Study of Pt(II)-aromatic amines complexes of the types cis- and trans-Pt(amine)2I2, [Pt(amine)4]I2 and I(amine)Pt(μ-I)2Pt(amine)I

Article abstract of DOI:10.1016/j.ica.2006.07.098

Pt(II) complexes of the types cis- and trans-Pt(amine)₂I₂ with amines containing a phenyl group were synthesized and studied mainly by IR and multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopies. The compounds are not very soluble. In ¹⁹⁵Pt NMR spectroscopy, the cis isomers were observed at slightly lower fields than the trans analogues (average Δδ = 11 ppm) in acetone. In ¹H NMR, the NH groups were also found at slightly lower fields in the cis isomers. The coupling constants ²J(¹⁹⁵Pt-¹HN) varied from 53 to 85 Hz and seem slightly smaller in the trans configuration. The ¹³C NMR spectra of most of the complexes were measured. No coupling constants J(¹⁹⁵Pt-¹³C) were detected due to the low solubility of the compounds. The cis isomers containing a phenyl group on the N atom could not be isolated except for Ph-NH₂ which was shown to be a mixture of isomers in acetone. The tetrasubstituted ionic compounds [Pt(amine)₄]I₂ for the less crowded ligands were also studied mainly by NMR spectroscopy in aqueous solution. The ¹⁹⁵Pt chemical shifts vary between -2855 and -2909 ppm. The coupling constants ³J(¹⁹⁵Pt-¹H) are about 40 Hz. The iodo-bridged dinuclear species I(amine)Pt(μ-I)₂Pt(amine)I were also synthesized and characterized. Two isomers are present in acetone solution for most of the compounds. Their δ(Pt) signals were observed at about -4000 ppm and their coupling constants ²J(¹⁹⁵Pt-¹HN) are around 69 Hz.

Full text of DOI:10.1016/j.ica.2006.07.098

Inorganica Chimica Acta 360 (2007) 461–472
www.elsevier.com/locate/ica
Study of Pt(II)-aromatic amines complexes of the types cis- and
trans-Pt(amine)2I2, [Pt(amine)4]I2 and I(amine)Pt(l-I)2Pt(amine)I
*
Fernande D. Rochon , Catherine Bonnier
`
´ ´
De´partement de chimie, Universite´ du Que´bec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Canada H3C 3P8
Received 20 July 2006; accepted 28 July 2006
Available online 12 August 2006
Abstract
Pt(II) complexes of the types cis- and trans-Pt(amine)2I2 with amines containing a phenyl group were synthesized and studied mainly
by IR and multinuclear (195Pt, 1H and 13C) magnetic resonance spectroscopies. The compounds are not very soluble. In 195Pt NMR spec-
troscopy, the cis isomers were observed at slightly lower fields than the trans analogues (average Dd = 11 ppm) in acetone. In 1H NMR,
the NH groups were also found at slightly lower fields in the cis isomers. The coupling constants 2J(195Pt–1HN) varied from 53 to 85 Hz
and seem slightly smaller in the trans configuration. The 13C NMR spectra of most of the complexes were measured. No coupling con-
stants J(195Pt–13C) were detected due to the low solubility of the compounds. The cis isomers containing a phenyl group on the N atom
could not be isolated except for Ph-NH2 which was shown to be a mixture of isomers in acetone. The tetrasubstituted ionic compounds
[Pt(amine)4]I2 for the less crowded ligands were also studied mainly by NMR spectroscopy in aqueous solution. The 195Pt chemical shifts
vary between ꢀ2855 and ꢀ2909 ppm. The coupling constants 3J(195Pt–1H) are about 40 Hz. The iodo-bridged dinuclear species I(amine)-
Pt(l-I)2Pt(amine)I were also synthesized and characterized. Two isomers are present in acetone solution for most of the compounds.
2
Their d(Pt) signals were observed at about ꢀ4000 ppm and their coupling constants J(195Pt–1HN) are around 69 Hz.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Platinum; Aromatic amine; Iodo; NMR; IR; X-ray crystal structure; Dimers
1. Introduction
few trans compounds have been shown to possess some
antitumor properties. Our research group has recently
undertaken a systematic study on complexes of the types
cis- and trans-Pt(amine)2I2 with different aliphatic amines
[7,8]. We have transformed these complexes into cis- and
trans-Pt(amine)2(NO3)2, which have also been studied in
The antitumor properties of Pt(II) compounds have
been known for several decades. The commercial com-
pound cisplatin (cis-Pt(NH3)2Cl2) is still one of the most
widely used drugs in chemotherapy. A good review of the
influence of the structure on the activity of Pt drugs has
been published [1]. When the ligand NH3 in cisplatin is
replaced by primary amines, the antitumor properties can
increase, especially with cyclic amines [2–5], but the latter
compounds have often a more limited activity spectrum.
Furthermore, several of the most active compounds are
quite insoluble [6]. In the amine system, the most active
compounds usually have the cis geometry, although a
1
the solid state by IR and in solution by 195Pt, H and 13C
NMR spectroscopy [8,9]. Conductivity measurements in
acetone have shown that the dinitrato complexes are not
dissociated. We have also recently reported Pt(II) com-
plexes with primary amines and dicarboxylate ligands
using a new method involving a Ag-dicarboxylato interme-
diate compound [10].
We have now started a similar study on Pt(II)-aromatic
amine compounds. There are very few of these complexes
reported in the literature. We have first synthesized the cis
and trans diiodo compounds which were characterized by
IR and by multinuclear magnetic resonance spectroscopies
*
Corresponding author. Tel.: +1 514 987 3000x4896; fax: +1 514 987
4054.
E-mail address: rochon.fernande@uqam.ca (F.D. Rochon).
0020-1693/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.07.098

