|Jmol-3D images||Image 1|
|Molar mass||67.425 g mol-1|
|Related compounds||Mercury(II) hydride|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Zinc hydride is a chemical compound of zinc and hydrogen, ZnH2, which is used as a reducing agent in organic synthesis. First reported in 1947, it is a white crystalline powder when freshly made which turns grey if left at room temperature for a few days, presumably due to the decompostion to metallic zinc. It can be prepared in a number of ways:
- 2LiH + ZnBr2 → ZnH2 + 2LiBr
- 2NaH + ZnI2 → ZnH2 + 2NaI
- ZnI2 + 2LiAlH4 → ZnH2 + AlH3 + 2LiI
- Zn(CH3)2 + LiAlH4 → ZnH2 + LiAlH3(CH3)
It decomposes at 90 °C into the elements. It is sensitive to air and moisture, and is hydrolysed slowly by water but violently by aqueous acids. Older samples may be pyrophoric. The solid state structure is not known but is believed to involve covalent bonding
Molecular zinc hydride 
Meta stable, gaseous ZnH2 have been discovered in an emission source that combines an electrical discharge with a high-temperature furnace. High-resolution infrared emission spectra of ZnH2 have been recorded with a Fourier transform spectrometer. The reaction of excited zinc atoms with molecular hydrogen in the gas phase was studied by Breckenridge et al using laserpump-probe techniques. The only spectroscopic studies on the zinc dihydride molecule are the infrared spectra of ZnH2 trapped in argon and krypton matrices at 10-12 K.
The average Zn-H bond energy was recently calculated to be 51.24 kcal mol-1, while the H-H bond energy is 103.3 kcal mol-1. Therefore, the overall reaction is nearly ergoneutral.
- Zn(g) + H2(g) → ZnH2(g)
Molecular zinc hydride was found to be linear with a Zn-H bond length of 153.5 pm.
The molecule can be found a singlet ground state of 1Σg+.
- A. E. Finholt, A. C. Bond, Jr., H. I. Schlesinger (1947). "Lithium Aluminum Hydride, Aluminum Hydride and Lithium Gallium Hydride, and Some of their Applications in Organic and Inorganic Chemistry". Journal of the American Chemical Society 69 (5): 1199–1203. doi:10.1021/ja01197a061.
- Herrmann, Wolfgang A. (1997). Synthetic Methods of Organometallic and Inorganic Chemistry. Georg Thieme Verlag. ISBN 3-13-103061-5.
- Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
- Mackay, Rosemary Ann; Henderson, W.; (2002). Introduction to Modern Inorganic Chemistry (6th ed.). CRC Press. ISBN 0-7487-6420-8.
- Shayesteh, Alireza; Appadoo, Dominique R. T.; Gordon, Iouli E.; Bernath, Peter F.; Journal of the American Chemical Society (2004). "Vibration−Rotation Emission Spectra of Gaseous ZnH2 and ZnD2". Journal of the American Chemical Society 126 (44): 14356–14357. doi:10.1021/ja046050b. PMID 15521746.
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