Phosphaalkyne

In chemistry, phosphaalkyne is a molecule which has a phosphorus-carbon triple bond. This type of compound is widely studied in organic chemistry but does not exist outside the laboratory.

There are two types of phosphaalkynes. One type of phosphaalkyne is a heavier analogue of nitriles (R-C≡N). Another type of phosphaalkyne has a five-valent three coordinate phosphorus. This molecule can also be described as ylide or a phosphinocarbene. The phosphorus pendant of the isonitriles R-P+≡C- called isophosphaalkynes has never been observed.

In 1950, H. Albers reported the first indication of the existence of the parent compound of phosphaalkynes (type A), H-C≡P. This compound was identified by infrared absorption spectrometry and its synthesis was improved by Manfred Regitz in 1987. The synthesis of the first kinetically stable phosphaalkyne, which has a tert-butyl group as a substituent R, was reported in 1981. These phosphaalkynes exhibit 1,2-addition reactions and cycloadditions in their reactivity.

In 2000, Guy Bertrand reported the first structure of the type B phosphaalkyne. Its P-C-R bond angle is 152.6 degrees, so this type of phosphaalkyne may be best described by a phosphorus vinyl ylide structure (B2).

The cyaphide ion P≡C- as the phosphorous cyanide cousin is not known as a salt and only observed in the gas phase. In silico measurements reveal that the -1 charge in this ion is location mainly on carbon (0.65). On the other hand the molecule does exist as a terminal ligand in a certain ruthenium transition metal complex trans-[(dppe)2Ru-(H)(C≡P)] stabilized by dppe.