.92 (s, C7), 39.77 (d, J(P,C) ˆ 4.7 Hz, C5), 66.02/78.38 (d,d,
1J(P,C) ˆ 14.8 Hz, 2J(P,C) ˆ 14.8 Hz, C13/C14), 104.48 (d, 1J(P,C) ˆ
16.6 Hz); 114.52 (d, 2J(P,C) ˆ 1.5 Hz, C10), 123.80 (d, 3J(P,C) ˆ 9.1 Hz,
C3), 124.26 (d, 1J(P,C) ˆ 23.4 Hz, C1), 151.63 (d, 4J(P,C) ˆ 2.4 Hz, C4),
157.85 (d, 2J(P,C) ˆ 17.7 Hz, C2); 31P{1H} NMR (162 MHz, CDCl3): d ˆ
(KBr): nÄ ˆ 2080 cmÀ1 (w, C C).
ꢂ
Butadiynediylbis[(2,4,6-tri-tert-butylphenyl)phosphinouschloride] (22)[38]
:
The chloroformyl derivative 21 (1.09 g, 1.50 mmol) was heated to 160 ±
1708C, until the elimination of CO ceased (15 ± 20 min). Column chroma-
tography (SiO2, diethyl ether/hexanes 1:2) and recrystallization from
benzene/CH3CN yielded yellow crystals of 22 (35%). M.p. 190 ± 1938C;
À64.86 (s); IR (film): nÄ ˆ 2110, 2080 cmÀ1 (w, C C); UV/Vis (n-hexane):
ꢂ
lmax (e) ˆ 279 (3800), 240 (17400), 210 nm(43400); MS (70 eV, EI): m/z
‡
‡
‡
(%): 561 (18) [M] , 546 (1) [M À CH3] , 517 (3) [M À C3H7] , 482 (9) [M À
1H NMR (80 MHz, CDCl3): d ˆ 1.27 (s, 18H, p-tBu), 1.67 (s, 36H, o-tBu),
‡
‡
‡
‡
Br] , 245 (6) [C18H29] , 231 (60) [C17H27] , 57 (100) [C4H9] ; elemental
analysis calcd (%) for C31H50BrPSi (561.7): C 66.29, H 8.97, Br 14.23; found
C 66.58, H 9.17, Br 14.15.
4
7.44 (d, J(P,H) ˆ 3.2 Hz, m-aryl); IR (KBr): nÄ ˆ 2060 cmÀ1 (w, C C).
ꢂ
Bis{(2,4,6-tri-tert-butylphenyl)[(triisopropylsilyl)ethynyl]phosphanyl}bu-
tadiyne (16a): Trimethylsilylacetylene-MgBr (1.82 mL, 0.74 mmol, 0.4m in
THF) was added dropwise to a stirred solution of 22 (190 mg, 0.28 mmol) in
THF (5 mL) at 08C. After 4 h at roomtemperature, hydrolytic workup, and
extraction with diethyl ether, a yellow-brown product was obtained which
was purified by column chromatography (SiO2, CH2Cl2/hexanes 1:5) to give
yellow crystals of 16a (56%). M.p. 44 ± 468C; 1H NMR (400 MHz,
[D8]THF, TMS): d ˆ 0.15 (s, 18H, Si(CH3)3), 7.49 (d, 4J(P,H) ˆ 3.2 Hz,
4H, m-aryl); 13C NMR (101 MHz, [D8]THF): d ˆ À0.60 (d, 4J(P,C) ˆ
0.9 Hz, C13), 31.32 (s, C8), 34.49 (d, 4J(P,C) ˆ 7.5 Hz, C6), 35.62 (s, C7),
40.47 (d, 3J(P,C) ˆ 4.9 Hz), 83.46 (m, C9, 9'), 93.28 (m, C10, C10'), 102.50 (d,
1J(P,C) ˆ 10 Hz, C11), 119.14 (d, 2J(P,C) ˆ 4.0 Hz, C12), 123.73 (d,
1J(P,C) ˆ 20 Hz, C1), 124.90 (d, 3J(P,C) ˆ 9.8 Hz), C3), 153.05 (d,
Cadiot ± Chodkiewicz coupling of 7a with 24 to give (2,4,6-tri-tert-
butylphenyl)bis-({(2,4,6-tri-tert-butylphenyl)[(triisopropylsilyl)ethynyl]-
phosphanyl}butadiynyl)phosphane (25b):
A solution of 7a (196 mg,
0.6 mmol) in THF (8 mL) was metallated at À788C with nBuLi
(0.80 mL, 1.26 mmol, 1.6m in n-hexane). After 30 min the temperature
was increased to 08C and CuCl (125 mg, 1.26 mmol) was added. The
mixture was stirred for a further 20 min at 08C and then 30 min at room
temperature. The solvent was removed under reduced pressure (not to
dryness!), and the residue was dissolved in oxygen-free, dry pyridine
(20 mL). A solution of the bromo compound 24 in THF (5 mL) was added
dropwise to the copper salt of 7a. The reaction mixture was stirred for 12 h,
the dark solution was poured into HCl (40 mL, 10%), and the mixture was
extracted with hexanes (3 Â 40 mL). The combined organic phases were
washed with HCl (2n, 20 mL) and saturated NaHCO3 solution (20 mL),
and dried over Na2SO4. Evaporation and column chromatography (Al2O3,
hexane) yielded a yellow oil of 16b (60.0 mg, 10%), the desired coupling
product 25b (210 mg, 27%) as a yellow resin, and 26 (10 mg, 2%). The
coupling reaction with CuCl/NH2OH ´ HCl/isopropylamine/THF produced
25b in 11% yield, with CuI/PdCl2(CH3CN)/isopropylamine/benzene
2
4J(P,C) ˆ 2.4 Hz, C4), 158.76 (d, J(P,C) ˆ 18 Hz, C2); IR (KBr): nÄ ˆ 2090,
2060 cmÀ1; UV/Vis (n-hexane): lmax (e) ˆ 331 (8600), 286 (40500), 261
(44600), 234 (55000), 209 nm(109600); MS (70 eV, EI): m/z (%): 794 (79)
‡
‡
‡
‡
[M] , 779 (15) [M À CH3] , 737 (16) [M À C4H9] , 721 (3) [M À C3H9Si] ,
‡
‡
‡
231 (35) [C17H27] , 73 (79) [C3H9Si] , 57 (100) [C4H9] ; elemental analysis
calcd (%) for C50H76P2Si2 (795.3): C 75.51, H 9.63; found C 75.48, H 9.67.
