Versatile and efficient synthesis of a new class of aza-based phosphinic amide ligands via unusual P-C cleavage

Article abstract of DOI:10.1002/hlca.200690270

A new class of bidentate, aza-based phosphinic amide ligands of the type RN(H)P(=O)(2-py)₂ (2-py=2-pyridyl) was synthesized within minutes via a one-pot process including Staudinger reaction of an organic azide (RN ₃) with 2-pyridylphosphines, followed by partial, unprecedented hydrolysis under loss of one aromatic substituent. The structure of the unusual-hydrolysis product H₂C=CH(CH₂)₉N(H)P(= O)(2-py)₂ (5a) was characterized by IR, ¹H- and ³¹P-NMR, as well as by X-ray crystal-structure analysis (Figure). The tetrahedral P-atom was found to be surrounded by a trigonal-pyramidal arrangement of the substituents. To gain insight into the formation of these novel phosphinic amides, a series of intermediate iminophosphoranes, H ₂C=CH(CH₂)₉N=P(Ar)_n(2-py) _3-n (n = 0-3), compounds 1a-1f, were synthesized, and their hydrolyses were studied. All tested compounds followed the classical hydrolysis route of P=N cleavage under acidic conditions. Sequential hydrolysis to 5a-5d only occurred under either basic conditions or in wet MeCN as solvent. Notably, H₂C=CH(CH₂)₉N=P(C₆H ₅)(4-MeO-2-py)₂ (1c) was hydrolyzed at a much slower rate compared to its analogue 1b lacking the MeO group. On the contrary, the halogenated compounds H₂C=CH(CH₂)₉N=P(4-X- C₆H₄)₃ (1f,g) (X = F, Cl) were hydrolyzed at a notably faster rate relative to the non-halogenated congener 1e (X = H).

Full text of DOI:10.1002/hlca.200690270

Helvetica Chimica Acta – Vol. 89 (2006)
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Versatile and Efficient Synthesis of a New Class of Aza-Based Phosphinic
Amide Ligands via Unusual PꢀC Cleavage
by Shih-Chung Tsai, Yaw-Shien Fu, Ju-Hsiou Liao, and Shuchun Joyce Yu*
Department of Chemistry and Biochemistry, National Chung Cheng University, Min-Hsiung, Chia-Yi,
Taiwan 621
(phone: +886-5-242-8138; fax: +886-5-272-1040; e-mail: chejyy@ccu.edu.tw)
A new class of bidentate, aza-based phosphinic amide ligands of the type RN(H)P(=O)(2-py)2 (2-
py=2-pyridyl) was synthesized within minutes via a one-pot process including Staudinger reaction of
an organic azide (RN3) with 2-pyridylphosphines, followed by partial, unprecedented hydrolysis under
loss of one aromatic substituent. The structure of the unusual-hydrolysis product H2C=CH(CH2)9-
N(H)P(=O)(2-py)2 (5a) was characterized by IR, 1H- and 31P-NMR, as well as by X-ray crystal-structure
analysis (Figure). The tetrahedral P-atom was found to be surrounded by a trigonal-pyramidal arrange-
ment of the substituents. To gain insight into the formation of these novel phosphinic amides, a series of
intermediate iminophosphoranes, H2C=CH(CH2)9N=P(Ar)n(2-py)3ꢀn (n=0–3), compounds 1a–1f,
were synthesized, and their hydrolyses were studied. All tested compounds followed the classical hydrol-
ysis route of P=N cleavage under acidic conditions. Sequential hydrolysis to 5a–5d only occurred under
either basic conditions or in wet MeCN as solvent. Notably, H2C=CH(CH2)9N=P(C6H5)(4-MeO-2-py)2
(1c) was hydrolyzed at a much slower rate compared to its analogue 1b lacking the MeO group. On the
contrary, the halogenated compounds H2C=CH(CH2)9N=P(4-X-C6H4)3 (1f,g) (X=F, Cl) were hydro-
lyzed at a notably faster rate relative to the non-halogenated congener 1e (X=H).
Introduction. – T heStaudinger reaction, reported in 1919 and later [1], proceeds ini-
tially by the nucleophilic attack of, e.g., triphenylphosphine (Ph3P) on an azide, fol-
lowed by elimination of N2 to afford an iminophosphorane. Iminophosphoranes are
valuable species since they undergo Wittig-type reactions with various functionalities
[2]. In addition, hydrolysis of Staudinger products with H2O, diluted acids, or ammonia
allows for the generation of a free amine and triphenylphosphine oxide (Ph3P=O) via
P=N cleavage with high chemo- and stereoselectivity. Since the azido (N3) group is
fairly easy to incorporate into molecules, is relatively inert under most biological con-
ditions, and can be selectively hydrolyzed, often without protection of distal function-
alities, the Staudinger reaction has been frequently employed as one of the mildest and
most-selective methods both in synthetic and biological chemistry to convert azides
into amines (for reviews, see [3]; for recent examples, see [4]).
In continuation of our efforts to develop a new series of P- an/or N-containing
ligands in coordination chemistry, we have recently reported the synthesis of a new
class of aza-based bidentate ligands of the type R(H)NꢀP(=O)(2-py)2 by hydrolysis
of N-substituted iminotris(2-pyridyl)phosphoranes ((2-py)3P=NR) after Staudinger
reaction between RN3 and (2-py)3P (Scheme 1,a) [5]. We also found that the hydrolysis
of (2-py)3P=NR may proceed via two possible pathways to afford totally different
products, depending on the reaction conditions. In acidic media, hydrolysis of the Stau-
ꢀ 2006 Verlag Helvetica Chimica Acta AG, Zürich

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Helvetica Chimica Acta – Vol. 89 (2006)
dinger product generates the free amine (RNH2) and (2-py)3P=O via P=N cleavage, as
expected. However, under basic conditions, the hydrolysis follows an unconventional
pathway, producing an N-substituted phosphinic amide (R(H)NꢀP(=O)(2-py)2) plus
one liberated pyridine.
Scheme 1
Usually, this type of N-substituted phosphinoyl amides are prepared by the cleavage
of a chemically much more labile ROꢀP bond in the Arbuzov rearrangement (Scheme
1,b) [6], which is often used for phosphinyl protection of amino groups in peptide syn-
thesis [7]. In contrast, the efficient formation of phosphinic amides in our study
involves the cleavage of the relatively inert PꢀCpy bond of the iminophosphoranes
P(2-py)3P=NꢀR.
