SYNTHESIS, STRUCTURE AND VIBRATIONAL-SPECTRA OF BA14INP11

Ba14InP11 was prepared from the elements in a sealed stainless steel a mpoule at 1345 K. The compound is black, brittle and very sensitive to air and moisture. Ba14InP11 crystallises in the tetragonal Ca14AlSb11 type (space group I4(1)/acd, No. 142; a = 17.097(2) Angstrom, c = 22. 940(5) Angstrom; Z = 8, Pearson code tI208). The structure contains is olated p(3-), linear [P-3](7-) and tetrahedral [InP4](9-) anions. The X-ray structure analysis and the vibrational spectra show that the [P- 3](7-) polyanion is strongly asymmetric with d(P-P) = 2.28 Angstrom an d 4.10 Angstrom, corresponding to a [P-2](4-) dumbbell weakly coupled to a single P3- anion. The tetraphosphidoindate(III) anion [InP4](9-) is slightly compressed along the (4) over bar axis, with bond length d (In-P) = 2.71 Angstrom. It is shown that the structure is hierarchical ly related to that of Cu2O, with two interpenetrating frameworks, in w hich the O and Cu atoms are replaced by condensed [InP4/2] tetrahedra and [BaP4P2/2] octahedra, respectively. Both frameworks are meso confi gured, containing alternate R and S fragments. The other Ba cations en velop the P-6 octahedra and P-3 triads forming condensed cubes, tetrag onal antiprisms and bicapped trigonal prisms. Therefore, the structure also forms a heterogeneous framework of centred PBa8/2tap tetragonal antiprisms and BaBa8/2cub cubes, consisting of two interpenetrating en antiomorphic nets (R and S) similar to those in the cubic phase RhBi4.