Syntheses, Crystal Structures and Magnetic Properties of Cr(NCNH₂)₄Cl₂ and Mn(NCNH₂)₄Cl₂

Abstract

The two isotypic compounds Cr(NCNH 2 ) 4 Cl 2 and Mn(NCNH 2 ) 4 Cl 2 have been synthesized and characterized by X-ray diffraction. They crystallize in the cubic space group Im3m (Z = 6) with a = 12.643(2)Å for Cr(NCNH 2 ) 4 Cl 2 and a = 12.821(1)Å for Mn(NCNH 2 ) 4 Cl 2 . The divalent transition metal ions are octahedrally coordinated by four H 2 NCN molecules in equatorial and two chloride ions in axial positions. The magnetic susceptibility data of the four Curie-paramagnetic compounds Cr(NCNH 2 ) 4 Cl 2 , Mn(NCNH 2 ) 4 Cl 2 , Co(NCNH 2 ) 4 Cl 2 , and Ni(NCNH 2 ) 4 Cl 2 have been analyzed in greater detail, including many-body quantum theory.

Cr(pyrazine)2(OSO2CH3)2: A two-dimensional coordination polymer with an antiferromagnetic ground state

“…To explore this possible redox phenomenon in Cr(pyrazine)2(OSO2CH3)2, X-ray absorption spectroscopy (XAS) measurements were performed at the Cr K-edge to confirm the +II-oxidation state of the chromium sites suggested by the X-ray structure analysis and DFT calculations (vide supra). XAS data were also collected for two reference compounds, trans-[Cr II Cl2(NCNH2)4] (Cr(II)) [20] and trans-[Cr III (pyridine)4Cl2](ClO4)•1/4H2O (Cr(III)) [5] in order to make a direct comparison of the XAS signature for Cr(pyrazine)2(OSO2CH3)2 and chromium-based complexes which have a well-established oxidation state. Systematically, the experimental data show intense rising edge features, corresponding to 1s → 4p transitions.…”