Fernande D. Rochon

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.

An Overview of 195Pt Nuclear Magnetic Resonance Spectroscopy

Abstract This brief, non‐exhaustive review describes some basic theoretical aspects of 195Pt nuclear magnetic resonance spectroscopy and also the empirical approach used by the researchers in the field. The different factors which influence the chemical shifts are discussed. The couplings constants between 195Pt and other isotopes, which have a spin of 1/2 (such as, 1H and 13C) bring further important information on the structures of Pt compounds. Recently, 195Pt‐NMR spectroscopy in the liquid state has been used successfully in many research fields, e.g., the determination of enantiomeric composition and absolute configuration, in the area of biosensors and biomarkers, in cluster chemistry, in cancer research and in kinetic studies. While liquid‐state 195Pt‐NMR spectroscopy encompasses a wide range of areas, the parallel solid‐state technique has only been employed over the past few years, mainly in studies of heterogeneous catalysis and is more industrially oriented.

Study of the aqueous reactions of metallic ions with benzenetetracarboxylate ions: Part 1. Crystal structures of compounds of the types [M(H2O)6][C6H2(COO)2(COOH)2] (M=Mn, Co and Ni) and Ni(H2O)5(μ-C6H2(COO)4)Ni(H2O)5·6H2O

The reactions of several divalent transition metals with 1,2,4,5-benzenetetracarboxylate ions were studied in aqueous solution. Mn(II), Co(II) and Ni(II) produced ionic products of formula [M(H2O)6][C6H2(COO)2(COOH)2]. The three compounds were characterized by crystallographic methods. The results have shown that the three crystals are isostructural and that they belong to the monoclinic C2/c space group. The metal atom and two O atoms (from two aqua ligands) are located on a two-fold axis, while the other four aqua ligands are located in general positions. The anions contain an inversion center. The two hydrogens on the carboxylic functions form intramolecular H bonds with the carboxylate groups. The average MOH2 bond distances are 2.181(1) A for Mn(II), 2.092(1) A for Co(II) and 2.056(1) A for Ni(II). The ions are linked together by extensive H bonds. With the Ni salt, a dinuclear species, containing a bridging benzenetetracarboxylato ligand was synthesized and characterized by X-ray diffraction. The compound Ni(H2O)5(μ-C6H2(COO)4)Ni(H2O)5·6H2O contains an inversion center in the center of the phenyl ring. The average NiOH2 distance is 2.0710(8) A and the sixth NiO bond is 2.0356(7) A. The Ni⋯Ni distance is 11.360(2) A. The crystal is stabilized by a very elaborate H-bonding system forming a H-bonded three-dimensional network.

Synthesis and characterization of Pt(II) complexes with amine and carboxylato ligands. Crystal structure of (1,1-cyclobutanedicarboxylato)di(ethylamine)platinum(II)·H2O

Abstract Two methods for the synthesis of compounds of the type cis -PtA 2 X 2 (A 2 =bidentate amine or two monodentate amines and X 2 =bidentate or two monodentate carboxylato ligands) were evaluated. The compounds were characterized by multinuclear NMR and IR spectroscopies. The 195 Pt NMR chemical shifts were in the range −1615 to −1976 ppm, the higher field values corresponding to the complexes containing bidentate ligands. The coupling constants 3 J ( 195 Pt– 1 H) are approximately 35 Hz, while the 2 J ( 195 Pt– 1 HN) are about 70 Hz. One coupling constant 2 J ( 195 Pt– 13 C) (53 Hz) was also measured. The crystal structure of the compound, cis -Pt(1,1-cyclobutanedicarboxylato)(C 2 H 5 NH 2 ) 2 ·H 2 O belongs to the P 2 1 / n space group with a =9.468(5), b =9.365(4), c =16.473(7) A, β =105.08(3)°, Z =4 and R 1 =0.0576. The PtN bond distances are 1.992(5) and 2.020(5) A, while the PtO bonds are 2.000(4) and 2.015(4) A. The molecules are held together by intermolecular H-bonds involving the lattice water molecules and the two free carbonyl O atoms and between the amino H atoms and the Pt-bonded CO groups.

