Incorporating Phosphaalkenes into Oligoacetylenes

Mind the gap! Replacing the two terminal carbon atoms of a tetrayne-linked bis-alkene by two phosphorus centers leads to a decrease of the HOMO–LUMO gap by 0.5 eV. The acetylenic phosphaalkenes are accessible from an ambivalent carbene-type C5 intermediate and are shown to be viable building blocks for the construction of elaborate phosphorus- and carbon-rich molecules (see picture; C gray, P purple).