Chlorination of platinum-bound salicylaldoxime. The first example of a structurally characterized monodentate salicylaldoxime-type ligand

Article abstract of DOI:10.1002/1099-0682(200104)2001:4<1031::aid-ejic1031>3.0.co;2-d

The reaction of K₂[PtCl₄] and salicylaldoxime in an approximate 1:2 molar ratio in water resulted in the isolation of a mixture of four compounds from which [Pt(o-OC₆H₄CH=NOH)₂] (1) and [PtCl(OC₆H₄CH=NOH)(HOC₆H₄CH=NOH)] (2) were isolated, whereas the other two were shown to be unstable and decomposed both in solution and on SiO₂ during chromatography. Chlorination of 1 and 2 with Cl₂ resuited in the oxidative addition of chlorine to the platinum(II) center and in the chlorination of the benzene ring, giving the platinum(IV) complexes [PtCl₂(3,5,2-Cl,Cl,OC₆H₂CH=NOH)₂] (3) and [PtCl₃(3,5,2-Cl,Cl,OC₆H₂CH=NOH)(3,5,2-Cl, Cl,HOC₆H₂CH=NOH)] (5), respectively, containing commercially unavailable 3,5-dichloro-2-hydroxybenzaldehye oxime. Alternatively, treatment of 1 with NOCl resulted only in the oxidation of the platinum(II) center to furnish [PtCl₂(o-OC₆H₄CH=NOH)₂] (4), whereas the benzene rings of salicylaldoximato ligands remained intact. All complexes were characterized by C, H, N, Cl and Pt elemental analyses, FAB⁺ mass spectrometry, IR and ¹H, ¹³C{¹H} and ¹⁹⁵Pt NMR spectroscopy. Compounds 1, 3 and 5 were analyzed by X-ray crystallography. In 1, the salicylaldoximato ligands adopt a trans configuration and the hydrogen atoms of the OH groups are involved in intramolecular hydrogen bonding, forming five-membered rings. In 3, every molecule of the complex forms the repeating unit for a self-assembly that produces infinite one-dimensional polymeric chains directed along the z axis held by hydrogen bonds. The complex 5 represents the first example of a structurally characterized metal complex with a monodentate salicylaldoxime-type ligand, although the conventional bidentate N,O-coordination mode is a classical topic in coordination chemistry.

Full text of DOI:10.1002/1099-0682(200104)2001:4<1031::aid-ejic1031>3.0.co;2-d

FULL PAPER
Chlorination of Platinum-Bound Salicylaldoxime. The First Example of a
Structurally Characterized Monodentate Salicylaldoxime-Type Ligand
Savelii F. Kaplan,[a] Vadim Yu. Kukushkin,*[a] Sergiu Shova,[b] Kinga Suwinska,[c]
Gabriele Wagner,[d] and Armando J. L. Pombeiro*[d]
Keywords: Salicylaldoxime complexes / Platinum / Ligand reactivity / Metal-mediated synthesis / Chlorination
The reaction of K2[PtCl4] and salicylaldoxime in an approx- aldoximato ligands remained intact. All complexes were
imate 1:2 molar ratio in water resulted in the isolation of a characterized by C, H, N, Cl and Pt elemental analyses, FAB+
mixture of four compounds from which [Pt(o-OC6H4CH=
NOH)2] (1) and [PtCl(OC6H4CH=NOH)(HOC6H4CH=NOH)]
(2) were isolated, whereas the other two were shown to be
unstable and decomposed both in solution and on SiO2 dur-
mass spectrometry, IR and 1H, 13C{1H} and 195Pt NMR spec-
troscopy. Compounds 1, 3 and 5 were analyzed by X-ray
crystallography. In 1, the salicylaldoximato ligands adopt a
trans configuration and the hydrogen atoms of the OH
ing chromatography. Chlorination of 1 and 2 with Cl2 re- groups are involved in intramolecular hydrogen bonding,
sulted in the oxidative addition of chlorine to the platinum(II)
center and in the chlorination of the benzene ring, giving the
forming five-membered rings. In 3, every molecule of the
complex forms the repeating unit for a self-assembly that
produces infinite one-dimensional polymeric chains directed
along the z axis held by hydrogen bonds. The complex 5 rep-
resents the first example of a structurally characterized metal
platinum(IV)
complexes
[PtCl2(3,5,2-Cl,Cl,OC6H2CH=
NOH)2] (3) and [PtCl3(3,5,2-Cl,Cl,OC6H2CH=NOH)(3,5,2-
Cl,Cl,HOC6H2CH=NOH)] (5), respectively, containing com-
mercially unavailable 3,5-dichloro-2-hydroxybenzaldehye complex with a monodentate salicylaldoxime-type ligand, al-
oxime. Alternatively, treatment of 1 with NOCl resulted only
in the oxidation of the platinum(II) center to furnish [PtCl2(o-
OC6H4CH=NOH)2] (4), whereas the benzene rings of salicyl-
though the conventional bidentate N,O-coordination mode is
a classical topic in coordination chemistry.
Introduction
the nitrile group upon Ru-assisted dehydration of aldox-
imes.[15] Following these studies, we turned our attention to
Although oximes (RRЈCϭNOH) display one of the most the reactions of peripheral R/RЈ groups and have recently
versatile modes of reactivity in metal-mediated processes, reported the chlorination, by molecular chlorine, of the
their conversions at a metal center have attracted attention platinum(II) salicylaldoxime, trans-(S,N)-[PtCl2(o-HOC6H4-
only in the last decade.[1,2] Being involved in these studies CHϭNOH)(Me2SO)]·H2O, and the salicylaldoximato(1Ϫ),
for the last five years, we have been investigating some as- trans-(S,N)-[PtCl(o-OC6H4CHϭNOH)(Me2SO)],
com-
pects of oxime ligand reactivity, in particular with respect plexes.[16] Instead of the Piloty reaction, which in the case
to (i) the OH group, e.g. their facile deprotonation and the of aldoximes leads to chloro oximes, RC(Cl)ϭNOH (via
self-assembly of the oxime-oximato species formed,[3] addi- RCH(Cl)ϪNϭO),[17] or to the formation of platinum(III)
tion to nitriles bound to PtIV,[4,5] ReIV [6] and RhIII [7] ions, derivatives previously detected upon the chlorination of
addition to ketones in a PtIV complex,[8] formation of (vic-dioximato)platinum(II) compounds,[18] we observed
metallacycles accompanied by the OH addition;[9] (ii) the both the chlorination of the salicylaldoxime benzene ring
NϪOH group, e.g. its oxidative addition to an electron-rich and the oxidative addition of Cl2 to the platinum(II) center.
