ELECTRONIC AND MAGNETIC-PROPERTIES OF ORGANOMETALLIC INTERCALATES OF ZIRCONIUM DICHALCOGENIDES

The organometallic sandwich complexes M(eta-C5H5)(2) (M = Co, Cr), Ti( eta-C5H5)(eta-C8H8), and M(eta-C(5)H(4)Me)(eta-C7H7) (M = Mo, W) have been intercalated into the lamellar host lattices ZrS2, ZrSSe, and ZrS e2. Variable-temperature electrical resistivity measurements have been performed on single-crystal samples of ZrS2{Co(eta-C5H5)(2)}(0.25), Z rS2{Ti(eta-C5H5)(eta-C8H8)}(0.2), and ZrS2{Cr(eta-C5H5)(2)}(0.2). The electrical resistivity measurements for ZrS2{(eta-C5H5)(2)}(0.25) and ZrS2{Ti(eta-C5H5)(eta-C8H8)}(0.2) indicate that they are metallic down to low temperature, exhibiting Limiting resistivities of 8.5 x 10(-3) and 5.4 x 10(-3) Ohm cm, respectively, at 4 K. In contrast, ZrS2{Cr(e ta-C5H5)(2)}(0.2) undergoes a metal-semiconductor transition below 25 K. Solid-state magnetic susceptibility measurements have been performe d on microcrystalline samples of ZrSxSe2-x{M(eta-C5H5)(2)}(y) (M = Co and Cr, x = 0, 1, and 2; y = 0.20-0.22), ZrS2{Ti(eta-C5H5)(eta-C8H8)}( 0.2) and ZrS2{M(eta-C(5)H(4)Me)(eta-C7H7)}(0.2) (M = Mo and W). The ma gnetic data for the metallic samples can be fitted to a function compr ising a temperature dependent component (chi(Curie-Weiss)) and a tempe rature-independent component (chi(Pauli)) due to contributions to the molar magnetic susceptibility from the guest ions and conduction elect rons respectively. The magnetic susceptibility data suggest that incom plete ionization of the organometallic guests occurs; there appears to be almost no correlation between the electrochemical reduction potent ial (E(1/2)) and the percentage of guests molecules which are ionized on intercalation.