Addition reactions of primary and secondary aliphatic amines to the benzonitrile ligands in cis- and trans-[PtCl2(NCPh)2] complexes. X-ray structure of the amidine complex trans-[PtCl 2{Z-N(H)=C(NHBut)Ph}2]

Article abstract of DOI:10.1016/S0020-1693(02)00866-6

The reactions of cis-[PtCl₂(NCPh)₂] with a fivefold excess of the primary aliphatic amines RNH₂ (R=Me, Et, Pr ⁱ) in CH₂Cl₂ at -10°C afford in high yield the di-amidine complexes cis-[PtCl₂{N(H)=C(NHR)Ph}₂]. The reaction of cis-[PtCl₂(NCPh)₂] with Bu^tNH ₂ yields the di-amidine complex trans-[PtCl₂{Z-N(H)= C(NHBu^t)Ph}₂] which has been characterized also by an X-ray diffraction analysis. The corresponding reactions of trans-[PtCl ₂(NCPh)₂] with a fivefold excess of RNH₂ (R=Me, Et) afford the di-amidine derivatives trans-[PtCl₂{N(H)=C(NHMe)Ph} ₂], while the reactions of PrⁱNH₂ and Bu ^tNH₂ lead, for the former, to a mixture of the mono-amidine derivative trans-[PtCl₂(NCPh){N(H)=C(NHPr ⁱ)Ph}] and the di-amine dicationic species derivative trans-[Pt(PrⁱNH₂)₂{N(H)=C(NHPr ⁱ)Ph}[Cl]₂ and, for the latter, to the mono-amidine complex derivative trans-[PtCl₂(NCPh){N(H)=C(NHBu^t)Ph}]. The reactions of cis- or trans-[PtCl₂(NCPh)₂] di-nitrile complexes with the secondary aliphatic amine Me₂NH yields the di-amidine complexes cis- or trans-[PtCl₂{N(H)=C(NMe ₂)Ph}₂], while the corresponding reactions with RR′NH (R, R′=Me, Et; R=Me, R′=Bu^t) produce the mono-amidine complexes cis- or trans-[PtCl₂(NCPh){N(H)= C(NRR′^t)Ph}]. The stereochemistry of the amidine ligands in the final products has been investigated by ¹H NMR spectroscopy.

Full text of DOI:10.1016/S0020-1693(02)00866-6

Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
www.elsevier.com/locate/ica
Addition reactions of primary and secondary aliphatic amines to the
benzonitrile ligands in cis- and trans-[PtCl2(NCPh)2] complexes. X-
ray structure of the amidine complex trans-[PtCl2{Z-N(H)ꢀ
/
C(NHBut)Ph}2]
Umberto Belluco a, Franco Benetollo b, Roberta Bertani a, Gabriella Bombieri c, Rino
A. Michelin a,*, Mirto Mozzon a, Oliviero Tonon a, Armando J.L. Pombeiro d, Fatima
Costa Guedes da Silva d
a Dipartimento di Processi Chimici dell’Ingegneria and Centro di Chimica e Tecnologia dei Composti Metallorganici degli Elementi di Transizione del
CNR, Universita` di Padova, Via F. Marzolo 9, 35131 Padova, Italy
b ICIS, Area di Ricerca del CNR, Corso Stati Uniti 4, 35020 Padova, Italy
c Istituto di Chimica Farmaceutica, Universita` di Milano, Viale Abruzzi 42, 20131 Milan, Italy
d Centro de Qu´ımica Estrutural, Complexo I, Instituto Superior Te´cnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
Received 30 January 2002; accepted 4 March 2002
Dedicated to Professor Andrew Wojcicki on the occasion of his retirement from The Ohio State University
Abstract
The reactions of cis-[PtCl2(NCPh)2] with a fivefold excess of the primary aliphatic amines RNH2 (Rꢀ
10 8C afford in high yield the di-amidine complexes cis-[PtCl2{N(H)ꢀC(NHR)Ph}2]. The reaction of cis-[PtCl2(NCPh)2] with
ButNH2 yields the di-amidine complex trans-[PtCl2{Z-N(H)ꢀC(NHBut)Ph}2] which has been characterized also by an X-ray
diffraction analysis. The corresponding reactions of trans-[PtCl2(NCPh)2] with a fivefold excess of RNH2 (RꢀMe, Et) afford the
di-amidine derivatives trans-[PtCl2{N(H)ꢀ
C(NHMe)Ph}2], while the reactions of PriNH2 and ButNH2 lead, for the former, to a
mixture of the mono-amidine derivative trans-[PtCl2(NCPh){N(H)ꢀ
C(NHPri)Ph}] and the di-amine dicationic species derivative
trans-[Pt(PriNH2)2{N(H)ꢀC(NHPri)Ph}[Cl]2 and, for the latter, to the mono-amidine complex derivative trans-
[PtCl2(NCPh){N(H)ꢀ
C(NHBut)Ph}]. The reactions of cis- or trans-[PtCl2(NCPh)2] di-nitrile complexes with the secondary
aliphatic amine Me2NH yields the di-amidine complexes cis- or trans-[PtCl2{N(H)ꢀC(NMe2)Ph}2], while the corresponding
reactions with RR?NH (R, R?ꢀMe, Et; RꢀMe, R?ꢀ
But) produce the mono-amidine complexes cis- or trans-
/
Me, Et, Pri) in CH2Cl2 at
ꢁ
/
/
/
/
/
/
/
/
/
/
/
/
[PtCl2(NCPh){N(H)ꢀ
C(NRR?t)Ph}]. The stereochemistry of the amidine ligands in the final products has been investigated by
/
1H NMR spectroscopy. # 2002 Published by Elsevier Science B.V.
Keywords: Platinum complexes; Nitrile complexes; Amidine complexes; X-ray structure
1. Introduction
to a low-valent electron-rich or an high-valent electron-
poor metal center, respectively [1]. In particular, the
metal-promoted addition reactions of protic nucleo-
philes such as water [1,2], alcohols [1,3], oximes [4],
Transition metal-coordinated organonitriles RCN
have been reported to exhibit a rich reaction chemistry,
which often results from the activation of the nitrile to
electrophilic or nucleophilic attack upon coordination
amines [1,5] and imines [6] to the Cꢁ/N triple bond of the
nitrile afford the corresponding amidates, imido esters,
iminoacylated species, amidines and 1,3-diaza-1,3-
dienes, respectively, which represent products of valu-
able synthetic and pharmacological interest. Thus, for
instance, platinum(II)-imino ester complexes of the
* Corresponding author. Tel.: ꢂ
5525.
E-mail address: rino.michelin@unipd.it (R.A. Michelin).
/
39-049-827 5522; fax: ꢂ39-049-827
/
0020-1693/02/$ - see front matter # 2002 Published by Elsevier Science B.V.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 0 8 6 6 - 6

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U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
general formula cis- and trans-[PtCl2{N(H)ꢀ
/
(primary or secondary), the nature of the R group(s)
of the amine and the geometry of the nitrile Pt(II)
complexes influence the stereochemistry of the resulting
amidine products in comparison with the analogous
reactions carried out with cis- and trans-
[PtCl2(NCMe)2].
C(OR?)R}2] (R?ꢀalkyl, Rꢀalkyl, aryl) [3] show unu-
/
/
sual antitumor activity [8,9] with the trans isomers more
active than the corresponding cis derivatives.
