Intramolecular Arene Bonds of Complexes Featuring Terphenyl Bis(carbene) Macrocyclic Ligands

A series of macrocyclic bis­(carbene) ligands were synthesized by linking 2,2″-bis­(imidazole)­terphenyl with a methylene, ethylene, propylene, or borate unit. Coordination complexes of iron were synthesized with the macrocyclic (bis)­carbene ligands linked by alkyls from the reactions with Fe­{N­(SiMe3)2}2 and 5% w/w Na/NaCl. The resulting Fe(0) compounds have unusually short Fe–C bonds with the central arene of the terphenyl. The borate linked ligand was used to synthesize the isoelectronic Co­(I) compound which shows similar structural characteristics to the iron compounds. We have characterized these compounds by spectroscopic methods, X-ray single-crystal diffraction analysis, and cyclic voltammetry

Activation of CO₂ by a Heterobimetallic Zr/Co Complex

At room temperature, the early/late heterobimetallic complex Co(iPr2PNMes)3Zr(THF) has been shown to oxidatively add CO2, generating (OC)Co(iPr2PNMes)2(μ-O)Zr(iPr2PNMes). This compound can be further reduced under varying conditions to generate either the Zr oxoanion (THF)3Na–O–Zr(MesNPiPr2)3Co(CO) or the Zr carbonate complex (THF)4Na2(CO3)-Zr(MesNPiPr2)3Co(CO). Additionally, reactivity of the CO2-derived product has been observed with PhSiH3 to generate the Co-hydride/Zr-siloxide product (OC)(H)Co(iPr2PNMes)3ZrOSiH2Ph

Activation of CO₂ by a Heterobimetallic Zr/Co Complex

At room temperature, the early/late heterobimetallic complex Co(iPr2PNMes)3Zr(THF) has been shown to oxidatively add CO2, generating (OC)Co(iPr2PNMes)2(μ-O)Zr(iPr2PNMes). This compound can be further reduced under varying conditions to generate either the Zr oxoanion (THF)3Na–O–Zr(MesNPiPr2)3Co(CO) or the Zr carbonate complex (THF)4Na2(CO3)-Zr(MesNPiPr2)3Co(CO). Additionally, reactivity of the CO2-derived product has been observed with PhSiH3 to generate the Co-hydride/Zr-siloxide product (OC)(H)Co(iPr2PNMes)3ZrOSiH2Ph

Synthesis, Structure, and Reactivity of an Anionic Zr–Oxo Relevant to CO₂ Reduction by a Zr/Co Heterobimetallic Complex

Oxidative addition of CO₂ to the reduced Zr/Co complex (THF)­Zr­(MesNP^<i>i</i>Pr₂)₃Co (<b>1</b>) followed by one-electron reduction leads to formation of an unusual terminal Zr–oxo anion [<b>2]­[Na­(THF)</b>_<b>3</b><b>]</b> in low yield. To facilitate further study of this compound, an alternative high-yielding synthetic route has been devised. First, <b>1</b> is treated with CO to form (THF)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO) (<b>3</b>); then, addition of H₂O to <b>3</b> leads to the Zr–hydroxide complex (HO)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO) (<b>4</b>). Deprotonation of <b>4</b> with Li­(N­(SiMe₃)₂) leads to the anionic Zr–oxo species <b>[2]­[Li­(THF)</b>_<b>3</b><b>]</b> or <b>[2]­[Li­(12-c-4)]</b> in the absence or presence of 12-crown-4, respectively. The coordination sphere of the Li⁺ countercation is shown to lead to interesting structural differences between these two species. The anionic oxo fragment in complex <b>[2]­[Li­(12-c-4)]</b> reacts with electrophiles such as MeOTf and Me₃SiOTf to generate (MeO)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO) (<b>5</b>) and (Me₃SiO)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO) (<b>6</b>), respectively, and addition of acetic anhydride generates (AcO)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO) (<b>7</b>). Complex <b>[2]­[Li­(12-c-4)]</b> is also shown to bind CO₂ to form a monoanionic Zr–carbonate, [(12-crown-4)­Li]­[(κ²-CO₃)­Zr­(MesNP^<i>i</i>Pr₂)₃Co­(CO)] (<b>[8]­[Li­(12-c-4)]</b>). A more stable version of this compound <b>[8]­[K­(18-c-6)]</b> is formed when a K⁺ counteranion and 18-crown-6 are used. Binding of CO₂ to <b>[2]­[Li­(12-c-4)]</b> is shown to be reversible using isotopic labeling studies. In an effort to address methods by which these CO₂-derived products could be turned over in a catalytic cycle, it is shown that the Zr–OMe bond in <b>5</b> can be cleaved using H⁺ and the CO ligand can be released from Co under photolytic conditions in the presence of I₂

