Phosphaalkyne

From Wikipedia, the free encyclopedia

In chemistry, phosphaalkyne is a molecule which has a phosphorus-carbon triple bond ^[1]. 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.

[edit] References