Nuclear magnetic resonance of donor atoms as a tool for determination of the structure of platinum metal complexes in solutions

Data on the NMR spectroscopy of C, N, O, Si, P, and Sn donor atoms of platinum metal complexes in solutions are surveyed. The chemical shift of a donor atom mainly depends on the ligand in the trans-position (due to the trans-effect). The chemical shift of a donor atom on a particular coordinate of the complex (coordinate shift, CSh) is an attribute of this coordinate and can be used to identify such a coordinate in platinum metal complexes and to determine the structures of complexes. Based on the known data, CSh diagrams were composed for ¹H, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ³¹P, and ¹¹⁹Sn. Examples of using the CShs for determining the structures of platinum metal complexes in solutions are presented.     

Structural Refinement of Carbimazole by NMR Crystallography

The characterization of the three-dimensional structure of solids is of major importance, especially in the pharmaceutical field. In the present work, NMR crystallography methods are applied with the aim to refine the crystal structure of carbimazole, an active pharmaceutical ingredient used for the treatment of hyperthyroidism and Grave’s disease. Starting from previously reported X-ray diffraction data, two refined structures were obtained by geometry optimization methods. Experimental ¹H and ¹³C isotropic chemical shift measured by the suitable ¹H and ¹³C high-resolution solid state NMR techniques were compared with DFT-GIPAW calculated values, allowing the quality of the obtained structure to be experimentally checked. The refined structure was further validated through the analysis of ¹H-¹H and ¹H-¹³C 2D NMR correlation experiments. The final structure differs from that previously obtained from X-ray diffraction data mostly for the position of hydrogen atoms.     

Synthesis and characterization of sulphonated PEES copolymers by NMR spectroscopy

Two sulphonated PEES copolymers were synthesized by reacting 75 or 60 mol% silylated hydroquinone sulphonic acid and 25 or 40 mol% of hydroquinone with 4,4′-difluorodiphenyl sulphone. The number average molecular weights determined by GPC were 13.250 and 12.050 g/mol. In the FTIR spectra, in addition to the characteristic absorption bands due to aromatic skeleton, absorption bands associated with sulphonic acid groups were observed at ∼3500, 1172, 1080, 1026, and 706 cm⁻¹. In ¹H NMR, the aromatic proton resonance signals were observed between δ = 6.99 and 7.96 ppm. ¹³C{¹H} NMR spectra of these copolymers were complex and in order to resolve this, two-dimensional (2D) NMR techniques were utilized. Heteronuclear single quantum coherence (HSQC), total correlated spectroscopy (TOCSY), and heteronuclear multiple bond correlation (HMBC) were used for assigning the structure of the copolymers.     

1D and 2D NMR studies of N-vinylcarbazole/butyl methacrylate copolymers

Copolymers containing N-vinylcarbazole (V) and butyl methacrylate (B) units of different compositions were synthesized and their compositions were determined from quantitative ¹³C{¹H} NMR spectroscopy. The reactivity ratios of the comonomers were estimated using the Kelen-Tudos and non-linear error in variable methods. The complete spectral assignment in terms of compositional and configurational sequences of the overlapping ¹H and ¹³C{¹H} spectra of the copolymers were done with the help of distortionless enhancement by polarization transfer, 2D heteronuclear single quantum correlation and total correlated spectroscopy experiments.     

H and C NMR spectroscopy of 9-acridinones

The ¹H and ¹³C NMR spectra of 9-acridinone and its five derivatives dissolved in CDCl₃, CD₃CN and DMSO-d₆ were measured in order to reveal the influence of the constitution of the compounds and features of the solvents on chemical shifts and ¹H-¹H coupling constants. Experimental data were compared with theoretically predicted chemical shifts, on the GIAO/DFT level of theory, for DFT (B3LYP)/6-31G^∗∗ optimized geometries of molecules—also for four other 9-acridinones. This comparison helped to ascribe resonance signals in the spectra to relevant atoms and enabled revelation of relations between chemical shifts and physicochemical features of the compounds. It was found that experimentally or theoretically determined ¹H and ¹³C chemical shifts of selected atoms correlate with theoretically predicted values of dipole moments of the molecules, as well as bond lengths, atomic partial charges and energies of HOMO.     

