Structural effects of the chelating rings in trans-[Ni{Ph2P(Se)NPPh2-Se,P}2] and trans-[Ni{Ph2P(Se)NPPh2-Se,P}{Ph2P(Se)N (H)PPh2-Se,P}]Cl·CH2Cl2·H 2</s

Article abstract of DOI:10.1016/j.poly.2009.05.006

The reaction of the monooxidised imidodiphosphinate ligand Ph₂P(Se)NHPPh₂ with NiCl₂·6H₂O in the presence of ^tBuOK afforded [Ni{Ph₂P(Se)NPPh₂-Se,P}₂] (1), which was ch

Full text of DOI:10.1016/j.poly.2009.05.006

Polyhedron 28 (2009) 3305–3309
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Structural effects of the chelating rings in trans-[Ni{Ph2P(Se)NPPh2-Se,P}2]
and trans-[Ni{Ph2P(Se)NPPh2-Se,P}{Ph2P(Se)N(H)PPh2-Se,P}]ClꢀCH2Cl2ꢀH2O
complexes
Nikolaos Levesanos a, Ioannis Stamatopoulos a, Catherine P. Raptopoulou b, Vassilis Psycharis b,
Panayotis Kyritsis a,
*
a Inorganic Chemistry Laboratory, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, GR 157 71 Athens, Greece
b Institute of Materials Science, NCSR ‘‘Demokritos”, GR 153 10 Aghia Paraskevi Attikis, Greece
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 12 May 2009
The reaction of the monooxidised imidodiphosphinate ligand Ph2P(Se)NHPPh2 with NiCl2ꢀ6H2O in the
presence of tBuOK afforded [Ni{Ph2P(Se)NPPh2-Se,P}2] (1), which was characterized by UV–Vis, IR and
NMR spectroscopies. X-ray crystallographic studies on a single crystal of 1 revealed the trans Ni(Se,P)2
arrangement in the solid state, showing a bis-chelating type of coordination. The diamagnetic 31P NMR
peaks of 1 in CDCl3 were interpreted as ‘‘deceptive” triplets, due to the conservation of the square–planar
trans-isomer of 1 in solution. The structure of 1 exhibits a center of symmetry, with the two five-mem-
bered Ni–Se–P–N–P rings being equivalent. The higher electronegativity of Se compared to P is consid-
ered as the likely cause of the P–N bond length differences observed in the chelating rings of 1. During
the reaction between NiCl2ꢀ6H2O and the ligand Ph2P(Se)N{(S)-CH(CH3)Ph}PPh2, single crystals were
obtained, the analysis of which by X-ray crystallography showed the formation of trans-[Ni{Ph2P
(Se)NPPh2-Se,P}{Ph2P(Se)N(H)PPh2-Se,P}]ClꢀCH2Cl2ꢀH2O (2). Complex 2 contains one Ni–Se–P–N(H)–P
and one Ni–Se–P–N–P ring. Structural comparison between 1 and 2 makes possible to establish structural
effects due to the protonation/deprotonation of the rings at their N atom.
This article is dedicated to Dr. Aris Terzis, on
the occasion of his retirement, for his
invaluable contribution to the advancement
of inorganic chemistry in Greece through
X-ray crystallography.
Keywords:
Nickel complex
(Se,P)-ligand
Chelating ring
NMR spectroscopy
X-ray crystallography
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
[10], trans-[Hg{Ph2P(O)NPPh2-O,P}2] [11], [ReCl3(H2O){Ph2-
P(O)NHPPh2-O,P}] [12], [Rh(cod){Ph2P(O)NHPPh2-O,P}]BF4 [13],
The coordination chemistry of bis-chalcogenated imi-
dodiphosphinate type of ligands, R2P(E)N(H)P(E0)PR02 (E,E0 = O, S,
Se) has been extensively explored in the course of the last 30 years
[1–5]. More recently, Chivers and coworkers have pioneered the
use of the Te-containing ligand [6–8]. On the other hand, the reac-
tivity of the corresponding monooxidised ligands, R2P(E)N(H)PPR02,
has been studied in a comparatively limited number of cases [2].
