  Citation: Aboud, M.F.A.; BinTaleb, A.M.; Yahia, H.B.; Albaid, A.; Albishi, S.; Arasheed, R.; Albinali, I.; Albaqi, F.; Anojaidi, K.; Alqahtani, F.; et al. Cyclohexylammonium Hexaisothiocyanatonickelate(II) Dihydrate as a Single-Source Precursor for High Surface Area Nickel Oxide and Sulfide Nanocrystals. Crystals 2022, 12, 315. https://doi.org/10.3390/cryst12030315 Academic Editors: Assem Barakat and Alexander S. Novikov Received: 29 December 2021 Accepted: 18 February 2022 Published: 23 February 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). crystals Article Cyclohexylammonium Hexaisothiocyanatonickelate(II) Dihydrate as a Single-Source Precursor for High Surface Area Nickel Oxide and Sulfide Nanocrystals Mohamed F. Aly Aboud 1,2,† , Abdulmalik M. BinTaleb 3,† , Hamdi Ben Yahia 4 , Abdelhamid Albaid 5 , Sultan Albishi 3 , Rasheed Arasheed 3 , Ibrahim Albinali 3 , Fahad Albaqi 3 , Khalid Anojaidi 3 , Fahad Alqahtani 6 , Asma M. Alenad 7 , Kamal Taha 8, * and Abdulaziz Bagabas 3, * 1 Sustainable Energy Technologies Center, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia; maboud@ksu.edu.sa 2 Mining, Metallurgical and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Nasr City, Cairo 11371, Egypt 3 National Petrochemical Technology Center (NPTC), Materials Science Research Institute (MSRI), King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Saudi Arabia; bintaleba@gmail.com (A.M.B.); s-albishi@outlook.sa (S.A.); rrisheed@kacst.edu.sa (R.A.); ialali@kacst.edu.sa (I.A.); f-albaqai@hotmail.com (F.A.); khalid.alnjaidi@gmail.com (K.A.) 4 Qatar Environment and Energy Research Institute (QEERI), Hamad Bin Khalifa University, Qatar Foundation, Doha P.O. Box 34110, Qatar; benyahia_hamdi@yahoo.fr 5 Department of Physics, Faculty of Science, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia; albaid1979@gmail.com 6 College of Sciences and Humanities, Prince Sattam Bin Abdulaziz University, P.O. Box 710, Aflaj 11912, Saudi Arabia; fahad.alqahtani@psau.edu.sa 7 Chemistry Department, College of Science, Jouf University, Sakaka P.O. Box 2014, Saudi Arabia; amenad@ju.edu.sa 8 Department of Chemistry & Industrial Chemistry, College of Applied and Industrial Sciences, University of Bahri, Khartoum 12217, Sudan * Correspondence: kamaltha60@gmail.com (K.T.); abagabas@hotmail.com (A.B.) † First co-authors. Abstract: Cyclohexylammonium hexaisothiocyanatonickelate(II) dihydrate, (C 6 H 11 NH 3 ) 4 [Ni(NCS) 6 ]·2H 2 O, was synthesized, for the first time, by a four-step method in a yield of 95%. The compound was fully characterized by elemental microanalysis, Fourier trans- form infrared (FTIR), ultraviolet-visible-near infrared (UV-Vis-NIR), and nuclear magnetic resonance (NMR) spectroscopy and thermogravimetry. A single crystal X-ray diffraction (SXRD) gave the mon- oclinic space group P2 1 /c with a = 15.8179 (5) Å, b = 10.6222 (3) Å, c = 13.8751 (4) Å, β = 109.362 (1) ◦ , V = 2199.45 (11) Å 3 , Z = 2 (T = 293 K) for this novel hybrid organic–inorganic compound. The title compound was employed as a single-source precursor for the synthesis of mesoporous, high surface area nickel oxide (53 Å; 452 m 2 /g) and nickel sulfide (46 Å; 220 m 2 /g) via pyrolysis under air at 550 ◦ C or helium atmosphere at 500 ◦ C, respectively. X-ray powder diffraction (XRPD) demonstrated the nanocrystalline nature of both NiO and NiS with an average crystallite size of 16 and 54 nm, respectively. Scanning electron microscope (SEM) indicated the formation of agglomerated, quasi- spherical particles of nickel oxide and agglomerated flake-like structures of nickel sulfide. The high surface area, porosity, and nanocrystallinity of both NiO and NiS, obtained via this approach, are promising for a wide spectrum of applications. Keywords: cyclohexylammonium; hexaisothiocyanatonickelate(II); pyrolysis; nickel oxide; nickel sulfide 1. Introduction For more than 100 years, the triatomic linear thiocyanate [SCN] − or isothiocyanate [NCS] − ligand has captured the attention of many researchers due to its low toxicity and Crystals 2022, 12, 315. https://doi.org/10.3390/cryst12030315 https://www.mdpi.com/journal/crystals