Structural Identification of the Factors That Prevent an Electronic Spin-State Crossover in Fe[(C₆H₅)B(3-Mepz)₃]₂ (pz = Pyrazolyl Ring)

Abstract

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 bond}C{triple bond, long}C{single bond}H, {single bond}C{triple bond, long}C{single bond}SiMe3, or {single bond}C{triple bond, long}C{single bond}C6H5] 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.

Department(s)

Chemistry

Keywords and Phrases

Iron(II); Magnetic Properties; Mössbauer Spectroscopy; N Ligands; Pyrazolylborates; Spin Crossover

International Standard Serial Number (ISSN)

0277-5387

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2006 Elsevier, All rights reserved.

Publication Date

01 Sep 2006

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