Synthesis, structure and light scattering properties of tetraalkylammonium metal isothiocyanate salts.

A series of ammonium and tetraalkylammonium metal isothiocyanate salts of the type Q(y)[M(NCS)x] (M = Cr(III), x = 6, y = 3, Q = NH4(+), Me4N(+), Et4N(+), n-Bu4N(+); M = Mn(II), x = 6, y = 4, Q = Me4N(+); M = Mn(II), x = 5, y = 3, Q = Et4N(+); M = Fe(III), x = 6, y = 3, Q = Me4N(+), Et4N(+), n-Bu4N(+); M = Co(II), x = 4, y = 2, Q = n-Bu4N(+); M = Eu(III), Gd(III), Dy(III), x = 6, y = 3, Q = Bu4N(+)) has been synthesized and structurally characterized. The octahedral Cr(III) salts are isostructural to previously and newly reported Fe(III) salts. The Ln(III)-containing anions are also octahedral. For Mn(II), although the Me4N(+) salt is octahedral, the Et4N(+) salt [Mn(NCS)5](3-) possesses a distorted trigonal bipyramidal geometry. For (Et4N)3[Fe(NCS)6] and (n-Bu4N)3[Fe(NCS)6], a solid-state size-dependent change in colour from red to green was observed and was attributed to a light scattering phenomenon in the crystalline samples.