First nickel(II) complexes containing tetrahedral NiO2S2 cores. The molecular structures of Ni[(OPPh2)(SPR2)N]2 (R = Ph, Me)

Article abstract of DOI:10.1016/S0020-1693(00)00118-3

Ni[(OPR'₂)(SPR₂)N]₂ complexes were obtained in good yields by reacting NiCl₂·6H₂O and the alkaline salts of the corresponding tetraorganomonothioimidodiphosphinic acids. All compounds were characterized by elemental analysis and IR. The molecular structure of Ni[(OPPh₂)(SPR₂)N]₂ (R = Ph, Me) has been determined by single-crystal X-ray diffractometry. Ni[(OPPh₂)-(SPPh₂)N]₂ (1) crystallizes in the monoclinic space group P2₁/c (no. 14), and Ni[(OPPh₂)(SPMe₂)N]₂ (2) crystallizes in the triclinic space group P1 (no. 2). The crystals of both compounds contain discrete mononuclear molecules. The asymmetric ligands act as monometallic biconnective units which results in a tetrahedral NiO₂S₂ core. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(00)00118-3

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 305 (2000) 106–110
Note
First nickel(II) complexes containing tetrahedral NiO2S2 cores. The
molecular structures of Ni[(OPPh2)(SPR2)N]2 (R =Ph, Me)
a
Anca Silvestru* a,1, Danut Bˆılc a, Roland Ro¨sler , John E. Drake* b,2, Ionel Haiduc
a Facultatea de Chimie, Uni6ersitatea ‘Babes-Bolyai’, RO-3400 Cluj-Napoca, Romania
b Department of Chemistry and Biochemistry, Uni6ersity of Windsor, Windsor, Ont., N9B 3P4, Canada
Received 15 December 1999; accepted 1 March 2000
Abstract
Ni[(OPR%2)(SPR2)N]2 complexes were obtained in good yields by reacting NiCl2·6H2O and the alkaline salts of the correspond-
ing tetraorganomonothioimidodiphosphinic acids. All compounds were characterized by elemental analysis and IR. The molecular
structure of Ni[(OPPh2)(SPR2)N]2 (R =Ph, Me) has been determined by single-crystal X-ray diffractometry. Ni[(OPPh2)-
(SPPh2)N]2 (1) crystallizes in the monoclinic space group P 21/c (no. 14), and Ni[(OPPh2)(SPMe2)N]2 (2) crystallizes in the triclinic
(
space group P 1 (no. 2). The crystals of both compounds contain discrete mononuclear molecules. The asymmetric ligands act as
monometallic biconnective units which results in a tetrahedral NiO2S2 core. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Nickel complexes; Chalcogenoimidodiphosphinato complexes; Tetrahedral complexes
1. Introduction
{OP(OEt)2}N]− [11,22], [(OPPh2){SP(OEt)2}N]− [22]
and [{OP(OPh)2}{SP(OPh)2}N]− [23].
The interest for the study of metal tetraorgan-
odichalcogenoimidodiphosphinates shown by various
research groups [1–5] was focused mainly on symmetri-
cal ligands [(XPR2)2N]− (i.e. the same organic group
and the same chalcogen atoms attached to the P atoms:
R =Ph, OPh, X=O; R =Me, Pri, Ph, OPh, X=S;
R =Ph, X=Se). In the last years, although several
asymmetric ligands containing different organic groups
and/or chalcogen atoms have become available, rela-
tively few studies have been reported on complexes con-
Nickel(II) complexes of the type Ni[(XPR2)-
(XPR%)N]2, containing the same chalcogen atoms in the
2
ligand unit, were reported, e.g. Ni[(SPR2)2N]2 (R =Me
[24,25], Ph [6,26]), Ni[(SePPh2)2N]2 [27] and
Ni[(SPMe2)(SPPh2)N]2 [6]. All these complexes are
monomeric and most of them contain a tetrahedral
NiX4 core. However, a square-planar NiS4 core was
found for Ni[(SPMe2)(SPPh2)N]2, thus reflecting the ca-
pacity of such ligands to accommodate different tetraco-
ordinated geometries required by the metal center [6].