The coordination modes of both types of ligands have been re-
viewed [2,9] and shown to predominately include the formation
of six- and five-membered rings, via coordination to the metal
ion of the (E,E0) and (E,P) atoms, respectively. Focusing on the latter
type of coordination compounds, it has been established that the
chelating ligand might be either protonated, M–E–P–N(H)–P, or
unprotonated, M–E–P–N–P, at their N atom. Representative cases
of structurally characterized mononuclear complexes with
coordinated chelating systems (E,P), E = O, S, Se, containing the
two types of five-membered rings, are the complexes cis-
[Pt{Ph2P(O)N(H)PPh2-O,P}2](BF4)2 and cis-[Pt{Ph2P(O)NPPh2-O,P}2]
[Rh(CO)(PPh3){Ph2P(O)NPPh2-O,P}]
NHPPh2-O,P}] [15], [Pd(C,N){Ph2P(O)NHPPh2-O,P}]BF4
[OsCl(
6-cym){Ph2P(O)NHPPh2-O,P}]BF4 [17], [(C3H5)Pd{Ph2P(O)-
NHPPh2-O,P}]BF4 [18], [(
5-C5Me5)MCl{Ph2P(S)NHPPh2-S,P}]BF4,
[14],
[PdCl(CH3){Ph2P(O)-
[16],
g
g
M = Rh, Ir [19], [ReO(OEt){Ph2P(Se)NPPh2-Se,P}2] [20], [Ag{Ph2P-
(Se)N(H)PPh2-Se,P}2]Br [21], [Ru(@CHPh){Ph2P(Se)NPPh2-Se,P}2]
[22], trans-[Pt{Ph2P(Se)N(H)PPh2-Se,P}2]Cl2 and cis-[Pt{Ph2P-
(Se)NPPh2-Se,P}2] [23], [Ru(Cl)(NO){Ph2P(Se)NP(Se)Ph2-Se,Se}-
{Ph2P(Se)NPPh2-Se,P}] [24], [(g
5-C5Me5)RhCl{Ph2P(Se)NPPh2Se,P}]
[25] and [Pd{Ph2P(Se)NPPh2}- Se, P}{Ph2P(Se)NP(Se)Ph2-Se,Se}]
[26].
The interest in this type of systems stems from their potential to
act as catalysts, or to establish previously unobserved coordination
spheres. For instance, recent studies have explored the catalytic
activity of [Rh(CO)(PPh3){Ph2P(O)NPPh2-O,P}] in the hydroformyla-
tion of styrene [14], while the structural characterization of the
[Ga(l
-Te){iPr2P(Te)NPiPr2-Te,P}]2 [27] and [M{Ph2P(Te)NPPh2-
Te,P}2] complexes, M = Zn, Cd, Hg [28], has been described.
In this work, the coordination of Ph2P(Se)N(H)PPPh2 to Ni(II)
has been studied. Under the appropriate conditions, the synthetic
procedure afforded trans-[Ni{Ph2P(Se)NPPh2-Se,P}2] (1), which
* Corresponding author. Tel.: +30 210 7274268; fax: +30 210 7274782.
E-mail address: Kyritsis@chem.uoa.gr (P. Kyritsis).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.05.006

3306
N. Levesanos et al. / Polyhedron 28 (2009) 3305–3309
was characterized by UV–Vis, IR and NMR spectroscopy, as well as
by X-ray crystallography. The structure of this complex enables
comparisons with the previously characterized [Ni{Ph2PNPPh2-
P,P}2] [29] and [Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2] [30] complexes, in
which there are four- and six-membered rings, respectively. Fur-
thermore, while investigating the coordination between
Ph2P(Se)N{(S)-CH(CH3)Ph}PPh2 [31] and Ni(II), single crystals were
isolated, the analysis of which revealed the trans-[Ni{Ph2P(Se)-
NPPh2-Se,P}{Ph2P(Se)N(H)PPh2-Se,P}]ClꢀCH2Cl2ꢀH2O (2) structure,
which contains one Ni–Se–P–N(H)–P and one Ni–Se–P–N–P ring,
in the same molecule. This unprecedented structure makes possi-
ble to compare the structural characteristics of such rings in the
same molecule, as well as in the structure of 1.
Table 1. The structures were solved by direct methods using SHEL-
XS-97 [33] and refined by full-matrix least-squares techniques on
F2 with SHELXL-97 [34]. Further crystallographic details for 1:
2hmax = 50°;
reflections
collected/unique/used,
3904/3664
[Rint = 0.0190]/3664; 340 parameters refined; (D/r) = 0.001;
max
(D
q)
max/(D
q
)
min = 0.664/ꢁ0.306 e/Å3; R/Rw (for all data), 0.0471/
0.0841. Hydrogen atoms were located by difference maps and were
refined isotropically. All non-H atoms were refined anisotropically.
Further crystallographic details for 2: 2hmax = 52°; reflections col-
lected/unique/used, 93095/9494 [Rint = 0.0426]/9494; 723 parame-
ters refined; (
D
/r)
max = 0.002; (
D
q)
max/(
D
q
)
min = 0.922/ꢁ0.705 e/
Å3; R/Rw (for all data), 0.0331/0.0841. Hydrogen atoms were lo-
cated by difference maps and were refined isotropically. All non-
H atoms were refined anisotropically.
2. Experimental
2.3. Synthesis
2.1. UV–Vis, IR and NMR spectroscopy
All manipulations were carried out under a pure Ar atmosphere.
All chemical reagents used were purchased from Aldrich. The li-
gands Ph2P(Se)NYPPh2 [23] and Ph2P(Se)N{(S)-CH(CH3)Ph}PPh2
[31] were prepared according to published procedures.