Bis[ethynyl(2,4,6-tri-tert-butylphenyl)phosphanyl]butadiyne (17): NaOH
(2n, 0.5 mL) was added to a stirred solution of 16a (79.5 mg, 0.10 mmol) in
MeOH/diethyl ether (3.0 mL, 2:1). After 1 min, HCl (2n, 5 mL) and
diethyl ether (2 mL) were added. The diethyl ether solution was washed
with water and dried over Na2SO4. Filtration over silica gel (CH2Cl2/
hexanes, 1:5) afforded 17 as yellow crystals (55%), which could not be
purified further. M.p. 164 ± 1678C (decomp); 1H NMR (400 MHz,
[D8]THF, TMS): d ˆ 1.30 (s, 18H, p-tBu), 1.64 (s, 36H, o-tBu), 3.86 (s,
1
(Elbaumet al. [36]) in 15% yield. H NMR (400 MHz, CDCl3): d ˆ 1.04 (s,
42H, iPr), 1.30 (s, 9H, p-tBu), 1.30 (s, 18H, p-tBu), 1.61 (s, 18H, o-tBu), 7.43
(d, 4J(P,H) ˆ 3.4 Hz, 4H, m-aryl), 7.45 (d, 4J(P,H) ˆ 4.00 Hz, 2H, m-aryl),
13C NMR (101 MHz, CDCl3): d ˆ 11.25 (d, 4J(P,C) ˆ 0.9 Hz, C15), 18.56 (s,
C16), 31.07 (s, C8b), 31.10 (s, C8a), 34.06 (d, 4J(P,C) ˆ 6.8 Hz, C6b), 34.11 (d,
4J(P,C) ˆ 7.2 Hz, C6a), 34.98 (d, 5J(P,C) ˆ 0.9 Hz, C7a), 35.01 (d, 5J(P,C) ˆ
0.9 Hz, C7b), 39.71 (d, 3J(P,C) ˆ 5.1 Hz, C5b), 39.73 (d, 3J(P,C) ˆ 4.7 Hz,
2H, CH), 7.44 (d, 4J(P,H) ˆ 3.2 Hz, 4H, m-aryl); 13C NMR (101 MHz,
1
6
C5a), 80.84 (ddd, J(Pa,C) ˆ 7.3 Hz, 4J(P,C) ˆ 4.8 Hz, J(P,C) ˆ 2.5 Hz, C9),
83.72 (dd, 1J(P,C) ˆ 8.8 Hz, 4J(P,C) ˆ 3.8 Hz, C12), 92.96 (dd, 2J(P,C) ˆ
17.4 Hz, 3J(P,C) ˆ 3.8 Hz, C10, C11), 93.96 (dd, 2J(P,C) ˆ 17.4 Hz,
3J(P,C) ˆ 4.7 Hz, C10, C11), 103.29 (dd, 1J(P,C) ˆ 13.0 Hz, 6J(P,C) ˆ
1.7 Hz, C13), 115.50 (d, 2J(P,C) ˆ 2.0 Hz, C14), 121.85 (m, C1b), 123.35,
(dd, 1J(P,C) ˆ 21.4 Hz, 6J(P,C) ˆ 1.7 Hz (C1a), 123.81 (d, 3J(P,C) ˆ 9.5 Hz,
C3a), 124.10 (d, 3J(P,C) ˆ 10.0 Hz, C3b), 151.91 (d, 4J(P,C) ˆ 2.5 Hz, C4a),
152.38 (d, 4J(P,C) ˆ 2.5 Hz, C4b), 157.91 (d, 2J(P,C) ˆ 17.4 Hz, C2a), 157.98
(d, 2J(P,C) ˆ 17.8 Hz, C2b); 31P{1H} NMR (162 MHz, CDCl3): d ˆ À63.99
ꢂ
[D8]THF): d ˆ 31.23 (s, C8), 34.38 (d, 4J(P,C) ˆ 7.6 Hz, C6), 35.54 (s, C7),
3
40.36 (d, J(P,C) ˆ 4.9 Hz, C5), 81.00, 83.19 (m, C9, C9', C10, C10'), 93.27
(m, C10, C10'), 100.11 (m, C12), 123.42 (d, 1J(P,C) ˆ 201 Hz, C1), 124.77 (d,
4
2
3J(P,C) ˆ 9.9 Hz, C3), 153.07 (d, J(P,C) ˆ 2.2 Hz, C4), 158.85 (d, J(P,C) ˆ
18 Hz, C2); 31P{1H} NMR (162 MHz, [D8]THF): d ˆ À67.88; IR (KBr): nÄ ˆ
À1
ꢂ
ꢂ
3260 (m, CH), 2060, 2030 cm (w, C C); UV/Vis (n-hexane): lmax (e) ˆ
326 (7000), 282 (31100), 265 (32700), 226 (39100), 206 nm(74100);
elemental analysis calcd (%) for C44H60P2 (650.9): C 81.19, H 9.29; found C
80.73, H 10.09.
(1P), À66.16 (2P); IR (film): nÄ ˆ 2140 (w), 2090, 2065 cmÀ1 (m, C C); UV/
ꢂ
Vis (n-hexane): lmax (e) ˆ 305 (59200), 273 (57500), 233 (73300), 211 nm
(131400); MS (FD, CH2Cl2): m/z: 1287; elemental analysis calcd (%) for
C84H129P3Si2 (1288.0): C 78.33, H 10.10; found C 78.71, H 10.48.