No Ni(II) complexes containing mixed-chalcogen
taining [(XPR2)(YPR%)N]− moieties, i.e. [(SPMe2)-
2
(SPPh2)N]−
[6–8],
[(OPMe2)(OPPh2)N]− [7,10], [(OPPh2){OP(OEt)2}N]−
[11], [12], [(OPMe2)-
[(OPEt2){OP(OPh)2}N]−
(SPPh2)N]− [7,13],
[(SPPh2){SP(OEt)2}N]−
[9],
[(XPR2)(YPR%)N]− have been reported so far, but for a
2
palladium(II) derivative, Pd[{OP(OPh)2}{SP(OPh)2}N]2
[23], an unusual S,N-coordination pattern was estab-
lished.
On the other hand, a Cambridge Structure Database
search for tetracordinated NiO2S2 core-containing com-
plexes revealed that for all Ni(ligand-O,S)2 compounds
characterized so far by X-ray diffraction a square-pla-
nar coordination geometry was achieved regardless of
[(SPMe2)(OPPh2)N]− [7,13],
[(OPPh2)(SPPh2)N]− [7,10,13–20], [(OPPh2)(SePPh2)-
N]− [16,19,20], [(SPPh2)(SePPh2)N]− [21], [(SPPh2)-
1 *Corresponding author.
2 *Corresponding author.
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(00)00118-3

A. Sil6estru et al. / Inorganica Chimica Acta 305 (2000) 106–110
107
the size of chelate ring formed, i.e. five- [28–45] or
2.1. Synthesis of Ni[(OPPh2)(SPPh2)N]2 (1)
six-membered [46–52].
Here we report on the synthesis and structural char-
acterization of the first nickel(II) derivatives containing
Clear methanol solutions containing K[(OPPh2)-
(SPPh2)N] (0.471 g, 1.0 mmol, in 10 ml methanol) and
NiCl2·6H2O (0.119 g, 0.5 mmol, in 10 ml methanol)
were mixed and stirred for 2 h at room temperature
(r.t.). The deep greenish-blue crystals of the title com-
pound, which deposited in time, were filtered and re-
monothioimidodiphosphinato
(SPR2)N]2.
ligands,
Ni[(OPR%)-
2
2. Experimental
crystallized
from
a
dichloromethane–methanol
mixture. Yield: 0.32 g (69%). M.p. 159–161°C. IR
(cm−1): was(P2N) 1245vs, 1220vs; w(PO) 1120s, 1045vs;
w(PS) 580m, 570vs.
Sodium or potassium dichalcogenoimidodiphosphin-
ates were prepared according to published methods:
K[(OPPh2)(SPPh2)N] [14], K[(SPMe2)(OPPh2)N] and
Na[(OPMe2)(SPPh2)N] [13]. The IR spectra were
recorded using KBr pellets on a Specord 75 IR Carl-
Zeiss-Jena (DDR) instrument, in the range 4000–400
2.2. Synthesis of Ni[(OPPh2)(SPMe2)N]2 (2)
A reaction mixture obtained from stoichiometric
amounts of K[(OPPh2)(SPMe2)N] (0.694 g, 2.0 mmol)
and NiCl2·6H2O (0.237 g, 1.0 mmol) in 20 ml of
methanol was stirred at r.t. for 4 h. A greenish solid
deposited and was filtered off. For purification it was
dissolved in 20 ml chloroform and the insoluble KCl
was removed by filtration. The title compound was
obtained as dark blue crystals by slow diffusion using a
1:5 chloroform–n-hexane (v/v) solvent mixture. Yield:
0.49 g (73%). M.p. 164°C. IR (cm−1): was(P2N)
1185vs,br; w(PO) 1120s; w(PS) 570m.
cm−1
.
