Dynamic covalent chemistry approach toward 18-Membered P4N2macrocycles and their nickel(II) complexes

Article abstract of DOI:10.1021/acs.joc.0c01317

A dynamic covalent chemistry approach was used for the stereoselective synthesis of 1,10-diaza-3,8,12,17- tetraphosphacyclooctadecanes via condensation reaction of 1,4- bis(organylphosphino)butane, formaldehyde, and primary amines. The obtained 18-membered P4N2 macrocycles were isolated in pure form as meso- (RPSPSPRP) or rac- (RPRPRPRP/SPSPSPSP) isomers. The structural features of the individual stereoisomers were revealed by NMR spectroscopy and X-ray structure analysis. All P4N2 macrocycles form square-planar nickel(II) complexes with the RPSPSPRP isomer only, in which the orientation of the lone pairs of electrons at phosphorus favors this coordination mode, independent of the initial configuration of the ligand, indicating the ability of the 18-membered P4N2 macrocycles to stereoisomerize in the course of the complexation.

Full text of DOI:10.1021/acs.joc.0c01317

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Article
Dynamic covalent chemistry approach toward 18-
4
2
membered PN macrocycles and their nickel(II) complexes
Elvira I. Musina, Tatiana I. Wittmann, Lenar Musin, Anna S. Balueva, Alena S. Shpagina, Igor
A. Litvinov, Peter Lönnecke, Evamarie Hey-Hawkins, Andrey A. Karasik, and Oleg G. Sinyashin
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.0c01317 • Publication Date (Web): 23 Sep 2020
Downloaded from pubs.acs.org on September 25, 2020
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Dynamic covalent chemistry approach toward 18-membered P4N2 macrocycles and
their nickel(II) complexes
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Elvira I. Musina,a* Tatiana I. Wittmann,a Lenar I. Musin,a Anna S. Balueva,a Alena S.
Shpagina,a Igor A. Litvinov,a Peter Lӧnnecke,b Evamarie Hey-Hawkins,b Andrey A.
Karasik,a Oleg G. Sinyashina
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aA. E. Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center
of the Russian Academy of Sciences, 420088 Kazan, Russian Federation. Fax: +7 843
273 9365; e-mail: elli@iopc.ru
b Faculty of Chemistry and Mineralogy, Institute of Inorganic Chemistry, Leipzig
University, Leipzig, Germany
Abstract. A dynamic covalent chemistry approach was used for the
stereoselective synthesis of 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecanes via
condensation reaction of 1,4-bis(organylphosphino)butane, formaldehyde and primary
amines. The obtained 18-membered P4N2 macrocycles were isolated in pure form as
meso- (RPSPSPRP) or rac- (RPRPRPRP/SPSPSPSP) isomers. The structural features of the
individual stereoisomers were revealed by NMR spectroscopy and X-ray structure
analysis. All P4N2 macrocycles form square-planar nickel(II) complexes with the
RPSPSPRP isomer only, in which the orientation of the lone pairs of electrons at
phosphorus favors this coordination mode, independent of the initial configuration of the
ligand, indicating the ability of the 18-membered P4N2 macrocycles to stereoisomerise in
the course of the complexation.
Introduction
Macroheterocyclic compounds are of particular interest due to their ability to isolate,
separate and transfer different ions. Thus, they are able to increase the solubility of
inorganic salts in organic solvents and activate the anion. These properties are the reason
for their application as highly selective receptors, molecular containers and reactors, as
well as catalytic systems,1-5 and their use in organic and inorganic synthesis, biochemistry
and biophysics, medicine, polymer chemistry, etc.1 The introduction of heteroatoms
(oxygen, nitrogen, sulfur) into the macrocyclic skeleton limits the conformational
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freedom and organizes the donor atoms for specific metal binding via coordination
bonds. The selective binding of macroheterocycles to specific metals depends on the
nature, position and number of heteroatoms in the ring, the ring size, as well as on the
presence of functional groups in the ring and in its periphery. Transition metal complexes
of macroheterocycles are of particular interest due to their potential catalytic and
biochemical activity. Unlike the most common macroheterocycles with hard O- and N-
donor atoms, P-containing macrocycles are able to bind soft cations,6 in particular late
transition metals. Despite the high potential of macrocyclic oligophosphines, their use in
coordination and supramolecular chemistry or catalysis is quite limited, due to their
challenging synthesis and the formation of mixtures of stereoisomers. Numerous
synthetic methodologies have been developed for the rational design of macrocyclic
phosphines, such as high dilution or template synthesis and – as a relatively novel
approach – the covalent self-assembly of macrocycle in dynamic covalent chemistry
(DCvC).7 The covalent self-assembly includes the formation of complicate structures
through the generation of dynamic system of molecular entities that able assemble and
disassemble due to the reversibility dynamic covalent bonds to give the more
termodynamically preferred product.8-14 Last approach has principally features in
comparison of classic synthetic organic chemistry. Most covalent chemistry is
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irreversible and so occurs under kinetic control while most dynamic covalent chemistry is
8-14
reversible and so occurs under thermodynamic control.
The covalent self-assembly
proceed at common concentrations of reagents and not required the high dilution or
template agents. The slow kinetic of dynamic covalent bond formation usually requires a
catalyst to help the system to equilibrate to the thermodynamically stable product on a
reasonable time scale.8-14 The most prominent example and most extensively used
dynamic, reversible covalent bond formation since the inception of DCvC is the C–N
bond in imines through condensation reaction of an aldehyde with an amine. Dynamic
imines have been applied in a remarkable variety of applications, including formation of
complex molecular architectures, self‐sorting systems, switches and molecular motors.15
A similar approach has been used for the synthesis of 22-membered P2N4 macrocycles
containing four imine and two phosphine groups 16, 17 and of 14- and 15-membered P2N2
macrocycles with two imine and two phosphine groups,18,19 where the phosphine groups
were included in the starting material and not involved in new bond formation. The
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synthesis of phosphorus macrocycles by self-assembly involving dynamic P-C bond
formation is quite rare, although many reactions in phosphorus chemistry can be
attributed to DCvC. For example, the condensation reaction of isophthaloyl chloride and
methyl-bis(trimethylsilyl)phosphane under mild conditions affords (1,10-dimethyl-1,10-
diphospha-[3.3]-metacyclophane-2,9,11,18-tetraone in high yield.20 Formation of a
tetraphosphonium macrocycle was observed in the tetramerization of 3-
(diphenylphosphino)propanal under acidic conditions.21 Our previous works clearly
demonstrates that the Mannich-like condensation reaction of primary phosphines or
secondary bis-phosphines, formaldehyde and primary or secondary amines and bis-
amines can be employed for the selective synthesis of a wide range of macrocyclic
aminomethylphosphines, namely [P2N2]2-cyclophanes, [P2N4]-cyclophanes, [P4N2]-
cryptand and [P4N2]-corands.22-29 Their synthesis, which is accompanied by reversible P-
C and C-N bond formation, proceeds with a remarkable stereoselectivity. Thus, in
accordance with the main principles of DCvC (reversibility, thermodynamic control,
interconversion of molecular components of dynamic system) in the covalent self-
assembly of [P4N2]-corands only one isomer with a preferred configuration of the four
endocyclic phosphorus atoms is isolated from the dynamic system containing five
possible stereoisomers of [P4N2]-сorands (Fig.1) and [P2N]-corands as products of [1+1]
condensations as well as cyclic and acyclic oligomers
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R
N
R
R
N
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R
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N
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N
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R
P
P
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n
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P
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n
P
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R'
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R
R
RSSR
SRSR
RRRR/SSSS
RRSS
RSSS/SRRR
rac-II
meso-I
meso-II
meso-III
rac-I
Figure 1. Five possible diastereomers of P4N2-macrocycles.
