Investigation on the reactivity of dithiophosphonato/dithiophosphato NiII complexes towards 2,4,6-tris-2-pyridyl-1,3,5-triazine: Developments and new perspectives

Article abstract of DOI:10.1039/b819326f

The reactions between tptz and differently substituted dithiophosphonato [Ni(ROpdt)₂] [ROpdt = (RO)(4-MeOC₆H₄)PS ₂^-; R = Et (2); Pr (3); i-Pr (4); Bu (5)] and dithiophosphato [Ni((EtO)₂PS₂)₂] (6) Ni ^II complexes have been investigated, and the characterisation of the resulting neutral mixed complexes (2·tptz)-(6·tptz) is reported. In all these complexes, tptz forces one of the two dithiophosphonato/ dithiophosphato ligands to behave as a monodentate ligand, a coordination mode rarely found in analogous Ni^II phosphorodithioato complexes. A comparison has been performed between the Ni-S bond distances of the new complexes and those of isologous dithiophosphonato, dithiophosphato and dithiophosphito Ni^II square-planar complexes, and of their penta- and hexa-coordinated adducts. The results, also supported by DFT calculations, are discussed and explained in terms of the structural trans-effect (STE). The reactivity of 2·tptz towards AgNO₃ and CuSO₄ to yield the complex [Ni(EtOpdt)(tptz)(H₂O)]NO₃ (7), and the dimer [(Ni(tptz)(μ-SO₄)(H₂O)]₂· 6H₂O (8), respectively, is consistent with the proposed bonding models.

Full text of DOI:10.1039/b819326f

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Investigation on the reactivity of dithiophosphonato/dithiophosphato NiII
complexes towards 2,4,6-tris-2-pyridyl-1,3,5-triazine: developments
and new perspectives†
M. Carla Aragoni,*a Massimiliano Arca,a Miriam Crespo,a Francesco A. Devillanova,a Michael B. Hursthouse,b
Susanne L. Huth,b Francesco Isaia,a Vito Lippolisa and Gaetano Verania
Received 30th October 2008, Accepted 16th December 2008
First published as an Advance Article on the web 17th February 2009
DOI: 10.1039/b819326f
The reactions between tptz and differently substituted dithiophosphonato [Ni(ROpdt)2] [ROpdt =
-
(RO)(4-MeOC6H4)PS2 ; R = Et (2); Pr (3); i-Pr (4); Bu (5)] and dithiophosphato [Ni((EtO)2PS2)2] (6)
NiII complexes have been investigated, and the characterisation of the resulting neutral mixed
complexes (2·tptz)-(6·tptz) is reported. In all these complexes, tptz forces one of the two
dithiophosphonato/dithiophosphato ligands to behave as a monodentate ligand, a coordination mode
rarely found in analogous NiII phosphorodithioato complexes. A comparison has been performed
between the Ni–S bond distances of the new complexes and those of isologous dithiophosphonato,
dithiophosphato and dithiophosphito NiII square-planar complexes, and of their penta- and
hexa-coordinated adducts. The results, also supported by DFT calculations, are discussed and
explained in terms of the structural trans-effect (STE). The reactivity of 2·tptz towards AgNO3 and
CuSO4 to yield the complex [Ni(EtOpdt)(tptz)(H2O)]NO3 (7), and the dimer
[(Ni(tptz)(m-SO4)(H2O)]2·6H2O (8), respectively, is consistent with the proposed bonding models.
to-face p–p interactions.5 Recently,7 we explored the reactivity of
Introduction
the dithiophosphonato NiII complex [Ni(MeOpdt)2] (1) towards
The preparation of coordination polymers by the self assembly
2,4,6-tris-2-pyridyl-1,3,5-triazine (tptz; Chart), which belongs to
the class of multi-modal ligands,8 since it contains both chelating
and monodentate donor sites, and is of current interest in the
design of multinuclear metal complexes.9 However, our plan to
use the multimodal tptz to build multidimensional networks was
not achieved since tptz behaved as a tridentate ligand rather than
achieving higher denticity, and we obtained an unusual mixed tptz-
dithiophosphonato complex [Ni(MeOpdt)2(tptz)] (1·tptz). In this,
the non-coordinating sites are available to interact with suitable
Lewis acids, exemplified by the preparation of some interesting
products on reaction with I2 and Br2.7 We have now extended
our investigations on the mixed complexes obtained by reacting
tptz with differently substituted dithiophosphonato [Ni(ROpdt)2]
[R = Et (2), Pr (3), i-Pr (4), Bu (5)] and dithiophosphato
[Ni((EtO)2PS2)2] (6) complexes (Chart 1).
of neutral metal complexes and donor molecules via coordina-
tion bonds or secondary bonding interactions is of increasing
importance in the field of crystal engineering.1 In this context,
we have started a synthetic program based on the ability of
neutral dithiophosphonato NiII complexes [Ni(ROpdt)2] [ROpdt =
(RO)(4-MeOC6H4)PS2 ; R = alkyl substituent]2 to act as building
-
blocks for the predictable assembly of inorganic coordination
polymers. Due to its coordinative unsaturation, the NiII ion in these
square-planar complexes tends to complete its coordination sphere
through axial binding of monodentate donor molecules, such as
pyridine, to yield octahedral complexes.3,4 Therefore, by using
suitable N-L-N bidentate bipyridyl-based spacers, we prepared
1D coordination polymers of the type [Ni(ROpdt)2(N-L-N)]•.5,6
The primary structural motif of the polymers has proved to depend
mainly on the features of the pyridyl-based spacers such as length,
rigidity, number and orientation of the donor atoms, whereas the
–OR substituents on the phosphorus atoms influence the final
3D-architecture through hydrogen bonds and face-to-face or edge-
aDipartimento di Chimica Inorganica ed Analitica, Universita` degli Studi
di Cagliari, S.S. 554 bivio per Sestu, 09042, Monserrato-Cagliari, Italy.
