Iron Olefin Metathesis: Unlocking Reactivity and Mechanistic Insights.

Olefin metathesis catalyzed by iron complexes has garnered substantial interest due to iron's abundance and nontoxicity relative to ruthenium, yet its full potential remains untapped, largely because of the propensity of iron carbenes to undergo cyclopropanation instead of cycloreversion from a metallacycle intermediate. In this report, we elucidate the reactions of [{PC(sp)P}Fe(L)(N)], ([PC(sp)P] = bis[2-(diisopropylphosphino)phenyl]methylene) with strained olefins, unveiling their capability to yield metathesis-related products. Our investigations led to the isolation of a structurally characterized metallacyclobutane during the reaction with norbornadiene derivatives, ultimately leading to a ring-opened iron alkylidene.

[2+2] Cycloadditions with an Iron Carbene: A Critical Step in Enyne Metathesis.

Ruthenium carbenes, famously used in olefin metathesis, have impacted numerous research areas, ranging from synthesis to materials and biology. Although in the same group as ruthenium, iron carbenes showing similar reaction patterns have not been reported. Such targets are of high interest because the use of a sustainable metal would lead to a decreased cost, toxicity, and environmental impact of the corresponding compounds.

Oxidation reactions of a nucleophilic palladium carbene: mono and bi-radical carbenes.

Palladium(ii) cationic carbene radical and neutral bi-radical complexes were synthesized from a previously reported Pd(ii) carbene in the presence of one and two electron oxidants. When [{PC(sp2)P}tBuPd(PMe3)] (1, [PC(sp2)P]tBu = (bis[2-(di-iso-propylphosphino)-4-tertbutylphenyl]methylene)) was treated with [Cp2Fe][X] (X = BArF4, ArF = 3,5-(CF3)2C6H3, or PF6), the corresponding radical cationic complexes [{PC˙(sp2)P}tBuPd(PMe3)][X] (2: X = BArF4, 3: PF6) were isolated and characterized. Magnetic moment measurements and EPR spectroscopy indicated the presence of a ligand centered unpaired electron.

NI(ii) phosphine and phosphide complexes supported by a PNP-pyrrole pincer ligand.

The reaction between [(PNP)NiCl] (1, PNP = 2,5-bis((di-iso-propylphosphino)-methyl)-1H-pyrrolide) and TlPF in the presence of a monodentate phosphine ligand led to cationic nickel phosphine and phosphite complexes, [(PNP)Ni(PHPh)][PF] (2), [(PNP)Ni(PMe)][PF] (3), and [(PNP)Ni{P(OMe)}][PF] (4). Compound 2 can be deprotonated resulting in the generation of a terminal phosphido complex, [(PNP)Ni(PPh)] (5). When 3 is subjected to a base, a methyl proton of PMe is abstracted to afford [(PNP)Ni(CHPMe)] (6), containing a methylene bridge between Ni and the external phosphine.

Formation of Palladium η -Bound Chalcogenoketones across a Pd -C Bond.

A series of chalcogen analogues encompassing a ketone and chalcogenoketones [{PC(=E)P}Pd(PMe )] (E=O, S, Se, Te) was generated from a nucleophilic palladium carbene compound, [{PC(sp )P}Pd(PMe )] ([PC(sp )HP]=bis[2-(diisopropylphosphino)-phenyl]methyl, iPr P-C H -CH-C H -PiPr ). The thio-, seleno-, and telluroketone were all synthesized by means of an atom transfer from the respective chalcogens. The ketone analogue, however, required the use of nitrobenzene or nitrosobenzene as the oxygen-atom transfer agent.