Thus, the 16- and 20- membered macrocycles (where n = 3 and 5 correspondingly) were
always isolated as the meso-I (RPSPSPRP) isomers22-24, but their 14-membered and one 18-
membered homologues (where n = 2 and 4 correspondingly)
were rac-I -
RPRPRPRP/SPSPSPSP isomers.22,25-28 Based on these observations, an empirical rule for
predicting the configuration of the preferred [P4N2]-macrocycle on the number of
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methylene fragments (even or odd) in the initial bis-phosphine was deduced.27
Unexpectedly, the meso-I isomer of 14-membered P4N2 macrocycles was recently
obtained from the reaction mixture of 1,2-bis(phenylphosphino)ethane, formaldehyde and
primary amine when a different work-up procedure of the reaction mixture was
employed, namely crystallization from diethyl ether or ethanol instead of crystallization
from DMF.28 Furthermore, an 18-membered P4N2 macrocycle was obtained as meso-I
isomer from the condensation reaction of 1,4-bis[hydroxymethyl(pyridine-2-
yl)phosphino]butane and 4-methylbenzylamine.29 These compounds were the first
exceptions for the abovementioned rule. The behavior of [P4N2]-corands in solutions
appears to be more complex than expected due to the lability of the P-CH2-N fragment.
Thus, the interconversion of isomers for 16-membered P4N2 macrocycles and splitting of
14-membered P4N2 macrocycles into two 7-membered P2N macrocycles have been
found.22-28 It turned out that many external factors, in particular temperature, solvent,
presence of protons or metal ions, influence these processes.
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In order to explore the scope of the covalent self-assembly approach to P4N2 macrocycles
design and “even/odd” rule in particulary as well as to study the behavior of P4N2
macrocycles in solution especially during complex formation, we here report the DCvC
of 18-membered P4N2 macrocycles and their nickel(II) complexes. We expect that on
complexation the most stable complex will be formed and, therefore, the best “fitting”
stereoisomer will be selected from the dynamic system.
Results and Discussion
The reaction of 1,4-bis[(hydroxymethyl)(R)phosphino]butane (R = Ph, 2-Py, 4-
methylpyridine-2-yl) obtained in situ from 1,4-bis[(R)phosphino]butane (R = Ph, 2-Py, 4-
methylpyridine-2-yl) and paraformaldehyde as diastereoisomeric mixtures (rac and meso
isomers), with primary alkyl- or benzyl-substituted amines in DMF at 80 °C gave 18-
membered 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecanes 1–6 (Scheme 1).
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OH
*
P
*
P
R
3
4
5
H
P
*
2 CH2O
P
R'NH2
R
*
R
*
P
P
H
R
*
R
N R'
R'
N
6
7
meso/rac
meso/rac
*
HO
P
*
R
P
R
1 6

8
9
1
2
( )
R = Ph, R' = i-Pr
R = Ph, R' = Pr
( )
rac-I
rac-I
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3
R = Ph, R' = Cy
R = Ph, R' = t-Bu
R = Py, R' = p-TolCH2
( )
rac-I
meso-I
) meso-I
[O]
5
for
4
( )
5, 5-O
O
(
*
*
R
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H3C
,
P
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O
N
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R'
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( ) mixture of isomers
R' = (R)-CH(CH3)Ph
O
R
*
P
O
5-O
Scheme 1. Synthesis of 18-membered P4N2 macrocycles 1–6.
31
Monitoring of the reaction mixtures by P{1H} NMR spectroscopy indicated that the
reactions proceed via the formation of a large number of intermediates and only at the
end the main macrocyclic product is formed. It indicates the reversibility of P-C and C-N
bonds formation and interconversion of all components of dynamic system and self-
correction of reaction which characterize the covalent self-assembly of macrocycle
according to DCvC principles. In the final reaction mixtures, several intensive signals in
the range of -30 to - 40 ppm were observed which are typical for macrocyclic
aminomethylphosphines.23-29 The intensity of the signals of by-products (acyclic
aminomethylphosphines or possible 9-membered cycles as products of [1+1]
cyclocondensation reactions in the range of -24 to -28 ppm) was noticeably lower than
that of macrocyclic product indicating that the formation of 18-membered macrocycles is
more favorable in comparison with other possible products of condensation reaction.
The macrocycles 1–5 crystallized from the concentrated reaction mixtures at 0 °C to -
10 °C in moderate or good yields of 31 to 61%, whereas all attempts to crystallize the
individual product 6 were unsuccessful. The isolated compounds 1–5 are air-stable in the
solid state and readily soluble in chloroform, dichloromethane and benzene. The
elemental analysis, mass spectra and NMR spectroscopy confirmed the structures of
macrocycles 1–5. The presence of only one narrow signal at -31.7 to -37.7 ppm in the
31P{1H} NMR spectra indicated that only one symmetric diastereoisomer of five possible
isomers was crystallized. On the contrary, the P{1H} NMR spectrum of the viscous oil
31
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of 6 showed a very large number of signals between -29 and -32 ppm indicating the
presence of probably all possible stereoisomers. The 1H NMR spectra of compounds 1–5
are similar to those of the previously reported 14- and 16-membered macrocycles.22-27
The protons of the P-(CH2)4-P fragment give two or three multiplets in the range of 1.5 to
1.9 and 1.9 to 2.3 ppm. The methylene protons of the -PCH2N- fragments of 1–3 are
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observed as two multiplets (doublets or doublets of doublets) at 2.55 to 2.70 ppm (2JHH
=
2
12.4 to 13.2 Hz, JРH = 10 to 17.2 Hz) and 3.47 to 3.63 ppm (2JHH = 12.4 to 13.2 Hz,
2JРH = 0 to 6.8 Hz). The similar patterns indicate analogous structures of these fragments;
thus, the isolated macrocycles 1–3 are probably the same diastereomer. In the case of
compounds 4 and 5, the corresponding signals of the butylene fragment are also observed
as two multiplets, but the doublet or doublet of doublets of the -PCH2N- fragments
undergo a noticeable low-field shift up to 3.30 to 3.33 ppm. The coupling constants also
differ from those of 1–3 (Table 1), indicating a different geometry of the P-CH2-N
fragments and thus another diastereoisomer of these 18-membered macrocycles.
