Azo Complexes of Osmium(II): Preparation and Reactivity of Organic Azide and Hydrazine Derivatives

Mixed-ligand hydride complexes OsHCl­(CO)­(PPh₃)₂L (<b>2</b>) [L = P­(OMe)₃, P­(OEt)₃] were prepared by allowing OsHCl­(CO)­(PPh₃)₃ (<b>1</b>) to react with an excess of phosphite P­(OR)₃ in refluxing toluene. Dichloro compounds OsCl₂(CO)­(PPh₃)₂L (<b>3</b>,<b> 4</b>) were also prepared by reacting <b>1</b>, <b>2</b> with HCl. Treatment of hydrides OsHCl­(CO)­(PPh₃)₂L (<b>2</b>), first with triflic acid and then with an excess of RN₃ afforded organic azide complexes [OsCl­(η¹-N₃R)­(CO)­(PPh₃)₂L]­BPh₄ (<b>5</b>–<b>7</b>) [R = 4-CH₃C₆H₄CH₂, C₆H₅CH₂, C₆H₅; L = P­(OEt)₃]. Benzylazide complexes react in CH₂Cl₂/ethanol solution, leading to the imine derivative [OsCl­(CO)­{η¹-NHC­(H)­C₆H₄-4-CH₃}­(PPh₃)₂{P­(OEt)₃}]­BPh₄ (<b>8b</b>). Hydrazine complexes [OsCl­(CO)­(RNHNH₂)­(PPh₃)₂L]­BPh₄ (<b>9</b>–<b>11</b>) [R = H, CH₃, C₆H₅; L = P­(OMe)₃, P­(OEt)₃] were prepared by allowing hydride species OsHCl­(CO)­(PPh₃)₂L (<b>2</b>) to react first with triflic acid and then with an excess of hydrazine. Aryldiazene derivatives [OsCl­(CO)­(ArNNH)­(PPh₃)₂L]­BPh₄ (<b>12</b>,<b> 13</b>) were also prepared following two different methods: (i) by oxidizing arylhydrazine [OsCl­(C₆H₅NHNH₂)­(CO)­(PPh₃)₂L]­BPh₄ (<b>11</b>) with Pb­(OAc)₄ in CH₂Cl₂ at −30 °C; (ii) by allowing hydride species OsHCl­(CO)­(PPh₃)₂L (<b>2</b>) to react with aryldiazonium cations ArN₂⁺ (Ar = C₆H₅, 4-CH₃C₆H₄) in CH₂Cl₂. The complexes were characterized spectroscopically and by X-ray crystal structure determination of OsHCl­(CO)­(PPh₃)₂[P­(OEt)₃] (<b>2b</b>) and [OsCl­{η¹-NHC­(H)­C₆H₄-4-CH₃}­(CO)­(PPh₃)₂{P­(OEt)₃}]­BPh₄ (<b>8b</b>)