SPIN CROSSOVER IN IRON(II) COMPLEXES WITH TRIS(PYRAZOL-1-YL)METHANE AND [Ag(CN)2]- AND [Au(CN)2]- ANIONS

New coordination compounds of iron(II) with tris(pyrazol-1-yl)methane (HC(pz)(3)) containing dicyanoargentate and dicyanoaurate ions of the composition [Fe(HC(pz)(3))[Ag(CN)(2)](2)]center dot 2H(2)O (1 center dot 2H(2)O), [Fe(HC(pz)(3))[Au(CN)(2)](2)]center dot H2O (2 center dot H2O) are synthesized and studied. The compounds are analyzed by powder X-ray diffraction, electron (diffuse reflectance spectroscopy), infrared, Mossbauer spectroscopy, and static magnetic susceptibility. The data obtained enable the conclusion that in the complexes under study, the coordination polyhedron is formed by three nitrogen atoms of the tridentately-cyclically coordinated HC(pz)(3) ligand, two nitrogen atoms of the bidentate bridging [M(CN)(2)](-) anion, and the nitrogen (or carbon) atom of the monodentately coordinated anion. Coordination cores acting as premises for spin crossover (SCO) in them (FeN6 and FeCN5) are formed in both compounds. Crystal field splitting parameters are calculated for low- and high-spin forms of 1 center dot 2H(2)O and 2 center dot H2O complexes. Dependences mu(eff)(T) are studied in the range of 80-400 K for 1 and 2 complexes obtained by dehydration of 1 center dot 2H(2)O and 2 center dot H2O. (1)A(1) <-> T-5(2) SCO is found to occur in both complexes; in 1, a one-step transition is observed; in 2, the transition becomes two-step.