Synthesis, physicochemical properties and crystal structure of isothiocianato [2-(diphenylphosphino)benzaldehyde selenosemicarbazonato(1 -)] nickel(II)

Article abstract of DOI:10.1016/j.inoche.2003.11.013

The syntheses of a new ligand 2-(diphenylphosphino)benzaldehyde selenosemicarbazone (HL) and the corresponding complex with Ni(II) of the formula [Ni(L)(NCS)] are reported. The complex was characterized by single crystal X-ray analysis. The compound complex is diamagnetic and has a markedly deformed square-planar structure with PNSe set of donor atoms of the ligand, the Schiff base monoanion, and the N atom of the coordinated NCS group. The phosphorus atom deviates even by 0.494(3) ? from the mean plane defined by the other coordination atoms (NSeN) and the metal atom.

Full text of DOI:10.1016/j.inoche.2003.11.013

Inorganic Chemistry Communications 7 (2004) 253–256
www.elsevier.com/locate/inoche
Synthesis, physicochemical properties and crystal structure
of isothiocianato [2-(diphenylphosphino)benzaldehyde
selenosemicarbazonato(1ꢀ)] nickel(II)
a
Ilija D. Brceski , Vukadin M. Leovac , Goran A. Bogdanovic
b
c,
*
ꢀ
ꢁ
,
a
Sofija P. Sovilj , Mihail Revenco
d
a
Faculty of Chemistry, University of Belgrade, Studentski trg 16, P.O. Box 158, Belgrade 11001, Serbia and Montenegro
Department of Chemistry, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradoviꢁca 3, Novi Sad 21000, Serbia and Montenegro
b
c
ꢀ
VINCA Institute of Nuclear Sciences, P.O. Box 522, Belgrade 11001, Serbia and Montenegro
Department of Chemistry, State University of Moldova, Mateevic 60, Kishinau 277014, Moldova
d
Received 9 September 2003; accepted 15 November 2003
Published online: 9 December 2003
Abstract
The syntheses of a new ligand 2-(diphenylphosphino)benzaldehyde selenosemicarbazone (HL) and the corresponding complex
with Ni(II) of the formula [Ni(L)(NCS)] are reported. The complex was characterized by single crystal X-ray analysis. The com-
pound complex is diamagnetic and has a markedly deformed square-planar structure with PNSe set of donor atoms of the ligand,
ꢂ
the Schiff base monoanion, and the N atom of the coordinated NCS group. The phosphorus atom deviates even by 0.494(3) A from
the mean plane defined by the other coordination atoms (NSeN) and the metal atom.
Ó 2003 Published by Elsevier B.V.
Keywords: Nickel(II) complex; 2-(Diphenylphosphino)benzaldehyde selenosemicarbazone; Crystal structure; IR spectra; Deformed coordination
geometry
1. Introduction
bazide and selenosemicarbazones and their metal com-
plexes is much smaller, and only crystalline structures of
two complexes with this class of ligands have been re-
ported [9,10].
The coordination chemistry of thiosemicarbazides
and their derivatives began in the 30s of the last century
with the works of Jensen and co-workers [1,2]. Because
of their good complexation properties, wide spectrum of
biological activity, and the application as analytical re-
agents, these compounds and their metal complexes
have become subject of intensive study of a large num-
ber of authors [3–8]. Hence it is not surprising that there
appeared a lot of papers, among them hundreds of
works dealing with the elucidation of crystal and mo-
lecular structures of these compounds. In contrast to
them, the number of works devoted to selenosemicar-
In our previous works [11,12] we described the crystal
and molecular structures of Ni(II) and Cu(I) complexes
with the tridentate PNS ligand, 2-(diphenylphosph-
ino)benzaldehyde thiosemicarbazone. In this work we
present the crystal and molecular structure of the
square-planar Ni(II) complex with the monoanion 2-
(diphenylphosphino)benzaldehyde selenosemicarbazone
(HL) (Fig. 1) of the formula [Ni(L)(NCS)], as the first
example of a complex synthesized with selenosemicar-
bazone derivatives as ligands and involving phosphorus
as one of the ligator atoms.
Synthesis of the ligand HL. A mixture of 0.58 g
(2 mmol) of 2-(diphenylphosphino)benzaldehyde and
0.28 g (2 mmol) of selenosemicarbazide, both prepared
* Corresponding author. Tel.: +381-63-871-77-09; fax: +381-11-344-
01-00.
ꢁ
E-mail address: goranb@vin.bg.ac.yu (G.A. Bogdanovic).
1387-7003/$ - see front matter Ó 2003 Published by Elsevier B.V.
doi:10.1016/j.inoche.2003.11.013

