Regioselective Direct C-H Bond Heteroarylation of Thiazoles Enabled by an Iminopyridine-Based α-Diimine Nickel(II) Complex Evaluated by DFT Studies.

Direct C-H bond arylation is a highly effective method for synthesizing arylated heteroaromatics. This method reduces the number of synthetic steps and minimizes the formation of impurities. We report an air- and moisture-stable iminopyridine-based α-diimine nickel(II) complex for direct C5-H bond arylation of thiazole derivatives. Under a low catalyst loading and performing the reactions at lower temperatures (80 °C) under aerobic conditions, we produced mono- and diarylated thiazole units. Competition experiments and density functional theory calculations revealed that the mechanism of C-H activation in 4-methylthiazole involves an electrophilic aromatic substitution.

Combining [MoVIO3] and [M0(CO)3] (M = Mo, Cr) Fragments within the Same Complex: Synthesis and Reactivity of the Single Oxo-Bridged Heterobimetallics Supported by Xanthene-Based Heterodinucleating Ligands.

A functional model of Mo-Cu carbon monoxide dehydrogenase (CODH) enzyme requires the presence of an oxidant (metal-oxo) and a metal-bound carbonyl in close proximity. In this work, we report the synthesis, characterization, and reactivity of a heterobimetallic complex combining Mo(VI) trioxo with Mo(0) tricarbonyl. The formation of the heterobimetallic complex is facilitated by the xanthene-bridged heterodinucleating ligand containing a hard catecholate chelate and a soft iminopyridine chelate. A catechol-coordinated square-pyramidal [MoVIO3] fragment interacts directly with the iminopyridine-bound [Mo0(CO)3] fragment via a single (oxo) bridge, with the overall disposition being related to the proposed first step in the CODH mechanism, where square-pyramidal [MoVIO2S] interacts with the [Cu-CO] via a single sulfido bridge. Our attempt to obtain a sulfido-bridged analogue (using [MoO3S]2- precursor) led to a mixture of products possibly containing different (oxo and sulfido) bridges. Despite a direct interaction between Mo(VI) and Mo(0) segments, no internal redox is observed, with the high lying occupied MOs being mostly d-π orbitals at Mo0(CO)3 and the low lying unoccupied MOs being d-π orbitals at MoVIO3. Due to the overall rigid structure, the heterobimetallic complex was found to be stable up to 100 °C in DMF-d7 (based on 1H NMR). The decomposition of the complex above this temperature does not produce CO2 (based on gas chromatography), dissociating stable Mo(CO)3(DMF)3 instead (based on IR). We also synthesized and studied the reactivity of the Mo(VI)/Cr(0) analogue. While this complex demonstrated more facile decomposition, no CO2 production was observed. Density functional theory calculations suggest that the formation of [CO2]2- and its subsequent reductive elimination is endergonic in the present system, likely due to the stability of fac-Mo0(CO)3 and the relative nucleophilic character of the carbonyl carbon engendered by back donation from Mo(0). The calculations also indicate that the replacement of one oxo by sulfido (both terminal and bridging), replacement of catechol with dithiolene, and replacement of Mo(0) with Cr(0) does not affect significantly the energetics of the process, likely requiring the use a less stable and less π-basic CO anchor.

A circular economy approach to drinking water treatment residue management in a catchment impacted by historic metal mines.

