Synthesis and characterization of complexes of the type [Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3C{single bond}N{double bond, long}C(CH3)2)2]I2 by crystallography and multinuclear magnetic resonance spectroscopy

Article abstract of DOI:10.1016/j.ica.2006.11.005

Complexes of the type [Pt(amine)₄]I₂ were synthesized and characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In ¹⁹⁵Pt NMR, the signals were observed between -2715 and -2769 ppm in D₂O. The coupling constant ³J(¹⁹⁵Pt-¹H) for the MeNH₂ complex is 42 Hz. In ¹³C NMR, the average values of the coupling constants ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH₂)₄]I₂ was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH₂ was found by crystallographic methods to be [Pt(n-BuNH₂)₄]₂I₃(n-BuNHCOO). The crystal contains two independent [Pt(CH₃NH₂)₄]²⁺ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO₂ from the air. When the compound [Pt(CH₃NH₂)₄]I₂ was dissolved in acetone, crystals identified as trans-[Pt(CH₃NH₂)₂(H₃C{single bond}N{double bond, long}C(CH₃)₂)₂]I₂ were isolated and characterized by crystallographic methods. Two trans bonded MeNH₂ ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.

Full text of DOI:10.1016/j.ica.2006.11.005

Inorganica Chimica Acta 360 (2007) 2255–2264
www.elsevier.com/locate/ica
Synthesis and characterization of complexes of the type
[Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3CAN@C(CH3)2)2]I2
by crystallography and multinuclear magnetic resonance spectroscopy
*
Fernande D. Rochon , Christian Tessier, Viorel Buculei
Chemistry Department, Universite´ du Que´bec a´ Montre´al, C.P. 8888, Succ. Centre-ville Montre´al, Que., Canada H3C 3P8
Received 10 October 2006; accepted 5 November 2006
Available online 11 November 2006
Abstract
1
Complexes of the type [Pt(amine)4]I2 were synthesized and characterized mainly by multinuclear (195Pt, H and 13C) magnetic reso-
nance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In
195Pt NMR, the signals were observed between ꢀ2715 and ꢀ2769 ppm in D2O. The coupling constant 3J(195Pt–1H) for the MeNH2 com-
2
3
plex is 42 Hz. In 13C NMR, the average values of the coupling constants J(195Pt–13C) and J(195Pt–13C) are 18 and 30 Hz, respec-
tively. The crystal structure of [Pt(EtNH2)4]I2 was determined by X-ray diffraction methods. The Pt atom is located on an inversion
center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH2 was found
by crystallographic methods to be [Pt(n-BuNH2)4]2I3(n-BuNHCOO). The crystal contains two independent [Pt(CH3NH2)4]2+ cations,
three iodide ions and a carbamate ion formed from the reaction of butylamine with CO2 from the air. When the compound
[Pt(CH3NH2)4]I2 was dissolved in acetone, crystals identified as trans-[Pt(CH3NH2)2(H3CAN@C(CH3)2)2]I2 were isolated and character-
ized by crystallographic methods. Two trans bonded MeNH2 ligands had reacted with acetone to produce the two N-bonded Schiff base
Pt(II) compound.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: X-ray crystal structures; Platinum complexes; Amine; IR; NMR; n-Butylcarbamate; Imine; Schiff base
1. Introduction
active complexes (for example, those with cyclic amines)
are too insoluble to be useful anticancer drugs [6].
The antitumor complex cisplatin, cis-Pt(NH3)2Cl2 has
been known for several decades and the compound is now-
adays one of the most widely used anticancer drug. Its
chemistry and its mechanism of action have been studied
by many authors. Hambley has published a good review
of the influence of structure on the activity of Pt drugs
[1]. If the ligand NH3 is replaced by primary amines, the
antitumor activity can increase with some amines [2–5],
but several of these neutral amine compounds have a more
limited activity spectrum. In addition, several of the most
Most Pt(II)-amine compounds which have antitumour
properties have the cis configuration, although some trans
Pt(II) complexes have been shown to possess some antican-
cer activity, but they seem more limited at the moment.
Our research group has recently undertaken a systematic
study of complexes of the types cis- and trans-Pt(amine)2I2
with different types of amines in order to determine the
purity of the complexes and find an easy method to deter-
mine the geometry of the compounds [7,8]. We have trans-
formed the diiodo compounds into the dinitrato species
and again these were studied by different methods, mainly
by IR and multinuclear magnetic resonance [8,9]. Finally,
the aqueous reactions of the dinitrato compounds were
studied at different pH in order to determine the different
species present in solution, especially at neutral pH, where
*
Corresponding author. Tel.: +1 514 987 3000 4896; fax: +1 514 987
4054.
E-mail address: rochon.fernande@uqam.ca (F.D. Rochon).
0020-1693/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.11.005

2256
F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
hydroxo-bridged oligomers are formed [8,10]. These oligo-
mers, especially the hydroxo-bridged dimers have been
shown to be quite toxic and might be partly responsible
for the toxicity of cisplatin [11,12].
added to the K2[PtI4] solution (0.5 mmol of K2[PtCl4] dis-
solved in 5 mL of water with 3 mmol de KI). A yellow pre-
cipitate forms immediately. The mixture is stirred for
several days until a colourless solution is obtained. The
solution is slightly concentrated at room temperature until
a white precipitate forms. With some amines, slight heating
is required to obtain the tetrasubstituted compound in a
larger yield. The precipitate is filtered, washed with cold
water, dried in air and in a dessicator under vacuum. The
complexes [Pt(amine)4]I2 were isolated for six aliphatic
amines, methylamine (MeNH2), ethylamine (EtNH2), n-
propylamine (n-PrNH2), n-butylamine (n-BuNH2), iso-pro-
pylamine (iso-PrNH2) and iso-butylamine (iso-BuNH2) and
two cyclic amines, cyclopropylamine (cyclo-PrNH2) and
cyclobutylamine (cyclo-BuNH2).
[Pt(MeNH2)4]I2: yield = 75%; m.p. = 148–155 °C (dec.).
IR (cmꢀ1): m(N–H) 3150 s, m(C–H) 2970 m, 2885 m, d(N–
H) 1585 s, d(C–H) 1470 m 1435 s 1390 m, m(C–N) 1195
m 1170 m, m(Pt–N) 580 w, other bands 1325 m, 1280 m,
1025 w, 980 m, 710 w. NMR (d (ppm)): 1H: H1 2.500
s + d 3J(195Pt – H1) = 42 Hz, 13C: C1 32.878, 2J(195Pt –
C1) = 19 Hz.
