A new approach to coordination chemistry involving phosphorus-selenium based ligands. Ring opening, deselenation and phosphorus–phosphorus coupling of Woollins’ Reagent

The facile reaction of [CpCr(CO)3]2 (1) with an equivalent of 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide or Woollins’ Reagent (WR) at ambient temperature gave mainly [CpCr(CO)2]2Se (3) as the main product. A similar reaction with an excess of 1 gave 3 (58%) and trans-[CpCr(CO)2(SePPh)]2 (5, 25%). However reaction with an equivalent of the triply bonded congener Cp2Cr2(CO)4 (2) at 60 °C took 3 h to complete and led to the isolation of trans-[CpCr(CO)2(SePPh)]2 (5, 3%), CpCr(CO)2(SeP(H)Ph) (4, 18%) and [CpCr(Se2P(O)Ph)]2 (6, 2%). The ring-opening reaction of WR via an initial homolytic P–Se bond cleavage by CpCr(CO)n· (n = 2 (2A) or 3 (1A)) depicts a new approach to coordination chemistry involving P–Se based ligands. A mechanistic pathway was proposed according to the evidences obtained from thermolysis, NMR and mass spectra studies. All the products of 4, 5 and 6 have been structurally characterized by single-crystal X-ray diffraction analysis.