Dimeric versus monomeric nickel(II) complexes with tetraorganodichalcogenoimidodiphosphinato ligands: Crystal structures of Ni2[(OPPh2)2N]4 · CH2Cl2, Ni[(OPPh2)2N]<sub

Article abstract of DOI:10.1016/j.poly.2008.04.006

Nickel(II) complexes of the type Ni [(XPR₂) (YPR₂^′) N]₂ [X = S (1) or O (2), Y = O, R = Ph, R′ = OEt] and Ni₂[(OPPh₂)₂N]₄ (3) were prepared by reacting either anhydrou

Full text of DOI:10.1016/j.poly.2008.04.006

Polyhedron 27 (2008) 2143–2150
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Dimeric versus monomeric nickel(II) complexes with
tetraorganodichalcogenoimidodiphosphinato ligands: Crystal
structures of Ni2[(OPPh2)2N]4 ꢀ CH2Cl2, Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O and
[KNi[(SPPh2){OP(OEt)2}N]3]2
Alexandra Cristurean a, Sevil Irisli b,1, Dragos Marginean a, Ciprian Rat a, Anca Silvestru a,
*
a Faculty of Chemistry and Chemical Engineering, ‘‘Babes-Bolyai” University, RO-400028 Cluj-Napoca, Romania
b Chemistry Department, Faculty of Science, Ege University, 35100 Bomova-Izmir, Turkey
a r t i c l e i n f o
a b s t r a c t
Nickel(II) complexes of the type Ni½ðXPR2ÞðYPR0 ÞNꢁ [X = S (1) or O (2), Y = O, R = Ph, R0 = OEt] and
Article history:
2
2
Received 11 October 2007
Accepted 9 April 2008
Available online 24 May 2008
Ni2[(OPPh2)2N]4 (3) were prepared by reacting either anhydrous NiCl2 or NiCl2 ꢀ 6H2O with the potas-
sium salt of the appropriate tetraorganodichalcogenoimidodiphosphinic acid, in 1:2 molar ratio.
Recrystallization of 3 from dimethylformamide resulted in Ni[(OPPh2)2N]2(DMF) (4). Reaction between
NiCl2 and K[(SPPh2){OP(OEt)2}N] in an 1:3 molar ratio resulted in the ionic species KNi[(SPPh2)-
{OP(OEt)2}N]3 (5). Compounds 1–5 were characterized by IR, electronic spectroscopy and mass
spectrometry. The molecular structures of 3 ꢀ CH2Cl2, 4 ꢀ 2H2O and 5 were determined by single-
crystal X-ray diffraction. A dimeric structure was found in case of complex 3 ꢀ CH2Cl2, with both
monometallic biconnective and homobimetallic triconnective [(OPPh2)2N]ꢂ units, while an octahedral
environment around nickel was established in the monomeric complex 4 ꢀ 2H2O by monometallic
biconnective [(OPPh2)2N]ꢂ and DMF ligands, respectively. The crystal of the ionic species 5 contains
discrete tetranuclear units in which the phosphorus ligands act heterobimetallic, either (O,O,S)-
triconnective or (S,O,O,OEt)-tetraconnective, and (N,O,O,S)-heterotrimetallic tetraconnective, resulting
Keywords:
Nickel complexes
Tetraorganodichalcogenoimido-
diphosphinato ligands
Crystal and molecular structure
in an octahedral environment around nickel and
respectively. Powder X-ray diffraction studies on
investigation.
a
5
square-pyramidal one around potassium,
are in agreement with the single-crystal
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
[(SPMe2)(SPPh2)N]2 [5] a square-planar NiS4 core was observed.
The monothio derivatives Ni[(OPPh2)(SPR2)N]2 (R = Me, Ph) are
also monomeric, with chelating monometallic biconnective li-
gands, resulting in tetrahedral NiO2S2 cores [8]. For the dioxo
derivative Ni[(OPPh2)2N]2, a dimeric structure was previously pro-
posed in benzene solution according to the molecular mass mea-
surements [9].
Here we report on the synthesis and spectroscopic characteriza-
tion of the new derivatives Ni[(SPPh2){OP(OEt)2}N]2 (1) and
Ni[(OPPh2){OP(OEt)2}N]2 (2), the ionic species KNi[(SPPh2){O-
P(OEt)2}N]3 (5) as well as the adduct Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O
(4 ꢀ 2H2O). The crystal and molecular structure of the dimeric
Ni2[(OPPh2)2N]4 ꢀ CH2Cl2 (3 ꢀ CH2Cl2), its adduct 4 ꢀ 2H2O and the
ionic derivative 5 are also discussed.
Metal complexes of tetraꢂorganodichalcogenoimidodiphosphi-
nato ligands, ½ðXPR2ÞðYPR0 ÞNꢁ , attracted an increased interest for
2
many years, due to their properties and potential applications as
catalysts in organic synthesis, components in optical or electronic
devices and sensors, NMR shift reagents, as well as derivatives
with biological activity. Inorganic and organometallic derivatives
either of Main Group [1] or transition metal complexes [2] were
previously described. Several nickel(II) complexes of type
Ni½ðXPR2ÞðYPR0 ÞNꢁ were reported so far. For compounds
2
2
containing the same chalcogen atoms, e.g. Ni[(SPR2)2N]2 (R = Me
[3,4], Ph [5,6]) and Ni[(SePPh2)2N]2 [7], monomeric structures with
a tetrahedral NiE4 core (E = S, Se) were found by single-crystal
X-ray diffraction, while in the case of the derivative Ni-
2. Experimental
* Corresponding author. Tel.: +40 264 593833; fax: +40 264 590818.
E-mail addresses: sevil.irisli@ege.edu.tr (S. Irisli), ancas@chem.ubbcluj.ro
(A. Silvestru).