E-mail: aragoni@unica.it; Fax: +39 070 6754456; Tel: +39 070 6754491
bSchool of Chemistry, University of Southampton, Highfield, Southampton,
UK SO17 1BJ
† Electronic supplementary information (ESI) available: Selected hydrogen
◦
˚
bond distances (A) and angles ( ) for compounds 2·tptz, 3·tptz, 4·tptz,
6·tptz, 7, and 8 are reported in Table S1. Molecular view of compound
6·tptz is reported in Figure S1. Packing views of compounds 2·tptz, 4·tptz,
7, and 8 are reported in Figures S2, S3, S4, and S5, respectively. CCDC
reference numbers 278292–707537. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/b819326f
Chart 1
2510 | Dalton Trans., 2009, 2510–2520
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Results and discussion
The reactions of the dithiophosphonato complexes [Ni(ROpdt)2]
-
[ROpdt = (RO)(4-MeOC6H4)PS2 ; R = Et (2); Pr (3); i-Pr (4);
Bu (5)] and tptz in 1 : 1 molar ratio in the corresponding
ROH alcohols, yielded crystals of the complexes [Ni(ROpdt)2tptz]
[R = Et (2·tptz); Pr (3·tptz); i-Pr (4·tptz); Bu (5·tptz)]. Sim-
ilarly, the reaction in EtOH of the dithiophosphato complex
[Ni((EtO)2PS2)2] (6) and tptz in 1 : 1 molar ratio, afforded com-
pound [Ni((EtO)2PS2)2tptz] (6·tptz). Single crystal X-ray diffrac-
tion has been performed on all compounds; crystallographic data
and selected bond lengths and angles for 2·tptz, 3·tptz, 4·tptz,
5·tptz, and 6·tptz are reported in Tables 1 and 2, respectively.10
As exemplified in Fig. 1 for the case of 2·tptz, in all compounds
2·tpz-6·tpz, a molecule of tptz coordinates the nickel ion imposing
an expansion and rearrangement of the metal coordination sphere
from square planar to distorted octahedral. The NiII ion is thus
coordinated by the three nitrogen atoms N1, N4, and N5 from
tptz and three sulfur atoms belonging to a bidentate (S1 and S2)
and a monodentate (S3) dithiophosphonato ligand, respectively,
arranged in a meridian fashion. The formation of five-membered
˚
chelate rings with small rigid N–Ni–N bites [N–Ni–N av. 77.0 A]
is reflected in the geometry around the nickel, with N–Ni–S angles
diverging from the ideal values of 90 and 180◦ (Table 2). The bond
distances Ni–N1 between the Ni ion and the triazine nitrogen
˚
atoms range from 1.968(2) to 1.990(6) A and are significantly
shorter than the other Ni–N4 and Ni–N5 distances [av. 2.141 and
˚
2.125 A, respectively], analogous to what was found in the case
of [Ni(MeOpdt)2tptz] (1·tptz)7 and other nickel complexes with
tptz.20,21
As evidenced by
a
Mogul geometry check,11 in com-
pounds 1·tptz–6·tptz the octahedral NiII coordination cores
present unusual Ni–S bond distances: the dithiophospho-
nato/dithiophosphato chelating moieties behave as strongly aniso-
bidentate ligands and feature one short and one long Ni–S distance
˚
(Ni–S1, av. 2.40; Ni–S2, av. 2.57 A, see Table 2). By searching
the Cambridge Structural Database (CSD) for appropriate data,
we compared the Ni–S distances in the bidentate fragments
of compounds 1·tptz–6·tptz with those of dithiophosphonato
fragments behaving as bidentate ligands belonging to square-
planar nickel(II) complexes or to their octahedral complexes with
both monodentate and bidentate pyridine based ligands (Fig. 2).12
The examination of the data confirms that both Ni–S1 and Ni–S2
bond distances are quite unusual, notwithstanding their average
values falling in the range expected for fragments belonging to
octahedral complexes. In fact, the short Ni–S1 bond distances
˚
(around 2.4 A, grey full bars in Fig. 2) fall in a range of values
intermediate between those observed in square planar dithiophos-
˚
phonato complexes (around 2.2 A, dashed bars in Fig. 2) and those
˚
reported for the octahedral adducts (around 2.5 A, empty bars,
˚
Fig. 2), whilst the Ni–S2 bond distances (around 2.6 A, black
full bars in Fig. 2) are somewhat longer than those commonly
observed. Similar but less pronounced elongations of one of the
two Ni–S bonds have been found in analogous dithiophosphato
bidentate fragments belonging to cis-octahedral adducts between
dithiophosphato nickel(II) complexes and pyridine based donors,
and explained in terms of the structural trans-effect (STE)13
of the nitrogen donors.14 We have thus extended the structural
comparison by plotting Ni–S1 vs. Ni–S2 bond distances of the
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2510–2520 | 2511
©

View Article Online
◦
7
˚
Table 2 Selected bond lengths (A) and angles ( ) for compounds 2·tptz–6·tptz, and 7. Values for 1·tptz are reported for completeness
1·tptz
2·tptz
3·tptz
4·tptz
5·tptz
6·tptz
7
Ni–N1
Ni–N4
Ni–N5
Ni–S1
Ni–S2
Ni–S3/O3
P1-S1
P1-S2
P2-S3
P2-S4
1.965(3)
2.170(3)
2.141(3)
2.384(1)
2.569(1)
2.459(1)
2.002(1)
1.994(1)
2.009 (1)
1.960(1)
1.968(2)
2.135(2)
2.125(2)
2.4005(9)
2.6045(9)
2.4130(9)
1.9992(13)
1.9864(13)
2.0254(10)
1.9579(10)
1.990(6)
2.135(7)
2.118(7)
2.419(2)
2.569(2)
2.421(2)
2.005(3)
1.988(3)
2.011(3)
1.970(3)
1.976(7)
2.143(8)
2.106(6)
2.402(3)
2.558(3)
2.437(2)
2.008(3)
1.982(3)
2.020(3)
1.942(3)
1.987(4)
2.153(5)
2.147(5)
2.411(2)
2.5470(19)
2.4369(17)
1.983(3)
1.969(3)
2.010(2)
1.965(2)
1.970(3)
2.139(3)
2.130(3)
2.4220(12)
2.5603(12)
2.4242(12)
1.9784(14)
1.9919(14)
1.9920(14)
1.9553(16)
1.981(5)
2.169(5)
2.147(6)
2.403(2)
2.501(2)
2.067(4)
2.009(2)
1.986(2)
—
—
N1-Ni–S1
N1-Ni–S2
N1-Ni–S3/O3
N1-Ni–N5
N4-Ni–N5
N4-Ni–S1
N4-Ni–N1
N5-Ni–S1
S1-Ni–S2
174.24(9)
92.54(9)
96.38(9)
76.8(1)
153.6(1)
102.35(9)
76.8(1)
104.02(9)
81.78(4)
108.63(7)
116.58(7)
169.24(7)
87.15(7)
103.37(7)
77.40(9)
154.06(9)
102.61(7)
76.71(9)
103.11(7)
82.11(3)
111.30(5)
117.81(4)
168.3(2)
87.12(19)
105.3(2)
77.1(3)
153.5(3)
102.54(19)
76.4(3)
103.32(19)
81.23(7)
108.92(13)
113.46(13)
172.52(19)
90.74(18)
100.18(18)
77.3(3)
154.2(3)
100.6(2)
77.1(3)
104.2(2)
82.00(8)
109.39(14)
120.49(15)
171.73(14)
90.70(13)
102.61(13)
77.0(17)
153.32(19)
102.87(15)
76.31(17)
103.56(15)
81.04(7)
173.04(9)
91.74(9)
98.19(9)
77.28(13)
154.07(11)
100.70(8)
76.97(13)
105.23(8)
81.72(4)
178.57(15)
85.82(15)
88.71(18)
76.9(2)
153.11(18)
104.33(13)
76.3(2)
102.48(15)
82.93(7)
108.79(11)
—
S1-P1-S2
S3-P2-S4
109.30(12)
118.23(10)
110.45(6)
114.33(7)
Fig. 1 Molecular view of compound 2·tptz. For clarity, only non-carbon atoms have been labelled and hydrogen atoms omitted. Displacement ellipsoids
are drawn at 50% probability level.
