Reactions of diorganotin(IV) oxides with isatin 3- and 2-thiosemicarbazones and with isatin 2,3-bis(thiosemicarbazone): influence of diphenyldithiophosphinic acid (isatin = 1H-indole-2,3-dione)

Abstract

Reaction between SnMe₂O and isatin 3-thiosemicarbazone (HL^I) in the presence of diphenyldithiophosphinic acid (HS₂PPh₂) afforded [SnMe₂(S₂PPh₂)₂] and [SnMe₂L^I{O(S)PPh₂}]·EtOH, which were studied by X-ray diffraction and IR spectroscopy in the solid state and by multinuclear (¹H, ¹³C, ³¹P and ¹¹⁹Sn) NMR spectroscopy in CDCl₃ or dmso-d₆ solution (isatin = 1H-indole-2,3-dione). In the bis(dithiophosphinate) derivative the tin atom is bound to two strongly anisobidentate ligands both in the solid state and in solution in chloroform. In the mixed-ligand complex the monothiophosphinate ligand is O-co-ordinated and the thiosemicarbazone (TSC) is bound primarily through its sulfur atom and the nitrogen atom of the azomethine group, although there is an additional weak bond with the remaining isatin oxygen atom [O(1)]. The NMR spectrum in dmso-d₆ suggests weakening of the Sn–S bond and reinforcement of the Sn–O(1) bond. For comparison, the structure of HL^I was also studied by X-ray diffraction. Reaction of SnMe₂O with isatin 2,3-bis(thiosemicarbazone) (H₂LL) afforded [SnMe₂(LL)]. X-Ray diffraction shows that one TSC chain is bound to the metal through the sulfur atom and the azomethine nitrogen atom, forming a five-membered metallacycle. The other chain co-ordinates through the nitrogen of the hydrazine group following its deprotonation. The co-ordination sphere changes in dmso-d₆ solution, in which a molecule of solvent probably occupies a co-ordination position to make the co-ordination number of the metal center up to six. The spectra of the other [SnR₂(LL)] complexes prepared (R = Et or Bu) suggest that both have structures similar to that of the methyl derivative. Reaction of SnMe₂O with isatin 2-thiosemicarbazone (H₂L^II) gave [SnMe₂L^II], the NMR spectra of which indicate a five-co-ordinated tin atom and an O,N,S-tridentate TSC ligand.