The metalla-Pinner reaction between Pt(IV)-bound nitriles and alkylated oxamic and oximic forms of hydroxamic acids

Article abstract of DOI:10.1039/b406600f

The nitrile ligands in the platinum(IV) complexes trans-[PtCl ₄(RCN)₂] (R = Me, Et, CH₂Ph) and cis/trans[PtCl₄(MeCN)(Me₂SO)] are involved in a metalla-Pinner reaction with N-methylbenzohydroxamic acid (N-alkylated form of hydroxamic acid, hydroxamic form; F1), PhC(=O)N(Me)OH, to achieve the imino species [PtCl₄{NH=C(R)ON(Me)C(=O)Ph}₂] (1-3) and [PtCl₄{NH=C(Me)ON(Me)C(=O)Ph}(Me₂SO)] (7), respectively. Treatment of trans-[PtCl₄-(RCN)₂] (R = Me, Et) and cis/trans-[PtCl₄(MeCN)(Me₂SO)] with the O-alkylated form of a hydroxamic acid (hydroximic form), i.e. methyl 2,4,6- trimethylbenzohydroximate, 2,4,6-(Me₃C₆H ₂)C(OMe)=NOH (F2A), allows the isolation of [PtCl₄{NH=C(R) ON=C(OMe)(2,4,6-Me₃C₆H₂)}2] (5,6) and [PtCl₄{NH=C(Me)ON=C(OMe)(2,4,6-Me₃C₆H ₂)}-(Me₂SO)] (8), correspondingly. In accord with the latter reaction, the coupling of nitriles in trans-[PtCl 2(EtCN)₂] with methyl benzohydroximate, PhC(OMe)=NOH (F2B), gives [PtCl ₄{NH=C(Et)ON=C(OMe)Ph}₂] (4). The addition proceeds faster with the hydroximic F2, rather than with the hydroxamic form F1. The complexes 1-8 were characterized by C, H, N elemental analyses, FAB₊ mass-spectrometry, IR, ¹H and ¹³C{¹H} NMR spectroscopies. The X-ray structure determinations have been performed for both hydroxamic and hydroximic complexes, i.e. 2 and 6, indicating that the imino ligands are mutually trans and they are in the E-configuration.

Full text of DOI:10.1039/b406600f

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
The metalla-Pinner reaction between Pt(IV)-bound nitriles and
alkylated oxamic and oximic forms of hydroxamic acids
Konstantin V. Luzyanin,a,b Vadim Yu. Kukushkin,*b Matti Haukka,c J. J. R. Fraústo da Silvaa
and Armando J. L. Pombeiro*a
a
Centro de Química Estrutural, Instituto Superior Técnico, Complexo I, Av. Rovisco Pais,
1049-001 Lisboa, Portugal. E-mail: pombeiro@ist.utl.pt
Department of Chemistry, St.Petersburg State University, 198504, Stary Petergof,
b
Russian Federation. E-mail: kukushkin@VK2100.spb.edu
Department of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101, Joensuu, Finland.
c
E-mail: matti.haukka@joensuu.fi
Received 4th May 2004, Accepted 1st July 2004
First published as an Advance Article on the web 23rd July 2004
The nitrile ligands in the platinum(IV) complexes trans-[PtCl4(RCN)2] (R = Me, Et, CH2Ph) and cis/trans-
[PtCl4(MeCN)(Me2SO)] are involved in a metalla-Pinner reaction with N-methylbenzohydroxamic acid (N-alkylated form
of hydroxamic acid, hydroxamic form; F1), PhC(O)N(Me)OH, to achieve the imino species [PtCl4{NHC(R)ON-
(Me)C(O)Ph}2] (1–3) and [PtCl4{NHC(Me)ON(Me)C(O)Ph}(Me2SO)] (7), respectively. Treatment of trans-[PtCl4-
(RCN)2] (R = Me, Et) and cis/trans-[PtCl4(MeCN)(Me2SO)] with the O-alkylated form of a hydroxamic acid (hydroximic
form), i.e. methyl 2,4,6-trimethylbenzohydroximate, 2,4,6-(Me3C6H2)C(OMe)NOH (F2A), allows the isolation of
[PtCl4{NHC(R)ONC(OMe)(2,4,6-Me3C6H2)}2] (5, 6) and [PtCl4{NHC(Me)ONC(OMe)(2,4,6-Me3C6H2)}-
(Me2SO)] (8), correspondingly. In accord with the latter reaction, the coupling of nitriles in trans-[PtCl4(EtCN)2] with
methyl benzohydroximate, PhC(OMe)NOH (F2B), gives [PtCl4{NHC(Et)ONC(OMe)Ph}2] (4). The addition
proceeds faster with the hydroximic F2, rather than with the hydroxamic form F1. The complexes 1–8 were characterized
by C, H, N elemental analyses, FAB+ mass-spectrometry, IR, 1H and 13C{1H} NMR spectroscopies. The X-ray structure
determinations have been performed for both hydroxamic and hydroximic complexes, i.e. 2 and 6, indicating that the
imino ligands are mutually trans and they are in the E-configuration.
performed at kinetically labile metal centres, e.g. Co(III),14 Ni(II)15
Introduction
and Zn(II)16,17—these systems became of a more applied character
insofar as they opened up attractive routes to synthesis of ami-
dines,14 acyl amides,15 imidoylamidines15 and to efficient catalytic
conversion of RCN to the corresponding carboxamides.16,17 The
latter findings gave a new strong motivation for further exploration
of the reactions with NOH-type nucleophiles.
