Synthesis and complexing properties of phosphoryl-substituted salicylaldimines

Article abstract of DOI:10.1007/s11172-007-0291-x

Starting from meta and ortho isomers of (diphenylphosphorylmethyl)anilines 2a,b, procedures were developed for the synthesis of new phosphoryl-substituted Schiff bases 3a,b serving as tridentate ligands. In alcoholic solutions, ligands 3a,b form complexes of different composition with praseodymium and neodymium nitrates. Only the M(L)₂(NO₃)₃ complexes crystallized from solution regardless of the reactant ratio. According to the X-ray diffraction study and IR spectroscopy, one of the ligands in the complexes with ortho ligand 3b is coordinated in a bidentate fashion via the oxygen atom of the P=O group and the phenoxy oxygen atom, whereas the second ligand molecule forms a coordination bond with metal only via the phosphoryl oxygen atom. In the Pr(3a)₂(NO₃)₃ complexes, both meta ligands 3a are involved in thebidentate O,O-coordination.

Full text of DOI:10.1007/s11172-007-0291-x

Russian Chemical Bulletin, International Edition, Vol. 56, No. 9, pp. 1891—1899, September, 2007
1891
Synthesis and complexing properties of
phosphorylꢀsubstituted salicylaldimines*
D. V. Aleksanyan, V. A. Kozlov, I. L. Odinets,ꢀ I. V. Fedyanin, K. A. Lyssenko, M. P. Pasechnik,
P. V. Petrovsky, and T. A. Mastryukova†
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5085. Eꢀmail: odinets@ineos.ac.ru
Starting from meta and ortho isomers of (diphenylphosphorylmethyl)anilines 2a,b, proceꢀ
dures were developed for the synthesis of new phosphorylꢀsubstituted Schiff bases 3a,b serving
as tridentate ligands. In alcoholic solutions, ligands 3a,b form complexes of different composiꢀ
tion with praseodymium and neodymium nitrates. Only the M(L)2(NO3)3 complexes crystalꢀ
lized from solution regardless of the reactant ratio. According to the Xꢀray diffraction study and
IR spectroscopy, one of the ligands in the complexes with ortho ligand 3b is coordinated in a
bidentate fashion via the oxygen atom of the P=O group and the phenoxy oxygen atom,
whereas the second ligand molecule forms a coordination bond with metal only via the phosꢀ
phoryl oxygen atom. In the Pr(3a)2(NO3)3 complexes, both meta ligands 3a are involved in the
bidentate O,Oꢀcoordination.
Key words: Schiff bases, (diphenylphosphorylmethyl)anilines, (diphenylphosphorylꢀ
methyl)nitrobenzenes, complexes, lanthanides, structure, Xꢀray diffraction study, hydrogen
bonds.
Schiff bases form catalytically active metal complexes,
whose structures are determined by both the structure of
the ligand and the nature of the metal.1,2 Salicylaldehyde
azomethines containing substituents with the coordiꢀ
nationꢀactive donor HO, H2N, or HS centers at the
imine nitrogen atom have been studied in most detail.
Data on the related compounds bearing an additional
phosphorusꢀcontaining donor center are limited to a few
phosphineꢀcontaining structures,3—5 which can form both
chelate mononuclear compounds involving all coordinatꢀ
ing groups of the molecules (A),5 and dinuclear comꢀ
plexes (B) with the chelateꢀchain coordination of the
ligands.4
M = Cr, Mo; X = NH, (CH2)n (n = 0, 1, 2);
M´ = Co2+, Ni2+, Cu2+, Zn2+
It should also be noted that the use of the phosphineꢀ
substituted ligand C in the alkylation of aromatic aldeꢀ
hydes with diethylzinc in the presence of chiral ferrocenylꢀ
substituted salicylaldimines as the basic catalysts results
in high enantioselectivity (up to 100% ee).
M = NiII, PdII
* Dedicated to Academician G. A. Abakumov on the occasion
of his 70th birthday.
† Deceased.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1827—1835, September, 2007.
1066ꢀ5285/07/5609ꢀ1891 © 2007 Springer Science+Business Media, Inc.

1892
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Aleksanyan et al.
Taking into account that tertiary phosphine oxides
can form strong coordination bonds with various metals
through the lone electron pair of the phosphoryl oxygen
atom, we carried out the condensation of salicylaldehyde
with orthoꢀ and metaꢀsubstituted αꢀdiphenylphosphorylꢀ
toluidines and synthesized new phosphorylꢀsubstituted
oligodentate ligands, viz., salicylaldimines containing the
phosphoryl substituent in the Nꢀaryl ring.
We used orthoꢀ and metaꢀsubstituted (diphenylphosꢀ
phorylmethyl)nitrobenzenes 1a,b as the precursors of the
amino component in the synthesis of Schiff bases. Comꢀ
pounds 1a,b were synthesized by the Arbuzov reaction
starting from the corresponding nitrobenzyl bromides
and ethyl diphenylphosphinite. The target αꢀdiphenylꢀ
phosphoryltoluidines 2a,b were synthesized by the reducꢀ
tion of aromatic nitro derivatives with tin chloride in an
acidic medium, which is widely employed in synthetic
organic chemistry. This approach proved to be very effiꢀ
cient. The yields of phosphorylꢀsubstituted anilines
were 94% (2a) and 87% (2b) (Scheme 1).
C(18)
C(19)
C(10)
C(9)
C(8)
C(11)
C(12)
O(1)
C(14)
C(17)
C(16)
C(13)
C(3)
P(1)
C(15)
C(1)
C(4)
C(5)
C(2)
C(7)
O(3)
C(6)
N(1)
O(2)
Fig. 1. Molecular structure of compound 1a.
C(11)
C(12)
C(10)
C(13)
C(19)
C(8)
P(1)
C(18)
C(17)
C(9)
Scheme 1
O(1)
C(3)
C(5)
C(4)
C(14)
C(1)
C(15)
C(2)
C(6)
O(3)
C(16)
C(7)
H(1B)
H(1A)
N(1)
O(2)
Fig. 2. Molecular structure of compound 1b.
of the P=O fragment and the nitro group. In ortho deꢀ
rivative 1b, these groups are on the same side of the
P(1)C(1)C(2) plane, whereas these groups in meta analog
1a are on opposite sides.