Electronic spectra were recorded in a Carry 300 Varian spectro-
photometer. IR spectra were run in the range 4000–200 cmꢁ1 on a
Perkin–Elmer 883 IR spectrophotometer, as KBR discs. 31P–{1H}
NMR spectra were recorded in a Varian Unity Plus 300 MHz instru-
ment, operating at 121 MHz, using CDCl3 solutions. The 31P chem-
ical shifts are relative to 85% H3PO4.
2.3.1. trans-[Ni{Ph2P(Se)NPPh2-Se,P}2] (1)
tBuOK (0.0591 g, 0.5 mmol) was added to
a solution of
Ph2P(Se)NHPPh2 (0.2322 g, 0.5 mmol) in methanol (20 mL) and
the mixture was stirred at room temperature for 30 min.
NiCl2ꢀ6H2O (0.0594 g, 0.25 mmol) was subsequently added to the
mixture, which was stirred for additional 2 h. The resulting dark
green precipitate was removed by filtration, washed with metha-
nol (2 ꢂ 10 mL) and dried in vacuo. Yield: 0.1841 g, 0.1868 mmol,
75%. Anal. Calc. for C48H40N2NiP4Se2: C, 58.51; H, 4.09; N, 2.84.
2.2. X-ray crystal structure determination
A dark green crystal of 1 (0.15 ꢂ 0.20 ꢂ 0.30 mm) was mounted
in air, and a yellow–brown crystal of 2 (0.07 ꢂ 0.36 ꢂ 0.48 mm)
was taken directly from the mother liquor and immediately cooled
to ꢁ93 °C. Diffraction measurements for 1 were made on a Crystal
Logic Dual Goniometer diffractometer using graphite monochro-
Found: C, 57.54; H, 4.34; N, 2.79%. IR (cmꢁ1
) m(P–N–P) 1127, m(P–
Se) 541. 31P–{1H} NMR (CDCl3): d = 89.5 [t, P(Ni), N 167.2 Hz],
d = 57.9 [t, P(Se), N 166.9 Hz].
mated Mo Ka radiation. Unit cell dimensions were determined
and refined by using the angular settings of 25 automatically cen-
tered reflections in the range 11 < 2h < 23°. Intensity data were re-
corded using a hꢁ2h scan. Three standard reflections monitored
every 97 reflections showed less than 3% variation and no decay.
Lorentz, polarization corrections were applied using CRYSTAL LOGIC
software. Diffraction measurements for 2 were made on a Rigaku
R-AXIS SPIDER Image Plate diffractometer using graphite mono-
2.3.2. trans-[Ni{Ph2P(Se)NPPh2-Se,P}{Ph2P(Se)N(H)PPh2-
Se,P}]ClꢀCH2Cl2ꢀH2O (2)
An appropriate amount of the ligand Ph2P(Se)N{(S)-
CH(CH3)Ph}PPh2 (0.1000 g, 0176 mmol) was added to a solution
of NiCl2ꢀ6H2O (0.0418 g, 0.176 mmol) in THF (10 mL). The mixture
was stirred for 8 h. During the first hour, the colour of the mixture
was dark red and finally changed to brown. The brown precipitate,
obtained by addition of 15 mL of Et2O, was then removed by filtra-
tion and dried in vacuo. Crystals were obtained from a 1:3 mixture
of CH2Cl2/n-hexane.
chromated Mo Ka radiation. Data collection (x-scans) and pro-
cessing (cell refinement, data reduction and empirical absorption
correction) were performed using the CRYSTALCLEAR program package
[32]. Important crystallographic and refinement data are listed in
Table 1
3. Results and discussion
Crystallographic data for 1 and 2.
1
2
3.1. Synthesis and spectroscopic study
Formula
Fw
Space group
a (Å)
C48H40N2NiP4Se2
985.34
P21/n
9.345(3)
21.908(8)
10.994(3)
102.85(1)
2194.4(12)
2
C49H45Cl3N2NiOP4Se2
1124.73
P21/n
9.7772(2)
16.9296(3)
29.4621(5)
96.329(1)
4846.9(2)
4
The reaction of Ph2P(Se)NHPPh2 with NiCl2ꢀ6H2O, in the pres-
t
ence of BuOK for the in situ deprotonation of the ligand, gave 1
in satisfactory yield, according to the metathesis reaction:
b (Å)
c (Å)
2½KfPh2PðSeÞNPPh2gꢃ þ NiCl2 ꢀ 6H2O
! ½NifPh2PðSeÞNPPh2g2ꢃ þ 2KCl þ 6H2O
b (o)
V (Å3)
Z
Single crystals of 1 were obtained by adding n-hexane into a
CH2Cl2 solution of 1. It is of interest to note that an attempt, in a
different experiment, to synthesize [Ni{Ph2P(Se)NHPPh2-Se,P}Cl2]
by mixing equivalent amounts of [Ni(PPh3)2Cl2] and
Ph2P(Se)NHPPh2, in the absence of tBuOK, afforded crystals, the
analysis of which revealed the formation of 1.
