Convenient synthetic access to fluorescent rhodacyclopentadienes via ligand exchange reactions

We report the synthesis of fluorescent 2,5-bis(arylethynyl)rhodacyclopentadienes by reaction of [Rh(κ2-O,O-acac)(P(p-tolyl3)2)] with α,ω-bis(arylbutadiynyl)alkanes, and subsequent phosphine ligand exchange. The rhodacyclopentadienes bearing P(p-tolyl3) show weak fluorescence, while no phosphorescence occurs despite the presence of the heavy atom. One P(p-tolyl3) ligand can also be exchanged for an NHC, giving unsymmetrically coordinated rhodacyclopentadienes.190