Structural Chemistry of Borophosphates, Metalloborophosphates, and Related Compounds

Abstract A concept for the classification of crystalline (metallo)borophosphates in terms of structural chemistry is proposed and the compounds known to date are classified in an overview. Similarities and differences with (alumo)silicates and Liebau 's classification are discussed with respect to the observation that the different borate and phosphate complexes are not interconnected arbitrarily in borophosphates. By combination and extension of existing concepts for silicates and borates a hierarchical system based on oligomeric building units has been developed. The observed connection rules are rationalized and the strong influence of the composition on dimensionality and structural motifs of the formed anions is pointed out. Likewise the effect of OH groups is taken into account by grading anions according to the degree of protonation (ratio O:OH). A general distinction is made between tetrahedral and mixed coordinated borophosphates. Metalloborophosphates are treated separately as special cases of borophosphates. Finally, anion‐substituted compounds, border cases, and borate‐phosphates complete the overview.