462
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
in order to determine the purity of the compounds. Two ser-
ies of primary amines were studied. The first series, corre-
spond to the amines containing a linear alkyl group
between the phenyl and the amine group and are of the type
Ph–X–NH2 (X = methyl, ethyl, n-propyl and n-butyl). The
second series include aniline (PhNH2) and its para deriva-
tives. A secondary amine PhNHMe was also investigated.
The ligands of the second series are sterically more demand-
ing around the N bonding atom than the first, while the ste-
ric hindrance is the greatest for the secondary amine
PhNHMe.
The complexes trans-Pt(amine)2I2 with the less crowded
ligands were synthesized from the tetrasubstituted interme-
diate complex [Pt(amine)4]2+. The latter were also charac-
terized by NMR. The tetrasubstituted compounds cannot
be isolated with the more bulky ligands. Therefore, only
the complexes containing the amines of the first series
could be studied.
The diiodo-bridged dimers I(amine)Pt(l-I)2Pt(amine)I
are important molecules since they can be the starting
material for many different compounds, especially the
mixed-amines complexes [11,12]. For example, cis-
Pt(NH3)(2-picoline)Cl2 was found quite active and it is
currently in clinical trials [13,14]. The dinuclear species
can also be the intermediate for the preparation of the
monoamine compounds [Pt(amine)Cl3]ꢀ [15]. The dimers
are usually synthesized from Pt(amine)2I2 and the two
types of complexes are very insoluble. Therefore, the
reacting time must be very long (2–3 weeks).
Furthermore, it is not easy to determine the end of the
reaction. The diiodo-bridged dimers are usually brownish
while the starting material is yellow, but the color of the
mixture is not always a good criterion. We have now
synthesized the dinuclear species with aromatic amines
and their characterization and their purity are discussed
below.
[7,8], but with slight modifications. Since the amines are
not soluble in water, they were dissolved in ethanol and
the reactions were performed in a mixture of H2O and
ethanol.
cis-Pt(PhMeNH2)2I2: Yield: 90%, m.p. 208–211 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3255w, 3207m, 3190m, m(@C–H)
3060w, m(C–H) 2940vs, d(N–H) 1569vs, other bands 1602s,
1493m, 1354m, 1219w, 1207w; 1197m, 1162w, 1155m,
1071m, 1028w, 1002w, 972s, 920m, 911m, 822w, 807w,
752s, 699s, 616w, 560w, 491w, 473m, 342w, 303w. NMR
1
2
(d(ppm)): H: NH 4.827(s + d) J(195Pt–N1H) = 63 Hz, H1
3.994t, H2–H3–H4 7.283m; 13C: C1 51.34, C2 139.17, C3
129.58, C4 129.78, C5 128.91.
cis-Pt(PhEtNH2)2I2: Yield: 86%, m.p. 183–217 ꢁC (dec.).
IR (cmꢀ1): m(N–H) 3263s, 3205m, 3189s, 3108w, m(@C–H)
3024m, m(C–H) 2982vs, 2908w, 2874w, 2845w, d(N–H)
1561vs, other bands 1600w, 1561w, 1493s, 1454s, 1386w,
1330w, 1206m, 1181w, 1140w, 1074w, 1032s, 987s, 905w,
749w, 716m, 697s, 622w, 590w, 524w, 432w, 353w, 312w.
NMR (d(ppm)): 1H: NH 4.525(s + d) 2J(195Pt–N1H) =
65 Hz, H1 3.238qt, H2 3.033t, H3–H4–H5 7.261m; 13C: C1
48.85, C2 38.01, C3 138.96, C4 129.47, C5 129.62, C6 127.42.
cis-Pt(PhPrNH2)2I2: Yield: 79%, m.p. 142–203 ꢁC (dec.).
IR (cmꢀ1): m(N–H) 3253s, 3192m, 3161w, 3118w, m(@C–H)
3078w, 3057w, 3021w, m(C–H) 2970w, 2943w, 2918w,
2880w, 2856w, d(N–H) 1569m, other bands 1601w, 1493m,
1462m, 1453m, 1374w, 1271w, 1203m, 1075w, 1027m,
1001w, 989s, 805w, 753s, 736m, 719s, 702m, 620w, 586m,
1
490m, 375w, 352w. NMR (d(ppm)): H: NH 4.447(s + d)
2J(195Pt–N1H) = 70 Hz, H1 2.967qt, H3–H4–H5 7.222m;
13C: C1 58.78, C2 33.50, C3 47.57, C4 142.43, C5 129.29, C6
129.31, C7 126.87.
cis-Pt(PhBuNH2)2I2: Yield: 65%, m.p. 177–201 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3264m, 3229w, 3190s, 3111w,
m(@C–H) 3082w, 3058w, 3022w, m(C–H) 2965w, 2929m,
2954w, d(N–H) 1562w, other bands 1601w, 1582w,
1496m, 1452m, 1381w, 1178w, 1081w, 1041w, 1030w,
998m, 751s, 719s, 700s, 608w, 562w, 495w, 377w, 348w.
NMR (d(ppm)): 1H: NH 4.450(s + d) 2J(195Pt–
N1H) = 77 Hz, H1 3.003t, H2–H3 1.696m, H4 2.634,
H5–H6–H7 7.218m; 13C: C1 59.10, C2 36.02, C3 31.58, C4
47.84, C5 143.04, C6 129.16, C7 129.30, C8 126.63.
cis-Pt(PhNH2)2I2: Yield: 88%, m.p. 108–197 ꢁC (dec.).
IR (cmꢀ1): m(N–H): 3219m, 3191m, 3121m, m(@C–H)
3036w, d(N–H): 1574s, other bands 1597m, 1561m,
1491s, 1463m, 1338w, 1209m, 1186s; 1156s, 1145s,
1067m, 1027m, 1004w, 974w; 906w, 800m, 753s, 722m,
685w, 618w, 575m, 558w, 538m, 437m, 365w, 302w. This
compound is not stable in acetone.
2. Experimental
K2[PtCl4] was purchased from Johnson–Matthey and
was recrystallized in water before use. The amines were
bought from Aldrich. D2O and CD3COCD3 were obtained
from CDN Isotopes.
The NMR spectra were measured on a Varian Gemini
300BB. The fields were 300.070, 75.460 and 64.311 or
1
64.267 MHz for H, 13C and 195Pt, respectively. For the
195Pt NMR spectra, K[Pt(DMSO)Cl3] (ꢀ2998 ppm in
D2O) or cis-Pt(tetramethylenesulfoxide)2Cl2 (ꢀ3450 ppm
in CDCl3) were the external standards. The NMR spectra
of the diiodo complexes and the iodo-bridged dimers were
measured in CD3COCD3, while the tetrasubstituted com-
pounds were studied in D2O.
2.2. [Pt(amine)4]I2
The tetrasubstituted compounds were synthesized by a
slight variation of the Kauffman [16] method and
more recently described by our group [7]. They were
obtained only with the less sterically demanding ligands
(series 1).
2.1. cis-Pt(amine)2I2
The compounds cis-Pt(amine)2I2 were synthesized as
described in our recent publication on aliphatic amines

F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
463
[Pt(PhMeNH2)4]I2: Yield: 65%, m.p. 81–118 ꢁC (dec.).
2.4. trans-Pt(amine)2I2
IR (cmꢀ1): m(N–H) 3145m, m(@C–H) 3076s, 3044s,
m(C–H) 2933w, d(N–H) 1584w, other bands 1603w,
1498w, 1358w, 1243m, 1204w, 1169w; 1155w, 1078w,
1026w, 1002w, 1028w, 1002w, 976m, 922w, 814w,
753w, 699s, 631w, 585w, 486w, 464w. 355w. NMR
(d(ppm)): 1H: H1 4.067s, 3J(195Pt–H1) = 40 Hz, H2–H3–
H4 7.392m.
2.4.1. amine = PhMeNH2, PhEtNH2, PhPrNH2, and
PhBuNH2
The complexes [Pt(amine)4]I2 are suspended in ethanol
and the mixture is heated while stirring until a clear yellow
solution is obtained. The solution is placed in an ice bath
until complete precipitation of the trans complex occur.
The crystals are filtered, washed with water and then cold
ethanol and dried in a desiccator under vacuum.
trans-Pt(PhMeNH2)2I2: Yield: 15%, m.p. 209–216 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3245w, 3201m, 3148m, m(@C–
H) 3076s, 3047m, m(C–H) 2954w, 2879w, d(N–H) 1559vs,
other bands 1602w, 1496w, 1453m, 1340w, 1204m,
1158w, 1075w, 1028w, 982m, 911w, 847w, 811w, 754s,
[Pt(PhEtNH2)4]I2: Yield: 72%, m.p. 155–163 ꢁC (dec.).
IR (cmꢀ1): m(N–H) 3163m, 3099vs, m(@C–H) 3061vs, m(C–
H) 2948w, 2854s, d(N–H) 1572m, other bands 1599m,
1495m, 1341w, 1222m, 1177w, 1157w; 1076w, 1027w,
1001w, 753s, 731w, 699s, 618w, 540m, 432w, 348w. NMR
(d(ppm)): 1H: NH 4.92, H1 3.195t (7.2 Hz), H2 2.960t
(7.2 Hz), H3–H4–H5 7.286m.
1
[Pt(PhPrNH2)4]I2: Yield: 65%, m.p. 138–152 ꢁC (dec.).
IR (cmꢀ1): m(N–H) 3147w, 3082vs, m(@C–H) 3024vs, m(C–
H) 2932m, 2856w, d(N–H) 1602m, other bands 1496s,
1452s, 1356w, 1204w, 1176w, 1154w; 1080w, 1031m,
1006w, 990w, 912w, 752s, 733m, 599w, 586w, 556w,
697vs, 631w, 587w, 479w, 350w. NMR (d(ppm)): H: NH
4.343(s + d) 2J(195Pt–N1H) = 53 Hz, H1 3.996t, H2–H3–
H4 7.399m; 13C: C1 52.87, C2 139.17, C3 129.43, C4
129.55, C5 128.84.
trans-Pt(PhEtNH2)2I2: Yield: 61%, m.p. 178–194 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3244m, 3210m, 3123w, m(@C–
H) 3082w, 3023w, m(C–H) 2972w, 2935w, 2873w, 2851w,
d(N–H) 1572vs, other bands 1601w, 1493w, 1455m,
1388w, 1329w, 1261w, 1206m, 1175w, 1153w, 1140m,
1075w, 1033w, 1002w, 825w, 789w, 756s, 697s, 620w,
592w, 542w, 489w, 351w. NMR (d(ppm)): 1H: NH
4.044(s + d) 2J(195Pt–N1H) = 60 Hz, H1 3.012t, H2
3.414m, H3–H4–H5 7.229m.
trans-Pt(PhPrNH2)2I2: Yield: 42%, m.p. 144–202 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3278w, 3250m, 3231m, 3210m,
3125w, m(@C–H) 3082w, 3060w, 3024w, m(C–H) 2969w,
2921w, 2855w, d(N–H) 1574w, other bands 1602w,
1496m, 1453m, 1369w, 1273w, 1226w, 1197w, 1185w,
1077w, 1029m, 879m, 751m, 729w, 700s, 582w, 418w,
367w. NMR (d(ppm)): 1H: NH 4.038(s + d) 2J(195Pt–
N1H) = 70 Hz, H1 2.866m, H2 1.999m, H3 2.717t, H4–
H5–H6 7.215m; 13C: C1 48.62, C2 33.39, C3 33.61, C4
142.45, C5 129.16, C6 129.23, C7 126.68.
trans-Pt(PhBuNH2)2I2: Yield: 66%, m.p. 177–207 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3243m, 3209s, 3128m, m(@C–
H) 3082w, 3060w, 3023w, m(C–H) 2922w, 2950w, d(N–H)
1574s, other bands 1601w, 1495w, 1465w, 1453w, 1373w,
1250w, 1191m, 1045w, 1028w, 977w, 789w, 745m, 698s,
611w, 510w, 493w, 351w. NMR (d(ppm)): 1H: NH
3.962(s + d) 2J(195Pt–N1H) = 67 Hz, H2–H3 1.689m, H4
2.628t, H5–H6–H7 7.206m; 13C: C1 48.62, C2 31.34, C3
29.17, C4 35.97, C5 143.06, C6 129.07, C7 129.26, C8
126.51.
1
536w, 493w, 474w, 348w. NMR (d(ppm)): H: H1 3.334t,
H2 1.281m, H3 2.208t, H4–H5–H6 7.360m.
[Pt(PhBuNH2)4]I2: Yield: 42%, m.p. 119–128 ꢁC (dec.).
IR (cmꢀ1): m(N–H) 3144s, 3082s, m(@C–H) 3036m, m(C–
H) 2934m, 2855m, d(N–H) 1602m, other bands 1496m,
1452m, 1378w, 1218w, 1154w, 1080w, 1048w, 1027w,
1002w, 974w, 747s, 699s, 613w, 570w, 507w, 352w. NMR
(d(ppm)): 1H: H1 2.982t, H2 1.269m, H3 1.675m, H4
2.675t, H5–H6–H7 7.340m.
2.3. I(amine)Pt(l-I)2Pt(amine)I
The diiodo-bridged complexes were synthesized by
slight variations of the published method [11,12,17]. The
complex cis-PtL2I2 (0.2 mmol) was added to 5 mL etha-
nol and 1.5 mL of 0.67 M perchloric acid and mixed until
the formation of a brown or orange precipitate (around
two weeks). The yellow color of the starting material
must have disappeared completely. The brownish product
was filtered, washed with water and cold ethanol and
dried under vacuum in a desiccator. The compound with
the secondary amine PhNHMe was synthesized directly
from the reaction of K2[PtI4] with an excess of amine
in water, as already described to synthesize cis-Pt(ami-
ne)2I2 [7,17]. The isolated product was a mixture of the
trans monomer and the dimer. There are usually two iso-
mers of the dinuclear species, the cis and the trans com-
pounds. Furthermore, the PhMeNH2 complex was
contaminated with the cis monomer (60%). The 1H
NMR spectra of the mixtures were measured but they
were difficult to interpret.
2.4.2. trans-Pt(amine)2I2 (amine = 4-EtPhNH2, 4-iso-
PrPhNH2, 4-t-BuPhNH2 and 4-BuPhNH2)
K2[PtCl4] (0.5 mmol) are dissolved in 5 mL of water. KI
(4.0 mmol) are added to the solution which is stirred for
10 min. The amine (10–12 mmol) is dissolved in ethanol
and the K2[PtI4] solution is added to the amine solution.
The mixture is stirred until the formation of a precipitate.
It is then heated and filtered. The yellow precipitate is
I(amine)Pt(l-I)2Pt(amine)I: The total yields were 73%
for PhMeNH2, 57% for PhEtNH2, 48% for PhPrNH2,
37% for PhBuNH2, 67% for PhNH2 and 53% for
1
PhNHMe. The H and 195Pt NMR spectra were measured
and the chemical shifts are discussed in the text.

