Structural Identification of the Factors That Prevent an Electronic Spin-state Crossover in Fe[(C₆H₅)B(3-Mepz)₃]₂ (pz = Pyrazolyl Ring)
The synthesis, structural, magnetic, and Mössbauer spectral properties of Fe[(C6H5)B(3-Mepz)3]2 (2, pz = pyrazolyl ring) are reported. The single crystal X-ray structural results indicate that at both 294 and 90 K Fe[(C6H5)B(3-Mepz)3]2 (2) has a distorted octahedral iron(II) coordination environment with Fe-N bond distances that average ca. 2.18 Å, distances that clearly indicate the high-spin nature of the complex at these temperatures. Both the magnetic and Mössbauer spectral results indicate that Fe[(C6H5)B(3-Mepz)3]2 (2) remains high-spin down to 4 K. This result is surprising because the closely related Fe[(p-R-C6H4)B(3-Mepz)3]2 [R = I, single bondCtriple bond, longCsingle bondH, single bondCtriple bond, longCsingle bondSiMe3, or single bondCtriple bond, longCsingle bondC6H5] complexes do exhibit electronic spin-state changes on cooling. The absence of a spin-state crossover in Fe[(C6H5)B(3-Mepz)3]2 (2) is the result of its molecular structure in which the three pyrazolyl rings of each tridentate ligand are highly twisted away from an ideal C3v coordination symmetry, a twisting distortion that favors the high-spin form of the complex with longer Fe-N bond distances. © 2006 Elsevier Ltd. All rights reserved.
D. L. Reger et al., "Structural Identification of the Factors That Prevent an Electronic Spin-state Crossover in Fe[(C₆H₅)B(3-Mepz)₃]₂ (pz = Pyrazolyl Ring)," Polyhedron, Elsevier, Jan 2006.
The definitive version is available at http://dx.doi.org/10.1016/j.poly.2006.03.014
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© 2006 Elsevier, All rights reserved.