Drinking water treatment residues (DWTR) from mining areas which remove and contain potentially toxic elements (PTE) could still potentially be used as a soil amendment to restore contaminated sites in the same catchment, thus eliminating waste and reducing the chemical and physical mobility of the pollutants. To assess this restorative and regenerative approach to DWTR management, field and pot trials were established with soils from a historic Pb-Zn mine site in the North East of England, amended with either local DWTR or the nearest available municipal green waste compost (GWC). Soils from the mine site were found to have very low levels of nutrients and very high levels of PTE (Pb and Zn > 13, 000 mg/kg). The perennial grass species Phalaris arundinacea, known for many ecosystem service benefits including soil stabilization, was used throughout this study. The application of the BCR sequential extraction to soils amended with the DWTR in the pot trials found a significant decrease in the bioavailability of Pb and Cu (p < 0.05) after plant growth when compared with an unamended control. The field trial involved 648 pre-grown grass plants planted-out into mine soils amended with either DWTR, GWC or a mixture (MIX) of the two, all at rates of 25-30% w/w. Both amendments and the MIX had significant positive effects on biomass production compared to the unamended control in the following order GWC > MIX > DWTR (p < 0.05). Results of the elemental analysis of biomass from the field trial were generally ambiguous and did not reflect the decreased bioavailability noted in the pot trials using the BCR procedure. Pot trials, however, showed increases in plant growth and decreases in concentrations of Cr, Cu, Pb and Zn in above ground biomass following the application of both amendments. Further work should involve the testing of a mixture of DWTR and other soil amendments to enhance plant growth. The success of these trials should provide confidence for those working in drinking water treatment and catchment management to reuse the waste residues in a circular economy and a sustainable way that could improve water quality over time.

Aziridination Reactivity of a Manganese(II) Complex with a Bulky Chelating Bis(Alkoxide) Ligand.

Treatment of Mn(N(SiMe3)2)2(THF)2 with bulky chelating bis(alkoxide) ligand [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol) (H2[O-terphenyl-O]Ph) formed a seesaw manganese(II) complex Mn[O-terphenyl-O]Ph(THF)2, characterized by structural, spectroscopic, magnetic, and analytical methods. The reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various nitrene precursors was investigated. No reaction was observed between Mn[O-terphenyl-O]Ph(THF)2 and aryl azides. In contrast, the treatment of Mn[O-terphenyl-O]Ph(THF)2 with iminoiodinane PhINTs (Ts = p-toluenesulfonyl) was consistent with the formation of a metal-nitrene complex. In the presence of styrene, the reaction led to the formation of aziridine. Combining varying ratios of styrene and PhINTs in different solvents with 10 mol% of Mn[O-terphenyl-O]Ph(THF)2 at room temperature produced 2-phenylaziridine in up to a 79% yield. Exploration of the reactivity of Mn[O-terphenyl-O]Ph(THF)2 with various olefins revealed (1) moderate aziridination yields for p-substituted styrenes, irrespective of the electronic nature of the substituent; (2) moderate yield for 1,1'-disubstituted α-methylstyrene; (3) no aziridination for aliphatic α-olefins; (4) complex product mixtures for the ß-substituted styrenes. DFT calculations suggest that iminoiodinane is oxidatively added upon binding to Mn, and the resulting formal imido intermediate has a high-spin Mn(III) center antiferromagnetically coupled to an imidyl radical. This imidyl radical reacts with styrene to form a sextet intermediate that readily reductively eliminates the formation of a sextet Mn(II) aziridine complex.

Cost Analysis of Integrated Behavioral Health in a Large Primary Care Practice.

A residency-based Family Medicine outpatient clinic chose to implement an integrated behavioral health care program in a large primary care clinic in the Southeast to improve patient access to behavioral health care. We hypothesized that embedding a BHP in a primary care setting would be a cost neutral intervention. We implemented a prospective cohort design and included expenses from both inpatient and outpatient visits. We implemented a mixed effects linear regression model to evaluate pre- and post-BHP exposure costs. A total of 1256 patients were identified in the post-BHP exposure period that had more than one-year post-exposure. After applying exclusion criteria, there were 926 patients included in analysis. These patient had an average total cost during the one-year pre-BHP exposure period of $5113 (SD = 7712) and one-year post-BHP exposure period of $5462 (SD = 7813). Our analysis shows a relatively cost neutral impact following the introduction of BHPs in a primary care setting. The results of this study provide a gauge for future planning of services.

Synthesis and Cu(I)/Mo(VI) Reactivity of a Bifunctional Heterodinucleating Ligand on a Xanthene Platform.