title compounds and of analogous bidentate dithiophosphonato
[(R¢(RO)PS2)-, circles in Fig. 3], dithiophosphato [((RO)2PS2)-,
triangles in Fig. 3], and dithiophosphito [(R2PS2)-, squares in
Fig. 3] fragments bound to nickel(II) ions present in the CSD;
the results are summarized in Fig. 3.15 Three main regions can be
recognized, as not depending on the nature of the P-substituents,
which represent complexes with analogous coordination geome-
tries: square-planar complexes (blue), octahedral (green) and
square-pyramidal penta-coordinate (red squares) adducts. It is
interesting to note that both octahedral adducts with configuration
trans and cis (empty and filled green markers, respectively) are
clustered in the same area, which shows a significant spread. This
is in agreement with a certain asymmetry found within the PS2Ni
fragments belonging to several octahedral adducts, in particular
those featuring a cis configuration, resulting from a STE of the
nitrogen donors.14 On the contrary, the Ni–S bond distances
in (1·tptz)-(6·tptz) (black circles) do not fall in the expected
region of octahedral complexes, but define a separate area. Only
2512 | Dalton Trans., 2009, 2510–2520
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Fig. 2 Histograms for the Ni–S bond lengths within dithiophosphonates behaving as bidentate ligands in NiII complexes; dashed bars: square
planar complexes;12 empty bars: octahedral complexes;12 full bars: compounds 1·tptz–6·tptz (grey, Ni–S1; black: Ni–S2); arrows on full bars point out
compound 7.
Fig. 3 Scatter plot of Ni–S1 vs. Ni–S2 bond lengths for the bidentate dithiophosphonato [(R(RO)PS2)-, circles], dithiophosphato [((RO)2PS2)-, triangles],
and dithiophosphito [(R2PS2)-, squares] fragments bound to nickel(II) ions.15 Different colours refer to different coordination geometries: square-planar
(blue); octahedral (green: cis and trans configurations are evidenced by using full and empty symbols, respectively); penta-coordinated (red: square
pyramidal and trigonal bipyramidal geometries are evidenced by using full and empty symbols, respectively); compounds 1·tptz–6·tptz full black;
compound 7 empty black.
two compounds, among the 105 analyzed, present Ni–S bond
lengths falling out of the three main regions, and both feature
a dithiophosphato moiety behaving as monodentate ligand trans
to the longer Ni–S distance (red triangles). Notwithstanding the
lack of comparable fragments providing more confidence, it can be
deduced that monodentate dithiophosphonato/dithiophosphato
ligands exercise a notable STE which causes a stretching of the
trans disposed Ni–S bonds, and a shortening of the corresponding
cis Ni–S bonds. This can be explained from a classical point of
view by using the Grinberg polarisation theory,16 which attributes
the weakening of the bond of a certain ligand to the presence of an
-
=
easily polarisable donor group [in our case the P( S)S fragment]
trans disposed with respect to the ligand itself, since it causes
an increase of negative charge on the metal and consequently
a partial repulsion of the ligand. This classical description of the
STE was rationalized in more recent years by Burdett and Albright
in terms of MO analyses of octahedral complexes,17 demonstrating
that if two different ligands are forced to share the same metal
atomic orbital a differential weakening of the metal–ligand bonds
occurs.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2510–2520 | 2513
©

View Article Online
In the second dithiophosphonato/dithiophosphato unit, which
behaves as monodentate ligand, the Ni–S3 bond distance is
only slightly elongated with respect to those observed in square-
planar dithiophosphonato NiII complexes, and the two P–S bond
distances are quite different since the one not involved in the
metal–sulfur bond (P2–S4) retains a double bond character. Tptz
is only roughly planar with the pyridyl rings unequally twisted
with respect to the central triazine ring due to intermolecular
H-bonds and p-interactions which control the crystal packing.
Notwithstanding the structure of complexes 2·tptz–6·tptz closely
resemble each other, the corresponding crystal packing are
different, mainly depending on the nature of the P-substituents.
The presence of aromatic P-substituents leads the molecules to
pack driven by aromatic interactions. Thus, compounds 2·tptz,
3·tptz, and 5·tptz, featuring an anisole and linear alkyl chains
of different length as the P-substituents, pack in pairs, disposed
around an inversion centre, interacting through either off-set or
slipped face-to-face p–p interactions between the aromatic rings
of tptz and anisole moiety to form layered piles or sheets (Fig. 4,
and Fig. S2 in ESI†). The OR chains protrude to join adjacent
piles or sheets through interactions of the type X ◊ ◊ ◊ H (X = S and
O; Fig. S2 and S3b in ESI†). In contrast, in the case of compound
4·tptz, the complex molecules do not pair off, but pack piled along
the direction of the c axis, positioned in order to enhance p–p
interactions between adjacent piles (Fig. S3 in ESI†).
to C–H ◊ ◊ ◊ S interactions between the sulfur atoms and the OEt
P-substituents and the tptz C5N(4) pyridine rings (Fig. 5).
DFT calculations
With the aim of a better understanding of the nature of the
bonding in the mixed tptz-dithiophosphonato/dithiophosphato
NiII complexes DFT calculations have been performed on the
compounds 2·tptz and 6·tptz. The electronic structures of the
two complexes show that they present similar features although
some differences in the relative energy order of the frontier Kohn–
Sham orbitals can be found due to the contribution of the
orbitals of the aromatic P-substituents in 2·tptz. In particular,
it is worth observing that both 2·tptz and 6·tptz feature filled
bonding molecular orbitals involving the interaction of the d
atomic orbitals of the central nickel ion with those localized on the
lone pairs of the sulfur atoms (S2 and S3) trans disposed to each
other (Fig. 6). This is in agreement with the structural trans-effect
(STE) evidenced on the ground of structural data discussed above.
Moreover, on the basis of recent work by Arden and Orpen,18
which analyzes the STE in terms of the involved molecular orbitals,
for M–L bonds having a substantial dNi-orbital character a certain
trans-influence13 accompanied by a less important cis-influence is
expected, in agreement with that discussed above. More detailed
information on the nature of the bonding between the central
metal ion and the ligands in complexes 2·tptz and 6·tptz come from
a natural bond orbital analysis. Natural charges, calculated on the
metal centre and on the S and N donor atoms are summarized
in Table 3. In both cases, as expected, sulfur atoms coordinating
the nickel centre are more negatively charged than nitrogen ones.
Interestingly, in compound 2·tptz, the central ion is more positively
charged than in 6·tptz, while the corresponding donor atoms are
more negatively charged, indicating a decrease in the polarization
Also in the case of 6·tptz, which features two OEt P-substituents,
aromatic interactions show their importance in organizing the
packing by ordering molecules of 6·tptz in pairs by means of a
perfect off-set p–p interaction between the two C5N(4) pyridine
rings of symmetry related tptz molecules (parallel planes at
˚
3.49 A). In contrast to what was observed in the previously
discussed structures, these interactions are isolated to the two
involved rings, the packing of the paired molecules being left
Fig. 4 Packing view of compound 3·tptz evidencing H-bonds and p–p interactions between the aromatic rings of tptz and anisole to form layered sheets
◦
˚
˚
[C2–H2 ◊ ◊ ◊ S2: 2.84, 3.478(8), 125.0; C32–H32 ◊ ◊ ◊ S4: 2.72, 3.581(10), 151.0; C5–H5 ◊ ◊ ◊ O2: 2.43 A, 3.312(11) A, 154.0 ; a: 3.71, 7.26; b: 3.93, 5.52; c:
◦
˚
3.75 A, 11.4 ]. Hydrogen atoms not involved in the interactions shown have been omitted for clarity reasons.
2514 | Dalton Trans., 2009, 2510–2520 This journal is
The Royal Society of Chemistry 2009
©

View Article Online
◦
˚
Fig. 5 Packing view of compound 6·tptz evidencing H-bonds and contacts between p–p paired molecules in the bc plane. [C3N3 ◊ ◊ ◊ C5N(4) 0 , 3.49 A;
◦
˚
˚
˚
C4–H4b ◊ ◊ ◊ S3: 2.84 A, 3.632(5) A, 138 ; O4 ◊ ◊ ◊ H26 2.67; N6 ◊ ◊ ◊ H8c 2.67; S1 ◊ ◊ ◊ H3B 3.05 A] Hydrogen atoms not involved in the interactions shown
have been omitted for clarity reasons.