The nitro group in ortho derivative 1b is rotated with
respect to the plane of the phenyl ring bound to this
group by 44.2(2)°. The N—O bonds are nonequivalent;
the N(1)—O(2) distance is 0.012 Å longer than the
N(1)—O(3) distance. The nonequivalence of the bonds
in the nitro group and the large angle of rotation of this
group suggest that there is a moderateꢀstrength intramoꢀ
lecular C—H...O contact with the geometric parameters
characteristic of very weak hydrogen bonds (O(2)…...C(1),
2.928(3) Å; O(2)…...H(1A), 2.29 Å; C(1)H(1A)O(1),
121°). At the same time, the nitro group in meta isomer 1a
is nearly parallel to the plane of the phenyl ring (the angle
between the planes is 6.2(3)°), and the N—O bond lengths
are equal within experimental error.
The spectroscopic study of the structures of nitro deꢀ
rivatives 1a,b showed that the positions of the absorption
bands of the functional nitro and phosphoryl groups in
the IR spectra depend only slightly on the mutual arꢀ
rangement of the substituents, whereas these differences
in the 1H NMR spectra are substantial. For example, the
signal of the methylene protons in ortho isomer 1b is
shifted downfield compared to that for meta analog 1a
(∆δ ~0.5) due to the orienting effect of the oꢀNO2 group.
The Xꢀray crystal structures of isomers 1a,b are also difꢀ
ferent. The molecular structures of compounds 1a and 1b
are presented in Figs 1 and 2, respectively. Selected bond
lengths and bond angles are given in Table 1.
Molecules 1a and 1b have a different arrangement of
the nitroꢀsubstituted benzyl fragment. In the crystal strucꢀ
tures, compounds 1a and 1b exhibit planar chirality with
respect to the mutual arrangement of the oxygen atom
An analysis of the crystal packings of 1a and 1b showed
that weak C—H...O and O...π interactions are the preꢀ
dominant contacts in the crystals of these compounds.
The shortest contacts are observed in ortho isomer 1b

Phosphorylated salicylaldimines
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1893
Table 1. Selected bond lengths (d) and bond angles (ω) in isoꢀ
meric (diphenylphosphorylmethyl)nitrobenzenes 1a,b
nol to give the target phosphorylmethylphenylꢀsubstituted
salicylaldehyde imines 3a,b (Scheme 2).
Parameter
Value
Scheme 2
1а
1b
Bond length
P(1)—O(1)
P(1)—C(1)
P(1)—C(8)
P(1)—C(14)
C(1)—C(2)
C(2)—C(7)
C(6)—C(7)
C(7)—N(1)
C(6)—N(1)
N(1)—O(2)
N(1)—O(3)
d/Å
1.496(1)
1.807(2)
1.802(2)
1.806(2)
1.513(3)
1.393(3)
1.377(3)
.—
1.484(2)
1.822(2)
1.807(2)
1.799(2)
1.503(3)
1.395(3)
1.380(3)
1.471(3)
.—
1.479(2)
1.228(2)
1.230(2)
1.232(2)
1.219(2)
Bond angle
ω/deg
O(1)—P(1)—C(1)
O(1)—P(1)—C(8)
O(1)—P(1)—C(14)
C(1)—P(1)—C(14)
C(8)—P(1)—C(14)
P(1)—C(1)—C(2)
C(1)—C(2)—C(7)
C(2)—C(7)—C(6)
C(2)—C(7)—N(1)
C(7)—C(6)—N(1)
113.85(8)
111.71(9)
111.50(9)
106.62(9)
106.22(9)
111.5(1)
119.2(2)
118.9(2)
—
112.95(9)
111.49(9)
112.21(9)
106.7(1)
106.57(9)
108.8(2)
124.1(2)
123.2(2)
120.5(2)
—
Both isomeric salicylaldimines 3a,b were isolated in
the individual state as yellow crystalline compounds
in high yields after recrystallization from a 1 : 1 benꢀ
zene—diethyl ether system. The 31P NMR spectra show
singlets with similar chemical shifts (δP 29.4 for 3a and
29.2 for 3b). The 1H NMR spectra of imines 3a,b contain
signals of the aromatic protons along with signals of the
protons of the hydroxy (δOH 13.13 for 3a and 12.92 for 3b)
and aldimine groups (δHC=N 8.38 for 3a and 7.86 for 3b).
Doublets of the methylene protons with the spinꢀspin
coupling constant of ~13.5 Hz are observed at δ 3.68 (3a)
and 3.93 (3b). The 13C NMR spectra of compounds 3a,b
show signals of the carbon atoms of the aromatic rings
along with the characteristic signals of the carbon atoms
of the methylene group (3a: δC 37.93 (1JP,C = 65.6 Hz);
3b: δC 33.34 (1JP,C = 66.4 Hz)) and the azomethine fragꢀ
ment (δC=N 162.72 (3a) and 163.14 (3b)).
118.7(2)
(O(3)...C(17), 3.149(3) Å; O(3)...C(2), 3.163(3) Å).
In meta isomer 1a, the O(2)...C(4) distance is 3.218(4) Å.
In both isomers 1a,b, the oxygen atom of the phosphoryl
group forms a C—H...O contact with the hydrogen atom
of the methylene group. This contact is substantially stronꢀ
ger in ortho isomer 1b than in meta isomer 1a (the O...H
distance is 2.28 and 2.52 Å in the ortho and meta isomers,
respectively).
1
The H NMR spectra of toluidines 2a,b, unlike those
of nitro derivatives 1a,b, show no substantial difference in
the position of the signals for the methylene protons.