On the other hand, crystals of 2 were isolated while studying
the reaction between NiCl2ꢀ6H2O and the ligand Ph2P(Se)N{(S)-
CH(CH3)Ph}PPh2 [31]. The IR spectrum of these crystals showed
T (°C)
25
Mo K
1.491
ꢁ93
Radiation
a
Mo Ka
qcalc. (g cmꢁ3
)
1.541
l
R1
wR2
(mmꢁ1
)
2.283
2.239
0.0327b
0.0775b
0.0331c
0.0797c
a
a
P
P
a
w = 1/[
r
2(F2o) + (
a
P)2 + bP] and P = ((max Fo2,0) + 2FC2)/3, R1
=
(|Fo|ꢁ|Fc|)/ (|Fo|)
P
P
and wR2 = { [w(F2oꢁF2C)2]/ [w(F2o)2]}1/2
.
b
For 3024 reflections with I > 2
For 7954 reflections with I > 2
r
(I).
(I).
c
r

N. Levesanos et al. / Polyhedron 28 (2009) 3305–3309
3307
the presence of N–H bond [3042 cmꢁ1
,
m
(N–H)], while the 31P NMR
[M{Ph2P(Se)CH2PPh2-Se,P}2]2+
,
M = Pt [36], Pd [37], trans-
showed additional peaks compared to the triplets of 1 (vide infra).
Therefore, the crystals were studied by X-ray crystallography but
no attempt was made to analyse their IR and NMR spectra. The
structure of 2 contains one Ni–Se–P–N(H)–P and one Ni–Se–P–
N–P five-membered ring (vide infra). Therefore, cleavage of the
N–C bond and removal of the –C{CH(CH3)Ph} moiety is responsible
for the formation of 2. A similar observation was previously re-
ported concerning the interaction of M(III) precursors, M = Rh, Ir,
with the same ligand Ph2P(Se)N{(S)-CH(CH3)Ph}PPh2, in acetone,
which resulted in the formation of the [(Cp*)MCl{Ph2P(S)NHPPh2-
S,P}]BF4 complexes [19]. The correlation between this type of
cleavage reactions and the nature of the solvent in which the reac-
tion takes place will be further investigated.
[M{Ph2P(Se)N(H)PPh2-Se,P}2]2+, M = Pd [23], Pt [23] and trans-
[Ni{iPr2P(Se)NPiPr2-Se,P}2] [38]. In all these cases, the separation
of the outermost lines of each triplet, N [= J(AꢁX) + J(AꢁX0)], is re-
ported [23]. In the case of 1, the values of N are 167.2 and 166.9 Hz.
The above pattern in the 31P NMR spectrum of 1 shows that the
trans-Ni(Se,P)2 arrangement, observed in the solid state, is main-
tained in solution. Moreover, the 31P chemical shifts in 1 are in
the diamagnetic part of the spectrum, which provides evidence
that the geometry of the NiSe2P2 core of the complex remains
square–planar in solution. This is in contrast to the analogous
square–planar NiSe4-containing complexes, in which the corre-
sponding 31P NMR peaks are in the paramagnetic part of the spec-
trum, most likely due to the formation of tetrahedral NiSe4 centers,
as was shown in the case of [Ni{iPr2P(Se)NP(Se)iPr2-Se,Se}2] [8]. The
above difference shows that in the latter case the coordination
sphere, which contains six-membered chelating rings, is more flex-
ible in solution compared to complex 1 with five-membered rings.
Fig. S1 shows the electronic spectrum of 1 in CH2Cl2. A band at
378 nm is well defined (
shoulders at 270 and 307 nm (
e
= 5860 Mꢁ1 cmꢁ1), whereas there are two
e
= 27 660 and 19 190 Mꢁ1 cmꢁ1).
Owing to the rather large extinction coefficients determined, most
likely these bands correspond to charge transfer transitions [35].
From the spectrum of 1, it was not possible to clearly identify
any bands due to d–d transitions, although a very broad and not
well defined feature is observed at about 490 nm, in agreement
with the spectra of typical square–planar complexes of Ni(II) [35].
One of the most characteristic IR peaks of chalcogenated imi-
3.2. Molecular structures
The structures of 1 and 2 were determined by single crystal
X-ray diffraction. The crystal data and refinement characteristics
are shown in Table 1. Selected bond lengths and angles are listed
in Table 2. In the case of 2, data are shown separately for its two
five-membered rings. The only available crystallographic struc-
tures for monooxidised imidodiphosphinate ligands are for
Ph2P(O)NHPPh2 [10] and iPr2P(Se)NHPiPr2 [39]. Therefore, it is
not possible to make direct comparisons with the structures of 1
and 2. However, from the data of Table 2, we can draw the conclu-
sions described in the following paragraphs.
dodiphosphinate systems is due to
m
(P–E), which in the case of 1
is observed at 541 cmꢁ1
[m(P–Se)]. Since the free ligand
Ph2P(Se)NHPPh2 exhibits the corresponding IR peak at 551 cmꢁ1
[23], it is concluded that the P–Se bond in 1 is slightly weakened
compared to the free ligand. This is a typical observation concern-
ing the coordination chemistry of either bis-chalcogenated or
monooxidised imidodiphosphinate ligands [2–5].