Table 1. Yields and selected NMR spectroscopic data of the macrocycles 1–5.
Compound
R
R’
Yield δP, ppm
P-CHA-N, δH
P-CHB-N, δH
[ppm], (2JHH,
2JPH in Hz)
2
%
[ppm], (2JHH, JPH
in Hz)
1
2
3
4
5
Ph
Ph
Ph
Ph
Py
Pri
38
33
39
35
61
-36.2
-37.7
-35.8
-36.2
-31.7
2.55 (13.2; 16.0)
2.69 (12.6; 10.0)
2.70 (12.4; 17.2)
3.30 (14.2; 0)
3.33 (13.0; 7.1)
3.47 (13.2; 0)
3.65 (12.6; 0)
3.53 (12.4; 6.8)
3.74 (14.2; 4.0)
4.00 (13.0; 2.0)
Pr
Сy
But
-CH2Tol-p
These assumptions were confirmed by X-ray structure analysis of macrocycles 1, 3 and 4.
As predicted by the even/odd rule,27 macrocycles 1 and 3 are the RPRPRPRP/SPSPSPSP
isomers of the corresponding 1,10-diaza-3,8,12,17-tetraphosphacyclooctadecanes (Fig.
2).
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a)
b)
Fig. 2. Molecular structures of macrocycles 1 (a) and 3 (b). Only one of the two isomers
(RPRPRPRP/SPSPSPSP), namely the RPRPRPRP isomer, is shown. Hydrogen atoms are
omitted for clarity. Molecule 1 on a special position on axe 2. Displacement ellipsoids are
drawn at the 50% probability level.
The substituents on phosphorus atoms are in equatorial position and the lone pair of
electrons at the phosphorus atoms have an anti-anti-anti orientation. The butylene
fragments including phosphorus atoms have zig-zag conformation so that the phosphorus
atoms are trans-oriented. Zig-zag like alkylene chains appear to be a common feature of
14-, 16-, 18- and 20-membered macrocyclic aminomethylphosphines. A zig-zag
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conformation provides the minimal number of eclipsed conformations of the CH2
fragments, which is probably the main reason for the predominance of the larger
macrocycles compared to smaller rings. The P-CH2-N-CH2-P fragments are twisted and
substituents at nitrogen atoms are in axial positions and syn-oriented. The lone pair of
electrons at the nitrogen atoms are directed towards the cavity of the macrocycle. The
overall structure of the macrocycles in 1 and 3 is similar to that of the RPRPRPRP/SPSPSPSP
isomers of 14-membered 1,8-diaza-3,6,10,13-tetraphosphacyclotetradecanes and differs
mainly in the longer hydrocarbon bridge which is also reflected in a larger P⋯P distance
(6.954 to 6.994 Å for 18- and 4.477 Å for 14-membered macrocycles)26 whereas the P⋯P
distance between phosphorus atoms bridged by the CH2–N–CH2 fragment have similar
values (4.527 to 4.695 Å for 18- and 4.738 Å for 14-membered macrocycles)26.
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Compound 4 whose NMR spectroscopy data differed from that of macrocycles 1–3
indeed crystallized as the RPSPSPRP isomer of the corresponding 1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane (Fig. 3) and adopted another conformation than
macrocycles 1 and 3. Moreover, the conformation of 4 is essentially different from that of
the meso-I isomer of 16-membered 1,9-diaza-3,7,11,15-tetraphosphacyclohexadecanes
with a zig-zag-type propylene chains between the phosphorus atoms,23,24 but is very
similar to the conformation of the RPSPSPRP isomer of 14-membered 1,8-diaza-3,6,10,13-
tetraphosphacyclotetradecane28. Both fragments P-CH2-N-CH2-P and P-CH2-CH2-CH2-
CH2-P in 4 have twisted conformations, in which all heteroatoms are located in the same
plane and all exocyclic substituents are in equatorial positions. The lone pairs of electrons
at the nitrogen atoms have anti orientation whereas the lone pairs of electrons at
phosphorus have a mutual syn-anti-syn arrangement. The P⋯P distances between
phosphorus atoms bridged by butylene chains (5.834 to 6.126 Å) or the CH2–N–CH2
fragment are shorter in comparison with the corresponding distances of the
RPRPRPRP/SPSPSPSP isomers of macrocycles 1 and 3 (6.954 to 6.994 Å and 4.524 to 4.694
Å). At the same time, the diagonal P⋯P distances are longer (8.16 Å in the RPSPSPRP
isomer compared to 6.95 Å for RPRPRPRP/SPSPSPSP-1 and -3)
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Fig. 3. Molecular structure of 4 (RPSPSPRP isomer). Hydrogen atoms are omitted for
clarity. Displacement ellipsoids are drawn at the 50% probability level.
The similar NMR spectra observed for macrocycles 4 and 5 allow the conclusion that 5
also forms the meso-I isomer. Furthermore, confirmation has been obtained with the
molecular structure of the corresponding tetrakisphosphine tetraoxide 5-O, as oxidation
of phosphines (including the macrocycles with several phosphine centers) proceeds with
retention of the configuration of the phosphorus atoms.30 The tetraoxide 5-O was
obtained on crystallizing 5 without protection from air. The 31P{1H} NMR spectrum of 5-
O showed one narrow singlet at 39.6 ppm indicating full oxidation of all four phosphorus
1
atoms. The H NMR spectrum of 5-O also indicates a symmetrical structure. The
methylene protons of the P-CH2-N fragments are observed as two doublets of doublets at
2.92 and 4.03 ppm; the high-field position of the first signal is typical for macrocyclic
aminomethylphosphines.
The X-ray structure analysis confirmed the RPSPSPRP isomer of the 18-membered
3,8,12,17-tetraoxo-1,10-diaza-3,8,12,17-tetraphosphacyclooctadecane 5-O (Fig. 4).
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Fig. 4 Molecular structure of tetrakisphosphine tetraoxide 5-O. Hydrogen atoms and
solvate molecules are omitted for clarity. Displacement ellipsoids are drawn at the 20%
probability level.
The conformation of the macrocycle 5-O essentially differs from the conformations of
unoxidized P4N2 macrocycles. The main difference is the spatial arrangement of the zig-
zag butylene fragments bridging the phosphorus atoms P1 (P1’) and P2 (P2’): all carbon
atoms (C3C4C5C6 and C3’C4’C5’C6’ are located in one plane. The phosphorus atoms
P1 and P1’, P2 and P2’, and the nitrogen atoms N1 and N1’ occupy mutual trans
positions relative to this plane. Exocyclic substituents on the phosphorus atoms are in
equatorial position, and the oxygen atoms have a mutual syn-anti-syn arrangement
corresponding to the RPSPSPRP isomer. The P-CH2-N-CH2-P fragments adopt twist
conformations so that the nitrogen atoms and their lone pairs of electrons are directed
towards the macrocyclic cavity. The P-O bond lengths (1.494(6) to 1.500(7) Å) are
typical for phosphine oxides.