It should be noted that the signals for the protons of the
central aromatic ring in 1a,b overlap with the signals for
the protons of the phenyl rings at the phosphoryl group,
whereas two distinct groups signals of aromatic protons
with different intensities are observed in this spectral reꢀ
gion for compounds 2a,b. The IR spectra of toluidines
2a,b contain a set of bands in the 3400—3200 cm–1 region
characteristic of stretching vibrations of the primary amino
group, which is, apparently, associated with the formaꢀ
tion of interꢀ and intramolecular hydrogen bonds with the
phosphoryl oxygen atom. The lowꢀfrequency shift of the
stretching band of the PO group and the presence of several
maxima at 1170 cm–1 in the spectrum of ortho isomer 2b
are consistent with this assumption.
1
It should be noted that the 13C, 31P, and H NMR
spectra of compounds 3a,b in CDCl3 show only one set of
the corresponding signals, which is apparently associated
with stabilization of the only isomeric form in solution.
This isomer contains the stable intramolecular hydrogenꢀ
bonded ring involving the C=N bond. The presence of
this isomer in the crystal structure of 3a was confirmed by
Xꢀray diffraction.
In the IR spectra of aldimines 3a,b in solution (c =
0.1 mol L–1; CHCl3), the positions of the stretching bands
of the imino and phosphoryl groups depend on their muꢀ
tual arrangement, each compound existing at least as two
conformers. The IR spectrum of meta isomer 3a shows
one intense ν(P=O) absorption band at 1190 cm–1 (with
a shoulder at lower frequencies) and two absorption bands,
The condensation of salicylaldehyde with αꢀphosꢀ
phoryltoluidines 2a,b readily proceeds on heating in ethaꢀ

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Aleksanyan et al.
C(18)
C(19)
C(20)
which can be assigned to ν(C=N), a strong band at
1622 cm–1 and a mediumꢀintensity band at 1600 cm–1
C(23)
C(22)
C(24)
.
C(17)
C(16)
On the contrary, the ν(P=O) vibrations of ortho isomer 3b
are observed as two bands at 1198 cm–1 (with a shoulder
at lower frequencies) and 1176 cm–1, and the ν(C=N)
vibration is observed as one band at 1617 cm–1 with a
shoulder at ~1620 cm–1. The spectra of polycrystalline
samples of compounds 3a and 3b are comparable with the
spectra in solutions and, apparently, they also cannot be
interpreted as those corresponding to the only conformer.
The 2300—3300 cm–1 region in the spectra of compounds
3a,b contains a broad lowꢀintensity band characteristic of
stretching vibrations of OH groups involved in weak
hydrogen bonding. This band overlaps with the CH
stretching bands of the aromatic and methylene groups.
Apparently, these spectroscopic manifestations are atꢀ
tributed not only to the mutual arrangement of the phosꢀ
phoryl group and the salicylaldimine fragment but also to
the characteristic features of different hydrogen bonds
between the OH, C=N, and P=O groups. Taking into
account the NMR spectroscopic data, the most probꢀ
able conformers are those, in which the intramolecular
C=N...H—O hydrogen bond is present and the hydrogen
bond with the phosphoryl oxygen atom is absent (the
highest ν(P=O) frequencies; ν(C=N) 1617—1622 cm–1),*
and those containing a bifurcated hydrogen bond formed
by the phosphoryl oxygen atom and the nitrogen atom
characterized by a decrease in the ν(C=N) frequency to
1600 cm–1,7 as was observed for meta isomer 3a.
Upon the repeated recrystallization of metaꢀsalicylꢀ
aldimine 3a from a CH2Cl2—ButOMe system, the prodꢀ
uct was isolated as the only conformer, whose structure
was confirmed by singleꢀcrystal Xꢀray diffraction. In the
crystal structure of meta isomer 3a, the rather strong intraꢀ
molecular O—H...N hydrogen bond is characterized by
the O(2)...N(1) distance of 2.592(2) Å (Fig. 3, Table 2).
The presence of this hydrogen bond leads to the expected
averaging of the other bond lengths. In the crystal strucꢀ
ture of meta isomer 3a, the salicylaldimine fragment is
nearly planar (the dihedral angle between the aromatic
ring of the central aromatic moiety and the C(9)—C(14)
ring is 13°), and the phosphoryl group is perpendicular to
the mean plane of this fragment. A slight distortion of the
planar conformation in the crystal structure of 3a is, apꢀ
parently, associated with the crystal packing effects, to be
more precise, with stacking interactions between the aroꢀ
matic rings C(2)—C(6) (the shortest C...C contacts are
3.384(2) Å), resulting in the formation of dimers. In addiꢀ
tion to the stacking interactions, these dimers are stabiꢀ
lized by a rather strong C—H...O contact (H...O, 2.39 Å)
formed by the hydrogen atom at the C=N bond and the
phosphoryl oxygen atom.
C(11)
C(10)
O(2)
C(21)
C(25)
C(12)
C(13)
C(15)
C(26)
H(20)
P(1)
O(1)
C(3)
C(1)
C(2)
N(1)
C(4)
C(9)
C(8)
H(8A)
C(14)
C(7)
C(5)
C(6)
O(1A)
P(1A)
Fig. 3. Formation of dimers in the crystal structure of
meta isomer 3a. The atomic numbering scheme is given only for
one symmetrically independent molecule.
Presumably, ligands 3a,b form complexes with lanꢀ
thanide ions with the involvement not only of the phosꢀ
phoryl group but also of the hydroxyazomethine fragꢀ
ment. The coordination properties of ligands 3a,b were
studied in the reactions with praseodymium and neoꢀ
dymium nitrates. Upon the mixing of the reagents in moꢀ
lar ratios from 1 : 1 to 1 : 3 in an ethanolic solution, the
31P NMR spectra show singlets shifted downfield with
respect to the signal of the free ligand in the same solvent
(δP = 33.5 (3a) and 32.7 (3b); see Table 3), whereas the
signal of the free ligand is absent. The positions of the
signals are indicative of fast exchange processes and the
formation of complexes of different composition. The
downfield shifts of the signals of the complexes provide
unambiguous evidence for the involvement of the phosꢀ
phine oxide group in the complexation.
The [LnL2(NO3)3] complexes (4a—c: L = 3a, Ln =
Pr (4a); L = 3b, Ln = Pr (4b); L = 3b, Ln = Nd (4c))
precipitate with time from solutions at different ligandꢀ
toꢀmetal molar ratios.
