Coordination modes of polydentate ligands. 4. The crystal and molecular structure of an oxo-bridged iron(III) complex containing a pentadentate imino-alkoxy ligand

Abstract

In the presence of Fe 3+, template condensation of the fluorinated keto-alcohol CH 3C(O)CH 2C- (CF 3) 2OH with the triamine CH 3C(CH 2NH 2) 3 leads to two products: a fully condensed, imino-alkoxy, iron(III) complex, Fe{CH 3C[CH 2NC(CH 3)CH 2C(CF 3) 2O] 3}, and a partially condensed iron(III) complex, O{FeCH 3C[CH 2NC(CH 3)CH 2C(CF 3) 2O] 2(CH 2NH 2)} 2, in which two six-coordinate iron(III) centers are linked by an oxide ion. A complete crystal and molecular structure determination of the latter has been made. Crystals are monoclinic, space group C2/ c, a= 13.886(4); b=23.206(5); c=15.241(4) Å; β= 106.55(2)°; V=4708 Å 3; Z=4. Least-squares refinement on F of 322 variables using 2627 observations converged at a conventional agreement factor of 3.8%. The Fe to bridging oxide distance is 1.811(1) Å, the FeFe distance 3.468 Å, and the FeOFe angle 146.6(2)°. A comparison is made between this structure and those of natural hemerythrin systems.