In general, the metal-mediated interaction between two organic
molecules and/or ligands to give a more complex molecular
fragment is of basic scientific interest and also has potential
industrial applications.1 In particular, transformations of organo-
nitriles involving metal centres play an important role in both
laboratory and industry due to the well-recognized chemical
versatility of the RCN species.
Recently, as a continuation of our studies on oxime and hydroxy-
lamine reactions with (RCN)[M] complexes, we attempted to
employ another type of nucleophile, i.e. hydroxamic acids (where
the N amide atom in the sp2 hybridization18 is different to the sp3
amine nitrogen in oximes and hydroxylamines) (HA1  HA2,
Scheme 1), and observed a coupling resulting in the imino com-
plexes [PtCl4{NHC(Et)ONC(OH)(C6H4R)}2], which derived
from a novel metalla-Pinner18 reaction. The results obtained18 give
collateral evidence in favor of a concurrent formation of the two
coordinated tautomers (which correspond to oxamic HA1 and
oximic HA2 forms of the nucleophile, Scheme 1), in a ratio depend-
ing on both experimental conditions and type of hydroxamic acid
employed. For a better understanding of the nitrile–hydroxamic acid
coupling we decided to perform a further study and to investigate
reactions between the two tautomeric forms (F1 vs. F2, Scheme 2)
of hydroxamic acids ‘frozen’ by N- or O-alkylation, respectively.
Nitrile ligands usually do not behave either as strong -donors
or effective -electron acceptors and this imparts them with a
labilecharacterand, consequently, theircomplexeshavebeenwidely
applied as convenient starting materials in coordination chemistry.2
However, in spite of their limited coordination ability, RCN species
can be effectively activated by ligation to a metal centre, which often
results in an enhancement of the electrophilicity of the unsaturated
nitrile carbon atom, thus promoting addition of a nucleophile which
results in a great variety of compounds with C–O, C–S and C–N
bonds of various types. The application of organonitrile transition
metal complexes in synthetic chemistry has been surveyed in a num-
ber of reviews2–7 including the ones written by two of us.2,6,7
One of the recent themes in the reactions of RCN ligands is
the application of nucleophiles with NOH moieties.6 Thus, our
group has observed a coupling between platinum(IV) complexes
of the type [PtCl4(RCN)2] and both ‘simple’ and functionalized
oximes (R1R2CNOH8), vic-dioximes [HON(spacer)NOH9]
or dialkylhydroxylamines (R1R2NOH10) which led to the for-
mation of [PtCl4{NHC(R)ONCR1R2}2], [PtCl4{NHC(R)-
ON(spacer)NOH})2]
and
[PtCl4{NHC(R)ONR1R2}2],
respectively. This RCN–‘NOH’ coupling has also been extended to
Re(IV)11 and Rh(III)12 organonitrile complexes. We also found that
Ag+ or Cu2+ ions catalyze the coupling of dialkylcyanamides with
oximes at a Pt(II) centre.13
It is worthwhile to mention that in the initial stage of our
studies, the reactions between nitriles and oximes observed at inert
metal centres had purely a basic character, whereas later—being
Scheme 1
2 7 2 8
D a l t o n T r a n s . , 2 0 0 4 , 2 7 2 8 – 2 7 3 2
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 4

View Article Online
Characterization of the complexes
Complexes 1–8 were isolated in 75–90% yields in both conven-
tional thermal and microwave syntheses. Elemental analyses
1
(C, H, N), FAB-MS, IR and H and 13C{1H} NMR spectra, and
X-ray data for 2 and 6 (see below) are in a good agreement with
the proposed structure of Pt(IV) complexes with the newly formed
imino ligands.
In the IR spectra, 1–8 show no bands of (CN) in the range of
2270–2400 cm−1 [for trans-[PtCl4(EtCN)2]19 (CN) at 2340 cm−1]
but display one intense band in the range between 1640 and
1670 cm−1 due to (CN) stretching vibrations from the imino
ligands NHC(R)ON(Me)C(O)R′ (1–3, 7) or two intense
bands in the ranges of 1640–1670 and 1610–1630 cm−1 (4–6, 8)
assigned, in the latter case, to two different (CN) stretches in
the imino species. All these observations are in a good agreement
with those for related addition products of oxime (e.g. trans-
[PtCl4{NHC(Me)ONCMe2}2]8) and hydroxamic acids (e.g.
trans-[PtCl4{NHC(Et)ONC(OH)(Ph)}2]18) to nitriles bound to
Pt(IV) centres.
