Structure and reactivity of [PtX2 (ketoxime)2] compounds. Cis-trans isomerization and X-ray structures of cis- [PtBr2 (Me2C=NOH)2] and trans- [PtBr2 (Me2C=NOH)2] · 2MeC (=O) NMe2

Article abstract of DOI:10.1016/S0277-5387(98)00041-2

The solid state thermal isomerization of cis- [PtX₂ (ketoxime)₂] (X = Cl, ketoxime = Me₂C=NOH, (CH₂)₄C = NOH, (CH₂)₅C=NOH ; X = Br, ketoxime = Me₂C=NOH) gives the corresponding trans-isomers in almost quantitative yields, thus showing that solid state isomerization is a general and convenient procedure for the synthesis of trans- [PtX₂ (ketoxime)₂] complexes. X-ray structure analyses were performed for both cis- [PtBr₂ (Me₂C=NOH)₂] and the bis-dimethylacetamide solvate of trans- [PtBr₂ (Me₂C=NOH)₂] . The former compound crystallizes in the orthorhombic space group Pbca with a = 9.593 (1) , b = 14.827 (2) , c = 17.218 (2) A ; V = 2449.0 (8) A³, Z = 8, and ρ_calcd = 2.718 cm^-3. The latter complex crystallizes in the orthorhombic space group Pbca with a = 10.543 (2) , b = 17.676 (4) , c = 12.398 (2) A ; V = 2310.5 (8) A³, Z = 4, and ρ_calcd = 1.941 g cm^-3. These two compounds are the first structurally characterized representatives of neutral Pt complexes with ''simple'' oximes.

Full text of DOI:10.1016/S0277-5387(98)00041-2

Polyhedron Vol[ 06\ No[ 04\ pp[ 1344Ð1350\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII ] S9166Ð4276"87#99930Ð1
Structure and reactivity of ðPtX1"ketoxime#1Ł
compounds[ Cis!trans isomerization and X!ray
structures of cis!ðPtBr1"Me1C1NOH#1Ł and
trans!ðPtBr1"Me1C1NOH#1Ł =
1MeC"1O#NMe1
Vadim Yu Kukushkin\aꢀ$ David Tudela\aꢀ Youlia A[ Izotova\a%
Vitaly K[ Belskyb and Adam I[ Stashb
a Departamento de Qu(mica Inorganica\ Universidad Autonoma de Madrid\ 17938 Madrid\
ꢁ
ꢁ
ꢁ
Spain
b L[ Ya[ Karpov Physico!Chemical Institute\ Obukha Str[ 09\ 092953 Moscow\
Russian Federation
"Received 06 November 0886 ^ accepted 10 January 0887#
Abstract*The solid state thermal isomerization of cis!ðPtX1"ketoxime#1Ł "X ꢂ Cl\ ketoxime ꢂ Me1C1NOH\
"CH1#3C ꢂ NOH\ "CH1#4C1NOH ^ X ꢂ Br\ ketoxime ꢂ Me1C1NOH# gives the corresponding trans!isomers
in almost quantitative yields\ thus showing that solid state isomerization is a general and convenient procedure
for the synthesis of trans!ðPtX1"ketoxime#1Ł complexes[ X!ray structure analyses were performed for both cis!
ðPtBr1"Me1C1NOH#1Ł and the bis!dimethylacetamide solvate of trans!ðPtBr1"Me1C1NOH#1Ł[ The former
compound crystallizes in the orthorhombic space group Pbca with a ꢂ 8[482"0#\ b ꢂ 03[716"1#\ c ꢂ 06[107"1#
Aý ^ V ꢂ 1338[9"7# Aý2\ Z ꢂ 7\ and rcalcd ꢂ 1[607 cm−2[ The latter complex crystallizes in the orthorhombic space
group Pbca with a ꢂ 09[432"1#\ b ꢂ 06[565"3#\ c ꢂ 01[287"1# Aý ^ V ꢂ 1209[4"7# Aý2\ Z ꢂ 3\ and rcalcd ꢂ 0[830
g cm−2[ These two compounds are the _rst structurally characterized representatives of neutral Pt complexes
with {{simple|| oximes[ Þ 0887 Elsevier Science Ltd[ All rights reserved
Keywords] oximes ^ complexes of Pt"II# with oximes ^ cis!trans isomerization ^ crystal structure
———————————————————————————————————————————————
Coordinated oxime ligands and oxime complexes dis! addition of coordinated oximes to acetone and some
play an impressively rich variety of reactivity modes other ketones ð3Ð5Ł\ addition of acetoxime to the
which lead to unusual types of chemical compounds allene ligand in a platinum"II# complex ð6Ł\ oxime
ÐPtIII derivatives
ð0Ł[ As far as the oxime chemistry of platinum is con! ligand supported stabilization of PtIII
ð7Ł\ increasing of equilibrium acidity of oxime ligands
on coordination ð8Ł\ cyclometallation of oxime ligands
in platinum"II# complexes ð09Ł\ Pt"IV#!mediated
hydrolysis of coordinated oxime ligand ð00Ł and oxi!
