Pressure and concentration dependent formation of oligomers of tetrakis(p-methylphenylisocyanide)rhodium(I)

Abstract

The optical absorption of [Rh(tol)₄]PF₆ (tol p-methylphenylisocyanide) dissolved in acetonitrile has been measured as function of concentration (10⁻⁴ <= c(0) <= 1.5 X 10⁻² mol/l) and of applied pressure (0.1 <= p <= 400 MPa) at room temperature. Analysis of the spectra indicates the formation of oligomers [Rh(tol)₄]n“⁺, n = 2, 3 with increase of both the concentration and the pressure, respectively. Application of pressure increases the dimer-monomer equilibrium constant and yields a blue shift (ca.0.3 cm⁻¹/MPa) of the monomer absorption
but a red shift ( ca. -0.6 cm⁻¹/MPa) of the dimer absorption.