The identity of complexes 4a—c isolated from the
reaction mixtures containing the starting reagents in difꢀ
ferent ratios was confirmed by comparing the physicoꢀ
chemical constants (melting points, IR spectra, and unit
cell parameters (4b)) and the elemental analysis data.
According to the Xꢀray diffraction study, the praseodyꢀ
mium atom in the crystal structure of complex 4b is coorꢀ
dinated by two neutral ligands (L = 3b) and three nitrate
anions (Fig. 4). The latter are coordinated to the metal
atom in a bidentate fashion with a slight asymmetry (the
Pr—O bond lengths in the NO3 ligands vary in a range of
0.03—0.07 Å). Complex 4b contains ligands 3b with difꢀ
ferent denticities. One of the ligands (B) serves as a
* For comparison, ν(C=N) for analogous unphosphorylated
salicylaldimines is 1628 cm–1 6
.

Phosphorylated salicylaldimines
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1895
Table 2. Selected bond lengths (d) in ligand metaꢀ3a and complex 4b
3а 4bА
4bВ
Bond
d/Å
Bond
d/Å
Bond
d/Å
P(1)—O(1)
P(1)—C(1)
P(1)—C(15)
P(1)—C(21)
N(1)—C(4)
N(1)—C(8)
O(2)—C(10)
C(8)—C(9)
C(9)—C(10)
C(10)—C(11)
C(11)—C(12)
C(12)—C(13)
С(13)—С(14)
C(9)—C(14)
1.481(1)
1.817(1)
1.807(1)
1.811(2)
1.431(1)
1.288(1)
1.359(1)
1.462(1)
1.406(1)
1.388(1)
1.398(1)
1.387(2)
1.3962(15)
1.404(1)
P(1)—O(1)
P(1)—C(1)
P(1)—C(15)
P(1)—C(21)
N(1)—C(3)
N(1)—C(8)
O(2)—C(10)
C(8)—C(9)
C(9)—C(10)
C(10)—C(11)
C(11)—C(12)
C(12)—C(13)
С(13)—С(14)
C(14)—C(9)
Pr(1)—O(1)
1.525(5)
1.814(7)
1.797(8)
1.812(8)
1.435(10)
1.301(9)
1.354(9)
1.457(11)
1.419(11)
1.390(11)
1.399(11)
1.401(11)
1.349(11)
1.429(11)
2.370(5)
2.570(5)
2.607(5)
2.585(5)
2.535(5)
P(1´)—O(1´)
P(1´)—C(1´)
P(1´)—C(15´)
P(1´)—C(21´)
N(1´)—C(3´)
N(1´)—C(8´)
O(2´)—C(10´)
C(8´)—C(9´)
C(9´)—C(10´)
C(10´)—C(11´)
C(11´)—C(12´)
C(12´)—C(13´)
С(13´)—С(14´)
C(9´)—C(14´)
Pr(1)—O(1´)
1.522(5)
1.833(2)
1.780(8)
1.787(8)
1.447(9)
1.315(9)
1.292(9)
1.429(10)
1.444(10)
1.409(10)
1.369(11)
1.392(10)
1.382(11)
1.420(11)
2.401(5)
2.341(5)
2.565(5)
2.636(5)
Pr(1)—O(1N)
Pr(1)—O(2N)
Pr(1)—O(4N)
Pr(1)—O(5N)
Pr(1)—O(2´)
Pr(1)—O(7N)
Pr(1)—O(8N)
Table 3. 31P NMR spectroscopic data (EtOH) for mixtures of Ln(L)n(NO3)3 (L = 3a,b)
Ligand/Metal
L : M = 1 : 1
L : M = 2 : 1
L : M = 3 : 1
δ
∆δ
δ
∆δ
δ
∆δ
Р
Р
Р
3а/Pr
3b/Pr
3b/Nd
55.22
50.8
73.1
11.7
18.1
40.4
40.2
59.9
43.7
6.7
27.2
11.0
35.3
52.0
52.8
1.8
19.3
20.1
bidentate ligand and forms coordination bonds with the
involvement of the oxygen atoms of the phosphoryl and
hydroxy groups, whereas another ligand (A) is coordiꢀ
nated to the metal atom in a monodentate fashion and
forms the coordination bond only via the phosphoryl oxyꢀ
gen atom. Therefore, the coordination number of praseoꢀ
dymium in complex 4b is nine.
The difference in the coordination mode of two molꢀ
ecules of ligand 3b results in the unexpected stabilization
of its different forms in complex 4b. Actually, coordiꢀ
nated ligand 3bA, like free molecule 3a, exists in the enolꢀ
imine form, whereas the structure of ligand 3bB is characꢀ
terized by the localization of the proton at the nitrogen
atom and is stabilized, apparently, by the Pr(1)...…O(2´)
coordination bond. The latter structure can be interpreted
as either a ketoꢀenamine tautomer (the quinomethide
form) or a zwitterionic form.2 The aboveꢀmentioned difꢀ
ferences in the structure of molecules A and B of ligand 3b,
in turn, lead to a substantial redistribution of the bond
lengths in the region of the hydrogenꢀbonded rings (see
Table 2) and a distortion of the planarity of the salicylꢀ
aldimine fragment in 3bB (the C(8´)N(1´)C(3´)C(2´)
torsion angle is 135.6°). It should be noted that ketoꢀ
enamine form 3bB contains, along with the intramolecuꢀ
lar hydrogen bond with the O(2´) atom (N(1´)...O(2´),
2.68 Å; N(1´)H(1N´)O(2´), 141°), the hydrogen bond
with the phosphoryl group (N(1)´...O(1´), 2.94 Å;
N(1´)H(1N´)O(1´), 126°). Apparently, the bifurcated
hydrogen bond also contributes to the stabilization of
form 3bB and is responsible for a substantial rotation of
the aromatic ring C(2´)—C(7´) with respect to the ring
C(9´)—C(14´).