The trans-Pt(amine)2X2 isomers are usually prepared
from the tetrasubstituted complex [Pt(amine)4]2+ which
have not been much studied in the literature. The synthesis
of [Pt(NH3)4]2+ has been reported by Kaufmann [13] in the
sixties and a few crystal structures have been published
with the cations [Pt(amine)4]2+. In the latter papers, the
anions were usually fairly large like [MX4]2ꢀ (M = Pt or
Pd) [14,15]. The only crystal structure reported with a smal-
ler anion like Iꢀ, Brꢀ or Clꢀ is the mixed-valent salt
[Pt(EtNH2)4][Pt(EtNH2)4Br2]X4 [16–19]. The compounds
[Pt(amine)4]X2 are more soluble and usually more difficult
to isolate than the [Pt(amine)4] [MX4] complexes.
We have now isolated several tetrasubstituted complexes
[Pt(amine)4]I2, which were characterized mainly by IR and
multinuclear (1H, 13C and 195Pt) magnetic resonance spec-
troscopies. Complexes with several primary amines were
studied. Amines cannot accept electron density from the
metal. Therefore the r bonds (ligand ! Pt) should cause
a deshielding effect on the ligand and a shielding effect on
the metal. The strength of the r bond should then be
related to the pKa value of the protonated amine or the
proton affinity of the ligand, although few of the latter val-
ues have been reported in the literature.
We have succeeded in obtaining stable single crystals of
[Pt(EtNH2)4]I2 and we have obtained adequate crystals of
the n-BuNH2 complex from aqueous solutions. The crystal
structure determination of the latter compound has shown
that the compound was not as expected. Since the crystal
quality was poor with the other amines, we have tried other
solvents for their recrystallization. In acetone, we obtained
good crystals for the methylamine complex. The crystallo-
graphic results on the compound have shown that the
structure was quite different, since the amine had partly
reacted with the solvent. All these structures will be dis-
cussed below.
[Pt(EtNH2)4]I2: yield = 81%; m.p. = 134–162 °C (dec.).
IR (cmꢀ1): m(N–H) 3144 s, m(C–H) 2963 m 2870 m, d(N–
H) 1523 s, d(C–H) 1415 s, 1403 s, 1393 m, m(C–N) 1218
m, 1190 m, m(Pt–N) 587 m, other bands 1338 m, 1315 m,
1292 m 1031 m, 1020 m, 985 m, 970 m, 830 m, 708 s, 675
1
3
s. NMR (d (ppm)): H: H1 2.756q J(H–H1) = 7.2 Hz, H2
1.263 t 3J(H–H1) = 7.2 Hz, 13C: C1 41.362 2J(195Pt–
3
C1) = 20 Hz, C2 15.529 J(195Pt–C2) = 34 Hz.
[Pt(n-PrNH2)4]I2:
yield = 71%;
m.p. = 132–153 °C
(dec.). IR (cmꢀ1): m(N–H) 3110 s, m(C–H) 2972 s, 2880 s,
d(N–H) 1610 s, d(C–H) 1475 s, 1393 m, m(C–N) 1265 m,
1215 m, m(Pt–N) 590 m, other bands 1335 m, 1315 m,
1105 m, 1047 m, 995 s, 961 s, 896 m, 747 s, 400 s. NMR
1
3
(d (ppm)): H: H1 2.658 t J(H–H1) = 7.5 Hz, H2 1.677 tq
3J(H–H1) = 7.5, 7.2 Hz, H3 0.931 t 3J(H–H1) = 7.2 Hz,
2
3
13C: C1 48.131 J(195Pt – C1) = 17 Hz, C2 23.983 J(195Pt
– C2) = 30 Hz, C3 10.369.
[Pt(n-BuNH2)4]I2: yield = 69%; m.p. = 99–122 °C (dec.).
IR (cmꢀ1): m(N–H) 3150 s, m(C–H) 2960 s, 2925 s, 2870 s,
d(N–H) 1575 s, d(C–H) 1470 s, 1375 m, m(C–N) 1240 m,
m(Pt–N): 580 m, other bands 1630 w, 1360 m, 1305 m,
1110 m, 1090 w, 1055 w, 980 w, 955 w, 895 w, 735 m.
2. Experimental
K2[PtCl4] was obtained from Johnson Matthey and was
recrystallized in water before use. The amines were bought
from Aldrich and D2O was purchased from CDN Isotopes.
The NMR spectra were measured on a Varian Gemini
300 BB in D2O. The fields were 300.075, 75.460 and
64.311 MHz, respectively, for 1H, 13C and 195Pt. The exter-
nal reference used for 195Pt was K[Pt(DMSO)Cl3] (in D2O),
adjusted at ꢀ2998 ppm from K2[PtCl6] (d (Pt) = 0 ppm in
D2O).
1
3
NMR (d (ppm)): H: H1 2.698 t J(H–H1) = 7.5 Hz, H2
1.656 tt 3J(H–H1) = 7.5, 7.2 Hz, H3 1.368 tq 3J(H–
3
H1) = 7.5, 7.2 Hz, H4 0.910 t J(H–H1) = 7.2 Hz, 13C: C1
46.204 2J(195Pt–C1) = 14 Hz, C2 32.680 3J(195Pt–
C2) = 29 Hz, C3 19.415, C4 13.116.
[Pt(iso-PrNH2)4]I2: yield = 74%; m.p. = 141–162 °C
(dec.). IR (cmꢀ1): m(N–H) 3145 s, m(C–H) 2965 s, 2890 m,
d(N–H) 1590 s, d(C–H) 1460 m, 1385 m, m(C–N) 1235 m,
1220 m, m(Pt–N): 578 m, other bands 1315 m, 1110 w,
2.1. Synthesis
1
1060 w, 980 m, 885 w, 755 w. NMR (d (ppm)): H: H1
The compounds [Pt(amine)4]I2 were synthesized by a
modified version of Kaufmann method described to pre-
pare [Pt(NH3)4]Cl2 [13]. The amine (10–12 mmol) is slowly
2.934 h 3J(H–H1) = 6.3 Hz, 3J(195Pt–H1) = 41 Hz, H2
1.357 d, 3J(H–H1) = 6.6 Hz, 13C: C1 48.799, 2J(195Pt–
3
C1) = 15 Hz, C2 22.845, J(195Pt – C2) = 30 Hz.

F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
2257
[Pt(iso-BuNH2)4]I2: yield = 65%; m.p. = 102–118 °C
(dec.). IR (cmꢀ1): m(N–H) 3090 s, m(C–H) 2965 s 2875 s,
d(N–H) 1605 m, d(C–H) 1473 s, 1395 s, 1378 s, m(C–N)
1265 s, 1215 m, m(Pt–N): 585 m, other bands 1345 m,
1315 m, 1175 m, 1125 m, 1005 s, 942 m, 815 w, 775 w,
but the fourth ion was found different. After many trials,
the residual electronic density was assigned to a n-butylcar-
bamate ion. Two C atoms (C63 and C64) on one of the
butyl chains were found to be disordered on two positions
with 70:30 proportions in crystal II. For crystal III, two
ligands in trans positions were found to be rearranged to
imine ligands, which are disordered on two positions (pro-
portions 63–37). The refinement of all the structures was
done on F2 by full matrix least-squares analysis. The
hydrogen atom positions were fixed in their calculated
position with Ueq = 1.2 Ueq (or 1.5 for methyl groups) of
the carbon to which they are bonded. Corrections were
made for absorption (from w-scans), Lorentz and polariza-
tion effects. The residual peaks were located in the close
environment of the platinum atoms. The calculations were
done using the Bruker SHELXTL system [21]. The perti-
nent crystal data and the experimental details are summa-
rized in Table 1.
