Crystal Structure of ClF 4 + SbF 6 - , Normal Coordinate Analyses of ClF 4 + , BrF 4 + , IF 4 + , SF 4 , SeF 4 , and TeF 4 , and Simple Method for Calculating the Effects of Fluorine Bridging on the Structure and Vibrational Spectra of Ions in a Strongly Interacting Ionic Solid