464
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
washed with water and cold ethanol. It is dried in air and
then under vacuum in a desiccator.
H2 7.258dd, H3 7.138d; 13C: C1 143.62, C2 126.36, C3
129.59, C4 129.23.
trans-Pt(4-EtPhNH2)2I2: Yield: 50%, m.p. 121–165 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3250w, 3226w, 3193m, 3121w,
m(C–H) 2960m, 2925w, 2867w, d(N–H) 1575vs, other bands
1595vs, 1565s, 1509vs, 1452w, 1370w, 1199m, 1187s, 1173s,
1155m, 1019w, 828s, 764w, 736w, 638w, 571m, 536m,
454w, 356w. NMR (d(ppm)): 1H: NH 6.389(s + d)
2J(195Pt–N1H) = 70 Hz, H1 7.476d, H2 7.091d, H3 2.565q,
H4 1.165t; 13C: C1 142.30, C2 124.25, C3 128.59, C4
140.31, C5 28.75, C6 15.88.
2.4.4. trans-Pt(PhNHMe)2I2
The iodo-bridged dimer was suspended in a water–etha-
nol mixture. A small excess of ligand was added and the
mixture was stirred for 2 days with slight heating. The pre-
cipitate was filtered out and washed with water, ethanol
and finally with ether. The product was dried in a desicca-
tor under vacuum.
trans-Pt(PhNHMe)2I2: Yield: 53%, m.p. = 64–234 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3196m, m(@C–H) 3033w, m(C–
H) 2941w, d(NH2) 1595m, other bands 1493s, 1464m,
1448m, 1198m, 1175m, 1074m, 1055s, 1030m, 1007m,
818w, 776m, 761tF, 693w, 616w, 569m, 480w, m(Pt–N)
352w. NMR (d(ppm)): 1H: NH 6.773s + d 2J(195Pt–
NH) = 85 Hz, H1 3.099t 3J(195Pt–H1) = 32 Hz, H2
7.167mult, H3 7.518mult, H4 7.321mult; 13C: C1 45.706,
trans-Pt(4-iso-PrPhNH2)2I2: Yield: 58%, m.p. 164–
196 ꢁC (dec.). IR (cmꢀ1): m(N–H) 3219m, 3184m, 3115m,
m(@C–H) 3057w, 3038w, m(C–H) 2955m, 2865w, d(N–H)
1571vs, other bands 1608w, 1599w, 1507s, 1461m, 1433m,
1381w, 1201s, 1178s, 1105w, 1052m, 1017m, 832vs, 813w,
767m, 641w, 574s, 543w, 515m, 357w. NMR (d(ppm)):
2
1H: NH 6.391(s + d) J(195Pt–N1H) = 64 Hz, H1 7.491d,
H2 7.129d, H3 2.825h, H4 1.190d; 13C: C1 146.91, C2
124.22, C3 127.18, C4 140.36, C5 34.26, C6 24.20.
C1 165.777, C2 126.740, C3 129.169, C4 122.991.
0
trans-Pt(4-t-BuPhNH2)2I2: Yield: 48%, m.p. 149–236 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3223m, 3187m, 3116w, m(@C–H)
3064w, m(C–H) 2961vs, 2864w, d(N–H) 1571s, other bands
1597w, 1509s, 1461w, 1364m, 1325w, 1196m, 1182m,
1072w, 1016w, 830s 818w, 765w, 641w, 575m, 552w,
375w. NMR (d (ppm)): 1H: NH 6.403(s + d) 2J(195Pt–
N1H) = 69 Hz, H1 7.500d, H2 7.290d, H3 1.279s; 13C: C1
153.03, C2 123.78, C3 126.16, C5 34.93, C6 31.55.
trans-Pt(4-BuPhNH2)2I2: Yield: 85%, m.p. 152–183 ꢁC
(dec.). IR (cmꢀ1): m(N–H) 3264w, 3213m, 3118w, m(@C–
H) 3038w, m(C–H) 2952m, 2923w, 2867w, 2854w, d(N–H)
1567vs, other bands 1595w, 1509s, 1468w, 1458w, 1428w,
1367w, 1206w, 1173w, 1158vs, 1067w 1019w 831m 816w,
789w, 757w, 641w, 573m, 554w, 420wm, 383w. NMR
(d(ppm)): 1H: NH 6.383(s + d) 2J(195Pt–N1H) = 66 Hz,
H1 7.472d, H2 7.083d, H3 2.547t, H4 1.554qt, H5 1.339s,
H6 0.903t; 13C: C1 140.95, C2 124.22, C3 129.14, C4
140.34, C5 35.55, C6 34.54, C7 22.94, C8 14.12.
2.5. Crystal structures
The crystal structures of the compounds trans-Pt(4-
EtPhNH2)I2 (1) and trans-Pt(4-iso-PrPhNH2)I2 (2) were
determined by X-ray diffraction methods. The data sets
were obtained from a Enraf-Nonius CAD-4 diffractometer
(graphite-monochromatized Mo Ka radiation) under the
control of the CAD-4 software [18]. The reduced cell was
initially determined from 25 spots located on a preliminary
Table 1
Crystal data
Crystal
1
2
Chemical formula
Diffractometer
Molecular weight
Space group
C
16H22N2I2Pt
C18H26N2I2Pt
Enraf-Nonius CAD-4
719.30
C2/c (No. 15)
29.680(10)
8.484(4)
Enraf-Nonius CAD-4
691.25
P21/c (No. 14)
6.018(3)
17.736(10)
9.075(5)
˚
a (A)
˚
b (A)
2.4.3. trans-Pt(PhNH2)2I2
˚
c (A)
8.746(6)
The compound was synthesized by a method very simi-
lar to the one used to prepare cis-Pt(amine)2I2. About
2.3 mmol of PhNH2 dissolved in ethanol are added to
0.5 mmol of K2[PtI4] in 5 mL of water. The solution is stir-
red for several hours while heating. The precipitate is then
filtered, washed with water and cold ethanol. The com-
pound is dried in air and then in a desiccator under vac-
uum. The yield is 81%.
b (ꢁ)
Volume (A )
102.22(4)
946.7(9)
2
2.425
0.41 · 0.06 · 0.05
10.668
Mo Ka, 0.71073
293(2)
27170
ꢀ7 6 h 6 7,
ꢀ22 6 k 6 22,
ꢀ11 6 l 6 11
1876 (0.083)
97.87(4)
2182(2)
4
2.190
0.64 · 0.53 · 0.05
9.264
Mo Ka, 0.71073
293(2)
11763
ꢀ37 6 h 6 37,
ꢀ10 6 k 6 10,
ꢀ10 6 l 6 11
2265 (0.150)
3
˚
Z
qcalc (g cmꢀ3
)
Crystal size (mm)
l (mmꢀ1
Radiation, k (A)
Temperature (K)
Reflections collected
Ranges of h, k, l
)
˚
This complex can also be synthesized from the isomeri-
zation of the cis complex dissolved in DMF. The solution is
heated, filtered and the filtrate is evaporated to dryness.
trans-Pt(PhNH2)2I2: m.p. 173–177 ꢁC (dec.). IR (cmꢀ1):
m(N–H) 3218s, 3190s, 3173w, 3121m, m(@C–H) 3072m,
3050w, 3037w, d(N–H) 1576vs, other bands 1596m,
1465m, 1340w, 1198w, 1174s; 1149w, 1069w, 1026m,
840w; 804w, 775w, 751vs, 685vs, 617w, 575s, 558m,
Independent
reflections (Rint
)
a
R1 (observed)
0.0312
0.0542
0.650
0.0515
0.1129
0.957
a
wR2 (all data)
S (all data)a
P
P
P
P
2
2
1=2
a
R1 = iFoj ꢀ jFci/ jFoj, wR2 ¼ f ½wðF 2o ꢀ F c2Þ ꢁ= ½wðF o2Þ ꢁg
;
P
2
1=2
S ¼ f ½wðF 2o ꢀ F c2Þ ꢁ=ðNreflns ꢀ NparamsÞg
.
1
444m, 365m. NMR (d(ppm)): H: NH 6.497s, H1 7.568d,

