Tetraethylammonium, ligand structure

It is pertinent to note the preparation and structure of the tris(ethylxanthato)teIlurium(II) anion in its tetraethylammonium salt, Et4N [Te(EtOCS2)3] (Figure 4), in which the five-coordinate teUurium(II) is coordinated to three ethyl xanthate ligands, one of which is monodentate whilst the other two are anisobidentate. The resulting TeSs coordination sphere is pentagonal planar. 

The labile intermediate (96) has been isolated from the low-temperature reaction of hydride ion (tri- ec-butylborohydride) with the complex [Cr(f/" -l,3-butadiene)(CO)3 P(OMe)3 ], and its structure confirmed from an X-ray structural analysis of the tetraethylammonium salt. NMR studies show that this unstable (Z)-allyl structure, with open face of the allyl group pointing toward the P(OMe)3 ligand, is retained at low temperature (— 5 C) in solution. However, at room temperature (96) isomerizes to the thermodynamically more stable E isomer (97) see Eq. 24. 

---