Rev Inorg Chem 2020; 40(1): 1–45 Muhammad Sohail, Muhammad Zeshan Ashraf, Raziya Nadeem, Shamsa Bibi, Rabia Rehman, Amanullah and Muhammad Adnan Iqbal* Techniques in the synthesis of organometallic compounds of tungsten https://doi.org/10.1515/revic-2019-0013 Received August 23, 2019; accepted November 4, 2019; previously published online December 19, 2019 Abstract: Tungsten is an elegant substance, and its com- pounds have great significance because of their extensive range of applications in diverse fields such as in gas sen- sors, photocatalysis, lithium ion batteries, H 2 produc- tion, electrochromic devices, dyed sensitized solar cells, microchip technology, and liquid crystal displays. Tung- sten compounds exhibit a more efficient catalytic behav- ior, and tungsten-dependent enzymes generally catalyze the transfer of an oxygen atom to or from a physiological donor/acceptor with the metal center. Furthermore, tung- sten has an n-type semiconductor band gap. Tungsten forms complexes by reacting with several elements such as H, C, N, O, and P as well as other numerous inorganic elements. Interestingly, all tungsten reactions occur at ambient temperature, usually with tetrahydrofuran and dichloromethane under vacuum. Tungsten has extraordi- narily high-temperature properties, making it very useful for X-ray production and heating elements in furnaces. Tungsten coordinates with diverse nonmetallic elements and ligands and produces interesting compounds. This article describes an overview of the synthesis of various organometallic compounds of tungsten. Keywords: organometallic compounds; synthesis; tech- niques; tungsten compounds. Dedicated to: This article is dedicated to the memory of Miss Saba Mushtaq (MPhil student at the corresponding author’s research laboratory), who died of colon cancer at a young age. Introduction Tungsten was discovered in 1783 by two Spanish brothers, Juan José and Fausto Elhuyar, both chemists, in samples of a mineral called wolframite (FeMn)WO 2 . Today, tungsten is obtained from wolframite and scheelite (CaWO 4 ) using the same basic method developed by the Elhuyar broth- ers. Tungsten ores are crushed, cleaned, and treated with alkalis to form tungsten trioxide (WO 3 ). Tungsten trioxide is then heated with carbon or hydrogen gas, forming tung- sten metal and carbon dioxide (CO 2 ) or tungsten metal and water vapor (H 2 O) (Leffler et al. 2015, Habashi 2017). Tungsten was selected in 2002 by the Centers for Infec- tion Control and the National Center for Environmental Health (NCEH) for the prevention of carcinogenesis and toxicology (Lemus and Venezia 2015). Tungsten in the air can be verified by flame atomic absorption (finding limit: 0.050 mg/m 3 ). Inductively coupled plasma atomic emission spectrometry can be helpful for the Environmental Protec- tion Agency, equivalent air depth detection limit of 1.0 mg/l (range: 5–2000 μg/m 3 ). The majority of tungsten is used in cemented carbides (WC-CO). Novel uses of tungsten com- pounds are being investigated and the numerous emerging applications of tungsten compounds will further advance. Tungsten-dependent substances can take part in various functions of fuel cell systems such as electrolytes, cata- lysts, catalyst supports, and co-catalysts of numerous types of fuel cells. Tungsten is mostly obtained in four geological forms: skarn deposits, vein deposits, sheeted vein deposits, and pegmatites (Wei et al. 2019). Reports revealed that organometallic compounds of various tran- sition metals play a significant role in medicinal chemis- try and organocatalysis (Ali et al. 2017, Melník and Mikuš 2017, Huda Noor et al. 2018, Umar et al. 2018, De et al. 2019, Kamal et al. 2019, Habib et al. 2019a,b, Majid Sheikh et al. 2019, Rabiee et al. 2019). Among different elements of d-block, tungsten coor- dinates with various salts, forming stable complexes. Among them, tungsten hexafluoride (WF 6 ) is very useful in the semiconductor industry, as it is used for depositing metal on circuit boards through chemical vapor deposition (Ruiz Bilbao 2017). Since the 1930s, the oil industry has been using tungsten-based compounds as catalysts for the *Corresponding author: Muhammad Adnan Iqbal, Department of Chemistry, University of Agriculture, Faisalabad, Pakistan; and Organometallic and Coordination Chemistry Laboratory, University of Agriculture, Faisalabad 38040, Pakistan, e-mail: adnan.iqbal@ uaf.edu.pk. https://orcid.org/0000-0001-6241-7547 Muhammad Sohail, Muhammad Zeshan Ashraf, Raziya Nadeem, Shamsa Bibi and Amanullah: Department of Chemistry, University of Agriculture, Faisalabad, Pakistan Rabia Rehman: Institute of Chemistry, University of the Punjab, Lahore 5400, Pakistan