Complexes formed from 2,4,6-trimercaptotriazine (H3TMT): Synthesis and structural characterization of [M(PhP(CH2CH 2P(Ph)2)2(HTMT)], M=Ni(II), Pd(II), Pt(II)

Article abstract of DOI:10.1016/j.ica.2004.01.040

Na₃TMT·9H₂O (H₃TMT=2,4,6- trimercaptotriazine) reacts with M(PPP)Cl₂, PPP=PhP(CH ₂CH₂PPh₂)₂, M=Ni, Pd, Pt, to give the compounds [M(PPP)(HTMT)]. The nickel and palladium complexes have been characterized by single-crystal X-ray diffraction analysis. PPP is tridentate in both complexes. The nickel complex has an irregular trigonal bipyramidal configuration in which the triazine is bidentate, coordinating through one sulfur and one nitrogen donor atom. The palladium complex has an approximately square planar geometry in which the triazine forms a strong Pd-S bond in the plane and also a very weak Pd-N interaction above the plane. The ³¹P NMR spectrum of the platinum complex is similar to that of the palladium complex, which is consistent with the Pt complex also having an approximately square-planar structure. Variable temperature NMR spectra show that two conformational isomers of the nickel complex are present in solution at low temperatures, though exchange is fast at room temperature. DFT calculations have confirmed the possible existence of two five-coordinate isomers of comparable stability.

Full text of DOI:10.1016/j.ica.2004.01.040

Inorganica Chimica Acta 357 (2004) 2615–2623
www.elsevier.com/locate/ica
Complexes formed from 2,4,6-trimercaptotriazine (H3TMT):
synthesis and structural characterization
of [M(PhP(CH2CH2P(Ph)2)2(HTMT)], M ¼ Ni(II), Pd(II), Pt(II) q
a
a,
a
b
Andrea Ienco , Stefano Midollini *, Annabella Orlandini , Alberto Vacca
a
Istituto di Chimica dei Composti Organo Metallici, CNR, Via Madonna del Piano, 50019 Sesto Fiorentino, Firenze, Italy
b
Dipartimento di Chimica, Universitꢀa di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy
Received 20 November 2003; accepted 12 January 2004
Available online 18 March 2004
Abstract
Na3TMT Æ 9H2O (H3TMT ¼ 2,4,6-trimercaptotriazine) reacts with M(PPP)Cl2, PPP ¼ PhP(CH2CH2PPh2)2, M ¼ Ni, Pd, Pt, to
give the compounds [M(PPP)(HTMT)]. The nickel and palladium complexes have been characterized by single-crystal X-ray dif-
fraction analysis. PPP is tridentate in both complexes. The nickel complex has an irregular trigonal bipyramidal configuration in
which the triazine is bidentate, coordinating through one sulfur and one nitrogen donor atom. The palladium complex has an
approximately square planar geometry in which the triazine forms a strong Pd–S bond in the plane and also a very weak Pd–N
interaction above the plane. The 31P NMR spectrum of the platinum complex is similar to that of the palladium complex, which is
consistent with the Pt complex also having an approximately square-planar structure. Variable temperature NMR spectra show that
two conformational isomers of the nickel complex are present in solution at low temperatures, though exchange is fast at room
temperature. DFT calculations have confirmed the possible existence of two five-coordinate isomers of comparable stability.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: 2,4,6-Trimercaptotriazine; Nickel; Palladium; Platinum; Triphosphine; X-ray structures; 31P NMR; Exchange processes; DFT
calculations
1. Introduction
Supramolecular systems with layered, channel and
capsule structures are obtained also by simple co-crys-
tallization of the triazine with organic molecules suitable
to hydrogen bonding interactions [20–23].
We have recently synthesized the trinuclear complex
(HgMe)3(TMT), in which each sulfur atom of the tri-
azine ligand is linked to a different HgMe moiety in a
‘‘manxane arrangement’’ [24]. We have also synthesized
and structurally characterized two polymeric alkali
metal TMT complexes [25].
We now present the synthesis of some ternary com-
plexes of nickel (II), palladium (II) and platinum (II)
with HTMT2ꢀ and the triphosphine bis(2-diph-
enylphosphinoethyl)phenylphosphine (PPP). These are
the first examples of molecular TMT derivatives of
palladium and platinum to be characterized, though
H3TMT is known to be an efficient reagent for removing
Na3TMT Æ 9H2O [1] (H3TMT ¼ 2,4,6-trimercaptotri-
azine, shown in Scheme 1) is in common use to precip-
itate heavy metals from polluted waters [2], but little is
known about chemistry and stability of the metal–TMT
complexes in aqueous solution. TMT3ꢀ (Scheme 1) is a
very versatile ligand which can use any one or more of
its six donor atoms to form both mono-nuclear and
poly-nuclear complexes [3–19]. The binary complexes
are generally insoluble in water, but ternary complexes
may be soluble.
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2004.01.040.
* Corresponding author. Fax: +39-055-5225-203.
E-mail address: stefano.midollini@iccom.cnr.it (S. Midollini).
0020-1693/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2004.01.040

2616
A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
Well shaped crystals, suitable for X-ray analysis, were
obtained as DMF solvates by recrystallization of the
compound from DMF/diethyl ether. Yield: 46%. Anal.
Calc. for C40H41N4NiOP3S3: C, 57.09; H, 4.91; N, 6.65.
Found: C, 55.36; H, 4.82; N, 6.38%.
2.3. Preparation of [Pd(PPP)(HTMT)] ꢁ 0.5H2O ꢁ 0.25
DMF (2)
Scheme 1.
A solution of Na3TMT Æ 9H2O (0.101 g, 0.25 mmol)
in DMF (7 cm3) was added to a solution of Pd(PPP)Cl2
(0.178 g, 0.25 mmol) in the same solvent (7 cm3), at ca.