The organophosphorus ligands were prepared according to
literature methods: K[(SPPh2){OP(OEt)2}N], K[(OPPh2){OP(OEt)2}N]
1
Tel.: +90 232 3884000.
0277-5387/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2008.04.006

2144
A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
[10]. K[(OPPh2)2N] was obtained by stirring the free acid with
KOBut in diethyl ether. NiCl2 was dehydrated by keeping
NiCl2 ꢀ 6H2O for two weeks in the oven at 120 °C and subsequently
stored under argon. Solvents were dried (THF on potassium, EtOH
and MeOH on magnesium and CH2Cl2 on CaCl2) and distilled under
argon prior to be used. IR spectra were recorded in the range
4000–400 cmꢂ1 in KBr pellets on a Jasco FT/IR-615 equipment,
while the electronic spectra were recorded on a Jasco V-550
spectrometer. Mass spectra were recorded on a FINNIGAN MAT
8200 (CI), a FINNIGAN MAT 8222 (FAB) and a Bruker Esquire LC
instrument (ESI), respectively. Magnetic moments were deter-
mined on a Sherwood MSB AUTO instrument and elemental anal-
ysis were performed on a VarioEL analyzer. The experimental
powder diffraction pattern was obtained with a Shimadzu XRD-
6000 diffractometer using a Cu Ka X-ray radiation, while the sim-
ulated X-ray powder diffraction pattern was obtained with the
MERCURY CSD 2.0 program [11].
(cmꢂ1), CH2Cl2 (yellow): 11904, 18182, 22727; THF (yellow):
12670, 23614. CIneg MS (m/z, %): 890 (100) ½NifðOPPh2Þ2Ng2ꢂꢁ,
416 (7) [{(OPPh2)2N}ꢂ], 216 (5) [{(OPPh2)N}ꢂ]. FAB + MS (m/z, %):
1783
(15)
[{Ni2[(OPPh2)2N]4 + 2H}+],
1366
(38)
[{Ni2-
[(OPPh2)2N]3 + 2H}+], 891 (100) [{Ni[(OPPh2)2N]2 + H}+]. l =
3.26 BM.
Compound 3 was dissolved at room temperature in dimethyl-
formamide. The yellow solution was concentrated in vacuum.
Yellow-green crystals of 4 quantitatively formed at ꢂ5 °C. M.p.
115 °C (dec.). Anal. Calc. for C54H54N4O6P4Ni: C, 62.52; H, 5.21;
N, 5.40. Found: C, 62.83; H, 5.32; N, 5.28%. IR (cmꢂ1): 1643vs
[m(CO)], 1230vs, br [mas(P2N)], 1130vs [m(PO)], 1105vs [m(PO)].
kmax (cmꢂ1), CH2Cl2 (yellow): 11904, 14706, 18248, 22727; THF
(yellow): 12658, 23809. CIneg MS (m/z, %): 890 (100) [{Ni-
[(OPPh2)2N]2}ꢂ], 416 (7) [{(OPPh2)2N}ꢂ], 216 (5) [{(OPPh2)N}ꢂ].
l = 3.10 BM.
2.4. Preparation of potassium [tris{P,P-diethoxi-P0,P0-diphenyl-
P0-thioimidodiphosphinato}nickel], KNi[(SPPh2){OP(OEt)2}N]3 (5)
2.1. Preparation of bis[P,P-diethoxi-P0,P0-diphenyl-P0-
thioimidodiphosphinato]nickel, Ni[(SPPh2){OP(OEt)2}N]2 (1)
(a) A mixture of K[(SPPh2){OP(OEt)2}N] (0.766 g, 1.86 mmol)
and NiCl2 (0.148 g, 0.62 mmol) was stirred for 16 h in methanol
(40 ml) at room temperature. The solvent was removed in vacuum
and the solid was treated with CH2Cl2. KCl was filtered off and the
solvent was removed in vacuum, resulting in a yellow-brown solid
product. Yield: 0.58 g (77%). M.p. 118–119 °C. Anal. Calc. for
A mixture of K[(SPPh2){OP(OEt)2}N] (0.511 g, 1.25 mmol) and
NiCl2 (0.148 g, 0.62 mmol) was stirred for 8 h in a mixture of
THF (40 ml) and ethanol (10 ml) at reflux. The solvent was re-
moved in vacuum and the solid was treated with CH2Cl2. KCl
was filtered off and the solution was concentrated in vacuum.
A yellow-brown solid product was isolated. Yield: 0.39 g (78%),
M.p. 99 °C. Anal. Calc. for C32H40N2O6P4S2Ni: C, 48.33; H, 5.03;
N, 3.52. Found: C, 47.98; H, 5.16; N, 3.48%. IR (cmꢂ1): 1255vs
[mas(P2N)], 1105s [m(PO)], 1043vs, br [m(POC)], 596s [m(PS)]. kmax
(cmꢂ1), CH2Cl2 (blue): 14620, 16129, 17921, 21209; THF (yel-
low): 12048, 22026. CIneg MS (m/z, %): 794 (85) [Mꢂ], 368
(100) [{(SPPh2){OP(OEt)2}N}ꢂ], 336 (38) [{(PPh2){OP(OEt)2}N}ꢂ].
l = 1.88 BM.
C48H60N3O9P6 S3KNi: C, 47.94; H, 4.99; N, 3.50. Found: C, 48.21;
H, 4.82; N, 3.24%.