1
In the H NMR spectra, 1–3 and 7 exhibit a signal from the
alkyl group of [N(Me)C(O)Ph] in the range of 3.25–3.40 ppm,
whereas 4–6 and 8 display the signal of the methoxy group
from [NC(OMe)R′] which emerges in the range of 3.50–
3.60 ppm. In addition, 1–8 display a broad peak in the range
of 8.20–8.80 ppm from the imine hydrogen of the imino ligand
and these data correspond well to those found for the imino-
complexes [PtCl4{NHC(R)R′}2] (R′ = ONR2″,10 ONCR2″,8
ONHC(O)R″18). This low field position of the NH signal in the
spectra is coherent with the position of the CNH proton involved
in hydrogen bond in solution,8 which is also detected in the crystal
structure of 6.
Scheme 2
The essential goals of this work were two-fold: (i) to shed
light on the mechanism of the nitrile–hydroxamic acid coupling
and (ii) to study the coupling between ligated nitriles and a
novel type of nucleophile such as OMe-functionalized oxime
(F2, Scheme 2). All obtained results are reported in this
article.
The 13C{1H} NMR spectra of 1–8 display no signal of the
carbon from the CN group (usually appears at 115–125 ppm,
e.g. at 119 ppm for trans-[PtCl4(EtCN)2]19) of the starting material,
whereas a new signal from the CN group emerges in the
typical8–10 range of 160–170 ppm. Complexes 1–3 and 7 display
the signal of the methyl group from [N(Me)C(O)] in the range
of 37–47 ppm, while 4–6 and 8 exhibit the peak from the methoxy
group [NC(OMe)R′] at a lower field (57–61 ppm).
Results and discussion
Platinum(IV)-mediated nucleophilic additions
The coupling between the nitriles ligated to a Pt(IV) centre and
hydroxamic (N-methylbenzohydroxamic acid F1) and hydroxi-
mic (methyl 2,4,6-trimethylbenzohydroximate F2A and methyl
benzohydroximate F2B) tautomeric forms of hydroxamic acids,
‘frozen’ by alkylation, readily occurs in CH2Cl2 to accomplish
complexes 1–6 (Scheme 2) and [PtCl4{NHC(Me)ON(Me)C-
(O)Ph}(Me2SO)] (7) and [PtCl4{NHC(Me)ONC(OMe)(2,4,
6-Me3C6H2)}(Me2SO)] (8) (see Experimental).
The propionitrile complex trans-[PtCl4(EtCN)2] is well soluble
in dichloromethane and the reactions can be conducted in homo-
geneous liquid phase thus allowing the qualitative comparison
of reaction rates of the two forms. Hence, trans-[PtCl4(EtCN)2]
reacts with F2A or F2B for ca. 15 min at 20–25 °C to give [PtCl4-
{NHC(Et)ONC(OMe)(2,4,6-Me3C6H2)}2] (6) and [PtCl4-
{NHC(Et)ONC(OMe)Ph}2] (4), respectively, while treatment
of trans-[PtCl4(EtCN)2] with F1, to furnish [PtCl4{NHC(Et)-
ON(Me)C(O)Ph}2] (2), proceeds under heating at 45–47 °C
for ca. 2–3 h. These observations illustrate a considerable differ-
ence in the reactivity for both types of reagents indicating that the
addition proceeds easily with the hydroximic F2, rather than with
the hydroxamic form F1.
X-ray structure determinations
The X-ray structure determinations have been performed for
both hydroxamic and hydroximic complexes, i.e., trans-[PtCl4-
{NHC(Et)ON(Me)C(O)Ph}2] (2) and trans-[PtCl4{NHC-
(Et)ONC(OMe){C6H2(2,4,6-Me3)}2] (6) (Figs. 1, 2).
For all other cases (i.e. in trans-[PtCl4(RCN)2] (R = Me, CH2Ph)
with F1 to give 1 and 3, respectively; in trans-[PtCl4(MeCN)2]
with F2A to yield 5; and in cis/trans-[PtCl4(MeCN)(Me2SO)]
with F1 and F2A to achieve 7 and 8, correspondingly) the reac-
tions are heterogeneous owing to the rather poor solubility of
the Pt(IV) starting materials and they all proceed under heating
(45–47 °C) for ca. 2–3 h. We anticipate that the rate determining
step of the overall process is then the dissolution of the starting
nitrile complexes. It is important that the heterogeneous reactions
can be drastically accelerated by microwave irradiation (100 W)
and good yields of 1, 3, 5, 7 and 8 can be achieved for 20 min at
45–47 °C.
Fig. 1 Molecular structure of 2. The thermal ellipsoids are drawn at the
50% probability level.
The coordination polyhedra of both compounds are slightly
distorted octahedra; the iminoacyl ligands are mutually trans and
both of them are in the E-configuration. The Pt–Cl [2.3151(10)–
2.3191(10) Å for 2 and 2.3272(9)–2.3086(8) Å for 6] and Pt–N
Neither F1 nor F2 react with RCN in the absence of Pt(IV) centre
and this indicates that the coupling is Pt(IV)-mediated.