323 K. The resulting pale yellow solution was filtered
and concentrated in air at 323 K until yellow crystals
precipitated. These were filtered, washed with cold
DMF and diethylether and dried in air. Yield: 48%.
Anal. Calc. for C37:75H36:75N3:25O0:75P3PdS3: C, 53.75;
H, 4.39; N, 5.40. Found: C, 53.62; H, 4.40; N, 5.43%.
palladium from organic reactions mixtures [26,27]. A
series of ternary high-spin mononuclear nickel(II)
complexes with HTMT2ꢀ and polyamine ligand have
been reported recently [5–8].
2. Experimental
2.1. Materials and methods
2.4. Preparation of [Pt(PPP)(HTMT)] ꢁ 0.5CH2Cl2 (3)
Na3(TMT) Æ 9H2O (Aldrich) was recrystallized from
H2O/EtOH. 2,4,6-Trimercaptotriazine (H3TMT) was
prepared as described previously [3]. Bis(2-diph-
enylphosphinoethyl) phenylphosphine (PPP) (STREM)
was used as received. Pd(PPP)Cl2 and Pt(PPP)Cl2 were
prepared as described previously [28].
1H NMR spectra were recorded using a Bruker AC-
200 spectrometer at 200.133 MHz (internal reference,
TMS). 31P{1H} spectra were obtained on the same in-
strument at 81.014 MHz (external reference, 83%
H3PO4). 31P{1H} spectra of nickel complex were re-
corded in d7-DMF between 248 and 353 K; these spectra
between 123 and 103 ppm were analyzed with the
program CAHOS [29], which can perform line shape
fitting by simultaneous refinement of several spectral
parameters.
A solution of Na3TMT Æ 9H2O (101 g, 0.25 mmol) in
methanol (20 cm3) was added to a solution of
Pt(PPP)Cl2 (0.20 g, 0.25 mmol) in dichloromethane (15
cm3) at room temperature. Concentration of the solu-
tion in air at room temperature caused the precipitation
of colorless crystals. These were filtered, washed with
methanol and dried in air. Yield: 46%. Anal. Calc. for
C37:5H35ClN3P3PtS3: C, 47.54; H, 3.72; N, 4.43. Found:
C, 47.14; H, 3.68; N, 4.46%. The prepared crystals of 3
were not suitable for an X-ray diffractometric analysis.
2.5. Crystallography
Diffraction data of 1 and 2 were collected at room
temperature on an Enraf Nonius CAD4 automatic dif-
fractometer Mo Ka radiation (graphite monochroma-
tor). Unit cell parameters of both structures were
determined from a least-squares refinement of the setting
angles of 25 carefully centered reflections. Crystal data
and data collection details are given in Table 1. The in-
tensities were rescaled and assigned a standard deviation
rðIÞ calculated using the value of 0.03 for the instability
factor k [30]. Lorentz-polarization and absorption cor-
rections were applied [31]. Atomic scattering factors were
taken from [32] and an anomalous dispersion correction,
real and imaginary part, was applied [33]. The structures
were solved by direct methods and refined by full-matrix
F 2 refinement, with anisotropic thermal parameters as-
signed to Ni, Pd, P and S. Phenyl rings of the PPP ligand
were treated as rigid bodies of D6h symmetry. Hydrogen
atoms of the PPP ligand were introduced in their calcu-
lated positions, with thermal parameters 20% larger than
those of the respective carbon atoms. While in 1 the hy-
drogen atom of the HTMT2ꢀ was detected in a difference
Fourier map and introduced, in 2 the corresponding hy-
Infrared spectra were recorded as KBr pellets on a
Perkin–Elmer 166 series FIR spectrometer.
2.2. Preparation of [Ni(PPP)(HTMT)] and [Ni(PPP)
(HTMT)] ꢁ DMF (1)
A solution of PPP (0.27 g, 0.5 mmol) in dichlorom-
ethane (20 cm3) was added to a solution of NiCl2 Æ 6H2O
(0.12 g, 0.5 mmol) in methanol (10 cm3) under a current
of nitrogen. Solid H3TMT (0.088 g, 0.5 mmol) was ad-
ded, with stirring, to the red-orange solution at room
temperature. Addition of triethylamine (0.1 g, 1 mmol)
caused the solid to dissolve and the color of the solution
turned dark-brown. n-Butanol (20 cm3) was added and
nitrogen was bubbled gently through the solution until
red brown crystals precipitated. These were removed by
filtration, washed with n-butanol and diethyl ether and
finally dried under a current of nitrogen. Yield: 67%.
Anal. Calc. for C37H34N3NiP3S3: C, 57.82; H, 4.46; N,
5.46. Found: C, 57.80; H, 4.58; N, 5.38%.

A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
2617
Table 1
Crystal data and structure refinement details for 1 and 2
1
2
Empirical formula
Formula weight
T (K)
C40H41N4NiOP3S3
841.57
293(2)
C37:75H36:75N3:25O0:75P3PdS3
843.44
293(2)
ꢁ
k (A)
0.71069
monoclinic
P21=n
0.71069
triclinic
Crystal system
Space group
Unit cell dimensions
ꢂ
P1
ꢁ
a (A)
13.277(9)
17.619(3)
12.622(2)
17.878(9)
ꢁ
b (A)
ꢁ
c (A)
18.021(9)
90
18.102(3)
86.19(4)
a (ꢁ)
b (ꢁ)
c (ꢁ)
96.78(8)
90
4186(4)
70.52(1)
88.57(4)
3842(2)
3
ꢁ
V (A )
Z
4
1.335
4
1.458
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F ð000Þ
)
0.764
1752
0.805
1724
Crystal size (mm)
h range for data collection (ꢁ)
Limiting indices
0.80 · 0.50 · 0.25
2.55–20.05
0.80 · 0.20 · 0.05
2.51–19.99
ꢀ12 6 h 6 12, 0 6 k 6 16, 0 6 l 6 17
ꢀ11 6 h 6 12, ꢀ17 6 k 6 17, 0 6 l 6 17
Reflections collected/unique
Refinement method
4316/3906
7594/7139
full-matrix least-squares on F 2
3906/0/192
1.000
full-matrix least-squares on F 2
7139/0/351
0.997
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices ½I > 2rðIÞꢂ
R1 ¼ 0:0584, wR2 ¼ 0:1423
R1 ¼ 0:0744, wR2 ¼ 0:1537
0.947 and )0.426
0.0499, wR2 ¼ 0:1159
0.0676, wR2 ¼ 0:1254
0.813 and )0.629
R indices (all data)
Largest difference peak and hole (e Aꢀ3
)
drogen was not found. In 2 the DMF solvent molecule,
being disordered near to a center of symmetry, was as-
signed a population parameter of 0.5 and its hydrogen
atoms were not introduced. The function minimized
It is worth mentioning that preliminary calculations
using a simplified model of the PPP ligand, in which the
phenyl rings bonded to the terminal phosphorus atoms
were replaced by hydrogen atoms, did not give the
expected structure. In particular, this failure may be
attributed to an interaction between a hydrogen atom
bonded to a phosphorus and the nitrogen atom of TMT
linked to the nickel atom.