The mutual arrangement of the ligands in complex 4b
is influenced not only by steric factors and the coordinaꢀ
tion to the metal atom but also by the intramolecular
stacking interaction between the salicylidene fragment
of ligand 3bA and the phenyl ring C(15)—C(20) of
ligand 3bB. Actually, the dihedral angle between these
aromatic rings is 11.7°, and the shortest C(14´)...C(18)
and C(10´)...C(16) contacts are 3.38 and 3.41 Å, respecꢀ
tively.
The IR spectrum of complex 4b (Fig. 5, spectrum d)
shows two absorption bands of differently coordinated
phosphoryl groups. The band at 1161 cm–1 is assigned

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Aleksanyan et al.
O(3N)
N(1N)
C(5)
C(6)
C(25)
C(4)
O(1N)
O(2N)
O(7N)
C(17´)
C(26)
C(3)
C(24)
C(23)
C(16´)
C(7)
O(5N)
O(9N)
C(18´)
C(19´)
C(23´)
C(22´)
N(2N)
C(2)
O(6N)
O(4N)
C(24´)
N(3N)
O(8N)
C(25´)
C(21)
C(8)
C(22)
C(21´)
Pr(1)
C(14)
C(13)
N(1)
C(26´)
O(1´)
C(15´)
P(1´)
O(1)
P(1)
C(9)
C(20´)
C(1)
H(20)
C(16)
O(2´)
C(10´)
C(12)
C(15)
C(1´)
C(10)
H(1N´)
O(2)
C(2´)
C(11)
C(11´)
C(7´)
C(6´)
C(3´)
N(1´)
C(20)
C(17)
C(9´)
C(12´)
C(5´)
C(4´)
C(8´)
C(18)
C(19)
C(13´)
C(14´)
Fig. 4. Molecular structure of complex 4b.
to monodentate ligand 3bA and is characteristic of
P=O groups bound to metal. Another band has a maxiꢀ
mum at 1133 cm–1; the additional lowꢀfrequency shift is
attributed to the hydrogen bonding between the P=O
group and the phenol proton in ligand 3bB. Earlier, we
have documneted this phenomenon upon complexation.8
A complicatedly structured band with a maximum at
1626 cm–1 and a shoulder at 1615 cm–1 is observed in the
absorption region of the C=N bond. It should be noted
that the assignment of the observed absorption bands to
the pure C=N vibration is incorrect due to the redistribuꢀ
tion of the bond orders in the salicylaldimine fragment
associated with intramolecular hydrogen bonding, which
was established by Xꢀray diffraction. This vibration is
mixed with the vibration of the conjugated CAr—N bond
and with the skeletal vibrations of the aromatic rings.
This, in particular, accounts for the fact that it is imposꢀ
sible to unambiguously determine the coordination mode
of the ligands in complexes 4a—c based on the IR spectra.
It should also be noted that if the observed frequencies
assigned to ν(C=N) are correlated to the lengths of this
bond determined by Xꢀray diffraction (see Table 2), no
length—frequency relationships are observed. However,
the fact that the IR spectra of complexes 4b,c formed by
the same ligand 3b are identical suggests that complexes
4b,c have identical structures.
band is shifted to 1153 cm–1, and the band of the free
P=O group is absent. Three absorption maxima at 1634,
1620, and 1602 cm–1 can be assigned to mixed vibrations
of the CNC fragment (Fig. 5, spectrum c). This fact is
indicative of the O,Oꢀbidentate coordination of both
ligands 3a in complex 4a with a pronounced shift of the
phenol proton to the nitrogen atom. It should be noted
that the nitrate groups in complexes 4a—c are coordiꢀ
nated to the metal ion in a bidentate fashion, as eviꢀ
denced by the characteristic absorption bands ν(N=O) at
~1480 cm–1 and νas(NO2) at ~1297 cm–1
.
Therefore, the new tridentate ligands, viz., phosphoꢀ
rylꢀsubstituted Schiff bases, synthesized in the present
study readily form complexes with lanthanides, whose
structures are determined by the mutual arrangement of
the complexꢀforming fragments in the ligands. It should
be noted that, in contrast to typical salicylaldimines, the
nitrogen atom in the new ligands is not involved in the
coordination to metal.
Experimental
The 1H, 13C, and 31P NMR spectra were recorded on Bruker
AMXꢀ400 (400.13, 100,61, and 161.98 MHz, respectively) and
Bruker AVꢀ300 (300.09, 75.47, and 121.49 MHz, respectively)
instruments in CDCl3 with the use of the signal of the residual
protons of the deuterated solvent as the internal standard
(1H and 13C) and 85% H3PO4 as the external standard (31P). For
The spectrum of complex 4a (L = 3a) shows that both
phosphoryl groups are coordinated. Thus, the ν(P=O)

Phosphorylated salicylaldimines
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1897
like crystals). M.p. 214—216 °C (EtOH). 31P NMR (CDCl3), δ:
28.91. 1H NMR (CDCl3), δ: 3.72 (d, 2 H, CH2, 2JP,H =13.3 Hz);
7.38 (t, 1 H, C6H4N, 3JH,H = 7.8 Hz); 7.43—7.48 and 7.51—7.55
(both m, 6 H each, PhP); 7.56 (d, 1 H, C6H4N, 3JH,H = 7.8 Hz);
7.66—7.71 (m, 4 H, PhP); 7.81 (dd, 1 H arom., 4JH,H = 1.4 Hz,
A
0.8
a
0.6
0.4
0.2
0
3
4JP,H = 4.3 Hz); 8.03 (d, 1 H, C6H4—N, JH,H = 7.8 Hz).
IR (KBr), ν/cm–1: 1524, 1349 (NO2); 1187 (PO). Found (%):
C, 67.64; H, 4.71; N, 4.27. C19H16NO3P. Calculated (%):
C, 67.65; H, 4.78; N, 4.15.
oꢀNitrobenzyldiphenylphosphine oxide (1b) was synthesized
according to an analogous procedure. The yield was 76%, m.p.
