G.I. Zharkova et al. / Polyhedron 40 (2012) 40–45
41
(CH3)3Pt(hfac)H2O (1); [(CH3)3Pt(CF3–CO–CH–CO–CH3)H2O], (CH3)3
Pt(tfac)H2O (2); [(CH3)3Pt(CF3–CO–CH–CO–C(CH3)3)H2O], (CH3)3
Pt(ptac)H2O (3), the synthesis, elemental analysis data, IR and 1H
and 13C NMR spectra, thermal study of the complexes, and their
crystal structures.
nor ligand, e.g., H2O, in the reaction mixture. This molecule has to
occupy the sixth coordination site in the monomeric trimethylplat-
inum b-diketonate complex. This is why we failed to obtain fluori-
nated trimethylplatinum b-diketonates in anhydrous solvents. On
adding a small amount of water in the reaction mixture (96% etha-
nol is sufficient), monomeric fluorinated complexes containing the
water molecule are prepared. Thus, fluorinated trimethylplatinum
2. Results and discussion
b-diketonates form no dimers through Pt–C bonding, as it occurs
c
in trimethylplatinum b-diketonates with phenyl or alkyl substitu-
ents in the ligand. Possibly, an increase in electronegativity of the
terminal b-diketonate group results in an increase in the positive
2.1. Synthesis and characterization of [(CH3)3Pt(CF3–CO–CH–CO–
CF3)H2O], (1); [(CH3)3Pt(CF3–CO–CH–CO–CH3)H2O], (2);
[(CH3)3Pt(CF3–CO–CH–CO–C(CH3)3 H2O], (3)
charge on C atom of the b-diketonate ligand. Thus the probability
c
for Pt–C bonding decreases allowing platinum to coordinate other
c
The complexes 1–3 were synthesized according the following
scheme:
donor ligands. Note that water molecule is bound to platinum only
in fluorinated b-diketonates. It was established that water is pre-
served in the composition even after repeated sublimation of the
complexes in vacuum.
þ3CH3
F;H2
!
K2PtCl6
!
MgIðCH3Þ PtI þKL
OðCH3Þ PtðLFÞH2O
3
3
where HLF – fluorinated b-diketone: 1,1,1,5,5,5-hexafluoro-2,4-pen-
tanedione – CF3COCH2COCF3 (Hhfac); 1,1,1-trifluoro-2,4-pentanedi-
one – CF3COCH2CO-CH3 (Htfac); 1,1,1-trifluoro-5,5-dimethyl-2,4-
hexanedione – CF3COCH2CO-C(CH3)3 (Hptac).
Trimethylplatinum iodide, (CH3)3PtI, was used as the starting
compound for the synthesis of volatile platinum(IV) b-diketonates.
This compound was previously prepared from anhydrous salt
K2PtCl6 and CH3MgI by the Grignard reaction according to the pro-
cedure from [16]. It should be noted we have modified this proce-
dure and increased the yield of the complex from 55% to 75%.
Potassium salts of the ligands (KLF) previously obtained by mixing
ethanol solutions of KOH and HLF in 1:1 ratio were used for the
synthesis of b-diketonates platinum(IV).
2.2. Structural characterization of 1, 2, and 3
The single crystals for X-ray study were prepared from their
solutions in hexane at 0 °C. The structures of compounds 1–3 belong
to the molecular type and are composed of neutral mononuclear
[(CH3)3Pt(L)H2O] complexes, the structures of 1 and 2 having two
crystallographically independent complexes each. Crystals of com-
pound 2 tend to be twinned. Fig. 1a–c shows the structures of the
molecules for all complexes. The coordination Pt polyhedron is
the slightly distorted PtC3O3 octahedron formed by three methyl
groups, water molecule, and two oxygen atoms of bidentately coor-
dinated b-diketonate ligand.
It is noteworthy that in the case of using the potassium ligand
salts (KLF) to synthesize fluorinated b-diketonates the yield of the
target product was no more than 50%. We succeeded in preparing
fluorinated trimethylplatinum(IV) b-diketonates with the 92–95%
yield by adding silver ions in the reaction mixture. The complexes
prepared are crystalline substances readily soluble in organic sol-
vents, they are not sensitive to oxygen and moisture and stable
for a long time upon storage.
The structure of 1 (Fig. 1a) has the average values of geometric
characteristics of the coordination groups as follows: the Pt–CH3,
Pt–OL, and Pt–OW distances, 2.013, 2.194, and 2.283 Å, respec-
tively; the deviations of the bond cis-angles from the ideal 90° an-
gle on the central Pt atom is no more than 4.7°. The C3 and O3
planes of two triangular faces of Pt octahedra are virtually parallel;
the dihedral angles do not exceed 3.8°. In the symmetric b-diketo-
nate hfa-ligand, the average values of the O–C, C–C , C–CMe, and C–
c
Mass spectra of the reported compounds recorded under electron
impact (EI) ionization (70 eV) are similar, peak at maximal mass-to-
charge (m/z) ratio corresponds to [(CH3)3PtLF]+, the most intensive
platinum containing peak is [(CH3)3Pt]+, there no molecular ion corre-
sponding to [(CH3)3PtLFH2O]+ was recorded. The last fact is obviously
explained by instability of the molecular ion formed under EI. We do
not use softer ionization technique since occurrence of water as a li-
gand in the complex was confirmed by other methods.
IR spectra of compounds 1–3 confirm the chelate type of plati-
num – b-diketonate bonding. The C–H and Pt–CH3 stretching
vibrations occur at 3000–2800 cmꢀ1. Characteristic C–O and C@C
vibrations of the chelate ring appear at 1650–1450 cmꢀ1. The less
intense bands at 500–600 cmꢀ1 are associated with the Pt–C vibra-
tions [18]. The presence of the water in the complexes is supported
by stronꢀg1absorption bands of the O–H vibrations at 3607 and
3435 cm (1), one wide band at 3437 cmꢀ1 (2), and at 3623 and
3352 cmꢀ1 (3), respectively [19]. In 1H NMR spectra of complexes
1–3 protons of the CH3 groups linked to the platinum atoms appear
as one triplet of the equivalent CH3 groups regardless of the b-dike-
tonate ligand composition. These and elemental analysis data con-
firm the successful preparation of complexes 1–3.
F bond lengths are 1.253, 1.378, 1.528, and 1.304 Å, respectively,
the average value of the chelate O–Pt–O angles being 87.8°. The
bending of the chelate rings along the O. . .O line may be as much
as 15.0° and the average intramolecular F. . .H contacts in the
c
complexes are ꢁ2.33 Å. A projection of the structure on the xy-
plane is shown in Fig. 2a. In the crystal, the complexes are linked
by weak hydrogen bonds involving the molecule of the coordi-
nated water of one complex and the hfa ligand oxygen atoms of
the other, the O. . .O separation being 2.88 Å. The intermolecular
F. . .F and F. . .H contacts between the terminal substituents are
2.91 and 2.59 Å, respectively. The shortest Pt. . .Pt separations be-
tween the centers of the complexes are 5.377–6.280 Å.
In the structure of 2 (Fig. 1b), the deviations of the bond cis-an-
gles from the ideal 90° angle on the central Pt atoms reach 7.1°, the
average chelate O–Pt–O angle being 88.9°. In the metal cycle, the
Pt–OL distances on the side of various substituents differ notice-
ably, the average value being 2.04 and 2.27 Å on the side of the
fluorinated substituent and the methyl one, respectively. In the
b-diketonate ligand, the difference in the O–C, C–C , and C–CMe
c
bond lengths is 0.14, 0.10, and 0.03 Å, respectively, on the side of
different substituents. The average C–F distance is 1.31 Å for CF3
groups. The bending of the chelate rings along the O. . .O line is
13.7 Å. In the coordination environment, the average Pt–OW bond
length is 2.25 Å. The scatter in the Pt–CH3 bonds is great with
the average value of 2.02 Å. The projection of the crystal structure
along the y-axis is shown in Fig. 2b. The structure belongs to the
layer type with the interlayer d200 distance of 9.25 Å. The mole-
cules in the layer are hydrogen-bonded those involving the mole-
While using fluorinated b-diketones for the synthesis, we ex-
pected the formation of dimeric chelates similar to trimethylplati-
num acetylacetonate [(CH3)3Pt(acac)]2, since the trifluoromethyl
group allows no steric hindrance to produce dimers [17]. However,
it was found that fluorinated b-diketones do not form dimeric com-
plexes. An obligatory condition for the formation of a monomeric
fluorinated trimethylplatinum b-diketonate is the presence of a do-