Our interest in the reactions of Pt(II) organonitriles
[1a,5b,5c,5g,7] and those of transition metal cyanamide
(Nꢁ
/
CNH2), organocyanamide (Nꢁ
/
CNR2; Rꢀ
/
Me, Et),
and cyanoguanidine (Nꢁ
/
CꢂNꢀC(NH2)2) derivatives
/
/
2. Experimental
[10], led us recently to undertake a detailed investigation
[11,12] on the addition of primary and secondary
aliphatic amines to Pt(II) nitrile complexes of the type
cis- and trans-[PtCl2(NCMe)2] to form di- and mono-
amidine complexes of the type cis- and trans-[PtCl2{Z
2.1. General procedures and materials
All work was carried out with the exclusion of
atmospheric oxygen under a N2 atmosphere using
standard Schlenck techniques. Solvents were distilled
under N2 prior to use; CH2Cl2 was distilled from CaH2,
Et2O and THF were distilled from sodium benzophe-
or E-N(H)ꢀ
[PtCl2(NCMe){Z or E-N(H)ꢀ
RƒꢀH, alkyl), respectively. The results of this study
indicate that the additions of aliphatic amines to the Cꢁ
/
C(NR?Rƒ)Me}2] and cis- and trans-
/
C(NR?Rƒ)Me}] (R?,
/
/
none. IR spectra were taken on a PerkinꢃElmer 983
/
N triple bond of the acetonitrile ligands proceed in a
selective manner. Thus, primary amines afford amidine
complexes exclusively with Z configuration, while
secondary amines yield amidine complexes only with E
configuration, corresponding to the trans or cis addition
(Nujol mulls), FT-IR AVATAR 320 of the Nicolet
Instrument Corporation (KBr or polyethylene (PE))
spectrophotometers; the wavenumbers (n) are given in
1
cmꢁ1. H and 13C {1H} NMR spectra were run at 298
K, unless otherwise stated, on a Bruker 200 AC
spectrometer operating at 200.13 and 50.32 MHz,
respectively. Peak positions are relative to Me4Si and
were calibrated against the residual solvent resonance
(1H) or the deuterated solvent multiplet (13C). 195Pt
NMR spectra were measured on a Varian UNITY 300
spectrometer at ambient temperature and the 195Pt
chemical shifts are given relative to Na2[PtCl6] (by using
of the amine along the Cꢁ
/
N triple bond, respectively
(Scheme 1).
The Z configuration of the amidine ligands appears
to be determined by the formation of strong intramo-
lecular hydrogen bonds between each chlorine atom and
the amino proton of the NHMe moiety forming a six-
membered ring. This experimental evidence would
explain the lack of Z to E isomerization as otherwise
observed [3a,3b] in the base-catalyzed addition reactions
of alcohols to one or both the coordinated nitriles of cis-
aq. K2[PtCl4]ꢀ
/
ꢁ1630 ppm as a standard). The ele-
/
mental analyses were performed by the Department of
Analytical, Inorganic and Organometallic Chemistry of
the University of Padova. The melting points were taken
on a hot plate apparatus and are uncorrected. The
amines were purchased from Aldrich and were used as
received.
and trans-[PtCl2(NCR)2] (RꢀMe, Ph). In particular, a
/
detailed investigation [3b] of the mechanism and stereo-
chemistry of the addition reactions of MeOH revealed
that the Z-imido ester isomers are kinetically favored,
then undergoing isomerization to the thermodynami-
cally more stable E form.
The complexes cis- and trans-[PtCl2(NCPh)2] were
prepared according to a reported procedure [13].
In this work, we report the study of the addition
Me, Et, Pri, But) and
reactions of primary RNH2 (Rꢀ
/
2.2. Reactions of cis-[PtCl2(NCPh)2] with primary
amines
secondary R2NH (RꢀMe, Et) aliphatic amines to cis-
/
and trans-[PtCl2(NCPh)2] complexes with the aim to
determine what factors such as the type of amine
2.2.1. Reaction with MeNH2. Synthesis of cis-
[PtCl2{N(H)ꢀ
A suspension of cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with a
/
C(NHMe)Ph}2] (1)
/
fivefold excess of MeNH2 (1.6 ml of a 2 M THF
solution, 3.2 mmol). The suspension turned to a yellow
solution after a few minutes. The reaction mixture was
stirred for 30 min at the low temperature and then the
solvent was removed under reduced pressure to approxi-
mately 10 ml. Addition of Et2O (40 ml) at the low
temperature gave a pale yellow solid, which was stirred
for an additional 60 min. It was then filtered off at room
Scheme 1.
temperature (r.t.) and washed with Et2O (3ꢄ5 ml). It
/

U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ
/447
439
was recrystallized from CH2Cl2/Et2O. Yield: 266 mg,
78.5%. Anal. Calc. for C16H20N4Cl2Pt: C, 35.96; H,
3.74; N, 10.49. Found: C, 34.39; H, 3.63; N, 10.20%. IR
2.2.4. Reaction with ButNH2. Synthesis of trans-
[PtCl2{N(H)ꢀ
C(NHBut)Ph}2] (4)
A suspension of cis-[PtCl2(NCPh)2] (300 mg, 0.635
/
(Nujol mull): n(NH) 3300, 3530, 3350 (m); n(Cꢀ
(s); n(PtCl) 310, 320 (m, br). 1H NMR (CD2Cl2, 270 K):
d 2.84, 2.38, 3.03 (d, CꢀNꢂCH3); 6.61, 6.07 (br, PtNH);
7.67 (br, NH); 8.18ꢃ8.23 (m, Ph); 6.94ꢃ6.98 (m, Ph);
7.3ꢃ
7.6 (m, Ph). 13C {1H} NMR (CD2Cl2): d 170.97,
170.50, 166.48 (C ꢀN); 132ꢃ126 (Ph); 31.65, 31.76 (s,
CH3). 195Pt NMR (CD2Cl2): d ꢁ
2039.
/
N) 1620
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with
/
an approximately fivefold excess of ButNH2 (334 ml,
3.17 mmol). On stirring for 1 h a yellow solution was
obtained. The solvent was removed under reduced
pressure to approximately 10 ml. Addition of Et2O (40
ml) at the low temperature gave a pale yellow solid,
which was stirred for an additional 60 min. It was then
/
/
/
/
/
/
/
/
filtered off at r.t. and washed with Et2O (3ꢄ5 ml). It
/
2.2.2. Reaction with EtNH2. Synthesis of cis-
[PtCl2{N(H)ꢀC(NHEt)Ph}2] (2)
A suspension of cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with a
fivefold excess of EtNH2 (1.6 ml of a 2 M THF solution,
3.2 mmol). The suspension became a yellow solution
after some minutes. The reaction mixture was stirred for
7 h at the low temperature and then the solvent was
removed under reduced pressure to approximately 10
ml. Addition of Et2O (40 ml) at the low temperature
gave a pale yellow solid, which was stirred for an
additional 60 min. It was then filtered off at r.t. and
was recrystallized from CH2Cl2/Et2O. Yield: 284 mg,
72.4%. Anal. Calc. for C22H32N4Cl2Pt: C, 42.72; H,
5.18; N, 9.06. Found: C, 41.93; H, 5.17; N, 8.94%. IR
/
/
(KBr): n(NH) 3260, 3280 (m); n(Cꢀ
/
N) 1610 (s). IR (PE):
n(PtCl) 338, 317 (m). 1H NMR (CD2Cl2, 290 K): d 1.43,
1.15, 0.96 (s, NC(CH3)3); 5.6, 6.05 (br, PtNH); 7.68,
6.78 (s, NH); 7.49ꢃ
8.2 (m, Ph). 13C {1H} NMR (CD2Cl2): d 170.56 (s, Nꢀ
C); 135ꢃ126 (Ph); 51.62 (s, NꢂC(CH3)3); 31.34 (s, Nꢂ
C(CH3)3).