Eglinton coupling of 17 to give 9, 11, and 23: The Eglinton coupling of 17
(87.6 mg, 150 mmol) according to the general procedure afforded 40 mg
(41% with respect to 17) of a yellow solid (m.p. ꢀ 1758C, decomp) as a
mixture of 9, 11, and 23, which could not be separated. 1H NMR (400 MHz,
CDCl3) of the mixture: d ˆ 1.286 (s), 1.295 (s), 1.303 (s, 9H, p-tBu), 1.64 (s,
18H, o-tBu), 7.43 (d, 4J(P,H) ˆ 3.2 Hz), 7.45 (d, 4J(P,H) ˆ 3.5 Hz), 7.46 (s, m-
Desilylation of 25b to (2,4,6-tri-tert-butylphenyl)bis{[ethynyl(2,4,6-tri-tert-
butyl-phenyl)phosphanyl]butadiynyl}phosphane (25a): A THF solution of
TBAF (0.25 mL, 1m in THF) was added to a solution of 25b (645 mg,
Chem. Eur. J. 2000, 6, No. 20
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0620-3817 $ 17.50+.50/0
3817

G. Märkl et al.
FULL PAPER
0.5 mmol) in THF (100 mL) at À788C. The mixture was stirred for 2.5 h
and then quenched with water. The organic layer was evaporated, and the
crude product purified by column chromatography (Al2O3, CH2Cl2/hexane
1:10) to give yellow crystals of 25a (307 mg, 63%). M.p. 170 ± 1758C
(decomp); 1H NMR (400 MHz, CDCl3): d ˆ 1.30 (s, 9H, p-tBu), 1.31 (s,
4J(P,C) ˆ 2.5 Hz, 4J(P,C) ˆ 2.5 Hz, C4a, C4b), 157.88/158.96 (d/d, 2J(P,C) ˆ
15.4 Hz, 2J(P,C) ˆ 15.7 Hz, C2a, C2b); 31P{1H} NMR (162 MHz, CDCl3,
218C): d ˆ À66.12, À66.28, À67.87; IR (film): nÄ ˆ 3280 cmÀ1 (m, CH),
ꢂ
2050, 2070 cmÀ1 (w, C C); UV/Vis (n-hexane): lmax (e) ˆ 330 (3800), 284
ꢂ
(28300), 273 (28500), 231 (36300), 210 nm(73200); MS (70 eV, EI): m/z
‡
‡
‡
ꢂ
18H, p-tBu), 1.61 (s, 18H, o-tBu), 1.64 (s, 36H, o-tBu), 3.25 (s, 2H, CH),
(%): 807 (2) [M] , 750 (2) [M À C4H9] , 562 (2) [M À C18H29] , 457 (4)
‡ ‡ ‡ ‡
7.45 (d, 4J(P,H) ˆ 3.5 Hz, 2H, m-aryl), 7.45 (d, 4J(P,H) ˆ 3.4 Hz, 4H, m-
aryl); 13C NMR (101 MHz, CDCl3): d ˆ 31.07 (s, C8b), 31.08 (s, C8a), 34.08
(d, 4J(P,C) ˆ 7.2 Hz, C6a, C6b), 34.99 (d, 5J(P,C) ˆ 0.9 Hz, C7a), 35.03 (d,
5J(P,C) ˆ 0.9 Hz, C7b), 39.70 (d, 3J(P,C) ˆ 4.9 Hz, C5b), 39.77 (d, 3J(P,C) ˆ
4.9 Hz, C5a), 81.02 (ddd, 1J(Pa,C) ˆ 8.1 Hz, 4J(P,C) ˆ 4.2 Hz, 6J(P,C) ˆ
[C23H50PSi] , 231 (100) [C17H27] , 73 (8) [C3H9Si] , 57 (76) [C4H9] ;
elemental analysis calcd (%) for C53H80P2Si (807.3): C 78.85, H 9.99; found
C 79.08, H 10.17.
3,8,13,18-Tetrakis(2,4,6-tri-tert-butylphenyl)-1,20-bis(triisopropylsilyl)-
3,8,13,18-tetraphosphaicosa-1,4,6,9,11,14,16,19-octayne (27): The modified
Eglinton coupling of 26 (1.13 g, 1.40 mmol) according to the general
procedure afforded 27 as yellow crystals (1.09 g, 97%). M.p. 76 ± 1118C;
1H NMR (400 MHz, CDCl3): d ˆ 1.04 (s, 42H, iPr), 1.302 (s, 18H, p-tBua),
1.299 (s, 18H, p-tBub), 1.60 (s, 36H, o-tBub), 1.64 (s, 36H, o-tBua), 7.43 (d,
4J(P,H) ˆ 3.3 Hz, 4H, m-aryla), 7.44 (d, 4J(P,H) ˆ 3.6 Hz, m-arylb); 13C NMR
(101 MHz, CDCl3): d ˆ 11.29 (d, 4J(P,C) ˆ 0.6 Hz, C17), 18.56 (s, C18),
31.07 (s, C8b), 31.10 (s, C8a), 34.06 (d, 4J(P,C) ˆ 7.0 Hz, C6b), 34.11 (d,
4J(P,C) ˆ 7.1 Hz, C6a), 34.96 (d, 5J(P,C) ˆ 0.7 Hz, C7a), 35.02 (d, 5J(P,C) ˆ
0.8 Hz, C7b), 39.71 (d, 3J(P,C) ˆ 4.9 Hz, C5b), 39.73 (d, 3J(P,C) ˆ 4.7 Hz,
C5a), 80.50 ± 80.65 (m, C11, C14, C15, C15'), 81.65 ± 81.83 (m, C11, C14, C15,
C15'), 83.75 ± 83.89 (m, C11, C14, C15, C15'), 92.77 ± 93.06 (m, C12, C13,
C16, C16'), 93.53 ± 93.76 (m, C12, C13, C16, C16'), 94.14 (dd, J(P,C) ˆ 17.9,
4.5 Hz, C12, C13, C16, C16'), 103.29 (dd, 1J(Pa,C) ˆ 12.7 Hz, 6J(Pb,C) ˆ
1.7 Hz, C9), 115.51 (d, 2J(P,C) ˆ 2.1 Hz, C10), 121.64 (ddd, 1J(Pb,C) ˆ
19.5 Hz, 6J(Pb,a,C) ˆ 1.6 Hz, C1b), 123.32 (dd, 1J(Pa,C) ˆ 21.3 Hz,
6J(Pb,C) ˆ 1.7 Hz, C1a), 123.81 (d, 3J(P,C) ˆ 9.5 Hz, C3a), 124.11 (d,
3J(P,C) ˆ 9.9 Hz, C3b), 151.91 (d, 4J(P,C) ˆ 2.5 Hz, C4b); 31P{1H} NMR
(162 MHz, CDCl3): d ˆ À63.87 (2Pb), À66.17 (2Pa); IR (KBr): nÄ ˆ
2065 cmÀ1 (w); UV/Vis (n-hexane): lmax, (e) ˆ 308 (72500), 278 (82900),
238 (98000), 211 nm(173400); eleemntal analysis calcd (%) for
C106H158P4Si2 (1612.5): C 78.96, H 9.88; found C 78.84, H 10.24.