Table 1
Crystallographic data for Ni[(OPPh2)(SPPh2)N]2 (1) and Ni[(OPPh2)-
(SPMe2)N]2 (2)
1
2
Molecular formula
C48H40O2N2P4S2 C28H32O2N2P4S2N
Ni
i
M
923.57
monoclinic
P 21/c
Mo Ka
12.517(4)
18.247(3)
19.590(4)
675.29
triclinic
Crystal system
Space group
Radiation
a (A)
b (A)
2.3. Synthesis of Ni[(OPMe2)(SPPh2)N]2 (3)
(
P 1
Mo Ka
,
,
11.360(2)
16.613(3)
8.737(3)
94.06(2)
99.39(2)
82.56(1)
1611.1(6)
2
A stoichiometric amount of Na[(OPMe2)(SPPh2)N]
(0.785 g, 2.37 mmol) was added to a solution of
NiCl2·6H2O (0.282 g, 1.19 mmol) in 20 ml of methanol.
The reaction mixture was stirred for 2 h at r.t. The
resulting green solid was filtered off and then dissolved
in 20 ml chloroform. The insoluble KCl was removed
by filtration and the clear filtrate was evaporated. The
title compound was isolated as light green crystals.
Yield: 0.48 g (60%). M.p. 186–188°C. IR (cm−1):
was(P2N) 1175vs,br; w(PO) 1110s; w(PS) 615m, 585m.
,
c (A)
h (°)
i (°)
k (°)
V (A )
Z
100.73(2)
3
,
4396(1)
4
Crystal size (mm)
0.40×0.35
0.38×0.38×0.35
×0.30
1.39
1912.00
2–50
Dcalc. (g cm−3
F000
2q Range (°)
v(Mo Ka) (cm−1
)
1.39
700.00
2–50
)
7.17
9.51
2.4. Crystallographic structure determination
Max. and min. transmission 0.70–1.00
factors
0.90–1.00
Details of the data collections and refinements are
summarized in Table 1. Blue block crystals of
Ni[(OPPh2)(SPPh2)N]2 (1) and Ni[(OPPh2)(SPMe2)N]2
(2), were mounted on glass fibers and sealed with epoxy
glue. Data were collected on a Rigaku AFC6S diffrac-
tometer with graphite-monochromated Mo Ka radia-
tion, operating at 50 kV and 35 mA. On the basis of
statistical analyses of intensity distributions and the
successful solution and refinement of the structure, the
space groups were determined to be P 21/c (No. 14) and
Temperature (°C)
Reflections measured
Reflections observed
[IoB3|(Io)], No
Parameters refined, Np
Largest shift/e.s.d. in final
cycle
23
8413
2259
23
6015
1876
272
0.001
212
0.001
Max., min. residual density
0.48, −0.37
0.42, −0.40
−3
,
peaks (e A
)
a
R
0.0605
0.0598
1.80
0.0601
0.0475
1.38
R% b
c
Goodness-of-fit , S
(
P 1 (no. 2) for 1 and 2, respectively. The data were
corrected for Lorentz and polarization effects. The
structures were solved by direct methods [53]. Only the
nickel, sulfur, and phosphorus atoms in 1 and all
a R =SꢀFoꢀ−ꢀFcꢀ/SꢀFoꢀ.
b R%=[Sw(ꢀFoꢀ−ꢀFcꢀ)2/SwFo2)]1/2, where w=1/|2(Fo).
c S=[S(ꢀFoꢀ−ꢀFcꢀ)/|]/(No−Np).

108
A. Sil6estru et al. / Inorganica Chimica Acta 305 (2000) 106–110
sion effects were included in Fc [56]; the values for Df %
and Df %% were those of Creagh and McAuley [57].
3. Results and discussion
The title compounds were obtained as crystalline
solids by reacting NiCl2·6H2O with the alkaline salt of
the appropriate monothioimidodiphosphinic acid, in
methanol, according to Eq. (1):
NiCl2·6H2O+2M[(OPR%)(SPR2)N]
2
“Ni[(OPR%)(SPR2)N]2+2MCl+6H2O
(1)
2
The strong infrared absorptions observed for all
these nickel(II) complexes in the regions 1250–1170,
1120–1040 and 620–570 cm−1 were assigned to
was(P2N), w(PO) and w(PS) stretching vibrations, respec-
tively, by comparison with the spectra of the free acids
and their alkaline salts, thus suggesting bidentate coor-
dination of the ligand unit through both chalcogen
atoms.