D a l t o n T r a n s . , 2 0 0 4 , 2 7 2 8 – 2 7 3 2
2 7 2 9

View Article Online
Experimental
Materials and instrumentation
N-methylbenzohydroxamic acid (F1, Scheme 2),21 methyl benzo-
hydroximate (methyl N-hydroxybenzimidate) (F2B)22 and methyl
2,4,6-trimethylbenzohydroximate [methyl N-hydroxy-(2,4,6-
trimethyl)benzimidate] (F2A)23 were synthesized using published
procedures. Solvents were obtained from commercial sources and
used as received but methanol and dichloromethane were dried
by conventional methods. The complexes trans-[PtCl4(RCN)2]
(R = Me, Et, CH2Ph)8,19 and cis/trans-[PtCl4(MeCN)(Me2SO)]24
were prepared as previously described. C, H, and N elemental anal-
yses were carried out by the Microanalytical Service of the Instituto
Superior Técnico. Positive-ion FAB mass spectra were obtained
on a Trio 2000 instrument by bombarding 3-nitrobenzyl alcohol
(NBA) matrixes of the samples with 8 keV (≈1.28 × 1015 J) Xe
atoms. Mass calibration for data system acquisition was achieved
using CsI. Infrared spectra (4000–400 cm−1) were recorded on a
1
JASCO FTS 3000MX instrument in KBr pellets. H and 13C{1H}
NMR spectra were measured on a Varian UNITY 300 spectrometer
at ambient temperature. The microwave irradiation experiments
were undertaken in a focused microwave CEM Discover reactor
(max power 300 W) which is fitted with a rotational system and
an IR detector of temperature.
Fig. 2 Molecular structure of 6. The thermal ellipsoids are drawn at the
50% probability level.
A. Addition of N-methylbenzohydroxamic acid to nitriles in
trans-[PtCl4(RCN)2]
In a typical experiment, trans-[PtCl4(RCN)2] (0.11 mmol) was
suspended in dichloromethane (5 mL) at 20–25 °C, N-methyl-
benzohydroxamic acid (0.033 g, 0.22 mmol) was added, and the
reaction mixture was treated with 100 W focused microwave
irradiation in a sealed tube at 45–47 °C for ca. 20 min (the reac-
tion also proceeds without microwave irradiation under heating at
45–47 °C for ca. 2–3 h) until the starting material was dissolved
and the mixture was homogenized. The solution was evaporated
to dryness and the bright yellow residue was washed with diethyl
ether (two 10 mL portions) and dried in air at room temperature.
Yield is 75–90%, based on Pt.
[2.016(3) Å for 2 and 2.012(3) Å for 6] bond lengths and also all
bond angles around the Pt centre are normal, and they agree with
those observed in the majority of the previously characterized
platinum(IV) complexes with iminoligands, i.e. trans-[PtCl4-
{NHC(Me)ONCR2}2]8 or trans-[PtCl4{NHC(Me)ONR2}2].10
The two CNH bonds in both compounds are equal within 3
[1.283(6) Å for 2 and 1.265(3) Å for 6] and these distances are
very close to the typical values (1.26–1.29 Å)20 for the CN
double bonds.
In 6, the CN–H and NHH distances in the imine ligand
and the C–N–H, C–O–N and N–HH angles clearly indicate
that the E-configuration of the ligands is stabilized by the
N–HH hydrogen bond between the imine CNH atom and
the hydroximic nitrogen [N(1)–H(1) 0.8800(5), N(1)–H(1)N(2)
2.07(3), and N(1)–H(1)–N(2) 113(8)°] and this agrees with the
E-configuration supported by H-bonding in similar systems, i.e.
trans-[PtCl4{NHC(Me)ONCR2}2].8 The H-bond was not
found in 2 insofar as the hydroxamic nitrogen is blocked by the
methyl group.
[PtCl4{NHC(Me)ON(Me)C(O)Ph}2] (1)
Anal. Calcd for C20H22N4Cl4O4Pt: C, 33.30; H, 3.35; N, 7.77.
Found: C, 33.53; H, 3.40; N, 7.60%. FAB+-MS, m/z: 748 [M]+, 678
[M − 2Cl]+, 643 [M − 3Cl]+. IR spectrum (selected bands), cm−1:
3216 mw (N–H), 1657 s (CN), 1438 s (CC), 830 s (C–H).
1H NMR spectrum in CDCl3, : 2.24 (s, 3H, Me), 3.38 (s, 3H, NMe),
7.47–7.61 (m, 5H, Ph), 8.67 (br, 1H, CNH). 13C{1H} NMR in
CDCl3, : 20.2 (Me), 38.2 (NMe), 127.5–134.2 (Ph), 164.8 and
178.5 (CO and HNC).
Concluding remarks
The results from this work can be considered from the
following perspectives. First, by reacting the (nitrile)Pt(IV)
complexes with the oxamic form F1 (Scheme 2), we proved
that the coupling might occur with NOH-type nucleophiles
where the N atom has the sp2 hybridization, whereas all other
NOH nucleophiles previously studied were of (sp3-N)OH-type.
Second, we observed that both oxamic (F1) and oximic (F2)
forms of hydroxamic acid, ‘frozen’ by alkylation, can act as a
nucleophile towards a metal-activated nitrile and be involved
in the metalla-Pinner reaction. Although the reactivity of both
forms is different and the oximic form reacts faster than the
oxamic one, conclusions on preferences in nucleophilic attack
by one or another tautomeric form of hydroxamic acid should
be taken with great care and only after a quantitative kinetic
study. Third, the current study confirms our assumption18 on con-
current formation of the two coordinated tautomers (Scheme 1).