1
6
2.2 Hz, C9), 81.15 (dd, J(P,C) ˆ 9.1 Hz, J(P,C) ˆ 2.0 Hz, C12, C13), 82.76
(dd, 1J(P,C) ˆ 10.2 Hz, 4J(P,C) ˆ 3.7 Hz, C12, C13), 93.11 (dd, 2J(P,C) ˆ
17.5 Hz, 3J(P,C) ˆ 3.8 Hz, C10, C11), 93.76 (dd, 2J(P,C) ˆ 17.4 Hz,
2
3J(P,C) ˆ 4.4 Hz, C10, C11), 97.32 (d, J(P,C) ˆ 11.9 Hz, C14), 121.53 (ddd,
1J(P,C) ˆ 19.8 Hz, 6J(Pa,b,C) ˆ 1.5 Hz, C1b), 122.11 (dd, 1J(P,C) ˆ 20.9 Hz,
6J(P,C) ˆ 1.6 Hz, C1a), 124.04 (d, 3J(P,C) ˆ 9.7 Hz, C3a), 124.11 (d, 3J(P,C) ˆ
9.9 Hz, C3b), 152.28 (d, 4J(P,C) ˆ 2.6 Hz, C4a), 152.51 (d, 4J(P,C) ˆ 2.6 Hz,
C4b), 158.01 (d, 2J(P,C) ˆ 17.8 Hz, C2b), 158.08 (d, 2J(P,C) ˆ 17.8 Hz, C2a);
31P{1H} NMR (162 MHz, CDCl3): d ˆ À63.86 (1P), À67.77 (2P); IR (KBr):
À1
ꢂ
ꢂ
nÄ ˆ 3300 (m, CH), 2140, 2065, 2035 cm (w, C C); UV/Vis (n-hexane):
lmax (e) ˆ 296 (30200), 275 (33000), 234 (34700), 207 nm(67900);
elemental analysis calcd (%) for C66H89P3 (975.4): C 81.27, H 9.20; found
C 81.44, H 9.61.
Eglinton coupling of 25b to give triphosphacyclopentadecahexayne 8 and
hexaphosphacyclotriacontadodecayne 11: The Eglinton coupling of 25b
(88.0 mg, 90 mmol) according to the general procedure afforded a yellow-
orange solid which was purified by column chromatography (SiO2, CH3CN/
n-hexane 1:200).
Compound 8: Yield: 61.4 mg (70%); yellow-orange crystals; m.p. 78 ± 848C
1
(decomp). H{31P} NMR (400 MHz, CDCl3): d ˆ 1.29 (s, 27H, p-tBu), 1.64
(s), 1.65 (s), 1.67 (s, 54H, o-tBu), 7.41 (s), 7.42 (s), 7.43 (s, 6H, m-aryl);
31P{1H} NMR (162 MHz, CDCl3, 218C): d ˆ À68.14, À68.62, À69.41
(integration ratio 1:2:0.8); À69.41 (s, isomer 8a), À68.14 (s), À68.62 (s,
integration ratio 1:2, isomer 8b); ratio 8a/8b ˆ 21:79; IR (KBr): nÄ ˆ 2145
Synthesis of 27 by Cadiot ± Chodkiewicz coupling of 17 with 24: A solution
of 17 (98.0 mg, 0.15 mmol) in THF (4 mL) was metallated at À788C with
nBuLi (0.20 mL, 0.31 mmol, 1.6m in n-hexane). After 30 min the temper-
ature was increased to 08C, and CuCl (30.9 mg, 0.31 mmol) was added. The
mixture was stirred for 20 min at 08C and finally for 20 min at room
temperature. The solvent was removed under reduced pressure (not to
dryness!) and replaced with dry, oxygen-free pyridine (5 mL). A solution of
24 (175 mg, 0.31 mmol) in THF (2.0 mL) was added within 30 min. After
12 h the dark reaction mixture was poured into HCl (2n, 10 mL). The
coupling product was extracted with hexane (3 Â 20 mL). The combined
extracts were washed with HCl (2n, 10 mL), saturated NaHCO3 solution
(10 mL), and water. Evaporation and column chromatography (Al2O3,
CH2Cl2/hexanes) afforded yellow crystals of 25 (41 mg, 2%), m.p. 111 ±
1138C, and the coupling product 27 as yellow crystals (40.0 mg, 16%), m.p.
78 ± 1118C, 15b as a yellow oil (10 mg, 6%) and 29 (10 mg, 6%).
(w), 2060 cmÀ1 (m, C C); UV/Vis (n-hexane); lmax (e) ˆ 300 (32800), 254
ꢂ
(95000), 206 nm(114200); MS (FD, CH 2Cl2): m/z: 972; elemental analysis
calcd (%) for C66H87P3 (973.3): C 81.44, H 9.01; found C81.11, H 9.14.