F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
465
rotation photograph and centered in the detector aperture.
[Pt(amine)4]I2 ! trans-Pt(amine)2I2 # + 2amine
Accurate cell parameters were then determined from the
positions of 25 high-angle reflections centered with the
SETANG and DETTH procedures. The intensities were
recorded over the whole sphere by x/2h scans and five stan-
dard reflections were measured every hour. An absorption
correction based on the crystal geometry was applied using
NRCVAX [19]. The data were finally corrected for the
effects of Lorentz and polarization.
The SHELXTL package [20] was used for all calculations.
The starting model was obtained from either a Patterson
synthesis or direct methods with SHELXS [21]. The positions
of all other non-hydrogen atoms were found by the stan-
dard Fourier technique and the structures were refined on
F 2o using all reflections with SHELXL [22]. All non-hydrogen
atoms were refined anisotropically. Hydrogens were added
to the model at idealized positions with standard C, N–H
distances. Their isotropic displacement factors Uiso were
adjusted to 20–50% above the value for the bonded atom.
At the end of the refinement, the VOID routine of PLATON
[23] was used to check for the presence of holes in the struc-
ture. The crystal data are summarized in Table 1.
For the other primary amines (second series), the trans
disubstituted compounds were prepared from the method
described above for the tetrasubstituted compounds. The
yields varied between 48% and 85%. The compound
trans-Pt(PhNH2)2I2 can also be obtained from the isomer-
ization of the cis isomer in hot DMF.
DMF
cis-PtðPhNH2Þ2I2 ! trans-PtðPhNH2Þ2I2
D
Finally, trans-Pt(PhNHMe)2I2 was obtained from the
cleavage of the diiodo-bridged dimer with the amine. The
reaction took about 2 days with slight heating in a H2O–
EtOH mixture.
IðPhNHMeÞPtðl-IÞ2PtðPhNHMeÞI þ PhNHMe
H O=EtOH trans-PtðPhNHMeÞ I
2
ꢀꢀꢀꢀ!
2
2
D
The iodo-bridged dimers were prepared following the
published procedure for aliphatic amines [11,17] from the
reaction of cis-Pt(amine)2I2 and perchloric acid in a water–
ethanol mixture. The brownish diiodo-bridged dimers are
obtained after one to three weeks of vigorous stirring.
For the ligand PhNHMe, the iodo-bridged dimer was
isolated following the procedure to synthesize cis-Pt(ami-
ne)2I2. The yields (from K2[PtCl4]) vary between 37% and
73%.
3. Results and discussion
3.1. Syntheses of the different complexes
The cis diiodo compounds were synthesized by a modi-
fied version of the published method [7,8,16] from the
aqueous reaction of K2[PtI4] with the amine dissolved in
ethanol. Compounds with phenylamine (PhNH2), phe-
nylmethylamine (PhMeNH2), phenylethylamine (PhEtNH2),
phenylpropylamine (PhPrNH2) and phenylbutylamine
(PhBuNH2) were isolated. A large excess of amine dis-
solved in ethanol was used to maximize the yields which
varied between 65% and 90%. The presence of ethanol is
required since the amines are quite insoluble in water.
The cis compounds with the other amines could not be syn-
thesized because of the steric hindrance close to the binding
site.
The PhMeNH2 dinuclear compound contained some cis
monomer (the reaction was not complete), while the sec-
ondary amine dimer contained some trans monomer. The
diiodo dimers can exist in two isomeric forms, the cis and
the trans compounds. The crystal structures of the
n-BuNH2 and Et2NH compounds were determined by
X-ray diffraction methods [17] and have shown a trans
configuration. The latter is probably thermodynamically
more stable.
3.2. Characterization of the complexes
3.2.1. Pt(amine)2I2
The tetrasubstituted compounds [Pt(amine)4]I2 were
synthesized by a modified version of Kauffman’s method
[7,16], from the aqueous reaction of K2[PtI4] with the
amine (20 equiv.) dissolved in ethanol. The mixture was
stirred for 3–4 days until a colorless solution and a white
precipitate is obtained. Slight heating was used to acceler-
ate the reaction. The yields from K2[PtCl4] were between
42% and 72%. Because of the important steric hindrance
of several ligands, only the tetrasubstituted complexes with
the following amines could be isolated: PhMeNH2,
PhEtNH2, PhPrNH2 and PhBuNH2.
The cis- and trans-Pt(amine)2I2 complexes have been
characterized mostly by IR and multinuclear magnetic res-
onance spectroscopies. The two isomers will be discussed
together in order to determine if these spectroscopic meth-
ods are good indicators to determine the geometry of the
compounds. The m(Pt–Cl) bands in IR spectroscopy are
usually a good criterion to determine the cis or trans con-
figuration of the dichloro complexes, but the m(Pt–I) bands
are below 200 cmꢀ1 and special instrumentation is required
for the study of these vibrations.
The decomposition points of the diiodo complexes are
shown in Section 2. Some of the cis compounds seem to
isomerize to the trans isomers when heated, since the final
decomposition points of the two isomers are often very
similar. Although these compounds were not studied, it
has been shown by DSC that other similar cis disubstituted
The trans compounds containing PhMeNH2, PhEtNH2,
PhPrNH2 and PhBuNH2 were prepared by heating the
tetrasubstituted compound in ethanol. The yields (from
K2[PtCl4]) are lower (between 15% and 66%), since it is
difficult to obtain the tetrasubstituted compounds
quantitatively.