In an effort to probe the feasibility of a model of Mo-Cu CODH (CODH = carbon monoxide dehydrogenase) lacking a bridging sulfido group, the new heterodinucleating ligand LH2 was designed and its Cu(I)/Mo(VI) reactivity was investigated. LH2 ((E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol) features two different chelating positions bridged by a xanthene linker: bis(pyridyl)amine for Cu(I) and catecholate for Mo(VI). LH2 was synthesized via the initial protection of one of the amine positions, followed by two consecutive alkylations of the second position, deprotection, and condensation to attach the catechol functionality. LH2 was found to exhibit dynamic cooperativity between two reactive sites mediated by H-bonding of the catechol protons. In the free ligand, catechol protons exhibit H-bonding with imine (intramolecular) and with pyridine (intermolecular in the solid state). The reaction of LH2 with [Cu(NCMe)4]+ led to the tetradentate coordination of Cu(I) via all nitrogen donors of the ligand, including the imine. Cu(I) complexes were characterized by multinuclear NMR spectroscopy, high-resolution mass spectrometry (HRMS), X-ray crystallography, and DFT calculations. Cu(I) coordination to the imine disrupted H-bonding and caused rotation away from the catechol arm. The reaction of the Cu(I) complex [Cu(LH2)]+ with a variety of monodentate ligands X (PPh3, Cl-, SCN-, CN-) released the metal from coordination to the imine, thereby restoring imine H-bonding with the catechol proton. The second catechol proton engages in H-bonding with Cu-X (X = Cl, CN, SCN), which can be intermolecular (XRD) or intramolecular (DFT). The reaction of LH2 with molybdate [MoO4]2- led to incorporation of [MoVIO3] at the catecholate position, producing [MoO3(L)]2-. Similarly, the reaction of [Cu(LH2)]+ with [MoO4]2- formed the heterodinuclear complex [CuMoO3(L)]-. Both complexes were characterized by multinuclear NMR, UV-vis, and HRMS. HRMS in both cases confirmed the constitution of the complexes, containing molecular ions with the expected isotopic distribution.

Synthesis of Chromium(II) Complexes with Chelating Bis(alkoxide) Ligand and Their Reactions with Organoazides and Diazoalkanes.

Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]Ph (H2[OO]Ph = [1,1':4',1''-terphenyl]-2,2''-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]Ph(THF)2 (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr2([OO]Ph)2 (in CH2Cl2/THF). The electronic structure and bonding in Cr[OO]Ph(THF)2 were probed by density functional theory calculations. Isolated Cr2([OO]Ph)2 undergoes facile reaction with 4-MeC6H4N3, 4-MeOC6H4N3, or 3,5-Me2C6H3N3 to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]Ph(N(4-MeC6H4))2 was confirmed by X-ray crystallography. The reaction of Cr2([OO]Ph)2 with bulkier azides N3R (MesN3, AdN3) forms paramagnetic products, formulated as Cr[OO]Ph(NR). The attempted formation of a Cr-alkylidene complex (using N2CPh2) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]Ph(NNCPh2)2. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr2([OO]Ph)2 or H2[OO]Ph with NO+ leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.

Mechanistic and Kinetic Studies of the Ring Opening Metathesis Polymerization of Norbornenyl Monomers by a Grubbs Third Generation Catalyst.

The mechanism of ring-opening metathesis polymerization (ROMP) for a set of functionalized norbornenyl monomers initiated by a Grubbs third generation precatalyst [(H2IMes)(pyr)2(Cl)2Ru═CHPh] was investigated. Through a series of 12C/13C and 1H/2H kinetic isotope effect studies, the rate-determining step for the polymerization was determined to be the formation of the metallacyclobutane ring. This experimental result was further validated through DFT calculations showing that the highest energy transition state is metallacyclobutane formation. The effect of monomer stereochemistry (exo vs endo) of two types of ester substituted monomers was also investigated. Kinetic and spectroscopic evidence supporting the formation of a six-membered chelate through coordination of the proximal polymer ester to the Ru center is presented. This chelation and its impact on the rate of polymerization are shown to vary based on the monomer employed and its stereochemistry. The combination of this knowledge led to the derivation of a generic rate law describing the rate of polymerization of norbornene monomers initiated by a Grubbs third generation catalyst.

Decreasing Risk of First and Subsequent Surgeries in Patients With Crohn's Disease in England From 1994 through 2013.

