Binary compounds of rhodium and zinc: RhZn, Rh2Zn11, and RhZn13

The title compounds were prepared by reaction of the elements at elevated t emperatures in sealed silica tubes. Single crystals of RhZn and RhZn13 were obtained by slow cooling of samples with a high zinc content after dissolv ing the zinc-rich matrix in hydrochloric acid. Their crystal structures wer e determined from single-crystal X-ray diffractometer data. RhZn has a CsCl type structure: Pm(3) over barm, a = 300.9(1) pm. RhZn13 has a CoZn13 type structure: C2/m, a = 1090.8(2) pm, b = 753.7(2) pm, c = 512.7(1) pm, beta = 101.02(2)degrees. The structure of Rh2Zn11 is isotypic with Cu-5-Zn-8, th e gamma -brass structure. It was refined from X-ray diffractometer powder d ata: I(4) over bar 3m, a = 909.1(1) pm. In these structures all atoms have high coordination numbers. The structure of RhZn13 contains relatively larg e unoccupied voids. It is suggested that they accommodate nonbonding electr ons. Electrical conductivity measurements of Rh2Zn11 and RhZn13 indicate me tallic behavior, however, with an unexpectedly high resistivity for Rh2Zn11 . The expected Pauli paramagnetism of these compounds is overcompensated by the core diamagnetism, suggesting a low density of states at the Fermi lev el especially for Rh2Zn11. This correlates with the high electrical resisti vity of this compound.