Synthesis, structure, and magnetic properties of Sr39Co12N31

Single crystals of Sr39Co12N31 have been synthesized in liquid sodium from strontium, cobalt, and sodium azide at 1000 degrees C in sealed niobium amp oules. The structure was solved by single-crystal X-ray diffraction (I m (3 ) over bar m (No. 229), a = 14.910 Angstrom, Z = 2, R(F) = 6.7%, R-w (F) = 6.3%) with a disordered strontium position. Sr39Co12N31 has a unique struct ure type incorporating cobalt in linear coordination as isolated nitridomet alate ions. All cobalt atoms are crystallographically equivalent, existing with a formal mixed valence of Co-I and Co-II. The magnetic susceptibility demonstrates antiferromagnetic Curie-Weiss behavior with an effective momen t on cobalt of 4.99 mu(B), which lies in the range expected for that of hig h-spin ground states. (C) 1998 Academic Press.