A MOSSBAUER 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(III)BIS[HYDRIDOTRIS (1H-PYRAZOL-1-YL)BORATE] TETRAFLUOROBORATE

A series of iron(II) or iron(III) complexes of type FeL(2) or [FeL(2)](+) X(-)(X = BF4 or BPh(4)) with L = hydridotris(1H-pyrazol-1-yl)borate(L(0)), tetrakis(1H-pyrazol-1-yl)borate(L(0)'), hydridotris(3-methyl-1H-pyrazol-1-yl)borate(L(1)), hydridotris(3,5-dimethyl-1H-pyrazol-1-yl)b orate(L(2)), hydridotris(4-chloro-3,5-dimethyl-1H-pyrazol-1-yl)borate(L(2Cl)), hydridotris(3,4,5-trimethyl-1H-pyrazol-1-yl)borate(L(3)), hydridotris(1,2,4-1H-triazol-1-yl)borate((tz)) and hydridotris(3a,7a-benzo-1,2,3-1H-triazol-1-yl)borate(L(btz)) has been prepared. The series has been characterized mainly by the Fe-57 Mossbauer effect. The Xray crystal structures of iron(II)bis[hydridotris(3-methyl-1H-pyrazol-1-yl)borate] (3) and iron(III)bis[hydridotris(1H-pyrazol-1-yl)borate] tetrafluoroborate (9) have been resolved. Discrete units with octahedral (FeN6)-N-II or Fe-III sites are present in each. The Fe-N bond length ranges from 2.197(4) to 2.215(4) Angstrom in 3 and from 1.948(6) to 1.964(6) Angstrom in 9. The bond angle ranges from 86.4(2)degrees to 93.7(2)degrees in 3 and from 88.3(4)degrees to 90.9(5)degrees in 9.