High Coordination Among SE and TE Fluorides

The high coordination chemistry of TeIV, SeIV, and TeVI fluorides is reviewed, and brought into context with fluorides of neighbor elements Br, I, and Xe, but also with Mo, W, and Re fluorides. Tellurium reaches the coordination number CN 8 in case of TeF8 2−. This has the same structure as IF8 2−, XeF8 2−, WF8 2−, ReF8 −, and ReF8 2−, namely square antiprismatic. TeF7 − is built like a pentagonal bipyramid. It is to be compared with IF7, IOF6 −, XeF7 −, WF7 −, MoF7 − and ReF7. Substítution gives CH3OTeF6 − and (CH3O)2TeF5 −, also pentagonal bipyramidal. The highest coordination obtained for selenium fluorides may be regarded as CN 7 in SeF6 2−. The slightly distorted octahedral structure is compared to BrF6 − (octahedral) and IF6 − and XeF6 (strongly distorted).