/
7.33 (m, Ph); 6.6ꢃ
/
7.0 (m, Ph); 8.1ꢃ
/
/
/
/
/
2.3. Reactions of trans-[PtCl2(NCPh)2] with primary
amines
washed with Et2O (3ꢄ5 ml). It was recrystallized from
/
CH2Cl2/Et2O and identified as 2. Yield: 310 mg, 86.9%.
Anal. Calc. for C18H24N4Cl2Pt: C, 38.43; H, 4.27; N,
9.96. Found: C, 39.07; H, 4.37; N, 9.73%. IR (Nujol
2.3.1. Reaction of trans-[PtCl2(NCPh)2] with MeNH2.
Synthesis of trans-[PtCl2{N(H)ꢀC(NHMe)Ph}2] (5)
The reaction has been performed as for 1, starting
from trans-[PtCl2(NCPh)2] (300 mg, 0.635 mmol) and
MeNH2 (1.6 ml of a 2 M THF solution, 3.2 mmol).
Yield: 226 mg, 66.7%. Anal. Calc. for C16H20N4Cl2Pt:
C, 35.96; H, 3.74; N, 10.49. Found: C, 34.33; H, 3.80; N,
/
mull): n(NH) 3280 (m); n(Cꢀ
/
N) 1624 (s); n(PtCl) 310
(m, br). H NMR (CD2Cl2): d 1.29, 1.15, 0.95 (t, CH3);
3.35, 3.15, 2.75 (m, NꢂCH2); 5.52, 6.25, 6.63 (br,
PtNH); d masked (NH); 7.56ꢃ7.38 (m, Ph); 8.20 (m,
Ph); 6.98 (m, Ph). 13C {1H} NMR (CD2Cl2): d 169.80 (s,
C ꢀN); 131ꢃ127 (m, Ph); 40.03 (s, CH2), 16.05 (s, CH3).
1
/
/
/
/
10.49%. IR (KBr): n(NH) 3340, 3234 (m); n(Cꢀ
/
N) 1603
1
(s). IR (PE): n(PtCl) 322 (m). H NMR (CD2Cl2, 270
K): d 2.92, 2.78, 2.47 (d, NCH3); 5.81, 5.50 (br, PtNH);
2.2.3. Reaction with PriNH2. Synthesis of cis-
[PtCl2{N(H)ꢀ
C(NHPri)Ph}2] (3)
A suspension of cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with a
/
8.48, 7.66 (br, NH); 7.3ꢃ
(CD2Cl2): d 165.99, 165.10 (s, Nꢀ
42.0, 37.5 (br, CH3).
/
7.6 (m, Ph). 13C {1H} NMR
C); 131ꢃ128 (m, Ph);
/
/
/
fivefold excess of PriNH2 (270 ml, 3.17 mmol). The
suspension turned to a yellow solution after a few
minutes. The reaction mixture was stirred for 7 h at
the low temperature and then the solvent was removed
under reduced pressure to approximately 10 ml. Addi-
tion of Et2O (40 ml) at the low temperature gave a pale
yellow solid, which was stirred for an additional 60 min.
2.3.2. Reaction with EtNH2. Synthesis of trans-
[PtCl2{N(H)ꢀC(NHEt)Ph}2] (6)
/
Compound 6 was prepared under experimental con-
ditions similar to those described for the synthesis of 2
starting from cis-[PtCl2(NCPh)2] (200 mg, 0.423 mmol)
and EtNH2 (1.05 ml of a 2 M THF solution, 2.10
mmol). The reaction mixture was stirred for 15 h at the
low temperature and then the solvent was removed
under reduced pressure to approximately 10 ml. Addi-
tion of Et2O (40 ml) at the low temperature gave a pale
yellow solid, which was stirred for an additional 60 min.
It was then filtered off at r.t. and washed with Et2O (3ꢄ
/
5 ml). It was recrystallized from CH2Cl2/Et2O. Yield:
240 mg, 63.8%. Anal. Calc. for C20H28N4Cl2Pt: C,
40.68; H, 4.75; N, 9.49. Found: C, 41.30; H, 5.20; N,
9.04%. IR (Nujol mull): n(NH) 3280 (m-s); n(Cꢀ
1624 (s); n(PtCl) 330, 317 (m, br). 1H NMR (CD2Cl2): d
1.20, 0.95 (d, CHCH3); 3.47, 3.20, 3.95 (m, CꢀNꢂCH);
5.95 (br, PtNH); d masked (br, NH); 8.13 (m, Ph);
7.31ꢃ7.58 (m, Ph); 7.06ꢃ
7.02 (m, Ph). 13C {1H} NMR
(CD2Cl2): d 168.97, 167.54 (C ꢀN); 133ꢃ127 (Ph); 47.19,
46.77 (CH); 23.96, 23.63, 22.64 (CH3).
/N)
It was then filtered off at r.t. and washed with Et2O (3ꢄ
/
/
/
5 ml). It was recrystallized from CH2Cl2/Et2O and
identified as 6. Yield: 154 mg, 65.5%. Anal. Calc. for
C18H24N4Cl2Pt: C, 38.43; H, 4.27; N, 9.96. Found: C,
37.95; H, 4.34; N, 9.78%. IR (Nujol mull): n(NH) 3350,
/
/
/
/
3194 (m); n(Cꢀ
/
N) 1609 (s); n(PtCl) 322 (m, br). 1H

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U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
NMR (CD2Cl2): d 3.21, 3.09, 2.65 (q, Nꢂ
1.16, 1.13 (t, CH3); 5.43, 6.05, 6.75 (br, PtNH); 9.31 (t,
3JHH 6.15, NH); 7.60ꢃ
7.20 (m, Ph); 7.72 (m, Ph); 6.97
(m, Ph); 8.11 (m, Ph). 13C {1H} NMR (CD2Cl2): d
170.11 (s, C ꢀN); 131ꢃ127 (m, Ph); 40.08 (s, CH2);
16.28, 15.89 (s, CH3).
/
CH2); 1.11,
117.88, 116.37, 110.07 (s, Nꢁ
/
C ꢂ
/
Ph); 56.83, 56.93, 55.24,
53.45 (s, NC(CH3)3); 31.17, 31.30, 30.35, 30.15 (s,
NC(CH3)3).
/
/
/
2.4. Reactions of cis-[PtCl2(NCPh)2] with secondary
amines
2.3.3. Reaction with PriNH2. Synthesis of trans-
[PtCl2{N(H)ꢀ
C(NHPri)Ph}2] (7) and trans-
[Pt(PriNH2)2{N(H)ꢀC(NHPri)Ph}2][Cl]2 (8)
/
2.4.1. Reaction with Me2NH. Synthesis of cis-
/
[PtCl2{N(H)ꢀ
/
C(NMe2)Ph}2] (10)
The reaction of trans-[PtCl2(NCPh)2] (300 mg, 0.635
Compound 10 was prepared as described previously
for 1 starting from cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) and a 5 M excess of Me2NH (1.6 ml of a 2 M
solution in THF, 3.2 mmol). Yield: 291 mg, 81.5%.
