Zusammenfassung

The opening of a PP edge in the P4 tetrahedron by a Rh complex fragment is the first reaction step in the three-component reaction between [RhCp(CO)2], P4, and [Cr-(CO)5(thf)]. The tetraphosphabicyclobutane ligand thus formed may then use the lone pairs of all the phosphorus atoms for the coordination of Cr(CO)5 units to give 1. Loss of CO and cleavage of a PP bond leads to a complex in which the cyclo-P4 ligand acts as a 12-valence-electron donor. Cp = 5 - C5H4tBu, .