One-Step Redox Route to N-Heterocyclic Phosphenium Ions

Abstract

One-step reactions of the appropriate N-alkyl-, N-cycloalkyl-, and N-aryl-substituted alpha-diimines with PI3 afforded >80% yields of the triiodide salts of the following N-heterocyclic phosphenium ions, [(R1NC(R2)C(R2)NR1)P]+: 3 (R1 = t-Bu; R2 = H); 4 (R1 = 2,6-i-Pr2C6H3; R2 = H), 5 (R1 = Mes; R2 = H), 6 (R1 = 2,6-i-Pr2C6H3; R2 = H), and 7 (R1 = cyclohexyl; R2 = H). Treatment of 3 and 6 with NaB(C6H5)4 resulted in virtually quantitative yields of the corresponding [B(C6H5)4]- salts 8 and 9, respectively. The X-ray crystal structures of 3 and 5-9 were determined.

A Cation-Captured Palladium(0) Anion: Synthesis, Structure, and Bonding of [PdBr(PPh3)2]− Ligated by an N-Heterocyclic Phosphenium Cation

“…The [uNHP Mes ] + cation has also been isolated by Cowley in both I3 -and BPh4 -salts. 13 Our spectroscopic data agreed with those previously reported. 9 Reaction of bromophosphine 1 with Pd(PPh3)4 in THF at rt gave (uNHP Mes )Pd(PPh3)2Br (4) pyridinylidenes.…”

Synthesis, Reactivity, and Computational Analysis of Halophosphines Supported by Dianionic Guanidinate Ligands

“…28,[73][74][75][76][77] One major difference between these two species is the additional stabilization gained from the delocalization of a 6π-electron system in the case of the fivemembered ring, contrary to the 4π-electrons present in the four-membered ring. While aromaticity is not a necessity for the isolation of NHPs 25,34,35,37,38,67 and has been found to be a weak factor in their stabilization, 75 the lack thereof in our four-membered diaminochlorophosphines may be a contributing factor to the difficulty in halide abstraction.…”

The 1,4-diazabutadiene/1,2-enediamido non-innocent ligand system in the formation of iridaheteroaromatic compounds: Spectroelectrochemistry and electronic structure

“…It is noteworthy that the ''Arduengo carbene" as prototypical N-heterocyclic carbene (NHC) displays a similar CC and CN bond length sequence [52] as compound 2 (which is unusual in that it contains a late transition metal associated with an enediamido(2À) ligand). All other reported enediamido chelates involve either early transition metals [36], specially zirconium [53], hafnium [54], tantalum [55], or chromium [56,57], or main group element atoms [34,38,[58][59][60][61][62].…”