Table 3 Selected NBO charges (e) calculated for 2·tptz and 6·tptz at DFT
level.a,b
2·tptz
6·tptz
Ni
P1
P2
S1
S2
S3
S4
N1
N4
N5
1.157
1.433
1.421
-0.580
-0.646
-0.695
-0.685
-0.591
-0.542
-0.542
1.138
1.676
1.642
-0.612
-0.627
-0.658
-0.650
-0.585
-0.541
-0.537
Fig. 6 Drawings of the filled Kohn–Sham molecular orbitals [HOMO-12,
(a); HOMO-5, (b)] showing the same d nickel atomic orbital shared
between the two axially bonded dithiophosphonato/dithiophosphato
ligands in complexes (2·tptz, a) and (6·tptz, b). Contour value =
0.05 e.
a mPW1PW functional; Shafer, Horn, and Ahlrichs pVDZ basis set.
b Numbering scheme refers to Fig. 1, and is consistent with all the structures
reported.
donor atoms S2 and S3 are bonded to the central ion with
different strengths: indeed in all cases the sulfur atom belonging
to the monodentate ligand (S3) features a more negative charge
and coordinates more strongly the nickel as compared to the
trans-disposed sulfur atom S2, belonging to the bidentate unit.
This accounts for the STE exerted by the monodentate unit,
in agreement with the theories of Grinberg16 and Burdett.17 In
contrast, the second sulfur atom of the bidentate unit (S1), is free
to strongly bind the nickel ion, and accordingly it shows the higher
Ni–S bond order. A further insight into the electronic structures of
complexes 2·tptz and 6·tptz arises from the analysis of the second
order perturbation of the Fock matrix in NBO basis. As regards
the tptz ligand, this approach confirms the more coordinating
of the bonds involving the metal when dithiophosphonato anions
are replaced by dithiophosphato ones. An examination of the
charge distribution on the tptz ligand shows that in both cases the
nitrogen donor atom belonging to the triazine ring (N1) is more
negatively charged than those (N4 and N5), more distant from
the nickel ion, belonging to the coordinating pyridine pendants.
Accordingly, Wiberg bond indexes (WBIs)28 between the metal
ion and N1 are remarkably higher than those involving N4 and
N5 (Table 4). WBIs also allow for a comparison between the
bond feature of monodentate and bidentate dithiophosphonato
and dithiophosphato ligands, in 2·tptz and 6·tptz, respectively.
In both cases, it is worth noting that the two axial sulfur
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2510–2520 | 2515
©

View Article Online
Table 4 Selected Wiberg bond indexes calculated for 2·tptz and 6·tptz at
DFT levela,b
2·tptz
6·tptz
Ni–S1
Ni–S2
Ni–S3
Ni–S4
Ni–N1
Ni–N4
Ni–N5
0.447
0.187
0.245
0.007
0.290
0.133
0.137
0.404
0.242
0.293
0.035
0.284
0.118
0.109
a mPW1PW functional; Shafer, Horn, and Ahlrichs pVDZ basis set.
b Numbering scheme refers to Fig. 1, and is consistent with all the structures
reported.
nature of N1, whose lone pair interaction with the d-type natural
bond orbitals localized on the nickel ion amounts to 58.7 and
56.5 Kcal/mol for 2·tptz and 6·tptz, respectively, compared to
average values of 30.05 and 28.11 Kcal/mol calculated for N4 and
N5, in compounds 2·tptz and 6·tptz, respectively. As regards the
coordinating dithiophosphonato/dithiophosphato ligands, three
types of interactions between two lone pairs localized on the sulfur
atoms and the empty d-NBOs on the nickel centre have been
calculated for both complexes. An examination of the trend of
the energies involved allows quantification of the STE described
before, which is expected to be more evident in the case of 2·tptz
as compared to 6·tptz, as experimentally found (Table 2). In fact,
the S3 atoms of the monodentate units interact with the nickel ion
with energies of 68.17 and 75.79 Kcal/mol, for 2·tptz and 6·tptz,
respectively, while the trans disposed S2 atoms show a remarkably
lower interaction energy of 38.16 and 52.81 Kcal/mol, for 2·tptz
and 6·tptz, respectively. Again, the S1 donor atoms, with no S
atoms in the trans position, feature the highest energy (105.31 and
90.36 Kcal/mol, for 2·tptz and 6·tptz, respectively).
Fig. 7 Molecular view of compound 7. For clarity, only non-carbon
atoms have been labelled and hydrogen atoms omitted. Displacement
ellipsoids are drawn at 50% probability.
˚
[Ni–S1, 2.403(2); Ni–S2, 2.501(2) A; arrows on full bars in Fig. 2,
empty black circle in Fig. 3]. The N–O distances in the nitrate
anion are quite similar, as expected when the negative charge is
delocalized over the whole anion. In contrast to what was observed
in the previous compounds, the tptz moiety shows less planarity,
with the three pyridyl rings being angled at 3.3, 8.4, and 14.3◦
with respect to the plane of the central triazine, due to packing
effects. In fact, due to the intrinsic differences between the two
compounds, the packing of 7 is quite different from that of 2·tptz,
and features planes of parallel ribbons built up by p–p interactions
between symmetry related moieties and a dense hydrogen-bonding
network involving the apical water molecules, the nitrate anions,
and the cationic complex (Fig. S4 in ESI†).
