The Dioxoosmium(VI) Complex [OsO 2 (H 2 biim) 2 ](NO 3 ) 2 as Oxygen‐Transfer Reagent − Synthesis and Solid‐State Structure of Bis(2,2′‐biimidazole)bis(triphenylphosphane oxide)osmium(III) Nitrate

Treatment of OsO 4 ( 1 ) with 2,2′‐biimidazole (H 2 biim) ( 2 ) in a methanol/acetone mixture, and in the presence of nitric acid produces the novel dioxoosmium(VI) complex [OsO 2 (H 2 biim) 2 ](NO 3 ) 2 ·CH 3 OH ( 3 ). Addition of 2 equiv. of PPh 3 ( 4 ) and 1 equiv. of nitric acid to 3 affords mononuclear [Os(H 2 biim) 2 (O=PPh 3 ) 2 ](NO 3 ) 3 ( 5 ) by a redox reaction which involves the transfer of oxygen from osmium to PPh 3 . The X‐ray crystal structure of 5 reveals an octahedral coordination sphere around the osmium(III) centre. This occurs as a result of the two H 2 biim chelating ligands in the equatorial positions and two datively bonded phosphane oxide groups O=PPh 3 in the axial positions. Hydrogen bonds are responsible for the formation of a polymeric structure in the solid state. The latter complex reacts with KOH to form monocationic [Os(Hbiim) 2 (O=PPh 3 ) 2 ]NO 3 ( 6 ).