Crystal structures of two (5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)iron(III) complexes

Abstract

tetraazacyclotetradecane)iron(III) chloride, [FeCl 2 (C 16 H 36 N 4 )]Cl or cis-[FeCl 2 (rac-HMC)]Cl (1), and dichlorido (5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)iron(III) tetrachloridoferrate, [FeCl 2 (C 16 H 36 N 4 )][FeCl 4 ] or trans-[FeCl 2 (meso-HMC)][FeCl 4 ] (2). Single-crystal X-ray diffraction studies revealed that both 1 and 2 adopt a pseudo-octahedral geometry, where the macrocycles adopt folded and planar geometries, respectively. The chloride ligands in 1 are cis to each other, while those in 2 have a trans configuration. The relevant bond angles in 1 deviate substantially from an ideal octahedral coordination geometry, with the angles between the cis substituents varying from 81.55 (5) to 107.56 (4) , and those between the trans-ligating atoms varying from 157.76 (8) to 170.88 (3) . In contrast, 2 adopts a less strained configuration, in which the N-Fe-N angles vary from 84.61 (8) to 95.39 (8) and the N-Fe-Cl angles vary from 86.02 (5) to 93.98 (5) .

Geometric isomers of dichloridoiron(III) complexes of CTMC (5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradecane)

“…The previously reported data for cis/trans-[Fe III (cyclam)-Cl 2 ] + and cis/trans-[Fe III (HMC)Cl 2 ] + are useful for the discussion pertaining to planar versus folded macrocycles (Clendening et al, 2019;Guilard et al, 1997). As with iron-CTMC, the Fe-Cl bond lengths of these Fe III complexes remain similar to one another regardless of a cis or trans nature.…”

“…The similarity of the hydrogen-bonding network among structural analogues extends to the cases of 2 (Pbcn), cis-[Fe III (HMC)Cl 2 ]Cl (Fdd2), and cis-[Fe III (cyclam)Cl 2 ]Cl (P2 1 /c) (Clendening et al, 2019;Guilard et al, 1997). As with 1b, neither of the chloride ligands participates in hydrogen bonding, nor do any of the cationic moieties hydrogen bond with each other.…”

“…The packing in 1a is strikingly similar to trans-[Fe III -(HMC)Cl 2 ]FeCl 4 (Clendening et al, 2019) and trans-[Fe III -(cyclam)Cl 2 ]FeCl 4 (Guilard et al, 1997), despite the differences in space group (C2/c, P2 1 /c, and P2 1 /n, respectively). The cationic units in all cases pack in a series of columns (see Fig.…”

“…It is further possible to compare the structural parameters as the number of methyl groups is systematically varied within either the cis or trans series. The averaged Fe-N bond lengths of cis-[Fe III (HMC)Cl 2 ]Cl (ca 2.21 A ˚) appears longer than those of 2 and cis-[Fe III (cyclam)Cl 2 ]Cl (both ca 2.18 A ˚) (Clendening et al, 2019;Guilard et al, 1997), which is likely due to the steric bulk of the two methyl groups at the same position of the macrocycle (e.g. 5,5 and 12,12), which forces at least one methyl group to be axially oriented.…”

Mono‐ and Bis‐Alkynyl Iron Complexes Supported by a “Softened” Tetraaza Macrocycle

“…This unsaturation results in FeÀ N distances (1.903(5)-1.936(4) Å) similar to those reported for Fe(TIM) complexes (TIM = 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene), [26,27] but significantly shorter than those in the tetraamine-type complexes, such as [Fe III (meso-HMC)Cl 2 ]FeCl 4 (ca. 2.05 Å) [28] and [Fe III (cyclam)(C 2 Si i Pr 3 ) 2 ]CF 3 SO 3 (ca. 2.01 Å).…”