Reaction of 2-hydroxyethylhydrazine with a trifluoromethyl-β-diketone: Study and structural characterization of a new 5-hydroxy-5-trifluoromethyl-4,5-dihydropyrazole intermediate

The reaction of the β-diketone 4,4,4-trifluoro-1-pyridin-2-yl-butane-1,3-dione and the monosubstituted hydrazine 2-hydroxyethylhydrazine has been investigated. Two products have been identified, 2-(2-hydroxyethyl)-3-pyridin-2-yl-5-trifluoromethyl-4,5-dihydropyrazole (P) and 2-(3-pyridin-2-yl-5-trifluoromethylpyrazol-1-yl)ethanol (L) in proportion 2:8, when the reaction was done at room temperature in ethanol for 15 h. The preparation of P as a pure product was performed in ethanol at 0 °C for 7 h. P has been characterized by ¹H, ¹³C{¹H} and ¹⁹F{¹H} NMR spectroscopy and by other techniques as appropriate.     

Effects of different GIAO and CSGT models and basis sets on 2-aryl-1,3,4-oxadiazole derivatives

The direct molecular structure implementations of the gage-including atomic orbital (GIAO), individual gages for atoms in molecules (IGAIM) and continuous set of gage transformations (CSGT) methods for calculating nuclear magnetic shielding tensors at both the Hartree-Fock (HF) and density functional (B3LYP) levels of theory with 6-31G(d), 6-311G(d), 6-31++G(d,p), 6-311++G(d,p), and 6-311++G(df,pd) basis sets are presented. Dependence on the ¹H and ¹³C NMR chemical shifts on the choice of method and basis set have been investigated. Also, these chemical shifts of 2-aryl-1,3,4-oxadiazoles 5a–g have been performed related to dihedral angles (C4–C3–C2–O) of two conformers. The optimized molecular geometries and ¹H and ¹³C chemical shift values of 2-aryl-1,3,4-oxadiazoles 5a–g in the ground state have been obtained. The linear correlation coefficients of ¹³C NMR chemical shifts for these molecules were given. The new nuclear magnetic shielding tensors of tetramethylsilane (TMS) were calculated. The data of 2-aryl-1,3,4-oxadiazole derivatives display significant molecular structure and NMR analysis. Also, these provide the basis for future design of efficient materials having the 1,3,4-oxadiazole core.     

13C, 15N and 113Cd NMR and Molecular Orbital Studies of Novel Bile Acid N-(2-aminoethyl)amides and Their Cd2+-complexes

Lithocholic acid N-(2-aminoethyl)amide (1) and deoxycholic acid N-(2-aminoethyl)amide(2) have been prepared and characterized by¹H, ¹³C and ¹⁵N NMR. The accurate molecular masses of 1 and 2 have been determined by ESI MS. The formation of the Cd²⁺-complexes (1+Cd and 2+Cd) in CD₃OD solution have been detected by ¹H,¹³C, ¹⁵N and ¹¹³Cd NMR. The ¹³C NMR chemical shift assignments of 1 and 2 and their Cd²⁺-complexes are based on DEPT-135 and z-GS ¹H,¹³C HMQC experiments as well as comparison with the assignments of the related structures. The ¹⁵N NMR chemical shiftassignments of the ligands and theirCd²⁺-complexes are based on z-GS¹H,¹⁵N HMBC experiments. ¹³C NMR chemical shift differences between 1and its 1:1 Cd²⁺-complex based on ab initiocalculations at Hartree-Fock SCI-PCM level using3-21G(d) basis set are in agreement with theexperimental shift changes observed onCd²⁺-complexation.     