(b) Alternatively, 5 was obtained by stirring a 1:1 mixture of 1
(0.794 g, 1 mmol) and K[(SPPh2){OP(OEt)2}N] (0.407 g, 1 mmol) in
methanol (50 ml) at room temperature, for 24 h. The solvent was
removed in vacuum from the blue-green solution, resulting quan-
titatively in a yellow-brown solid. M.p. 118–119 °C. Anal. Calc. for
C48H60N3O9S3P6KNi: C, 47.94; H, 4.99; N, 3.50. Found: C, 47.82;
H, 4.92; N, 3.53%. IR (cmꢂ1): 1261vs [mas(P2N)], 1103s [m(PO)],
1033vs, br [m(POC)], 590s [m(PS)]. kmax (cmꢂ1), CH2Cl2 (blue):
14652, 16168, 17746, 21459; THF (yellow): 12053, 22321. CIneg
MS (m/z, %): 794 (78) [M-K[(SPPh2){OP(OEt)2}N]ꢂ], 407 (5)
[K[(SPPh2){OP(OEt)2}N]ꢂ] 368 (100) [{(SPPh2){OP(OEt)2}N}ꢂ],
336 (38) [{(PPh2){OP(OEt)2}N}ꢂ], ESIꢂ (m/z, %): 1166 (100),
½Ni½ðSPPh2ÞfOPðOEtÞ2gNꢁ3ꢂꢁ, 833 (82) ½K2Ni½ðSPPh2ÞfOPðOEtÞ2g-
Nꢁ2ꢂꢁ, 407 (35) [K[(SPPh2){OP(OEt)2}N]ꢂ]. l = 3.36 BM.
2.2. Preparation of bis[P,P-diethoxi-P0,P0-diphenyl-imido-
diphosphinato]nickel, Ni[(OPPh2){OP(OEt)2}N]2 (2)
A mixture of K[(OPPh2){OP(OEt)2}N] (0.720 g, 1.84 mmol) and
NiCl2 (0.119 g, 0.92 mmol) was stirred for 8 h in a mixture of THF
(40 ml) and ethanol (10 ml) at reflux, under argon atmosphere.
The solvent was removed in vacuum and the solid was treated with
CH2Cl2. KCl was filtered off and the solution was concentrated in
vacuum. A pale yellow solid product was isolated. Yield: 0.63 g
(90%), M.p. 108–110 °C. Anal. Calc. for C32H40N2O8P4Ni: C, 50.36;
H, 5.25; N, 3.67. Found: C, 5.31; H, 5.17; N 3.52%. IR (cmꢂ1):
1261vs [mas(P2N)], 1103vs [m(PO)], 1041vs, 1028vs [m(POC)]. kmax
(cmꢂ1), CH2Cl2 (blue): 14652, 16181, 18099, 21276; THF (yellow):
12706, 22321. CIneg MS (m/z, %): 762 (92) [Mꢂ], 352 (100)
[{(OPPh2){OP(OEt)2}N}ꢂ], 336 (23) [{(PPh2){OP(OEt)2}N}ꢂ]. l =
2.19 BM.
2.5. Crystal structure determinations
Block crystals of Ni2[(OPPh2)2N]4 ꢀ CH2Cl2 (3 ꢀ CH2Cl2) (yellow),
Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O (4 ꢀ 2H2O) (yellow-green) and
KNi[(SPPh2){OP(OEt)2}N]3 (5) (yellow-brown) were attached with
epoxy glue on cryoloops. The data were collected at room
temperature on a Bruker SMART APEX CCD diffractometer using
graphite-monochromated Mo Ka radiation (k = 0.71073 Å). The
details of the crystal structure determination and refinement are
given in Table 1.
The structures were refined with anisotropic thermal parame-
ters. The hydrogen atoms were refined with a riding model and a
mutual isotropic thermal parameter. For structure solving and
refinement the software package SHELX-97 was used [12]. The draw-
ings were created with the DIAMOND program [13].
2.3. Preparation of tetrakis[tetraphenylimidodiphosphinato]dinickel,
Ni2[(OPPh2)2N]4 (3) and bis(dimethylformamide)bis(tetraphenyl-
imidodiphosphinato)nickel, Ni[(OPPh2)2N]2(DMF)2 (4)
A solution of NiCl2 ꢀ 6H2O (0.24 g, 1.0 mmol) in methanol
(15 ml) was added to a solution of K[(OPPh2)2N] (0.88 g, 2.0 mmol)
in methanol (15 ml). The reaction mixture was stirred at room
temperature for 12 h. The solvent was removed in vacuum and
the solid was extracted with benzene (20 ml). The benzene solu-
tion was concentrated in vacuum to ca. 10 ml and layered with
hexane. Yellow crystals of 3 were isolated by filtration. Yield
0.80 g (86%), M.p. 290 °C. Anal. Calc. for C48H40N2O4P4Ni: C,
64.66; H, 4.53; N, 3.14. Found: C, 64.58; H, 4.37; N, 3.16%. IR
(cmꢂ1): 1232vs [mas(P2N)], 1136vs [m(PO)], 1097vs [m(PO)]. kmax
3. Results and discussion
The title nickel(II) complexes were obtained by salt
metathesis reactions between anhydrous NiCl2 or NiCl2 ꢀ 6H2O
and the potassium salt of the corresponding tetraorganodichal-
cogenoimidodiphosphinic acid, according to the following
equations:

A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
2145
The reactions between K½ðXPR2ÞðYPR0 ÞNꢁ and nickel dichloride
All isolated compounds are stable as solids in open atmosphere
for weeks. They are paramagnetic in solid state. Attempts to char-
acterize these compounds as CDCl3 solutions by NMR spectroscopy
failed suggesting their paramagnetic nature in solution too.
The CIneg mass spectra of compounds 1 and 2 show the molec-
ular ion with high intensity (85% for 1 and 92% for 2, respectively).
In case of compounds 3 and 4 the [Ni{(Ph2PO)2N}2]ꢂ ion appeared
with 100% intensity in CIneg mass spectra. The dimeric species 3
was confirmed by FAB mass spectroscopy, while the formation of
5 was revealed by ESI mass spectra.
