SYNTHESIS, CRYSTAL-STRUCTURE, AND PHYSICAL-PROPERTIES OF KNA2[NIO2] AND K-3[NIO2] CONTAINING LINEAR [NIO2](3-) ANIONS

The synthesis and the crystal structure refinement for the superstruct ure of KNa2[NiO2] are reported (orthorhombic, Cmca, Z = 8, a = 6.261(3 ) Angstrom, b = 10.474(3) Angstrom, 12.472(7) Angstrom). It is compare d with the subcell, described recently. EPR measurements of powder and single crystal samples of K-3[NiO2] and KNa2[NiO2] are presented, and confirm a (2) Sigma(g) ground state for the ''Linear'' [NiO2](3-) com plexes in these compounds. Absorption spectra have been measured betwe en 4500 and 20000 cm(-1) For the first time both d-d transitions of a ''Linear'' d(9)-system are resolved, and the energies of these have be en analyzed using the angular overlap model. The near-infrared bands o f K-3[NiO2] exhibit fine structure at low temperature, allowing compar ison of the Ni-O symmetric stretching frequencies and bond lengths in the ground and excited states.