254
I.D. Brꢀceski et al. / Inorganic Chemistry Communications 7 (2004) 253–256
found in difference Fourier maps but they were placed at
calculated positions using a riding model and isotropic
displacement parameters were set equal to 1.2 times the
equivalent isotropic displacement parameter of the
parent atoms. Details of the crystal structure analysis,
full tables of atomic positions, bond lengths, angles,
anisotropic thermal parameters for nonhydrogen atoms,
hydrogen coordinates and their respective isotropic
displacement parameters, torsion angles and hydrogen
bonds are available from the corresponding author on
request.
Fig. 1. Structural formula of 2-(diphenylphosphino)benzaldehyde
selenosemicarbazone (HL).
Elemental (C, H, N) analysis of air-dried compounds
was carried out by standard micromethods in the Center
for Instrumental Analysis, Faculty of Chemistry, Bel-
grade. Molar conductivity of freshly-prepared 1 ꢂ 10ꢀ3
M solution in DMF was measured on a Jenway 4010
conductivity meter. FT-IR spectra (KBr disc) were run
on a Perkin–Elmer FT-IR 31725X.
according to the previously described procedures
[13,14], was dissolved at heating in a mixture of EtOH
(10 cm3) and glacial acetic acid (3 cm3); the heating
being continued at stirring for 10 min. The yellow nee-
dle-like crystals of the ligand, that appeared still in the
warm solution, were separated after 5 h by filtration and
washed with EtOH and Et2O. Yield: 0.61 g (74%). Anal.
Calcd. for C20H18N3PSe (M ¼ 410.30 g molꢀ1): C, 58.54;
H, 4.42; N, 10.24%. Found: C, 58.35; H, 4.50; N,
10.43%.
2. Results and discussion
Synthesis of the complex [Ni(L)(NCS)]. A mixture of
0.17 g (0.6 mmol) of Ni(NO3)2 ꢁ 6H2O and 0.20 g (0.5
mmol) of HL was poured over with MeOH (10 cm3) and
heated. To the red solution, 0.10 g (1 mmol) of KNCS
was added and heated for 2–3 min. Along with KNO3,
red thin needle-like crystals appeared already in the
warm solution. In the mother liquor, in the course of 10
h, the latter completely transformed into brown mono-
crystals of title complex. The crystals were filtered, the
precipitated KNO3 removed by washing with water, and
the complex was dried on the filter by washing with
MeOH and Et2O. Yield: 0.20 g (78%). Anal. Calcd. for
C21H17N4Ni PS Se (M ¼ 526.06 g molꢀ1): C, 47.94; H,
3.26; N, 10.65%. Found: C, 48.02; H, 3.41; N, 10.51%.
The X-ray experimental data were collected on an
Enraf-Nonius CAD4 diffractometer [15] by using
The ligand HL was obtained in a good yield by the
reaction of mildly acidic (AcOH) warm EtOH solutions
of the stoichiometric amounts of 2-(diphenylphosph-
ino)benzaldehyde and selenosemicarbazide. The reali-
zation of the condensation reaction, apart from the
elemental analysis, was also confirmed by the absence of
the m(C@O) band in the spectrum of the ligand, which in
the spectrum of the aldehyde precursor is observed as a
very strong doublet at 1696 and 1677 cmꢀ1 [13] and by
the appearance of a strong m(C@N) + d (NH2) band at
1577 cmꢀ1 [20]. The absence of the m(Se–H) band at 2300
cmꢀ1 [21] speaks in favor of a non-enolized form of the
ligand in its crystalline state. The obtained ligand is
soluble in DMF and DMSO and sparingly soluble in
MeOH and EtOH. Brown monocrystals of title
[Ni(L)(NCS)] complex were obtained by the reaction of
Ni(NCS)2 with the ligand in a warm MeOH. The iso-
lated complex is diamagnetic, suggesting its square-
planar structure, which was confirmed by X-ray analysis
(vide infra). This analysis showed that square-planar
surroundings of the nickel atom are formed by the tri-
dentate PNSe coordination of the ligand monoanion
and the coordinated monodentate isothiocyanato group
(Fig. 2). This mode of ligand coordination was also
confirmed by the IR spectra. First of all, in the ligand
spectrum, in the region of the m(NH2/NH) vibrations,
there are three bands of medium intensity at 3431, 3288
and 3138 cmꢀ1 which can be ascribed to the mas=s(NH2)
and m(NH) vibrations, respectively. In contrast to this,
the spectrum of the complex has in the same range only
two bands, at 3280 and 3177 cmꢀ1, corresponding to the
ma=s(NH2) vibrations, which, due to intermolecular hy-
drogen bonds (Fig. 2), are shifted to lower energies.
ꢂ
graphite-monochromated Mo Ka (0.71073 A) radiation
at 293(2) K. A total of 6421 reflections (in 1.64–29.97° h
range) were collected by using x=2h scans. The data
were corrected for Lorentz and polarization effects [16].
A gaussian-type absorption correction [17,18] based on
the crystal morphology was applied (Tmin ¼ 0.543,
Tmax ¼ 0.673; single-crystal dimensions were 0.29 ꢂ
0.18 ꢂ 0.18 mm). Crystallographic data: formula C21H17
ꢃ
N4NiPSSe, Fw ¼ 526.06, triclinic, space group ¼ P1,
ꢂ
ꢂ
ꢂ
a ¼ 9.430(2) A, b ¼ 9.688(2) A, c ¼ 12.894(2) A,
a ¼ 77.67(2)°, b ¼ 77.29(2)°, c ¼ 74.55(2)°, V ¼ 1092.4(4)
A , Z ¼ 2, Dc ¼ 1.599 g cmꢀ3, l ¼ 2.737 mmꢀ1
.
3
ꢂ
The structure was solved by the heavy atom method
[19a] and difference Fourier methods and refined on F 2
by full-matrix least-square method [19b] to R1 ¼ 0:0404
and wR2 ¼ 0:0842 for 262 refined parameters and 3335
reflections with I > 2rðIÞ. Almost all H atoms were

