Extraction Equilibria of 4-(2-Pyridylazo)resorcinolatovanadium(V) Complexes with Quaternary Ammonium Salt and with Trioctylphosphine Oxide

Abstract

Extraction equilibria for vanadium(V) complexes with 4- (2-pyridylazo)resorcinol (PAR, H₂L) at 25°C were investigated in the Na₂SO₄ solution with the ionic strength of O.1. The complexes are extracted into chloroform either as an ion-pair with benzyldimethyltetradecyl- ammonium (Q⁺) cation, Q[V0₂L] (A=560nm, e=3.35x10⁴dm³mol^-1cm^-1), or as an adduct complex with trioctylphosphine oxide (topo), [V0₂(HL)(topo)] (A=560 nm, e=1.40x10⁴dm³mol^-1cm^-1).
The extraction constants of these complexes were estimated as,
K^VO₂L-_ex=[Q[VO₂L]]_(o)/[Q⁺][[VO₂L]^-]=10^8.54±0.18
and
K_ad=[[VO₂(HL)(topo)]]_(o)/[[VO₂(HL)]][topo]_(o)=10^2.07±0.06
The adduct formation constant in chloroform was calculated to be,
β₁=[[VO₂(HL)(topo)]]_(o)/[[VO₂(HL)]]_(o)[topo]_(o)=10^2.37±0.09
The equilibrium diagram for the extraction of the vanadium(V)-PAR complexes were p.o-posed on Fig.8.