Compound 11: Yield: 4.62 mg (5%); yellow crystals; m.p. 1758C (de-
1
comp); H{31P} NMR (400 MHz, CDCl3): d ˆ 1.29 (s, 54H, p-tBu), 1.64 (s,
108H, o-tBu), 7.45 (d, 4J(P,H) ˆ 3.5 Hz, 12H, m-aryl); 31P{1H} NMR
(162 MHz, CDCl3, 218C): d ˆ À63.95 (brs); 31P{1H} NMR (162 MHz,
CDCl3, 508C): d ˆ À63.95 (s, sharp); IR (KBr): nÄ ˆ 2145 (w), 2100 (w),
2060 cmÀ1 (w, C C); UV/Vis (n-hexane): lmax (e) ˆ 290 (72400), 266
ꢂ
(128600), 205 nm(188100); MS (FD, CH 2Cl2): m/z: 1946 (in agreement
with the calculated spectrum); elemental analysis calcd (%) for C132H174P6
(1946.9): calcd C 81.44, H 9.01; found C 81.17 H 9.11.
[Ethynyl(2,4,6-tri-tert-butylphenyl)phosphanyl]{(2,4,6-tri-tert-butylphen-
yl)[(triisopropylsilyl)ethynyl]phosphanyl}butadiyne (26) by monodesilyl-
ation of 16b: A solution of 16b (1.21 g, 1.25 mmol) in THF (50 mL) at
À788C was treated with TBAF (0.2 mL, 0.2 mmol, 1m in THF) for 1 h.
Water (5 mL) was added, and the organic layer dried over Na2SO4.
Evaporation yielded a yellow oil, which was purified by column chroma-
tography (Al2O3, hexane). The first fraction was the starting material 16b,
yellow crystals, m.p. 111 ± 1138C (390 mg, 30%). With CH2Cl2/hexanes
(1:20) 26 was eluted, yellow oil (390 mg, 39%), and finally with CH2Cl2/
hexanes (1:6) the bis-desilylation product 17 was obtained, yellow crystals,
m.p. 164 ± 1688C (125 mg, 15%). Compound 26: 1H NMR (400 MHz,
3,8,13,18-Tetrakis(2,4,6-tri-tert-butylphenyl)-3,8,13,18-tetraphosphaicosa-
1,4,6,9,11,14,16,19-octayne (28) by desilylation of 27: A solution of TBAF
(0.20 mmol, 0.20 mL, 1m in THF) was added to the solution of 27 (161 mg,
0.1 mmol) in THF (10 mL) at À788C and stirred for 2 h. After quenching
of the mixture with water, evaporation of the organic solution and column
chromatography (Al2O3, CH2Cl2/hexanes 1:6) afforded 28 as pale yellow
1
crystals (53%). M.p. 124 ± 1508C (decomp); H NMR (400 MHz, CDCl3):
d ˆ 1.30 (s, 18H, p-tBub), 1.31 (s, 18H, p-tBua), 1.61 (s, 36H, o-tBub), 1.64 (s,
a
3
4
ꢂ
36H, o-tBu ), 3.25 (d, J(P,H) ˆ 0.4 Hz, 2H, CH), 7.45 (d, J(P,H) ˆ 3.5 Hz,
4H, m-arylb), 7.46 (d, J(P,H) ˆ 3.4 Hz, 4H, m-aryla); 13C NMR (101 MHz,
4
CDCl3): d ˆ 31.06 (s, C8b), 31.08 (s, C8a), 34.06 (d, 4J(P,C) ˆ 7.2 Hz, C6b),
34.08 (d, 4J(P,C) ˆ 7.2 Hz, C6a), 34.99 (d, 5J(P,C) ˆ 0.8 Hz, C7a), 35.03 (d,
5J(P,C) ˆ 0.9 Hz, C7b), 39.70 (d, 3J(P,C) ˆ 4.8 Hz, C5b), 39.77 (d, 3J(P,C) ˆ
4.8 Hz, C5a), [80.82 ± 81.03 (m), 81.15 (dd, J(P,C) ˆ 9.3, 1.7 Hz), 83.50 ± 81.75
(m), 82.77 (dd, J(P,C) ˆ 10.1, 3.6 Hz)]: C9, C11, C14, C15, C15'; [92.99 ±
93.24 (m), 93.30 ± 94.01 (m), 97.32 (d, 2J(P,C) ˆ 11.9 Hz)]: C12, C13, C16,
C16'; 121.45 (m, C1b), 122.11 (dd, 1J(Pa,C) ˆ 21.2 Hz, 6J(Pb,C) ˆ 1.7 Hz,
C1a), 124.04 (d, 3J(P,C) ˆ 9.3 Hz, C3a), 124.12 (d, 3J(P,C) ˆ 9.8 Hz, C3b),
152.28 (d, 4J(P,C) ˆ 2.4 Hz, C4b), 152.52 (d, 4J(P,C) ˆ 2.5 Hz, C4a), 158.02
CDCl3): d ˆ 1.05 (s, 24H, iPr), 1.30 (s, 18H, p-tBu), 1.63 (s, 18H, o-tBu), 1.64
3
(s, 18H, o-tBu), 3.24 (d, J(P,H) ˆ 0.4 Hz, 1H, CH), 7.43 (d, 4J(P,H) ˆ
ꢂ
3.3 Hz, 2H, m-arylb), 7.44 (d, 4J(P,H) ˆ 3.4 Hz, 2H, m-aryla); 13C NMR
(101 MHz, CDCl3): d ˆ 11.24 (d, 4J(P,C) ˆ 0.7 Hz, C17), 18.56 (s, C18),
31.09/31.10 (s/s, C8a, C8b), 34.07/34.11 (d/d, 4J(P,C) ˆ 7.3 Hz, 4J(P,C) ˆ
7.2 Hz, C6a, C6b), 34.96/34.98 (d/d, 5J(P,C) ˆ 0.9 Hz, 5J(P,C) ˆ 1.3 Hz, C7a,
C7b), 39.73/39.77 (d/d, 3J(P,C) ˆ 4.7 Hz, 3J(P,C) ˆ 4.7 Hz, C5a, C5b), 81.40
(dd, J(P,C) ˆ 2.2, 9.6 Hz, C9, C11, C14), 81.78 (dd, J(P,C) ˆ 4.4, 8.8 Hz, C9,
C11, C14), 83.19 (dd, J(P,C) ˆ 8.5, 4.0 Hz, C9, C11, C14), 92.96/93.48 (m/m,
