Golden Age of Fluorenylidene Phosphaalkenes–Synthesis, Structures, and Optical Properties of Heteroaromatic Derivatives and Their Gold Complexes

Abstract

The substitution of 2,7-dibromo-9-fluorenyl phosphaalkenes with heteroaromatic substituents (bithiophene, benzothiophene, pyridine) offers access to interesting push–pull dye molecules. Steric shielding due to the bulky P-substituent gives marked different reactivities at the 2- and 7-positions, allowing the synthesis of mixed/asymmetric derivatives. Further functionalization via gold(I) coordination was demonstrated and increased the acceptor character, concomitant with a red-shifted absorption.

The Phospha-Bora-Wittig Reaction

“…After the formation of the 1,2,3-phosphaboraoxetanes 2a – e (80 °C, 2 h), AlBr 3 addition affords known and novel phosphaalkenes 3a – e in good purity and yield (Figure a, 53–95%). Fluorenylidene phosphaalkenes (e.g., 3c ) are promising components for organic materials based on their optoelectronic and redox properties. − …”

Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

“…The 31 P NMR spectrum of a CDCl 3 solution of the solid showed a sharp singlet resonance at 196.5 ppm assigned to [Au­( E - 1a )­Cl]. The upfield chemical shift relative to that of E - 1a (Δδ = −67.8) is in the range expected for known phosphaalkene-Au I complexes (Δδ −31.5 to −87.1) …”

The Phospha-Bora-Wittig Reaction

“…3c) are promising components for organic materials based on their optoelectronic and redox properties. [32][33][34][35][36] When diphosphadiboretane 1 was reacted with esters in place of ketones/aldehydes, direct conversion to the 2-alkoxyphosphaalkene products occurred (Figure 3). For example, the reaction of 1 and ethyl acetate led to the new phosphaalkene 4a as a mixture (22:78) of E and Z isomers, identified by signals in the 31 with those for 2a-e (Figure S1).…”