Christian Tessier

Multinuclear NMR study and crystal structures of complexes of the types cis- and trans-Pt(Ypy)2X2, where Ypy=pyridine derivative and X=Cl and I

Abstract 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.

Synthesis, IR and multinuclear NMR spectroscopies and crystallographic studies of complexes of the type cis- and trans-Pt(pyridine)2(NO3)2

Abstract 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.

trans-Bis(3-acetyl­pyridine-κN)diiodoplatinum(II)

In the square-planar title complex, [PtI2(C7H7NO)2], the Pt atom lies on a crystallographic inversion center, coinciding with an anti arrangement of the 3-acetylpyridine ligands. The dihedral angles between the pyridine rings and the Pt coordination plane are 67.5 (2) degrees, while those between the pyridine rings and the acetyl planes are 20.8 (5) degrees. The 195Pt NMR resonance of the title complex (CD2Cl2) was observed at -3224 p.p.m. The major structural parameters are compared with those from previously reported related structures.

cis-Bis[(1-adamantylmeth­yl)amine-κN]­dichloridoplatinum(II) N,N-dimethyl­formamide solvate

The asymmetric unit of the title compound {systematic name: cis-dichloridobis[(3,7-dimethylbicyclo[3.3.1]non-1-ylmethyl)amine-κN]platinum(II) N,N-dimethylformamide solvate}, [PtCl2(C11H19N)2]·C3H7NO, consists of two metrically similar Pt complexes and two dimethylformamide solvent molecules. Each PtII center is coordinated by the amine groups of two (1-adamantylmethyl)amine ligands and two Cl atoms in a cis-square-planar arrangement. The PtII centers lie slightly outside [0.031 (4) and 0.038 (4) Å] the coordination planes. The N—Pt—N and Cl—Pt—Cl angles [92.1 (4)–92.30 (11)°] are slightly more open than the N—Pt—Cl angles [87.3 (3)–88.3 (3)°]. N—H⋯O and N—H⋯Cl intermolecular hydrogen bonds are observed, forming two discrete pairs of complexes and solvent molecules.