Vanadium bis-phosphine imido and oxo chloride alkylidenes have been extensively applied in the ring-closing metathesis of various acyclic olefins. However, their reactions involving ethylene have shown limited productivity due to rapid decomposition. The primary degradation pathway involving V bis-phosphine imido complexes is β-H elimination at an unsubstituted metallacyclobutane. In contrast, β-H elimination is disfavored for V oxo species, but bimolecular decomposition precludes its high productivity. Herein, we present the synthesis of V imido NHC complexes that are the most productive V catalysts toward various terminal olefins in ring-closing metathesis reactions. Experimental and computational studies suggest that β-H elimination and bimolecular decomposition are disfavored for V imido NHC complexes.

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New Mn(i)-based photoCORMs with a fac-{Mn(CO)3} moiety exhibit facile CO release upon simple exposure to light within the phototherapeutic region (no two photon excitation required).

The structure of 4-chloro-1H-pyrazole, C3H3ClN2, at 170 K has orthorhombic (Pnma) symmetry and is isostructural to its bromo analogue. Data were collected at low temperature since 4-chloro-1H-pyrazole sublimes when subjected to the localized heat produced by X-rays. The structure displays intermolecular N—H...N hydrogen bonding and the packing features a trimeric molecular assembly bisected by a mirror plane (m normal to b) running through one chlorine atom, one carbon atom and one N—N bond. The asymmetric unit therefore consists of one and one-half 4-chloro-1H-pyrazole molecules. Thus, the N—H proton is crystallographically disordered over two positions of 50% occupancy each.