No abstract

No abstract

H-'H coupling pattern may not be resolved, precluding the use of this method for assigning sugar pucker. Clearly, the 'H and 13C methods are complementary and both can be very useful. Finally, l3C signals are useful in defining metal-binding sites. The same advantages of this method for mononucleotide studies are passed on to oligonucleotide studies.25 Signals for carbons remote from the metal binding site appear to be most useful. discussions with Prof. David Live.

We report in this communication the first example of catalytic alkyne metathesis reactions mediated by well-defined non-d 0 alkylidyne complexes. The air-stable d 2 Re(V) alkylidyne complex Re4, bearing two PO-chelating ligands and a labile pyridine ligand, could catalyze homometathesis of internal alkynes with a broad substrate scope, including alcohols, amines, and even carboxylic acids. The catalyst can tolerate heating, air, and moisture in both solid and solution states, and the catalytic metathesis reactions could proceed normally in wet solvents.

No abstract

Metallacyclobutadienes are analogues of cyclobutadienes in which one of the cyclobutadiene CR groups has been formally replaced by a transition-metal fragment. These metallacycles are interesting because they can play an important role in catalysis and can serve as starting materials for the syntheses of organometallic compounds such as metallabenzene, η -cyclopentadienyl, and η -cyclopropenyl complexes. Unlike cyclobutadienes, metallacyclobutadienes can be significantly more stable. A number of metallacyclobutadienes have now been isolated and thoroughly characterized, especially for those that contain transition metals of groups 5-9. Their properties have also been actively investigated. This article highlights the chemistry of metallacyclobutadienes with reference to their syntheses, reactivity, and structural properties.

The new ethynylaryl isocyanide ligands 4-C=NCeH4C=CH (la) and 4-C=N-3-MeCeH3-C=CH (lb) have been prepared. They react with [AuCl(SMe2)] and with [(AuC=C-f-Bu)x] to give the isocyanide complexes [ClAu(4-C=NArC=CH) j (2a, Ar = CeH4; 2b, Ar = 3-MeC3H3) and [í-BuO^CAu(4-C=NArC^CH)] (6a, Ar = C3H4; 6b, Ar = 3-MeCeH3), respectively. The complex [í-BuC=CAuC=NXy] (Xy = 2,6-Me2CeH3) reacts with the acidic alkyne 4-N02-C3H4C=CH to give . A similar reaction uses the more acidic alkyne in 6 to displace -BuC^CH from 6 and so give the linear rigid-rod oligomers [í-BuC^C(AuC=NArC=C-)xH] (7a, Ar = C6H4; 7b, Ar = S-MeCeHg). The complexes 2a and 6b have been characterized by X-ray structure determinations (2a, monoclinic, P2Jm, a =

Aqueous organic redox flow batteries (AORFBs) employing synthetically tailorable organic electroactive compounds have received significant attention for energy storage technologies. There have been many efforts in developing electroactive materials for AORFBs with anion-exchange membranes. On the contrary, electroactive compounds that are compatible with cationexchange membranes in AORFBs are less studied. Here, we report an electroactive 4-carboxylic-2,2,6,6-tetramethylpiperidin-N-oxyl (4-CO 2 Na-TEMPO) molecule for neutral AORFBs. The compound exhibits a good solubility of 1.5 M in an aqueous sodium-based solution, which is 3 times more than that of the pristine 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (4-OH-TEMPO). When paired with a 1,10-bis(3-sulfonatopropyl)-4,4′-bipyridinium (SPr) 2 V anolyte, the resulting RFB operating through a cation-exchange membrane achieved an open-circuit voltage of 1.19 V and a high energy density of 14.7 W h L −1 . In the long-term cycling study, the RFB features a stable capacity retention of 99.94% per cycle over 400 cycles with nearly 100% Coulombic efficiency.