Complex sentence: The monoclinic form contains tetramers, Sn 4 F 8, where there are two distinct coordination environments for the Sn atoms but in each case there are three nearest neighbours with Sn at the apex of a trigonal pyramid and the lone pair of electrons is sterically active.
Split into simpler sentences: The monoclinic form contains tetramers, Sn 4 F 8, where there are two distinct coordination environments for the Sn atoms. In each case, there are three nearest neighbours, with Sn at the apex of a trigonal pyramid, and the lone pair of electrons sterically active.