Preparation and Reactivity of Mixed-ligand Ruthenium(II) Hydride Complexes with Phosphites and Polypyridyls

Chloro complexes [RuCl(N-N)P3]BPh4 (1−3) [N-N = 2,2‘-bipyridine, bpy; 1,10-phenanthroline, phen; 5,5‘-dimethyl-2,2‘-bipyridine, 5,5‘-Me2bpy; P = P(OEt)3, PPh(OEt)2 and PPh2OEt] were prepared by allowing the [RuCl4(N-N)]·H2O compounds to react with an excess of phosphite in ethanol. The bis(bipyridine) [RuCl(bpy)2{P(OEt)3}]BPh4 (7) complex was also prepared by reacting RuCl2(bpy)2·2H2O with phosphite and ethanol. Treatment of the chloro complexes 1−3 and 7 with NaBH4 yielded the hydride [RuH(N-N)P3]BPh4 (4−6) and [RuH(bpy)2P]BPh4 (8) derivatives, which were characterized spectroscopically and by the X-ray crystal structure determination of [RuH(bpy){P(OEt)3}3]BPh4 (4a). Protonation reaction of the new hydrides with Brønsted acid was studied and led to dicationic [Ru(η2-H2)(N-N)P3]2+ (9, 10) and [Ru(η2-H2)(bpy)2P]2+ (11) dihydrogen derivatives. The presence of the η2-H2 ligand was indicated by a short T1min value and by the measurements of the JHD in the [Ru](η2-HD) isotopomers. From T1min and JHD values the H−H distances of the dihydrogen complexes were also calculated. A series of ruthenium complexes, [RuL(N-N)P3](BPh4)2 and [RuL(bpy)2P](BPh4)2 (P = P(OEt)3; L = H2O, CO, 4-CH3C6H4NC, CH3CN, 4-CH3C6H4CN, PPh(OEt)2], was prepared by substituting the labile η2-H2 ligand in the 9, 10, 11 derivatives. The reactions of the new hydrides 4−6 and 8 with both mono- and bis(aryldiazonium) cations were studied and led to aryldiazene [Ru(C6H5N=NH)(N-N)P3](BPh4)2 (19, 21), [{Ru(N-N)P3}2(μ-4,4‘-NH=NC6H4−C6H4N=NH)](BPh4)4 (20), and [Ru(C6H5N=NH)(bpy)2P](BPh4)2 (22) derivatives. Also the heteroallenes CO2 and CS2 reacted with [RuH(bpy)2P]BPh4, yielding the formato [Ru{η1-OC(H)=O}(bpy)2P]BPh4 and dithioformato [Ru{η1-SC(H)=S}(bpy)2P]BPh4 derivatives.