Fourth, we found that the OMe-functionalized oxime effectively
couples with the (nitrile)Pt species to give imino complexes and
this reaction is an extension of the previously observed addition
of other oximes RR′CNOH (R′ = alkyl, aryl, NH2, Cl)8–12 to
another type of oxime, i.e. with R′ = OMe.
[PtCl4{NHC(Et)ON(Me)C(O)Ph}2] (2)
Anal. Calcd for C22H26N4Cl4O4Pt: C, 35.26; H, 3.77; N, 7.48.
Found: C, 35.53; H, 3.68; N, 7.50%. FAB+-MS, m/z: 720 [M]+, 685
[M − Cl]+, 650 [M − 2Cl]+. IR spectrum (selected bands), cm−1:
3210 mw (N–H), 1655 s (CN), 810 s (C–H). 1H NMR spec-
trum in CDCl3, : 2.63 (t, J 7.5 Hz, 3H, Me), 3.36 (s, 3H, NMe),
7.47–7.61 (m, 5H, Ph), 8.65 (br, 1H, CNH). 13C{1H} NMR in
CDCl3, : 10.2 (CH3) and 25.3 (CH2)(Et), 37.5 (NMe), 127.0–133.0
(Ph), 164.8 and 178.5 (CO and HNC).
[PtCl4{NHC(CH2Ph)ON(Me)C(O)Ph}2] (3)
Anal. Calcd for C32H32N4Cl4O4Pt: C, 44.08; H, 3.70; N, 6.43. Found:
C, 42.50; H, 3.68; N, 6.50%. FAB+-MS, m/z: 837 [M − Cl]+, 802
[M − 2Cl]+, 731 [M − 4Cl]+. IR spectrum (selected bands), cm−1:
3228 mw (N–H), 1665 s (CN), 840 s (C–H). 1H NMR spec-
trum in CDCl3, : 3.29 (s, 3H, NMe), 4.53 (s, 2H, CH2Ph), 7.10–
8.14 (m, 10H, Ph), 8.85 (br, 1H, CNH). 13C{1H} NMR in CDCl3,
: 37.5 (NMe), 64.5 (CH2Ph), 127.0, 128.1, 129.9 and 133.0 (Ph),
164.8 and 178.5 (CO and HNC).
2 7 3 0
D a l t o n T r a n s . , 2 0 0 4 , 2 7 2 8 – 2 7 3 2

View Article Online
Table 1 Crystallographic data for 2 and 6
Table 2 Selected bond lengths and angles for 2 and 6
2
6
2
6
Empirical formula
FW
T/K
Crystal system
Space group
a/Å
b/Å
c/Å
C22H28N4Cl4O4Pt
749.37
100(2)
Monoclinic
C2/c
21.8355(7)
8.6425(4)
15.8421(6)
112.260(3)
4
5.492
15484
3119
0.0432
0.0359
0.0912
C28H40N4Cl4O4Pt
833.53
100(2)
Orthorhombic
F d d 2
18.5176(12)
28.9131(15)
12.3169(12)
90
Pt(1)–Cl(1)
Pt(1)–Cl(2)
Pt(1)–Cl(3)
Pt(1)–N(1)
N(1)–C(1)
C(1)–O(1)
O(1)–N(2)
2.316(1)
2.319(1)
2.3286(8)
2.3072(9)
2.012(2)
1.265(3)
1.354(3)
1.459(3)
2.016(3)
1.283(6)
1.358(5)
1.442(5)
Cl(1)–Pt(1)–Cl(2)
Cl(2)–Pt(1)–Cl(3)
N(1)–Pt(1)–Cl(1)
N(1)–Pt(1)–Cl(2)
N(1)–Pt(1)–Cl(3)
Pt(1)–N(1)–C(1)
N(1)–C(1)–O(1)
C(1)–O(1)–N(2)
90.51(4)
/°
Z
178.48(4)
8
85.25(10)
85.19(11)
(Mo K)/mm−1
Collected reflections
Unique reflections
RInt
4.618
12006
3481
0.0192
0.0169
0.0447
85.24(8)
94.25(8)
135.3(2)
122.1(2)
110.7(2)
134.9(3)
120.7(4)
114.0(3)
R1a (I ≥ 2)
wR2b (I ≥ 2)
2
a R1 = ∑||Fo| − |Fc||/∑|Fo|. b wR2 = [∑[w(Fo2 − Fc2)2]/ ∑[w(Fo )2]]1/2
.
Complexes 7 and 8 were prepared by methods A and B, respec-
tively, in accord with the procedures described above for synthesis of
the corresponding complexes starting from trans-[PtCl4(MeCN)2].
B. Addition of methyl benzohydroximate and methyl 2,4,6-
trimethylbenzohydroximate to nitriles in trans-[PtCl4(RCN)2]
[PtCl4{NHC(Me)ON(Me)C(O)Ph}(Me2SO)] (7)
In a typical experiment, trans-[PtCl4(RCN)2] (0.11 mmol) was
suspended in dichloromethane (5 mL) at 20–25 °C, and the
corresponding oxime (0.22 mmol) was added. The reaction mixture
was stirred for 15 min (in the case of trans-[PtCl4(MeCN)2] heated
at 45–47 °C for ca. 1 h) until the homogenization of the mixture
was completed. The slight yellow solution was evaporated to dry-
ness and the bright yellow residue was washed with diethyl ether
(two 10 mL portions) and dried in air at room temperature. Yield is
85–90%, based on Pt.
