Less than 10% of the plastics generated globally are recycled, while the rest are incinerated, accumulated in landfills, or leach into the environment. New technologies are emerging to chemically recycle...

A cationic iron(III) complex was active for the polymerization of various epoxides, whereas the analogous neutral iron(II) complex was inactive. Cyclohexene oxide polymerization could be "switched off" upon in situ reduction of the iron(III) catalyst and "switched on" upon in situ oxidation, which is orthogonal to what was observed previously for lactide polymerization. Conducting copolymerization reactions in the presence of both monomers resulted in block copolymers whose identity can be controlled by the oxidation state of the catalyst: selective lactide polymerization was observed in the iron(II) oxidation state and selective epoxide polymerization was observed in the iron(III) oxidation state. Evidence for the formation of block copolymers was obtained from solubility differences, GPC, and DOSY-NMR studies.

It has previously been demonstrated that complexes of the form (iPrPNP)­Fe­(H)­(CNR) (iPrPNP = N­(CH2CH2P­(iPr)2)2 –, R = 2,6-dimethylphenyl or 4-methoxyphenyl), which contain a pincer ligand capable of metal–ligand cooperation (MLC), are active for CO2 hydrogenation. Herein, the synthesis and catalytic activity of a second-generation of precatalysts containing a tertiary amine ligand, which cannot participate in MLC, are presented. Specifically, the complexes (iPrPNMeP)­Fe­(H)­(HBH3)­(CNR) (iPrPNMeP = MeN­(CH2CH2P­(iPr)2)2, R = 2,6-dimethylphenyl (2a), tert-butyl (2b), or adamantyl (2c)) have been prepared and crystallographically characterized. These complexes are precatalysts for both formic acid dehydrogenation and CO2 hydrogenation to formate, and give improved activity compared to first-generation systems with isonitrile ligands. The second-generation systems 2a–c, however, give inferior activity compared to the related carbonyl complexes (iPrPNP)­Fe­(H)­(CO) and (iPrPNMeP)­Fe­(H)­(HBH3)­(CO), which have been previously reported. This study demonstrates that a ligand which can participate in MLC is not universally advantageous for promoting the hydrogenation and dehydrogenation reactions studied in this work and provides guidance for the rational design of improved catalysts for reactions relevant to energy storage.

Surface functionalization with organic electron donors (OEDs) is an effective doping strategy for 2D materials, which can achieve doping levels beyond those possible with conventional electric field gating. While the effectiveness of surface functionalization has been demonstrated in many 2D systems, the doping efficiencies of OEDs have largely been unmeasured, which is in stark contrast to their precision syntheses and tailored redox potentials. Here, using monolayer MoS2 as a model system and an organic reductant based on 4,4′‐bipyridine (DMAP‐OED) as a strong organic dopant, it is established that the doping efficiency of DMAP‐OED to MoS2 is in the range of 0.63 to 1.26 electrons per molecule. The highest doping levels to date are also achieved in monolayer MoS2 by surface functionalization and demonstrate that DMAP‐OED is a stronger dopant than benzyl viologen, which is the previous best OED dopant. The measured range of the doping efficiency is in good agreement with the values predicted from first‐principles calculations. This work provides a basis for the rational design of OEDs for high‐level doping of 2D materials.

The iron complex (iPrPNMeP)Fe(H)2(CO) (iPrPNMeP=CH3N(CH2CH2PiPr2)2), which features a pincer ligand with a tertiary amine, can give up to 100,000 turnovers for additive‐free formic acid dehydrogenation (FADH). This is two orders of magnitude higher than any previously reported base metal system. Mechanistic studies reveal the catalytic reaction pathway and provide guidance for the development of improved catalytic systems for additive‐free FADH.