Thallium Salts Research Articles

Statement of Retraction: Complexions Therapy and Severe Intoxication by Thallium Salts

Statement of Retraction: Complexions Therapy and Severe Intoxication by Thallium Salts

Optimised syntheses and purifications of 3-aryl/heterocyclic dihydrobis- and hydrotris-(pyrazolyl)borate ligands as their alkali salts.

Though poly(pyrazolyl)borate ligands, namely dihydrobis(pyrazolyl)borate (Bp) and hydrotris(pyrazolyl)borate (Tp), have been used in coordination chemistry for decades, their synthesis and purification are of great importance, when targeting high purity and yield of metal complexes. As borohydride substitutions is temperature and pyrazolyl dependent, determining the reaction conditions for each ligand is non-trivial and does not always result in a temperature where only the desired products form. Herein we report the purification of two known TpR (R = phenyl, 2'-thienyl), as their tris-substituted temperatures coincide with their tetrakis-temperatures via fraction crystallisation from MeCN, and an optimised safe procedure for 3-aryl/heterocyclic BpR ligands (R = 2'-pyridyl, 2'-furyl, 2'-thineyl). These novel techniques allow for the safe isolation of alkali salts of poly(pyrazolyl)borate ligands in high yields and purities without the use of highly toxic thallium(i) salts.

Attempted Self-Harm with Elemental Thallium Purchased Online: Case Report with Analytical Confirmation

IntroductionThallium is a highly toxic metal, with most publications demonstrating poisoning from thallium salts. We report on a patient with elevated serum and urine thallium concentrations from an intentional ingestion of elemental thallium purchased from the internet for self-harm.Case ReportThe regional poison center was contacted about an 18-year-old man who ingested a fragment from a 100-gram bar reported to be elemental thallium. Serial serum and urine thallium concentrations were obtained. Prussian blue was started on hospital day (HD) 2. A metal fragment was seen on abdominal x-ray and removed via colonoscopy on HD3. The ingested fragment was analyzed via inductively coupled plasma mass spectrometry (ICP-MS) and found to be 87.0% elemental thallium. The initial serum thallium concentration obtained on HD1 was 423.5 mcg/L (reference range < 5.1 mcg/L), which subsequently decreased to 4.5 mcg/L, 29 days after the ingestion. An initial random urine thallium concentration obtained on HD 3 was 1850.5 mcg/g creatinine (reference range < 0.4 mcg/g creatinine). The patient remained hospitalized for 23 days and, when seen in follow-up, had not developed any signs or symptoms of thallium toxicity.DiscussionElemental thallium ingestion is a rare toxicologic exposure, with limited published clinical and analytical experience to guide management. This case report describes a patient with ingestion of elemental thallium who developed elevated serum and urine thallium concentrations and was treated with Prussian blue. Despite having elevated serum and urine thallium concentrations consistent with previous fatal exposures, more evidence is needed to understand the differences between elemental thallium and thallium salts.

Exploring opportunities for tuning phenyltris(pyrazol-1-yl)borate donation by varying the extent of phenyl substituent fluorination.

The importance of electron deficient Tp ligands motivates the introduction of electron-withdrawing substituents into the scorpionate framework. Since perfluorophenyltris(pyrazol-1-yl)borate affects significant anodic shifts in half-cell potentials in their metal complexes relative those of phenyltris(pyrazol-1-yl)borate analogues, the tuning opportunities achieved using 3,4,5-trifluorophenyl- and 3,5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates were explored. Bis(amino)boranes ((3,4,5-F)C6H2)B(NMe2)2 and ((3,5-CF3)C6H3)B(NMe2)2 are precursors to fluorinated tris(pyrazol-1-yl)phenylborates. Thallium salts of these scorpionates exhibit bridging asymmetric κ3-N,N,N coordination modes consistent with the reduced π-basicity of the fluorinated phenyl substituents relative those of other structurally characterized tris(pyrazol-1-yl)phenylborates. While a comparative analysis of the spectral and X-ray crystallographic data for classical Mo(0), Mo(II), Mn(I), Fe(II) and Cu(II) complexes of [((3,4,5-F)C6H2)Bpz3]- and [((3,5-CF3)C6H3)Bpz3]- could not differentiate these ligands with respect to their metal-based electronic impacts, cyclic voltammetry suggests that 3,4,5-trifluorophenyl- and 3,5-bis(trifluoromethyl)phenyl(pyrazol-1-yl)borates affect similar anodic shifts within their metal complexes, with coordination of [((3,5-CF3)C6H3)Bpz3]- rendering metal centers more difficult to oxidize, and sometimes even more difficult to oxidize than their [C6F5Bpz3]- analogues. These data suggest that the extent of phenyl substituent fluorination necessary to minimize metal center electron-richness in phenyltris(pyrazol-1-yl)borate complexes cannot be confidently predicted.

