New types of mixed-ligands Pt(II) complexes were synthesized and characterized by IR and multinuclear magnetic resonance spectroscopies. These compounds are the monomers
cis- and
...trans-Pt(amine)(pyrimidine)X
2 and the dinuclear species
trans,
trans-Cl
2(amine)Pt(μ-pyrimidine)Pt(amine)Cl
2, where X
=
I and Cl.
Mixed-ligand complexes of the type Pt(amine)(pm)I
2, (pm
=
pyrimidine) were synthesized and characterized by IR spectroscopy and by multinuclear (
195Pt,
1H and
13C) magnetic resonance spectroscopy. The
cis compounds were prepared from the reaction of I(amine)Pt(μ-I)
2Pt(amine)I with pyrimidine (1:2 proportion) in water, while the
trans isomers were synthesized from the isomerization of the
cis complexes in acetone. The
cis isomers could not be isolated with several amines, especially the more bulky ones. In
1H NMR, the pyrimidine protons of the
cis compounds were found at lower fields than those of the
trans analogs and the
J(
195Pt–
1H) coupling constants are slightly larger in the
cis geometry. For
n-butylamine, the reaction produced also I
2(
n-butylamine)Pt(μ-pm)Pt(
n-butylamine)I
2. No such dimer could be isolated with the other amines. The compounds Pt(amine)(pm)Cl
2 were also prepared (amine
=
methylamine and
t-butylamine) from the ionic complex KPt(amine)Cl
3 using an excess of pyrimidine. The IR and NMR characterization showed that the methylamine compound was a
cis–
trans mixture, while only the
trans isomer was isolated with
t-butylamine. When the same reaction was performed using a Pt:pm ratio of 2:1, Cl
2(amine)Pt(μ-pm)Pt(amine)Cl
2 was isolated. The pyrimidine-bridged dimers were identified by IR and multinuclear magnetic resonance spectroscopies as the
trans–
trans isomers. The
trans monomers and dimers showed only one
ν(Pt–Cl) band. The
195Pt NMR signals of the dimers were found close to those of the monomer
trans-Pt(amine)(pm)Cl
2.
A new type of mixed-ligand Pt(II) complexes, Pt(R
2
SO)(pyrazine)Cl
2
, was synthesized from the aqueous reaction of KPt(R
2
SO)Cl
3
with pyrazine. The compounds were characterized mainly by IR and ...multinuclear magnetic resonance spectroscopies (
1
H,
13
C, and
195
Pt) and crystallography. Compounds with dimethylsulfoxide, tetramethylenesulfoxide, di-n-propylsulfoxide, di-n-butylsulfoxide, dibenzylsulfoxide, and diphenylsulfoxide were studied. IR spectroscopy suggested a cis geometry for the di-n-propylsulfoxide complex and trans geometry for the other compounds. The
195
Pt NMR resonances of the complexes were observed between 3042 and 3121 ppm, with that of the diphenylsulfoxide complex being at higher field than those of the others. The pyrazine
3
J(
195
Pt-
1
H) coupling constant was observed for the DMSO compound (33 Hz), suggesting a trans geometry. No J(
195
Pt-
13
C) coupling could be detected. The crystal structures of trans-Pt(tetramethylenesulfoxide)(pyrazine)Cl
2
and of cis-Pt(di-n-propylsulfoxide)(pyrazine)Cl
2
were determined and confirmed the geometry suggested by IR and NMR spectroscopies. The compound with di-n-butylsulfoxide could not be isolated, because it rapidly formed the pyrazine-bridged dimer.
Key words: platinum, sulfoxide, pyrazine, crystal structure, NMR, IR.
