Cadmium(I) tetrachloroaluminate

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IUPACName = dicadmium(2+) bis( tetrachoridoaluminate(1−))
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CASNo = 79110-87-5
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Formula = Cd₂Al₂Cl₈
MolarMass = 562.4123 g/mol
Appearance = white crystale
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MeltingPt = 227 ° (decomp)
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Cadmium(I) tetrachloroaluminate is the chemical compound with the formula Cd₂(AlCl₄)₂. It was the first compound reported (1961 [Stabilization of the Cadmium(I) Oxidation State. The System Cd-Cd₂I(AlCl₄)₂- Cd₂(AlCl₄)₂ ,Corbett J.D., Burkhard W.J., Druding L.F.,J. Am. Chem. Soc.; 1961; 83(1); 76-80.doi|10.1021/ja01462a016 ] ) that contained cadmium in the +1 oxidation state. Subsequent studies of the raman vibrational spectrum indicated the presence of a cadmium - cadmium bond [The Cadmium(I) Ion Cd₂²⁺. Raman Spectrum and Relationship to Hg₂²⁺, Corbett J.D, Inorganic Chemistry, 1,(1962), 3, 700 - 703, doi|10.1021/ic50003a051] and this was confirmed by two separate X-Ray diffraction studies of single crystals. The cadmium(I) ion, Cd₂²⁺; X-ray crystal structure of Cd₂(AlCl₄)₂ Faggiani R., Gillespie R.J., Vekris J.E., J. Chem. Soc., Chem. Commun., 1986, 517 - 518, doi|10.1039/C39860000517] Synthesis and crystal structures of Cd [AlCl₄] ₂ and Cd₂ [AlCl₄] ₂ Staffel T, Meyer G., Zeitschrift für anorganische und allgemeine Chemie, 548, 5, 45 - 54, doi|10.1002/zaac.19875480505 ] The compound can therefore be compared to mercury(I), (mercurous), compounds (e.g. mercury(I) chloride) that contain Hg₂²⁺.

Preparation and properties

Cd₂(AlCl₄)₂ was originally prepared by dissolving Cd metal in molten CdCl₂ followed by the addition of AlCl₃. :CdCl₂ + Cd → Cd₂Cl₂ :Cd₂Cl₂ + 2AlCl₃ → Cd₂(AlCl₄)₂

Cd₂(AlCl₄)₂ is diamagnetic, i.e. contains no unpaired electrons and reacts readily with water disproportionating to give Cd metal and Cd²⁺.
The compound has a complex structure and contains ethane like Cd₂Cl₆ units sharing vertices with AlCl₄ units with a Cd-Cd bond length reported as 257.6 pm, 256.1pm

References