Anal. Calc. for C18H24N4Cl2Pt: C, 38.43; H, 4.27; N,
9.96. Found: C, 37.16; H, 4.12; N, 9.48%. IR (KBr):
mmol) in CH2Cl2 (30 ml) with a fivefold excess of
PriNH2 (270 ml, 3.17 mmol) at ꢁ
10 8C for 3 h gave a
/
mixture of 7 and 8 (in about 2:1 ratio) which could not
be separated by fractional crystallization, but they were
identified by 1H NMR spectroscopy. 7. IR (Nujol mull):
n(NH) 3349, 3308, 3190 (m); n(Cꢀ
/
N) 1618 (s); n(PtCl)
321(m, br). 1H NMR (CD2Cl2): d 1.22, 1.15 (d,
NCHCH3); 3.53, 3.41 (m, NCHCH3); 6.18 (br,
n(NH) 3480, 3265, 3240 (m); n(Cꢀ
/
N) 1590 (s). IR (PE):
n(PtCl) 330, 323 (m). 1H NMR (CD2Cl2, 260 K): d 2.38
and 2.70, 3.06 and 2.88, 3.10 and 2.58 (s, CH3); 4.98,
PtNH); 6.95 (br, NH); 7.40ꢃ7.50 (m, Ph); 7.64 (m, Ph).
/
5.95, 6.65 (br, NH); 7.76ꢃ
(CDCl3): d 166.01, 165.28 (s, Cꢀ
40.77, 42.64 (br, CH3).
/
7.10 (m, Ph). 13C {1H} NMR
N); 134ꢃ121 (m, Ph);
On the other hand, the same reaction carried out with
a 50-fold molar excess of the amine gave 8. Yield: 378
mg, 84.3%. Anal. Calc. for C26H44N6Cl2Pt: C, 44.19; H,
6.23; N, 11.90. Found: C, 43.75; H, 6.60; N, 11.33%. IR
/
/
(KBr): n(NH) 3344, 3165 (m); n(Cꢀ
NMR (CD2Cl2): d 1.32 (d, ꢀCꢂNHCH(CH3)2); 1.33 (d,
H2NCH(CH3)2); 2.90 (m, H2NCH(CH3)2); 3.40 (m, ꢀ
/
N) 1629 (s). 1H
2.4.2. Reaction with Et2NH. Synthesis of cis-
[PtCl2(NCPh){N(H)ꢀC(NEt2)Ph}] (11)
/
/
/
/
Compound 11 was prepared as described previously
for 1 starting from cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) and a 5 M excess of Et2NH (329 ml, 3.17 mmol).
Yield: 213 mg, 61.5%. Anal. Calc. for C18H21N3Cl2Pt:
C, 39.63; H, 3.85; N, 7.71. Found: C, 38.37; H, 3.68; N,
3
Cꢂ
(br, PtNHamidine); 9.34 (d, 3JHH 10.4,
NHCH(CH3)2); 7.43ꢃ
7.41 (m, Ph). 13C {1H} NMR
(CD2Cl2): d 168.89 (s, NꢀC); 133ꢃ127 (m, Ph); 48.30
and 48.25 (s, ꢀCꢂNHCH(CH3)2 and NH2CH(CH3)2);
23.32 (s, ꢀCꢂNHCH(CH3)2); 24.10 (s, NH2CH(CH3)2.
/
NCH(CH3)2; 5.27 (br, JHPt 59.8, PtNHamine); 6.75
ꢀ
/
Cꢂ
/
/
/
/
/
/
7.39%. IR (KBr): n(NH) 3365, 3272 (m); n(Cꢁ
/
N) 2280;
N) 1582 (s). IR (PE): n(PtCl) 345, 321 (m). 1H
/
/
n(Cꢀ
/
NMR (CD2Cl2, 280 K): d 1.47, 1.34, 1.19 (t, CH3); 3.35,
3.62, 3.82 (q, CH2); 6.0, 5.75 (br, PtNH); 8.32, 7.0 (br,
2.3.4. Reaction with ButNH2. Synthesis of trans-
[PtCl2(NCPh){N(H)ꢀ
C(NHBut)Ph}] (9)
7.89 (m, Ph). 13C {1H} NMR (CD2Cl2): d
/
NH); 7.07ꢃ
165.99 (s, C ꢀ
47.71, 45.04, 44.51 (s, CH2); 13.85, 13.06, 11.72 (s,
CH3). 195Pt NMR: d ꢁ
2101.
/
Compound 9 was prepared by reaction of a suspen-
sion of trans-[PtCl2(NCPh)2] (300 mg, 0.635 mmol) in
CH2Cl2 (30 ml) with an equimolar amount of ButNH2
(334 ml, 3.17 mmol). The reaction mixture was stirred at
/
N); 134ꢃ
/
123 (m, Ph); 115.60 (s, Nꢁ
/
C ꢂ/Ph);
/
ꢁ10 8C for 3 h. The reaction mixture appeared to be a
/
suspension also after further addition of other 5 equiv.
(331 ml) of amine. The unreacted starting material was
filtered off and the remaining yellow solution was
reduced to 10 ml under vacuum. Addition of n-C6H14
(40 ml) at the low temperature gave a pale yellow solid,
which was stirred for an additional 30 min. It was then
2.4.3. Reaction with MeButNH. Synthesis of cis-
[PtCl2(NCPh){N(H)ꢀ
C(NMeBut)Ph}] (12)
/
Compound 12 was prepared reacting cis-
[PtCl2(NCPh)2] (200 mg, 0.423 mmol) with a 5 M excess
of MeButNH (254 ml, 2.12 mmol) at r.t. for 3 h. Yield:
130 mg, 55.0%. Anal. Calc. for C19H23N3Cl2Pt: C,
40.79; H, 4.11; N, 7.51. Found: C, 38.78; H, 3.99; N,
filtered off and washed with n-C6H14 (3ꢄ15 ml). The
/
solid residue was analyzed as 9. Yield: 264 mg, 76.2%.
Anal. Calc. for C18H21N3Cl2Pt: C, 39.85; H, 3.87; N,
7.75. Found: C, 40.96; H, 4.82; N, 8.43%. IR (KBr):
7.51%. IR (KBr): n(NH) 3300, 3194 (m); n(Cꢁ
(w); n(Cꢀ
N) 1592 (s). IR (PE): n(PtCl) 348, 358 (m). 1H
NMR (CD2Cl2): d 1.45, 1.48 (s, C(CH3)3); 3.24, 2.75 (s,
CH3); 6.10 (br, PtNH); 7.26ꢃ
7.95 (m, Ph). 13C {1H}
NMR (CD2Cl2): d 165.12 (s, C ꢀN); 135ꢃ127 (Ph);
60.78 (s, NꢂC(CH3)3); 37.50 (s, NꢂCH3); 28.18, 26.13
(s, NꢂC(CH3)3); the signal of the benzonitrile carbon
(NꢁC ꢂPh) was of too low intensity to be observed.
