PRESSURE AND CONCENTRATION-DEPENDENT FORMATION OF OLIGOMERS OF TETRAKIS-(P-METHYLPHENYLISOCYANIDE)RHODIUM(I)

The optical absorption of [Rh(tol)4]PF6 (tol: p-methylphenylisocyanide ) dissolved in acetonitrile has been measured as function of concentra tion (10(-4) less-than-or-equal-to c0 less-than-or-equal-to 1.5 x 10(- 2) mol/l) and of applied pressure (0.1 less-than-or-equal-to p less-th an-or-equal-to 400 MPa) at room temperature. Analysis of the spectra i ndicates the formation of oligomers [Rh(tol)4]n(n+), n = 2,3, with inc rease of both the concentration and the pressure, respectively. Applic ation of pressure increases the dimer-monomer equilibrium constant and yields a blue shift (almost-equal-to 0.3 cm-1/MPa) of the monomer abs orption but a red shift (almost-equal-to -0.6 cm-1/MPa) of the dimer a bsorption.