P
2
during the refinement was
wðFo2 ꢀ Fc2Þ , where
2
w is defined as 1=½r2ðFo2Þ þ ð0:0698PÞ þ 16:82Pꢂ and
2
1=½r2ðFo2Þ þ ð0:0472PÞ þ 23:39Pꢂ in 1 and 2, respectively,
½P ¼ ðmaxðFo2; 0Þ þ 2Fc2Þ=3ꢂ. All the calculations were
performed on a PC using the WINGX [34] package with
SIR-97 [35], SHELX-97 [36] and ORTEP-3 [37] programs.
A collection of Cartesian coordinates and total en-
ergies for the optimized molecules is available from the
authors upon request.
2.6. Computational details
Two structures were optimized using GAUSSIAN-98
[38] (the first one was derived from experimental struc-
tural parameters of 1 and the other from its conforma-
tional isomer). A hybrid density functional theory
(DFT) with Becke’s three-parameter hybrid exchange-
correlation functional [39] and non-local gradient cor-
rection of Lee, Yang and Parr (B3LYP) [40] was used.
During the optimization, the carbon and hydrogen at-
oms in the phenyl rings and in the aliphatic chains were
described with a 3-21G basis set in order to reduce the
computational load. The Ni atom utilized the effective
core potentials of SDD [41] with the associated double-f
valence basis functions. The basis set for the remaining
atomic species was the 6-31+G(d,p) [42].
3. Discussion
The complexes are sparingly soluble in strongly polar
organic solvents such as DMSO and DMF. Solutions of
the Ni complex slowly decompose even under nitrogen.
The IR spectra of the complexes show the characteristic
absorptions of DMF and the solvate molecules were
1
also identified in the H NMR spectra. All three com-
plexes show a broad signal in the 1H NMR spectra at ca.
11.0 ppm, which can be attributed to the N-H group of
the HTMT2ꢀ ligand.
An ORTEP diagram of the molecule Ni(PPP)-
(HTMT) is shown in Fig. 1 and selected bond distances
and angles are given in Table 2. The nickel ion resides at

2618
A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
the center of an irregular trigonal bipyramid of ligand
atoms, consisting of the three PPP phosphorus atoms
and triazine nitrogen and sulfur atoms; the axial donors
are represented by the central phosphorus of the PPP
and the coordinated sulfur of the triazine (P2–Ni–S1
175.22(8)ꢁ). The triazine forms strong bonds with the
nickel, as indicated by the magnitude of the Ni–N1
ꢁ
ꢁ
(2.105(5) A) and Ni–S1 (2.263(2) A) bond lengths. There
appears to be some repulsion between the phenyl ring on
the central phosphorus atom and the triazine ring, re-
sulting in a dihedral angle of 58.6ꢁ. This repulsion arises
because of the short Ni–N and Ni–S bonds, which force
the triazine ring to be close to the phenyl ring.
Two features of the crystal packing merit special
mention. The DMF solvate molecules are simply inter-
calated in the crystal lattice and do not interact specifi-
cally with the five-coordinate complex. Also, the triazine
part of one molecule interacts weakly with that of a
second molecule, forming a kind of dimer. The inter-
action consists of the formation of a hydrogen bond
between the proton on N2 and the sulphide para to the
coordinated nitrogen atom: S3ꢁ ꢁ ꢁN2 ð2 ꢀ x; ꢀy; ꢀzÞ is
Fig. 1. ORTEP drawing of the complex molecule [Ni(PPP)(HTMT)]
(1) (30% probability ellipsoids).
ꢁ
3.402 A.
Table 2
ꢁ
Selected bond lengths (A) and angles (ꢁ) for 1
The asymmetric unit of Pd(PPP)(HTMT) consists of
two crystallographically independent complex mole-
cules, with DMF and water solvate units. An ORTEP
diagram of the A molecule is shown in Fig. 2 and a
diagram of the B molecule is available as Fig. S1 in the
supplementary material. Selected bond distances and
angles are given in Table 3. The two independent mol-
ecules are similar: in both, the palladium complex is
essentially square-planar, with the three phosphorus
atoms and a triazine sulfur atom as the donor atom set.
