R, S

https://doi.org/10.1351/goldbook.R05423
The approved designations (devised by Cahn, Ingold and Prelog) of @A00020@ at four-coordinate (quadriligant) and six-coordinate (sexiligant) @S05980@ centres.
Source:
PAC, 1996, 68, 2193. (Basic terminology of stereochemistry (IUPAC Recommendations 1996)) on page 2216 [Terms] [Paper]