New cyclopentadienyl molybdenum polynuclear clusters from ring opening of Woollins’ reagent via phosphorus–selenium bond scission, phosphorus–phosphorus coupling and deselenation pathways

Abstract Cothermolysis of [(Ph)P(Se)(μ-Se)] 2 or Woollins’ reagent (WR) with Cp 2 Mo 2 (CO) 4 ( 2 ) in toluene at 110 °C led to the isolation of three different metal clusters, [Cp 2 Mo 2 {(μ-Se) 2 (PPh(Se))}{(μ-Se)(PPh) 3 ] ( 3 ), Cp 4 Mo 4 (CO) 3 (μ-Se) 4 ( 4 ) and a pair of isomer complexes of Cp 3 Mo 3 (CO) 4 [Se 3 (PPh) 2 ] ( 5a and 5 b ) in 17.5%, 3.1% and 4.9% yields, respectively. A similar reaction at 70 °C gave only 5a and 5 b in 2.0% and 4.9% yields, respectively. All complexes have been fully characterized via NMR, IR and ESI mass spectroscopy. Molecular structures of 3 , 4 and 5a were confirmed by single crystal X-ray diffraction analyses. A variable temperature 1 H NMR study of 4 was carried out. Finally, a free-radical addition pathway by selenation of WR was postulated.