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)2] (3c) as well as ferric 1:1 complexes [NEt4][Fe(bpza)Cl3] (4a) and [NEt4][Fe(bdmpza)Cl3] (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(III) high-spin complexes. Crystallographic information: 2c (C24H39ClFeN4O2·CH2Cl2·CH3CN) is triclinic, P , a = 12.171(16) (ANGSTROM), b = 12.851(14) (ANGSTROM), c = 13.390(13) (ANGSTROM), (alpha)= 98.61(9) °, (beta)= 113.51(11) , (gamma)= 108.10(5) , Z = 2; 3a (C8H7Fe0.5N4O2) is monoclinic, P21/n, a = 7.4784(19) (ANGSTROM), b = 7.604(3) (ANGSTROM), c = 16.196(4) (ANGSTROM), (beta)= 95.397(9) °, Z = 4; 3c (C24H39Fe0.5N4O2) is monoclinic, P21/n, a = 9.939(6) (ANGSTROM), b = 18.161(10) (ANGSTROM), c = 13.722(8) (ANGSTROM), (beta)= 97.67(7) °, 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) °, Z = 8.