The ESR spectrum and structure of the mixed alkali metal cluster Na2K5 prepared using a rotating cryostat

The ESR spectrum of the mixed alkali metal cluster, Na2K5, in an adamantane matrix prepared using a rotating cryostat has been observed. Its isotropic ESR parameters are g = 1.996, a(2Na) = 12.9 mT and a(5K) ≈ 0.035 mT, indicating a SOMO with most of the unpaired spin density (82%) in the 3s orbitals of two sodium atoms. Like its congeners, Na7, K7 and Li7, the mixed cluster has a pentagonal bipyramid structure (D5h symmetry) with a 2A″2 ground state. The sodium atoms occupy the two apical positions and the five potassium atoms lie in the pentagonal basal plane.