rhenium(I) center,[10] (iii) the oxime N atom, e.g. its oxida- Conclusions that can be derived from the latter work indic-
tion to give (nitrosoalkane)Pt complexes[11,12] or its reduc- ate that platinum acts as a protecting center for the oxime
tion in a strongly acidic solution,[13] (iv) the CϭN group, functionality and this allows for the formation of the chlor-
e.g. its metal-mediated hydrolysis[14] and the conversion into inated species, which cannot be synthesized by direct chlor-
ination of the corresponding salicylaldoxime.
[a]
Department of Chemistry, St. Petersburg State University,
Our interest in the continuation of the chlorination ex-
Universitetsky Pr. 2, 198904 Stary Petergof, Russian Federation
periments lied in at least three areas. Firstly, we wondered
if the protection of the NOH group and the concomitant
chlorination of the benzene ring was peculiar for the com-
plexes being investigated or if the reaction could be ex-
tended to other salicylaldoxime platinum compounds. Sec-
ondly, it was expected to contribute to the almost unex-
plored chemistry of salicylaldoxime coordinated to plat-
E-mail: kukushkin@VK2100.spb.edu
[b]
[c]
[d]
Department of Chemistry, State University of Moldova,
MD 2009, Chisinau, Republic of Moldova
Institute of Physical Chemistry, Polish Academy of Sciences,
Warsaw, Poland
´
Centro de Quımica Estrutural, Complexo I, Instituto Superior
´
Tecnico,
Av. Rovisco Pais, 1049Ϫ001 Lisboa, Portugal
E-mail: pombeiro@ist.utl.pt
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ1948/01/0404Ϫ1031 $ 17.50ϩ.50/0
1031

V. Y. Kukushkin, A. J. L. Pombeiro et al.
FULL PAPER
inum. Thirdly, our own observations[16] and also some
The 195Pt NMR spectrum of the crude mixture, prepared
earlier studies[19] indicated the possibility of N-monodentate according to a known procedure,[19] showed four signals of
coordination of classical bidentate chelating ligands such as similar intensities, and TLC showed four well-defined spots.
salicylaldoxime and its derivatives. We therefore focused our The signal at δ ϭ Ϫ1611 (480 Hz) in the spectrum was as-
efforts on the structural determination of previously un- signed to [Pt(o-OC6H4CHϭNOH)2] (1) and the peak at δ ϭ
characterized monodentate species. In this paper we present Ϫ1842 (360 Hz) was ascribed to [PtCl(OC6H4CHϭ
the revisited synthesis (previously reported by Cox et al.[19]
)
NOH)(HOC6H4CHϭNOH)] (2) (both are depicted in
of two salicylaldoxime complexes of platinum(II). We re- Scheme 1). The former was isolated by following the
port the X-ray structure of one of the compounds, as well method of Cox,[19] and the latter was separated from the
as the isolation of a new product, chlorination studies of mixture by chromatography, and both were characterized
the two platinum(II) compounds with Cl2 and NOCl giving, by C, H, N, Cl and Pt elemental analyses, FABϩ mass spec-
in one case, a PtIV-based monodentate chlorinated salicylal- trometry, IR and 1H, 13C{1H} and 195Pt NMR spectro-
doxime that was successfully characterized by X-ray single- scopy. Compound 1 was analyzed by X-ray crystallography.
crystal diffraction. Furthermore, an unusual intermolecular Our attempts to isolate two other compounds [195Pt NMR:
hydrogen bonding was shown by an X-ray study of one of δ ϭ Ϫ1999 (500 Hz) and δ ϭ Ϫ2064 (250 Hz)] failed be-
the PtIV products. This hydrogen bonding results in a self- cause of their decomposition both in solution and on SiO2
assembly, forming infinite one-dimensional polymeric during chromatography. Although the values of the chem-
chains, and is significant in the developing field of self-as- ical shifts for these yet unidentified species seem to be reas-
sembly of metal complexes by hydrogen bonding, which has onable for cis and trans isomers of 1, no further evidence
applications in crystal engineering and materials science.[3]
in favor of these complexes was obtained.
Complex 1 was characterized by X-ray single-crystal dif-
fractometry. The coordination polyhedron of the centro-
symmetric compound is a slightly distorted square plane
(Figure 1).
Results and Discussion
Synthesis of Platinum(II) Compounds with
Salicylaldoxime(ato) Ligands
The salicylaldoximato ligands in the structure adopt a
trans configuration and the hydrogen atoms of the OH
Cox and co-authors[19] reported the reaction of K2[PtCl4] groups are involved in intramolecular hydrogen bonding,
and salicylaldoxime in a molar ratio of approximately 1:2 forming a five-membered ring. Interestingly, these H atoms,
in water, resulting in the isolation of a mixture of the bis- found from the difference synthesis, are disordered by two
chelate [Pt(o-OC6H4CHϭNOH)2] and the complex positions with a 50% population at each one, i.e. at the ox-
[PtCl2(o-HOC6H4CHϭNOH)2] that contains, as had been ime ϭNOH group and at the phenol OH group, thus indic-
suggested,[19] monodentate salicylaldoxime ligands. It was ating the existence of two solid tautomers. However, careful
pointed out[19] that the latter complex is unstable in solu- comparison of bond lengths in the chelated ring of 1 with
tions and decomposes on standing.
