Citation: Malinowski, J.; Drze ˙ zd ˙ zon, J.; Jarzembska, K.N.; Kami ´ nski, R.; Rybi ´ nski, P.; Gawdzik, B.; Jacewicz, D. Catalytic Properties of Two Complexes of chromium(III) and cobalt(II) with Nitrilotriacetate, Dipicolinate, and 4-Acetylpyridine. Materials 2023, 16, 3308. https:// doi.org/10.3390/ma16093308 Academic Editors: Bogdan E. Cojocaru and Simona M. Coman Received: 2 March 2023 Revised: 20 April 2023 Accepted: 21 April 2023 Published: 23 April 2023 Copyright: © 2023 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/). materials Article Catalytic Properties of Two Complexes of chromium(III) and cobalt(II) with Nitrilotriacetate, Dipicolinate, and 4-Acetylpyridine Jacek Malinowski 1 , Joanna Drze ˙ zd˙ zon 1, * , Katarzyna N. Jarzembska 2 , Radoslaw Kami ´ nski 2 , Przemyslaw Rybi ´ nski 3 , Barbara Gawdzik 3 and Dagmara Jacewicz 1 1 Faculty of Chemistry, University of Gdansk (Gda´ nsk), Wita Stwosza 63, 80-308 Gdansk, Poland 2 Departmentof Chemistry, University of Warsaw, ˙ Zwirki iWigury 101, 02-089 Warsaw, Poland 3 Institute of Chemistry, Jan Kochanowski University, Uniwersytecka 7, 25-406 Kielce, Poland * Correspondence: joanna.drzezdzon@ug.edu.pl Abstract: In this paper, a synthesis of two innovative coordination compounds, based on chromium(III) and cobalt(II) ions with N,O-donor ligands (nitrilotriacetate, dipicolinate) and 4-acetylpyridine, is reported. The obtained metal-organic compounds were structurally characterized using the single- crystal X-ray diffraction (XRD) method. The well-defined chromium(III) and cobalt(II) complexes were used as precatalysts in the oligomerization reaction of 2-chloro-2-propen-1-ol and 2-propen-1-ol with methylaluminoxane (MMAO) as an activator. The products of the oligomerization reaction were subjected to full physicochemical characteristics, i.e., time-of-flight mass spectrometry (MALDI- TOF-MS), TGA, and differential scanning calorimetry (DSC) methods. The catalytic activity of the precatalysts in both reactions was calculated and compared with other catalysts known in the literature. Keywords: crystal structure; cobalt(II) and chromium(III) complexes; oligomerization; methylaluminoxane; 2-chloro-2-propen-1-ol 1. Introduction The most commonly used catalysts in the oligomerization of olefins are acids and transition metal coordination compounds. They are used in the industrial oligomerization processes of light olefins, which find applications in the production of fuels, lubricants, petrochemicals, and other chemicals [1–4]. Each catalyst produces or leads to the formation of an oligomer with a different microstructure and properties. The obtained materials may differ in thermal durability, for example [5–9]. For instance, nickel(II)-centre catalysts show the ability to carry out oligomerization reactions of linear butenes or propenes, which most often undergo chain dimerization reactions [10–16]. Precatalysts based on heavy-atom metal centers have been quite well studied and described in the last three decades. The structure of the precatalyst, the choice of activator or solvents, and the parameters for conducting the oligomerization process make it possible to obtain a product with a different structure or to finetune the catalytic activity of the precatalyst used [17–30]. Catalysts based on nickel or palladium cations are considered to have played an early role in the development of Ziegler–Natta catalysts. These catalysts are most often used in the initial stages of the oligomerization of olefins. The Shell Higher Olefin Process (SHOP), which yields linear alpha-olefins, uses a nickel catalyst that has phosphorus and oxygen donor atoms in its structure [31]. Metallocene and post-metallocene catalysts of early and further transition metals are built with a metal center and coordinated organic ligands. The most widely used ligands are compounds whose structure contains donor atoms such as P, O, N, and S. This is due to Materials 2023, 16, 3308. https://doi.org/10.3390/ma16093308 https://www.mdpi.com/journal/materials