The single crystal X-ray analysis of 8 shows a dimeric structure
where two Ni(tptz) units are bridged about a centre of symmetry
by two bidentate sulfate anions. Table 1 contains the crystal
data for 8·6H2O and Fig. 8 shows the dimeric unit, along with
the atom labeling scheme. The dithiophosphonato ligands have
been completely detached and each NiII ion displays a distorted
octahedral environment where three nitrogen atoms from tptz
and an oxygen atom (O4) from one sulfate anion define the
equatorial plane of the octahedron; one oxygen atom from the
symmetry related sulfate anion and one from a water molecule
(O4 and O5, respectively) occupy the axial positions. Nickel–
nitrogen bond distances and angles are comparable to those found
for complexes 1·tptz–6·tptz, and for other complexes containing
a Ni(tptz) moiety.20,21 The S–O distances in the sulfate anions are
similar, thus suggesting a delocalization of the negative charge
over the whole anion. The triazine and the two pyridyl rings of
tptz bound to the central ion show a good planarity, while the
terminal pyridyl ring deviates from planarity, being angled at
19◦ with respect to the central triazine plane, due to a strong
Reactivity
A common feature of complexes (1·tptz)–(6·tptz) is the presence
of donor atoms (N2, N3, N6, and S4, Fig. 1) potentially available
to interact with suitable Lewis acids. However, when 2·tptz
was made to react with AgNO3 and CuSO4 we experienced
the partial or complete expulsion of the dithiophosphonato
ligands from the NiII coordination sphere, obtaining the complex
[Ni(EtOpdt)(tptz)(H2O)]NO3 (7), and the dimer [(Ni(tptz)(m-
SO4)(H2O)]2·6H2O (8), respectively. Single crystal X-ray analysis
of 7 reveals that the cationic complex [Ni(EtOpdt)(tptz)(H2O)]+
presents a coordination environment similar to that of the starting
[Ni(EtOpdt)2(tptz)] (2·tptz) with one water molecule in place
of one of the two dithiophosphonato ligands EtOpdt originally
present. A nitrate anion counterbalances the positive charge.
Crystal data and selected bond lengths and angles for 7 are
reported in Tables 1 and 2; Fig. 7 shows the complex unit, along
with the atom labeling scheme. Nickel–nitrogen bond distances
and angles are comparable to those found for complexes 2·tptz;
˚
the Ni–O distance [2.067(4) A] is similar to that normally found
in nickel(II)–aquo complexes.19 The dithiophosphonato ligand
shows similar P–S bond lengths, compatible with a delocalization
of the negative charge on the whole fragment. In contrast, the
Ni–S bond distances differ slightly from each other, with values
falling outside the Ni–S bond-regions previously described
2516 | Dalton Trans., 2009, 2510–2520
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Fig. 8 Molecular view of compound 8. For clarity, only non-carbon atoms have been labelled and hydrogen atoms and solvent water molecules omitted.
Displacement ellipsoids are drawn at 50% probability. Selected bond lengths and angles: Ni–N1, 1.978(6); Ni–N4, 2.127(6); Ni–N5, 2.152(6); Ni–O1,
˚
2.063(5); Ni–O4¢, 2.002(5); Ni–O5, 2.123(5); S1-O1, 1.483(5); S1-O2, 1.476(5); S1-O3, 1.478(5); S1-O4, 1.496(5) A; N1-Ni–N4, 77.2(2); N1-Ni–N5,
76.7(2); O1-Ni–O5, 177.4(2); O1-Ni–N1, 90.2(2)◦. Symmetry codes: ¢ -x, -y, 2 - z.
Fig. 9 Packing view of compound 8 showing p–p interactions within and between the ladders. Hydrogen atoms not involved in the interactions shown
have been omitted for clarity reasons; water molecules have been evidenced using the red colour. Symmetry codes: ¢ -x, -y, 1 - z; ¢¢ 1 + x, y, z; ¢¢¢ -x,
-1 - y, 2 - z.
H-bond involving the nitrogen atom and a hydrogen of the
triazine and the C5N(4) pyridine rings [angle between planes:
◦
˚
˚
˚
coor◦dinated water molecule (O5-H5a ◊ ◊ ◊ N2¢: 2.02 A, 2.794(7) A,
153 ). The simultaneous presence in the nickel(II) coordination
sphere of sulfate anions, water molecules, and aromatic (tptz)
ligands leads to a nicely assembled packing where hydrophobic
and hydrophilic forces work in concert. The dimeric units are
connected with each other in three dimensions by means of p–p
interactions between adjacent tptz units: along axis c the dimers
are stacked in ladders piled through interactions involving the
1.66 , intercentroid distance: 3.65 A]; the terminal C5N(6) pyridine
rings are protruded out of the ladders along the a direction and
◦
˚
interact with each other [0 , 3.54 A] connecting the ladders (Fig. 9).
Interactions between the C5N(4) and C5N(5) pyridine rings of
adjacent ladders extend the network of aromatic interactions into
the b direction (Fig. S6 in ESI†). Clustered in the hydrophilic
areas, and ringed all around the sulfate groups, the solvent
water molecules cement the molecular packing through numerous
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2510–2520 | 2517
©

View Article Online
hydrogen-bonding interactions mainly involving the sulfate anions
(Fig. 9).
dark purple solid, which was then recrystallised using 10 mL of
a solution of 1 : 1 ratio of CH2Cl2 and EtOH to give long purple
crystals. Yield 0.399 g, 0.930 mmol, 87%. Mp 105 ◦C. Elemental
analysis found (calc. for C8H20O4P2S4Ni): C, 22.00 (22.39); H, 4.68
(4.70); S, 29.67 (29.88). FT-IR (1700–50 cm-1): 1432 s, 1173 vs,
1020 s, 796 vs, 654 vs, 532 m, 469 m, 433 m, 396 m, 369 m, 353 m,
351 m, 333 w, 326 w, 325 vw, 302 w, 279 w, 246 w, 225 vw, 179 w,
151 m, 120 vw, 107 w, 74 w cm-1. FT-Raman (1700–50 cm-1; relative
intensities in parentheses related to the highest peak taken equal
to 10.0): 1472 (0.5), 1452 (1.1), 1388 (0.6), 1104 (1.5), 1053 (0.8),
1005 (0.4), 824 (2.0), 781 (1.1), 635 (3.4), 547 (9.6), 402 (1.9), 345
(2.2), 332 (4.4), 304 (4.7), 242 (3.3), 159 (6.3), 95 (10.0) cm-1.
Conclusions
The reactivity between tptz and the differently substituted dithio-
phosphonato and dithiophosphato NiII complexes [Ni(ROpdt)2]
[ROpdt = (4-MeOPh)(RO)PS2, R = Et (2), Pr (3), i-Pr (4),
Bu (5),] and [Ni((EtO)2PS2)2] (6) has been explored and the
obtained neutral mixed complexes (2·tptz)–(6·tptz) have been
characterised by means of single crystal X-ray diffraction. In
all cases the incoming of one tptz molecule acting as triden-
tate ligand in the NiII coordination sphere detaches one of
the sulfur atoms previously coordinated to the metal forcing
one of the two dithiophosphonato/dithiophosphato ligands to
behave as monodentate ligand. The presence of the monodentate
dithiophosphonato/dithiophosphato ligands introduces a notable
asymmetry in the Ni–S bond distances within isologous bidentate
fragments, not found in similar NiII complexes. This asymmetry
has been explained in terms of structural trans-effect (STE), as
supported by DFT calculations. In our opinion, the lengthening
of the trans-disposed Ni–S bonds might be responsible for the
peculiar reactivity of the mixed complexes that easily undergo to
partial or total replacement of the dithiophosphonato ligands.
As a confirmation, the reaction of 2·tptz with AgNO3 and
CuSO4 yielded the complex [Ni(EtOpdt)(tptz)(H2O)]NO3 (7), and
the dimer [(Ni(tptz)(m-SO4)(H2O)]2·6H2O (8), respectively. It is
interesting to note that the coordination chemistry of tptz and
the nickel(II) ion has been recently explored, but among the range
of different nickel-tptz complexes isolated in different reaction
conditions, not one can be compared with the unusual dimer 8,
engendered from the mixed dithiophosphonato/tptz complexes.