Moreover, there is a weak interaction with a triazine
nitrogen atom above the plane: molecule A, Pd1ꢁ ꢁ ꢁN1
Ni(1)–P(1)
Ni(1)–P(2)
Ni(1)–P(3)
Ni(1)–S(1)
Ni(1)–N(1)
P(1)–C(21)
P(1)–C(4)
P(1)–C(11)
P(2)–C(31)
P(2)–C(5)
P(2)–C(6)
P(3)–C(41)
P(3)–C(7)
2.284(3) P(3)–C(51)
2.141(2) S(1)–C(1)
2.201(2) S(2)–C(2)
2.263(2) S(3)–C(3)
2.105(5) N(1)–C(1)
1.836(4) N(1)–C(2)
1.839(7) N(2)–C(3)
1.864(4) N(2)–C(2)
1.812(4) N(3)–C(1)
1.817(7) N(3)–C(3)
1.851(7) C(4)–C(5)
1.809(4) C(6)–C(7)
1.830(7)
1.846(4)
1.748(6)
1.660(6)
1.694(7)
1.357(7)
1.381(8)
1.373(8)
1.380(8)
1.335(7)
1.361(8)
1.515(9)
1.514(9)
ꢁ
ꢁ
2.870(6) A, molecule B, Pd2ꢁ ꢁ ꢁN4 3.074(6) A. The pal-
N(1)–Ni(1)–P(2)
N(1)–Ni(1)–P(3)
P(2)–Ni(1)–P(3)
N(1)–Ni(1)–S(1)
P(2)–Ni(1)–S(1)
P(3)–Ni(1)–S(1)
N(1)–Ni(1)–P(1)
P(2)–Ni(1)–P(1)
P(3)–Ni(1)–P(1)
S(1)–Ni(1)–P(1)
C(21)–P(1)–C(4)
C(21)–P(1)–C(11)
C(4)–P(1)–C(11)
C(21)–P(1)–Ni(1)
C(4)–P(1)–Ni(1)
C(11)–P(1)–Ni(1)
C(31)–P(2)–C(5)
C(31)–P(2)–C(6)
C(5)–P(2)–C(6)
C(31)–P(2)–Ni(1)
C(5)–P(2)–Ni(1)
C(6)–P(2)–Ni(1)
C(41)–P(3)–C(7)
C(41)–P(3)–C(51)
107.4(1)
131.3(1)
86.13(8)
C(7)–P(3)–C(51)
C(41)–P(3)–Ni(1)
C(7)–P(3)–Ni(1)
106.1(3)
120.3(2)
109.4(2)
112.8(2)
81.0(2)
71.69(14) C(51)–P(3)–Ni(1)
175.22(8)
91.03(7)
96.07(15) C(1)–N(1)–Ni(1)
C(1)–S(1)–Ni(1)
C(1)–N(1)–C(2)
117.8(5)
96.7(3)
86.27(7)
132.01(9)
98.49(7)
102.1(3)
104.9(2)
106.3(3)
122.1(2)
106.5(2)
113.4(2)
108.2(3)
103.8(3)
108.2(3)
119.2(2)
111.6(2)
105.1(2)
103.1(3)
104.0(2)
C(2)–N(1)–Ni(1)
C(3)–N(2)–C(2)
C(1)–N(3)–C(3)
N(3)–C(1)–N(1)
N(3)–C(1)–S(1)
N(1)–C(1)–S(1)
N(2)–C(2)–N(1)
N(2)–C(2)–S(2)
N(1)–C(2)–S(2)
N(3)–C(3)–N(2)
N(3)–C(3)–S(3)
N(2)–C(3)–S(3)
C(5)–C(4)–P(1)
C(4)–C(5)–P(2)
C(7)–C(6)–P(2)
C(6)–C(7)–P(3)
143.3(4)
124.2(5)
116.3(5)
126.6(5)
122.9(4)
110.5(4)
115.7(5)
120.2(5)
124.1(5)
118.9(5)
122.4(5)
118.7(5)
111.1(5)
108.0(5)
106.8(5)
108.2(5)
Fig. 2. ORTEP drawing of one (A) of the two independent molecules
of the complex [Pd(PPP)(HTMT)] (2) (30% probability ellipsoids).

A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
2619
Table 3
Selected bond lengths (A) and angles (ꢁ) for 2
Table 3 (continued)
ꢁ
A
B
A
B
C(5)–C(4)–P(1)
C(4)–C(5)–P(2)
C(7)–C(6)–P(2)
C(6)–C(7)–P(3)
110.6(5)
105.6(5)
109.2(5)
112.3(5)
C(120)–C(110)–P(4) 111.1(6)
C(110)–C(120)–P(5) 108.0(6)
C(140)–C(130)–P(5) 107.8(5)
C(130)–C(140)–P(6) 111.4(5)
Pd(1)–P(1)
Pd(1)–P(2)
Pd(1)–P(3)
Pd(1)–S(1)
Pd(1)ꢁ ꢁ ꢁN(1)
P(1)–C(11)
P(1)–C(21)
P(1)–C(4)
P(2)–C(31)
P(2)–C(6)
P(2)–C(5)
P(3)–C(41)
P(3)–C(51)
P(3)–C(7)
S(1)–C(1)
S(2)–C(2)
S(3)–C(3)
N(1)–C(1)
N(1)–C(2)
N(2)–C(2)
N(2)–C(3)
N(3)–C(1)
N(3)–C(3)
C(4)–C(5)
C(6)–C(7)
2.328(2) Pd(2)–P(4)
2.244(2) Pd(2)–P(5)
2.321(2) Pd(2)–P(6)
2.403(2) Pd(2)–S(4)
2.870(6) Pd(2)ꢁ ꢁ ꢁN(4)
1.813(4) P(4)–C(61)
1.806(5) P(4)–C(71)
1.844(8) P(4)–C(110)
1.807(4) P(5)–C(81)
1.812(8) P(5)–C(120)
1.824(8) P(5)–C(130)
1.819(5) P(6)–C(91)
1.819(5) P(6)–C(101)
1.836(8) P(6)–C(140)
1.733(8) S(4)–C(8)
1.670(8) S(5)–C(9)
1.708(8) S(6)–C(10)
1.336(9) N(4)–C(8)
1.352(9) N(4)–C(9)
1.393(9) N(5)–C(9)
1.353(9) N(5)–C(10)
1.356(9) N(6)–C(8)
1.333(9) N(6)–C(10)
1.530(10) C(110)–C(120)
1.521(10) C(130)–C(140)
2.335(2)
2.242(2)
2.325(2)
2.392(2)
3.074(6)
1.802(4)
1.798(6)
1.850(9)
1.810(5)
1.807(9)
1.813(8)
1.831(4)
1.795(6)
1.839(8)
1.734(8)
1.682(8)
1.684(8)
1.328(9)
1.354(9)
1.391(10)
1.356(10)
1.368(9)
1.346(10)
1.522(11)
1.521(11)
ladium ions are displaced from the mean plane of the
ꢁ
ꢁ
donor atoms by 0.22 A in the A molecule and 0.17 A in
the B molecule. The dihedral angles between the triazine
ring and the phenyl ring on the central phosphorus atom
are 7.5ꢁ (A) and 10.4ꢁ (B), which indicate minimal re-
pulsion. In comparison to the nickel complex, the pal-
ladium complex is less sterically crowded both because
the palladium ion is larger and because it forms larger
linkages with the triazine (Pd1–S1 2.403(2) A and Pd1–
ꢁ
N1 2.870(6) A in A molecule; Pd2–S4 2.392(2) A and
ꢁ
Pd2–N4 3.074(6) A in B molecule). This allows the two
rings to be almost parallel.