Carbon-fluorine two-dimensional NMR correlation spectra

Direct detection heteronuclear correlation (HETCOR) ¹³C{¹⁹F} and indirect detection gHMQC and gHSQC ¹⁹F{¹³C} two-dimensional correlation spectra have been compared for 1,3-perfluoro dimethylcyclohexane. Correlations to the geminally non-equivalent fluorine atoms in the CF₂ groups are more difficult to unambiguously observe using gHMQC or HETCOR in this typical cyclic fluorochemical in which ²J_FF ∼ > ¹J_CF, but they are readily observed and assigned in the gHSQC experiment. Excellent 2D gHSQC ¹⁹F{¹³C} correlation spectra have also been obtained on H(CF₂)₄CH₂OH without proton decoupling, although half of the correlations within the several FH multiplets have zero intensity.     

1H{15N} GHMQC study of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]pyrimidine and 1H, 13C and 15N NMR coordination shifts in Au(III) chloride complexes of 1,2,4‐triazolo[1,5‐a]pyrimidines

The ¹H{¹⁵N} NMR spectrum of 5,7‐diphenyl‐1,2,4‐triazolo[1,5‐a]‐pyrimidine ( 3 ) was measured by GHMQC, unambiguously assigned and compared with the spectra of 1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) and 5,7‐dimethyl‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 2 ). A series of Au(III) chloride complexes of general formula AuLCl₃, where L = 1 , 2 , 3 , was synthesized and studied by ¹HH{¹⁵N} GHMQC and ¹H{¹³C} GHMBC. Low‐frequency shifts of 72–74 ppm (¹⁵N) and 5–6 ppm (¹³C) were observed upon complexation by Au(III) ions for the coordination site N‐3 and adjacent C‐2, C‐3a atoms, respectively. The ¹³C signals of C‐5, C‐6, C‐7 and the ¹H resonances of H‐2, H‐6 were shifted to higher frequency. Comparison with analogous Pd(II), Pt(II) and Pt(IV) complexes revealed that in the case of Au(III) coordination the ¹⁵N shifts were relatively smaller, whereas those for ¹³C and ¹H were larger. Copyright © 2002 John Wiley & Sons, Ltd.     

Kinetic Study of Radical Polymerization v. Determination of Reactivity Ratio in Copolymerization of Acrylonitrile and Itaconic Acid by 1H‐NMR

Many reports exist in the literature about the application of ¹H and ¹³C‐NMR techniques to analyze the copolymer structure and composition and also determination of reactivity ratios. In this work, on‐line ¹H‐NMR spectroscopy has been applied to identify reactivity ratios of itaconic acid and acrylonitrile in the solution phase (DMSO as the solvent) and in the presence of AIBN as the radical initiator. All the peaks corresponding to the existing protons were assigned quietly. Therefore, the kinetics of the copolymerization reaction was investigated by studying the variation of integral of two characteristic peaks regarding each monomer. The obtained data were used to find the reactivity ratios of acrylonitrile and itaconic acid by linear least‐squares methods such as Finemann‐Ross, inverted Finemann‐Ross, Mayo‐Lewis, Kelen‐Tudos, extended Kelen‐Tudos and Mao‐Huglin. In addition, a non‐linear least‐square method (Tidwell‐ Mortimer) was used at low conversions. Extended Kelen‐ Tudos and Mao‐Huglin were applied to determine reactivity ratio values at high conversions as well.     

13C-{1H} NMR spectra of episulphide copolymers

Ethylene sulphide-isobutylene sulphide and propylene sulphide-isobutylene sulphide copolymers have been prepared using anionic catalysts and investigated by ¹³C-{¹H} NMR spectroscopy. The carbon-13 NMR spectra are assigned in terms of diad and triad sequences. There is discussion of the effects of mono- or dimethyl substitution in the α, β, γ or δ positions on the chemical shift of the main chain carbon atoms. It has also been shown that for isobutylene sulphide, as for propylene sulphide, under the influence of an anionic catalyst, there is a normal ring opening only at the primary carbon atom.     