[Ni(EtOpdt)2tptz] (2·tptz). Tptz (15.0 mg; 0.0480 mmol) and
2 (26.6 mg; 0.0480 mmol) were heated in 30 mL of EtOH in
an Ace pressure tube until complete dissolution. The product was
obtained as deep green crystals by slow evaporation of the solution
◦
at room temperature. Mp 89 C. Elemental analysis found (calc.
for C36H36O4P2S4N6Ni·C2H5OH): C, 50.14 (50.06); H, 4.18 (4.64);
N, 9.42 (9.22); S, 13.73 (14.07). Yield: 29.7 mg, 0.0326 mmol, 68%.
FT-IR (1700–50 cm-1): 1594 s, 1573 m, 1557 vs, 1532 vs, 1498 m,
1374 s, 1293 ms, 1253 vs, 1174 m, 1110 s, 1027 vs, 1011 ms, 953 ms,
904 m, 830 m, 801 m, 768 vs, 684 mw, 664 vs, 653 vs, 636 m, 621 vs,
548 ms, 536 s, 332 w, 319 vw, 310 mw, 239 ms, 218 ms, 185 m,
145 ms, 136 w, 114 m cm-1. FT-Raman (1700–50 cm-1; relative
intensities in parentheses related to the highest peak taken equal
to 10.0): 1600 (3.7), 1571 (3.7), 1486 (5.0), 1402 (2.5), 1100 (3.7),
1026 (7.5), 1010 (2.5), 802 (1.2), 663 (3.7), 545 (5.0), 94 (10.0) cm-1.
[Ni(PrOpdt)2tptz] (3·tptz). Tptz (16.0 mg; 0.0512 mmol) and
3 (29.8 mg; 0.0512 mmol) were heated in 20 mL of PrOH in
an Ace pressure tube until complete dissolution. The product was
obtained as deep green crystals by slow evaporation of the solution
at room temperature. MP 113 ◦C (dec). Elemental analysis found
(calc. for C38H40O4P2S4N6Ni): C, 51.38 (51.07); H, 4.80 (4.51); N,
9.35 (9.40); S, 14.09 (14.35). Yield: 26.8 mg, 0.030 mmol, 59%.
FT-IR (1700–50 cm-1): 1594 m, 1573 m, 1558 vs, 1533 vs, 1497 ms,
1390 m, 1373 s, 1293 m, 1250 s, 1177 m, 1112 s, 1010 s, 829 m,
801 m, 766 s, 683 mw, 664 s, 640 s, 623 s, 547 m, 522 mw, 419 w,
352 m, 316 ms, 279 w, 253 w, 181 mw, 153 mw, 133 w, 106 mw,
87 mw cm-1. FT-Raman (1700–50 cm-1; relative intensities in
parentheses related to the highest peak taken equal to 10.0): 1600
(5.2), 1570 (6.0), 1481 (7.6), 1398 (4.8), 1044 (6.2), 1011 (6.5), 549
(3.0), 90 (10.0) cm-1.
Experimental
Materials and methods
All the reagents and solvents were purchased from Aldrich or Lan-
caster, and used without further purification. Elemental analyses
were performed with an EA1108 CHNS-O Fisons instrument.
FT-Infrared spectra were recorded on a Thermo Nicolet 5700
spectrometer at room temperature using a flow of dried air. Middle
IR spectra (resolution 4 cm-1) were recorded as KBr pellets,
with a KBr beam-splitter and KBr windows. FT-Raman spectra
(resolution of 4 cm-1) were recorded as KBr solid mixtures on a
Bruker RFS100 FT-Raman spectrometer, fitted with an In–Ga–As
detector (room temperature) operating with a Nd-YAG laser
(excitation wavelength 1064 nm) with a 180◦ scattering geometry.
The excitation power was modulated between 100 and 250 mW.
[Ni(i-PrOpdt)2tptz] (4·tptz). Tptz (15.5 mg; 0.0496 mmol) and
4 (28.9 mg; 0.0496 mmol) were heated in 30 mL of i–PrOH in
an Ace pressure tube until complete dissolution. The product was
obtained as deep green crystals by slow evaporation of the solution
at room temperature. Mp 113 ◦C. Elemental analysis found (calc.
for C38H40O4P2S4N6Ni): C, 51.23 (51.07); H, 4.80 (4.51); N, 9.39
(9.40); S, 14.09 (14.35). Yield: 23.8 mg, 0.0266 mmol, 54%. FT-IR
(1700–50 cm-1): 1594 m, 1575 ms, 1559 s, 1536 vs, 1497 m, 1394 m,
1375 s, 1293 s, 1257 s, 1247 s, 1175 ms, 1105 ms, 1026 m, 1011 m,
968 vs, 952 s, 877 m, 827 m, 800 m, 771 s, 753 s, 683 mw, 664 s,
646 m, 623 s, 559 s, 550 s, 399 s, 343 m, 293 m, 268 m, 185 s, 161 m,
146 w, 129 m, 104 ms cm-1. FT-Raman (1700–50 cm-1; relative
intensities in parentheses related to the highest peak taken equal
to 10.0): 1601 (5.0), 1570 (6.7), 1482 (8.3), 1401 (5.0), 1042 (6.7),
1028 (6.7), 1009 (5.0), 549 (3.3), 85 (10.0) cm-1.
Syntheses
Trans-bis[O-alkyl-(4-methoxyphenyl)dithiophosphonato]Ni com-
plexes {[Ni(ROpdt)2]; R = Et (2), Pr (3), i-Pr (4), Bu (5)} were
synthesised according to previously reported procedures.2,3
[Ni((EtO)2PS2)2] (6). NiCl2·6H2O (0.238 g, 1.001 mmol) and
P2S5 (0.222 g, 0.499 mmol) were dissolved in 50 mL of EtOH and
heated at reflux for 1 hour. After cooling to room temperature
most of the solvent was removed by rotary evaporation to give a
2518 | Dalton Trans., 2009, 2510–2520
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
[Ni(BuOpdt)2tptz] (5·tptz). Tptz (15.6 mg; 0.050 mmol) and
5 (26.8 mg; 0.050 mmol) were heated in 30 mL of BuOH in
an Ace pressure tube until complete dissolution. The product
was obtained as deep green crystals by slow evaporation of the
solution at room temperature. Mp 86 ◦C. Elemental analysis found
(calc. for C40H44O4P2S4N6Ni): C, 52.36 (52.13); H, 5.01 (4.81); N,
8.94 (9.12); S, 13.64 (13.91). Yield: 26.0 mg, 0.0282 mmol, 56%.
FT-IR (1700–350 cm-1): 1594 vs, 1575 vs, 1558 vs, 1536 vs, 1497 s,
1465 ms, 1450 ms, 1403 m, 1392 ms, 1375 vs, 1300 m, 1290 ms,
1255 ms, 1177 ms, 1110 s, 1059 ms, 1021 s, 1012 s, 999 ms, 970 s,
830 m, 800 ms, 770 vs, 683 m, 670 s, 649 ms, 637 s, 623 s, 565 m,
552 ms cm-1. FT-Raman (1700–50 cm-1; relative intensities in
parentheses related to the highest peak taken equal to 10.0): 1583
(8.9), 1484 (10.0), 1438 (4.0), 1402 (7.0), 1373 (3.4), 1255 (1.5),
1182 (1.5), 1110 (2.6), 1046 (5.1), 1029 (9.4), 1010 (4.0), 993 (2.8),
802 (1.3), 635 (1.3), 83 (8.5) cm-1.