dation of Pt"II# complexes by 1!propanone oxime in
concentrated hydrochloric acid ð01Ł[ Recently\ two
of us have reported self!assembly by hydrogen
bonding in the ketoxime:ketoximato platinum"II#
cerned\ these complexes show a number of intriguing
and little explored reactivity modes\ e[g[ oxidative
coupling of two neighbouring oximes in Pt"IV# com!
plexes ð1\2Ł\ oxidation of oximes in Pt"II# complexes
with the formation of nitrosoalkyl derivatives ð3\4Ł\
ꢀ Authors to whom correspondence should be addressed[
$ On sabbatical leave from Department of Chemistry\ St
Petersburg State University\ 087893 Stary Petergof\ Russian
Federation[
% On leave from St Petersburg Technological Institute\
Zagorodny Pr[ 38\ 087902\ St Petersburg\ Russian Feder!
ation[
complexes
cis!ðPtCl"Me1C1NO#"Me1C1NOH#1Ł
and ðPt"Me1C1NO#1"Me1C1NOH#1Ł = 1H1O ð02Ł[
Moreover\ a novel type of hydrogen bonding\ i[e[ "m3!
Cl−# = cis!ð" = = = H0O0#1" = = = H0CH10#1Ł\ has been
observed ð02Ł[ These _ndings prompted us to inves!
1344

1345
V[ Y[ Kukushkin et al[
tigate more deeply both reactivity and other possible plates with layer thickness 9[1 mm have been used[ C\
structural types of "ketoxime#platinum"II# com! H and N elemental analyses were carried out by the
plexes[
Microanalytical Service\ Universidad Autonoma de
ꢁ
In spite of the fact that two cases of cis!trans Madrid[ EI mass!spectra were obtained with a VG
rearrangement of ðPtX1"ketoxime#1Ł have been docu! Autospec instrument[ Infrared spectra "3999Ð119
mented ð1\03Ł\ the general synthetic utility of solid! cm−0# were recorded on a PerkinÐElmer 0549 FT!IR
state isomerisation for the preparation of trans! spectrometer\ using Nujol mulls between CsI
ðPtX1"ketoxime#1Ł complexes had not been estab! windows[ Raman spectra were measured on a Dilor
lished\ and no X!ray crystal structure of ðPtX1"ke! XY spectrophotometer\ using an Ar laser "4034 Aý#
toxime#1Ł complexes had been published[ We focused with the powdered samples sealed in capillary tubes[
our attention on the cis!trans isomerization of 0H NMR spectra were measured on a Bruker AMX!
ðPtX1"ketoxime#1Ł for the following reasons ] "i# these 299 instrument[
data are useful for the planned synthesis of the iso!
meric compounds\ which display a very rich chemical
reactivity ð3Ð5Ł\ but had not been completely charac! Synthetic work and characterization
terised ^ "ii# the geometrical isomerization should be
taken into account in potential studies of biological
activity\ since in the vast majority of cases\ the geo! complexes
Synthesis of cis!ðPtX1"ketoxime#1Ł compounds[ The
cis!ðPtCl1"ketoxime#1Ł "ketoxime ꢂ
metric isomers of ðPtX1"amine#1Ł exhibit di}erent Me1C1NOH\ "CH1#3C1NOH\ "CH1#4C1NOH#
structure!activity relationships ð04Ð06Ł ^ "iii# the crys! were prepared according to the published methods
tal structure of ðPt"Me1C1NOH#3ŁCl1 is suggestive of ð1\19Ł from K1ðPtCl3Ł and two equivalents of the
C0H = = = Pt and C0H = = = Cl interactions ð02Ł that are appropriate oxime in water[
similar to the so!called intermolecular multicenter het!
