ASIAN JOURNAL OF CHEMISTRY ASIAN JOURNAL OF CHEMISTRY https://doi.org/10.14233/ajchem.2018.21014 INTRODUCTION An octahedral chromium(III) complexes with two triden- tate iminodiacetate (ida) or N-methyliminodiacetate (mida; C 5 H 7 NO 4 ) ligands can coordinate to a central metal ion as a tridentate ligand through one N atom and two O atoms. The bis(tridentate)chromate(III) complex with N-alkyliminodi- acetate ion can form three configurational isomers potentially (Fig. 1). u-fac s-fac O N O N O O O O O O N N Cr Cr R R R mer O N N O O O Cr R R R Fig. 1. Three possible geometrical isomers of [Cr(R-ida)2] - The ligand mida differs from iminodiacetate (ida) in the substitution of imino hydrogen with methyl group. This change in the structure has significant consequences in the geometry of bischromate(III) complexes with these ligands. Two facial Crystal Structure and Hirshfeld Surface Analysis of Potassium sym-fac-Bis(N-methyliminodiacetato)chromate(III) DOHYUN MOON 1 , KEON SANG RYOO 2 and JONG-HA CHOI 2,* 1 Pohang Accelerator Laboratory, POSTECH, Pohang 37673, Republic of Korea 2 Department of Chemistry, Andong National University, Andong 36729, Republic of Korea *Corresponding author: E-mail: jhchoi@anu.ac.kr Received: 31 August 2017; Accepted: 11 November 2017; Published online: 31 January 2018; AJC-18749 The structure of K[Cr(C5H7NO4)2] (C5H7NO4 is methyliminodiacetate; mida) was confirmed from synchrotron X-ray data at 173 K. The complex crystallized in the space group C2/c of the monoclinic system with four mononuclear formula units in a cell of dimensions a = 16.875(3), b = 6.3970(3), c = 13.784(3) Å and β = 113.81(3)°. The Cr(III) ion is located on a center of symmetry with one independent Cr–N bond length of 2.0740 (14) Å and two Cr–O bond lengths of 1.9547 (12) and 1.9661 (12) Å. The Cr(III) ion is coordinated by two N atoms and four O atoms of symmetrical-facial mida ligands, displaying a distorted octahedral geometry. Hirshfeld surface analysis with 2D fingerprint plots revealed that the O···H, H···H and O···K interactions are the main intermolecular interactions. The crystal structure is stabilized by the O···H, H···H and O···K interactions among potassium cation, H atoms and O atoms of carboxylate group from neighbouring mida groups. Keywords: Crystal structure, Synchrotron radiation, Potassium salt, Sym-facial configuration, Hirshfeld-surface analysis. Asian Journal of Chemistry; Vol. 30, No. 3 (2018), 585-588 configurations in cis (unsymmetrical-facial, u-fac) or trans- (symmetrical-facial, s-fac) geometry with respect to the two N atoms have been observed: for example K[Cr(ida)2]·3H2O [1] and Na[Cr(ida)2]·1.5H2O [2] are u-fac structures while Na[Cr(mida) 2] and [(NH4) 0.8K0.2][Cr(mida) 2] are s-fac structures [3,4]. The substituent R = i-C3H7 or tert-C4H9 also yielded s-fac configuration [5,6]. The structural analysis of (NH4)[Cr(pydc)2] shows that the two tridentate pyridine-2,6- dicarboxylate (pydc) dianions octahedrally coordinate to the Cr metal center through one N atom and two carboxylate O atoms in a trans meridional arrangement [7]. The trans meridional isomer was also found in the structure of Na[Fe(mida)2](NaClO4)2·3H2O [8]. A search of the Cambridge Structural Database (Version 5.38, May 2017 with 3 updates) [9] gave just two hits for a complex anion [Cr(C5H7NO4)2] - unit. The crystal structures of Na[Cr(mida)2] with three diffe- rent space groups have been reported and compared previously [3,10]. Recently, we have reported the crystal structure of [(NH4) 0.8K0.2][Cr(mida) 2] [4] . However, no structure of [Cr(mida)2] - with pure potassium cation has been deposited. Here we report the crystal structure of K[Cr(C5H7NO4)2], (Scheme-I) in order to clarify unambiguously the bonding mode of the two methyliminodiacetato ligands and the geo- metrical arrangement of neat potassium salt.