As mentioned above, the macrocyclic aminomethylphosphines demonstrate dynamic
behavior in solution due to the labile P-CH2-N fragment. There are processes of isomers
interconversion and partial splitting of 16-membered P4N2 macrocycles into two 8-
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membered P2N cycles23 and practically full splitting of 14-membered P4N2 macrocycles
31
into two 7-membered P2N cycles25, 26. According to P{H} NMR spectroscopic studies,
5
in solution the pure stereoisomers of the 18-membered P4N2 macrocycles 1–5 form a
dynamic system of cyclic aminomethylphosphines where the initial isomer (rac-I for
compounds 1–3, meso-I for compounds 4, 5) prevails (Fig. S25-S29). The second main
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31
signal in the P{1H} spectra of macrocycles 1–5 in the region from -31 to -37 ppm
belong to another stereoisomer of 18-membered P4N2 macrocycle (the most probably it is
meso-I for 1–3, and rac-I for compounds 4, 5). The number signals with low intensity
indicates the possible formation of other cyclic aminomethylphosphines. However, in
31
contrast to the P{1H} spectra of 14- and 16-membered P4N2 macrocycles the intensity
of signals of possible 9-membered cycles in the spectra of 18-membered macrocycles is
very low that indicates the predominant process of stereoisomerization whereas the
splitting into 9-membered cycles is negligible. The mechanism of transformation of
macrocyclic aminomethylphosphines has been proposed recently.23 Process includes the
proton-induced rupture of endocyclic C–N bond and formation of
a
methylenephosphonium intermediate and the following intra- or intermolecular
nucleophilic attack of the nitrogen atom at the carbon atom of methylenephosphonium
intermediate which should result in formation of the corresponding 1-aza-3,8-
diphosphacyclononanes or 18-membered macrocycles with all possible configurations at
phosphorus (Scheme 2).
R
R
R
R
R
S
R
P
R
R
S
R
P
P
P
+ H+
- H+
+ H+
- H+
R'
N
N
R'
R'
N
N R'
H
S
R
R
S
P
P
P
P
R
R
R
intramolecular
R
R
P
R
P
P
P
S/R
N
S/R
P
+ H+
- H+
+ H+
- H+
S/R
R
CH2
S
R' NH
CH2
CH2
HN R'
R'
P
HN
HN R'
R
S/R
S
R'
P
P
P
P
intermolecular
R
R
R
R
R
R
R
S/R
P
S/R
P
R'
N
N
R
S/R
S/R
'
P
P
R
Scheme 2. Proposed mechanism illustrating transformations of RPSPSPRP isomer of 1,10-
diaza-3,8,12,17-tetraphosphacyclooctadecane
.
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The predominantly stereoizomerisation of 18-membred macrocycles testify the
intermolecular way of nucleophilic attack for 18-membered cycles which caused
probably by longer chain between reactive centres then for 14- and 16-membered cycles.
A key advantage of DCvC is the ability of dynamic systems to response to external
interventions. For the dynamic reaction a number of external factors, such as temperature,
concentration, pressure, and impurities, can have a dramatic effect upon the equilibrium
and so change the product distribution. This adjustable set of parameters opens up the
attractive possibility of being able to design and make molecules that can adapt to their
surroundings.8 Recently, we demonstrated that complexation of copper(I) by P4N2
macrocycles results in retention or in stereoisomerisation of the P4N2 ligand depending on
the geometry of the initial tetrakisphosphine. Namely, the RPRPRPRP/SPSPSPSP isomers of
14-membered P4N2 macrocycles form very stable tetrahedral cationic mononuclear
complex,31 whereas the RPSPSPRP isomer of 14-membered P4N2 macrocycles gives
dicopper bis-P,P-chelate complexes28 independent of the stoichiometry employed. In both
cases, the tetrakisphosphine ligands retain their configuration. Both RPRPRPRP/SPSPSPSP
and RPSPSPRP isomers of 16-, 18- and 20-membered P4N2 macrocycles give dicopper bis-
P,P-chelate complexes with the RPRPSPSP isomer of the P4N2 ligand.31 Apparently, in
solution reorganization of the orientation of the lone pairs of electrons at the phosphorus
atoms to allow formation of the thermodynamically most stable transition metal complex
is a very important feature of tetrakisphosphine ligand. Here, we report the reaction of
various isomers of 18-membered P4N2 macrocycles with nickel(II) tetrafluoroborate as
precursor of tetrakisphosphine complexes with square-planar geometry.
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The reactions of the pure RPRPRPRP/SPSPSPSP isomer of 2, the RPSPSPRP isomers of 4 and 5
and even a mixture of isomers of 6 with one equivalent of hexaaquanickel(II) or
hexaacetonitrilenickel(II) tetrafluoroborate in acetonitrile or THF proceeded through the
formation of a variety of unidentified intermediate complexes according to 31P{1H} NMR
monitoring, but finally led to the formation of mononuclear cationic complexes 7–10
only (Scheme 3) which were isolated in 38 to 76 % yield.
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7
8
9
2+
P
R
P
R
R
P
P
N
R
[NiL6](BF4)2
N R'
N
(BF4)2
R' N
Ni
R'
R'
L = CH3CN, H2O
P
P
R
P
R
P
R
R
2 4 6
, 
7 10

10
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2, 7
)
R = Ph, R' = Pr
R = Ph, R' = But
R = Py, R' = CH2Tolp
H C
(
4, 8
(
)
)
5, 9
(
6, 10
)
R =
, R' = (R)-CH(CH3)Ph (
3
N
Scheme 3. Synthesis of complexes 7 – 10
The 31P{1H} spectra of complexes 7–10 showed one narrow signal in the range of -10 to
10 ppm indicative of a symmetrical structure. A noticeable difference in the chemical
shifts between P-phenyl-substituted complexes 7 and 8 (ca. -6 ppm) and P-pyridyl-
substituted complexes 9 and 10 (ca. 8 to 11 ppm) was observed. The solubility of P-
phenyl- and P-pyridyl-substituted complexes was also different. Complexes 7 and 8 were
soluble in most organic solvents (acetonitrile, dichloromethane etc.) whereas complexes
9 and 10 were satisfactorily soluble only in DMF. The 1H NMR spectra of 7, 8 and 9, 10
also differed. For 7–10, the two halves of the macrocycle are equivalent and the protons
of the P-CH2-N fragments are observed as two doublets at 2.86 and 3.17 ppm for 7, at
2.90 and 3.15 ppm for 8, and at lower field for complexes 9 and 10, namely at 3.26 and
3.34 ppm for 9, at 3.24 and 3.30 ppm for 10. The reason for the observed different
physical and spectroscopic properties was established from the X-ray crystal structure
data of complexes 7, 9 and 10 (Figs. 5 to 7).
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Fig. 5. Molecular structure of the cation in 7. Hydrogen atoms are omitted for clarity.
Anions are not shown. Displacement ellipsoids are drawn at the 50% probability level.
