A study of the preparations of the complex hydriclic anions [MH6](4-)(M = Fe and Ru) reveals a number of distinctive features. Here a soluble homoleptic ruthenium hydride has been prepared for the first time. For example, both FeX2 and [Ru(eta(4)-1,5-COD)X2(]), X = Cl and Br, react with PhMgBr solutions under hydrogen to produce the title compounds. The benzene liberated in these reactions is more readily hydrogenated in the case of a homogeneous room temperature ruthenium hydride preparation to both cyclohexane and cyclohexene. The H-1 NMR spectroscopic data show that the two complex anions have hydride absorptions in the low-frequency region, delta -20.3 and -14.7, respectively. Further, H-1 spin-lattice relaxation times (T-1) for M-H are longer in the case of Ru vs Fe.