Anal. Calcd for C20H22N4Cl4O4Pt: C, 23.74; H, 2.99; N, 4.61. Found:
C, 23.94; H, 3.07; N, 4.50%. FAB+-MS, m/z: 572 [M − Cl + H]+,
536 [M − 2Cl]+. IR spectrum (selected bands), cm−1: 3274 mw
(N–H), 1657 s (CN), 1444 s (CC), 855 s (C–H). 1H NMR
spectrum in CDCl3, : 2.75 (s, 3H, Me), 3.38 (s, 3H, NMe), 7.34–
7.64 (m, 5H, Ph), 8.13 (br, 1H, CNH). 13C{1H} NMR spectrum
in DMSO-d6, : 11.5 (Me), 41.0 (Me2SO), 113.7–130.2 (Ph), 164.8
and 178.5 (CO and HNC).
[PtCl4{NHC(Me)ONC(OMe)(2,4,6-Me3C6H2)}(Me2SO)] (8)
[PtCl4{NHC(Et)ONC(OMe)Ph}2] (4)
Anal. Calcd for C22H26N4Cl4O4Pt: C, 27.75; H, 3.73; N, 4.31. Found:
C, 28.87; H, 3.31; N, 4.29%. FAB+-MS, m/z: 613 [M − Cl]+, 578
[M − 2Cl]+. IR spectrum (selected bands), cm−1: 3216 mw (N–H),
1660 s (CN), 1614 s (CN), 1448 s (CC), 854 s (C–H).
1H NMR spectrum in CDCl3, : 2.18 (s, 3H, Me), 2.27 (s, 6H,
o-Me) and 2.35 (s, 3H, p-MeC6H2), 2.80 (s, 6H, Me2SO), 3.59 (s,
3H, OMe), 6.97 (s, 2H, Ph), 8.25 (br, 1H, CNH). 13C{1H} NMR in
DMSO-d6, : 10.7 (CH3), 19.6 and 21.2 (C6H2Me3), 41.2 (Me2SO),
57.1 (OMe), 123.2, 128.6, 137.3 and 141.1 (Ph), 163.2 and 176.7
[NC(OMe) and HNC].
Anal. Calcd for C22H26N4Cl4O4Pt: C, 35.26; H, 3.77; N, 7.48.
Found: C, 35.53; H, 3.68; N, 7.50%. FAB+-MS, m/z: 748 [M]+, 678
[M − 2Cl]+, 643 [M − Cl]+. IR spectrum (selected bands), cm−1:
3220 mw (N–H), 1655 s (CN), 1610 s (CN), 1448 s (CC),
1
854 s (C–H). H NMR spectrum in CDCl3, : 1.33 (t, J 7.5 Hz,
3H, CH2Me), 2.20 (s, 3H, OMe), 3.18 (quart, J 7.5 Hz, 2H, CH2Me),
7.47–7.61 (m, 5H, Ph), 8.65 (br, 1H, CNH). 13C{1H} NMR in
CDCl3, : 11.0 (CH3) and 24.3 (CH2)(Et), 57.5 (OMe), 127.2–133.5
(Ph), 164.8 and 178.5 [NC(OMe) and HNC].
[PtCl4{NHC(Me)ONC(OMe)(2,4,6-Me3C6H2)}2] (5)
X-ray structure determinations
Anal. Calcd for C26H36N4Cl4O4Pt: C, 38.77; H, 4.50; N, 6.96. Found:
C, 38.87; H, 4.55; N, 6.80%. FAB+-MS, m/z: 769 [M − Cl]+, 734
[M − 2Cl]+, 699 [M − 3Cl]+. IR spectrum (selected bands), cm−1:
3210 mw (N–H), 1666 s (CN), 1616 s (CN), 1448 s (CC),
The X-ray diffraction data were collected with a Nonius
KappaCCD diffractometer using Mo K radiation ( = 0.71073 Å).
Single crystals of 2 and 6 were mounted in inert oil within the
cold gas stream of the diffractometer. The Denzo-Scalepack25
program package was used for cell refinements and data reduc-
tion. Structures were solved by direct methods using the SIR-97
or SIR-2002 programs.26,27 A multiscan absorption correction
based on equivalent reflections (XPREP in SHELXTL v. 6.14
or SADABS v.2.10)28,29 was applied to all data (Tmin/Tmax values
were 0.38061/0.47286 and 0.4204/0.5894 respectively for 2 and
6). All structures were refined with SHELXL-9730 and WinGX
graphical user interface.31 In 2, NH hydrogens were located from
the difference Fourier map but not refined. All other hydrogens
were placed in idealized positions and constrained to ride on their
parent atom. The crystallographic data are summarized in Table 1.
Selected bond lengths and angles are shown in Table 2.