Zn(II) and Cd(II) complexes with N,N′-dimethyl-2,2′-biimidazole (Me
2
biim) were synthesized and characterized by IR spectroscopy and by X-ray crystallographic methods. The reaction of zinc ...perchlorate with Me
2
biim produced the dinuclear compound (Me
2
biim)Zn(µ-Me
2
biim)
3
Zn(Me
2
biim)(ClO
4
)
4
, containing two monodentate and three bridging Me
2
biim ligands bonded to Zn atoms in a distorted tetrahedral environment. A related neutral (NO
3
)
2
Cd(µ-Me
2
biim)
3
Cd(NO
3
)
2
complex, containing only bridging Me
2
biim ligands, was also synthesized, in which the distorted octahedral coordination of each Cd atom is completed by one monodentate and one bidentate nitrato ligand. Two ionic trinuclear Cd compounds were also obtained, which include two sets of three bridging Me
2
biim ligands connecting a central Cd atom to two terminal Cd centers. An extra Me
2
biim ligand is chelated to each terminal metal, and the sixth coordination site is occupied by water molecules in the symmetric (Me
2
biim)(H
2
O)Cd(µ-Me
2
biim)
3
Cd(µ-Me
2
biim)
3
Cd(H
2
O)(Me
2
biim)(ClO
4
)
6
complex, whereas the aqua ligand is replaced by methanol at one of the terminal units in the non-symmetric (Me
2
biim)(H
2
O)Cd(µ-Me
2
biim)
3
Cd(µ-Me
2
biim)
3
Cd(CH
3
OH)(Me
2
biim)(ClO
4
)
6
compound. In the chelating ligands, dihedral angles of ~38° between the two imidazole rings reduce repulsion between the N-methyl groups, but considerable strain remains, as evidenced from one of the Cd-N bonds being much longer than the other. In the various compounds, dihedral angles of 60-80° are found between the imidazole rings in the bridging ligands, and intramolecular inter-ligand π-π stacking contributes to stabilization.Key words: zinc, cadmium, dimethylbiimidazole, crystal structure, dinuclear, trinuclear.
The reaction of 3-(
R)-(C
10H
7)CHMeNCHC
4H
3S (
2a) with Pt
2Me
4(μ-SMe
2)
2 in acetone gave the new chiral cyclometallated platinum(II) compound PtMe{3-(
R)-(C
10H
7)CHMeNCHC
4H
2S}SMe
2 (
3a). ...Addition of PPh
3 produced compound PtMe{3-(
R)-(C
10H
7)CHMeNCHC
4H
2S}PPh
3 (
4a) which was characterized by X-ray diffraction methods. While oxidative addition of methyl iodide to
3a gave two pairs of diastereomers, the analogous reaction for
4a produced only one diastereomer of the platinum(IV) compound PtMe
2I{3-(
R)-(C
10H
7)CHMeNCHC
4H
2S}PPh
3 (
7a). Subsequent isomerization of the resulting platinum(IV) compound gave a new pair of diastereomers in relative amounts 90 and 10%. Analogous proportions of final diastereomers were obtained for the oxidative addition of methyl iodide to the new chiral compounds PtMe{3-(
R)-(C
10H
7)CHMeNCHAr}PPh
3 (Ar=C
6H
4 (
4b), 2-FC
6H
3 (
4c), 2-CF
3C
6H
3 (
4d)). The reaction of Pt
2Me
4(μ-SMe
2)
2 with imines (
R)-(C
10H
7)CHMeNCH(2-BrC
6H
4) (
2e) and (
R)-(C
10H
7)CHMeNCH(2,6-Cl
2C
6H
3) (
2f) produced intramolecular oxidative addition to yield platinum(IV) compounds with some degree of stereoselectivity.
Stereoselective oxidative addition of methyl iodide to chiral cyclometallated platinum(II) compound PtMe{3-(
R)-(C
10H
7)CHMeNCHC
4H
2S}PPh
3 is reported together with the results obtained for inter and intramolecular oxidative addition in related platinum compounds.
The hydrolyis or the aquation reactions of compounds of the types cis- and trans-Pt(Ypy)
2
(NO
3
)
2
(Ypy = pyridine derivative) were studied in D
2
O and characterized by multinuclear (
195
Pt,
13
...C, and
1
H) NMR spectroscopy. In acidic pD, the product of the cis complexes is cis-Pt(Ypy)
2
(D
2
O)
2
2+
, whereas in basic medium cis-Pt(Ypy)
2
(OD)
2
is formed. The
195
Pt NMR resonances of the products containing ligands with an ortho substituent were observed at lower fields than the other complexes. The average coupling constant (
3
J(
195
Pt
1
H) and
3
J(
195
Pt
13
C)) is 44 Hz for the diaqua species and 42 Hz for the dihydroxo compounds. At neutral pD, several hydrolyzed species were observed, except for the 2-picoline and 2,4-lutidine complexes, which contained only one compound, cis-Pt(Ypy)
2
(D
2
O)(OD)
+
. The other hydrolyzed products for the ligands with no ortho substituent were identified as the dihydroxo-bridged dimer, the monohydroxo-bridged dimer, the trimer, and possibly the tetramer. The trans analogues have shown two signals in acidic pD corresponding to the diaqua monomer and the monohydroxo-bridged aqua dimer. Two species (the dihydroxo compound and the monohydroxo-bridged hydroxo dimer) were also observed in basic pD. In neutral medium, a third signal assigned to a longer chain hydroxo-bridged oligomer or polymer was detected.Key words: platinum, pyridine derivative, nitrato, hydrolysis, NMR, aquation.