Synthesis of cis!ðPtBr1"Me1C1NOH#1Ł[ "i# Starting
ero!acceptor "IMH# hydro`en bond ð07Ł\ and it is inter! from K1ðPtCl3Ł[*Potassium bromide "9[61 g\ 5[9
esting to study whether this kind of interaction is mmol# is added to a solution of K1ðPtCl3Ł "9[4 g\ 0[1
present in other Pt"II#!oxime complexes[ In addition\ mmol# in water "09 ml# and the mixture is left to stand
there is current interest in the stacking of d7!ML3 at 19Ð14>C for 1 h[ After addition of acetone oxime
complexes ð08Ł[
"9[07 g\ 1[3 mmol#\ the reaction mixture is left to stand
In the course of this work we have determined at the same temperature for 2 d\ and the released
the experimental conditions for the preparation of crystals are _ltered o} and dried in air at 69>C[ The
the isomeric pairs of ðPtX1"ketoxime#1Ł "X ꢂ Cl\ yield of cis!ðPtBr1"Me1C1NOH#1Ł is 9[24 g\ 47)
ketoxime ꢂ Me1C1NOH\ "CH1#3C1NOH\ "CH1#4 based on Pt[
C1NOH ^ X ꢂ Br\ ketoxime ꢂ Me1C1NOH#\ and
"ii# Starting from cis!ðPtCl1"Me1"C1NOH#1Ł[*
solved the crystal structures of both cis!ðPtBr1"Me1 Solid silver nitrate "9[41 g\ 2[0 mmol# is added during
C1NOH#1Ł and the bis!dimethylacetamide solvate of 09 min to a suspension of cis!ðPtCl1"Me1C1NOH#1Ł
trans!ðPtBr1"Me1C1NOH#1Ł[ To the best of our "9[52 g\ 0[4 mmol# in water "19 ml#[ After stirring
knowledge these two compounds are the _rst struc! the suspension for 3 h at room temperature\ AgCl is
turally characterized representatives of neutral Pt _ltered o} and washed with water "4 ml#[ Potassium
complexes with so!called {{simple|| oximes*ligands bromide "9[35 g\ 2[7 mmol# is added to the pale!yellow
which have merely one oxime group as the only coor! _ltrate\ the reaction mixture is stirred for 04 min and
dination site*although the structures of ðPt"Me1 a small amount of precipitate is _ltered o}[ The yellow
C1NOH#3ŁCl1 ð02Ł and some platinum"II# complexes _ltrate is left to stand for 01 h at room temperature\
with vic!dioxime ligands are known ð08Ł[ Previous and prism!like crystals are collected on a _lter and
attempts to solve the structure of cis!ðPtCl1"Me1 dried in air at 19Ð14>C[ The yield of cis!ðPtBr1"Me1
C1NOH#1Ł\ failed due to decomposition under X! C1NOH#1Ł is 9[98 g[ 00) based on Pt[ Crystals suit!
ray irradiation ð1Ł[
able for X!ray analysis were grown directly from the
reaction mass[
Yellow prisms from water\ mp ꢂ 069>C[ TLC on
SiO1\ MeCN ] CHCl2 ꢂ 1 ] 0\ Rf ꢂ 9[44[ EI!MS\ m:z ]
499 "099)#\ 490 "64)# and 491 "84)# "M#¦[ Anal[
Calcd for C5H03Br1N1O1Pt ] C\ 03[3 ^ H\ 1[7 ^ N\ 4[5[
Found ] C\ 03[6 ^ H\ 1[6 ^ N\ 4[6[ IR data\ cm−0 ] 0548
EXPERIMENTAL
Materials and instrumentation
m!s n"C1N#\ 123 ms n"Pt0Br#[ Raman data\ cm−0
]
The ketoxime ligands were purchased from Aldrich 0550 m n"C1N#\ 123 s and 198 m n"Pt0Br#[ 0H NMR
and used as received[ K1ðPtCl3Ł was obtained from in D1O\ d\ ppm ] singlets at 1[07 and 1[53[ JPtH coupling
Reakhim and recrystallized from water[ All other constants are not well resolved[
chemicals and solvents were obtained from com!