466
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
amine complexes isomerize to the trans compounds when
heated [8].
the corresponding cis isomers (Table 3). The four cis com-
plexes were observed at slightly lower fields and the Dd val-
ues vary between 6 and 20 ppm. The trans complexes of the
second series were observed at lower fields (ꢀ3233 and
ꢀ3247 ppm) than the trans analogues of the first series.
The trans complex containing the secondary amine
(PhNHMe) was observed at much lower fields
(ꢀ2947 ppm) as expected for more hindered ligands. This
observation is due to the solvent effect. In solution, the
molecules of solvents can normally approach the Pt atom
on both sides of the coordination plane, which increases
the electron density in the immediate environment of the
Pt atom. When the binding atom of the ligand is sterically
more demanding, the molecules of solvent cannot
approach the Pt atom as easily and the electron density
in the close environment of the Pt atom is reduced. The
chemical shifts of secondary amines complexes have been
observed at lower fields than primary amines compounds.
For example, the d(Pt) for cis- and trans-Pt(MeNH2)I2
were reported at ꢀ3342 and ꢀ3360 ppm, respectively, while
it was found at ꢀ3247 and ꢀ3057 ppm for cis- and trans-
Pt(Me2NH)I2 [7]. The solvent effect is probably also
responsible for the lower field shifts of the trans complexes
of the second series of ligands compared to the amines of
the first series. The solvent effect is more important for sol-
vents containing donor atoms like water and acetone.
The 195Pt NMR spectrum of cis-Pt(PhNH2)I2, has
shown the presence of three species at ꢀ3141, ꢀ3183 and
ꢀ3247 ppm. The most shielded signal is caused by the pres-
ence of the trans isomer. The complexes with PhNH2 are
much less soluble in acetone than the other compounds.
Long accumulation times were required especially for the
cis isomer. Therefore, the complex cis-Pt(PhNH2)I2 was
probably pure when placed in the NMR tube, and isomer-
ized during the measurement. A few other solvents were
tried, but the solubility were even lower. DMF is probably
a better solvent, but isomerization should be faster than in
acetone. The cis-PhNH2 complex is sterically more
demanding than the other cis isomers, which contain
amines of the first series only. The two other signals were
observed at lower fields ꢀ3141 and ꢀ3183 ppm than the
3.2.1.1. IR spectroscopy. The IR spectra of the complexes
were measured in the solid state and the observed bands
are shown in Section 2. Most cis compounds (C2v symme-
try for the squeleton PtN2I2) have shown two bands in the
far IR region and these were assigned to m(Pt–N) vibrations
between 302 and 377 cmꢀ1, while the trans analogues (D2h
symmetry) have shown only one band between 350 and
383 cmꢀ1 (Table 2). These results are as expected from
group theory [24]. The m(Pt–N) vibrations of cis- and
trans-Pt(PhNH2)I2 were reported at 300 and 350 cmꢀ1 for
the cis isomer and at 366 cmꢀ1 for the trans compound
[25]. These values for aromatic amines are at lower energy
that the corresponding vibrations for the aliphatic amine
complexes, which were reported between 433 and
585 cmꢀ1 [7,8]. The m(Pt–N) bands have low intensity and
these vibrations might not be pure since they may couple
with other vibrations. The m(Pt–N) bands are usually diffi-
cult to interpret and are probably not reliable to determine
the geometry of the complexes.
3.2.1.2. NMR spectroscopy. The solubility of these com-
pounds are quite low. The NMR spectra of all the diiodo
complexes were measured in CD3COCD3. Several of these
compounds are slightly soluble in normal chloroform but
they decompose quite rapidly in CDCl3. Similar problems
were observed with CD2Cl2. DMSO reacts rapidly with
the compounds and was rapidly eliminated. DMF reacts
more slowly and isomerization of some of the cis com-
pounds is possible. Acetone was chosen, since no reaction
was observed over a longer period of time, even if it is
not a completely inert solvent. No solvolysis was observed
in acetone for the aliphatic amines system [8]. The cis
dichloro compounds can isomerize to the trans compounds
in acetone, especially when heated but no isomerization
was observed for the diiodo complexes after one week of
standing in CD3COCD3.
The 195Pt NMR signals of the trans diiodo compounds
were observed between ꢀ3363 and ꢀ3375 ppm (average
ꢀ3369 ppm) for the four ligands of the first series and
between ꢀ3355 and ꢀ3367 ppm (average ꢀ3358 ppm) for
Table 3
d(195Pt) and Dd = dcis ꢀ dtrans (ppm) of the complexes Pt(amine)2I2 and
I(amine)Pt(l-I)2Pt(amine)I (in CD3COCD3) and [Pt(amine)4]I2 (in D2O)
Table 2
amine
pKa [28] Proton cis
trans
Dd
m(Pt–N) (cmꢀ1) for the complexes cis- and trans-Pt(amine)2I2
affinity
amine
cis
trans
PhMeNH2
PhEtNH2
PhPrNH2
PhBuNH2
PhNH2
4-BuPhNH2
4-t-BuPhNH2
4-iso-PrPhNH2
4-EtPhNH2
PhNHMe
a
9.62
9.83
913
936
ꢀ3355
ꢀ3367
ꢀ3355
ꢀ3355
ꢀ3375 20
PhMeNH2
PhEtNH2
PhPrNH2
PhBuNH2
PhNH2
4-BuPhNH2
4-t-BuPhNH2
4-iso-PrPhNH2
4-EtPhNH2
PhNHMe
342, 303
353, 312
375, 352
377, 348
365, 302
350
351
367
351
365
383
375
357
356
352
ꢀ3373
ꢀ3363
ꢀ3363
6
8
8
10.28a
10.66a
4.603
4.90a
4.93a
5.01a
5.09a
4.85
883
ꢀ3141, ꢀ3183 ꢀ3247 106, 64
ꢀ3240
ꢀ3233
ꢀ3242
ꢀ3242
ꢀ2947
917
These values were calculated with the software Solaris V4.67 [29].

F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
467
trans compound, with Dd of 106 and 64 ppm (Table 3).
These values are at much lower fields than the other cis
complexes. PhNH2 is a weaker base (pKa of 4.603) than
the other ligands of the first series (pKa around 9–10) and
the d(Pt) of cis-Pt(PhNH2)I2 should be expected at lower
fields. The compounds cis-Pt(NH3)2I2 and cis-Pt(pyri-
dine)2I2 were reported in the same region (ꢀ3198 ppm in
DMF [26] and ꢀ3199 ppm in CD2Cl2 [27], respectively).
The two signals observed for cis-Pt(PhNH2)I2 at ꢀ3141
and ꢀ3183 ppm (Dd of 42 ppm) could be caused by the
presence of rotamers in solution. The two phenyl rings
could be on the same side of the coordination place or
on different sides. Rotamers have been observed for cis-
Pt(2-picoline)2I2 (at ꢀ3281 and ꢀ3312 ppm, Dd of
31 ppm) and for cis-Pt(2,4-lutidine)2I2 (at ꢀ3261 and
ꢀ3288 ppm, Dd of 27 ppm) in chloroform [27].
for the two rotamers, 85 ppm). For the other ligands, the
cis isomers could not be isolated because of steric
hindrance.
The strength of the r Pt–N bond should be related to
the basicity of the ligand. The formation of the r bond
(amine ! Pt) should transfer some electron density from
the amine to the platinum atom, resulting in a shielding
on the Pt atom and a deshielding effect on the ligands
(1H and 13C signals). We have found a relatively good rela-
tion between the pKa values [28] of the protonated amines
and the d(Pt) of the trans complexes containing the primary
amines (Fig. 1) as expected. For the cis compounds, there
are not enough data available and other factors due to
the steric hindrance are more important factors. The pKa
values are measured in a solvent (water or alcohol) and
are influenced by the presence of the substituents on the
protonated N atom. The proton affinity value, which is
measured in the gas phase is probably a better indicator
of basicity, but these values are still not common in the lit-
erature. A few data are available and are shown in Table 3.
For the cis isomers, only three values are available and the
d(Pt) of the complexes are in accordance with the basicity
of the three protonated amines. There is also a linear cor-
relation between the d(Pt) of the complexes and the pub-
lished proton affinity values for the three trans isomers
containing primary amines. The trans secondary amine
complex is alone in its category and is very influenced by
the solvent effect as already discussed.
The 195Pt chemical shifts observed for the complexes
Pt(amine)2I2 containing aromatic amines from the first ser-
ies (daverage ꢀ3363 ppm) are very similar to those published
on aliphatic amines (daverage ꢂ ꢀ3356 ppm [7,8]). These
ligands contain an alkyl group between the aromatic ring
and the amine group. The results on the complexes of the
second series resemble those published for the pyridine
ligand, which is an aromatic molecule, but quite different
in nature. The cis compounds containing pyridine deriva-
tives were reported at slightly higher fields than the trans
corresponding complexes, which might suggest that p-
bonding is present. Ligands like sulfoxides which contain
empty p* orbitals can accept electron density from plati-
num, which reduces the electron density on the metallic
center. For these compounds, the cis isomers are more sta-
ble than the trans compounds, since p-bonding is much
more efficient in the cis geometry. Pyridines also contains
empty p* orbitals which can form p-bonds with platinum,
but to a much smaller extent. Therefore, the cis compounds
with pyridine are observed at slightly higher fields than the
trans. Amines cannot accept p back-donation and the trans
compounds are more stable than the cis analogues. For the
amine systems, the trans isomers are observed at higher
fields than the cis, but the difference is small for primary
amine complexes. For secondary amines, the difference is
larger due to the solvent effect as discussed above.
For the ligands of the second series, the aromatic ring is
a phenyl group attached directly to a NH2 group. The
ligands should contain empty p* orbitals, but p-bonding
with platinum is probably absent, because of the presence
of the amine group between the phenyl ring and the Pt
atom. But these amines present a larger steric hindrance
around the Pt atom, and their 195Pt chemical shifts are at
lower fields than the complexes of the first series. For the
cis compounds of the second series, the chemical shifts
are at much lower fields, at least for the only compound
isolated (cis-Pt(PhNH2)2I2). For the first series, the results
show that the value Dd (dcis ꢀ dtrans) is small (average
11 ppm), as observed for aliphatic primary amines com-
plexes [7,8]. For the second series, the cis compound was
isolated only with PhNH2, but the Dd is larger (average
1
The H NMR spectra are shown in Section 2. Most of
the spectra are very complicated due to the multiplicity
of the signals. The amino group chemical shifts and the
2
coupling constants J(195Pt–1HN) are shown in Table 4.
The chemical shifts of the cis compounds are found at
lower fields (between 4.45 and 4.83 ppm) than those of
the trans analogues in the first series (between 3.96 and
4.34 ppm). These results are similar to those observed
for the aliphatic amines complexes [7,8]. The NH signal
in the complexes containing a phenyl ring directly
bonded to the N atom was observed at much lower fields
(6.4–6.8 ppm). In the latter free amines, the amino groups
are not very different (d(1HN) = 4.3–4.8 ppm) from those
of the free amines of the first series (d(1HN) = 3.1–
4.4 ppm).
For the compounds of the first series, the d(1HN) values
are shifted slightly to higher fields as the number of C
atoms between the phenyl and the amine groups is
increased (average cis–trans, 4.575–4.097 ppm) contrary
to the expected results. The basicity of the ligands should
increase as the number of C atoms increases. The pKa val-
ues for PhMeNH2 and PhEtNH2 are 9.62 and 9.83 [28].
For PhPrNH2 and PhBuNH2 the values were calculated
using the software Solaris V4.67 [29] (Table 3). As the basi-
city of the ligand is increased, the r bond should transfer a
greater electron density to the metal. Therefore, a larger
deshielding should be observed on the ligands as the pKa
increases. For the aliphatic amines, the NH2 signal is
almost constant in the MeNH2, EtNH2, nPrNH2, and

