Synthesis, structure, and magnetic properties of Co2([N(CN)2]4bpym).H2O and M([N(CN)2]2bpym).H2O (M = Mn, Fe, Co; bpym = 2,2'-bipyrimidine).
Co2([N(CN)2]4bpym).H2O (1) and M([N(CN)2]2bpym).H2O [M = Mn (2a), Fe (2b), Co (2c); bpym = 2,2'-bipyrimidine] have been synthesized and characterized structurally and magnetically. All of the compounds crystallize in the orthorhombic space group Pnma. The unit cell parameters for 1 are a = 16.1684(5) A, b = 12.9860(3) A, c = 10.4207(3) A, and Z = 4. Compound 1 is a 2-D layered structure with water intercalated between sheets. The sheets are composed of ...M-[NCNCN]2-M-bpym-M-[NCNCN]2-M... chains, which are linked together by dicyanamides. 2a-c are isomorphic with the unit cell parameters a = 17.5112(4) A, b = 11.9955(4) A, c = 7.4684(2) A for 2a, a = 17.5814(7) A, b = 11.9453(5) A, c = 7.3292(3) A for 2b, a = 17.8642(2) A, b = 11.9216(2) A, c = 7.2860(2) A for 2c, and Z = 4 for all. They crystallize as chains containing metal centers coordinated to two bridging dicyanamides, one terminal dicyanamide, one terminal chelating bpym, and one water molecule. 2a-c are the first examples of compounds containing terminal and mu-bound dicyanamides in the same structure. The broad maximum in the magnetic susceptibility of 1 could not be fit to any known dimer models. However, the high-temperature data were fit to the Curie-Weiss expression with g = 2.86 and theta = -42 K. 2a-c could best be modeled as uniform 1-D chains with g = 2.04, theta = -0.76, and J/kB = -0.15 K for 2a, g = 2.34, theta = -7.6, and J/kB = -0.42 K for 2b, and g = 2.58, theta = -5.4, and J/kB = -1.42 K for 2c. Because of small exchange coupling throughout the extended networks, no long-range magnetic ordering was observed.
Marshall
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Department of Chemistry, University of Utah, 315 S. 1400 E. RM 2124, Salt Lake City, Utah 84112-0850, USA.
Incarvito
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Manson
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Rheingold
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Miller
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