The effect of the 3-trifluoromethyl substituent in polypyrazolylborato complexes on the iron(II) spin state; X-ray diffraction and absorption and Mössbauer studies

✍ Scribed by P Cecchi; M Berrettoni; M Giorgetti; G Gioia Lobbia; S Calogero; L Stievano

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 203 KB
• Volume: 318
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(01)00399-1

✦ Synopsis

A series of bis(polypyrazolylborato)iron(II) complexes (with Tp 3CF3 , Tp 4Me , Tp 4Br , and pzTp 4Me ) has been prepared and characterised by 57 Fe Mo ¨ssbauer spectroscopy. In addition, the Tp 3CF3 has been studied and compared with Tp 3CH3 by X-ray absorption investigation. The X-ray crystal structure of iron(II)bis(3-trifluoromethyl-1H-pyrazol-1-yl)borato has been resolved. In Fe(Tp 3CF3 ) 2 the coordination geometry around the Fe centre is distorted octahedral, with the Fe N bond distances in the range 2.219(3)-2.251(3) A , that are slightly longer than typical distances for high-spin iron(II) complexes. A close comparison of the Tp 3CF3 and Tp 3CH3 has revealed small but nonetheless significant differences as evidenced from low-temperature Mo ¨ssbauer studies and from X-ray absorption near-edge structure approach. At variance with Fe(Tp 3CHF3 ) 2 , the high spin state for Fe(Tp 3CF3 ) 2 is to be taken as the most stable one.