Short-term toxicity studies of thallium (I) sulfate administered in drinking water to Sprague Dawley rats and B6C3F1/N mice.

Thallium is a heavy metal that is known to induce a broad spectrum of adverse health effects in humans including alopecia, neurotoxicity, and mortality following high dose acute poisoning events. Widespread human exposure to thallium may occur via consumption of contaminated drinking water; limited toxicity data are available to evaluate the corresponding public health risk. To address this data gap, the Division of Translational Toxicology conducted short-term toxicity studies of a monovalent thallium salt, thallium (I) sulfate. Thallium (I) sulfate was administered via dosed drinking water to time-mated Sprague Dawley (Hsd:Sprague Dawley® SD®) rats (F0 dams) and their offspring (F1) from gestation day (GD) 6 until up to postnatal day (PND) 28 at concentrations of 0, 3.13, 6.25, 12.5, 25, or 50mg/L, and adult male and female B6C3F1/N mice for up to 2 weeks at concentrations of 0, 6.25, 12.5, 25, 50, or 100mg/L. Rat dams in the 50mg/L exposure group were removed during gestation, and dams and offspring in the 25mg/L exposure group were removed on or before PND 0 due to overt toxicity. Exposure to thallium (I) sulfate at concentrations ≤12.5mg/L did not impact F0 dam body weights, maintenance of pregnancy, littering parameters, or F1 survival (PND 4-28). However, in F1 pups, exposure to 12.5mg/L thallium (I) sulfate resulted in decreased body weight gains relative to control rats and onset of whole-body alopecia. Measurement of thallium concentrations in dam plasma, amniotic fluid, fetuses (GD 18), and pup plasma (PND 4) indicated marked maternal transfer of thallium to offspring during gestation and lactation. Mice exposed to 100mg/L thallium (I) sulfate were removed early due to overt toxicity, and mice exposed to ≥25mg/L exhibited exposure concentration-related decreases in body weight. Lowest-observed-effect levels of 12.5mg/L (rats) and 25mg/L (mice) were determined based on the increased incidence of clinical signs of alopecia in F1 rat pups and significantly decreased body weights for both rats and mice.

Experimental Study of Antitumor Activity of Pefagtal Addressed to αvβ3 Integrins.

We studied the effect of a new targeted drug Pefagtal that represents a conjugate in which the MS2 phage filled with a substance toxic to cells (thallium salts) is covalently linked to peptides containing the RGD motif. The antitumor and pronounced antimetastatic effects of Pefagtal were demonstrated on transplanted mouse tumors differing in histological type and status of metastasis: Krebs-2 ascites adenocarcinoma of the mammary gland, Lewis lung adenocarcinoma, hepatoma-29, and lung adenocarcinoma. It is assumed that the RGD motif mediates primary binding of the construct to αvβ3 and αvβ5 integrins that are predominantly overexpressed in the endothelial cells of tumor blood vessels and in tumor and metastatic cells.

Thallium(I) Salts: New Partners for Calix[4]pyrroles.

Calix[4]pyrrole 1 can form host-guest complexes with certain thallium salts, for example, TlF, not only in the gas phase but also in solution and in the solid state. The complexation of TlF by calix[4]pyrrole 1 was found to promote self-assembly and the formation of well-defined and highly ordered fibrous supramolecular morphologies, as revealed by polarizing microscopy and scanning electron microscopy. The findings reported here serve to broaden the scope of cationic substrates that may be complexed as ion pairs by calix[4]pyrrole receptors while setting the stage for the development of new hosts for thallium(I) salts.