BACKGROUND & AIMS: Gastrointestinal (GI) surgery is an important part of the treatment algorithm for patients with Crohn's disease (CD) that is complicated or does not respond to medical therapy. Cohort studies from Denmark and Canada have shown that the risk of primary surgery is decreasing but there is a lack of contemporary data on subsequent resections. We examined trends in first and second GI resections in patients with CD. METHODS: We performed a retrospective cohort study using the United Kingdom primary care database ResearchOne, collecting data from patients with Crohn's disease from 1994 through 2013. We compared rates of first and second GI resections with etiological factors. RESULTS: Among 3059 incident cases of CD, 13%, 21%, and 26% of the patients underwent surgical resections after 1, 5, and 10 years, respectively. Of patients with an initial resection, 20% required an additional operation when followed for 10 years after the initial resection. We found a significant reduction in first surgery, from 44% to 21% after 10 years of disease, from 1994 to 2003 (χ2 for trend, P < .05). There was a significant reduction in second resections, in a 10-year follow-up period, from 40% in 1994 to 17% in 2003 (χ2 for trend, P < .05). Duration of disease, younger age at diagnosis, smoking, and immunomodulator use were positively associated with first surgeries. Duration of disease was significantly associated with the risk of undergoing a second resection. CONCLUSION: In a retrospective analysis of a United Kingdom primary care database, we observed a significant reduction in first and subsequent GI surgeries among patients with CD over the past 20 years in England.

Characterization of Terminal Iron(III)-Oxo and Iron(III)-Hydroxo Complexes Derived from O2 Activation.

O2 activation at nonheme iron centers is a common motif in biological systems. While synthetic models have provided numerous insights into the reactivity of high-valent iron-oxo complexes related to biological processes, the majority of these complexes are synthesized using alternative oxidants. This report describes O2 activation by an iron(II)-triflate complex of the imino-functionalized tris(pyrrol-2-ylmethyl)amine ligand framework, H3[N(piCy)3]. Initial reaction conditions result in the formation of a mixture of oxidation products including terminal iron(III)-oxo and iron(III)-hydroxo complexes. The relevance of these species to the O2 activation process is demonstrated through reactivity studies and electrochemical analysis of the iron(III)-oxo complex.

A Series of 4- and 5-Coordinate Ni(II) Complexes: Synthesis, Characterization, Spectroscopic, and DFT Studies.

A series of four- and five-coordinate Ni(II) complexes Cz tBu(Pyr iPr)2NiX (1-3 and 1·THF-3·THF), where X = Cl, Br, and I, were synthesized and fully characterized by NMR and UV-vis spectroscopy, X-ray crystallography, cyclic voltammetry, and density functional theory calculations. The solid-state structures of 1-3 reveal rare examples of seesaw Ni(II) complexes. In solution, 1-3 bind reversibly to a THF molecule to form five-coordinate adducts. The electronic transitions in the visible region (630-680 nm), attributed to LMCT bands, for 1 → 3 exhibit a bathochromic shift. The thermochromic tendency of the five-coordinate complexes implies the loss of THF coordination at elevated temperatures. Finally, the electronic properties of all Ni(II) complexes were studied by time-dependent density functional theory calculations to characterize the nature of the excited states.

Catalytic Nitrene Homocoupling by an Iron(II) Bis(alkoxide) Complex: Bulking Up the Alkoxide Enables a Wider Range of Substrates and Provides Insight into the Reaction Mechanism.

The reaction of HOR' (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide) with an iron(II) amide precursor forms the iron(II) bis(alkoxide) complex Fe(OR')2(THF)2 (2). 2 (5-10 mol %) serves as a catalyst for the conversion of aryl azides into the corresponding azoarenes. The highest yields are observed for aryl azides featuring two ortho substituents; other substitution patterns in the aryl azide precursor lead to moderate or low yields. The reaction of 2 with stoichiometric amounts (2 equiv) of the corresponding aryl azide shows the formation of azoarenes as the only organic products for the bulkier aryl azides (Ar = mesityl, 2,6-diethylphenyl). In contrast, formation of tetrazene complexes Fe(OR')2(ArNNNNAr) (3-6) is observed for the less bulky aryl azides (Ar = phenyl, 4-methylphenyl, 4-methoxyphenyl, 3,5-dimethylphenyl). The electronic structure of selected tetrazene complexes was probed by spectroscopy (field-dependent 57Fe Mössbauer and high-frequency EPR) and density functional theory calculations. These studies revealed that Fe(OR')2(ArNNNNAr) complexes contain high-spin ( S = 5/2) iron(III) centers exchange-coupled to tetrazene radical anions. Tetrazene complexes Fe(OR')2(ArNNNNAr) produce the corresponding azoarenes (ArNNAr) upon heating. Treatment of a tetrazene complex Fe(OR')2(ArNNNNAr) with a different azide (N3Ar') produces all three possible products ArNNAr, ArNNAr', and Ar'NNAr'. These experiments and quantum mechanics/molecular mechanics calculations exploring the reaction mechanism suggest that the tetrazene functionality serves as a masked form of the reactive iron mono(imido) species.