The A and B molecules, besides the differences above
envisaged, slightly differentiate in the orientation of the
triazine ligand, the dihedral angle between Pd1–S1-N1
(or Pd2–S4–N4) and the least-square plane passing
through the triazine ligand being 6.97ꢁ and 9.97ꢁ, re-
spectively, in A and B.
ꢁ
ꢁ
P(1)–Pd(1)–P(2)
P(1)–Pd(1)–P(3)
P(2)–Pd(1)–P(3)
P(1)–Pd(1)–S(1)
P(2)–Pd(1)–S(1)
P(3)–Pd(1)–S(1)
83.96(8) P(4)–Pd(2)–P(5)
158.83(8) P(4)–Pd(2)–P(6)
85.33(8) P(5)–Pd(2)–P(6)
95.69(8) P(4)–Pd(2)–S(4)
176.37(8) P(5)–Pd(2)–S(4)
93.85(8) P(6)–Pd(2)–S(4)
84.17(8)
159.94(8)
84.05(8)
96.79(8)
178.42(8)
94.67(8)
104.0(3)
101.2(3)
107.7(4)
123.0(2)
112.5(3)
107.2(3)
106.9(4)
105.8(3)
The crystal of the palladium complex contains inter-
calated molecules of DMF and water, neither of which
interact significantly with the metal center. In the A
molecule there is an effective dimerization of triazines
through the hydrogen bonding S3ꢁ ꢁ ꢁN2 ðꢀx; 1 ꢀ y; 3 ꢀ zÞ
C(21)–P(1)–C(11) 107.0(3)
106.0(3)
104.2(3)
C(61)–P(4)–C(71)
C(61)–P(4)–C(110)
C(71)–P(4)–C(110)
C(61)–P(4)–Pd(2)
C(71)–P(4)–Pd(2)
C(110)–P(4)–Pd(2)
C(81)–P(5)–C(120)
C(81)–P(5)–C(130)
ꢁ
of 3.252 A, as in the crystal of the nickel complex. Dif-
C(21)–P(1)–C(4)
C(11)–P(1)–C(4)
ferently the B molecule shows only a weak hydrogen
bonding interaction between the triazine and the water
C(21)–P(1)–Pd(1) 111.3(2)
C(11)–P(1)–Pd(1) 120.1(2)
ꢁ
solvent molecule (O2ꢁ ꢁ ꢁN6 3.056 A).
C(4)–P(1)–Pd(1)
C(31)–P(2)–C(6)
C(31)–P(2)–C(5)
C(6)–P(2)–C(5)
107.1(3)
107.0(3)
104.5(3)
110.9(4)
Bond distances and angles in the ligand PPP appear
normal, with the bond involving the central phosphorus
donor to the metal somewhat shorter than the others in
both the nickel and the palladium complexes. The ter-
minal M–P bonds are substantially the same length in
the palladium complex but are slightly different in the
C(120)–P(5)–C(130) 110.9(4)
C(31)–P(2)–Pd(1) 115.7(2)
C(81)–P(5)–Pd(2)
C(120)–P(5)–Pd(2)
C(130)–P(5)–Pd(2)
C(91)–P(6)–C(101)
C(91)–P(6)–C(140)
113.4(2)
110.2(3)
109.5(3)
104.2(3)
103.6(3)
C(6)–P(2)–Pd(1)
C(5)–P(2)–Pd(1)
C(51)–P(3)–C(41) 104.2(3)
109.8(3)
108.8(3)
ꢁ
nickel complex: 2.284(3) and 2.20(2) A.
C(51)–P(3)–C(7)
C(41)–P(3)–C(7)
105.3(3)
107.0(3)
Within the triazine ligand, the value of the M–S dis-
tance reflects on the corresponding C–S bond. Stronger
is the M–S bond, weaker is the C–S, which lengthens
significantly with respect to the other C–S, while ac-
quires thiolic character. In both 1 and 2 the C1–S1
present values as expected for single bonds (1.748(6) and
1.733(8) or 1.734(8) A, respectively), unlike to the others
ꢁ
which display thionic nature and average 1.68(2) A in 1
ꢁ
and 1.69(2) or 1.683(1) A in 2.