1
854 s (C–H). H NMR spectrum in CDCl3, : 2.75 (s, 3H, Me),
2.26 (s, 6H, o-Me) and 2.35 (s, 3H, p-MeC6H2), 3.59 (s, 3H, OMe),
6.96–6.98 (d, 2H, Ph), 8.64 (br, 1H, CNH). 13C{1H} NMR in
DMSO-d6, : 10.8 (CH3), 19.7 and 21.0 (C6H2Me3), 57.2 (OMe),
123.5, 129.6, 138.3 and 142.3 (Ph), 163.2 and 176.6 [NC(OMe)
and HNC].
[PtCl4{NHC(Et)ONC(OMe)(2,4,6-Me3C6H2)}2] (6)
Anal. Calcd for C28H40N4Cl4O4Pt: C, 40.35; H, 4.84; N, 6.72. Found:
C, 38.73; H, 4.88; N, 6.30%. FAB+-MS, m/z: 797 [M − Cl]+, 762
[M − 2Cl + H]+. IR spectrum (selected bands), cm−1: 3225 mw
(N–H), 1655 s (CN), 1618 s (CN), 1448 s (CC), 854 s
CCDC reference numbers 237749 and 237750.
See http://www.rsc.org/suppdata/dt/b4/b406600f/ for crystallo-
graphic data in CIF or other electronic format.
1
(C–H). H NMR spectrum in CDCl3, : 1.68 (t, J 7.5 Hz, 3H,
CH2Me), 2.27 (s, 6H, o-Me) and 2.34 (s, 3H, p-MeC6H2), 3.26
(s, J 7.5 Hz, 2H, CH2Me), 3.58 (s, 3H, OMe), 6.95 (s, 2H, Ph),
8.51 (br, 1H, CNH). 13C{1H} NMR in DMSO-d6, : 10.7 (CH3)
and 25.2 (CH2)(Et), 19.6 and 21.2 (C6H2Me3), 60.6 (OMe), 127.3,
128.3, 128.6, 128.8, 128.9, 131.9 and 132.1 (Ph), 162.4 and 176.5
[NC(OMe) and HNC].
Acknowledgements
This work has been partially supported by the Fundação para a
Ciência e a Tecnologia (FCT), Portugal, and its POCTI program
D a l t o n T r a n s . , 2 0 0 4 , 2 7 2 8 – 2 7 3 2
2 7 3 1

View Article Online
9 V. Yu. Kukushkin, T. B. Pakhomova, N. A. Bokach, G. Wagner, M. L.
Kuznetsov, M. Galanski and A. J. L. Pombeiro, Inorg. Chem., 2000,
39, 216.
10 G. Wagner,A. J. L. Pombeiro, Yu. N. Kukushkin, T. B. Pakhomova,A. D.
Ryabov and V. Yu. Kukushkin, Inorg. Chim. Acta, 1999, 292, 272.
11 G. Wagner, A. J. L. Pombeiro, N. A. Bokach and V. Yu. Kukushkin,
J. Chem. Soc., Dalton Trans., 1999, 4083.
12 V. Yu. Kukushkin, I. V. Ilichev, G. Wagner, J. J. R. Fraústo da Silva
and A. J. L. Pombeiro, J. Chem. Soc., Dalton Trans., 1999, 3047;
V. Yu. Kukushkin, I. V. Ilichev, M. A. Zhdanova, G. Wagner and
A. J. L. Pombeiro, J. Chem. Soc., Dalton Trans., 2000, 1567.
13 C. M. P. Ferreira, M. F. C. Guedes da Silva, J. J. R. Fraústo da Silva,
A. J. L. Pombeiro, V. Yu. Kukushkin and R. A. Michelin, Inorg. Chem.,
2001, 40, 1134.
14 M. N. Kopylovich, V. Yu. Kukushkin, M. F. C. Guedes da Silva,
M. Haukka, J. J. R. Fraústo da Silva and A. J. L. Pombeiro, J. Chem.
Soc., Perkin Trans. 1, 2001, 1569.
15 M. N. Kopylovich, A. J. L. Pombeiro, A. Fischer, L. Kloo and V. Yu.
Kukushkin, Inorg. Chem., 2003, 42, 7239.
16 M. N. Kopylovich, V. Yu. Kukushkin, M. Haukka, J. J. R. Fraústo
da Silva and A. J. L. Pombeiro, Inorg. Chem., 2002, 41, 4798.
17 A. J. L. Pombeiro, V. Yu. Kukushkin, M. N. Kopylovich and J. J. R.
Fraústo da Silva, Patent PT 102 618 P, 2001.
18 K. V. Luzyanin, V. Yu. Kukushkin, M. L. Kuznetsov, D. A. Garnovskii,
M. Haukka and A. J. L. Pombeiro, Inorg. Chem., 2002, 41, 2981.
19 K. V. Luzyanin, M. Haukka, N. A. Bokach, M. L. Kuznetsov, V. Yu.
Kukushkin and A. J. L. Pombeiro, J. Chem. Soc., Dalton Trans., 2002,
1882.
(POCTI/QUI/43415/2001 project)(FEDER funded). K. V. L.
expresses gratitude to FCT and the POCTI program (FEDER
funded), Portugal for a fellowship (grant SFRH/BD/10464/2002).