Be and P NMR analyses on Be complexation with cyclo-tri-μ-imidotriphosphate anions in aqueous solution

Microscopic information on the complexation of Be²⁺ with cyclo-tri-μ-imidotriphosphate anions in aqueous solution has been gained by both ⁹Be and ³¹P NMR techniques at −2.3 °C. Separate NMR signals corresponding to free and complexed species have been observed in both spectra. Based on an empirical additivity rule, i.e., proportionality observed between the ⁹Be NMR chemical shift values and the number of coordinating atoms of ligand molecules, the ⁹Be NMR spectra have been deconvoluted. By precise equilibrium analyses, the formation of [BeX(H₂O)₃]⁺ and [BeX₂(H₂O)₂]⁰ (X = non-bridging oxygen donor as a coordination atom in the phosphate groups) has been verified, and the formation of complexes coordinating with the nitrogen atoms of the cyclic framework in the ligand molecule has been excluded. Instead, the formation of one-to-one (ML) complexes, one-to-two (ML₂), together with two-to-one (M₂L) complexes (L = cP₃O₆(NH)₃) has been disclosed, the stability constants of which have been evaluated as log K_ML = 3.87 ± 0.03 (mol dm⁻³)⁻¹, log K_ML2 = 2.43 ± 0.03 (mol dm⁻³)⁻² and log K_M2L = 1.30 ± 0.02 (mol dm⁻³)⁻², respectively. ³¹P NMR spectra measured concurrently have verified the formation of the complexes estimated by the ⁹Be NMR measurement. Intrinsic ³¹P NMR chemical shift values of the phosphorus atoms belonging to ligand molecules complexed with Be²⁺, together with the ³¹P-³¹P spin-spin coupling constants have been determined.     

Nitropyrazoles

The structures of substitutedN-aminonitropyrazoles and 1- and 2-amino-4-nitro-1,2,3-triazoles as well as the site of protonation of 1-aminopyrazole were determined based on the¹H,¹³C, and¹⁵N (¹⁴N) NMR spectra. The¹³C NMR spectra were recorded under conditions of¹³C-{¹H,¹⁴N} triple resonance. Effects of substituents in the pyrazole ring on the¹³C and¹⁴N chemical shifts were studied. The¹³C,¹H and¹⁵N,¹H spin-spin coupling constants, obtained using techniques of [¹H]¹³C and [¹H]¹⁵N polarization transfer (SPT, INEPT), were measured, fully assigned, and discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2181–2186, November, 1995.For Part 8, see Ref. 1.     

Structural investigations on diorgano- and triorganotin(IV) derivatives of [meso-tetra(4-sulfonatophenyl)porphine] metal chlorides

Several new complexes of organotin(IV) moieties with MCl_n[meso-tetra(4-sulfonatophenyl)porphine], (R₂Sn)₂MCl_n[meso-tetra(4-sulfonatophenyl)-porphinate]s and (R₃Sn)₄MCl_n [meso-tetra(4-sulfonatophenyl)porphinate]s, [M = Fe(III), Mn(III): n = 1, R = Me, n-Bu; Ph; M = Sn(IV): n = 2, R = Me, n-Bu] have been synthesized and their solid state configuration investigated by infrared (IR) and Mössbauer spectroscopy, and by ¹H and ¹³C NMR in D₂O.The electron density on the metal ion coordinated inside the porphyrin ring is not influenced by the organotin(IV) moieties bonded to the oxygen atoms of the side chain sulfonatophenyl groups, as it has been inferred on the basis of Mössbauer spectroscopy and, in particular, from the invariance of the isomer shift of the Fe(III) and Sn(IV) atoms coordinated into the porphyrin square plane of the newly synthesized complexes, with respect to the same atoms in the free ligand.As far as the coordination polyhedra around the peripheral tin atoms are concerned, infrared spectra and experimental Mössbauer data would suggest octahedral and trigonal bipyramidal environments around tin, in polymeric configurations obtained, respectively, in the diorganotin derivatives through chelating or bridging sulfonate groups coordinating in the square plane, and in triorganotin(IV) complexes through bridging sulfonate oxygen atoms in axial positions.The structures of the (Me₃Sn)₄Sn(IV)Cl₂[meso-tetra(4-sulfonatophenyl)porphinate] and of the two model systems, Me₃Sn(PS)(HPS) and Me₂Sn(PS)₂ [HPS = phenylsulfonic acid], have been studied by a two layer ONIOM method, using the hybrid DFT B3LYP functional for the higher layer, including the significant tin environment. This approach allowed us to support the structural hypotheses inferred by the IR and Mössbauer spectroscopy analysis and to obtain detailed geometrical information of the tin environment in the compounds investigated.¹H and ¹³C NMR data suggested retention of the geometry around the tin(IV) atom in D₂O solution.     