1
715 w, 480 w, 445 w, 400 w. NMR (d (ppm)): H: H1
3
3
2.574 d, J(H–H1) = 6.6 Hz, H2 1.855 th, J(H–H1) = 6.9,
6.0 Hz, H3 0.944, 3J(H–H1) = 6.6 Hz, 13C: C1 53.853,
2J(195Pt–C1) = 20 Hz, C2 29.265, J(195Pt–C2) = 28 Hz, C3
3
19.157.
[Pt(cyclo-PrNH2)4]I2: yield = 65%. NMR (d (ppm)): 1H:
3
0
H1 2.523tt, J = 3.3 Hz, H2 0.823m, J = 7.3 Hz, H2 0.716
m, J = 3.5 Hz.
[Pt(cyclo-BuNH2)4]I2: yield = 65%. NMR (d (ppm)): 1H:
H1 3.387tt, 3J = 8.0 Hz, H2 2.343 m, H2 2.002 m, H3,3
0
0
1.707 m.
2.2. Crystal structures
3. Results and discussion
The crystallographic study of the EtNH2 (I), n-BuNH2
(II) and the MeNH2 (III) complexes were made at room
temperature on a Bruker P4 diffractometer using graph-
3.1. Synthesis
˚
ite-monochromatized Mo Ka (k = 0.71073 A) radiation.
The tetrasubstituted complexes [PtL4]X2 (X = Cl or I)
have been used as intermediates in the preparation of
the compounds trans-PtL2X2. In the literature, the
[PtL4]I2 compounds were synthesized from the reaction
of [PtL4]Cl2 (L = pyridine and its derivative) with potas-
sium iodide [22]. The intermediate [PtL4]Cl2 was synthe-
sized by Kaufmann method [13] with a large excess of
ligand (Pt:L ꢁ20)
The crystals were selected after examination under a polar-
izing microscope for homogeneity. The cell dimensions
were determined at room temperature, from a least-squares
refinement of the angles 2h, x and v obtained for well-cen-
tered reflections. The data collections were made by the 2h/
x scan technique using the XSCANS program [20]. The coor-
dinates of the Pt atoms were determined by direct methods.
All the other non-hydrogen atoms were found by the usual
Fourier methods. For crystal II, there are two independent
cations in the unit cell. Three iodide ions were easily found
L=H2O
ꢀꢀ!
D
KI=H2O
ꢀꢀ!
ꢀKCl
K ½PtCl ꢂ
½PtL ꢂCl
½PtL ꢂI
2
4
4
2
4
2
Table 1
Crystallographic data for the three crystals
Crystal
I
II
III
Name
Chemical formula
Mw
Space group
Unit cell dimensions
[Pt(EtNH2)4]I2
C8H28I2N4Pt
629.23
[Pt(n-BuNH2)4]I3 (n-BuNHCOO)
C37H98I3N9O2Pt2
1472.12
[Pt(MeNH2)2(H3CAN@C(CH3)2)2]I2
C10H28I2N4Pt
653.25
Pbca
ꢀ
P1
P21/n
˚
a (A)
7.3094(9)
7.7600(16)
8.5369(12)
92.205(14)
113.391(10)
97.860(14)
437.95(12)
1
17.547(4)
16.369(4)
21.209(5)
90
98.92(1)
90
6018(2)
4
1.625
12.912(3)
11.082(3)
13.229(3)
90
90
90
1892.9(8)
4
2.292
10.665
1200
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
qcalc (g cmꢀ3
)
2.386
11.519
288
l (Mo Ka) (mmꢀ1
F(000)
)
6.216
2856
Measured reflections
Independent reflections (Rint
R1(I > 2r(I))
wR2 (all data)
S
4012
2006 (0.026)
0.0317
0.0866
1.052
21503
10591 (0.088)
0.0671
0.1640
0.972
16164
2173 (0.083)
0.0351
0.0853
1.126
)
P
P
P
P
2
2
1=2
R1 ¼ ðjF o ꢀ F cjÞ= jF oj; wR2 ¼ ½ ðwðF 2o ꢀ F c2Þ Þ= ðwðF o2Þ Þꢂ
.

2258
F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
Table 2
The product usually contains an impurity of the type
[PtL4][PtX4] which cannot be separated from the main com-
plex. In order to eliminate the formation of this impurity,
the method was modified in our laboratories and the results
have shown a great purity of the products. The starting
material is now K2[PtI4] instead of the tetrachloro salt. A
large excess of amine is used. The cis yellow diiodo species
is formed immediately and slowly react with the excess li-
gand to form the white tetrasubstituted compound. The to-
t(Pt–N) (cmꢀ1) vibrations for the complexes [Pt(amine)4]I2 and analogous
examples from the literature
Complex
t(Pt–N)
Reference
[Pt(NH3)4]Cl2
510
522
542
536
535
532
580
587
590
580
578
585
[27]
[28]
[25]
[24]
[29]
[29]
[Pt(MeNH2)4]Cl2
[Pt(MeNH2)4]Br2
[Pt(MeNH2)4]I2
[Pt(EtNH2)4]I2
[Pt(n-PrNH2)4]I2
[Pt(n-BuNH2)4]I2
[Pt(iso-PrNH2)4]I2
[Pt(iso-BuNH2)4]I2
tal time of reaction is 2–4 days, depending on the amine.
?
amine= H2O
ꢀꢀꢀꢀꢀꢀ!
ꢀ2KI
amine=H2O
ꢀꢀꢀꢀꢀ!
D
?
y
K ½PtI ꢂ
cis-PtðamineÞ I
½PtðamineÞ ꢂI
2
4
2
2
2
4
This type of compound cannot be prepared with bulky
amines. For dimethylamine and sec-butylamine, the reac-
tion with an excess amine produced trans-Pt(amine)2I2 as
shown by multinuclear magnetic resonance spectroscopy
[7]. For these more bulky amines, the ionic trisubstituted
species [Pt(amine)3I]I probably formed but readily decom-
posed to the insoluble more stable neutral trans-Pt
(amine)2I2 compound. For the more sterically demanding
ligands like diethylamine and t-butylamine, it has been
shown that it is not possible to coordinate 2 amine ligands
in cis position [7]. The reaction of these amines with
K2[PtI4] produces the iodo-bridged dimers I(amine)Pt-
(l-I)2Pt(amine)I, which can be rearranged to trans-
Pt(amine)2I2 when heated for 20 min at about 50–60 °C
[23].
spectra of the complexes [Pt(MeNH2)4]X2 have shown
one band at 536 cmꢀ1 for X = Cl [24,29] and at 532 cmꢀ1
for X = Br [29]. These results are shown in Table 2. Based
on these reported values, we have assigned a band observed
between 578 and 590 cmꢀ1 to a stretching m(Pt–N) vibra-
tion (Table 2). It seems that the energy of the m(Pt–N)
bands is larger in the iodide compounds than in the bro-
mides or chlorides. The H-bonding system should be more
important in the chloride complexes than in the iodide
compounds, which might partially explain the higher
energy of the m(Pt–N) bands in the iodide compounds.
