Structure and magnetic properties of Ca14MnP11

The compound Ca14MnP11 crystallizes in the Ca14AlSb11 structure type with the tetragonal space group I41/acd (Z=8) and lattice parameters of a=15.3255(7)A, c=20.7565(9) at 90K. The structure consists of MnP49- tetrahedron, P37- trimer, 4 P3- isolated anions and 14 Ca2+ cations. Similar to other compounds of this structure type containing phosphorous, the P37- trimer has a central P atom that is best modeled in the structure as being equally split between two sites. In addition, there is no additional distortion of the manganese-containing tetrahedron compared with the main group analog, Ca14GaP11, suggesting that the Mn oxidation state is Mn2+. Temperature-dependent magnetic susceptibility shows that the compound is paramagnetic over the entire temperature range measured (2-300K). The data can be fit with a modified Curie-Weiss law and provide an effective magnetic moment of 5.80 (2) B.M. with a Weiss constant of -2.13(2)K and χ0=-9(1)x1-5emu/mol. This moment is significantly higher than those measured for any of the Mn-containing analogs and is consistent with Mn2+. This result will be discussed in light of the electron counting scheme for Mn compounds of the Ca14AlSb11 structure-type