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Zinc compounds, like those of main group elements, are mostly colourless. Exceptions occur when the compound contains a coloured anion or ligand. However, zinc selenide and zinc telluride are both coloured due to charge-transfer processes. Zinc oxide turns yellow when heated due to the loss of some oxygen atoms and formation of a defect structure
The major drawback of the Negishi coupling, aside from its water and oxygen sensitivity, is its relative lack of functional group tolerance when compared to other cross-coupling reactions. [ 39 ] (−)-stemoamide is a natural product found in the root extracts of ‘’Stemona tuberosa’’.
The reaction is effected with zinc. The key zinc-intermediate formed is a carbenoid (iodomethyl)zinc iodide which reacts with alkenes to afford the cyclopropanated product. The rate of forming the active zinc species is increased via ultrasonication since the initial reaction occurs at the surface of the metal.
The reaction is named after its co-discoverer, John E. McMurry. The McMurry reaction originally involved the use of a mixture TiCl 3 and LiAlH 4, which produces the active reagents. Related species have been developed involving the combination of TiCl 3 or TiCl 4 with various other reducing agents, including potassium, zinc, and magnesium.
The oxygen on an aldehyde or ketone coordinates to the zinc to form the six-member chair like transition state 3. A rearrangement occurs in which zinc switches to the aldehyde or ketone oxygen and a carbon-carbon bond is formed 4. Acid workup 5,6 removes zinc to yield zinc(II) salts and a β-hydroxy-ester 7. [5]
Zinc acetylacetonate is an acetylacetonate complex of zinc, with the chemical formula of Zn(C 5 H 7 O 2) 2. The compound is in fact a trimer, Zn 3 (acac) 6 , in which each Zn ion is coordinated by five oxygen atoms in a distorted trigonal bipyramidal structure.
Zinc complexes merit inclusion in the Irving-Williams series as zinc forms many complexes with the same stoichiometry as complexes of copper(II), albeit with smaller stability constants. [25] There is little similarity between cadmium and silver as compounds of silver(II) are rare and those that do exist are very strong oxidizing agents.
Zinc has an electron configuration of [Ar]3d 10 4s 2 and is a member of the group 12 of the periodic table. It is a moderately reactive metal and strong reducing agent. [48] The surface of the pure metal tarnishes quickly, eventually forming a protective passivating layer of the basic zinc carbonate, Zn 5 (OH) 6 (CO 3) 2, by reaction with ...