C12, C13), 97.12 (d, 2J(P,C) ˆ 12.0 Hz, C10), 103.36 (dd, 6J(P,C) ˆ 1.9 Hz,
1J(P,C) ˆ 12.7 Hz, C15), 115.35 (d, 2J(P,C) ˆ 2.1 Hz, C16), 122.34/123.38
(d/d, 1J(P,C) ˆ 21.0 Hz, 1J(P,C) ˆ 21.6 Hz, C1a, C1b), 123.79/124.03
(d/d, 3J(P,C) ˆ 9.5 Hz, 3J(P,C) ˆ 9.6 Hz, C3a, C3b), 151.91/152.21 (d/d,
(d, J(P,C) ˆ 17.9 Hz, C2b, 158.07 (d, J(P,C) ˆ 18.0 Hz, C2a); 31P{1H} NMR
2
2
(162 MHz, CDCl3): d ˆ À63.85 (Pb), À67.81 (Pa); IR (KBr): nÄ ˆ 3300 (w,
À1
ꢂ
ꢂ
CH), 2060 cm (w, C C); UV/Vis (CH2Cl2): lmax (e) ˆ 308 (60500),
280 nm(75100); MS (FD, CH 2Cl2): m/z: 1299; elemental analysis calcd (%)
for C88H118P4 (1299.8): C 81.32, H 9.15; found C 80.80, H 9.35.
3818
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0947-6539/00/0620-3818 $ 17.50+.50/0
Chem. Eur. J. 2000, 6, No. 20

Polyphosphacarbons
3806±3820
Oxidative coupling of 28 to 9 and 23: The modified Eglinton coupling of 28
(104 mg, 80 mmol) according to the general procedure afforded a yellow-
orange solid that was purified by column chromatography (SiO2, CH2Cl2/
hexane 1:3), followed by (SiO2, CH3CN/n-hexane 1:200). Two fractions of
yellow solids were obtained: 9 (68 mg, 65%) and 23 (5.5 mg, 5%).
After 2.5 h, the mixture was quenched with water. The resulting yellow
precipitate was separated by centrifugation, washed with THF (2 Â 5 mL),
and dried in vacuo to give 32 as yellow powder (76.1 mg, 83%). M.p.
ꢀ1908C (decomp), insoluble in all usual organic solvents; IR (KBr): nÄ ˆ
À1
À1
ꢂ
ꢂ
3300 (w, CH), 2160 (w), 2060 cm (w, C C); the Si ± C band nÄ ˆ 795 cm
(m) had disappeared.
1
Compound 9: M.p. ꢀ2508C (decomp); H{31P} NMR (400 MHz, CDCl3):
4
d ˆ 1.29 (s, 36H, p-tBu, 1.64 (s, 72H, o-tBu), 7.43 (d, J(P,H) ˆ 3.1 Hz, 8H,
Synthesis of octaphosphacyclotetracontahexadecayne (23) by an intra-
molecular Eglinton coupling of 32: Compound 32 (20.8 mg, 8.00 mmol) was
added to a solution of [Cu(OAc)2] ´ H2O (25.6 mg, 128 mmol) and CuCl
(9.50 mg, 96 mmol) in small portions over a period of 4 h at 658C. The
mixture was stirred for a further 2 h at 658C and 12 h at roomtemperature.
The solvent was removed and the residue treated with CH2Cl2/H2O (30 mL,
1:1); the organic phase was washed successively with water (5 mL), HCl
(5 mL, 10%), NaHCO3 solution (5 mL), and water (5 mL). Purification by
column chromatography (Al2O3, CH2Cl2/n-hexane 1:10) afforded 23 as
yellow crystals (5.80 mg, 27%). M.p. ꢀ 2808C (decomp).
m-aryl); at À208C the inversion rate was reduced, the signal at 1.29 split to
give a doublet, the other signals gave broad multiplets; 31P{1H} NMR
(162 MHz, CDCl3, 218C): several broad signals from d ˆ À64.7 to À67.2;
31P{1H} NMR (162 MHz, C2D2Cl4, 1408C): d ˆ À64.91 (s, sharp), fast
inversion of all pyramidal phosphine phosphorus atoms; 31P{1H} NMR
(162 MHz, CDCl3, À208C): d ˆ À68.13 (s, 9a), À66.26 (s, 9b), À65.56 (s,
9c), À65.56 (t, 1P, J(P,P) ˆ 1 Hz, 9d), À66.17 (t, 1P, J(P,P) ˆ 8.4 Hz, 9d),
À66.80 (dd, 2P, J(P,P) ˆ 8.4, 1.1 Hz, 9d); the ratio of 9a:9b:9c:9d ˆ
1:5.1:6.2:10.6; IR (KBr): nÄ ˆ 2165 (w), 2065 cmÀ1 (w, C C); UV/Vis (n-
ꢂ
hexane): lmax (e) ˆ 300 (47800), 282 (72400), 256 (130200), 234 (133200),
208 nm(153300); MS (FD, CH 2Cl2): m/z: 1296; elemental analysis calcd
(%) for C88H116P4 (1297.8): C 81.44, H 9.01; found C 80.22 H 9.12.
[1] a) C. Glaser, Ber. Dtsch. Chem. Ges. 1869, 2, 422 ± 424; b) C. Glaser,
Ann. Chem. 1870, 154, 137 ± 171.
[2] a) G. Eglinton, A. R. Galbraith, Chem. Ind. (London) 1956, 737 ± 738;
b) O. M. Behr, G. Eglinton, A. R. Galbraith, R. A. Raphael, J. Chem.
