Iron(III) chelates with hexadentate ligands from triethylenetetramine and .beta.-diketones or salicylaldehyde. Spin state dependent crystal and molecular structures of [Fe(acac)2trien]PF6(S = 5/2), [Fe(acacCl)2trien]PF6(S = 5/2), [Fe(sal)2trien]Cl.2H2O(S = 1/2), and [Fe(sal)2trien]NO3.H2O(S = 1/2)