mercial sources and were used as received[ Melting trans!ðPtCl1"Me1C1NOH#1Ł\
and:or decomposition points were determined in C1NOH#1Ł "n ꢂ 3\ 4# and trans!ðPtBr1"Me1
capillary[ For TLC Riedel!deHaen 59 F 143 SiO ! C1NOH#1Ł were prepared by keeping the cis!isomers
Syntheses of trans!ðPtX1"ketoxime#1Ł compounds[
trans!ðPtCl1""CH1#n
Ã
1

Structure and reactivity of ðPtX1"ketoxime#1Ł compounds
1346
at 039>C for 3 h\ 024>C for 5 h\ 039>C for 5 h and X!ray structure determination of cis!ðPtBr1"Me1
C1NOH#1Ł and trans!ðPtBr1"Me1C1NOH#1Ł = 1Me
C"1O#NMe1 "data for the latter complex are `iven
below in square brackets#[
039>C for 4 h\ respectively[ In all cases the solid!state
isomerization was monitored by TLC on SiO1[ The
properties of trans!ðPtCl1"Me1C1NOH#1Ł have been
described previously ð1Ł[
Di}raction data were collected on an Enraf!Nonius
CAD!3 ðNicolet P2Ł di}ractometer[ Cell parameters
for both complexes were obtained from 01 centred
re~ections with u between 09 and 01>\ 1421 ð0248Ł
re~ections were measured up to 49> by the u:1u scan
technique[ Three standard re~ections were measured
every 59 min and showed practically no change with
time ðin the case of the solvate ðPtBr1"Me1C!
1NOH#1 = 1MeC"1O#NMe1\ the crystal was packed
in Cyacrine glue to prevent decomposition\ but crystal
decay was 1)Ł[ Di}ractometer data were processed
by the program PROFIT ð10Ł with pro_le analysis of
re~ections[ The structures were solved by means of
Fourier synthesis based upon the Pt!atom coordinates
obtained from the Patterson synthesis using the
SHELXTL package ð11Ł[ After that\ all re~ections
with I ³ 1s"I# were excluded from calculations[
Re_nement was done by full!matrix least squares
based on F1 using the SHELX!82 package ð12Ł[ All
non H!atoms were treated anisotropically[ H!atom
coordinates were found from di}erence syntheses and
were included in re_nement with _xed positional and
thermal parameters[ An extinction correction has been
applied "x ꢂ 9[903 ð9[904Ł# Lorentz\ polarization and
absorption corrections were made ð13Ł[ Scattering fac!
tors were obtained from the International Tables for
X!ray Crystallo`raphy ð14Ł[ All important crys!
tallographic and re_nement parameters for both
structures are summarized in Table 0\ and bond dis!
tances and angles are collected in Tables 1 and 2[
Tables of atom coordinates and thermal parameters
have been deposited at the Cambridge Crys!
tallographic Data Centre[
trans!ðPtCl1""CH1#3C1NOH#1Ł[ This compound
has no characteristic melting point[ On slow heating
in a capillary it decomposes from ca 089>C[ EI!MS\
m:z ] 353 "69)# "M#¦\ 317 "04)# "M−HCl#¦\ 280
"099)# "M−1HCl#¦\ 250 "44)# "M−1HCl\
−NO#¦[ TLC on SiO1\ CHCl2 ] Me1CO ꢂ 5 ] 0\
Rf"trans# ꢂ 9[54\ cf with Rf"cis# ꢂ 9[24 for the cis!
isomer[ Anal[ Calcd for C09H07Cl1N1O1Pt ] C\ 14[8 ^
H\ 2[8 ^ N\ 5[9[ Found ] C\ 14[5 ^ H\ 2[8 ^ N\ 4[7[ IR
data\ cm−0 ] 0557 ms nas"C1N#\ 225 s nas"Pt0Cl#[
Raman data\ cm−0 "decomposes in the laser beam# ]
0
229 w ns"Pt0Cl#[ H NMR in acetone!d5\ d\ ppm ]
multiplets centered at 0[71 "7 H\ b!CH1#\ 1[61 "3 H#
and 2[98 "3 H# "a!CH1#\ singlet at ca 09[9 "1 H\ OH ^
very broad#[
trans!ðPtCl1""CH1#4C1NOH#1Ł[ The compound
has no characteristic melting point[ On slow heating
in a capillary it decomposes from ca 089>C[ EI!MS\
m:z ] 381 "44)# "M#¦\ 345 "04)# "M−HCl#¦\ 308
"099)# "M−1HCl#¦\ 278 "59)# "M−1HCl\
−NO#¦[ TLC on SiO1\ CHCl2 ] Me1CO ꢂ 5 ] 0\
Rf"trans# ꢂ 9[79\ cf\ with Rf"cis# ꢂ 9[34 for the cis!
isomer[ Anal[ Calcd for C01H11Cl1N1O1Pt ] C\ 18[2 ^
H\ 3[4 ^ N\ 4[6[ Found ] C\ 18[4 ^ H\ 3[6 ^ N\ 4[6[ IR
data\ cm−0 ] 0542 m nas"C1N#\ 229 s nas"Pt0Cl#[
Raman data\ cm−0 "decomposes in the laser beam# ]
0
214 w ns"Pt0Cl#[ H NMR in acetone!d5\ d\ ppm ]
multiplets centered at 0[50 "3 H\ g!CH1#\ 0[70 "7 H\ b!
CH1#\ 1[60 "3 H# and 2[14 "3 H# "a!CH1#\ singlet at
8[80 "1 H\ OH ^ broad#[
trans!ðPtBr1"Me1C1NOH#1Ł[ Pale!yellow small
crystals after recrystallization from boiling MeNO1\
mp ꢂ 131Ð134>C[ TLC on SiO1\ MeCN ] CHCl2 ꢂ
0 ] 2\ Rf ꢂ 9[59[ EI!MS\ m:z ] 499 "099)#\ 490 "79)#
and 491 "099)# "M#¦[ Anal[ Calcd for
C5H03Br1N1O1Pt ] C\ 03[3 ^ H\ 1[7 ^ N\ 4[5[ Found ] C\
03[5 ^ H\ 1[4 ^ N\ 4[5[ IR data\ cm−0 ] 0556 m!s
n"C1N#\ 135 s n"Pt0Br#[ 0H NMR in acetone!d5\ d\
ppm ] singlets at 1[07 "5 "H#\ 1[59 "5 H# and 09[91
"1 H\ broad#[ JPtH coupling constants are not well
resolved[ Recrystallization of trans!ðPtBr1"Me1
C1NOH#1Ł from boiling dimethylacetamide gives the
bis!solvate trans!ðPtBr1"Me1C1NOH#1Ł = 1MeC"1O#
NMe1 as yellow crystals\ mp ꢂ 039Ð032>C[ Anal[
Calcd for C03H21Br1N3O3Pt ] C\ 13[8 ^ H\ 3[7 ^ N\ 7[2[
Found ] C\ 13[8 ^ H\ 3[2 ^ N\ 6[8[ IR data\ cm−0 ] 0503
RESULTS AND DISCUSSION
The interest in processes of geometrical iso!
merization of platinum"II# complex ðPtX1L1Ł "where
X ꢂ halide or pseudohalide\ L ꢂ N!donor ligand# is
partly due to the anticancer activity of some ðPtX1L1Ł
compounds ð04Ð06Ł[ Additionally\ these rearrange!
ments are of synthetic utility for the preparation of
the trans!isomers[ A fairly large number of studies
concerning the cis!trans conversion of ðPtX1L1Ł
"L ꢂ NH2 ð15Ð17Ł and other ligands with sp2! ð18Ð20Ł\
sp1! ð21Ð23Ł and sp!hybridized N!donor atoms ð24Ł#
have been carried out\ but very little is known about
the cis!trans isomerization of ketoxime complexes
ðPtX1"ketoxime#1Ł[ In continuation of a DTA:TG
study ð02Ł\ two of us recently observed that on heating
cis!ðPtCl1"Me1C1NOH#1Ł undergoes a cis!trans iso!
merization ð1Ł[
vs\ br[ n"C1O#\ 133 s nas"Pt0Br#[ Raman data\ cm−0
]
0
0553 m ns"C1N#\ 196 vs ns"Pt0Br#[ The H NMR
spectrum in acetone!d5 shows\ in addition to the sin!
glets corresponding to trans!ðPtBr1"Me1C1NOH#1Ł
ð1[07 "5 H#\ 1[50 "5 H# and 09[94 br "1 H# ppmŁ\ the
singlets corresponding to MeC"1O#NMe1 at d\ ppm ]
0[86 "5 H\ MeC"1O##\ 1[72 "5 H# and 2[99 "5 H#
"NMe1#[
We report herein that the solid!state cis!trans
rearrangement occurs in a similar way for the oxime

1347
V[ Y[ Kukushkin et al[
Table 0[ Crystal data and structure re_nement
Compound
cis!ðPtBr1"Me1C1NOH#1Ł
trans!ðPtBr1"Me1C1NOH#1Ł = 1MeC"1O#NMe1
Empirical formula
Formula weight
Colour
C5H03Br1N1O1Pt
490[0
yellow
C03H21Br1N3O3Pt
564[3
yellow
Crystal size "mm#
Crystal system
Space group
a "_#
9[26×9[17×9[97
orthorhombic
Pbca "No[ 50#
8[482"0#
03[716"1#
06[107"1#
1338[9"7#
7
9[34×9[39×9[04
orthorhombic
Pbca "No[ 50#
09[432"1#
06[565"3#
01[287"1#
1209[4"7#
3
b "_#
c "_#
V "_2#
Z
rc "g cm−2
T "K#
1[607
182"1#
0[830
182"1#
Radiation\ l"_#
MoÐKa\ 9[60962
06[850
MoÐKa\ 9[60962
8[444
m\ mm−0
Di}ractometer
u range ">#
Index ranges
CAD!3
Nicolet P2
1[29Ð14[93
h ꢂ 9Ð01
k ꢂ 9Ð19
l ꢂ 9Ð03
0248
0941
9[121 and 9[917
005
0[963
9[923
9[978
0[244 and −0[165
1[26Ð13[86
h ꢂ 9Ð00
k ꢂ 9Ð05
l ꢂ 9Ð19
1421
0973
9[134 and 9[906
008
0[988
9[917
9[968
0[006 and −0[217
No[ of coll[ re~cns
No[ of unique re~cns with I − 1s"I#
Max\ min transmission
Re_ned parameters
Goodness!of!Fit on F1
Ra
wR1b
Largest di}[ peak and hole "e_−2
#
a R ꢂ S"=Fo=−=Fc=#:S=Fo=
b wR1 ꢂ ðSw"F1o −F1c #1:SwF3o Ł0:1
Table 1[ Bond lengths "_# and angles "># for cis!ðPtBr1"Me1C1NOH#1Ł
Bond lengths
Pt0N"0#
Pt0Br"1#
O"0#0N"0#
N"0#0C"1#
C"0#0C"1#
C"3#0C"4#
1[911"01#
1[274"1#
0[30"1#
0[29"1#
0[35"1#
0[49"1#
Pt0N"1#
Pt0Br"0#
O"1#0N"1#
N"1#0C"4#
C"1#0C"2#
C"4#0C"5#
1[931"00#
1[282"1#
0[31"1#
0[16"1#
0[36"1#
0[37"1#
Bond angles
N"0#0Pt0N"1#
N"1#0Pt0Br"1#
N"1#0Pt0Br"0#
C"1#0N"0#0O"0#
O"0#0N"0#0Pt
C"4#0N"1#0Pt
N"0#0C"1#0C"0#
C"0#0C"1#0C"2#
N"1#0C"4#0C"3#
89[5"4#
78[6"2#
N"0#0Pt0Br"1#
N"0#0Pt0Br"0#
Br"1#0Pt0Br"0#
C"1#0N"0#0Pt
C"4#0N"1#0O"1#
O"1#0N"1#0Pt
N"0#0C"1#0C"2#
N"1#0C"4#0C"5#
C"5#0C"4#0C"3#
067[7"2#
89[2"2#
065[8"2#
002[5"01#
004[5"7#
020[7"00#
012"1#
78[32"7#
029[7"09#
002[8"01#
003[9"7#
019[6"03#
007[1"03#
010[9"03#
006"1#
010"1#

Structure and reactivity of ðPtX1"ketoxime#1Ł compounds
1348
Table 2[ Bond lengths "_# and angles "># for trans!ðPtBr1"Me1C1NOH#1Ł =
1MeC"1O#NMe1
Bond lengths
Pt0Br
Pr0N"0#
O"0#0N"0#
N"0#0C"0#
C"0#0C"1#
C"0#0C"2#
1[308"1#
1[905"7#
0[273"01#
0[157"03#
0[36"1#
C"3#0C"4#
O"1#0C"3#
N"1#0C"3#
N"1#0C"5#
N"1#0C"6#
0[38"1#
0[11"1#
0[21"1#
0[36"1#
0[33"1#
0[40"1#
Bond angles
N"0#0Pt0N"0#?
N"0#?0Pt0Br
079[9
N"0#0Pt0Br
Br0Pt0Br?
89[6"2#
079[9
78[2"2#
002[0"8#
007[9"5#
011[8"03#
013[5"01#
006[6"09#
019[0"02#
C"0#0N"0#0O"0#
O"0#0N"0#0Pt
C"3#0N"1#0C"5#
N"0#0C"0#0C"1#
C"1#0C"0#0C"2#
O"1#0C"3#0C"4#
C"0#0N"0#0Pt
C"3#0N"1#0C"6#
C"6#0N"1#0C"5#
N"0#0C"0#0C"2#
O"1#0C"3#0N"1#
N"1#0C"3#0C"4#
017[8"8#
008[3"01#
006[4"02#
006[6"09#
010[1"03#
007[6"03#
Symmetry code ] "?# 0−x\ −y\ −z
complexes ðPtX1"ketoxime#1Ł studied[ In all these
cases\ heating the cis!isomers at 024Ð039>C for 3Ð5 h
led to the corresponding trans!ðPtX1"ketoxime#1Ł with
almost quantitative yields[ The direction of the
rearrangement agrees with that predicted by the ther!
mal isomerization rule ð25Ł[ A similar behaviour has
been observed for both octahedral platinum"IV# ð26Ł
and tin"IV# halide complexes ð27\28Ł[
An alternative method for preparation of trans!
ðPtX1"ketoxime#1Ł consists of prolonged re~uxing of
cis!ðPtX1"ketoxime#1Ł in aqueous media in the pres!
ence of free ketoxime ð19Ł[ We have established that
the procedure can be successfully applied for the syn!
thesis of trans!ðPtX1"Me1C1NOH#1Ł "X ꢂ Cl\ Br#
but it is not e.cient for the other complexes with more
bulky and hydrophobic oximes\ ðPtX1"ketoxime#1Ł
"X ꢂ Cl\ ketoxime ꢂ "CH1#3C1NOH\ "CH1#4C1N
OH#\ probably due to the poorer solubility of the
starting cis!isomers in water[ Therefore\ solid!state
isomerisation is a general and convenient procedure
for the synthesis of trans!ðPtX1"ketoxime#1Ł
complexes[
Fig[ 0[ View of cis!ðPtBr1"Me1C1NOH#1Ł with atomic num!
bering[
We have performed X!ray structure analyses for
both cis!ðPtBr1"Me1C1NOH#1Ł "0# and trans!
ðPtBr1"Me1C1NOH#1Ł = 1MeC"1O#NMe1 "1#[ The ations from the least!square planes through PtO"0#
centrosymmetric solvate 1 was obtained after recrys! N"0#C"0#C"1#C"2# ðPtO"1#N"1#C"3#C"4#C"5#Ł in 0
tallization of trans!ðPtBr1"Me1C1NOH#1Ł from boil! and PtN"0#O"0#C "0#C"1#C"2# in 1 of −9[996 Aý for
ing dimethylacetamide[ In 0 and 1\ two Br and two N N"0# ð9[911 Aý for N"1#Ł and −9[910 Aý for O"0#\
atoms form a slightly distorted square!planar coor! respectively[ The Pt0N interatomic distances
dination polyhedron around the Pt atoms\ as shown ð1[911"01# and 1[931"00# Aý for 0 and 1[905"7# for 1Ł
in Figs 0 and 1\ with angles around the Pt atoms close are consistent with those found in ðPt"Me1C1NOH#3Ł
to 89 and 079>[ Two acetoxime ligands are in cis! Cl1 ð02Ł[ In the case of oximato ligands the negative
positions to each other in 0 and in trans!positions in charge makes them better donors than oxime ligands\
1\ and in both cases the ligands are coordinated to Pt thus shortening the Pt0N distance[ So\ for cis!
through their nitrogen atoms[ As expected\ the ligands ðPtCl"Me1C1NO#"Me1C1NOH#1Ł\ with two crys!
are planar in both complexes\ with maximum devi! tallographically
independent
molecules\
the

1359
V[ Y[ Kukushkin et al[
A qualitative theoretical study has found that p!
acidic ligands enhance the M = = = M stacking inter!
actions in square!planar d7!ML3 complexes\ and
ðPt"vic!dioximato#1Ł complexes show columnar stack!
ing with short "in the range 2[06Ð2[49 Aý# Pt = = = Pt
distances ð08Ł[ In 0 and 1\ however\ the steric hin!
drance due to the bulky 1CMe1 moieties leads to
dihedral angles between the ligand planes and the
coordination plane of 56[0> and 62[4> for 0 and 74[0>
for 1[ This\ in turn\ prevents the square!planar com!
plexes from stacking and gives rise to long Pt = = = Pt
separations[ Indeed\ the shortest Pt = = = Pt distances are
4[253 Aý in 0 and 7[026 Aý in 1[ Unfortunately\ hydro!
gen atoms could not be re_ned in the presence of the
heavy Pt and Br atoms\ and nothing can be discussed
about the possibility of O0H = = = Br\ O0H = = = Pt\
C0H = = = Pt and C0H = = = Br interactions[
To the best of our knowledge\ this study is the
_rst one supported by X!ray di}raction for the occur!
rence of cis!trans isomerization in ketoxime
ðPtX1"RR?C1NOH#1Ł compounds[
Fig[ 1[ View of trans!ðPtBr1"Me1C1NOH#1Ł = 1MeC"1O#
NMe1 with atomic numbering[
Acknowled`ements*The authors are grateful to the Spanish
Direccion General de Investigacion Cient(_ca y Tecnica for
ꢁ
ꢁ
ꢁ
ꢁ
_nancial support "Project PB82!9166# and the award of a
sabbatical fellowship to V[ Yu[ Kukushkin "Grant SAB 83!
9206#[ V[ K[ Belsky and V[ Yu[ Kukushkin thank the Russian
Fund of Basic Research for the Grants 86!92!22665 and 86!
92!22515a\ respectively[
Pt0N"oximato# distances "0[882"6# and 0[881"6# Aý#
are shorter than the Pt0N"oxime# distances
"1[911"6#01[922"7# Aý# ð02Ł[ The C0N distances are
also consistent with those previously reported for
trans!ðPdCl1"Me1C1NOH#1Ł ð39Ł and ðPt"Me1C!
1NOH#3ŁCl1 ð02Ł[ In the solvate 1\ the OH group of
the oxime ligand is involved in a strong intermolecular
hydrogen bond with a molecule of dimethylacetamide[
The O"0# = = = O"1# distance\ 1[51"1# Aý\ is in the range
of strong hydrogen bonds ð30Ł\ which agrees with the
acidic character of acetoxime ligands coordinated to
Pt"II# ð31Ł[ According to Gutmann|s second bond
length variation rule ð32Ł\ we could expect the for!
mation of the hydrogen bond should lead to a short!
ening of the N0O bond distance[ Nevertheless\ the
shortening of the N0O bond distance in 1 as com!
pared to the N0O distances in 0 is not signi_cant in
terms of the standard deviations[ Indeed\ the N0O
bond distances for both 0 "0[30"1# and 0[31"1# Aý# and
1 "0[273"01# Aý#\ agree with those found in ðPt"Me1
C1NOH#3ŁCl1 "0[274"4#Ð0[390"4# Aý# ð02Ł[
The Pt0Br bond lengths in the cis!complex 0
ð1[282"1# and 1[274"1# AýŁ are shorter than in the trans!
isomer 1 "1[308"1# Aý#\ and in both K1ðPtBr3Ł "1[334"1#
Aý# ð33Ł and Rb1ðPtBr3Ł = H1O "1[324"2# Aý# ð34Ł\ but
agree well with the Pt0Br bond lengths "trans to N#
in cis!ðPtBr1"Me1SO#"MeC2N#Ł "Pt0Br trans to S
are 1[316"1#\ 1[318"1# and Pt0Br trans to N are
1[286"1#\ 1[283"1# Aý ^ data are given for two crys!
tallographically independent molecules ð35Ł#[ The
di}erence in the Pt0Br interatomic distances for 0\ 1
and ðPtBr3Ł1− complexes suggests that the ground!
state trans!in~uence of acetoxime is smaller than that
of the bromide ligand[
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