Soc. 1960, 3614 ± 3625.
Compound 23: M.p. ꢀ 2808C (decomp); 1H{31P} NMR (400 MHz, CDCl3):
d ˆ 1.30 (s, 72H, p-tBu), 1.63 (s, 144H, o-tBu), 7.45 (d, 4J(P,H) ˆ 3.5 Hz,
16H, m-aryl); 31P{1H} NMR (162 MHz, CDCl3): d ˆ À63.52 (brs); IR
(KBr): nÄ ˆ 2200 (w), 2165 (w), 2100 cmÀ1 (m, C C); UV/Vis (n-hexane):
ꢂ
lmax (e) ˆ 290 (72500), 267 (130100), 205 nm(208200); elemental analysis
[3] a) A. S. Hay, J. Org. Chem. 1960, 25, 1275 ± 1276; b) A. S. Hay, J. Org.
Chem. 1962, 27, 3320 ± 3321.
calcd (%) for C167H232P8 (2595.6): C 81.44, H 9.01; found C 80.47 H 9.10.
[4] [18]-Annulene: a) F. Sondheimer, R. Wolovsky, Tetrahedron Letters
1959, 3, 3 ± 6; b) F. Sondheimer, R. Wolovsky, J. Am. Chem. Soc. 1962,
84, 274 ± 278; c) L. M. Jackman, F. Sondheimer, Y. Amiel, D. A. Ben-
Efraim, Y. Gaoni, R. Wolovsky, A. A. Bothner-By, J. Am. Chem. Soc.
1962, 84, 4307 ± 4312.
3,8,3,18-Tetrakis(2,4,6-tri-tert-butylphenyl)-1-(triisopropylsilyl)-3,8,13,18-
tetraphosphaicosa-1,4,6,9,11,14,16,19-octayne (30) by partial desilylation of
27: TBAF (0.20 mmol, 0.20 mL, 1m in THF) was added to a solution of 27
(1.08 g, 0.67 mmol) in THF (100 mL) at À788C. After stirring for 2 h, the
reaction mixture was quenched with water. The organic phase was dried
over Na2SO4 and evaporated under reduced pressure. The resulting yellow
oil was purified by column chromatography (Al2O3, hexane) to give the
starting material 27 as yellow crystals (254 mg, 24%), m.p. 76 ± 1118C,
followed by eluting with CH2Cl2/hexanes (1:20) to afford 30 as yellow
crystals (323 mg, 33%), m.p. 90 ± 1158C, and finally with CH2Cl2/hexanes
(1:6) to give the bis-desilylated octayne 28 as yellow crystals (181 mg,
21%), m.p. 124 ± 1508C (decomp). Compound 30: 1H NMR (400 MHz,
CDCl3): d ˆ 1.04 (s, 21H, Si(iPr)), 1.30 (s, 9H, p-tBu, (Pd), 1.30 (s, 18H, p-
tBu, (Pb,c), 1.31 (s, 9H, p-tBu (Pa), 1.61 (s, 36H, o-tBu, Pb,c), 1.63 (s, 18H, o-
[5] F. Sondheimer, R. Wolovsky, J. Am. Chem. Soc. 1959, 81, 1771, J. Am.
Chem. Soc. 1962, 84, 260 ± 269.
[6] a) M. M. Haley, S. C. Brand, J. J. Pak, Angew. Chem. 1997, 109, 864 ±
866; Angew. Chem. Int. Ed. Engl. 1997, 36, 836; b) O. M. Behr, G.
Eglinton, R. A. Raphael, Chem. Ind. 1959, 699 ± 700; c) Q. Zhou, P. J.
Carroll, T. M. Swager, J. Org. Chem. 1994, 59, 1294 ± 1301; see also
ref. [2b].
[7] a) A. de Meijere, F. Jaekel, A. Simon, H. Bormann, J. Köhler, D.
Johels, L. T. Scott, J. Am. Chem. Soc. 1991, 113, 3935 ± 3941; b) A.
de Meijere, S. Kozhushkov, C. Puls, T. Haumann, R. Boese, M. J.
Cooney, L. T. Scott, Angew. Chem. 1994, 106, 934 ± 936; Angew. Chem.
Int. Ed. Engl. 1994, 33, 869 ± 871.
[8] A. M. Boldi, F. Diederich, Angew. Chem. 1994, 106, 482 ± 485; Angew.
Chem. Int. Ed. Engl. 1994, 33, 469 ± 471.
[9] a) Y. Rubin, F. Diederich, J. Am. Chem. Soc. 1989, 111, 6870 ± 6871;
b) F. Diederich, Y. Rubin, Angew. Chem. 1992, 104, 1123 ± 1146;
Angew. Chem. Int. Ed. Engl. 1992, 31, 1101 ± 1123; c) Nachr. Chem.
Tech. Lab. 1989, 37, 1022.
[10] F. Diederich, Y. Rubin, C. B. Knobler, R. L. Whetten, K. E. Schriver,
K. N. Houk, Y.Li, Science 1989, 245, 1088 ± 1090; see also ref. [9b, c].
[11] a) L. T. Scott, M. J. Cooney, D. W. Rogers, K. Dejroongruang, J. Am.
Chem. Soc. 1988, 110, 7244 ± 7245; b) L. T. Scott, M. J. Cooney, D.
Johnels, J. Am. Chem. Soc. 1990, 112, 4054 ± 4055.
[12] a) Y. Rubin, M. Kahr, C. B. Knobler, F. Diederich, C. L. Wilkins, J.