2
2
were performed using either dehydrated NiCl2 or NiCl2 ꢀ 6H2O in a
tetrahydrofurane/ethanol mixture (1 and 2), or methanol as sol-
vent (3 and 5), respectively. The use of anhydrous NiCl2 and argon
atmosphere resulted in a considerable increase in the yields of
compounds 1 and 2. The formation of the ionic species 5 through
both methods of preparation was confirmed by powder X-ray dif-
fraction studies. The experimental spectrum is in a good agreement
with the simulated one based on the single-crystal X-ray diffrac-
tion data (Fig. 1).
Table 1
Crystal data and structure refinement for Ni2[(OPPh2)2N]4 ꢀ CH2Cl2 (3 ꢀ CH2Cl2), Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O (4 ꢀ 2H2O) and KNi[(SPPh2){OP(OEt)2}N]3 (5)
3 ꢀ CH2Cl2
97H82Cl2N4Ni2O8P8
4 ꢀ 2H2O
C54H58N4NiO8P4
1073.61
5
Molecular formula
M
C
C96H116K2N6Ni2O18P12S6
2401.60
1867.75
Temperature (K)
293(2)
297(2)
297(2)
Crystal size (mm)
Crystal system
Space group
0.30 ꢃ 0.28 ꢃ 0.21
Monoclinic
P2(1)/n
0.60 ꢃ 0.55 ꢃ 0.44
Monoclinic
P2(1)/n
0.35 ꢃ 0.29 ꢃ 0.23
Orthorhombic
Pbca
Radiation
Mo Ka, 0.71073 Å
Mo Ka, 0.71073 Å
Mo Ka, 0.71073 Å
Unit cell dimension
a (Å)
b (Å)
c (Å)
a (°)
b (°)
c (°)
16.433(3)
21.222(3)
26.375(4)
90
104.266(3)
90
8915(2)
4
1.392
9.4672(15)
20.951(3)
13.363(2)
90
94.442(3)
90
2642.6(7)
2
1.349
24.9858(10)
17.6058(7)
25.8683(10)
90
90
90
11379.3(8)
4
1.402
V (Å3)
Z
Dcalc (g cmꢂ3
)
F000
3864
0.686
1124
0.545
4992
0.746
l(Mo Ka) (mmꢂ1
)
h Range for data collections (°)
Reflections collected
1.25–26.37
71288
1.81–26.37
20850
1.62–25.00
79397
Independent reflections [Rint
Maximum and minimum transmissions
Refinement method
]
18241 [0.0465]
0.87 and 0.803
5387 [0.0362]
0.7954 and 0.7356
Full-matrix least-squares on F2
5387/0/332
1.220
10020 [0.1005]
0.8471 and 0.7802
Data/restraints/parameters
18241/0/1095
1.210
10020/0/646
1.243
Goodness-of-fit on F2
R1 = 0.0709
wR2 = 0.1472
R1 = 0.0832
wR2 = 0.1528
0.629 and ꢂ0.761
R1 = 0.0503
wR2 = 0.1088
R1 = 0.0530
wR2 = 0.1101
0.449 and ꢂ0.440
R1 = 0.1129
wR2 = 0.2344
R1 = 0.1317
wR2 = 0.2444
0.798 and ꢂ1.458
R indicies (all data)
Largest difference peak and hole (e Åꢂ3
)

2146
A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
solutions, around 21000, 18000, 16000 and 14600 cmꢂ1, assign-
able to tetracoordinate species [5,8]. According to the magnetic
moments (about 2.0 BM) found for compounds 1 and 2 in solid
state, the formation of a mixture of tetrahedral and square-planar
species might be suggested [15]. It can be mentioned here that the
crystal of the related copper(II) complex, Cu[(OPPh2)(SPPh2)N]2,
was reported to contain both tetrahedral and square-planar iso-
mers [16].
For the derivative 3 in CH2Cl2 solution the observed absorptions
(22727, 18182 and 11904 cmꢂ1) are similar to those reported pre-
viously for the dimeric Ni2[(OPPh2)2N]4 species in benzene solution
[9], while in case of its adduct with dimethylformamide (4) a
fourth absorption appeared around 14700 cmꢂ1. This behavior
might be consistent with a mixture of octahedral and pentacoordi-
nate species in solution. The magnetic moments recorded in solid
state for compounds 3–5 (3.26, 3.10 and 3.36 BM, respectively)
are consistent with paramagnetic species with two unpaired elec-
trons. In THF all compounds gave strong absorptions in the region
22000–24000 cmꢂ1 accompanied by weaker absorptions in the re-
Fig. 1. (a) Experimental powder diffraction pattern and (b) the simulated X-ray
powder diffraction spectrum obtained from the single-crytal cif file of 5.
gion 12000–13000 cmꢂ1
.
3.1. Crystal and molecular structure of Ni2[(OPPh2)2N]4 ꢀ CH2Cl2-
(3 ꢀ CH2 Cl2) and Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O (4 ꢀ 2H2O)
Strong infrared absorptions were observed for all complexes in
the region 1260–1230, 1140–1100, 1050–1030 and about 600
cmꢂ1 and they were assigned to mas(P2N), m(PO), m(POC) and m(PS)
stretching vibrations, respectively, by comparison with the IR
spectra of the free acids and their alkali metal salts [1,10,14], thus
suggesting the coordination of the ligand units through both chalco-
gen atoms. For the adduct 4 the coordination of the DMF molecules
to the metal atom is reflected in a shift of the C@O vibration from
1675 cmꢂ1 in the free DMF to 1643 cmꢂ1 in the adduct spectrum.
All derivatives are well soluble in CH2Cl2, resulting in blue-
green (1, 2 and 5) or yellow (3 and 4) solutions, respectively. The
solutions of all compounds in coordinating solvents, i.e. tetrahy-
drofurane or methanol, are yellow. The electronic spectra of com-
pounds 1, 2 and 5 exhibit four absorption maxima in CH2Cl2
Single crystals of Ni2[(OPPh2)2N]4 ꢀ CH2Cl2 (3 ꢀ CH2Cl2), suitable
for X-ray diffraction studies, were obtained from CH2Cl2/n-hexane
(1:4, v:v).
