Anthony J. Arduengo

Carbene adducts of magnesium and zinc

Abstract The syntheses and characterizations of adducts of dialkylmagnesium and dialkylzinc with nucleophilic carbenes are described. These carbene adducts are available directly from the reaction of the stable nucleophilic carbenes 1,3-dimesitylimidazol-2-ylidene or 1,3-di(1-adamantyl)imidazol-2-ylidene and the dialkylmetal compounds. The X-ray crystal structures of the 1,3-di(1-adamantyl)imidazol-2-ylidene · diethylzinc adduct and 1,3-dimesitylimidazol-2-ylidene · diethylmagnesium are reported. The adamantyl substituted carbene gave a monomeric metal adduct whereas the mesityl substituted carbene shows a structure with bridging alkyl groups.

Subchronic Toxicity Study in Rats with 1-Methyl-3-propylimidazole-2-thione (PTI): Effects on the Thyroid

A 90-day gavage study was performed to evaluate the subchronic toxicity of 1-methyl-3-propylimidazole-2-thione (PTI) when administered to Crl:CD BR rats. PTI is a chemical catalyst and is structurally similar to the thioureas, which are known to adversely affect the thyroid. Therefore, this study was designed to investigate the effects of PTI on the thyroid. Male and female rats were dosed with 0, 5, 10, 25, or 75 mgPTI/kg/day for 13 weeks. Clinical pathology examinations and pathology examination were performed and the following were measured periodically: serum T3, T4, and TSH, hepatic UDP-glucuronyltransferase activity, and cell proliferation of the thyroid and liver. Under the conditions of this study, the overall no-observed-adverse-effect level (NOAEL) for the subchronic effects of PTI in male and female rats was 10 mg PTI/kg/day. The NOAEL was based on the effects on the thyroid gland in male and female rats dosed with 25 and 75 mg PTI/kg/day, as well as the hepatic centrilobular fatty change, increased severity of chronic progressive nephropathy, fatty change in the adrenal medulla, and the substantial reduction in body weight and body weight gain. The primary target organs were the thyroid and liver. Alterations in thyroid hormones (T3, T4, and TSH) occurred predominantly at 25 and 75 mg/kg/day. Toxicologically significant alterations in T3, T4, and TSH levels, cell proliferation, and UDP-glucuronyltransferase activity occurred in rats dosed with 25 and 75 mg/kg/day, which correlated with organ weight and histopathological effects. Additionally, the effect of PTI on thyroid peroxidase activity, a key step in thyroid hormone synthesis, was evaluated in vitro using microswine thyroid microsomes. PTI was shown to inhibit thyroid peroxidase, with an IC50 of 0.02 M. These data suggest that PTI enhances the excretion of T4 via induction of glucuronyltransferase and inhibits thyroid hormone synthesis via a direct affect on thyroid peroxidase. Both of these effects contribute to the disruption of the hypothalamic-pituitary-thyroid axis and result in sustained elevation of TSH and the corresponding thyroid hypertrophy and hyperplasia.

Reactions of imidazol(in)-2-ylidenes with electron deficient fluoroolefins

GRAPHICAL ABSTRACT ABSTRACT 1,3-Bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene forms stable 1:1 adducts with tetrafluoroethylene (2), hexafluorocyclobutene (3), and octafluorocyclopentene (4). Adduct 2 shows properties typical for nonpolarized olefins, as indicated by NMR spectroscopy and X-ray crystallography. By contrast, adducts 3 and 4 are best described as ylides with a significant charge separation between the imidazoline ring and the perfluorocycloalkyl unit. Similarly, 1,3-di-1-adamantylimidazol-2-ylidene reacts with tetrakis(trifluoromethyl)allene to form a polarized trimethylenemethane derivative, and bis(trifluoromethyl)ketene to form an imidazolium enolate zwitterion. The synthesis and characterization of a number of fluorinated methyleneimidazolines are described herein.

The Chemistry of 10-Pn-3 Systems1: Tricoordinate Hypervalent Pnictogen Compounds and Related Systems

Abstract The unusual hypervalent tricoordinate pnictogen systems, 10-Pn-3 ADPnO, provide a convenient starting point for the study of a wide range of main group chemistry. Differences in reactivity patterns among the pnictogens are readily apparent from the variety of chemistry exhibited. The ADPnO systems also provide a model for the recently recognized edge inversion mechanism for 3 and 4 coordinate 8-electron main group species.

LOWEST ENERGY DISTORTIONS IN HYPERVALENT SULFUR COMPOUNDS: THIAPENTALENES

Abstract The molecular and electronic structures of two model thiapentalenes have been calculated with high quality ab inirio molecular orbital theory. At the SCF level, the lowest energy structures correspond to in-plane distortions of a C, structure. The inclusion of a correlation energy correction leads to the symmetric C2v structure having the lowest energy. The out-of-plane bending distortion has also been investigated and has shown to lead to much higher energy structures. These results are contrasted to the distortions calculated for ADPO which lead to a folded structure as the lowest energy structure at the SCF level. The different types of distortions are related to the charge and electronic nature of the central atom, S or P.

Coordination Chemistry of ADPO

Abstract The hypervalent phosphorus compound, 3,7-di-t-butyl-5-aza-2,8-dioxa-1-phosphabicyclo-[3.3.0]octa-2,4,6-triene (ADPO) forms adducts with chromium, tungsten, nickel and palladium metal centers. All four new adducts contain tetrahedral phosphorus atoms as a result of folding of the ADPO unit. This folding of the planar 10-P-3 ADPO molecule to provide an 8-P-3 center for coordination to the transition metal center is the result of the close energy balance between 10-P-3 ADPO and 8-P-3 ADPO and the strength of the phosphorus-metal interaction. In the case of a homoleptic palladium(II) complex, dimerizati on of the coordinated ADPO unit was observed.