/
N) 2284
/
n(NH) 3340, 3240 (m); n(Cꢁ
/
N) not observed; n(Cꢀ
/
N)
1621 (s). IR (PE): n(PtCl) 320, 340 (m). 1H NMR
(CD2Cl2): d 1.48, 2.17, 1.16, 1.14 (s, NC(CH3)3); 6.79,
/
/
/
/
/
7.80 (br, PtNH); 8.07ꢃ
/
7.25 (m, Ph). 13C {1H} NMR
C); 109.71,
/
(CDCl3): d 170.38, 169.68, 170.21 (s, Nꢀ
/
/
/

U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ
/447
441
2.5. Reactions of trans-[PtCl2(NCPh)2] with secondary
amines
7.34%. IR (KBr): n(NH) 3306 (m); n(Cꢁ
/
N) 2270; n(Cꢀ
/
1
N) 1587 (s). IR (PE): n(PtCl) 339, 300 (m). H NMR
(CD2Cl2, 260 K): d 5.05, 3.41, 3.10, 3.06, 2.77, 2.48 (q,
CH2); 1.48, 1.30, 0.99 (t, CH3); 5.20 (br, PtNH); d
2.5.1. Reaction of trans-[PtCl2(NCPh)2] with Me2NH.
Synthesis of trans-[PtCl2{N(H)ꢀ
and trans-[PtCl2(NCMe){N(H)ꢀ
A suspension of cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with a
/
C(NMe2)Ph}2] (13)
masked (br, NH); d 7.3ꢃ
(CD3CN): d 167.03 (s, C ꢀ
NꢁC ꢂPh); 47.63, 42.22 (br, CH2); 13.66, 12.06 (br,
CH3). 195Pt NMR: d ꢁ
2108.
/
7.8 (m, Ph). 13C {1H} NMR
N); 136ꢃ128 (Ph); 110.54 (s,
/
C(NMe2)Ph}] (14)
/
/
/
/
/
/
20-fold excess of Me2NH (6.4 ml of a 2 M THF
solution, 12.8 mmol). The suspension became a yellow
solution after some minutes. The reaction mixture was
stirred for 7 h at the low temperature and then the
solvent was removed under reduced pressure to approxi-
mately 10 ml. Addition of Et2O (40 ml) at the low
temperature gave a pale yellow solid, which was stirred
for an additional 60 min. It was then filtered off at r.t.
2.5.3. Reaction with MeButNH. Synthesis of trans-
[PtCl2(NCPh){N(H)ꢀ
C(NMeBut)Ph}] (16)
Compound 16 was prepared reacting trans-
[PtCl2(NCPh)2] (200 mg, 0.423 mmol) and a 5 M excess
of MeButNH (254 ml, 2.12 mmol) at r.t. for 3 h. Yield:
150 mg, 63.4%. Anal. Calc. for C19H23N3Cl2Pt: C,
40.79; H, 4.11; N, 7.51. Found: C, 37.90; H, 4.25; N,
/
and washed with Et2O (3ꢄ5 ml). It was recrystallized
/
7.40%. IR (KBr): n(NH) 3420, 3231 (m); n(Cꢁ
(m); n(Cꢀ
N) 1591 (s). IR (PE): n(PtCl) 321, 345 (m). 1H
NMR (CD2Cl2): d 1.20, 1.49 (s, C(CH3)3); 2.76 (s, CH3);
/N) 2287
from CH2Cl2/Et2O and identified as 13. Yield: 300 mg,
84.0%. Anal. Calc. for C18H24N4Cl2Pt: C, 38.43; H,
4.27; N, 9.96. Found: C, 36.49; H, 3.94; N, 9.11%. IR
/
5
4.04 (s, JHPt
(m, Ph). 13C {1H} NMR (CD2Cl2): d 178.31 (s, C ꢀ
135ꢃ Ph); 56.44 (s,
B
/
0.1, CH3); 5.49 (br, PtNH); 7.37ꢃ
/
7.83
(Nujol mull): n(NH) 3280 (m); n(Cꢀ
/
N) 1595 (s); n(PtCl)
320 (m, br). 1H NMR (CD2Cl2, 250 K): d 3.10 and 2.86,
3.05 and 2.81, 2.92 and 2.70, 2.86 and 2.62 (s, NCH3);
5.12, 5.20, 5.45 (br, PtNH); d masked (br, NH). 13C
{1H} NMR (CD2Cl2): d 169.13, 168.39, 167.84, 165.34
/
N);
/
129 (m, Ph); 117.26 (s, Nꢁ
C(CH3)3); 37.53 (s, CH3), 25.67, 26.41 (s, C(CH3)3).
/
C ꢂ
/
(s, C ꢀ
CH3).
A suspension of trans-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) in CH2Cl2 (30 ml) was treated at ꢁ10 8C with a
twofold excess of Me2NH (0.6 ml of a 2 M THF
solution, 1.3 mmol). The suspension became a yellow
solution after a few minutes. The reaction mixture was
stirred for 3 h at the low temperature and then the
solvent was removed under reduced pressure to approxi-
mately 10 ml. Addition of Et2O (40 ml) at the low
temperature gave a pale yellow solid, which was stirred
for an additional 60 min. It was then filtered off at r.t.
/
N); 135ꢃ
/
121 (Ph); 42.69, 41.50, 40.93, 40.77 (s,
2.6. X-ray measurements and structure determination
/
2.6.1. Crystal data for C22H32N4Cl2Pt (4)
¯
Mwꢀ
bꢀ10.108(2), cꢀ
104.89(2), gꢀ108.99(2)8; Vꢀ
Dcalc
1.693 g cmꢁ3; F(000)ꢀ
0.71073 A; mꢀ
colorless crystal of dimensions 0.22ꢄ
/
394.4 triclinic, space group P1; aꢀ
/
10.918(2),
˚
/
/
6.020(1) A, aꢀ
606.8(2) A ; Zꢀ
304; l(Mo Ka)ꢀ
293(2) K. A prismatic
0.28ꢄ0.30 mm
/
83.46(2), bꢀ
/
3
˚
/
/
/
1,
ꢀ
/
/
/
/
6.01 mmꢁ1, Tꢀ
/
˚
/
/
was centered on a four-circle Philips PW1100 (Febo
System) [14] diffractometer operating in u/2u scan mode
with graphite-monochromated Mo Ka, following stan-
dard procedures. There were no significant fluctuations
of intensities other than those expected from Poisson
statistics. The intensity data were corrected for Lp
effects and for absorption, as described by North et al.
[15]. The structure was solved by heavy atoms methods
[16]. Refinement was carried out by full-matrix least-
squares. The t-butyl group is found statistically dis-
tributed on two positions with occupancy factors of 0.6
and 0.4, respectively, the function minimized was
S w(Fo2 ꢁFc2)2; with weighting scheme wꢀ1=[s2(Fo2)ꢂ
(0:0320P)2 ꢂ1:17P]; where Pꢀmax(Fo2 ꢂ2Fc2)=3: All
non-hydrogen atoms were refined with anisotropic
thermal parameters. The H-atoms were placed in
calculated positions with fixed, isotropic thermal para-
meters (1.2 Uequiv of the parent carbon atom). wRꢀ
and washed with Et2O (3ꢄ5 ml). It was recrystallized
/
from CH2Cl2/Et2O and identified as 14. Yield: 230 mg,
70.0%. Anal. Calc. for C16H17N3Cl2Pt: C, 37.13; H,
3.29; N, 8.12. Found: C, 37.49; H, 3.36; N, 8.03%. IR
(Nujol mull): n(NH) 3276 (m); n(Cꢁ
/
N) 2282 (m); n(Cꢀ
/
1
N) 1591 (s); n(PtCl) 317 (m, br). H NMR (CD2Cl2): d
3.07, 2.87 (m, NCH3); 4.20 (br, PtNH); 5.25 (br, NH);
7.40ꢃ
(s, C ꢀ
signal of the benzonitrile carbon (Nꢁ
low intensity to be observed.
