Effects of sulfur dioxide, bisulfite(1-), and sulfite(2-) as auxiliary ligands on the reactivity of ammineruthenium(II)-ligand bonds

Abstract

The values of pK corresponding to the equilibria (trans forms) [Ru(NH3)4S02H20]2+ + H20 = (Ru(NH3)4(HS03)H20]+ + H+ and [Ru(NH3)4(HS03)H20]+ = [Ru(NH3)4S03H20] + H+ at 25°and ionic strength ca. 0.10 have been measured as 2.15 + 0.1 and 5.05 ± 0.1, respectively. These values have been applied in interpreting data on the rate of replacement of water in the trans tetraammine by pyrazine (pz) as a function of pH. The specific rates for substitution into the sulfito, the bisulfito, and sulfur dioxide complexes at 25°have been determined as 13.5 ± 0.1,0.20 ± 0.01, and 0.033 ± 0.004 M~'

Immobilized ruthenium complexes and aspects of their reactivity

“…These pK a values are comparable with those observed by Isied and Taube for the trans-[Ru(H 2 O)(NH 3 ) 4 (SO 2 )] 2+ complex in solution (pK 1 2.15 and pK 2 5.05) [72] for Eqs. (10) and (11).…”

“…The same behavior is observed for trans-[Ru(H 2 O)(NH 3 ) 4 (SO 2 )]Cl 2 immobilized in the 4-PVP polymer [3]. In this system, the calculated pK a values for equations 11 and 12 are 2.4 ± 0.2 and 4.4 ± 0.4 respectively, which are near the calculated values (1.7 ± 0.1 and 4.9 ± 0.1) for the trans-[Ru(NH 3 ) 4 (SO 2 )(py)] 2+ complex in solution [72].…”

“…For the trans-[Ru(H 2 O)(NH 3 ) 4 (SO 2 )](tfms) 2 complex, the position of the bands is pH dependent, since the ligand SO 2 shows SO 2 /HSO 3 − /SO 3 2− acid-base equilibria. At pH < 2.0, the complex is mostly in the SO 2 form in solution; when pH > 5.5, the SO 3 2− species predominates [72,118]. This is confirmed by the pK a measurements for the occluded and non-occluded complexes carried out by electrochemical methods [3,103].…”

“…The SO 2 /SO 4 2− pathway is preceeded by SO 3 2− /SO 2 aqueous equilibrium [72]. At pH values above 9.0 trans-[Ru(SO 3 )(NH 3 ) 4 (OH 2 )] predominates which allows formation of Ru-L(support) bonds due to the water lability in the Ru(II) complex, thereby leading to an immobilized sulfito complex.…”

A regenerable ruthenium tetraammine nitrosyl complex immobilized on a modified silica gel surface: Preparation and studies of nitric oxide release and nitrite-to-NO conversion

“…This is possibly due to the trans labilizing effect of the sulfito ligand [85]. As mentioned earlier, the immobilized Ru(II) and Ru(III) are inert regarding substitution of the ligands, except for the aqua ligand in the Ru(II) species, which, as will be shown latter, would be responsible for the recycling properties of the material.…”