[Cr(bipy)(C2O4)2]−—a versatile building block for the design of heteropolymetallic systems 2. Syntheses and crystal structures of and (AgCr(bipy)(μ-C2O4)2(H2O)2)2 and magnetic properties of the copper(II) derivative

The compounds (1) and (AgCr(bipy)(μ-C2O4)2(H2O)2)2 (2) have been obtained by self-assembling [Cr(bipy)(C2O4)2]− building blocks with Cu(II) and Ag(I) ions, respectively. The molecular and crystal structures of the two compounds were determined. Crystal 1 is monoclinic, , Z = 4 and R = 0.0369. Its structure consists of discrete linear {CrCuCr} trinuclear species with the copper atom lying on an inversion center. The copper atom exhibits [4 + 2] axially elongated octahedral geometry, the apical positions being occupied by two oxalato oxygen atoms. The CuO bond distances are 1.953(4) (H2O), 1.998(3) and 2.357(3) A, the CrO bonds vary from 1.945(3) to 1.982(3) A, and the CrN bonds are 2.031(4) and 2.054(3) A. The Cr…Cu distances are 5.288 A. Crystal 2 is monoclinic, P21/c, a = 14.639(16), b = 15.553(10), , and contains discrete tetranuclear cycles formed by two chromium and two silver atoms bridged by the oxalato groups. The silver atoms are penta-coordinated, exhibiting distorted trigonal bipyramidal geometries. The AgO bond distances vary from 2.350(8) to 2.548(7) A, while the CrO bonds are in the range 1.942(7) to 1.982(6) A. The magnetic susceptibility data of 1 reveal an irregular spin state structure with S = 5/2 ground state and an antiferromagnetic interaction between the central copper(II) and the chromium(III) atoms (J = −18.8 cm−1.

Study of the aqueous reactions of metallic ions with benzenetetracarboxylate ions: Part 2. Crystal structures of compounds of the type M(H2O)5(μ-C6H2(COO)4)M(H2O)5 (M=Mn and Co) and a novel mixed-metallic Mn–Co dimeric compound

Abstract The reactions of barium 1,2,4,5-benzenetetracarboxylate with CoSO4 produced the dinuclear species Co(H2O)5(μ-C6H2(COO)4)Co(H2O)5 which was characterized by crystallographic methods. The results have shown that the compound belongs to the monoclinic C2/c space group and it crystallized with six molecules of water in the lattice. The crystal is stabilized by a very elaborate H-bonded 3D network. The molecule contains an inversion center. The average Co–OH2 distance is 2.0710(8) A and the sixth Co–O bond is 2.0356(7) A. The reaction of MnCl2 with benzenetetracarboxylate ions produced a similar dinuclear species, Mn(H2O)5(μ-C6H2(COO)4)Mn(H2O)5·H2O (2). The crystallographic results have shown that there are two independent molecules, which each contains an inversion center. This compound crystallized with only one molecule of water, and again the H-bonding system is very elaborate. The aqueous reaction of K2Mn(C6H2(COO)4)·3H2O with CoSO4 produced a compound containing two dinuclear species {Mn(H2O)5(μ-C6H2(COO)4)Mn(H2O)5}{Co(H2O)5(μ-C6H2(COO)4)Co(H2O)5}·2H2O, which was characterized by X-ray diffraction methods. The results have shown that the latter compound is isomorphous with the Mn(II) compound. One of the Mn(II) dimer in 2 has been replaced by a Co(II) dimer.

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.