There are some documented examples of metal- or strong-base-catalyzed PꢀC
cleavages [8]. For instance, treatment of R3P with an alkali metal results in the forma-
tion of R2Pꢀ [8]. In addition, the alkaline hydrolysis of R4P+, affording R3P=O and RH
by nucleophilic substitution (or addition–elimination) at the tetracoordinated P center
has been reported [9]. The hydrolyses of R3P=O and R3P=S involving PꢀC cleavage
are also known to proceed in the presence of strong acids or strong bases [10]. Recently,
fragmentation of one of the PꢀCꢀP bonds of a novel class of phosphazenes has been
demonstrated [11]. Herein, we report the first example of a base-catalyzed PꢀC cleav-
age of simple iminophosphoranes.
Results and Discussion. – In the current study, a new class of bidentate aza-based
ligands of type CH2=CH(CH2)9NHP(=O)(2-py)2 were readily synthesized within a
few minutes via one-pot reaction of an organic azide (RN3) with (2-py)3P under alka-
line hydrolytic conditions (Scheme 2). In contrast to the conventional P=N cleavage
upon hydrolysis of Staudinger products, the formation of N-substituted phosphinoyl
amides proceeds via cleavage of the PꢀCpy bond of simple iminophosphoranes (2-
py)3P=NR. To gain insight into this ꢁunconventionalꢂ hydrolysis, a series of iminophos-
phorane intermediates, compounds 1a–1g, were prepared from the azide 2 and com-
pounds 3a–3g, and isolated for further investigations. While acidic hydrolysis gener-
ated the expected primary amine 4 and the corresponding phosphine oxides, hydrolysis
under basic conditions afforded the corresponding phosphinoyl amides (5a–5d) under
loss of pyridine (Scheme 2).
As stated earlier, acidic hydrolysis of 1a generates H2C=CH(CH2)9NHþ3 (6) and (2-
py)3P=O·(HCl)n through the conventional path (Scheme 3). However, hydrolysis of 1a
in the presence of NaOH, or simply in wet MeCN, was found to proceed not only much

Helvetica Chimica Acta – Vol. 89 (2006)
3009
Scheme 2
faster, but also gave H2C=CH(CH2)9N(H)P(=O)(2-py)2 (5a) and pyridine. For exam-
ple, the hydrolysis of 1a (46.3 mM) in MeCN in the presence of 20 equiv. of H2O and 5
equiv. of HCl was complete within 5 min. However, hydrolysis under the same condi-
tions, but in the presence of 1.2 equiv. of NaOH (instead of HCl) was finished in 30 s.
Even in the absence of acid or base, hydrolysis in hydrous MeCN was also completed
within 30 s.
Scheme 3
a) H2O, MeCN. b) H2O, OHꢀ, MeCN. c) H2O, H+, MeCN.
Interestingly, 5a could be further hydrolyzed to 6 and O=P(OH)(2-py)2 ·n H+ (7)
only in acidic media (Scheme 4). For comparison, H2C=CH(CH2)9N=PPh3 (1e) was
also hydrolyzed. Here, ꢁconventionalꢂ hydrolysis under P=N cleavage occurred, afford-
ing exclusively Ph3P=O and 4 or 6, depending on the reaction conditions (Scheme 3).
This means that no hydrolytic PꢀCPh cleavage occurred in 1e. No significant rate differ-
ences were observed when the hydrolysis of 1e was carried out in the presence of either
HCl or NaOH. In a particular set of experiments, a 46.6 mM MeCN solution of 1e was
exposed to 12 equiv. of H2O and hydrolyzed for 10 min, which gave 28% completion.
The same reaction mixture, but in the presence of 1.2 equiv. of NaOH or 1.2 equiv.

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Helvetica Chimica Acta – Vol. 89 (2006)
of HCl, respectively, gave 26 and 25% completion after 10 min. Further, we found that,
under pseudo-first-order conditions, the initial hydrolysis rate of 1e was doubled when
the amount of H2O was doubled.
Scheme 4
The NMR and IR spectroscopic data of 5a [d(1H) 4.45 (m, NH), d(31P) 14.5 (s, P=
O); 3270 (NꢀH) and 1247 cmꢀ1 (P=O)] were in agreement with the proposed structure,
which was unequivocally proved by single-crystal X-ray analysis (Figure; see also Table
3 in the Exper. Part). In the ORTEP drawing of 5a, a tetrahedral P-atom with a trigonal-
pyramidal arrangement of the substituents around the P center can be seen, with NꢀP
and PꢀO bond lengths of 1.63 and 1.48 Š, respectively, two 2-pyridyl residues having a
bond angle pyꢀPꢀpy of 106.258.
Figure. X-Ray crystal structure of H2C=CH(CH2)9N(H)P(=O)(2-py)2 (5a). ORTEP Representation
with thermal ellipsoids at the 50%-probability level. Selected bond distances [Š] and angles [8]: Pꢀ
O(1), 1.482(4); PꢀN(1), 1.627(3); PꢀC(6), 1.807(3); PꢀC(1), 1.811(3); O(1)ꢀPꢀN(1), 115.03(15);
O(1)ꢀPꢀC(6), 108.54(15); O(1)ꢀPꢀC(1), 113.19(14); N(1)ꢀPꢀC(6), 107.74(16); N(1)ꢀPꢀC(1),
105.62(15); C(1)ꢀPꢀC(6), 106.25(15).

Helvetica Chimica Acta – Vol. 89 (2006)
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It has been reported that the conventional hydrolysis of both (Rꢂ)3P=NꢀR and
R4P+ proceeds under inversion of configuration at the P centers1). The stereochemistry
involved in both cases possibly results from initial protonation of the basic phosphin-
imine N-atom, followed by an SN2 type backside attack of either H2O or OHꢀ, with
both RNH and the nucleophile residing in the axial positions of the trigonal-bipyrami-
dal transition state or intermediate. It is reasonable to postulate that, in basic environ-
ment, an additional pathway is open for the hydrolysis of, e.g., 1a, in which there is a 2-
pyridyl (2-py) group instead of the RNH group, the OHꢀ being in axial positions. Most
likely, the transition state or intermediate of this new pathway is stabilized by the higher
electron-acceptor quality of the 2-py groups under basic conditions. Similar suggestions
have been made by Uchida and Kozawa [10b] in studying the ligand coupling/exchange
reactions in the hydrolysis of R4P+ and R3P=O.
We reasoned that, if the hydrolysis of 1a proceeds via PꢀCpy cleavage in basic envi-
ronment, a similar behavior might also be observed for the structurally related but
much simpler phosphine oxide (2-py)3P=O, which was synthesized by oxidation of
(2-py)3P with 30% H2O2 in acetone. As can be seen from Scheme 4, (2-py)3P=O did
not undergo hydrolysis in H2O or wet MeCN; and in acidic media, only protonation
was observed. However, PꢀCpy cleavage of (2-py)3P=O was clearly noticed in
NaOH/D2O, which gave (2-py)3P(=O)ONa (8) and [2-2H]pyridine.
Note that (2-py)3P=O is a weaker base in comparison to 1a. The pH of a saturated
(53 mM) aqueous solution of (2-py)3P=O was found to be 7.7. An additional base
seemed to be required for (2-py)3P=O to undergo hydrolytic PꢀCpy cleavage. It has
been reported that, at elevated temperature and under basic conditions, ligand coupling
in (2-py)
A
ligand exchange/coupling reactions has also been reported for (2-py)3P=O at reflux in
aqueous HCl [10b]. However, so far, no pyridyl coupling has been noticed for (2-
py)3P=O under our experimental conditions. In addition, Ph3P=O was found to be
unreactive toward hydrolysis in the presence of either strong bases or strong acids at
temperatures of 25–1908.
Two mixed phenyl/pyridyl phosphorane intermediates, H C=CH(CH2)9N=
2
P(Ph)n(2-py)3ꢀn, compounds 1b (n=1) and 1d (n=2), were synthesized and studied
as model compounds. Under basic conditions or in wet MeCN, the two phosphoranes
were found to be hydrolyzed via the unconventional route, affording 5b and 5d, respec-
tively (Scheme 5). In contrast, acidic hydrolyses of 1b,d gave the conventional product 6
(not shown). These results clearly indicate that the 2-pyridyl moiety is a decisive factor
in the observed unconventional PꢀC cleavages.
Furthermore, when compared to the non-substituted pyridyl phosphoranes 1a,b,d,
compound H2C=CH(CH2)9N=P(Ph)(4-MeO-2-py)2 (1c), which carries an electron-
donating MeO substituent in para position, was hydrolyzed at a much slower rate to
afford H2C=CH(CH2)9N(H)P(=O)(Ph)(4-MeO-2-py) (5c) and 4-methoxypyridine
(see Scheme 4 and Table 1). On the contrary, the halogenated phosphoranes H2C=
CH(CH2)9N=P(4-X-C6H4)3 (X=F, Cl), i.e., compounds 1f (X=F) and 1g (X=Cl),
1
)
For hydrolysis of Staudinger products under basic conditions, see [12a]; under acidic conditions, see
[12b,c]. For alkaline hydrolysis of phosphonium salts, see [8c][12a][13].

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Helvetica Chimica Acta – Vol. 89 (2006)
Scheme 5
a) H2O, MeCN. b) H2O, OHꢀ, MeCN.
Table 1. Hydrolysis of Compounds 1a–d as a Function of Reaction Time. Conditions: 0.38 mmol of
substrate, hydrous MeCN (2 ml), r.t.
Time [s]
Conversion [% ]a)
1a
1b
1c
1d
30
60
90
100
100
100
65
70
81
8.8
9.3
9.6
53
65
71
a) Determined by 1H-NMR integration.
Table 2. Hydrolysis of Compounds 1e–g as a Function of Reaction Time. Conditions: 0.38 mmol of
substrate, (D6)DMSO (2 ml) containing 1 equiv. of H2O, r.t.
Time [min]
Conversion [% ]a)
1e (X=H)
1f (X=F)
1g (X=Cl)
15
25
40
11
15
20
28
33
47
26
32
35
a) Determined by 1H-NMR integration.
underwent hydrolysis to 4 significantly faster when compared to the parent compound
1e (X=H) (Table 2).
These results demonstrate that both basicity and electronic effects are major deter-
minants for the observed unusual PꢀCpy cleavages. Similar results have been found for
the alkaline hydrolysis of Ar4P+: aryl (Ar) groups with electron-withdrawing substitu-
ents are more easily displaced due to the preferential loss of a more stable Arꢀ anion
[8c]. Therefore, by carefully adjusting the electronic effects, one might be able to design

Helvetica Chimica Acta – Vol. 89 (2006)
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a mixed phenyl/pyridyl system with electron-withdrawing substituents on the phenyl
ring and electron-donating substituents on the pyridyl ring to engage competition
between both hydrolytic P=N vs. PꢀC cleavage.
Conclusions. – A new class of phosphinic-amide ligands can be readily synthesized
in a one-pot process of Staudinger reactions of organic azides and 2-pyridylphosphines,
followed by sequential hydrolysis. This novel methodology not only provides the sim-
plest way to construct phosphinic amides, but also demonstrates a new route for base-
induced PꢀC cleavage. Our results may also be helpful for researchers in the area of
synthetic and biological chemistry dealing with amine or amide syntheses and phospho-
rus chemistry.
This work was supported by the National Science Council of Taiwan (NSC-93-2113-M-194-004). The
authors thank Prof. Wei-Ping Hu for helpful discussions.
Experimental Part
General. 2,2’,2’’-Phosphanetriyltripyridine ((2-py)3P; 3a) was synthesized by modification of a
reported procedure [14]. Compounds (Ph)
C
NMR Spectra: recorded at 278; chemical shifts d and coupling constants J in ppm and Hz, resp. Mass
spectra: in m/z (rel. %).
11-Bromoundec-1-ene. To a soln. of H C=CH(CH2)9OH (10 g, 58.8 mmol) in THF (20 ml) was
2
added (CF3CO)2O (14.85 g, 70.56 mmol). The mixture was stirred for 20 min at r.t., and the excess
(CF3CO)2O was removed under vacuum to give a light-yellow soln. LiBr (5.2 g, 60 mmol) in THF (40
ml) and HMPA (30 ml) were added, and the mixture was stirred for 5 h at 708. The salt was filtered
off, and the filtrate was extracted with hexane (6”30 ml). The extract was dried to afford the title com-
pound: 11.6 g (85%). 1H-NMR (400 MHz, CDCl3): 1.25–1.40 (br. s, 12 H); 1.34–1.44 (m, 2 H); 2.01–2.07
(m, 2 H); 3.25 (t, J=3.4, 2 H); 4.92–5.02 (m, 2 H); 5.78–5.85 (m, 1 H). 13C-NMR (100 MHz, CDCl3, 278):
28.2; 28.7; 28.9; 29.1; 29.4; 32.8; 33.8; 33.8; 114.1; 139.1.
11-Azidoundec-1-ene (2). 11-Bromoundec-1-ene (2.0 g, 8.62 mmol) was added to a soln. of NaN3
(0.672 g, 10.34 mmol) in DMF (20 ml). The mixture was stirred for 6 h at r.t. The NaBr was filtered
off, the filtrate was extracted with hexane (6”15 ml), and the extract was dried: 1.55 g (92%). 1H-
NMR (400 MHz, CDCl3): 1.29–1.44 (br. s, 12 H); 1.56–1.61 (m, 2 H); 2.01–2.66 (m, 2 H); 3.40 (t,
J=3.5, 2 H); 4.91–5.01 (m, 2 H); 5.77–5.84 (m, 1 H). 13C-NMR (100 MHz, CDCl3): 26.7; 28.8; 28.9;
29.0; 29.3, 29.4; 33.7; 51.4; 114.1; 139.1. Anal. calc. for C11H21N3 (195.31): C 67.65, H 10.84, N 26.51;
found: C 67.54, H 10.67, N 26.60.
2-(P,P-Dipyridin-2-yl-N-undec-10-en-1-ylphosphorimidoyl)pyridine (1a). Compound 2 (0.2 g, 1.02
mmol) and (2-py)3P (3a; 0.27 g, 1.02 mmol) were placed in a 20-ml reaction vial, and the mixture was stir-
red for 5 min at 1008 (immediate gas evolution). Yield: 0.43 g (99%). 1H-NMR (400 MHz, CDCl3):
1.17–1.35 (br. s, 12 H); 1.48–1.54 (m, 2 H); 1.94–2.00 (m, 2 H); 3.22–3.30 (m, 2 H); 4.84–4.94 (m, 2
H); 5.70–5.77 (m, 1 H); 7.23–7.26 (m, py); 7.68–7.44 (m, py); 8.01–8.67 (m, py); 8.65 (d, J=2.3, py).
13C-NMR (100 MHz, CDCl3): 26.8; 28.4; 28.5; 28.6; 28.9; 29.1; 29.1; 33.3; 113.6; 124.2 (3J(P,C)=3);
128.4 (2J(P,C)=19); 135.2 (3J(P,C)=9); 138.6; 149.5 (2J(P,C)=18); 155.0 (1J(P,C)=122). 31P-NMR (160
MHz, CDCl3): ꢀ1.0. EI-MS: 432 (25, ([M+H]+, C26H34N4P+).
2,2’-(Phenylphosphanediyl)dipyridine (3b). To a soln. of BuLi (45 ml of a 1.6M soln. in hexane; 63
mmol) in Et2O (70 ml) was added 2-bromopyridine (10 g, 63 mmol) in Et2O (25 ml) at ꢀ908, and the
dark-red soln. was stirred at this temp. for 4 h. Then, a soln. of Cl2PPh (4.3 ml, 32 mmol) in Et2O (40
ml) was added dropwise, and the mixture was stirred at ꢀ908 for another 2 h. The mixture was finally
extracted with 2M aq. H2SO4 (80 ml), and then neutralized with sat. aq. NaOH soln. The precipitate
was collected and washed first with H2O (3”30 ml) and then with petroleum ether (3”15 ml). Recrys-

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Helvetica Chimica Acta – Vol. 89 (2006)
tallization of the crude from acetone gave the product: 4.6 g (56%). 1H-NMR (400 MHz, CHCl3):
7.09–7.17 (m, py); 7.30–7.31 (m, py); 7.43–7.45 (m, Ph); 7.48–7.49 (m, Ph); 8.62 (d, py). 13C-NMR
(100 MHz, CHCl3): 122.0; 127.9 (1J(P,C)=18); 128.3 (2J(P,C)=8); 129.1; 134.5 (1J(P,C)=20); 134.73
(2J(P,C)=10); 135.3; 149.8 (2J(P,C)=12); 162.5. 31P-NMR (160 MHz, CHCl3): ꢀ2.4.
2-(P-Phenyl-P-pyridin-2-yl-N-undec-10-en-1-ylphosphorimidoyl)pyridine (1b). Compounds 2 (75 mg,
0.38 mmol) and 3b (0.1 g, 0.38 mmol) were placed in a 20-ml reaction vial, and the mixture was stirred at
1008 (immediate gas evolution). Yield: 0.13 g (99%). 1H-NMR (400 MHz, CDCl3): 1.12–1.25 (br. s, 12 H);
1.44–1.49 (m, 2 H); 1.88–1.92 (m, 2 H); 3.10–3.18 (m, 2 H); 4.79–4.89 (m, 2 H); 5.63–5.72 (m,
1 H); 7.17–7.26 (m, py); 7.31–7.35 (m, Ph); 7.61–7.62 (m, py); 7.82–7.90 (m, Ph, py); 8.59 (d, J=2.1, py).
13C-NMR (100 MHz, CDCl3): 26.5; 27.1; 28.6; 28.7; 28.6; 28.9; 29.2; 29.4; 33.6; 113.9; 124.4 (3J(P,C)=3);
127.9 (1J(P,C)=11); 128.3 (2J(P,C)=20); 131.1; 132.9 (2J(P,C)=7); 135.2 (3J(P,C)=9); 138.9; 149.8 (2J(P,
C)=18); 156.0 (1J(P,C)=122). 31P-NMR (160 MHz, CDCl3): 3.1. FAB-MS: 432 (25, [M+H]+, C27H35N3P+).
2,2’-(Phenylphosphanediyl)bis(4-methoxypyridine) (3c). To a soln. of BuLi (29 mmol; 1.6M soln. in
hexane) in Et2O (50 ml) was added a soln. of 2-bromo-4-methoxypyridine (5 g, 29 mmol) in Et2O (25
ml). The resulting dark-red soln. was stirred at ꢀ908 for 4 h. A soln. of Cl2PPh (2.59 g, 15 mmol) in
Et2O (30 ml) was added dropwise, and the mixture was stirred at ꢀ908 for another 2 h. The mixture
was finally extracted with 2M aq. H2SO4 (50 ml), neutralized with sat. aq. NaOH soln., and re-extracted
with CHCl3 (4”50 ml). The CHCl3 extract was dried to give the product. Yield: 4.35 g (65%). 1H-NMR
(400 MHz, CHCl3): 3.9 (s, 3 H); 6.71 (d, J=4.18); 7.26–7.34 (m, Ph); 7.48–7.49 (m, py); 8.05 (d, J=3.22).
13C-NMR (100 MHz, CHCl3): 3.5; 123.8 (2J(P,C)=12); 128.6 (2J(P,C)=6); 128.8; 132.8 (2J(P,C)=19);
143.4 (2J(P,C)=17); 151.2 (1J(P,C)=29); 164.7. 31P-NMR (160 MHz, CHCl3): ꢀ21.4. EI-MS: 324 (100,
[M+H]+, C18H18N2O2P+).
4-Methoxy-2-[P-(4-methoxypyridin-2-yl)-P-phenyl-N-undec-10-en-1-ylphosphorimidoyl]pyridine
(1c). A mixture of 2 (75 mg, 0.38 mmol) and 3c (0.12 g, 0.38 mmol) in a 20-ml reaction vial was stirred for
1
5 min at 1008 (immediate gas evolution). Yield: 0.14 g (99%). H-NMR (400 MHz, CDCl3): 1.12–1.26
(br. s, 12 H); 1.46–1.48 (m, 2 H); 1.88–1.94 (m, 2 H); 2.94–3.02 (m, 2 H); 3.84 (s, 2 MeO); 4.78–4.89
(m, 2 H); 5.58–5.71 (m, 1 H); 6.70 (d, py); 7.34–7.36 (m, Ph); 7.51–7.54 (m, Ph); 7.71–7.37 (m, py);
8.22 (d, J=2, py). 13C-NMR (100 MHz, CDCl3): 27.1; 28.7; 28.9; 29.2; 29.3; 29.4; 33.6; 35.5; 45.2; 53.5;
110.9 (2J(P,C)=10); 113.9; 128.3 (1J(P,C)=12); 132.0 (2J(P,C)=9); 139.0; 141.8; 151.6 (1J(P,C)=15);
165.8. 31P-NMR (160 MHz, CDCl3): 4.9. EI-MS: 492 (51, [M+H]+, C29H39N3O2P+).
2-(P,P-Diphenyl-N-undec-10-en-1-ylphosphorimidoyl)pyridine (1d). A mixture of 2 (75 mg, 0.38
mmol) and (Ph)2(2-py)P (3d; 0.1 g, 0.38 mmol) in a 20-ml reaction vial was stirred at 1008 for 5 min
G
1
(immediate gas evolution). Yield: 0.13 g (99%). H-NMR (400 MHz, CDCl3): 1.20–1.33 (br. s, 12 H);
1.53–1.60 (m, 2 H); 1.97–2.03 (m, 2 H); 3.08–3.17 (m, 2 H); 4.88–4.98 (m, 2 H); 5.74–5.81 (m, 1 H);
7.25–7.26 (m, py); 7.35–7.45 (m, Ph); 7.70–7.75 (m, Ph); 8.18 (t, J=3.0, py); 8.67 (d, J=2.1, py). 13C-
NMR (100 MHz, CDCl3): 26.6; 28.8; 28.9; 29.0; 29.1; 33.7; 114.0; 124.5 (3J(P,C)=3); 128.0 (1J(P,
C)=11); 128.2 (2J(P,C)=12); 131.0; 131.5; 132.6; 135.7 (3J(P,C)=9); 139.1; 149.8 (2J(P,C)=18); 156.6
(1J(P,C)=127). 31P-NMR (160 MHz, CDCl3): 6.9. FAB-MS: 431 (34, [M+H]+, C28H37N2P+).
Triphenyl(undec-10-en-1-ylimino)-l5-phosphane (1e). A mixture of 2 (0.2 g, 1.02 mmol) and Ph3P
(3e; 0.27 g, 1.03 mmol) in a 20-ml reaction vial was stirred for 5 min at 1008 (immediate gas evolution).
Yield: 0.43 g (99%). 1H-NMR (400 MHz, CDCl3): 1.22–1.36 (br. s, 12 H); 1.55–1.59 (m, 2 H); 2.01–2.06
(m, 2 H); 3.04–3.13 (m, 2 H); 4.92–4.97 (m, 2 H); 5.78–5.82 (m, 1 H); 7.27–7.52 (br. s, Ph); 7.63–7.69
(m, Ph). 13C-NMR (100 MHz, CDCl3): 28.9; 29.1; 29.4; 29.5; 29.5; 33.7; 114.0; 128.2 (1J(P,C)=11);
131.9 (2J(P,C)=10); 132.5 (2J(P,C)=9); 139.2. 31P-NMR (160 MHz, CDCl3): 10.9. FAB-MS: 430 (100,
[M+H]+, C29H37NP+).
Tris(4-fluorophenyl)(undec-10-en-1-ylimino)-l5-phosphane (1f). A mixture of 2 (75 mg, 0.38 mmol)
and (4-F-C6H4)3P (3f; 0.12 g, 0.38 mmol) in a 20-ml reaction vial was stirred at 1008 for 5 min (immediate
gas evolution). Yield: 0.14 g (99%). 1H-NMR (400 MHz, CDCl3): 1.18–1.32 (br. s, 12 H); 1.49–1.52 (m, 2
H); 1.97–1.99 (m, 2 H); 2.96–3.04 (m, 2 H); 4.85–4.95 (m, 2 H); 5.75–5.76 (m, 1 H); 7.07–7.12 (m,
C6H4); 7.55–7.61 (m, C6H4). 13C-NMR (100 MHz, CDCl3): 27.3; 28.8; 29.0; 29.35; 29.43; 29.5; 33.7;
35.5; 45.3; 114.0; 115.5; 115.7; 115.8; 115.9; 127.0 (3J(P,C)=3); 127.5 (1J(F,C)=99); 128.0 (3J(P,C)=3);
134.5; 134.6 (2J(P,C)=9); 134.7 (2J(P,C)=9); 139.1; 164.7 (1J(P,C)=253). 31P-NMR (160 MHz, CDCl3):
7.3. EI-MS: 484 (53, [M+H]+, C26H34F3NP+).

Helvetica Chimica Acta – Vol. 89 (2006)
3015
Tris(4-chlorophenyl)(undec-10-en-1-ylimino)-l5-phosphane (1g). A mixture of 2 (75 mg, 0.38 mmol)
and (4-Cl-C6H4)3P (3g; 0.14 g, 0.38 mmol) in a 20-ml reaction vial was stirred for 5 min at 1008 (imme-
diate gas evolution). Yield: 0.20 g (99%). 1H-NMR (400 MHz, CDCl3): 1.18–1.33 (br. s, 12 H);
1.48–1.52 (m, 2 H); 1.96–2.02 (m, 2 H); 2.95–3.04 (m, 2 H); 4.87–4.97 (m, 2 H); 5.76–5.77 (m, 1 H);
7.38–7.44 (m, C6H4); 7.50–7.57 (m, C6H4). 13C-NMR (100 MHz, CDCl3): 27.2; 28.8; 29.0; 29.4; 29.4;
29.5; 33.7; 35.4; 45.2; 114.0; 128.8 (1J(P,C)=12); 133.2 (1J(Cl,C)=11); 133.6; 138.0; 138.6 (3J(P,C)=3).
31P-NMR (160 MHz, CDCl3): 7.5. EI-MS: 532 (47, [M+H]+, C26H34Cl3NP).
P,P-Dipyridin-2-yl-N-undec-10-en-1-ylphosphinic Amide (5a). Method A. To a soln. of 1a (0.4 g, 0.93
mmol) in MeCN (8 ml) was added H2O (2 ml), the mixture was stirred for 30 min at r.t., and then con-
centrated and dried under vacuum. Yield: 0.33 g (95%).
Method B. To a soln. of1a (0.4 g, 0.93 mmol) in MeCN (8 ml) was added 0.6M aq. NaOH soln. (2 ml),
and the mixture was stirred for 30 min at r.t. All volatiles were removed, and the residue was extracted
with CHCl3 (3”15 ml). The org. layer was separated and dried. Yield: 0.30 g (87%).
1
Data of 5a. Light-yellow solid. IR (nujol): 3270 (NH), 1247 (P=O). H-NMR (400 MHz, CDCl3):
1.20–1.35 (br. s, 12 H); 1.48–1.54 (m, 2 H); 1.97–2.02 (m, 2 H); 2.94–3.01 (m, 2 H); 4.44–4.47 (m,
1 H); 4.88–4.98 (m, 2 H); 5.74–5.81 (m, 1 H); 7.31–7.34 (m, py); 7.74–7.77 (m, py); 8.05–8.07 (m,
py); 8.72 (d, J=2.22, py). 13C-NMR (100 MHz, CDCl3): 26.6; 28.8; 29.0; 29.1; 29.30; 29.33; 32.0; 32.1;
33.7; 39.8; 114.0; 125.3 (3J(P,C)=3); 128.2 (2J(P,C)=22); 136.03 (3J(P,C)=10); 139.1; 150.1 (2J(P,
C)=19.2); 155.3 (1J(P,C)=154). 31P-NMR (160 MHz, CDCl3): 14.5. Anal. calc. for C21H30N3OP
(371.21): C 67.90, H 8.14, N 11.31; found: C 67.95, H 8.16, N 11.34. X-Ray crystal structure: see below.
P-Phenyl-P-pyridin-2-yl-N-undec-10-en-1-ylphosphinic Amide (5b). To a soln. of 1b (0.13 g, 0.38
mmol) in MeCN (4 ml) was added H2O (1 ml), the mixture was stirred for 30 min at r.t., and then con-
centrated and dried under vacuum. Yield: 0.12 g (87%). Light-yellow solid. 1H-NMR (400 MHz,
CDCl3): 1.21–1.33 (br. s, 12 H); 1.50–1.55 (m, 2 H); 1.98–2.03 (m, 2 H); 2.90–2.98 (m, 2 H);
3.83–3.85 (m, 1 H); 4.89–4.98 (m, 2 H); 5.75–5.82 (m, 1 H); 7.33–7.42 (m, py); 7.43–7.35 (m, Ph);
7.72–7.73 (m, py); 7.92–7.97 (m, Ph, py); 8.71 (d, J=2.2, py). 13C-NMR (100 MHz, CDCl3): 26.7; 28.9;
29.0; 29.1; 29.3; 29.7; 32.0; 32.1; 33.7; 40.1; 114.0; 125.1 (3J(P,C)=3); 127.9 (1J(P,C)=22); 128.3 (2J(P,
C)=13); 131.3; 131.8 (2J(P,C)=3); 132.6 (2J(P,C)=20); 136.1 (3J(P,C)=10); 139.1; 149.7 (2J(P,C)=19);
156.3 (1J(P,C)=153). 31P-NMR (160 MHz, CDCl3): 18.2. Anal. calc. for C22H31N2OP: C 71.35, H 8.37,
N 7.56; found: C 71.12, H 8.40, N 7.48.
P-(4-Methoxypyridin-2-yl)-P-phenyl-N-undec-10-en-1-ylphosphinic Amide (5c). To a soln. of1c (0.18
g, 0.38 mmol) in MeCN (4 ml) was added H2O (1 ml), the mixture was stirred at r.t. for 30 min, and then
concentrated and dried under vacuum. The resulting light-yellow solid was washed with hexane (3”30
1
ml) and hot H2O (5”20 ml), and finally dried. Yield: 0.028 g (20%). Light-yellow solid. H-NMR (400
MHz, CDCl3): 1.25–1.32 (br. s, 12 H); 1.67–1.71 (m, 2 H); 2.04–2.08 (m, 2 H); 7.94–7.96 (m, 2 H);
3.97 (s, MeO); 4.03–4.04 (m, 1 H); 5.75–5.90 (m, 1 H); 6.80 (d, J=3.4, 2 H); 7.45–7.52 (m, arom. H);
7.84–7.89 (m, arom. H); 8.04–8.06 (m, 1 H); 8.64 (d, J=4.0, 2 H). 13C-NMR (100 MHz, CDCl3): 26.7;
28.9; 29.0; 29.2; 29.4; 29.5; 32.1; 33.8; 40.9; 54.1; 114.1; 128.7 (1J(P,C)=12); 131.9 (2J(P,C)=10); 132.1;
139.2; 142.6; 166.1. 31P-NMR (160 MHz, CDCl3): 22.2.