Complexions therapy and severe intoxication by Thallium salts

We, the Editors and Publisher of Journal of Environmental Science and Health, Part A, have retracted the following article: Rayisyan, M., Zakharova, N., & Babaskina, L. (2021). Complexions therapy and severe intoxication by Thallium salts. Journal of Environmental Science and Health, Part A, 56(4), 445–453. https://doi.org/10.1080/10934529.2021.1885905 Following publication, significant concerns have been raised about the authorship, ethical approval, and the integrity of the data in the article. Despite our best efforts to contact the authors for an explanation, we have not been able to do so. As the editorial team no longer have confidence in the reported conclusions within the article, the decision has been made to retract the article. We have been informed in our decision-making by our editorial policies and the COPE guidelines. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’.

Synthesis and characterisation of some mixed ligand complexes of thallium (i) metal with isonitrosoethylmethyl ketone

The present investigation has been undertaken to examine complex formation by thallium (I) derivatives of 2-nitro phenol (ONP), 2,4-dinitrophenol (DNP), 2,4,6-trinitrophenol (TNP), 1-nitroso-2-naphthol (1N2N), 8-hydroxyquinoline (8HQ), and 2-aminobenzoic acid (OABA) with Isonitrosoethylmethyl Ketone. They have general formula [ML (HL′)], where M = Tl (I), L = deprotonated ONP, DNP, TNP, 8-HQ, 1N2N and OABA and L′ = Isonitrosoethylmethyl Ketone. Isonitrosoethylmethyl Ketone is ambidentate ligand and can donate through oxygen or nitrogen or both. The preparation of mixed ligand complex with the thallium (I) salt of 2,4-dinitrophenol and 2,4,6-trinitrophenol with the Isonitrosoethylmethyl Ketone (INEMK) have very low yield.

Stepwise Functionalization of N2 at Mo: Nitrido to Imido to Amido – Factors Favoring Amine Elimination from the Amido Complex

Functionalization of nitrido complex [(PPhP2Cy)Mo(N)(I)] by a bis‐silane in concentrated medium generates the hydrido‐imido complex [(PPhP2Cy)Mo(H)(=NSiMe2CH2CH2SiMe2H)(I)]. Abstraction of the iodide by thallium salt TlX (X = PF6, OTf) results in a second N–Si bond formation and forms the bis‐hydride amide complex [(PPhP2Cy)Mo(H)2(NSiMe2CH2CH2SiMe2)]+. An alternative synthesis relies on the abstraction of the iodide from the nitride complex [(PPhP2Cy)Mo(N)(I)] to generate the corresponding cationic complex [(PPhP2Cy)Mo(N)]+ followed by addition of the bis‐silane. Addition of PMe3 to the [(PPhP2Cy)Mo(H)2(NSiMe2CH2CH2SiMe2)]+ complex liberates the silylamine and forms the Mo(II) cationic complex [(PPhP2Cy)Mo(H)(PMe3)]+. DFT calculations rationalizing the observed reactivity are presented.

Crystal structure of poly[(μ3-4-amino-1,2,5-oxa-diazole-3-hydroxamato)thallium(I)

The title compound represents the thallium(I) salt of a substituted 1,2,5-oxa-diazole, [Tl(C3H3N4O3)] n , with amino- and hydroxamate groups in the 4- and 3- positions of the oxa-diazole ring, respectively. In the crystal, the deprotonated hydroxamate group represents an inter-mediate between the keto/enol tautomers and forms a five-membered chelate ring with the thallium(I) cation. The coordination sphere of the cation is augmented to a distorted disphenoid by two monodentately binding O atoms from two adjacent anions, leading to the formation of zigzag chains extending parallel to the b axis. The cohesion within the chains is supported by π-π stacking [centroid-centroid distance = 3.746 (3) Å] and inter-molecular N-H⋯N hydrogen bonds.