Novel mixed-ligands Pt(II) complexes: synthesis, multinuclear magnetic resonance and crystal structures of cis- and trans-Pt(sulfoxide)(pyrimidine)Cl2

Abstract New types of mixed-ligands Pt(II) complexes, cis- and trans-Pt(R2SO)(pyrimidine)Cl2, were synthesized and characterized by IR and multinuclear magnetic resonance spectroscopies and by crystallographic methods. Compounds with R2SO=dimethylsulfoxide (DMSO), tetramethylenesulfoxide (TMSO), di-n-propylsulfoxide (DPrSO), di-n-butylsulfoxide (DBuSO), dibenzylsulfoxide and diphenylsulfoxide were studied. The aqueous reaction of K[Pt(R2SO)Cl3] with pyrimidine (pm) in a 1:1 ratio produced trans-Pt(R2SO)(pm)Cl2, which can isomerize to the cis isomer in an organic solvent. The 195Pt NMR resonances of the trans complexes were observed at higher field (ave. −3079 ppm) than the cis analogues (ave. −2932 ppm). The 195Pt coupling constants with the pyrimidine atoms 3J(195Pt1H) and 3J(195Pt13C) are larger in the cis configuration (∼40 Hz) than in the trans analogues (∼30 Hz). One ν(PtCl) vibration was observed for the trans compounds, while two such bands were observed for the cis isomers. The crystal structures of cis-Pt(R2SO)(pm)Cl2 (R2SO=DMSO, TMSO, DPrSO and DBuSO) and of trans-Pt(TMSO)(pm)Cl2 were determined. The trans influence of the three different ligands was compared.

Preparation and crystal structure of bis(acetato) (trans-1,2-diaminocyclohexane) platinum(II)

Abstract The structure of the complex [Pt( trans -1,2-di- aminocyclohexane) (acetate) 2 ]·H 2 O has been determined by X-ray diffraction. This racemic compound is orthorhombic, space group Ab a2, a = 20.813(9), b = 7.926(5), c = 17.296(8) A, Z = 8. The structure was refined on 1214 nonzero Cu Kα reflections to R = 0.028. The square planar environment of Pt includes the amino groups of the diamine in cis positions and oxygens from two monodentate acetates. The PtN and PtO distances average 2.00(3) and 2.02(3) A, respectively. The bite of the diamine ligand imposes a NPtN angle of 85(1)°, whereas the small OPtO angle of 85(1)° probably results from packing effects. The average plane through the puckered cyclohexyl ring makes an angle of 19° with the PtN 2 O 2 plane. The molecules are stacked by pairs along the b axis. The two molecules of each pair are 180° apart about the stacking axis, and form altogether four NH···O hydrogen bonds.

Crystal structures of diammine(oxalato)platinum(II)and diammine(malonato)platinum(II)

Abstract [Pt(NH 3 ) 2 malonate] belongs to the monoclinic space group P 1 / c , a = 4.063(2), b = 14.150(2), c = 11.414(2) A, β = 93.27(2)°, Z = 4. The structure was refined on 1274 nonzero CuKα reflections to R = 0.035. The crystal contains individual square planar molecules with two cis NH 3 ligands at 2.036(9) A from Pt. The Pt-O distances to the bidentate malonate average 2.022(6) A and the chelate ring has a boat conformation. The angles around Pt lie in the range 86.0–93.5° (σ = 0.3°). The molecules are stacked along the a axis and form NH⋯O bonds with adjacent molecules. [Pt(NH 3 ) 2 oxalate] is monoclinic, space group P 2 1 / m , a = 3.865(2), b =10.703(4), c = 6.774(3) A, β = 94.29(4)°. Z = 2. The structure was refined on 449 non-zero MoKα reflections to R = 0.045. The square planar monomeric molecule possesses a crystallographic mirror plane perpendicular to the coordination plane and bisecting the N-Pt-N and O-Pt-O angles. The oxalate imposes an O-Pt-O angle of 82.0° in the chelate ring. The molecules are stacked in columns in the a direction, and form inter-column hydrogen bond in the b and c directions.