  Chlorine covalently bonded to an open shell metal is present in many
materials with desirable or intriguing physical properties. Materials include
highly luminescent nontoxic alternatives to lead halide perovskites for
optoelectronic applications K2CuCl3 and Rb2CuCl3, enantiomorphic CsCuCl3 that
presents magneto-chiral dichroism at a low temperature, and cubic K2RuCl6 that
possesses a singlet ground state generated by antiparallel spin and orbital
angular momenta. Structural chirality of CsCuCl3 has been confirmed by resonant
x-ray Bragg diffraction. We explore likely benefits of the technique at the
chlorine K-edge using a symmetry inspired method of calculation applied to
chlorine multipoles. Already, a low energy feature in corresponding x-ray
absorption spectra of many compounds has been related to the chlorine-metal
bond. Bragg diffraction from chlorine in cubic K2RuCl6 is treated in detail.
Diffraction patterns for rhombohedral compounds that present space-group
forbidden Bragg spots are found to be relatively simple.