C(101)–P(6)–C(140) 107.1(4)
C(51)–P(3)–Pd(1) 122.9(2)
C(41)–P(3)–Pd(1) 109.6(2)
C(91)–P(6)–Pd(2)
C(101)–P(6)–Pd(2)
C(140)–P(6)–Pd(2)
C(8)–S(4)–Pd(2)
C(8)–N(4)–C(9)
C(9)–N(5)–C(10)
C(8)–N(6)–C(10)
N(4)–C(8)–N(6)
N(4)–C(8)–S(4)
N(6)–C(8)–S(4)
N(4)–C(9)–N(5)
N(4)–C(9)–S(5)
N(5)–C(9)–S(5)
N(5)–C(10)–N(6)
N(5)–C(10)–S(6)
N(6)–C(10)–S(6)
120.6(2)
112.6(2)
107.9(3)
101.1(3)
116.8(6)
122.5(7)
115.9(6)
127.1(7)
118.4(6)
114.5(5)
118.2(7)
123.2(6)
118.6(6)
119.4(7)
117.7(6)
122.9(6)
C(7)–P(3)–Pd(1)
C(1)–S(1)–Pd(1)
C(1)–N(1)–C(2)
C(2)–N(2)–C(3)
C(1)–N(3)–C(3)
N(1)–C(1)–N(3)
N(1)–C(1)–S(1)
N(3)–C(1)–S(1)
N(1)–C(2)–N(2)
N(1)–C(2)–S(2)
N(2)–C(2)–S(2)
N(3)–C(3)–N(2)
N(3)–C(3)–S(3)
N(2)–C(3)–S(3)
106.9(3)
96.3(3)
116.8(6)
122.5(7)
115.0(7)
127.7(7)
116.9(6)
115.4(6)
117.2(6)
123.6(6)
119.2(6)
120.4(7)
121.9(6)
117.7(6)
ꢁ
It is interesting to compare the structure of the
nickel(II) complex obtained with TMT and PPP with
those formed with TMT and polyamines. With the tri-
dentate
amine
2,5,8-trimethyl-2,5,8-triazanonane
(N,N,N0,N0,N00-pentamethyldiethylenetriamine, pmdien),
a five-coordinate complex is formed and the polyamine

2620
A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
allows the triazine to approach the metal closely. In
[Ni(pmdien)(HTMT)] [8], the Ni–N distance is 2.096(3)
ꢁ
ꢁ
A and the Ni–S distance is 2.339(1) A. The tridentate
ligand 1,5,9-triazanonane (dipropylenetriamine, dpta) is
more flexible and allows the formation of a six-coordi-
nate complex [Ni(dpta)(HTMT)H2O] Æ H2O [5], where a
water molecule is allowed in the coordination sphere.
With the tetradentate amines 1,5,8,12-tetraazadode-
cane (N,N0-bis(3aminopropyl) ethylendiamine, bapen)
[7] and 4-(2-aminoethyl)-1,4,7-tetraazaheptane (tris-(2-
aminoethyl)amine, tren) [6], the species formed are
[Ni(bapen)(HTMT)] Æ 2H2O and [Ni(tren)(HTMT)]. In
both these cases, the nickel is five-coordinate. All four
nitrogen atoms of the amine act as ligands. The fifth
bond is with a nitrogen donor of HTMT2ꢀ, as would be
expected in view of the hard acceptor character of
ꢁ
nickel(II). The Ni–S distances, at 2.521 and 2.66 A, re-
spectively, are significantly longer than the sum of co-
ꢁ
valent radii of nickel and sulfur (2.17 A).
The 31P{1H} NMR spectrum of Pd(PPP)(HTMT) in
DMSO solution shows an AM2 pattern, which is con-
sistent with the approximately square-planar structure
found in the solid state: dA ¼ 114:9 ppm (t, 1P),
Fig. 3. Variable temperature 31P{1H} NMR spectra of
[Ni(PPP)(HTMT)] in DMF solution.
2
dM ¼ 47:8 ppm (d, 2P), JPP ¼ 14 Hz. The correspond-
ing spectrum of the platinum complex shows a singlet at
1
parameters DHz ¼ 41 ꢃ 2 kJ molꢀ1 and DSz ¼ 54 ꢃ 6 J
Kꢀ1 molꢀ1 were obtained. Thus, all the evidence points
to there being an equilibrium between configurational
90.1 ppm (1P, JPtP ¼ 3075 Hz) and another singlet at
1
43.2 ppm (2P, JPtP ¼ 2475 Hz). In spite of the absence
of P–P coupling, a square planar structure can be as-
signed to the platinum complex on the basis of the
similarity in spectra.
By contrast the 31P{1H} NMR spectrum of the nickel
complex 1 varies with temperature, showing three broad
signals in the range 40–120 ppm at room temperature
which sharpen up to a pair of triplets and doublets, as
shown in Fig. 3. The lowest temperature spectrum shows
an AM2 pattern {dA ¼ 116:9 ppm (t), dM ¼ 55:7 ppm (d),
2JPP ¼ 47 Hz} and a BN2 pattern {dB ¼ 113:3 ppm (d),
dN ¼ 42:4 ppm (t), 2JPP ¼ 44 Hz}. The ratio of integrated
intensities of the two patterns is ca. 1.4. The same ratio
was found in the spectra performed with samples from
different preparations and at different concentrations.
The spectrum appears to be consistent with the presence
of two different complexes of similar structure. As tem-
perature increases, the two triplets first broaden and
coalesce to a single broad band and then sharpen until a
little fine structure can still be seen at room temperature,
suggestive of a 1:2:1 triplet in the making. The two
doublets also first broaden and coalesce, then sharpen to
a poorly resolved doublet. The ratio of intensities of the
two bands at room temperature is ca. 1:2. All signals shift
toward high field with increasing temperature.
Analysis of the non-mutual exchange process
AM2 () BN2 with the program CAHOS [29] gave rate
constants for the exchange process. These are shown,
together with the spectra calculated using them, in
Fig. 4. Applying the Eyring equation, the activation
Fig. 4. 31P{1H} NMR spectra of [Ni(PPP)(HTMT)] in DMF solution
at different temperatures (left) compared with spectra calculated by
line-shape analysis (right).