Comprehensive database of Manufactured Gas Plant tars. Part C. Heterocyclic and hydroxylated polycyclic aromatic hydrocarbons.

RATIONALE: Coal tars are a mixture of organic and inorganic compounds that were by-products from the manufactured gas and coke making industries. The tar compositions varied depending on many factors such as the temperature of production and the type of retort used. For this reason a comprehensive database of the compounds found in different tar types is of value to understand both how their compositions differ and what potential chemical hazards are present. This study focuses on the heterocyclic and hydroxylated compounds present in a database produced from 16 different tars from five different production processes. METHODS: Samples of coal tar were extracted using accelerated solvent extraction (ASE) and derivatized post-extraction using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). The derivatized samples were analysed using two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC/TOFMS). RESULTS: A total of 865 heterocyclic compounds and 359 hydroxylated polycyclic aromatic hydrocarbons (PAHs) were detected in 16 tar samples produced by five different processes. The contents of both heterocyclic and hydroxylated PAHs varied greatly with the production process used, with the heterocyclic compounds giving information about the feedstock used. Of the 359 hydroxylated PAHs detected the majority would not have been be detected without the use of derivatization. CONCLUSIONS: Coal tars produced using different production processes and feedstocks yielded tars with significantly different heterocyclic and hydroxylated contents. The concentrations of the individual heterocyclic compounds varied greatly even within the different production processes and provided information about the feedstock used to produce the tars. The hydroxylated PAH content of the samples provided important analytical information that would otherwise not have been obtained without the use of derivatization and GCxGC/TOFMS.

Comprehensive database of Manufactured Gas Plant tars. Part A. Database.

RATIONALE: Coal tars are a mixture of organic and inorganic compounds that were by-products from the manufactured gas and coke making industries. Different manufacturing processes have resulted in the production of distinctly different tar compositions. This study presents a comprehensive database of compounds produced using two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC/TOFMS), analysing 16 tar samples produced by five distinct production processes. METHODS: Samples of coal tar were extracted using accelerated solvent extraction (ASE) and derivatised post-extraction using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). The derivatised samples were analysed using two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC/TOFMS). RESULTS: A total of 16 tar samples originating from five different production processes: Low Temperature Horizontal Retorts, Horizontal Retorts, Vertical Retorts, Carbureted Water Gas and Coke Ovens, were analysed. A total of 2369 unique compounds were detected with 948 aromatic compounds, 196 aliphatic compounds, 380 sulfur-containing compounds, 209 oxygen-containing compounds, 262 nitrogen-containing compounds and 15 mixed heterocycles. Derivatisation allowed the detection of 359 unique compounds, the majority in the form of hydroxylated polycyclic aromatic hydrocarbons, many of which would not have been detected without derivatisation. Of the 2369 unique compounds detected, 173 were found to be present within all samples. CONCLUSIONS: A unique comprehensive database of compounds detected within 16 tar samples from five different production processes was produced. The 173 compounds identified within every sample may be of particular importance from a regulatory standpoint. This initial study indicates that different production processes produce tars with different chemical signatures and it can be further expanded upon by in-depth analysis of the different compound types. The number of compounds presented within this database clearly demonstrates the analytical power of GCxGC/TOFMS.

Comprehensive database of Manufactured Gas Plant tars. Part B. Aliphatic and aromatic compounds.

