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

Mixed-ligand hydride complexes OsHCl­(CO)­(PPh3)2L (2) [L = P­(OMe)3, P­(OEt)3] were prepared by allowing OsHCl­(CO)­(PPh3)3 (1) to react with an excess of phosphite P­(OR)3 in refluxing toluene. Dichloro compounds OsCl2(CO)­(PPh3)2L (3, 4) were also prepared by reacting 1, 2 with HCl. Treatment of hydrides OsHCl­(CO)­(PPh3)2L (2), first with triflic acid and then with an excess of RN3 afforded organic azide complexes [OsCl­(η1-N3R)­(CO)­(PPh3)2L]­BPh4 (57) [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 (8b). Hydrazine complexes [OsCl­(CO)­(RNHNH2)­(PPh3)2L]­BPh4 (911) [R = H, CH3, C6H5; L = P­(OMe)3, P­(OEt)3] were prepared by allowing hydride species OsHCl­(CO)­(PPh3)2L (2) to react first with triflic acid and then with an excess of hydrazine. Aryldiazene derivatives [OsCl­(CO)­(ArNNH)­(PPh3)2L]­BPh4 (12, 13) were also prepared following two different methods: (i) by oxidizing arylhydrazine [OsCl­(C6H5NHNH2)­(CO)­(PPh3)2L]­BPh4 (11) with Pb­(OAc)4 in CH2Cl2 at −30 °C; (ii) by allowing hydride species OsHCl­(CO)­(PPh3)2L (2) 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] (2b) and [OsCl­{η1-NHC­(H)­C6H4-4-CH3}­(CO)­(PPh3)2{P­(OEt)3}]­BPh4 (8b).