The authors thank NATO for the Collaborative Linkage Grant
PST.CLG.979289. V. Yu. K. is very much obliged to the Russian
Fund for Basic Research for a grant (03-03-32363), POCTI
program (FEDER funded) (Cientista Convidado/Professor at
the Instituto Superior Técnico, Portugal), the Royal Society of
Chemistry for the Grant for International Authors, the Academy
of Finland for support of the cooperation with the University of
Joensuu and ISSEP for the Soros Professorship. M. H. would
like to thank the Academy of Finland for financial support. The
authors thank Dr D. A. Garnovskii for experimental assistance.
References
1 A. J. L. Pombeiro and V. Yu. Kukushkin, Reactions of coordinated
ligands: General introduction, in Comprehensive Coordination
Chemistry, Elsevier, Amsterdam, 2nd edn., 2003, ch. 1.29, vol. 1,
pp. 585–594 and references therein.
2 A. J. L. Pombeiro and V. Yu. Kukushkin, in Comprehensive Coordi-
nation Chemistry, Elsevier, Amsterdam, 2nd edn., 2003, vol. 1,
pp. 639–660.
3 R. A. Michelin, M. Mozzon and R. Bertani, Coord. Chem. Rev., 1996,
147, 299.
4 J. Eglin, Comments Inorg. Chem., 2002, 23, 23; S. I. Murahashi and
H. Takaya, Acc. Chem. Res., 2000, 33, 225; A. W. Parkins, Platinum
Metals Rev., 1996, 40, 169; J. Chin, Acc. Chem. Res., 1991, 24, 145;
Z. N. da Rocha, G. Chiericato, Jr. and E. Tfouni, Adv. Chem. Ser., 1997,
297.
20 F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and
R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
21 L. De Luca, G. Giacomelli and M. Taddei, J. Org. Chem., 2001, 66,
2534.
22 A. Werner and H. Buss, Berichte, 1894, 27, 2193.
5 E. C. Constable, Metals and Ligand Reactivity. An Introduction to
the Organic Chemistry of Metal Complexes, VCH, Weinheim, 1995,
p. 65; H. Endres, in Comprehensive Coordination Chemistry, ed.
G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon Press,
Oxford, 1987, vol. 2, p. 261.
6 V. Yu. Kukushkin and A. J. L. Pombeiro, Chem. Rev., 2002, 102, 1771
and references therein.
7 V. Yu. Kukushkin and A. J. L. Pombeiro, Inorg. Chim. Acta, 2004,
accepted for publication.
23 C. Grundmann and H.-D. Frommeld, J. Org. Chem., 1966, 31, 157.
24 V. Yu. Kukushkin, A. J. L. Pombeiro, C. M. P. Ferreira and L. I. Elding,
Inorg. Synth., 2002, 33, 189.
25 Z. Otwinowski and W. Minor, Processing of X-ray Diffraction Data
Collected in Oscillation Mode, in Methods in Enzymology, vol. 276,
Macromolecular Crystallography, part A, ed. C. W. Carter, Jr. and R. M.
Sweet, Academic Press, New York, 1997, pp. 307–326.
26 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C. Giacovazzo,
A. Guagliardi, A. G. G. Moliterni, G. Polidori and R. Spagna, J. Appl.
Crystallogr., 1999, 32, 115.
27 M. C. Burla, M. Camalli, B. Carrozzini, G. L. Cascarano, C. Giacovazzo,
G. Polidori and R. Spagna, J. Appl. Crystallogr., 2003, 36, 1103.
28 G. M. Sheldrick, SHELXTL, Bruker Analytical X-ray Systems,
Madison, WI, USA, 2003, ver. 6.14.
29 G. M. Sheldrick, SADABS - Bruker Nonius scaling and absorption
correction, BrukerAnalytical X-ray Systems, Madison, WI, USA, 2003,
ver. 2.10.
8 V. Yu. Kukushkin,
T. B. Pakhomova,
Yu. N. Kukushkin,
R. Herrmann, G. Wagner and A. J. L. Pombeiro, Inorg. Chem.,
1998, 37, 6511; M. L. Kuznetsov, N. A. Bokach, V. Yu. Kukushkin,
T. Pakkanen, G. Wagner and A. J. L. Pombeiro, J. Chem. Soc.,
Dalton Trans., 2000, 4683; G. Wagner, T. B. Pakhomova, N. A.
Bokach, J. J. R. Fraústo da Silva, J. Vicente, A. J. L. Pombeiro
and V. Yu. Kukushkin, Inorg. Chem., 2001, 40, 1683; A. V.
Makarycheva-Mikhailova, M. Haukka, N. A. Bokach, D. A.
Garnovskii, M. Galanski, B. K. Keppler, A. J. L. Pombeiro and
V. Yu. Kukushkin, New J. Chem., 2002, 26, 1085; D. A. Garnovskii,
A. J. L. Pombiero, M. Haukka, P. Sobota and V. Y. Kukushkin,
Dalton Trans., 2004, 1097.
30 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Göttingen, Germany, 1997.
31 L. J. Farrugia, J. Appl. Crystallogr., 1999, 32, 837.
2 7 3 2
D a l t o n T r a n s . , 2 0 0 4 , 2 7 2 8 – 2 7 3 2