Bis(pyrazol-1-yl)acetates as tripodal heteroscorpionate Ligands in iron chemistry:: Syntheses and structures of Iron(II) and Iron(III) complexes with bpza, bdmpza, and bdtbpza ligands

The molecular structure of the previously reported species [Fe(bdtbpza)Cl] has been revealed by X-ray structure determination to be a ferrous dimer [Fe(bdtbpza)Cl]2 (2c) [bdtbpza = bis(3,5-di-tert-butylpyrazol-1-yl) acetate]. The syntheses of ferrous 2:1 complexes [Fe(bpza)2] (3a) and [Fe(bdtbpza)21 (3c) as well as ferric 1:1 complexes [NEt4][Fe(bpza)Cl-3] (4a) and [NEt4][Fe(bdmpza)Cl-3] (4b) [bpza = bis(pyrazol-1-yl)acetate, bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] are reported. Complexes 3a, previously reported [Fe(bdmpza)(2)](3b), and 3c are high-spin. No spin crossover to the low-spin state was observed in the temperature range of 5-350 K. 4a and 4b are synthesized in one step and in high yield from [NEt4](2)[Cl3FeOFeCl3]. 4a and 4b are iron(Ill) high-spin complexes. Crystallographic information: 2c (C24H39ClFeN4O2.CH2Cl2.CH3CN) is triclinic, 1:1, a = 12.171(16) Angstrom ,b = 12,851(14) Angstrom, c = 13.390(13) Angstrom, alpha = 98.61(9)degrees, beta = 113.51(11)degrees, gamma = 108.10(5)degrees, Z = 2; 3a (C8H7Fe0.5N4O2) is monoclinic, P2(1)/n, a = 7.4784(19) Angstrom, b = 7.604(3)Angstrom, c = 16.196(4) Angstrom, beta = 95.397(9)degrees, Z = 4; 3c (C24H39Fe0.5N4O2) is monoclinic, P2(1)/n, a = 9,939(6) Angstrom, b = 18.161(10)Angstrom, c = 13.722(8) Angstrom, p = 97.67(7)degrees, Z = 4; 4b (C20H35Cl3FeN5O2) is monoclinic, C2/c, a = 30,45(6) Angstrom, b = 12.33(2) Angstrom, c = 16.17(3) Angstrom, beta = 118.47(5)degrees, Z = 8.