Stabilisation of unusual metal co-ordination geometries using an oxo-cubane ligand; syntheses and structures of [{Sn-4((NBu)-Bu-t)(3)O}(3)-LiCl]center dot 3thf and [{Sn-4((NBu)-Bu-t)(3)O}(3)FeCl2]center dot 3thf

摘要

Complexation of LiCl and FeCl2 with the oxo-cubane [Sn-4((NBu)-Bu-t)(3)O] 1 (3 equivalents) gave [{Sn-4((NBu)-Bu-t)(3)O}(3)LiCl]. 3thf 2 and [{Sn-4((NBu)-Bu-t)(3)O}(3)FeCl2]. 3thf 3, respectively; the co-ordination of three sterically demanding, 'ether-like' [Sn-4((NBu)-Bu-t)(3)O] ligands to the Li+ and Fe2+ centres of 2 and 3 results in unusual geometries for these metals. The geometry in 2 can be described as a distorted trigonal bipyramid with one vertex missing, while in 3 it is trigonal bipyramidal. Model semi-empirical calculations combined with the structural findings stress that although sterically encumbered 1 is a highly effective ligand for oxophilic metals. [References: 31]