Solid pure osmium phthalocyanine, as obtained from its adduct [PcOs(py)(2)], is an air-stable solid amorphous material. Its structure has been examined by the wide-angle X-ray scattering (WAXS) technique. Experimental data are best fitted by assuming the molecule to consist of a dimeric unit, (PcOs)(2), held together by a direct metal-metal linkage. The short Os-Os distance (2.38(1) Angstrom) is consistent with the presence of a double bond between the two Os(II) atoms. Each Pc skeleton has a domed conformation with displacement of the respective Os atom from the plane of the four coordinating nitrogen atoms (0.40 Angstrom) toward the other Os atom. The solid-state structure consists of disordered couples of parallel chains of (PcOs)(2). On average, six dimeric units are aligned along the stacking direction within each chain. The relative orientation of the two intradimer Pc units is 30 degrees, eclipsing occurring for the interdimer adjacent Pc units along the chain. Magnetic susceptibility measurements in the temperature range 5-300 K indicate a strong spin-spin coupling for the two metal centers in the dimer and suggest an electronic energy level sequence sigma(2)pi(4)delta(2)delta(*2)pi(*2) and a nonmagnetic ground state for the complex, Room-temperature electrical conductivity measurements show a sigma(RT) value of 1 x 10(-5) Omega(-1) cm(-1).