RATIONALE: Coal tars are a mixture of organic and inorganic compounds that were produced as a by-product from the manufactured gas and coke making industries. The composition of the tar produced varies depending on many factors; these include the temperature of production and the type of retort used. As different production processes produce different tars, a comprehensive database of the compounds present within coal tars from different production processes is a valuable resource. Such a database would help to understand how their chemical properties differ and what hazards the compounds present within these tars might pose. This study focuses on the aliphatic and aromatic compounds present in a database of 16 different tars from five different production processes. METHODS: Samples of coal tar were extracted using accelerated solvent extraction (ASE) and derivatised post-extraction using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane (TMCS). The derivatised samples were analysed using two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GCxGC/TOFMS). RESULTS: A total of 198 individual aliphatic and 951 individual aromatic compounds were detected within 16 tar samples produced by five different production processes. The polycyclic aromatic hydrocarbon (PAH) content of coal tars varies greatly depending on the production process used to obtain the tars and this is clearly demonstrated within the results. The aliphatic composition of the tars provided an important piece of analytical information that would have otherwise been missed with the detection of petrogenic compounds such as alkyl cyclohexanes. CONCLUSIONS: The aromatic compositions of the tar samples varied greatly between the different production processes investigated and useful analytical information was obtained about the individual production process groups. Alkyl cyclohexanes were detected in all samples from sites known to operate Carbureted Water Gas plants and not detected in those that did not. This suggests that petrogenic material may be expected at many UK gaswork sites.

Ligand Design toward Multifunctional Substrate Reductive Transformations.

The synthesis of bis(N1-phenyl-5-hydroxypyrazol-3-yl)pyridines ("L") is described, and these are silylated to achieve analogues ("Si2L") without the variable of the hydroxyl proton mobility. One hydroxyl example is characterized in its bis-pincer iron(II) complex, which shows every OH proton involved in hydrogen bonding. The steric bulk of the silylated N-phenyl-substituted ligands allows the synthesis and characterization of paramagnetic (Si2L)FeCl2 complexes, and one of these is reduced, under CO, to give the diamagnetic (Si2L)Fe(CO)2 species. Structural comparison and density functional theory calculations of the dichloride and dicarbonyl species show that much, but not all, of the reduction occurs at both the ligand pyridine and pyrazole rings, and thus this ligand type is more resistant to reduction than the simpler bis(iminopyridines). The OSiR3 substituent offers a useful diagnostic of reduction at pyrazole via the degree of π-donation to pyrazole by the oxygen lone pairs, and the stereoelectronic features of the NPh moiety are analyzed. The X-ray photoelectron spectroscopy binding energies of both iron and nitrogen are analyzed to show details of the locus of reduction.

Tuning the Fe(II/III) Redox Potential in Nonheme Fe(II)-Hydroxo Complexes through Primary and Secondary Coordination Sphere Modifications.

The derivatization of the imino-functionalized tris(pyrrolylmethyl)amine ligand framework, N(XpiR)3 (XLR; X = H, Br; R = cyclohexyl (Cy), phenyl (Ph), 2,6- diisopropylphenyl (DIPP)), is reported. Modular ligand synthesis allows for facile modification of both the primary and secondary coordination sphere electronics. The iron(II)-hydroxo complexes, N(XpiR)(XafaR)2Fe(II)OH (XLRFeIIOH), are synthesized to establish the impact of the ligand modifications on the complexes' electronic properties, including their chemical and electrochemical oxidation. Cyclic voltammetry demonstrates that the Fe(II/III) redox couple spans a 400 mV range across the series. The origin of the shifted potential is explained based on spectroscopic, structural, and theoretical analyses of the iron(II) and iron(III) compounds.

Synthesis and Characterization of a Stable High-Valent Cobalt Carbene Complex.

The formally Co(IV) carbene Co(OR)2(═CPh2) is formed upon the reaction of diphenyldiazomethane with the cobalt bis(alkoxide) precursor Co(OR)2(THF)2. Structural, spectroscopic, and theoretical studies demonstrate that Co(OR)2(═CPh2) has significant high-valent Co(IV)═CPh2 character with non-negligible spin density on the carbene moiety.