Jp. Smit et al., KINETICS OF THE SUBSTITUTION-REACTION BETWEEN AQUAOXOTETRACYANOMOLYBDATE(IV) AND CYANIDE HYDROGEN-CYANIDE, Polyhedron, 12(18), 1993, pp. 2271-2277
The kinetics of the substitution reaction between aquaoxotetracyanomol
ybdate (IV) ions and CN- and HCN, as an important intermediate step in
the formation of the [Mo(CN)8]4- complex, was studied by stopped-flow
spectrometry. The aqua ligand in the [MoO(H2O)(CN)4]2- Complex is sub
stituted by both CN- ions and hydrogen cyanide according to the reacti
on: [GRAPHICS] At 15.0-degrees-C and mu = 1.0 M (KNO3) the equilibrium
, forward and reverse rate constants of the reaction with CN- ions wer
e determined as 92(5) M-1, 83(1) M-1 s-1 and 0.87(3) s-1, and for HCN
as 3(1) M-1, 458(5) M-1 s-1 and 140(30) s-1, respectively. Coordinatio
n of the HCN to the metal centre results in a decrease in the pK(a) va
lue of hydrogen cyanide by approximately 1.5 pH units to ca 7.6(2).