Actinide 2-metallabiphenylenes that satisfy Hückel's rule.

Aromaticity and antiaromaticity, as defined by Hückel's rule, are key ideas in organic chemistry, and are both exemplified in biphenylene1-3-a molecule that consists of two benzene rings joined by a four-membered ring at its core. Biphenylene analogues in which one of the benzene rings has been replaced by a different (4n + 2) π-electron system have so far been associated only with organic compounds4,5. In addition, efforts to prepare a zirconabiphenylene compound resulted in the isolation of a bis(alkyne) zirconocene complex instead6. Here we report the synthesis and characterization of, to our knowledge, the first 2-metallabiphenylene compounds. Single-crystal X-ray diffraction studies reveal that these complexes have nearly planar, 11-membered metallatricycles with metrical parameters that compare well with those reported for biphenylene. Nuclear magnetic resonance spectroscopy, in addition to nucleus-independent chemical shift calculations, provides evidence that these complexes contain an antiaromatic cyclobutadiene ring and an aromatic benzene ring. Furthermore, spectroscopic evidence, Kohn-Sham molecular orbital compositions and natural bond orbital calculations suggest covalency and delocalization of the uranium f2 electrons with the carbon-containing ligand.

Evidence for Iron-Catalyzed α-Phosphinidene Elimination with Phenylphosphine.

The ubiquitous half-sandwich iron complex [CpFe(CO)2 Me] (Cp=η5 -C5 H5 ) appears to be a catalyst for α-phosphinidene elimination from primary phosphines. Dehydrocoupling reactions provided initial insight into this unusual reaction mechanism, and trapping reactions with organic substrates gave products consistent with an α elimination mechanism, including a rare example of a three-component reaction. The substrate scope of this reaction is consistent with generation of a triplet phosphinidene. In all, this study presents catalytic phosphinidene transfer to unsaturated organic substrates.

Atmospheric Concentrations and Potential Sources of Dioxin-Like Contaminants to Acadia National Park.

Acadia National Park (ANP) is located on Mt. Desert Island, ME on the U.S. Atlantic coast. ANP is routinely a top-ten most popular National Park with over four million visits in 2022. The overall contribution and negative effects of long-range atmospheric transport and local sources of dioxin-like contaminants endangering natural and wildlife resources is unknown. Dioxin-like (DL) contaminants polychlorinated dibenzo-p-dioxins (∑PCDD) and polychlorinated dibenzofurans (∑PCDF), non-ortho coplanar PCBs (∑CP4), and polychlorinated naphthalenes (∑PCNs) were measured at the McFarland Hill air monitoring station (44.37°N, 68.26°W). On a mass/volume basis, total PCNs averaged 90.9 % (788 fg/m3) of DL contaminants measured annually, with 92.9 % of the collected total in the vapor-phase. Alternatively, total dioxin/furans (∑PCDD/Fs) represented 71.6 % of the total toxic equivalence (∑TEQ) (1.018 fg-TEQ/m3), with 69.7 % in the particulate-phase. Maximum concentrations measured for individual sampling events for ∑PCDD/F, ∑CP4, and ∑PCN were 159 (winter), 139 (summer), and 2100 (autumn), fg/m3 respectively. Whereas the maximum ∑TEQ concentrations for individual sampling events for ∑PCDD/F, ∑CP4, and ∑PCN were 2.8 (autumn), 0.38 (summer), and 0.71 (autumn), fg-TEQ/m3 respectively. Pearson correlations were calculated for ∑PCDD/Fs and ∑PCN particulate/vapor-phase air concentrations and PM2.5 wood smoke "indicator" species. The most significant correlations were observed in autumn for particulate-phase ∑PCDD/Fs suggesting a relationship between visitation-generated combustion sources (campfires and/or waste burning) or climate-change mediated forest fires. Significant Clausius-Clapeyron (C-C) correlations observed for particulate-phase ∑PCDDs (r2=0.567) as ambient temperatures decreased suggests a connection between localized domestic heating sources or visitor-based burning of wood/trash resources. Alternatively, highly significant C-C vapor-phase ∑CP4-PCBs correlations (r2=0.815) implies that the majority of ∑CP4-PCB loading to ANP is from long-range atmospheric transport processes. Based on these findings, Acadia National Park should be classified as a remote site with minor depositional impacts from ∑PCDD/Fs, ∑CP4-PCBs, and ∑PCN atmospheric transport or local diffuse sources.