The assignments of these bands are not easy, since they
are usually very weak and they often couple with other
vibrations. Therefore, these results should be taken only
as suggested assignments at the moment.
The yields (between 65% and 81%) and the decomposi-
tion points of the compounds [Pt(amine)4]I2 are listed in
Section 2. The decomposition points are related to the
transformation of the white ionic complexes into the yellow
neutral trans-Pt(amine)2I2 compounds. The latter com-
plexes decompose at much higher temperatures [7]. The
compounds [Pt(amine)4]I2 decompose at lower temperature
as the length of the alkyl group increases (148–155 °C for
MeNH2 and 99–122 °C for n-BuNH2). Ramification of
the alkyl group increases the stability of the complexes as
expected (132–153 °C for n-PrNH2 and 141–162 °C for
iso-PrNH2).
3.3. Crystal structures
The crystallographic study of the EtNH2 (I) compound
confirmed the structure of the ionic complex. A drawing
3.2. IR spectroscopy
The IR spectra were measured in the solid state in KBr
pellets. All the compounds have shown a large band
around 3100 cmꢀ1 corresponding to m(N–H) vibrations.
The deformation mode was observed as a single very
intense band around 1600 cmꢀ1
.
The far IR region was closely examined in order to
assign the Pt–N vibrations. According to group theory,
the symmetry for the skeletal PtN4 group is D4h. One
non-symmetric stretching m(Pt–N) (Eu) vibration and two
deformation modes (A2u and Eu) are active in IR spectros-
copy [24–26], but the two latter modes could not be seen on
our instrument. A few studies on [Pt(NH3)4]Cl2 have been
reported in the literature. The single m(Pt–N) band was
assigned between 510 and 542 cmꢀ1 [25,27,28]. The IR
Fig. 1. Labelled diagram of [Pt(EtNH2)4]I2. The ellipsoids correspond to
50% probability.

F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
2259
Table 3
of the structure is shown in Fig. 1. The crystal belongs to the
centric P1 space group and the Pt atom is located on an
˚
Selected bond lengths (A) and angles (°) for the three crystals
ꢀ
[Pt(EtNH2)4]I2 (I)
Pt–N1
N1–C1
C1–C2
N1ꢃ ꢃ ꢃI1
N2ꢃ ꢃ ꢃI1
N1–Pt–N2
N1–Pt–N1a
Pt–N1–C1
N1–C1–C2
N1–Hꢃ ꢃ ꢃI1
N2–Hꢃ ꢃ ꢃI1
inversion centre. The environment around the Pt(II) atom
2.052(5)
1.482(8)
1.509(9)
3.888(5)
3.682(5)
Pt–N2
2.059(4)
1.500(7)
1.524(9)
3.755(5)
3.673(5)
is a perfect square plane. The Pt–N bond distances are
N2–C3
C3–C4
˚
2.052(5) and 2.059(4) A (Table 3). The trans N–Pt–N angles
N1ꢃ ꢃ ꢃI1b
are 180° by symmetry, while the cis angles are 89.6(2) and
90.4(2)°. The amine bond distances are normal with average
N1ꢃ ꢃ ꢃI1c
˚
˚
N–C = 1.491(8) A and C–C = 1.517(9) A. The average Pt–
N–C angle is 117.3(4)°, and the mean N–C–C angle is
111.6(6)°. The dihedral angles between the amine ligands
(N–C–C) and the Pt plane are 71.7(4) and 80.4(4)°.
89.64(19)
180
116.6(4)
112.8(6)
142.0
N1–Pt–N2a
N2–Pt–N2a
Pt–N2–C3
N2–C3–C4
N1–Hꢃ ꢃ ꢃI1b
N1–Hꢃ ꢃ ꢃI1c
90.36(19)
180
117.9(4)
110.3(5)
152.9
The crystal structure of a few [Pt(EtNH2)4]2+ salts have
been reported with larger anions like [PtX4]2ꢀ [14] and in
the mixed-valence compound [Pt(EtNH2)4][Pt(EtNH2)4-
Br2]X4 [16–19]. The present crystal is stabilized with hydro-
gen bonds between the amine groups and the iodide ions.
All the N–H groups are involved in hydrogen bonding.
The distances and angles are shown in Table 3. The dis-
156.7
177.8
a
c
ꢀx, ꢀy + 1, ꢀz + 1; bx ꢀ 1, y, z; ꢀx + 1, ꢀy + 1, ꢀz + 1.
[Pt(n-BuNH2)4]2I3 (n-BuNHCOO) (II)
[Pt(nBuNH2)4]2+
Pt1–N1
Pt1–N2
Pt1–N3
Pt1–N4
N–C (ave.)
N–Pt1–N (cis)
2.074(12)
2.047(13)
2.036(13)
2.062(12)
1.46(2)
89.3(5)–
90.1(5)
179.2(6)
Pt2–N5
Pt2–N6
Pt2–N7
Pt2–N8
2.055(13)
2.031(14)
2.050(13)
2.003(16)
˚
tances Nꢃ ꢃ ꢃI vary between 3.673(5) and 3.888(5) A and
the angles N–Hꢃ ꢃ ꢃI are between 142.0 and 177.8°.
The structure of the n-BuNH2 complex (crystal II) was
also examined. There are two independent Pt atoms in
the unit cell. The two cations [Pt(n-BuNH2)4]2+ and three
Iꢀ ions were readily located, but the fourth Iꢀ ion could
not be found. There were several residual peaks present
and after numerous efforts of interpretation, they were
assigned to a n-butylcarbamate anion. This ion was
obtained from the reaction of n-butylamine with CO2 from
the air. The reaction mixture for the synthesis of the tetra-
substituted complex is basic, since a rather large excess of
amine must be used to accelerate the reaction. Steric hin-
drance is an important factor in the preparation of this
type of compound. A good review on the methods to con-
vert CO2 into carbamato derivatives was published in 2003
[30]. In our work, the presence of carbamate ions in our
solution was probably very limited. It might have formed
during the synthetic procedure or during the recrystalliza-
tion process. The compound was recrystallized in air sev-
eral times in water, before crystals adequate for
diffraction studies could be obtained.
The crystal structure of only one related compound was
found in the literature. It contains the same n-butylcarba-
mate ion, although it was prepared in a different way
[31]. A Co(III) compound [Co(nBuNH2)4(CO3)](n-BuNH-
COO) Æ H2O was very slowly crystallized from a mixture
containing cobalt(II) oxalate, n-butylamine and water.