I.D. Brꢀceski et al. / Inorganic Chemistry Communications 7 (2004) 253–256
255
Fig. 2. ORTEP [7] drawing of complex dimer with atom numbering scheme. The thermal ellipsoids correspond to 50% probability. Symmetry code:
ꢂ
(i) ꢀx þ 1, ꢀy, ꢀz þ 1. Selected bond lengths (A) and angles (°): Ni–N4 1.827(3), Ni–N1 1.898(2), Ni–P 2.1791(9), Ni–Se 2.2692(6), Se–C1 1.862(3),
P–C4 1.796(3), P–C16 1.814(3), P–C10 1.823(4), S–C9 1.600(4), N1–C2 1.299(4), N1–N2 1.404(3), N2–C1 1.303(4), N3–C1 1.338(4), N4–C9 1.150(4),
C2–C3 1.449(4), C3–C4 1.404(4), N4–Ni–N1 174.99(13), N4–Ni–P 90.11(10), N1–Ni–P 93.80(8), N4–Ni–Se 87.32(9), N1–Ni–Se 89.44(8), P–Ni–Se
168.67(3), N4–C9–S 177.5(4).
The m(C@N) band of a medium intensity in the
spectrum of the complex, due to the effect of nitrogen
coordination, is shifted to higher energies [20,22,23] and
is observed at 1629 cmꢀ1. As a consequence of the co-
ordination of the selenium atom the m(C–Se) band is
the square-planar geometry would be of a regular form.
However, since the phosphorus atom in the molecule
forms four bonds, the preferred angle between these
bonds would be about 109°, which is in contrast to the
planar form of the ring, requiring the angle Ni–P–C4 to
be about 125° [27]. A consequence of this is that the
phosphorus atom is protruding out from the ring plane,
attaining thus an Ni–P–C4 angle of 112.63(11)°, and
distorting drastically the square-planar surroundings
around Ni [the N1–Ni–P–C4 torsion angle is 29.63(2)°].
The mutual positions of the atoms in coordination are
visible from Fig. 3.
Similar deformation of the square-planar surround-
ings of Ni(II) has also been found in the structure of its
complex with the analogous thiosemicarbazone ligand
[11]. In these two structures the Ni–P and Ni–N1 bonds
are practically identical. In contrast to these bonds, the
shifted to lower energies [24,25], from 760 to 713 cmꢀ1
.
In contrast to the m(C@N) and m(C–Se) bands, the po-
sition of the m(C–P) band after the phosphorus coordi-
nation remains practically unchanged (ꢃ1434 cmꢀ1
)
[20]. Especially strong intensity shows the m(CN) band of
the coordinated isothiocyanato group, observed at 2109
cmꢀ1 [26]. The isothiocyanato group remains coordi-
nated in DMF solutions too, which is evident from the
very low value of the molar conductivity (kM ¼ 7:2 S
cm2molꢀ1).
In the crystal structure of [Ni(L)(NCS)] Ni is found in
a square-planar environment of the P, N1 and Se atoms
of the monoanion of the selenosemicarbazone ligand
and of the isothiocyanato group nitrogen (Fig. 2). The
chelate Schiff base forms with Ni two fused rings, one
of which [(2-diphenylphosphino)benzaldehyde] is six-
membered and the other (selenosemicarbazide) five-
