Executive Summary : | Metal hydrides are known for their pleasing structural diversity and bonding features, as well as their potential applications in hydrogen storage and various catalytic processes.¹ In comparing copper hydrides, the study of Ag/Au hydrides is in its infancy and has accelerated dramatically. The finding of novel coinage metal hydrides with stability in air and moisture is immensely interesting and a topical demand. The first molecular hexameric [Cu(PPh₃)H]₆ (Stryker`s reagent) catalyzes the selective reduction of α,β-unsaturated hydrocarbons.² Copper hydrides (CuHs) have found widespread use in various applications, including but not limited to hydrogen storage and catalytic hydrogenation.³ Until now, only a dozen high-nuclearity copper hydride clusters have been supported by phosphine or dicahlcogen types of ligands, as exemplified by Cu₂₅,⁴ Cu₂₉,⁵ Cu₆₁,⁶ Cu₂₃, Cu₅₃, Cu₃₂, Cu₃₁, Cu₃₀, Cu₂₀, Cu₃₆, Cu₂₈ etc. Where the dichalcogenide (dithiolates) stabilized copper hydrides are a few and found more stable than phosphine ligands.⁷-⁸ Dithiolates were efficiently able to stabilize [Cu₂₈H₁₅(S₂CNnPr)₁₂]+,⁹ [Cu20H11{EP(OiPr)9}12] (E = S, Se),¹⁰-¹¹ [Cu₃₀H₁₈{S2P(OnPr)₂}₁₂],¹² [Cu₃₂H₂₀{SP(OiPr)₉}₁₂]₁₃ and [Cu₂₈H₂₀(S₂P(OiPr)₂)₉]-,¹⁴ dithiocarbamate (dtc) and dithiophosphate (dtp) type ligands. The Cu₂₈H₁₅, Cu₂₀H₁₁ and Cu₃₂H₂₀ serve as model for hydrogen diffusion in metals to create metal hydrides for H₂ storage.⁷ The electrochemical reduction by Cu₃₂H₂₀ of CO₂ into formic acid over the low potential was aspiring.¹⁵ The single Pd metal doping improve stability of Cu rich hydrides and efficiently catalyzed the electrolytic water splitting to evolve hydrogen.¹⁶ On the other side, the heavy (Ag, Au) congeners are more scarce. There were only [Ag₇(H){E₂P(OR)₂}₆], [Ag₈(H){E₂P(OR)₂}₆]+ (E = S, Se),¹⁷-¹⁸ and [Ag₁₁(H)(S₂CNR2)₉]+,¹⁹ were stabilized and structurally characterized. To the best of our knowledge, no any AuH has been fabricated using dithiolates.¹ Thus, limited copper hydrides were structurally known to store renewable energy in various forms and suggests exploring them and their congeners by design and using a variety of symmetric and asymmetric dithiolates such as (dithiocarbamate, dithiophosphinate, dithiophosphonato, xanthate, thioxanthate and 1,1-dicyanoethylene-2,2-dithiolate (i-MNT). Further, the isolated homometallic and heterometallic coinage metal hydrides will be tested for a variety of applications in CO₂ reduction, water splitting, and selective hydrogenation of unsaturated bonds of organic substrates. The isolated compounds will be analyzed by single crystal X-ray diffraction, ESI-Mass analysis, NMR (¹H, ²H, ³¹P, ¹³C, ⁵⁷Se, etc.), ICP-MS, SEM, and EDS. A computational study of atomically precise metal hydrides will support the prime location of hydrides in metallic frame and explains the unique physical properties such as optical absorption, emission etc. with significant modulation in the electronic structure. |