Ternary Phosphide Ho2Cu6-xP5-y, Its Crystal Structure, and REm+n(Cu2P3)m(Cu4P2)n Relationship with Other Rhombohedral Rare-Earth Copper Phosphides

A new layered aluminophosphate [NH3CH2CH(OH)CH3]3·Al3P4O16 containing a racemic mixture of isopropanolamine has been synthesized using isopropanolamine as the predominant solvent and the template and its structure was determined by means of single-crystal X-ray diffraction. The title compound crystallizes in the trigonal space group R with M=689.18, a= 13.1068(15) ?, c=26.935(4) ?, Z=6, V=4007.2(9) ?3, R=0.0338, and Rw=0.0982. The structure consists of [Al3P4O16]3macroanionic sheets with a 4×6×12 network stacked in an ABCABC sequence. The inorganic layers are constructed from alternating AlO4 and PO3(=O) tetrahedral units. The protonated isopropanolamine cations between inorganic layers are arranged in a double-layer fashion with each layer containing only one type of enantiomer. The as-synthesized product is characterized by powder X-ray diffraction, IR spectroscopy, inductive coupled plasma analysis, TGA and DTA.