Organotin Complexes of Alizarin and Purpurin

Five novel organotin complexes with the anthraquinone dyes alizarin (1,2‐dihydroxyanthraquinone) and purpurin (1,2,4‐trihydroxyanthraquinone) were synthesized and characterized by elemental analyses, FTIR and NMR spectroscopy (1H, 13C and 119Sn). The crystal and molecular structures of four complexes were determined by X‐ray diffraction on single crystals: [Bu2Sn(aliz)(H2O)]·C2H5OH (A1·EtOH), [Bu2Sn(aliz)(dmso)]2(A3), [(Bu2Sn)3O(Hpurp)2] (P1) and [Bu2Sn(Hpurp)(dmso)]2(P2), where H2aliz = alizarin and H3purp = purpurin. The coordination mode of the ligands is identical to that found in their Al/Ca complexes, where they act as dianionic tridentate ligands forming five and six‐membered fused chelate rings. The coordination to the tin atoms occurs exclusively viathe 1,2‐ phenolate oxygen and the adjacent quinoid oxygen atoms. The complexes A1, A3and P1are dimers with hepta‐coordinated tin atoms in form of a slightly distorted pentagonal bipyramid. The trinuclear complex P2contains two pentacoordinated and one heptacoordinated tin atoms.