The N,O-bidentate pyridyl functionalized alkoxy ligands 2-(6-methyl-2-pyridinyl)-1,1-dimethyl-1-ethanol (L1–H) and 2-(6-methyl-2-pyridinyl)-1,1-diphenyl-1-ethanol (L2–H) have been prepared by treatment of acetone and benzophenone with monolithiated 2,6-lutidine. Deprotonolysis of the ligands L1–H and L2–H with 1 equiv of Mg n Bu2 and ZnEt2 in toluene by releasing butane and ethane, respectively, gave the corresponding dimeric metal-monoalkyl complexes [L1Mg n Bu]2 (1), [L2Mg n Bu]2 (2), [L1ZnEt]2 (3), and [L2ZnEt]2 (4). Complexes 1–4 were characterized by 1H and 13C NMR spectroscopy analysis, and the molecular structures of 1, 3, and 4 were further confirmed by X-ray diffraction analysis. The investigation of the catalytic behavior of these complexes toward ε-caprolactone (ε-CL) and l-lactide (l-LA) polymerizations showed that the Mg-based complexes gave higher activity than those attached to zinc metal, probably owing to the greater ionic character of the magnesium metal. Remarkably, the magnesium complex 2 exhibited a striking “immortal” nature in the presence of primary alcohols where up to 500 PCL chains grew from each Mg active center when benzyl alcohol was employed, while, in particular, in the presence of triethanolamine, complex 2 also displayed an immortal mode for the polymerization of l-LA.

Hydrogenolysis of the half‐sandwich penta‐arylcyclopentadienyl‐supported heavy alkaline‐earth‐metal alkyl complexes (CpAr)Ae[CH(SiMe3)2](S) (CpAr=C5Ar5, Ar=3,5‐iPr2‐C6H3; S=THF or DABCO) in hexane afforded the calcium, strontium, and barium metal–hydride complexes as the same dimers [(CpAr)Ae(μ‐H)(S)]2 (Ae=Ca, S=THF, 2‐Ca; Ae=Sr, Ba, S=DABCO, 4‐Ae), which were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. 2‐Ca, 4‐Sr, and 4‐Ba catalyzed alkene hydrogenation under mild conditions (30 °C, 6 atm, 5 mol % cat.), with the activity increasing with the metal size. A variety of activated alkenes including tri‐ and tetra‐substituted olefins, semi‐activated alkene (Me3SiCH=CH2), and unactivated terminal alkene (1‐hexene) were evaluated.

Polymer photodetector based on a novel low-bandgap polymer showed a detectivity of greater than 1012 Jones in the spectral region of 300–980 nm and over 1010 Jones at 300–1600 nm under 0.1 V.

The developments of theoretical studies on NHC‐catalyzed [n+2] (n=2, 3, 4) and other cycloaddition/annulation reactions have been summarized in this review. The detailed mechanisms, role of NHC, and origin of chemo‐ and stereoselectivity of these kinds of reactions were illustrated to provide valuable insights for rational design of new NHC‐catalyzed cycloaddition/annulation reactions with high selectivities. Moreover, computational and theoretical methods commonly used were also mentioned to open the door for deep exploration of the general principle for NHC‐catalyzed reactions within theoretical chemistry.

The possible reaction mechanisms of stereoselective [4 + 2] cycloaddition of enals and chalcones catalyzed by N-heterocyclic carbene (NHC) have been investigated using density functional theory (DFT). The calculated results indicate that the most favorable reaction channel occurs through five steps. The first step is the nucleophilic attack on the enal by NHC. Then, there are two consecutive acid (AcOH)-assisted proton-transfer steps. Subsequently, the fourth step is the [4 + 2] cycloaddition process associated with the formation of two chiral centers, followed by dissociation of NHC and product. Our computational results demonstrate that the [4 + 2] cycloaddition is the rate-determining and stereoselectivity-determining step. The energy barrier for the SS configurational channel (17.62 kcal/mol) is the lowest one, indicating the SS configurational product should be the main product, which is in agreement with experiment. Moreover, the role of NHC catalyst in the [4 + 2] cycloaddition of enal and chalcone was explored by the analysis of global reactivity indexes. This work should be helpful for realizing the significant roles of catalyst NHC and the additive AcOH and thus provide valuable insights on the rational design of potential catalyst for this kind of reactions.

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The DFT perspective toward the [3 + 2] annulation reaction through NHC and Brønsted acid cooperative catalysis has been investigated.

The mechanism and stereoselectivity of the NHC-catalyzed [4 + 2] annulation reaction of enals with azodicarboxylates have been investigated using the DFT method.