Fig. 6. Molecular structure of the cation in 9 (the molecule is located on an inversion
center). Hydrogen atoms are omitted for clarity. The second independent cation and the
anions are not shown. Displacement ellipsoids are drawn at the 20% probability level.
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Fig. 7. Molecular structure of the cation in 10. Hydrogen atoms are omitted for clarity.
Anions are not shown. Displacement ellipsoids are drawn at the 20% probability level.
Compounds 7, 9 and 10 are cationic mononuclear complexes. The nickel(II) has an
almost ideal square-planar environment (7, 9 and 10, sum of bond angles is 360.58(2)°,
360° and 359.99(8)°, respectively, in 9, Ni1 is located on an inversion center) formed by
the four phosphorus atoms of the macrocyclic ligand. The average Ni-P bond length
(2.194 to 2.236 Å) in agreement with the usual values found in square-planar nickel(II)
complexes.32,33 The P-Ni-P bite angles are 87.23(8) to 92.58(2)°. In all complexes, the
RPSPSPRP isomers of the ligands are present. The exocyclic substituents at the phosphorus
atoms are in a syn-anti-syn arrangement. Four chelate rings – two six- and two seven-
membered rings – are formed as a result of nickel(II) coordination. The six-membered
rings have a half-chair conformation, the seven-membered rings a twist-chair
conformation. The position of the aminomethyl fragments relative to the P4Ni plane are
different for complex 7 and complexes 9 and 10. In 7, both amino groups are located on
the same side relative to the P4Ni plane, whereas in complexes 9 and 10, they are located
on opposite sides of the plane. The two nitrogen atoms of the ligands have a pyramidal
coordination (sum of bond angles is 336.0(2) to 341.1(1)o); their lone pairs of electrons
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are directed towards the metal center without coordination, but in close proximity (Ni···N
3.589(2) to 3.790(7) Å).
6
7
8
Conclusions
9
We have demonstrated that the principles of DCvC (reversibility of reactions, dynamic
systems, self-assembly) are also applicable for the stereoselective synthesis of 18-
membered P4N2 macrocycles as individual rac-I (RPRPRPRP/SPSPSPSP) or meso-I
(RPSPSPRP) isomers, via Mannich-like condensation reactions of 1,4-
bis(organylphosphino)butane, formaldehyde and primary amines. This approach can be
applied for the synthesis of a large variety of P4N2 macrocycles with variably ring sizes
and substituents at the heteroatoms. The obtained 18-membered P4N2 macrocycles form
square-planar nickel(II) complexes as meso-I isomers exclusively, in spite of the
configuration of the initial ligand, indicating their ability to stereoisomerize in the course
of the complexation of nickel(II) salts to give the most stable complex. This fact and the
recently described stereoselective formation of tetrahedral mononuclear copper(I)
complexes with exclusively the rac-I RPRPRPRP/SPSPSPSP isomer of P4N2 macrocycles and
formation of dicopper bis-P,P-chelate complexes with only the meso-II RPRPSPSP isomer
of the P4N2 macrocycles suggest that macrocylic aminomethylphosphines behave like
“smart” ligands that can adjust to the requirements of the metal ion via the described
dynamic systems, thus allowing the quantitative formation of the thermodynamically
preferred complex with only one stereoisomer as ligand.
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EXPERIMENTAL SECTION
General Methods. All reactions and manipulations with phosphines 1–6 were carried out
under a dry argon atmosphere using standard vacuum-line and Schlenk techniques. All
manipulations with complexes 7–10 were carried out under normal conditions without
inert atmosphere. Solvents were purified, dried, deoxygenated, and distilled before use.
1H NMR spectra were recorded on a Bruker Avance DRX 400 (400 MHz) and Bruker
Avance-600 (600 MHz) spectrometer. Chemical shifts are reported in parts per million
from tetramethylsilane with the solvents resonances as internal standards. Data are
reported as follows: chemical shift, multiplicity (s = singlet, d = doublet, t = triplet, q =
quartet, br = broad, m = multiplet), coupling constants (Hertz), integration, and
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assignment. 13C NMR spectra were recorded on a Bruker Avance DRX 400 spectrometer
(100.5 MHz) with complete proton decoupling. Chemical shifts are reported in parts per
31
million with the solvents as internal standards. P NMR spectra were recorded on a
Bruker Avance DRX 400 (162 MHz) and Bruker Avance-600 (242 MHz) spectrometer,
and chemical shifts are reported relative to external 85% H3PO4. MALDI-TOF mass
spectrometry was performed using an Ultraflex III TOF/TOF (Bruker Daltonics,
Germany) spectrometer. The FlexAnalysis 3.0 (Bruker Daltonics) program was used to
process the mass spectrometry data. ESIpos mass spectrometry was performed using an
AmazonX (Bruker Daltonic GmbH, Bremen, Germany) spectrometer at a capillary
voltage of 3500 V. The DataAnalysis 4.0 (Bruker Daltonic GmbH, Bremen, Germany)
program was used to process the mass spectrometry data. The mass spectra are reported
as m/z values. Determination of the CHN content was carried out on a CHNS analyzer
EuroEA3028-HT-OM (Eurovector SpA, Italy). Determination of the phosphorus content
was provided by combustion in an oxygen stream.
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1,4-[Bis(pyridine-2’-yl)phosphino]butane and 1,4-bis[(4’-methyl-pyridine-2’-
yl)phosphino]butane
were
prepared
by
the
reported
method.34
1,4-
Bis(phenylphosphino)butane was prepared by an improved method used for the synthesis
of other secondary bis-phosphines.35
1,4-Bis(phenylphosphino)butane. A solution of 1,4-bis(diphenylphosphino)butane (38.3
g, 0.09 mol) in dry degassed THF (150 mL) was added dropwise to lithium chips (6.2 g,
0.56 mol) in dry degassed THF (150 mL) at 0 °C for 4 h and the reaction mixture was
stirred under reflux for 2 h. The hot reaction mixture was filtered to remove the unreacted
lithium and the filtrate was cooled to 0 °C. A THF/water mixture (4:1) (25 mL) was
added dropwise to this deep red filtrate. Decolorization and formation of a white
precipitate were observed. THF was removed in vacuo and the residual aqueous solution
was extracted with ethyl ether (3 × 80 mL). The combined organic fractions were dried
with MgSO4 overnight and the ethyl ether was removed by distillation under atmospheric
pressure. The residue was heated to 150 °C on the oil bath at 0.01 torr for 30 min to
remove all volatiles. The residual viscous oil was 1,4-bis(phenylphosphino)butane (17.3
g, 70 %). 1H NMR (400 MHz, CDCl3) δ = 7.41 – 7.49 (m, 4Н), 7.25 – 7.29 (m, 6Н), 4.06
(ddd, 1JPH = 209.8 Hz, 2JPH = 7.1 Hz, 2JPH = 6.8 Hz, 2H), 1.74 – 1.85 (m, 2Н), 1.65 – 1.71
(m, 2Н), 1.42 – 1.57 (m, 4Н); 31P{1H} NMR (162 MHz, CDCl3) δ -52.16, -52.13.