/
7.75 (m, Ph). 13C {1H} NMR (CD2Cl2): d 173.52
/
N); 139ꢃ/130 (m, Ph); 47.30, 42.80 (br, CH3); the
/
C ꢂPh) was of too
/
2.5.2. Reaction with Et2NH. Synthesis of trans-
[PtCl2(NCPh){N(H)ꢀC(NEt2)Ph}] (15)
/
Compound 15 was prepared as described previously
for 1 starting from cis-[PtCl2(NCPh)2] (300 mg, 0.635
mmol) and a 5 M excess of Et2NH (329 ml, 3.17 mmol).
Yield: 213 mg, 61.5%. Anal. Calc. for C18H21N3Cl2Pt:
C, 39.63; H, 3.85; N, 7.71. Found: C, 38.37; H, 3.92; N,
fS [w(Fo2 ꢁFc2)2]=S [w(Fo2)2]g1=2 ꢀ0:060; Sꢀ
/
1.065, and
conventional Rꢀ0.023, based on the F values of 2898
/
reflections having Fo2 ꢀ2s(Fo2):
/

442
U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
Structure refinement and final geometrical calcula-
tions were carried out with SHELXL-97 [16] program,
drawings were produced using ORTEP II [17].
ð1Þ
The analogous reaction of cis-[PtCl2(NCPh)2] with
the sterically hindered ButNH2 proceeds with the
inversion of the geometry at the metal center affording
3. Results and discussion
the
di-amidine
complex
trans-[PtCl2{Z-N(H)ꢀ
/
C(NHBut)Ph}2] (4) (Eq. (2)), which has been character-
ized also by an X-ray diffraction analysis.
3.1. Reactions of cis- and trans-[PtCl2(NCPh)2]
complexes with primary amines
In contrast with the reactions with the acetonitrile
derivatives [11,12], the corresponding reactions of the
benzonitrile complexes cis- and trans-[PtCl2(NCPh)2]
with primary and secondary aliphatic amines afford, on
the basis of 1H NMR data, a complex mixture of
isomers, which can be referred to the structures reported
in Scheme 2. The Z and Z? isomers show the presence of
ð2Þ
the Nꢂ
/
H and Nꢂ
/
R groups, respectively, close to the
Such a cis to trans isomerization was not previously
observed in the addition reactions of amines as well as of
other nucleophiles [7,11] to the Pt(II) nitrile complexes
metal center; thus, it is expected that they would
experience a deshielding effect by the metal that will
cause a downfield shift of the corresponding signals in
the 1H NMR spectra [3a]. It is also expected, as
previously reported [11,12], that the Z configuration
will likely predominate over Z? since the former will be
cis-[PtCl2(NCR)2] (RꢀMe, Ph) and it is likely due to
/
the sterical hindrance of the two amidines. Eq. (2) was
1
also followed by H NMR spectroscopy in CD2Cl2 at
ꢁ10 8C using a fivefold molar excess of amine with
/
stabilized by the formation of strong intramolecular Nꢂ
/
respect to the metal complex. The immediate appear-
ance of a singlet at 1.08 ppm was attributed to the t-
butyl resonance of the amidine ligands in cis-
HÁ Á ÁCl hydrogen bonds involving the NH amino proton
and an adjacent chlorine atom bonded to the metal
center. On the other hand, the presence of more down-
field shifted signals in the region of the phenyl protons
would suggest the presence of E and E? isomers, where
the ortho protons of the phenyl ring are now close to the
metal center [3a].
[PtCl2{N(H)ꢀ
/
C(NHBut)Ph}2], which is initially formed.
The intensity of the signal at 1.08 ppm was observed to
slowly decrease with time (ca. 3 h), while a new
resonance at 1.15 ppm formed, which corresponds to
the t-butyl groups of the amidine ligands in the final
complex 4.
Thus, cis-[PtCl2(NCPh)2] reacts with an excess of the
primary aliphatic amines RNH2 (Rꢀ
10 8C in CH2Cl2 to give in high yield the di-amidine
derivatives cis-[PtCl2{N(H)ꢀC(NHR)Ph}2] (1ꢃ3) (Eq.
/
Me, Et, Pri) at
The molecular structure of 4 shows a perfect trans
orientation of the ligands with the metal ion lying in an
inversion center due to the crystallographic imposed Ci
symmetry. A view of the molecule with the atom
numbering scheme is shown in Fig. 2, while significant
bond distances and angles are reported in Table 2. The
molecules in the crystal cell are separated only by Van
der Waals contacts as shown in Fig. 3. The square
planar coordination geometry around Pt is character-
ꢁ
/
/
/
(1)), where the amidine ligands are present in different
configurations as summarized in Table 1. A typical
example of the 1H NMR spectrum of an amidine
complex is reported in Fig. 1.
ized by the values of the Ptꢂ
/
N and Ptꢂ
/
Cl bond distances
˚
of 2.015(3) and 2.306(1) A, respectively, in agreement
with literature data [11,12] for similar Pt(II) derivatives
with coordinated amidine ligands. The amidine ligands
are shown to be in the Z configuration. The molecular
structure is characterized by two strong intramolecular
hydrogen bonds involving the N(2)ꢂ
chlorine atom (Cl?) (? at ꢁx, ꢁy, ꢁ
centrosymmetrically related part of the molecule. The
/H proton and the
/
/
/z) as well as the
˚
N(2)Á Á ÁCl? separation is 3.094(4) A, while the N(2)ꢂ
/
˚
H(2)Á Á ÁCl? contact is 2.17(7) A with a N(2)ꢂH(2)Á Á ÁCl?
/
angle of 1758. It is likely that this interaction, coupled
with the steric hindrance of the t-butyl group, may
Scheme 2.

