Diphosphene

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In chemistry, diphosphene is a molecule that has a phosphorus-phosphorus double bond, indicated by R-P=P-R'. Diphosphenes are heavier analogues of azo compounds.

In 1887, H. Köhler and A. Michaelis reported the isolation of a compound that was thought to be the phosphorus analogue of azobenzene, "Ph-P=P-Ph", but it later turned out to be wrong.

In 1981, Masaaki Yoshifuji reported the first stable diphosphene,[1] which is kinetically stabilized by very bulky two substituents attached to the phosphorus atoms. Numerous other diphosphenes with a variety of substituents have been synthesized and structurally characterized. In addition, there are several transition metal complexes where the diphosphene behaves as an end-on donor through one or both phosphorus atoms.

Most uncomplexed diphosphenes have trans-bent structures, in which the angles to the phosphorus are strongly influenced by the electronic effects of the substituents. The P-P distances are in the range 195.4 to 204.4 pm (1.954 to 2.044 Å) (compared to the single P-P bond length of 222 pm).


[edit] References

  1. ^ M. Yoshifuji, I. Shima, N. Inamoto, K. Hirotsu, and T. Higuchi, "Synthesis and Structure of Bis(2,4,6-Tri-Tert-Butylphenyl)Diphosphene - Isolation of A True Phosphobenzene", J.Am.Chem.Soc. 103 (15):4587-4589, 1981.