A Mössbauer study of some iron(II) and iron(III) poly(pyrazolyl)borates. The x-ray crystal structures of iron(II)bis[hydridotris(3-methyl-1H-pyrazol-1-yl)borate] and iron(II)bis[hydridotris(1H-pyrazol-1-yl)borate] tetrafluoroborate

Dramatic Remote Substitutent Effects on the Electronic Spin State of Bis(scorpionate) Iron(II) Complexes

“…In the solid state, the prototypical purple bis[hydrotris(pyrazolyl)borato]iron(II) derivative, [Fe{HB(pz) 3 } 2 ] (pz=1‐pyrazolyl; Scheme , A ), is LS at room temperature and undergoes a SCO transition to the colorless HS state above approximately 420 K 9. In contrast, its colorless counterpart, bearing a methyl group at the 3‐position of the pyrazolyl ring, [Fe{HB(3‐Mepz) 3 } 2 ] (Scheme , B ), is HS at room temperature and undergoes a spin conversion into the purple LS state on cooling to 4.2 K 10. 11 This behavior is also detected in iron(II) species having a fourth substituent placed on the central boron, [Fe{R′B(pz) 3 } 2 ] (Scheme , C ),12, 13a,b which are purple LS complexes, whereas the 3‐methylated analogues, [Fe{R′B(3‐Mepz) 3 } 2 ] (Scheme , D ),13, 14 are colorless HS species at room temperature.…”

Crystal structure of bis{(3,5-dimethylpyrazol-1-yl)dihydro[3-(pyridin-2-yl)pyrazol-1-yl]borato}iron(II)

“…Furthermore, numerous crystal structures of iron complexes based on the tripodal hydrotris(pyrazol-1-yl)borate ligand with different modifications of the pyrazole unit (Oliver et al, 1980;Calogero et al, 1994;Rheingold et al, 1997;Cecchi et al, 2001;Reger et al, 2006;Ni et al, 2011;Salmon et al, 2009) and/ or another fourth substituent in place of the hydrogen atom (Sohrin et al, 1995;Reger et al, 2005a,b) or triazole (Janiak, 1994) have been reported in the literature.…”

Bis[hydrotris(1-pyrazolyl)borato-κ3N,N′,N′′]iron(III) tetrachloroferrate(III) acetonitrile solvate

“…Atom Fe1 in the [Fe(HBpz 3 ) 2 ] + cation is coordinated in an octahedral geometry by six pyrazolyl N atoms from two HBpz 3 À ligands. The Fe-N bond lengths of 1.943 (3)-1.950 (3) Å are similar to those found in tris{bis[hydrotris-(1-pyrazolyl)borato-3 N 2 ,N 2 0 ,N 2 00 ]iron(III)} hexaisothio-cyanatoiron(III) [Fe-N = 1.941 (2)-1.953 (2) Å ; Wang et al, 2004], bis[hydridotris(1H-pyrazol-1-yl)borato]iron(III) tetrafluoroborate [Fe-N = 1.948 (6)-1.964 (6) Å ; Calogero et al, 1994], and bis [hydrogentris(pyrazolyl) Cho et al, 1992]. The geometry about atom Fe2 in the FeCl 4…”