This review is dedicated to the chemistry of Mo iodides. These compounds have a humble origin, and for a long time their chemistry has been almost completely neglected. Although important work on mononuclear and dinuclear Mo iodide complexes was done in 1980-1990s, the situation has dramatically changed within the last decade. The finding that the IntroductionThe iodides of transition metals attract much less attention than their chloride and bromide analogues, even though a book dealing exclusively with metal iodides was published half a century ago. [1] This is partly explainable by general lack of current or proposed practical use for this class of compounds. A notable exception offer the volatile iodides of Ti, Zr, and Hf, and of a few other metals, that can be used in the iodide process of van Arkel and de Boer. [2] Among the group 6 metals, this process can be applied for preparation of high purity chromium, which [a] Nikolaev His research interests focus on the coordination chemistry of 4d and 5d transition metals. Maxim Mikhaylov was born in Novosibirsk, (Russia). In 2009-2013 he completed his Ph. D. at the Laboratory of cluster and supramolecular compounds in the Nikolaev Institute of Inorganic Chemistry (NIIC) under suporevision of Prof. Dr. M. N. Sokolov. Now he is a researcher working in the Laboratory of synthesis of cooridnation compounds at NIIC. His research interests include synthesis of novel clusters and cluster complexes for the development of new materials.

Catalytic properties of the cluster compound (TBA)2[Mo6Ii8(O2CCH3)a6] (TBA = tetrabutylammonium) and a new hybrid material (TBA)2Mo6Ii8@GO (GO = graphene oxide) in water photoreduction into molecular hydrogen were investigated. New hybrid material (TBA)2Mo6Ii8@GO was prepared by coordinative immobilization of the (TBA)2[Mo6Ii8(O2CCH3)a6] onto GO sheets and characterized by spectroscopic, analytical, and morphological techniques. Liquid and, for the first time, gas phase conditions were chosen for catalytic experiments under UV–Vis irradiation. In liquid water, optimal H2 production yields were obtained after using (TBA)2[Mo6Ii8(O2CCH3)a6] and (TBA)2Mo6Ii8@GO) catalysts after 5 h of irradiation of liquid water. Despite these remarkable catalytic performances, “liquid-phase” catalytic systems have serious drawbacks: the cluster anion evolves to less active cluster species with partial hydrolytic decomposition, and the nanocomposite completely decays in the process. Vapor water photoreduction showed lower catalytic performance but offers more advantages in terms of cluster stability, even after longer radiation exposure times and recyclability of both catalysts. The turnover frequency (TOF) of (TBA)2Mo6Ii8@GO is three times higher than that of the microcrystalline (TBA)2[Mo6Ii8(O2CCH3)a6], in agreement with the better accessibility of catalytic cluster sites for water molecules in the gas phase. This bodes well for the possibility of creating {Mo6I8}4+-based materials as catalysts in hydrogen production technology from water vapor.

The reactions between (Bu4N)2[{W6I8}I6] (1) and silver carboxylates RCOOAg in CH2Cl2 afforded new luminescent carboxylate complexes (Bu4N)2[{W6I8}(RCOO)6] [R = CH3 (2), C6H5 (3), C2F5 (4), C3F7 (5), C6F5 (6)]. The complexes were characterized by single‐crystal X‐ray diffraction, elemental analysis, cyclic voltammetry, and IR and NMR spectroscopy. Complexes 1–6 all exhibit intense and long‐lived photoluminescence. The carboxylate complexes undergo reversible electrochemical oxidation in two consecutive one‐electron steps.

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