(Sr6N)[CoN2][CN2]2:: The first low-valency nitridometalate carbodiimide

The first nitridocobaltate carbodiimide (Sr6N)[CoN2][CN2]2 has been synthesized from the elements Sr, Co, and graphite powder and NaN3 (as a nitrogen source). The crystal. structure was determined from X-ray single-crystal 3 diffraction data as orthorhombic (space group P2(1)2(1)2, No. 18, a = 9.8807(6)angstrom, b = 14.6474(9)angstrom, c = 3.8569(3)angstrom, V= 558.2 angstrom(3), Z = 2, R-1 = 0.0265, wR(2) = 0.0383). (Sr6N)[CoN2][CN2](2) is the first low-valency 3d-transition nitridometalate containing additional [CN2](2-) groups. The crystal structure can be described as an array of rocksalt-like columns of Sr and N linked via common corners and connected by [N = C = N]2- and [(CoN2)-N-1](5-) units located within structural channels running along [0 0 1]. The magnetic susceptibility follows the Curie Weiss law with an effective moment of 3.26 mu(B) consistent with two unpaired spins (d(8), Co-1). The compound is a bad metallic conductor with a resistivity of order 1 m Omega(2) cm at 300 K. Vibrational spectroscopic data support the existence of carbodiimide [N = C = N](2-) species. The Co K-edge X-ray absorption spectra (XAS) of Ca-5[CoN2](2) and (Sr6N)[CoN2][CN2]2 confirm the presence of Cot within the complex anions. (c) 2007 NIMS and Elsevier Ltd. All rights reserved.