468
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
-3220
-3240
-3260
-3280
-3300
-3320
-3340
-3360
-3380
-3400
4-tertBuPhNH
2
4
5
6
2
7
8
9
10
11
4-EtPhNH
4-BuPhNH
2
R2= 0,9675
4-isoPrPhNH
2
PhNH
2
PhPrNH
2
PhBuNH
2
PhMeNH
2
PhEtNH
2
pKa
Fig. 1. d(195Pt) (ppm) of the complexes trans-Pt(amine)2I2 vs. the pKa of the protonated amines.
Table 4
d(1H), Dd (dcomplex ꢀ damine) ppm and 2J(195Pt–1HN) (Hz) for Pt(amine)2I2
For the amines of the second series, the pKa values are
much smaller, 4.603 for PhNH2 and between 4.90 and
5.09 (calculated) for its para derivatives. For the trans com-
pounds of the para derivatives of aniline, the Dd(NH2) val-
ues are very uniform (2.05–2.09 ppm), while it is 2.18 ppm
for trans-Pt(PhNH2)2I2. For the secondary amine
PhNHMe, the Dd value is 1.97 ppm.
in CD3COCD3
amine
NH
Dd
0.402
ꢀ0.082
0.839
0.358
1.384
2J(195Pt–1HN)
PhMeNH2
cis
trans
cis
4.827
4.343
4.525
4.044
4.499
4.038
4.450
3.962
6.497
6.383
6.403
6.391
6.389
6.773
63
53
65
60
70
69
73
67
PhEtNH2
PhPrNH2
PhBuNH2
trans
cis
For the amines of the first series, the coupling constants
2J(195Pt–1HN) are larger for the cis compounds (average
68 Hz) than for the trans complexes (average 62 Hz) as
observed for the aliphatic amines system [7,8]. For the other
trans
cis
0.923
a
a
trans
trans
trans
trans
trans
trans
trans
PhNH2
2.175
2.070
2.059
2.088
2.048
1.967
2
trans complexes, the coupling constants J(195Pt–1HN) are
4-BuPhNH2
4-t-BuPhNH2
4-iso-PrPhNH2
4-EtPhNH2
PhNHMe
a
66
69
64
70
84
64–70 Hz for the primary amines and 85 Hz for the
secondary amine (Table 4). Only one coupling constant
3J(195Pt–1H) could be calculated because all the other signals
are multiplets of lower intensity. In trans-Pt(PhNHMe)2I2
the coupling constant of the methyl group is 32 Hz, in agree-
ment with published values for aliphatic amines [7,8].
The 13C NMR spectra of the diiodo complexes were also
studied in acetone and the results are shown in Section 2.
The spectra of the free amines were also measured in
NH2 of free BuPhNH2 hidden by CH2.
nBuNH2 complexes [7]. But for aromatic amines of the first
series, opposite results are observed for both isomers.
But if we consider the Dd (dcomplex ꢀ dfree amine) values,
the difference is larger as the length of the chain is increased
acetone for comparison. Several Dd values (dcomplex
ꢀ
1
dfree amine) are shown in Table 5. The interpretation of
the signals was not always evident, since some of the signals
have very low intensity due to the low solubility of most of
the complexes. The results shown on Table 5 can be consid-
ered as a tentative assignment and they are not easy to
interpret. For the complexes containing amines of the first
series, most of the C atoms located in ortho, meta and para
positions on the aromatic ring are all deshielded upon
coordination as expected. The cis compounds are slightly
more deshielded than the trans isomers and the deshielding
decreases as the length of the alkyl group between the
amine and phenyl groups is increased. The chemical shifts
of the C atom in the phenyl group attached to the alkyl
group in the complexes is always shielded compared to
as expected. The H NMR spectra of the free amines were
measured in acetone, in order to evaluate the real Dd val-
ues, which are shown in Table 4. The signal of the –NH2
group in PhBuNH2 was hidden under the peak of the most
deshieded –CH2 group. For the three amines of the first
series, the Dd values vary between 0.402 and 1.384 ppm
for the cis isomers and between ꢀ0.082 and 0.923 ppm
for the trans compounds. Therefore, the electron donation
from the amine (r bond) to Pt increases as the C chain
between the Ph and the NH2 group increases as expected.
The Dd values are larger in the cis geometry as observed
for other reported aliphatic amines [7,8]. Acetone is not
an inert solvent for amines and these values might not be
theoretically significant.

F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
469
Table 5
important influence on the electronic system in these
molecules.
Dd(13C) (dcomplex ꢀ damine) ppm for Pt(amine)2I2 in CD3COCD3
amine
C–NH
ꢀ4.068 ꢀ2.565
trans ꢀ2.535 ꢀ2.565
cis
ꢀ4.720 ꢀ2.656
trans ꢀ3.339 ꢀ2.489
cis
ꢀ3.448 ꢀ0.913
trans ꢀ2.462 ꢀ0.891
cis
ꢀ3.665 ꢀ0.406
C(Ph)
Cortho
Cmeta
Cpara
No coupling constant could be measured because of the
low solubility of the compounds. The accumulation times
were quite long, but the background was still too important
to evaluate the J(195Pt–13C) coupling constants.
PhMeNH2
cis
1.153
1.002
0.569
0.987
0.759
0.076
2.019
1.943
0.941
0.835
0.539
0.439
0.345
0.224
PhEtNH2
PhPrNH2
PhBuNH2
0.508 ꢀ0.061
0.311
0.182
0.231
0.136
0.129
0.046
0.220
0.171
3.2.1.3. Crystal structures. The crystal structures of the
complexes trans-Pt(4-EtPhNH2)I2 (1) and trans-Pt(4-iso-
PrPhNH2)I2 (2) were determined by X-ray diffraction
methods. The results have confirmed the trans geometry
of the complexes. Labelled diagrams of the two crystals
are shown in Figs. 2 and 3. Both crystals belong to a cen-
trosymmetric space group and the Pt atom is located on an
inversion center. Selected bond distances and angles are
shown in Table 6.
trans ꢀ2.883 ꢀ0.387
PhNH2
4-BuPhNH2
4-tBuPhNH2
4-iso-PrPhNH2 trans
4-EtPhNH2
PhNHMe
trans
trans
trans
ꢀ3.342 11.247 ꢀ0.045 11.762
ꢀ5.859
8.970 ꢀ0.410
8.875 ꢀ0.183
9.970 ꢀ0.213
8.940 ꢀ0.326
8.833
3.613
2.626
7.285
6.131
6.481
0.364
trans
trans
ꢀ4.538
15.264
14.858 14.039 ꢀ0.501
˚
The Pt–I bonds are 2.597(1) and 2.591(1) A, and the
˚
Pt–N bond lengths are 2.060(7) A for the 4-EtPhNH2 com-
the free amine and the shielding decreases as the length of
the alkyl chain is increased. The aromatic ring is an elec-
tron attracting group which should decrease the strength
of the r-bond (amine ! Pt), but its influence should
decrease as the length of the alkyl group increases between
the amine and the phenyl groups. The results on trans-
Pt(PhNH2)2I2 show that the ortho and para H atoms are
much more affected by coordination than the proton in
meta position as expected. For the complexes of the second
series, no pattern was detected. These results on Pt(II) com-
pounds with amines containing an aromatic group are
quite different from those containing aliphatic amines.
Therefore, the presence of the phenyl ring has a very
˚
pound and 2.029(11) A for the 4-iso-PrPhNH2 complex.
The cis angles vary between 89.2(2)ꢁ and 90.8(2)ꢁ, while
the trans angles are 180ꢁ by symmetry. The Pt(II) coordina-
tion plane is perfectly planar by symmetry. Since the Pt
atom is on an inversion center, the two amine ligands in
both crystals are on opposite sides of the Pt plane. This
conformation of the molecule should be the thermodynam-
ically most stable. The Pt–N–C angles are 116.6(6)ꢁ (1) and
116.3(7)ꢁ (2).
The dihedral angles between the Pt(II) coordination
plane and the aromatic plane are 112.6ꢁ for 1 and 72.6ꢁ
for 2. The torsion angle of the 4-ethyl group with the
Fig. 2. Labelled diagram of the molecule trans-Pt(4-EtPhNH2)I2 in crystal 1 (the ellipsoids correspond to a 30% probability).
Fig. 3. Labelled diagram of the molecule trans-Pt(4-iso-PrPhNH2)I2 in crystal 2 (the ellipsoids correspond to a 30% probability).