Higher polythionic acids – the precursors for formation of thallium sulphide layers on polyethylene surface

The method of thallium sulphide thin films deposition on low density polyethylene (LDPE), based on applying solutions of higher polythionic acids (H2SnO6, n = 21, 33, 45), was developed and investigated. The concentration of sulphur in the LDPE film increases with the increase of temperature of higher polythionic acid solution and its sulphurity, as well as the duration of retention of LDPE in its solution is prolonged. The sulphur concentration in the PE film under the same duration of sulphurisation and repetition of treatment cycles insignificantly changes. When the sulphurised LDPE was treated with a thallium Tl(I) salt solution, sulphur present in the polymer reacts with thallium ions and the layers of thallium sulphides, TlxSy, of different composition are formed. The stoichiometric composition of the layer changes from Tl0.1S to Tl2.6S. The amount of thallium increases in the sulphide layers when the number of the cycles of LDPE sulphurisation in the H2S33O6 solution and treatment of sulphurised polymer with the Tl(I) salt solution is increased. The stoichiometric composition of TlxSy coats of one treatment cycle samples changes from Tl0.5S to Tl1.1S. The X-ray diffraction analysis of the polyethylene, treated with the solution of higher polythionic acid, H2S33O6, and then with the Tl(I) salt solution, confirmed the premise that on the LDPE surface the layers of thallium sulphides, TlxSy, were formed. Five phases of thallium sulphides were identified: TlS, Tl2S, Tl2S2, Tl4S3 and Tl2S5. The TlS phase prevailed in diffractograms. The chemical and phase composition of the TlxSy layers surface (up to 1 nm depth) is identified by X-ray photo-electronic spectroscopy analysis. The analysis data confirmed that the compounds of TlS, Tl2S, Tl2SO4, Tl(OH)3, S8 and Tl2O3 were formed on the surface of the layers. The morphology of thallium sulphide layers and the mechanism of their formation are determined by means of scanning atomic force and electronic microscopy. Two processes take place during the formation of the layer: desorption of sulphur and reaction of thallium ions from the thallium(I) salt solution with sulphur present on the LDPE surface. The layer of thallium sulphides is formed on the surface of the sulphur layer. Deposition of thallium sulpfide films from the solution of higher polythionic acid on the LDPE films is not homogeneous, it has the separated island type morphology. The identified regularities let purposively choose the conditions for sulphurisation of LDPE films by using the solution of higher polythionic acid as the agent of polymer sulphurisation in order to compose the layers of thallium sulphides, TlxSy, of the desired chemical and phasic composition on the surface of this polymer by means of the sorption–diffusion method.

Synthesis and redox activity of the ruthenium complexes based on 9-hydroxy-2,4,6,8-tetra-(tert.-butyl)phenoxazin-1-one ligands

The redox-active bis-chelate hexacoordinate ruthenium complex 2 Ru(ONO)2 comprising two redox-active 2,4,6,8-tetrakis(tert.-butyl)-9-hydroxyphenoxazin-1-one ligands 1 was synthesized by coupling ruthenium trichloride with 1 or its thallium salt. Reduction of 2 with zinc amalgam produces its radical-anion 2a, which readily reacts with pyridine in aerobic conditions resulting in substitution of one of the tridentate hydroxyphenoxazinone ligand by three pyridine molecules and the formation of a salt of tris(pyridine)(tetra-(tert.-butyl)oxyphenoxazin-1-onate) Ru(II) cation 5. The structure of this salt was established by X-ray crystallography and its redox activity investigated using cyclic voltammetry. The mechanism of the RuIII/RuII conversion observed in this reaction was suggested based on the data of ESR, UV-Vis spectra and DFT B3LYP/6-311++G(d,p)/SDD calculations.

Expedient Synthesis of Thioether‐Functionalized Hydrotris(indazolyl)borate as an Anchoring Platform for Rotary Molecular Machines

Major improvements in the synthesis of surface‐mounted rotary molecular machines based on ruthenium(II) complexes are reported. The development of a one‐pot indium(III)‐mediated “N‐deprotection/ester reductive sulfidation” sequence allowed step economy, reproducibility and high efficiency in the synthesis of the thioether‐functionalized tripodal ligand. Switching to the thallium salt of hydrotris(indazolyl)borate and to microwave heating further optimized the preparation of the common intermediate in the modular synthesis of symmetric and dissymmetric molecular motors and gears. The penta(4‐bromophenyl)cyclopentadienyl ruthenium(II) key precursor is now reproducibly synthesized in 5 steps and 31 % overall yield on the longest linear sequence. Subsequent fivefold Suzuki–Miyaura coupling with ferroceneboronic acid led to a new C5‐symmetric pentaferrocenyl molecular motor.