The crystal of 3 consists of distinct dinuclear units separated by
normal van der Waals distances between heavy atoms. An ORTEP-
like view with the atoms numbering scheme is given in Fig. 2. Se-
lected bond lengths and angles are listed in Table 2.
Three of the phosphorus ligands act as homobimetallic tricon-
nective units, bridging the two metal centers, while the fourth
one acts monometallic biconnective. The result is a fused polycy-
clic system formed by three six-membered NiO2P2N rings and
three non-planar four-membered Ni2O2 rings [dihedral angles:
Fig. 2. ORTEP plot of the dinuclear unit in the crystal of 3 ꢀ CH2Cl2. The atoms are drawn with 40% probability ellipsoids. Hydrogen atoms and CH2Cl2 are omitted.

A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
2147
Table 2
Selected interatomic distances (Å) and angles (°) in Ni2[(OPPh2)2N]4 ꢀ CH2Cl2
(3 ꢀ CH2Cl2)
Ni(1)–O(1)
Ni(1)–O(2)
Ni(1)–O(4)
Ni(1)–O(6)
Ni(1)–O(8)
1.982(3)
1.970(3)
2.031(2)
2.052(2)
2.062(2)
Ni(2)–O(3)
Ni(2)–O(4)
Ni(2)–O(5)
Ni(2)–O(6)
Ni(2)–O(7)
Ni(2)–O(8)
1.997(2)
2.208(2)
2.011(2)
2.086(2)
2.020(2)
2.131(2)
P(1)–O(1)
P(1)–N(1)
P(2)–N(1)
P(2)–O(2)
1.513(3)
1.589(3)
1.583(4)
1.512(3)
P(5)–O(5)
P(5)–N(3)
P(6)–N(3)
P(6)–O(6)
1.499(2)
1.592(3)
1.578(3)
1.520(2)
P(3)–O(3)
P(3)–N(2)
P(4)–N(2)
P(4)–O(4)
1.505(2)
1.589(3)
1.579(3)
1.524(2)
P(7)–O(7)
P(7)–N(4)
P(8)–N(4)
P(8)–O(8)
1.506(3)
1.589(3)
1.570(3)
1.517(2)
Fig. 3. View of the Ni2O8P8N4 core in the crystal of 3 ꢀ CH2Cl2.
O(1)–Ni(1)–O(6)
O(2)–Ni(1)–O(8)
174.99(11)
149.00(11)
O(3)–Ni(2)–O(8)
O(4)–Ni(2)–O(5)
O(6)–Ni(2)–O(7)
165.77(10)
165.54(10)
169.25(10)
the isobidentate, monometallic biconnective ligand which
coordinate the Ni(1) atom. They are considerably shorter than
the corresponding metal–oxygen bonds in the adduct 4 ꢀ 2H2O in
which the phosphorus ligands exhibit an anisobidentate, monome-
tallic biconnective pattern [Ni(1)–O(1) 2.1133(17), Ni(1)–O(2)
2.0542(17) Å]. The bridging Ni–O–Ni systems are not symmetric
(Table 2), with Ni(1)–O distances shorter than Ni(2)–O distances.
The remaining, terminal, Ni(2)–oxygen bond distances are of inter-
mediate magnitude between the bridging metal–oxygen and
Ni(1)–O bonds established by the monometallic biconnective li-
gand, respectively.
The phosphorus–nitrogen [1.570(3)–1.592(3) Å] and phospho-
rus–oxygen [1.499(2)–1.524(2) Å] distances are intermediate be-
tween single and double bonds [cf. Ph2P(@S)–N@P(–SMe)Ph2
[19]: P@N 1.562(2) Å, P–N 1.610(2) Å, Ph2P(O)OH [20]: P@O
1.486(6) Å, P–O 1.526(6) Å], thus suggesting some delocalization
of the p electrons. However the resulting NiO2P2N rings are not pla-
nar. All ligands acting as homobimetallic triconnective units estab-
lish six-membered NiO2P2N rings which exhibit distorted boat
conformation, with Ni(2) and nitrogen atoms in apices. The fourth
six-membered NiO2P2N ring, established by the monometallic
biconnective ligand, has an envelope conformation, folded on the
imaginary P(1)ꢀ ꢀ ꢀP(2) axis, with the nitrogen atom ꢂ0.31 Å out of
the almost planar NiO2P2 skeleton.