The oxalate was oxidized to CO2, which was trapped by
the basic medium and converted into carbonate and n-
butylcarbamate ions. The n-butylcarbamate anion is not
bonded to the metal atom, but it is involved in the H-bond-
ing system.
N–Pt2–N (cis)
89.8(6)–
90.7(6)
179.3(6)
N–Pt1–N
(ave. trans)
Pt1–N–C (ave.)
N–C–C (ave.)
N–Pt2–N
(ave. trans)
Pt2–N–C (ave.)
117.1(11)
111.7(19)
116.6(13)
nBuNHCOOꢀ
C1–O1
C1–N10
C–C (ave.)
O1–C1–O2
O2–C1–N10
1.26(2)
1.283(17)
1.51(4)
119.5(16)
118.3(15)
C1–O2
N10–C2
1.26(2)
1.459(16)
O1–C1–N10
C1–N10–C2
121.9(15)
123.9(19)
[Pt(MeNH2)2(H3CAN@C(CH3)2)2]I2 (III) (the imine ligands are
disordered on two positions with the two sets of atoms labeled and
0
00
,
respectively)
Pt1–N1
Pt1–N200
N20–C30
N20–C20
C30–C50
C30–C40
2.046(5)
Pt1–N20
N10–0 C1
2.045(9)
1.474(9)
1.238(14)
1.48(2)
1.499(14)
1.499(13)
2.026(14)
1.255(11)
1.487(15)
1.495(12)
1.501(11)
N2 –C300
N200–C200
C300–C500
C300–C400
N1–Pt1–N1a
N1–Pt1–N20
N1–Pt1–N200
Pt1–N10–0 C1
180
N2–Pt1–N2a
180.
89.5(2)
90.7(4)
124.0(9)
116.5(10)
119.5(13)
122.1(15)
125.2(13)
112.7(14)
a
90.5(2)
89.3(4)
116.4(4)
124.2(15)
113.9(18)
122(2)
127(2)
123(2)
110(2)
3.610(5)
156.4
N1–Pt1–N20
N1–Pt1–N200
Pt1–N20–C30
Pt1–N20–C20
a
Pt1–N2 –C300
Pt1–N200–C200
C200–N200–C300
N200–C300–C500
N200–C300–C400
C500–C300–C400
N1ꢃ ꢃ ꢃI1
C20–N20–C30
N20–C30–C50
N20–C30–C40
C50–C30–C40
N1ꢃ ꢃ ꢃI1b
3.622(5)
156.5
N1–H1Aꢃ ꢃ ꢃI1
N1–H1Aꢃ ꢃ ꢃI1b
a
b
ꢀx, ꢀy, ꢀz; ꢀx + 1/2, yꢀ1/2, z.
The structure of one of the cation in our compound
[Pt(n-BuNH2)4]2I3 (n-BuNHCOO) (II) is shown in Fig. 2.
The replacement of one iodo ion by the larger n-butylcarba-
mate anion brings a larger stability to the crystal, which
contains the very large cations [Pt(n-BuNH2)4]2+. Carba-
mate anions were probably present in small concentration,
but compound II would crystallized before the totally iodo
complex, since it would be slightly less soluble in water. Free
carbamate ions are not common in reported crystal struc-
tures. There are a few structures containing a carbamate

2260
F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
for the Pt1 cation and downward for the Pt2 cation. The
anions are located between the pairs of cations.
The C–O bonds in the carbamate anion are 1.26(2) A.
˚
0
0
˚
The C1@N1 is 1.283(17) A, while the N1 –C2 bond is
0
˚
longer (1.459(16) A). The angles around C1 and N1 are
close to 120°.
The compound is stabilized by an extensive hydrogen-
bonding system, which is maximized in crystal II. All the
NH2 groups of the amines and the NH group of the carba-
mate anion act as donors, while the two O atoms of the car-
bamate ion and the three iodide ions are acceptors. Some
of the H-bonds are shown in Fig. 3. A more elaborate
drawing of the H-bonding system is available in the Sup-
plementary material (Fig. S1).
Fig. 2. Labelled diagram of one cation [Pt(nBuNH2)4]2+ in crystal II. The
ellipsoids correspond to 25% probability.
The Nꢃ ꢃ ꢃI distances are between 3.617(14) and 3.734
˚
(14) A and the angles N–Hꢃ ꢃ ꢃI range from 165.9 and
175.9°, while the distances Nꢃ ꢃ ꢃO are between 2.79(2) and
coordinated to a metal center [32–34]. Our compound (II) is
a rare example of a free carbamate ion, besides the Co(III)
complex [31] mentioned above and the two Cu(II) com-
pounds containing anions of N-carboxyglycine and ethylen-
ediaminebiscarboxylic acid [35].
˚
3.00(2) A and the N–Hꢃ ꢃ ꢃO angles range from 158.2 and
167.0°.
Several other tetrasubstituted compounds were recrys-
tallized in water, but the quality of the crystals was too
poor for crystallographic methods. Therefore several other
solvents were tried. The MeNH2 compound was recrystal-
lized in acetone and crystals of good quality were obtained.
The results of its crystal structure determination were quite
surprising. The crystal belongs to a centrosymmetric space
group and the Pt atom is located on an inversion center.
Two MeNH2 ligands (in trans position by symmetry) were
easily determined, but the two other ligands were found to
be quite different. The two other amines had reacted with
the solvent (acetone) used for recrystallization generating
bonded imine ligands. The structure of the new ligands
was found to be H3CAN@C(CH3)2, bonded to Pt through
the N atom. Since the Pt atom is on an inversion center the
compound has a trans geometry. Crystal III is therefore the
ionic compound trans-[Pt(MeNH2)2(H3CAN@C(CH3)2)2]I2.
The reaction of acetone with bonded MeNH2 can be
explained in organic chemistry. The reaction of aldehydes
or ketones with amines is known to form imine derivatives
also known as Schiff bases. Water is eliminated in the
process
The Pt–N bonds in II vary between 2.003(16) to
˚
2.074(12) A and the N–Pt–N angles are close to the ideal
values (Table 3). The average Pt–N–C angle is 116.9(12)°.
