Interaction of SbCl52− and Thioether Groups at the Open Coordination Sites of Platinum(II) Diimine Complexes

In the solid-state, the approximately square planar cation in orange crystals of Pt(NO(2)phen)(ttcn)(PF(6))(2) (NO(2)phen = 5-nitro-1,10-phenanthroline; ttcn = 1,4,7-trithiacyclononane) has a short apical Pt...S(ttcn) distance (2.9415(15) A). In acetonitrile solution, the electronic spectrum shows a long-wavelength absorption band (412 nm; 2200 M(-1) cm(-1)), consistent with the notion that the axial Pt...S(ttcn) interactions stabilize states having metal-to-ligand charge-transfer (MLCT) character. Reaction with the hexachloroantimonate(V) salt of tris(4-bromophenyl)aminium (TBPA(+)) results in complex redox chemistry, involving the platinum complex, SbCl(5)(2-) and TBPA(+). In the case of Pt(bpy)(ttcn)(2+), orange-yellow crystals of Pt(bpy)(ttcn)(2)(Sb(4)Cl(16)) were isolated from the reaction, whereas the reaction with Pt(NO(2)phen)(ttcn)(2+) consistently yielded red crystals of Pt(NO(2)phen)(ttcn)(SbCl(5)) x 2 CH(3)CN. In the latter case, the geometry of the cation, including the apical Pt...S(ttcn) distance (2.9390(12) A), is very similar to that of the PF(6)(-) salt. However, the basal plane of each square pyramidal SbCl(5)(2-) opposes the nearly parallel coordination plane of an adjacent Pt(NO(2)phen)(ttcn)(2+) complex, resulting in an unusually short intermolecular Pt...Sb distance of 3.4259(3) A. The longest wavelength maximum in the diffuse reflectance spectrum and the solid-state emission maximum are shifted by approximately 1200 cm(-1) and approximately 700 cm(-1), respectively, to the red of those of the PF(6)(-) salt, consistent with perturbation of the complex's electronic structure because of the Pt...Sb interaction.