Different reactivity of cyclooctadiene complexes 3,3-(cod)-8-SMe2-closo-3,1,2-RhC2B9H10 and 1,8-Me2-2,2-(cod)-11-SMe2-2,1,8-closo-RhC2B9H8 toward iodine

Reaction of the thallium salt Tl[7,8-Me2-10-SMe2-7,8-nido-C2B9H8] with [(cod)RhCl]2 in THF furnishes new rhodacarborane 1,2-Me2-3,3-(cod)-8-SMe2-3,1,2-closo-RhC2B9H8 (1). The latter undergoes 1,2 → 1,7 carbon atom isomerization upon reflux in o-xylene for 5 h producing complex 1,8-Me2-2,2-(cod)-11-SMe2-2,1,8-closo-RhC2B9H8 (2). Reaction of complex 2 with 1 equiv of I2 in benzene results in a loss of the cod ligand and formation of product 3, consisting of cationic [(1,8-Me2-11-SMe2-closo-2,1,8-RhC2B9H8)2I3]+ (3a+) and anionic [(1,8-Me2-11-SMe-closo-2,1,8-RhC2B9H8)2I3]− (3b–) iodide species. In contrast, unisomerized analog 3,3-(cod)-8-SMe2-closo-3,1,2-RhC2B9H10 reacts with I2 affording dimeric iodide [3,3-I2-8-SMe2-closo-3,1,2-RhC2B9H10]2 (5). The structures of 2 and 5 were determined by a single crystal X-ray diffraction.

Iridium Halide Complexes [1,1‐X2‐8‐SMe2‐1,2,8‐IrC2B9H10]2 (X = Cl, Br, I): Synthesis, Reactivity and Catalytic Activity

The reactions of thallium salt Tl[7‐SMe2‐7,8‐C2B9H10] with [(cod)RhCl]2 and [Cp*RuCl]4 are accompanied by room‐temperature polyhedral rearrangement, giving rhoda‐ and ruthenacarboranes 1‐cod‐8‐SMe2‐1,2,8‐RhC2B9H10 (2) and 1‐Cp*‐8‐SMe2‐1,2,8‐RuC2B9H10 (3), respectively. According to DFT calculations, the rearrangement could be attributed to the triangular face rotation mechanism. The reaction of iridium derivative 1‐cod‐8‐SMe2‐1,2,8‐IrC2B9H10 (1) with anhydrous hydrohalic acids HX (X = Cl, Br, I) results in the dimeric halide iridacarboranes [1,1‐X2‐8‐SMe2‐1,2,8‐IrC2B9H10]2 [4a–c; X = Cl (a), Br (b), I (c)]. Bromide 4b reacts with Tl[Tl(η‐7,8‐C2B9H11)] and TlCp giving iridacarboranes 8′‐SMe2‐1,1′‐Ir(2,3‐C2B9H11)(2′,8′‐C2B9H10) (5) and 1‐Cp‐8‐SMe‐1,2,8‐IrC2B9H10 (6). The formation of the latter compound is accompanied by demethylation of the SMe2 substituent. The structures of 2, 3, 5 and 6 were determined by single‐crystal X‐ray diffraction. Iridacarboranes 4b and [1,1‐Br2‐4‐SMe2‐1,2,3‐IrC2B9H10]2 (7) catalyze the dimerization of diphenylacetylene, giving 1,2,3‐triphenylnaphthalene in 20–24 % yields. Compounds 4b and 7 also effectively catalyze the reductive amination reaction between aldehydes (or ketones) and primary (or secondary) amines in the presence of carbon monoxide, giving the corresponding secondary and tertiary amines in high yields (60–85 %).

Genotoxicity assessment of human peripheral Lymphocytes induced by thallium(I) and thallium(III)

ABSTRACTThallium is a non-essential metal with a wide range of industrial uses. However, thallium is also a potential pollutant with high potential toxicity to humans. In the present study, we analyzed and compared the cellular and genotoxic effects of thallium in two main oxidation states by applying chromosome aberration assays to human peripheral lymphocytes. We observed that thallium(I) sulfate reduced the mitotic index at all tested concentrations (0.5, 1, 5, 50 and 100 μg/mL), whereas thallium(III) chloride was toxic at concentrations ≥1 μg/mL. Thallium(I) and thallium(III) treatment significantly increased structural chromosomal aberrations, with and without gaps, and increased the percentage of aberrant cells without gaps. Furthermore, satellite associations and numerical chromosomal aberration tests showed significant differences at a few of the tested concentrations. The satellite association test is related to aneuploidy. Thallium salts increased satellite associations when hyperploid cells were observed. Our results indicated that the two oxidation states of thallium induced toxicity in vitro – i.e. cyto/genotoxic (clastogenic and aneuploidogenic) effects.