All the n-butylamine ligands adopt the fully extended all-
anti conformation, except one ligand bonded to Pt2. In
the latter, the two terminal C atoms are disordered on
two positions. The most populated one (70%) has the all-
anti conformation, while the minor component has a
gauche conformation. The relative conformation of the
ligands in the two cations is very interesting. For each com-
plex cation, all the four N–C bonds point away on the same
side of the Pt square plane. The two cations are arranged in
pairs as shown in Fig. 3, where all the C–N point upward
CH3COCH3 þ C0H3NH2 ! C0H3NH–CðCH3Þ ðOHÞ
2
! C0H3N ¼ CðCH Þ þ H2O
3
2
A
Pt(II) compound containing a tridentate ligand
(pip2NCN) was recently reported containing the same
imine, which was also produced from the reaction of
CH3NH2 with acetone used as solvent and bonded to the
Pt(II) atom [36]. The complex [Pt(pip2NCN)Cl]+ was first
reacted with AgCF3SO3 in acetone and after the removal
of AgCl, the compound [Pt(pip2NCN)(acetone)]2+ proba-
bly formed in acetone solution. The N-bonded Schiff base
adduct [Pt(pip2NCN)CH3N@C(CH3)2][CF3SO3] was pro-
duced in good yield after the addition of CH3NH2. Kozel-
ba and Bois had previously suggested that the Pt(II) center
could activate a coordinated acetone ligand towards
Fig. 3. Diagram of the two cations and the anions in crystal II showing
the conformation of the two cations and some H-bonds. A diagram
showing the more elaborate H-bonding system can be visualized in Fig. S1
(deposit).

F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
2261
condensation with a primary amine [37]. In our case, the re-
verse situation was observed. The amine was bonded to the
Pt(II) atom, since the characterization of the product in the
solid state and by NMR in aqueous solution confirmed
that the compound isolated was indeed [Pt(CH3NH2)4]I2.
Amines are usually stronger ligands for Pt(II) than acetone.
The reaction probably took place between bonded
CH3NH2 and free acetone. Only two ligands in trans posi-
tions reacted with acetone. The other two amine ligands re-
mained unchanged.
and 89.6(4)° with the Pt(II) coordination square plane.
This conformation reduces the steric hindrance around
the Pt atom to a minimum, leading to the most stable
structure.
The crystal is stabilized by hydrogen bonding between
the NH2 groups and the iodo ions as shown in Fig. 2.
˚
The N1ꢃ ꢃ ꢃI1 distances are 3.610(5) and 3.622(5) A and
the angles N1–Hꢃ ꢃ ꢃI1 are 156.4 and 156.5°.
3.4. NMR
The Pt atom in crystal III is located on an inversion cen-
ter and the coordination around the metal atom is square
planar. The imine ligands in the crystal trans-[Pt(MeNH2)2
(H3CAN@C(CH3)2)2]I2 are disordered on two positions
(proportions 63–37%), as shown in Fig. 4. The first set of
1
The 195Pt, H and 13C NMR spectra of all the tetrasub-
stituted complexes were measured in D2O. The compounds
are quite soluble, but the times of accumulations were
increased in order to obtain good data on the coupling con-
stants. The 13C spectra were accumulated during 12–15 h.
0
atoms is labeled and the second set is labeled 00. It is inter-
esting to observe that in the crystal structure reported for
[Pt(pip2NCN)CH3N@C(CH3)2] [CF3SO3], the imine moi-
ety is also disordered over two positions in similar propor-
tions (65–35%) [36].
3.4.1. 195Pt NMR
The d(195Pt) chemical shifts of all the compounds are
listed in Table 4. They vary between ꢀ2715 and
ꢀ2769 ppm. For all the products, only one signal was
observed confirming the purity of the complexes. In the lit-
erature, the complex ion [Pt(NH3)4]2+ was reported at
ꢀ2580 ppm [38]. The Pt(II) complexes containing primary
amines are usually found at higher fields than the corre-
sponding NH3 compounds, as observed in this work.
Amines cannot form p-bonds with the Pt atom. There-
fore the 195Pt chemical shifts of the metal complex should
depend on the strength of the r bonds. A stronger bond
will transfer more electron density to the Pt atom and its
d(195Pt) will be observed at higher fields. The pKa values
of the protonated amines should be a good criterion for
the strength of the r bonds. These are shown in Table 4.
The pKa values of the non-cyclic protonated amines are
very close to each other (10.62–10.78 [39]) and their errors
are not negligible. The error of the 195Pt chemical shifts is
also a few ppm. Therefore no relation can be found at this
moment. The pKa values are influenced by the solvent and
its effect cannot be neglected, especially in relation to the
steric hindrance around the N atom. The influence of a sol-
vent like water is most important. The proton affinity of
the amines might be a better criterion for the basicity of
a ligand, since it is measured in the gas phase. But these
˚
The Pt–N bond distances with CH3NH2 are 2.046(5) A,
˚
while the N1–C1 bonds are 1.474(9) A. The cis N1–Pt–N2
angles are between 89.3(4) and 90.7(4)°, while the trans
bond angles are 180° by symmetry. The Pt–N1–C1 angles
are 116.4(4)°, while the torsion angles C1–N1–Pt1–N2 are
91.4(5) and 67.4(6)°.
The Pt–N bond distances with the imine ligands are
˚
˚
2.026(14) and 2.045(9) A (Table 3). The N@C bonds =
1.238(14) and 1.255(11) A and the other bond lengths are
normal. The angle C4–C3–C5 is smaller (ave. 112(2)°) than
the N2–C3–C (ave. 124(2)°) and C2–N2–C3 (ave. 121(2)°)
angles as expected. The angles Pt–N2–C2 (ave. 115.2(14)°)
are also smaller than the Pt–N2–C3 angles (ave.
124.1(12)°). The imine ligands are perpendicular to the
platinum(II) plane. All the non-H atoms of the two con-
formers of the imine ligands are in a plane (mean devia-
˚
tion = 0.006 and 0.055 A), with dihedral angles of 89.4(4)
Table 4
d(195Pt) (ppm) of the complexes [Pt(amine)4]I2 (in D2O), pKa and proton
affinity (AP, kJ/mole)
Amine
AP
pKa [39]
d(195Pt)
NH3
MeNH2
EtNH2
n-PrNH2
n-BuNH2
iso-PrNH2
iso-BuNH2
cyclo-PrNH2
cyclo-BuNH2
854
914
930
933
924
9.25
10.62
10.67
10.708
10.777
10.63
10.72
8.67
ꢀ2580 [38]
ꢀ2769
ꢀ2753
ꢀ2741
ꢀ2743
ꢀ2724
ꢀ2748
ꢀ2715
ꢀ2766
Fig. 4. Labelled diagram of trans-[Pt(MeNH2)2(H3CAN@C(CH3)2)2]I2
(crystal III). The ellipsoids correspond to 40% probability. The H atoms
have been omitted for clarity.
9.34

2262
F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
-2720
data are not very common in the literature. Those of the
linear amines have been published and they are shown in
Table 4. Again the values (proton affinity and d(Pt)) are
too similar to reach any conclusion.
isoPrA
-2730
-2740
-2750
-2760
-2770
nPrA
nBuA
For the non-cyclic amines, the lowest field signal was
observed for the iso-propylamine compound. This amine
is the most sterically hindered close to the binding N atom.
