Palladium, cadmium and mercury complexes of 2-((2-((2-hydroxyethyl)amino)ethyl)amino)cyclohexanol: Synthesis, structural, spectral and solution studies Mohammad Hakimi a,⇑ , Zahra Mardani a , Keyvan Moeini a , Fabian Mohr b , Manuel A. Fernandes c a Chemistry Department, Payame Noor University, 19395-4697 Tehran, Islamic Republic of Iran b Fachbereich C – Anorganische Chemie, Bergische Universität Wuppertal, 42119 Wuppertal, Germany c Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, Wits 2050, Johannesburg 2050, South Africa article info Article history: Received 18 June 2013 Accepted 9 August 2013 Available online 7 September 2013 Keywords: Palladium chloride Cadmium complex Mercury chloride Amino alcohol Cyclic voltammetery X-ray crystal structure abstract In this work, 2-((2-((2-hydroxyethyl)amino)ethyl)amino)cyclohexanol, HEAC, was prepared in solvent by the ring opening of cyclohexene oxide with 2-(2-amino-ethylamino)ethanol. Four complexes of HEAC, including [Pd(HEAC)Cl 2 ](1), [Cd 2 (HEAC) 2 (l-Br) 2 Br 2 ](2), [Cd(HEAC)(OAc) 2 ](3) and [Hg(HEAC)Cl 2 ](4), were prepared and identified by elemental analysis, FT-IR, Raman, 1 H NMR spectroscopy and single-crys- tal X-ray diffraction. Redox properties of HEAC before and after complexation were investigated in DMSO. In the crystal structure of HEAC, the two hydroxyl arms are trans to each other and the cyclohexane ring has a chair conformation with two C-chiral centers. Two new N-chiral centers are produced during the complexation process. In the crystal structure of 1, the palladium atom has a distorted square planar PdN 2 Cl 2 environment. X-ray analysis of 2 reveals a dimer structure containing two bromide bridges. Each cadmium atom in 2 is found to be in a CdN 2 OBr 3 distorted octahedral environment. The Cd 2 (l-Br) 2 moi- ety is placed on a plane and forms a parallelogram. The complex has a center of inversion at the center of the parallelogram and C i symmetry. In the crystal structure of 3, the cadmium atom with a CdN 2 O 5 envi- ronment has a distorted capped trigonal prismatic geometry. Complex 4 also has a distorted square-pyra- midal geometry (HgN 2 OCl 2 ). In the networks of HEAC and the complexes 1–4, intermolecular hydrogen bonds form different types of hydrogen bond motifs between adjacent molecules. Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. 1. Introduction Amino alcohol functional groups are often found in biologically active molecules, ligands, and chiral auxiliaries [1,2]. b-Amino alcohols and related derivatives are employed in various industrial fields, like in the synthesis of high polymers and plastics, the pro- duction of detergents, gas purifiers [3] and as cross-linking re- agents in the synthesis of precursor systems for superconductors [4,5]. These compounds play an important role in controlling a range of asymmetric transformations through forming five-mem- bered chelate rings with metals. This can occur through both the amino and hydroxyl groups of these compounds [6]. Halogeno complexes form various structures due to the bridg- ing ability of the halogen ions. For a study of the coordination aspects of metal-halide complexes with 2-((2-((2-hydroxy- ethyl)amino)ethyl)amino)cyclohexanol (HEAC, Fig. 1) and the ability of HEAC to coordinate by different coordination modes, pre- viously we reported its cadmium iodide and chloride complexes [1]. In this work, the preparation and characterization of the palladium chloride, [Pd(HEAC)Cl 2 ](1), cadmium bromide, [Cd 2 (HEAC) 2 (l-Br) 2 Br 2 ](2), cadmium acetate, [Cd(HEAC)(OAc) 2 ](3), and mercury chloride, [Hg(HEAC)Cl 2 ](4), complexes and also the structure of HEAC are described. Their spectral (IR, Raman, 1 H NMR), structural properties and solution experiments (cyclic vol- tammetery) are also presented. 2. Experimental 2.1. Materials and instrumentation All starting chemicals and solvents were reagent or analytical grade and used as received. A conventional three-electrode system for voltammetry was employed, with a PGSTAT101 and glassy car- bon working electrode. The infrared spectra of KBr pellets in the range 4000–400 cm À1 were recorded with a FT-IR 8400-Shimadzu spectrometer. The Raman spectra were recorded using a Nicolet Model 910 Fourier-transform spectrometer. 1 H and 13 C NMR spectra were recorded on a Bruker Aspect 3000 instrument; chem- ical shifts (d) are given in parts per million, relative to TMS as an 0277-5387/$ - see front matter Crown Copyright Ó 2013 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.poly.2013.08.065 ⇑ Corresponding author. Tel.: +98 511 8691090; fax: +98 511 8683001. E-mail address: mohakimi@yahoo.com (M. Hakimi). Polyhedron 67 (2014) 27–35 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly