2,2′-Azobispyridine in Phosphorus Coordination Chemistry: A New Approach to 1,2,4,3-Triazaphosphole Derivatives

Article abstract of DOI:10.1002/ejic.201800831

Oxidative addition of 2,2′-azobispyridine (abpy) to PCl₃ in CH₂Cl₂ or THF gave the 1:1 addition product, containing phosphorus in high oxidation state (+5) and a reduced form of the ligand. 2,2′-Hydrazobispyridine (hbpy) was prepared by reduction of abpy with hydrazine-hydrate in 63 % yield. Interaction of hbpy with PCl₃ in the presence of triethylamine gave (abpy)^2–PCl (2) in 25 % preparative yield. A similar reaction of hbby with (Et₂N)₂PCl afforded (abpy)^2–PNEt₂ (4) in 89 % yield. Compound 4 after work-up with PCl₃ or PBr₃ gave 2 and (abpy)^2–PBr (6) respectively in high yields. Diethylamino-derivative 4 formed (κ²-N,N) adduct with SiCl₄ 7 (coordination by Py and azo-functions), while the chloro-derivative 2 did not. Reaction of 2 with PCl₅ is accompanied with liberation of PCl₃ and formation of spirocyclic ate complex [(abpy)^2–₂P]⁺PCl₆^–. All structurally characterized compounds demonstrated short distances between pyridyl nitrogen and the phosphorus atom. However, the QTAIM analysis did not reveal the presence of appropriate bond critical points (3, –1) for the intramolecular noncovalent interactions N···P in 2, 4, and 6. We theoretically estimated values of the rotation barriers for the pyridyl and Et₂N moieties in 4 using the relaxed potential energy surface scan at the B3LYP/6-31G(d) level of theory. The values of rotation barriers are very close to each other, viz. 13.2 (pyridyl) and 13.0 (Et₂N) kcal/mol.

Full text of DOI:10.1002/ejic.201800831

DOI: 10.1002/ejic.201800831
Full Paper
P–N Adducts | Very Important Paper |
2
,2′-Azobispyridine in Phosphorus Coordination Chemistry:
A New Approach to 1,2,4,3-Triazaphosphole Derivatives
[a]
[a]
[a]
Yulia S. Panova, Alexandra V. Sheyanova, Nataliya V. Zolotareva,
[a]
[a]
[b]
[a,c]
Vyacheslav V. Sushev, Alla V. Arapova, Alexander S. Novikov, Evgenii V. Baranov,
[a]
[a]
Georgy K. Fukin, and Alexander N. Kornev*
Abstract: Oxidative addition of 2,2′-azobispyridine (abpy) to tion of 2 with PCl is accompanied with liberation of PCl and
5
3
–
2
–
+
PCl in CH Cl or THF gave the 1:1 addition product, containing formation of spirocyclic ate complex [(abpy) P] PCl . All
3
2
2
2
6
phosphorus in high oxidation state (+5) and a reduced form structurally characterized compounds demonstrated short dis-
of the ligand. 2,2′-Hydrazobispyridine (hbpy) was prepared by tances between pyridyl nitrogen and the phosphorus atom.
reduction of abpy with hydrazine-hydrate in 63 % yield. Interac- However, the QTAIM analysis did not reveal the presence of
tion of hbpy with PCl in the presence of triethylamine gave appropriate bond critical points (3, –1) for the intramolecular
3
2
–
(
abpy) PCl (2) in 25 % preparative yield. A similar reaction of noncovalent interactions N···P in 2, 4, and 6. We theoretically
2–
hbby with (Et N) PCl afforded (abpy) PNEt (4) in 89 % yield. estimated values of the rotation barriers for the pyridyl and
2
2
2
Compound 4 after work-up with PCl or PBr3 gave 2 and Et N moieties in 4 using the relaxed potential energy surface
3
2
2
–
(
abpy) PBr (6) respectively in high yields. Diethylamino-deriva- scan at the B3LYP/6-31G(d) level of theory. The values of rota-
2
tive 4 formed (κ -N,N) adduct with SiCl 7 (coordination by Py tion barriers are very close to each other, viz. 13.2 (pyridyl) and
4
and azo-functions), while the chloro-derivative 2 did not. Reac- 13.0 (Et N) kcal/mol.
2
Introduction
Phosphorus(V) halides are known to form numerous Lewis acid-
base adducts with tertiary amines in which phosphorus appears
Scheme 1. Interaction of tertiary amines with halophosphines. Square brack-
ets designate the buffer zone for X group which is located between the sum
of covalent and the sum of van der Waals radii of the elements.
[
1]
in hexacoordinate state. At the same time, complexation of
III
P
centers with Lewis bases may be complicated by the repul-
sion of their lone electron pairs. Complex formation is strongly
dependent on the value of a positive charge at phosphorus
which is determined by the nature of substituents. Equally im-
portant is the e-donating properties of a base. However, the
particular significance is seen in the polarizability and ionizabil-
ity of the P–X bond which give rise to the formation of hyperva-
lent phosphorus(III) compounds. Whereas unstable complexes
If ionizability of the P–X bond is not sufficient for moving
the X group to the buffer zone (Scheme 1), weak pnictogen
[5]
bonding takes place (Scheme 2), which has the same nature
[6]
[7,8]
as related “halogen bonds” or “halcogen bonds”
from σ-hole interactions.
arising
[9,10]
of PCl with trialkylamines were detected only at low tempera-
3
2,3]
[
tures,
adducts between organoamines and PBr are quite
3
[
4]
stable at room temperature. Complexes formed in such a way
usually have the N–P bond which is close to covalent one, and
the P–X bond which is longer than covalent, but do not exceed
the sum of van der Waals radii of the elements (Scheme 1).
Scheme 2. Pnictogen bonding interaction.
The specific situation takes place, when interaction of donor
and acceptor centers is accompanied by charge transfer to an-
other atom. In this case zwitterion is formed (Scheme 3).
[
a] G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of
Sciences
[
11]
4
9 Tropinin str., 603137 Nizhny Novgorod, Russia
E-mail: akornev@iomc.ras.ru
b] Saint Petersburg State University,
On the other hand, electron-delocalizing groups at phos-
phorus also support the covalent N–P bonding and the forma-
tion of zwitterionic compounds based on 3a,6a-diaza-1,4-di-
[
[
7
/9 Universitetskaya Nab., 199034 Saint Petersburg, Russia
c] Lobachevsky State University of Nizhny Novgorod, Chemical Department,
3 Gagarina Pr., 603950 Nizhny Novgorod, Russia
phosphapentalene (Scheme 4), whereas R C substituents, which
2
2
do not possess such property, lead to the noncovalent weak N–
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201800831.
[
12]
P interaction.
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Following our interest in the chemistry of hypervalent phos-
[
21–24]
phorus(III) compounds,
we have studied the reaction of
2
,2′-azobispyridine and its reduced form (2,2′-hydrazobispyr-
idine, hbpy) with PCl . An open question also concerns the sta-
3
bility of hypervalent phosphorus compounds A and A′ depicted
in Scheme 7, which are analogs of phenylpyrazol-based hyper-
valent phosphorus compounds (B, B′) reported previously:
Scheme 3. Intramolecular redox process between phosphino- and azo-func-
tions.
[
21]
Scheme 4.
2,2′-Azobispyridine (abpy) as formally derived from the ubiq-
uitous 2,2′-bipyridine ligand is now known to form a variety
of complexes. The structurally identified alternatives for abpy
metallic complexes include mainly mono- and dinuclear coordi-
nations I and II, with five-membered chelate ring forma-
Scheme 7. Possible isomers of abpy-based hypervalent phosphorus
compounds (A, A′) and previously reported phenylpyrazole-based analogs (B,
B′).
[21]
[
13,14]
[15]
tion,
and tridentate coordination (IV)
Scheme 5).
while coordination only by the pyridine group (III)
[
16,17]
are rarely observed
Results and Discussion
(
Reaction of PCl with 2,2′-Azobispyridine (abpy)
3
A sample of 2,2′-azobispyridine was allowed to react with an
excess of PCl in toluene or dichloromethane at room tempera-
3
3
1
ture overnight. The P NMR spectrum of the reaction mixture
demonstrates a weak signal at –92.9 ppm which is in the field,
typical for cyclic compounds containing phosphorus(V) atom in
[
25]
Cl N surrounding. Cooling of the reaction mixture or solvent
3
2
removal lead to the loss of solubility of the product in organic
solvents (THF, Et O, PhMe, CH Cl ). Light-brown non-crystalline
2
2
2
solid has elemental composition corresponded to abpy/PCl =
3
1
:1 ratio. Anaerobic hydrolysis of the abpy-PCl adduct in water-
3
base media gave 2,2′-hydrazobispyridine (Py-NHNH-Py, hbpy)
that confirms the redox reaction between abpy and phosphorus
trichloride. A similar work-up procedure with methanol yielded
Scheme 5. Coordination modes of 2, 2′-azobispyridyl ligand.
The majority of mononuclear species (I) may be described
0
hbpy(HCl)
2
together with trimethyl phosphate, (MeO) PO, ac-
3
as complexes of unreduced abpy containing N=N bonds in the
3
1
cording to the P spectrum (Scheme 8).
range 1.25–1.30 Å. Nevertheless, in several complexes (Ru, Os)
2
,2′-azobispyridyl exists as an anion-radical displaying the elon-
[
18–20]
gated N–N bond (1.34–1.37 Å).
With reference to complexes of abpy with PCl , the resulting
3
oxidation state of phosphorus and the structure of the adduct
are not obvious (Scheme 6).
3
Scheme 8. Methanolysis of abpy-PCl adduct (1).
Raman Spectroscopy confirms that azo-bispyridine is
–1
reduced in the reaction with PCl since the band 1300 cm
3
(N=N, abpy) is absent in the product.
Geometry optimization for the asumed abpy-PCl adduct at
3
the B3LYP/6-31G(d) level of theory results in the structure 1 as
Scheme 6. Two possible adducts of abpy with PCl
3
.
shown in Figure 1.
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3
Scheme 10. Reaction of 2,2′-hydrazobispyridine with PCl .
3
Figure 1. Equilibrium optimized structure of the abpy-PCl adduct (1) at the
B3LYP/6-31G(d) level of theory and its graphic formula with selected bond
lengths in Å.
The structure of 2 was determined by X-ray crystallographic
analysis (Figure 2). Crystal data and some details of the data
collection and refinement are given in Table S1 (Supporting
Information).
The length of nitrogen–nitrogen bond in 1 (1.397 Å) testified
to its single bond character whereas the neighboring C=N bond
in the five-membered ring (1.306 Å) has a double bond charac-
ter.
The phosphorus atom in 1 has a trigonal-bipyramidal envi-
ronment in which one of the chlorine atom and the nitrogen
atom of the “former” pyridine ring occupy axial positions. Thus,
calculated structure may be represented as a pentavalent phos-
phorus compound with reduced abpy backbone.
Let's notice, that related phosphorus(III)-containing 2-pyrid-
ylazo-species (Scheme 9) undergo intramolecular oxidative ad-
[
26]
dition to form compounds of pentavalent phosphorus.
Figure 2. Molecular structure of 2 together with the atomic numbering sys-
tem. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are
drawn at 30 % probability. Selected bond lengths [Å] and angles [°]: P(1)–
N(2) 1.6839(8), P(1)–N(3) 1.7056(8), P(1)–Cl(1) 2.2247(3), N(3)–C(1) 1.3992(11),
C(1)–N(1) 1.3058(12), N(1)–N(2) 1.3986(11), N(2)–C(6) 1.4008(11); N(2)–P(1)–
N(3) 85.64(4), N(2)–P(1)–Cl(1) 102.51(3), N(3)–P(1)–Cl(1) 99.54(3), P(1)–N(3)–
C(1) 112.53(6), N(3)–C(1)–N(1) 115.57(8), C(1)–N(1)–N(2) 106.30(7), N(1)–N(2)–
P(1) 118.44(6), N(1)–N(2)–C(6) 119.14(7).
Scheme 9. Intramolecular oxidative addition of phosphorus(III) to azopyridine
fragment.
[
25]
Despite all received indirect data, abpy-PCl adduct 1 cannot
3
Complex 2 is chiral, and two pairs of enantiomers cocrystal-
lize in the unit cell. The phosphorus atom P(1) in 2 exhibits a
pyramidal geometry. The length of the P(1)–Cl(1) bond,
be assigned to the individual molecular compound. More prob-
ably, this is coordination polymer having irregular structure
with multiple close intermolecular contacts P–Cl, Cl–Cl, N–P. The
widened absorption bands in the IR spectrum confirm this as-
sumption. Nevertheless, oxidation of phosphorus atom in PCl3
and the corresponding reduction of abpy at their interaction
were established beyond any doubt.
2
.2247(3) Å, is in accordance with the P–Cl bond lengths in
[
27,28]
related 1,3,2-diazaphospholidines.
Five-membered hetero-
cycle in 2 is not planar, but nitrogen atoms N(1) and N(2) lie in
the plane of the annelated six-membered heterocycle, whereas
deviation of the phosphorus atom from this plane is 0.23 Å. The
nitrogen–nitrogen bond length in 2 [1.399(2) Å] corresponds to
the single N–N bond, whereas the neighboring N(1)–C(1) bond,
Reactions of PCl with 2,2′-Hydrazobispyridine (hbpy) and
3
1
.306(2) Å, is of the double bond character [compare to the
Its Derivatives
single bond N(2)–C(6) of 1.401(2) Å]. The pyridine ring after
Solutions of 2,2′-hydrazobispyridine and PCl in THF after mix- coordination to phosphorus partly losses its aromaticity and
3
ing gave abundant pale-yellow precipitate, containing all prod- demonstrates appreciable distinctions between alternating
ucts of the reaction. By repeated recrystallization from different bonds. The crystal packing analysis of 2 revealed intermolecular
solvents we succeeded in separating only 15 % of pure phos- H···Cl and H···N interactions, which are less or close to the sum
phorus-containing product 2 according to Scheme 10.
of the van der Waals radii of the elements. Part of the chain is
Using triethylamine as an HCl abstractor allowed increasing depicted in Figure S1 (Supporting information).
3
1
1
the yield of 2 up to 25 %. No other phosphorus-containing
The P{ H} NMR spectrum of 2 in pyridine showed a single
products were found in these reactions. Low preparative yields resonance at δ = 115.0 ppm. Measuring of NMR spectra in com-
of 2 are caused by difficulty in separation from byproducts mon organic solvents is unavailable because of very poor solu-
(
hydrochlorides).
bility of 2.
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Reactions of Dilithium Salt of 2,2′-Hydrazobispyridine with
Complex 4 is chiral, and two pairs of enantiomers cocrystal-
lize in the unit cell. According to the X-ray data, the phosphorus
atom in 4 has a pyramidal configuration. The P(1)–N(3) bond
length [1.656(2) Å] is in the range characteristic of P–N single
PCl and (Et N) PCl
3
2
2
We attempted to synthesize hypervalent phosphorus deriva-
tives of abpy (A and A′, Scheme 7) using dilithiation of hbpy
[
29]
bonds of phosphinoamines
but noticeably shorter then en-
followed by the reaction with PCl . However, no individual
3
docyclic P(1)–N(2) 1.739(2) Å and P(1)–N(4) 1.758(2) Å bonds in
the five-membered heterocycle of 4. At the same time, the sum
of angles around the N(3) atom is close to 360° showing its
trigonal-planar environment. This phenomenon has already
been observed and discussed for related 2-amino-1,3,2-diaza-
products were formed in this process. Meanwhile, interaction
of dilithium salt of hbpy (3) with (Et N) PCl unexpectedly gave
2
2
compound 4, containing only one phosphorus atom incorpo-
rated into abpy backbone (Scheme 11).
[
30,31]
phospholenes and triaminophosphines,
and may be as-
signed, most likely, to the necessity and possibility to extinguish
the big positive charge at the phosphorus atom more effec-
tively.
Exploring the reaction mechanism has shown that extrusion
of (Et N) P is observed only after addition of the second equiva-
2
3
lent of (Et N) PCl to dilithium salt of hbpy (3), whereas addition
2
2
of the first equivalent results in the formation of an intermedi-
ate 5 (Scheme 12).
Scheme 11.
The 31P NMR spectrum of 4 showed a single resonance at
δ = 82.9 ppm. The second phosphorus-containing product
found in this reaction was tris(dimethylamino)phosphine, show-
31
ing a single resonance at δ = 118.3 ppm in the P NMR spec-
trum.
The structure of 4 was proven by X-ray analysis (Figure 3).
Crystal data and some details of the data collection and refine-
ment are given in Table S1 (Supporting Information).
Scheme 12.
Compound 5 shows two close and broadened resonances in
the 3 P NMR spectrum at δ = 111.0 and 113.3 ppm, which tes-
tify, obviously, to the existence of a couple of slightly different
coordination modes for monolithium derivative.
1
It was found that the diethylamido group in 4 may be easily
replaced by halogen (Cl, Br) after addition of PCl or PBr re-
3
3
spectively (Scheme 13).
Scheme 13.
Figure 3. Molecular structure of 4 together with the atomic numbering sys-
tem. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are
drawn at 30 % probability. Selected bond lengths [Å] and angles [°]: P(1)–
N(3) 1.656(2), P(1)–N(2) 1.739(2), P(1)–N(4) 1.758(2), N(4)–C(1) 1.396(2), C(1)–
N(1) 1.298(2), N(1)–N(2) 1.412(2), N(2)–C(6) 1.384(2), N(3)–C(13) 1.467(2), N(3)–
C(11) 1.468(2); N(3)–P(1)–N(2) 106.36(5), N(3)–P(1)–N(4) 103.74(5), N(2)–P(1)–
N(4) 83.19(5), P(1)–N(4)–C(1) 113.41(8), N(4)–C(1)–N(1) 116.30(2), C(1)–N(1)–
N(2) 106.55(9), N(1)–N(2)–P(1) 118.63(7), N(1)–N(2)–C(6) 117.57(9), P(1)–N(2)–
C(6) 122.99(8), C(13)–N(3)–C(11) 116.81(10), C(13)–N(3)–P(1) 124.78(8), C(11)–
N(3)–P(1) 118.26(8).
The structure of 6 determined by X-ray crystallographic anal-
ysis shows close similarity to the chloro-analog 2 (Figure S2 and
Table S1 in Supporting information). The molecule 6 is also chi-
ral like 2 and 4, and two pairs of enantiomers cocrystallize in
the unit cell. The crystal packing analysis of 6 revealed inter-
molecular H···Br and H···N interactions, which are less or close
to the sum of the van der Waals radii of the elements. Part of
the chain is depicted in Figure S3 in Supporting information.
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Considering solid-state crystal structures of complexes 2, 4,
and 6, it was noticed, that the nitrogen atom in the pyridyl
fragment turns to the phosphorus atom in all cases. Further-
more, the observed distances N···P (2.827, 2.912, 2.824 Å for 2,
4
, and 6 respectively) are significantly shorter than the sum of
van der Waals radii for appropriate atoms (3.35 Å). Thus, in addi-
tion to structural analysis, a detailed computational study is de-
sirable.
Computational Study
In order to confirm or deny the hypothesis on the existence of
these noncovalent interactions in 2, 4, and 6, we carried out
DFT calculations at the M06-2X/6-311++G(d,p) level of theory
and performed topological analysis of the electron density dis-
tribution within the framework of Bader's theory (QTAIM
Figure 4. Molecular graph from QTAIM analysis of 4. The Poincare–Hopf rela-
tionship was satisfied, thus all critical points have been found. Bond critical
points (3, –1) are shown in orange, nuclear critical points (3, –3) – in violet,
ring critical points (3, +1) – in yellow.
[
32]
method).
This approach has already been successfully used
by us upon studies of different noncovalent interactions (viz.
hydrogen, halogen and chalcogen bonding, metallophilic inter-
actions, stacking) in various organic, organometallic, and coor-
[
33–37]
dination compounds.
The QTAIM analysis did not reveal
the presence of appropriate bond critical points (3, –1) for the
intramolecular noncovalent interactions N···P in 2, 4, and 6, and
negligible values of the Wiberg bond indices for these contacts
(
(
viz. 0.03–0.04), computed by using the natural bond orbital
NBO) partitioning scheme additionally confirm this observa-
[
38]
tion. The molecular graph from QTAIM analysis of 4 is presented
in Figure 4. The contour line diagram of the Laplacian distribu-
2
tion P ρ(r), bond paths, and selected zero-flux surfaces as well
as isosurface from the reduced density gradient (RDG) analy-
sis of 4 are shown in Figure 5.
Scheme 14.
[
39]
In order to explain similar and stable orientation of the pyr-
idyl fragment relative to the phosphorus atom in 2 and 4, in the respectively, compared to their rotation isomers 2′ and 4′. This
absence of noncovalent interaction we performed a geometry result may be explained simply by Coulomb attraction in one
optimization for the rotation isomers 2′ and 4′ at the B3LYP/6- case (between negatively charged nitrogen and positively
31G(d) level of theory (Scheme 14).
charged phosphorus atoms) and Coulomb repulsion in other
It was found that the optimized geometries of 2′ and 4′ cor- case (between negatively charged nitrogen atoms), the Mul-
respond to energy minima, as indicated by frequency computa- liken charge distribution in complexes 2, 2′, 4, 4′ is shown in
tions. Molecules 2 and 4 are favored by 7.7 and 8.7 kcal/mol Figure S4 (Supporting information).
2
Figure 5. Contour line diagram of the Laplacian distribution P ρ(r), bond paths and selected zero-flux surfaces (left) and RDG isosurface (right) referring to
the absence of any intramolecular noncovalent interactions N···P in 4. Bond critical points (3, –1) are shown in blue, nuclear critical points (3, –3) – in pale
brown, ring critical points (3, +1) – in orange. Length units: Å, RDG isosurface values are given in Hartree.
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We theoretically estimated values of the rotation barriers for acceptor complex 7, since chloro-derivative 2 does not form
the pyridyl and Et N moieties in 4 using the relaxed potential such complex.
2
energy surface scan at the B3LYP/6-31G(d) level of theory.
Based on the obtained equilibrium geometry of 4, we define
appropriate dihedral angles N–C–N–P and C–N–P–N, respec-
tively, to be scanned in the range of 180° by increments of 5°,
assuming that the energy barriers associated with the rotation
by these dihedral angles can be estimated as the difference
between the obtained minimum and maximum values of the
calculated total energies. The values of rotation barriers calcu-
lated by this technique are relatively small and very close to
each other, viz. 13.2 (pyridyl) and 13.0 (Et N) kcal/mol.
2
We performed also a geometry optimization and frequency
calculation at the B3LYP/6-31G(d) level of theory for the struc-
tures A and A′ (Scheme 7). It was shown that A and A′ have
planar abpy-backbones (Figure S5, Supported Information). It
should be noticed, however, that the frequency calculation
found one imaginary frequency for A′. This indicated that we
had not found a minimum but rather a first-order saddle point
on the potential energy surface.
Figure 6. Molecular structure of 7 together with the atomic numbering sys-
tem. Hydrogen atoms and the solvate molecule of THF have been omitted
for clarity. Thermal ellipsoids are drawn at 30 % probability. Selected bond
Interaction of 2 and 4 with Lewis Acids (SiCl and PCl )
4
5
lengths [Å] and angles [°]: Si(1)–N(2) 1.8749(9), Si(1)–N(3) 1.9462(9), Si(1)–Cl(1)
.2384(4), Si(1)–Cl(2) 2.1591(4), Si(1)–Cl(3) 2.1681(4), Si(1)–Cl(4) 2.1816(4),
P(1)–N(5) 1.6409(11), P(1)–N(1) 1.7293(9), P(1)–N(4) 1.7909(10), N(2)–C(6)
.3343(13), N(2)–N(1) 1.4138(12), N(1)–C(1) 1.3643(13), N(5)–C(13) 1.4721(14),
2
Since molecules 2 and 4 contain Lewis-base centers we tried
to elucidate their further coordination activity. Whereas chloro-
substituted triazaphospholene 2 does not react with silicon tet-
rachloride, diethylamino-derivative 4 easily forms adduct 7 by
coordination of two nitrogen atoms to silicon (Scheme 15). It
1
N(5)–C(11) 1.4689(15); Cl(4)–Si(1)–Cl(1) 177.30(2), N(3)–Si(1)–Cl(2) 171.63(3),
N(2)–Si(1)–Cl(3) 173.70(3), Cl(2)–Si(1)–Cl(3) 93.00(2), N(2)–Si(1)–N(3) 79.91(4),
N(5)–P(1)–N(1) 104.02(5), N(5)–P(1)–N(4) 104.06(5), N(1)–P(1)–N(4) 83.17(4),
C(6)–N(2)–N(1) 108.98(8), C(1)–N(1)–N(2) 111.97(8), C(1)–N(1)–P(1) 126.49(7),
N(2)–N(1)–P(1) 117.39(7), C(13)–N(5)–C(11) 117.16(10), C(13)–N(5)–P(1)
should be noticed that cleavage of N–P bonds by SiCl was not
4
observed.
1
15.84(9), C(11)–N(5)–P(1) 125.17(8).
It should be noted also, that coordination of SiCl4 causes
notable redistribution of bond lengths in five-membered ring.
The bonding of phosphorus with the nitrogen atom of the pyr-
idyl fragment is weakened [1.758(2) Å in 4 and 1.791(2) Å in
7] together with weakening of π-character of the C=N bond
[1.298(2) Å in 4 and 1.334(2) Å in 7]. The crystal structure of 7
reveals multiple H···Cl and C···Cl intermolecular short contacts;
Cl···Cl short contacts were not observed in contrast to related
Scheme 15.
[40]
SiCl (phen) molecule.
4
The 31P NMR spectrum of 7 shows a single resonance at δ =
5.0 ppm, high field shifted by ca. 7 ppm as compared to 4.
Since the five-membered ring in 2 has the labile halogen
atom, we tried to fix the aromatic 6π-electron triazaphos-
7
phalene cation by addition of PCl (Scheme 16).
5
A single-crystal X-ray diffraction study of 7 shows SiCl mol-
4
ecule is incorporated into 4 with the formation of the chelate
five-membered heterocycle (Figure 6, Table S1). The hypercoor-
dinate silicon atom appears in a slightly distorted octahedral
environment where two chlorine atoms occupy axial positions
and other two chlorine atoms lie in the equatorial plane to-
gether with nitrogen atoms N(2) and N(3). The Si–Cl bond
lengths are comparable to those of silicon tetrachloride com-
Scheme 16.
[
40,41]
plexes with nitrogen bases.
The silicon atom forms shorter
bond with the nitrogen atom of the five-membered ring [Si(1)–
The experiment showed, however, that redox process took
N(2) 1.8749(9) Å] compared to the Py→Si coordination [Si(1)– place with the formation of tetrahedral phosphorus(V) complex
N(3) 1.9462(9) Å]. It is remarkable, the Et N-group is more 8 and liberation of phosphorus trichloride (Scheme 17).
2
tightly bonded to the phosphorus atom in adduct 7 [1.641(2) Å]
Since compound 8 has the salt-like nature and completely
in comparison with the free ligand 4 [1.656(2) Å]. Obviously, its insoluble in common organic solvents, its NMR spectra were
donor properties play a crucial role in the formation of donor– unavailable. However, mother liquor of the reaction mixture
Eur. J. Inorg. Chem. 0000, 0–0
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6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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bonded to the abpy ligand. The N–P bonds in 8 are shorter by
approximately 0.05 Å in comparison with 2 and by ≈ 0.1 Å in
comparison with diethylamino derivative 4. Other bond lengths
in abpy fragments of 2, 4, and 8 do not notably differ.
Remarkably, the intramolecular N···P contact N(4)–P(1),
2
4
.764 Å, is clearly shorter than the related distances N···P in 2,
and 6 (2.827, 2.912, 2.824 Å respectively) which has a direct
relationship with the charge of the phosphorus atom (Figure
S6, Supporting information). It is known that spyrocyclic tet-
raazophosphonium cations like 8 may be formed by the cyclo-
addition reactions of 1,3,2-diazaphosphalenes with diaza-1,3-
Scheme 17.
contained three single resonances. Two of them we assigned to
[42]
butadienes.
PCl (δ =219.6 ppm) and cationic part of 8 (δ =4.2 ppm). The
3
third signal (–220.7 ppm) may be assigned to the adduct of
PCl with nitrogen base, not to the hexachlorophosphate anion Conclusions
5
[
1]
(
–280 to –310 ppm). Crystals of 8 suitable for X-ray analysis
In the present work we have applied 2,2′-azobispyridine (abpy)
and its reduced form – 2,2′-hydrazobispyridine (hbpy) to the
were grown from the reaction mixture at room temperature.
Cationic part of complex 8 contains the chiral tetrahedral phos-
phorus atom; two pairs of enantiomers cocrystallize in the unit
cell together with dichloromethane as a solvate molecule. Crys-
tal data and some details of the data collection and refinement
are given in Table S1 (Supporting Information); the molecular
structure of 8 is depicted in Figure 7. Both five-membered het-
erocycles in 8 are planar, with the dihedral angle between
planes of 89.0°. The crystal structure of 8 revealed the packing
arrangement with multiple C···H, C···Cl, H···Cl, and Cl···Cl short
contacts.
phosphorus chemistry. It was shown that PCl reduces abpy in
3
dichloromethane or toluene with the formation of the oxidative
addition product (1:1). Application of PCl in the reaction with
3
2
–
hbpy gave (abpy) PCl (2), containing the 1,2,4,3-triazaphos-
phole ring. Dilithium salt of hbpy gave no individual products
in the reaction with PCl , but excellent yield of (abpy) PNEt
2–
3
2
(
4) in the reaction with (Et N) PCl. Diethylamido-group in 4 may
2 2
be easily substituted by Cl or Br atoms in the reaction of 4 with
PCl or PBr respectively. SiCl and compound 4 in the mixture
3
3
4
(
1:1) do not demonstrate exchange between the Et N group
2
and the Cl atom, but form complex 7 with coordination of sili-
con by pyridyl- and azo-functions. The donor Et N group plays
2
a crucial role in this coordination since Cl-derivative (2) does
not form complex with SiCl . We have found that compound 2
4
reacts with PCl with liberation of PCl and the formation of
5
3
2
–
+
–
spirocyclic ate complex [(abpy) P] PCl . Structural analysis re-
2
6
veals short distances between pyridyl nitrogen and the phos-
phorus atom in all structurally characterized compounds which
may be explained by Coulomb attraction since the QTAIM anal-
ysis demonstrated no appropriate bond critical points (3, –1)
for the intramolecular noncovalent interactions N···P in 2, 4,
and 6. Rotation barriers for the pyridyl and Et N groups in 4
2
were theoretically estimated to be very close to each other [13.2
(
pyridyl) and 13.0 (Et N) kcal/mol].
2
Experimental Section
General Procedures: All preparations were performed by using
standard Schlenk techniques under dry, oxygen-free dinitrogen or
argon. Solvents were distilled from appropriate drying agents im-
[
43]
mediately prior to use:
diethyl ether and THF were dried and
distilled from Na/benzophenone, pyridine was distilled from KOH
Figure 7. Molecular structure of 8 together with the atomic numbering sys-
and kept over CaH , toluene and hexane were thoroughly dried and
2
–
tem. Hydrogen atoms, the anion PCl
6
and the solvate molecule of CH
2
Cl
2
distilled from sodium prior to use. Bis(N,N-diethylamino)chlorophos-
have been omitted for clarity. Thermal ellipsoids are drawn at 30 % probabil-
ity. Selected bond lengths [Å] and angles [°]: P(1)–N(2) 1.641(2), P(1)–N(3)
phine, 2-aminopyridine, PCl , PBr , and silicon tetrachloride were
3
3
purchased from Sigma–Aldrich Chemical Co. and distilled before
1
1
1
.648(2), N(1)–N(2) 1.404(2), N(1)–C(1) 1.303(2), N(3)–C(1) 1.409(2), N(2)–C(6)
.413(2); N(2A)–P(1)–N(2) 125.14(11), N(2)–P(1)–N(3) 90.03(7), N(2)–P(1)–N(3A)
20.17(7), N(3A)–P(1)–N(3) 113.80(11).
[
44]
use. For the synthesis of known compounds (2,2′-azobispyridine
[
45]
and 2,2′-hydrazobispyridine ) we used modified methods de-
scribed below.
Comparison of 8 with other abpy-containing species was in- NMR spectra were recorded on a Bruker DPX-200 and AV-400 spec-
structive: the tetrahedral phosphorus(V) atom is more tightly trometers. IR spectra were recorded with a Perkin–Elmer 577 spec-
Eur. J. Inorg. Chem. 0000, 0–0
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7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
trometer from 4000 to 400 cm–1 in Nujol or with a Perkin–Elmer FT-
IR Spectrometer System 2000 as KBr discs.
Abpy-PCl3 Adduct (1): A solution of PCl3 (0.93 g, 6.77 mmol) in
10 mL of toluene or CH Cl2 was added to a solution of 2,2′-azo-
2
bispyridine (0.50 g, 2.71 mmol) in 10 mL of the same solvent. The
mixture was kept overnight at room temperature, then solvent was
X-ray Crystallography: The X-ray diffraction data were collected
on a SMART APEX (for 8) and a Bruker D8 Quest (for 2, 4, 6 and 7)
removed in vacuo together with the rest of PCl . The product losses
3
diffractometers (Mo-K radiation, ω-scan technique, λ = 0.71073 Å).
α
solubility after solvent removal and may be washed with pure THF
or CH Cl . The precipitate was filtered off and dried in vacuo. Yield:
[46]
The intensity data were integrated by SAINT.
All structures were
2
2
solved by direct methods using a dual-space algorithm with the
1.51 g (94 %). IR (Nujol): ν˜ = 1642 (m), 1608 (m), 1554 (w), 1528 (w),
1285 (m), 1227 (w), 1163 (m), 1107 (w), 1027 (w), 992 (m), 934 (w),
854 (m), 771 (s), 738 (w), 677 (w), 619 (w), 545 (m), 516 (m).
[
47]
SHELXT program.
Refinement of the structures was carried out
2
[48,49]
on F
using SHELXTL package.
All non-hydrogen atoms were
hkl
refined anisotropically. Hydrogen atoms were placed in calculated
positions and were refined in the riding model with the exception
of those located at the solvate dichloromethane molecule in 8 from
a difference Fourier synthesis of electron density and refined iso-
tropically SADABS[ was used to perform area-detector scaling and
absorption corrections. Crystal of 7 contains the solvate molecule
of THF. The main crystallographic data and structure refinement
details for 2, 4, 6, 7 and 8 are presented in Table S1.
C H Cl N P (319.96): calcld. C, 37.35; H, 2.51; Cl, 33.08; P, 9.63;
10
8
3 4
found C 37.40; H, 2.47; Cl, 32.95; P, 9.56.
Dilithium Salt of hbpy (3): A solution of MeLi in diethyl ether
50]
(0.85
M, 1.89 mL, 1.60 mmol) was added to a solution of 2,2′-hy-
drazobispyridine (0.15 g, 0.80 mmol) in 10 mL of THF at – 70 °C.
The mixture immediately turns deep-red. Formation of gas – CH –
4
was detected. Prepared dilithium salt of hbpy (3) was used in situ.
CCDC 1826171 (for 2), 1826172 (for 4), 1826173 (for 6), 1826174
N,N-Diethyl-2-(pyridin-2-yl)-[1,2,4,3]triazaphospholo[4,5-a]pyr-
idin-3(3H)-amine (4): A solution of (Et N) PCl (0.34 g, 1.60 mmol)
in 3.0 mL of THF was added to the solution of 3 (0.80 mmol) in THF
at – 70 °C. The reaction mixture was kept at room temperature
overnight. THF was replaced by toluene. The precipitate of LiCl was
filtered off and toluene was replaced by hexane. The solution was
concentrated; pale-yellow crystals were separated from the mother
(for 7), and 1826175 (for 8) contain the supplementary crystallo-
2
2
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre.
Details of QTAIM Analysis: The single point calculations based on
the experimental X-ray geometries have been carried out at the
DFT level of theory using the M06-2X functional[51] (this functional
was parameterized for main group elements and specifically devel- liquor, washed with hexane and dried in vacuo. Yield: 0.20 g, 89 %.
1
oped to describe weak dispersion forces and noncovalent interac-
tions) with the help of Gaussian-09 (see General information in SI)
program package. The standard 6-311++G(d,p) basis sets were used
H NMR (C D , 300 K): δ = 8.20 (ddd, J = 4.9, 1.8, 0.8 Hz, 1 H), 7.78
6 6
(d, J = 8.4 Hz, 1 H), 7.24–7.19 (m, 1 H), 6.78 (ddt, J = 7.2, 5.0, 1.2 Hz,
1 H), 6.58 (dd, J = 9.5, 1.1 Hz, 1 H), 6.4 (ddd, 7.2, 4.9, 1.0 Hz, 1 H),
for all atoms. The topological analysis of the electron density distri- 6.18 (ddt, J = 9.5, 6.1, 1.1 Hz, 1 H), 5.34 (ddd, J = 7.1, 6.3, 1.1 Hz, 1
bution with the help of the atoms in molecules (QTAIM) method
H), 2.84 (m, 4 H,CH CH ), 0.78 ppm (t, J = 7.1 Hz, 6 H,CH CH ) ppm.
2
3
2
3
[
52]
13
developed by Bader
has been performed by using the Multiwfn
C NMR (C D , 50 MHz): δ = 157.63 (d, J = 11.0 Hz), 147.65 (d, J =
The Cartesian atomic coordinates of 8.0 Hz), 147.25 (s), 137.48 (s), 132.02 (s), 131.58 (s), 130.42 (d, J =
6 6
program (version 3.3.8)[
53]
model species are presented in Table S2 (Supporting Information).
1.9 Hz), 115.51–114.73 (m), 109.38 (d, J = 1.2 Hz), 105.49 (d, J =
3
1
7.7 Hz), 40.43 (d, J = 18.3 Hz), 14.16 (d, J = 3.0 Hz) ppm. P NMR
Synthesis
(
C D , 81 MHz): δ = 82.9 ppm. IR (Nujol): ν = 1634 (s), 1604 (m),
6
6
˜
2
0
(
1
,2′-Azobispyridine (abpy): A solution of 2-aminopyridine (4.70 g,
.05 mol) in 100 mL of toluene was added to a manganese(IV) oxide
30.43 g, 0.35 mol). The reaction mixture was stirred for 10 days at
15 °C. The solution was filtered and the solvent was removed un-
1591 (s), 1555 (s), 1525 (m), 1434 (s), 1400 (w), 1345 (s), 1303 (s),
1203 (m), 1175 (m), 1159 (w), 1141 (m), 1059 (m), 1045 (s), 1015 (s),
995 (w), 982 (w), 970 (m), 930 (m), 918 (w), 852 (m), 787 (m), 764
(m), 748 (m), 730 (w), 713 (w), 676 (s), 659 (m), 542 (m), 514 (w).
C H N P (287.30): calcld. C, 58.53; H, 6.31; P, 10.78; found C 58.58;
der vacuum, leaving a deep-red solid. The residual starting 2-amino-
pyridine was removed from the crude product by sublimation at
14 18 5
H, 6.27; P, 10.82.
5
7 °C/0.05 Torr. The reddish-brown product was recrystallized from
1
3-Chloro-2-(pyridin-2-yl)-2,3-dihydro-[1,2,4,3]triazaphos-
toluene and dried in vacuo. Yield: 1.95 g, 40 %. H NMR (CDCl3,
00 K): δ = 8.79 (br. s, 2 H), 8.13–7.87 (m, 4 H), 7.57–7.39 (m, 2 H)
pholo[4,5-a]pyridine (2): 1) An excess of PCl (0.66 g, 4.83 mmol)
3
3
–
1
was added to a solution of 4 (0.23 g, 0.80 mmol) in 20 mL of Et O;
ppm. IR (Nujol): ν = 1578 cm (m), 1423 (m), 1263 (w), 1144 (w),
1
MS: m/z (%) = 184.3 (20) [M] , 156.1 (100) [M – N ] . C H N (184.2):
2
˜
–
1
a yellow crystalline precipitate was formed immediately. The solu-
tion was concentrated; crystals were separated from the mother
liquor, washed with diethyl ether and dried in vacuo. Yield: 0.19 g,
097 (w), 990 (m), 796 (s), 737 (s), 625 (m), 559 (m), 522 (m) cm .
+
+
2
10 8 4
calcd. C 65.21; H, 4.38; found C 65.12; H, 4.43 %.
9
5 %. 31P NMR (Pyridine, 81 MHz, 243 K): δ = 115.0 ppm. IR (Nujol):
2,2′-Hydrazobispyridine (hbpy): Hydrazine hydrate (13.5 g,
ν˜ = 1639 (m), 1612 (w), 1592 (m), 1568 (w), 1543 (w), 1527 (w), 1446
0
.27 mol) was added to a solution of abpy (0.50 g, 2.71 mmol) in
(
(
(
s), 1340 (w), 1291 (s), 1259 (w), 1213 (w), 1160 (w), 1146 (w), 1075
w), 1048 (w), 1033 (wide w), 990 (w), 855 (m), 833 (w), 789 (s), 749
s), 739 (s), 699 (w), 681 (m), 620 (w), 520 (m). C H ClN P (250.62):
1
0 mL of ethanol. The mixture was stirred at 30 °C for 24 h in
open flask before crystalline product started to form. The reaction
mixture was concentrated up to 3 mL; pale-yellow crystals were
separated from the mother liquor, washed with EtOH and dried in
10
8
4
calcld: C, 47.92; H, 3.22; Cl, 14.15; N, 22.35; P, 12.36; found C 47.89;
H, 3.26; Cl, 14.11; P, 12.32.
1
vacuo. Yield: 0.32 g, 63.4 %. H NMR ([D ]THF, 300 K): δ = 6.18 [d,
8
3
3
J(H,H) = 4.8 Hz, 2 H], 5.84 (br. s, 2 H, NH), 5.56 (t, J = 7.8 Hz, 2
H), 4.6–4.9 (m, 4 H) ppm. C NMR ([D ]THF, 50 MHz): δ = 159.3 (s),
2) Phosphorus trichloride (0.33 g, 2.4 mmol) was added to the mix-
H,H
1
3
ture of Et N (0.16 g, 1.61 mmol) and hbpy (0.15 g, 0.8 mmol) in
8
3
–
1
1
46.1 (s), 135.2 (s), 112.3 (s), 103.6 (s) ppm. IR (Nujol): ν˜ = 3206 cm
100 mL of THF. The plentiful precipitate was formed immediately.
(
s), 3155 (s), 3063 (s), 1593 (vs), 1452 (vs), 1432 (vs), 1309 (s), 1279 The precipitate [mixture of 2 and Et N(HCl)] was filtered off and
3
(
m), 1252 (m), 1147 (s), 991 (s), 772 (vs), 732 (vs), 625 (w), 597 wide
extracted with hot THF. Solubility of 2 in hot THF is slightly better
–1
(w), 510 (m) cm . C H N (186.21): calcd. C 64.50; H, 5.41; found than of Et N(HCl) that allowed to separate 2 from the united mother
10
10
4
3
C 64.46; H, 5.45 %.
liquors in 25 % yield (0.49 g).
Eur. J. Inorg. Chem. 0000, 0–0
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8
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Full Paper
3
-Bromo-2-(pyridin-2-yl)-2,3-dihydro-[1,2,4,3]triazaphos-
[8] D. J. Pascoe, K. B. Ling, S. L. Cockroft, J. Am. Chem. Soc. 2017, 139, 15160–
1
5167.
pholo[4,5-a]pyridine (6): An excess of PBr3 (0.56 g, 2.08 mmol)
was added to the solution of 4 (0.1 g, 0.35 mmol) in 20 mL of
Et O; a yellow crystalline precipitate was formed immediately. The
[
9] H. Wang, W. Wang, Wei J. Jin, Chem. Rev. 2016, 116, 5072–5104.
[
[
10] T. Clark, Faraday Discuss. 2017, 203, 9–27.
11] M. Yamamura, N. Kano, T. Kawashima, J. Am. Chem. Soc. 2005, 127,
2
solution was concentrated; precipitate was separated from the
mother liquor, washed with diethyl ether and dried in vacuo. Yield:
1
1954–11955.
[
12] A. N. Kornev, V. E. Galperin, Y. S. Panova, A. V. Arapova, E. V. Baranov,
G. K. Fukin, G. A. Abakumov, Z. Anorg. Allg. Chem. 2017, 643, 1208–1214.
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15] M. Bardají, M. Barrio, P. Espine, Dalton Trans. 2011, 40, 2570–2577.
0
.08 g, 79 %. 31P NMR (CH Cl , 81 MHz, 243 K): δ = 135.5 ppm (br).
2 2
IR (Nujol): ν˜ = 1637 (m), 1614 (very w), 1592 (m), 1568 (w), 1539
[
[
[
(
(
(
w), 1525 (w), 1444 (s), 1339 (w), 1304 (w), 1290 (s), 1263 (w), 1210
w), 1159 (w), 1144 (w), 1077 (w), 1049 (m), 991 (w), 855 (m), 834
vw), 788 (s), 751 (s), 743 (s), 700 (w), 683 (m), 621 (w), 518 (m).
[16] M. Camalli, F. Caruso, G. Mattogno, E. Rivarola, Inorg. Chim. Acta 1990,
170, 225–231.
C H BrN P (295.08): calcd. C 40.70; H, 2.73; Br, 27.08; P, 10.50 %;
10
8
4
C, 40.67; H, 2.76; Br, 27.03; P, 10.44 %.
[17] H. Tsurugi, H. Tanahashi, H. Nishiyama, W. Fegler, T. Saito, A. Sauer, J.
Okuda, K. Mashima, J. Am. Chem. Soc. 2013, 135, 5986–5989.
Complex of 4 with SiCl (7): SiCl (0.5 g, 2.94 mmol) was added to
4
4
[
18] A. Das, T. M. Scherer, S. M. Mobin, W. Kaim, G. K. Lahiri, Chem. Eur. J.
012, 18, 11007–11018.
19] K. Pramanik, M. Shivakumar, P. Ghosh, A. Chakravorty, Inorg. Chem. 2000,
9, 195–199.
the solution of 4 (0.11 g, 0.38 mmol) in 10 mL of THF. The mixture
was left at room temperature overnight. The solution was concen-
trated, orange crystals were filtered, washed with THF and dried in
2
[
3
3
1
vacuo. Yield: 0.12 g, 68.6 %. P NMR (THF, 81 MHz, 243 K): δ =
[20] S. Sengupta, I. Chakraborty, A. Chakravorty, Eur. J. Inorg. Chem. 2003,
1157–1160.
[21] A. N. Kornev, V. V. Sushev, Y. S. Panova, N. V. Zolotareva, E. V. Baranov,
G. K. Fukin, G. A. Abakumov, Eur. J. Inorg. Chem. 2015, 2057–2066.
7
5.1 ppm. IR (Nujol): ν˜ = 1631 (s), 1617 (s), 1566 (w), 1508 (s), 1352
(
(
m), 1306 (w), 1267 (w), 1204 (w), 1160 (m), 1131 (w), 1092 (w), 1036
w), 1017 (s), 1001 (w), 947 (w), 892 (m), 788 (w), 767 (s), 757 (s),
[
22] A. N. Kornev, N. V. Zolotareva, V. V. Sushev, A. V. Cherkasov, G. A. Aba-
kumov, Mendeleev Commun. 2015, 25, 236–238.
7
34 (m), 687 (w), 669 (w), 659 (w), 601 (w), 544 (w), 472 (vs), 456
(
vs). Chemical Formula: C18H26Cl N OPSi (529.30): calcd. C 40.84;
4
5
[
[
23] A. N. Kornev, Phosphorus Sulfur Silicon Relat. Elem. 2016, 191, 1497–1500.
24] A. N. Kornev, V. V. Sushev, Y. S. Panova, O. V. Lukoyanova, S. Yu. Ketkov,
E. V. Baranov, G. K. Fukin, M. A. Lopatin, Y. G. Budnikova, G. A. Abakumov,
Inorg. Chem. 2014, 53, 3243–3252.
H, 4.95; Cl, 26.79; found C 40.80; H, 5.02; Cl, 26.83 %.
(
R)-2,2′-Di(pyridin-2-yl)-2H,2′H-3,3′-spirobi[[1,2,4,3]triazaphos-
pholo[4,5-a]pyridin]-3-ium Hexachlorophosphate (8): A solution
of PCl5 (0.09 g, 0.46 mmol) in CH Cl (10 mL) was added to the
[25] A. Schmidpeter, Y. Tautz, F. Schreiber, Z. Anorg. Allg. Chem. 1981, 475,
2
2
suspension of 2 (0.13 g, 0.52 mmol) in 5 mL of the same solvent.
The mixture was left at room temperature overnight. The solution
was decanted and concentrated. Yellow crystals were filtered,
211–231.
[
[
[
26] A. Schmidpeter, J. H. Weinmaier, Angew. Chem. Int. Ed. Engl. 1977, 16,
65–866; Angew. Chem. 1977, 89, 903.
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Anorg. Allg. Chem. 2011, 637, 988–994.
8
washed with CH Cl2 and dried in vacuo. Yield: 0.06 g, 34.6 %. IR
2
(Nujol): ν˜ = 1643 (m), 1620 (w), 1599 (m), 1571 (w), 1553 (m), 1530
(w), 1449 (s), 1339 (w), 1305 (w), 1290 (m), 1255 (w), 1182 (m), 1171
(w), 1148 (w), 1132 (w), 1101 (w), 1058 (w), 994 (very w), 852 (m),
[
[
29] Z. Fei, P. J. Dyson, Coord. Chem. Rev. 2005, 249, 2056–2074.
30] Z. Benkő, S. Burck, D. Gudat, M. Nieger, L. Nyulászi, N. Shorea, Dalton
Trans. 2008, 4937–4945.
8
07 (w), 773 (m), 749 (m), 738 (m), 679 (w), 563 (w), 491 (w), 481
(
w), 445 (s). C H Cl N P (727.97): calcd. C 34.65; H, 2.49; Cl, 38.96;
21
18
8 8 2
P, 8.51; found C 34.60; H, 2.53; Cl, 30.00; P, 8.46 %.
[31] S. Burck, D. Gudat, F. Lissner, K. Nättinen, M. Nieger, T. Schleid, Z. Anorg.
Allg. Chem. 2005, 631, 2738–2745.
[
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The work was performed using the instrumental base of the
Analytical Center of the G. A. Razuvaev Institute of Organome-
tallic Chemistry, Russian Academy of Sciences and supported
by the Russian Science Foundation (grant no. 14-13-01015-P).
Alexander S. Novikov is grateful to Russian Foundation for Basic
Research for support (project No. 16-33-60063).
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P–N Adducts
Y. S. Panova, A. V. Sheyanova,
N. V. Zolotareva, V. V. Sushev,
A. V. Arapova, A. S. Novikov,
E. V. Baranov, G. K. Fukin,
A. N. Kornev* .................................... 1–11
2,2′-Azobispyridine in Phosphorus
Coordination Chemistry: A New Ap-
proach to 1,2,4,3-Triazaphosphole
Derivatives
Like transition metals phosphorus may change its valency by reactions of
exist in different oxidation states in oxidative addition and oxidative elimi-
2
,2′-azobispyridine surrounding and nation
DOI: 10.1002/ejic.201800831
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim