Crystal structure of bis(3,5-dichloro-2-hydroxybenzyl)(2-methoxyethyl)amine

The title compound was prepared via a modified Mannich reaction between 2-methoxyethylamine, 2,4-dichlorophenol, and aqueous formaldehyde. The resulting amine bis(phenol) provides an interesting comparison to related species as a result of the electron-withdrawing substituents on the phenol rings, in combination with similar steric parameters.


Chemical context
Complexes of early transition-and rare-earth metals featuring diaminebis(phenols) have been employed as efficient catalysts for the polymerization of olefins and cyclic esters (Tshuva et al., 2000;Carpentier et al., 2015), while those of late transition metals have been shown to be effective at promoting crosscoupling (Hasan et al., 2011;Qian et al., 2011;Reckling et al., 2011).Several reports have noted that the coordination mode and donor-atom identity play an important role in the activity of the resulting complexes (Tshuva et al., 2001;Qian et al., 2011;Chard et al., 2014).We have previously observed both 2 and 3 coordination modes for Pd II complexes of related aminebis(phenols), in which steric parameters of the phenolate moiety played a significant role in the coordination behavior (Graziano, Collins et al., 2019;Graziano, Wile et al., 2019).
Diaminebis(phonols) may be readily prepared via a Mannich reaction (Tshuva et al., 2000(Tshuva et al., , 2001;;Kasting et al., 2015), and the ligand framework may be modified by altering the steric or electronic parameters of the commercially available reaction components.Both bridging and pendant diamine variants are known, depending on whether the ligand precursor is prepared using an N,N-or N,N 0 -disubstituted amine.Prior reports of Fe II complexes supported by halogenated aminebis(phenols) bearing an alkyl ether donor group suggest poorer catalytic activity when compared with ligands bearing bulky alkyl-substituted phenols (Hasan et al., 2011;Reckling et al., 2011).However, it is speculated that the inferior catalytic activity is related to the air sensitivity of these Fe complexes, and potential catalyst decomposition pathways under the conditions employed for this Kumada coupling.Based on these reports and our interest in extending the range of aminebis(phenols) suitable for use as ligands, we prepared the title compound 1 and obtained single crystals suitable for X-ray diffraction studies.It was speculated that a direct comparison of the metrical parameters for 1 with those of related aminebis(phenols) with pendant ether groups would provide insight into the choice of halogenated phenols in the design of this ligand, for use in combination with late transition metals.
Compound 1 is chemically similar to the related ligands featuring alkyl substituents in place of the Cl substituents in 1.A comparison of bond lengths and angles for compound 1 and CAKDUP (Hasan et al., 2011), ZAVTEX (Dean et al., 2012), SOJBIE and SOJBUQ (Chapurina et al., 2014) is presented in Table 2. Despite the differences in space group, all compounds exhibit similar metrical parameters.The most notable differences between these structures are the shorter C-O phenol bond lengths for compound 1 [1.354 (1) and 1.346 (2) A ˚], consistent with the electron-withdrawing effect of the Cl substituents on the phenol rings.In contrast, compounds containing electron-donating alkyl substituents exhibit slightly longer C-O phenol bond lengths.Bond lengths for other moieties are more similar between 1 and these previously reported structures.The sum of C-N-C bond angles and the C-O-C bond angles indicate a similar electronic environment for the amine and ether donors of all compounds.This supports the hypothesis that compound 1 would have similar steric parameters to closely related ligands, but function as a more electrophilic donor.

Synthesis and crystallization
Compound 1 was prepared using a method analogous to that reported for related compounds (Graziano, Collins et al., 2019;Reckling et al., 2011).This reaction scheme is shown in Fig. 3. 2,4-Dichlorophenol (1.957 g, 12.0 mmol, 2 eq.) and a 37 wt.% aqueous solution of formaldehyde (0.974 g, 12.0 mmol, 2 eq.) were added to a 20 mL scintillation vial containing 5.0 mL of methanol and a PTFE-coated magnetic stir bar.2-Methoxyethylamine (0.521 mL, 6.00 mmol, 1 eq.) was added, and the vial was immediately capped and placed in an aluminum heating block maintained at 343 K.The clear colorless solution turned bright yellow within 1 h of heating, and maintained this appearance for 18 h, at which time the vial was removed from the heating block.The reaction mixture was poured into cold water (20 mL), and extracted with ethyl acetate (3 Â 20 mL).The organic layers were combined, dried over MgSO 4 , and concentrated in vacuo to yield a yellow oil.The product was purified using an automated column chromatography system with an ethyl acetate/hexanes gradient (0% EtOAc hold 1 min !20% EtOAc in 2 min, hold 4 min !100% EtOAc in 4 min, hold 2 min).The desired product was isolated as a yellow oil (0.594 g, 1.40 mmol, 23%, R f = 0.40 in 40% EtOAc) that generated single crystals suitable for X-ray diffraction studies upon standing.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. Atoms H1 and H2 were located in difference-Fourier maps and freely refined.All other hydrogen atoms were placed at calculated positions (aromatic: 0.93 A ˚, methylene: 0.97 A ˚, methyl: 0.96 A ˚) using suitable HFIX commands and refined as riding with U iso (H) = 1.2-1.5Ueq (C).The methyl group was refined as an idealized rotating group.Cl2 was modeled as a two-component disorder with partial occupancies of 0.49 (3) and 0.51 (3).The pendant ether group was modeled as a two-component disorder with research communications Figure 3 Reaction scheme.

Figure 2
Depiction of the centrosymmetric dimer formed as a result of hydrogen bonding.See Table 1 for symmetry codes.partial occupancies of 0.867 (3) and 0.133 (3).Atomic displacement parameters were restrained using SIMU with a sigma of 0.01 for internal and 0.02 for terminal atoms.The atoms within the disordered group were restrained to have similar bond distances.Cl2 was modeled as a two-component disorder with partial occupancies of 0.52 (4) and 0.48 (4).1.3-ac4 (Dolomanov et al., 2009); software used to prepare material for publication: Olex2 1.3-ac4 (Dolomanov et al., 2009), PLATON (Spek, 2020).

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Table 3
Experimental details.