Andrzej Surdykowski

The X-ray structure and spectroscopy of platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines and dimethylsulfoxide

Abstract Platinum(II) complexes with 1,2,4-triazolo[1,5-a]pyrimidines of general formula trans-[PtCl2(dmso)(L)], where L=1,2,4-triazolo[1,5-a]pyrimidine (tp), 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp), 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) have been prepared by direct reaction between cis-[PtCl2(dmso)2] and respective 1,2,4-triazolo[1,5-a]pyrimidine in molar ratio M:L=1:1. All new platinum(II) compounds were characterized by 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR upfield shifts (75–87 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. Crystal structure of trans-[PtCl2(dmso)(dmtp)] (2) has been determinated. The molecular structure indicates that Pt(II) ion has the square-planar geometry with N(3) bonded dmtp, S-bonded dimethylsulfoxide and two trans chloride anions.

Spectroscopy and stereochemistry of the optically active copper(II), cobalt(II) and nickel(II) complexes with Schiff bases N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(3-methylbenzylideneiminato) and N,N′-(1R,2R)-(−)-1,2-cyclohexylenebis(5-methylbenzylideneiminato)

Abstract Schiff bases obtained from N,N′-(1R,2R)-1,2-cyclohexanediamine and 2-hydroxy-3-methylbenzaldehyde, 2-hydroxy-5-methylbenzaldehyde, have been used as ligands for copper(II), cobalt(II) and nickel(II). The complexes were characterized with UV–Vis, circular dichroism (CD), infrared, diamagnetic and paramagnetic 1H NMR spectroscopy. CD spectra revealed exciton coupled π→π* transitions. Assignments of LMCT and d–d transitions in CD spectra of Ni(II), Co(II) and Cu(II) complexes is proposed. CD data are characteristic for central ion tetrahedral distortion from the planarity and λ conformation of the cyclohexane ring. 1H NMR of Ni(II) complexes exhibited significant coordination shifts of CHN and ring protons which are in the closest proximity to Ni(II). The 1H NMR paramagnetic spectra of Co(II) complexes revealed the most upfield shifted resonance at −60 ppm assigned to CHN and −28 ppm to hydrogen atom at C(5′) of the phenyl ring. Results of spectral analyses suggest central ions in a distorted square-planar geometry with N2O2 chromofore group.

The X-ray structure of bis(5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidinium) hexachloroplatinate(IV) and spectroscopic properties of Pt(II) and Pt(IV)chloride complexes with 1,2,4-triazolo-[1,5α]-pyrimidines

Abstract Pt(II) and Pt(IV) chloride complexes with 1,2,4-triazolo-[1,5α]-pyrimidines: trans-[Pt(tp)2Cl2], trans-[Pt(dmtp)2Cl2], trans-[Pt(tp)2Cl4] and trans-[Pt(dmtp)2Cl4] where tp=1,2,4-triazolo-[1,5α]-pyrimidine and dmtp=5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidine were synthesised and studied by 1H, 13C, 15N, 195Pt NMR and IR spectroscopies. Significant 15N NMR upfield coordination shifts (92–96 ppm) were observed for the N(3) atom indicating that this nitrogen is the metallation site. The X-ray structure of an ionic pair (dmtpH)2[PtCl6] {bis(5,7-dimethyl-1,2,4-triazolo-[1,5α]-pyrimidinium) hexachloroplatinate(IV)} was determined, exhibiting the presence of unique (dmtpH)22+ dimeric cations, protonated at N(3), N(3′) atoms and linked by hydrogen bonding.