The assignments in the 31P NMR spectrum of the two different P
atoms of 1, namely the metal bound, P(Ni), and Se-bound, P(Se), are
based on the fact that the former is less shielded than the latter.
This is borne out by the fact that the P(Se)–N bond is stronger com-
pared to the corresponding P(Ni)–N bond (vide infra). The 31P NMR
spectrum of 1 (Fig. 1), shows a pair of mutually coupled triplets,
consisting of an AA0XX0 type pattern. These triplets are ‘‘deceptive”
since, based on the structure of 1, a pair of mutually coupled
doublets would have been expected instead. Similar patterns were
previously observed in analogous complexes, like trans-
3.2.1. trans-[Ni{Ph2P(Se)NPPh2-Se,P}2] (1)
The ORTEP representation of the crystal structure is shown in
Fig. 2. The crystals of 1 contain discrete monomeric molecules,
exhibiting square–planar NiSe2P2 cores, in which Ni(II) ions are
coordinated by two (Se,P) chelates in trans arrangement. Overall,
the structure contains a center of symmetry, and therefore the
two five-membered Ni–Se–P–N–P rings are identical. The equiva-
lent equatorial Ni–Se and N–P bond lengths are 2.296 and
2.239 Å, respectively, and very similar to the corresponding bond
100
50
ppm
Fig. 1. 31P NMR spectrum of 1 in CDCl3.

3308
N. Levesanos et al. / Polyhedron 28 (2009) 3305–3309
Table 2
to the P–N bonds in Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2]. Related to the
Selected bond lengths (Å) and angles (°) for 1 and 2.
above effects, it should be noted that the Ni–Se bond length in 1
(2.296 Å) is smaller by 0.054 Å compared to the Ni–Se bond lengths
(average 2.350 Å) in [Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2] [30]. For com-
parison, the Ni–P bond lengths of 1 (2.239 Å) and [Ni{Ph2PNPPh2-
P,P}2] (2.222 Å) [29] differ only by 0.02 Å. These differences might
be justified by the higher electronegativity of Se compared to P,
which, in complex 1, would result in electron density flow from N
to P2 to Se. A similar trend is also observed in the case of trans-
[Ni{iPr2P(Se)NPiPr2-Se,P}2] [38], which should be extended in other
systems containing five-membered M–E–P–N–P rings by the coor-
dination of monooxidised imidodiphosphinate ligands [10–26].
By comparing the endocyclic angles X–Ni–Y, X, Y = P, P or Se, P
or Se, Se, in [Ni{Ph2PNPPh2-P,P}2] (67.43°) [29], complex 1 (91.16°)
and [Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2] (99.41°) [30], it is obvious that
only 1 exhibits an angle very close to the value of the ideal square–
planar geometry, a fact that should be critical in conserving its
square–planar NiSe2P2 core geometry in solution (vide supra).
Complex
1
2
Distances
{Ni–Se–P–N–P} ring
(Ni–Se2) 2.2995(4)
(Ni–P4) 2.2404(7)
(Se2–P3) 2.2210(7)
(N2–P4) 1.644(2)
(N2–P3) 1.593(2)
{Ni–Se–P–N(H)–P} ring
(Ni–Se1) 2.3057(4)
(Ni–P2) 2.2063(7)
(Se1–P1) 2.1939(7)
(N1–P2) 1.693(2)
(N1–P1) 1.639(2)
Ni–Se
Ni–P1
Se–P2
P1–N
P2–N
2.2961(5)
2.2391(9)
2.2098(10)
1.639(3)
1.586(3)
Angles
Se–Ni–Se
P1–Ni–P1
P1–Ni–Se
Ni–P1–N
P1–N–P2
N–P2–Se
P2–Se–Ni
P1–Ni–Se0
180.00(3)
180.00(3)
91.16(3)
114.63(9)
118.42(15)
111.33(10)
98.04(3)
(Se1–Ni–Se2) 178.228(18)
(P2–Ni–P4) 178.34(3)
(P4–Ni–Se2) 90.53(2)
(Ni–P4–N2) 114.93(8)
(P3–N2–P4) 117.42(13)
(N2–P3–Se2) 111.43(8)
(P3–Se2–Ni) 99.28(2)
(P2–Ni–Se1) 91.28(2)
(Ni–P2–N1) 111.36(8)
(P1–N1–P2) 120.08(13)
(N1–P1–Se1) 107.50(8)
(P1–Se1–Ni) 101.38(2)
88.84(3)
(P2–Ni–Se2) 87.98(2), (P4–Ni–Se1) 90.18(2)
3.2.2. trans-[Ni{Ph2P(Se)NPPh2-Se,P}{Ph2P(Se)N(H)PPh2-
Se,P}]ClꢀCH2Cl2ꢀH2O (2)
The ORTEP representation of the crystal structure is shown in
Fig. 3. The crystal was shown to contain the [Ni{Ph2P(Se)NPPh2-
Se,P}{Ph2P(Se)N(H)PPh2-Se,P}]+ ion, along with a Clꢁ as a counter
ion, one solvent molecule (CH2Cl2) and a H2O molecule. As in the
case of 1, the system contains square–planar NiSe2P2 cores, in
which Ni(II) ions are coordinated by two (Se,P) chelates in trans
arrangement. However, unlike 1, complex 2 contains two different
rings, one protonated at the N atom, Ni–Se–P–N(H)–P, and one
unprotonated, Ni–Se–P–N–P, a fact that introduces asymmetry to
the system, and affects the bond lengths and angles (Table 2).
