
TY  - JOUR
A1  - Childs, Bradley J. 
A1  - Craig, Donald C. 
A1  - Scudder, Marcia L. 
A1  - Goodwin, Harold A. 
T1  - Coordination of the Strong Field Terimine System 6-Triazol-3-yl-2,2&#8242;-bipyridine and Substituted Derivatives. Electronic and Structural Properties of Bis(ligand)iron(II) Complexes
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1998
VL  - 51
IS  - 10
SP  - 895
EP  - 906
KW  - 
UR  - https://doi.org/10.1071/C97202 
N2  - A terminal pyridine ring in terpyridine has been replaced by a triazole or substituted triazole moiety to give the tridentates 6-(1,2,4-triazol-3-yl)-2,2&acute;-bipyridine, 6-(1-methyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine, 6-(5-methyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine and 6-(1,5-dimethyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine. The effects of coordination of these on the electronic and structural properties of the &#91;FeN6&#93;2+ species are considered. The primary effect is a reduction in the ligand field but salts of the &#91;FeN6&#93;2+ derivatives are essentially low spin (singlet ground state) at room temperature. A small and temperature-dependent population of quintet state species is indicated by M&ouml;ssbauer spectra but in no instance is a complete singlet &rarr; quintet transition observed up to 383 K. The electronic spectra of the &#91;FeN6&#93;2+ species are similar to that of &#91;Fe(trpy)2&#93;2+ but the energy of the charge-transfer transition is higher, indicating less effective metal ion &rarr; donor &#960;-interaction than in the terpyridine complex. Consistent with this, the M&ouml;ssbauer isomer-shift values are greater than for &#91;Fe(trpy)2&#93;2+ and the E&frac12; values for the &#91;FeN6&#93;3+ /&#91;FeN6&#93;2+ couples are less positive than for &#91;Fe(trpy)2&#93;2+. Structural data reveal average Fe&#8211;N distances normal for low-spin iron(II) but with greater distortion of the coordination environment than in &#91;Fe(trpy)2&#93;2+. When present, the &#62;NH group of the triazole moiety is hydrogen-bonded to solvate water and the anion in the hydrated tetrafluoroborate salts. Bis(6-(1,2,4-triazol-3-yl)-2,2&acute;-bipyridine)iron(II) tetrafluoroborate tetrahydrate: monoclinic, space group P21/c, a 15&#183;917(7), b 18&#183;432(5), c 10&#183;845(5) &#197;, &#946; 94&#183;36(2)&#176;, Z 4; bis(6-(1-methyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine)iron(II) tetrafluoroborate: triclinic, space group P&#8722;1, a 11&#183;68(1), b 11&#183;96(2), c 12&#183;46(2) &#197;, &#945; 82&#183;93(8), &#946; 72&#183;30(9), &#947; 68&#183;49(10)&#176;, Z 2; bis(6-(5-methyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine)iron(II) tetrafluoroborate monohydrate: monoclinic, space group P21/c, a 10&#183;715(4), b 25&#183;818(5), c 11&#183;039(4) &#197;, &#946; 90&#183;08(2)&#176;, Z 4; bis(6-(1,5-dimethyl-1,2,4-triazol-3-yl)-2,2&acute;-bipyridine)iron(II) triflate tetrahydrate: orthorhombic, space group P bcn; a 20&#183;654(6), b 11&#183;618(3), c 16&#183;080(6) &#197;, Z 4. 
ER  -