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General procedure for the synthesis of 1,10-diaza-3,8,12,17-tetraphosphacycloocta-
decanes (1–5). A solution of 1,4-bis[(hydroxymethyl)arylphosphino]butane (1 mmol)
(obtained in situ by heating a mixture of 1,4-bis(arylphosphino)butane (1 mmol) and
paraformaldehyde (2 mmol) at 100-110 °C on the oil bath until homogenization
occurred) and the primary amine (1 mmol) in DMF (10 mL) was stirred at 80 °C on the
oil bath for 7 to 24 h. The reaction mixture was cooled and concentrated in vacuo to 1/4
to 1/6 of the initial volume. The residue was crystallized at 0 to -10 °C. The crystalline
precipitate was filtered off, washed with ethanol or ethyl ether and dried for 4 to 5 h at
0.01 torr.
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1,10-Diisopropyl-3,8,12,17-(RRRR/SSSS)-tetraphenyl-1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane (1). Reaction time 24 h. Yield of 1: 0.136 g (38 %); white
solid, mp 98–100 °С. 1H NMR (400 MHz, C6D6) δ 7.49 – 7.57 (m, 8H), 7.10 – 7.24 (m,
12H), 3.91 (m, 2H), 3.47 (br.d, 2JHH = 13.2 Hz, 4H), 2.55 (dd, 2JHH = 13.2 Hz, 2JPH = 16.0
3
Hz, 4H), 2.14 – 2.25 (m, 4H), 1.89 – 1.92 (m, 4H), 1.67 – 1.77 (m, 8H), 1.08 (d, JHH
=
3
31
6.6 Hz, 6Н), 0.70 (d, JHH = 6.6 Hz, 6Н); P{1H} NMR (162 MHz, C6D6) δ -36.2;
1
2
13C{1H} NMR (100 MHz, C6D6) δ 139.2 (d, JCP = 14.2 Hz), 133.5 (d, JCP = 19.5 Hz),
1
129.3 (s), 129.0 (d, 3JCP = 5.8 Hz), 55.7 (d, JCP = 6.5 Hz), 50.5 (t, 3JCP = 23.7 Hz), 30.2
1
4
2
(dd, JCP ≈ JCP ≈ 23.7 Hz), 29.1 (d, JCP = 14.3 Hz), 22.2 (s), 12.7 (s); MALDI MS m/z
778 [M + 4O]+. Anal. calc. for C42H58N2P4 [714.82] C 70.57, H 8.18, N 3.92, P 17.33 %,
found: C 70.67, H 8.24, N 3.69, P 17.42 %.
1,10-Dipropyl-3,8,12,17-(RRRR/SSSS)-tetraphenyl-1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane (2). Reaction time 10 h. Yield of 2: 0.118 g (33 %); white
solid, mp 116–118 °С. 1H NMR (400 MHz, C6D6) δ 7.52 – 7.59 (m, 8H), 7.10 – 7.16 (m,
12H), 3.65 (br.d, 2JHH = 12.6 Hz, 4H), 2.98 – 3.18 (m, 2H), 2.69 (dd, 2JHH = 12.6 Hz, 2JPH
= 10.0 Hz, 4H), 2.32 – 2.39 (m, 2H), 2.02 – 2.09 (m, 4H), 1.74 – 1.83 (m, 12H), 1.35 –
3
31
1.44 (m, 4H), 0.85 (t, JHH = 7.2 Hz, 6Н); P{1H} NMR (162 MHz, C6D6) δ -37.7;
1
2
13C{1H} NMR (100 MHz, C6D6) δ 139.5 (d, JCP = 15.8 Hz), 133.1 (d, JCP = 19.0 Hz),
1
128.8 (s), 128.7 (d, 3JCP = 7.2 Hz), 59.8 (d, JCP = 10.6 Hz), 59.5 (t, 3JCP = 8.0 Hz), 28.4
1
4
2
(dd, JCP = 15.6, JCP = 12.1 Hz), 28.1 (d, JCP = 13.4 Hz), 20.6 (s), 12.0 (s). ESIpos MS
m/z 778 [M + 4O - H]+. Anal. calc. for C42H58N2P4 [714.82] C 70.57, H 8.18, N 3.92, P
17.33 %, found: C 70.70, H 8.28, N 3.82, P 17.35 %.
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1,10-Di(cyclohexyl)-3,8,12,17-(RRRR/SSSS)-tetraphenyl-1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane (3). Reaction time 7 h. Yield of 3: 0.155 g (39 %); white
solid, mp 129–132 С. 1H NMR (400 MHz, C6D6) δ 7.55 – 7.65 (m, 8H), 7.10 – 7.18 (m,
12H), 3.53 (dd, 2JHH = 12.6 Hz, 2JPH = 6.6 Hz, 4H), 3.42 – 3.50 (m, 2H), 2.70 (dd, 2JHH
12.6 Hz, 2JPH = 17.4 Hz, 4H), 2.23 (ddd, 2JHH ≈ 2JPH ≈ 12.4 Hz, 2JPH = 4.2 Hz, 4H), 1.81
=
10
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2
2
– 1.95 (m, 8H), 1.70 – 1.78 (m, 6H), 1.64 (d, JHH = 13.2 Hz, 4Н), 1.54 (d, JHH = 13.2
Hz, 4Н), 1.29 – 1.40 (m, 4H), 1.07 – 1.19 (m, 2H), 0.92 – 1.02 (m, 2H), 0.75 – 0.84 (m,
31
13
2H); P{1H} NMR (162 MHz, C6D6) δ -35.8; C{1H} NMR (100 MHz, C6D6) δ 139.0
(d, 1JCP = 14.6 Hz, i-C6H5), 133.2 (d, 2JCP = 27.9 Hz, o-C6H5), 128.9 (d, 3JCP = 12.6 Hz),
128.7 (s), 59.5 (s), 56.1 (d, 1JCP = 5.9 Hz), 32.7 (s); 29.8 (dd, 1JCP ≈ 4JCP ≈ 15.5 Hz), 28.7
(d, 2JCP = 14.6 Hz), 26.8 (s), 26.2 (s). ESIpos MS m/z 873 [M + O + K + Na]+. Anal. calc.
for C48H66N2P4 [794.95] C 72.52, H 8.37, N 3.52, P 15.58 %, found: C 72.67, H 8.38, N
3.76, P 15.85 %.
