Cluster models are constructed for mono- and dinuclear Cr(II) sites and mononuclear Cr(III) sites on the Cr/SiO2 Phillips catalyst and used to compute d-d transition energies and intensities. Mononuclear pseudo-tetrahedral Cr(II) gives rise to two bands of electric-dipole-allowed d-d transitions, at 8,400 and 12,300 cm(-1). This doublet is lowered in energy and intensity as the bond angle about chromium, angle OCrO, opens up. The dinuclear site gives rise to bands at 5,200 and 10,300 cm(-1), consistent with calculations for a mononuclear cluster of comparable value for angle OCrO. A tri-coordinated Cr(DI) cluster shows bands of comparable oscillator strengths at energies of 11,000, 16,000, 18,000-20,000 and 33,000 cm(-1). The predicted bands correspond well with d-d bands in experimental diffuse reflectance spectra.