Influence of the anionic part of the stabilizer on electroless nickel-boron plating

ABSTRACTSelectivity and smooth operation of electroless nickel plating require that a stabilizing agent is used. It operates by blocking catalytic activity on unwanted germination sites and regulating the activity of the substrate. In the case of alkaline electroless nickel-boron plating systems, which use sodium (or potassium) borohydride as reducing agent, lead and thallium salts are the most popular stabilizers. However, there is little knowledge about the way the stabilizer acts. In this study, 4 different lead-based stabilizers (tungstate, sulphate, nitrate and chloride) have been used, all other things left constant, in electroless nickel-boron plating baths. The thickness, composition, roughness, morphology, hardness and structure of all the obtained coatings have been investigated. Chloride led to thinner deposits and the boron content varied between 5.5 wt.% for lead tungstate and 6.5 wt.% for lead nitrate and lead sulphate, with a lead content between 0.2 and 0.25 wt.%. Coatings obtained with a lead tungstate stabilized bath were thicker, harder and contained less boron and lead than the others. This shows the influence of the anionic part of the stabilizing agent on the plating process.

Polyhedral Rearrangements in the Complexes of Rhodium and Iridium with Isomeric Carborane Anions [7,8-Me2-X-SMe2-7,8-nido-C2B9H8]− (X = 9 and 10)

Polyhedral rearrangement of iridacarborane 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-IrC2B9H8 (1) proceeds in a solution at RT and affords a product of 1,2 → 1,7 isomerization 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-IrC2B9H8 (2). Rhodium derivative 1,2-Me2-3,3-(cod)-4-SMe2-3,1,2-closo-RhC2B9H8 (3) is significantly more stable toward heating than iridium complex 1 and isomerizes at 110 °C by 1,2 → 1,2 and 1,2 → 1,7 reaction schemes with 1,2 → 1,2 being the predominant route forming 1,2-Me2-4,4-(cod)-8-SMe2-4,1,2-closo-RhC2B9H8 (4) and 1,8-Me2-2,2-(cod)-7-SMe2-2,1,8-closo-RhC2B9H8 (5). Complexes 4 and 5 were characterized by 11B{1H}–11B{1H} COSY NMR spectrometry. A mechanism of 1,2 → 1,2 isomerization of 3 to 4 was proposed on the basis of DFT calculations. Reaction of the thallium salt Tl[7,8-Me2-9-SMe2-7,8-nido-C2B9H8] (CarbTl) with [Cp*RuCl]4 in THF furnishes new ruthenacarborane 1,2-Me2-3-(Cp*)-4-SMe2-3,1,2-closo-RuC2B9H8 (6). Heating of 6 at 80 and 144 °C leads to the partial and complete decomposition, respec...

The structures of two scorpionates: thallium tetrakis(3-phenyl-1H-pyrazol-1-yl)borate and potassium tetrakis(3-cyclopropyl-1H-pyrazol-1-yl)borate.

The introduction of poly(1H-pyrazolyl)borate anions, better known as scorpionates, as negatively charged ligands for a great diversity of metal cations has had a tremendous influence in coordination chemistry. The structures of two salts of tetrakispyrazolylborate, namely [tetrakis(3-phenyl-1H-pyrazol-1-yl)borato]thallium(I), [Tl(C36H28BN8)], and catena-poly[potassium-[μ2-tetrakis(3-cyclopropyl-1H-pyrazol-1-yl)borato]], [K(C24H28BN8)]n, have been determined at 296 K in the monoclinic P21/c and C2/c space groups, respectively. In their crystal structures, the thallium salt presents discrete molecular motifs, while the potassium salt shows infinite polymeric chains. The 13C and 15N CPMAS (cross polarization magic angle spinning) NMR spectra of these compounds were recorded and the chemical shifts compared with theoretically calculated ones at the GIAO/B3LYP/6-311++G(d,p) level. Both techniques are complementary and mutually consistent.