The Ni–Se bond lengths in 2 are rather similar to those in 1. On
the other hand, a notable difference is the ca. 0.03 Å decrease in
the Ni–P2 bond length, in the Ni–Se–P–N(H)–P ring, compared to
both the Ni–Se–P–N–P ring of 2, as well as of 1.
The trend in the P–N bond lengths described above for 1 is con-
served in 2 (Table 2). Moreover, the presence of the N–H bond in
the Ni–Se–P–N(H)–P ring of 2 weakens the P–N bonds compared
to both the Ni–Se–P–N–P ring of 2, as well as of 1, since part of
the electronic density of N is devoted to the N–H bond formation.
With respect to the angles in 1 and 2, Table 2 shows that these
are rather similar between 1 and the Ni–Se–P–N–P ring of 2, but
Fig. 2. Partially labelled ORTEP plot of
1 with ellipsoids drawn at the 30%
probability level. Primed atoms are generated by symmetry (0 = ꢁx, 1ꢁy, ꢁz).
lengths (2.305 and 2.239 Å, respectively) in the recently character-
ized trans-[Ni{iPr2P(Se)NPiPr2-Se,P}2] complex [38]. The Se–Ni–P
and P–N–P angles in 1 (91.16 and 118.42°) and the latter complex
(91.33 and 119.03°) are also very similar. Therefore, the difference
of the R peripheral groups in the two complexes (Ph or iPr) has no
effect in their structural characteristics. This observation is in con-
trast to the marked difference between the corresponding
[Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2] and [Ni{iPr2P(Se)NP(Se)iPr2-Se,Se}2]
complexes, since the former crystallizes in square–planar [30] and
the latter in a mixture of tetrahedral and square–planar NiSe4 poly-
morphs [8]. It is concluded that the six-membered Ni–Se–P–N–P–
Se rings in these complexes provide structural flexibility to the
NiSe4 core, the geometry of which is affected by the nature of
the R groups, not only in solution (vide supra) but also in the solid
state. This is in contrast to the corresponding five-membered Ni–
Se–P–N–P rings of 1 and trans-[Ni{iPr2P(Se)NPiPr2-Se,P}2] [38],
which maintain a rather rigid square–planar NiSe2P2 coordination
sphere, irrespective of the nature of the R groups.
The P–N bond lengths in Ni{Ph2P(Se)NP(Se)Ph2-Se,Se}2] are al-
most identical (1.600 and 1.602 Å) [30]. On the other hand, in the
case of 1, these bond lengths are not equal (P2–N, 1.586 and P1–
N, 1.639 Å). Therefore, the P–N bond adjacent to the Se atom is
strengthened, whereas the other P–N bond is weakened, compared
Fig. 3. Partially labelled ORTEP plot of
probability level.
2 with ellipsoids drawn at the 30%

N. Levesanos et al. / Polyhedron 28 (2009) 3305–3309
3309
there are notable differences in the angles of the Ni–Se–P–N(H)–P
ring of 2. For instance, the P–N–P angle in the latter is increased by
2.7°, whereas the N–P–Se angle is decreased by 3.9°, compared to
the Ni–Se–P–N–P ring of 2. Moreover, the P–N–P angle in the Ni–
Se–P–N(H)–P ring of 2 is larger by 1.7° compared to the equivalent
P–N–P angles of 1. Also, the P–Se–Ni angle in the Ni–Se–P–N(H)–P
ring of 2 is larger by 3.3°, whereas the N–P–Se is smaller by 3.8°
and the N–P–Ni smaller by 3.3° compared to the corresponding
angles of 1. The P–N–P angles in other complexes containing
M–Se–P–N(H)–P rings are close to 120° [21,23], indicating an sp2
hybridization of the N atom [40].