(i) typical bond lengths in oxime/oximato compounds; (ii)
Scheme 1
1032
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038

Chlorination of Platinum-Bound Salicylaldoxime
FULL PAPER
Figure 1. View of trans-(N,N)-[Pt(o-OC6H2CHϭNOH)2] (1) with atomic numbering
Table 1. Selected bond lengths for the (salicylaldoximato)PtII complexes and literature data
˚
Complexes/bond lengths, A
ϭNϪO
CϭN
CϪC(H)ϭ
CϭC
CϪO
[Pt(o-OC6H4CHϭNOH)2] (1)
[PtCl2(3,5,2-Cl,Cl,OC6H2CHϭNOH)2] (3)
[PtCl3(3,5,2-Cl,Cl,OC6H2CHϭNOH)-
(3,5,2-Cl,Cl,HOC6H2CHϭNOH)] (5)
monodentate ligand
1.385(8)
1.367(7)
1.268(9)
1.292(9)
1.434(11)
1.452(10)
1.415(11)
1.409(10)
1.327(9)
1.331(8)
1.390(16)
1.390(17)
1.402[a]
1.299(17)
1.270(19)
1.281[c]
1.44(2)
1.43(2)
1.455[d]
1.40(2)
1.41(2)
1.397[e]
1.36(2)
bidentate ligand
1.340(16)
ref. average[31,32]
1.321[f]
1.367Ϫ1.393[b]
[a]
[b]
[c]
[d]
NϪO in oxime and oximato PtII complexes.[3]
Ϫ
CϭN in oximes. Ϫ
Csp ϪCCsp
3
3
2
NϪO in (Cϭ)(CCsp )ϪCϭNϪOH oximes. Ϫ
[e]
[f]
conjugated. Ϫ In substituted phenyl ring. Ϫ Aryloxy complexes.
distances within both the chelated salicylaldoximato ring complexes gave a variety of products due to oxidative de-
and the monodentate salicylaldoxime ligand in the two plat- oximation[1,2] and chlorination, with no dominant com-
inum(IV) complexes from both the current (see Table 1) and pound. The latter fact suggests that coordination affects
previous work;[16] and (iii) bond lengths in some other sal- the reaction by blocking and thus protecting the oxime N
icylaldoximato complexes,[20] does not give any further atom from oxidation, thus also making the chlorination
evidence in favor of the phenol tautomeric structure.
selective.
The structure of 3 was determined by X-ray crystallo-
graphy. In the centrosymmetric complex, the coordination
polyhedron of platinum is a slightly distorted octahedron
with the ligands in a trans configuration (Figure 2). All
bonds around the Pt center have normal values. The chelate
ring is in the envelope-like conformation where the Pt atom
Chlorination of [Pt(o-OC6H4CH؍NOH)2] (1)
Passage of excess Cl2 through a chloroform solution of
1 for 20 min at room temperature resulted in the oxidative
addition of chlorine to the platinum(II) center and in the
chlorination of the benzene ring (Scheme 1). As a result of
the overall process, the platinum(IV) complex [PtCl2(3,5,2-
Cl,Cl,OC6H2CHϭNOH)2] (3) (Scheme 1), containing
˚
deviates from the organic unit by 0.256 A.
The oxime group is involved in an unusual hydrogen
commercially unavailable 2-hydroxy-3,5-dichlorobenzal- bonding (Figure 3), e.g. the intermolecular Ϫ rather than
dehyde oxime was isolated in 85% yield. The oxime 3,5,2- intramolecular as in the case of [Pt(o-OC6H4CHϭNOH)2]
Cl,Cl,HOC6H2CHϭNOH was prepared earlier by the (1) Ϫ O(2)ϪH···Cl(3) hydrogen bond [O(2)···Cl(3)(x,y,z Ϫ
˚
chlorination
of
salicylaldehyde
to
give
3,5,2- 1) ϭ 3.155, H···Cl(3) 2.34 A, angle O(2)ϪH···Cl(3) 161°].
Cl,Cl,HOC6H3CHϭO and its subsequent condensation According to Wells,[22] O···ClϪ distances in the range
with hydroxylamine.[21] We have also observed that when 2.95Ϫ3.4 A are found for OϪH···Cl hydrogen bonds (for
Ϫ
˚
nitrosyl chloride is used instead of molecular chlorine, ClϪ···H3Oϩ the distance is 2.95[22]). Every molecule of the
only oxidation of the central ion is observed, to give complex forms the repeating unit for a self-assembly that
[PtCl2(o-OC6H4CHϭNOH)2] (4), and the benzene rings produces infinite one-dimensional polymeric chains dir-
remain intact.
ected along the z axis held by H-bonds. It is worth noting
As already indicated,[16] chlorination of free salicylal- that the study of self-assembly of metal complexes, in par-
doxime under the same conditions as for the platinum(II) ticular by hydrogen bonding, is a rapidly developing field
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038
1033

V. Y. Kukushkin, A. J. L. Pombeiro et al.
FULL PAPER
Figure 2. View of trans-(N,N)-[PtCl2(3,5,2-Cl,Cl,OC6H2CHϭNOH)2] (3) with atomic numbering
Figure 3. Packing diagram for trans-(N,N)-[PtCl2(3,5,2-Cl,Cl,OC6H2CHϭNOH)2] (3) showing the hydrogen-bonding scheme
that is intrinsic for crystal engineering and materials sci- (5), the platinum exhibits a slightly distorted octahedral
ence,[3] and from that point of view, it is likely that the ob- geometry with three meridian Cl ligands (Figure 4).
servation of hydrogen bonding in the (salicylaldoximato)-
The values of the PtϪCl bond lengths (Table 2) agree well
with those of previously characterized platinum(IV) chlor-
ide compounds,[4,5] although the PtϪCl(2) bond [2.316(4)
PtIV compound deserves further investigation.
˚
A] is slightly shorter that the other two [2.338(4) and
Chlorination of [PtCl(OC6H4CH؍NOH)(HOC6H4CH؍
NOH)] (2) and Crystal Structure of trans-(N,N)-
[PtCl3(3,5,2-Cl,Cl,OC6H2CH؍NOH)(3,5,2-
Cl,Cl,HOC6H2CH؍NOH)] (5)
˚
2.336(4) A]. The most interesting feature of the structure is
the presence of two different salicylaldoxime species, i.e. one
is an unusual monodentate ligand and the other is the con-
ventional N,O-salicylaldoximato chelate. Surprisingly, the
corresponding bond lengths in the two types of salicylal-
doximato ligands are the same within 3σ. Although the hy-
drogen atoms at the ϭNOH moieties were not found, the
bond lengths indicated in Table 1 favor the oxime tauto-
meric structure in both cases.