U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ
/447
443
Table 1
Selected 1H NMR data for compounds 1ꢃ
/
9
Compound
R group
Z (%)
Z? (%)
E, E? (%)
3
2.84 d (60), JHH 5.10
3
3.03 d (20), JHH 4.50
3
2.38 d (20), JHH 4.45, Ph: 8.20 m, 6.96 m
1
2
CH3
CH2CH3
CH2CH3
CH(CH3)2
C(CH3)3
CH3
3.15 m (60)
1.15 t (60), JHH 7.10
3.35 m (20)
0.95 t (20), JHH 7.02
2.75 m (20)
1.29 t (60), JHH 7.20, Ph: 8.20 m, 6.98 m
3
3
3
3
4
5
6
3.47 m (90)
1.15 s (90)
2.78 d (85), JHH 4.00
3.95 m (5)
1.43 s (5)
2.92 d (15), JHH 4.60
3.20 m (5), Ph: 8.13 m, 7.00 m
0.96 s (5), Ph: 8.15 m, 7.00 m
3
3
CH2CH3
CH2CH3
CH(CH3)2
C(CH3)3
3.09 q (40)
1.13 t (40), JHH 7.22
3.21 q (40)
1.17 t (40), JHH 7.00
2.65 m (20)
1.11 t (20), JHH 7.05, Ph: 6.97 m, 7.72 m, 8.11 m
3
3
3
3
1.15 d (68), JHH 6.30
3
1.22 d (30), JHH 6.31
3
1.01 d (2), JHH 6.02, Ph: 7.64 m
7
9
1.48 s (28)
2.17 s (8)
1.16 s (32), 1.14 s (32), Ph: 8.07 m, 7.25 m
determine a wider opening of the angle Ptꢂ
/
N(1)ꢂ/C(1)
(138.7(3)8) with respect to that found in the correspond-
ing methyl derivative
trans-[PtCl2{Z-N(H)ꢀ
C(NHMe)Me}2] [11a] of 131.9(7)8. Short contacts
/
˚
ClÁ Á ÁHꢂ
both derivatives [(C6H4CH2NHMe2ꢂ
MPP-P,OMe)](PF6) and [(C6H4CH2NHMe2ꢂ
/
N of the order of 2.16 A have been found in
C2)PdCl(MD-
C2)-
/
/
PdCl(TDMPP-P,OMe)](PF6) [18]. The six-membered
ring involving Pt, N(1), C(1), N(2), H(2), Cl? is about
planar, the deviations from least-square plane ranging
˚
Fig. 1. 1H NMR spectrum at 270 K (CD2Cl2) of complex 1.
from ꢁ
The N(1)ꢂ
same order of magnitude of the C(1)ꢂ
/
0.029(3) to 0.020(2) A.
˚
/
C(1) bond distance of 1.304(4) A is of the
N(2) bond length
of 1.321(5) A, suggesting an extensive electron deloca-
lization along the N(1)ꢂC(1)ꢂN(2) system from which
/
˚
/
/
the phenyl group is rotated by 105.3(2)8. Similar values
for the same type of distances have been found in the
previously quoted derivative trans-[PtCl2{Z-N(H)ꢀ
C(NHMe)Me}2] [11a], which shows equal N(1)ꢂC(1)
N(2) values of 1.32(1) A, even though in the
/
/
˚
and C(1)ꢂ
presence of a longer intramolecular interaction of 2.61 A
(with a N(2)ꢂ
/
˚
/
HÁ Á ÁCl? angle of 1278) between the N(2)ꢂ
/
H proton and the adjacent chlorine atom, with respect
to that found in the present derivative (see above).
The results reported here seem to suggest that the
electron delocalization is peculiar of this type of ligands,
Fig. 2. ORTEP view of the molecule trans-[PtCl2{Z-N(H)ꢀ
C(NHBut)Ph}2] (4) (ellipsoids are at 40% probability); the t-butyl
positions are those with the higher occupancy factor.
/
as shown by the reported examples, where the Nꢂ
/
C(R)ꢂ
/
N system is about planar in analogy with the same
evidence reported for the imino ether moiety in the free
ligand [19].
Table 2
The nitrile complex trans-[PtCl2(NCPh)2], under
experimental conditions analogous to those used for
the reactions of the parent cis complex, reacts with a
˚
Relevant bond distances (A) and angles (8) for trans-[PtCl2{Z-
N(H)ꢀC(NHBut)Ph}2] (4)
Bond lengths
PtꢂCl
fivefold excess of RNH2 (Rꢀ
amidine derivatives trans-[PtCl2{N(H)ꢀ
(RꢀMe, 5; Etꢀ
6) (Scheme 3), for which the 1H
/
Me, Et) to give the di-
2.306(1)
1.304(4)
1.485(5)
PtꢂN(1)
N(2)ꢂC(1)
C(1)ꢂC(2)
2.015(3)
1.321(5)
1.497(4)
/
C(NHR)Ph}2]
N(1)ꢂC(1)
N(2)ꢂC(8)
/
/
NMR spectra showed the formation of Z and Z?
isomers (Table 1). On the other hand, the corresponding
reaction with PriNH2 gives different products depending
on the amine concentration. Thus, with a fivefold excess
of the amine, a mixture of the di-amidine derivative
Bond angles
ClꢂPtꢂN(1)
82.3(1)
131.7(4)
122.0(3)
113.1(7)
PtꢂN(1)ꢂC(1)
138.7(3)
121.5(3)
116.4(3)
114.0(8)
C(1)ꢂN(2)ꢂC(8)
N(2)ꢂC(1)ꢂC(2)
N(2)ꢂC(8)ꢂC(10)
N(1)ꢂC(1)ꢂN(2)
N(1)ꢂC(1)ꢂC(2)
N(2)ꢂC(8)ꢂC(9)

444
U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
Fig. 3. Packing diagram for trans-[PtCl2{Z-N(H)ꢀ
C(NHBut)Ph}2] (4) viewed down the c-axis.
/
Complexes 1ꢃ9 have been characterized by micro-
/
1
analysis, IR, H and 13C {1H} NMR (see Section 2). In
the 195Pt {1H} NMR spectrum of 1, the observed broad
resonance (d ꢁ
/
2039) lies within the range (d from
ꢁ
/
2028 to ꢁ2091) [20] exhibited by related neutral
/
dichloroplatinum(II) complexes with imine ligands
formed upon nucleophilic addition of oximes to ligated
nitriles. The IR spectra (KBr pellets or Nujol mulls)
show the Nꢂ
range 3530ꢃ
appears in the range 1624ꢃ
stretchings in the range 310ꢃ
/
H vibrations of the amidine ligands in the
3190 cmꢁ1, while the Cꢀ
N absorption
1603 cmꢁ1 and the Ptꢂ
Cl
340 cmꢁ1
/
/
Scheme 3.
/
/
/
.
trans-[PtCl2{N(H)ꢀ
/
C(NHPri)Ph}2] (7) with the dicatio-
trans-[Pt(PriNH2)2{N(H)ꢀ
nic complex
/
C(NHPri)-
Ph}2][Cl]2 (8), having two coordinated amine molecules,
was formed (Scheme 3). This latter complex could be
obtained in a pure form by reaction of the trans di-
nitrile derivative with a 50-fold excess of the amine. An
analogous behavior was previously observed in the
reaction of trans-[PtCl2(NCMe)2] with PriNH2 [11b].
The reaction of trans-[PtCl2(NCPh)2] with ButNH2,
even in the presence of a large excess of the amine, gave
the mono-amidine derivative trans-[PtCl2(NCPh)-
3.2. Reactions of cis- and trans-[PtCl2(NCPh)2]
complexes with secondary amines
The reaction at low temperature of cis-
[PtCl2(NCPh)2] with a fivefold excess of Me2NH leads
to the formation of the di-amidine complex cis-
[PtCl2{N(H)ꢀ
/
C(NMe2)Ph}2] (10), which is present,
1
according to H NMR data, as a mixture of E and Z
isomers (Scheme 4, Table 3). It is noteworthy that in the
case of the reactions of cis-[PtCl2(NCMe)2] with
Me2NH, under the same experimental conditions, the
{N(H)ꢀ
/
C(NHPri)Ph}] (9), whose 1H NMR spectrum
shows the simultaneous presence of the Z, Z?, E and E?
isomers almost in the same amounts (Table 1).
di-amidine complex cis-[PtCl2{N(H)ꢀ
/
C(NMe2)Me}2],

U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ
/447
445
Scheme 4.
Scheme 5.
having both the amidine ligands only in the E config-
uration, was formed [11b].