470
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
Table 6
amines compounds. These values are at lower energies than
those reported for aliphatic amines [30–34].
˚
Selected bond lengths (A) and angles (ꢁ) for crystals 1 and 2
Crystal
1
2
The tetrasubstituted compounds were studied by nuclear
magnetic resonance spectroscopy in aqueous solution. The
PhPrNH2 and PhBuNH2 complexes are much less soluble
than the two others in water and their accumulation times
in NMR were much longer. The d(195Pt) vary between
ꢀ2855 and ꢀ2909 ppm (Table 7). There is no correlation
between the d(Pt) and the basicity of the ligands. These
data can be compared to those determined on aliphatic
amines [35] which have shown d(Pt) values of about
ꢀ2750 ppm. Our values on aromatic amines are at higher
fields. The phenyl group is an electron-attracting group,
which should decrease the strength of the r-bond com-
pared to aliphatic amine complexes. Our values are not
in agreement with this statement. In the aliphatic system,
the d(Pt) values are slightly shifted towards lower fields
as the length of the C chain is increased (ꢀ2769 for MeNH2
to ꢀ2743 for n-BuNH2), contrary to the basicity of the pro-
tonated amines. Our results on the aromatic amines are
almost identical for the PhMeNH2, PhEtNH2 and
PhPrNH2 compounds (ꢀ2860 ppm) and slightly at higher
field for the PhBuNH2 complex (ꢀ2909 ppm) as expected
for the most basic amine. Therefore, other factors like ste-
ric hindrance and the solvent effects (especially water) must
have a greater influence on the 195Pt chemical shifts than
the electronic factors. Steric hindrance is a very important
Pt–I
Pt–N
N–C
2.5968(12)
2.060(7)
1.487(11)
1.390(13)
1.520(13)
2.5907(13)
2.029(11)
1.498(17)
1.37(2)
C–C (average aromatic)
Other C–C (average)
1.47(2)
I–Pt–I0
180
180
90.8(2)
89.2(2)
116.6(6)
180
180
89.7(3)
90.3(3)
116.3(7)
N–Pt–N0
I–Pt–N
I–Pt–N0
Pt–N–C
aromatic ring is ꢂ60ꢁ, while the dihedral angle between the
isopropyl group and the phenyl ring is 86.9ꢁ. The bond dis-
tances and angles in the amine ligands are normal.
The crystal structures are stabilized by intermolecular
H-bonds between the amine groups and the iodo ligands.
In 1, the distances N–I and H–I are 3.684(7) and 2.85 A
with an N–H–I angle of 154.1ꢁ. In crystal 2, these distances
are 3.802(10) and 2.92 A with an N1–H1A–I angle of
0
0
˚
0
˚
0
˚
168.4ꢁ, and 3.719(9) and 2.94 A with an N1–H1B–I angle
of 145.9ꢁ.
3.2.2. [Pt(amine)4]I2
The tetrasubstituted complexes have usually been
reported in the literature as starting materials for the syn-
thesis of trans disubstituted compounds. Only the Pt(II)
complexes with the ligands PhMeNH2, PhEtNH2,
PhPrNH2, and PhBuNH2 (first series) could be isolated.
The other ligands are too sterically hindered close to the
N atom to form stable tetrasubstituted compounds. The
measurements of the decomposition points have shown
that all the white complexes, except [Pt(PhEtNH2)4]I2
decompose to the yellow trans-Pt(amine)2I2 compounds.
The experimental conditions for the synthesis of trans-
Pt(PhEtNH2)2I2 from [Pt(PhEtNH2)4]I2 was quite different
from the other amines, since a much longer heating time in
ethanol solution was required.
The four complexes were characterized by IR spectros-
copy. One m(Pt–N) band is expected for the D4h PtN4 skel-
eton and two normal deformation modes. The latter two
modes could not be observed on our instrument. One band
observed between 348 and 355 cmꢀ1 was assigned to the
m(Pt–N) vibration (Table 7). These values are close to those
observed for the diiodo complexes discussed above. There
are no published values in the literature on Pt-aromatic
factor in complexes of the type [Pt(amine)4]2+
.
The d(N1H) groups were not observed in D2O. The
3J(195Pt–1H) coupling constant could be calculated only
for the PhMeNH2 complex, which was found to be
40 Hz. We can compare with the value (42 Hz) determined
for [Pt(MeNH2)4]I2 [35] in D2O.
3.2.3. (amine)IPt(l-I)2PtI(amine)
The iodo-bridged dimers were isolated with the four
amines of the first series and also with PhNH2 and the sec-
ondary amine PhNHMe.
The compounds were characterized by 195Pt and 1H
NMR spectroscopy. The spectra have shown the presence
of more than one species in acetone solution. The reported
paper on iodo-bridged dimers on aliphatic amines has
shown for many ligands the presence of three compounds,
the disubstituted compound (cis or trans) and the two iso-
mers of the iodo-bridged dimers, which seem reasonably
stable in acetone. In 195Pt NMR, the two isomeric dimers
were reported at about ꢀ4000 ppm and are separated by
about 12 ppm for the aliphatic primary amines and by
26 ppm for two secondary amines [17]. In the present
study, two Pt(II) compounds were present in solution for
the five ligands shown in Table 8. The trans disubstituted
compound was observed in 195Pt NMR for the secondary
amine PhNHMe at ꢀ2947 ppm (see results above) in a
80% proportion. The iodo-bridged dimers are observed
at much higher fields (around ꢀ4000 ppm) and therefore,
they can easily be differentiated. The d(195Pt) of the studied
compounds are shown in Table 8. For four amines, the two
Table 7
m(Pt–N) (cmꢀ1), d(Pt) ppm and 3J(195Pt–1H) (Hz) for [Pt(amine)4]I2 in
D2O
amine
m(Pt–N)
d(195Pt)
3J(195Pt–1H)
PhMeNH2
PhEtNH2
PhPrNH2
PhBuNH2
355
348
348
352
ꢀ2868
ꢀ2855
ꢀ2858
ꢀ2909
40