The chlorination of 2 with molecular chlorine proceeded
similarly to that described above for 1 (Scheme 1), but the
reaction with NOCl gave a variety of products, which were
not separated. In the former case, both monodentate and
chelating ligands are chlorinated selectively at the 3- and 5-
positions of the aromatic ring rather than at the oxime
CHϭN group, indicating that coordination of the phenolic
oxygen has no influence on the course of the chlorination.
However, the most interesting result from this part of the
IR and NMR Spectroscopic Characterization of 5
In IR spectra, only one band of ν(CϭN) stretching vibra-
work is that the salicylaldoxime ligand maintains its mon- tions appears for the bis-chelated species 1 and 3, whereas
odentate coordination, which was unambiguously con- complexes 2 and 5, containing both chelating and monod-
firmed by X-ray study. In trans-(N,N)-[PtCl3(3,5,2- entate ligands, display two ν(CϭN) bands. 1H and 13C{1H}
Cl,Cl,OC6H2CHϭNOH)(3,5,2-Cl,Cl,HOC6H2CHϭNOH)] NMR spectra of 1 and 3 show only one set of signals for
1034
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038

Chlorination of Platinum-Bound Salicylaldoxime
FULL PAPER
Figure 4. View of trans-(N,N)-[PtCl3(3,5,2-Cl,Cl,OC6H2CHϭNOH)(3,5,2-Cl,Cl,HOC6H2CHϭNOH)] (5) with atomic numbering
˚
Table 2. Bond lengths (A) and bond angles (°) for 1, 3 and 5
consequently, the average distance between the correspond-
ing protons is much larger than in the chelated ligand.
Therefore, one would expect a much weaker or even no ob-
servable NOE signal for the monodentate ligand. In agree-
ment with this hypothesis, in both compounds 2 and 5, only
one CHϭN proton revealed a strong NOE interaction with
the 6-H proton (δ ϭ 8.44 to 7.53 for 2, δ ϭ 8.64 to 7.76 for
5), whereas irradiation of the second CHϭN proton (δ ϭ
8.84 for 2 and δ ϭ 9.03 for 5) did not show any NOE inter-
action. Furthermore, a comparison of the chemical shift
Bond
Complex
1
3
5
Pt(1)ϪO(1)
1.978(5)
1.974(6)
1.980(5)
1.997(5)
2.316(2)
2.023(10)
2.032(13)
2.338(4)
2.316(4)
2.336(4)
2.030(12)
90.54(15)
178.77(15)
89.5(3)
Pt(1)ϪN(1)
Pt(1)ϪCl(1)
Pt(1)ϪCl(2)
Pt(1)ϪCl(3)
Pt(1)ϪN(11)
Cl(1)ϪPt(1)ϪCl(2)
Cl(1)ϪPt(1)ϪCl(3)
Cl(1)ϪPt(1)ϪO(1)
Cl(1)ϪPt(1)ϪO(1)*
Cl(1)ϪPt(1)ϪN(1)
Cl(1)*ϪPt(1)ϪN(1)
Cl(1)ϪPt(1)ϪN(11)
Cl(2)ϪPt(1)ϪCl(3)
Cl(2)ϪPt(1)ϪO(1)
Cl(2)ϪPt(1)ϪN(1)
Cl(2)ϪPt(1)ϪN(11)
Cl(3)ϪPt(1)ϪO(1)
Cl(3)ϪPt(1)ϪN(1)
Cl(3)ϪPt(1)ϪN(11)
O(1)ϪPt(1)ϪN(1)
O(1)ϪPt(1)ϪN(1)*
O(1)ϪPt(1)ϪN(11)
N(1)ϪPt(1)ϪN(11)
3
89.9(2)
90.1(2)
90.6(2)
89.5(2)
and the coupling constants JPtH of the CHϭN protons of
the two ligands shows that, for the monodentate ligand, the
91.5(4)
δ value is higher (δ ϭ 8.84Ϫ9.03 vs. δ ϭ 8.44Ϫ8.77 for
3
89.6(3)
90.07(15)
177.8(3)
90.2(4)
94.3(3)
89.9(3)
89.6(4)
89.3(3)
92.0(5)
the chelate), while the JPtH value is smaller (23Ϫ30 Hz vs.
35Ϫ45 Hz for the chelate).
1H NMR spectroscopic experiments with 2 or 5 also
showed that the monodentate ligands do not interconvert
into chelating ligands. For 2, slow decomposition occurs
upon prolonged storage (3 weeks at 20Ϫ25 °C) or on heat-
ing (3 d at 56 °C) to give a mixture of unidentified products.
In contrast, 5 is stable and even after storage at room tem-
perature for two months or on heating at 56 °C for 4 d
in the presence of pyridine, neither transformation into the
corresponding bis-chelated complex 3, substitution of the
monodentate ligand for pyridine, or decomposition were
observed.
93.6(2)
86.4(2)
83.5(4)
175.4(5)
the salicylaldoximato-type ligands, while two sets are ob-
served for 2 and 5. Full assignment of the H NMR peaks
for 1Ϫ3 and 5 was made by means of one-dimensional
1
homodecoupling and NOE experiments. By measuring
It is also worth mentioning that chlorination of the mix-
NOE interactions between the oxime CHϭN proton and ture of (salicylaldoxime)PtII complexes, prepared according
the proton at the 6-position of the aromatic ring, one might to the method of Cox and co-authors,[19] gave, besides
distinguish between signals arising from the chelating and [PtCl2(3,5,2-Cl,Cl,OC6H2CHϭNOH)2] (3) and [PtCl3-
the monodentate ligands. In the chelate, in which the con- (3,5,2-Cl,Cl,OC6H2CHϭNOH)(3,5,2-Cl,Cl,HOC6H2-
formation of the ligand is fixed, the CHϭN and 6-H pro- CHϭNOH)] (5), a purely organic material, i.e. 3,5,2-
˚
tons are held at a distance of approximately 2.47 A, as con- Cl,Cl,HOC6H2C(Cl)ϭNOH. The latter is, at least formally,
firmed by the X-ray analysis of 5 (see above). This distance derived from both the Piloty reaction and the chlorination
is sufficiently short to give rise to a NOE signal, and indeed of the benzene ring. Since this compound was not observed
this peak was observed for the bis-chelated complex [Pt(o- in the course of the chlorination of salicylaldoxime itself,[16]
OC6H4CHϭNOH)2] (1) (δ ϭ 8.51 to 7.50). The monodent- and furthermore, chlorination of the individual plat-
ate ligand, however, has more conformational freedom and, inum(II)
complexes
does
not
give
3,5,2-
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038
1035