4. Concluding remarks
The results reported above show that the addition
reactions of primary and secondary aliphatic amines to
The reactions of cis-[PtCl2(NCPh)2] with the more
hindered amines Et2NH and MeButNH afforded only
the Cꢁ
/
N triple bond of the benzonitrile ligands in cis-
the mono-amidine derivatives cis-[PtCl2(NCPh){N(H)ꢀ
/
and trans-[PtCl2(NCPh)2] complexes afford the corre-
sponding amidine derivatives thus paralleling the ob-
served reactivity of the acetonitrile ligands in cis- and
trans-[PtCl2(NCMe)2]. However, while the reactions of
the latter complexes with primary or secondary amines
afford amidine complexes exclusively with Z or E
configuration, respectively, those with the benzonitrile
ligands always afford a mixture of Z and E isomers as
reported in Scheme 2 and Tables 1 and 3. This
observation is in agreement with previous studies
performed on the reactions of cis- and trans-
[PtCl2(NCPh)2] complexes with MeOH under basic
conditions to yield the imino ether complexes cis- and
C(NRR?)Ph}] [RꢀR?ꢀEt, 11; RꢀMe, R?ꢀ
/
/
/
/
But, 12],
even in the presence of a large excess of the amine
(Scheme 4).
The reactions of trans-[PtCl2(NCPh)2] with twenty- or
twofold of Me2NH yields the di-amidine complex trans-
[PtCl2{N(H)ꢀ
/
C(NMe2)Ph}2] (13) or the mono-amidine
derivative
trans-[PtCl2(NCPh){N(H)ꢀC(NMe2)Ph}]
/
(14), respectively, as illustrated in Scheme 5. Similar
type of complexes, i.e. 15 and 16, were obtained (see
Scheme 5) also by reaction with the more sterically
hindered amines Et2NH and MeButNH, respectively.
Complexes 10ꢃ16 have been characterized by micro-
/
analysis, IR, 1H and 13C {1H} NMR (see Section 2). The
195Pt {1H} NMR spectra of 11 and 15 display broad
trans-[PtCl2{N(H)ꢀ
/C(OMe)Ph}2] [3a], where the ob-
resonances at d ꢁ
are only very slightly higher field than that of 1 (see
above), approaching those reported (d from ꢁ2104 to
/
2101 and ꢁ
/
2108, respectively, which
served Z to E isomerization takes place about the Cꢀ
/N
double bond being promoted by MeOꢁ ions. However,
no evidence of such isomerization has been obtained by
NMR studies in the corresponding reactions with
amines. It is noteworthy to mention that different
isomers have been also obtained in the reactions of
cis- and trans-[PtCl2(NCPh)2] with aziridine [5g].
/
ꢁ2210) [21] for neutral dichloroplatinum(II) complexes
/
with D4-1,2,4-oxadiazoline ligands derived from cy-
cloaddition of nitrones to coordinated nitriles. The IR
spectra show the Nꢂ
in the range 3480ꢃ
3194 cmꢁ1, while the Cꢀ
tion appears in the range 1590ꢃ
1582 cmꢁ1 and the Ptꢂ
Cl stretchings in the range 300ꢃ
358 cmꢁ1
/H vibrations of the amidine ligands
/
/
N absorp-
The addition reactions described in this paper confirm
previous studies [11,12] that the dinitrile complexes of
cis geometry are more reactive (under analogous
/
/
/
.
Table 3
Selected 1H NMR data for compounds 10ꢃ
/16
Compound
R and R? groups
E, E? (%)
Z, Z? (%)
10
11
RꢀR?ꢀCH3
RꢀR?ꢀCH2CH3
RꢀR?ꢀCH2CH3
RꢀCH3
2.38 s and 2.70 s (33)
3.35 q, 3.21 q (60)
3.06 s and 2.88 s (33), 3.10 s and 2.58 s (33)
3.82 q (40)
3
3
3
1.47 t, JHH 7.30; 1.17 t, JHH 7.10 (60)
2.75 s (70)
1.45 s (70)
1.19 t, JHH 7.14 (40)
3.24 s (30)
1.48 s (30)
12
R?ꢀBut
13
14
15
RꢀR?ꢀCH3
RꢀR?ꢀCH3
RꢀR?ꢀCH2CH3
RꢀR?ꢀCH2CH3
RꢀCH3
2.92 s and 2.70 s, 2.86 s and 2.62 s (70)
2.87 s (70)
3.06 q, 3.41 q (80)
3.10 s and 2.86 s, 3.05 s and 2.81 s (30)
3.09 s (30)
3.10 q, 5.05 q (20)
3
3
3
3
1.30 t, JHH 7.20; 0.99 t, JHH 7.13 (80)
2.76 s (70)
1.49 s (70)
1.48 t, JHH 7.00; 1.30 t, JHH 7.13 (20)
5
4.04 s, JHPt 0.06 (30)
16
R?ꢀBut
1.20 s (30)

446
U. Belluco et al. / Inorganica Chimica Acta 334 (2002) 437ꢃ447
/
kin, J. Chem. Soc., Dalton Trans. (1999) 4083;
(h) G. Wagner, A.J.L. Pombeiro, Y.N. Kukushkin, T.B. Pakho-
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experimental conditions) than the corresponding trans
isomers. Finally, it is also observed that the addition
reactions are influenced both by the sterical hindrance of
the R group(s) of the entering amine and the nature
(primary or secondary) of the amine.
(i) V.Yu. Kukushkin, I.V. Ilichev, G. Wagner, J.J.R. Frausto da
Silva, A.J.L. Pombeiro, J. Chem. Soc., Dalton Trans. (1999) 3047;
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Hermann, G. Wagner, A.J.L. Pombeiro, Inorg. Chem. 37 (1998)
6511.
5. Supplementary material
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379;
(b) L. Calligaro, R.A. Michelin, P. Uguagliati, Inorg. Chim. Acta
76 (1983) L83;
Tables of additional material, including atomic co-
ordinates, full listing of bond lengths/angles and aniso-
tropic thermal parameters are available from the
Cambridge Crystallographic Data Centre, CCDC No.
178619 for compound 4. Copies of this information can
be obtained free of charge from The Director, CCDC,
(c) P. Uguagliati, U. Belluco, R.A. Michelin, P. Guerriero, Inorg.
Chim. Acta 81 (1984) 61;
(d) C.A. Amodio, K.B. Nolan, Inorg. Chim. Acta 113 (1986) 27;
(e) C.A. Amodio, D.J. Eastwood, Inorg. Chim. Acta 122 (1986)
L3;
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(1986) 1180;
12 Union Road, Cambridge, CB2 1EZ, UK (fax: ꢂ44-
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk or www:
http://www.ccdc.cam.ac.uk).
/
(g) R.A. Michelin, M. Mozzon, R. Bertani, F. Benetollo, G.
Bombieri, R.J. Angelici, Inorg. Chim. Acta 222 (1994) 327.
[6] D.A. Garnovskii, V.Yu. Kukushkin, M. Haukka, G. Wagner,
A.J.L. Pombeiro, J. Chem. Soc., Dalton Trans. (2001) 560.
[7] (a) R.A. Michelin, R. Bertani, M. Mozzon, G. Bombieri, F.
Benetollo, R.J. Angelici, Organometallics 10 (1991) 1751;
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Acknowledgements
R.A.M thanks MURST Cofin-99 and the University
of Padova for financial support.
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