178—179 °C (cf. lit. data12: m.p. 179—180 °C). 31P NMR
(CDCl3), δ: 29.35. 1H NMR (CDCl3), δ: 4.32 (d, 2 H, CH2,
2JP,H = 13.9 Hz); 7.38—7.60 (m, 8 H, arom.); 7.67—7.77 (m,
5 H, arom.); 7.89 (d, 1 H, C6H4—N, 3JH,H = 8.2 Hz). IR (KBr),
ν/cm–1: 1525, 1357 (NO2); 1187 (PO).
1600
1400
1200
ν/cm–1
A
b
2.0
1.5
1.0
0.5
0
mꢀ(Diphenylphosphorylmethyl)aniline (2a). A solution of
SnCl2 (8 g, 0.035 mol) in concentrated hydrochloric acid (20 mL)
was slowly added dropwise to a solution of (mꢀnitrobenzyl)diꢀ
phenylphosphine oxide 1a (3.4 g, 0.01 mol) in glacial acetic acid
(20 mL) for 2.5 h. The temperature of the reaction mixture
raised to 35 °C without external heating. Then the mixture was
stirred at 40—42 °C for 2 h, cooled, and poured onto ice, pH was
brought to 12 with a NaOH solution, and the mixture was exꢀ
tracted with chloroform (3×25 mL). The combined extracts were
dried over sodium sulfate and filtered. The solvent was evapoꢀ
rated in vacuo, and the residue was recrystallized from benzene.
Compound 2a was obtained in a yield of 2.9 g (94%) as white
crystals, m.p. 132—134 °C (C6H6). 31P NMR (CDCl3), δ: 29.65.
1H NMR (CDCl3), δ: 3.40 (br.s, 2 H, NH2); 3.54 (d, 2 H, CH2,
2JP,H = 13.8 Hz); 6.38 (d, 1 H, C6H4N, 3JH,H =7.7 Hz); 6.47 (d,
1600
1400
1200
ν/cm–1
A
0.4
0.2
0
c
1600
1400
1200
ν/cm–1
A
3
1 H, C6H4N, JH,H = 7.7 Hz); 6.54 (br.d, 1 H, C6H4—N, J =
d
0.4
0.2
0
3
1.9 Hz); 6.92 (t, 1 H, C6H4N, JH,H = 7.7 Hz); 7.41—7.50 and
7.62—7.72 (both m, 6 H + 4 H, PhP). IR (KBr), ν/cm–1: 3425,
3364, 3328, 3200 (NH2), 1190 (PO). Found (%): C, 74.37;
H, 5.96; N, 4.42. C19H18NOP. Calculated (%): C, 74.25;
H, 5.90; N, 4.56.
oꢀ(Diphenylphosphorylmethyl)aniline (2b) was synthesized acꢀ
cording to an analogous procedure from 1b in 87% yield, m.p.
198—200 °C (C6H6). 31P NMR (CDCl3), δ: 34.06. 1H NMR
(CDCl3), δ: 3.72 (d, 2 H, CH2, 2JP,H = 12.8 Hz); 4.75 (br.s, 2 H,
1600
1400
1200
ν/cm–1
Fig. 5. Fragments of the IR spectra (Nujol) of crystalline samples
of compounds 3a (a) and 3b (b) and praseodymium comꢀ
plexes 4a (c) and 4b (d). Bands associated with Nujol are exꢀ
cluded.
3
NH2); 6.56 (t, 1 H, C6H4—N, JH,H = 7.3 Hz); 6.63 (d, 1 H,
C6H4—N, 3JH,H = 7.3 Hz); 6.76 (d, 1 H arom., 3JH,H = 8.0 Hz);
3
3
7.04 (dd, 1 H, C6H4N, JH,H = 7.3 Hz, JH,H = 8.0 Hz);
7.42—7.55 and 7.75—7.80 (both m, 6 H + 4 H, PhP). IR (KBr),
ν/cm–1: 3402, 3305, 3250, 3219 (NH2); 1173 (PO). Found (%):
C, 74.14; H, 5.76; N, 4.51. C19H18NOP. Calculated (%):
C, 74.25; H, 5.90; N, 4.56.
the 31P NMR spectra of the reaction mixtures, D2O was used as
the external standard. The IR spectra were measured on a Nicolet
MagnaꢀIR 750 infrared Fourierꢀtransform spectrometer; the
resolution was 2 cm–1, the number of scans was 128 (KBr pellets
or Nujol mulls).
Nitrobenzyl bromides were synthesized from oꢀ or mꢀnitroꢀ
benzaldehyde by the Cannizzaro reaction9 followed by the broꢀ
mination of nitrobenzyl alcohols that formed with phosphorus
tribromide according to known procedures.10,11
(mꢀNitrobenzyl)diphenylphosphine oxide (1a). Ethyl diphenylꢀ
phosphinite (29.0 g, 0.126 mol) was slowly added dropwise to a
solution of mꢀnitrobenzyl bromide (27.2 g, 0.126 mol) in refluxꢀ
ing toluene. The reaction mixture was refluxed with stirring
for 2 h and then cooled. The precipitate was filtered off and
recrystallized from ethanol. Compound 1a was obtained in a
yield of 42.4 g (85%) as a white crystalline compound (needleꢀ
2ꢀ[3ꢀ(Diphenylphosphorylmethyl)phenyliminomethyl]phenol
(3a). A solution of salicylaldehyde (0.36 g, 0.003 mol) in ethanol
(2 mL) was slowly added dropwise to a solution of meta isoꢀ
mer 2a (0.9 g, 0.003 mol) in ethanol. The reaction mixture was
refluxed for 2 h. The solution was concentrated to dryness, and
the residue was recrystallized from a 1 : 1 benzene—diethyl ether
mixture. Imine 3a was obtained in a yield of 0.8 g (67%) as a
yellow crystalline compound, m.p. 164—166 °C. 31P NMR
(CDCl3), δ: 29.43. 1H NMR (CDCl3), δ: 3.68 (d, 2 H, CH2,
2JP,H = 13.5 Hz); 6.92 (dt, 1 H, arom., 3JH,H = 7.3 Hz, 3JH,H
=
3
8.0 Hz); 6.94 (br.d, 1 H, arom., JH,H = 7.4 Hz); 6.98 (d, 1 H,
3
3
arom., JH,H = 8.0 Hz); 7.02 (d, 1 H, arom., JH,H = 7.4 Hz);
3
7.09 (d, 1 H, arom., JH,H = 7.4 Hz); 7.23 (t, 1 H, arom.,

1898
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
Aleksanyan et al.
