ELECTRON-DENSITY IN POTASSIUM TETRACHLOROPALLADATE (K2PDCL4) FROM SYNCHROTRON-RADIATION DATA

The difference electron density has been evaluated for potassium tetra chloropalladate, K2PdCl4, using synchrotron radiation at 0.7 and 0.9 a ngstrom at room temperature. A similar data set was measured with Mo K alpha radiation. The DELTArho maps for the synchrotron data sets are c onsistent, and agree approximately with the Mo Kalpha map away from th e Pd nucleus. There is marked depletion of electrons near the Pd core, and substantial movement of electron density near the structural cavi ties. The Pd-atom charge is approximately + 2, but the K-atom charge i s significantly negative. These charges result from transfer of electr on density from tightly packed to more open regions of the structure, and do not necessarily reflect atomic electronegativities. K2PdCl4, P4 /mmm, Z = 1, mu0.7 = 4.1784, mu0.9 = 8.6075 mm-1, F(000) = 152, T = 29 3 K, M(r) = 326.4, a = 7.0750 (5), c = 4.1158 (5) angstrom, V = 206.02 (4) angstrom3 , D(x) = 2.631 Mg m-3.