Fig. 1. An ORTEP plot of Ni[(OPPh2)(SPPh2)N]2 (1) (the heavy atoms
are drawn with 20% probability ellipsoids. Hydrogen atoms are
omitted for clarity).
The solid-state structures of Ni[(OPPh2)(SPR2)N]2
[R =Ph (1), Me (2)] were determined by single-crystal
X-ray diffraction. For both compounds the crystal con-
tains discrete monomeric molecules separated by nor-
mal van der Waals distances. The ORTEP plots of the
molecular structures of 1 and 2 are displayed in Figs. 1
and 2. Important bond lengths and angles are listed in
Table 2.
The molecular structure of 1 and 2 complexes are
very similar. In a molecular unit both monothioimi-
dodiphosphinato ligands are coordinated to a metal
center in a monometallic biconnective pattern through
both chalcogen atoms. The result is a spiro-bicyclic
system with a tetrahedral NiO2S2 core, which is pre-
served in solution too as reflected by paramagnetic
behavior which prevents the NMR study of these com-
plexes. This contrasts with the square-planar NiO2S2
core observed for bis(monothio-b-diketonato)nickel(II)
[28–34] and related complexes [37–43].
,
The PꢀS [range 2.012(5)–2.026(5) A] and the PꢀN
,
bonds [range 1.57(1)–1.610(9) A] are equal, within the
Fig. 2. An ORTEP plot of Ni[(OPPh2)(SPMe2)N]2 (2) (the heavy atoms
are drawn with 20% probability ellipsoids. Hydrogen atoms are
omitted for clarity).
experimental errors, and their lengths are intermediate
between single and double phosphorusꢀsulfur and
phosphorusꢀnitrogen bonds, cf. the free acids
(OꢁPPh2)(SꢁPPh2)NH [17]: PꢁS 1.935(2), (S)PꢀN
,
1.694(4), (O)PꢀN 1.668(5), PꢁO 1.491(4) A;
non-hydrogen atoms except carbon in 2 were treated
anisotropically. The hydrogen atoms were included in
(OꢁPPh2)(SꢁPMe2)NH [13]: PꢁS 1.944(3), (S)PꢀN
,
1.681(7), (O)PꢀN 1.662(7), PꢁO 1.480(5) A; and
their idealized positions with CꢀH set at 0.95 A and
[(Me3Si)2NꢀP(ꢁNBut)S]2 [58]: PꢁN 1.529(2), PꢀN
,
,
with isotropic thermal parameters set at 1.2 times that
of the carbon atom to which they were attached. Refin-
ements were made by full-matrix least-squares using the
TEXSAN [54] crystallographic package of the Molecular
Structure Corp. Neutral-atom scattering factors were
taken from Cromer and Waber [55]. Anomalous disper-
1.662(2) A. The PꢀO bond distances have also interme-
diate values between single and double phospho-
rusꢀoxygen bonds (cf. Ph2P(ꢁO)OH [59]: PꢀO 1.526(6),
,
PꢁO 1.486(6) A), but some small differences are ob-
served probably due to the nature of the organic groups
attached to the corresponding phosphorus atoms, i.e.