1,10-Di(tert-butyl)-3,8,12,17-(RSSR)-tetraphenyl-1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane (4). Reaction time 24 h. Yield of 4: 0.130 g (35 %); white
solid, mp 130–132 С. 1H NMR (400 MHz, C6D6) δ 7.35 – 7.40 (m, 8H), 6.84 – 6.97 (m,
12H), 3.74 (ddd, 2JHH = 13.9 Hz, 2JPH ≈ 4JНH ≈ 4.1 Hz, 4H), 3.30 (dd, 2JHH = 13.9 Hz, 2JPH
= 2.2 Hz, 4H), 1.91 – 1.98 (m, 4H), 1.71 – 1.79 (m, 12Н), 0.92 (s, 18H); P{1H} NMR
31
(162 MHz, C6D6) δ -36.1; C{1H} NMR (100 MHz, C6D6) δ 140.3 (d, JCP = 17.9 Hz),
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133.6 (d, JCP = 18.9 Hz), 129.0 (s), 128.6 (d, JCP = 6.5 Hz), 55.2 (br.s), 54.4 (t, JCP =
9.1 Hz), 28.6 (dd, 1JCP ≈ 4JCP ≈ 14.6 Hz), 27.9 (s), 27.8 (d, 2JCP = 12.3 Hz). ESIpos MS m/z
805 [M + 4O - H]+. Anal. calc. for C44H62N2P4 [742.87] C 71.14, H 8.41, N 3.77, P
16.68 %, found: C 71.09, H 8.39, N, 3.72, P, 16.55%
1,10-Di(4’-methylbenzyl)-3,8,12,17-(RSSR)-tetra(pyridine-2’-yl)-1,10-diaza-
3,8,12,17-tetraphosphacyclooctadecane (5). Reaction time 24 h. Yield of 5: 0.131 g (31
%); white solid, mp 128-130 С. 1H NMR (600 MHz, C6D6) δ 8.48 (ddd, JHH = 4.8 Hz,
4JHH ≈ 4JHH ≈ 1.4 Hz, 4H), 7.24 – 7.29 (m, 8H), 7.01 (d, 3JHH = 7.8 Hz), 6.95 (ddd, 3JHH
3
=
4
4
3
4
7.6 Hz, JHH = 2.5 Hz, JHH = 2.0 Hz, 4H), 6.55 (dd, JHH = 7.6 Hz, JHH = 4.8 Hz, 4H),
4.49 (d, 2JHH = 13.1 Hz, 2H), 4.00 (dm, 2JHH = 13.0 Hz, 2JPH = 2.0 Hz, 4H), 3.59 (d, 2JHH
= 13.1 Hz, 2H), 3.33 (dd, 2JHH =13.0 Hz, 2JPH = 7.1 Hz, 4H), 2.18 – 2.26 (m, 4H), 2.17 (s,
6Н), 2.09 – 2.14 (m, 4H), 1.90 – 2.01 (m, 8Н); 31P{1H} NMR (242 MHz, C6D6) δ -31.7;
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ESIpos MS m/z 905 [M + 4O - H]+. Anal. calc. for C48H58N6P4 [842.91] C 68.40, H 6.94,
N 9.97, P 14.70 %, found: C 68.71, H 7.09, N 10.12, P 14.65 %.
5
1,10-Di(4’-methylbenzyl)-3,8,12,17-(RSSR)-tetra(pyridine-2’-yl)-3,8,12,17-tetraoxo-
1,10-diaza-3,8,12,17-tetraphosphacyclooctadecane (5-O). A solution of 5 (0.050 g, 0.06
mmol) in dry toluene (5 mL) was kept under dry air for 2 weeks. The white crystalline
precipitate formed was filtered off, washed with benzene and dried for 6 h at 0.01 torr.
Yield of 5-O: 0.04 g (75 %), mp 213–215 °С. 1H NMR (400 MHz, CDCl3) δ 8.68 (d, 3JHH
6
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8
9
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= 4.8 Hz, 4H), 8.07 (dd, JHH = 7.6 Hz, JHH = 4.8 Hz, 4H), 7.78 (ddm, JHH = 7.6 Hz,
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4
3
3JHH =7.6 Hz, JHH = 1.7 Hz, JРH = 3.3 Hz, 4H), 7.34 (dd, JHH = 7.6 Hz, 3JPH = 8.3 Hz,
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2
4H), 7.21 (d, JHH = 7.8 Hz, 4H), 7.08 (d, JHH = 7.8, 4H), 4.58 (d, JHH = 13.0 Hz, 2H),
4.03 (dd, 2JHH = 15.0 Hz, 2JPH = 7.5 Hz, 4H), 3.50 (d, 2JHH = 13.0 Hz, 2H), 2.92 (dd, 2JHH
2
= 15.0 Hz, JPH = 5.5 Hz, 4H), 2.30 (s, 6Н), 1.83 – 1.98 (m, 12H), 1.47 – 1.60 (m, 4H);
31P{1H} NMR (162 MHz, CDCl3) δ 39.6; ESIpos MS m/z 907 [M + H]+; Anal. calc. for
C48H58N6O4P4 [906.91] C 63.57, H 6.45, N 9.27, P 13.66 %, found: C 63.51, H 6.54, N
9.20, P 13.49 %.
[(1,10-Dipropyl-3,8,12,17-(RSSR)-tetraphenyl-1,10-diaza-3,8,12,17-
tetraphosphacyclooctadecane)nickel(II)]tetrafluoroborate (7).
A
solution of
[Ni(H2O)6](BF4)2 (47.7 mg, 0.140 mmol) in dry acetonitrile (5 mL) was added to a
solution of the ligand 2 (100.0 mg, 0.140 mmol) in dry acetonitrile (5 mL) and the
reaction mixture was stirred overnight at ambient temperature. The volatiles were
removed in vacuo, the residue was crystallized from ethyl ether, filtered off, washed with
1
ethyl ether and dried for 5 h at 0.01 torr. Yield of 7: 50.4 mg (38 %), 183 °С (dec.). H
NMR (400 MHz, CD3CN) δ 7.41 (dd, 3JHH = 7.4 Hz, 3JHH = 7.4 Hz, 4H), 7.28 – 7.34 (m,
3
2
8H), 7.20 (dd, JHH = 7.7 Hz, 3JHH = 7.6 Hz, 8H), 3.17 (d, JHH = 13.9 Hz, 4H), 2.81 (d,
2JHH = 13.9 Hz, 4H), 2.51 – 2.77 (m, 16H), 2.12 – 2.14 (m, 4H), 0.93 (dq, 3JHH = 7.4 Hz,
3
31
2JHH = 13.5 Hz, 4H), 0.51 (t, JHH = 7.4 Hz, 6H); P{1H} NMR (162 MHz, CD3CN) δ -
13
6.5; C{1H} NMR (100 MHz, CD3CN) δ 134.3 (br.s), 133.1 (br.s), 132.8 (s), 130.0 (s),
65.5 (dd, 1JCP ≈ 3JCP ≈ 5.4 Hz), 56.7 (s), 26.5 (br.s), 21.4 (d, 2JCP = 6.9 Hz), 19.5 (s), 11.5
(s); MALDI MS m/z 775 [M - 2BF4+H]+. Anal. calc. for C42H58B2F8NiN2P4 [947.12] C
53.26, H 6.17, N 2.96, Ni 6.20, P 13.08%, found C 53.15, H, 6.08, N 2.75, Ni 6.32, P
13.21%.