A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
2621
would place the phenyl and triazine rings on opposite
sides of the PPP plane. Starting from a geometry anal-
ogous to that found in the solid state of 1, two possible
mechanisms for the interconversion of these conformers
could be shown in Scheme 2. In Scheme 2(a), a Ni–P
bond is broken to give an intermediate four-coordinate
complex from which either isomer may be formed. In
Scheme 2(b), one of the Ni–TMT bonds is broken. The
weaker bond appears to be the Ni–N1 bond. In this case
rotation of the triazine group about the S atom, with
approaching of the N3 to the metal, can lead to the
other isomer being formed.
The possible existence of two isomers of this sort was
confirmed by DFT calculations. Two structures (1a and
1b) were obtained by optimization, as shown in Fig. 6.
Isomer 1a is similar to the one found in the crystal
structure of 1. Selected angles and bond lengths after
optimization are compared to the crystallographic val-
ues in Table 4.
Fig. 5. Perspective view of [Ni(PPP)(HTMT)], showing the triazine
ring and the phenyl ring on P2 on the same side of the plane defined by
the three phosphorus atoms.
Isomer 1b (Fig. 6) has an irregular square pyramidal
ꢁ
structure. The nickel metal atom is only 0.06 A above
the plane formed by the atoms S1, P1, P2, and P3. The
dihedral angle N1–Ni–P2–C31 is 180.3ꢁ, compared to
20.9ꢁ in isomer 1a. The triazine group and the phenyl
ring attached to the central P2 lie on opposite sides of
the plane of the three phosphorus atoms. The Ni–P1 and
isomers of Ni(PPP)(HTMT), with rapid dynamic pro-
cess at room temperature and slow dynamic process at
248 K.
ꢁ
Another view of the structure of the nickel complex is
shown in Fig. 5. This view emphasizes the fact that both
the central phenyl ring of the PPP ligand and the triazine
ring are located on the same side of the plane containing
the three phosphorus atoms. A likely second isomer
Ni–P3 distances are equal at 2.228 A and slightly longer
ꢁ
than the Ni–P2 distance at 2.156 A. The Ni–S1 distance
ꢁ
is 2.229 A, almost the same value as in 1a, but the Ni–
ꢁ
N1 distance of 2.211 A is somewhat longer than the
ꢁ
distance of 2.047 A found in 1a.
Scheme 2.

2622
A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
Cambridge Crystallographic Data Centre, CCDC Nos.
224320 and 224321 for compounds 1 and 2, respectively.
Acknowledgements
The computing time provided by CINECA under the
agreement with the CNR is kindly acknowledged.
Financial support by Ministero dell’Istruzione, Univer-
ꢀ
sita e Ricerca (MIUR, Italy) is also acknowledged.
Fig. 6. DFT optimized structures 1a and 1b. Phenyl rings have been
omitted for sake of clarity.
References
Table 4
ꢁ
Selected angles (ꢁ) and bond lengths (A) in the DFT optimized struc-
ture of isomer 1a compared to the values from the crystal structure of 1
[1] K.R. Henke, J.C. Bryan, M.P. Elless, Powder Diffr. 12 (1997) 7.
[2] K.R. Henke, D. Robertson, M.K. Krepps, D.A. Atwood, Water
Res. 34 (2000) 3005.
Crystal structure
DFT calculated
[3] K. Henke, D.A. Atwood, Inorg. Chem. 37 (1998) 224.
[4] W. Clegg, J.E. Davies, M.R.J. Elsegood, E. Lamb, J.J. Longridge,
J.M. Rawson, R. Snaith, A.E.H. Wheatley, Inorg. Chem. Com-
mun. 1 (1998) 58.
N1–Ni–P1
N1–Ni–P3
P1–Ni–P3
96.07(15)
131.29(15)
132.01(9)
98
129
133
[5] P. Kopel, Z. Travnicek, R. Panchartkova, Z. Sindelar, J. Marek,
J. Coord. Chem. 44 (1998) 205.
Ni–P1
Ni–P2
Ni–P3
Ni–S1
Ni–N1
2.284(3)
2.141(2)
2.201(2)
2.263(2)
2.105(5)
2.360
2.206
2.204
2.279
2.047
[6] P. Kopel, Z. Travnicek, R. Panchartkova, M. Biler, J. Marek,
Transition Met. Chem. 24 (1999) 239.
[7] P. Kopel, Z. Travnicek, L. Kvitek, R. Panchartkova, M. Biler, J.
Marek, M. Nadvornik, Polyhedron 18 (1999) 1779.
[8] P. Kopel, Z. Travnicek, L. Kvitek, M. Biler, M. Pavlicek, Z.
Sindelar, J. Marek, Transition Met. Chem. 26 (2001) 282.
[9] Y. Zhao, W. Su, R. Cao, M. Hong, Acta Crystallogr., Sect. C 56
(2000) 227.
Isomer 1b was found to be slightly more stable than
1a by 7 kJ molꢀ1. This value is sufficiently small to ex-
plain the conformational equilibrium in solution.
[10] J.R. Bailey, M.J. Hatfield, K.R. Henke, M.K. Krepps, J.L.
Morris, T. Otieno, K.D. Simonetti, E.A. Wall, D.A. Atwood, J.
Organomet. Chem. 623 (2001) 185.
[11] K. Yamanari, Y. Kushi, M. Yamamoto, A. Fuyuhiro, S. Kaizaki,
T. Kawamoto, Y. Kushi, J. Chem. Soc., Dalton Trans. (1993)
3715.
4. Conclusion
HTMT2ꢀ interacts with nickel(II) and palladium(II),
in the presence of the tridentate phosphine ligand, to
form an electrically neutral complex, but in quite dif-
ferent ways. Nickel forms a bidentate complex resulting
in a coordination number of five with evidence of steric
crowding. Palladium, on the other hand, generally pre-
fers the square-planar structure to one of higher coor-
dination number. This means that HTMT2ꢀ is a
monodentate ligand in the palladium complex. More-
over, palladium being a soft acceptor prefers to bond
with sulfur rather than nitrogen. The nickel complex is
fluxional in DMF solution, allowing the formation of
two conformational isomers. The structure of the pal-
ladium complex reported here is the first for a complex
of palladium with TMT; one can only speculate on the
structure of the precipitate formed when TMT reacts
with Pd(II) from catalytic industrial processes [27].