An optically active nickel(II) Schiff base coordination compound N,N%-(1R,2R)-()-1,2-cyclohexylenebis (2-hydroxyacetophenonylideneiminato)nickel(II)

The Schiff base between trans-(1R,2R)-1,2-cyclohexanediamine and 2 mol of 2-hydroxyacetophenone has been used as a ligand for nickel(II). The coordination compound has been studied by NMR, UV‐Vis absorption and circular dichroism spectroscopy in solution. The crystal structure of the N,N%-(1R,2R)-( )-1,2-cyclohexylenebis(2-hydroxyacetophenonylideneiminato)nickel(II) complex ([Ni(R,R)-chxn(hapi)2]) was determined by the X-ray diffraction method. The molecule has an umbrella geometry, the dihedral angle between the planes defined by the two acetophenonylideneimine moieties of the ligand is 43.5(1)°. The Ni(II) atom is situated in a slightly distorted square-planar environment. The NiO distances vary from 1.811(4) to 1.824(4) A, and NiN distances are 1.857(5) and 1.873(5) A, . The cyclohexane ring of the Schiff base is in the chair conformation. Both the cyclohexane ring chiral carbon atoms C11 and C16 are positioned on the same side of the coordination NiN2O2 plane, the distances to the best plane being 0.849 and 0.303 A, , respectively. The crystal data and nuclear Overhauser effect (NOE) experiment revealed interaction of the methyl group with protons from cyclohexyl methine and methylene and phenyl hydrogens, both in the crystal and solution.

The bonding of ribavirin to platinum(II) ion.: The X-ray and spectroscopy of Pt(II) complexes with 1-β-d-ribofuranosyl-1,2,4-triazole-3-carboxamide and dimethylsulfoxide

Abstract A platinum(II) complex with 1-β- d -ribofuranosyl-1,2,4-triazole-3-carboxamide is obtained and characterised spectroscopically with 1H, 13C, 15N, 195Pt NMR and IR. Significant 15N NMR coordination shifts (−92.7 and +18.4 ppm) were observed, respectively for N(4) and N(7) indicating these nitrogen atoms as a metallation sites. The X-ray crystal structures of two hydrates [PtCl(dmso)(N4N7-rib)]·H2O (1) and [PtCl(dmso)(N4N7-rib)]·2H2O (2) have been solved. Both complexes revealed square-planar coordination geometry for the Pt atoms with chelate ribavirin, S-bonded dimethylsulfoxide and chloride anion, the distances being as follows: PtN(4) 2.009(4), PtN(7) 2.041(4), PtS 2.218(1), PtCl 2.304(1) A for 1 and PtN(4) 2.032(7), PtN(7) 2.028(7), PtS 2.212(2), PtCl 2.290(2) A for 2.

1H, 13C, 15N NMR and 13C, 15N CPMAS studies of cobalt(III)-chloride-pyridine complexes, spontaneous py → Cl substitution in trans-[Co(py)4Cl2]Cl, and a new synthesis of mer-[Co(py)3Cl3]

Abstracttrans-[Co(py)4Cl2]Cl·6H2O, mer-[Co(py)3Cl3] and mer-[Co(py)3(CO3)Cl] were studied by UV-Vis, far-IR and 1H, 13C, 15N NMR. The formation of Co-N bonds lead to variable in sign and magnitude changes of 1H NMR chemical shifts, heavily dependent on proton position, coordination sphere geometry and character of auxiliary ligands. 13C nuclei were deshielded upon Co(III) coordination, while 15N NMR studies exhibited ca. 85–110 ppm shielding effects (ca. 15–25 ppm more expressed for nitrogens trans to N than trans to Cl or O). 13C and 15N CPMAS spectra revealed a slight inequivalency of formally identical Co-py bonds in trans-[Co(py)4Cl2]Cl·6H2O and mer-[Co(py)3Cl3], suggesting for the latter complex an existence of distortion isomers. In chloroform, a spontaneous trans-[Co(py)4Cl2]Cl → mer-[Co(py)3Cl3] + py reaction was monitored by 1H NMR and UV-Vis. This process of py → Cl substitution allowed the design of a more convenient and efficient method of mer-[Co(py)3Cl3] preparation.

