NMR STUDIES ON 6-ARENE)(P(OPh)3)2>ClO4 IN THE PRESENCE OF ACETONE-d6. ARENE DISSOCIATION AND DYNAMIC BEHAVIOUR OF THE SOLVENT COMPLEX

Article abstract of DOI:10.1016/0022-328X(85)87262-4

Dissociation of the complexes 6-arene)L2>ClO4 (arene = mesitylene (Ia),toluene (Ib) and benzene (Ic); L = P(OPh)3) with loss of the arene ligand in CD2Cl2/acetone-d₆ (95/5 mol/mol) has been studied by 31P NMR spectroscopy; for initial 0.025 M concentrations of degrees of dissociation were 0.23, 0.33 and 0.85, respectively.The dissociations were first-order, with half-lifes of 31 (Ia), 1.2 (Ib) and 0.7 (Ic) h.The solvent complex mL2>ClO4 produced by these dissociation reactions showed unusual dynamic structural behavior.In dry acetone the two phosphorus nuclei were magnetically equivalent (species II-A₂), whereas in acetone solutions containing up to 3percent water a new molecular species was formed having two non-equivalent phosphorus atoms (species II-AB).The molecules II-A₂ and II-AB undergo rapid interconversion on the NMR time scale with an activation barrier of ca. 50 kJ/mol.