P,P-Diphenyl-N-undec-10-en-1-ylphosphinic Amide (5d). To a soln. of 1d (0.13 g, 0.38 mmol) in
MeCN (4 ml) was added H2O (1 ml), the mixture was stirred for 30 min at r.t., and then concentrated
and dried under vacuum. Yield: 0.13 g (95%). Light-yellow solid. 1H-NMR (400 MHz, CDCl3):
1.22–1.35 (br. s, 12 H); 1.51–1.56 (m, 2 H); 1.98–2.03 (m, 2 H); 2.86–2.94 (m, 2 H); 4.89–4.99 (m, 2
H); 5.75–5.82 (m, 1 H); 7.39–7.48 (m, Ph); 7.86–7.90 (m, Ph). 13C-NMR (100 MHz, CDCl3): 26.6;
28.8; 29.0; 29.1; 29.27; 29.33; 32.0; 32.1; 33.7; 40.7; 114.0; 128.4 (1J(P,C)=13); 131.7 (2J(P,C)=3);
131.9; 132.1; 133.2; 139.1. 31P-NMR (160 MHz, CDCl3): 23.8. Anal. calc. for C23H32NOP: C 74.79, H
8.67, N 3.79; found: C 74.51, H 8.64, N 3.80).
Undec-10-en-1-amine (4). Method A. To a soln. of 1a (0.4 g, 0.93 mmol) in MeCN (8 ml) was added
1.8M aq. HCl (2 ml), and the mixture was stirred for 30 min at r.t. All volatiles were removed, the residue
was extracted with CHCl3 (4”5 ml), and the org. layer was separated, concentrated, and dried. Yield:
0.147 g (78%).

3016
Helvetica Chimica Acta – Vol. 89 (2006)
Method B. To a soln. of1e (0.4 g, 0.93 mmol) in MeCN (8 ml) was added 1.8M aq. HCl (2 ml), and the
mixture was stirred for 30 min at r.t. All volatiles were removed, the residue was extracted with CHCl3
(4”15 ml), and the org. layer was separated, concentrated, and dried. Yield: 0.147 g (82%).
Method C. To a soln. of 5a (0.2 g, 0.54 mmol) in MeCN (8 ml) was added aq. 1.8M HCl (2 ml). The
mixture was stirred for 1 h at r.t. All volatiles were removed, and the residue was extracted with
CHCl3 (4”15 ml), concentrated, and dried. Yield: 0.083 g (76%).
Data of 5a. 1H-NMR (400 MHz, CDCl3): 1.29–1.44 (br. s, 12 H); 1.83–1.99 (m, 2 H); 2.04–2.06 (m, 2
H); 4.91–5.01 (m, 2 H); 5.75–5.86 (m, 1 H). 13C-NMR (100 MHz, CDCl3): 26.8; 28.7; 29.2; 29.3; 29.7;
33.3; 33.4; 42.5; 113.8; 138.8.
Undec-10-en-1-aminium (6). Method A. To a soln. of 1e (0.4 g, 0.93 mmol) in MeCN (8 ml) was
added H2O (2 ml). The soln. was stirred for 30 min at r.t. All volatiles were removed. The residue was
extracted with hexane (4”15 ml), and the org. extract was dried. Yield: 0.13 g (83%).
Method B. To a soln. of1e (0.4 g, 0.93 mmol) in MeCN (8 ml) was added 0.6M aq. NaOH soln. (2 ml).
The mixture was stirred for 30 min at r.t. All volatiles were removed, and the residue was extracted with
hexane (4”15 ml). The org. extract was concentrated and dried. Yield: 0.122 g (78%).
Data of 6. 1H-NMR (400 MHz, CDCl3): 1.29–1.38 (br. s, 16 H); 1.75–1.77 (m, 2 H); 2.00–2.05 (m, 2
H); 2.68 (t, J=3.5, 2 H); 4.91–5.00 (m, 2 H); 5.76–5.83 (m, 1 H). 13C-NMR (100 MHz, CDCl3): 26.8;
28.9; 29.1; 29.4; 29.5; 33.4; 33.7; 42.0; 114.0; 139.2.
Sodium Dipyridin-2-ylphosphinate (8). To a soln. of (2-py) P=O (0.2 g, 0.73 mmol) in D2O (1 ml)
3
and (D6)DMSO (2 ml) was added NaOH (59 mg, 1.47 mmol). The soln. was stirred for 6 h at r.t. All vol-
atiles were removed, and the residue was extracted with MeOH (3”15 ml), concentrated, and dried.
1
Yield: 0.15 g (95%). Colorless solid. H-NMR (400 MHz, D2O): 7.38–7.41 (m, py); 7.85–7.88 (m, py);
7.93–7.95 (m, py); 8.44–8.45 (m, py). 13C-NMR (100 MHz, D2O): 125.9; 127.5 (2J(P,C)=16); 137.5
(3J(P,C)=8); 149.9 (2J(P,C)=15); 158.63 (1J(P,C)=128). 31P-NMR (160 MHz, D2O): 16.8. FAB-MS:
221 (82, C10H8DN2O2P+).
Dipyridin-2-ylphosphinic Acid (7). Compound 8 (0.1 g, 4.16 mmol) was added to a 1.8M aq. HCl soln.
(2 ml). The mixture was stirred for 30 min at r.t., and concentrated under vacuum. Colorless solid. IR
(nujol): 2725, 2663 (PꢀOH), 1302 (P=O). 1H-NMR (400 MHz, D2O): 8.19–8.22 (m, py); 8.43–8.47
(m, py); 8.67–8.71 (m, py); 8.91–8.92 (m, py). 13C-NMR (100 MHz, D2O): 130.5; 132.15 (2J(P,C)=9);
144.0 (3J(P,C)=5); 148.2 (2J(P,C)=6); 149.1 (1J(P,C)=111). 31P-NMR (160 MHz, D2O): ꢀ2.7.
