Crystal structures and solution behavior of paramagnetic divalent transition metal complexes (Fe, Co) of the sterically encumbered tridentate macrocycles 1,4,7-R-3-1,4,7-triazacyclononane: Coordination numbers 5 (R = i-Pr) and 6 (R = i-Bu)

摘要

The coordination chemistry of the sterically hindered macrocyclic triamines, 1,4,7-R-3-1,4,7-triazacyclononane (R i-Pr, i-Pr(3)tacn, and R = i-Bu, i-Bu(3)tacn) with divalent transition metals has been investigated. These ligands form a series of stable novel complexes with the triflate salts M-II(CF3SO3)(2) (NI Fe, Co, or Zn) under anaerobic conditions. The complexes Fe(i-Pr(3)tacn)(CF3SO3)(2) (2), [Co(i-Pr(3)tacn)(SO3CF3)(H2O)] (CF3SO3) (3), [Co(i-Pr(3)tacn)(CH3CN)(2)](BPh4)(2) (4), Zn(i-PT(3)tacn)(CF3SO3)(2) (5), [Fe(i-Bu(3)tacn)(CH3CN)(2)(CF3SO3)](CF3SO3) (6), Fe(i-Bu(3)tacn)-(H2O)(CF3SO3)(2) (7), and Co(i-Bu(3)tacn)(CF3SO3)(2) (8) have been isolated. The behavior of these paramagnetic complexes in solution is explored by their 'H NMR spectra. The solid-state structures of four complexes have been determined by X-ray single-crystal crystallography. Crystallographic parameters are as follows. 2: C17H33F6FeN3O6S2, monoclinic, P2(1), a 10.895(1) Angstrom, b=14.669(1) Angstrom, c 16.617(1) Angstrom, beta =101.37(1)degrees, Z 4. 3: C17H35CoF6N3O7S2, monoclinic, P2(1)/c, a 8.669(2) Angstrom, b = 25.538(3) Angstrom, c 12.4349(12) Angstrom, beta = 103.132(13)degrees, Z 4. 6: C24H45F6FeN5O6S2, monoclinic, P2(1)/c, a = 12.953(6) Angstrom, b = 16.780(6) Angstrom, c = 15.790(5) Angstrom, beta = 96.32(2)degrees, Z = 4. 7: C20H41F6FeN3O7S2, monoclinic, C2/c, a 22.990(2) Angstrom, b = 15.768(2) Angstrom, c = 17.564(2) Angstrom, beta = 107.65(1)degrees, Z = 8. The ligand i-Pr(3)tacn leads to complexes in which the metal ions are five-coordinate, while it's isobutyl homologue affords six-coordinate complexes. This difference in the stereochemistries around the metal center is attributed to steric interactions involving the bulky alkyl appendages of the macrocycles. [References: 43]