O(4)–Ni(1)–O(1)
O(4)–Ni(1)–O(2)
O(4)–Ni(1)–O(6)
O(4)–Ni(1)–O(8)
102.09(11)
125.46(11)
80.30(10)
81.52(10)
O(3)–Ni(2)–O(4)
O(3)–Ni(2)–O(5)
O(3)–Ni(2)–O(6)
O(3)–Ni(2)–O(7)
90.97(9)
95.50(10)
93.23(10)
96.41(10)
O(1)–Ni(1)–O(2)
O(2)–Ni(1)–O(6)
O(6)–Ni(1)–O(8)
O(8)–Ni(1)–O(1)
93.23(11)
88.86(10)
80.49(9)
O(8)–Ni(2)–O(4)
O(8)–Ni(2)–O(5)
O(8)–Ni(2)–O(6)
O(8)–Ni(2)–O(7)
76.02(9)
95.95(10)
78.14(9)
91.46(10)
95.45(10)
O(4)–Ni(2)–O(6)
O(6)–Ni(2)–O(5)
O(5)–Ni(2)–O(7)
O(7)–Ni(2)–O(4)
75.57(9)
91.13(10)
92.67(10)
99.45(10)
Ni(1)–O(1)–P(1)
O(1)–P(1)–N(1)
P(1)–N(1)–P(2)
O(2)–P(2)–N(1)
Ni(1)–O(2)–P(2)
131.79(17)
116.97(17)
124.2(2)
116.40(17)
132.17(16)
Ni(2)–O(5)–P(5)
O(5)–P(5)–N(3)
P(5)–N(3)–P(6)
O(6)–P(6)–N(3)
Ni(2)–O(6)–P(6)
Ni(1)–O(6)–P(6)
122.77(14)
118.92(15)
126.88(19)
116.00(15)
124.13(14)
148.47(15)
Ni(2)–O(3)–P(3)
O(3)–P(3)–N(2)
P(3)–N(2)–P(4)
O(4)–P(4)–N(2)
Ni(2)–O(4)–P(4)
Ni(1)–O(4)–P(4)
121.25(14)
118.34(15)
128.3(2)
115.59(15)
121.08(13)
153.97(16)
Ni(2)–O(7)–P(7)
O(7)–P(7)–N(4)
P(8)–N(4)–P(7)
O(8)–P(8)–N(4)
Ni(2)–O(8)–P(8)
Ni(1)–O(8)–P(8)
120.27(14)
117.67(15)
126.5(2)
115.77(15)
122.06(13)
152.09(15)
Ni(1)–O(4)–Ni(2)
Ni(1)–O(6)–Ni(2)
84.57(9)
87.24(9)
Ni(1)–O(8)–Ni(2)
85.83(9)
Recrystallization of 3 from dimethylformamide led to isolation
of the adduct Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O (4 ꢀ 2H2O). Its crystal
consists of discrete molecules with Ni atom as inversion center,
separated by normal van der Waals distances. An ORTEP-like view
with the atoms numbering scheme is given in Fig. 4 and selected
bond lengths and angles are listed in Table 3.
O(4)Ni(1)O(6)/O(4)Ni(2)O(6) 54.6°; O(4)Ni(1)O(8)/O(4)Ni(2)O(8)
57.8°; O(4)Ni(1)O(8)/O(4)Ni(2)O(8) 54.2°]. The two nickel atoms
are in different environments: Ni(1) has a distorted square-pyra-
midal coordination geometry, with O(4) atom in apical position
and the nickel atom out of the best O(1)O(2)O(6)O(8) plane
(0.29 Å), while Ni(2) has a distorted octahedral geometry being
surrounded by six oxygen atoms. The Ni2O8 core may be consid-
ered as resulted from a Ni(1)O5 square pyramid and a Ni(2)O6 octa-
hedron, with a common trigonal face described by the O(4), O(6)
and O(8) atoms (Fig. 3). The two nickel atoms are brought very
The two imidodiphosphinato ligands act as monometallic
biconnective units, chelating the metal center through both oxygen
atoms. This results in a spiro-bicyclic system with Ni as spiro atom,
occupying an inversion center. The NiO4 system is planar, with
different Ni–O distances [Ni–O(1) 2.1134(16) Å, Ni–O(2)
2.0541(16) Å]. The six-membered NiO2P2N rings are of boat confor-
mations [with Ni(1) and nitrogen atoms in apices] and folded along
the imaginary O(1)ꢀ ꢀ ꢀO(2a) and O(1a)ꢀ ꢀ ꢀO(2) axis [dihedral angle of
16.4° between the best P2O2 and NiO4 planes] on opposite sides of
the planar NiO4 core [deviations from NiO4 plane: P(1) ꢂ0.462,
P(2a) ꢂ0.385, N(1a) ꢂ0.703 Å, and P(1a) 0.462, P(2) 0.385, N(1)
0.703 Å, respectively]. The phosphorus–oxygen [P(1)–O(1)
1.5106(18), P(2)–O(2) 1.5088(17) Å] and phosphorus–nitrogen
[P(1)–N(1a) 1.593(2), P(2)–N(1) 1.582(2) Å] distances, respectively,
are equivalent and intermediate between single P–E and double
P@E (E = O, N) bonds. The two dimethylformamide groups com-
plete the axial position of the octahedral environment around the
metal center and the Ni–ODMF bond lengths are intermediate be-
tween the short and the long metal–oxygen bonds established by
close each other, at a distance less than the sum of their van der
P
Waals radii [Ni(1)ꢀ ꢀ ꢀNi(2) 2.8552(8) Å versus vdWðNi; NiÞ 3.20 Å
[17]. This compound displays a different structure compared with
the related dimeric manganese(II) derivative, [Mn{(OPPh2)2N}2]2,
where both metal centers have the same coordination geometry,
i.e. trigonal bipyramidal, with two of the imidodiphosphinato li-
gands acting as monometallic biconnective units, with a cis orien-
tation with respect to the four-membered Mn2O2 ring; the other
two phosphorus ligands are homobimetallic triconnective, the re-
sult being a fused tricyclic Mn2O4P4N2 system [18].
The nickel–oxygen distances are different. The shorter bonds
[Ni(1)–O(1) 1.982(3), Ni(1)–O(2) 1.970(3) Å] are established by

2148
A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
Fig. 4. ORTEP plot at 30% probability and the atom numbering scheme for 4 ꢀ 2H2O. The hydrogen atoms are omitted.
Table 3
a phosphorus ligand unit. The distortion of the octahedral NiO6
core is reflected in the difference between the endo and exo cyclic
O–Ni–O bond angles in the equatorial plane [O(1)–Ni(1)–O(2a)
(endo) 92.43(7)°, O(1)–Ni(1)–O(2) (exo) 87.57(7)°].