F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
471
Table 8
d(195Pt) (ppm) and 2J(195Pt–1HN) (Hz) of I(amine)Pt(l–I)2Pt(amine)I in CD3COCD3
amine
d(195Pt)
Dd(cis ꢀ trans)
2J(195Pt–1HN)
trans
cis
trans
cis
PhMeNH2
PhEtNH2
PhPrNH2
PhBuNH2
PhNH2
too insoluble
ꢀ4016
ꢀ4010
ꢀ4008
ꢀ3973
ꢀ4002
ꢀ3999
ꢀ3996
ꢀ3915
14
11
12
58
64
72
71
54
75
77
PhNHMe
ꢀ3848
isomers of the iodo-bridged dimers were observed, while
for the secondary amine, PhNHMe, only one isomer was
detected. The structures of the two isomers are shown
below.
reaction was probably stopped too rapidly. For the second-
ary amine, PhNHMe complexes, the trans disubstituted
complex was observed in large concentration and the dimer
was observed in much smaller proportion as observed in
195Pt NMR.
2
amine
I
The coupling constants J(195Pt–1HN) for three com-
I
I
I
I
I
plexes could be measured. They vary between 54 and
77 Hz (Table 8). The values are not different for the two
isomers. In monomers, the cis isomers have usually larger
coupling constants than the trans. But the iodo-bridged
compounds are very different, since the two amine ligands
are located on two different Pt atoms. Therefore, their
2J(195Pt–1HN) coupling constants cannot be compared to
those of monomers. For aliphatic amines, the
2J(195Pt–1HN) in the iodo-bridged dimers were slightly lar-
ger for the trans compounds (average 68 Hz) than those in
the cis configuration (average 56 Hz) [17].
Pt
Pt
Pt
Pt
amine
amine
I
amine
I
cis
trans
In a previous paper on iodo-bridged dimers with ali-
phatic amines, we have assigned the higher field isomer
to the trans compound, especially because it was present
in much greater concentration. In this study, the propor-
tions of the two isomers are more equal and it is not pos-
sible at the moment to make definite assignments, but we
suggest again that the signal at higher field is the trans iso-
mer. We will therefore assume these configurations in the
remaining discussion.
The PhEtNH2, PhPrNH2, and PhBuNH2 dimeric com-
plexes were observed around ꢀ4000 ppm, and the separa-
tion Dd between the two isomers is about 12 ppm, very
close to the results reported for primary amine complexes
[17]. The PhNH2 dimers were observed at slightly lower
fields (average ꢀ3945 ppm), close to the values reported
for secondary amines [17], and the Dd is larger (58 ppm).
For the secondary aromatic amine, PhNHMe, only one
dimer was observed at even lower field as expected
(ꢀ3848 ppm). It is not possible to determine which isomer
is present. The product isolated with the ligand PhMeNH2
was not sufficiently soluble in acetone to measure its 195Pt
NMR spectrum. After 24 h of accumulations, no signal
was evident.
4. Conclusions
The cis- and trans-Pt(amine)2I2 complexes with amines
containing a phenyl ring have been synthesized and charac-
terized mainly by IR and multinuclear magnetic resonance
spectroscopies. Two trans isomers have also been charac-
terized by crystallographic methods. In 195Pt NMR, the
trans compounds were observed at higher fields than the
cis isomers. For the primary amines of the first series, the
Dd (dcis ꢀ dtrans) is small, but it is larger for PhNH2.
For the latter cis compound, two signals were observed,
which were assigned to the presence of rotamers in solu-
tion. For the other amines containing a phenyl group
attached to the amine group, no cis complexes could be iso-
lated probably because of steric hindrance close to the
binding atom. The d(195Pt) of the cis-PhNH2 compound
were observed at lower fields than the one of the other
cis complexes. The trans-PhNH2 isomer was observed in
the same region as the other trans compounds containing
amines of the second series. The trans complex containing
the secondary amine was observed at much lower field,
because of the solvent effect.
1
The H NMR spectra of the products were measured,
but because of the presence of two to three species, most
of the assignments could not be determined. The assign-
ments of the two iodo-bridged dimers were particularly dif-
ficult, since their proportions are almost equal. The signals
are also in the same regions as those of the disubstituted
compound, which is present for two ligands. The 1H
NMR spectrum of the PhMeNH2 product was measured
and showed the presence of three species including the
presence of cis-Pt(PhMeNH2)2I2 in ꢂ60% proportion.
The other two species are probably the two isomers of
the dimer. The cis disubstituted compound is the interme-
diate in the synthesis of the iodo-bridged dimer and the
The coupling constants J(195Pt–1HN) are larger in the
2
cis isomers than in the trans analogues. Multinuclear mag-
netic resonance spectroscopy seems a good criterion to
evaluate the purity of the disubstituted compounds. For
example, cis-Pt(PhNH2)I2 was shown to contain some trans

472
F.D. Rochon, C. Bonnier / Inorganica Chimica Acta 360 (2007) 461–472
compound. The geometry of the isomer can be evaluated
References
2
by the coupling constants J(195Pt–1HN) and sometimes
3
by J(195Pt–1H). The study of these complexes in solution
[1] T.W. Humbley, Coord. Chem. Rev. 166 (1997) 181.
[2] M.J. Cleare, Coord. Chem. Rev. 12 (1974) 349.
[3] M.J. Cleare, P.C. Hydes, B.W. Malerbi, D.M. Watkins, Biochimie 60
(1978) 835.
[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., Sect. C 42 (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 (8) (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, G. Massarweh, Inorg. Chim. Acta 359 (2006)
4095.
[11] F.D. Rochon, P.C. Kong, Can. J. Chem. 64 (1986) 1894.
[12] F.D. Rochon, P.C. Kong, US Patent No. 4,533,502, August 6,
1985.
[13] Y. Chen, Z. Guo, J.A. Parkinson, S. Parsons, P.J. Sadler, Chem.
Eur. J. 4 (4) (1998) 672.
[14] J. Holford, F. Raynaud, B.A. Murrer, K. Grimaldi, J.A. Hartley, M.
Abrams, L.R. Kelland, Anti-Cancer Drug Des. 13 (1998) 1.
[15] F.D. Rochon, R. Melanson, M. Doyon, Inorg. Chem. 26 (1987)
3065.
[16] G.B. Kauffman, Inorg. Synth. 7 (1963) 249.
[17] F.D. Rochon, V. Buculei, Inorg. Chim. Acta 358 (2005) 3919.
[18] Enraf-Nonius, CAD-4 Software Version 5.0. Enraf-Nonius, Delft,
Netherlands, 1989.
[19] E.J. Gabe, Y. LePage, J.P. Charland, F.L. Lee, P.S. White, J. Appl.
Crystallogr. 22 (1989) 384.
[20] SHELXTL: The Complete Software Package for Single Crystal Structure
Determination, Bruker AXS Inc., Madison, WI, USA, 1997.
[21] G.M. Sheldrick, SHELXS-86: Program for the Solution of Crystal
Structures, University of Go¨ttingen, Go¨ttingen, Germany, 1990.
[22] G.M. Sheldrick, SHELXL-93: Program for the Refinement of Crystal
Structures (Beta Test 03), University of Go¨ttingen, Go¨ttingen,
Germany, 1993.
[23] A.L. Spek, PLATON: Molecular Geometry Program, University of
Utrecht, Utrecht, The Netherlands, 2000.
[24] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, fifth ed., Wiley, New York, 1997.
[25] T.P.E. Auf Der Heyde, G.A. Foulds, D.A. Thornton, G.M. Watkins,
J. Mol. Struct. 77 (1981) 19.
is hindered by their very low solubility.
The tetrasubstituted ionic complexes [Pt(amine)4]I2
could be synthesized only with the four amines of the first
series, due again to steric hindrance. These compounds are
observed at lower fields than the disubstituted compounds,
at d(195Pt) = ꢀ2873 ppm (average in D2O). The molecules
were used as starting material for the synthesis of the trans
disubstituted complexes.
The iodo-bridged dinuclear species of the type described
in this paper are important molecules for the synthesis of
several types of compounds, especially those containing
mixed-ligands. The preparation of mixed-amines Pt(II)
complexes is particularly important in the synthetic field
of new potential antitumor compounds. The cleavage of
the iodo-bridged dimers in water has been shown to produce
only the cis isomers unless the ligands are very sterically hin-
dered. The products can be easily transformed in the cis
dichloro species. The dimers have also been used as interme-
diates in the preparation of the monosubstituted ionic com-
plex K[Pt(amine)Cl3], which can be the starting material for
the synthesis of all kinds of mixed ligands complexes. We
have also used the dimers as intermediates for the synthesis
of the trans disubstituted complexes with bulky ligands. The
normal method to prepare trans compounds from the reac-
tion of the tetrasubstituted compounds cannot be used for
sterically more demanding ligands.
The purity of these dimers is important especially in the
field related to chemotherapy. We have shown that they
might contain some Pt(amine)2I2. The latter compounds
will be an impurity in the preparation of the mixed-ligands
complexes. It is therefore essential to develop methods to
verify the purity of the complexes. 195Pt NMR seems an
excellent method to identify the purity of the different com-
pounds. Iodo-bridged dimers have two geometric isomers
which can both be observed around ꢀ4000 ppm, far from
the Pt(amine)2I2 compounds (around ꢀ3300 ppm).
[26] T.G. Appleton, J.R. Hall, S.F. Ralph, Inorg. Chem. 24 (1985)
4685.
[27] C. Tessier, F.D. Rochon, Inorg. Chim. Acta 295 (1999) 25.
[28] D.D. Derrin, Dissociation Constants of Organic Bases in Aqueous
Solution, Butterworths, London, 1965, pp. 140–183.
[29] Advanced Chemistry Development (ACD/Labs), Software Solaris
V4.67.
[30] L.A. Degen, A.J. Rowlands, Spectrochim. Acta A 47 (1991) 1263.
[31] P.J.D. Park, P.J. Hendra, Spectrochim. Acta A 25 (1969) 909.
[32] J. Hiraishi, I. Nakagawa, T. Shimanouchi, Spectrochim. Acta A 24
(1968) 819.
5. Supplementary material
The CIF tables for the two crystals have been deposited
to the Cambridge Data File Centre. The deposit numbers
are: CCDC Nos. 615207–615208.
Acknowledgements
[33] Y.Y. Kharitonov, I.K. Dymina, T.N. Leonova, Russ. Inorg. Chem.
13 (5) (1968) 709.
[34] G.B. Watt, B.B. Hutchinson, D.S. Klett, J. Am. Chem. Soc. 89 (1967)
2007.
[35] F.D. Rochon, V. Buculei, Inorg. Chim. Acta, manuscript in
preparation.
The authors are grateful to the Natural Sciences and
Engineering Research Council of Canada for financial sup-
port of the project and a NSERCC undergraduate summer
scholarship to C.B.