Long-Range Ferromagnetic Ordering in Two-Dimensional Coordination Polymers Co[N(CN)2]2(L) [L ) Pyrazine Dioxide (pzdo) and 2-Methyl Pyrazine Dioxide (mpdo)] with Dual µ- and µ3-[N(CN)2] Bridges

Hao-Ling Sun,† Song Gao,*,† Bao-Qing Ma,† and Gang Su‡

College of Chemistry and Molecular Engineering, State Key Laboratory of Rare Earth Materials Chemistry and Applications, PKU-HKU Joint Laboratory on Rare Earth Materials and Bioinorganic Chemistry, Peking UniVersity, Beijing 100871, China, and Department of Physics, The Graduate School of the Chinese Academy of Sciences, P.O. Box 3908, Beijing 100039, China

Received February 23, 2003

Two novel coordination polymers of Co(II) with dicyanamide (dca) were obtained by the addition of ancillary ligands of pyrazine dioxide (pzdo) and 2-methyl pyrazine dioxide (mpdo) into the Co−dca binary system, respectively. Co[N(CN)2]2(pzdo) (1) crystallizes in the orthorhombic space group of Pnnm (No. 58) with a ) 9.4699(5) Å, b ) 14.9984(3) Å, c ) 7.4313(7) Å, and Z ) 4, while Co[N(CN)2]2(mpdo) (2) is in the monoclinic space group C2 (No. 5) with a ) 16.5391(4) Å, b ) 9.6065(2) Å, c ) 7.5001(2) Å, â ) 105.779(1)°, and Z ) 4. Both complexes contain similar two-dimensional triangular Co−dca layers, which offer rare examples of mixed 1,5-µ- and µ3-dca bridging coordination polymers with long-range ferromagnetic ordering below ca. 2.5 K.