The solvent effect is an important phenomenon in 195Pt
NMR and it is particularly important for a solvent like
water. In aqueous solution, the water molecules can
approach the Pt atom on both sides of the square plane,
which increases the electron density of the Pt atom. When
there is steric hindrance close to the binding atom of the
ligand, the molecules of solvent cannot approach the Pt
atom so easily and the electron density on the Pt atom will
slightly decrease, which will bring a deshielding effect in
195Pt NMR. Therefore, the complex containing iso-propyl-
amine should be observed at lower field (ꢀ2724 ppm) than
the one containing n-propylamine (ꢀ2741 ppm). Here the
difference is not very large since the steric hindrance on
iso-propylamine is not very large. It is not possible to syn-
thesize this type of tetrasubstituted complex with more ste-
rically demanding amines.
If we consider only the four linear amine complexes, the
195Pt chemical shifts were observed at higher fields for the
smaller amines. These results are in agreement with the sol-
vent effect as mentioned above. The amines with longer
chains will reduce the approach of the water molecules in
the close environment of the metallic atom, leading, to a
reduced electron density around the Pt atom. The 195Pt
chemical shifts should therefore be observed at slightly
lower fields for the larger amines.
isoBuA
EtA
MeA
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.3
Δδ of H1
Fig. 5. d(Pt) vs. Dd of H1 for the complexes [Pt(amine)4]I2 (non-cyclic
amines).
electron density on the Pt atom will cause a decrease in
electron density on the H atoms of the ligands.
For the cyclic amines complexes, the two H atoms on all
the CH2 groups are not equivalent. The H atom closer to
the N atom of the ligands will be more deshielded upon
coordination than the second H atom on the same C atom.
In the free amine, the difference is small, but in the com-
plex, the difference is much larger. For example, in the
cyclo-BuNH2 complex, the two H protons on C2 were
observed at 2.34 and 2.00 ppm, while the two H protons
on C3 were too close to be separated (ave. 1.707 ppm).
All these signals are multiplets since they can couple with
all the H present (2J–4J).
3
The J(195Pt–1H) coupling constant of only the MeNH2
compound could be calculated. The value is 42 Hz. There is
no comparable values in the literature for this type of com-
plexes, but it is very similar to those reported for cis-Pt-
(amine)2X2 (45 Hz for X = I [7], 40 Hz for X = NO3 [9],
43 Hz for X = D2O [10] and 43 Hz for X = OD [10]). The
3J(195Pt–1H) coupling constants with the other ligands were
not observed, because the latter signals are multiplets of
low intensity and the satellites were not observed, even with
long accumulation times.
Complexes with only two cyclic amines were studied.
The compound with cyclopropylamine was observed at
slightly lower field, while the cyclobutylamine complex is
similar to the methylamine compound. Tension inside the
ring is probably a factor, but there are not enough data
at the moment to comment on its effect on 195Pt NMR
chemical shifts.
1
3.4.2. H NMR
3.4.3. 13C NMR
The proton chemical shifts of the complexes are shown
in Section 2. The d(NH) signals were not observed in
D2O. The signals of all the protons in the bonded amines
were observed at lower fields than in the free amine, except
for H1 in the iso-propylamine complex. The bonding of the
amines to Pt will increase the electron density on the metal
atom, but will decrease it on the ligand. Therefore, there
should be a linear relation between the d(195Pt) and the
Dd(1H) (d of complex ꢀ d of the free amine in the same sol-
vent) values. A plot of the different values for the non-cyc-
lic amines is shown in Fig. 5. The H closest to the Pt atom
was chosen (H1) and Dd = dcomplex ꢀ dfree amine. Fig. 5
shows that the d(195Pt) is shifted to higher fields as Dd
increases (shift towards lower fields). Therefore, there is a
good agreement between the values observed in 195Pt
The d(13C) chemical shifts of the compounds are shown
in Section 2. The 13C NMR spectra of the free amines were
also measured in water and the Dd(dcomplex ꢀ dfree amine
)
values are shown in Table 5. Again, these results are in
agreement with the results observed in the 195Pt and H
1
1
NMR spectra as discussed in the H NMR section. An
increase of electron density on the Pt atom (195Pt NMR)
will correspond with a decrease of electron density on the
ligand (1H and 13C NMR). A linear relationship between
the d(195Pt) and the Dd(13C) values of the complexes con-
taining the linear amines can be observed in Fig. 6. For
the iso-propylamine and iso-butylamine compounds, other
local factors based on the structure of the ligand play a
more important role on the 13C chemical shifts.
2
Most of the J(195Pt–13C1) coupling constants could be
1
NMR with those observed in H NMR. An increase of
calculated and are shown in Table 5. They vary between

F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
2263
Table 5
Dd(C) (ppm) and J(195Pt–13C) (Hz) of the complexes [Pt(amine)4]I2 in D2O
Amine
C1
C2
C3
C4
2J(195Pt–C1)
3J(195Pt–C2)
MeNH2
EtNH2
n-PrNH2
n-BuNH2
iso-PrNH2
iso-BuNH2
6.238
6.010
5.600
5.935
6.951
5.282
19
20
17
14
15
20
ꢀ1.382
ꢀ0.911
ꢀ1.169
ꢀ1.290
ꢀ0.759
34
30
29
30
28
ꢀ0.304
ꢀ0.045
0.878
ꢀ0.243
This type of reaction seems new in the literature. A Pt com-
plex containing a tridentate ligand and an acetone ligand
was reported to produce a Pt compound containing the
same H3(C–N@C(CH3)2)2 ligand [36]. But the reaction took
place between bonded acetone and free CH3NH2. We have
observed the reverse process. Bonded CH3NH2 reacted with
free acetone used as a solvent. Therefore, not only the Pt(II)
center can activate a coordinated acetone ligand towards
condensation with primary amines, but it can also activate
a coordinated amine ligand towards condensation with
acetone.
-2720
-2730
-2740
-2750
-2760
-2770
-2780
-2790
nBuA
nPrA
EtA
MeA
6.2
5.5
5.6
5.7
5.8
5.9
6
6.1
6.3
This work has shown that special care should be taken
to ascertain the purity of reaction products especially if
the compounds were recrystallized in an organic solvent.
This is particularly important if the Pt complexes are pre-
pared for antitumor evaluation. It is already known that
cis-Pt(amine)2Cl2 can isomerise to the trans compounds
in several organic solvents, particularly acetone. The two
novel compounds discussed in this paper seem to indicate
that the rearrangement of amines is not uncommon
although not very well known. In one case, the amine
reacted with CO2 of air and in the second case, it reacted
with acetone, a solvent commonly used to recrystallize
and purify the Pt products. Therefore, the end-products
should always be characterized just prior to antitumor
Δδ of C1
Fig. 6. d(Pt) vs. Dd of C1 for the complexes [Pt(amine)4]I2 (linear amines).
14 and 20 Hz. No such values exist in the literature on sim-
ilar compounds, but we can compare with the compounds
Pt(amine)2I2, where the reported average values are 18 Hz
for the cis isomers and 11 Hz for the trans analogues [7].
For most of the complexes, the 3J(195Pt–13C2) coupling
constants were detected and they vary between 28 and
34 Hz. Again no such values have been reported yet in
the literature for this type of complexes. They are close
to the values reported for trans-Pt(amine)2I2 [7].