Atom transfer radical copolymerizationof acrylonitrile/n‐butyl acrylate: Microstructure determination by two‐dimensional nuclearmagnetic resonance spectroscopy

Atom transfer radical polymerization conditions were optimized and standardized with different initiator and catalyst systems. Acrylonitrile/n‐butyl acrylate copolymers were synthesized with 2‐bromopropionitrile as the initiator and CuCl/Cu(0)/2,2′‐bipyridine as the catalyst system. Variations of the feed composition led to copolymers with different compositions. The number‐average molecular weight and the polydispersity index were determined by gel permeation chromatography. Quantitative ¹³C{¹H} NMR was employed to determine the copolymer composition. The reactivity ratios calculated with a methodology based on the Mao–Huglin terminal model were r_A = 1.30 and r_B = 0.68 for acrylonitrile and n‐butyl acrylate, respectively. The reactivity ratios determined by the modified Kelen–Tudos method were r_A = 1.29 ± 0.01 and r_B = 0.67 ± 0.01. ¹³C{¹H} NMR and distortionless enhancement by polarization transfer (DEPT‐45, 90, and 135) were used to distinguish methyl, methylene, methine, and quaternary carbon resonance signals. The overlapping and broad signals of the copolymers were assigned completely to various compositional and configurational sequences by the correlation of one‐dimensional (¹H, ¹³C{¹H}, and DEPT) and two‐dimensional (heteronuclear single quantum coherence, total correlation spectroscopy, and heteronuclear multibond correlation) NMR spectral data. The complete spectral assignments of carbonyl and nitrile carbons were performed with the help of heteronuclear multibond correlation spectra. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2810–2825, 2005     

A 13C, 15N and 77Se NMR Study of Some Diseleno Sulfonamides

¹³C, ¹⁵N and ⁷⁷Se NMR data are reported for ten title compounds. Some linear correlations of selenium, nitrogen and carbon chemical shifts values are described. A number of one- and two- bond ⁷⁷Se-¹³C coupling constants values are also given.     

Dihydrogen Splitting by Intramolecular Borane-Phosphane Frustrated Lewis Pairs: A Comprehensive Characterization Strategy Using Solid State NMR and DFT Calculations

Four hydrogenated intramolecular phosphane-borane frustrated Lewis pair (B/P FLP) compounds bearing unsaturated cyclic or aromatic carbon backbones have been synthesized and structurally characterized using ¹¹B, ³¹P, ¹H and ²H solid-state NMR spectroscopy. A comparison of the spectra with those of the corresponding free B/P FLPs shows that both ¹¹B isotropic chemical shifts as well as nuclear electric quadrupolar coupling constants decrease significantly upon FLP hydrogenation, revealing the breakage of the partial B−P bond present in the starting materials. Likewise, the ³¹P isotropic chemical shift, the chemical shift anisotropy, and the asymmetry parameter decrease significantly upon FLP hydrogenation, reflecting the formation of a more symmetric, C_3v-like local environment. ¹¹B{³¹P} rotational echo double resonance (REDOR) experiments can be used to measure the B−P internuclear distance (about 3.2 Å) of these compounds. Observation of the hydrogen atoms bound to the Lewis centers is best accomplished via ³¹P{¹H} and ¹¹B{¹H} cross-polarization-heteronuclear correlation experiments or by direct observation of the ²H MAS NMR signals on especially prepared FLP-D₂ adducts. For accurately measuring the phosphorus-deuterium distance via ³¹P{²H} rotational echo adiabatic passage double resonance (REAPDOR), it is essential to take the secondary dipolar coupling of ³¹P with the boron-bonded ²H nuclei explicitly into consideration, by simulating a ²H_P-³¹P-²H_B three-spin system based on structural input. All of the experimental NMR interaction parameters are found in excellent agreement with values calculated by DFT methods, using the geometries obtained either by energy optimization or from single-crystal structures.     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002