It is of interest that in the case of [Pd{Ph2P(S)NP(S)Ph2-
S,S}{Ph2P(S)N(H)P(S)Ph2-S,S}]Cl [41], which contains one Ni–S–P–
N(H)–P–S and one Ni–S–P–N–P–S six-membered ring, the latter
contains longer P–S bonds and shorter P–N bonds compared to
the former [41]. However, the angles in the two rings are rather
similar [41], unlike what has been described above for 1 and 2.
In [Pd{Ph2P(S)NP(S)Ph2-S,S}{Ph2P(S)N(H)P(S)Ph2-S,S}]Cl [41],
the counter ion Clꢁ is hydrogen bonded to the Ni–S–P–N(H)–P–S
ring (distances HꢀꢀꢀCl 2.20 Å, NꢀꢀꢀCl 2.93 Å and angle N–HꢀꢀꢀCl
134°) [41]. In the case of the Ni–Se–P–N(H)–P ring of 2, the analo-
gous distances and angle are HꢀꢀꢀCl, 2.19 Å, NꢀꢀꢀCl, 3.01 Å and
N–HꢀꢀꢀCl, 175.2°. The situation is analogous to other systems which
contain M–Se–P–N(H)–P five-membered rings, like trans-
[Pt{Ph2P(Se)N(H)PPh2-Se,P}2]Cl2 [23] and [Ag{Ph2P(Se)N(H)PPh2-
Se,P}2]Br [21].
free of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033;
or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data associated
with this article can be found, in the online version, at doi:10.1016/
j.poly.2009.05.006.
References
[1] F.T. Wang, J. Najdzionek, K.L. Leneker, H. Wasserman, D.M. Braitsch, Synth.
React. Inorg. Met. Org. Chem. 8 (1978) 119.
[2] T.Q. Ly, J.D. Woollins, Coord. Chem. Rev. 176 (1998) 451.
[3] C. Silvestru, J.E. Drake, Coord. Chem. Rev. 223 (2001) 117.
[4] I. Haiduc, J. Organomet. Chem. 623 (2001) 29.
[5] I. Haiduc, Comprehensive Coordination Chemistry II, Elsevier Ltd., Amsterdam,
2003.
[6] G.G. Briand, T. Chivers, M. Parvez, Angew. Chem., Int. Ed. Engl. 41 (2002) 3468.
[7] T. Chivers, J. Konu, J.S. Ritch, M.C. Copsey, D.J. Eisler, H.M. Tuononen, J.
Organomet. Chem. 692 (2007) 2658.
[8] N. Levesanos, S.D. Robertson, D. Maganas, C.P. Raptopoulou, A. Terzis, P.
Kyritsis, T. Chivers, Inorg. Chem. 47 (2008) 2949.
[9] J.D. Woollins, J. Chem. Soc., Dalton Trans. (1996) 2893.
[10] P. Bhattacharyya, A.M.Z. Slawin, M.B. Smith, J.D. Woollins, Inorg. Chem. 35
(1996) 3675.
[11] R. Haid, R. Gutmann, G. Czermak, C. Langes, W. Oberhauser, H. Kopacka, K.H.
Ongania, P. Bruggeller, Inorg. Chem. Commun. 6 (2003) 61.
[12] R. Rossi, L. Marvelli, A. Marchi, L. Magon, V. Bertolasi, V. Ferretti, J. Chem. Soc.,
Dalton Trans. (1994) 339.
[13] A.M.Z. Slawin, M.B. Smith, J.D. Woollins, J. Chem. Soc., Dalton Trans. (1996)
1283.
[14] K.A. Chatziapostolou, K.A. Vallianatou, A. GrigoropouloS, C.P. Raptopoulou, A.
Terzis, I.D. Kostas, P. Kyritsis, G. Pneumatikakis, J. Organomet. Chem. 692
(2007) 4129.
[15] M.R.J. Elsegood, M.B. Smith, S.H. Dale, Acta Crystallogr., Sect. C-Cryst. Struct.
Commun. 63 (2007) M7.
[16] M.B. Smith, A.M.Z. Slawin, Inorg. Chim. Acta 299 (2000) 172.
[17] J. Parr, M.B. Smith, M.R.J. Elsegood, J. Organomet. Chem. 664 (2002) 85.
[18] M.B. Smith, A.M.Z. Slawin, J.D. Woollins, Polyhedron 15 (1996) 1579.
[19] E. Simon-Manso, M. Valderrama, P. Gantzel, C.P. Kubiak, J. Organomet. Chem.
651 (2002) 90.
The atoms that are coordinated to the Ni(II) ions in 1 and 2 are
in the same plane. The five-membered rings exhibit a pseudo-boat
conformation. The protonation at the N atom of one ring in 2 does
not seem to cause major changes to the ring conformation.
4. Conclusions
[20] R. Rossi, A. Marchi, L. Marvelli, M. Peruzzini, U. Casellato, R. Graziani, J. Chem.