Selected interatomic distances (Å) and angles (°) in Ni[(OPPh2)2N]2(DMF)2 ꢀ 2H2O
(4 ꢀ 2H2O)
Ni(1)–O(1)
Ni(1)–O(3)
2.1133(17)
2.0921(19)
Ni(1)–O(2)
2.0542(17)
P(1)–O(1)
P(1)–N(1a)
1.5106(18)
1.593(2)
P(2)–O(2)
P(2)–N(1)
1.5088(17)
1.582(2)
3.2. Crystal and molecular structure of [KNi[(SPPh2){OP(OEt)2}N]3]2
(5)
O(1)–Ni(1)–O(1a)
O(3)–Ni(1)–O(3a)
180.00
180.00
O(2)–Ni(1)–O(2a)
180.00
Yellow-brown crystals of (5) were grown from a CH2Cl2/n-hex-
ane (1:4, v:v) mixture.
O(3)–Ni(1)–O(1)
O(3)–Ni(1)–O(1a)
O(1)–Ni(1)–O(2)
87.25(7)
92.75(7)
87.57(7)
O(3)–Ni(1)–O(2)
O(3)–Ni(1)–O(2a)
O(1)–Ni(1)–O(2a)
90.36(7)
89.64(7)
92.43(7)
Compound 5 displays a tetranuclear structure and its ORTEP-
like diagram with the atom numbering scheme is depicted in
Fig. 5. Selected bond distances and angles are given in Table 4.
The phosphorus ligands exhibit different bridging patterns.
They are coordinated to the nickel center through the sulfur atoms
Ni(1)–O(1)–P(1)
O(1)–P(1)–N(1a)
P(1)–N(1a)–P(2a)
127.49(10)
118.84(10)
127.92(13)
Ni(1)–O(2)–P(2)
O(2)–P(2)–N(1)
129.92(10)
118.66(10)
Symmetry equivalent positions (2 ꢂ x, ꢂy, ꢂz) are given by ‘‘a”.
Fig. 5. ORTEP plot of the dimer unit in the crystal of 5. The atoms are drawn with 30% probability ellipsoids. For clarity, only ipso carbons of the phenyl groups are shown and
the hydrogen atoms are omitted.

A. Cristurean et al. / Polyhedron 27 (2008) 2143–2150
2149
Table 4
BiCl[(XPPh2)2N] (X = S, Se) [23]. As result of the coordination pat-
terns of the phosphorus ligands different metalocycles are formed.
The six-membered Ni(1)S(2)P(4)N(2)P(3)O(4) and Ni(1)S(3)-
P(6)N(3)P(5)O(7) chelate rings have twisted boat or chair confor-
mations, with Ni(1)/N(2) and Ni(1)/N(3) atoms, respectively, in
apices. The K2O2 ring is planar, while the NiKO2 ring is folded
[dihedral angle O(4)Ni(1)O(7)/O(4)K(1)O(7) 22.1°]. The dihedral
angle between the K2O2 ring and the KO2 fragment of the NiKO2
is 88.6°.
Selected interatomic distances (Å) and angles (°) in KNi[(SPPh2){OP(OEt)2}N]3 (5)
Ni(1)–O(4)
Ni(1)–O(7)
Ni(1)–S(1)
Ni(1)–S(2)
Ni(1)–S(3)
Ni(1)–N(1)
2.094(5)
2.086(5)
2.464(2)
2.477(2)
2.422(2)
2.238(6)
K(1)–O(1)
K(1)–O(1a)
K(1)–O(4)
K(1)–O(7)
K(1)–O(8)
2.362(6)
2.346(6)
2.387(6)
2.419(6)
2.540(6)
P(1)–O(1)
P(1)–N(1)
P(1)–O(2)
P(1)–O(3)
1.480(6)
1.610(7)
1.583(6)
1.568(6)
P(2)–S(1)
P(2)–N(1)
1.984(3)
1.611(6)
The Ni–chalcogen distances are similar for the three ligand
units. The Ni–S bond lengths [Ni(1)–S(1) 2.464(2), Ni(1)–S(2)
2.477(2), Ni(1)–S(3) 2.422(2) Å] are longer than in other Ni(II) thio-
ato derivatives, i.e. the tetrahedral Ni[(OPPh2)(SPR2)N]2 [2.306(4)/
2.305(4) Å, R = Me; 2.306(4)/2.286(4) Å, R = Ph] [8] or Ni-
[(SPPh2)2N]2 [2.281(2)–2.316(2) Å] [5] and the square-planar
Ni[(SPMe2)(SPPh2)N]2 [2.231(1)/2.247(1) Å] [5], Ni3S2(S2COR)2-
(dppe) [2.170(1)–2.235(1) Å, R = Me; 2.151(4)–2.247(6) Å, R = Et]
or Ni(S2CO)(dppe) [2.1853(8)–2.1970(8) Å] [24] complexes.
The Ni–O distances [Ni(1)–O(4) 2.094(5), Ni(1)–O(7) 2.086(5) Å]
are similar to those found in compounds 3 ꢀ CH2Cl2 and 4 ꢀ 2H2O,
but slightly longer in comparison with the values found in
Ni[(OPPh2)(SPR2)N]2 [1.950(7)/1.959(7) Å, R = Me; 1.950(8)/
1.956(7) Å, R = Ph] [8]. Significant differences were observed in
case of the K–O distances [range 2.346(6)–2.540(6) Å]. The shortest
bonds correspond to the K–O–K bridge [K(1)–O(1) 2.362(6), K(1)–
O(1a) 2.346(6) Å], while the longest one corresponds to the K–OEt
interaction [K(1)–O(8) 2.540(6) Å]. It can be mentioned that only
one OEt group is involved in interaction to each potassium center.
The phosphorus–nitrogen and phosphorus–chalcogen distances
suggest that the monothioimidodiphosphinato ligands are primar-
ily coordinated to nickel through sulfur. The phosphorus–sulfur
[P(2)–S(1) 1.984(3), P(4)–S(2) 1.999(3) and P(6)–S(3) 1.984(3) Å]
and terminal phosphorus–oxygen [P(1)–O(1) 1.480(6), P(3)–O(4)
1.489(6) and P(5)–O(7) 1.485(5) Å] bond lengths are equivalent
in all three ligand units. Their magnitude is intermediate between
single P–S and the double P@S bonds [cf. Ph2P(@S)–N@P(–SMe)Ph2
[19]: P–S 2.071(1) and P@S 1.954(1) Å] and consistent with double
P@O bonds, respectively [cf. Ph2P(O)OH [20]: P@O 1.486(6) Å, P–O
1.526(6) Å].
