Diorganotin(IV) complexes of imidazole-2-carbaldehyde thiosemicarbazone (H(2)ImTSC). The crystal and molecular structures of the "free" ligand and of[SnMe2(ImTSC)]

The compounds [SnR2(ImTSC)] (R = Me, Bu-n or Ph; H(2)ImTSC = imidazole-2-ca rbaldehyde thiosemicarbazone) were synthesized by treating the appropriate diorganotin(IV) oxide with the ligand in ethanol. The structures of H(2)ImT SC . 0.5H(2)O and [SnMe2(ImTSC)]. EtOH were determined by X-ray diffractome try. The thiosemicarbazone chain of the former has E,E,E configuration and is almost coplanar with the imidazole ring. A rich network of hydrogen bond s involving all potential donor and acceptor groups of H(2)ImTSC and the wa ter molecule stabilizes the crystal lattice. The crystal of the dimethyltin (IV) complex is composed of discrete molecules that are likewise linked by hydrogen bonds. The Sn is bound to the two methyl groups and to an N,N,S-tr identate thiosemicarbazonato dianion (ImTSC(2-)) in a highly distorted trig onal bipyramidal arrangement with the thioamide sulfur and the imidazole ni trogen apical. The Sn-N bond lengths [2.129(5) and 2.174(5) Angstrom] are c lose to the sum of the covalent radii and dominate the metal-ligand interac tion. The Sn-S bond length [2.659(2) Angstrom] suggests a weak bond. The un usual co-ordination mode of the ImTSC(2-) anion creates four- and six-membe red stannole rings. The EtOH is bound to the complex via hydrogen bonds inv olving the nitrogen of the imidazole that is not co-ordinated to the tin an d the thiosemicarbazone NH2 group. The IR spectra of the Bu-n and Ph deriva tives suggest that they are structurally similar to the methyl complex. H-1 , C-13 and Sn-119 NMR spectroscopy indicates that the structure of the comp lexes in the solid state persists in CDCl3 solution. For H(2)ImTSC, N-15 NM R data are presented in addition to IR and H-1 and C-13 NMR data.