Table 4. Principal crystallographic data and the refinement statistics for 1a,b, 3a, and 4b
Parameter
1а
1b
3а
4b
Molecular formula
Molecular weight
C
19H16NO3P
337.30
C19H16NO3P
337.30
C26H22NO2P
411.42
C52H44N5O13P2Pr
1149.77
Crystal dimensions
T/K
0.19×0.18×0.15
0.26×0.18×0.15
120
0.4×0.2×0.2
120
0.11×0.04×0.02
100
120
Crystal system
Space group
Triclinic
Orthorhombic
P212121
Monoclinic
P21/n
Triclinic
–
–
P1
P1
Z(Z´)
a/Å
b/Å
с/Å
α/deg
β/deg
2(1)
5.7534(9)
11.125(2)
13.844(3)
112.257(5)
98.96(3)
96.319(5)
801.3(2)
1.398
4(1)
4(1)
2(1)
9.9318(13)
11.601(2)
23.540(3)
84.688(9)
80.645(8)
71.769(6)
2539.4(7)
1.504
5.6835(6)
13.872(1)
20.501(2)
13.208(2)
7.3837(1)
16.025(3)
92.371(4)
γ/deg
V/Å3
1616.3(3)
1.368
1.87
1561.5(5)
1.635
1.42
dcalc/g cm–3
µ/cm–1
1.89
10.92
F(000)
352
704
808
1168
2θmax/deg
60
60
58
54
Number of measured reflections (Rint
Number of independent reflections
)
10445 (0.0723)
4680
12573 (0.0473)
4642
12087 (0.0203)
5411
24352 (0.1745)
11034
Number of reflections with I > 2σ(I )
2386
2958
4155
5060
Number of variables
217
217
329
652
R1
wR2
GOOF
0.0489
0.1226
0.848
0.48/–0.55
0.0454
0.0827
0.952
0.0417
0.1124
1.079
0.0747
0.1356
0.935
1.114/–1.717
Residual electron density/e Å–3
0.43/–0.38
0.42/–0.25
(dmin/dmax
)
3
4
4
JH,H = 8.0 Hz); 7.32 (dt, 1 H, arom., JH,H = 7.4 Hz, JP,H
=
118.45 (d, C(4), JP,C = 2.9 Hz); 118.93 (s, C(13)); 119.16
3
4
2
1.6 Hz); 7.35 (dt, 1 H, arom., JH,H = 8.0 Hz, JP,H = 1.6 Hz);
7.43—7.55, 7.68—7.73 (m, 6 H + 4 H, PhP); 8.38 (s, 1 H,
CH=N); 13.13 (s, 1 H, OH). 13C NMR (CDCl3), δ:* 37.93 (d,
C1, JP,C = 65.6 Hz); 117.06 (s, C(11)); 118.91 (s, C(13)); 119.01
(s, C(9)); 120.32 (d, C(7), JP,C = 2.9 Hz); 122.06 (d, C(6),
5JP,C = 5.1 Hz); 128.47 (d, C(17), C(23), C(19), C(25), 3JP,C
11.7 Hz); 128.58 (s, C(5)); 129.20 (d, C(3), JP,C = 2.9 Hz);
131.05 (d, C(16), C(22), C(20), C(26), JP,C = 8.7 Hz);
131.83 (d, C(18), C(24), JP,C = 2.2 Hz); 131.97 (d, C(15),
C(21), JP,C = 99.2 Hz); 132.14 (s, C(14)); 132.46 (d, C(2),
2JP,C = 8.0 Hz); 133.00 (s, C(12)); 148.29 (s, C(4)); 160.96 (s,
C(10)); 162.72 (s, C(8)). IR (Nujol), ν/cm–1: 512, 524, 694,
719, 755, 793, 891, 946, 998, 1119, 1148, 1182, 1278, 1437,
1484, 1572, 1591, 1619, 2300—3300. Found (%): C, 75.98;
H, 5.36; N, 3.31. C26H22NO2P. Calculated (%): C, 75.90;
H, 5.39; N, 3.40.
The ortho isomer of salicylaldimine (3b) was synthesized
analogously in 85% yield, m.p. 158—160 °C (benzene—diethyl
ether, 1 : 1). 31P NMR (CDCl3), δ: 29.20. 1H NMR (CDCl3), δ:
3.93 (d, 2 H, CH2, 2JP,H = 13.7 Hz); 6.91—7.02 (m, 2 H, arom.);
(s, C(9)); 125.16 (d, C(2), JP,C = 8.7 Hz); 126.84 (d, C(6),
4JP,C = 2.9 Hz); 128.19 (d, C(17), C(23), C(19), C(25), 3JP,C
=
11.7 Hz); 128.28 (s, C(5)); 130.94 (d, C(16), C(22), C(20),
C(26), 2JP,C = 8.7 Hz); 131.50 (d, C(18), C(24), 4JP,C = 2.2 Hz);
131.90 (d, C(7), 3JP,C = 4.4 Hz); 131.96 (d, C(15), C(21), 1JP,C
=
4
=
97.8 Hz); 132.45 (s, C(14)); 133.07 (s, C(12)); 147.64 (d, C(3),
3JP,C = 5.8 Hz); 160.57 (s, C(10)); 163.14 (s, C(8)). IR (Nujol),
ν/cm–1: 512, 524, 694, 719, 746, 767, 910, 1121, 1148, 1187,
1282, 1436, 1482, 1569, 1592, 1617, 2300—3300. Found (%):
C, 75.71; H, 5.27; N, 3.34. C26H22NO2P. Calculated (%):
C, 75.90; H, 5.39; N, 3.40.