membered. The square-planar structure is markedly
distorted. Namely, the phosphorus atom deviates from
the mean plane defined by the NiN4SeN1 atoms even by
ꢂ
Ni–Se bond in our complex [2.2692(6) A] is somewhat
longer than the same in the square-planar Ni(II) com-
plex with the dianionic salicylaldehyde selenosemicar-
ꢂ
bazone [9] where the Ni–Se bond distance is 2.241(2) A.
The molecules are bound into dimers (Fig. 2), forming
two N3–Hꢁ ꢁ ꢁN2 intermolecular hydrogen bonds: N3–
i
i
ꢂ
ꢂ
ꢂ
H ¼ 0.86 A, N3ꢁ ꢁ ꢁN2 ¼ 3.005(4) A, Hꢁ ꢁ ꢁN2 ¼ 2.17 A,
N3–Hꢁ ꢁ ꢁN2i ¼ 163.8(2)° ; symmetry code: (i) )x + 1,)y,
)z + 1. The N3H2 group forms also another intermo-
lecular hydrogen bond with sulfur atom of the NCS
ꢂ
0.494(3) A. It should be noticed that the NiN4SeN1
atoms that define the plane are approximately co-pla-
nar, with the mean deviation from the plane of 0.026 A.
group: N3–H ¼ 0.86 A, N3ꢁ ꢁ ꢁSii ¼ 3.375(4) A,
ꢂ
ꢂ
ꢂ
Hꢁ ꢁ ꢁSii ¼ 2.54 A, N3–Hꢁ ꢁ ꢁSii ¼ 162.6(2)°; symmetry
ꢂ
This structural deformation can be explained by the
participation of the phosphorus atom in the formation
of the six-membered chelate ring. Namely, the N1, C2,
C3, C4 atoms forming this ring are sp2-hybridized and
consequently they favor a planar form of the ring. Thus,
the Ni–N1–C2–C3 and N1–C2–C3–C4 torsion angles
are 2.2(6)° and 11.1(6)°, respectively. Planar form of the
six-membered ring would also make possible position of
the phosphorus atom in an approximately same plane
with the other coordination atoms (N1, Se, N4) so that
code: (ii) )x, )y + 1, )z + 1. Apart from those already
Fig. 3. View of complex fragment showing the coordination geometry
and chelate rings conformation. Displacement ellipsoids are shown at
the 20% probability level and H atoms are omitted for clarity.

256
I.D. Brꢀceski et al. / Inorganic Chemistry Communications 7 (2004) 253–256
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mentioned, there are no other significant hydrogen
bonds or intermolecular interactions.
[15] Enraf-Nonius, CAD4 Software, Version 5, Enraf-Nonius, Delft,
The Netherlands, 1989.
[16] CAD4 Express Softvare. Enraf-Nonius, Delft, The Netherlands,
1994.
Acknowledgements
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[19] (a) G.M. Sheldrick, SHELXS97 Program for the Solution
The authors are grateful to the Ministry of Science,
Technology and Development of the Republic of Serbia
for financial support (Project 1318 – Physicochemical,
Structural and Biological Investigation of Complex
Compounds).
€
of Crystal Structures, University of Gottingen, Germany,
1997;
(b) G.M. Sheldrick, SHELXL97. Program for the Refinement of
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