Infrared, Raman and resonance Raman spectra of the solid nickel(II) thiophosphate compound (PPh4)(3) [(NiPS4)(3)] and force constants in the trinickel [Ni3P3S12](3-) cyclic anion

The UV-visible (350-900 nm), infrared and Raman (30-800 cm(-1)) spectra of a new transition metal thiophosphate solid compound, (PPh4)(3)[(NiPS4)(3)], were analyzed using powder samples. Electronic transitions of the F-1(2) < -- (1)A(1) type originating in the (PS4)(3-) groups were detected from visi ble absorbance measurements in the 440-520 mm range and most of the expecte d infrared and Raman vibrational modes of the trimetallic ring anion [Ni3P3 S12](3-) were observed in the 600-30 cm(-1) region. Also, resonance Raman s pectra were recorded using exciting radiation of several wavelengths in the 680-450 mn range and the Raman excitation profiles of several fundamentals were established: they all peak near 488 nm and exhibit the strongest enha ncements for totally symmetric and non-totally symmetric stretching and ben ding modes of (NiS4) groups. It is therefore concluded that several ligand to metal charge-transfer electronic transitions are overlapped and involved in vibronic coupling mechanisms. Furthermore, the vibrational assignments were checked by a valence force field calculation for an isolated [Ni3P3S12 ](3-) anion of C-3 nu symmetry, The potential energy distributions and mean squared vibrational amplitudes revealed strong nu(Ni-S) and delta(S-P-S) c ouplings and relatively high nu(Ni-S) stretching modes at near 310 cm(-1). Compared with results in the one-dimensional KNiPS4 compound containing inf inite anionic chains (1)(infinity)[NiPS4](-), one notes a force constant in crease on the P-S exocyclic (mu(1)) bonds, no change on the bridged (mu(2) and mu(3)) P-S bonds and a slight increase in the Ni-S stretching force con stants varying from 75 to 85 N m(-1) in accordance with a localized ligand to metal charge-transfer mechanism. Hence a comparison of the induced Raman scattering processes in the (PPh4)(3) [(NiPS4)(3)] and KNiPS4 solid compou nds shows that the ligand to metal charge transfers and the crystal field e ffects have a strong influence on the vibrational properties in these thiop hosphate compounds, Copyright (C) 1999 John Whey & Sons, Ltd.