Visible-light and thermal driven double hydrophosphination of terminal alkynes using a commercially available iron compound.

A commercially available iron compound, [CpFe(CO)2]2 (1) (Cp = η5-C5H5), is an efficient catalyst for the double hydrophosphination of terminal aryl alkynes with diphenylphosphine under visible light irradiation or thermal conditions with a reduction of reaction times of up to two orders of magnitude for some substrates over literature reports. The 1,2-bis(diphenylphosphino)ethane products generated in these reactions are readily isolated in high yields.

A sulphur and uranium fiesta! Synthesis, structure, and characterization of neutral terminal uranium(vi) monosulphide, uranium(vi) η2-disulphide, and uranium(iv) phosphine sulphide complexes.

Three new uranium species (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)([double bond, length as m-dash]S), (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(η2-S2), and (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(S[double bond, length as m-dash]PMe3) were synthesized and fully characterized by a combination of NMR, IR, and UV/vis-NIR spectroscopies, elemental analysis, and cyclic voltammetry. The solid state structures of (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)([double bond, length as m-dash]S) and (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(η2-S2) were also determined. The compound (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)([double bond, length as m-dash]S) is the first neutral uranium complex with a terminal sulphido ligand, and (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(S[double bond, length as m-dash]PMe3) is the first uranium compound with a coordinated phosphine sulphide ligand. The phosphine sulphide adduct, (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(S[double bond, length as m-dash]PMe3), can be synthesized either by reaction of the uranium(iv) complex (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)(thf) with S[double bond, length as m-dash]PMe3 or by the reaction of the uranium(vi) terminal sulphido complex (C5Me5)2U([double bond, length as m-dash]N-2,6-iPr2-C6H3)([double bond, length as m-dash]S) with PMe3.

Cobalt-catalyzed ammonia borane dehydrocoupling and transfer hydrogenation under aerobic conditions.

Two cobalt compounds, Cp*Co(CO)I2 (1) and CpCo(CO)I2 (2) (Cp* = η(5)-C5Me5, Cp = η(5)-C5H5), catalyze the dehydrogenation of ammonia borane under either anaerobic or aerobic conditions and are also effective hydrogenation catalysts for alkenes and alkynes using ammonia borane as a hydrogen source, also in the presence of air.

Phenylsilane as a safe, versatile alternative to hydrogen for the synthesis of actinide hydrides.

The thorium and uranium dihydride dimer complexes [(C5Me5)2An(H)(µ-H)]2 (An = Th, U) have been easily prepared using phenylsilane, which is an efficient and safer alternative to hydrogen gas. The synthetic utility of this new hydriding method has been demonstrated by the preparation of a variety of organometallic complexes, including, for the first time, (C5Me5)2U(SMe)2, (C5Me5)2Th(C4Ph4), (C5Me5)2U(C4Ph4), (C5Me5)2ThS5, and (C5Me5)2U(bipy) using [(C5Me5)2An(H)(µ-H)]2 (An = Th, U) as multi-electron reductants.

A general synthesis of phosphaalkenes at zirconium with liberation of phosphaformamides.

A general, atom-economical method for the synthesis of phosphaalkenes is reported via the net coupling of primary alkyl or aryl phosphines with aryl or alkyl isocyanides at zirconium. The phosphorus-containing ligand can be liberated as the phosphaformamide from zirconium by reaction with an organic electrophile.