Crystal structure of (1,4,7,10,13, 16-hexaoxacyclooctadecane- κ 6 O 6 )

C 28 H 53.5 KN 5.5 O 6 , monoclinic, Pc (no. 7), a = 18.7986(12) Å, b = 8.3431(6) Å, c = 22.4638(16) Å, β = 100.554(5) ° , V = 3463.6(4) Å 3 , Z = 4, R gt ( F ) = 0.0712, wR ref ( F 2 ) = 0.2226, T = 150 K.

The molecular structure is shown in the figure. Table 1 contains crystallographic data and Table 2 contains the list of the atoms including atomic coordinates and displacement parameters.

Source of material
The title compound was obtained as an unintended side product from a synthesis aiming at functionalized Zintl cluster compounds [5]. All reactions were performed under the exclusion of oxygen and moisture using standard Schlenk line and glove box techniques. Glyoxal (Merck), BBr 3 (Sigma Aldrich) and 2-methylanilin (Sigma Aldrich) were used without further purification. 1,4,7,10,13, 16-hexaoxacyclooctadecane (18-crown-6; Merck) was purified by sublimation. Bromo-1,3,2-diazaborolidine (DAB o−tol -Br) was prepared according to a published procedure [5,6]. K 4 Ge 9 was prepared by fusing stoichiometric amounts of the elements in stainless-steel tubes at 650°C. Liquid ammonia was dried over sodium metal for 2 h prior to condensing it onto the reaction mixture. K 4 Ge 9 (80 mg, 98.7 μmol, 1 equiv.), DAB o−tol -Br (32.5 mg, 98.7 μmol, 1 equiv.), and 18-crown-6 (47.0 mg, 177.7 μmol, 1.8 equiv.) were weighed into a Schlenk tube and liquid ammonia (2 mL) was condensed onto the reactants, causing the formation of a red solution. Yellow spherical crystals of the title compound were isolated from the reaction mixture after 9 months. An exact yield could not be determined due to the experimental setup.

Experimental details
A single crystal was selected under a microscope equipped with a light source using a cooling table [7]. Subsequently, the crystal was transferred under liquid nitrogen to the   ).     . For the data collection the crystal was cooled in a 150 K cold stream of dry nitrogen. The single crystal structure was determined by direct methods using the program SHELXS-97 [2]. Structure refinements were performed by full-matrix least-squares calculations against F 2 (SHELXL-2014) [3]. Non-hydrogen atoms were refined with anisotropic displacement parameters. The hydrogen atoms at N2 and N4 were located from the difference Fourier map and were refined with independent positional and isotropic displacement parameters. No similar strong residual electron densities could be detected at N1 and N3. Some hydrogen atoms of the ammonia molecules around N6, N7, N10, and N11 were localized from the difference Fourier map, the remaining ones were positioned in direction to close neighboured atoms where hydrogen bonds are probable. The methyl and ammonia H atoms were finally refined using a riding model with U iso set to 1.5 U eq (C) and U eq (N), respectively, all other H atoms with U iso set to 1.2 U eq (C) [3].

Comment
The title compound (1) [6]. Most probably, trace amounts of N1,N2-di(o-CH 3 C 6 H 4 )ethylene-1,2-diamine remained in the synthesized precursor DAB o−tol -Br, which were transferred into the reaction mixture in liquid ammonia by weighing in the precursor. Even though an exact formation mechanism for the generation of the amide cannot be determined, the generation of amides in liquid ammonia or ethylenediamine is an oftentimes described process [8][9][10][11].
The potassium cations are coordinated in equatorial positions by oxygen atoms of [18]crown-6 molecules and are located in the molecular plane. The mean interatomic distances K-O, C-O, and C-C were determined to 2.814, 1.431, and 1.507 Å, respectively. Additionally, ammonia molecules coordinate the potassium cations in axial positions. For K2, two NH 3 molecules are observed at distances of 2.852(9) Å (N8) and 2.871(9) Å (N9), forming an almost linear H 3 N-K-NH 3 unit with an angle of 168.6(3)°. K1 is coordinated by an NH 3 molecule at 2.851(8) Å, while on the opposite side of the molecule there are NH 3 molecules at a greater distance from the K + ion, which form hydrogen bonds to oxygen atoms of the crown ether molecule [13]. The longish anions are arranged with their major extension roughly along the crystallographic c (1a) or a (1b) axes and stacked in the b direction, respectively. The cation complexes and the solvent molecules are located in the channels parallel to b formed in this way.