Phosphaalkyne

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In chemistry, phosphaalkyne is a molecule which has a phosphorus-carbon triple bond. There are two types of phosphaalkynes. One type of phosphaalkyne is a heavier analogue of nitriles (R-C≡N), depicted as A. Another type of phosphaalkyne has a five-valent three coordinate phosphorus, depicted as B1. This molecule can also be described as ylid (B2) or phosphinocarbene (B3).

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).