Structural Flexibility in Octahedral Tin(IV) Bischelates: Electronic and Hybridization Effects

Abstract

Theoretical calculations had been used as a diagnostic tool successfully to probe into the molecular structures of organotin complexes. 10 The geometry of bisdithiocarbamates(dtc) containing two monodentate ligands had been probed by us theoretically using PM3 calculations. 11 Electron rich groups prefer cis orientation. In order to elucidate the influence of other effects viz., hybridization of tin and weak interactions between the ligands, PM3 calculations with two sets of complexes containing acetylacetonate(acac) and nitrate ligands have been made in this study. The results are compared with the analogous dithiocarbamates.The PM3 optimized structures of some selected XYSn[S 2 CN(C 2 H 5 ) 2 ] 2 , XYSn(acac) 2 and XYSn(NO 3 ) 2 [X, Y = monodentate ligands] complexes are given in Figs 1-3, respectively. In the dithiocarbamate complexes, 23,27,28 the variation of Sn-S bond lengths within the tin-diethyldithiocarbamate indicates anisobidentate bonding for the chelating group. In contrast, the variation of Sn-O bond lengths within one Sn-NO 3 entity, in the nitrato complexes is high and indicates strong and weak bonding of the oxygens of each of the nitrato groups. All the nitrato complexes can exist in two forms and exhibit weak Sn...O interactions with bite angles around 50 o although nitrate ion can bind to the metals in bidentate fashion with bite angles around 70°. 31 The nitrato complexes are unstable compared to the acetylacetonato complexes but more stable than the dithiocarbamato complexes as expected from the strength of Sn-O bonds. It must be noted

Main Group Dithiocarbamate Complexes

“…The two chloride ligands are cis (ClSnCl ¼ 91.8 ). The other dihalide complexes that have been characterized crystallographically are structurally analogous (133,134,140,168).…”

Tin dithiocarbamates: applications and structures

“…5. The robustness of this motif is exemplified by the observation that, for the homologous Sn(S 2 CNEt 2 ) 2 X 2 , X D Cl, [36] Br [38] and I, [40] series, except for the expected lengthening of the Sn-X bond distances, there are no systematic trends in the bond distances or angles describing the tin atom geometries. In the same vein, no apparent trends are found to distinguish the structures of Sn(S 2 CNR 0 2 ) 2 Cl 2 , R 0 D Et [36] and n-Bu.…”