Bis{2ꢀ[3ꢀ(diphenylphosphorylmethyl)phenyliminomethyl]pheꢀ
nol}praseodymium trinitrate (4a). The Pr(NO3)3•6H2O comꢀ
pound (51.8 mg, 0.12 mmol) was added to a solution of
salicylaldimine 3a (97.9 mg, 0.24 mmol) in ethanol (2.5 mL),
and the reaction mixture was heated until the reagents were
completely dissolved. Then the mixture was kept for 12 h, and
the precipitate that formed was separated and recrystallized
from EtOH. The complex was obtained in a yield of 125.1 mg
(90.1%), m.p. 158—160 °C (with decomp.). IR (Nujol),
ν/cm–1: 518, 694, 736, 756, 817, 1028, 1094, 1124, 1140, 1153,
1297, 1438, 1462, 1483, 1534, 1571, 1592, 1602, 1620,
1634. 31P NMR (EtOH), δ: 40.2. Found (%): C, 54.14;
H, 3.87; N, 6.12. C52H44N5O13P2Pr. Calculated (%): C, 54.32;
H, 3.86; N, 6.09.
3
2
4
1
3
7.08 (d, 1 H, arom., JH,H = 8.0 Hz); 7.21 (t, 1 H, arom.,
3JH,H = 7.5 Hz); 7.29—7.47 (m, 9 H, arom.); 7.63—7.69 (m,
5 H, arom.); 7.86 (s, 1 H, CH=N); 12.92 (s, 1 H, OH). 13C NMR
(CDCl3), δ: 33.34 (d, C(1), 1JP,C = 66.4 Hz); 116.98 (s, C(11));
* For comparison, ν(C=N) for analogous unphosphorylated
Under analogous conditions, bis{2ꢀ[2ꢀ(diphenylphosphorylꢀ
methyl)phenyliminomethyl]phenol}praseodymium trinitrate (4b)
salicylaldimines is 1628 cm–1 6
.

Phosphorylated salicylaldimines
Russ.Chem.Bull., Int.Ed., Vol. 56, No. 9, September, 2007
1899
was synthesized from imine (3b) (82.0 mg) and Pr(NO3)3•6H2O
(43.3 mg) in a yield of 102.1 mg (89.2% ), m.p. 220—222 °C.
IR (Nujol), ν/cm–1: 521, 692, 748, 818, 1032, 1093, 1122, 1133,
1141, 1161, 1296, 1436, 1457, 1475, 1497, 1537, 1571, 1597,
1617, 1626. 31P NMR (EtOH), δ: 59.9. Found (%): C; 54.66;
H, 3.84; N, 5.77. C52H44N5O13P2Pr. Calculated (%): C, 54.32;
H, 3.86; N, 6.09.
References
1. A. D. Garnovskii and I. S. Vasil´chenko, Usp. Khim., 2002,
71, 1064 [Russ. Chem. Rev., 2002, 71 (Engl. Transl.)].
2. A. D. Garnovskii and I. S. Vasil´chenko, Usp. Khim., 2005,
74, 211 (and references herein) [Russ. Chem. Rev., 2005, 74
(Engl. Transl.)].
3. T.ꢀJ. Kim, H.ꢀY. Lee, E.ꢀS. Ryu, D.ꢀK. Park, C. S. Cho,
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M. Jan, Inorg. Chim. Acta, 2001, 314, 133.
Neodymium complex 4c was synthesized under analogous
conditions from ligand 3b (88.5 mg, 0.215 mmol) and
Nd(NO3)3•6H2O (47.2 mg, 0.1075 mmol). The yield was 91%,
m.p. 165—167 °C (with decomp.). IR (Nujol mulls), ν/cm–1
:
520, 691, 720, 755, 818, 1040, 1092, 1122, 1132 (PO); 1143,
1161 (PO); 1297 (NO3); 1377, 1436, 1463, 1480 (NO3); 1536,
1595, 1615, 1623 (NCN). 31P (EtOH), δ: 43.7. Found (%):
C, 54.19; H, 3.85; N, 6.34. C52H44N5NdO13P2. Calculated (%):
C, 54.16; H, 3.85; N, 6.07.
Xꢀray diffraction study. Xꢀray diffraction data for compounds
1a,b and 3a were collected on a SMART 1000 CCD diffractoꢀ
meter; for complex 4b, on a SMART APEXII CCD diffractoꢀ
meter (MoꢀKα radiation, graphite monochromator, ωꢀscanning
technique). Crystals suitable for Xꢀray diffraction were grown
from EtOH (1a,b), CH2Cl2—ButOMe (3a), and CH3CN (4b).
Semiempirical absorption corrections were applied based on
equivalent reflections with the use of the Sadabs program. The
rather high Rint factor for complex 4b is accounted for by small
crystal sizes and the low reflecting ability even when the expoꢀ
sure time of 60 s per frame was used. The structures were solved
by direct methods and refined anisotropically by the fullꢀmatrix
leastꢀsquares method based on F 2hkl. The hydrogen atoms at the
nitrogen and oxygen atoms in 3a and 4b were located in differꢀ
ence Fourier maps. The other hydrogen atoms were positioned
geometrically. An analysis of difference Fourier maps for
meta isomer 3a showed that one phenyl ring is disordered over
two positions with occupancies of 0.4 and 0.6. Principal crystalꢀ
lographic data and the refinement statistics are given in Table 4.
All calculations were carried out with the use of the SHELXTL
PLUS program package.
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303, 116.
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(b) Azometiny: stroenie, svoistva, primenenie [Azomethines:
Structures, Properties, and Application], Izdꢀvo Rostovskogo
unꢀta, RostovꢀonꢀDon, 1967, 285—289 (in Russian).
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Coordination Compounds, 4th ed., J. Wiley and Sons, New
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Chem. Bull., 1996, 45, 1466 (Engl. Transl.)].
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Bachmann, J. R. Johnson, L. F. Fieser, and H. R. Snyder,
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12. G. Aksnes, R. Gierstae, and E. A. Wulvik, Phosphorus and
Sulfur, 1988, 39, 141.
This study was financially supported by the Russian
Foundation for Basic Research (Project Nos 05ꢀ03ꢀ33094
and 05ꢀ03ꢀ32692).
Received April 4, 2007;
in revised form June 8, 2007