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)

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-B u(3)tacn) with divalent transition metals has been investigated. These liga nds form a series of stable novel complexes with the triflate salts M-II(CF 3SO3)(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 sp ectra. The solid-state structures of four complexes have been determined by X-ray single-crystal crystallography. Crystallographic parameters are as f ollows. 2: C17H33F6FeN3O6S2, monoclinic, P2(1)/n, a 10.895(1) Angstrom, b=1 4.669(1) Angstrom, c 16.617(1) Angstrom, beta =101.37(1)degrees, Z 4. 3: C1 7H35CoF6N3O7S2, monoclinic, P2(1)/c, a 8.669(2) Angstrom, b = 25.538(3) Ang strom, c 12.4349(12) Angstrom, beta = 103.132(13)degrees, Z 4. 6: C24H45F6F eN5O6S2, monoclinic, P2(1)/c, a = 12.953(6) Angstrom, b = 16.780(6) Angstro m, c = 15.790(5) Angstrom, beta = 96.32(2)degrees, Z = 4. 7: C20H41F6FeN3O7 S2, 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 lea ds to complexes in which the metal ions are five-coordinate, while it's iso butyl homologue affords six-coordinate complexes. This difference in the st ereochemistries around the metal center is attributed to steric interaction s involving the bulky alkyl appendages of the macrocycles.