X-Ray crystal structure of [Ag4(μ-dppm)2(μ-C2F5COO)4]. Synthesis and spectroscopy of silver(I) perfluorinated carboxylate complexes with bis(diphenylphosphino)methane

Complexes of Ag(I) carboxylates with dppm = bis(diphenylphosphino)methane of general formula [Ag2(RCOO)2(dppm)], where R = CF3, C2F5, C3F7, C4F9, C6F13, C9F19, were obtained and characterized with 1H, 13C, 19F, 31P NMR and IR. The X-ray crystal structure of [Ag4(μ-dppm)2(μ-C2F5COO)4] determined at 100(1) K (R = 0.0316) revealed a centrosymmetric tetranuclear aggregate with the silver atoms bridged by two dppm and four pentafluoropropionates forming two monoatomic μ2-(η1-O) and two triple μ3-(η2-O, η1-O′) bridges. Of the two crystallographically independent Ag(I) atoms one has distorted tetrahedral geometry with one Ag–P bond and three Ag–O bonds, while the second has trigonal planar geometry with an Ag–P and two Ag–O bonds. The 31P CP MAS NMR spectra demonstrate splitting due to 1J(107,109Ag–31P) and 2J(P–P) coupling between crystallographically inequivalent phosphorus atoms. Variable-temperature 31P NMR spectra were recorded between 323 and 223 K and 1J(107Ag–31P), 3J(107Ag–31P), 1J(109Ag–31P), 3J(109Ag–31P) spin–spin coupling constants calculated. Analysis of coordination shifts and coupling constants is in favor, in solution, of binuclear trigonal Ag(I) complexes with bridging carboxylates and dppm.

Optically active cobalt(II) and copper(II) complexes with tetradentate Schiff bases derived from (N,N′)-(1R,2R)-(−)-cyclohexylenediamine and salicylaldehyde, 2-hydroxynaphthaldehyde or 2-hydroxyacetophenone

The Schiff bases obtained from (1R,2R)-1,2-cyclohexanediamine and salicylaldehyde, 2-hydroxynaphthaldehyde or 2-hydroxyacetophenone have been used as ligands for copper(II) and cobalt(II). The coordination compounds have been studied by u.v.–vis. absorption and by circular dichroism spectroscopy in solution. The complexes are four-coordinated in a slightly distorted square-planar geometry. The distortion from planarity is a main factor influencing the chiral surroundings of the metal ion. The d–d and c.t. transitions are consistent with the observed distortion which arises from intramolecular interactions between substituents at the Schiff base imine carbon and hydrogens of the cyclohexylene ring. Distortion is more pronounced in CoII than in CuII complexes. In the Schiff base chelates the cyclohexane ring is trans-fused to the central chelate ring, forming a rigid structure in which the chelate ring is locked stereospecifically in the λ conformation.

Cyclovoltammetric and spectroscopic characterization of optically active cobalt(II) and copper(II) complexes with the Schiff base derived from (N,N′)-(1R,2R)-(−)-cyclohexylenediamine and 2-hydroxyacetophenone

The Schiff base prepared by reacting (−)-(1R,2R)-1,2-cyclohexanediamine with 2-hydroxyacetophenone was used as a ligand for CoII and CuII. The coordination compounds were studied by u.v.–vis. absorption and by circular dichroism (c.d.) spectroscopy in solution. The complexes are four-coordinated in a slightly distorted square planar symmetry. The distortion from planarity is a main factor influencing the chiral surroundings of the metal ion. The d–d and c.t. transitions are consistent with the observed distortion, which arises from intramolecular interactions between the methyl groups attached to the Schiff base imine carbon and hydrogen atoms of the cyclohexane ring. The electrochemical properties of the CoII and CuII complexes were observed in MeCN but investigations revealed weaker oxygen activation than of CoII analogue with salicylaldehyde. The CuII complex is reduced in H2O to CuI which disproportionates to CuII and Cu0.

Hexakis(1H-imidazole-κN3)cobalt(III) tris­(hexa­fluoridophosphate) hexa­hydrate

In the crystal structure of the title compound, [Co(C3H4N2)6](PF6)3·6H2O, the CoIII atom lies on a special position with site-symmetry and the P atom is located on a special position with site symmetry . The CoIII atom has an almost ideal octahedral coordination formed by the N atoms of six imidazole ligands. The water molecules form hydrogen-bonded helical chains propagating in [001] by O—H⋯O interactions with a distance of 2.913 (2) Å. They simultaneously interact as hydrogen-bond acceptors and donors with the cations and anions, respectively, resulting in the formation of a three-dimensional assembly. Weak C—H⋯F interactions further stabilize the crystal structure.