A. Sil6estru et al. / Inorganica Chimica Acta 305 (2000) 106–110
109
Table 2
Important bond lengths (A) and angles (°) for Ni[(OPPh2)(SPPh2)N]2 (1) and Ni[(OPPh2)(SPMe2)N]2 (2)
,
1
2
1
2
Ni(1)ꢀO(1)
Ni(1)ꢀS(1)
1.950(8)
2.306(4)
1.959(7)
2.306(4)
Ni(1)ꢀO(2)
Ni(1)ꢀS(2)
1.956(7)
2.286(4)
1.950(7)
2.305(4)
P(1)ꢀO(1)
P(1)ꢀN(1)
P(2)ꢀN(1)
P(2)ꢀS(1)
1.561(8)
1.57(1)
1.59(1)
2.016(5)
1.521(7)
1.610(9)
1.589(9)
2.023(5)
P(3)ꢀO(2)
P(3)ꢀN(2)
P(4)ꢀN(2)
P(4)ꢀS(2)
1.588(8)
1.57(1)
1.59(1)
2.012(5)
1.530(7)
1.589(9)
1.599(9)
2.026(5)
O(1)···S(1)
3.388(8)
3.363(8)
O(2)...S(2)
3.425(8)
3.377(8)
O(1)ꢀNi(1)ꢀS(1)
O(1)ꢀNi(1)ꢀS(2)
O(1)ꢀNi(1)ꢀO(2)
105.2(2)
112.5(3)
107.7(3)
103.8(2)
127.0(2)
101.8(3)
O(2)ꢀNi(1)ꢀS(2)
O(2)ꢀNi(1)ꢀS(1)
S(1)ꢀNi(1)ꢀS(2)
107.4(3)
116.1(3)
107.9(2)
104.7(2)
112.2(3)
107.2(1)
Ni(1)ꢀO(1)ꢀP(1)
Ni(1)ꢀS(1)ꢀP(2)
126.5(5)
98.9(2)
129.3(4)
100.0(2)
Ni(1)ꢀO(2)ꢀP(3)
Ni(1)ꢀS(2)ꢀP(4)
125.6(5)
101.2(2)
125.4(4)
102.5(2)
O(1)ꢀP(1)ꢀN(1)
P(1)ꢀN(1)ꢀP(2)
S(1)ꢀP(2)ꢀN(1)
117.8(5)
133.7(6)
116.7(4)
116.0(5)
123.9(6)
114.9(4)
O(2)ꢀP(3)ꢀN(2)
P(3)ꢀN(2)ꢀP(4)
S(2)ꢀP(4)ꢀN(2)
119.1(5)
130.5(7)
117.4(4)
117.3(4)
122.6(5)
116.5(4)
,
PꢀO=1.561(8) and 1.588(8) A for 1 and 1.521(7) and
4. Supplementary material
,
1.530(7) A for 2, respectively.
,
The NiꢀS [range 2.286(4)–2.306(4) A] and NiꢀO
[range 1.950(7)–1.959(7) A] bond distances are similar
in both 1 and 2, within the experimental errors. The
nickel-sulfur bond distances are very close to those
found in tetrahedral Ni[(SPMe2)2N]2 (av. 2.282 A),
A complete listing of the crystal data is provided in
the Supporting Information which contains tables giv-
ing final fractional coordinates and Beq for non-hydro-
gen atoms, anisotropic thermal parameters for
non-hydrogen atoms, atomic coordinates and Beq for
hydrogen atoms, all bond lengths and angles and OR-
,
,
i
,
Ni[(SPPr2)2N]2 (av. 2.284 A) or Ni[(SPPh2)2N]2 (av.
,
2.299 A), but longer than the predicted covalent NiꢀS
TEP
drawings
for
Ni[(OPPh2)(SPPh2)N]2
and
distance in a tetrahedral environment [Scov(NiTD,S),
Ni[(OPPh2)(SPMe2)N]2 (17 pages). Structure-factor ta-
bles are available from the authors (J.E.D. and A.S.)
upon request.
,
2.23 A], as are the nickelꢀoxygen bond distances
,
[Scov(NiTD,O) 1.94 A] [60,61].
The tetrahedral NiO2S2 cores are slightly distorted,
the bond angles at the Ni center range from 105.2(2) to
116.1(3)° in 1, and 101.8(3) to 127.0(2)° in 2, respec-
tively. The higher distortion of 2 from the ideal tetrahe-
dral bond angle of 109.5° is also reflected by the
dihedral angles between the S(1)Ni(1)O(1) and
S(2)Ni(1)O(2) planes: 79.9° in 2 and 85.3° in 1. The
high flexibility of the OPNPS skeleton, which allows an
Acknowledgements
This work was supported by the Romanian Academy
and the Romanian National Council for High Educa-
tion Scientific Research (CNCSIS) and by the Natural
Sciences and Engineering Research Council of Canada.
,
O···S ligand bite larger [3.388(8), 3.425(8) A in 1, and
,
3.363(8), 3.377(8) A in 2] than in the related monothio-
b-diketonato ligands (e.g. Ni[(OCMe)(SCMe)CH]2 [30]:
av. O···S, 3.00 A), seems to be one contributing factor
to the achievement of the tetrahedral coordination
around the nickel center.
,
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