Sustainable Fertilizers: Publication Landscape on Wastes as Nutrient Sources, Wastewater Treatment Processes for Nutrient Recovery, Biorefineries, and Green Ammonia Synthesis

The ability of modern agriculture to meet future food demand imposed by accelerating growth of the world’s population is a major challenge, and fertilizers play a key role by replacing nutrients in agricultural soil. Given the need for fertilizers, their cost in nonrenewable resources and energy, and the consequences of the greenhouse gas emissions required to make them, people have begun to explore ways to make fertilizer manufacturing and use more sustainable. Using data from the CAS Content Collection, this review examines and analyzes the academic and patent literature on sustainable fertilizers from 2001 to 2021. The breakdown of journal and patent literature publication over time on this topic, country or region of publications, the substances included in published research, among other things allow us to understand the general progress in the field as well as the classes of materials and concepts driving innovation. We hope that this bibliometric analysis and literary review will assist researchers in relevant industries to discover and implement ways to supplement conventional fertilizers and nutrient sources while improving the efficiency and sustainability of waste management and ammonia production

One-Electron Oxidation Chemistry and Subsequent Reactivity of Diiron Imido Complexes

The chemical oxidation and subsequent group transfer activity of the unusual diiron imido complexes Fe­(iPrNP­Ph2)3FeNR (R = tert-butyl (tBu), 1; adamantyl, 2) was examined. Bulk chemical oxidation of 1 and 2 with Fc­[PF6] (Fc = ferrocene) is accompanied by fluoride ion abstraction from PF6– by the iron center trans to the FeNR functionality, forming F–Fe­(iPrNP­Ph2)3FeNR (iPr = isopropyl) (R = tBu, 3; adamantyl, 4). Axial halide ligation in 3 and 4 significantly disrupts the Fe–Fe interaction in these complexes, as is evident by the >0.3 Å increase in the intermetallic distance in 3 and 4 compared to 1 and 2. Mössbauer spectroscopy suggests that each of the two pseudotetrahedral iron centers in 3 and 4 is best described as FeIII and that one-electron oxidation has occurred at the tris­(amido)-ligated iron center. The absence of electron delocalization across the Fe–FeNR chain in 3 and 4 allows these complexes to readily react with CO and tBuNC to generate the FeIIIFeI complexes F–Fe­(iPrNP­Ph2)3Fe­(CO)2 (5) and F–Fe­(iPrNPPh2)3­Fe­(tBuNC)2 (6), respectively. Computational methods are utilized to better understand the electronic structure and reactivity of oxidized complexes 3 and 4

One-Electron Oxidation Chemistry and Subsequent Reactivity of Diiron Imido Complexes

The chemical oxidation and subsequent group transfer activity of the unusual diiron imido complexes Fe­(^<i>i</i>PrNP­Ph₂)₃FeNR (R = <i>tert</i>-butyl (^<i>t</i>Bu), <b>1</b>; adamantyl, <b>2</b>) was examined. Bulk chemical oxidation of <b>1</b> and <b>2</b> with Fc­[PF₆] (Fc = ferrocene) is accompanied by fluoride ion abstraction from PF₆^– by the iron center <i>trans</i> to the FeNR functionality, forming F–Fe­(^<i>i</i>PrNP­Ph₂)₃FeNR (^<i>i</i>Pr = isopropyl) (R = ^<i>t</i>Bu, <b>3</b>; adamantyl, <b>4</b>). Axial halide ligation in <b>3</b> and <b>4</b> significantly disrupts the Fe–Fe interaction in these complexes, as is evident by the >0.3 Å increase in the intermetallic distance in <b>3</b> and <b>4</b> compared to <b>1</b> and <b>2</b>. Mössbauer spectroscopy suggests that each of the two pseudotetrahedral iron centers in <b>3</b> and <b>4</b> is best described as Fe^III and that one-electron oxidation has occurred at the tris­(amido)-ligated iron center. The absence of electron delocalization across the Fe–FeNR chain in <b>3</b> and <b>4</b> allows these complexes to readily react with CO and ^<i>t</i>BuNC to generate the Fe^IIIFe^I complexes F–Fe­(^<i>i</i>PrNP­Ph₂)₃Fe­(CO)₂ (<b>5</b>) and F–Fe­(^<i>i</i>PrNPPh₂)₃­Fe­(^<i>t</i>BuNC)₂ (<b>6</b>), respectively. Computational methods are utilized to better understand the electronic structure and reactivity of oxidized complexes <b>3</b> and <b>4</b>