Table 3. X-Ray Crystal Data and Details of Structure Refinement for 5a
Formula
Mr [g/mol]
C21H30N3OP
371.45
Temperature [K]
Radiation (l [nm])
Crystal system
Space group
298(2)
MoKa (0.7107)
monoclinic
P 21/c
Lattice parameters:
a [Š]
b [Š]
c [Š]
a [8]
b [8]
23.423(4)
8.421(2)
10.943(2)
90.0
101.99(1)
90.0
g [8]
Z
4
V [Š3]
2111.4(7)
1.169
1calc [Mg/m3]
q Range [8]
3.56–50.04
4948
3709 (R(int)=0.0307)
R1=0.0606, wR2=0.1193
Reflections collected
Independent reflections
Final R indices (I>2s(I))
3
Largest difference peak and hole
0.544, ꢀ0.911 e/Š

Helvetica Chimica Acta – Vol. 89 (2006)
3017
X-Ray Crystal Structure of P,P-Dipyridin-2-yl-N-undec-10-en-1-ylphosphinic Amide (5a). General X-
ray-operation procedures (SHELXS97 and SHELXL97) used are described in [15]. Selected crystallo-
graphic data and data-collection parameters are summarized in Table 3. A suitable, colorless crystal
(ca. 0.32”0.22”0.16 mm) was grown at r.t. from a MeCN soln. Diffraction data were recorded at ambient
temperature on a Bruker-P4 diffractometer using graphite-monochromated MoKa radiation. Unit-cell
dimensions were determined from 25 well-centered reflections, with 2q values near 258.
REFERENCES
[1] H. Staudinger, J. Meyer, Helv. Chim. Acta 1919, 2, 635; H. Staudinger, E. Hauser, Helv. Chim. Acta
1921, 4, 861.
[2] H. Schmidbaur, G. Jonas, Chem. Ber. 1967, 100, 1120; N. Wiberg, G. Schwenk, K. H. Schmid, Chem.
Ber. 1972, 105, 1209; R. A. Shaw, B. W. Fitzsimmons, B. C. Smith, Chem. Rev. 1962, 62, 247; E. W.
Abel, S. A. Mucklejohn, Phosphorus Sulfur 1981, 9, 235.
[3] E. F. V. Scriven, K. Turnbull, Chem. Rev. 1988, 88, 297; Y. G. Gololobov, L. F. Kasukhin, Tetrahe-
dron 1992, 48, 1353; S. Gilbertson, Chemtracts 2001, 14, 524.
[4] E. Saxon, C. R. Bertozzi, Science 2000, 287, 2007; K. L. Kiick, E. Saxon, D. A. Tirrell, C. R. Ber-
tozzi, Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 19; E. Saxon, S. J. Luchansky, H. C. Hang, C. Yu, S.
C. Lee, C. R. Bertozzi, J. Am. Chem. Soc. 2002, 124, 14893; C. C. Wang, T. S. Seo, Z. Li, H. Ruparel,
J. Ju, Bioconjugate Chem. 2003, 14, 697.
[5] Y.-S. Fu, S. J. Yu, Angew. Chem., Int. Ed. 2001, 40, 437.
[6] V. A. Gilyarov, E. I. Matrosov, F. I. Belꢂskii, M. I. Kabachnik, Zh. Obshch. Khim. 1980, 50, 44; M. N.
Dimukhametov, I. A. Nuretdinov, Zh. Obshch. Khim. 1985, 55, 2483; T. A. Mastryukova, N. V.
Mashchenko, I. L. Odinets, P. V. Petrovskii, M. I. Kabachnik, Zh. Obshch. Khim. 1988, 58, 1967;
B. A. Arbuzov, E. N. Dianova, Izv. Akad. Nauk. SSSR. Ser. Khim. 1983, 418.
[7] C. Shin, Y. Yonezawa, K. Watanabe, J. Yoshimura, Bull. Chem. Soc. Jpn. 1981, 54, 3811.
[8] a) R. F. Hudson, in ꢁStructure and Mechanism in Organophosphorus Chemistryꢂ, Academic Press,
New York, 1965, pp. 233–245; b) B. J. Walker, in ꢁOrganophosphorus Chemistryꢂ, Penguin, Har-
mondsworth, 1972, Vol. 5, pp. 83–111; c) D. J. H. Smith, in ꢁComprehensive Organic Chemistryꢂ,
Eds. D. H. R. Barton, W. D. Ollis, Pergamon Press, Oxford, 1979, Vol. 2, pp. 1127–1187.
[9] H. J. Cristau, F. Plenat, in ꢁThe Chemistry of Organophosphorus Compoundsꢂ, Eds. R. F. Hartley, S.
Patai, John Wiley & Sons, New York, 1994, Vol. 3. pp. 111–137.
[10] a) G. R. Newkome, D. C. Hager, J. Am. Chem. Soc. 1978, 100, 5567; b) Y. Uchida, H. Kozawa,
Tetrahedron Lett. 1989, 30, 6365; c) R. S. Edmundson, in ꢁThe Chemistry of Organophosphorus
Compoundsꢂ, Eds. R. F. Hartley, S. Patai, John Wiley & Sons, New York, 1992, Vol. 2, pp. 380–381.
[11] M. Alajarín, C. López-Leonardo, P. Llamas-Lorente, Tetrahedron Lett. 2001, 42, 1041.
[12] a) L. Horner, H. Winkler, Tetrahedron Lett. 1964, 175; b) N. G. Andersen, P. D. Ramsden, D. Che,
M. Parvez, B. Keay, Org. Lett. 1999, 1, 2009; c) N. G. Andersen, P. D. Ramsden, D. Che, M. Parvez,
B. Keay, J. Org. Chem. 2001, 66, 7478.
[13] K. F. Kumli, W. E. McEwen, C. A. Vander Werf, J. Am. Chem. Soc. 1959, 81, 3805; M. Zanger, C. A.
Vander Werf, W. E. McEwen, J. Am. Chem. Soc. 1959, 81, 3807; W. E. McEwen, Top. Phosphourus
Chem. 1965, 2, 1.
[14] W. C. Davies, F. G. Mann, J. Chem. Soc. 1944, 276; F. G. Mann, J. Watson, J. Org. Chem. 1948, 13,
502; K. Kurtev, D. Ribola, R. A. Jones, D. J. Cole-Hamilton, G. Wilkinson, J. Chem. Soc., Dalton.
Trans. 1980, 55.
[15] G. M. Sheldrick, Acta Crystallogr., Sect. A 1990, 46, 467; G. M. Sheldrick, ꢁSHELXS97 and
SHELXL97: Program for the Refinement of Crystal Structuresꢂ, University of Gçttingen, Germany,
1997.
Received August 23, 2006