The interaction of triphenylphosphine with methanolic solutions of commercial hydrated ruthenium trichloridet leads to mononuclear compleses [RUC~~{P(C&%)~) 41 and [RuC121 P(C&ts)3} s ] , the product depending upon the reaction conditions.1 However, similar reactions, involving mixed alkyl aryl tertiary phosphines, yield binuclear compleses of the type [ R U~C~~( P R~)~] C~ [R = (C2H 5) 2 (CeH d, (C2H d (CsHs) 2, etC.1. * supply "ruthenium trichloride trihydrate" with ca. 44.6% Ru; other suppliers' products are similar. These materials are mainly ruthenium(1V) complexes. On repeated evaporation almost to dryness with concentrated hydrochloric acid, a solution containing the ruthenium (111) complex ion R u C l P is obtained. For the present purpose, the commercial material may be used; identical complexes are obtained by using the Ru(II1) solutions, however.
~V E have shown1 that tris(tripheny1phosphine)dichlororuthenium,2 RuCl,(PPh,) , , in benzeneethanol, may be as effective an homogeneous hydrogenation catalyst as RhCl(PPh,) , ;3 however
In dilute aqueous solution pyridine-2-aldehyde-2-pyridylhydrazone (PAPHY) is a diacid base with acid dissociation constants p&i = 2.87 and ph = 5.71. Stability constants have been measured for complexes of this base with Mn, Fe, Ni, Cu, Zn, and Cd, all in the +2 oxidation state. The Fe(II) complex is exceptionally stable. In strongly alkaline solution the neutral PAPHY molecule undergoes a third, very feebly acid dissociation with pk¡ between 14 and 15. The marked effect of metal coordination upon this third dissociation has been quantitatively examined.
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