X-Ray diffraction
X-Ray structure determinations and crystallographic data were
collected at 293(2) K for compound 2·tptz, and at 120(2) K for
compounds 4·tptz, 3·tptz, 5·tptz, 6·tptz, 7, and 8, by means of
combined phi and omega scans on a Bruker-Nonius KappaCCD
area detector, situated at the window of a rotating anode (graphite
Mo-Ka radiation for 4·tptz, 3·tptz, 6·tptz, and 10 cm confocal
˚
mirrors for 5·tptz, 7, and 8, respectively, l = 0.71073 A). The
structures were solved by direct methods, SHELXS-97 and refined
on F2 using SHELXL-97.22 Anisotropic displacement parameters
were assigned to all non-hydrogen atoms. Hydrogen atoms were
included in the refinement, but thermal parameters and geometry
were constrained to ride on the atom to which they are bonded.
The data were corrected for absorption effects using SORTAV23
for 2·tptz, 4·tptz, and using SADABS V2.1024 for 3·tptz, 5·tptz,
6·tptz, 7, and 8. The disorder in compounds 2·tptz, 5·tptz, and 8
was modeled by splitting the respective residues of the molecules
into two parts allowing the populations of the two sites to refine
freely. In structure 5·tptz the geometries of the disordered parts
of the molecule had to be restrained to be the same for the two
positions and rigid-body constraints were also applied.
[Ni((EtO)2PS2)2tptz] (6·tptz). Tptz (0.15 g; 0.48 mmol) and
6 (0.21 g; 0.49 mmol) were heated in 30 mL of EtOH in
an Ace pressure tube until complete dissolution in 50 mL of
EtOH. The product was obtained as deep green crystals by slow
evaporation of the solution at room temperature. Yield 0.236 g,
0.32 mmol, 67%. Mp 198 ◦C. Elemental analysis found (calc.
for C26H32N6NiO4P2S4): C, 42.00 (42.12); H, 4.39 (4.35); N, 11.21
(11.33) S, 16.87 (17.30). FT-IR (1700–50 cm-1): 1608 m, 1577 s,
1559 s, 1537 vs, 1486 m, 1473 m, 1443 m, 1395 ms, 1377 vs,
1258 mw, 1156 mw, 1098 m, 1042 s, 1011 vs, 947 s, 930 s, 774 vs,
684 ms, 658 vs, 635 ms, 551 m, 472 mw, 419 mw, 376 m cm-1. FT-
Raman (1700–50 cm-1; relative intensities in parentheses related to
the highest peak taken equal to 10.0): 1608 (4.6), 1586 (6.9), 1575
(8.4), 1484 (10.0), 1442 (3.5), 1402 (5.7), 1377 (3.0), 1260 (1.2),
1185 (1.3), 1046 (4.5), 1030 (8.4), 1010 (5.9), 994 (2.1), 815 (1.0),
780 (1.4), 706 (0.9), 664 (1.1), 634 (2.4), 553 (2.1), 492 (1.0), 374
(0.7), 334 (0.8) cm-1.
Theoretical calculations
Quantum-chemical DFT calculations were carried out on com-
pounds 2·tptz and 6·tptz with the mPW1PW25 hybrid functional
and Schafer, Horn, and Ahlrichs double-zeta plus polarization all-
electron BSs26 using the commercially available suite of programs
Gaussian03.27 NBO populations28 and Wiberg bond indexes29
were calculated at the geometries obtained from structural data.30
The programs Gabedit 2.0.731 and Molden 4.632 were used to
investigate the charge distributions and molecular orbital shapes.
Acknowledgements
CINECA (Consorzio Interuniversitario per il Calcolo Automatico
dell’Italia Nord Orientale) is gratefully acknowledged.
[Ni(EtOpdt)(tptz)(H2O)]NO3 (7).
A CH3CN solution of
AgNO3 (5.0 mL; 7.0 mg; 0.04 mmol) was layered on a CH2Cl2
solution of 2·tptz (5.0 mL; 34.6 mg; 0.04 mmol) in a dark tube, and
stored in the darkness. After five weeks few deep ruby crystals have
been isolated from a light brown solution. Due to the paucity of
the product, only X-ray crystal structure and FT-IR analyses have
been performed. FT-IR (4000–400 cm-1): 3447 ms(br), 2982 m,
1653 w, 1589 ms, 1559 m, 1541 mw, 1497 ms, 1458 m, 1437 mw,
1386 mw, 1291 ms, 1254 s, 1181 ms, 1107 vs, 1016 s, 947 ms, 833 m,
800 mw, 773 mw, 658 ms, 633 ms, 621 s, 547 s, 517 m, 421 mw cm-1.
References
1 A.-L. Cheng, N. L. Yan-Feng Yue, Y.-W. Jiang, E.-Q. Gao, C.-H.
Yan and M.-Y. He, Chem. Commun., 2007, 407–409; K. Biradha, M.
Sarkar and L. Rajput, Chem. Commun., 2006, 4169–4179; I. Goldberg,
Chem. Commun., 2005, 1243–1254; D. Braga, L. Brammer and N. R.
Champness, CrystEngComm, 2005, 7(1), 1–19; L. Brammer, Chem.
Soc. Rev., 2004, 33, 476–489; S. Kitagawa, R. Kitaura and S.-I. Noro,
Angew. Chem. Int. Ed., 2004, 43, 2334–2375; C. B. Aakero¨y, J. Desper
and J. Valde´s-Mart´ınez, CrystEngComm, 2004, 6, 413–418; B. Rather
and M. J. Zaworotko, Chem. Commun., 2003, 830–831; N. L. Rosi,
M. Eddaoudi, J. Kim, M. O’Keeffe and O. M. Yaghi, CrystEngComm,
2002, 4, 401–404; F. A. Cotton, C. Lin and C. A. Murillo, J. Chem. Soc.
Dalton Trans., 2001, 499–501.
2 M. Arca, A. Cornia, F. A. Devillanova, A. C. Fabretti, F. Isaia,
V. Lippolis and G. Verani, Inorg. Chim. Acta, 1997, 262, 81–
84.
3 M. C. Aragoni, M. Arca, F. Demartin, F. A. Devillanova, C. Graiff, F.
Isaia, V. Lippolis, A. Tiripicchio and G. Verani, J. Chem. Soc., Dalton
Trans., 2001, 2671–2677.
[Ni(tptz)(l-SO4)(H2O)]2·6H2O (8). A MeOH solution of
CuSO4·5H2O (5.0 mL; 5.0 mg; 0.02 mmol) was added to a CH2Cl2
solution of 2·tptz (5.0 mL; 18.0 mg; 0.02 mmol) in a dark tube.
