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Pt(II) and Pd(II) compounds containing the free radical 4-aminoTEMPO (4amTEMPO) were synthesized and characterised by X-ray diffraction methods. The disubstituted complexes cis- and trans-Pt(4amTEMPO)2I2 were studied. The trans isomer was prepared from the isomerisation of the cis analogue. The two Pd(II) compounds trans-Pd(4amTEMPO)2X2 (X = Cl and I) were also characterised by crystallographic methods. A mixed-ligand complex cis-Pt(DMSO)(4amTEMPO)Cl2 was synthesized from the isomerisation of the trans isomer in hot water. Its crystal structure was also determined. In all the complexes, the 4amTEMPO ligand is bonded to the metal through the –NH2 group, since the nitroxide O atom is not a good donor atom for the soft Pt(II) and Pd(II) metals. The conformation of the 4-aminoTEMPO ligand was compared to those of the few reported structures in the literature.

The crystal structures of several Pt(II) complexes containing sulfoxide ligands are described. The two iodo bridged dimers of the type I(R2SO)Pt(μ-I)2Pt(R2SO)I (where R is ethyl or n-butyl) are twinned structures. The dinuclear species are the trans isomers. Two compounds of the type trans-Pt(DMSO)(amine)X2 were studied by X-ray diffraction methods. The diiodo MeNH2 compound forms H-bonded chains, formed by maximizing the H-bonds between the amine group with the O atom of DMSO and one iodo ligand. The H-bonding pattern is quite different in the dichloro t-BuNH2 complex. In the latter crystal, there are two independent molecules which are H-bonded in pairs. The methyl groups of DMSO and the t-butyl group of the amine are oriented towards the outside of the pairs of molecules, while the H-bonds link the two independent molecules. Again, the amino group forms the maximum H-bonds with the O atom of DMSO and one chloro ligand. The crystal structures of trans-Pt(DMSO)(pyridine)I2 and of trans-Pt(MeBzSO)(pyrimidine)I2 (Bz = benzyl) were also studied. In the pyridine complex, the O atom of DMSO is in the Pt(II) plane by symmetry, while in the pyrimidine compound, the C atom of the –CH3 group is in the Pt(II) plane. The pyridine and the pyrimidine ligands are perpendicular to the Pt(II) square plane. The trans influence of the different ligands is discussed.

Pt(II) complexes of the types K[Pt(R2SO)X3], NR4[Pt(R2SO)X3] and Pt(R2SO)2Cl2 (where X = Cl or Br) were characterized by multinuclear magnetic resonance spectroscopy (195Pt, 1H and 13C). In 195Pt NMR, the chloro ionic compounds have shown signals between −2979 and −3106 ppm, while the cis disubstituted complexes were observed at higher fields, between −3450 and −3546 ppm. The signal of the compound trans-Pt(DPrSO)2Cl2 was found at higher field (−3666 ppm) than its cis analogue (−3517 ppm), since π-back-donation is considerably less effective in the trans geometry. In 1H NMR, a single signal was observed for the sulfoxide in [Pt(DMSO)Cl3]−, but for the other more sterically hindered ligands, two series of resonances were observed for the protons in α and β positions. The coupling constant 3J(195Pt–1H) are between 15 and 33 Hz. The 13C NMR results were interpreted in relation to the concept of inversed polarization of the π sulfoxide bond. The 2J(195Pt–13C) values vary between 35 and 66 Hz, while a few 3J(195Pt–13C) couplings were observed (13–26 Hz). The crystal structures of five monosubstituted ionic compounds N(n-Bu)4[Pt(TMSO)Cl3], N(Me)4[Pt(DPrSO)Cl3], K[Pt(EMSO)Cl3], K[Pt(TMSO)Br3] · H2O and N(Et)4[Pt(DPrSO)Br3] and one disubstituted complex cis-Pt(DBuSO)2Cl2 were determined. The trans influence of the different ligands is discussed.

