Preparation and reactivity of osmium(II) hydride complexes with phosphites and polypyridyls

Abstract

Chloro-complexes [OsCl(N–N)P 3]BPh 4 ( 1, 2) [N–N=2,2 ′-bipyridine (bpy) and 1,10-phenanthroline (phen); P=P(OEt) 3 and PPh(OEt) 2] were prepared by allowing OsCl 4(N–N) to react with zinc dust in the presence of phosphites. Treatment of the chloro-complexes 1, 2 with NaBH 4 yielded, in the case of bpy, the hydride [OsH(bpy)P 3]BPh 4 ( 4) derivatives. Mono-phosphite [OsCl(bpy) 2P]BPh 4 ( 3) complexes were also prepared by reacting the [OsCl 2(bpy) 2]Cl compound with zinc dust in the presence of phosphite. Protonation reaction of the hydride [OsH(bpy)P 3] + ( 4) cations with Brønsted acid was studied and led to thermally unstable (above 0 °C) dihydrogen [Os(η 2-H 2)(bpy)P 3] 2+ ( 4*) derivatives. The presence of the H 2 ligand is supported by variable-temperature NMR spectra and T 1min measurements. Carbonyl [Os(CO)(bpy){P(OEt) 3} 3](BPh 4) 2 ( 5), nitrile [Os(CH 3CN)(bpy){P(OEt) 3} 3](BPh 4) 2 ( 6), and hydrazine [Os(bpy)(NH 2NH 2){P(OEt) 3} 3](BPh 4) 2 ( 7) complexes were prepared by substituting the H 2 ligand in the η 2-H 2 ( 4*) derivatives. Aryldiazene complex [Os(C 6H 5NNH)(bpy){P(OEt) 3} 3](BPh 4) 2 ( 8) was also obtained by allowing the hydride [OsH(bpy)P 3]BPh 4 to react with phenyldiazonium cation.