The resulting yellow opaque solution was filtered and diethyl ether
diffused on it. After three months few small green cubic crystals
have been isolated. Due to the paucity of the product, only X-ray
crystal structure and FT-IR analyses have been performed. FT-IR
(4000–400 cm-1): 3404 s(br), 1637 w, 1611 w, 1576 s, 1560 vs,
1542 vs, 1490 ms, 1477 ms, 1395 s, 1381 s, 1261 m, 1112 vs, 1048 s,
1032 ms, 860 m, 770 s, 740 w, 685 ms, 667 ms, 618 s, 490 m, 417 mw,
374 ms cm-1.
4 I. Haiduc, Handbook of Chalcogen Chemistry, F. A. Devillanova, Ed.,
Royal Society of Chemistry, 2006, 593–643.
5 M. C. Aragoni, M. Arca, N. R. Champness, A. V. Chernikov, F. A.
Devillanova, F. Isaia, V. Lippolis, N. S. Oxtoby, G. Verani, S. Z.
Vatsadze and C. Wilson, Eur. J. Inorg. Chem., 2004, 10, 2008–2012.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 2510–2520 | 2519
©

View Article Online
6 M. C. Aragoni, M. Arca, N. R. Champness, M. De Pasquale, F. A.
Devillanova, F. Isaia, V. Lippolis, N. S. Oxtoby, G. Verani and C.
Wilson, CrystEngComm, 2005, 7(60), 363–369.
7 M. C. Aragoni, M. Arca, F. A. Devillanova, M. B. Hursthouse, S. L.
Huth, F. Isaia, V. Lippolis, A. Mancini, S. Soddu and G. Verani, Dalton
Trans., 2007, 21, 2127–2134.
18 K. M. Anderson and A. G. Orpen, Chem. Commun., 2001, 2682–2683.
˚
19 Search in the CSD (2008, v. 5.29) gave a mean value of 2.072 A for 274
structures (628 fragments) with R < 0.05.
20 M. E. D. de Vivar, S. Baggio and R. Baggio, Acta Crystallogr. Sect.E,
2006, 62, m986-m988; E. Freire, S. Baggio, J. C. Munoz and R. Baggio,
Acta Crystallogr. Sect. C, 2002, 58, m221-m224; P. Byers, G. Y. S. Chan,
M. G. B. Drew and M. J. Hudson, Polyhedron, 1996, 15(17), 2845–2849;
G. A. Barclay, R. S. Vagg and E. C. Watton, Acta Crystallogr. Sect. B,
1977, 33, 3487–3491.
21 R. Zibaseresht and R. M. Hartshorn, Aust. J. Chem., 2005, 58, 345–353.
22 G. M. Sheldrick, SHELX suite of programs for crystal structure solution
and refinement, Univ. of Go¨ttingen, Germany, 1997.
8 N. S. Oxtoby, A. J. Blake, N. R. Champness and C. Wilson, Dalton
Trans., 2003, 3838–3839.
9 X.-P. Zhou, X. Zhang, S.-H. Lin and D. Li, Cryst. Growth Des., 2007,
7, 485–487; X.-P. Zhou, D. Li, T. Wu and X. Zhang, Dalton Trans.,
2006, 2435–2443; X.-P. Zhou, D. Li, S.-L. Zheng, X. Zhang and T.
Wu, Inorg.Chem., 2006, 45, 7119–7125; T. Glaser, T. Lugger and R.
Frohlich, Eur. J. Inorg. Chem., 2004, 394–400; N. Gupta, N. Grover, A.
Neyhart, P. Singh and H. H. Thorp, Inorg. Chem., 1993, 32, 310–316.
10 Due to different reasons, commented in the cif files, the completeness
for the structures of compounds 3·tptz, 4·tptz, 7, and 8 is rather poor,
and the overall data are not very good (high Rint values). However, the
connectivity of the compounds could be established unambiguously.
The resulting bond lengths are consistent with each other and with
those here reported for analogous complexes, and have been considered
in the following discussion.
23 R. H. Blessing, J. Appl. Cryst., 1997, 30, 421–426.
24 G. M. Sheldrick, SADABS, V2.10, 2003.
25 C. Adamo and V. Barone, J. Chem. Phys., 1998, 108, 664.
26 A. Schafer, H. Horn and R. Ahlrichs, J. Chem. Phys., 1992, 97, 2571.
27 Gaussian 03, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N.
Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone,
B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X.
Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R.
Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A.
Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich,
A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y.
Peng, A. Nanayakkara, M. Challacombe, W. P. M. Gill, B. Johnson,
W. Chen, M. W. Wong, C. Gonzalez and J. A. Pople, Gaussian, Inc.,
Wallingford CT, 2004.
28 (a) A. E. Reed and F. Weinhold, J. Chem. Phys., 1983, 78, 4066; (b) A. E.
Reed, R. B. Weinstock and F. Weinhold, J. Chem. Phys., 1985, 83, 735;
(c) A. E. Reed, L. A. Curtiss and F. Weinhold, Chem. Rev., 1988, 88,
899.
29 K. Wiberg, Tetrahedron, 1968, 24, 1083.
30 NBO Version 3.1, E. D. Glendening, A. E. Reed, J. E. Carpenter and
F. Weinhold.
31 Gabedit is a free Graphical User Interface for computational chemistry
packages. It is written by Abdul-Rahman Allouche. Gabedit is available
from http://lasim.univ-lyon1.fr/allouche/gabeditb.
11 Mogul 1.1.2, CSD 2008 release.
12 The data refer to 34 PS2Ni fragments belonging to 29 different
compounds (20 square-planar and 9 octahedral complexes), and were
retrieved from the CSD using CCDC software (2008, v. 5.29). Oxidation
states and coordination geometries were checked and ambiguous cases
eliminated.
13 Originally, the term “trans-effect” was used to describe kinetic phenom-
ena, whilst the term “trans-influence” was used to describe structural
and thermodynamic phenomena. Following the recent review by
B. J. Coe, and S. J. Glenwright, we’ll adopt here the “expressions
‘structural trans-effect’ (STE) to refer to the effect of a ligand on the
bond distance to a trans ligand and ‘kinetic trans-effect’ (KTE) to
describe the effect on the lability of a trans ligand.”B. J. Coe and S. J.
Glenwright, Coord. Chem. Rev., 2000, 203, 5–80.
14 I. Haiduc and D. B. Sowerby, Polyhedron, 1996, 15, 2469–2521; I.
Haiduc, D. B. Sowerby and S.-F. Lu, Polyhedron, 1995, 14, 3389–3472.
15 Data were retrieved from the CSD using CCDC software (2008, v.
5.29). Oxidation states and coordination geometries were checked and
ambiguous cases eliminated: the reported data refer to 141 PS2Ni
fragments belonging to 105 different compounds {29 dithiophos-
phonato [(R(RO)PS2)-], 58 dithiophosphato [((RO)2PS2)-], and 18
dithiophosphito [(R2PS2)-] complexes}.
16 A. A. Grinberg, Izv. Inst. Izucheniyu Platiny, 1932, 10, 58.
17 J. K. Burdett and T. A. Albright, Inorg. Chem., 1979, 18, 2112.
32 G. Schaftenaar and J. H. Noordik, J. Comput.-Aided Mol. Design, 2000,
14, 123.
2520 | Dalton Trans., 2009, 2510–2520
This journal is
The Royal Society of Chemistry 2009
©