Am. Chem. Soc. 1991, 113, 495 ± 500; b) S. W. McElvany, M. M. Ross,
N. S. Goroff, F. Diederich, Science 1993, 259, 1594 ± 1596; c) N. S.
Goroff, Acc. Chem. Res. 1996, 29, 77 ± 83.
a
d
tBu, P ), 1.64 (s, 18H, o-tBu, P ), 3.25 (s, 1H, CH), 7.43 (d, 4J(P,H) ˆ
ꢂ
4
3.2 Hz, 2H, m-aryl, Pd), 7.44 (d, J(P,H) ˆ 3.4 Hz, 2H, m-aryl, Pc), 7.45 (d,
4J(P,H) ˆ 3.5 Hz, 2H, m-aryl, Pb), 7.45 (d, 4J(P,H) ˆ 3.2 Hz, 2H, m-aryl, Pa);
13C NMR (101 MHz, CDCl3): d ˆ 11.24 (d, 4J(P,C) ˆ 1.35 Hz, Si-
CH(CH3)2), 18.56 (s, Si-CH(CH3)2), 103.27 (dd, 1J(P,C) ˆ 13.0 Hz,
6J(P,C) ˆ 1.8 Hz, P C C Si), 115.53 (d, 2J(P,C) ˆ 2.2 Hz,
P
d
d
ꢂ À
À ꢂ À
C C Si);
31P{1H} NMR (162 MHz, CDCl3): d ˆ À63.82 (Pb), À63.88 (Pc), À66.16
d
a
À1
ꢂ
ꢂ
(P ), À67.78 (P ); IR (KBr): nÄ ˆ 3300 (w, CH), 2065 cm (w, C C); UV/
Vis (n-hexane): lmax (e) ˆ 308 (70400), 278 (83800), 256 (86900), 238
(94000), 210 nm(167800); MS (FD, CH 2Cl2): m/z: 1455; elemental analysis
calcd (%) for C97H138P4Si (1456.2): C 80.01, H 9.55; found: C 80.18, H 9.70.
1,40-Bis(triisopropylsilyl)-3,8,13,18,23,28,33,38-octakis(2,4,6-tri-tert-butyl-
phenyl)-3,8,13,18,23,28,33,38-octaphosphatetraconta-1,4,6,9,11,14,16,19,21,
24,26,29,31,34,36,39-hexadecayne (31) by Eglinton coupling of 30: The
modified Eglinton coupling of 30 (291 mg, 0.20 mmol) according to the
general procedure afforded 31 as yellow powder (255 mg, 87%). M.p. 180 ±
1908C (decomp); 1H NMR (400 MHz, CDCl3): d ˆ 1.04 (s, 42H, Si-iPr, 1.30
(s, 72H, p-tBu), 1.60 (s, 108H, o-tBu, Pb,c,d), 1.64 (s, 36H, o-tBu, Pa), 7.43 (d,
4J(P,H) ˆ 3.3 Hz, 4H, m-aryl, Pa), 7.44 (d, 4J(P,H) ˆ 3.5 Hz, 4H, m-aryl, Pb),
7.45 (d, 4J(P,H) ˆ 3.5 Hz, 8H, m-aryl, Pc,d); 13C NMR (101 MHz, CDCl3):
[13] L. T. Scott, G. J. DeCicco, J. L. Hyun, G. Reinhardt, J. Am. Chem. Soc.
1985, 107, 6546 ± 6555; see also ref. [7a].
[14] L. T. Scott, M.Unno, J. Am. Chem. Soc. 1990, 112, 7823 ± 7825.
[15] a) L. Horner, Pure Appl. Chem. 1964, 9, 225 ± 244; b) L. Horner, H.
Winkler, A. Rapp, A. Mentrup, P. Beck, H. Hoffmann, Tetrahedron
Lett. 1961, 161 ± 164; c) L. Horner, H. Winkler, Tetrahedron Lett. 1964,
461 ± 464.
[16] A. Rauk, J. D. Andose, W. G. Frick, R. Tang, K. Mislow, J. Am. Chem.
Soc. 1971, 93, 6507 ± 6515; See also K. Mislow in Organophosphorus
Stereochemistry, Part I-Origins and P(III and IV)Compounds (Eds.:
W. E. McEwen, K. D. Berlin), Dowden, Hutchinson, and Ross, 1975,
pp. 195 ± 210.
d ˆ 11.24 (d, 4J(P,C) ˆ 0.9 Hz, Si-CH(CH3)2), 18.57 (s, Si-CH(CH3)2), 103.29
6
(dd, 1J(P,C) ˆ 12.6 Hz, J(P,C) ˆ 1.8 Hz), P-C C Si), 115.53 (d, 2J(P,C) ˆ
ꢂ À
2.2 Hz, P-C C Si); 31P{1H} NMR (162 MHz, CDCl3): d ˆ À63.70, (Pc, Pd),
ꢂ À
À63.87 (Pb), À66.17 (Pa); IR (KBr): nÄ ˆ 2065 (w), 2120 cmÀ1 (w, C C); UV/
ꢂ
Vis (n-hexane); lmax (e) ˆ 248 (376000), 217 nm(617000); elemental
analysis calcd (%) for C194H274P8Si2 (2908.4): C 80.12, H 9.50; found C
80.33, H 9.54.
3,8,13,18,23,28,33,38-Octakis(2,4,6-tri-tert-butylphenyl)-3,8,13,18,23,28,33,
38-octaphosphatetraconta-1,4,6,9,11,14,16,19,21,24,26,29,31,34,36,39-hexa-
decayne (32) by desilylation of 31. A solution of TBAF (1m, 35 mL) was
added to a solution of 31 (102 mg, 35.0 mmol) in THF (50 mL) at À788C.
[17] a) E. H. Braye, I. Caplier, R. Saissez, Tetrahedron 1971, 27, 5523 ±
5537; b) G. Kaufmann, F. Mathey, Phosphorus 1974, 4, 231 ± 235; c) F.
Chem. Eur. J. 2000, 6, No. 20
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0947-6539/00/0620-3819 $ 17.50+.50/0
3819

G. Märkl et al.
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Â
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[30] Calculations where carried out with the program Gaussian98,
Revision A.3, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A. Montgom-
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[45] R. Hennig, Dissertation 1994, University Regensburg; see also
ref. [38].
Received: August 12, 1999
Revised version: April 20, 2000 [F1975]
3820
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