An Unprecedented 5-Phosphasemibullvalene Derivative

Phosphinines belong to an intriguing class of low-coordinate aromatic phosphorus heterocycles with rather different steric, electronic and coordination properties compared to classical P(III) species. During our extensive... [ view full abstract ]

Phosphinines belong to an intriguing class of low-coordinate aromatic phosphorus heterocycles with rather different steric, electronic and coordination properties compared to classical P(III) species. During our extensive research on 2,4,6-triaryl-λ³-phosphinines and the related phosphabarrelenes^[1,2], we recently discovered an unprecedented class of phosphorus cage compounds with interesting properties. We could demonstrate for the first time that phosphabarrelenes, such as 1, can undergo a quantitative photochemical di-π-methane rearrangement towards a racemic mixture of a 5-phosphasemibullvalene derivative (2/2’, Scheme 1).^[3] This hitherto unknown conversion of unsaturated phosphorus compounds leads to stable, chiral products as proven by means of HPLC analysis as well as X-ray crystallography.

First results concerning the ligand properties of these novel compounds show that they are stronger net donors compared to phosphabarrelenes. These preliminary investigations pave the way for their use as (chiral) ligands in (asymmetric) homogeneous catalysis.

References:

[1] a) G. Märkl, Angew. Chem. 1966, 5, 846; b) G. Märkl, F. Lieb, Angew. Chem. 1968, 80, 702.

[2] M. Rigo, J. Sklorz, N. Hatje, F. Noack, M. Weber, J. Wiecko, C. Müller, Dalton Trans., 2016, 45, 2218.

[3] M. Rigo, M. Weber, C. Müller, Chem. Commun. 2016, 52, 7090-7093.