Homoleptic versus Heteroleptic Formation of Mononuclear Fe(II) Complexes with Tris-Imine Ligands

• Published in: Inorganic chemistry Vol. 55; no. 9; pp. 4110 - 4116
• Main Authors: Barrios, Leoní A, Bartual-Murgui, Carlos, Peyrecave-Lleixà, Eugènia, Le Guennic, Boris, Teat, Simon J, Roubeau, Olivier, Aromí, Guillem
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.05.2016; American Chemical Society (ACS)
• Subjects: Chemical Sciences; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.5b02058

We show a marked tendency of Fe­(II) to form heteroleptic [Fe­(L)­(L′)]­(ClO4)2 complexes from pairs of chelating tris-imine 3bpp, tpy, or 2bbp ligands. New synthetic avenues for spin crossover research become thus available, here illustrated with three new heteroleptic compounds with differing magnetic behaviors: [Fe­(H4L1)­(Cl-tpy)]­(ClO4)2·C3H6O (1), [Fe­(H2L3)­(Me3bpp)]­(ClO4)2·C3H6O (2), [Fe­(H4L1)­(2bbp)]­(ClO4)2·3C3H6O (3). Structural studies demonstrate that 1 is in the low-spin (LS) state up to 350 K, while complexes 2 and 3 are, by contrast, in the high-spin (HS) state down to 2 K, as corroborated through magnetic susceptibility measurements. Upon exposure to the atmosphere, the latter exhibits the release of three molecules of acetone per complex, turning into the solvent-free analogue [Fe­(H4L1)­(2bbp)]­(ClO4)2 (3a), through a single-crystal-to-single-crystal transformation. This guest extrusion process is accompanied by a spin switch, from HS to LS.