Soc., Dalton Trans. (1992) 435.
[21] J. Wilton-Ely, A. Schier, H. Schmidbaur, J. Chem. Soc., Dalton Trans. (2001)
3647.
[22] W.H. Leung, K.K. Lau, Q.F. Zhang, W.T. Wong, B.Z. Tang, Organometallics 19
(2000) 2084.
[23] P. Bhattacharyya, A.M.Z. Slawin, D.J. Williams, J.D. Woollins, J. Chem. Soc.,
Dalton Trans. (1995) 3189.
[24] W.M. Cheung, Q.F. Zhang, C.Y. Lai, I.D. William, W.H. Leung, Polyhedron 26
(2007) 4631.
[25] M. Valderrama, R. Contreras, P. Munoz, M.P. Lamata, D. Carmona, F.J. Lahoz, S.
Elipe, L.A. Oro, J. Organomet. Chem. 633 (2001) 182.
[26] P. Bhattacharyya, A.M.Z. Slawin, D.J. Williams, J.D. Woollins, J. Chem. Soc.,
Dalton Trans. (1995) 2489.
The work described here adds more information on the struc-
tural and spectroscopic properties of coordination compounds
containing monooxidised imidodiphosphinate ligands. The main
conclusions drawn from the analysis of spectroscopic and struc-
tural data, are the following: (i) The square–planar trans-Ni(Se,P)2
arrangement in 1, established in the solid state by X-ray crystallog-
raphy, is maintained in solution and justifies the ‘‘deceptive” trip-
lets in the diamagnetic part of its 31P NMR spectrum. (ii)
Availability of the structures of 1 and 2 makes possible to establish
structural effects due to the higher electronegativity of Se com-
pared to P, as well as to the protonation/deprotonation at the N
atom of the five-membered rings. These effects will be further
probed by appropriate theoretical calculations, as in the case of
the analogous bis-chalcogenated imidodiphosphinate ligands and
their complexes [40]. In addition, the NMR properties of 1 will be
further investigated by studies in the solid state [42].
[27] M.C. Copsey, T. Chivers, Chem. Commun. (2005) 4938.
[28] J.S. Ritch, T. Chivers, Dalton Trans. (2008) 957.
[29] V.V. Sushev, A.N. Kornev, Y.V. Fedotova, Y.A. Kursky, T.G. Mushtina, G.A.
Abakumov, L.N. Zakharov, A.L. Rheingold, J. Organomet. Chem. 676 (2003) 89.
[30] C. Papadimitriou, P. Veltsistas, J. Novosad, R. CeaOlivares, A. Toscano, P.G.Y.
Garcia, M. LopezCardosa, A.M.Z. Slawin, J.D. Woollins, Polyhedron 16 (1997)
2727.
[31] J.W. Faller, J. Lloret-Fillol, J. Parr, New J. Chem. 26 (2002) 883.
[32] Rigaku/MSC, Rigaku/MSC Inc., The Woodlands, Texas, USA, 2005.
[33] G.M. Sheldrick, SHELXS-97: Structure Solving Program, University of Göttingen,
Germany, 1997.
Acknowledgements
[34] G.M. Sheldrick, SHELXL-97: Crystal Structure Refinement Program, University of
Göttingen, Germany, 1997.
[35] B.N. Figgis, M.A. Hitchman, Ligand Field Theory and its Applications, Wiley-
VCH, 2000.
[36] P. Peringer, J. Schwald, J. Chem. Soc., Chem. Commun. (1986) 1625.
[37] D. Cauzzi, C. Graiff, M. Lanfranchi, G. Predieri, A. Tiripicchio, Inorg. Chim. Acta
273 (1998) 320.
[38] S.D. Robertson, T. Chivers, J. Akhtar, M. Afzaal, P. O’Brien, Dalton Trans. (2008)
7004.
We would like to thank the Special Account of the University of
Athens (Grant 70/4/7575), as well as the Empirikion Foundation,
for funding. Eleftherios Ferentinos is thanked for technical
assistance and helpful discussions. This article is dedicated with
gratitude to Dr. Aris Terzis, whose contribution, over the years, to
the advancement of our projects, has been invaluable.
[39] S.D. Robertson, T. Chivers, Dalton Trans. (2008) 1765.
[40] D. Maganas, S.S. Staniland, A. Grigoropoulos, F. White, S. Parsons, N. Robertson,
P. Kyritsis, G. Pneumatikakis, Dalton Trans. (2006) 2301.
[41] D. Cupertino, R. Keyte, A.M.Z. Slawin, J.D. Woollins, D.J. Williams, Polyhedron
15 (1996) 4441.
Appendix A. Supplementary data
CCDC 721470 and 721471 contains the supplementary crystal-
[42] B.A. Demko, R.E. Wasylishen, Inorg. Chem. 47 (2008) 2786.
lographic data for 1 and 2, respectively. These data can be obtained