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[{1,10-Di(tert-butyl)-3,8,12,17-(RSSR)-tetraphenyl-1,10-diaza-3,8,12,17-
4
5
6
7
tetraphosphacyclooctadecane}nickel(II)] tetrafluoroborate (8). 8 was prepared like
complex 7, but from ligand 4 (100.0 mg, 0.135 mmol) and [Ni(H2O)6](BF4)2 (45.9 mg,
1
0.135 mmol). Yield of 8: 100.1 mg (76 %), mp 180 °С (dec). H NMR (400 MHz,
8
9
CD3CN) δ 7.55 – 7.57 (m, 4H), 7.43 – 7.60 (m, 8H), 7.37 – 7.41 (m, 8H), 3.37 (d, 2JHH
=
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13.2 Hz, 4H), 3.26 (br.d, JHH = 13.2 Hz, 4H), 2.41 – 2.75 (m, 16H), 0.65 (s, 18H).
31P{1H} NMR (162 MHz, CD3CN) δ -6.1; Anal. calc. for C44H62B2F8NiN2P4 [975.17] C
54.19, H 6.41, N 2.87, Ni 6.02, P 12.70 %, found C 54.23, H, 6.44, N 2.73, Ni 6.12, P
12.75%.
[{1,10-Di(4’-methylbenzyl)-3,8,12,17-(RSSR)-tetra(pyridine-2’-yl)-1,10-diaza-
3,8,12,17-tetraphosphacyclooctadecane}nickel(II)] tetrafluoroborate (9).
9 was prepared like complex 7, but from ligand 5 (100.0 mg, 0.119 mmol) and
[Ni(CH3CN)6](BF4)2 (57.9 mg, 0.119 mmol). Yield of 9: 87.8 mg (43 %). 1H NMR (400
MHz, DMF-d7) δ 8.76 (br.s, 4Н, Py), 7.55 – 7.62 (m, 8H, Py), 7.34 – 7.41 (m, 4H, Py),
3
3
6.88 (d, JHH = 7.8 Hz, 4H), 6.67 (d, JHH = 7.8 Hz, 4H), 3.43 – 3.77 (m, 4Н, partially
2
2
overlapped by the signal of water in the solvent), 3.34 (dd, JHH = 12.4 Hz, JPH = 13.3
Hz, 4H), 3.26 (br.d, 2JHH = 12.4 Hz, 4H), 2.47 – 2.68 (m, 8H), 2.24 – 2.37 (m, 8H), 2.20
(s, 6Н); 31P{1H} NMR (162 MHz, DMF-d7) δ 11.3; ESIpos MS m/z 903 [M - 2 BF4 + H]+.
Anal. calc. for C48H58B2F8N6NiP4 [1075.21]: C 53.62, H 5.44, N 7.82, Ni 5.46, P
11.52 %, found C 53.54, H 5.46, N 7.94, Ni 5.58, P 11.76 %.
[{1,10-Di((R)-(1’-phenylethyl)-3,8,12,17-(RSSR)-tetra(4-methylpyridine-2’-yl)-1,10-
diaza-3,8,12,17-tetraphosphacyclooctadecane}nickel(II)] tetrafluoroborate (10). A
solution of 1,4-bis[(hydroxymethyl)(4’-methylpyridine-2-yl)phosphino]butane (2.47
mmol) (obtained in situ by heating of a mixture of 1,4-bis(4’-methylpyridine-2-
yl)phosphino)butane (0.75 g, 2.47 mmol) and paraformaldehyde (0.15 g, 4.9 mmol) at
100 to 110 °C on the oil bath up to homogenization) and (R)-(1’-phenylethyl)amine (0.30
g, 2.48 mmol) in DMF (10 mL) was stirred at 80 °C on the oil bath for 24 h. The reaction
mixture was cooled and the solvent was fully evaporated in vacuo. The residue
containing a mixture of isomers 6 was dissolved in dry acetonitrile and
[Ni(CH3CN)6](BF4)2 (1.18 g, 2.46 mmol) in dry acetonitrile (5 mL) was added. The
reaction mixture was stirred overnight at ambient temperature. The volatiles were
removed in vacuo, the residue was crystallized from ethyl ether, filtered off, washed with
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ethyl ether and dried for 5 h at 0.01 torr. Yield of 10: 64.3 mg (23 %) . H NMR (600
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3
3
MHz, DMF-d7) δ 8.67 (br.s, JHH ≈ 4.9 Hz, 4Н), 7.42 (br.dd, JHH ≈ JHH ≈ 6 Hz, 4H),
7.19 – 7.22 (m, 6H), 7.13 – 7.16 (m, 4H), 6.99 – 7.03 (br.s, 2H), 6.93 – 6.97 (br.s, 2H),
3.59 – 3.69 (m, 2Н, partially overlapped by the signal of water in the solvent), 3.30 (d,
9
2
2JHH = 13.4 Hz, 4H), 3.24 (d, JHH = 13.4 Hz, 4H), 2.76 – 2.83 (m, 4H, partially
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overlapped by the signal of the solvent), 2.39 – 2.67 (m, 12H), 0.97 (d, JHH = 6.8 Hz,
3Н), 0.82 (d, JHH = 6.5 Hz, 3Н); P{1H} NMR (242 MHz, DMF-d7) δ 7.7; ESIpos MS
m/z 957 [M - 2 BF4+H]+. Anal. calc. for C52H66B2F8N6NiP4 [1130.37]: C, 55.21; H, 5.88;
N, 7.43; Ni, 5.19; P, 10.95 %, found C 55.55, H 5.87, N 7.49, Ni 5.43, P 11.06 %.
3
31
Notes
The authors declare no competing financial interest.
Supporting Information. NMR spectra and X-ray crystallography details are reported in
the supporting information. X-ray crystallographic information is available through
CCDC 2002519 (1), 2002520 (3), 2002521 (4), 2003204 (5-O), 2002522 (7), 2003205
(9) and 2003207 (10).
ACKNOWLEDGEMENT
We would like to thank DFG (He1376/44-1) and Erasmus+ program for financial support.
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35.Dickson, R.S.; Elmes, P.S.; Jackson, W.R. Further Improvements in the
Preparation of Disecondary Phosphines PhHP(CH2)nPHPh, n = 2, 3, and Their
Tetracarbonyltungsten Complexes:ꢀ Analysis of Their Multinuclear NMR
Spectra. Organometallics. 1999, 18, 2912 – 2914
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Table of Contents graphic
(CH2)4
R'
+ 4 CH2O
+
2 H
2
P
H
R
R
P
H
N
H
self-assembly
R'
R
R'
R
2+
R
R

P

P
P

N
P
N
Ni(BF4)2
-
(H2C)4
2BF4
(CH2)4
Ni
(H2C)4
(CH2)4
P 
metal-contolled
isomerisation

N
N
 P
R
P
 P
R
R
R'
R
R'
RSSR- or RRRR/SSSS-isomer
only RSSR-isomer
26
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