The crystal structures of two Pt(II) amine–alkyne complexes cis -Pt(cyclobutylNH 2 )(DHMD)Cl 2 ( I ) and cis -Pt(2,5-lutidine)(DMHD)Cl 2 ( II ) were determined (DMHD = (CH 3 ) 2 (OH)C–C C–C(OH)(CH 3 ) 2 ). The DMHD ligand in I is perpendicular to the Pt(II) plane and the mid-point of the C C bond occupies the fourth corner of the square plane. This geometry of the DMHD ligand in I is similar to the few other Pt(R–C C–R)Cl 2 L (L = amine or Cl) complexes, where the two acetylenic carbon atoms are roughly equally located on both sides of the Pt plane. The Pt–C bonds are 2.161(13) and 2.100(14) A, while the Pt–Cl bond distances are 2.298(4) and 2.332(5) A. The Pt–MP (midpoint of the C C bond) is 2.044 A. In II , the steric hinderance of the 2,5-lutidine ligand located in cis position is very important and the geometry of bonded DMHD is quite different. The alkyne ligand is pushed away from 2,5-lutidine, so that one of the C atoms of the triple bond lies in the Pt(II) plane. A linear trans Cl–Pt–C angle (175.2(3) A), a lengthening of the Pt–Cl bond (2.433(4) A) located trans to the Pt–C bond and a shortening of the latter (2.021(14) A) are observed in complex II . There results are without precedent in the literature. The two structures are disordered over two positions, but the low R factors (respectively 3.61% and 3.44% for I and II ) confirm the reliability of the results. A complete description of the disordered arrangement is provided for both complexes. Crystal I crystallized with a molecule of H 2 O and the two structures are stabilized by an extensive H-bonding system.

Complexes of the type [Pt(amine)4]I2 were synthesized and characterized mainly by multinuclear (195Pt, 1H and 13C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In 195Pt NMR, the signals were observed between −2715 and −2769 ppm in D2O. The coupling constant 3J(195Pt–1H) for the MeNH2 complex is 42 Hz. In 13C NMR, the average values of the coupling constants 2J(195Pt–13C) and 3J(195Pt–13C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH2)4]I2 was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH2 was found by crystallographic methods to be [Pt(n-BuNH2)4]2I3(n-BuNHCOO). The crystal contains two independent [Pt(CH3NH2)4]2+ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO2 from the air. When the compound [Pt(CH3NH2)4]I2 was dissolved in acetone, crystals identified as trans-[Pt(CH3NH2)2(H3C N C(CH3)2)2]I2 were isolated and characterized by crystallographic methods. Two trans bonded MeNH2 ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.

Compounds of the type cis- and trans-Pt(Ypy)2(NO3)2 (Ypy=pyridine or its methyl derivatives) have been synthesized and characterized by IR and multinuclear (195Pt, 13C and 1H) NMR spectroscopies. The 195Pt NMR resonances of the trans complexes were observed at lower fields (ave. −1450 ppm) than the cis analogs (ave. −1509 ppm). The complexes containing a methyl substituent in ortho position on the pyridine ligand were observed at lower fields than the others. The coupling constants 3J(195Pt–1H) and 3J(195Pt–13C) are larger in the cis configuration (ave. 44 and 46 Hz, respectively) than in the trans analogs (ave. 33 and 35 Hz, respectively). The covalent character of the PtO bond seems greater in the trans complexes than in the cis compounds. The crystal structures of cis-Pt(3,5-lut)2(NO3)2, cis-Pt(2-pic)2(NO3)2, cis-Pt(py)2(NO3)2·1/2CH2Cl2, trans-Pt(3,5-lut)2(NO3)2 and trans-Pt(py)2(NO3)2 were determined. Except for the cis pyridine complex, which contains some molecules of solvent, the two nitrato groups are on opposite sides of the coordination plane. The trans influence of the different ligands is compared.

Complexes of the types cis- and trans-Pt(Ypy)2X2 where Ypy is a methyl derivative of pyridine and X=Cl or I were studied by spectroscopic methods, especially by multinuclear NMR spectroscopy. In 195Pt MNR, the cis-dichloro compounds were observed between −1998 and −2021 ppm in CDCl3, while the trans compounds were found at slightly lower field, between −1948 and −1973 ppm. The diiodo species were observed at much higher field, between −3199 and −3288 ppm for the cis isomers and between −3122 and −3264 ppm for the trans isomers. In 1H NMR, the 3J(195Pt1H) coupling constants are larger for the cis compounds (about 42 ppm) than for the trans isomers (about 33 ppm). In 13C NMR, the values of 3J(195Pt13C) were also found to be larger for the cis complexes. There seems to be a slight dependence of the pKa values of the protonated ligands on the δ(Pt) chemical shifts. The presence of π-bonding between Pt and the pyridine ligands do not seem very important. The crystal structures of three dichloro and five diiodo complexes were determined, in an attempt to obtain information on the trans influence of the three ligands. The results have shown that the iodo ligand has the greatest trans influence. Chloro and pyridine ligands seem to have similar trans influence, although, the chloro ligand seems to have a slightly larger influence than pyridine derivatives. One structure, trans-Pt(2-pic)2I2, has shown a syn conformation of the two 2-picoline ligands.