V. Y. Kukushkin, A. J. L. Pombeiro et al.
FULL PAPER
133.9, 134.9, 135.4 (aromatic CH’s), 146.1 (JPtC not observed) and
148.1 (JPtC not observed, NϭCH), 158.3 and 158.9 (quaternary C’s,
two signals were not detected). Ϫ 195Pt NMR ([D6]acetone): δ ϭ
Ϫ1842 (360 Hz).
Cl,Cl,HOC6H2C(Cl)ϭNOH, we anticipate that the chlor-
ination occurs in the benzene ring of coordinated ligand
followed by liberation of the chlorinated species. An investi-
gation of this reaction is underway in our group.
[Pt(o-OC6H4CH؍NOH)2] (1): Ϫ C14H12N2O4Pt: calcd. C 35.98, H
2.59, N 5.99, Pt, 41.74; found C 35.96, H 2.61, N 5.95, Pt, 41.97.
Ϫ FABϩ-MS, m/z: 467 [M]ϩ. Ϫ M.p. 255 °C (melting with concom-
itant sublimation), 276 °C (melting of the sublimed compound). Ϫ
TLC, Rf ϭ 0.57 (eluent CHCl3/CCl4 1:1, v/v). Ϫ IR spectrum in
KBr (selected bands) cmϪ1: ν˜ ϭ 1645 m-w ν(CϭN), 1599 m-s ν(Cϭ
Experimental Section
Materials and Apparatus: Salicylaldoxime (Aldrich) and solvents
were obtained from commercial sources and used as received. Cl2
for chlorination was obtained from the reaction of KMnO4 and
HCl by a standard procedure.[23] Traces of HCl were removed by
bubbling through water and dried over H2SO4. Nitrosyl chloride
was obtained by the reaction of an aqueous solution of NaNO2
with concentrated HCl. Residues of HCl were removed over
NaNO2, and NO2 was removed by treatment with moist KCl. The
nitrosyl chloride was finally dried over CaCl2.[24] Ϫ Melting points
were determined on a Kofler table. For TLC, Silufol UV 254 SiO2-
plates were used. Ϫ Positive-ion FAB mass spectra were obtained
on a Trio 2000 instrument by bombarding 3-nitrobenzyl alcohol
(NBA) matrices of the samples with 8 keV (ca. 1.28 ϫ 1015 J) Xe
atoms. Mass calibration for the data-system acquisition was
achieved using CsI. EI-MS of 3,5,2-Cl,Cl,HOC6H2C(Cl)ϭNOH
was measured on the same mass spectrometer. Ϫ Infrared spectra
(4000Ϫ400 cmϪ1) were recorded on a BIO-RAD FTS 3000MX in-
strument in KBr pellets, while spectra in the range 400Ϫ140 cmϪ1
were measured on a Hitachi FYS-3 spectrometer in polyethylene
1
C), 1188 m ν(CϪO), 741 δ(CϪH). Ϫ H NMR ([D6]acetone): δ ϭ
6.76 (ddd, JHH ϭ 8.1 Hz, 7.2 Hz, 1.2 Hz, 1 H), 7.16 (d, 8.4 Hz, 1
H), 7.39 (ddd, JHH ϭ 8.7 Hz, 6.9 Hz, 1.8 Hz, 1 H), 7.50 (dd, JHH ϭ
3
7.8 Hz, 1.8 Hz, 1 H, phenyl H), 8.51 [s ϩ d, JPtH ϭ 45.5 Hz, 1 H,
3
strong NOE to the signal at δ ϭ 7.50, ϭC(H)Ϫ], 10.91 (s, JPtH
ϭ
23.6 Hz, 1 H, OH). Ϫ 13C{1H} NMR ([D6]acetone): δ ϭ 118.3,
120.4, 134.0, 134.3 (aromatic CH’s), 144.8 (broad, NϭCH), qua-
ternary C’s not observed. Ϫ 195Pt NMR ([D6]acetone): δ ϭ
Ϫ1611 (480 Hz).
Chlorination of [Pt(o-OC6H4CH؍NOH)2] (1) by Cl2: Molecular
chlorine was passed through a lemon-yellow solution of 1 (0.136 g,
0.29 mmol) in CHCl3 (80 mL) for 20 min at 20Ϫ25 °C. A cherry-
brown solution formed, and was left to evaporate at 14Ϫ18 °C in
an open 100-mL beaker to ca. 10 mL. Transparent, glittering rhom-
bic-like
brownish
crystals
of
trans-(N,N)-[PtCl2(3,5,2-
Cl,Cl,OC6H2CHϭNOH)2] (3) were separated by filtration, washed
with a Me2CO/CCl4 mixture (1:2, v/v, 3 ϫ 3 mL), diethyl ether (3
ϫ 3 mL) and dried in a vacuum-desiccator at room temperature
over CaCl2. Yield: 0.167 g, 85%.
1
pellets. Ϫ H, 13C{1H} and 195Pt NMR spectra were obtained on
a Varian UNITY 300 spectrometer at ambient temperature. 195Pt
chemical shifts are reported relative to aqueous K2[PtCl4] ϭ
Ϫ1630 ppm, half-height line widths are given in parenthesis.
trans-(N,N)-[PtCl2(3,5,2-Cl,Cl,OC6H2CH؍NOH)2]
(3):
Ϫ
C14H8N2Cl6O4Pt: calcd. C 24.85, H 1.18, N 4.14, Cl 31.46, Pt
28.85; found C 24.60, H 1.26, N 3.94, Cl 32.00, Pt 28.52. Ϫ FABϩ-
MS, m/z: 606 [M Ϫ 2Cl]ϩ, 588 [M Ϫ 2Cl Ϫ OH]ϩ, 571
[M Ϫ 2HCl Ϫ 2OH]ϩ. Ϫ M.p. 238 °C. Ϫ TLC, Rf ϭ 0.48 (eluent
CHCl3). Ϫ IR (KBr, selected bands): ν˜ ϭ 1645 mw ν(CϭN), 1596
s ν(CϭC), 1422 s, br. δ(OϪH), 1189 ms ν(CϪO), 912 s ν(NϪO),
Synthetic Work and Characterization
Preparation of (Salicylaldoximato)PtII Complexes: The complexes
were prepared by treatment of K2[PtCl4] with salicylaldoxime as
described by Cox et al.[19] Complex [PtCl(OC6H4CHϭ
NOH)(HOC6H4CHϭNOH)] (2) was separated from the other spe-
cies by TLC on SiO2 (Silica gel L 5/40 µ, CHEMAPOL) with
CHCl3 as eluent (Rf [Pt(o-OC6H4CHϭNOH)2] (1) ϭ 0.62, Rf
[PtCl(OC6H4CHϭNOH)(HOC6H4CHϭNOH)] (2) ϭ 0.29, while
other species remain on the baseline). [PtCl(OC6H4CHϭ
NOH)(HOC6H4CHϭNOH)] (2) was then desorbed with acetone,
and the solvent was removed in vacuo at room temperature. The
residue was crystallized over a layer of cold water (5Ϫ10 °C). The
bis-chelate [Pt(o-OC6H4CHϭNOH)2] (1) was obtained in accord-
ing to a published method[19] and recrystallized from acetone.
1
358 ms ν(PtϪCl) cmϪ1. Ϫ H NMR ([D6]acetone): δ ϭ 7.82 and
3
7.84 (two d, 2.2 Hz, 1H each, phenyl H), 8.91 [s ϩ d, JPtH
ϭ
37.9 Hz, 1 H, ϭC(H)Ϫ], 11.00 (s, 1 H, NOH). Ϫ 13C{1H} and 195Pt
NMR spectra were not measured even at high acquisition time ow-
ing to the low solubility of the complex in common deuterated solv-
ents.
Chlorination of [PtCl(OC6H4CH؍NOH)(HOC6H4CH؍NOH)] (2)
by Cl2: Complex 2 (0.034 g, 0.068 mmol) was dissolved in CHCl3
(10 mL) and molecular chlorine was passed through this solution
for 20 min at 18Ϫ20 °C. The color of the reaction mixture turned
from lemon-yellow to dark red during the chlorination. The reac-
tion mixture was transferred to a long narrow tube, the solvent was
evaporated at room temperature and cherry-red crystals of trans-
(N,N)-[PtCl3(3,5,2-Cl,Cl,OC6H2CHϭNOH)(3,5,2-
Cl,Cl,HOC6H2CHϭNOH)] (5) were collected from the bottom
part of the tube (0.015 g, 29%). A brownish material was collected
from the upper part of the tube. Stirring this brownish material in
heptane gave an additional amount of less pure 5 (0.021 g, 41%).
[PtCl(OC6H4CH؍NOH)(HOC6H4CH؍NOH)] (2): Ϫ C14H13N2-
ClO4Pt: calcd. C 33.38, H 2.60, N 5.56, Cl 7.04, Pt 38.72; found C
33.78, H 2.91, N 5.71, Cl, 6.60, Pt 38.94. Ϫ FABϩ MS; m/z: 504
[M]ϩ. Ϫ M.p. 197Ϫ198 °C (dec.). Ϫ TLC, Rf ϭ 0.58 (eluent
Me2CO/CHCl3, 1:8, v/v). Ϫ IR (KBr, selected bands): ν˜ ϭ 3488 m,
br ν(OH), 1627 mw and 1601 vs ν(CϭN) ϩν(CϭC), 1458 vs and
1475 vs br. δ(OϪH), 1198 ms ν(CϪO), 912 ms ν(NϪO), 742 s
δ(CϪH) cmϪ1. Ϫ 1H NMR ([D6]acetone): δ ϭ 6.99 (t, JHH
7.5 Hz, 1 H), 7.05 (d, JHH ϭ 8.1 Hz, 1 H), 7.44 (t, JHH ϭ 7.5 Hz,
1 H), 8.44 (d, JHH ϭ 8.0 Hz, 1 H) (phenyl H), 8.84 (s ϩ d, JPtH
30.0 Hz, 1 H, ϭC(H)Ϫ, monodentate ligand), 6.83 (t, JHH
ϭ
3
ϭ
trans-(N,N)-[PtCl3(3,5,2-Cl,Cl,OC6H2CH؍NOH)(3,5,2-
Cl,Cl,HO-C6H2CH؍NOH)] (5): Ϫ C14H9N2Cl7O4Pt: calcd. C
ϭ
7.5 Hz, 1 H), 7.18 (d JHH ϭ 8.7 Hz, 1 H), 7.44 (t, JHH ϭ 7.5 Hz, 23.58, H 1.26, N 3.93, Cl 34.83, Pt 27.38; found C 23.85, H 1.28,
3
1 H), 7.53 (d, JHH ϭ 8.5 Hz, 1 H, phenyl H), 8.44 (s ϩ d, JPtH
40.0 Hz, 1 H, strong NOE to the signal at δ ϭ 7.53, ϭC(H)Ϫ, 603 [M Ϫ 3HCl]ϩ. Ϫ M.p. 211 °C (dec.). Ϫ TLC, Rf ϭ 0.62 (eluent
bidentate ligand), 9.67 (br, OH), 10.12 (s, OH), 12.16 (br., OH). Ϫ acetone/ chloroform 1:2, v/v). Ϫ IR spectrum (KBr, selected
13C{1H} NMR ([D6]acetone): δ ϭ 116.8, 119.0, 119.4, 120.6, 133.1, bands): ν˜ ϭ 1655 w and 1635 w ν(CϭN) and ν(CϭC), 1187 m
ϭ
N 3.87, Cl 35.00, Pt 27.52. Ϫ FABϩ-MS, m/z: 643 [M Ϫ 2Cl ϩ H]ϩ,
1036
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038

Chlorination of Platinum-Bound Salicylaldoxime
FULL PAPER
1
ν(CϪO), 357 m and 347 m ν(PtϪCl) cmϪ1. Ϫ H NMR ([D6]ace-
v/v, 3 ϫ 3 mL), diethyl ether (3 ϫ 3 mL), and dried at room temper-
tone): δ ϭ 7.83 (d, JHH ϭ 2.7 Hz, 1 H, phenyl H), 8.47(d, JHH
2.7 Hz, 1 H, phenyl H), 9.03 [s ϩ d, JPtH ϭ 23.4 Hz, 1 H, ϭ
ϭ
ature in a vacuum-desiccator over CaCl2. Yield: 0.11 g, 73%.
3
trans-(N,N)-[PtCl2(o-OC6H4CH؍NOH)2] (4):
Ϫ
C14H12N2-
C(H)Ϫ, monodentate ligand], 7.76 (d, JHH ϭ 2.7 Hz, 1 H, phenyl
Cl2O4Pt: calcd. C 31.24, H 2.25, N 5.20, Cl 13.17, Pt 36.24; found
C 30.99, H 2.30, N 5.11, Cl 13.69, Pt 35.8. Ϫ FABϩ-MS, m/z: 538
[M]ϩ. Ϫ M.p. 149Ϫ152 °C (dec.). Ϫ IR (KBr, selected bands): ν˜ ϭ
1652 m ν(CϭN), 1597 s ν(CϭC), 912 s ν(NϪO) cmϪ1. Ϫ 1H NMR
3
H), 7.79 (d, JHH ϭ 2.7 Hz, 1 H, phenyl H), 8.64 [s ϩ d, JPtH
ϭ
35.7 Hz, 1 H strong NOE to the signal at δ ϭ 7.76, ϭC(H)Ϫ,
bidentate ligand], 10.94 (br., OH). Ϫ 13C{1H} NMR ([D6]acetone):
δ ϭ 131.0, 132.7, 135.8 and 136.0 (aromatic CH’s), 149.1 (JPtC
28 Hz) and 151.4 (JPtC not observed)(NϭCH), 118.7 (JPtC
22 Hz), 119.8 (JPtC ϭ 25 Hz), 122.0, 123.5, 124.8, 125.6, 132.0 and
136.7 (quaternary C’s). Ϫ 195Pt NMR ([D6]acetone): δ ϭ ϩ252
(440 Hz).
ϭ
ϭ
([D6]DMSO): δ ϭ 6.82 (t, JHH ϭ 7.7 Hz, 1 H), 7.29 (d, JHH
ϭ
9.2 Hz, 1 H), 7.45 (t, JHH ϭ 7.2 Hz, 1 H), 7.56 (d, JHH ϭ 7.2 Hz,
1 H each o-phenyl H), 8.77 [s ϩ d, 3JPtH ϭ 34.8 Hz, 1 H, ϭC(H)Ϫ],
11.78 (s, br, 1 H, NOH). Solubility of the complex in [D6]DMSO
was insufficient to allow for the accumulation of either 13C{1H} or
195Pt NMR spectra, even with long acquisition times.
3,5,2-Cl,Cl,HOC6H2C(Cl)؍NOH: This purely organic material
was formed by the chlorination of a mixture of salicylaldoxime
complexes, prepared in agreement with Cox et al.,[19] and was sep-
arated mechanically upon fractional crystallization of the products
of the reaction from an acetone/toluene (3:1, v/v) mixture. Color-
less needles. Ϫ C7H4NCl3O2: calcd. C 34.94, H 1.66, N 5.83, Cl
44.29; found C 34.45, H 2.10, N 5.65, Cl 45.10. Ϫ EI-MS, m/z: 241
[M]ϩ, 203 [M Ϫ HCl]ϩ. Ϫ M.p. 141 °C [vs. ref. m.p. 194Ϫ195 °C
for 3,5-Cl,Cl-C6H3CHϭNOH[21]). Ϫ TLC, Rf ϭ 0.67 (eluent: chlo-
roform). Ϫ IR (KBr, selected bands): ν˜ ϭ 3423 vs ν(OϪH), 1651
mw and 1605 mw ν(CϭN) and ν(CϭC), 1180 m ν(CϪO) cmϪ1. Ϫ
1H NMR (CDCl3): δ ϭ 7.48 (d, 1 H, JHH ϭ 2.2 Hz), 7.76 (d, 1 H,
X-ray Crystal Structure Determinations
(i) Dark yellow prismatic crystals of 1 were grown by the slow
evaporation of a solution in CCl4 at room temperature. Diffraction
data were collected on an EnrafϪNonius CAD 4 diffractometer.
Diffractometer data were processed by the program PROFIT,[25]
with profile analysis of reflections. The structures were solved by
means of Fourier synthesis based on the Pt-atom coordinates ob-
tained from the Patterson synthesis using SHELXTL package.[26]
All non-hydrogen atoms were treated anisotropically. H atoms were
located in a difference Fourier map and refined isotropically. An
extinction correction was applied. Lorentz, polarization and ab-
sorption corrections were made.[27]
J
HH ϭ 2.6 Hz), 9.02 (s, 1 H, CϪOH), 10.64 (s, 1 H, oximic OH). Ϫ
13C{1H} NMR (CDCl3): δ ϭ 132.01 (CH), 127.34 (CH) quaternary
carbons were not observed owing to the low solubility of the com-
pound.
(ii) Transparent, glittering rhombic-like brownish crystals of 3 were
obtained directly from the reaction mixture. The crystallographic
Chlorination of [Pt(o-OC6H4CH؍NOH)2] (1) by NOCl: Nitrosyl measurements were performed on an EnrafϪNonius CAD-4 CCD
chloride was passed through a lemon-yellow solution of 1 (0.13 g,
diffractometer using the technique described in ref.[28] The structure
0.28 mmol) in a mixture of CCl4 (10 mL) and CHCl3 (50 mL) for was solved by direct methods and refined anisotropically for non-
20 min at 5 °C. A cherry-brown solution was formed and left to
evaporate at 14Ϫ18 °C in an open 100-mL beaker to ca. 10 mL.
hydrogen atoms and isotropically for H atoms using SHELXL-
97.[29] Positions of hydrogen atoms bonded to carbons were calcu-
Transparent, glittering rhombic-like brownish crystals of 4 were lated based on known atom geometry. These hydrogen atoms were
separated by filtration, washed with a Me2CO/CCl4 mixture (1:2,
allowed to ride on their neighboring carbons during the refinement.
Table 3. Crystal data and structure refinement for 1, 3 and 5
Empirical formula
Formula weight
Space group
C14H12N2O4Pt
467.34
C14H8N2Cl6O4Pt
676.0
C14H9N2Cl7O4Pt
712.5
monoclinic
P21/n (No 14)
4.5410(10)
25.007(5)
5.847(10)
90
triclinic
triclinic
¯
¯
Crystal system
P1
P1
˚
a [A]
6.9940(8)
8.2560(7)
9.1310(11)
66.026(6)
77.142(5)
89.253(7)
467.91(9)
1
9.559(4)
10.266(5)
10.565(3)
93.64(3)
93.45(3)
97.82(4)
1023(3)
2
˚
b [A]
˚
c [A]
α [°]
β[°]
97.65(3)
90
γ [°]
3
˚
V [A ]
658.1(2)
2
Z
Dc [Mg/m3]
F(000)
2.358
2.399
2.314(3)
672
440
318
µ(MoϪKα) [mmϪ1
]
10.679
8.378
8.148
2θmax [°] and sinθ/λ for data collection
51.9
52.0
59.94 and 0.703
Refinement method
full-matrix (anisotropic for all non-H atoms)
least squares on F2 for 1 and 3, and based on F for 5
Crystal size, mm
Index ranges
0.18 ϫ 0.42 ϫ 0.52
Ϫ5ϽhϽ5
Ϫ0ϽkϽ30
0ϽlϽ7
0.30 ϫ 0.10 ϫ 0.10
0ϽhϽ8
0.3 ϫ 0.2 ϫ 0.1
0ϽhϽ12,
Ϫ7ϽkϽ7
Ϫ7ϽlϽ7
2024
1800 [F(hkl)Ն4σ(F)]
327
Ϫ
Ϫ10ϽkϽ10
Ϫ10ϽlϽ11
1834
Collected reflections
Unique reflections
Refinement parameters
Extinction coefficient
Goodness-of-fit on F
R
1365
802 [I р2σ(I)]
118
1834 [I р2σ(I)]
125
0.003(6)
1.093
0.032(3)
1.014
1.101
0.0227
0.0389
0.0373
wR
0.0590
0.0411
0.0353
Eur. J. Inorg. Chem. 2001, 1031Ϫ1038
1037

V. Y. Kukushkin, A. J. L. Pombeiro et al.
FULL PAPER
Benetollo, V. Yu. Kukushkin, Inorg. Chim. Acta (Topical Vol-
ume on Platinum Chemistry) 1997, 265, 267.
Their thermal parameters were assigned the value of 1.2 times the
initial equivalent isotropic thermal parameters of their neighboring
carbons and were not refined. The oxime H atom was located by
difference Fourier synthesis and refined with restraints to maintain
the geometry derived from the difference map. Its thermal para-
meter was assigned the value of 1.5 times the initial equivalent iso-
tropic thermal parameter of its neighboring oxygen and was not
refined. The final R-value was 0.0389 for 1779 reflections with
I ϭ 2σ(I).
[10]
C. M. P. Ferreira, M. F. C. Guedes da Silva, V. Yu. Kukushkin,
´
J. J. R. Frausto da Silva, A. J. L. Pombeiro, J. Chem. Soc.,
Dalton Trans. 1998, 325.
[11]
[12]
[13]
[14]
[15]
[16]
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(iii) Dark cherry-red prismatic crystals of 5 were obtained after the
slow evaporation of a solution in acetone/toluene (3:1, v/v) in a
long (150 mm) narrow (5 mm) tube. Diffraction data were collected
on a Syntex P21 diffractometer. An extinction correction was not
made. Before anisotropic refinement, an absorption correction was
made using DIFABS[30] program. The contributions of hydrogen
atoms were included at fixed calculated positions, based on geomet-
rical requirements. All experimental data processing, solving and
refinement were performed using the CSD[27] program. Crystal
data for 1, 3 and 5 are given in Table 3.
[17] [17a]
[17b]
O. Piloty, Ber. Dtsch. Chem. Ges. 1898, 31, 452. Ϫ
O.
Piloty, A. Stock, Ber. Dtsch. Chem. Ges. 1902, 35, 3093. Ϫ [17c]
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Am. Chem. Soc. 1992, 114, 6944.
Crystallographic data (excluding structure factors) for the struc-
ture(s) reported in this paper have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary publication
no. CCDC-144573 (1), CCDC-144575 (3) and CCDC-144574 (5).
Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: (in-
ternat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
[18]
[19]
E. G. Cox, F. W. Pinkard, W. Wardlaw, K. C. Webster, J. Chem.
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[20] [20a]
R. C. Srivastava, E. C. Lingafelter, P. C. Jain, Acta Crys-
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[20c]
Chem. 1995, 621, 645. Ϫ
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[20d]
Acknowledgments
C. E.
[20e]
V. Yu. K., S. K. and S. S. thank INTAS for the grant (97Ϫ0166).
V. Yu. K. is very grateful for financial support of this study by the
PRAXIS XXI program (grant BCC16428/98). G. W. is grateful to
the PRAXIS XXI program for a fellowship (BPD11779/97). A. J.
L. P. thanks the FCT (Foundation for Science and Technology)
and the PRAXIS XXI program for financial support.
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[22]
[23] [23a]
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[25]
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