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Reaction of a chelating N-heterocyclic carbene Pt(II) dimethyl complex with phenyl iodide and excess KI results in the direct detection of a Pt(IV) phenyl intermediate by 1H NMR spectroscopy. This finding provides experimental evidence that the reaction between Pt(II) dimethyl complexes and aryl halides proceeds via a concerted oxidative addition (OA) mechanism. Additionally, we report on the selective reductive elimination (RE) of Csp3–I vs Csp2–Csp3and Csp3–Csp3bonds. Lastly, OA, different RE pathways, and reactivity of different isomers were investigated by computational methods that are consistent with experimental observations. We believe that these results have important implications for the development of new Pt-catalyzed transformations.

In projected structure–activity relationship studies of the novel diheteroarylamide-based anti-HIV agent 2(1C8), one objective was to evaluate the influence of incorporating the central amide motif in 2into a five-membered pyrazolone ring, as found in 3. It was envisaged that compound 3could be prepared through reaction of 3-hydrazino-5-nitrobenzisothiazole 5with the methyl ester of 4-chloropyridine-3-carboxylic acid, followed by N-methylation of the pyridine nitrogen. However, the reaction of 3-methoxyl-5-nitrobenzisothiazole with hydrazine resulted in formation of ring-opened hydrazonate product 18. In the corresponding reaction with 3-chloro-5-nitrobenzisothiazole, a different rearrangement product 19was formed, in which two 2,1-benzisothiazole units are joined by a sulfur bridge. Meisenheimer complex formation, favored by the presence of the 5-nitro substituent on the benzisothiazole ring, was postulated to be a key feature in the formation of these deep-seated rearrangement products. Support for the proposed formation of the pivotal Meisenheimer complexes and their subsequent evolution to the observed products in which the benzisothiazole sulfur atom is either expelled or maintained in the isomeric 2,1-benzisothiazole system was obtained by density function theory calculations.

Redox noninnocent ligands enhance the reactivity of the metal they complex, a strategy used by metalloenzymes and in catalysis. Herein, we report a series of copper complexes with the same ligand framework, but with a pendant nitrogen group that spans five different redox states between nitro and amine. Of particular interest is the synthesis of a unprecedented copper(I)-arylhydroxylamine complex. While hydroxylamines typically disproportionate or decompose in the presence of transition metal ions, the reactivity of this metastable species is arrested by the presence of an intramolecular hydrogen bond. Two-electron oxidation yields a copper(II)-(arylnitrosyl radical) complex that can dissociate to a copper(I) species with uncoordinated arylnitroso. This combination of ligand redox noninnocence and hemilability provides opportunities in catalysis for two-electron chemistry via a one-electron copper(I/II) shuttle, as exemplified with an aerobic alcohol oxidation.

Thermolysis of a pair of dibenzo-7-phosphanorbornadiene compounds is shown to lead to differing behaviors: phosphinidene sulfide release and formation of amorphous P2S. These compounds, tBuP(S)A(1, A= C14H10or anthracene; 59% isol. yield) and HP(S)A(2; 63%), are available through thionation of tBuPAand the new secondary phosphine HPA(5), prepared from Me2NPAand DIBAL-H in 50% yield. Phosphinidene sulfide [tBuP═S] transfer is shown to proceed efficiently from 1to 2,3-dimethyl-1,3-butadiene to form Diels–Alder product 3with a zero-order dependence on diene. Platinum complex (Ph3P)2Pt(η2-tBuPS) (4, 47%) is also accessed from 1and structurally characterized. In contrast, heating parent species 2(3 h, 135 °C) under vacuum instead produces an insoluble, nonvolatile yellow residual material 6of composition P2S that displays semiconductor properties with an optical band gap of 2.4 eV. Material 6obtained in this manner from molecular precursor 2is in a poorly characterized portion of the phosphorus–sulfur phase diagram and has therefore been subjected to a range of spectroscopic techniques to gain structural insight. X-ray spectroscopic and diffraction techniques, including Raman, XANES, EXAFS, and PDF, reveal 6to have similarities with related compounds including P4S3, Hittorf’s violet phosphorus. Various possible structures have been explored as well using quantum chemical calculations under the constraint that each phosphorus atom is trivalent with no terminal sulfide groups, and each sulfur atom is divalent. The structural conclusions are supported by data from phosphorus-31 magic angle spinning (MAS) solid state NMR spectroscopy, bolstering the structural comparisons to other phosphorus–sulfur systems while excluding the formulation of P2S as a simple mixture of P4S3and phosphorus.

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Molecules containing sulfur–nitrogen bonds, like sulfonamides, have long been of interest because of their many uses and interesting chemical properties. Understanding the factors that cause sulfonamide reactivity is important, yet there continues to be controversy regarding the relevance of S–N π bonding in describing these species. In this paper, we use sulfur K-edge X-ray absorption spectroscopy (XAS) in conjunction with density functional theory (DFT) to investigate the role of S3pcontributions to π-bonding in sulfonamides, sulfinamides, and sulfenamides. We explore the nature of the electron distribution of the sulfur atom to its nearest neighbors and widen our scope to its effects on rotational barriers along the sulfur–nitrogen axis. The experimental XAS data together with time-dependent DFT calculations confirm that sulfonamides—and the other sulfinated amides in this series—have essentially no S–N π bonding involving S3pcontributions and that electron repulsion is the dominant force affecting rotational barriers along the S–N axis.