title: Convenient Preparation and Detailed Analysis of a Series of NHC-Stabilized Phosphorus(I) Dyes and Their Derivatives.
abstract: A safe, convenient, and P-atom-efficient synthesis of N-heterocyclic-carbene- (NHC-) stabilized phosphorus(I) bromide salts is reported that involves P(+) transfer from an easily prepared triphosphenium precursor. The resulting family of phosphamethine cyanine dyes featuring N,N'-dialkyl-substituted 4,5-dimethylimidazole-2-ylidenes ((R)NHC(Me)) and benzimidazole-2-ylidenes ((R)NHC(B)) (R = Me, Et, iPr) have been fully characterized. We found that increasing N-alkyl group size causes increased twisting of the carbene fragments from the C-P-C plane, which decreases the magnitude of hyperconjugation between the π-type lone pair on phosphorus and the carbene fragments. This decrease is manifested as changes in the (31)P NMR chemical shifts, magnitudes of the P-C coupling constants, and electronic spectra of the cations. The reactivities of these ions toward various oxidants are reported: Oxidation by sulfur generates dithiophosphinium salts, protonation or methylation gives dicationic phosphines, and coordination to 1 or 2 equiv of gold(I) chloride results in mono or bimetallic complexes, respectively.
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Charles L B
authors.initials: CL
authors.lastname: Macdonald
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Justin F
authors.initials: JF
authors.lastname: Binder
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Ala'aeddeen
authors.initials: A
authors.lastname: Swidan
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Nguyen
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Stephanie C
authors.initials: SC
authors.lastname: Kosnik
authors.affiliation: Department of Chemistry and Biochemistry, University of Windsor , Windsor, Ontario N9B 3P4, Canada.
authors.forename: Bobby D
authors.initials: BD
authors.lastname: Ellis