Ammonium dimolybdate

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| OtherNames = ADM

|Section1={{Chembox Identifiers

| CASNo = 27546-07-2

| ChemSpiderID = 9306724

| EINECS = 248-517-2

| PubChem = 21895884

| InChI=1S/2Mo.H3N.8O/h;;1H3;;;;;;;;/q;;;;;;;4*-1/p+1

| InChIKey = UHQWHVHZVHVJFE-UHFFFAOYSA-O

| SMILES = [NH4+].[O-][Mo](=O)(=O)O[Mo](=O)(=O)[O-].[NH4+] }}

|Section2={{Chembox Properties

| Formula = H₈N₂Mo₂O₇

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| Appearance = white solid

| Density = 2.97 g/cm³

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Ammonium dimolybdate (ADM) is the inorganic compound with the formula (NH₄)₂Mo₂O₇. It is a white, water-soluble solid. ADM is an intermediate in the production of molybdenum compounds from its ores. Roasting typical ore produces crude molybdenum(VI) oxides, which can be extracted into aqueous ammonia, affording ammonium molybdate. Heating solutions of ammonium molybdate gives ADM. Upon heating, solid ammonium dimolybdate decomposes to molybdenum trioxide:{{cite encyclopedia|author=Roger F. Sebenik|display-authors=et al|title=Molybdenum and Molybdenum Compounds|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|year=2005|publisher=Wiley-VCH|location=Weinheim|doi=10.1002/14356007.a16_655|isbn=3527306730|s2cid=98762721 }}

: (NH₄)₂Mo₂O₇ → 2 MoO₃ + 2 NH₃ + H₂O

In terms of its chemical structure, the anion is a polymeric consisting of distorted octahedral Mo centers linked by tetrahedral molybdate centers.Armour, A. W.; Drew, M. G. B.; Mitchell, P. C. H. "Crystal and molecular structure and properties of ammonium dimolybdate" Journal of the Chemical Society, Dalton Transactions,1975, p1493-p1496. {{DOI: 10.1039/DT9750001493}} When prepared in the absence of water as its tetrabutylammonium salt, dimolybdate adopts the centrosymmetric structure observed for dichromate.{{cite journal|author=Day, V. W.|author2-link=Walter G. Klemperer|author2=Klemperer, W. G. |title=Metal Oxide Chemistry in Solution: The Early Transition Metal Polyoxoanions|journal =Science|year=1985|volume=228|issue=4699 |pages=533–541|doi=10.1126/science.228.4699.533|pmid=17736064 |bibcode=1985Sci...228..533D |s2cid=32953306 }}