P(3)–O(4)
P(3)–N(2)
P(3)–O(5)
P(3)–O(6)
1.489(6)
1.551(8)
1.577(7)
1.565(7)
P(4)–S(2)
P(4)–N(2)
1.999(3)
1.587(8)
P(5)–O(7)
P(5)–N(3)
P(5)–O(8)
P(5)–O(9)
1.485(5)
1.565(6)
1.591(6)
1.574(6)
P(6)–S(3)
P(6)–N(3)
1.984(3)
1.601(6)
O(4)–Ni(1)–S(1)
N(1)–Ni(1)–S(3)
168.64(16)
167.52(17)
O(7)–Ni(1)–S(2)
175.70(15)
O(4)–Ni(1)–O(7)
O(4)–Ni(1)–N(1)
O(4)–Ni(1)–S(2)
O(4)–Ni(1)–S(3)
84.2(2)
93.5(2)
91.86(16)
98.94(16)
S(1)–Ni(1)–O(7)
S(1)–Ni(1)–N(1)
S(1)–Ni(1)–S(2)
S(1)–Ni(1)–S(3)
92.89(15)
75.30(17)
90.67(8)
92.25(8)
O(7)–Ni(1)–N(1)
N(1)–Ni(1)–S(2)
86.4(2)
92.18(18)
S(2)–Ni(1)–S(3)
O(7)–Ni(1)–S(3)
87.03(7)
95.24(15)
K(1)–O(1)–P(1)
O(1)–P(1)–N(1)
P(1)–N(1)–P(2)
S(1)–P(2)–N(1)
Ni(1)–S(1)–P(2)
Ni(1)–O(4)–P(3)
O(4)–P(3)–N(2)
P(3)–N(2)–P(4)
S(2)–P(4)–N(2)
Ni(1)–S(2)–P(4)
123.7(3)
117.6(3)
133.0(4)
105.9(2)
81.27(9)
132.2(3)
119.9(4)
132.9(5)
118.6(3)
105.68(10)
K(1a)–O(1)–P(1)
K(1)–O(1)–K(1a)
141.4(3)
87.9(2)
Ni(1)–N(1)–P(1)
Ni(1)–N(1)–P(2)
Ni(1)–O(7)–P(5)
O(7)–P(5)–N(3)
P(5)–N(3)–P(6)
S(3)–P(6)–N(3)
Ni(1)–S(3)–P(6)
128.3(3)
97.4(3)
138.2(3)
120.3(3)
130.2(4)
120.0(2)
110.61(10)
K(1)–O(4)–P(3)
K(1)–O(8)–P(5)
Ni(1)–O(4)–K(1)
124.1(3)
95.0(3)
100.1(2)
K(1)–O(7)–P(5)
103.1(3)
Ni(1)–O(7)–K(1)
99.3(2)
O(1)–K(1)–O(4)
O(1)–K(1)–O(7)
O(1)–K(1)–O(8)
O(1)–K(1)–O(1a)
90.2(2)
92.3(2)
132.2(3)
92.1(2)
O(4)–K(1)–O(7)
O(4)–K(1)–O(8)
O(4)–K(1)–O(1a)
71.32(19)
110.8(2)
130.0(2)
Acknowledgements
O(7)–K(1)–O(8)
O(7)–K(1)–O(1a)
58.24(18)
158.2(2)
O(8)–K(1)–O(81a)
104.0(2)
This work was supported by the National University Research
Council of Romania (CNCSIS Grant: A-358/2006). S.I. is grateful
for financial support in form of the Scientific and Technical Re-
search Council of Turkey (TUBITAK) - NATO B2 fellowship.
Symmetry equivalent positions (ꢂx, ꢂy, 1 ꢂ z) are given by ‘‘a”.
which describe a triangular face of the distorted octahedral envi-
ronment. The oxygen atoms of the SPNPO skeletons are involved
in bridges between metal centers, i.e. O(4) and O(7) atoms bridge
the metal atoms of a KNi[(SPPh2){OP(OEt)2}N]3 unit, while O(1)
atom is involved in a bridge between the two potassium atoms
of the [KNi[(SPPh2){OP(OEt)2}N]3]2 dimer. The N(1) atom com-
pletes the octahedral coordination of the nickel atom (NiNO2S3
core), while the coordination sphere around the potassium atom
is completed by an oxygen atom from an ethoxy group belonging
to the KNi[(SPPh2){OP(OEt)2}N]3 unit [K(1)–O(8) 2.540(6) Å]. Thus
phosphorus ligands can be described as (O,O,S)-heterobimetallic
triconnective, (S,O,O,OEt)-heterobimetallic tetraconnective and
(N,O,O,S)-heterotrimetallic tetraconnective, respectively. As far
very few examples of complexes are known in which the nitrogen
atom of the imidodiphosphinato ligand is involved in interaction
with the metal center, i.e. S,N-monometallic biconnective in
Pd[(SPR2){OP(OPh)2}N]2 (R = Ph, Pri) [21], O,N-monometallic
biconnective in the dimeric [PhHg{OP(OPh)2}2N]2 [22] and X,X,N-
monometallic triconnective coordination in [2-(Me2NCH2)C6H4]
Appendix A. Supplementary data
CCDC 612983, 612984 and 626929 contain the supplementary
crystallographic data for 3 ꢀ CH2Cl2, 4 ꢀ 2H2O and 5. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.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.2008.04.006.
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