[12] C.-K. Chan, K.-K. Cheung, C.-M. Che, J. Chem. Soc., Chem.
Commun. (1996) 227.
[13] I. Haiduc, M.F. Mahon, K.C. Molloy, M.M. Venter, J. Organo-
met. Chem. 627 (2001) 6.
[14] E.W. Ainscough, A.M. Brodie, R.K. Coll, A.J.A. Mair, J.M.
Waters, Inorg. Chim. Acta 214 (1993) 21.
[15] D.R. Corbin, L.C. Francesconi, D.N. Hendrikson, G.D. Stucky,
Inorg. Chem. 18 (1979) 3069.
[16] S. Kar, T.A. Miller, S. Chakraborty, B. Sarkar, B. Pradhan, R.K.
Sinha, T. Kundu, M.D. Ward, G. Kumar Lahiri, Dalton Trans.
(2003) 2591.
[17] W.J. Hunks, M.C. Jennings, R.J. Puddephatt, Inorg. Chem. 38
(1999) 5930.
[18] B.-C. Tzeng, C.-M. Che, S.-M. Peng, Chem. Commun. (1997)
1771.
[19] D.R. Armstrong, J.E. Davies, N. Feeder, E. Lamb, J.J. Long-
ridge, J.M. Rawson, R. Snaith, A.E.H. Wheatley, J. Mol. Model.
6 (2000) 234.
[20] V.R. Pedireddi, S. Chatterjee, A. Ranganathan, C.N.R. Rao, J.
Am. Chem. Soc. 119 (1997) 10867.
[21] A. Ranganathan, V.R. Pedireddi, S. Chatterjee, C.N.R. Rao, J.
Mater. Chem. 9 (1999) 2407.
[22] A. Ranganathan, V.R. Pedireddi, C.N.R. Rao, J. Am. Chem. Soc.
121 (1999) 1752.
5. Supplementary material
[23] S. Aoki, M. Shiro, E. Kimura, Chem. Eur. J. 8 (2002) 929.
[24] F. Cecconi, C.A. Ghilardi, S. Midollini, A. Orlandini, J. Orga-
nomet. Chem. 645 (2002) 101.
Positional and thermal parameters and complete
bond distances and angles have been deposited with

A. Ienco et al. / Inorganica Chimica Acta 357 (2004) 2615–2623
2623
€ €
[36] G.M. Sheldrick, University of Gottingen, Gottingen, Germany,
[25] F. Cecconi, C.A. Ghilardi, S. Midollini, A. Orlandini, Inorg.
Chim. Acta 343 (2003) 377.
1997.
[37] M.N. Burnett, C.K. Johnson, Report ORNL-6895, Oak Ridge
National Laboratory, Oak Ridge, TN, 1996.
[26] V.W. Rosso, D.A. Lust, P.J. Bernot, J.A. Grosso, S.P. Modi, A.
Rusowicz, T.C. Sedergran, J.H. Simpson, S.K. Srivastava, M.J.
Humora, N.G. Anderson, Org. Process Res. Dev. 1 (1997) 311.
[27] K. Ishihara, M. Nakayama, H. Kurihara, A. Itoh, H. Haraguchi,
Chem. Lett. (2000) 1218.
[38] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A.
Robb, J.R. Cheeseman, V.G. Zakrzewski, J.A. Montgomery Jr.,
R.E. Stratmann, J.C. Burant, S. Dapprich, J.M. Millam, A.D.
Daniels, K.N. Kudin, M.C. Strain, O. Farkas, J. Tomasi, V.
Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C.
Adamo, S. Clifford, J. Ochterski, G.A. Petersson, P.Y. Ayala, Q.
Cui, K. Morokuma, D.K. Malick, A.D. Rabuck, K. Raghava-
chari, J.B. Foresman, J. Cioslowski, J.V. Ortiz, A.G. Baboul, B.B.
Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.
Gomperts, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham,
C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B.
Johnson, W. Chen, M.W. Wong, J.L. Andres, C. Gonzalez, M.
Head-Gordon, E.S. Replogle, J.A. Pople, GAUSSIAN-98 (Revision
A.9), Gaussian, Inc, Pittsburgh, PA, 1998.
[28] M.I. Garcia-Seijo, A. Castineiras, B. Mahieu, L. Janosi, Z.
Berente, L. Kollar, M.E. Garcia-Fernandez, Polyhedron 20 (2001)
855.
[29] F. Cecconi, C.A. Ghilardi, P. Innocenti, S. Midollini, A. Orlan-
dini, A. Ienco, A. Vacca, J. Chem. Soc., Dalton Trans. (1996)
2821.
[30] P.W.R. Corfield, R.J. Doedens, J.A. Ibers, Inorg. Chem. 6 (1967)
197.
[31] S. Parkin, B. Moezzi, H. Hope, J. Appl. Crystallogr. 28 (1995) 53.
[32] J.C. Wilson, in: International Tables for X- ray Crystallography,
Dordrecht, 1992, p. 500.
[33] J.C. Wilson, in: International Tables for X-ray Crystallography,
Dordrecht, 1992, p. 219.
[39] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
[40] C. Lee, W. Yang, R.G. Parr, Phys. Rev.
785.
B 37 (1988)
[34] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[35] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C.
Giacovazzo, A. Guagliardi, A.G.G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 32 (1999) 115.
[41] M. Dolg, U. Wedig, H. Stoll, H. Preuss, J. Chem. Phys. 86 (1987)
866.
[42] P.C. Hariharan, J.A. Pople, Theor. Chim. Acta 28 (1973) 213.