1
4. Conclusion
evaluation and multinuclear (especially H) magnetic reso-
nance seems a very adequate method. Again, the solvent
for recording the spectrum should be carefully chosen.
The ionic complexes [Pt(amine)4]I2 were synthesized and
characterized in the solid state by IR spectroscopy and by
X-ray diffraction methods. The compounds were also stud-
ied in aqueous solution by multinuclear (195Pt, 1H and 13C)
magnetic resonance spectroscopy. Our new method is
slightly different from the published method and prevents
the formation of side-products such as [Pt(amine)4][PtX4],
which are impossible to separate completely from [Pt(ami-
ne)4]X2. If the tetrasubstituted compounds are used for the
preparation of trans-Pt(amine)2X2, the products will be
contaminated with [Pt(amine)4][PtX4].
The tetrasubstituted amine complexes are important
molecules for the synthesis of trans diamine compounds,
but it cannot be isolated for bulky ligands. Therefore its
use is limited to less hindered amines. The halide complexes
are interesting since they are quite soluble. The compounds
are stable in aqueous medium. [Pt(CH3NH2)4]I2 was found
to react partly when dissolved in acetone to form a Schiff
base Pt adduct, trans-[Pt(MeNH2)2(H3CAN@C(CH3)2)2]I2.
Acknowledgement
The authors are grateful to the Natural Sciences and
Engineering Research Council of Canada for financial sup-
port of the project.
Appendix A. Supplementary material
CCDC 623134, 623135 and 623136 contain the supple-
mentary crystallographic data for this paper. These data
can be obtained free of charge via http://www.ccdc.cam.a-
c.uk/conts/retrieving.html, or from the Cambridge Crystal-
lographic Data Centre, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with
this article can be found, in the online version, at
doi:10.1016/j.ica.2006.11.005.

2264
F.D. Rochon et al. / Inorganica Chimica Acta 360 (2007) 2255–2264
[21] SHELXTL (PC version 5, 1995) Programs, Bruker Analytical X-ray
References
Systems.
[22] C. Tessier, F.D. Rochon, Inorg. Chim. Acta 295 (1999) 25.
[23] F.D. Rochon, V. Buculei, Inorg. Chim. Acta 358 (2005) 3919.
[24] Y.Y. Kharitonov, I.K. Dymina, T.N. Leonova, Russ. Inorg. Chem.
13 (5) (1968) 709.
[1] T.W. Hambley, Coord. Chem. Rev. 166 (1997) 181.
[2] M.J. Cleare, Coord. Chem. Rev. 12 (1974) 349.
[3] M.J. Cleare, P.C. Hydes, B.M. Malerbi, D.M. Watkins, Biochimie 60
(1978) 835.
[25] L.A. Degen, A.J. Rowlands, Spectrochim. Acta 47A (1991) 1263.
[26] P.J. Hendra, N. Sadasivan, Spectrochim. Acta 21 (1967) 1275.
[27] J. Hiraishi, I. Nakagawa, T. Shimanouchi, Spectrochim. Acta 24A
(1968) 819.
[28] P.J.D. Park, P.J. Hendra, Spectrochim. Acta 25A (1969) 909.
[29] G.B. Watt, B.B. Hutchinson, D.S. Klett, J. Am. Chem. Soc. 89 (1967)
2007.
[30] D.B. Dell’Amico, F. Calderazzo, L. Labella, F. Marchetti, G.
Pampaloni, Chem. Rev. 103 (2003) 3857.
[31] T.D. Keene, M.B. Hursthouse, D.J. Price, Acta Crystallogr. E60
(2004) m381.
[32] O. Blacque, H. Brunner, M.M. Kubicki, J.-C. Leblanc, W. Meier, C.
Moize, Y. Mugnier, A. Sadorge, J. Wachter, M. Zabel, J. Organomet.
Chem. 634 (2001) 47.
[33] A. Duatti, A. Marchi, V. Bertalasi, V. Ferretti, J. Am. Chem. Soc.
113 (1991) 9680.
[34] S. Schmid, J. Stra¨hle, Z. Naturforsch. Teil. B46 (1991) 235.
[35] L.A. Kovbasyuk, I.O. Fritsky, V.N. Kokozay, T.S. Iskenderov,
Polyhedron 16 (1997) 1723.
[36] H. Jude, J.A. Krause Bauer, W.B. Connick, Inorg. Chem. 41 (2002)
2275.
[4] P.D. Braddock, T. Connors, M. Jones, A.R. KhorHar, D.H.
Melzack, M.L. Tobe, Chem. Biol. Interact 11 (1975) 145.
[5] F.D. Rochon, R. Melanson, Acta Crystallogr. C42 (1986)
1291.
[6] M. Nicolini, Platinum and other metal coordination compounds in
cancer chemotherapy, University of Padua, Italy, 1987.
[7] F.D. Rochon, V. Buculei, Inorg. Chim. Acta 357 (2004) 2218.
[8] F.D. Rochon, V. Buculei, Inorg. Chim. Acta 358 (2005) 2040.
[9] F.D. Rochon, V. Buculei, Can. J. Chem. 82 (4) (2004) 524.
[10] F.D. Rochon, V. Buculei, Can. J. Chem. 82 (4) (2004) 1606.
[11] J.A. Broomhead, D.P. Fairlie, M.W. Whitehouse, Chem.-Biol.
Interact. 31 (1980) 113.
[12] S.K. Aggarwal, J.A. Broomhead, D.P. Fairlie, M.W. Whitehouse,
Cancer Chemother. Pharmacol. 4 (1980) 249.
[13] G.B. Kauffman, Inorg. Synth. 7 (1963) 249.
[14] M.E. Cradwick, D. Hall, R.K. Phillips, Acta Crystallogr. B27 (1971)
480.
[15] M.L. Rodgers, D.S. Martin, Polyhedron 6 (1987) 225.
[16] K.L. Brown, D. Hall, Acta Crystallogr. Sect. B Struct. Crystallogr.
Cryst. Chem. 32 (1976) 279.
[17] B.M. Craven, D. Hall, Acta Crystallogr. 21 (1966) 177.
[18] H. Endres, H.J. Keller, B. Keppler, R. Martin, Acta Crystallogr.
Sect. B Struct. Crystallogr. Cryst. Chem. 36 (1980) 760.
[19] S. Sato, K. Kobayashi, Acta Crystallogr. Sect. C Cryst. Struct.
Commun. 43 (1987) 1863.
[37] J. Kozelka, C. Bois, Inorg. Chem. 27 (1988) 3866.
[38] Y. Qu, N. Farrell, M. Velsecchi, L. de Greco, S. Spinelli, Magn. Res.
Chem. 31 (1993) 920.
[39] D.D. Derrin, Dissociation Constants of Organic Bases in Aqueous
Solution, Butterworths, London, 1965, pp. 140–183.
[20] XSCANS (V. 2.20) Program, Bruker Analytical X-ray Systems.